JP6719320B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus that forms a developer image on a medium.

When forming an image on a medium such as a film, the conventional image forming apparatus transfers the toner image of the same color to the film multiple times in order to obtain a high-quality image with high gradation by sufficiently increasing the maximum density. One image is obtained (for example, see Patent Document 1).

JP, 10-186748, A

However, in the related art, since a single image is formed by superposing a plurality of developer images of the same color, it is possible to reduce the concentration of the developer in any one of the plurality of developer images. If such a problem occurs, there is a problem in that the resolution becomes insufficient and sufficient printing quality cannot be obtained.

An object of the present invention is to solve such a problem, and an object thereof is to improve print quality when a plurality of developer images are overlapped to form one developer image.

Therefore, the present invention supplies a developer to the electrostatic latent image is formed of the same color developer image, a plurality of developing devices capable of superimposing the same color developer image, each of said developing units A density control unit for controlling the density of each developer image formed by the image forming apparatus, and the density of each of the developer images are detected to reduce the density of each developer image formed at a predetermined density by the density control unit. A density detecting section for detecting, and a control section for controlling the density control section based on a detection result of the density detecting section, wherein the control section detects the density decrease among the plurality of developing devices. It is characterized in that the density of the developer of the developing device on which the developed developer image is formed is lowered by the density control section, and the density of the developer of another developing apparatus is raised by the density control section.

The present invention thus configured has the effect of improving the printing quality when a plurality of developer images are overlapped to form one developer image.

Schematic side sectional view showing the configuration of the printer in the embodiment Schematic side cross section showing the configuration of the ID unit in the embodiment Block diagram showing the control configuration of the printer in the embodiment Flowchart showing the flow of toner image forming processing in the embodiment Explanatory drawing of the printed image in the embodiment Explanatory drawing of printing density in the example Flowchart showing the flow of solid defect density adjustment processing in the embodiment Explanatory drawing of the print pattern in the embodiment Explanatory drawing of the level of DB and solid blur in the embodiment

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic side sectional view showing the configuration of the printer in the embodiment.
In FIG. 1, a printer 1 as an image forming apparatus forms and prints a developer image on a recording medium. The printer 1 of this embodiment prints, for example, a medical image on a transparent film as a recording medium, and includes a plurality of ID units that handle toner as a developer of the same color, and a plurality of ID units formed by the ID units. To form a background image in the image as one toner image.

The printer 1 includes a paper cassette 2, a hopping roller 31, a conveyance path 32, a registration roller 18, a conveyance roller 19, an ID (image drum) unit S1(K), an ID unit S2(Y), and an ID unit S3( M), the ID unit S4 (C), the ID unit S5 (K), the LED (Light Emitting Diode) heads 61, 62, 63, 64, 65, the intermediate transfer belt 11, the secondary transfer roller 21, The paper cassette 2 having the fixing device 50, the re-conveyance path 34, and the discharge roller 36 is for accommodating the recording media 3 which are media before printing in a stacked manner.

The hopping roller 31 separates the recording media 3 housed in the paper cassette 2 one by one and sends them to the transport path 32.
The transport path 32 is a path for transporting the recording medium 3 sent out by the hopping roller 31.
The registration roller 18 corrects the skew of the recording medium 3 delivered to the transport path 32 and transports the recording medium 3 to the transport roller 19.

The transport roller 19 transports the transported recording medium 3 together with the registration roller 18 to a nip portion as a secondary transfer portion formed by the secondary transfer roller 21 and the intermediate transfer belt 11 at a predetermined timing. ..

The ID unit S1(K), the ID unit S2(Y), the ID unit S3(M), the ID unit S4(C), and the ID unit S5(K) are four color toners (K: black) as color developers. , Y: yellow, M: magenta, C: cyan). In this embodiment, the ID unit S1(K) and the ID unit S5(K) are black toner produced by a polymerization method, the ID unit S2(Y) is a yellow toner, the ID unit S3(M) is a magenta toner, and the ID unit is an ID unit. In S4(C), cyan toner is handled and each toner image is formed.

The ID unit S1(K), the ID unit S2(Y), the ID unit S3(M), the ID unit S4(C), and the ID unit S5(K) are configured to be detachable from the printer 1.

The LED heads 61, 62, 63, 64, 65 are image drums of the ID unit S1(K), the ID unit S2(Y), the ID unit S3(M), the ID unit S4(C), and the ID unit S5(K). Is arranged so as to face the photoconductor drum, and the photoconductor drum is irradiated with light to form an electrostatic latent image.

In this embodiment, the ID unit S1(K) as the first developing device supplies black toner to the electrostatic latent image formed on the photosensitive drum to form the first toner image, and the second toner image is formed. The ID unit S5(K) as a developing unit supplies black toner to the electrostatic latent image formed on the photosensitive drum to form a second toner image, and the first toner image and the second toner image are formed. And can be overlapped.

