JP7406723B2 - Image forming apparatus, image forming method, and image forming program - Google Patents

Description

The present invention relates to an image forming apparatus, an image forming method, and an image forming program, and particularly relates to proofreading processing.

In an image forming apparatus using an electrophotographic process, a method has been proposed in which a patch is formed on an intermediate transfer belt and the density of the patch is actually measured to calibrate the exposure amount and development bias. In such a calibration process, Patent Document 1 discloses an image correction method that corrects images formed at a plurality of process speeds, using a reference pattern created by a medium-speed VM before image formation at a medium speed. The present invention discloses a technique for creating a density correction table TBM for a medium-speed VM, and using a conversion table TB0 from the density correction table TBM for a medium-speed VM to create a density correction table TBM for a high-speed VH. Patent Document 1 further makes it possible to create a medium-speed VM density correction table TBM from the high-speed VH using the conversion table TB0. As a result, when correcting images formed at multiple process speeds, Patent Document 1 reduces the time required for process control (image quality adjustment) corresponding to each process speed each time each process speed is changed, and It is said that by eliminating the idling of the image carrier, it is possible to suppress abrasion (film wear) on the surface of the image carrier.

JP2007-286460A

However, with the conventional technology, there is a concern that, for example, if process control continues only with medium-speed VM, the reliability of the high-speed VH concentration correction table TBM, which is created using the conversion table TB0 from the medium-speed VM, may decrease. be done. On the other hand, since the density correction table TBM is created before image formation, there is a problem in that it takes a long time to complete image formation, which reduces productivity.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique that increases the reliability of calibration while suppressing a decrease in productivity.

The image forming apparatus of the present invention includes a developing section having a photoreceptor, an intermediate transfer belt on which toner is transferred from the photoreceptor at a plurality of conveyance speeds and the transferred toner is transferred onto an image forming medium, and the intermediate transfer belt. a density sensor that measures the density of toner transferred to the transfer belt; an operation display unit that accepts selection of a reference linear velocity that is one of the plurality of transport speeds; and a selection via the operation display unit. The calibration setting value of at least one linear speed other than the reference linear speed among the plurality of transport speeds is set as the reference setting value using the reference setting value that is the calibration setting value of the reference linear speed that has been set. a storage unit that stores converted values for converting and generating from set values; and a storage unit that stores converted values for generating by converting from set values; and when forming an image at the reference linear velocity, adjusts the developing unit using the reference set values; In the case of forming an image at a linear speed other than the linear speed, the calibration processing section is provided with a calibration processing section that adjusts the developing section using the reference setting value and the conversion value; In response to acceptance of the speed selection, it is determined whether the selection results in a change in the reference linear speed, and if it is determined that the selection results in a change in the reference linear speed, the concentration of the toner at the reference linear speed is determined. measurement is performed, and the reference setting value is updated based on the measurement.

The present invention provides an image forming method using a developing section having a photoreceptor, and an intermediate transfer belt that transfers toner from the photoreceptor at a plurality of conveying speeds and transfers the transferred toner onto an image forming medium. do. The image forming method includes a density measurement step of measuring the density of the toner transferred to the intermediate transfer belt, and an operation display step of accepting selection of a reference linear speed that is one of the plurality of transport speeds. , a reference setting value that is a calibration setting value of the reference linear velocity selected through the operation display step, and at least one of the plurality of transport speeds other than the reference linear velocity using the reference linear velocity. a storage step of storing a conversion value for converting and generating a linear velocity calibration setting value from the reference setting value; and a storing step of storing a conversion value for generating a calibration setting value of the linear velocity; when adjusting the developing section and forming an image at a linear velocity other than the reference linear velocity, a calibration processing step of adjusting the developing section using the reference setting value and the conversion value; In the calibration processing step, in response to receiving the selection of the reference linear velocity, it is determined whether the selection is a change in the reference linear velocity, and if it is determined that the selection is a change in the reference linear velocity, The density of the toner at the reference linear velocity is measured, and the reference set value is updated based on the measurement.

The present invention provides a developing section having a photoreceptor, an intermediate transfer belt that transfers toner from the photoreceptor at a plurality of conveying speeds and transfers the transferred toner onto an image forming medium, and a transfer belt that transfers toner to the intermediate transfer belt. An image forming program for controlling an image forming apparatus having a density sensor that measures the density of toner. The image forming program includes an operation display unit that accepts selection of a reference linear velocity that is one of the plurality of transport speeds, and a calibration setting value of the reference linear velocity selected via the operation display unit. for generating a calibration setting value of at least one linear velocity other than the reference linear velocity among the plurality of transport speeds by converting from the reference setting value using a certain reference setting value and the reference linear velocity; a storage unit that stores a conversion value, and when forming an image at the reference linear velocity, adjusts the developing unit using the reference setting value and forms an image at a linear velocity other than the reference linear velocity; In this case, the image forming apparatus functions as a calibration processing section that adjusts the developing section using the reference setting value and the conversion value, and the calibration processing section accepts selection of the reference linear velocity. , it is determined whether the selection results in a change in the reference linear velocity, and if it is determined that the selection results in a change in the reference linear velocity, measurement of the density of the toner at the reference linear velocity is performed. , updating the reference set value based on the measurement.

According to the present invention, it is possible to increase the reliability of calibration while suppressing a decrease in productivity.

