Image forming apparatus

Abstract

To reduce occurrence of a problem in which target image density cannot be obtained.SOLUTION: While printing is not performed, a first adjustment mode is executed which is for adjusting an image formation condition so as to adjust a result of detection of an amount of attached toner in a toner pattern for detection transferred to a secondary transfer belt 72 in a predetermined transfer condition, to a target value, without performing conveyance of a sheet P. Before the start of printing, a detection mode is executed which is for detecting the amount of attached toner in the toner pattern for detection transferred to the secondary transfer belt 72 in the transfer condition adjusted by transfer condition adjustment means on the basis of a predetermined condition. During printing, a second adjustment mode is executed which is for detecting the amount of attached toner in the toner pattern for detection transferred to the secondary transfer belt 72 in the same transfer condition as that in the detection mode, and adjusting the image formation condition to adjust a correction value obtained by adding, to a result of the detection, a difference between a detection result in the first adjustment mode and a detection result in the detection mode, to a target value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine thereof. [Background technology]

[0002] Conventionally, in image forming devices such as copiers and printers, there has been known a technique for adjusting image creation conditions so that the image density of a toner image formed on the surface of an image carrier such as an intermediate transfer belt or a photosensitive drum is targeted, in order to print a good image on a sheet (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 1 discloses a technology in which, when printing is interrupted, a first density control (adjustment of image-making conditions) is performed based on the toner adhesion amount of a toner pattern (detection toner pattern) secondarily transferred from an intermediate transfer belt to a secondary transfer belt without passing a sheet through, and, during printing, a second density control is performed based on the toner adhesion amount of a toner pattern secondarily transferred from outside the image area of ​​the intermediate transfer belt to the secondary transfer belt while passing a sheet through. Summary of the Invention [Problem to be solved by the invention]

[0004] With the technology of Patent Document 1, depending on external environments such as temperature and humidity, and usage environments such as sheet type, variations can occur in the adjustment of the first image-making conditions, which is made based on the toner adhesion amount of the detection toner pattern transferred from the image carrier to the transfer member when printing is interrupted and no sheet is passed through, and the adjustment of the second image-making conditions, which is made based on the toner adhesion amount of the detection toner pattern transferred from the image carrier to the transfer member while a sheet is being passed through during printing, and the target image density cannot be obtained.

[0005] SUMMARY OF THE PRESENT DISCLOSURE The present invention has been made in order to solve the above-mentioned problems, and has an object to provide an image forming apparatus which is less susceptible to problems such as failure to obtain a target image density. [Means for solving the problem]

[0006] The image forming apparatus of the present invention includes a transfer member for transferring a toner image formed on the surface of an image carrier to a sheet, a detection means for detecting a toner adhesion amount of a detection toner pattern formed on the surface of the image carrier and then transferred to the surface of the transfer member, an image creation condition adjustment means for adjusting image creation conditions for forming a toner image on the surface of the image carrier, and a transfer condition adjustment means for adjusting the transfer conditions of the transfer member during printing. The image forming apparatus is configured to be capable of executing a first adjustment mode in which, during a non-printing period in which a printing operation is not performed on a sheet, the detection means detects a toner adhesion amount of the detection toner pattern formed on the surface of the image carrier and then transferred to the transfer member under predetermined transfer conditions without conveying a sheet, and the image creation conditions are adjusted by the image creation condition adjustment means so that the detection result becomes a target value, a detection mode in which, before start of printing immediately before a printing operation for a target is performed, the detection means detects an amount of toner adhesion of the detection toner pattern which has been formed on the image carrier and then transferred to the transfer member under transfer conditions adjusted by the transfer condition adjustment means under predetermined conditions; and a second adjustment mode in which, during the printing, the detection means detects an amount of toner adhesion of the detection toner pattern which has been formed outside an image area on the image carrier and then transferred to the transfer member under the same transfer conditions as in the detection mode, and the image-forming conditions are adjusted by the image-forming condition adjustment means so that a correction value obtained by adding a difference between a detection result detected by the detection means in the first adjustment mode and a detection result detected by the detection means in the detection mode to the detection result becomes the target value. Effect of the Invention