The intermediate transfer belt 11 is an endless belt that is stretched around a drive roller 12, a belt driven roller 13, and a secondary transfer backup roller 14 and that rotates in the direction indicated by an arrow A in the figure by the rotation of the drive roller 12. The intermediate transfer belt 11 includes primary transfer rollers 71, 72, 73, 74, 75, an ID unit S1(K), an ID unit S2(Y), an ID unit S3(M), an ID unit S4(C), and an ID. It is movably arranged between the unit S5(K), the ID unit S1(K), the ID unit S2(Y), the ID unit S3(M), the ID unit S4(C), and the ID unit S5(K). The toner image formed in step 1 is transferred. The intermediate transfer belt 11 is made of a high-resistance semiconductive plastic film.

Thus, the toner images formed by the ID unit S1(K), the ID unit S2(Y), the ID unit S3(M), the ID unit S4(C), and the ID unit S5(K) are the intermediate transfer belt. 11 is once transferred.
The ID unit S1(K), the ID unit S2(Y), the ID unit S3(M), the ID unit S4(C), and the ID unit S5(K) are arranged in this order from the upstream side in the rotation direction of the intermediate transfer belt 11. It is arranged.

A cleaning blade 15 is disposed on the intermediate transfer belt 11 at a position facing the belt driven roller 13 so as to contact the intermediate transfer belt 11.
Adhered substances such as toner scraped off by the cleaning blade 15 are stored in a cleaner container 16.

The secondary transfer roller 21 is arranged to face the secondary transfer backup roller 14 via the intermediate transfer belt 11 and transfers a toner image transferred to the intermediate transfer belt 11 to the recording medium 3 by applying a transfer voltage. is there.
Further, on the upstream side of the secondary transfer roller 21 in the rotation direction of the intermediate transfer belt 11 shown by an arrow A in the figure, a light reflection sensor or the like for detecting the amount of toner transferred to the surface of the intermediate transfer belt 11 is configured. The density sensor 17 is arranged to face the intermediate transfer belt 11.

The density sensor 17 serving as a density detecting unit detects the density of the first toner image (the toner image formed by the ID unit S1(K)) formed on the intermediate transfer belt 11 and The density of the second toner image (the toner image formed by the ID unit S5(K)) is detected.

The fixing device 50 heats, melts, and presses the toner transferred to the recording medium 3 by the heating unit 51 and the pressure roller 52 to fix the toner on the recording medium 3. The temperatures of the heating section 51 and the pressure roller 52 are measured by the heating section temperature sensor 55 and the pressure roller temperature sensor 56, and controlled by the fixing temperature control section described later.

The recording medium 3 having the toner fixed by the fixing device 50 is conveyed to the re-conveyance path 34 or the discharge roller 36 by the selection operation of the conveyance separator 33.
The re-conveyance path 34 is a path for conveying the recording medium 3 to the conveyance path 32 by the re-conveyance rollers 35a, 35b, and 35c.
The ejection roller 36 ejects the recording medium 3 to the outside of the apparatus.

The writing sensor 37 and the ejection sensor 38 are sensors that detect passage of the recording medium 3 and that operate each time the recording medium 3 passes.

FIG. 2 is a schematic side cross section showing the configuration of the ID unit in the embodiment. Since the ID unit S2(Y), the ID unit S3(M), the ID unit S4(C), and the ID unit S5(K) have the same configuration as the ID unit S1(K), the ID unit S1 will be described below. The configuration of (K) will be described.

In FIG. 2, the ID unit S1(K) includes a photosensitive drum 41, a charging roller 42, a developing roller 43, a supply roller 44, a toner cartridge 45, and an RFID (Radio Frequency IDentifier) 47. ..

The photosensitive drum 41 is an image carrier on the surface of which an electrostatic latent image is formed, and is rotatably supported. Around the photosensitive drum 41, a charging roller 42, an LED head 61, and a developing roller 43 are arranged in order from the upstream side in the rotation direction indicated by arrow B in the figure.

The charging roller 42 as a charging unit is arranged to face the photosensitive drum 41 and uniformly charges the surface of the photosensitive drum 41. The surface of the photosensitive drum 41 charged by the charging roller 42 is selectively irradiated with light by the LED head 61 as an exposure unit to form an electrostatic latent image.

The developing roller 43 as a developing unit conveys toner to the electrostatic latent image formed on the photosensitive drum 41 and develops it to form a toner image.
The supply roller 44 serving as a supply unit supplies toner to the developing roller 43 and also frictionally charges the developing roller 43.

The toner cartridge 45 stores the toner to be supplied to the supply roller 44. The toner stored in the toner cartridge 45 passes through a duct 49 which is a toner transport path and is supplied to the supply roller 44.
The respective voltages of CH (charge bias), DB (developing bias), and SB (toner supplying bias), which will be described later, are applied to the charging roller 42, the developing roller 43, and the supplying roller 44, and the surface of the photosensitive drum 41 is It is used for charging and forming a toner image.

The color toner image formed on the photosensitive drum 41 is transferred to the intermediate transfer belt 11 by the transfer voltage applied to the primary transfer roller 71 shown in FIG.
The RFID 47 is capable of writing color information of toner stored in the toner cartridge 45, identification information such as a serial number of the toner cartridge 45, and reading the information.

Further, the ID unit S1(K) includes a developer regulating blade 46 for adjusting the layer thickness and charge amount of the toner attached to the developing roller 43 and a cleaning blade 48 for removing the transfer residual toner remaining on the surface of the photosensitive drum 41. Have

FIG. 3 is a block diagram showing the control configuration of the printer in the embodiment.
In FIG. 3, the printer 1 is communicatively connected to a PC (Personal Computer) 100 as an information processing apparatus.

