Image formation apparatus

Abstract

To suppress an increase in deteriorated toner in an image formation unit that does not perform image formation during printing.SOLUTION: An image formation apparatus 1 comprises: a first image formation unit 10, which is one of the image formation units 10 that rotates a photosensitive drum 14 to perform image formation in black; a second image formation unit 10, which is the other of the image formation units 10 that rotates the photosensitive drum 14 to perform image formation in black; a waste dot count calculation unit 53 that calculates deteriorated toner generated in the first image formation unit 10 and the second image formation unit 10; and a print management unit 50 that selects one of the first image formation unit 10 and the second image formation unit 10 to perform image formation on the basis of the value of the deteriorated toner when the photosensitive drum 14 of the image formation unit 10 of the first image formation unit 10 or the second image formation unit 10 which does not perform image formation, is in a rotating state.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, and is suitable for application to an image forming apparatus that forms an image by transferring a developer image onto a recording medium. [Background technology]

[0002] In conventional electrophotographic image forming devices, repeated printing using toner results in an insufficient density of toner consumed for the printed image during the printing operation, which causes the toner to come into contact with a member charged to a high voltage for a long period of time, resulting in the generation of degraded toner in the developing device within the image forming unit. Because this degraded toner is a cause of a decrease in image quality, the image forming device discards the degraded toner in the developing device onto the photosensitive drum and collects it in a waste toner collection container within the image forming unit, thereby disposing of the degraded toner.

[0003] Furthermore, when the print data coverage is high, the toner is developed before it deteriorates, making it less likely that degraded toner will be produced. In response to this, an image forming device has been proposed that discards degraded toner by changing the image forming unit used during printing depending on the print data coverage, i.e., the amount of toner consumed during printing (see, for example, Patent Document 1).

[0004] In addition, in some image forming devices, the photosensitive drum in the image forming unit can be moved up and down so as to abut against or separate from the transfer roller, and can be switched between a transfer position in which the photosensitive drum abuts against the transfer roller and a non-transfer position in which the photosensitive drum is separated from the transfer roller. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-160358 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in an image forming device, if an image forming unit that is not performing image formation during printing is not separated from the transfer roller and an image is formed by another image forming unit, there is a problem in that the amount of degraded toner in the image forming unit that is not performing image formation increases.

[0007] The present invention has been made in consideration of the above points, and aims to propose an image forming apparatus that can prevent an increase in degraded toner in an image forming unit that does not form an image during printing. [Means for solving the problem]

[0008] In order to solve this problem, the image forming apparatus of the present invention is provided with a first image forming unit that rotates a first photosensitive drum to form an image in a first color, a second image forming unit that rotates a second photosensitive drum to form an image in the first color, a calculation unit that calculates the amount of deteriorated toner generated in the first image forming unit and the second image forming unit, and a control unit that, when the photosensitive drum of either the first image forming unit or the second image forming unit that is not performing image formation is rotating, selects either the first image forming unit or the second image forming unit based on the value of the deteriorated toner and causes it to perform image formation.

[0009] As a result, the present invention can reduce the cumulative value of deteriorated toner in an image forming unit with a large cumulative value of deteriorated toner by preferentially using the image forming unit with a large cumulative value of deteriorated toner to form an image, even if the photosensitive drum of an image forming unit not used for image formation is rotating during image formation in the image forming unit used for image formation. [Effects of the Invention]

[0010] According to the present invention, when forming an image in an image forming unit used for image formation, even if the photosensitive drum of an image forming unit not used for image formation is in a rotating state, the image forming unit with a large cumulative value of deteriorated toner is used preferentially to form the image, thereby reducing the cumulative value of deteriorated toner in the image forming unit with a large cumulative value of deteriorated toner, and thus realizing an image forming device that can suppress an increase in deteriorated toner in image forming units that do not form images during printing. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a left side view showing the overall configuration of an image forming apparatus. [Figure 2] FIG. 2 is a left side view showing the configuration of the image forming unit. [Figure 3] FIG. 2 is a block diagram showing a control configuration of the image forming apparatus. [Figure 4] FIG. 10 is a diagram showing a deteriorated toner discarding pattern. [Figure 5] 10 is a flowchart illustrating a printing process procedure. [Figure 6] 10 is a flowchart showing a procedure for determining the order of image forming units to be used. [Figure 7] 10 is a table illustrating a procedure for determining the order of image forming units to be used; DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0013] [1. Overall configuration of image forming device] As shown in FIG. 1, image forming apparatus 1 is a color electrophotographic printer that prints a desired color image on paper P, which is a leaf-like medium. This image forming apparatus 1 has various components arranged inside a roughly box-shaped housing 2. In the following description, the right-hand end of FIG. 1 is defined as the front of image forming apparatus 1, and the up-down, left-right, and front-rear directions are defined when viewed from the front. Image forming apparatus 1 is controlled by a control unit 40. Image forming apparatus 1 is also connected wirelessly or wired to a host device (not shown) such as a computer. When a print job representing an image to be printed is provided from the host device and printing of the print job is instructed, control unit 40 executes a print process to form a print image on the surface of paper P.

[0014] A paper feed cassette 3 that stores paper sheets P is provided at the bottom of the housing 2. A pickup roller 4 is provided above and in front of the paper feed cassette 3. The pickup roller 4 has its lower portion in contact with the upper surface of the paper sheets P stored in the paper feed cassette 3, and rotates to send the uppermost sheet of paper sheets P stored therein forward.

[0015] A transport path W for transporting paper P is formed inside the housing 2. A plurality of transport rollers 5a, 5b, 5c, 5d, 5e, 5f, 5g, and 5h (hereinafter collectively referred to as transport rollers 5) are also provided inside the housing 2. The transport rollers 5 are made up of a plurality of rollers that face and contact each other across the transport path W, and transport paper P on the transport path W by rotating in a predetermined direction.

[0016] Additionally, multiple media detection sensors 6a, 6b, 6c, 6d, 6e, 6f, and 6g (hereinafter collectively referred to as media detection sensors 6) are installed inside the housing 2 at multiple locations along the conveyance path W. The media detection sensors 6 detect the presence or absence of paper P on the conveyance path W and notify the control unit 40. Based on this, the control unit 40 can recognize the presence or absence of paper P at the location on the conveyance path W where each media detection sensor 6 is installed, i.e., can grasp the position of paper P on the conveyance path W. Therefore, based on the detection results obtained from each media detection sensor 6, the control unit 40 can appropriately print an image based on image data on one or both sides of the paper P while appropriately controlling the conveyance of paper P and the operation timing of each module, and can also detect delays in paper conveyance, paper jams, etc.

[0017] Furthermore, an environmental temperature sensor 7 that measures temperature and humidity, and a belt thermistor 8 that measures the temperature of a transfer belt 21 (described later) are provided inside the housing 2. The temperature measured by the belt thermistor 8 is used as the temperature inside the housing 2.

[0018] Also provided within the housing 2 is an image forming section 9 for forming a print image by printing a color image of the print target on the surface of the paper P. The image forming section 9 comprises three image forming units 10 (image forming units 10a, 10b, and 10c) arranged in order from the front side (upstream side) to the rear side (downstream side) at the top end of the housing 2. The image forming units 10 develop electrostatic latent images representing black (K), which is a similar color component of the print image, using toner as a developer to form a toner image corresponding to the print data.

[0019] The image forming units 10a, 10b, and 10c are configured identically and use the same color toner to develop electrostatic latent images. For this reason, hereinafter, the image forming units 10a, 10b, and 10c will be collectively referred to as image forming unit 10. As shown in FIG. 2, the image forming unit 10 is made up of a toner cartridge 18, a print head 11, and a developing device 19.

[0020] The toner cartridge 18 is disposed above the developing device 19, contains toner, and is configured to be detachable from the developing device 19. The developing device 19 includes a supply roller 12, a developing roller 13, a photosensitive drum 14, a charging roller 15, a cleaning blade 16, and a drum waste toner collection container 17.

[0021] The print head 11 is an LED (Light Emitting Diode) head, and is provided adjacent to the upper side of the photosensitive drum 14. A plurality of LED elements are aligned in the left-right direction, and each LED element is turned on or off under the control of the control unit 40. The print head 11 exposes the surface of the photosensitive drum 14, which has been charged by the application of a charging bias voltage, which is a negative voltage, based on print data, to form an electrostatic latent image.

