JP6996265B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus including an image forming unit having a photoconductor and a developer.

In a laser printer, the print density changes due to changes in the environment and changes in characteristics due to long-term use of the developer. Conventionally, in order to correct changes in print density, a pattern image is created and read, and based on the result, a bias setting process for setting a development bias and a correspondence between a target density specified by a print command and a pattern image. It is known that a gradation setting process for setting a relationship is performed (see Patent Document 1). Specifically, in this technique, when performing image adjustment, the gradation setting process is always performed after the bias setting process is executed.

Japanese Unexamined Patent Publication No. 2005-331658

By the way, since the development bias is usually defined as an upper limit value or a lower limit value that can be set, the development bias value calculated based on the reading result of the pattern image in the process of setting the development bias is from the upper limit value. If it deviates from the predetermined range up to the lower limit, it may not be possible to set the development bias to the desired value. In such a case, it may not be possible to bring the density and gradation close to the print data.

On the other hand, in the prior art, since the gradation setting process is performed after the bias setting process, it is possible to bring the density and gradation closer to the print data. However, since the gradation setting process is performed even when the development bias is set within a predetermined range in the bias setting process, there is a problem that the time required for image quality adjustment becomes long and the consumption of the developer increases.

Therefore, it is an object of the present invention that the density and gradation can be brought close to those of print data, and the time required for image quality adjustment and the consumption of a developer can be reduced.

In order to solve the above problems, the image forming apparatus according to the present invention includes an image forming unit having a photoconductor and a developing device, a detecting unit for detecting an image formed by the image forming unit, and a control unit. ..
When the control unit performs image quality adjustment, the image forming unit forms a pattern image corresponding to a predetermined exposure density, and a bias setting process for setting a development bias based on the detection result of the detection unit. A gradation setting process in which a plurality of pattern images corresponding to a plurality of exposure densities are formed in the image forming unit, and a correspondence relationship between the target density and the exposure density is set based on the detection result in the detection unit. Is feasible.
In the bias setting process, the control unit executes a calculation process for calculating a development bias so that the pattern image corresponding to the predetermined exposure density has a predetermined print density, and the value calculated by the calculation process is predetermined. The first setting process, which is executed when the value is within the range and sets the calculated value as the development bias, and the value calculated by the calculation process are executed when the value is outside the predetermined range, and is calculated within the predetermined range. It is possible to execute the second setting process of setting the value closest to the value as the development bias, and when the second setting process is executed, the gradation setting process is executed and the first setting process is performed. When it is executed, it is configured not to execute the gradation setting process unless a predetermined condition is satisfied.

According to this configuration, when the development bias is out of the predetermined range, the gradation setting process is always executed, so that the density and gradation can be brought close to the print data. Further, when the first setting process is executed, the gradation setting process is not executed unless a predetermined condition is satisfied, so that the frequency of the gradation setting process can be reduced, and the time required for image quality adjustment and the developer can be reduced. The amount of can be reduced.

Further, the predetermined condition can be assumed that the second setting process has been executed in the previous bias setting process.

When the first setting process is performed after the second setting process, the difference between the current value and the previous value of the development bias to be set may become large. Therefore, by performing the gradation setting process in this case, the density is increased. And the gradation can be kept good.

Further, the control unit executes image quality adjustment when the operating amount of the developer from the previous image quality adjustment exceeds a predetermined threshold value, and when the first setting process is executed, the predetermined threshold value is set. When the first threshold value is set and the second setting process is executed, the predetermined threshold value may be set to a second threshold value smaller than the first threshold value.

Since there is a possibility that the development bias is out of the predetermined range for a relatively short period of time, the next image quality adjustment start timing is set by setting the predetermined threshold value to a small second threshold value when the second setting process is executed. It is possible to set the development bias by the first setting process earlier.

Further, the control unit executes the image quality adjustment when the amount of change in temperature or humidity from the previous image quality adjustment becomes a predetermined value or more, and when the first setting process is executed, the predetermined value is set. When the first predetermined value is set and the second setting process is executed, the predetermined value may be set to a second predetermined value smaller than the first predetermined value.

Since the environmental conditions may be special when the development bias is out of the predetermined range, the next image quality adjustment can be started by setting the predetermined value to a small second predetermined value when the second setting process is executed. The timing can be advanced, and the development bias can be set earlier by the first setting process.

Further, when the image forming apparatus includes a cartridge for accommodating the developer and the control unit performs image quality adjustment based on the replacement of the cartridge, the predetermined condition is that the cartridge is replaced. It can be said that it was done.