The PC 100 has a PC display unit 110 and a PC input unit 120, and creates print data. The PC 100 sends the created print data to the printer 1. The PC 100 also receives information such as an instruction transmitted from the printer 1.

The PC display unit 110 has a display or the like as a display unit that displays a print image created by application software operating on the PC 100 and displays an instruction or the like transmitted from the printer 1. The PC display unit 110 may be an operation panel including a display unit, operation buttons and keys, a touch panel, and the like.

The PC input unit 120 has a keyboard, a mouse, a touch panel, etc. as input means for creating an image of print data via application software operating on the PC 100 and inputting a response to an instruction or the like transmitted from the printer 1. It is a thing.
The printer 1 has a controller control unit 200, a process control unit 300, and a printer display unit 400.

The controller control unit 200 includes a CPU (Central Processing Unit) 210, a ROM (Read Only Memory) 220, a RAM (Random Access Memory) 230, a timer 240, a host I/F (InterFace) 250, and an external I/F. F260 and.

The CPU 210 sends and receives commands for controlling the RAM 230, the timer 240, the host I/F 250, and the external I/F 260 based on a control program (software) stored in the ROM 220, and controls them. Further, the CPU 210 sends and receives a command for controlling the process control unit 300 via the external I/F 260.

The ROM 220 is composed of a non-volatile memory or the like and stores a control program. The ROM 220 includes a predetermined density data storage unit 221 that stores density data, which is a threshold value of the density of image data printed by the developing unit of the ID unit S1(K), as predetermined density data.

The host I/F 250 transmits/receives various control signals, print data, etc. to/from the PC 100.
The RAM 230 is composed of a volatile memory or the like, and temporarily stores print data received from the PC 100, information generated when the CPU 210 performs control, and the like.

The timer 240 is a time measuring means for measuring the passage of time and time, and outputs the measured result to the CPU 210.
The external I/F 260 outputs the density measurement result output from the density sensor 17, the output signal output from the registration sensor 37 and the discharge sensor 38, and the temperature measurement result output from the heating section temperature sensor 55 and the pressure roller temperature sensor 56. It also receives various commands with the process control unit 300.

The process control unit 300 as a control unit includes a high voltage control unit 310, an exposure control unit 320, a motor control unit 330, and a fixing temperature control unit 340, and conveys a recording medium and charges, develops, transfers, and fixes the recording medium. This is to appropriately control the image forming process such as.

The high-voltage controller 310 transfers the toner image onto the recording medium, so that the primary transfer rollers 71 to 75, the secondary transfer roller 21, and the ID units S1(K), S2(Y), S3(M), and S4( C), S5 (K), the charging roller, the developing roller, and the voltage applied to the various rollers of the supply roller are properly controlled.

The high voltage controller 310 has an ID unit internal voltage controller 311 and a transfer controller 315.
The ID unit internal voltage controller 311 controls the CH 351 of the ID units S1(K), S2(Y), S3(M), S4(C), and S5(K) (charging bias applied to the charging roller 42 shown in FIG. 2). Voltage), DB352 (developing bias voltage applied to the developing roller 43 shown in FIG. 2), and SB353 (supply bias voltage applied to the supplying roller 44 shown in FIG. 2) are properly controlled.

The ID unit internal voltage control unit 311 as the density control unit controls the developing bias voltage of the DB 352 so that the ID units S1(K), S2(Y), S3(M), S4(C), and S5(K) are controlled. The density of the formed toner image is controlled.

The process control unit 300 controls the ID unit internal voltage control unit 311 based on the concentration measurement result as the detection result output from the concentration sensor 17, and the ID units S1(K), S2(Y), and S3(M). , S4(C), S5(K) control the density of the toner image formed.

The transfer control unit 315 should primarily transfer the toner images of the respective colors formed by the ID units S1(K), S2(Y), S3(M), S4(C), and S5(K) to the intermediate transfer belt. The control of applying the primary transfer voltage to the primary transfer rollers 71 to 75 and the control of applying the secondary transfer voltage to the secondary transfer roller 21 in order to transfer the toner image carried by the intermediate transfer belt onto the recording medium are performed. It is something to do.

The exposure control unit 320 controls the exposure of the LED heads 61 to 65.
The motor control unit 330 controls each motor in the printer 1 to drive them to rotate. The motor control unit 330 includes the ID units S1(K), S2(Y), S3(M), S4(C), and S5(K), the paper feed roller 31, the registration roller 18, and the roller shown in FIG. The operation of a motor that drives the transport roller 19, the transport separator 33, the discharge roller 36, the pressure roller 52, the drive roller 12 of the intermediate transfer belt 11, and the like is controlled.

The fixing temperature control section 340 controls the temperature of the heating section 51 of the fixing device 50 shown in FIG. 1 according to the measurement results of the heating section temperature sensor 55 and the pressure roller temperature sensor 56.
The printer display unit 400 has display means such as a display, and displays various information in the printer 1 on the display means to notify the user.