[0022] A supply bias voltage, which is a negative voltage, is applied to the supply roller 12, which supplies toner contained in a toner cartridge 18 to the developing roller 13. The charging roller 15 uniformly charges the surface of the photosensitive drum 14 to a negative voltage. A development bias voltage, which is a negative voltage, is applied to the developing roller 13, which charges the toner and electrostatically attaches it to the electrostatic latent image formed on the photosensitive drum 14, thereby forming a toner image of a certain thickness. The photosensitive drum 14 carries the electrostatic latent image and also carries a toner image obtained by developing the electrostatic latent image with toner.

[0023] The cleaning blade 16 is a blade made of urethane rubber that comes into contact with the photosensitive drum 14 downstream of the contact position with the transfer roller 22 (described later) in the rotation direction of the photosensitive drum 14 to scrape off and remove residual toner and waste toner remaining on the surface of the photosensitive drum 14 during the printing process and during the disposal of deteriorated toner, which will be described later. The drum waste toner collection container 17 is a container that collects and stores the residual toner and waste toner removed by the cleaning blade 16. This drum waste toner collection container 17 is integrated with the developing device 19, and when the drum waste toner collection container 17 becomes full, the developing device 19 needs to be replaced. The developing device 19 also needs to be replaced when the photosensitive drum 14 reaches the end of its life.

[0024] In addition, in the image forming section 9 (FIG. 1), a transfer unit 20 is arranged from below the image forming unit 10a to below the image forming unit 10c, which transfers the toner images formed by the image forming units 10a, 10b, and 10c onto the surface of the paper P. The transfer unit 20 is composed of a transfer belt 21, a transfer roller 22 (FIG. 2), a belt cleaning blade 23, and a belt waste toner collection container 24.

[0025] The transfer belt 21 is an endless belt that carries the paper P on its upper surface and transports it rearward. Three transfer rollers 22 (FIG. 2) are rotatably provided inside the transfer belt 21, corresponding to the three photosensitive drums 14, facing the image forming unit 10, and a positive transfer bias voltage is applied to the transfer rollers 22. As a result, when forming a print image, the transfer unit 20 pinches the paper P carried by the transfer belt 21 between the upper portion of the surface of the transfer roller 22 and the lower portion of the surface of the corresponding three photosensitive drums 14, and transfers the toner image on the surfaces of the four photosensitive drums 14 to the surface of the paper P by applying the transfer bias voltage to the transfer roller 22.

[0026] The belt cleaning blade 23 is a blade made of urethane rubber, and by contacting the transfer belt 21, it scrapes off and removes waste toner carried by the transfer belt 21 when discarding degraded toner. The belt waste toner collection container 24 is a container that collects and stores the waste toner removed from the transfer belt 21 by the belt cleaning blade 23. This belt waste toner collection container 24 is integrated with the transfer unit 20, and when the belt waste toner collection container 24 becomes full, the transfer unit 20 needs to be replaced. The transfer unit 20 also needs to be replaced when the transfer belt 21 reaches the end of its life.

[0027] In this configuration, the image forming unit 10 supplies toner from the toner cartridge 18 to the developing device 19. Next, while rotating the photosensitive drum 14, the image forming unit 10 uniformly charges the surface of the photosensitive drum 14 using the charging roller 15, and exposes the surface of the photosensitive drum 14 using the print head 11 based on print data to form an electrostatic latent image. Next, the image forming unit 10 applies a development bias voltage to the developing roller 13, thereby electrostatically attaching toner supplied by the supply roller 12 to the electrostatic latent image formed on the photosensitive drum 14, thereby forming a toner image. Furthermore, the image forming unit 10 sandwiches the paper P transported by the transfer belt 21 between the transfer roller 22 and the photosensitive drum 14, and transfers the toner image on the surface of the photosensitive drum 14 to the surface of the paper P. In this way, the transfer unit 20 transfers a single black toner image onto the surface of the paper P, and then passes the paper P with the transferred toner image to the fixing unit 26.

[0028] The image forming section 9 is provided with a fixing unit 26, which fixes the toner image to the surface of the paper P, behind the transfer unit 20. The fixing unit 26 has a paper path for passing the paper P, located approximately in the vertical center. The fixing unit 26 also has a heating roller 27 rotatably mounted above the paper path and a pressure roller 28 rotatably mounted below the paper path. Thus, when forming a print image, the fixing unit 26 takes the paper P, onto whose surface the toner image has been transferred from the transfer unit 20, into the paper path and sandwiches it between the heating roller 27 and the pressure roller 28, which rotate in opposite directions. The fixing unit 26 then fixes the toner image to the surface of the paper P by applying heat and pressure between the heating roller 27 and the pressure roller 28, which rotate in opposite directions. The fixing unit 26 fixes the black toner image to the surface of the paper P to form a print image, and delivers the paper P with the printed image formed thereon to the discharge unit 30 above or the duplex printing unit 31 below.

[0029] In this configuration, the image forming apparatus 1 transports paper P stored in a paper feed cassette 3 to the image forming unit 9 using transport rollers 5a, 5b, and 5c. In the image forming unit 9, toner is transferred onto the paper P using an image forming unit 10 while the paper P is transported using a transfer belt 21. The paper P is transported to a fixing unit 26 by the transfer belt 21. As the paper P passes through the fixing unit 26, the toner on the paper P is fixed to the paper P by high temperature. The transport direction of the paper P is switched, and the paper P is transported to an ejection unit 30 and then discharged to a media collection tray 32, or is transported to a duplex printing unit 31. The paper P transported to the duplex printing unit 31 is transported again to the image forming unit 9, where an image is formed on the opposite side of the paper, and the paper P passes through the fixing unit 26 again before being discharged to the media collection tray 32.

[0030] The image forming apparatus 1 does not have a mechanism for moving the photosensitive drum 14 in the image forming unit 10 up and down so as to contact or separate it from the transfer roller 22, thereby simplifying the configuration.

[0031] [2. Control configuration of image forming device] As shown in FIG. 3, the image forming apparatus 1 is composed of a control unit 40, a memory unit 42, a display unit 44, an input unit 46, an image forming unit 9, and a communication unit 48, and the control unit 40 controls the entire image forming apparatus 1.

[0032] [2-1. Control Unit Configuration] The control unit 40 is configured around a CPU (Central Processing Unit) not shown, and controls each unit to perform various processes by reading and executing predetermined programs from a program storage unit 81 in the memory unit 42. The control unit 40 also has a print management unit 50, a dot count calculation unit 51, a deteriorated toner disposal determination unit 52, a waste dot count calculation unit 53, a deteriorated toner disposal execution unit 54, a waste dot count update unit 55, and a used image forming unit order determination unit 56.

[0033] When the print management unit 50 receives a print instruction from the outside, it instructs the deteriorated toner disposal determination unit 52 to perform the deteriorated toner disposal process described below, then executes printing, and then instructs the waste dot count calculation unit 53 to calculate the waste dot count.

[0034] The dot count calculation unit 51 calculates the dot count for each image forming unit 10 due to printing, and also calculates a page-by-page dot count 68, which is the dot count for each page in the print job.

[0035] The deteriorated toner disposal determination unit 52 determines whether or not to perform deteriorated toner disposal for each image forming unit 10 by performing the deteriorated toner disposal process described below, and instructs the deteriorated toner disposal execution unit 54 to perform deteriorated toner disposal for the image forming unit 10 for which it has been determined that deteriorated toner disposal should be performed.

[0036] The waste dot count calculation unit 53 calculates a waste dot count 64 (described later) based on the dot count 61 and the drum count advance during printing 62, and updates the waste dot count 65 by adding the waste dot count 64 to the total waste dot count 65.

[0037] The deteriorated toner disposal execution unit 54, which functions as a disposal unit, executes the deteriorated toner disposal of the image forming unit 10 instructed by the deteriorated toner disposal determination unit 52 when the cumulative disposal dot count 65 calculated by the disposal dot count calculation unit 53 reaches the deteriorated toner disposal execution dot count 83. Specifically, the deteriorated toner disposal execution unit 54 instructs the print head 11 to emit LED light to form an electrostatic latent image of a deteriorated toner disposal pattern Ptd, for example, as shown in FIG. 4, on the surface of the photosensitive drum 14 charged by the charging roller 15. The deteriorated toner disposal pattern Ptd is an electrostatic latent image pattern with a printing rate (print duty) of 50% that repeats 1, 0, 1, 0 ... in the main scanning direction dm (left and right direction), and is formed across a range from one end to the other end in the main scanning direction dm of the image formation area, which is the area in which the image forming device 1 can form one page's worth of image in the printed result.

