Image forming apparatus

Abstract

To provide an image forming apparatus that can reduce unnecessary toner consumption, and can achieve both prevention of the occurrence of faulty cleaning and satisfactory removal of filming on an image carrier.SOLUTION: An image forming apparatus comprises: an intermediate transfer belt as an image carrier; a secondary transfer roller as a transfer member that is in contact with the intermediate transfer belt to form a transfer nip; and a cleaning blade as a cleaning member that cleans the surface of the intermediate transfer belt. When the linear velocity of the intermediate transfer belt is a standard speed (Yes in S11), the image forming apparatus forms a plurality of scraping patterns as toner image patterns that are not transferred to a recording medium and input to the cleaning blade at a predetermined interval (S14), and when, on the other hand, the linear velocity of the intermediate transfer belt is set to a medium speed or a low speed that is slower than the standard speed (No in S11), forms one scraping pattern (S13).SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Conventionally, there has been known an image forming apparatus that includes an image carrier, a transfer member that contacts the image carrier to form a transfer nip, and a cleaning member that cleans the surface of the image carrier, and that forms a toner image pattern on the image carrier without transferring it to a recording medium and inputting the toner image pattern to the cleaning member.

[0003] Patent document 1 describes an image forming device in which a long belt-like pattern is formed in a direction perpendicular to the surface movement direction of an intermediate transfer belt as a toner image pattern for removing filming on the intermediate transfer belt, which serves as an image carrier, and this belt-like pattern is passed through a transfer nip as the intermediate transfer belt moves, and is finally input to the point where the cleaning member contacts the image carrier. Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the linear speed of an image carrier such as an intermediate transfer belt, there is a risk that toner may be wasted or that it may not be possible to simultaneously suppress cleaning defects and effectively remove filming from the image carrier. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus comprising an image carrier, a transfer member that contacts the image carrier to form a transfer nip, and a cleaning member that cleans the surface of the image carrier, and in which a toner image pattern that is input to the cleaning member is formed on the image carrier without being transferred to the recording medium, the number of toner image patterns formed being changed according to the linear speed of the image carrier, and when multiple toner image patterns are formed, the multiple toner image patterns are formed at a predetermined interval in the direction of surface movement of the image carrier. Effect of the Invention

[0006] According to the present invention, it is possible to suppress wasteful toner consumption, and simultaneously suppress the occurrence of cleaning defects and effectively remove filming on the image carrier. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a tandem type color copier (hereinafter simply referred to as a copier) which is an image forming apparatus according to an embodiment of the present invention. [Diagram 2] 5A and 5B are schematic diagrams illustrating gradation patterns on an intermediate transfer belt. [Diagram 3] 5 is a schematic diagram showing an example of an image adjustment pattern formed on the intermediate transfer belt when image adjustment is performed in parallel with a printing operation. FIG. [Figure 4] 5A and 5B are diagrams for explaining positions at which scraping patterns are formed on the intermediate transfer belt. [Diagram 5] FIG. 13 is a diagram showing an example of a flowchart for forming a scraping pattern. [Figure 6] FIG. 11 is a diagram showing an example of a timing chart of a cleaning operation. [Figure 7] 5A to 5C are diagrams illustrating the formation of a scraping pattern according to the embodiment. [Figure 8] FIG. 13 is a diagram showing an example in which three scraping patterns are in different colors. [Figure 9] FIG. 4 is a flow chart for forming a scraping pattern according to the present embodiment. [Figure 10]11A to 11C are diagrams illustrating the scraping patterns under conditions (1) to (3) in the verification experiment. [Figure 11] FIG. 13 is a diagram for explaining the scraping patterns under conditions (4) to (6) in the verification experiment. [Figure 12] 11 is a timing chart illustrating passage of a plurality of scraping patterns through the secondary transfer nip during a cleaning operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The best mode for carrying out the present invention will be described below with reference to the drawings. Note that a person skilled in the art can easily modify and alter the present invention within the scope of the claims to create other embodiments, and these modifications and alterations are included in the scope of the claims. The following description is an example of the best mode for carrying out the present invention, and does not limit the scope of the claims.

[0009] FIG. 1 is a schematic diagram of a tandem type color copier (hereinafter simply referred to as a copier) which is an image forming apparatus according to this embodiment. 1, a tandem type color copier 1 (hereinafter simply referred to as the copier) as an image forming apparatus includes an original transport section 3 that transports an original to the original reading section, and an original reading section 4 that reads image information of the original. The copier also includes a paper output tray 5 on which output images are stacked, and a paper feed section 7 in which paper P as a recording medium is stored.

[0010] The copier 1 also includes registration rollers 9 (timing rollers) that adjust the timing of transport of the paper P, and an image forming unit 10 that forms toner images of each color (yellow, magenta, cyan, black). The image forming unit 10 includes, for example, photoconductor drums 11Y, 11M, 11C, and 11BK that serve as latent image carriers on which the toner images are formed, and a writing unit (exposure unit) 6. The image forming unit 10 also includes a charging device 12, a developing device 13, a cleaning unit 15, and the like that are disposed around each of the photoconductor drums 11Y, 11M, 11C, and 11BK.

[0011] The charging device 12 uniformly charges the surface of the photoconductor drum, and the writing section (exposure section) 6 emits laser light based on input image information to write an electrostatic latent image on each of the photoconductor drums 11Y, 11M, 11C, and 11BK. The developing device 13 develops the electrostatic latent image written on the photoconductor drum. The cleaning section 15 removes untransferred toner remaining on the photoconductor drum.

[0012] The copying machine 1 also includes an intermediate transfer belt 17 as an image carrier onto which a plurality of color toner images are transferred in a superimposed manner, and a primary transfer bias roller 14 that transfers the toner images formed on each of the photoconductor drums 11Y, 11M, 11C, and 11BK in a superimposed manner onto the intermediate transfer belt. The copying machine 1 also includes a secondary transfer roller 18 as a transfer member for transferring the color toner images on the intermediate transfer belt 17 onto a sheet of paper P. The copying machine 1 also includes a fixing device 20 that fixes an unfixed image on the sheet of paper P, and a toner container 28 that contains toner of each color (yellow, cyan, magenta, and black) to be supplied to the developing device 13. The copying machine 1 also includes a belt cleaning device 30 that removes toner (untransferred toner) adhering to the surface of the intermediate transfer belt 17. The copying machine 1 also includes a waste toner collection container 80 in which the untransferred toner removed by the belt cleaning device 30 or the like is collected as waste toner. The copying machine 1 also includes a control unit 90 (processor) including a CPU or the like equipped with a RAM and a ROM.

[0013] Hereinafter, the operation of the image forming apparatus during normal color image formation will be described. First, the document is transported from the document table by the transport rollers of the document transport unit 3 and placed on the contact glass of the document reading unit 4. Then, the document reading unit 4 optically reads image information of the document placed on the contact glass.

[0014] More specifically, the document reading unit 4 scans the image of the document on the contact glass while irradiating it with light emitted from an illumination lamp, and the light reflected by the document is imaged on the color sensor via a group of mirrors and a lens. The color image information of the document is read by the color sensor for each color separation light of RGB (red, green, blue), and then converted into an electrical image signal. Furthermore, the image processing unit performs processing such as color conversion processing, color correction processing, and spatial frequency correction processing based on the RGB color separation image signal, and obtains color image information of yellow, magenta, cyan, and black.

