Image forming apparatus

Abstract

To maintain the quality of an image to be printed, while preventing excessive disposal of toner.SOLUTION: An image forming apparatus 1 is provided with: an image forming unit 70 that forms an image with toner; an entire area printing rate calculation unit 72 that calculates an entire area printing rate that is a printing rate of an entire image forming area ARI; an each-area printing rate calculation unit 74 that calculates an each-area printing rate that is a printing rate of each of a plurality of areas AR formed by dividing the image forming area ARI in a main scanning direction dm; and a deteriorated toner disposal execution unit 76 that, when the entire area printing rate is equal to or less than an entire area printing rate threshold, executes deteriorated toner disposal for the area AR where the each-area printing rate is equal to or less than an each-area printing rate threshold.SELECTED DRAWING: Figure 5

Description

Technical Field

[0005] ,

[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 Art

[0002] Conventionally, in an image forming apparatus using an electrophotographic method, by repeating printing using toner, since the density of the toner consumed for the printed image in the printing operation is not sufficient, the toner comes into contact with a member charged to a high voltage for a long time. Therefore, deteriorated toner is generated in the developing device of the image forming unit. Since this deteriorated toner is a factor causing a decrease in image quality, an image forming apparatus has been proposed that discharges the deteriorated toner in the developing device onto the photosensitive drum and collects it in a waste toner collection container in the image forming unit to discard the deteriorated toner (see, for example, Patent Document 1).

[0003] Also, when the printing rate of print data is high, since the toner is developed before it deteriorates and deteriorated toner is unlikely to be generated, the image forming apparatus discards the deteriorated toner based on the printing rate of the print data, that is, the amount of toner consumed in printing, to prevent the accumulation of deteriorated toner. That is, the image forming apparatus executes the disposal of deteriorated toner when a printing pattern with a low printing rate and low toner consumption continues.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with conventional image forming machines, if printing continues with low overall print density on a page but high print density in a specific area in the main scanning direction, the high-density area consumes toner, so not much degraded toner is generated, and there is no need to discard toner in that area. However, because the overall print density on the page is low and toner consumption is small, there is a problem in that toner is wasted unnecessarily in the high-density area.

[0006] This invention was made with the above points in mind, and aims to propose an image forming apparatus that can maintain the quality of printed images while suppressing the waste of excessive toner. [Means for solving the problem]

[0007] To solve these problems, the image forming apparatus of the present invention includes an image forming unit that forms an image with a developer, and a unit that calculates the total area printing rate, which is the printing rate of the entire image forming area. Then, the total toner waste count is calculated, with smaller values ​​added the higher the total area printing rate. The system includes a unit for calculating the total area print coverage and a unit for calculating the print coverage for each area, which is the print coverage for each of the multiple areas formed by dividing the image formation region in the main scanning direction. Then, the area toner waste count is calculated by adding a smaller value the higher the printing density of each area, and adding a larger value the higher the area toner waste threshold. Each area print density calculation unit, The toner waste threshold for each area is gradually increased, starting from the area located in the center of the main scanning direction and moving towards the areas located at the edges of the main scanning direction, until the toner waste count for all areas exceeds the total threshold for all areas. In the case of, The toner waste count for each area exceeds the threshold for each area. A deteriorated toner disposal unit is provided to perform deteriorated toner disposal in a specific area.

[0008] This invention allows for the maintenance of print image quality by suppressing excessive toner waste in areas with high print density and low toner degradation, by not disposing of degraded toner in areas where degraded toner disposal is unnecessary, while maintaining print image quality in areas with low print density and high toner degradation, by disposing of degraded toner in areas where it is necessary. [Effects of the Invention]

[0009] According to the present invention, an image forming apparatus can be realized that can maintain the quality of printed images while suppressing the waste of excessive toner. [Brief explanation of the drawing]

[0010] [Figure 1] This is a left side view showing the overall configuration of the image forming apparatus. [Figure 2] This is a block diagram showing the control configuration of an image forming apparatus. [Figure 3] This is a diagram showing the image-forming region. [Figure 4] This is a table showing the toner disposal threshold. [Figure 5] This is a flowchart showing the printing process. [Figure 6] This is a block diagram showing the functional configuration of an image forming apparatus. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[0012] [1. Overall configuration of the image forming apparatus] As shown in Figure 1, the image forming apparatus 1 is a color electrophotographic printer that prints a desired color image onto a sheet of paper P. The image forming apparatus 1 has various components arranged inside a roughly box-shaped casing 2. For the purposes of this explanation, the rightmost portion of Figure 1 will be considered the front of the image forming apparatus 1, and the vertical, horizontal, and front-to-back directions will be defined and explained based on a view from this front. The image forming apparatus 1 is entirely controlled by a control unit 40. The image forming apparatus 1 is also connected wirelessly or via wired connection to a higher-level device (not shown), such as a computer. When the control unit 40 receives a print job representing the image to be printed from this higher-level device and is instructed to print the print job, it executes a printing process to form the printed image on the surface of the paper P.

[0013] At the very bottom of the enclosure 2 is a paper feed cassette 3 for storing paper P. A hopping roller 4 is located above and in front of the paper feed cassette 3. The lower part of the hopping roller 4 is in contact with the upper surface of the paper P stored in the paper feed cassette 3, and by rotating, it feeds the uppermost sheet of the stored paper P forward.