[0007] According to the present invention, it is possible to provide an image forming apparatus which is less susceptible to problems such as failure to obtain a target image density. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an enlarged view showing a part of an image forming unit; [Diagram 3] FIG. 2 is a schematic diagram showing an intermediate transfer belt and its vicinity. [Figure 4] (A) is a schematic diagram showing the positional relationship in the main scanning direction between a detection toner pattern formed on the surface of the intermediate transfer belt and a first density detection sensor installed in a secondary transfer device, and (B) is a schematic diagram showing the positional relationship in the main scanning direction between an adjustment toner pattern formed on the surface of the intermediate transfer belt and a second density detection sensor installed downstream of a fixing device. [Diagram 5] 11 is a graph showing an example of the amount of adhered toner detected by a first concentration detection sensor in a first adjustment mode, a detection mode, and a second adjustment mode. [Figure 6] 10 is a graph showing, as a comparative example, an example of the amount of adhered toner detected by the first concentration detection sensor in the first adjustment mode and the second adjustment mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and the duplicated description will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 100 will be described with reference to FIGS. FIG. 1 is a diagram showing the configuration of a printer as an image forming apparatus, and FIG. 2 is an enlarged view showing a part of the image forming section. 1, an intermediate transfer belt 8 (intermediate transfer body) serving as an image carrier is provided in the center of the image forming apparatus main body 100. In addition, imaging units 6Y, 6M, 6C, and 6K corresponding to each color (yellow, magenta, cyan, and black) are arranged in parallel to face the intermediate transfer belt 8.

[0011] 2, the imaging unit 6Y corresponding to yellow is composed of a photoconductor drum 1Y as a photoconductor, a charging device 4Y, a developing device 5Y, a cleaning device 2Y, a lubricant supplying device 3, a discharging device (not shown), etc., which are arranged around the photoconductor drum 1Y. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process, discharging process) is performed on the photoconductor drum 1Y, and a yellow image is formed on the photoconductor drum 1Y.

[0012] The other three image forming units 6M, 6C, and 6K have almost the same configuration as the image forming unit 6Y corresponding to yellow, except for the toner colors used, and form images corresponding to the respective toner colors. In the following, the explanation of the other three image forming units 6M, 6C, and 6K will be omitted as appropriate, and only the image forming unit 6Y corresponding to yellow will be explained.

[0013] 2, the photoconductor drum 1Y as a photoconductor is rotated counterclockwise by a motor. Then, at the position of the charging device 4Y, the surface of the photoconductor drum 1Y is uniformly charged (charging process). Note that the charging device 4Y in this embodiment is a charging roller, to which a charging bias is applied from a charging power source 110. Also, the charging bias can be adjusted by the control of the charging power source 110 by the control unit 90. Thereafter, the surface of the photoconductor drum 1Y reaches a position irradiated with the exposure light L (laser light) emitted from the exposure device 7, and an electrostatic latent image corresponding to yellow is formed by exposure scanning in the width direction (the direction perpendicular to the paper surface of FIGS. 1 and 2, which is the main scanning direction) at this position (exposure process). Note that in this embodiment, the exposure device 7 is controlled by the control unit 90 so that the magnitude of the exposure energy (exposure amount) of the exposure light L irradiated from the exposure device 7 to the photoconductor drum 1Y can be adjusted.

[0014] Thereafter, the surface of the photoconductor drum 1Y reaches a position facing the developing device 5Y, where the electrostatic latent image is developed to form a yellow toner image (developing process). Thereafter, the surface of the photoconductor drum 1Y reaches a position facing the intermediate transfer belt 8 (image carrier) and the primary transfer roller 9Y (primary transfer member) as an intermediate transfer body, and the toner image formed on the surface of the photoconductor drum 1Y at this position is primarily transferred onto the surface of the intermediate transfer belt 8 (primary transfer process). At this time, a small amount of untransferred toner remains on the photoconductor drum 1Y.