[0015] Image information for each color, yellow, magenta, cyan, and black, is transmitted to the writing unit 6. Then, laser light L based on the image information for each color is emitted from the writing unit 6 toward the surfaces of the corresponding photoconductor drums 11Y, 11M, 11C, and 11BK.

[0016] Meanwhile, the four photoconductor drums 11Y, 11M, 11C, and 11BK each rotate in the clockwise direction in FIG. 1. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portions facing the charging device 12 (charging process). Thus, a charging potential is formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK. After that, the charged surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.

[0017] In the writing unit 6, laser beams corresponding to the image signals are emitted from four light sources, one for each color. Each laser beam passes through a separate optical path for each color component: yellow, magenta, cyan, and black (this is the exposure process).

[0018] The laser light corresponding to the yellow component is irradiated onto the surface of the first photoconductor drum 11Y from the left side of the drawing. At this time, the laser light of the yellow component is scanned in the direction of the rotation axis of the photoconductor drum 11Y (main scanning direction) by a polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the surface of the photoconductor drum 11Y after it has been charged by the charging device 12.

[0019] Similarly, the laser light corresponding to the magenta component is irradiated onto the surface of the second photoconductor drum 11M from the left on the paper, forming an electrostatic latent image corresponding to the magenta component. The laser light corresponding to the cyan component is irradiated onto the surface of the third photoconductor drum 11C from the left on the paper, forming an electrostatic latent image of the cyan component. The laser light corresponding to the black component is irradiated onto the surface of the fourth photoconductor drum 11BK from the left on the paper, forming an electrostatic latent image of the black component.

[0020] Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color are formed reach positions facing the developing devices 13. Then, toner of each color is supplied from each developing device 13 onto the photoconductor drums 11Y, 11M, 11C, and 11BK, and the latent images on the photoconductor drums 11Y, 11M, 11C, and 11BK are developed (this is the developing process).

[0021] After the development process, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK each reach a portion facing the intermediate transfer belt 17 as an image carrier. Here, a primary transfer bias roller 14 is provided at each facing portion so as to abut against the inner circumferential surface of the intermediate transfer belt 17. Then, at the position of the primary transfer bias roller 14, the toner images of each color formed on the photoconductor drums 11Y, 11M, 11C, and 11BK are primarily transferred onto the intermediate transfer belt 17 in a sequentially overlapping manner (this is the primary transfer process).

[0022] After the transfer process, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK each reach a position facing the cleaning unit 15. Then, the cleaning unit 15 removes and collects the untransferred toner remaining on the photoconductor drums 11Y, 11M, 11C, and 11BK (cleaning process). The untransferred toner removed and collected by the cleaning unit 15 is transported as waste toner to a waste toner collection container 80 via a transport path and collected. Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK pass through a charge removing unit, and a series of image formation processes on the photoconductor drums 11Y, 11M, 11C, and 11BK is completed.

[0023] Meanwhile, intermediate transfer belt 17 (image carrier) carrying a color toner image formed by superimposing and primarily transferring the toners of the respective colors on photoreceptor drums 11Y, 11M, 11C, and 11BK travels in the counterclockwise direction in FIG. 1 and reaches a position facing secondary transfer roller 18. Secondary transfer roller 18 abuts against intermediate transfer belt 17 to form a secondary transfer nip, which is a transfer nip. In this secondary transfer nip, the color toner image carried on intermediate transfer belt 17 is secondarily transferred onto paper P (secondary transfer process).

[0024] A secondary transfer bias is applied to an opposing roller 18A that faces the secondary transfer roller 18 via the intermediate transfer belt 17, and the secondary transfer roller 18 is electrically grounded. When the color toner image on the intermediate transfer belt 17 is secondarily transferred to the paper P, a transfer bias of negative polarity, which is the normal charging polarity of the toner, is applied to the opposing roller 18A, and the normally charged toner of negative polarity on the intermediate transfer belt is repulsively transferred to the paper P.

[0025] The surface of the intermediate transfer belt 17 after the secondary transfer process reaches the position of the belt cleaning device 30. The belt cleaning device 30 has a cleaning blade 31 as a cleaning member. The cleaning blade 31 removes toner (untransferred toner) adhering to the intermediate transfer belt 17. The toner removed by the cleaning blade is transported as waste toner to a waste toner collection container 80 via a transport path and collected.

[0026] Here, the paper P transported between the intermediate transfer belt 17 and the secondary transfer roller 18 (secondary transfer nip) is transported from the paper feed section 7 via the registration rollers 9 and the like. More specifically, the paper P fed by the paper feed roller 8 from the paper feed unit 7 storing the paper P passes through a conveyance guide and is then guided to the registration rollers 9. The paper P that has reached the registration rollers 9 is conveyed in a timely manner toward the secondary transfer nip.

[0027] The paper P onto which the full-color image has been transferred in the secondary transfer process is then guided to the fixing device 20. In the fixing device 20, the color image is fixed onto the paper P at the nip between a fixing roller and a pressure roller. Then, the paper P after the fixing process is discharged as an output image outside the device body by a paper discharge roller and stacked on the paper discharge tray 5, completing a series of image formation processes.

[0028] In this copying machine, a control called process control is carried out at a predetermined timing in order to stabilize image quality against environmental changes and over time. FIG. 2 is a schematic diagram for explaining a gradation pattern on the intermediate transfer belt.

[0029] The gradation patterns are made up of a plurality of toner patches having different image densities, and these gradation patterns are formed at positions (the center and both ends in the width direction) facing the optical sensor of the intermediate transfer belt 17. In the example shown in Fig. 2, gradation patterns of black, cyan, magenta, and yellow are formed from the top.

[0030] The optical sensor unit 40 has a plurality of optical sensors 40R, 40C, and 40F as adhesion amount detection means arranged at a predetermined interval in the belt width direction of the intermediate transfer belt 17. Each optical sensor outputs a signal according to the optical reflectance of the intermediate transfer belt 17 and the gradation patterns PK, PC, PM, and PY on the intermediate transfer belt 17, and detects the amount of toner adhesion. The copier 1 adjusts the image formation conditions such as the development bias Vb based on the detected toner adhesion amount.

[0031] The optical sensors 40R and 40F, which are arranged to face the width direction end regions of the intermediate transfer belt 17, are arranged outside the paper passing region. Therefore, as shown in Fig. 3, during the formation of a toner image to be transferred to paper, an image adjustment pattern is formed outside the paper passing region, and the optical sensors 40R and 40F detect the amount of toner adhesion of the image adjustment pattern. Then, based on the amount of toner adhesion detected by the optical sensors 40R and 40F, the developing bias, etc. can be adjusted to adjust the image density, etc.

[0032] The base component of the toner, silica or titanium oxide added to the toner, and other so-called external additives of the toner are transferred from the photoconductor drum 11 to the intermediate transfer belt 17. The external additives of the toner transferred to the intermediate transfer belt 17 may adhere to the intermediate transfer belt 17, causing filming on the intermediate transfer belt 17. If the surface of the photoconductor drum 11 has a lubricant application section that applies a lubricant, various components contained in the lubricant, such as boron nitride and zinc stearate, are also transferred from the photoconductor drum 11 to the intermediate transfer belt 17 in addition to the external additives of the toner. The external additives of the toner and the lubricant may interact with each other, causing the filming on the intermediate transfer belt 17 to worsen. Furthermore, at the secondary transfer nip, paper dust may be transferred from the paper P to the intermediate transfer belt 17 and adhere to the intermediate transfer belt 17, causing paper dust filming.

