JP7159646B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus having a photoreceptor.

In laser printers, print density changes due to changes in the environment and changes in the characteristics of the developer due to long-term use. In order to compensate for changes in print density, conventionally, multiple pattern images with different gradations are created and read, and based on the result, the correspondence relationship between the target density and the pattern image specified by the print command is set. There is known a gradation setting process, a so-called gamma correction (see Patent Document 1).

JP 2015-191020 A

By the way, when the photoreceptor is used for a long time for continuous printing, the state of the photoreceptor may temporarily change to a state in which it is difficult to be charged (hereinafter also referred to as a "long-term drive state"). However, if the gamma correction execution conditions are met in this long-term drive state and gamma correction is executed, it is possible to print with the optimum print density in the long-term drive state, but after the state of the photoreceptor returns to the normal state, the optimum print density is obtained. Since it is not possible to print with a sufficient print density, there arises a problem that the developer consumed by the gamma correction performed in the long-term driving state is wasted.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress wasteful consumption of developer due to gradation setting processing in a long-term driving state.

In order to solve the above-described problems, an image forming apparatus according to the present invention includes a replaceable photoreceptor, a replaceable developing device including a developing roller, and a bias applying section that applies a developing bias to the developing roller, an image forming unit for forming a plurality of pattern images having different gradations; a detecting unit for detecting the plurality of pattern images; the image forming unit forming the plurality of pattern images; and a control unit capable of executing a gradation setting process for setting a correspondence relationship between the target density and the plurality of pattern images based on the gradation setting process.
When the developing device is replaced, the control unit executes the gradation setting process on condition that the continuous driving time of the photoreceptor within a predetermined time period is less than a first specified time period. The gradation setting process is not executed on condition that the continuous driving time of the photoreceptor is not less than the first specified time.

Further, an image forming apparatus according to the present invention includes a replaceable photoreceptor, a replaceable developing device including a developing roller, and a bias applying section for applying a developing bias to the developing roller. a detection unit for detecting the plurality of pattern images; the image formation unit forming the plurality of pattern images; and a control unit capable of executing a gradation setting process for setting a correspondence relationship between the plurality of pattern images.
When the developing device is replaced, the control unit executes the gradation setting process on condition that the total driving time of the photoreceptor within a predetermined time period is less than a second specified time period. The gradation setting process is not executed on condition that the total driving time of the photoreceptor within the time period is not less than the second specified time.

According to each configuration described above, when the continuous driving time of the photoreceptor within the predetermined time is not less than the first specified time, or when the total driving time of the photoreceptor within the predetermined time is not less than the second specified time, that is, Since the gradation setting process is not executed when the photoreceptor is in the long-term drive state, wasteful consumption of developer due to the gradation setting process in the long-term drive state can be suppressed.

Further, the control unit can execute determination processing for determining whether or not the continuous driving time of the photoreceptor within a predetermined time period is less than a first specified time period. If it is determined in the determination process that the continuous driving time of the photoreceptor within the predetermined time is less than the first specified time, the gradation setting process is performed and The gradation setting process may not be executed when it is determined that the continuous driving time of the photoreceptor is not less than the first specified time.

Further, when the control unit determines that the continuous driving time of the photoreceptor within the predetermined time is not less than the first specified time and does not execute the gradation setting process, regardless of the predetermined condition, The gradation setting process may be performed when the determining process is performed and it is determined that the continuous driving time of the photoreceptor within a predetermined period of time is less than a first specified time.

According to this, the gradation setting process is executed when the state of the photoreceptor is no longer in the long-term driving state, so that the image quality of the image formed thereafter can be improved.

Further, the control section forms a predetermined pattern image in the image forming section, and can execute a bias setting process for setting a developing bias based on the detection result of the detection section. The bias setting process may be executed regardless of the driving time.

According to this, the bias setting process is executed even when the photoreceptor is in the long-term driving state, so that it is possible to prevent the image quality from being extremely deteriorated in the long-term driving state.

Further, when the photosensitive member is replaced with a new one, the control section may set the correspondence relationship between the target density and the plurality of pattern images to a default value.

Further, when the image forming apparatus further includes a cartridge including the photoreceptor, and a memory provided in the cartridge, the control unit controls the continuous driving time of the photoreceptor within a predetermined time as a first period. Information may be stored in the memory indicating that the gradation setting process was not executed because it was determined that the specified time was not exceeded.

According to this, even if the cartridge is once removed and then remounted, the information indicating that the gradation setting process has not been executed is stored in the memory of the cartridge, so that the process is executed for the cartridge. The gradation setting process that was not performed can be executed.

According to the present invention, wasteful consumption of developer due to gradation setting processing in a long-term driving state can be suppressed.

1 is a diagram showing a schematic configuration of a color printer according to one embodiment of the present invention; FIG. It is a block diagram which shows each structure relevant to a control part. FIG. 4 is a diagram showing a print pattern image; FIG. 4 is a diagram showing a correspondence relationship between target densities and exposure densities; 4 is a flow chart showing control executed based on the open/closed state of the top cover; 4 is a flowchart showing first correction processing; 9 is a flowchart showing second correction processing; 4 is a flow chart showing control executed based on the presence or absence of a print command; 7 is a flowchart showing re-correction processing; It is a flow chart which shows the modification of the 2nd amendment processing.

Next, one embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the schematic configuration of a color printer 1 as an example of an image forming apparatus will be briefly described, and then the configuration of the characteristic portion of the present invention will be described in detail.

Moreover, in the following description, directions are described in the directions shown in FIG. That is, the left side in FIG. 1 is defined as "front", the right side as "rear", the back side as "left", and the front side as "right". Also, the upper side in FIG. 1 is referred to as "upper", and the lower side as "lower".