When the first setting process is performed after the cartridge is replaced, the charge amount of the developer may be different. Therefore, by performing the gradation setting process in this case, the density and gradation can be kept good. ..

Further, the control unit performs an exposure process for exposing the photoconductor based on the binary image and a counting process for counting the amount of the developer used based on the result of the binary image and the gradation setting process. You may do it.

According to this, since the amount of the developer used is counted based on the binary image and the result of the gradation setting process, the actual amount of the developer used can be counted accurately.

Further, the control unit may notify the remaining amount of the developer based on the result counted in the counting process.

According to this, it is possible to accurately notify the user of the remaining amount of the developer.

According to the present invention, the density and gradation can be brought close to those of print data, and the time required for image quality adjustment and the consumption of a developer can be reduced.

It is a figure which shows the schematic structure of the color printer which concerns on one Embodiment of this invention. It is a block diagram which shows each structure related to a control part. It is a figure which shows the pattern image for printing. It is a flowchart which shows the operation of a control part. It is a flowchart which shows the image quality adjustment. It is a graph which shows the relationship between the target density | concentration, and the exposure density.

Next, an 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 the color printer 1 as an example of the image forming apparatus will be briefly described, and then the configuration of the characteristic portion of the present invention will be described in detail.

Further, in the following description, the direction will be described in the direction shown in FIG. That is, the left side in FIG. 1 is "front", the right side is "rear", the back side is "left", and the front side is "right". Further, the upper side in FIG. 1 is referred to as "upper" and the lower side is referred to as "lower".

As shown in FIG. 1, the color printer 1 includes a main body housing 10, a top cover 11, a paper feeding unit 20 and an image forming unit 30 provided in the main body housing 10. Further, in the main body housing 10, a temperature sensor 13 for detecting the temperature inside the main body housing 10, a detection unit 75, and a control unit 800 are provided.

The top cover 11 is arranged on the upper part of the main body housing 10, is rotatably provided with respect to the main body housing 10 around the rear rotation shaft 11A, and is formed on the upper part of the main body housing 10. The opening 10A is opened and closed. Specifically, the top cover 11 can be moved to a closed position where the opening 10A is closed and an open position where the opening 10A is opened.

The paper feed unit 20 is provided in the lower part of the main body housing 10 and includes a paper feed tray 21 for accommodating the paper P and a paper supply mechanism 22 for supplying 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 unit 30.

The image forming unit 30 includes four exposure heads 40, four process cartridge PCs, a transfer unit 70, and a fixing unit 80.

The exposure head 40 has a light emitting element and an imaging lens at its tip, and is held by the top cover 11 so as to be suspended from the top cover 11. With the top cover 11 closed, the photoconductor 51 described later It is placed facing above the top of the. Specifically, the exposure head 40 can be moved between a reference position closer to the photoconductor 51 and a retracted position farther from the photoconductor 51 than the reference position by opening and closing the top cover 11. The exposure head 40 exposes the surface of the photoconductor 51 by blinking the light emitting element based on the binary raster image.

Each process cartridge PC is arranged in parallel between the top cover 11 and the paper feed tray 21 along the front-rear direction. Each process cartridge PC can be attached and detached through the opening 10A of the main body housing 10 in a state where the top cover 11 is opened. The process cartridge PC includes a drum unit 50 and a developer 60. The developer 60 is removable from the drum unit 50.

The drum unit 50 includes a photoconductor 51 which is a cylindrical photoconductor drum, a scorotron type charger 52 for charging the photoconductor 51, a pressing spring 53 for urging the developer 60 toward the photoconductor 51, and cleaning. It includes a roller 54 and a drum frame 55 that supports the photoconductor 51 and the like.

The developer 60 mainly includes a toner accommodating portion 61 for accommodating toner and a developing roller 62 for supplying the toner in the toner accommodating portion 61 to the photoconductor 51. The toner is a developer that develops an electrostatic latent image on the photoconductor 51. The toner accommodating portion 61 of each developing device 60 accommodates yellow, magenta, cyan, and black toners in this 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 drive roller 71, a driven roller 72, an endless transfer belt 73, and four transfer rollers 74. The transport belt 73 is stretched between the drive roller 71 and the driven roller 72. The outer surface of the transport belt 73 is in contact with each photoconductor 51, and each transfer roller 74 is arranged inside the transport belt 73 so as to sandwich the transport belt 73 with each photoconductor 51.

A detection unit 75 is provided diagonally below the rear of the conveyor belt 73. The detection unit 75 is a sensor that detects a toner image for image quality adjustment, that is, a print density of an image formed on the conveyor belt 73, and is arranged so as to face the rear portion of the conveyor belt 73. In the following description, the image for image quality adjustment formed on the transport belt 73 is also referred to as a “patch”. The detection unit 75 is a light reflection type sensor including 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 toward the heating roller 81.