[0015] Thereafter, the surface of the photoreceptor drum 1Y reaches a position facing the cleaning device 2Y, and the untransferred toner remaining on the photoreceptor drum 1Y at this position is collected into the cleaning device 2Y by the cleaning blade 2a (cleaning process). Here, a lubricant supplying device 3 (photoconductor lubricant supplying device) consisting of a lubricant supplying roller 3a, a solid lubricant 3b, a compression spring 3c, etc. is installed inside the cleaning device 2Y. The lubricant supplying roller 3a, which rotates clockwise in FIG. 2, scrapes off the lubricant little by little from the solid lubricant 3b, and the lubricant is supplied to the surface of the photoconductor drum 1Y by the lubricant supplying roller 3a. Finally, the surface of the photoconductor drum 1Y reaches a position facing the charge eliminating device, where the residual potential on the photoconductor drum 1Y is eliminated. Thus, a series of image forming processes carried out on the photosensitive drum 1Y is completed.

[0016] The above-mentioned image forming process is performed in the other image forming units 6M, 6C, and 6K in the same manner as in the yellow image forming unit 6Y. That is, exposure light L based on image information is irradiated from an exposure device 7 disposed above the image forming units onto the photoconductor drums 1M, 1C, and 1K of the image forming units 6M, 6C, and 6K. Thereafter, the toner images of each color formed on each photoconductor drum 1M, 1C, 1K through the developing process by each developing device 5M, 5C, 5K are primarily transferred onto the intermediate transfer belt 8 in a superimposed manner. In this way, a color image is formed on the intermediate transfer belt 8.

[0017] 3, the intermediate transfer belt device is composed of an intermediate transfer belt 8 (intermediate transfer body) as an image carrier, primary transfer rollers 9Y, 9M, 9C, and 9K as four primary transfer members, a drive roller 16, a driven roller 17, a pre-transfer roller 18, a tension roller 19, a cleaning opposed roller 20, a lubricant opposed roller 21, a backup roller 22, an intermediate transfer cleaning device 10, a lubricant supply device 30 (intermediate transfer lubricant supply device), a secondary transfer opposed roller 80 as a secondary transfer opposed member, and secondary transfer devices 70 to 73. The intermediate transfer belt 8 is stretched and supported by a plurality of roller members 16 to 22, and 80, and is endlessly moved in the direction of the arrow in FIG. 3 by the rotational drive of one roller member (drive roller 16) by a drive motor.

[0018] The four primary transfer rollers 9Y, 9M, 9C, and 9K (primary transfer members) form primary transfer nips by sandwiching an intermediate transfer belt 8 as an intermediate transfer body between the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. A transfer voltage (primary transfer bias) having a polarity opposite to that of the toner is applied from a primary transfer power source 112 to the primary transfer rollers 9Y, 9M, 9C, and 9K. Then, the intermediate transfer belt 8 travels in the direction of the arrow and passes through the primary transfer nips of the primary transfer rollers 9Y, 9M, 9C, and 9K in sequence. In this way, the toner images of each color on the photoconductor drums 1Y, 1M, 1C, and 1K are primarily transferred onto the surface of the intermediate transfer belt 8 in a superimposed manner (this is the primary transfer process). In this embodiment, the control unit 90 controls the primary transfer power supply 112 so that the magnitude of the primary transfer bias can be adjusted.

[0019] In the intermediate transfer belt device, the drive roller 16 is disposed downstream of the four photosensitive drums in the running direction of the intermediate transfer belt, so as to abut against the inner circumferential surface of the intermediate transfer belt 8 with the intermediate transfer belt 8 wrapped around it at a wrapping angle of about 120 degrees. The drive roller 16 is driven to rotate in the clockwise direction in FIG. 3 by a drive motor Mt1 controlled by the control unit 90. This causes the intermediate transfer belt 8 to run in a predetermined running direction (clockwise in FIG. 3).