[0038] Here, the printing rate is the ratio of the area of ​​the image actually formed on the paper P to the area when a solid image is formed in the image formation area when viewed on one page of the paper P, and when viewed on one print job, it is the average printing rate of all pages included in one print job. In other words, when viewed on one page, the printing rate is the ratio of the count value of actually printed dots to the case where dots are formed on the entire surface of an area within a specified area on the paper P, where the state where dots are formed on the entire surface of an area within a specified area on the paper P is taken as 100%.

[0039] When the discarded toner is discarded, the discarded dot count updating unit 55 as an updating unit subtracts the discarded toner discard execution dot count 83 of the amount of the deteriorated toner used in the current discard of the deteriorated toner from the discarded dot count cumulative 65, thereby updating the discarded dot count cumulative 65 of the image forming unit 10 that has discarded the deteriorated toner.

[0040] The image forming unit use order determination section 56 determines the image forming unit 10 that will perform image formation during printing for each page, and updates the image forming unit use order management data 67 .

[0041] [2-2. Memory Configuration] The storage unit 42 includes a RAM (Random Access Memory) 60, a ROM (Read Only Memory) 80, and a flash memory (not shown).

[0042] [2-2-1. RAM configuration] The RAM 60 stores a dot count 61, a drum count advance during printing 62, a discard threshold dot count 63, a discard dot count 64, a discard dot count cumulative total 65, a predicted discard dot count cumulative total 66, image forming unit order management data 67, a page-by-page dot count 68, a page-by-page printing drum count advance 69, and a page-by-page discard dot count 70.

[0043] The dot count 61 indicates the dot count for each image forming unit 10 during printing. The dot count is the number of lit dots (number of pixels) when dots are formed by the print head 11. In other words, the dot count is the toner amount converted into a value in dot units, which are the exposure units of the print head 11.

[0044] The drum count advance during printing 62 indicates the advance of the drum count for each image forming unit 10 due to printing. The drum count is a measurement of the number of rotations (printing distance) of the photosensitive drum 14. In other words, the drum count is the usage count of the photosensitive drum 14 for each image forming unit 10. For example, one drum count is one-third the amount of drum rotation when three A4 sheets are printed consecutively.

[0045] The waste threshold dot count 63 indicates the dot count at the waste threshold (degraded toner waste slice value 82) for each image forming unit 10. The waste dot count 64 is calculated based on the dot count and indicates the degree of accumulation of degraded toner. This waste dot count 64 is added to the cumulative waste dot count 65, which is a cumulative value, for each print. The cumulative waste dot count 65 indicates the cumulative value of the waste dot count 64, and the waste dot count 64 is added for each print.

[0046] The predicted total discard dot count value 66 is a predicted total discard dot count value during printing in each image forming unit 10, and is a value that is updated for each page. The predicted total discard dot count value 66 is used to determine the image forming unit usage order management data 67.

[0047] The image forming unit usage order management data 67 is data that manages the order of the image forming units 10 used for each page in one print job. For example, if the image forming unit usage order management data 67 describes image forming unit 10a → image forming unit 10b → image forming unit 10c, the image forming apparatus 1 will print the first page of this print job using image forming unit 10a, the second page using image forming unit 10b, and the third page using image forming unit 10c.

[0048] The page dot count 68 indicates the dot count for each page. The page printing drum count advance 69 indicates the advance of the drum count for each page. The page waste dot count 70 indicates the waste dot count for each page. This page waste dot count 70 is added to the waste dot count cumulative predicted value 66 for each page.

[0049] [2-2-2. ROM configuration] The ROM 80 includes a program storage section 81, a deteriorated toner discard slice value 82, and a deteriorated toner discard execution dot count 83.

[0050] The degraded toner discard slice value 82 is used as a threshold value for determining degraded toner when calculating the discard dot count 64, which will be described later. The degraded toner discard slice value 82 also represents the print duty [%] per drum count.

[0051] Deteriorated toner disposal execution dot count 83 is used as a threshold value when determining whether or not to discard deteriorated toner. Specifically, deteriorated toner disposal is not performed until the total discard dot count 65 reaches the deteriorated toner disposal execution dot count 83. When the total discard dot count 65 reaches the deteriorated toner disposal execution dot count 83, the deteriorated toner disposal execution unit 54 discards deteriorated toner of the image forming unit 10 as instructed by the deteriorated toner disposal determination unit 52.

[0052] [2-3. Configuration of the display unit, input unit, image forming unit, and communication unit] The display unit 44 is made up of, for example, a liquid crystal display panel, and displays the status of the image forming apparatus 1. The input unit 46 is made up of, for example, a touch sensor or an operation keyboard, and detects input operations by the user.

[0053] The image forming unit 9 mainly includes a toner cartridge 18, a photosensitive drum 14, a charging roller 15, a print head 11, a supply roller 12, a developing roller 13, a cleaning blade 16, a transfer roller 22, and a fixing unit .

[0054] The communication unit 48 is an interface that executes wireless network communication using a wired LAN (Local Area Network) system or a wireless LAN system, and performs communication such as sending and receiving data with the outside.

[0055] [3. Disposal of Deteriorated Toner] Here, we will explain the disposal of deteriorated toner. The image forming unit 10 applies a negative voltage to the supply roller 12 and the development roller 13 to move toner supplied from the toner cartridge 18 to the photosensitive drum 14, but once the toner has been charged, it deteriorates over time. Furthermore, if the print duty is defined as the ratio of the print rate to the entire paper P, when high-duty printing (i.e., printing with a high print rate for the entire paper P) is common, once the toner has been charged it is used for printing quickly, so there is a high possibility that it will be used before it deteriorates. On the other hand, when low-duty printing (i.e., printing with a low print rate for the entire paper P) is common, once the toner has been charged it takes a long time to be used for printing, making it more likely that it will deteriorate.

[0056] For example, let's say the dot count when printing on A4 paper with a print duty of 5% is 792 dots (6,488,064 dots / 8192). This 6,488,064 dots is the actual dot count (amount of dots) when printing on A4 paper with a print duty of 5%. Also, 8192 is 2 to the 13th power. In this embodiment, the actual dot count is divided by 2 to the 13th power to reduce the dot count value to 792.

[0057] The deteriorated toner waste slice value 82 is then set to S. For example, if the dot count 61 in printing A is set to D and the printing drum count advance 62 in printing A is set to O, the waste dot count calculation unit 53 can calculate SL [%], which is the dot count (discard threshold dot count 63) at the waste threshold (deteriorated toner waste slice value 82) in printing A, by calculating SL [%] = 792 / 5 * S * O.

[0058] Thus, the waste dot count calculation unit 53 can calculate WL, which is the waste dot count (waste dot count 64) in printing A, by calculating WL=SL[%]-D.

[0059] For example, Degraded toner disposal slice value 82: S=1.5[%] Dot count for print A: 61: D=95.04 ·Drum count advances 62 when printing A: O=2 In this case, SL[%]=792 / 5*1.5*2=475.2, and WL=475.2-95.04=380.16.

[0060] In other words, the waste dot count 64 for print A is 380.16 dot counts. This waste dot count 64 is added to the total waste dot count 65, which is a cumulative value, for each print. Therefore, if the dot count 61 for print A is larger than the waste threshold dot count 63, the waste dot count 64 will be a negative value, and the value of the total waste dot count 65 will be small. On the other hand, if the dot count 61 for print A is smaller than the waste threshold dot count 63, the waste dot count 64 will be a positive value, and the value of the total waste dot count 65 will be large.

[0061] The degraded toner disposal execution dot count 83 is set to 831 dot count (6,809,088 dots / 8192 rounded to the nearest whole number). This 6,809,088 dots is 4992 (dots) * 1364 (lines), which is the dot count of the degraded toner disposal pattern Ptd shown in FIG. 4. 8192 is 2 to the 13th power. In this embodiment, as described above, the actual dot count is divided by 2 to the 13th power to reduce the dot count value to 831.