[0033] Such filming on the intermediate transfer belt 17 occurs when filming substances, such as various components contained in toner additives such as silica and lubricants, adhere to the intermediate transfer belt 17 due to external pressure (mainly contact pressure with the photosensitive drum). If filming occurs on the intermediate transfer belt 17, when a full solid image or halftone image is output, toner does not adhere to the areas corresponding to the filming, resulting in abnormal images such as white spots.

[0034] Furthermore, when filming occurs, the glossiness of the belt decreases. Therefore, when filming occurs in the area of ​​the intermediate transfer belt 17 facing the optical sensors 40R, 40C, and 40F, the output signal changes and it becomes impossible to properly detect the amount of the gradation pattern attached on the intermediate transfer belt. In addition, there is also a problem that the output of the optical sensor becomes unstable due to unevenness in the filming state, making it impossible to perform correct image adjustment.

[0035] Furthermore, filming may deteriorate the cleaning performance of the cleaning blade 31. In the belt width direction, gradation patterns with a large amount of adhesion per unit area are often input to the positions of the cleaning blade 31 corresponding to the positions of the optical sensors 40R, 40C, and 40F. Therefore, if filming occurs in the areas of the intermediate transfer belt 17 facing the optical sensors 40R, 40C, and 40F, there is a high risk of poor cleaning (toner slipping through) occurring when the gradation pattern is input to the cleaning blade 31.

[0036] The filming can be scraped off by toner remaining at the contact point between the cleaning blade 31 and the surface of the intermediate transfer belt 17 (hereinafter referred to as the "cleaning point"), and removed from the surface of the intermediate transfer belt 17. Specifically, the filming on the surface of the intermediate transfer belt is scraped off by the unevenness of the surface of the toner remaining at the cleaning point and the pressure of the cleaning blade 31 applied to the toner.

[0037] Therefore, in order to suppress filming on the intermediate transfer belt 17, the copying machine 1 forms a scraping pattern on the intermediate transfer belt 17 at a predetermined timing. Then, by inputting this scraping pattern to the cleaning blade 31, a sufficient amount of toner is allowed to remain at the cleaning location.

[0038] FIG. 4 is a diagram for explaining the positions at which the scraping patterns are formed on the intermediate transfer belt. FIG. 4 shows the case where three sheets are printed continuously in a normal image forming operation. As shown in FIG. 4, the formation position of the scraping pattern is as follows: 1. Position before the first sheet of paper into the secondary transfer nip 2. Position outside the width of the paper passing through the secondary transfer nip 3. Position of non-image forming area at the rear end of the paper passing through the secondary transfer nip 4. Position of the paper gap 5. Position after the final sheet passes through the secondary transfer nip Some examples include: The above 2. can be adopted in a configuration in which the width of the intermediate transfer belt is wider than the axial length of the secondary transfer roller, and the secondary transfer roller does not contact the intermediate transfer belt 17 at the position 2. This is because, in a configuration in which the secondary transfer roller 18 contacts the intermediate transfer belt 17 at the position 2, the scraping pattern formed at the position 2 is transferred to the secondary transfer roller 18. Furthermore, at the position 2 alone, filming can only be removed from the ends of the intermediate transfer belt in the width direction, so it is necessary to combine it with the strip-shaped scraping pattern that is long in the width direction of the intermediate transfer belt as described above in 1 and 3 to 5.

[0039] Regarding 3 above, it may be a position in a non-image forming area at the leading edge of the paper passing through the secondary transfer nip. Regarding 1 and 3 to 5 above, when the scraping pattern on the intermediate transfer belt passes through the secondary transfer nip, a positive bias is applied to the opposing roller 18A. By applying a positive bias to the opposing roller 18A, the scraping pattern is electrostatically attracted to the intermediate transfer belt 17, so that the scraping pattern is not transferred to the secondary transfer roller 18 or the paper P.

[0040] FIG. 5 is a diagram showing an example of a flowchart for forming the scraping pattern. When the control unit 90 receives a print command and starts driving the intermediate transfer belt 17, it starts measuring the travel distance of the intermediate transfer belt 17 (S1). When the drive of the intermediate transfer belt 17 stops, it calculates the necessary toner input amount to the cleaning blade 31 based on the filming state on the surface of the intermediate transfer belt 17 based on the measured travel distance of the intermediate transfer belt 17. Specifically, it calculates the necessary toner input amount by multiplying the travel distance of the intermediate transfer belt 17 by a coefficient. Then, it adds the calculated necessary toner input amount to calculate an integrated value of the necessary toner input amount (S2). Next, the control unit judges whether the integrated value of the necessary toner input amount exceeds a threshold value (S3). If the integrated value does not exceed the threshold value (No in S3), the flow of FIG. 5 ends. On the other hand, if the integrated value exceeds the threshold value (Yes in S3), for example, a scraping pattern is formed during the cleaning operation as described below. Then, the toner amount of the formed scraping pattern (the amount of toner input to the cleaning blade) is subtracted from the integrated value (S4). Thus, the flow of FIG. 5 ends.

[0041] In the case of a device that detects the presence or absence of filming with an optical sensor and forms a scraping pattern, even if filming occurs outside the detection range of the optical sensor, the filming in the area of ​​the intermediate transfer belt facing the optical sensor is not removed until filming occurs in the area of ​​the intermediate transfer belt facing the optical sensor. As a result, there is a risk that the occurrence of abnormal images such as blank areas due to filming cannot be effectively suppressed.

[0042] In contrast, in this embodiment, a scraping pattern is formed based on the travel distance of the intermediate transfer belt 17. As a result, even if no filming occurs in the area of ​​the intermediate transfer belt 17 facing the optical sensor, if there is a possibility that filming occurs in other areas, a scraping pattern is formed. Therefore, filming on the intermediate transfer belt 17 can be removed more effectively than when a scraping pattern is formed based on the detection result of the optical sensor.

[0043] The above coefficient may be a fixed value, or for example, the coefficient may be changed between a color image mode and a monochrome image mode. This is because filming may deteriorate more in the color image mode than in the monochrome image mode. In the color image mode, the fixing set temperature is higher and the number of operating motors increases compared to the monochrome image mode, so the temperature inside the machine tends to rise. When the temperature inside the machine rises, the amount of stick slip of the cleaning blade 31 increases, and filming may deteriorate. Also, when there is a lubricant application part for applying a lubricant to the surface of the photoreceptor drum 11, in the color image mode, the amount of lubricant, which is a component of the filming substance adhering to the intermediate transfer belt 17, increases compared to the monochrome mode. Therefore, filming may deteriorate more in the color image mode than in the monochrome image mode.

[0044] Therefore, for example, the coefficient B in the color image mode is set to a value higher than the coefficient A in the monochrome image mode (A < B). Then, when forming an image (when driving the intermediate transfer belt), it is determined whether it is the monochrome image mode or the color image mode. In the monochrome image mode, the required toner input amount is calculated using the coefficient A, and in the color image mode, the required toner input amount is calculated using the coefficient B.