The operation of the above configuration will be described.
First, the printing operation performed by the printer will be described with reference to FIGS.
The recording mediums 3 stored in the paper tray 2 in a state of being stacked are separated one by one from the uppermost recording medium 3 by the hopping roller 31 and fed to the transport path 32.

The skew of the recording medium 3 delivered to the transport path 32 is corrected when the recording medium 3 passes through the registration roller 18, and the registration roller 18 and the transport roller 19 cause the secondary transfer roller 21 and the intermediate transfer belt 11 to perform the predetermined timing. The sheet is conveyed to a nip portion as a secondary transfer portion to be formed.

Meanwhile, the intermediate transfer belt 11 has ID units S1(K), S2(Y), and S3 having black (K), yellow (Y), magenta (M), cyan (C), and black (K) toners. Toner formed by developing the electrostatic latent image on the photosensitive drum 41 formed by the LED heads 61, 62, 63, 64, and 65 when passing through (M), S4 (C), and S5 (K) The image is transferred onto the recording medium 3 being conveyed. When the toner image is formed on the photosensitive drum 41 and when the toner image is transferred to the recording medium 3, respective voltages are applied to the respective rollers and the like.

In this embodiment, when forming a background image, as shown in FIG. 5, the image is formed by the ID units S1(K) and S5(K), and the ID units S2(Y), S3(M) and S4 are formed. (C) moves to a position where it does not come into contact with the intermediate transfer belt 11 by driving a motor or the like so that an image is not formed.

The various voltages applied to the respective members in the ID units S1(K) and S5(K) are determined by the first correction value which is the density correction value and the second correction value which is determined by the adjusting operation. It is determined.

The first correction value is a density correction value calculated by detecting the density of the predetermined adjustment pattern transferred to the intermediate transfer belt 11 by the density sensor 17 and calculating based on the detected density value. The detection of the density of the adjustment pattern and the calculation of the first correction value are performed when the printing operation is not performed.

In addition, the second correction value is derived by a blur adjustment that detects a blur caused when a solid image with a print duty (a ratio of pixels to be printed out of all pixels) of 100% is printed and calculates a correction value. These are the corrected values, which will be described in detail later.

Here, the DB 352 that is a development bias voltage applied to the developing roller 43 shown in FIG. 3 that has a high contribution to the print density is, for example, in the case of the DB 352 (DB(S1)) of the ID unit S1(K), It is calculated as the correction value of 1 (S1)+the second correction value (S1).

DB(S1)=first correction value (S1)+second correction value (S1)
The toner image primarily transferred onto the intermediate transfer belt 11 is transferred by the secondary transfer roller 21 to the print medium 3 conveyed to the secondary transfer portion, and is conveyed to the fixing device 50.

The toner image of the print medium 3 conveyed to the fixing device 50 is fixed by the fixing device 50, and the discharging roller 36 discharges the toner image to the outside of the apparatus to complete the printing operation.

FIG. 5 is an explanatory diagram of a print image in the embodiment.
As shown in FIG. 5, the toner image 81 is formed in the ID unit S1(K), and the toner image 82 is formed in the ID unit S5(K). In this case, the toner image formed on the recording medium 3 becomes the toner image 83 in which the toner image 81 and the toner image 82 are superimposed.

The toner image 82 is a toner image in which an image designated by print data or the like is directly formed in the ID unit S5(K). The ID unit S5(K) forms the toner image of the print data transmitted from the PC 100 as it is under the control of the control control unit 200 and the process control unit 300 shown in FIG.

Further, the toner image 81 is a toner image formed in the ID unit S1(K) with an image having a predetermined density or higher with respect to the image designated by the print data or the like.
That is, the ID unit S1(K) forms a toner image having a predetermined density or higher in the toner image formed by the ID unit S5(K).

Here, the toner image forming process in the ID unit S1(K) will be described with reference to FIGS. 1 and 3 in accordance with the step represented by S in the flowchart of the flow chart of the toner image forming process in the embodiment of FIG. ..

S101: The controller control unit 200 of the printer 1 reads out the predetermined density data (predetermined density value) stored in the predetermined density data storage unit 221. In the present embodiment, the predetermined density value is described as being stored in the predetermined density data storage unit 221, but the predetermined density value may be input from the PC 100.

S102: The controller control unit 200 compares the density value of each portion (each pixel) of the image data designated by the print data with a predetermined density value.
S103: When the controller control unit 200 determines that the density value of the image data instructed by the print data is equal to or higher than the predetermined density value, the process proceeds to S104, and the density value of the image data instructed by the print data is the predetermined density value. If it is determined that the value is less than the value, the process proceeds to S105.

S104: When the controller control unit 200 determines that the density value of the image data instructed by the print data is equal to or higher than the predetermined density value, the corresponding portion is used as the image data for printing as the portion to be printed by the ID unit S1(K). It is stored in the RAM 230 and the process proceeds to S106.
S105: On the other hand, when the controller control unit 200 determines that the density value of the image data instructed by the print data is less than the predetermined density value, the part is not printed by the ID unit S1(K) and The process proceeds to S106 without storing the image data.

The processes of S102 to S105 are performed on all parts (all pixels) of the image data designated by the print data.