[0014] A transport path W for transporting paper P is formed inside the housing 2. A registration roller 5 is provided downstream of the hopping roller 4 in the transport direction of paper P inside the housing 2. The registration roller 5 is composed of multiple rollers that face each other and contact each other across the transport path W, and transports the paper P on the transport path W while correcting its skew. Furthermore, a discharge roller 6 is provided downstream of the fixing unit 29 in the transport direction of paper P inside the housing 2. The discharge roller 6 is composed of multiple rollers that face each other and contact each other across the transport path W, and transports the paper P on the transport path W and discharges it to the outside of the image forming apparatus 1.

[0015] Furthermore, the housing 2 is equipped with an image forming unit 9 for forming a printed image by printing the color image to be printed onto the surface of the paper P. The image forming unit 9 has four image forming units 10 (image forming units 10K, 10Y, 10M, and 10C) arranged in order from the front (upstream) to the rear (downstream) at the upper end of the housing 2. These units develop electrostatic latent images representing the different color components of the printed image, namely black (K), yellow (Y), magenta (M), and cyan (C), using toner as a developer to form a toner image corresponding to the print data.

[0016] The image forming units 10K, 10Y, 10M, and 10C are identically configured except that the color of the toner used for developing the electrostatic latent image is different. Therefore, hereinafter, the image forming units 10K, 10Y, 10M, and 10C will be collectively described as the image forming unit 10. The image forming unit 10 is composed of a print head 11, a developing device 19, a photosensitive drum 14, a charging roller 15, a cleaning blade 16, a drum waste toner collection container 17, and a charge removing unit 20.

[0017] The developing device 19 is a device for developing a toner image on the electrostatic latent image formed on the photosensitive drum 14, and is provided with a supply roller 12, a developing roller 13, and a regulating blade 18.

[0018] The print head 11 is an LED (Light Emitting Diode) head, and a plurality of LED elements are arranged in alignment along the left - right direction. Above the photosensitive drum 14, it is arranged at a position where the irradiation light from the LED elements forms an image on the surface of the photosensitive drum 14, and each LED element is turned on or off based on the control of the control unit 40. This print head 11 selectively exposes the surface of the uniformly charged photosensitive drum 14 to form an electrostatic latent image.

[0019] The supply roller 12 is arranged to contact the developing roller 13, and supplies the toner stored in a toner cartridge (not shown) to the developing roller 13 side. The charging roller 15 uniformly charges the surface of the photosensitive drum 14 to a negative voltage. The developing roller 13 is arranged to contact the surface of the photosensitive drum 14, charges the toner, and electrostatically adheres it onto the electrostatic latent image formed on the photosensitive drum 14 to form a toner image with a certain layer thickness. The photosensitive drum 14 as an image carrier carries the electrostatic latent image and also carries the toner image obtained by developing the electrostatic latent image with toner.

[0020] The regulating blade 18 is a plate - like member arranged such that the tip portion is pressed against the developing roller 13, and forms a uniform thin layer of toner on the developing roller 13.

[0021] The cleaning blade 16 is a urethane rubber blade that contacts the photosensitive drum 14 downstream of the contact point with the transfer roller 26 (described later) in the rotational direction of the photosensitive drum 14, thereby removing toner remaining on the surface of the photosensitive drum 14 after transfer. The drum waste toner collection container 17 is a container that collects and stores residual toner and waste toner remaining on the photosensitive drum 14 during printing operations and the disposal of deteriorated toner described later.

[0022] The static elimination unit 20 has multiple LED elements aligned along the left-right direction and is positioned opposite the photosensitive drum 14. Based on the control of the control unit 40, it turns each LED element on or off. The static elimination unit 20 exposes the surface of the photosensitive drum 14 and resets the surface potential of the photosensitive drum 14.

[0023] Furthermore, the image forming unit 9 has a transfer unit 22 that extends from below the image forming unit 10K to below the image forming unit 10C and transfers the toner image formed by the image forming units 10K, 10Y, 10M, and 10C to the surface of the paper P. The transfer unit 22 consists of a transfer belt 23, a drive roller 24, an idler roller 25, a transfer roller 26, a belt cleaning blade 27, and a belt waste toner collection container 28.

[0024] The transfer belt 23 is an endless belt that is stretched between the rear drive roller 24 and the front idler roller 25 and rotates to carry the paper P to the rear on its top surface. The drive roller 24 drives the transfer belt 23 by rotating. The idler roller 25 rotates in conjunction with the transfer belt 23, stabilizing the drive of the transfer belt 23. Four transfer rollers 26 are rotatably mounted inside the transfer belt 23, corresponding to the four photosensitive drums 14, and facing the image forming unit 10. A positive transfer voltage is applied to them. As a result, when forming a printed image, the transfer unit 22 sequentially sandwiches the paper P being carried by the transfer belt 23 between the upper part of the surface of the transfer roller 26 and the lower part of the surface of the corresponding four photosensitive drums 14, and transfers the toner images on the surfaces of the four photosensitive drums 14 to the surface of the paper P by applying the transfer voltage to the transfer roller 26.

[0025] The belt cleaning blade 27 is a urethane rubber blade that, by contacting the transfer belt 23, scrapes off and removes the waste toner transported by the transfer belt 23 during the disposal of deteriorated toner. The belt waste toner collection container 28 is a container that collects and stores the waste toner removed from the transfer belt 23 by the belt cleaning blade 27.