[0020] Thereafter, the intermediate transfer belt 8 onto which the toner images of each color are superimposed and primarily transferred reaches a position facing the secondary transfer belt 72 as a transfer member (secondary transfer member). At this position, a secondary transfer opposing roller 80 sandwiches the intermediate transfer belt 8 and the secondary transfer belt 72 between itself and the secondary transfer roller 70 to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 8 are then secondarily transferred onto a sheet P such as paper conveyed to the position of this secondary transfer nip (secondary transfer process). At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 8.

[0021] Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning device 10. At this position, any deposits such as untransferred toner adhering to the surface of the intermediate transfer belt 8 are removed. Furthermore, the intermediate transfer belt 8 reaches the position of a lubricant supplying device 30 serving as an intermediate transfer lubricant supplying device. At this position, a lubricant is supplied to the surface of the intermediate transfer belt 8. Thus, a series of transfer processes carried out on the intermediate transfer belt 8 is completed.

[0022] Here, referring to FIG. 1, the sheet P transported to the position of the secondary transfer nip is transported from a paper feed device 26 arranged below the image forming apparatus main body 100 via a paper feed roller 27, a pair of registration rollers 28, etc. More specifically, a plurality of sheets P such as paper are stacked and stored in the paper feed device 26. When the paper feed roller 27 is rotated counterclockwise in FIG. 1, the topmost sheet P is fed toward between the rollers of the registration roller pair 28 via the first transport path K1.

[0023] The sheet P conveyed to the registration roller pair 28 (timing roller pair) is temporarily stopped at the roller nip position of the registration roller pair 28, which has stopped rotating. Then, in synchronization with the color image on the intermediate transfer belt 8, the registration roller pair 28 is rotated and the sheet P is conveyed toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0024] Thereafter, the sheet P onto which the color image has been transferred at the secondary transfer nip position is transported by the secondary transfer belt 72, and after being separated from the secondary transfer belt 72, is transported by the transport belt 60 to the position of the fixing device 50. Then, at this position, the color image transferred to the surface is fixed onto the sheet P by heat and pressure from the fixing belt and pressure roller (fixing process). In addition, a second density detection sensor 96 as a second detection means is installed downstream of the fixing device 50 (downstream in the sheet transport direction) so as to face the image surface (fixing surface) of the sheet P, but this will be described in detail later. Thereafter, the sheet P passes through the second transport path K2 and is discharged to the outside of the apparatus by the pair of discharge rollers. The sheet P discharged to the outside of the apparatus by the pair of discharge rollers is sequentially stacked on a stack unit as an output image. In this manner, a series of image forming processes in the image forming apparatus is completed.

[0025] Next, the configuration and operation of the developing device 5Y in the image forming section will be described in more detail with reference to FIG. The developing device 5Y is composed of a developing roller 51Y facing the photosensitive drum 1Y, a doctor blade 52Y facing the developing roller 51Y, two conveying screws 55Y disposed in a developer storage section, a toner concentration sensor 56Y for detecting the toner concentration in the developer, etc. The developing roller 51Y is composed of a magnet fixed inside and a sleeve rotating around the magnet, etc. A two-component developer G consisting of a carrier and a toner is stored in the developer storage section.