In such an image forming unit 30, the surface of the photoconductor 51 is uniformly charged by the charger 52 and then exposed by the exposure head 40, so that the electrostatic latency based on the image data is applied on the photoconductor 51. An image is formed. Then, by applying a voltage to the developing roller 62, toner is supplied from the developing roller 62 to the photoconductor 51, the electrostatic latent image is visualized, and a toner image is formed on the photoconductor 51. The voltage applied to the developing roller 62 is also referred to as a developing bias. That is, the developer 60 develops the electrostatic latent image on the photoconductor 51.

The toner image formed on each photoconductor 51 is sequentially superposed on the paper P transported on the transport belt 73 and transferred by the transfer roller 74. The paper P on which the toner image is 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 inside of the main body housing 10 to the outside by the transport roller 91, and is placed on the paper discharge tray 11B formed on the upper surface of the top cover 11.

As shown in FIG. 2, the control unit 800 includes a CPU, RAM, ROM, and an input / output circuit, and is output from a print job output from an external computer 900 and output from a temperature sensor 13 and a detection unit 75. Control is executed by performing various arithmetic processes based on the incoming information and the programs and data stored in the ROM or the like. Specifically, the control unit 800 includes a calculation unit 810 such as a CPU, a control circuit 820 that controls a developing roller 62, an exposure head 40, and the like, and a memory 830. The control unit 800 operates based on the program stored in the memory 830 to execute print control and image quality adjustment.

The control unit 800 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 the print control, the control unit 800 determines the amount of toner used based on the results of the exposure process of exposing the photoconductor 51 based on the print pattern image which is a binary image and the result of the binary image and the gradation setting process. The counting process for counting and the counting process are executed. Specifically, when printing an image on paper P when executing print control, the control unit 800 is used for printing a plurality of prints having different exposure densities so that the print density of the image becomes a predetermined target density. One print pattern image is selected from the pattern images and the exposure process is executed. The print pattern image is composed of a binary image as shown in FIG. The exposure density refers to the area ratio of the pixels to be exposed in the pattern image for printing.

Here, the print density is the density of the toner image developed by the developing roller 62, and is the density detected by the detection unit 75. The target density means the target density specified in the printing command. For example, when the target density specified by the print command is 20%, the control unit 800 selects a print pattern image having an exposure density of 20% and executes the exposure process on the print pattern image. However, the relationship between the target density and the exposure density is changed by the gradation setting process described later. For example, the state in which a print pattern image having an exposure density of 20% is associated with a target density of 20% has been changed to a state in which a print pattern image having an exposure density of 10% is associated with a target density of 20%. In this case, when the image is formed at the target density of 20%, the exposure process is executed on the print pattern image having the exposure density of 10%.

Specifically, when the control unit 800 receives the print data, it executes a decompression process of expanding the received print data into a binary raster image. In the expansion process, the control unit 800 arranges the first process of expanding the received print data into object data consisting of vector data or bitmap data, and the object data in a virtual paper, and arranges the object data in a plurality of band data. It is possible to execute the second process of expanding to 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 800 performs a decompression process of expanding the print data composed of a page description language or the like into a raster image which is the data for exposure. Then, when the control unit 800 executes the exposure process on the predetermined portion of the raster image, the control unit 800 selects a print pattern image corresponding to the target density of the predetermined portion of the raster image, and executes the exposure process on the print pattern image. ..

Further, in the counting process, the control unit 800 calculates the amount of toner used and the total amount of toner used based on the number of dots in the print pattern image used in the exposure process. Here, the total amount of toner used is the amount of toner used from the time when a new process cartridge PC is installed to the present, and is counted by the first counter CF. Further, the amount of toner used is a parameter used as a condition for starting the image quality adjustment described later, and is counted by the second counter CS described later.

Further, the control unit 800 has a function of notifying the remaining amount of toner based on the result counted in the counting process. Specifically, the control unit 800 sends a message to the operation panel of the color printer 1 when the first counter CF indicating the total amount of toner used after mounting the new process cartridge PC becomes the specified value α or more. Notify the user that the remaining amount of toner is low by display or voice. The first counter CF is reset every time the process cartridge PC is replaced with a new one.

As described above, the control unit 800 selects one print pattern image corresponding to the target density from the plurality of print pattern images, and then exposes and develops the print pattern image using the print pattern image. A toner image having a target density is formed on the photoconductor 51.