As shown in FIG. 1, the color printer 1 includes a main housing 10, a top cover 11, a paper feeding unit 20 and an image forming unit 30 provided in the main housing 10, and a control unit 100. ing.

The top cover 11 is arranged on the upper part of the main body housing 10, and is provided so as to be rotatable with respect to the main body housing 10 about the rear-side turning shaft 11A. The opening 10A is opened and closed. Specifically, the top cover 11 is movable between a closed position for closing the opening 10A and an open position for opening the opening 10A.

The paper feed unit 20 is provided in the lower part of the main body housing 10 and includes a paper feed tray 21 that stores the paper P and a paper supply mechanism 22 that supplies the paper P from the paper feed tray 21 to the image forming unit 30 . ing. The paper P in the paper feed tray 21 is separated one by one by the paper supply mechanism 22 and supplied to the image forming section 30 .

The image forming section 30 includes four exposure heads 40 , four process cartridges PC, a transfer unit 70 and a fixing unit 80 .

The exposure head 40 has a light-emitting element and an image forming lens at its tip, and is held by the top cover 11 so as to be suspended from the top cover 11. When the top cover 11 is closed, a photosensitive drum 51, which will be described later, is attached to the exposure head 40. are arranged above and facing each other. Specifically, the exposure head 40 can move between a reference position close to the photosensitive drum 51 and a retracted position farther from the photosensitive drum 51 than the reference position by opening and closing the top cover 11 . The exposure head 40 is an exposure member that exposes the surface of the photosensitive drum 51, and performs exposure by blinking light-emitting elements based on a binary raster image.

Each process cartridge PC is arranged in parallel along the front-rear direction between the top cover 11 and the paper feed tray 21 . Each process cartridge PC is detachable through an opening 10A of the main housing 10 with the top cover 11 opened. The process cartridge PC includes a drum cartridge 50 as an example of a cartridge and a developer cartridge 60 as an example of a developer. The developer cartridge 60 is detachable from the drum cartridge 50 .

The drum cartridge 50 includes a photosensitive drum 51 as an example of a photosensitive member, a scorotron charger 52 that charges the photosensitive drum 51, a cleaning roller 54, and a drum frame 55 that supports the photosensitive drum 51 and the like. .

The developer cartridge 60 mainly includes a toner storage portion 61 that stores toner and a development roller 62 that supplies the toner in the toner storage portion 61 to the photosensitive drum 51 . The toner is a developer that develops the electrostatic latent image on the photosensitive drum 51 . The toner containing portion 61 of each developing cartridge 60 contains yellow, magenta, cyan, and black toners in order from the front.

The transfer unit 70 is provided between the paper feed tray 21 and the process cartridge PC. The transfer unit 70 includes a driving roller 71 , a driven roller 72 , an endless conveying belt 73 and four transfer rollers 74 . The conveying belt 73 is stretched between the driving roller 71 and the driven roller 72 . The conveying belt 73 has an outer surface in contact with each photosensitive drum 51 , and each transfer roller 74 is arranged inside the conveying belt 73 so as to sandwich the conveying belt 73 with each photosensitive drum 51 .

A detection unit 75 is provided obliquely below the rear of the conveying belt 73 . The detection unit 75 is a sensor that detects a toner image for image quality adjustment formed on the conveying belt 73 , that is, the print density of the image, and is arranged opposite the rear portion of the conveying belt 73 . In the following description, the image for image quality adjustment formed on the conveyor belt 73 is also referred to as a "patch". The detection unit 75 is a light reflective sensor that includes a light emitting element such as an LED and a light receiving element such as a phototransistor, and irradiates the patch with light to detect the reflected light.

The fixing unit 80 is provided behind the process cartridge PC and the transfer unit 70 and includes a heating roller 81 and a pressure roller 82 that is pressed against the heating roller 81 .

In the image forming unit 30 as described above, the surface of the photosensitive drum 51 is uniformly charged by the charger 52 and then exposed by the exposure head 40 . An image is formed. By applying a voltage to the developing roller 62 , toner is supplied from the developing roller 62 to the photosensitive drum 51 to visualize the electrostatic latent image and form a toner image on the photosensitive drum 51 . That is, the developer cartridge 60 develops the electrostatic latent image on the photosensitive drum 51 .

The toner images formed on the respective photosensitive drums 51 are sequentially superimposed and transferred onto the paper P conveyed on the conveying belt 73 by the transfer rollers 74 . The paper P onto which the toner image has been transferred is conveyed between the heating roller 81 and the pressure roller 82 so that the toner image is thermally fixed. After that, the paper P is discharged from the body housing 10 to the outside by the transport rollers 91 and placed on the paper discharge tray 11B formed on the top surface of the top cover 11 .

As shown in FIGS. 1 and 2, four reader/writers 12, an open/close sensor 13, and a detector 75 are connected to the controller 100. FIG. The control unit 100 includes a CPU, a RAM, a ROM, and an input/output circuit, and handles print jobs output from the external computer 900 and information output from the reader/writer 12, the open/close sensor 13, the detection unit 75, and the like. Then, control is executed by performing various arithmetic processing based on the programs and data stored in the ROM or the like. Specifically, the control unit 100 includes a calculation unit 110 such as a CPU, a control circuit 120 that controls the developing roller 62, the exposure head 40, and the like, and a storage unit . The control unit 100 executes print control and image quality adjustment by operating based on a program stored in the storage unit 130 .