[0026] The developing device 5Y thus configured operates as follows. The sleeve of the developing roller 51Y rotates in the direction of the arrow in FIG. 2. The developer G carried on the developing roller 51Y by the magnetic field formed by the magnet moves on the developing roller 51Y as the sleeve rotates. Here, the developer G in the developing device 5Y is adjusted so that the ratio of toner in the developer G (toner concentration) falls within a predetermined range. Specifically, when a toner concentration sensor 56Y installed in the developing device 5Y detects a low toner concentration, the control unit 90 controls the toner supply device 113 (see FIG. 3) to supply new toner from the toner container 58 into the developing device 5Y so that the toner concentration falls within the predetermined range. Thereafter, the toner supplied from the toner container 58 to the developer storage section circulates between the two separated developer storage sections (movement in the direction perpendicular to the paper surface of FIG. 2) while being mixed and stirred with the developer G by the two transport screws 55Y. The toner in the developer G is attracted to the carrier due to frictional charging with the carrier, and is carried on the developing roller 51Y together with the carrier by the magnetic force formed on the developing roller 51Y.

[0027] The developer G carried on the developing roller 51Y is transported in the direction of the arrow in FIG. 2 and reaches the position of the doctor blade 52Y. Then, the developer G on the developing roller 51Y is adjusted to an appropriate amount at this position, and then transported to a position facing the photoconductor drum 1Y (the developing area). Then, the toner is attracted to the latent image formed on the photoconductor drum 1Y by the electric field formed in the developing area. Thereafter, the developer G remaining on the developing roller 51Y reaches above the developer storage section as the sleeve rotates, and is separated from the developing roller 51Y at this position. In the developing device 5Y in this embodiment, a developing bias is applied to the developing roller 51Y from a developing power source 111. Also, the developing power source 111 is controlled by the control unit 90 to adjust the magnitude of the developing bias. A developing electric field is formed in the developing gap by the developing bias and the latent image potential, and the toner on the developing roller 51Y is attached to the latent image by the developing electric field, thereby developing the image. The toner container 58 is detachably (replaceably) installed in the developing device 5Y (image forming apparatus 100). When the new toner contained therein becomes empty, the toner container 58 is removed from the developing device 5Y (image forming apparatus 100) and replaced with a new toner.

[0028] Next, the secondary transfer devices 70 to 72 in this embodiment will be described in detail with reference to FIG. Referring to FIG. 3, the secondary transfer device includes a secondary transfer belt 72, a secondary transfer roller 70, a separation roller 71, a secondary transfer blade 73 (cleaning blade), a first density detection sensor 95 as a detection means (first detection means), and the like. The secondary transfer belt 72 as a secondary transfer member (transfer member) is an endless belt stretched and supported by two rollers (secondary transfer roller 70 and separation roller 71), and is made of approximately the same material as the intermediate transfer belt 8. The secondary transfer belt 72 abuts against the intermediate transfer belt 8 (intermediate transfer body) to form a secondary transfer nip, and conveys the sheet P sent out from the secondary transfer nip.

[0029] The secondary transfer roller 70 and the secondary transfer opposing roller 80 sandwich the intermediate transfer belt 8 and the secondary transfer belt 72 therebetween to form a secondary transfer nip. In addition, the secondary transfer roller 70 is driven to rotate in the counterclockwise direction in Figure 3 by a drive motor Mt2 controlled by the control unit 90, causing the secondary transfer belt 72 to rotate (run) in the counterclockwise direction in Figure 3 and causing the separation roller 71 to rotate counterclockwise in Figure 3. In this embodiment, the linear speed difference of the secondary transfer belt 72 (secondary transfer member) relative to the intermediate transfer belt 8 (intermediate transfer body) at the secondary transfer nip is adjustable. Specifically, the rotation speed of at least one of the drive motor Mt1 that drives the drive roller 16 around which the intermediate transfer belt 8 is stretched and the drive motor Mt2 that drives the secondary transfer roller 70 around which the secondary transfer belt 72 is stretched is adjusted and controlled by the control unit 90 to appropriately adjust the linear speed difference (secondary transfer linear speed) at the secondary transfer nip.