The plurality of print pattern images correspond to the exposure densities and are stored in the memory 830 in advance. Further, the plurality of print pattern images are stored in the memory 830 in advance corresponding to the respective colors of yellow, magenta, cyan, and black.

The control unit 800 can perform image quality adjustment for adjusting the image quality of the printed toner image. The control unit 800 determines when the operating amount of the developing device 60 from the previous image quality adjustment becomes the predetermined threshold value Cth or more, when the temperature change amount from the previous image quality adjustment becomes the predetermined value Tth or more, or the process. When the cartridge PC is replaced, the image quality adjustment is executed. Here, the operating amount of the developer 60 includes the number of rotations of the developing roller 62, the amount of toner used, and the like, but in the present embodiment, it will be described as the amount of toner used. Specifically, the control unit 800 counts the amount of toner used for comparison with the predetermined threshold value Cth by the second counter CS. The second counter CS is updated every time CS ≧ Cth is determined. Here, as a method of updating, a method of resetting the second counter CS to 0 and a method of updating the second counter CS to CS-Cth can be mentioned.

The control unit 800 has a function of executing a bias setting process and a gradation setting process based on the detection result of the detection unit 75 when the image quality adjustment is executed. Specifically, the control unit 800 can execute a mode in which only the bias setting process is performed and a mode in which both the bias setting process and the gradation setting process are performed, based on various conditions described in detail later.

In the bias setting process, the control unit 800 forms a pattern image using the first printing pattern image corresponding to the predetermined exposure density in the image forming unit 30, and the development bias is based on the result detected by the detecting unit 75. To set. Specifically, the control unit 800 selectively executes the calculation process, the first setting process, and the second setting process in the bias setting process.

In the calculation process, the control unit 800 calculates a development bias such that the pattern image printed using the first print pattern image corresponding to the predetermined exposure density, that is, the toner image has the predetermined print density. Here, the predetermined exposure density and the predetermined print density are 40% as an example, and the control unit 800 selects the 40% print pattern image shown in FIG. 3 as the first print pattern image. .. Specifically, in the calculation process, the control unit 800 uses two types of development biases to form two toner images corresponding to the two first printing pattern images. More specifically, in the calculation process, the control unit 800 forms two electrostatic latent images on the photoconductor 51 using the first printing pattern image, and develops two types of the two electrostatic latent images. By developing each with a bias, two types of print density patches are formed on the photoconductor 51. After that, the control unit 800 transfers each patch from the photoconductor 51 to the transfer belt 73, and the detection unit 75 detects each patch on the transfer belt 73. Then, the control unit 800 converts the intensity of the reflected light from each patch detected by the detection unit 75 into a print density, and the print density becomes the target density based on the two types of print densities and the two types of development bias. Calculate the development bias. Then, the control unit 800 executes the first setting process when the value calculated by the calculation process is within the predetermined range, and executes the second setting process when the value is outside the predetermined range.

In the first setting process, the control unit 800 sets the value calculated in the calculation process as the development bias. In the second setting process, the control unit 800 sets the value closest to the value calculated in the calculation process in the predetermined range as the development bias. Specifically, in the second setting process, when the value calculated in the calculation process is larger than the upper limit value in the predetermined range, the control unit 800 sets the upper limit value as the development bias, and the value calculated in the calculation process is predetermined. If it is smaller than the lower limit of the range, the lower limit is set as the development bias.

Then, when the second setting process is executed, the control unit 800 executes the gradation setting process, and when the first setting process is executed, the control unit 800 executes the gradation setting process unless a predetermined condition is satisfied. It is configured not to. In the present embodiment, the predetermined conditions are that the second setting process is executed in the previous bias setting process and that the process cartridge PC is replaced.

Further, when the second setting process is executed, the control unit 800 sets the predetermined threshold value Cth and the predetermined threshold value Cth as described above so that the timing for starting the next image quality adjustment is earlier than when the first setting process is executed. It has a function to set the value Tth. Specifically, the control unit 800 sets the predetermined threshold value Cth to the first threshold value C1 when the first setting process is executed, and sets the predetermined threshold value Cth to the first threshold value C1 when the second setting process is executed. It is set to a second threshold value C2 smaller than that. Further, the control unit 800 sets the predetermined value Tth to the first predetermined value T1 when the first setting process is executed, and sets the predetermined value Tth to the first predetermined value when the second setting process is executed. The second predetermined value T2, which is smaller than T1, is set.

In the gradation setting process, the control unit 800 forms a toner image (pattern image) of 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 forms the toner image. It is detected by the detection unit 75. Here, the plurality of types of print pattern images are a plurality of print pattern images corresponding to a plurality of exposure densities, for example, a second print pattern image corresponding to an exposure density of 20% and an exposure density of 40%. A third print pattern image, a fourth print pattern image corresponding to an exposure density of 60%, and the like are used.