[0045] For example, when there are many color image modes, the risk of filming deterioration is higher than in the monochrome image mode as described above. However, when there are many color image modes, since the integrated value of the required toner input amount exceeds the threshold value at a short running distance of the intermediate transfer belt 17, the scraping pattern is formed at an early timing. On the other hand, when there are many monochrome image modes, filming is less likely to deteriorate compared to the color image mode. Therefore, when there are many monochrome image modes, the running distance at which the integrated value of the required toner input amount exceeds the threshold value becomes longer, and the scraping pattern is formed at a late timing.

[0046] In this way, by forming the scraping pattern based on the image mode, the scraping pattern can be formed at an appropriate timing, and wasteful toner consumption and worsening filming can be effectively suppressed.

[0047] When the copier 1 is in operation, background staining toner is continuously supplied from the developing device 13, and this background staining toner may adhere to the paper gap of the intermediate transfer belt 17. The background staining toner adhered to the paper gap adheres to the secondary transfer roller at the secondary transfer nip, and the secondary transfer roller 18 becomes stained with the toner. If the secondary transfer roller 18 becomes stained with toner in this way, when a toner image is transferred to the paper P, the toner of the secondary transfer roller 18 may adhere to the back surface of the paper P, causing back staining.

[0048] Therefore, the copying machine 1 is adapted to execute a cleaning operation for cleaning the secondary transfer roller 18. By executing this cleaning operation, the toner adhering to the secondary transfer roller 18 is moved to the intermediate transfer belt 17.

[0049] FIG. 6 is a diagram showing an example of a timing chart of the cleaning operation. As shown in FIG. 6, when the cleaning operation is performed, a negative polarity bias and a positive polarity bias are alternately applied to the opposing roller 18A to form an alternating electric field in the secondary transfer nip. By forming an alternating electric field, the toner adhering to the secondary transfer roller 18 can be efficiently cleaned by a hopping effect. Here, the hopping effect is an effect in which the toner on the secondary transfer roller 18 is easily moved to the intermediate transfer belt 17 by reciprocating between the secondary transfer roller 18 and the intermediate transfer belt 17. In this way, by forming an alternating electric field, the toner of both polarities adhering to the secondary transfer roller 18 can be moved to the intermediate transfer belt 17, and the surface of the secondary transfer roller 18 can be satisfactorily cleaned. This makes it possible to suppress back stains on the paper.

[0050] The period of negative and positive application that forms the alternating electric field is the period during which the secondary transfer roller 18 rotates once or more. In the cleaning operation performed before the first sheet of paper passes through the secondary transfer nip in FIG. 6, after negative and positive application are performed three times, the bias is temporarily set to zero and then a positive bias is applied again. The length of the positive bias that is applied again is adjusted according to the timing of paper feed. It is not necessary to temporarily set the bias to zero.

[0051] Like the cleaning operation performed after the final paper in Fig. 6 has passed through the secondary transfer nip, negative application → positive application may be performed once, or negative application → positive application may be performed four or more times. Also, the bias value for the first and second negative application → positive application does not have to be constant (it may show a behavior in which the bias is amplified or attenuated stepwise). Also, if the paper interval is wide, the cleaning operation may be performed between the papers.

[0052] As described above, it is preferable that a sufficient amount of toner remains at the cleaning area, because this effectively removes filming on the surface of the intermediate transfer belt 17. However, if the amount of toner in the scraping pattern is increased and a large amount of toner is input to the cleaning area at one time, the toner may slip through, resulting in poor cleaning.

[0053] This copier has multiple image formation modes in which the linear speed of the intermediate transfer belt 17 differs from one another, such as standard speed, medium speed, and low speed, and is configured to switch between image formation modes depending on the type of paper, the installation environment of the image forming device, and the customer's usage conditions.

[0054] In the standard speed image forming mode, the linear speed of the intermediate transfer belt 17 is increased in order to improve productivity, and such an increase in speed tends to worsen filming. As a result, in the standard speed image forming mode, in order to effectively remove filming on the intermediate transfer belt 17, it is necessary to input a larger amount of toner to the cleaning area compared to the medium speed and low speed image forming modes.

[0055] However, as described above, if the amount of toner in the scraping pattern is increased and a large amount of toner is input to the cleaning area at one time, poor cleaning results.

[0056] Therefore, in this embodiment, multiple scraping patterns KP are formed at short intervals, as shown in Fig. 7. This makes it possible to ensure that the amount of toner in the scraping patterns KP is sufficient to prevent cleaning failure, and that the number of scraping patterns KP is sufficient to ensure the amount of toner sufficient to remove filming on the intermediate transfer belt.

[0057] As shown in FIG. 7B, each scraping pattern KP is a strip-shaped pattern that is long in the main scanning direction, and is longer than the maximum paper width that the device can convey, and extends in the main scanning direction to the opposing areas of the optical sensors 40R and 40F arranged opposite both ends of the intermediate transfer belt 17. This makes it possible to effectively suppress filming in the maximum paper width area of ​​the intermediate transfer belt 17 where the toner image to be transferred to the paper P is formed, and effectively suppress the occurrence of abnormal images such as blank areas. In addition, the scraping pattern KP extends to the opposing areas of the optical sensors 40R and 40F arranged opposite both ends of the intermediate transfer belt 17. This makes it possible to effectively suppress filming in the opposing parts of the intermediate transfer belt 17 where the optical sensors 40R and 40F face each other, and effectively detect the amount of adhesion.

[0058] The interval Sp is set so that the next scraping pattern is input before the toner forming the previous scraping pattern is completely removed from the cleaning area. The interval Sp is also set so that when the next scraping pattern KP is input to the cleaning area, the amount of toner remaining at the cleaning area is equal to or less than the amount of toner that would cause a cleaning defect. This prevents cleaning defects and effectively prevents filming.

[0059] It is also preferable to form the three scraping patterns with toners of different colors, as shown in Fig. 8. This makes it possible to prevent toner consumption from being concentrated in a specific color.

[0060] In addition, in FIG. 8, the scraping pattern at the most downstream of the intermediate transfer belt 17 is C color, the scraping pattern at the center is M color, and the scraping pattern at the most upstream is Y color, following the arrangement order of the image forming units 10 shown in FIG. 1. In this way, the image forming time for forming three scraping patterns can be shortened by making the order of the colors of the scraping patterns follow the arrangement order of the image forming units 10. Also, three scraping patterns may be formed on the intermediate transfer belt 17 in the order of K, C, and M colors. Even with this configuration, for example, the image forming time for forming three scraping patterns can be shortened compared to the case where the order is K, M, and Y colors, skipping C color. The image forming time is the time from when one of the three image forming units starts the series of image forming processes described above to when the last one of the three image forming units ends the series of image forming processes described above.

[0061] As shown in Figs. 7 and 8, by forming multiple scraping patterns KP at short intervals, cleaning failure can be suppressed and filming can be removed well in the standard speed image forming mode where filming is likely to worsen. However, in the medium and low speed image forming modes, the linear speed of the intermediate transfer belt 17 is slower than in the standard speed image forming mode, so the level of filming is lower than in the standard speed image forming mode. Therefore, if multiple scraping patterns KP are formed in the medium and low speed image forming modes as shown in Figs. 7 and 8, the amount of toner input to the cleaning area will be excessive for the filming state, which will increase the amount of toner consumed unnecessarily. Therefore, it is preferable to reduce the number of scraping patterns KP in the medium and low speed image forming modes compared to the standard speed image forming mode.