[0062] Here, 831 dot counts of the degraded toner disposal execution dot count 83 are defined as one unit of degraded toner disposal. Before printing, etc., the degraded toner disposal determination unit 52 checks whether the accumulated disposal dot count 65 has reached the degraded toner disposal execution dot count 83. If the accumulated disposal dot count 65 has reached the degraded toner disposal execution dot count 83, the degraded toner disposal execution unit 54 discards 831 dot counts of degraded toner. Here, an electrostatic latent image pattern is assumed to have a print rate of 50[%], repeating 1, 0, 1, 0 ... in the main scanning direction dm of the photosensitive drum 14, as shown in Figure 4.

[0063] [4. Printing process] Next, the specific processing procedure of the print processing by the control unit 40 will be described in detail using the flowcharts shown in Figures 5 and 6. When the image forming apparatus 1 is powered on, the control unit 40 starts the print processing procedure RT1 by reading and executing the print processing program from the storage unit 42, and proceeds to step SP1. In step SP1, the control unit 40 receives a print instruction together with a print job from the outside via the print management unit 50, and proceeds to step SP2.

[0064] In step SP2, control unit 40 instructs print management unit 50 to degraded toner disposal determination unit 52 to perform degraded toner disposal processing, which will be described later, and degraded toner disposal determination unit 52 determines for each image forming unit 10 whether there is an image forming unit 10 whose cumulative waste dot count 65 is equal to or greater than degraded toner disposal execution dot count 83 (i.e., cumulative waste dot count 65 ≥ degraded toner disposal execution dot count 83). If a negative result is obtained here, this means that the cumulative waste dot count 65 of all image forming units 10 is less than degraded toner disposal execution dot count 83 and has not accumulated to one unit, so degraded toner disposal will not be executed, and in this case control unit 40 skips steps SP3 and SP4 and proceeds to step SP5.

[0065] On the other hand, if a positive result is obtained in step SP2, this indicates that the cumulative discard dot count 65 is equal to or greater than the degraded toner discard execution dot count 83, and there is an image forming unit 10 in which one unit's worth of toner has accumulated, so it is necessary to discard degraded toner in that image forming unit 10, and in this case the control unit 40 proceeds to step SP3.

[0066] In step SP3, the control unit 40 instructs the deteriorated toner disposal determination unit 52 to the deteriorated toner disposal execution unit 54 to execute deteriorated toner disposal, and the deteriorated toner disposal execution unit 54 executes the deteriorated toner disposal of the image forming unit 10 whose cumulative disposal dot count 65 is equal to or greater than the deteriorated toner disposal execution dot count 83, and then the process proceeds to step SP4. In this deteriorated toner disposal, the image forming device 1 irradiates the surface of the photosensitive drum 14 with LED light so as to form an electrostatic latent image of the deteriorated toner disposal pattern Ptd (FIG. 4) from the print head 11.

[0067] In step SP4, the control unit 40 instructs the deteriorated toner disposal execution unit 54 to the waste dot count update unit 55 to update the cumulative waste dot count 65, and the waste dot count update unit 55 updates the cumulative waste dot count 65 of the image forming unit 10 that has performed deteriorated toner disposal this time by subtracting the deteriorated toner disposal execution dot count 83 for the amount of deteriorated toner used in the current waste disposal from the cumulative waste dot count 65 of the image forming unit 10 that has performed deteriorated toner disposal this time, and then proceeds to step SP5.

[0068] For example, if the cumulative waste dot count 65 of a certain image forming unit 10 is 1000, then the cumulative waste dot count 65 (1000) is equal to or greater than the deteriorated toner disposal execution dot count 83 (831), so the control unit 40 obtains a positive result in step SP2, proceeds to step SP3, and discards deteriorated toner for this image forming unit 10, and then proceeds to step SP4. In step SP4, since the control unit 40 has discarded 831 dot counts of toner, it subtracts the deteriorated toner disposal execution dot count 83 (831) for the amount of toner used in this deteriorated toner disposal from the cumulative waste dot count 65 of this image forming unit 10, thereby updating the cumulative waste dot count 65 to 1000-831=169.

[0069] In step SP5, the control unit 40 instructs the image forming unit order determination unit 56 from the print management unit 50 to perform the image forming unit order determination process described below, and after going through the image forming unit order determination process procedure SRT1 shown in Figure 6, determines the image forming unit 10 to be used for printing in the current print job for each page, and proceeds to step SP6.

[0070] In step SP6, the control section 40 starts printing by the print management section 50 using the image forming unit usage order management data 67, and proceeds to step SP7. When the print management section 50 has finished printing, the control section 40 proceeds to step SP8.

[0071] In step SP8, control unit 40 sends dot count 61 and printing drum count advance 62 for the current printing for each image forming unit 10 from print management unit 50 to waste dot count calculation unit 53, and issues an instruction to calculate the waste dot count. Based on dot count 61 and printing drum count advance 62, waste dot count calculation unit 53 performs the calculation for degraded toner disposal described above to calculate waste dot count 64, and issues an instruction to waste dot count update unit 55 to update cumulative waste dot count 65. Waste dot count update unit 55 adds waste dot count 64 to cumulative waste dot count 65, thereby updating it. Next, control unit 40 proceeds to step SP9, where print processing procedure RT1 ends.

[0072] [5. Processing for Determining the Order of Image Forming Units to be Used] Next, the specific processing steps of the image forming unit use order determination process by the control unit 40 will be described using the flowchart in Fig. 6. In step SP5 of the print processing procedure RT1 (Fig. 5), the control unit 40 starts the image forming unit use order determination processing procedure SRT1 shown in Fig. 6, and then proceeds to step SP11. In step SP11, the control unit 40 copies the cumulative waste dot count 65 of each image forming unit 10 to the predicted cumulative waste dot count value 66 by the image forming unit use order determination section 56, and then proceeds to step SP12. In step SP12, the control unit 40 clears the image forming unit use order management data 67, and then proceeds to step SP13.

[0073] In step SP13, the control unit 40 determines whether or not the image forming units to be used, which are the image forming units 10 to be used for all pages to be printed, have been determined using the image forming unit to be used order determination unit 56. If a negative result is obtained here, this means that there are pages in the print job for which the image forming units to be used have not yet been determined, and in this case the control unit 40 first sets the page currently being checked, that is, the check target page, as the first page, and proceeds to step SP14.

[0074] In step SP14, control unit 40, using image forming unit order determination section 56, selects the image forming unit with the largest predicted discard dot count cumulative value 66 among the predicted discard dot count cumulative values ​​66 of each image forming unit 10 stored in RAM 60 as the image forming unit to be used when printing the page to be checked, updates image forming unit order management data 67, and proceeds to step SP15. At this time, image forming unit order determination section 56 registers the selected image forming unit 10 (image forming unit to be used) as the image forming unit 10 to be used next in order to the image forming units 10 already registered in image forming unit order management data 67. Furthermore, if an image forming unit 10 has not yet been registered in image forming unit order management data 67, image forming unit order determination section 56 registers the selected image forming unit 10 in image forming unit order management data 67.

[0075] In step SP15, the control unit 40 pre-calculates the page-by-page dot count 68, which is the dot count used in printing the page to be checked, and the page-by-page printing drum count advance 69 for printing the page to be checked, using the dot count calculation unit 51. Next, the control unit 40 performs the calculation for the degraded toner disposal described above using the waste dot count calculation unit 53 based on the page-by-page dot count 68 and the page-by-page printing drum count advance 69, to calculate the page-by-page waste dot count 70, and proceeds to step SP16. At this time, the control unit 40 also performs the calculation for the degraded toner disposal described above using the waste dot count calculation unit 53, assuming that the image forming units 10 not used when printing the page to be checked are equivalent to printing at 0% duty, because it is necessary to rotate the developing rollers 13, etc.

[0076] In step SP16, control unit 40 updates predicted waste dot count cumulative value 66 by adding the calculated value of page-based waste dot count 70 to predicted waste dot count cumulative value 66 for each image forming unit 10 using waste dot count calculation unit 53. This predicted waste dot count cumulative value 66 is also used in printing the next page.

[0077] In this way, the control unit 40 determines the image forming unit 10 to be used for the first page, updates the predicted cumulative discard dot count value 66 of each image forming unit 10 when the first page is printed, returns to step SP13, sets the page to be checked to page 2, and repeats the above-mentioned process until the image forming units to be used have been determined for all pages to be printed from page 2 onwards. When the image forming units to be used have been determined for all pages to be printed in one job, the control unit 40 obtains a positive result in step SP13, moves to step SP17, ends the image forming unit to be used order determination process procedure SRT1, and returns to step SP5 of the printing process procedure RT1 (FIG. 5).