After that, the control unit 800 sets the correspondence between the target density and the print pattern image based on the result detected by the detection unit 75. By setting the correspondence between the target density and the pattern image for printing in this way, the correspondence between the target density and the toner image actually printed, that is, the exposure density is set.

More specifically, in the gradation setting process, the control unit 800 uses, for example, five electrostatic latent images on the photoconductor 51 using print pattern images corresponding to exposure densities of 20, 40, 60, 80, and 100%. And develop each electrostatic latent image with the development bias set at that time to form patches with five different print densities. After that, the control unit 800 detects each patch transferred from the photoconductor 51 to the transport belt 73 by the detection unit 75. The control unit 800 converts the intensity of the reflected light from each patch into the print density. Then, the control unit 800 compares each of the calculated print densities with the corresponding exposure densities, and if the compared print densities and the exposure densities are different, the control unit 800 corrects the relationship between the print densities and the exposure densities to make a target. Change the relationship between the density and the print pattern image. The details of this correction will be described later.

In addition to storing the above-mentioned print pattern images, the memory 830 stores various threshold values used for control, a program for operating the control unit 800, and the like.

Next, the operation of the control unit 800 will be described in detail. The control unit 800 executes the process shown in FIG. 4 when a print command is received or when the power of the color printer 1 is turned on.

In the process of FIG. 4, the control unit 800 first determines whether or not the second counter CS indicating the amount of toner used is equal to or greater than the predetermined threshold value Cth (S1). If it is determined in step S1 that CS ≧ Cth (No), the control unit 800 acquires the current temperature and determines whether or not the amount of change in temperature from the previous image quality adjustment is equal to or greater than the predetermined value Tth. Judgment (S2).

If it is determined in step S2 that the amount of change in temperature is not equal to or greater than the predetermined value Tth (No), the control unit 800 determines whether or not the process cartridge PC has been replaced (S3). If it is determined in step S3 that the process cartridge PC has not been replaced (No), the control unit 800 determines whether or not the print command has been received (S4).

If it is determined in step S4 that the print command has not been received (No), the control unit 800 ends this process. If it is determined in step S4 that the print command has been received (Yes), the control unit 800 executes the print process on one sheet of paper P (S5). Specifically, the control unit 800 executes the development process and the exposure process described above in the print process.

After step S5, the control unit 800 counts up the first counter CF and the second counter CS based on the print pattern image used in the exposure process (S6). Specifically, in step S6, the control unit 800 counts the number of dots corresponding to the toner usage amount of the printed image based on the print pattern image and the conversion rate. Here, the conversion rate is a rate for correcting the density of the print pattern image to the density of the actually printed image when the density of the print pattern image and the density of the actually printed image deviate from each other. In the state where the gradation setting process has not been performed even once, the rate is shown by the two-dot chain line shown in FIG. When the graph of FIG. 6 is viewed as a conversion rate, the target density on the vertical axis can be replaced with the print density. When the conversion rate is the rate shown by the two-point chain line shown in FIG. 6, if printing is performed with a printing pattern image having an exposure density of 20%, an image having a printing density of 20% will be printed. Therefore, for example, printing By multiplying the number of dots in the pattern image by 1, the number of dots corresponding to the amount of toner used can be obtained.

Then, based on the result of the gradation setting process, for example, when a part of the conversion rate is set to the rate shown by the broken line in FIG. 6, when a print pattern image having an exposure density of less than 40% is used, the print pattern image is used. , The dashed conversion rate is used. In this case, for example, when printing with a print pattern image having an exposure density of 20%, an image having a print density of 10% is printed. Therefore, for example, by multiplying the number of dots of the print pattern image by 1/2. , The number of dots corresponding to the amount of toner used can be obtained.

After step S6, the control unit 800 determines whether or not the first counter CF indicating the total amount of toner used is equal to or greater than the specified value α (S7).

If it is determined in step S7 that CF ≧ α, the control unit 800 notifies the user that the remaining amount of toner is low (S8). After step S8 or when it is determined as No in step S7, the control unit 800 determines whether or not all printing of the number of prints specified by the print command has been completed (S9).

If it is determined in step S9 that printing has not been completed (No), the control unit 800 returns to the process of step S5. If it is determined in step S9 that printing is completed (Yes), the control unit 800 ends this process.