[0062] FIG. 9 is a flow diagram relating to the formation of the scraping pattern KP in this embodiment. As described with reference to Fig. 5, when the integrated value of the required toner input amount exceeds the threshold value and it is time to form a scraping pattern, the control unit 90 checks whether the set linear speed of the intermediate transfer belt 17 is standard speed or not (S11). When the image formation mode is the standard speed image formation mode and the linear speed of the intermediate transfer belt 17 is set to the standard speed (high speed) (Yes in S11), multiple scraping patterns KP are formed at short intervals (S12) as shown in Figs. 7 and 8.

[0063] On the other hand, when the image forming mode is a medium or low speed image forming mode and the linear speed of the intermediate transfer belt 17 is set to medium or low speed (No in S11), one scraping pattern KP is formed (S13). Then, the toner amount of the formed scraping pattern (the amount of toner input to the cleaning blade) is subtracted from the integrated value (S14).

[0064] In this way, in the medium-speed or low-speed image forming mode, where the deterioration of filming is milder than in the standard-speed image forming mode, there is only one scraping pattern KP. Even if there is only one scraping pattern KP and the amount of toner input to the cleaning area is small, the filming on the intermediate transfer belt 17 can be effectively removed. This makes it possible to reduce unnecessary toner consumption.

[0065] In addition, the threshold value of the integrated value of the necessary toner input amount for determining whether or not to form the scraping pattern may be made different between the standard speed image forming mode and the medium and low speed image forming modes, as described with reference to Fig. 5. Specifically, the threshold value in the standard speed image forming mode may be made lower than the threshold value in the medium and low speed image forming modes, and the frequency of forming the scraping pattern may be increased in the standard speed image forming mode compared to the medium and low speed image forming modes.

[0066] 5, the required toner input amount is calculated by multiplying the travel distance of the intermediate transfer belt 17 by a coefficient, but the coefficient may be changed between the standard speed image forming mode and the medium and low speed image forming modes. Specifically, the value of the coefficient in the standard speed image forming mode is set to be larger than the value of the coefficient in the medium and low speed image forming modes. This makes it possible to increase the frequency of formation of scraping patterns in the standard speed image forming mode compared to the medium and low speed image forming modes, and to suppress the deterioration of filming in the standard speed image forming mode.

[0067] The verification experiments carried out by the present inventors will be described below. As shown in Figs. 10 and 11, verification experiments were carried out under conditions (1) to (6) in which the length of the scraping pattern in the surface movement direction and the number of scraping patterns were different from one another.

[0068] Condition (1) is a condition in which one scraping pattern KP with a length in the moving direction of 32.5 mm is formed, and condition (2) is a condition in which one scraping pattern KP with a length in the moving direction of 97.5 mm is formed. Condition (3) is a condition in which three scraping patterns KP with a length in the moving direction of 32.5 mm are formed at intervals of 13 mm, and condition (4) is a condition in which one scraping pattern KP with a length in the moving direction of 80 mm is formed. Condition (5) is a condition in which one scraping pattern KP with a length in the moving direction of 200 mm is formed. Condition (6) is a condition in which three scraping patterns KP with lengths in the moving direction of 70 mm, 60 mm, and 70 mm are formed at intervals of 80 mm. Under conditions (1) to (6), the cleaning performance and filming performance were evaluated for each of two linear speed levels of the intermediate transfer belt: a standard speed of 300 mm / s and a medium speed of 256 mm / s.

[0069] <Cleaning performance evaluation> The cleaning performance was evaluated under the following conditions. Cleaning blade contact pressure: 20N / m -Intermediate transfer belt linear speed: 2 levels: 300mm / s and 256mm / s The cleaning performance was evaluated based on the image printed after the scraping pattern KP was formed. When no streaky abnormal image was observed in the printed image, the cleaning performance was evaluated as "○", and when streaky abnormal image was observed in the printed image, the cleaning performance was evaluated as "×".

[0070] <Filming Evaluation> The filming property was evaluated by printing 150,000 sheets of a running chart with an image area ratio of 5%, and then forming a test pattern on the intermediate transfer belt. If no error occurred when the optical sensors 40R, 40C, and 40F detected the adhesion amount of the test pattern, the filming property was evaluated as "good". On the other hand, if an error occurred when the optical sensors 40R, 40C, and 40F detected the adhesion amount of the test pattern, the filming property was evaluated as "bad". The scraping pattern KP was calculated by calculating the toner input amount based on the travel distance of the intermediate transfer belt 17, and when the load value of the toner input amount exceeded a threshold, the scraping pattern was formed.

[0071] The results of the verification experiment are shown in the following Table 1. Note that the condition (0) in the following Table 1 is the result when the scraping pattern KP was not formed. [Table 1]

[0072] As shown in Table 1, under conditions (2) and (5) in which one scraping pattern KP with a length in the moving direction of 97.5 mm or more was formed, the cleaning performance was rated as "X" regardless of whether the linear speed of the intermediate transfer belt 17 was 256 mm / s or 300 mm / s. This is thought to be because a large amount of toner was input to the cleaning area at once, and the tip of the cleaning blade 31 was unable to withstand the pressure of the toner input to the cleaning area, causing the toner to slip through, resulting in streaky abnormal images.

[0073] On the other hand, in cases (1), (3), (4), and (6) where the length of the scraping pattern KP in the moving direction was 80 mm or less, no cleaning failure occurred. This shows that by setting the length of the scraping pattern KP in the moving direction to 80 mm or less, the amount of toner in the scraping pattern KP can be reduced to the amount of toner at which cleaning failure occurs or less.

[0074] Moreover, under conditions (2) and (5), the filming evaluation was "good" when the linear speed of the intermediate transfer belt 17 was either 256 mm / s or 300 mm / s. Because a large amount of toner is input to the cleaning blade 31, the toner can be made to remain at the cleaning location for a long time. This allows the toner that remains at the cleaning location for a relatively long period of time to remove filming. As a result, it is believed that filming on the intermediate transfer belt 17 can be suppressed over time, resulting in the filming evaluation of "good."

[0075] Furthermore, as shown in Table 1, when the linear velocity of the intermediate transfer belt 17 was 256 mm / s, the filming evaluation was "good" under conditions (1) to (6). On the other hand, when the linear velocity of the intermediate transfer belt 17 was 300 mm / s, the filming evaluation was "bad" under conditions (1) and (4) with one scraping pattern.

[0076] As described above, in this embodiment, the toner amount of the formed scraping pattern (the amount of toner input to the cleaning blade) is subtracted from the cumulative value of the toner input amount, and when the cumulative value of the toner input amount exceeds the threshold value, the scraping pattern is formed. In condition (1), the amount of toner input to the cleaning blade 31 is small, so the subtraction value is small, and the frequency of the toner scraping pattern formation operation is high compared to the other conditions (2) to (6). However, since the amount of toner input to the cleaning blade in one scraping pattern formation operation is small, the filming is not sufficiently scraped off in one scraping pattern formation operation. As a result, even if the frequency of the toner scraping pattern formation operation is high, under the condition of a linear speed of 300 mm / s, which is prone to filming deterioration, the filming on the intermediate transfer belt 17 cannot be removed well, and the filming on the intermediate transfer belt 17 deteriorates over time, and it is considered that the filming evaluation was "x".

[0077] On the other hand, when the linear speed of the intermediate transfer belt 17 was 256 mm / s, the filming property was also rated as “good” under condition (1), which was the smallest amount of toner input to the cleaning blade in one scraping pattern formation operation among conditions (1) to (6).