[0078] [6. Specific processing flow] Next, a specific flow of the processing of the printing process procedure RT1 (FIG. 5) and the image forming unit use order determination process procedure SRT1 (FIG. 6) described above will be explained using the example shown in FIG. 7. In this example, image forming apparatus 1 receives print jobs from a host device in the order of first job, second job, and third job, and prints them in the order of first job, second job, and third job. Job 1 has three pages, and the print data has a duty of 1.89% for page 1, a duty of 0.63% for page 2, and a duty of 0.75% for page 3. Job 2 has two pages, and the print data has a duty of 0.38% for page 1 and a duty of 0.63% for page 2. Job 3 has two pages, and the print data has a duty of 0.51% for page 1 and a duty of 0.38% for page 2.

[0079] [6-1.1st Job] First, the first job will be described. As shown in row a of Fig. 7A, the total discard dot counts of the image forming units 10a, 10b, and 10c, which are 65, start from 0.

[0080] When printing the first job, first in step SP2 (FIG. 5), the control unit 40 determines whether there is any image forming unit 10 whose cumulative waste dot count 65 is equal to or greater than the deteriorated toner disposal execution dot count 83. Because the cumulative waste dot count 65 of all image forming units 10 is 0 and is not equal to or greater than the deteriorated toner disposal execution dot count 83, 831, the control unit 40 obtains a negative result in step SP2 and does not perform deteriorated toner disposal in any image forming unit 10. Therefore, as shown in line b of FIG. 7(A), the cumulative waste dot count 65 remains 0 at the start of the image forming unit use order determination process procedure SRT1.

[0081] In step SP11 (FIG. 6), the control unit 40 copies the cumulative waste dot count 65 of each image forming unit 10 to the predicted cumulative waste dot count value 66, as shown in line c of FIG. 7(A), proceeds to step SP12, clears the image forming unit order management data 67, and proceeds to step SP13.

[0082] Since checking of all pages has not yet been completed, the control unit 40 obtains a negative result in step SP13, sets the page to be checked to page 1, and proceeds to step SP14. In step SP14, the control unit 40 selects the image forming unit 10 with the largest predicted cumulative discard dot count value 66 from all image forming units 10 as the image forming unit to be used, and proceeds to step SP15. Actually, at this point, as shown in line c of FIG. 7A, all image forming units 10 have the same predicted cumulative discard dot count value 66 of 0, so the control unit 40 may select any image forming unit 10. In this embodiment, if the predicted cumulative discard dot count values ​​66 are the same, the control unit 40 prioritizes selection in the order of image forming units 10a, 10b, and 10c. Therefore, this time, the control unit 40 selects, for example, image forming unit 10a. Therefore, the control unit 40 registers image forming unit 10a in the image forming unit use order management data 67, as shown in line d of FIG. 7A.

[0083] In step SP15, for printing the first page of the first job, the page dot count 68 is 792 / 5*1.89 ≒ 300 dot counts, and the page-based printing drum count advance 69 is 1. If the degraded toner waste slice value 82 is S (1.5), the page dot count 68 is D (300), and the page-based printing drum count advance 69 is O (1), the control unit 40 calculates SL [%], which is the dot count (page-based waste dot count 70) at the waste threshold (degraded toner waste slice value 82) for printing the first page of the first job, as follows: SL [%] = 792 / 5 * S * O = 792 / 5 * 1.5 * 1 = 237.6. Next, the control unit 40 calculates WL, which is the waste dot count (page-based waste dot count 70) for printing the first page of the first job, as follows: WL = SL [%] - D = 237.6 - 300 = -62.4.

[0084] Furthermore, the developing roller 13 and the like must also be rotated in the image forming units 10 that are not used in printing (image forming units 10b and 10c in the case of printing the first page of the first job). In this case, since the image forming units 10 are not used in printing, the situation is the same as when printing is performed at 0% duty. In the case of such an image forming unit 10 that is not used in printing, the control unit 40 calculates the page-wise waste dot count 70 (WL) in the same manner as in the calculation method described above, as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-0=237.6 It is calculated as follows.

[0085] In step SP16, the control unit 40 updates the predicted total waste dot count value 66 as shown in line d of Figure 7(A) by adding the calculated value of the page-based waste dot count 70 to the predicted total waste dot count value 66 of each image forming unit 10. Specifically, the predicted total waste dot count value 66 of each image forming unit 10 is updated as follows. The predicted cumulative discard dot count value of the image forming unit 10a is 66:0-62.4=-62.4. The predicted cumulative discard dot count value of the image forming unit 10b is 66:0+237.6=237.6. The predicted cumulative discard dot count value of the image forming unit 10c is 66:0+237.6=237.6.

[0086] Subsequently, because checking of all pages has not been completed, the control unit 40 obtains a negative result in step SP13, moves to the next page, page 2, and proceeds to step SP14. In step SP14, as shown in line d of FIG. 7A, the control unit 40 selects, for example, image forming unit 10b based on the priority order described above, because the discard dot count cumulative predicted value 66 of image forming unit 10b or 10c is the largest but is the same value. Therefore, as shown in line e of FIG. 7A, the control unit 40 registers image forming unit 10b next to image forming unit 10a in the image forming unit usage order management data 67. Therefore, the order in the image forming unit usage order management data 67 is image forming unit 10a, then image forming unit 10b.

[0087] In step SP15, when printing the second page of the first job, the page unit dot count 68 is 792 / 5*0.63 ≒ 100 dot counts, and the page unit printing drum count advance 69 is 1. In the same manner as in the calculation method described above, the control unit 40 calculates the page unit waste dot count 70 (WL) as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-100=137.6 In addition, in the case of the image forming units 10 that are not used in printing (in the case of printing the second page of the first job, the image forming units 10a and 10c), the control unit 40 calculates the page-wise waste dot count 70 (WL) in the same manner as in the calculation method described above, as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-0=237.6 It is calculated as follows.

[0088] In step SP16, the control unit 40 adds the calculated value of the page-based waste dot count 70 to the predicted total waste dot count 66 of each image forming unit 10, thereby updating the predicted total waste dot count 66, as shown in line e of Figure 7(A). Specifically, the predicted total waste dot count 66 of each image forming unit 10 is updated as follows. The predicted cumulative discard dot count value of the image forming unit 10a is 66: -62.4 + 237.6 = 175.2 The predicted cumulative discard dot count value of the image forming unit 10b is 66: 237.6 + 137.6 = 375.2 The predicted cumulative discard dot count value of the image forming unit 10c is 66: 237.6 + 237.6 = 475.2

[0089] Subsequently, because checking of all pages has not been completed, the control unit 40 obtains a negative result in step SP13, moves to the next page, page 3, as the page to be checked, and proceeds to step SP14. In step SP14, the control unit 40 selects image forming unit 10c because image forming unit 10c has the largest predicted discard dot count cumulative value 66, as shown in line e of FIG. 7A. Therefore, the control unit 40 registers image forming unit 10c next in order to image forming unit 10b in the image forming unit usage order management data 67, as shown in line f of FIG. 7A. Therefore, the order in the image forming unit usage order management data 67 is image forming unit 10a, image forming unit 10b, image forming unit 10c.

[0090] In step SP15, when printing the third page of the first job, the page unit dot count 68 is 792 / 5*0.75 ≒ 120 dot counts, and the page unit printing drum count advance 69 is 1. In the same manner as in the calculation method described above, the control unit 40 calculates the page unit waste dot count 70 (WL) as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-120=117.6 In addition, in the case of the image forming units 10 that are not used in printing (in the case of printing the third page of the first job, the image forming units 10a and 10b), the control unit 40 calculates the page-wise waste dot count 70 (WL) in the same manner as in the calculation method described above, as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-0=237.6 It is calculated as follows.