The reader/writer 12 can read/write information from/to the first memory M1 provided in the drum cartridge 50, and read/write information from/to the second memory M2 provided on the developing cartridge 60. It is a possible device. Based on information from the reader/writer 12, the control unit 100 can execute new product detection processing for determining whether the drum cartridge 50 is new and whether the developing cartridge 60 is new. It's becoming

In the new product detection process, for example, each cartridge 50, 60 is provided with a projection that moves irreversibly, and the cartridge sensor, which is an optical sensor, detects whether or not this projection pushes a detection lever in the main body housing 10. You can do it by doing

The open/close sensor 13 is a sensor that detects the open/close state of the top cover 11 . As the open/close sensor 13, for example, an optical sensor can be used.

The control unit 100 has a function of executing print control for forming an image on the paper P based on a print job output from the computer 900 . In printing control, the control unit 100 executes exposure processing for exposing the photosensitive drum 51 based on a printing pattern image, which is a binary image. More specifically, in executing print control, when printing an image on the paper P, the control unit 100 sets different exposure densities (tones) so that the print density of the image becomes a predetermined target density. One printing pattern image is selected from a plurality of printing pattern images and exposure processing is executed. The print pattern image consists of a binary image as shown in FIG. The exposure density refers to the area ratio of exposed pixels in the pattern image for printing.

Here, the printing density is the density of the toner image developed by the developing roller 62 and is the density detected by the detection section 75 . The target density is the target density specified by the print command. For example, when the target density specified by the print command is 20%, the control unit 100 selects a print pattern image with an exposure density of 20%, and performs exposure processing using this print pattern image. However, the relationship between the target density and the exposure density is changed by tone setting processing, which will be described later. For example, a state in which a print pattern image with an exposure density of 20% is associated with a target density of 20% is changed to a state in which a print pattern image with an exposure density of 10% is associated with a target density of 20%. In this case, when forming an image with a target density of 20%, exposure processing is executed with a print pattern image with an exposure density of 10%.

Specifically, upon receiving the print data, the control unit 100 executes a rasterization process for rasterizing the received print data into a binary raster image. In the rasterization process, the control unit 100 performs a first process of rasterizing the received print data into object data consisting of vector data or bitmap data, and arranges the object data on a virtual sheet to form a plurality of band data. It is possible to execute a second process of developing into a raster image consisting of.

Here, the print data is data created by an external device such as a computer and configured in a page description language or the like, and cannot be handled as data for exposure of the color printer 1 . Therefore, the control unit 100 performs a development process for developing print data in a page description language or the like into a raster image, which is data for exposure. Then, when performing exposure processing on a predetermined portion of the raster image, the control unit 100 selects a printing pattern image corresponding to the target density of the predetermined portion of the raster image, and performs exposure processing using this printing pattern image. .

As described above, the control unit 100 selects one printing pattern image corresponding to the target density from a plurality of printing pattern images, and then performs exposure and development using the printing pattern image. A toner image having a target density is formed on the photosensitive drum 51 .

A plurality of printing pattern images are stored in the storage unit 130 in advance in correspondence with exposure densities. A plurality of printing pattern images are stored in advance in the storage unit 130 in association with the respective colors of yellow, magenta, cyan, and black.

The control unit 100 has a function of executing determination processing for determining whether the state of the photosensitive drum 51 is the long-term driving state based on a parameter that increases as the driving time of the photosensitive drum 51 increases. there is Here, in the present embodiment, as a parameter that increases as the driving time of the photosensitive drum 51 increases, the continuous execution time of print control from the current time, that is, the time of determination in the determination process to the time before a predetermined time. Illustrate.

Here, in print control, since all the photosensitive drums 51 rotate, the continuous execution time of print control corresponds to the time during which the photosensitive drums 51 are continuously driven (hereinafter also referred to as "continuous drive time"). Note that when at least one photosensitive drum 51 is replaced, the continuous execution time corresponding to the replaced photosensitive drum 51 is reset.

The continuous driving time of the photosensitive drum 51 is calculated by multiplying (1) the number of rotations of the photosensitive drum, (2) the number of rotations of the developing roller, and (3) the number of prints, etc., by a specified value for time conversion. or you can use a watch to measure it.

In the determination process, the control unit 100 determines whether or not the continuous execution time of print control within the predetermined time is less than the first specified time. It is determined that the photosensitive drum 51 is in the driving state, and if it is less than the first specified time, it is determined that the photosensitive drum 51 is not in the long-term driving state. Specifically, the control unit 100 determines that the state of at least one photosensitive drum 51 is in the long-term drive state when the continuous execution time of print control is not less than the first specified time, and is less than the first specified time. In this case, it is determined that all the photosensitive drums 51 are not in the long-term driving state.

The control unit 100 can execute image quality adjustment for adjusting the image quality of the printed toner image. The control unit 100 executes image quality adjustment when a predetermined condition is satisfied. The control unit 100 has a function of executing bias setting processing and gradation setting processing based on the detection result of the detection unit 75 when executing image quality adjustment.

Specifically, when a predetermined condition is satisfied, the control unit 100 executes the bias setting process, executes the above-described determination process, and executes/non-executes the gradation setting process according to the determination result of the determination process. decided to execute. In other words, when the predetermined condition is satisfied, the control unit 100 executes the bias setting process regardless of the result of the determination process described above, that is, regardless of the state of the photosensitive drum 51 .

Here, in the present embodiment, the first condition that the drum cartridge 50 has been replaced with a new one, the second condition that the developing cartridge 60 has been replaced with a new one, and the environment such as temperature and humidity, which are predetermined conditions, If either the third condition that the image quality adjustment has changed by a predetermined value or more, or the fourth condition that the number of printed sheets since the previous execution of the image quality adjustment has exceeded the predetermined number Image quality adjustment is performed.