[0078] When the linear velocity of the intermediate transfer belt 17 is 300 mm / s, the cleaning performance and filming resistance were both evaluated as "good" under conditions (3) and (6). First, under conditions (3) and (6), the length of the scraping pattern KP in the movement direction is 80 mm or less, and the toner amount of the scraping pattern KP is kept below the toner amount at which cleaning defects occur, so no cleaning defects occur.

[0079] Moreover, under conditions (3) and (6), three scraping patterns are formed at a predetermined interval, and the next scraping pattern KP is input to the cleaning spot before the toner at the cleaning spot is completely removed by the cleaning blade 31. This allows the filming caused by the toner at the cleaning spot to be continuously scraped off. Under condition (3), the total length of the three scraping patterns in the moving direction is 97.5 mm, the same as under condition (2). This allows the same amount of toner as under condition (2) to be input to the cleaning spot. Therefore, as under condition (2), the filming on the intermediate transfer belt 17 can be removed by the toner that has been retained at the cleaning spot for a certain amount of time. As a result, it is considered that the filming evaluation was "good" even when the linear speed of the intermediate transfer belt 17 is 300 mm / s, which is prone to worsening filming.

[0080] In addition, the length of each scraping pattern in the movement direction is longer under condition (6) than under condition (3). Therefore, the amount of toner input to the cleaning area at one time is greater than under condition (3). Therefore, even if the interval between the scraping patterns is longer than under condition (3), the next scraping pattern can be input to the cleaning area before the toner at the cleaning area is completely removed by the cleaning blade 31. Therefore, under condition (6), the filming on the intermediate transfer belt 17 can be removed by the toner that has been retained at the cleaning area for a certain amount of time. Therefore, it is considered that the filming evaluation was "good" even when the linear speed of the intermediate transfer belt 17 was 300 mm / s.

[0081] On the other hand, in condition (6), if the interval between the scraping patterns is set to 13 mm as in condition (3), too much toner will remain at the cleaning points, which may result in poor cleaning. Therefore, it is necessary to set the interval between the scraping patterns according to the length of each scraping pattern in the movement direction (the amount of toner in the scraping pattern).

[0082] Condition (3) has a shorter distance from the first to the last scraping pattern than condition (6), and the period of the scraping pattern formation operation is shorter than condition (6), which reduces the downtime of the device. On the other hand, condition (6) has a larger total amount of toner input to the cleaning area in one scraping pattern formation operation than condition (3), and the toner also remains at the cleaning area for a longer period. Therefore, condition (6) has a higher filming removal effect than condition (3).

[0083] From the above, conditions (1), (2), (4), and (5), it was found that by setting at least the length of the scraping pattern KP in the movement direction to 80 mm or less, the amount of toner in the scraping pattern KP can be made less than the amount of toner that would cause cleaning defects, and the occurrence of cleaning defects can be suppressed.

[0084] It was also found that when the linear speed of the intermediate transfer belt is 300 mm / s in the standard image formation mode, filming on the intermediate transfer belt 17 can be suppressed over time by making the length in the moving direction of the scraping pattern KP at least 97.5 mm. And from conditions (3) and (6), it was found that when the linear speed of the intermediate transfer belt is 300 mm / s in the standard image formation mode, filming and cleaning defects can be suppressed by forming multiple scraping patterns at short intervals and making the total length in the moving direction of the scraping pattern KP 97.5 mm or more.

[0085] On the other hand, in an image formation mode where the linear speed of the intermediate transfer belt 17 is slower than the standard image formation mode of 256 mm / s, it was found that filming can be suppressed if the length in the moving direction of the scraping pattern KP is 32.5 mm or more. Therefore, in a medium-speed or low-speed image formation mode where the linear speed of the intermediate transfer belt is 256 mm / s or less, it was found that by forming one scraping pattern KP with a length in the moving direction of 32.5 mm, it is possible to suppress filming and reduce wasteful toner consumption.

[0086] From the above, when the linear speed of the intermediate transfer belt is such that the length of the scraping pattern in the moving direction required to suppress filming over time exceeds 80 mm, multiple scraping patterns are formed. This makes it possible to suppress filming over time while suppressing cleaning defects.

[0087] On the other hand, when the linear speed requires the length of the scraping pattern in the moving direction to be 80 mm or less to suppress filming over time, one scraping pattern is used, and the length of the scraping pattern in the moving direction is set according to the linear speed of the intermediate transfer belt. This makes it possible to suppress filming over time while suppressing cleaning defects and to reduce unnecessary toner consumption.

[0088] From the above verification experiments, as shown in Figure 9, in the standard speed image formation mode, multiple scraping patterns are formed. On the other hand, in the medium and low speed image formation modes, only one scraping pattern is formed. This has confirmed that it is possible to reduce wasteful toner consumption, while simultaneously suppressing filming over time and cleaning defects.

[0089] When multiple scraping patterns KP are formed, it is preferable to make the length of each scraping pattern KP in the movement direction shorter than the circumferential length of the secondary transfer roller 18 and make the interval Sp between the scraping patterns KP longer than the circumferential length of the secondary transfer roller 18.

[0090] As described above, when the scraping pattern KP passes through the secondary transfer nip, a positive bias is applied to the opposing roller 18A, and the negative toner is electrostatically attracted to the intermediate transfer belt 17, suppressing the toner from moving to the secondary transfer roller 18. However, at this time, there is a risk that the reversely charged toner of the positive scraping pattern may electrostatically move to the secondary transfer roller 18. In addition, the surface layer of the secondary transfer roller 18 is made of a foaming agent such as sponge, and many micro cells are mixed in. Therefore, there is a risk that the negatively normally charged toner of the scraping pattern may also be scraped off by the secondary transfer roller 18 at the secondary transfer nip and adhere to the secondary transfer roller 18.

[0091] If the length of the scraping pattern KP in the movement direction is equal to or greater than the circumferential length of the secondary transfer roller 18, the portion of the secondary transfer roller 18 that contacts the scraping pattern KP at the secondary transfer nip will contact the scraping pattern again after one rotation of the secondary transfer roller. In this way, if the length of the scraping pattern KP in the movement direction is equal to or greater than the circumferential length of the secondary transfer roller 18, there will be a portion of the secondary transfer roller 18 that continuously contacts the scraping pattern, and there is a risk that toner contamination in that portion will be worse than in other portions.

[0092] Even if the length of the scraping pattern KP in the movement direction is made shorter than the circumferential length of the secondary transfer roller 18, if the interval Sp of the scraping pattern KP is shorter than the circumferential length of the secondary transfer roller 18, there will be a portion of the secondary transfer roller 18 that is in continuous contact with the scraping pattern. Therefore, there is a risk that the toner contamination in that portion will be worse than in other portions.

[0093] By making the length of each scraping pattern KP in the moving direction shorter than the circumferential length of the secondary transfer roller 18 and making the interval Sp between the scraping patterns KP longer than the circumferential length of the secondary transfer roller 18, it is possible to prevent the secondary transfer roller 18 from having a portion that continuously comes into contact with the scraping patterns KP. As a result, the portion that comes into contact with the scraping patterns KP at the secondary transfer nip comes into contact with the intermediate transfer belt 17 after one rotation, and a portion of the toner that adheres to the secondary transfer roller 18 when it comes into contact with the scraping patterns KP can be transferred to the intermediate transfer belt 17. Therefore, toner contamination of the secondary transfer roller can be suppressed compared to when the length of the scraping patterns KP in the moving direction is set to be equal to or greater than the circumferential length of the secondary transfer roller 18, or when the interval Sp between the scraping patterns KP is set to be equal to or less than the circumferential length of the secondary transfer roller 18.