When it is determined in step S1 that CS ≧ Cth (Yes), or when it is determined in step S2 that the amount of change in temperature is equal to or greater than the predetermined value Tth (Yes), the control unit 800 adjusts the image quality. Execute (S11). If it is determined in step S3 that the process cartridge PC has been replaced (Yes), the control unit 800 sets the flag F for executing the gradation setting process to 1 (S10), and then executes the image quality adjustment. (S11). The image quality adjustment will be described later. After executing the image quality adjustment, the control unit 800 shifts to the process of step S4.

Next, the image quality adjustment will be described in detail with reference to FIG.
As shown in FIG. 5, in the image quality adjustment, the control unit 800 first forms a pattern image for performing the bias setting process on the transport belt 73 (S21). After step S21, the control unit 800 reads the formed pattern image by the detection unit 75, and calculates the development bias based on the result (S22).

After step S22, the control unit 800 determines whether or not the value calculated in step S22 is within the predetermined range (S23). If it is determined in step S23 that the calculated value is within the predetermined range (Yes), the control unit 800 executes the first setting process of setting the development bias to the calculated value (S24).

After step S24, the control unit 800 determines whether or not the flag F for executing the gradation setting process is 1 (S25). If it is determined in step S25 that the flag F is 1 (Yes), the control unit 800 executes the gradation setting process (S26).

Here, in step S26, when the gradation setting process has not been performed even once in the past, the target density and the exposure density have the same value as shown by the two-dot chain line in FIG. Here, the graph shown in FIG. 6 is a graph showing the relationship between the target density and the exposure density, that is, when printing at a predetermined target density, a printing pattern having a predetermined exposure density corresponding to the predetermined target density is obtained. It is a graph which shows that it is selected.

In the gradation setting process, for example, as shown by a black circle in the figure, when a patch formed by using a second print pattern image corresponding to an exposure density of 20% is detected by the detection unit 75, the print density of the patch is detected. When the value becomes 10%, the control unit 800 re-stores the second printing pattern image as a pattern image corresponding to the target density of 10%. That is, in the next print control, when the image is formed at the target density of 10%, the print density becomes 10% if the image is formed with the second print pattern image corresponding to the exposure density of 20%. Section 800 associates a second printing pattern image with an exposure density of 20% with respect to a target density of 10%. That is, the control unit 800 changes the relationship between the target density and the exposure density.

Further, in the gradation setting process, when the print density when the third print pattern image having an exposure density of 40% is detected by the detection unit 75 is 40%, that is, the target density, the exposure density, and the print density match. In this case, as shown by the broken line in the figure, the relationship between the target density and the exposure density is linearly interpolated. As a result, for example, in the next printing control, when a patch is formed at a target density of 20%, a print pattern image corresponding to the exposure density X corresponding to the intersection of the line having the target density of 20% and the broken line in the figure. Is selected, so that the print pattern image can be printed at an appropriate print density. As a result, the gradation can be satisfactorily expressed based on the target density indicated by the print command.

Returning to FIG. 5, the control unit 800 sets the flag F to 0 after executing the gradation setting process in step S26 (S27). After step S27, the control unit 800 sets the conversion rate of the toner usage amount described above based on the result of the gradation setting process (S28). For example, in the gradation setting process, when the relationship between the target density and the exposure density is set as shown by the broken line in FIG. 6, the rate with an exposure density of less than 40% is shown by the broken line in FIG. 6 as the conversion rate. The rate is set to a high rate, and a rate having an exposure density of 40% or more is set to a rate as shown by the two-dot chain line in FIG.

After step S28, the control unit 800 sets the predetermined threshold value Cth used in step S1 to the first threshold value C1 (S29). If No is determined in step S25, the control unit 800 skips the processes of steps S26 to S28 and shifts to the process of step S29. Here, since the flag F is not set to 1 unless predetermined conditions are met, in principle, when the control unit 800 performs the first setting process of setting the development bias to the calculated value in step S24, the floor Do not execute the key setting process.

After step S29, the control unit 800 sets the predetermined value Tth used in step S2 to the first predetermined value T1 (S30). After step S30, the control unit 800 stores the temperature at the end of the image quality adjustment in the memory 830, and updates the second counter CS when the current image quality adjustment is executed through the process of step S1. This process ends.

If it is determined in step S23 that the calculated value of the development bias is out of the predetermined range (No), the control unit 800 executes the second setting process of setting the development bias to the upper limit value or the lower limit value of the predetermined range. (S32). After step S32, the control unit 800 executes the gradation setting process (S33) and sets the conversion rate based on the result of the gradation setting process (S34). Since the processing of steps S33 and S34 is the same as the processing of steps S26 and S28 described above, the description thereof will be omitted.