In the bias setting process, the control unit 100 causes the image forming unit 30 to form a pattern image using the first printing pattern image corresponding to the predetermined exposure density, and based on the result detected by the detecting unit 75, sets the developing bias. set. Here, the developing bias is a bias applied to the developing roller by a bias applying section (not shown). The image forming section 30 has a bias applying section. In the bias setting process, the control unit 100 calculates a development bias such that a pattern image printed using the first printing pattern image corresponding to a predetermined exposure density, that is, a toner image, has a predetermined print density. Here, the predetermined exposure density and the predetermined print density are 40% as an example, and the control unit 100 selects the 40% print pattern image shown in FIG. 3 as the first print pattern image. . Specifically, in the bias setting process, the control unit 100 uses two types of developing biases to form two toner images corresponding to the two first print pattern images. More specifically, in the bias setting process, the control unit 100 forms two electrostatic latent images on the photosensitive drum 51 using the first printing pattern image, and applies two types of electrostatic latent images to the two electrostatic latent images. By performing development with the development bias, patches with two different print densities are formed on the photosensitive drum 51 . After that, the control unit 100 transfers each patch from the photosensitive drum 51 to the conveying belt 73 , and the detecting unit 75 detects each patch on the conveying belt 73 . Then, the control unit 100 converts the intensity of the reflected light from each patch detected by the detection unit 75 into print density, and the print density becomes the target density based on the two types of print density and the two types of development bias. Calculate the development bias.

That is, the control unit 100 forms a pattern image using the printing pattern image associated with the target density in the gradation setting process, calculates the developing bias so that the printing density of the pattern image becomes the target density, Setting is made so that the calculated developing bias is applied to the developing roller 62 . This is because if at least one of temperature and humidity changes, the toner may not move from the developing roller 62 to the photosensitive drum 51 so as to achieve the target density even with the same developing bias. If more toner moves from the developing roller 62 to the photosensitive drum 51 than the target density, the developing bias is decreased to reduce the amount of toner that moves. On the other hand, when the amount of toner from the developing roller 62 to the photosensitive drum 51 is less than the target density, the developing bias is increased to increase the amount of toner that moves.

In the gradation setting process, the control unit 100 forms toner images (pattern images) with a plurality of types of print densities corresponding to a plurality of types of print pattern images with the development bias set by the bias setting process, and prints the toner images. Detected by the detector 75 . Here, the plurality of types of printing pattern images are a plurality of printing pattern images corresponding to a plurality of exposure densities. For example, a second printing pattern image corresponding to an exposure density of 20% and a A third pattern image for printing, a fourth pattern image for printing corresponding to an exposure density of 60%, and the like are used.

After that, the control unit 100 sets the correspondence relationship between the target density and the pattern image for printing based on the result detected by the detection unit 75 . By setting the correspondence relationship between the target density and the pattern image for printing in this way, the correspondence relationship between the target density and the actually printed toner image, that is, the exposure density is set.

More specifically, in the gradation setting process, the control unit 100 creates five electrostatic latent images on the photosensitive drum 51 using respective printing pattern images corresponding to, for example, exposure densities of 20, 40, 60, 80 and 100%. are formed, and each electrostatic latent image is developed with the development bias set at that time, thereby forming patches of five different print densities. After that, the control unit 100 causes the detection unit 75 to detect each patch transferred from the photosensitive drum 51 to the conveying belt 73 . The control unit 100 converts the intensity of reflected light from each patch into print density. Then, the control unit 100 compares each calculated print density with the corresponding exposure density, and if the compared print density and the exposure density are different, corrects the correspondence relationship between the print density and the exposure density. Change the correspondence relationship between the target density and the pattern image for printing.

Specifically, if the gradation setting process has not been performed even once in the past, the correspondence relationship between the target density and the pattern image for printing (exposure density) is, for example, default as indicated by the chain double-dashed line in FIG. gamma table. In the following description, the correspondence relationship between target densities and printing pattern images is also referred to as a "gamma table".

The gamma table is a table for selecting a printing pattern with a predetermined exposure density corresponding to a predetermined target density when printing at a predetermined target density. The gamma table indicated by the chain double-dashed line, that is, the default gamma table, has the same value for the target density and the exposure density.

In the gradation setting process, for example, as indicated by black circles in the figure, when the detection unit 75 detects a patch formed using the first printing pattern image corresponding to an exposure density of 20%, the printing density of the patch is determined. becomes 10%, the control unit 100 stores the first pattern image for printing again as a pattern image corresponding to the target density of 10%. That is, in the next print control, when forming an image with a target density of 10%, if the image is formed with the first print pattern image corresponding to an exposure density of 20%, the print density will be 10%. The unit 100 associates the first print pattern image with the exposure density of 20% with the target density of 10%.

Further, in the gradation setting process at this time, if the print density is 40% when the detection unit 75 detects the second print pattern image with an exposure density of 40%, that is, the target density, the exposure density, and the print density , the relationship between the target density and the exposure density is linearly interpolated as indicated by the dashed line in the figure. As a result, for example, in the next print control, when a patch is formed with a target density of 20%, a print pattern image corresponding to the exposure density X corresponding to the intersection of the line of the target density of 20% and the dashed line in the figure is selected. Note that the gamma table at this time is such that the lines of the default gamma table (double-dot chain line) where the exposure density is less than 40% are replaced with the dashed lines in the figure. That is, the gap between the black circle shown in the figure and the white circle corresponding to the exposure density of 40% is compensated as indicated by the dashed straight line.