1 is a block diagram showing a functional configuration of an image forming apparatus 1 according to a first embodiment of the present invention. 1 is a cross-sectional view showing the overall configuration of an image forming apparatus 1 according to a first embodiment. FIG. 3 is a side cross-sectional view showing the structure of a developing section 100k according to the first embodiment. FIG. 3 is a conceptual diagram showing how trailing end accumulation occurs in the developing process according to the first embodiment. 7 is a flowchart showing the details of image forming apparatus control processing according to the first embodiment. FIG. 3 is an explanatory diagram showing the contents of light amount calibration processing according to the first embodiment. 3 is a flowchart showing the content of print proofing processing according to the first embodiment. FIG. 2 is an explanatory diagram showing a light amount calibration patch and a bias voltage setting patch used in the image forming apparatus 1 according to the first embodiment. FIG. 3 is an explanatory diagram showing the contents of development bias positive processing according to the first embodiment. 7 is a flowchart showing the contents of dot area ratio adjustment processing according to the first embodiment. FIG. 3 is an explanatory diagram showing gamma adjustment patches used in gamma calibration processing according to the first embodiment. FIG. 7 is an explanatory diagram showing the contents of light amount calibration processing according to the second embodiment. 12 is a flowchart showing the details of image forming apparatus control processing according to a third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the drawings.
A. First embodiment:
B. Second embodiment:
C. Third embodiment:
D. Variant:

A. First embodiment:
FIG. 1 is a block diagram showing the functional configuration of an image forming apparatus 1 according to a first embodiment of the present invention. The image forming apparatus 1 includes a control section 10, an image forming section 20, a storage section 40, an image reading section 50, a fixing section 80, and an operation display section 90. The image reading unit 50 reads an image from a document and generates an image data ID that is RGB digital data. The operation display unit 90 functions as a touch panel, displays various menus as input screens, and receives operation inputs from the customer.

The image forming section 20 includes a color conversion processing section 21, a halftone processing section 22, a calibration density sensor 28, an exposure section 29, and photoreceptor drums (image carriers) 30c to 30k that are amorphous silicon photoreceptors. , developing sections 100c to 100k, and charging sections 25c to 25k. The color conversion processing unit 21 converts the image data ID, which is RGB data, into CMYK data. The color conversion processing section 21 also functions as a gamma correction section, and performs gamma correction using input and output gamma correction values. The halftone processing unit 22 performs halftone processing on the CMYK data to generate print data PD including CMYK halftone data. Halftone data represents the formation state of dots formed by each CMYK toner, and is also called dot data. The calibration concentration sensor 28 is also simply called a concentration sensor.

The control unit 10 includes main storage means such as RAM and ROM, and control means such as MPU (Micro Processing Unit) and CPU (Central Processing Unit). Further, the control unit 10 has controller functions related to interfaces such as various I/Os, a USB (universal serial bus), a bus, and other hardware, and controls the entire image forming apparatus 1 . The control section 10 includes a calibration processing section 11. The functions of the calibration processing section 11 will be described later.

The storage unit 40 is a storage device that is a non-temporary storage medium such as a hard disk drive or a flash memory, and stores control programs and data for processing executed by the control unit 10. In this embodiment, the storage unit 40 further includes a calibration data storage area 41.

FIG. 2 is a sectional view showing the overall configuration of the image forming apparatus 1 according to the first embodiment. The image forming apparatus 1 of this embodiment is a tandem color printer. In the image forming apparatus 1, photosensitive drums (image carriers) 30m, 30c, 30y, and 30k are arranged in a row in a housing 70, corresponding to each color of magenta, cyan, yellow, and black. Developing sections 100m, 100c, 100y, and 100k are arranged adjacent to the photosensitive drums 30m, 30c, 30y, and 30k, respectively.

The photoreceptor drums 30m, 30c, 30y, and 30k are irradiated (exposed) with laser beams Lm, Lc, Ly, and Lk for each color from the exposure section 29. By this irradiation, electrostatic latent images are formed on the photoreceptor drums 30m, 30c, 30y, and 30k. The developing units 100m, 100c, 100y, and 100k adhere the toner to the electrostatic latent images formed on the surfaces of the photoreceptor drums 30m, 30c, 30y, and 30k while stirring the toner. As a result, the developing process is completed, and toner images of each color are formed on the surfaces of the photoreceptor drums 30c to 30k.

The image forming apparatus 1 includes an endless intermediate transfer belt 27. The intermediate transfer belt 27 is stretched around a tension roller 24, a driving roller 26a, and a driven roller 26b. The intermediate transfer belt 27 is driven to circulate at a predetermined conveyance speed (also called linear speed) by rotation of the drive roller 26a.

A cleaning device 200 is disposed at a position upstream of the photosensitive drum 30k and opposite the driven roller 26b with the intermediate transfer belt 27 in between. The cleaning device 200 includes a fur brush 210 in which fine fibers are planted and rotates at high speed. The fur brush 210 can mechanically remove the toner on the intermediate transfer belt 27 using the scraping force of the brush tip. In this way, the image forming apparatus 1 employs a brush cleaning method that uses the fur brush 210 that comes into contact with the intermediate transfer belt 27 to scrape off and discard used toner.

For example, the black toner image on the photoreceptor drum 30k is transferred to the intermediate transfer belt 27 by the intermediary transfer belt 27 being sandwiched between the photoreceptor drum 30k and the primary transfer roller 23k, and the intermediate transfer belt 27 being driven in circulation. transcribed. This also applies to the three colors cyan, yellow, and magenta.

A full-color toner image is formed on the surface of the intermediate transfer belt 27 by performing primary transfer such that the toner images are superimposed on each other at a predetermined timing. The calibration density sensor 28 is arranged at a position where the density of the toner image after the primary transfer is completed and before the secondary transfer can be measured.