[0030] The separation roller 71 is disposed at a position downstream of the secondary transfer nip in the transport direction of the sheet P. The sheet P sent out from the secondary transfer nip is transported along the secondary transfer belt 72 traveling in the counterclockwise direction in FIG. 3, and then separated from the secondary transfer belt 72 at the position of the separation roller 71 by the secondary transfer belt 72, which has a curved surface formed along the outer periphery of the separation roller 71 (curvature separation). The secondary transfer blade 73 comes into contact with the surface of the secondary transfer belt 72 to remove foreign matter such as toner and paper powder adhering to the surface of the secondary transfer belt 72. The secondary transfer blade 73 is in pressure contact with the secondary transfer roller 70 via the secondary transfer belt 72 so as to come into contact in a counter direction to the running direction of the secondary transfer belt 72. In addition, the secondary transfer device is provided with a first density detection sensor 95 as a detection means (first detection means) so as to face the outer circumferential surface of the secondary transfer belt 72, which will be described in detail later.

[0031] Here, in this embodiment, a secondary transfer bias is applied to the secondary transfer roller 70 from the secondary transfer power source 115. That is, the secondary transfer belt 72 as the secondary transfer member is applied with the secondary transfer bias from the secondary transfer power source 115 via the secondary transfer roller 70. This secondary transfer bias is for secondarily transferring the toner image primarily transferred onto the surface of the intermediate transfer belt 8 onto the sheet P conveyed to the secondary transfer nip, and is a secondary transfer bias (a DC voltage or a DC current superimposed with an AC current) of a polarity different from that of the toner (positive polarity in this embodiment). As a result, the toner carried on the toner carrying surface (outer peripheral surface) of the intermediate transfer belt 8 is electrostatically moved toward the secondary transfer devices 70 to 73 by the secondary transfer electric field. In this embodiment, the control unit 90 controls the secondary transfer power supply 115 so that the magnitude of the secondary transfer bias can be adjusted. In this embodiment, the secondary transfer roller 70 is configured to be applied with a secondary transfer bias of a polarity different from the toner polarity, but the secondary transfer opposing roller 80 may be configured to be applied with a secondary transfer bias of the same polarity as the toner polarity, or the secondary transfer biases of the above-mentioned polarities may be applied to both rollers 70, 80. In such a case, the secondary transfer bias applied to the secondary transfer opposing roller 80 is also configured to be adjustable.

[0032] Here, in the image forming apparatus 100 of the present embodiment, the secondary transfer pressure (nip pressure) when the secondary transfer belt 72 as the secondary transfer member contacts the intermediate transfer belt 8 (intermediate transfer body) can be adjusted. Specifically, a secondary transfer pressure mechanism 116 (see FIG. 3) is provided that can move the secondary transfer roller 70 up and down. The secondary transfer pressure mechanism 116 is controlled by the control unit 90 to adjust the secondary transfer pressure (nip pressure) at the secondary transfer nip. As the secondary transfer pressure mechanism 116, a cam mechanism in which a cam that comes into contact with the shaft portion of the secondary transfer roller 70 can be used.

[0033] Hereinafter, the control of image forming apparatus 100, which is a feature of this embodiment, will be described in detail with reference to FIGS. As previously described using Figure 3 etc., the image forming apparatus 100 in this embodiment is provided with a secondary transfer belt 70 as a transfer member for transferring a toner image (image) formed on the surface of the intermediate transfer belt 8 as an image carrier onto a sheet P. Now, referring to Figures 1, 3, etc., the image forming apparatus 100 in this embodiment is provided with a first density detection sensor 95 as a detection means (first detection means), a second density detection sensor 96 as a second detection means, and a control unit 90 which also functions as an image creation condition adjustment means and a transfer condition adjustment means (secondary transfer condition adjustment means).