If the controller 100 determines that the state of the photosensitive drum 51 is not in the long-term driving state in the determination processing executed when the predetermined condition is satisfied, the control unit 100 executes the gradation setting processing, and the state of the photosensitive drum 51 is It is configured not to execute the gradation setting process when it is determined that it is in the long-term drive state. If the control unit 100 determines that the photosensitive drum 51 is in the long-term drive state and does not execute the gradation setting process, the control unit 100 executes the determination process regardless of the predetermined conditions. When it is determined that the state of the photosensitive drum 51 is not in the long-term drive state, the gradation setting process is executed.

Specifically, when the control unit 100 determines that the long-term driving state has occurred and does not execute the gradation setting process, the control unit 100 sets an unfinished flag F(n), which is information indicating this fact. Then, when the unfinished task flag F(n) is set, the control unit 100 executes determination processing regardless of the predetermined conditions, and when the state of the photosensitive drum 51 returns to the non-long-term drive state, , the gradation setting process is executed.

Here, the leftover flag F(n) is individually set for each drum cartridge 50, that is, for each color. The control unit 100 is configured to store the leftover flag F(n) in the first memory M1 provided in the corresponding drum cartridge 50 . Specifically, for example, F(0) corresponds to black, F(1) corresponds to yellow, F(2) corresponds to magenta, and F(3) corresponds to cyan. These flags are stored in the first memory M1 corresponding to each color.

The storage unit 130 stores various thresholds used for control, a program for operating the control unit 100, and the like, in addition to storing each printing pattern image and the default gamma table described above.

Next, operation of the control unit 100 will be described in detail. The control unit 100 always executes the control shown in FIGS. 5 and 8. FIG.

In the control shown in FIG. 5, the control unit 100 first determines whether the top cover 11 is opened or closed based on the signal from the open/close sensor 13 (S1). If it is determined that the door is not opened or closed in step S1 (No), the control unit 100 terminates this control.

If it is determined that it has been opened and closed in step S1 (Yes), the control unit 100 determines whether or not the drum cartridge 50 has been replaced with a new one for each color based on the information read by the reader/writer 12 of each color ( S2). If it is determined in step S2 that at least one color has been replaced with a new one (Yes), the controller 100 executes the first correction process for the color corresponding to the replaced drum cartridge 50 (S3).

Here, the first correction process is a process of performing image adjustment for the color corresponding to the drum cartridge 50 that has been replaced with a new one. Details of the first correction process will be described later.

After step S3, the controller 100 determines whether or not the first correction process has been completed for all the colors corresponding to all the drum cartridges 50 that have been replaced with new ones (S4). If it is determined in step S4 that the process has not been completed (No), the control section 100 returns to step S3 and executes the first correction process for the colors for which the first correction process has not been executed. If it is determined that the process has ended in step S4 (Yes), the control unit 100 ends this control.

If it is determined in step S2 that all the drum cartridges 50 have not been replaced with new ones (No), the control section 100 determines whether or not the developing cartridges 60 have been replaced with new ones for each color (S5). If it is determined in step S5 that all the developing cartridges 60 have not been replaced with new ones (No), the control section 100 terminates this control. If it is determined in step S5 that at least one color has been replaced with a new one (Yes), the control section 100 executes the second correction process for the color corresponding to the replaced developing cartridge 60 (S6).

Here, the second correction process is a process of adjusting the image for the color corresponding to the new developing cartridge 60 that has been replaced. Details of the second correction process will be described later.

After step S6, the controller 100 determines whether or not the first correction process has been completed for all colors corresponding to all the new developing cartridges 60 (S7). If it is determined in step S7 that the process has not been completed (No), the control section 100 returns to step S6 and executes the second correction process for the colors for which the second correction process has not been executed. If it is determined that the process has ended in step S7 (Yes), the control unit 100 ends this control.

As shown in FIG. 6, in the first correction process, the control unit 100 first executes the bias setting process for the color corresponding to the drum cartridge 50 that has been replaced with a new one, that is, one predetermined color, and sets the developing bias. Correct (S11). After step S11, the control unit 100 determines whether or not the photosensitive drum 51 is in the long-term driving state (S12).

If it is determined in step S12 that it is in the long-term drive state (Yes), the control unit 100 sets the gamma table corresponding to one predetermined color as the default gamma table (S13). That is, when the photosensitive drum 51 corresponding to the predetermined color is replaced with a new one (S2: Yes) and the state of the photosensitive drum 51 corresponding to the predetermined color is the long-term drive state (S12 : Yes), the gamma table corresponding to the predetermined color is set as the default gamma table (S13). After step S13, the control unit 100 sets the unfinished flag F(n) corresponding to one predetermined color to 1 (S14), and ends this control.

That is, when the control unit 100 determines that the long-term driving state is set in step S12 (Yes), the control unit 100 does not execute the gradation setting process, but instead sets the unfinished flag F(n) and is configured to execute the gradation setting process. Note that the process of setting the gamma table to the default gamma table is simply a process of rewriting the default gamma table stored in the storage unit 130 as the gamma table. This process is different from the setting process.

If it is determined in step S12 that it is not in the long-term driving state (No), the control unit 100 executes gradation setting processing for one predetermined color and sets a new gamma table (S15). After step S15, the control unit 100 sets the unfinished flag F(n) corresponding to one predetermined color to 0 (S16), and terminates this control.

As shown in FIG. 7, the second correction process is a process obtained by removing the process of step S13 from the first correction process. Here, since the second correction process is performed when the drum cartridge 50 is not new, the gamma table is already set when the second correction process is executed. Therefore, in the second correction process, the process of setting the gamma table to the default gamma table (S13) is unnecessary. Since each process of the second correction process is the same as steps S11, S12, and S14 to S16 of the first correction process, the same reference numerals are assigned to each process, and description thereof will be omitted.