The full-color toner image is then secondarily transferred onto the printing paper P supplied from the paper feed cassette 60 and fixed onto the printing paper P by the fixing roller pair 81 of the fixing section 80 . The cleaning device 200 can also remove residual toner remaining on the intermediate transfer belt 27 from the intermediate transfer belt 27 regarding the proofing patch. Print media is also referred to as imaging media. The fixing unit 80 includes an induction heating unit (not shown) that heats one of the pair of fixing rollers 81.

FIG. 3 is a side sectional view showing the structure of the developing section 100k according to the first embodiment. The developing units 100m, 100c, and 100y have the same configuration as the developing unit 100k, and are also simply referred to as the developing unit 100. The developing section 100 includes two stirring and conveying members 141 and 142, a magnetic roller 143, a developing roller (developer carrier) 144, a developing container 145, and a regulating blade 146.

The developing container 145 constitutes the outer shell of the developing section 100 . A partition portion 145b is provided at the bottom of the developer container 145. The partition portion 145b partitions the inside of the developer container 145 into a first transport chamber 145a and a second transport chamber 145c. The first transport chamber 145a and the second transport chamber 145c extend in a columnar manner in a direction perpendicular to FIG. 3, and contain a two-component developer (also simply referred to as developer) consisting of a magnetic carrier and a black toner.

The developer container 145 further holds a magnetic roller 143 and a developer roller 144. The developer container 145 is formed with an opening 147 that exposes the developer roller 144 toward the photoreceptor drum 30 (30k).

The two agitation conveyance members 141 and 142 circulate and move the developer inside the first conveyance chamber 145a and the second conveyance chamber 145c, respectively, while stirring the developer. The stirring and conveying member 142 serves as a magnetic brush and supplies positively charged developer to the magnetic roller 143 . The magnetic roller 143 includes a non-magnetic rotating sleeve 143a and a fixed magnet body 143b fixed inside the rotating sleeve 143a. The magnetic roller 143 and the developing roller 144 face each other with a predetermined clearance. The regulating blade 146 adjusts the magnetic brush to a predetermined height.

The developing roller 144 includes a rotatable non-magnetic developing sleeve 144a and a developing roller side magnetic pole 144b fixed inside the developing sleeve 144a. A magnetic roller potential Vmag is applied to the magnetic roller 143 . A developing bias potential Vslv is applied to the developing roller 144.

In this embodiment, the surface potential of the photosensitive drum 30 is set to 20 V, and a developing electric field is formed between the photosensitive drum 30 and the developing roller 144 . On the other hand, an alternating bias in which a DC potential of 20 to 80 V as a developing bias potential Vslv and a sine wave potential with a peak-to-peak value of 2000 V at a frequency of 2 kHz are superimposed is applied to the developing roller 144. A DC potential of 200 V is applied to the magnetic roller 143 as the magnetic roller potential Vmag during development, and a DC potential of −200 V is applied to the magnetic roller 143 during non-development.

As a result, during development, the time in which the developing bias potential Vslv<magnetic roller potential Vmag (the potential state in which toner is supplied to the developing roller 144) becomes longer, and the time in which toner is supplied to the developing roller 144 becomes longer. During non-development, the time for development bias potential Vslv>magnetic roller potential Vmag (potential state in which toner is collected from the developing roller 144) becomes longer, and the time for collecting toner from the developing roller 144 becomes longer.

Further, by adjusting the magnetic roller potential Vmag applied to the magnetic roller 143 during development and during non-development, the toner layer forming potential difference ΔV during development between the development bias potential Vslv and the magnetic roller potential Vmag can be changed. Can be done. As a result, the developing roller 144 has a toner thin layer (simply a toner layer) having a thickness D (see FIG. 4(a) described later) according to the toner layer forming potential difference ΔV between the developing bias potential Vslv and the magnetic roller potential Vmag. ) is formed.

The developing roller 144 forms a toner image on the surface of the photoreceptor drum 30 by attaching toner to the photoreceptor drum 30 through an opposing portion (development nip) having a predetermined clearance between the developing roller 144 and the photoreceptor drum 30 . . The toner image is formed based on the potential difference between the potential of the electrostatic latent image on the surface of the photosensitive drum 30 and the developing bias potential Vslv applied to the developing roller 144.

Amorphous silicon photoreceptors have a relative dielectric constant about three times higher than organic photoreceptors (OPC), and are characterized in that they can hold a large amount of toner relative to the development contrast potential. Therefore, the amorphous silicon photoreceptor can hold more toner than the normally used solid density. Therefore, if an amorphous silicon photoreceptor is used in a saturated state, it will retain more than the amount necessary for solid density. Therefore, in this embodiment, the amorphous silicon photoreceptor is used in an unsaturated state even in solid density, and when almost all of the toner formed on the developing roller 144 is developed on the photoreceptor and development is completed, the solid density is reduced. is used to determine.

FIG. 4 is a conceptual diagram showing how trailing end accumulation occurs in the developing process according to the first embodiment. FIG. 4(a) shows how an image is formed at the leading edge and center of the image. FIG. 4B shows how an image is formed at the rear end of the image. In this specification, the front end, the center, and the rear end are defined as the front end, the center, and the rear end in order from the traveling direction of the photoreceptor drum 30, based on the traveling direction of the photoreceptor drum 30.

In this embodiment, as shown in FIG. 4A, the photosensitive drum 30 receives toner from the developing sleeve 144a of the developing roller 144 while neutralizing the potential of the latent image. At this time, the developing process is configured to be completed when the thin toner layer formed on the developing sleeve 144a is consumed in a non-saturated state, rather than when the potential is saturated. The thickness D of the toner thin layer is set to have a thickness T1 to achieve the maximum density during solid development in image formation.