[0034] The first concentration detection sensor 95 functions as a detection means (first detection means) that detects the toner adhesion amount (image density) of the detection toner patterns TY, TM, TC, and TK (see Figure 4(A)) that are formed on the surface of the intermediate transfer belt 8 as an image carrier and then transferred to the surface of the secondary transfer belt 72 as a transfer member. In detail, the first concentration detection sensor 95 is a reflective photosensor installed at a position corresponding to the position in the main scanning direction (the up and down direction in Figure 4) where the detection toner patterns TY, TM, TC, and TK are formed on the intermediate transfer belt 8, and at a position opposite the secondary transfer belt 72. Then, by the image forming process previously described with reference to FIGS. 1 and 2, the four color detection toner patterns TY, TM, TC, and TK formed on the surfaces of the four photoconductor drums 1Y, 1M, 1C, and 1K, respectively, are primarily transferred onto the intermediate transfer belt 8 so as not to overlap (see FIG. 4(A)). Then, the four color detection toner patterns TY, TM, TC, and TK on the intermediate transfer belt 8 are secondarily transferred onto the secondary transfer belt 72 at the position of the secondary transfer nip. Then, the toner adhesion amounts of the four color detection toner patterns TY, TM, TC, and TK on the secondary transfer belt 72 are optically detected by a first density detection sensor 95. The four color detection toner patterns TY, TM, TC, and TK correspond to yellow, magenta, cyan, and black, respectively. In addition, the first density detection sensor 95 (reflective photosensor) irradiates light emitted from a light-emitting element onto the detection toner patterns TY, TM, TC, and TK, and determines the toner adhesion amount (image density) of the detection toner patterns TY, TM, TC, and TK based on the magnitude of the output value when the reflected light is received by a light-receiving element.

[0035] The control unit 90 is responsible for various controls in the image forming apparatus 100, and also functions as an image creation condition adjustment means for adjusting the image creation conditions for forming a toner image on the surface of the intermediate transfer belt 8 (image carrier). Here, the "image creation conditions" adjusted and controlled by the control unit 90 as an image creation condition adjustment means are at least one of the charging bias, exposure energy, development bias, toner concentration of the developer, and primary transfer bias, all of which are factors for adjusting the image density.

[0036] 1 to 3, the charging bias is applied to the charging device 4Y to charge the surface of the photoconductor drum 1Y (photoconductor) facing the intermediate transfer belt 8 (intermediate transfer body as an image carrier). When the charging bias is adjusted to a large value by the control of the charging power source 110 by the control unit 90, the image density is adjusted to a lower value compared to when the charging bias is adjusted to a small value. The exposure energy is the exposure energy of the exposure light L irradiated onto the photoconductor drum 1Y to form a latent image on the surface of the photoconductor drum 1Y charged by the charging device 4Y. When the exposure energy is adjusted to a large value by the control of the exposure device 7 by the control unit 90, the image density is adjusted to be higher than when the exposure energy is adjusted to a small value. The developing bias is applied to the developing device 5Y (developing roller 51Y) that develops the latent image formed on the surface of the photosensitive drum 1Y. When the developing bias is adjusted to a large value by the control of the developing power source 111 by the control unit 90, the image density is adjusted to be higher than when the developing bias is adjusted to a small value. The toner concentration is the concentration (the ratio of toner) of the developer G (two-component developer) contained inside the developing device 5Y. When the toner concentration is adjusted to a large value by the control of the toner supply device 113 by the control unit 90, the image density is adjusted to a higher value than when the toner concentration is adjusted to a small value. The primary transfer bias is applied to a primary transfer roller 9Y (primary transfer member) for transferring the toner image formed on the surface of the photosensitive drum 1Y to the surface of the intermediate transfer belt 8. When the primary transfer bias is adjusted to a large value by the control of the primary transfer power source 112 by the control unit 90, the image density is adjusted to be higher than when the primary transfer bias is adjusted to a small value.