[0026] In this configuration, the image forming unit 10 supplies toner from the toner cartridge to the developing unit 19. Subsequently, the image forming unit 10 rotates the photosensitive drum 14 and uniformly charges the surface of the photosensitive drum 14 with the charging roller 15, and the print head 11 exposes the surface of the photosensitive drum 14 based on the print data to form an electrostatic latent image. Next, the image forming unit 10 applies a developing voltage to the developing roller 13, thereby electrostatically depositing the toner supplied by the supply roller 12 onto the electrostatic latent image formed on the photosensitive drum 14 to form a toner image. Furthermore, the image forming unit 10 sandwiches the paper P, which is transported by the transfer belt 23, between the transfer roller 26 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 22 transfers toner images for all four colors to the surface of the paper P and hands over the paper P with the transferred toner images to the fixing unit 29.

[0027] In the image forming unit 9, a fixing unit 29 is positioned behind the transfer unit 22 to fix the toner image to the surface of the paper P. The fixing unit 29 has a paper passage formed approximately in the center in the vertical direction for passing the paper P through. The fixing unit 29 also has a heating roller 30 rotatably mounted above the paper passage and a pressure roller 31 rotatably mounted below the paper passage. Thus, when forming a printed image, the fixing unit 29 takes the paper P, on which the toner image has been transferred to the surface, from the transfer unit 22 into the paper passage and sandwiches it between the heating roller 30 and the pressure roller 31, which are rotating in opposite directions. The fixing unit 29 then heats and pressurizes the paper P between the heating roller 30 and the pressure roller 31, which are rotating in opposite directions, thereby fixing the toner image to the surface of the paper P. The fixing unit 29 fixes the toner images for four colors to the surface of the paper P to form a printed image, and then passes the paper P with the printed image to the discharge roller 6 above.

[0028] In this configuration, the image forming apparatus 1 transports the paper P stored in the paper feed cassette 3 to the image forming unit 9 using the registration roller 5. The image forming unit 9 transports the paper P using the transfer belt 23 and transfers a toner image onto the paper P using the image forming unit 10. The paper P is then transported to the fixing unit 29 by the transfer belt 23. As the paper P passes through the fixing unit 29, the toner image on the paper P is fixed to the paper P by high temperature. The paper P is then transported to the discharge roller 6 and discharged to the outside of the image forming apparatus 1.

[0029] Incidentally, as shown in Figure 3, in the image forming apparatus 1, an image forming area ARI is set over a predetermined range in the main scanning direction dm (left-right direction) perpendicular to the direction in which the paper P is transported, and in the sub-scanning direction ds (front-back direction) perpendicular to the main scanning direction dm, and in which an image for one page can be formed in the printed result. In this image forming area ARI, the range of the main scanning direction dm corresponds to the range from the LED element at the right end to the LED element at the left end of the print head 11 (hereinafter also referred to as the entire area). Furthermore, if the image forming area ARI is divided into, for example, six equally spaced areas with respect to the main scanning direction dm, each of the divided areas will be called areas AR1, AR2, AR3, AR4, AR5, and AR6 (hereinafter collectively referred to as area AR).

[0030] [2. Control Configuration of Image Forming Apparatus] As shown in Figure 3, the image forming apparatus 1 consists of a control unit 40, a receiving unit 42, a drive control unit 44, a voltage control unit 45, an exposure control unit 46, a fixing control unit 47, a belt motor 50, a drum motor 51, a charging roller 15, a developing roller 13, a supply roller 12, a regulating blade 18, a transfer roller 26, a static elimination unit 20, a print head 11, and a fixing unit 29, with the control unit 40 providing overall control of the image forming apparatus 1. When the receiving unit 42 receives a print instruction from a higher-level device (not shown), it sends the print instruction to the control unit 40.

[0031] The control unit 40 is centered around a CPU (Central Processing Unit) (not shown) and controls each part to perform various processes by reading and executing a predetermined program from a storage unit (not shown). The control unit 40 also includes a drum count measurement unit 54, a dot count measurement unit 56, a toner waste threshold holding unit 58, a toner waste count calculation unit 60, a toner waste count holding unit 62, and a toner waste pattern creation unit 64.

[0032] The toner waste threshold holding unit 58 holds a toner waste threshold (described later) in advance. The drum count measurement unit 54 measures the drum count. The drum count indicates the number of rotations corresponding to the rotation speed of the photosensitive drum 14, and the number of drum rotations in a printing operation that prints three A4 sheets of paper is measured as 3 counts.

[0033] The dot count measurement unit 56 measures the dot count. Specifically, the dot count measurement unit 56 measures the dot count of each area AR (Figure 3). The dot count measurement unit 56 also uses the sum of the dot counts of areas AR1, AR2, AR3, AR4, AR5, and AR6 as the dot count for the entire area. The dot count indicates the count corresponding to the number of light-emitting dots of the print head 11, and is the value obtained by dividing the number of light-emitting dots by 8192, with 792 counts corresponding to an image density (printing rate) of 5% on an A4 size sheet of paper. Specifically, the dot count when printing on A4 paper with a print duty cycle of 5% is 792 dots (6,488,064 dots / 8192). This 6,488,064 dots is the actual dot count when printing on A4 paper with a print duty cycle of 5%. Also, 8192 is 2 to the power of 13. In this embodiment, the dot count value is reduced by dividing the number of dots that actually emitted light by 2 to the power of 13.

[0034] Here, print coverage is the ratio of the area of ​​the image actually formed on the paper P to the area where a solid image is formed in the image forming area ARI when viewed on a single page of paper P, and when viewed on a single print job, it is the average print coverage of all pages included in that print job. In other words, print coverage is the ratio of the dots actually printed to the area where dots are formed on the entire surface of a predetermined area on paper P, with 100% representing the state where dots are formed on the entire surface of a predetermined area on paper P when viewed on a single page. Therefore, the print coverage of each area AR in a single print job is the average print coverage of each area in all pages included in that print job.