As shown in FIG. 4B, the developing sleeve 144a has a circumferential speed of Vs, and is configured to form an image while passing the photosensitive drum 30, which has a circumferential speed of Vd. Therefore, when developing a solid image, there is a surface of the developing sleeve 144a on which toner is not consumed in the vicinity of the rear end of the solid image. This surface on which toner has not been consumed will overtake the rear end of the solid latent image on the amorphous silicon photoreceptor 30.

At this time, since the photoreceptor drum 30 as an amorphous silicon photoreceptor is in an unsaturated state, toner is further developed from the surface of the developing sleeve 144a where toner is not consumed. As a result of this development, a trailing end puddle (thickness T2) becomes apparent as a solid density higher than the density expected in advance.

FIG. 4C shows, as an example, the state of toner adhesion (stacked state) during image formation of the solid image TP. In the solid image TP, the toner layer is raised at the rear end portion during image formation. This bulge in the toner layer is called a trailing edge pool.

Such a problem of trailing edge accumulation can be suppressed by expressing a solid image with a half patch, which is a patch image with a reduced dot area ratio. In this example, it is assumed that the image forming apparatus 1 expresses solid density using half patches with a dot area ratio of 70% to 90%. In this embodiment, the solid density by half patch is calibrated by adjusting the development bias potential Vslv, which is the potential applied to the development sections 100m, 100c, 100y, and 100k, and the dot area ratio.

In this way, the problem of trailing edge pooling can be solved by expressing the solid density using a preset dot area ratio as a result of the trade-off between the occurrence of jaggies caused by a decrease in the dot area ratio and the occurrence of trailing edge pooling. This is achieved by doing.

FIG. 5 is a flowchart showing the details of the image forming apparatus control process according to the first embodiment. The image forming apparatus control process also includes a sleep state as a form of standby state for waiting for a print job. In the sleep state, the fixing unit 80 controls the temperature of the fixing roller pair 81 to be lower than the temperature required for the fixing process from the viewpoint of energy saving. A print job is also called an image forming job.

In step S100, the control unit 10 of the image forming apparatus 1 is activated in response to the power being turned on, and starts processing to enable the image forming apparatus 1 to print. In step S200, the calibration processing unit 11 of the control unit 10 executes an overall calibration process in response to completion of startup of the control unit 10.

FIG. 6 is an explanatory diagram showing the contents of the light amount calibration process according to the first embodiment. In the overall calibration process, the calibration processing unit 11 executes all calibration processes for the four conveyance speeds of the intermediate transfer belt 27, that is, the four linear velocities. As shown in FIG. 6(a), the four linear speeds include high linear speed, standard linear speed, intermediate linear speed, and half linear speed. In the overall calibration process, the calibration processing unit 11 measures and updates the actual calibration values of high linear velocity, standard linear velocity, intermediate linear velocity, and half linear velocity. In this example, the actual calibration value means the calibration value set in the overall calibration process.

The high linear speed is the transport speed in the print mode of monochrome printing on standard paper. The standard linear speed is the transport speed in a print mode for printing in full color on standard paper. The intermediate linear speed is the transport speed in a print mode in which full color printing is performed on the thick paper 1. The half-linear speed is the transport speed in a print mode in which full color printing is performed on cardboard 2, which is thicker than cardboard 1. In the first embodiment, the standard linear speed is full-color printing that uses all CMYK color materials, including the K color material used in monochrome printing, and is the most frequently used linear speed as the standard in the conversion table. The reference linear speed is automatically selected.

In step S300, the calibration processing unit 11 executes conversion table generation processing. In the conversion table generation process, the calibration processing unit 11, in this example, calculates the ratio of the high linear velocity (D), intermediate linear velocity (B), and half linear velocity (C) to the standard linear velocity (A) (an example of a converted value). D/A, B/A, and C/A) are calculated to generate a conversion table. The conversion table is a table for converting a standard linear speed calibration setting value, which is a reference, into a high linear speed, intermediate linear speed, and half linear speed calibration setting value. In this example, the calibration settings are the high linear speed, intermediate linear speed, and half linear speed calibration settings, which are generated by converting the standard linear speed calibration measurements using a conversion table, and the standard linear speed calibration settings. This means the actual calibration value.

Thereby, the image forming apparatus 1 uses the actual calibration values as the calibration setting values in response to receiving a print job, for example, copying using the image reading unit 50 or receiving a print job from outside the image forming apparatus 1. Immediately, the image forming process can be performed, i.e., forming an image on a print medium (eg, standard paper). On the other hand, if a predetermined period of time (for example, 10 minutes of the image forming apparatus) has elapsed until the print job is received, the image forming apparatus 1 enters a sleep state. The image forming apparatus 1 returns from the sleep state in response to receiving the print job (step S400).

In step S500, the proofreading processing unit 11 determines whether proofreading is necessary before printing. This determination is made based on environmental changes, that is, changes in temperature and humidity within the image forming apparatus 1. In this example, the calibration processing unit 11 pre-prints when at least one of the temperature and humidity exceeds a predetermined threshold value (for example, a temperature of 5 degrees and a humidity of 5%) compared to the previous calibration process of the standard linear velocity. It is determined that calibration is necessary.

When the proofreading processing unit 11 determines that proofreading before printing is necessary, the process proceeds to step S600, and when it determines that proofreading before printing is not necessary, the process proceeds to step S700. On the other hand, the control unit 10 changes the target value of the temperature of the pair of fixing rollers 81 to a temperature at which image formation is possible, and starts increasing the temperature of the pair of fixing rollers 81. In this example, it is assumed that the image forming apparatus 1 receives a job for high linear speed printing, that is, monochrome printing on standard paper.