In the control shown in FIG. 8, the control unit 100 first determines whether or not a print command has been received (S31). If it is determined in step S31 that a print command has been received (Yes), the control unit 100 determines whether the current environment has changed from the environment when the gamma table was set last time (S32). Here, the environmental change can be determined, for example, based on the temperature or humidity detected by the temperature/humidity sensor. Specifically, for example, by determining whether the difference between the current temperature (or humidity) and the temperature (or humidity) when the gamma table was set last time is greater than or equal to a predetermined value, environmental changes can be determined. . In addition, the main housing 10 has a temperature/humidity sensor.

If it is determined that there is no environmental change in step S32 (No), the control unit 100 determines whether or not the number of printed sheets from the time the gamma table was set last time to the present is equal to or greater than a predetermined number of sheets (S33). . If there is a change in the environment in step S32 (Yes), or if it is determined in step S33 that the number of printed sheets is equal to or greater than the predetermined number of sheets (Yes), the control unit 100 executes bias setting processing for all colors, The development bias is corrected for all colors (S34).

After step S34, the control unit 100 determines whether or not the photosensitive drum 51 is in the long-term drive state (S35). If it is determined in step S35 that it is in the long-term drive state (Yes), the control unit 100 sets the unfinished flag F(n) to 1 for all colors (S36).

That is, when the control unit 100 determines that the long-term driving state is set in step S35 (Yes), the control unit 100 does not execute the gradation setting process for all colors, but instead sets the unfinished flag F(n). is configured to execute gradation setting processing later. After step S36, the control unit 100 executes print control (S37), and then terminates this control.

If it is determined in step S35 that it is not in the long-term drive state (No), the control section 100 executes gradation setting processing for all colors (S38). After step S38, the control unit 100 sets the unprinted flag F(n) to 0 for all colors (S39), and executes print control (S37).

If it is determined that there is no print command in step S31 (No), the control section 100 executes re-correction processing (S40). In this case, the re-correction process is executed because the photosensitive drum 51 is in the long-term driving state even though the predetermined condition for executing the gradation setting process is satisfied. This is the processing for performing the gradation setting processing when the state of the photosensitive drum 51 returns to the state where it is not in the long-term drive state when the state of the photosensitive drum 51 is not set. The re-correction process will be detailed later.

After step S40, the control unit 100 terminates this control. If it is determined in step S33 that the number of printed sheets is not equal to or greater than the predetermined number (No), the control section 100 executes re-correction processing similar to step S40 (S41). After executing the re-correction process in step S41, the control unit 100 executes print control (S37).

As shown in FIG. 9, in the re-correction process, the control unit 100 first determines whether or not the unfinished flag F(n) is 1 for one predetermined color (S51). Specifically, for example, it is determined whether the unfinished flag F(0) corresponding to black is 1 or not.

If it is determined that F(n)=1 for one predetermined color in step S51 (Yes), the control unit 100 determines whether the state of the photosensitive drum 51 is the long-term drive state ( S52). If it is determined that the photosensitive drum 51 is not in the long-term drive state in step S52 (No), that is, if the state of the photosensitive drum 51 returns to the non-long-term drive state, the control unit 100 executes the bias setting process for one predetermined color. Then, the developing bias is corrected (S53).

After step S53, the control unit 100 executes the gradation setting process for one predetermined color (S54), and sets the unfinished flag F(n) corresponding to one predetermined color to 0 (S55). After step S55, if No is determined in step S51, or if Yes is determined in step S52, the control unit 100 determines whether the flag determination process in step S51 has been completed for all colors (S56). ).

If it is determined in step S56 that the flag determination process has not been completed for all colors (No), the control section 100 returns to step S51 and executes the flag determination process for the next color. If it is determined in step S56 that the flag determination process has been completed for all colors (Yes), the control section 100 ends this control.

Next, an example of operation of the control unit 100 will be described.
As shown in FIG. 8, when the control unit 100 receives the print command (S31: Yes), if the predetermined condition is not satisfied and the unfinished flag F(n) is all 0, is determined as No in each of the processes of steps S32, S33, and S51 (see FIG. 9) of step S41, print control is executed without image adjustment (S37), and the continuous execution time of print control is memorize

In print control, when the number of printed sheets is large and each photosensitive drum 51 is driven for a long time, each photosensitive drum 51 is in a long-term driving state. When each photosensitive drum 51 is in a long-term driving state and a predetermined condition (for example, the condition of the number of printed sheets) is satisfied, the control unit 100 determines Yes in step S33, and develops all colors. Bias correction is performed (S34).

After that, in step S35, the control unit 100 determines that the long-term driving state is in effect from the continuous execution time of print control (Yes), so the gradation setting process is not executed, and in step S36 all unfinished flags F ( n) is set to 1. As described above, since the gradation setting process is not executed when the photosensitive drum 51 is in the long-term drive state, wasteful toner consumption due to the gradation setting process in the long-term drive state can be suppressed. Note that the control unit 100 stores each unfinished flag F(n) set in step S36 in the first memory M1 of the corresponding drum cartridge 50, respectively.

After step S36, the control unit 100 executes print control (S37). In this print control, the previous uncorrected gamma table is used, but since the development bias is corrected in step S34, it is possible to prevent the image quality from deteriorating significantly during long-term driving. .