[0094] Furthermore, if the cleaning operation and the scraping pattern forming operation are performed at different times, the travel distance of the intermediate transfer belt 17 may be extended, shortening the life of the intermediate transfer belt 17. In addition, the number of times the device is downtime may increase.

[0095] In particular, in this embodiment, in the standard speed image forming mode, multiple scraping patterns KP are formed at predetermined intervals (at intervals such that the amount of toner remaining at the cleaning area does not fall below a predetermined amount), so the period of the scraping pattern formation operation may be long. As a result, if the cleaning operation and the scraping pattern formation operation are performed at different times, the travel distance of the intermediate transfer belt 17 is likely to be extended, shortening the life of the intermediate transfer belt 17.

[0096] Therefore, as shown in FIG. 12, it is preferable to pass the secondary transfer nip when applying a positive bias in the cleaning operation. In this embodiment, as described above, an alternating electric field is formed in the secondary transfer nip to clean the toner adhering to the secondary transfer roller 18 by the hopping effect. As shown in FIG. 12, the polarity of the alternating electric field is switched at a timing shorter than the paper-present section in the secondary transfer nip. Therefore, when multiple scraping patterns are formed by passing the scraping pattern while a positive bias is being applied in this alternating electric field, the next scraping pattern can be input to the cleaning location before the toner remaining in the cleaning location is completely removed. This makes it possible to remove filming on the intermediate transfer belt by the toner remaining in the cleaning location for a certain long period of time. Therefore, filming can be suppressed over time in the standard speed image formation mode.

[0097] As shown in FIG. 12, the positive bias and the negative bias are applied for at least one revolution of the secondary transfer roller. Therefore, when forming a plurality of scraping patterns, the length of each scraping pattern KP in the moving direction can be made shorter than the circumference of the secondary transfer roller 18, and the interval Sp between the scraping patterns KP can be made longer than the circumference of the secondary transfer roller 18. This makes it possible to suppress toner staining of the secondary transfer roller and to suppress back staining of the paper. Note that even if the scraping pattern passes through the secondary transfer nip when the positive bias is applied, the toner of negative polarity attached to the secondary transfer roller can be electrostatically attached to the intermediate transfer belt (scraping pattern). Therefore, the scraping pattern has almost no effect on cleaning of the secondary transfer roller.

[0098] Even if the scraping pattern KP is passed when the cleaning operation is performed at zero bias, the scraping pattern KP is not transferred to the secondary transfer roller 18. However, unlike when a positive bias is applied, the toner of the scraping pattern is not electrostatically attracted to the intermediate transfer belt 17. Therefore, at the secondary transfer nip, the toner may be scraped off by the secondary transfer roller 18, and more toner may adhere to the secondary transfer roller 18, which may worsen the toner stain on the secondary transfer roller 18. Therefore, it is not preferable to pass the scraping pattern when the cleaning operation is performed at zero bias.

[0099] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the spirit of the present invention described in the claims, unless otherwise specifically limited in the above description.

[0100] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) In an image forming apparatus that includes an image carrier such as an intermediate transfer belt 17, a transfer member such as a secondary transfer roller 18 that contacts the image carrier to form a transfer nip, and a cleaning member such as a cleaning blade 31 that cleans the surface of the image carrier, and that forms a toner image pattern such as a scraping pattern KP that is input to the cleaning member on the image carrier without transferring it to a recording medium, the number of toner image patterns formed is changed according to the linear speed of the image carrier, and when multiple toner image patterns are formed, the multiple toner image patterns are formed at predetermined intervals in the surface movement direction of the image carrier. It is known to change the linear speed of an image carrier such as the intermediate transfer belt 17 depending on the type of paper, the installation environment of the image forming apparatus, the usage conditions, etc. The faster the linear speed of the image carrier, the more likely filming on the image carrier is to deteriorate. By increasing the amount of toner in a toner image pattern such as the scraping pattern KP and increasing the amount of toner input to the cleaning member to enhance the filming removal effect, it is possible to remove filming well even when the linear speed of the image carrier is set to be fast. However, when the amount of toner in the toner image pattern is increased, a large amount of toner is input to the cleaning member at one time, and the amount of toner blocked by the cleaning member increases. When the amount of toner blocked by the cleaning member increases, the pressure from the blocked toner applied to the cleaning member increases, and there is a risk that toner will slip through the contact portion of the cleaning member with the image carrier, causing a cleaning failure, and there is a risk that it is not possible to simultaneously suppress cleaning failure and effectively remove filming on the image carrier. Furthermore, when the linear speed of the image carrier is set to be slow, the amount of toner input to the cleaning member becomes excessive for the filming condition, resulting in wasteful toner consumption. Therefore, in the first embodiment, the number of toner image patterns is changed according to the linear speed of the image carrier. As a result, the toner amount of the toner image pattern is set to a toner amount that does not cause cleaning defects, and the toner amount input to the cleaning member can be adjusted according to the number of toner image patterns to be formed to a toner amount that corresponds to the filming state on the image carrier according to the linear speed of the image carrier. In addition, since the multiple toner image patterns are formed at predetermined intervals in the moving direction of the image carrier, the toner of the toner image pattern blocked by the cleaning member is removed to a certain extent from the surface of the image carrier, and the toner blocked by the cleaning member is reduced to a certain extent before the next toner image pattern can be input to the cleaning member. Therefore, the amount of toner blocked does not become the amount of toner that causes cleaning defects. Therefore, when the linear speed is set to be fast at which filming is likely to worsen, the number of toner image patterns formed is increased, thereby effectively removing filming and suppressing the occurrence of cleaning defects, and when the linear speed is slow, the number of toner image patterns formed is reduced compared to when the linear speed is fast, thereby suppressing the occurrence of unnecessary toner consumption.

[0101] (Aspect 2) In embodiment 1, there are multiple image formation modes in which the linear speed of an image carrier such as the intermediate transfer belt 17 differs from one another, and when the image formation mode in which the linear speed of the image carrier is the fastest among the multiple image formation modes, such as a standard speed image formation mode, multiple toner image patterns such as scraping patterns KP are formed. As described in the embodiment, this prevents a large amount of toner from being input at once to the cleaning spot, which is the contact point between the cleaning member such as the cleaning blade 31 and the image carrier such as the intermediate transfer belt, and allows the toner remaining at the cleaning spot for a long period of time to remove filming on the image carrier. This makes it possible to suppress the occurrence of cleaning defects and to effectively remove filming on the image carrier.

[0102] (Aspect 3) In aspect 2, multiple image forming means such as image forming units 10, each of which forms a toner image of a different color, are arranged side by side in the direction of surface movement of an image carrier such as an intermediate transfer belt 17, and when multiple toner image patterns such as scraping patterns KP are formed, the colors of the toner image patterns are made different from each other. According to this, as described in the embodiment, it is possible to suppress the consumption of toner in a specific color from being biased, compared to the case where a plurality of toner image patterns are formed in one color.