In the image forming process (step S700) that does not go through the pre-print proofing process, the proofing processing unit 11 executes the proofing process using the high linear velocity calibration setting value D′ as a calibration value, and the image forming unit 20 Monochrome printing on standard paper is started in response to completion of temperature rise of the pair of fixing rollers 81. The calibration set value D' is a calibration value calculated using the calibration actual measurement value A.

If the pre-print proofreading process is to be performed, in step S600, the proofreading processing unit 11 executes the pre-print proofreading process in parallel with raising the temperature of the pair of fixing rollers 81. In the pre-print proofreading process, the proofreading processing unit 11 executes a proofreading process for high linear speed, and measures and updates the actual measured value D of the high linear speed.

In the image forming process (step S700) after the pre-print proofing process, the calibration processing unit 11 executes the calibration process using the high linear velocity actual measurement value D as a calibration value, and the image forming unit 20 uses the fixing roller Monochrome printing on standard paper is started in response to completion of both the temperature increase and the pre-print proofing process of pair 81.

In step S800, the proofreading processing unit 11 determines whether post-print proofreading is necessary. This determination is made based on environmental changes, that is, changes in the temperature and humidity inside the image forming apparatus 1 and the number of printed sheets since the previous calibration. In this example, the calibration processing unit 11 performs the following operations when at least one of temperature and humidity exceeds a predetermined threshold value compared to the previous calibration process for the standard linear speed, and when printing from the previous calibration process for the standard linear velocity is performed. It is determined that post-print proofreading is necessary if at least one of the following conditions applies: the number of sheets exceeds a predetermined threshold. Note that after printing, that is, after image formation, means a state in which one print job is completed and there are no print jobs waiting.

Specifically, the calibration processing unit 11 determines whether at least one of the temperature and humidity exceeds a predetermined first threshold (for example, a temperature of 5 degrees and a humidity of 5%) compared to the previous calibration process of the standard linear velocity. If at least one of the following applies: the number of sheets printed since the previous standard linear speed calibration process exceeds a predetermined first threshold (for example, 100 sheets), It is determined that calibration is necessary.

Further, the calibration processing unit 11 determines that at least one of the temperature and humidity is a predetermined second threshold value (a threshold value larger than the first threshold value, for example, the temperature 10 If the number of sheets printed since the previous standard linear speed calibration exceeds a predetermined second threshold (for example, 500 sheets), It is determined that calibration is required for all three linear velocities. That is, when the second threshold value is exceeded, the calibration processing unit 11 determines that there is a possibility that the reliability of the conversion table (in this example, the conversion value) has been lost.

In step S900, the calibration processing unit 11 performs calibration of the "standard linear speed" or "all four linear speeds" based on the above-described determination. If there is no print job on standby, the image forming apparatus 1 returns to the sleep state after a predetermined period of time has elapsed. The image forming apparatus 1 continues such processing until the power is turned off (step S950).

In this way, the image forming apparatus 1 according to the first embodiment can immediately start the image forming process without executing the calibration process again if the environmental change is small, so that it is possible to suppress a decrease in productivity. . Furthermore, even if there is a large environmental change, the image forming apparatus 1 effectively utilizes the temperature rise time of the fixing roller pair 81 when returning from the sleep state to calibrate only the linear speed required for the print job. It is possible to suppress a decline in sexual performance. On the other hand, for significantly large environmental changes (including processing a significantly large number of prints), calibration for "all four linear speeds" is performed after the print job is completed (no print jobs are waiting). Therefore, it is possible to maintain the reliability of calibration using converted values while suppressing a decrease in productivity.

FIG. 7 is a flowchart showing the content of the print proofing process (step S600) according to the first embodiment. FIG. 8 is an explanatory diagram showing a light amount calibration patch and a bias voltage setting patch used in the image forming apparatus 1 according to the first embodiment. The light amount calibration patch is a patch used in the light amount calibration process (step S610). The bias voltage setting patch is a patch used in the development bias calibration process (step S620). In this example, half patch P80 is used as the patch for development bias correction processing.

In step S610, the calibration processing unit 11 executes a light amount calibration process. In the light intensity calibration process, the calibration processing unit 11 exposes the exposure unit 29 with laser light of a plurality of light intensities that are changed stepwise in a plurality of preset stages to create a chart having a plurality of light intensity calibration patches PL. It is formed on the intermediate transfer belt 27. Image data representing the light amount calibration patch PL is stored in the calibration data storage area 41 of the storage unit 40.

The calibration processing unit 11 exposes the photoreceptor drums 30c to 30k to a plurality of laser beams of different light intensities to form light intensity calibration patches PL. In this example, the light amount calibration patch PL has a dot area ratio of 25%, which is an appropriate dot area ratio for light amount calibration. The plurality of different amounts of light are 80%, 100%, 120%, and 140% (see FIG. 6(b)).

The calibration processing unit 11 uses the calibration density sensor 28 to measure the density of each color (for example, black (K)) patch. The calibration processing unit 11 performs, for example, interpolation calculation using the reflected light of a plurality of light intensity calibration patches PL exposed with a plurality of laser beams of different light intensities to achieve a preset target density. The actual calibration value is measured and updated as the calibration light amount (set value of exposure amount), which is the light amount.

FIG. 6(b) shows the contents of the entire calibration process (step S200). The calibration processing unit 11 obtains a value corresponding to the target concentration (target concentration 0.6) as the actual calibration value. Specifically, the calibration processing unit 11 calculates the actual calibration value D (120) of high linear velocity, the actual calibration value A (110) of standard linear velocity, the actual calibration value B (100) of intermediate linear velocity, and the actual calibration value B (100) of half linear velocity. The actual calibration value C (93) is measured and updated. The calibration processing unit 11 stores the calibration light amount in the calibration data storage area 41 of the storage unit 40 .