S106: The controller control unit 200 and the process control unit 300 use the ID unit S1(K) to print the toner image on the intermediate transfer belt 11 based on the image data for printing of the ID unit S1(K) stored in the RAM 230. This is formed, printing is performed, and this processing is ended.

As described above, in this embodiment, the control control unit 200 and the process control unit 300 convert the print data itself transmitted from the PC 100 into a toner image formed by the ID unit S5(K) and an image instructed by the print data. On the other hand, a portion having a predetermined density or higher is superposed on the toner image formed by the ID unit S1(K) to form a predetermined toner image.

Note that the print data itself may be formed by the ID unit S1(K), and a portion having a predetermined density or higher for the image designated by the print data may be formed by the ID unit S5(K). However, since the toner image formed by the ID unit S1(K) may be peeled off by the ID unit S5(K), the print data itself is formed by the ID unit S5(K), and the print data is instructed. It is preferable that the ID unit S1(K) forms a portion having a predetermined density or higher with respect to the formed image.

Here, the blurring of the toner image formed by the ID unit S1(K) and the ID unit S5(K) will be described.
The toner images formed by the ID unit S1(K) and the ID unit S5(K) are different from each other when the amount of toner supplied from the toner supply roller 44 to the developing roller 43 decreases due to deterioration of the ID unit or toner over time. The toner density is lower than that of the above area.

This is because the toner supply roller 44 is abraded over time and the toner is repeatedly subjected to various stresses in the ID unit, which deteriorates the fluidity and the charging property and reduces the toner supply amount to the developing roller 43. This is because when the amount of toner supplied to the developing roller 43 is reduced, white stripes due to lack of toner are formed on the image formed on the print medium as blurs. This blur is a region where the toner density is lower than that of other regions, and the blur that is visually recognized especially when a solid image is printed is called a solid blur.

Next, the density adjustment processing performed by the controller control unit 200 and the process control unit 300 in order to suppress the occurrence of sticky spots will be described according to the step represented by S in the flowchart of the flowchart showing the flow of the sticky spot density adjustment processing in the embodiment of FIG. A description will be given with reference to FIG.

The solid density adjustment process is performed when instructed by the PC 100, when the user's input operation is accepted on the operation panel of the printer 1, when the power of the printer 1 is turned on, or when the environmental conditions of the printer 1 are changed. This is performed when the consumable items of the printer 1 are replaced (for example, when the ID unit, the toner cartridge, etc. are replaced) when the humidity or the like changes.

S201: The controller control unit 200 and the process control unit 300 of the printer 1 use the ID unit S1(K) to intermediately print a solid image (for example, a rectangular solid image) on the intermediate transfer belt 11 with the maximum gradation value. This is performed with a length of 450 mm in the transport direction of the transfer belt 11.

S202: The controller control unit 200 uses the density sensor 17 to measure the density of a portion 10 mm from the leading edge of the solid image in the transport direction of the intermediate transfer belt 11 (the leading edge in the sub-scanning direction as the first portion).

Here, the density of the toner image detected by the density sensor 17 will be described with reference to FIG.
FIG. 6 is an explanatory diagram of the print density in the embodiment, in which the horizontal axis represents the print duty (%) and the vertical axis represents the density (optical density value: OD (Optical Density) value). The OD value is an index indicating that the larger the numerical value, the lower the light transmittance (higher the density).

In this embodiment, for example, the OD value is 0 when the print duty is 0%, the OD value is 1.5 when the print duty is 99%, and the OD value is 2.0 when the print duty is 100%.
In this embodiment, the density of the toner image is represented by the OD value.

S203: Next, the controller control unit 200 uses the density sensor 17 to measure the density of the portion 440 mm from the front end of the solid image in the transport direction of the intermediate transfer belt 11 (the rear end in the sub-scanning direction as the second portion). To measure.
S204: The controller control unit 200 calculates the difference between the density of the portion 10 mm from the front end of the solid image and the density of the portion 440 mm from the front end of the solid image as the blurring density (S1).

Here, it is assumed that KASUURE(S1)=(density at 10 mm from tip)-(density at 440 mm from tip).
KASURE(S1) is an index value indicating the degree of sticky stain of the ID unit S1(K), and the larger the value, the larger the solid stain (decrease in density).

In this way, the controller control unit 200 uses the density sensor 17 to form a solid image (toner image) formed by the ID unit S1(K) to which the ID unit internal voltage control unit 311 applies the developing bias voltage as the predetermined density. To detect a decrease in concentration.

S205: Next, the controller control unit 200 and the process control unit 300 cause the ID unit S5(K) to print a solid image on the intermediate transfer belt 11 with the maximum gradation value in the conveyance direction of the intermediate transfer belt 11 by 450 mm. Do in length.

S206: The controller control unit 200 uses the density sensor 17 to measure the density of the portion 10 mm from the front end of the solid image in the transport direction of the intermediate transfer belt 11 (the front end in the sub-scanning direction as the first portion).
S207: Next, the controller control unit 200 uses the density sensor 17 to print the density of the portion 440 mm from the front end of the solid image in the transport direction of the intermediate transfer belt 11 (the rear end in the sub-scanning direction as the second portion). To measure.