[0035] The toner waste count calculation unit 60 calculates the toner waste count based on the drum count measured by the drum count measurement unit 54, the dot count measured by the dot count measurement unit 56, and the toner waste threshold held by the toner waste threshold holding unit 58, and sends it to the toner waste count holding unit 62. The toner waste count holding unit 62 holds the calculated toner waste count. The toner waste pattern creation unit 64 creates a toner waste pattern.

[0036] In this configuration, when the control unit 40 receives a print command from the receiving unit 42, it refers to the toner waste count in the toner waste count holding unit 62 to check whether there is an area AR where deteriorated toner should be disposed of. If there is an area AR where deteriorated toner should be disposed of, the control unit 40 creates a toner waste pattern using the toner waste pattern creation unit 64. The control unit 40 sends the created toner waste pattern and the print information from the host device to the drive control unit 44, voltage control unit 45, exposure control unit 46, and fuser control unit 47 and issues a print operation command. On the other hand, if there is no area AR where deteriorated toner should be disposed of, the control unit 40 does not dispose of deteriorated toner, but instead sends the print information from the host device to the drive control unit 44, voltage control unit 45, exposure control unit 46, and fuser control unit 47 and issues a print operation command.

[0037] When the drive control unit 44 receives instructions from the control unit 40, it rotates the drum motor 51 and the belt motor 50 to rotate the photosensitive drum 14 and the drive roller 24 in the direction of the arrow in Figure 1. When the voltage control unit 45 receives instructions from the control unit 40, it controls the voltage applied to the charging roller 15, developing roller 13, supply roller 12, regulating blade 18, transfer roller 26 and static elimination unit 20. When the exposure control unit 46 receives instructions from the control unit 40, it causes the print head 11 to emit light. When the fuser control unit 47 receives instructions from the control unit 40, it controls the temperature of the fuser unit 29. The drum count measurement unit 54 and the dot count measurement unit 56 measure the drum count and dot count during degraded toner disposal and printing operations.

[0038] [3. Printing Operation] Next, the printing operation will be described. The image forming apparatus 1 applies a charging voltage to the charging roller 15 using the voltage control unit 45 to uniformly charge the surface of the photosensitive drum 14, and then the exposure control unit 46 causes the print head 11 to emit light, forming an electrostatic latent image on the surface of the photosensitive drum 14.

[0039] The image forming apparatus 1 then applies a developing voltage to the developing roller 13, on which a thin layer of toner has been formed on its surface, using the voltage control unit 45, to develop the electrostatic latent image on the photosensitive drum 14. Here, the supply voltage and regulating voltage are applied to the supply roller 12 and the regulating blade 18 by the voltage control unit 45 in order to uniformly form the thin layer of toner on the developing roller 13 and to set the charge amount of toner in the toner layer to a predetermined value.

[0040] Next, the image forming apparatus 1 applies a transfer voltage to the transfer roller 26 via the voltage control unit 45 to transfer the toner image on the photosensitive drum 14 onto the paper P. After that, the toner image on the paper P is fixed to the paper P by the fixing unit 29. The paper P with the fixed toner image is discharged to the outside of the image forming apparatus 1 by the discharge roller 6. This completes the printing operation of the image forming apparatus 1. Any toner remaining on the photosensitive drum 14 that was not transferred is removed by the cleaning blade 16. In addition, the surface potential of the photosensitive drum 14 is reset by exposure by the static elimination unit 20.

[0041] When operating the image forming apparatus 1 in a normal temperature and humidity environment using negatively charged toner, the applied voltage settings are, for example, -1050[V] for the charging voltage, -200[V] for the developing voltage, -300[V] for the supply voltage, and -300[V] for the regulating blade voltage. The surface of the photosensitive drum 14 is charged when a charging voltage of a predetermined value or higher is applied to the charging roller 15, and the surface potential changes in proportion to the charging voltage. In this embodiment, when a charging voltage of -1050[V] is applied, the surface potential of the photosensitive drum 14 becomes -500[V]. The latent image potential of the electrostatic latent image formed by the light emission of the print head 11 becomes -50[V], and toner is inverted and developed from the developing roller 13 onto the electrostatic latent image. In the case of positively charged toner, the sign of the voltage is reversed.

[0042] Incidentally, in the image forming apparatus 1, the toner consumption of all developing units 19 may become excessively low, or the toner consumption of a specific developing unit 19 may become excessively low when a particular color is selected when forming a color image. When toner consumption is low, the toner is continuously stirred within the developing unit 19, and the toner adhering to the developing roller 13 is continuously rubbed by the supply roller 12, regulating blade 18, and photosensitive drum 14. In this case, the toner on the developing roller 13 tends to become triboelectrically charged, and its potential increases, and if it becomes too high, it can cause smudges and other defects in the image. Also, the toner is damaged when it is continuously rubbed, and the external additives it contains peel off from the surface of the toner. In that case, the image forming apparatus 1 cannot properly charge the toner, which can cause smudges, fogging, streaking, and deterioration of granularity.

[0043] As described above, if toner consumption becomes excessively low, the image forming apparatus 1 cannot properly charge the toner, resulting in smudges, fogging, streaking, and deterioration of granularity, thus reducing image quality. Therefore, in order to maintain image quality, the image forming apparatus 1 performs a deteriorated toner disposal procedure, which involves discarding a predetermined amount of toner, when printing with low toner consumption is repeated.