In this embodiment, the calibration concentration sensor 28 emits infrared light from, for example, an LED (not shown), passes through a polarizing filter that transmits only P waves, and irradiates the patch with the P waves of the infrared light. , the density is detected based on the ratio of P waves and S waves of the reflected light detected by the light receiving element. Note that the calibration density sensor 28 may be of a specular reflection type that detects specularly reflected light from a patch or a diffuse reflection type that detects diffusely reflected light from a patch.

In step S620, the calibration processing unit 11 executes development bias calibration processing. In the development bias calibration process, the calibration processing unit 11 uses the half patch P80 and transfers a chart having a plurality of patch images in which the development bias potential Vslv is changed stepwise at a plurality of preset stages to the intermediate transfer belt 27. to form. The half patch P80 is a patch having a dot area ratio of 80%, which is preset as a result of a trade-off between the occurrence of jaggies and the occurrence of trailing edge pooling due to a decrease in the dot area ratio, for example.

FIG. 9 is an explanatory diagram showing the contents of the developing bias positive processing according to the first embodiment. The reason for using a plurality of patch images in which the developing bias potential Vslv is changed stepwise is that the toner image is formed by changing the potential of the electrostatic latent image on the surface of the photoreceptor drum 30 and the developing bias potential Vslv applied to the developing roller 144. This is because it is formed based on a potential difference. A plurality of half-patches are formed for each of CMYK. In the following, a cyan (C) half patch will be explained as an example.

Specifically, the calibration processing unit 11 performs, for example, interpolation calculation using a plurality of cyan (C) half patches in which the developing bias potential Vslv is changed in four stages of 100V, 200V, 300V, and 400V. The actual calibration value is measured and updated as a calibration bias potential (set value of bias potential), which is a bias potential that can be executed to achieve a preset target density.

FIG. 9(b) shows the contents of the overall calibration process (step S620). The calibration processing unit 11 measures and updates a value that is a target concentration (target concentration) as an actual calibration value. Specifically, the calibration processing unit 11 calculates the actual calibration value D (300) of high linear velocity, the actual calibration value A (250) of standard linear velocity, the actual calibration value B (200) of intermediate linear velocity, and the actual calibration value B (200) of half linear velocity. The actual calibration value C (167) is measured and updated. The calibration processing unit 11 stores the calibration development bias potential in the calibration data storage area 41 of the storage unit 40 .

In step S630, if the calibration of the half patch is possible within the adjustment range of the development bias, the calibration processing unit 11 advances the process to step S650, and if the calibration of the half patch is possible within the adjustment range of the development bias potential Vslv. If it is not possible, the process advances to step S640.

If half patch calibration is not possible within the development bias adjustment range, it means that there is no patch among the multiple cyan (C) patches that has reached the preset solid image target density. ing. Normally, one of the plurality of half patches reaches the solid image target density, but the solid image target density may not be reached in a state where the amount of toner charge increases due to environmental changes, for example.

FIG. 10 is a flowchart showing the contents of the dot area ratio adjustment process (step S640) according to the first embodiment. In step S641, the calibration processing unit 11 sets the development bias potential Vslv to the maximum value, adjusts the dot area ratio, and starts calibration processing. The maximum value of the developing bias potential Vslv is also called a potential limit value, and is set (for example, 400 V) from the viewpoint of the output limit of the developing bias and adverse effects (fogging, etc.) on images.

In step S642, the proof processing unit 11 forms, on the intermediate transfer belt 27, a chart having a plurality of half patch images whose dot area ratios are changed in stages.

In step S643, the calibration processing unit 11 executes concentration measurement processing. In the density measurement process, the calibration processing unit 11 measures the density of the cyan (C) patch image with the calibration density sensor 28 using the adjustment data. The calibration concentration sensor 28 detects the ratio of P waves and S waves. Similar processing is performed for MYK.

In step S644, the calibration processing unit 11 executes dot area ratio setting processing. Specifically, when there is a half patch in which the ratio of P waves and S waves is less than or equal to a preset threshold, the calibration processing unit 11 selects a half patch with the lowest dot area ratio among the half patches. Obtain the dot area ratio of as calibration data.

In step S650 (see FIG. 7), the calibration processing unit 11 executes gamma setting processing using the gamma adjustment patch. As a result, the calibration processing unit 11 linearly converts the output gradation value as an image density from 0 to 255 (density 0% to 100%) to the input gradation value from 0 to 255 (density 0% to 100%). You can set the input and output gamma to achieve this.

FIG. 11 is an explanatory diagram showing a gamma adjustment patch used in the gamma correction process according to the first embodiment. The gamma adjustment patches are half patch P20 with 20% dot area, half patch P40 with 40% dot area, half patch P60 with 60% dot area, half patch P80 with 80% dot area, and solid patch P100 with 100% dot area. have. This embodiment is configured such that the density measurement value is saturated at 255 gradations of solid (solid image target density) at half patch P80, so gamma calibration processing is performed using half patch P20 to half patch P80. It will be executed.

In step S<b>660 , the calibration processing unit 11 acquires calibration data as the adjusted dot area ratio and the maximum value of the development bias potential Vslv, and stores it in the calibration data storage area 41 of the storage unit 40 .

In this way, the image forming apparatus 1 according to the first embodiment can immediately start the image forming process without executing the calibration process again if the environmental change is small, so that it is possible to suppress a decrease in productivity. . Furthermore, even if there is a large environmental change, the image forming apparatus 1 effectively utilizes the temperature rise time of the fixing roller pair 81 when returning from the sleep state to calibrate only the linear speed required for the print job. It is possible to suppress a decline in sexual performance.