If the print command is not received for a while after the end of print control, the control unit 100 repeats the processes from S31 to S40. Specifically, the control unit 100 determines No in step S31, determines Yes in step S51 of step S40 (see FIG. 9), and determines Yes in step S52, so that the state of the photosensitive drum 51 does not return to the non-long-term drive state. Do not perform image adjustments unless

As time elapses, the ratio of the continuous execution time of print control to the time interval from the current time to the time before the predetermined time gradually decreases. Then, when the continuous execution time from the current time point to the time point before the predetermined time period becomes shorter than the first specified time period, the control unit 100 determines in step S52 that the long-term drive state has not been reached, that is, the state has returned to the non-long-term drive state. (No), the development bias is corrected for all colors (S53), and the unfinished gradation setting process is executed (S54).

In this way, when the state of the photosensitive drum 51 returns to the state of not being driven for a long period of time, the development bias correction and the gradation setting process are executed, so that the image quality of the image formed thereafter can be improved. In addition, since the unfinished gradation setting process is performed when no print command is received, there is no need to perform the gradation setting process the next time a print command is received, and print control is immediately executed. can do.

Note that if the state of the photosensitive drum 51 returns to the non-long-term driving state at the time of receiving the print command, the control unit 100 executes the development bias correction and tone setting processing by the re-correction processing in step S41. do. In this case also, the unfinished gradation setting process can be performed before printing, so that the image quality of the image to be formed thereafter can be improved.

When the user replaces, for example, the black drum cartridge 50 with a new one while the unfinished flags F(n) are all 0, in the control shown in FIG. Then, the first correction process is executed (S3). As shown in FIG. 6, in the first correction process, after correcting the black developing bias (S11), the control unit 100 determines whether or not the photosensitive drum 51 is in the long-term driving state (S12). .

If it is determined in step S12 that it is in the long-term drive state (Yes), the control unit 100 sets the black gamma table to the default gamma table (S13), and sets the black unfinished flag F(0) to 1. (S14). After that, if no print command is received for a while, the control unit 100 repeats the processes from S31 to S40 in the control shown in FIG.

If the state of the photosensitive drum 51 changes from the long-term drive state to the non-long-term drive state while repeating this process, the controller 100 returns to the non-long-term drive state in step S52 of FIG. After determination (No), the development bias is corrected for black (S53), and the unfinished gradation setting process is executed (S54). This allows the black gamma table to be replaced with a table that is more suitable for printing than the default gamma table.

For example, when the user once removes the black process cartridge PC and then reinserts it, the control unit 100 determines No in the processes of steps S1, S2, and S5 in the control of FIG. At this time, if the unfinished flag F(0) stored in the first memory M1 of the black drum cartridge 50 is 1, the control unit 100 keeps the first memory M1 even after the process cartridge PC is reattached. The re-correction process (S40) can be performed based on the unfinished task flag F(0)=1 stored in .

According to the above, the following effects can be obtained in this embodiment.
Since the gradation setting process is not executed when the photosensitive drum 51 is in the long-term drive state, wasteful toner consumption due to the gradation setting process in the long-term drive state can be suppressed.

When the state of the photosensitive drum 51 returns to the non-long-term drive state, the gradation setting processing that was not executed in the long-term drive state is executed, so that the image quality of the image formed thereafter can be improved.

Even when the photosensitive drum 51 is in the long-term drive state, the developing bias correction (bias setting process) is executed, so that it is possible to prevent the image quality from deteriorating significantly in the long-term drive state.

Even if the drum cartridge 50 is once removed and remounted, information indicating that the gradation setting processing was not executed, that is, the unfinished flag F(n) is stored in the first memory M1 of the drum cartridge 50. Therefore, the gradation setting process that was not executed for the drum cartridge 50 can be executed.

The present invention is not limited to the above-described embodiments, and can be used in various forms as exemplified below. In the following description, members having substantially the same structure as those of the above-described embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

In the above-described embodiment, the state of the photosensitive drum 51 is directly determined based on the driving time of the photosensitive drum 51 in the determination processing (S12) of the second correction processing performed when the developing cartridge is replaced. is not limited to For example, as shown in FIG. 10, the result of the determination process (S12) may be indirectly determined using flag A(n). Specifically, the flowchart of FIG. 10 has the same processing (S11, S12, S14 to S16) as the flowchart of FIG. 7, and also has new steps S61 and S62.

In the control shown in FIG. 10, if the control unit 100 determines that the state of the photosensitive drum 51 is in the long-term drive state for one predetermined color in step S12 (Yes), the control unit 100 determines that the predetermined one color is in the long-term drive state. is set to 1 (S61). After step S61, or when it is determined No in step S12, the control section 100 determines whether or not the flag A(n) corresponding to one predetermined color is 1 (S62).

If it is determined that the flag A(n)=1 in step S62 (Yes), the control unit 100 does not execute the gradation setting process, and sets the unfinished flag F(n) corresponding to one predetermined color. ) is set to 1 (S14). If it is determined in step S62 that flag A(n) is not 1 (No), the control unit 100 executes gradation setting processing for one predetermined color (S15). Even in such a form, the same effect as that of the above-described embodiment can be obtained.

In the above-described embodiment, the continuous execution time of print control (the continuous driving time of the photosensitive drum 51) is used to determine whether it is in the long-term driving state. A total may be used. In other words, when the driving time of the photosensitive member intermittently exists within a predetermined time, the total of these driving times may be used as the parameter used in the determination process. In this case, the control unit executes the gradation setting process on the condition that the total driving time of the photoreceptor within the predetermined time is less than the second specified time. is not less than the second specified time, the gradation setting process is not executed.