[0091] In step SP16, the control unit 40 updates the predicted total waste dot count value 66 as shown in line f of Figure 7(A) by adding the calculated value of the page-based waste dot count 70 to the predicted total waste dot count value 66 of each image forming unit 10. Specifically, the predicted total waste dot count value 66 of each image forming unit 10 is updated as follows. The predicted cumulative discard dot count value of the image forming unit 10a is 66: 175.2 + 237.6 = 412.8 The predicted cumulative discard dot count value of the image forming unit 10b is 66: 375.2 + 237.6 = 612.8 The predicted cumulative discard dot count value of the image forming unit 10c is 66: 475.2 + 117.6 = 592.8

[0092] Subsequently, because checking of all pages has been completed, control unit 40 obtains a positive result in step SP13, moves to step SP6 of print processing procedure RT1 (FIG. 5), and prints the first job in accordance with image forming unit usage order management data 67. Specifically, control unit 40 prints the first page with image forming unit 10a, the second page with image forming unit 10b, and the third page with image forming unit 10c. After printing is complete, control unit 40 updates waste dot count cumulative total 65 in step SP8.

[0093] [6-2.2nd Job] Next, the second job will be described. As shown in row a in Figure 7(B), the cumulative discard dot counts of the image forming units 10a, 10b, and 10c, which are 65, are 412.8, 612.8, and 592.8 at the time when printing of the first job is completed.

[0094] When printing the second job, first in step SP2 (FIG. 5), the control unit 40 determines whether there is any image forming unit 10 whose cumulative waste dot count 65 is equal to or greater than the deteriorated toner disposal execution dot count 83. Because the cumulative waste dot count 65 of all image forming units 10 is not equal to or greater than 831, which is the deteriorated toner disposal execution dot count 83, the control unit 40 obtains a negative result in step SP2 and does not perform deteriorated toner disposal in any image forming unit 10. Therefore, as shown in line b of FIG. 7(B), the cumulative waste dot count 65 remains 0 at the start of the image forming unit usage order determination process procedure SRT1.

[0095] In step SP11 (FIG. 6), the control unit 40 copies the cumulative waste dot count 65 of each image forming unit 10 to the predicted cumulative waste dot count value 66, as shown in line c of FIG. 7(B), proceeds to step SP12, clears the image forming unit order management data 67, and proceeds to step SP13.

[0096] Since checking of all pages has not yet been completed, control unit 40 obtains a negative result in step SP13, sets the page to be checked to page 1, and proceeds to step SP14. In step SP14, control unit 40 selects image forming unit 10b because image forming unit 10b has the largest predicted discard dot count cumulative value 66, as shown in line c of Figure 7(B). Therefore, control unit 40 registers image forming unit 10b in image forming unit usage order management data 67, as shown in line d of Figure 7(A).

[0097] In step SP15, when printing the first page of the second job, the page unit dot count 68 is 792 / 5*0.38 ≒ 60 dot counts, and the page unit printing drum count advance 69 is 1. In the same manner as in the calculation method described above, the control unit 40 calculates the page unit waste dot count 70 (WL) as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-160=177.6 In addition, in the case of the image forming units 10 that are not used in printing (in the case of printing the first page of the second job, the image forming units 10a and 10c), the control unit 40 calculates the page-wise waste dot count 70 (WL) in the same manner as in the calculation method described above, as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-0=237.6 It is calculated as follows.

[0098] In step SP16, the control unit 40 adds the calculated value of the page-based waste dot count 70 to the predicted total waste dot count 66 of each image forming unit 10, thereby updating the predicted total waste dot count 66, as shown in line d of Figure 7(B). Specifically, the predicted total waste dot count 66 of each image forming unit 10 is updated as follows. The predicted cumulative discard dot count value of the image forming unit 10a is 66: 412.8 + 237.6 = 650.4 The predicted cumulative discard dot count value of the image forming unit 10b is 66: 612.8 + 177.6 = 790.4 The predicted cumulative discard dot count for the image forming unit 10c is 66: 592.8 + 237.6 = 830.4

[0099] Subsequently, because checking of all pages has not been completed, the control unit 40 obtains a negative result in step SP13, moves to the next page, page 2, as the page to be checked, and proceeds to step SP14. In step SP14, the control unit 40 selects image forming unit 10c because image forming unit 10c has the largest predicted discard dot count cumulative value 66, as shown in line d of FIG. 7B. Therefore, the control unit 40 registers image forming unit 10c next in order to image forming unit 10b in the image forming unit usage order management data 67, as shown in line e of FIG. 7B. Therefore, the order in the image forming unit usage order management data 67 is image forming unit 10b, then image forming unit 10c.

[0100] In step SP15, when printing the second page of the second job, the page unit dot count 68 is 792 / 5*0.63 ≒ 100 dot counts, and the page unit printing drum count advance 69 is 1. In the same manner as in the calculation method described above, the control unit 40 calculates the page unit waste dot count 70 (WL) as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-100=137.6 In addition, in the case of the image forming unit 10 that is not used in printing (in the case of printing the second page of the second job, the image forming units 10a and 10b), the control unit 40 calculates the page-wise waste dot count 70 (WL) in the same manner as in the calculation method described above, as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-0=237.6 It is calculated as follows.

[0101] In step SP16, the control unit 40 updates the predicted total waste dot count value 66 as shown in line e of Figure 7(B) by adding the calculated value of the page-based waste dot count 70 to the predicted total waste dot count value 66 of each image forming unit 10. Specifically, the predicted total waste dot count value 66 of each image forming unit 10 is updated as follows. The predicted cumulative discard dot count for the image forming unit 10a is 66: 650.4 + 237.6 = 888 The predicted cumulative discard dot count for the image forming unit 10b is 66:790.4+237.6=1028 The predicted cumulative discard dot count value of the image forming unit 10c is 66:830.4+137.6=968

[0102] Subsequently, since checking of all pages has been completed, control unit 40 obtains a positive result in step SP13, moves to step SP6 of print processing procedure RT1 (FIG. 5), and prints the second job in accordance with image forming unit usage order management data 67. Specifically, control unit 40 prints the first page with image forming unit 10b, and prints the second page with image forming unit 10c. After printing is completed, control unit 40 updates waste dot count cumulative total 65 in step SP8.

[0103] [6-3.3rd Job] Next, the third job will be described. As shown in row a of Figure 7(C), the cumulative discard dot counts of the image forming units 10a, 10b, and 10c, which are 65, are 888, 1028, and 968, respectively, at the time when printing of the second job is completed.

[0104] When printing the third job, first in step SP2 (FIG. 5), the control unit 40 determines whether there is any image forming unit 10 whose cumulative waste dot count 65 is equal to or greater than the degraded toner disposal execution dot count 83. Because the cumulative waste dot count 65 of all image forming units 10 is equal to or greater than 831, which is the degraded toner disposal execution dot count 83, the control unit 40 obtains a positive result in step SP2, moves on to step SP3, executes degraded toner disposal in all image forming units 10, and moves on to step SP4.

[0105] In step SP4, the control unit 40 updates the cumulative waste dot count 65 by subtracting the degraded toner disposal execution dot count 83 used for the current degraded toner disposal from the cumulative waste dot count 65 for each image forming unit 10, as shown in line b of Figure 7(C), and then proceeds to step SP5. Specifically, the cumulative waste dot count 65 for each image forming unit 10 is updated as follows. The predicted cumulative discard dot count value of the image forming unit 10a is 66:888-831=57. The predicted cumulative discard dot count for the image forming unit 10b is 66:1028-831=197. The predicted cumulative discard dot count value of the image forming unit 10c is 66:968-831=137.

[0106] In step SP11 (FIG. 6), the control unit 40 copies the cumulative waste dot count 65 of each image forming unit 10 to the predicted cumulative waste dot count value 66, as shown in line c of FIG. 7(C), proceeds to step SP12, clears the image forming unit order management data 67, and proceeds to step SP13.

[0107] Since checking of all pages has not yet been completed, control unit 40 obtains a negative result in step SP13, sets the page to be checked to page 1, and proceeds to step SP14. In step SP14, control unit 40 selects image forming unit 10b because image forming unit 10b has the largest predicted discard dot count cumulative value 66, as shown in line c of Figure 7(C). Therefore, control unit 40 registers image forming unit 10b in image forming unit usage order management data 67, as shown in line d of Figure 7(C).

[0108] In step SP15, when printing the first page of the third job, the page unit dot count 68 is 792 / 5*0.51 ≒ 80 dot counts, and the page unit printing drum count advance 69 is 1. In the same manner as in the calculation method described above, the control unit 40 calculates the page unit waste dot count 70 (WL) as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-80=157.6 In addition, in the case of the image forming units 10 that are not used in printing (in the case of printing the first page of the third job, the image forming units 10a and 10c), the control unit 40 calculates the page-wise waste dot count 70 (WL) in the same manner as in the calculation method described above, as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-0=237.6 It is calculated as follows.