S208: The controller control unit 200 calculates the difference between the density of the portion 10 mm from the front end of the solid image and the density of the portion 440 mm from the front end of the solid image as the blurring density (S5).
Here, KASURE (S5)=(density at 10 mm portion from tip)-(density at 440 mm portion from tip).

KASURE (S5) is an index value indicating the degree of sticky wear of the ID unit S5 (K), and the larger the value, the greater the quantity of sticky wear (decrease in density).

In this way, the controller control unit 200 uses the density sensor 17 to apply a developing bias voltage as a predetermined density by the ID unit internal voltage control unit 311 to form a solid image (toner image) formed by the ID unit S5(K). To detect a decrease in concentration.

S209: The controller control unit 200 determines whether the smaller one of the values of KASURE (S1) and KASURE (S5) is smaller than the determination value (threshold value), and if it is determined that it is smaller than the determination value, the process is executed. The process proceeds to S210, and if it is determined that it is equal to or greater than the determination value, the process proceeds to S219. That is, the controller control unit 200 determines whether or not a good ID unit with less occurrence of sticky blur is at a predetermined adjustable level. If the ID unit is at the adjustable level, the process proceeds to the next step S210, and if it is at the unadjustable level, both the ID unit S1(K) and the ID unit S5(K) need to be replaced. If there is, the process proceeds to S219.

In this embodiment, the judgment value is set to 0.3, for example. However, the judgment value is not limited to 0.3.

S219: The controller control unit 200 displays on the printer display unit 400 that both the ID unit S1(K) and the ID unit S5(K) need to be replaced, and ends this processing.

S210: The controller control unit 200 determines which one of the ID units S1(K) and S5(K) has less stickiness. The controller control unit 200 determines whether or not (KASURE(S1)-KASURE(S5)) is 0 or more, and when it is determined to be 0 or more, the ID unit S5(K) is more than the ID unit S1(K). If it is determined that (KASURE(S1)-KASURE(S5)) is less than 0, the process proceeds to S211 because the ID unit S1(K) is better than the ID unit S5(K). The process proceeds to S215.

S211: The controller control unit 200, which has determined that the ID unit S5(K) is better than the ID unit S1(K), determines whether (KASURE(S1)-KASURE(S5)) is greater than 0.1. However, if it is determined that the value is larger than 0.1, the process proceeds to S212 because the adjustment of the ID unit S1(K) is necessary, and if it is determined that (KASURE(S1)-KASURE(S5)) is 0.1 or less. Since the ID unit S1(K) is sufficiently good, it is determined that adjustment is unnecessary, and the process proceeds to S218.

For example, if (KASURE(S1)-KASURE(S5))=0.05, the ID unit S1(K) is more sticky than the ID unit S5(K), but it may not be adjusted enough. It is determined not to.
Although the determination value is set to 0.1 in the present embodiment, the determination value is not limited to 0.1 and can be set according to the required image quality.

S212: The controller control unit 200 that has determined that the adjustment of the ID unit S1(K) is necessary forms the ID unit S1(K) because the condition of the sticky stain occurring in the ID unit S1(K) is bad. The solid deviation correction value (S1) of the ID unit S1(K) is determined to be +45V so as to reduce the density of the toner image.

S213: Further, the controller control unit 200 determines the solid defect correction value (S5) of the ID unit S5(K) to be −45V in order to increase the density of the toner image formed by the ID unit S5(K).

As described above, the controller control unit 200 controls the toner of the one developing device (ID unit S1(K)) that forms a toner image with a large decrease in density among the ID unit S1(K) and the ID unit S5(K). The density is lowered and the toner density of another developing device (ID unit S5(K)) is increased.

In this embodiment, the solid correction value is described as 45V, but the correction value is not limited to 45V and can be determined in accordance with the density characteristic of the ID unit.

Further, the solid correction amount may be changed according to the value of the difference between KASURE (S1) and KASUURE (S5). In this case, the correction table determined so that the solid correction value (absolute value) also increases as the value of the difference between KASURE (S1) and KASURE (S5) increases is stored in advance in the ROM 220, and the correction table is stored. The solid blur correction value may be determined with reference.

S214: The controller control unit 200 sets the solid correction amount (S1) to the second correction value (S1), and sets the value of the DB 352 of the ID unit S1 (K) to
DB(S1)=first correction value (S1)+second correction value (S1)
Calculate as

In addition, the controller control unit 200 sets the solid correction amount (S5) to the second correction value (S5), and sets the value of the DB 352 of the ID unit S5 (K) to
DB(S5)=first correction value (S5)+second correction value (S5)
And the present process is terminated.

The controller control unit 200 notifies the calculated DB(S1) and DB(S5) to the process control unit 300, and the process control unit 300 determines the ID unit S1( based on the notified DB(S1) and DB(S5). The DB 352 of K) and the DB 352 of the ID unit S5(K) are output to form a toner image.

For example, when the first correction value (S1) is -200V, the DB 352 of the ID unit S1(K) is output as -155V and the DB 352 of the ID unit S5(K) is output as -245V.

In this way, the controller control unit 200 forms one toner image by superimposing the toner image whose density has been reduced by the process control unit 300 and the toner image whose density has been increased by the process control unit 300.