After step S34, the control unit 800 sets the predetermined threshold value Cth used in step S1 to the second threshold value C2 smaller than the first threshold value C1 (S35). After step S35, the control unit 800 sets the predetermined value Tth used in step S2 to the second predetermined value T2, which is smaller than the first predetermined value T1 (S36).

After step S36, the control unit 800 sets the flag F to 1 (S37) and shifts to the process of step S31.

Based on the above, the following effects can be obtained in the present embodiment.
When the calculated value of the development bias is out of the predetermined range (S23: No), the gradation setting process is always executed (S33), so that the density and the gradation can be brought closer to the print data. Further, when the first setting process is executed (S24), the gradation setting process is not executed unless a predetermined condition (S3: Yes, S32) is satisfied, so that the frequency of the gradation setting process can be reduced. It is possible to reduce the time required for image quality adjustment and the amount of developer.

When the first setting process (S24) is performed in the image adjustment after the second setting process (S32) is executed, the difference between the current value and the previous value of the development bias to be set may become large. In the present embodiment, the predetermined condition is that the second setting process is executed in the previous bias setting process. Specifically, the flag F is set to 1 after the second setting process (S32) is executed. Therefore, in the image adjustment after the second setting process is executed, when the first setting process (S24) is performed, the gradation setting process is always performed, so that the density and the gradation can be kept good. can.

Since the state in which the development bias calculated by the calculation process is out of the predetermined range (S23: No) may be in a relatively short period of time, the predetermined threshold value Cth is set small when the second setting process (S32) is executed. By setting the second threshold value C2 (S35), the start timing of the next image quality adjustment can be advanced, and the development bias can be set earlier by the first setting process (S24). When the development bias calculated by the calculation process is out of the predetermined range, specifically, the condition that the absolute value of the development bias exceeds the upper limit is, for example, a state in which the amount of charge of the toner is high due to low humidity. Therefore, there is a relatively high possibility that the charge amount of the toner will decrease due to the continuation of printing and the condition will be solved.

Since the temperature condition may be special in the state where the development bias calculated by the calculation process is out of the predetermined range (S23: No), the predetermined value Tth is made small when the second setting process (S32) is executed. By setting the second predetermined value T2 (S36), the start timing of the next image quality adjustment can be advanced, and the development bias can be set earlier by the first setting process (S24).

When the first setting process (S24) is performed after replacing the process cartridge PC, the amount of charge of the toner may be different. In the present embodiment, the predetermined condition is that the process cartridge PC has been replaced. Specifically, when the process cartridge PC has been replaced (S3: Yes), the flag F is set to 1. When the first setting process (S24) is performed after the process cartridge PC is replaced, the gradation setting process is always performed, so that the density and gradation can be kept good.

Since the amount of toner used is counted based on the raster image which is a binary image and the result of the gradation setting process, the actual amount of toner used can be counted accurately.

Since the remaining amount of toner is notified based on the result counted in the counting process, the remaining amount of toner can be notified to the user with high accuracy.

The present invention is not limited to the above embodiment, and can be used in various forms as illustrated below.

In the above embodiment, the image quality adjustment (S11) is executed when the amount of change in temperature becomes the predetermined value Tth or more (S2: Yes), but the present invention is not limited to this, and for example, the humidity. When the amount of change exceeds a predetermined value, the image quality adjustment may be executed.

In the above embodiment, the photoconductor drum is exemplified as the photoconductor 51, but the present invention is not limited to this, and for example, a belt-shaped photoconductor may be used.

In the above embodiment, the patch for reading by the detection unit 75 is formed on the transport belt 73, but the present invention is not limited to this, and the patch may be formed on another transfer medium such as paper for detection. A reading device for detecting a patch formed on the transfer medium may be used as a unit. Alternatively, a patch may be formed on the photoconductor 51 for detection.

In the above embodiment, the process cartridge PC is exemplified as the cartridge, but the present invention is not limited to this, and the cartridge may be, for example, a developer 60 configured as a cartridge in the present embodiment, or a developing roller. In the structure including the developing cartridge provided with the above and the toner cartridge detachable from the developing cartridge, the toner cartridge may be used. Alternatively, the cartridge may be a photoconductor cartridge provided with a photoconductor.

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 devices such as monochrome printers, copiers, and multifunction devices. good.

Each element described in the above-described embodiment and modification may be arbitrarily combined and carried out.