[0044] [4. Disposal of deteriorated toner Next, the disposal of degraded toner will be explained. The image forming apparatus 1 performs degraded toner disposal as a preparatory operation before printing, which is performed after receiving a print instruction. The image forming apparatus 1 performs degraded toner disposal by illuminating the photosensitive drum 14, which has been uniformly charged by the charging roller 15, with the print head 11 to form an electrostatic latent image on the surface of the photosensitive drum 14, and developing the toner with the developing roller 13. When degraded toner disposal is performed in all areas, the amount of toner discarded in one degraded toner disposal is equivalent to one count in the toner disposal count described later (i.e., 5% of the print coverage). Also, the amount of toner discarded in one degraded toner disposal in each area AR is equivalent to one count in each area AR in the toner disposal count described later (i.e., 5% of the print coverage within each area AR).

[0045] In conventional image forming apparatuses, if the overall toner consumption across the entire area (Figure 3) is low for a print pattern, toner may be uniformly discarded in the main scanning direction dm. However, looking specifically at area AR1 in Figure 3, more toner is consumed than the predetermined amount, so image quality does not deteriorate even without discarding degraded toner. Therefore, image forming apparatus 1 avoids discarding more toner than necessary by determining whether to discard degraded toner based on the toner consumption of each area AR, in addition to the toner consumption across the entire main scanning direction dm (all areas).

[0046] [5. Method for calculating toner waste count] The method for calculating the toner waste count is explained below. In the formula described later, x can range from 1 to 6, corresponding to areas AR1 to AR6, respectively. If the drum count per print operation is Drum Count Dr, the dot count for each area AR per print operation is Area Dot Count Dtx, the conversion coefficient for the toner waste count across all areas is Total Area Toner Waste Count Conversion Coefficient Y (792 in this embodiment), the toner waste threshold for all areas is Total Area Toner Waste Threshold A, and the toner waste threshold for each area AR is Each Area Toner Waste Threshold Bx, then the total area toner waste count K, which is the toner waste count across all areas, and the toner waste count for each area AR, which is the toner waste count for each area Lx, are calculated using the following formulas. In the following, each area dot count Dt1 to Dt6 will be collectively referred to as each area dot count Dt, each area toner waste threshold B1 to B6 will be collectively referred to as each area toner waste threshold B, and each area toner waste count L1 to L6 will be collectively referred to as each area toner waste count L.

[0047] K = K + (A*Dr - ΣDtx) / Y ... (1) Lx=Lx+((Bx / 6)*Dr-Dtx) / (Y / 6)……(2)

[0048] The toner waste threshold Bx for each area is set to a value six times the actual consumed image density (dot count). This ensures that when the total toner waste amount for the entire area is equal to the toner waste amount for each area AR, the total toner waste threshold A and the toner waste threshold Bx for each area become the same threshold.

[0049] Furthermore, as shown in Figure 4, the toner discard thresholds Bx for each area were set to an image density (printing rate) of 2% for areas B1 and B6, 1.5% for areas B2 and B5, and 1% for areas B3 and B4. In addition, the toner discard threshold A for all areas was set to an image density (printing rate) of 1.5%.

[0050] As shown in equation (2), the larger the value of the toner disposal threshold Bx for each area, the more likely the toner disposal count Lx for each area is to increase. Also, as the toner disposal threshold Bx for each area increases, even if the amount of toner disposed of in a single degraded toner disposal does not change, the toner disposal count tends to increase even if the dot count remains the same, and the frequency of degraded toner disposal increases.

[0051] In this embodiment, the image forming apparatus 1, due to the characteristics of toner circulation within the developing apparatus 19 in relation to the main scanning direction dm, which differ depending on the design of the developing apparatus 19, tends to accumulate at the edges of the developing apparatus 19 rather than in the center in the main scanning direction dm.

[0052] In contrast, as shown in Figure 4, the image forming apparatus 1 sets the area toner discard thresholds B3 and B4 of areas AR3 and AR4, located in the central part with respect to the main scanning direction dm, to a print density of 1 [%], the area toner discard thresholds B2 and B5 of areas AR2 and AR5, which are adjacent to areas AR3 and AR4 on the outer side with respect to the main scanning direction dm, to 1.5 [%], which is higher than the area toner discard thresholds B3 and B4, and the area toner discard thresholds B1 and B6 of areas AR1 and AR6, which are adjacent to areas AR2 and AR5 on the outer side with respect to the main scanning direction dm (i.e., located at the ends of the main scanning direction dm), to 2 [%], which is even higher than the area toner discard thresholds B2 and B5.

[0053] In this way, the image forming apparatus 1 gradually increases the toner disposal threshold B for each area as it moves from the center to the edges with respect to the main scanning direction dm. As a result, the image forming apparatus 1 can increase the toner disposal count more easily in areas AR that move from the center to the edges with respect to the main scanning direction dm, thereby increasing the frequency of degraded toner disposal. This allows the image forming apparatus 1 to increase the amount of toner disposed of in areas AR that move from the center to the edges with respect to the main scanning direction dm during operation. Thus, the image forming apparatus 1 can actively discharge degraded toner that tends to accumulate at the edges of the main scanning direction dm.

[0054] [6. Printing Process] Next, the specific processing procedure for printing by the control unit 40 will be explained in detail using the flowchart shown in Figure 5. When the power to the image forming apparatus 1 is turned on, the control unit 40 starts the printing procedure RT1 by reading and executing the printing program from the storage unit and moves to step SP1. In step SP1, the control unit 40 waits until it receives a print command from an external source via the receiving unit 42, and when the print command is received and printing is started, it moves to step SP2.