[0109] In step SP16, the control unit 40 adds the calculated value of the page-based waste dot count 70 to the predicted total waste dot count 66 of each image forming unit 10, thereby updating the predicted total waste dot count 66, as shown in line d of Figure 7(C). Specifically, the predicted total waste dot count 66 of each image forming unit 10 is updated as follows. The predicted cumulative discard dot count value of the image forming unit 10a is 66:57+237.6=294.6. The predicted cumulative discard dot count value of the image forming unit 10b is 66:197+157.6=354.6 The predicted cumulative discard dot count value of the image forming unit 10c is 66:137+237.6=374.4.

[0110] Subsequently, since the check of all pages has not been completed, the control unit 40 obtains a negative result in step SP13 and moves the page to be checked to the next page, page 2. 7C, the control unit 40 selects the image forming unit 10c because the discard dot count cumulative predicted value 66 of the image forming unit 10c is the largest, as shown in line d of FIG. 7C. Therefore, the control unit 40 registers the image forming unit 10c next to the image forming unit 10b in the image forming unit usage order management data 67, as shown in line e of FIG. 7C. Therefore, the image forming unit usage order management data 67 has the order of the image forming unit 10b, then the image forming unit 10c.

[0111] In step SP15, when printing the second page of the third job, the page unit dot count 68 is 792 / 5*0.38 ≒ 60 dot counts, and the page unit printing drum count advance 69 is 1. In the same manner as in the calculation method described above, the control unit 40 calculates the page unit waste dot count 70 (WL) as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-60=177.6 In addition, in the case of the image forming unit 10 that is not used in printing (in the case of printing the second page of the third job, the image forming units 10a and 10b), the control unit 40 calculates the page-wise waste dot count 70 (WL) in the same manner as in the calculation method described above, as follows: SL[%]=792 / 5*1.5*1=237.6 WL=237.6-0=237.6 It is calculated as follows.

[0112] In step SP16, the control unit 40 updates the predicted total waste dot count value 66 as shown in line e of Figure 7(C) by adding the calculated value of the page-based waste dot count 70 to the predicted total waste dot count value 66 of each image forming unit 10. Specifically, the predicted total waste dot count value 66 of each image forming unit 10 is updated as follows. The predicted cumulative discarded dot count value of the image forming unit 10a is 66: 294.6 + 237.6 = 532.2 The predicted cumulative discard dot count value of the image forming unit 10b is 66: 354.6 + 237.6 = 592.2 The predicted cumulative discarded dot count value of the image forming unit 10c is 66: 374.6 + 177.6 = 552.2

[0113] Subsequently, because checking of all pages has been completed, control unit 40 obtains a positive result in step SP13, moves to step SP6 of print processing procedure RT1 (FIG. 5), and prints the third job in accordance with image forming unit usage order management data 67. Specifically, control unit 40 prints the first page with image forming unit 10b, and prints the second page with image forming unit 10c. After printing is completed, control unit 40 updates waste dot count cumulative total 65 in step SP8.

[0114] [7. Effects, etc.] As described above, the image forming apparatus 1 has a simplified configuration because it does not have a contact / separation mechanism that moves the photosensitive drum 14 in the image forming unit 10 up and down so as to contact or separate it from the transfer roller 22.

[0115] Therefore, in the image forming device 1, the photosensitive drum 14 of the image forming unit 10 that does not form an image during printing cannot be separated from the transfer roller 22, and therefore even when image formation is performed using another image forming unit 10, the photosensitive drum 14 of the image forming unit 10 that does not form an image during printing remains in contact with the transfer roller 22.

[0116] In addition, when printing on paper P that is short in length along the transport direction, even if the image forming device 1 is provided with a separation mechanism, it is necessary to abut the photosensitive drums 14 of all image forming units 10 against the transfer rollers 22, and transport the paper P by sandwiching it between the photosensitive drums 14 and the transfer rollers 22.

[0117] Therefore, in the image forming device 1, even though the image forming unit 10 does not form images during printing, the toner inside the image forming unit 10 may be deteriorated due to being rubbed by various rollers including the developing roller 13 or coming into contact with components charged to a high voltage for a long period of time.

[0118] If the image forming device 1 performs the disposal of deteriorated toner in response to this, the quality of the image can be maintained, but the deterioration of each component inside the developing device 19 will progress, for example, deterioration of the photosensitive drum 14 due to the rotation of the photosensitive drum 14, and time will be required to perform the disposal of deteriorated toner before printing is performed, which will increase the time required to print multiple print jobs consecutively and reduce performance, which is the time efficiency when printing.

[0119] In response to this, prior to printing a print job, image forming apparatus 1 calculates page-by-page waste dot count 70 for each page, updates predicted waste dot count cumulative value 66 for each page, and selects the image forming unit with the largest predicted waste dot count cumulative value 66 as the image forming unit to be used for each page, thereby determining the image forming unit 10 to be used for image formation for each page and updating image forming unit use order management data 67, which indicates the order of image forming units 10 for each page on which images are to be formed during printing. Subsequently, image forming apparatus 1 selects image forming units 10 for each page in the order stored in image forming unit use order management data 67, and performs image formation.

[0120] Therefore, when forming an image in an image forming unit 10 used for image formation, even if the photosensitive drum 14 of an image forming unit 10 not used for image formation is in a rotating state, the image forming device 1 preferentially uses the image forming unit 10 with a large cumulative waste dot count 65 to form an image, thereby reducing the cumulative waste dot count 65 of the image forming unit 10 with a large cumulative waste dot count 65.

[0121] This prevents the image forming apparatus 1 from increasing the amount of degraded toner in the image forming units 10 that are not used for image formation, and reduces the frequency of degraded toner disposal. Thus, even if multiple image forming units 10 store toner of the same color and the photosensitive drums 14 of all image forming units 10 need to rotate during printing, the image forming apparatus 1 can prevent the time required to print multiple print jobs consecutively from increasing and prevent a decline in performance.

[0122] According to the above configuration, the image forming device 1 is provided with a first image forming unit 10 that rotates the photosensitive drum 14 as the first photosensitive drum of the first image forming unit 10, which is one of the image forming units 10, to form an image in black as the first color, a second image forming unit 10 that rotates the photosensitive drum 14 as the second photosensitive drum of the second image forming unit 10, which is the other of the image forming units 10, to form an image in black, a waste dot count calculation unit 53 that calculates the amount of deteriorated toner generated in the first image forming unit 10 and the second image forming unit 10, and a print management unit 50 that selects either the first image forming unit 10 or the second image forming unit 10 based on the value of the deteriorated toner when the photosensitive drum 14 of the image forming unit 10 that is not performing image formation, of the first image forming unit 10 or the second image forming unit 10, is rotating.

[0123] As a result, when forming an image in an image forming unit 10 used for image formation, even if the photosensitive drum 14 of an image forming unit 10 not used for image formation is in a rotating state, the image forming device 1 preferentially uses the image forming unit 10 with a large cumulative waste dot count 65 to form an image, thereby reducing the cumulative waste dot count 65 of the image forming unit 10 with a large cumulative waste dot count 65.

[0124] 8. Other Embodiments In the above-described embodiment, the image forming apparatus 1 has been described as selecting, as the image forming unit to be used, the image forming unit 10 having the largest predicted cumulative discard dot count value 66. However, the present invention is not limited to this, and the image forming apparatus 1 may select, as the image forming unit to be used, an image forming unit 10 other than the image forming unit 10 having at least the smallest predicted cumulative discard dot count value 66.

[0125] Furthermore, in the above-described embodiment, the image forming apparatus 1 is described as not being provided with a contact / separation mechanism that moves the photosensitive drums 14 of the image forming units 10 up and down so as to contact or separate them from the transfer rollers 22. The present invention is not limited to this, and the image forming apparatus 1 may be provided with a contact / separation mechanism. Even if a contact / separation mechanism is provided, when printing on paper P that is short in the transport direction, the image forming apparatus 1 may need to contact the photosensitive drums 14 of all image forming units 10 with the transfer rollers 22 and transport the paper P while sandwiching it between the photosensitive drums 14 and the transfer rollers 22. Therefore, the present invention is applicable even in such a case.