Note that the predetermined period of time is not limited to the period from the time of determination in the determination process to the point of time before the predetermined period of time, as in the above-described embodiment. For example, the predetermined time may be set to a period as shown in (1) to (6) below.
(1) A period from when the cover, which is operated when replacing the developing device, starts moving from the closed position to the open position until a predetermined time before. In other words, the predetermined time may be a period from the time when the open/close sensor that detects the opening and closing of the cover detects that the cover is opened to the time before the predetermined time.
(2) A period from when the cover is moved from the open position to the closed position until a predetermined time before. In other words, the predetermined time may be a period from the time when the open/close sensor that detects the opening and closing of the cover detects that the cover is closed to the time before the predetermined time.

(3) A period from the start of energization of the image forming unit to a predetermined time before.
(4) A period from the end of power supply to the image forming unit to a predetermined time before.
(5) A period from the time when the print command is received to the time before a predetermined time.
(6) A period from the time when the memory is accessed to the time before a predetermined time while the cover is in the closed position.

Further, the drive time of the photoreceptor may be appropriately replaced with the drive time of other members that are driven together with the photoreceptor. For example, the driving time of the photosensitive member may be the driving time of the developing roller, the application time of the developing bias, the application time of the charging bias, the number of printed sheets, and the like.

In the above embodiment, the re-correction process (S40, S41) is executed both when there is a print command and when there is no print command, but the present invention is not limited to this. The re-correction process may be executed in either case of absence.

Although the photosensitive drum 51 is used as an example of the photosensitive member in the above embodiment, the present invention is not limited to this, and the photosensitive member may be, for example, a belt-shaped photosensitive member.

In the above-described embodiment, the patches to be read by the detection unit 75 are formed on the conveying belt 73, but the present invention is not limited to this, and the patches may be formed on other transfer media such as paper. A reading device that detects patches formed on the transfer medium may be used as a unit. Alternatively, a patch may be formed on the photoreceptor and detected.

In the above embodiment, the present invention is applied to the color printer 1, but the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as monochrome printers, copiers, multi-function machines, and the like. good.

Each element described in the above embodiment and modifications may be implemented in any combination.

1 color printer 30 image forming unit 40 exposure head 51 photosensitive drum 75 detection unit 100 control unit

Claims (8)

an image forming unit that includes a replaceable photoreceptor, a replaceable developing device including a developing roller, and a bias applying unit that applies a developing bias to the developing roller, and forms a plurality of pattern images with different gradations;
a detection unit that detects the plurality of pattern images;
Gradation setting for forming the plurality of pattern images by the image forming unit and executing a gradation setting process for setting a correspondence relationship between target densities and the plurality of pattern images based on detection results by the detection unit. a control unit capable of executing a process,
The control unit
When a predetermined condition including that the photoreceptor has not been replaced and the developer has been replaced ,
executing the gradation setting process when the continuous driving time of the photoreceptor within a predetermined time is less than a first specified time;
An image forming apparatus, wherein the gradation setting process is not executed when the continuous driving time of the photoreceptor within a predetermined time is not less than a first specified time. The control unit
determining whether or not the continuous driving time of the photoreceptor within a predetermined time period is less than a first specified time period;
executing the determination process when the predetermined condition is satisfied;
In the judgment process,
If it is determined that the continuous driving time of the photoreceptor within the predetermined time is less than the first specified time, executing the gradation setting process,
2. The image forming apparatus according to claim 1, wherein the gradation setting process is not executed when it is determined that the continuous driving time of the photoreceptor within the predetermined time is not less than the first specified time. When the controller determines that the continuous driving time of the photoreceptor within a predetermined time period is not less than the first specified time period and does not execute the gradation setting process, the gradation setting process is not performed regardless of the predetermined condition. executing the determination process based on information indicating that the tone setting process was not executed;
3. The image forming apparatus according to claim 2, wherein the gradation setting process is executed when it is determined that the continuous driving time of the photoreceptor within a predetermined time period is less than a first specified time. The control unit
forming a predetermined pattern image in the image forming unit and executing a bias setting process for setting a developing bias based on the detection result of the detecting unit;
4. The image forming apparatus according to claim 1 , wherein when the predetermined condition is satisfied, the bias setting process is executed regardless of the continuous drive time of the photoreceptor. . an image forming unit that includes a replaceable photoreceptor, a replaceable developing device including a developing roller, and a bias applying unit that applies a developing bias to the developing roller, and forms a plurality of pattern images with different gradations;
a detection unit that detects the plurality of pattern images;
Gradation setting for forming the plurality of pattern images by the image forming unit and executing a gradation setting process for setting a correspondence relationship between target densities and the plurality of pattern images based on detection results by the detection unit. a control unit capable of executing a process,
The control unit
When a predetermined condition including that the photoreceptor has not been replaced and the developer has been replaced ,
executing the gradation setting process when the total driving time of the photoreceptor within a predetermined time is less than a second specified time;
An image forming apparatus, wherein the gradation setting process is not executed when the total driving time of the photoreceptor within a predetermined time is not less than a second specified time. a cartridge comprising the photoreceptor;
a memory provided in the cartridge,
The control unit does not execute the gradation setting process when determining that the continuous driving time of the photoreceptor within the predetermined time period is not less than a first specified time period when the predetermined condition is satisfied. 4. The image forming apparatus according to claim 3, wherein information indicating is stored in said memory. 7. The image forming apparatus according to claim 1, wherein the predetermined condition includes that the temperature has changed by a predetermined amount or more since the previous predetermined condition was satisfied. 8. The image forming apparatus according to claim 1, wherein the predetermined condition includes that the number of printed sheets has reached a predetermined number or more since the previous predetermined condition was satisfied.

Images