1 Color printer 30 Image forming unit 51 Photoconductor 60 Developer 75 Detection unit 800 Control unit

Claims (6)

An image forming unit having a photoconductor and a developing device,
A detection unit that detects an image formed by the image forming unit, and a detection unit.
With a control unit,
When the control unit performs image quality adjustment,
A bias setting process in which a pattern image corresponding to a predetermined exposure density is formed by the image forming unit and a development bias is set based on the detection result of the detection unit.
A gradation setting process of forming a plurality of pattern images corresponding to a plurality of exposure densities in the image forming unit and setting a correspondence relationship between the target density and the exposure density based on the detection result of the detection unit is executed. It is possible and
In the bias setting process
A calculation process for calculating the development bias so that the pattern image corresponding to the predetermined exposure density has the predetermined print density is executed.
The first setting process, which is executed when the value calculated by the calculation process is within a predetermined range and sets the calculated value as the development bias,
It is possible to execute the second setting process, which is executed when the value calculated by the calculation process is outside the predetermined range, and the value closest to the calculated value in the predetermined range is set as the development bias.
When the second setting process is executed, the gradation setting process is executed.
When the first setting process is executed, the gradation setting process is not executed unless a predetermined condition is satisfied.
The image forming apparatus is characterized in that the predetermined condition is that the second setting process is executed in the previous bias setting process . An image forming unit having a photoconductor and a developing device,
A detection unit that detects an image formed by the image forming unit, and a detection unit.
With a control unit,
When the control unit performs image quality adjustment,
A bias setting process in which a pattern image corresponding to a predetermined exposure density is formed by the image forming unit and a development bias is set based on the detection result of the detection unit.
A gradation setting process of forming a plurality of pattern images corresponding to a plurality of exposure densities in the image forming unit and setting a correspondence relationship between the target density and the exposure density based on the detection result of the detection unit is executed. It is possible and
In the bias setting process
A calculation process for calculating the development bias so that the pattern image corresponding to the predetermined exposure density has the predetermined print density is executed.
The first setting process, which is executed when the value calculated by the calculation process is within a predetermined range and sets the calculated value as the development bias,
It is possible to execute the second setting process, which is executed when the value calculated by the calculation process is outside the predetermined range, and the value closest to the calculated value in the predetermined range is set as the development bias.
When the second setting process is executed, the gradation setting process is executed.
When the first setting process is executed, the gradation setting process is not executed unless a predetermined condition is satisfied.
When the operating amount of the developer from the previous image quality adjustment exceeds a predetermined threshold value, the image quality adjustment is executed.
When the first setting process is executed, the predetermined threshold value is set to the first threshold value.
An image forming apparatus characterized in that when the second setting process is executed, the predetermined threshold value is set to a second threshold value smaller than the first threshold value. An image forming unit having a photoconductor and a developing device,
A detection unit that detects an image formed by the image forming unit, and a detection unit.
With a control unit,
When the control unit performs image quality adjustment,
A bias setting process in which a pattern image corresponding to a predetermined exposure density is formed by the image forming unit and a development bias is set based on the detection result of the detection unit.
A gradation setting process of forming a plurality of pattern images corresponding to a plurality of exposure densities in the image forming unit and setting a correspondence relationship between the target density and the exposure density based on the detection result of the detection unit is executed. It is possible and
In the bias setting process
A calculation process for calculating the development bias so that the pattern image corresponding to the predetermined exposure density has the predetermined print density is executed.
The first setting process, which is executed when the value calculated by the calculation process is within a predetermined range and sets the calculated value as the development bias,
It is possible to execute the second setting process, which is executed when the value calculated by the calculation process is outside the predetermined range, and the value closest to the calculated value in the predetermined range is set as the development bias.
When the second setting process is executed, the gradation setting process is executed.
When the first setting process is executed, the gradation setting process is not executed unless a predetermined condition is satisfied.
When the amount of change in temperature or humidity from the previous image quality adjustment exceeds the specified value, the image quality adjustment is executed and the image quality is adjusted.
When the first setting process is executed, the predetermined value is set to the first predetermined value, and the predetermined value is set to the first predetermined value.
An image forming apparatus characterized in that when the second setting process is executed, the predetermined value is set to a second predetermined value smaller than the first predetermined value. Equipped with a cartridge to store the developer
The control unit executes image quality adjustment based on the replacement of the cartridge, and performs image quality adjustment.
The image forming apparatus according to any one of claims 1 to 3 , wherein the predetermined condition is that the cartridge has been replaced. The control unit
An exposure process that exposes the photoconductor based on a binary image,
The image according to any one of claims 1 to 4 , wherein a counting process for counting the amount of the developer used is executed based on the result of the binary image and the gradation setting process. Forming device. The image forming apparatus according to claim 5 , wherein the control unit notifies the remaining amount of the developer based on the result counted in the counting process.

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