[0126] Furthermore, in the above-described embodiment, the image forming apparatus 1 calculates the predicted cumulative waste dot count value 66 for each page in a print job, and selects, for each page, the image forming unit 10 with the largest predicted cumulative waste dot count value 66 as the image forming unit to be used. However, the present invention is not limited to this, and the image forming apparatus 1 may calculate the predicted cumulative waste dot count value 66 for each print job, and select, for each print job, the image forming unit 10 with the largest predicted cumulative waste dot count value 66 as the image forming unit to be used.

[0127] Furthermore, in the above-described embodiment, the image forming apparatus 1 has been described as preferentially selecting image forming units 10a, 10b, and 10c in this order when the waste dot count cumulative predicted values ​​66 are the same. However, the present invention is not limited to this. Therefore, when the waste dot count cumulative predicted values ​​66 are the same, the image forming apparatus 1 may preferentially select image forming units 10 located closer to the fixing unit 26 because the toner stored in the image forming units 10 located closer to the fixing unit 26 tends to be easily deteriorated by the heat generated by the fixing unit 26. Furthermore, when calculating the page-based waste dot count 70, the image forming apparatus 1 may adjust a coefficient so that the page-based waste dot count 70 tends to be larger for image forming units 10 located closer to the fixing unit 26.

[0128] Furthermore, in the above-described embodiment, the image forming apparatus 1 has been described as making the values ​​of the degraded toner disposal slice value 82 and the degraded toner disposal execution dot count 83 in the ROM 80 the same for all image forming units 10. However, the present invention is not limited to this, and the image forming apparatus 1 does not need to make at least some of the values ​​of the degraded toner disposal slice value 82 and the degraded toner disposal execution dot count 83 the same for all image forming units 10. In this case, since toner stored in an image forming unit 10 located near the fixing unit 26 tends to be easily deteriorated by heat generated by the fixing unit 26, the value of the degraded toner disposal slice value 82 may be changed depending on the distance between the image forming unit 10 and the fixing unit 26.

[0129] Furthermore, in the above-described embodiment, the image forming device 1 is described as setting the degraded toner disposal slice value 82 to 1.5% and the degraded toner disposal execution dot count 83 to 831 dot counts. However, the present invention is not limited to this, and the image forming device 1 may set the degraded toner disposal slice value 82 and the degraded toner disposal execution dot count 83 to various other values.

[0130] Furthermore, in the above-described embodiment, the image forming apparatus 1 has been described as having the drum waste toner collection container 17 inside the developing device 19. However, the present invention is not limited to this, and the image forming apparatus 1 may have the drum waste toner collection container 17 inside the toner cartridge 18, rather than inside the developing device 19. In this case, when the drum waste toner collection container 17 becomes full, the toner cartridge 18 needs to be replaced.

[0131] Furthermore, in the above-described embodiment, the storage unit 42 is provided on the main body side of the image forming apparatus 1. However, the present invention is not limited to this, and the values ​​related to each image forming unit 10 in the storage unit 42 may be stored in the storage unit of each image forming unit 10. In this case, the control unit 40 may acquire information from the storage unit of the image forming unit 10 by, for example, wirelessly communicating with a wireless tag such as an RFID (Radio Frequency Identifier) ​​provided in each image forming unit 10.

[0132] Furthermore, in the above-described embodiment, the present invention has been described as being applied to an image forming apparatus 1 having a 9984 dot print head 11 corresponding to the A4 paper size. However, the present invention is not limited to this, and may be applied to an image forming apparatus 1 having a print head 11 with various other dot counts.

[0133] Furthermore, in the above-described embodiment, the present invention has been described as being applied to an image forming apparatus 1 having three image forming units 10 corresponding to black toner. However, the present invention is not limited to this, and may be applied to image forming apparatuses having various numbers of image forming units, such as two or less or four or more. Furthermore, the present invention may be applied to image forming apparatuses having multiple image forming units 10 corresponding to toners of various colors other than black.

[0134] Furthermore, in the above-described embodiment, the present invention has been described as being applied to an image forming apparatus 1 that writes a latent image onto a photosensitive drum 14 using a print head 11 that is an LED head. However, the present invention is not limited to this, and may be applied to an image forming apparatus 1 that writes a latent image using a print head 11 of various other types, such as a laser head.

[0135] Furthermore, the present invention is not limited to the above-described embodiment and other embodiments. That is, the scope of application of the present invention extends to embodiments in which the above-described embodiment and the other embodiments are combined in part or in whole. The scope of application of the present invention also extends to embodiments in which part of the configuration described in any of the above-described embodiment and other embodiments is extracted and used as part of the configuration of any of the above-described embodiment and other embodiments, or in which part of the extracted configuration is added to any of the above-described embodiment.

[0136] Furthermore, in the above-described embodiment, the image forming apparatus 1 is configured as an image forming apparatus by using one of the image forming units 10 as a first image forming unit, one of the image forming units 10 as a second image forming unit, the waste dot count calculation unit 53 as a calculation unit, and the print management unit 50 as a control unit. However, the present invention is not limited to this, and the image forming apparatus may be configured by using a first image forming unit, a second image forming unit, a calculation unit, and a control unit having various other configurations. [Industrial Applicability]

[0137] The present invention can be used in printers that discard depleted toner. [Explanation of symbols]

[0138] 1...image forming apparatus, 2...casing, 3...paper feed cassette, 4...pickup roller, 5...conveyor roller, 6...media detection sensor, 7...environmental temperature sensor, 8...belt thermistor, 9...image forming section, 10...image forming unit, 11...print head, 12...supply roller, 13...developing roller, 14...photosensitive drum, 15...charging roller, 16...cleaning blade, 17...drum waste toner collection container, 18...toner cartridge, 19...developing device, 20...transfer unit, 21...transfer belt, 22...transfer roller, 23...belt cleaning blade, 24...belt waste toner collection container, 26...fixing unit, 27...heating roller, 28...pressure roller, 30...ejection unit, 31...duplex printing unit, 32...media collection tray, W...conveyor path, 40...controller, 42...memory unit, 44...display unit, 46...input unit 48...Communication unit, 50...Print management unit, 51...Dot count calculation unit, 52...Deteriorated toner disposal determination unit, 53...Discard dot count calculation unit, 54...Deteriorated toner disposal execution unit, 55...Discard dot count update unit, 56...Image forming unit usage order determination unit, 60...RAM, 61...Dot count, 62...Drum count advance during printing, 63...Discard threshold dot count, 64...Discard dot count, 65...Cumulative waste dot count, 66...Predicted cumulative waste dot count value, 67...Image forming unit usage order management data, 68...Page unit dot count, 69...Drum count advance during page unit printing, 70...Page unit waste dot count, 80...ROM, 81...Program storage unit, 82...Deteriorated toner disposal slice value, 83...Deteriorated toner disposal execution dot count, dm...Main scanning direction, Ptd...Deteriorated toner disposal pattern.

Claims

1. a first image forming unit that rotates a first photosensitive drum to form an image in a first color; a second image forming unit that rotates a second photosensitive drum to form an image in the first color; a calculation unit that calculates deteriorated toner generated in the first image forming unit and the second image forming unit; a control unit that selects either the first image forming unit or the second image forming unit to perform image formation based on the value of the deteriorated toner when a photosensitive drum of an image forming unit that does not perform image formation is in a rotating state; and An image forming apparatus comprising:

2. a storage unit that stores the cumulative value of the deteriorated toner calculated by the calculation unit; At least the first image forming unit and the second image forming unit and The control unit an image forming unit other than the image forming unit having the smallest cumulative amount of deteriorated toner is selected to perform image formation; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. The control unit The image forming unit having the largest accumulated amount of deteriorated toner is selected to perform image formation.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. The calculation unit calculating the amount of deteriorated toner generated in the first image forming unit and the second image forming unit for each page; The control unit The image forming unit having the largest cumulative amount of deteriorated toner is selected for each page to perform image formation.

4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium.

5. a discarding unit that discards the deteriorated toner when the cumulative value of the deteriorated toner exceeds a threshold value; 4. The image forming apparatus according to claim 2, further comprising:

6. an updating unit that updates the cumulative total value of the deteriorated toner by subtracting the value of the discarded deteriorated toner from the cumulative total value of the deteriorated toner; 6. The image forming apparatus according to claim 5, further comprising:

Images