[0103] (Aspect 4) In the third aspect, the color order of the plurality of toner image patterns from the downstream side in the surface movement direction follows the color order of the plurality of image forming means from the downstream side in the surface movement direction. According to this, as described with reference to FIG. 8, it is possible to shorten the image forming time for forming a toner image pattern such as a plurality of scraping patterns.

[0104] (Aspect 5) In the fourth embodiment, the color order of the toner image patterns such as the multiple scraping patterns KP from the downstream side in the surface movement direction is set to a continuous color order from the downstream side in the surface movement direction of the imaging means such as the multiple image forming units 10. According to this, as explained using Figure 8, for example, the imaging means are arranged in the order of K, C, M, Y from the downstream side in the surface movement direction of the image carrier, and the color order of the multiple scraping patterns is K, M, Y, skipping C, and the imaging time for imaging the multiple scraping patterns can be shortened compared to a case in which the color order is not consecutive, that is, K, M, Y, skipping C.

[0105] (Aspect 6) In any of aspects 2 to 5, the length of a toner image pattern such as the scraping pattern KP in the surface movement direction of an image carrier such as the intermediate transfer belt 17 is shorter than the circumferential length of a transfer member such as the secondary transfer roller 18, and the spacing SP of the toner image patterns is greater than or equal to the circumferential length of the transfer member. According to this, as described in the embodiment, the portion of the transfer member that has been in contact with the toner image pattern at the transfer nip can be brought into contact with the image carrier after one rotation, so that the toner of the toner image pattern that has adhered to the transfer member at the transfer nip can be moved to the surface of the image carrier after one rotation of the transfer member, thereby suppressing contamination of the transfer member.

[0106] (Aspect 7) In any of the embodiments 1 to 6, the toner image pattern such as the scraping pattern KP is a belt-like pattern that is long in a direction perpendicular to the direction of movement of the surface of an image carrier such as the intermediate transfer belt 17. This makes it possible to remove filming on the surface of an image carrier such as the intermediate transfer belt 17 evenly.

[0107] (Aspect 8) In the seventh aspect, the length of the belt-like pattern in the orthogonal direction is equal to or greater than the paper passing area of ​​the image carrier. According to this, as described in the embodiment, the occurrence of abnormal images such as blank areas due to filming in an image formed on a recording medium such as paper P can be effectively suppressed.

[0108] (Aspect 9) In embodiment 7 or 8, an adhesion amount detection means such as optical sensors 40R, 40F is provided at both ends in the perpendicular direction of an image carrier such as intermediate transfer belt 17, and detects the toner adhesion amount of a toner image on the image carrier, and the length of the belt-shaped pattern in the perpendicular direction is equal to or greater than the length in the perpendicular direction from the adhesion amount detection means at one end in the perpendicular direction to the adhesion amount detection means at the other end in the perpendicular direction. This effectively prevents abnormal images such as blank areas from appearing in images formed on recording media such as paper P. Also, it effectively prevents filming in the opposing areas of adhesion amount detection means such as optical sensors 40R and 40F arranged opposite both ends of the image carrier, and allows the adhesion amount to be effectively detected.

[0109] (Aspect 10) In any of the aspects 1 to 9, a reverse polarity bias having a polarity opposite to that of a transfer bias for transferring at least a toner image on an image carrier to a recording medium is applied to the transfer nip, and a cleaning operation is performed to move any deposits adhering to a transfer member such as a secondary transfer roller 18 to the image carrier and clean the transfer member, and a toner image pattern such as a scraping pattern KP is passed through the transfer nip when the reverse polarity bias is applied in the cleaning operation. According to this, as described with reference to FIG. 12, the number of times that the apparatus is down can be reduced compared to the case where the toner image pattern is formed at a timing separate from the cleaning operation. [Explanation of symbols]

[0110] 1: Copy machine 17: Intermediate transfer belt 18: Secondary transfer roller 18A: Opposing roller 30: Belt cleaning device 31: Cleaning blade 40: Optical sensor unit 40C: Optical sensor 40F: Optical sensor 40R: Optical sensor 90: Control section KP: Scraping pattern P:Paper PK: Gradation pattern [Prior art documents] [Patent documents]

[0111] [Patent Document 1] JP 2016-020970 A

Claims

1. An image carrier; a transfer member that contacts the image carrier to form a transfer nip; a cleaning member for cleaning the surface of the image carrier; In an image forming apparatus, a toner image pattern input to the cleaning member is formed on the image carrier without being transferred to a recording medium, changing the number of toner image patterns formed in accordance with the linear velocity of the image carrier; In the case where a plurality of toner image patterns are formed, the plurality of toner image patterns are formed at predetermined intervals in the surface movement direction of the image carrier.

2. 2. The image forming apparatus according to claim 1, a plurality of image forming modes in which the linear speed of the image carrier is different from each other; an image forming apparatus comprising: an image forming mode in which the linear speed of said image carrier is the fastest among a plurality of image forming modes; and a plurality of said toner image patterns are formed in said image forming mode.

3. 3. The image forming apparatus according to claim 2, A plurality of image forming means for forming toner images of different colors are arranged in a direction in which the surface of the image carrier moves, and forming a toner image pattern on the recording medium in a recording medium storing the toner image pattern and a recording medium storing the toner image pattern on the recording medium.

4. 4. The image forming apparatus according to claim 3, 1. An image forming apparatus, comprising: a plurality of toner image patterns each having a color sequence from a downstream side in a surface movement direction thereof, the color sequence following a plurality of image forming means each having a color sequence from a downstream side in the surface movement direction thereof.

5. 5. The image forming apparatus according to claim 4, an image forming apparatus including: a plurality of toner image patterns arranged in a color order from a downstream side in said surface movement direction, the plurality of toner image patterns arranged in a color order from a downstream side in said surface movement direction, the plurality of image forming means arranged in a continuous color order from the downstream side in said surface movement direction.

6. 3. The image forming apparatus according to claim 2, an image forming apparatus comprising: a toner image pattern having a length in a surface movement direction of the image carrier that is shorter than a circumferential length of the transfer member; and a spacing between the toner image patterns that is equal to or greater than the circumferential length of the transfer member.

7. 2. The image forming apparatus according to claim 1, The image forming apparatus according to claim 1, wherein the toner image pattern is a stripe-shaped pattern that is long in a direction perpendicular to a surface movement direction of the image carrier.

8. 8. The image forming apparatus according to claim 7, 2. An image forming apparatus comprising: a belt-shaped pattern having a length in the perpendicular direction that is equal to or greater than a paper passing area of ​​the image carrier.

9. 8. The image forming apparatus according to claim 7, an adhesion amount detection unit disposed on both ends of the image carrier in the perpendicular direction and configured to detect an adhesion amount of a toner image on the image carrier; an image forming apparatus characterized in that the length of the belt-shaped pattern in the orthogonal direction is greater than or equal to the length in the orthogonal direction from the adhesion amount detection means at one end of the orthogonal direction to the adhesion amount detection means at the other end of the orthogonal direction;

10. 2. The image forming apparatus according to claim 1, a cleaning operation for applying a reverse polarity bias to the transfer nip, the reverse polarity bias being a polarity of a transfer bias for transferring at least the toner image on the image carrier to a recording medium, and moving any deposits adhering to the transfer member to the image carrier, thereby cleaning the transfer member; the toner image pattern is passed through the transfer nip when the reverse polarity bias is applied in the cleaning operation.

Images