Furthermore, even if there is a relatively large environmental change that exceeds the first threshold, the calibration for "one of the four linear speeds" is performed, and the conversion value is used to calibrate the "four linear speeds". Since it is possible to calibrate three of the three linear velocities, it is possible to maintain image quality while suppressing a decrease in productivity. On the other hand, for a significantly large environmental change that exceeds a second threshold (which is larger than the first threshold) (including processing a significantly large number of prints), after the print job is completed (the waiting print job Since the calibration is performed for "all four linear velocities" (without any), it is possible to maintain the reliability of the calibration using converted values while suppressing a decrease in productivity.

Note that if a print job is received while the computer is not in sleep mode, it is extremely unlikely that a large environmental change has occurred because a long time has not passed since the previous print job was completed. . Therefore, the image forming apparatus 1 according to the first embodiment executes the minimum amount of proofreading processing by effectively utilizing the time required to return from the sleep state, thereby realizing an effective sequence of proofreading processing and print processing. There will be.

B. Second embodiment:
FIG. 12 is an explanatory diagram showing the contents of the light amount calibration process according to the second embodiment. The image forming apparatus 1 according to the second embodiment is different from the first embodiment in that the standard linear velocity is automatically set as the reference linear velocity in the first embodiment, whereas the reference linear velocity can be freely selected in the user settings. It is different from the form. FIG. 12A shows an example in which the half linear velocity is used as the reference linear velocity as an example of the light amount calibration value in the second embodiment. FIG. 12(b) shows an example in which the half linear velocity is used as the reference linear velocity as an example of the bias potential calibration value in the second embodiment. The image forming apparatus 1 according to the second embodiment accepts selection of a reference linear velocity via the operation display section 90.

The second embodiment is particularly suitable when it is assumed in advance that the image forming apparatus 1 will be mainly used at a specific linear speed. In this example, it is assumed that the user installs the image forming apparatus 1 to create a poster by printing in full color on thick paper 2, and makes it available for other uses (line speed) as needed. The user can use the operation display section 90 of the image forming apparatus 1 to select the half linear velocity as the reference linear velocity.

Furthermore, the user can also set a password if necessary. Specifically, the operation display unit 90 accepts the registration of a password for changing the selection of the reference linear speed, and after the registration, changes the reference linear speed according to the input of a password that matches the registered password. Can accept selections. This can prevent a situation where the selection of the reference linear velocity is changed against the user's intention.

In response to receiving the selection of the reference linear velocity, the calibration processing unit 11 determines whether or not the selection results in a change in the reference linear velocity. If the calibration processing unit 11 determines that the reference linear velocity is to be changed, it causes the operation display unit 90 to display a screen (not shown) for accepting permission to calibrate the changed reference linear velocity. Upon receiving permission to perform calibration, the calibration processing unit 11 immediately executes calibration of the reference linear velocity. In addition, depending on the user input, the conversion value may be generated by performing calibration of other linear speeds in addition to the calibration of the standard linear speed, or the conversion value from the changed standard linear speed may be It may be calculated from the converted value of .

In this example, the image forming apparatus 1 according to the second embodiment can perform half linear velocity calibration preferentially. As a result, the present image forming apparatus 1 realizes efficient printing processing with top priority given to the image quality and productivity of printing the poster described above, while allowing printing at other linear speeds while suppressing proofing processing. be able to. In this way, the image forming apparatus 1 according to the second embodiment can suppress the calibration process while improving the image quality of printing at a specific linear speed according to the user settings.

C. Third embodiment:
FIG. 13 is a flowchart showing the details of image forming apparatus control processing according to the third embodiment. In the image forming apparatus 1 according to the third embodiment, the content of the pre-print proofreading necessity determination (step S500) of the first embodiment is changed, and a print job analysis process (step S450) is added before that. This embodiment is different from the first embodiment in that it is different from the first embodiment, but it is common in other configurations.

In the print job analysis process (step S450), the control unit 10 functions as a job analysis unit and analyzes the content of the print job. Specifically, the proof processing unit 11 analyzes and identifies the number of prints and the contents of the image quality setting, and determines whether the number of prints exceeds a preset threshold number of sheets and whether the image quality setting is set to the highest image quality. Determine whether or not there is.

In the pre-print proofreading necessity determination (step S500a), the linear speed used in executing the print job is specified, the determination is made that the number of prints exceeds a preset number, and the image quality setting is selected among multiple image quality settings. If at least one of the judgments is made that the image quality is set to the highest image quality in conduct.

The image forming apparatus 1 according to the third embodiment is preferably configured to accept selection of the threshold number of sheets for each linear velocity via the operation display section 90. This allows the user to set the threshold for each linear speed, such as 1000 sheets for monochrome printing (high linear speed), 100 sheets for full color printing (standard paper), and 50 sheets for full color printing (thick paper 1 and thick paper 2). You can set the number of sheets. In this manner, the image forming apparatus 1 according to the third embodiment can individually and specifically improve the image quality of printing at a specific linear velocity while suppressing the calibration process.

D. Variant:
The present invention can be implemented not only in the above embodiment but also in the following modifications.

Modification 1: In the above embodiment, one of the four linear speeds is set as the reference linear speed, and the calibration values of all the other (three) linear speeds are converted from the reference linear speed calibration value. However, it is not necessary to be able to perform calibrations for all other linear speeds using the converted values; at least one linear speed calibration setting must be generated from the reference setting. Anything that can be converted is fine.