[0055] In step SP2, the control unit 40 determines whether the total area toner waste count K is 1 or greater (i.e., total area toner waste count K ≥ 1). If a positive result is obtained, this indicates that the total area toner waste count K is 1 or greater as the total area threshold, and that a predetermined amount of degraded toner equivalent to 1 count or more has accumulated. Therefore, it is necessary to perform degraded toner waste in area AR where degraded toner waste is required, and at this point the control unit 40 moves to step SP3.

[0056] In step SP3, the control unit 40 checks the toner waste count Lx for each area (x is 1 to 6), and in area AR where the toner waste count Lx for each area is 1 or greater than the area threshold (i.e., each toner waste count Lx ≥ 1), it performs the disposal of one count of deteriorated toner, and then proceeds to step SP4.

[0057] In step SP4, the control unit 40 updates the total area toner disposal count K and the individual area toner disposal count Lx, and then proceeds to step SP5. Specifically, when the number of areas AR where deteriorated toner disposal was performed in step SP3 is denoted as the number of toner disposal areas C, the control unit 40 recalculates the total area toner disposal count K as follows:

[0058] K = KC / 6 ... (3)

[0059] Furthermore, the control unit 40 recalculates the area toner disposal count Lx for each area AR where deteriorated toner disposal was performed in step SP3 (where x is the value of x for the area AR where deteriorated toner disposal was performed in step SP3, from 1 to 6) according to the following formula.

[0060] Lx = Lx - 1 ... (4)

[0061] In this way, the control unit 40 updates the area toner waste count L for each area AR where deteriorated toner disposal was performed by subtracting 1, which is the count used for the deteriorated toner disposal this time, from each area toner waste count L.

[0062] Furthermore, the control unit 40 recalculates the area toner disposal count Lx for each area AR where deteriorated toner disposal was not performed in step SP3 (where x is the value of x for area AR where deteriorated toner disposal was not performed in step SP3, out of 1 to 6) according to the following formula.

[0063] Lx = Lx ... (5)

[0064] On the other hand, if a negative result is obtained in step SP2, this indicates that the total area toner disposal count K is less than 1 and has not accumulated to the predetermined amount of 1 count, so there is no need to perform deteriorated toner disposal. In this case, the control unit 40 skips steps SP3 and SP4 and moves to step SP5.

[0065] In step SP5, the control unit 40 executes the printing operation and moves to step SP6. In step SP6, the control unit 40 uses the drum count measurement unit 54 and the dot count measurement unit 56 to obtain the drum count Dr and the area dot counts Dt1 to Dt6 for the printing operation performed in step SP5, and moves to step SP7. In step SP7, the control unit 40 uses the toner waste count calculation unit 60 to perform the calculations of equations (1) and (2) described above based on the drum count Dr and the area dot counts Dt1 to Dt6 obtained in step SP6, updates the total area toner waste count K and the area toner waste count Lx, and moves to step SP8 to end the printing process procedure RT1.

[0066] [7. Functional configuration of the image forming apparatus] Here, the basic functions related to the printing process in the image forming apparatus 1 are represented by a functional block diagram as shown in Figure 6.

[0067] The image forming unit 70 corresponds to the image forming unit 9 (Figure 1) and forms an image using toner as a developer. The total area print rate calculation unit 72 corresponds to the control unit 40 (Figure 2) and calculates the print rate of the total area AR, which is the print rate of the entire area of ​​the image forming region ARI. The individual area print rate calculation unit 74 corresponds to the control unit 40 (Figure 2) and calculates the print rate of each area AR, which is the print rate of each of the multiple areas AR formed by the division of the image forming region ARI in the main scanning direction dm. The degraded toner disposal execution unit 76 corresponds to the control unit 40 (Figure 2) and, when the total area toner disposal count K is 1 or more (i.e., the print rate of the total area AR is below the total area print rate threshold), it performs degraded toner disposal for area ARs where the individual area toner disposal count Lx (x is 1 to 6) is 1 or more (i.e., the print rate of each area AR is below the individual area print rate threshold).

[0068] [8. Effects, etc.] In the above configuration, the image forming apparatus 1 performs degraded toner disposal of area AR only when the print density of the entire image forming area ARI is low, and the print density of each area AR is low. In other words, even if the print density of the entire image forming area ARI is low, the image forming apparatus 1 does not perform degraded toner disposal of area AR if the print density of each area AR is high. To put it another way, even if the print density of each area AR is low, the image forming apparatus 1 does not perform degraded toner disposal of area AR if the print density of the entire image forming area ARI is high.

[0069] Therefore, when the overall print density of the page is low and toner consumption is low, the image forming apparatus 1 can perform degraded toner disposal only for areas AR with even lower print density, while not performing degraded toner disposal for areas AR with high print density. In this way, the image forming apparatus 1 can suppress excessive toner disposal by not performing degraded toner disposal for areas AR where the print density is high and not much degraded toner is generated, and thus maintain the quality of the printed image by performing degraded toner disposal for areas AR where the print density is low and degraded toner is generated and therefore degraded toner disposal is necessary.