S215: On the other hand, in S210, the controller control unit 200 that determines that the ID unit S1(K) is better than the ID unit S5(K) has (KASURE(S5)-KASURE(S1)) greater than 0.1. If it is determined that it is larger than 0.1, it is necessary to adjust the ID unit S5(K), so the process proceeds to S216, and (KASURE(S5)-KASURE(S1)) is 0.1. If it is determined that there is the following, the ID unit S5(K) is sufficiently good and no adjustment is necessary, and the process proceeds to S218.

For example, if (KASURE(S5)-KASURE(S1))=0.05, the ID unit S5(K) is more sticky than the ID unit S1(K), but it may not be adjusted enough. It is determined not to.

Although the determination value is set to 0.1 in the present embodiment, the determination value is not limited to 0.1 and can be set according to the required image quality.

S216: The controller control unit 200, which has determined that the adjustment of the ID unit S5(K) is necessary, forms with the ID unit S5(K) because the situation of the sticky stain occurring in the ID unit S5(K) is bad. The solid deviation correction value (S5) of the ID unit S5(K) is determined to be +45V so as to reduce the density of the toner image.

S217: Further, the controller control unit 200 determines the solid defect correction value (S1) of the ID unit S1(K) to be −45V in order to increase the density of the toner image formed by the ID unit S1(K), and the processing is S214. Move to.

In this case, in S214, for example, when the first correction value (S1) is -200V, the DB 352 of the ID unit S1(K) is output as -245V and the DB 352 of the ID unit S5(K) is output as -155V. ..

As described above, the controller control unit 200 controls the toner of one developing device (ID unit S5(K)) that forms a toner image with a large decrease in density among the ID unit S1(K) and the ID unit S5(K). The density is lowered and the toner density of another developing device (ID unit S1(K)) is increased.

S218: If it is determined in S211 that the adjustment of the ID unit S1(K) is unnecessary, or if it is determined in S215 that the adjustment of the ID unit S5(K) is unnecessary, the adjustment of the ID unit S1(K) The processing advances to S214 with the solid correction value (S1) and the solid correction value (S5) of the ID unit S5(K) set to 0.

As described above, according to the present exemplary embodiment, the correction for lowering the toner concentration is performed by lowering the developing bias (DB) having a large contribution to the toner concentration for the ID unit in which a large amount of solid blur occurs. It is possible to reduce the amount of toner used during the printing operation of the ID unit, and it is possible to reduce the sticky blurring that occurs.

FIG. 9 is an explanatory diagram of the level of DB and solid blur in the embodiment, where the horizontal axis represents the development bias DB (−V) and the vertical axis represents the level of solid blur (10: good, 0: bad). In FIG. 9, for example, when DB is −200V, the level of solid wear is “5”, but when DB is lowered to −155V, the level of solid wear is “8”, and the solid wear can be reduced.

In addition, by increasing the developing bias (DB) for a good ID unit that does not cause a solid image blur and performing correction to increase the toner density, the amount of toner used during the printing operation of the ID unit is increased, Increase the concentration.

Final print density=(print density of ID unit with large stickiness)+(print density of ID unit with small stickiness), and the density of the toner image finally printed on the recording medium is the toner image before correction. The same as the concentration of.

Therefore, the developing bias (DB) of the ID unit in which the solid image blur is large is lowered to reduce the density of the toner image, making it difficult to visually recognize the occurrence of the solid image blur, while the developing bias (DB) of the ID unit in which the solid image blur is small is generated. By increasing the density of the toner image to increase the density of the toner image, good print quality can be obtained without changing the density of the final toner image formed by the ID units and superposed.

When the printer 1 prints the medical image, the controller control unit 200 and the process control unit 300 print the background image of the medical image by the ID unit S1(K) and the ID unit S5(K). , Print the entire image of the medical image. The ID unit S1(K) prints with an OD value of 1.5 to 1.8, and the ID unit S5(K) prints with an OD value of 1.5 to 1.8, resulting in an OD print result. It is possible to obtain a print of a medical image having a value of 2.0 to 2.2. However, when blurring occurs in the image printed by the ID unit S1(K) and it is necessary to perform solid blur correction, the ID unit S1(K) has an OD value of 1.35 by using the above-described solid blur correction value. Image is printed, the image having the OD value of 1.65 is printed by the ID unit S5(K), and as a result of the printing, a medical image printed matter having the OD value of 2.0 can be obtained.

In this embodiment, the controller control unit 200 selects one of the ID unit S1(K) and the ID unit S5(K) that develops a toner image with a large decrease in density (ID unit S1(K)). The toner density of the other developing device (ID unit S5(K)) is increased and the toner density of the other developing device is increased, but the toner image is formed by three or more ID units and the density is controlled. You can

In this case, the controller control unit 200 lowers the density of the toner agent of the ID unit that has formed the toner image in which the density decrease (density lower than the threshold value) is detected among the three or more ID units, and the developing unit of the other developing device decreases the density. Control to increase the concentration of the agent.