The image forming apparatus 1 may be configured to be able to automatically set a convertible linear speed among all other linear speeds according to the frequency of use. Specifically, for example, the most frequently used linear speed is set as the reference linear speed, and the converted value is used to calibrate the linear speed that is used more than a preset frequency (for example, when the number of printed sheets is 5% or more). You may also be able to use it to run it.

Modification 2: Although an amorphous silicon photoreceptor is used in the above embodiment, the present invention is not limited to the use of an amorphous silicon photoreceptor. The present invention can be applied to an image forming apparatus that uses an organic photoconductor (OPC).

1 Image forming apparatus 10 Control section 11 Calibration processing section 20 Image forming section 21 Color conversion processing section 28 Density sensor for calibration 29 Exposure section 40 Storage section 50 Image reading section 60 Paper cassette 70 Housing

Claims (7)

a developing section having a photoreceptor;
an intermediate transfer belt that transfers toner from the photoreceptor at a plurality of conveying speeds and transfers the transferred toner onto an image forming medium;
a density sensor that measures the density of the toner transferred to the intermediate transfer belt;
an operation display unit that accepts selection of a reference linear speed that is one of the plurality of transport speeds;
A reference setting value that is a calibration setting value of the reference linear velocity selected via the operation display section, and at least one line other than the reference linear velocity among the plurality of transport speeds using the reference linear velocity. a storage unit that stores a conversion value for converting and generating a speed calibration setting value from the reference setting value;
When forming an image at the standard linear speed, the developing section is adjusted using the standard setting value, and when forming an image at a linear speed other than the standard linear speed, adjusting the developing section using the standard setting value. a calibration processing section that adjusts the developing section using the converted value;
Equipped with
In response to receiving the selection of the reference linear velocity, the calibration processing unit determines whether the selection results in a change in the reference linear velocity, and if it is determined that the selection is a change in the reference linear velocity, An image forming apparatus that measures the density of the toner at the reference linear velocity and updates the reference setting value based on the measurement. The image forming apparatus according to claim 1,
The operation display unit accepts registration of a password for changing the selection of the reference linear speed, and after the registration, selects the reference linear speed in response to input of a password that matches the registered password. Image forming device that accepts. The image forming apparatus according to claim 1 or 2,
When the environmental change since the previous calibration exceeds a first threshold, the calibration processing unit measures the toner concentration at the reference linear velocity, and adjusts the reference setting value based on the measurement. updating, and if the environmental change exceeds a second threshold value larger than the first threshold value after image formation, measuring the density of the toner at a linear velocity other than the reference linear velocity; An image forming apparatus that generates the converted value based on measurement, and stores the updated reference setting value and the generated converted value in the storage unit. The image forming apparatus according to claim 3,
In the image forming apparatus, the calibration processing section updates the reference setting value before the image formation if the environmental change exceeds the first threshold before the image formation. The image forming apparatus according to claim 4, further comprising:
a fixing unit that performs a fixing process for fixing the toner transferred from the intermediate transfer belt to an image forming medium;
The image forming apparatus can be put into a sleep state in which the temperature of the fixing section is controlled to a temperature lower than the temperature required for the fixing process,
In the image forming apparatus, the calibration processing unit updates the reference setting value when returning from the sleep state if the environmental change exceeds the first threshold before the image formation. An image forming method using a developing section having a photoreceptor, and an intermediate transfer belt that transfers toner from the photoreceptor at a plurality of conveyance speeds and transfers the transferred toner onto an image forming medium, the method comprising:
a density measurement step of measuring the density of the toner transferred to the intermediate transfer belt;
an operation display step of accepting a selection of a reference linear speed that is one of the plurality of transport speeds;
A reference setting value that is a calibration setting value of the reference linear velocity selected through the operation display step, and at least one line other than the reference linear velocity among the plurality of transport speeds using the reference linear velocity. a storage step of storing a converted value for generating a speed calibration setting value by converting it from the reference setting value;
When forming an image at the standard linear speed, the developing section is adjusted using the standard setting value, and when forming an image at a linear speed other than the standard linear speed, adjusting the developing section using the standard setting value. a calibration processing step of adjusting the developing section using the converted value;
Equipped with
In the calibration processing step, in response to receiving the selection of the reference linear velocity, it is determined whether the selection is a change in the reference linear velocity, and if it is determined that the selection is a change in the reference linear velocity, An image forming method that measures the density of the toner at the reference linear velocity and updates the reference setting value based on the measurement. a developing section having a photoreceptor; an intermediate transfer belt that transfers toner from the photoreceptor at a plurality of conveying speeds and transfers the transferred toner onto an image forming medium; An image forming program for controlling an image forming apparatus having a density sensor that measures density,
an operation display unit that accepts selection of a reference linear speed that is one of the plurality of transport speeds;
A reference setting value that is a calibration setting value of the reference linear velocity selected via the operation display section, and at least one line other than the reference linear velocity among the plurality of transport speeds using the reference linear velocity. a storage unit that stores a conversion value for generating a linear speed calibration setting value by converting it from the reference setting value, and when forming an image at the reference linear velocity, using the reference setting value to generate the When adjusting the developing section and forming an image at a linear velocity other than the reference linear velocity, the image forming apparatus functions as a calibration processing section that adjusts the developing section using the reference setting value and the conversion value. function,
In response to receiving the selection of the reference linear velocity, the calibration processing unit determines whether or not the selection results in a change in the reference linear velocity, and if it is determined that the selection is a change in the reference linear velocity, An image forming apparatus that measures the density of the toner at the reference linear velocity and updates the reference setting value based on the measurement. Image formation program.

Images