[0070] Furthermore, the image forming apparatus 1 is configured to gradually increase the toner disposal threshold B for each area, from area AR located in the center of the main scanning direction dm towards area AR located at the edge of the main scanning direction dm. As a result, the image forming apparatus 1 can perform degraded toner disposal in such a way that the amount of toner disposed of gradually increases from area AR located in the center of the main scanning direction dm towards area AR located at the edge of the main scanning direction dm. This allows the image forming apparatus 1 to increase the amount of toner disposed of in areas AR from the center towards the edge of the main scanning direction dm as it operates, and to actively discharge degraded toner that tends to accumulate at the edge of the main scanning direction dm.

[0071] With the above configuration, the image forming apparatus 1 includes an image forming unit 70 that forms an image with toner, an overall area print rate calculation unit 72 that calculates the overall area print rate, which is the print rate of the entire area of ​​the image forming region ARI, an individual area print rate calculation unit 74 that calculates the individual area print rate, which is the print rate of each of the multiple areas AR formed by the division of the image forming region ARI in the main scanning direction dm, and a deteriorated toner disposal execution unit 76 that, when the overall area print rate is below the overall area print rate threshold, executes deteriorated toner disposal for areas AR whose individual area print rate is below the individual area print rate threshold.

[0072] As a result, the image forming apparatus 1 can maintain the quality of printed images by not disposing of degraded toner in areas AR where the print density is high and not much degraded toner is generated, thus avoiding the disposal of degraded toner, while disposing of degraded toner in areas AR where the print density is low and degraded toner is generated, thus avoiding the disposal of degraded toner.

[0073] [9. Other Embodiments] In the above-described embodiment, the image forming apparatus 1 is described as having a case where the area toner discard threshold B is gradually increased from the center to the edges with respect to the main scanning direction dm. The present invention is not limited to this, and the image forming apparatus 1 may at least make the area toner discard threshold B of each area AR located at the edges of the main scanning direction dm larger than that of the area AR located at the center of the main scanning direction dm. Furthermore, if, for example, deteriorated toner tends to accumulate in the central part of the main scanning direction dm of the developing apparatus 19 rather than at the edges, the image forming apparatus 1 may make the area toner discard threshold B of each area AR located at the center of the main scanning direction dm larger than that of the area AR located at the edges of the main scanning direction dm. In short, the image forming apparatus 1 may make the area toner discard threshold B of each area AR where deteriorated toner tends to accumulate with respect to the main scanning direction dm larger than the area toner discard threshold B of each area AR where deteriorated toner does not tend to accumulate with respect to the main scanning direction dm.

[0074] Furthermore, in the above-described embodiment, the image forming apparatus 1 increases the toner disposal count and the frequency of degraded toner disposal by gradually increasing the toner disposal threshold B for each area as it moves from the center to the edges in the main scanning direction dm, without changing the amount of toner disposed of in a single degraded toner disposal. The present invention is not limited to this, and the image forming apparatus 1 may also increase the amount of toner disposed of in a single degraded toner disposal as it moves from the center to the edges in the main scanning direction dm.

[0075] Furthermore, in the embodiment described above, the case in which the image forming apparatus 1 sets the area toner waste threshold B for each area toner to be the same for all image forming units 10 has been described. The present invention is not limited to this, and the image forming apparatus 1 does not need to set the area toner waste threshold B for each area toner to be the same for all image forming units 10. In that case, since toner contained in image forming units 10 located near the fuser unit 29 tends to deteriorate easily due to the heat emitted by the fuser unit 29, the value of each area toner waste threshold B may be increased for image forming units 10 that are closer to the fuser unit 29.

[0076] Furthermore, in the above-described embodiment, the image forming apparatus 1 was described in a case where the image forming region ARI is divided into, for example, six areas AR at equal intervals with respect to the main scanning direction dm. The present invention is not limited to this, and the image forming apparatus 1 may divide the image forming region ARI into any number of areas AR, five or fewer, or seven or more, at equal intervals with respect to the main scanning direction dm. Also, the image forming apparatus 1 does not have to divide the image forming region ARI at equal intervals with respect to the main scanning direction dm.

[0077] Furthermore, in the embodiment described above, the image forming apparatus 1 performs deteriorated toner disposal at the same time for all areas AR where each area toner disposal count Lx is 1 or more in step SP3 of the printing process RT1 (Figure 5). The present invention is not limited to this, and the image forming apparatus 1 may not perform deteriorated toner disposal at the same time for all areas AR where each area toner disposal count Lx is 1 or more, but may perform it at different times for at least some areas AR.

[0078] Furthermore, in the above-described embodiment, the case in which the image forming apparatus 1 calculates the print density for each print job was mentioned. The present invention is not limited to this, and the image forming apparatus 1 may also calculate the print density for each print page.

[0079] Furthermore, in the above-described embodiment, the image forming apparatus 1 receives a print command from an external source in step SP1 of the printing process procedure RT1 (Figure 5), and when printing is initiated, it performs deteriorated toner disposal as necessary. The present invention is not limited to this, and the image forming apparatus 1 may also perform deteriorated toner disposal as necessary at various other timings, such as when the power to the image forming apparatus 1 is turned on, when the cover of the image forming apparatus 1 is opened or closed, when various correction operations are performed, or after the printing operation is completed. In addition, deteriorated toner disposal may be performed as necessary at multiple timings by combining these timings.

[0080] Furthermore, in the above-described embodiment, the image forming apparatus 1 discards a toner amount equivalent to one count during the disposal of deteriorated toner. The present invention is not limited to this, and the image forming apparatus 1 may discard toner of various other amounts during the disposal of deteriorated toner.