Further, in the present embodiment, an example in which the solid image is printed on the intermediate transfer belt 11 with the maximum gradation value by the ID unit S1(K) and the ID unit S5(K) has been described. A print pattern of a solid image of gradation values may be printed on a recording medium and a correction value may be input from the operation panel unit or the PC 100. In this case, the print patterns are six print patterns 91 to 96 that are stretched (for example, 450 mm in length) in the recording medium conveyance direction, and are print patterns in which a predetermined interval is maintained in the direction orthogonal to the medium conveyance direction. .. For example, the print patterns 91, 93, 95 are solid images printed by the ID unit S1(K), and the print patterns 92, 94, 96 are solid images printed by the ID unit S5(K).

As described above, in the present embodiment, the developing bias of the developing unit of the ID unit in which the solid image blur is large is lowered to reduce the density of the toner image, and the developing bias of the ID unit in which the solid image spot is small is raised. By performing the correction, it is possible to obtain the effect of improving the printing quality when a plurality of toner images are overlapped to form one toner image.

In this embodiment, the image forming apparatus is described as a printer, but the invention is not limited to this, and may be a copying machine, a facsimile machine, a multi-function peripheral (MFP), or the like.

1 Printer 2 Paper Cassette S1(K), S2(Y), S3(M), S4(C), S5(K) ID Unit 11 Intermediate Transfer Belt 18 Registration Roller 19 Conveying Roller 21 Secondary Transfer Roller 31 Hopping Roller 32 Conveyance path 34 Re-conveyance path 36 Ejection roller 41 Photosensitive drum 42 Charging roller 43 Development roller 44 Supply roller 45 Toner cartridge 50 Fixing device 61, 62, 63, 64, 65 LED head 200 Controller control unit 210 CPU
220 ROM
230 RAM
240 timer 250 host I/F
260 external I/F
300 Process Control Unit 310 High Voltage Control Unit 320 Exposure Control Unit 330 Motor Control Unit 340 Fixing Temperature Control Unit 400 Printer Display Unit

Claims (13)

A plurality of developing devices capable of supplying a developer to the electrostatic latent image to form a developer image of the same color and superposing the developer images of the same color,
A density control unit for controlling the density of each developer image formed by each of the developing devices,
A density detecting unit that detects the density of each of the developer images and detects a density decrease in each of the developer images formed at a predetermined density by the density control unit,
A control unit for controlling the concentration control unit based on the detection result of the concentration detection unit;
Have
Among the plurality of developing devices, the control unit lowers the density of the developer of the developing device that has formed the developer image in which the density decrease is detected by the density control unit, and reduces the density of the developer of another developing device. An image forming apparatus, wherein the density is raised by the density control unit. The image forming apparatus according to claim 1,
The plurality of developing units form a first developing unit for forming a first developer image and a second developing unit image, and form the first developing unit image and the second developing unit image. A second developing device that can be overlaid,
The density controller controls the density of a developer image formed by the first developing device and the second developing device,
The density detector detects the density of the first developer image and the density of the second developer image, and the density controller forms the first developer image and the first developer image formed at a predetermined density. The decrease in density in the developer image of 2 is detected,
The control unit lowers the density of the developer of the one of the first developing unit and the second developing unit that has formed the developer image having the large density decrease by the density control unit, and An image forming apparatus, wherein the density control section raises the density of the developer in the developing device. The image forming apparatus according to claim 2,
An image characterized in that the control section forms a single developer image by superposing the developer image whose density has been reduced by the density control section and the developer image whose density has been increased by the density control section. Forming equipment. The image forming apparatus according to claim 2 or 3,
The density detecting unit detects the density decrease by detecting a density difference between a first portion and a second portion in the first developer image and the second developer image. Image forming apparatus. The image forming apparatus according to claim 4,
The first portion is a tip portion in the sub-scanning direction of the first developer image and the second developer image formed with the predetermined density,
The image forming apparatus, wherein the second portion is a rear end portion in the sub-scanning direction of the first developer image and the second developer image formed with the predetermined density. The image forming apparatus according to any one of claims 2 to 5,
The image forming apparatus, wherein the controller controls the density of the developer by the density controller when the density decrease is smaller than a threshold value. The image forming apparatus according to any one of claims 2 to 6,
The image forming apparatus, wherein the first developer image and the second developer image are black developer images. The image forming apparatus according to any one of claims 2 to 7,
The image forming apparatus, wherein the density control unit controls the developing voltage applied to the first developing device and the second developing device to control the density. The image forming apparatus according to any one of claims 2 to 7,
An intermediate transfer belt that is rotatably provided and on which the first developer image and the second developer image are formed,
The image forming apparatus, wherein the first developing device is arranged upstream of the second developing device in the rotation direction of the intermediate transfer belt. The image forming apparatus according to claim 9,
The image forming apparatus, wherein the density detector detects the density of the first developer image and the density of the second developer image formed on the intermediate transfer belt. The image forming apparatus according to any one of claims 2 to 10,
The image forming apparatus, wherein the first developing device forms a first developer image having a predetermined density or higher in a second developer image formed by the second developing device. The image forming apparatus according to any one of claims 2 to 11,
The image forming apparatus, wherein the controller forms a medical image by the plurality of developing devices. The image forming apparatus according to claim 12,
The first developer forms an image of the background of the medical image,
The second developing device, an image forming apparatus and forming an image of the entire medical images.

Images