[0081] Furthermore, the above-described embodiment described the case in which the present invention is applied to an image forming apparatus 1. The present invention is not limited to this, and may also be applied to various other electronic devices that perform various image-related processes, such as photocopiers, facsimile machines, and MFPs (Multi-Function Peripherals).

[0082] Furthermore, the present invention is not limited to the embodiments described above and other embodiments. That is, the scope of the present invention extends to embodiments that arbitrarily combine some or all of the embodiments described above and other embodiments. In addition, the scope of the present invention extends to embodiments in which a part of the configuration described in any embodiment among the embodiments described above and other embodiments is extracted and substituted or adapted for a part of the configuration of any embodiment among the embodiments described above and other embodiments, or to embodiments in which a part of the extracted configuration is added to any embodiment.

[0083] Furthermore, in the above-described embodiment, the image forming apparatus 1 is configured with an image forming unit 70 as an image forming unit, an all-area print coverage calculation unit 72 as an all-area print coverage calculation unit, an area print coverage calculation unit 74 as an area print coverage calculation unit, and a deteriorated toner disposal execution unit 76 as a deteriorated toner disposal execution unit. The present invention is not limited to this, and the image forming apparatus may be configured with an image forming unit having an all-area print coverage calculation unit, an area print coverage calculation unit, and a deteriorated toner disposal execution unit having various other configurations. [Industrial applicability]

[0084] This invention can be used in printers that dispose of degraded toner. [Explanation of Symbols]

[0085] 1...Image forming apparatus, 2...Housing, 3...Paper feed cassette, 4...Hopping roller, 5...Registration roller, 6...Discharge roller, 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...Regulating blade, 19...Developing apparatus, 20...Static removal section, 22...Transfer unit, 23...Transfer belt, 24...Drive roller, 25...Idler roller, 26...Transfer roller, 27...Belt cleaning blade, 28...Belt waste toner collection container, 29...Fusing unit, 30...Heating roller, 31...Pressure roller, W...Conveyor path, AR...Area, 40...Control unit, 42...Receiving unit, 44... 45... Drive control unit, 46... Voltage control unit, 47... Exposure control unit, 50... Belt motor, 51... Drum motor, 54... Drum count measurement unit, 56... Dot count measurement unit, 58... Toner waste threshold holding unit, 60... Toner waste count calculation unit, 62... Toner waste count holding unit, 64... Toner waste pattern creation unit, 70... Image forming unit, 72... Total area print rate calculation unit, 74... Each area print rate calculation unit, 76... Degraded toner waste execution unit, K... Total area toner waste count, Lx... Each area toner waste count, Dr... Drum count, Dtx... Each area dot count, Y... Total area toner waste count conversion coefficient, A... Total area toner waste threshold, Bx... Each area toner waste threshold, dm... Main scanning direction, ARI... Image forming area.

Claims

1. An image forming unit that forms an image using a developer, A total area print rate calculation unit calculates the total area print rate, which is the print rate of the entire image forming area, and calculates a total area toner waste count, in which a smaller value is added as the total area print rate increases. An area print rate calculation unit calculates the print rate for each of the multiple areas formed by dividing the image forming region in the main scanning direction, and calculates an area toner waste count where a smaller value is added as the area print rate increases, and a larger value is added as the area toner waste threshold increases. A deteriorated toner disposal execution unit sets the area toner disposal threshold to be gradually larger from the area located in the center of the main scanning direction toward the area located at the end of the main scanning direction, and when the total area toner disposal count is equal to or greater than the total area threshold, it performs deteriorated toner disposal for the area where the area toner disposal count is equal to or greater than the respective area threshold. An image forming apparatus having

2. The aforementioned deteriorated toner disposal unit is: Even if the total toner waste count for all areas is equal to or greater than the total area threshold, the deteriorated toner waste will not be performed for areas where the toner waste count for each area is less than the respective area threshold. The image forming apparatus according to claim 1.

3. The aforementioned deteriorated toner disposal unit is: For areas where the toner waste count for each area is equal to or greater than the threshold for each area, if the total toner waste count for all areas is less than the threshold for all areas, the degraded toner waste will not be performed. The image forming apparatus according to claim 1.

4. The aforementioned total area printing rate calculation unit is: The total area printing rate is calculated based on the total number of dots obtained by summing the number of dots for each area and the rotation speed of the image carrier. Each of the area printing rate calculation units described above is: The printing ratio for each area is calculated based on the number of dots in each area and the rotation speed of the image carrier. The image forming apparatus according to claim 1.

5. The aforementioned deteriorated toner disposal unit is: The image forming unit is controlled to discard degraded toner into the image carrier. The image forming apparatus according to claim 1.

6. An image forming unit that forms an image with a developer, A total area print rate calculation unit calculates the total area print rate, which is the print rate across the entire image forming region, An area print rate calculation unit calculates the print rate for each area, which is the print rate for each of the multiple areas formed by dividing the image forming region in the main scanning direction. A toner waste count calculation unit calculates a total area toner waste count which becomes smaller as the overall area printing rate increases, and a toner waste count for each area which becomes smaller as the printing rate for each area increases. When the total area toner waste count is equal to or greater than the total area threshold, a deteriorated toner waste execution unit executes deteriorated toner waste for the areas where the toner waste count for each area is equal to or greater than the respective area threshold. It has, The aforementioned area toner waste count will be higher the larger the area toner waste threshold is. The aforementioned deteriorated toner disposal unit is: The toner waste threshold for each area is set to be larger from the area located in the center of the main scanning direction toward the area located at the end of the main scanning direction. Image forming apparatus.

Images