[0037] The second concentration detection sensor 96 functions as a second detection means for detecting the image density of the adjustment toner patterns RY, RM, RC, and RK (see Figure 4(B)) that are formed on the surface of the intermediate transfer belt 8 (image carrier) and then transferred to the surface of the sheet P by the secondary transfer belt 72 (transfer member). In detail, the second concentration detection sensor 96 is a reflective photosensor installed at a position corresponding to the position in the main scanning direction (the up and down direction in Figure 4) where the adjustment toner patterns RY, RM, RC, and RK are formed on the intermediate transfer belt 8, and at a position facing the sheet P after the fixing process sent out from the fixing device 50. Then, by the image forming process previously described with reference to FIGS. 1 and 2, the four color adjustment toner patterns RY, RM, RC, and RK formed on the surfaces of the four photoconductor drums 1Y, 1M, 1C, and 1K, respectively, are primarily transferred to the intermediate transfer belt 8 within the range of image area M (the central portion in the main scanning direction in this embodiment) so as not to overlap (see FIG. 4(B)). Then, the four color adjustment toner patterns RY, RM, RC, and RK on the intermediate transfer belt 8 are secondarily transferred onto the sheet P at the position of the secondary transfer nip. Then, the image densities of the four color adjustment toner patterns RY, RM, RC, and RK on the sheet P after the fixing process are optically detected by the second density detection sensor 96. The four color adjustment toner patterns RY, RM, RC, and RK are adjustment toner patterns corresponding to yellow, magenta, cyan, and black, respectively. In addition, the second density detection sensor 96 (reflective photosensor) irradiates the adjustment toner patterns RY, RM, RC, and RK with light emitted from a light-emitting element, and determines the image density of the adjustment toner patterns RY, RM, RC, and RK based on the magnitude of the output value when the reflected light is received by a light-receiving element.

[0038] As described above, the control unit 90 functions as an image creation condition adjustment means, but also functions as a transfer condition adjustment means that adjusts the transfer conditions of the secondary transfer belt 72 (secondary transfer device) as a transfer member during printing. Specifically, the transfer condition adjustment means adjusts the transfer conditions (secondary transfer conditions) of the secondary transfer belt 72 (secondary transfer device) during printing based on the detection results of the second density detection sensor 96 (second detection means). Here, the “transfer conditions (secondary transfer conditions)” adjusted and controlled by the control unit 90 as a transfer condition adjustment means are at least one of the secondary transfer bias, the secondary transfer pressure (nip pressure), and the linear speed difference (secondary transfer linear speed), all of which are factors for adjusting the image density on the sheet P.

[0039] 2 and the like, the secondary transfer bias is applied to at least one of the secondary transfer belt 72 (secondary transfer member) and the secondary transfer opposing roller 80 as a secondary transfer opposing member that contacts the secondary transfer belt 72 via the intermediate transfer belt 8, and in this embodiment, it is applied to the secondary transfer belt 72 via the secondary transfer roller 70. When the secondary transfer bias is adjusted to a large value by the control of the secondary transfer power source 115 by the control unit 90, the image density is adjusted to be higher than when it is adjusted to a small value. The secondary transfer pressure (nip pressure) is the contact pressure when the secondary transfer belt 72 (secondary transfer member) contacts the intermediate transfer belt 8 (intermediate transfer body). When the secondary transfer pressure is adjusted to a large value by the control of the secondary transfer pressure mechanism 116 by the control unit 90, the image density is adjusted to be higher than when the secondary transfer pressure is adjusted to a small value. The linear speed difference (secondary transfer linear speed) is the linear speed difference of the secondary transfer belt with respect to the intermediate transfer belt 8 (intermediate transfer body) at the secondary transfer nip where the secondary transfer belt 72 (secondary transfer member) abuts against the intermediate transfer belt 8 (intermediate transfer body). When the linear speed difference (secondary transfer linear speed) is adjusted to be large by the control of the drive motors Mt1, Mt2 by the control unit 90, the image density is adjusted to be low compared to when it is adjusted to be small.

[0040] The adjustment of the transfer conditions (secondary transfer conditions) by the transfer condition adjustment means (control unit 90) is performed every time a new type of sheet P is set in the paper feeder 26, by passing the sheet P as an adjustment sheet at a timing separate from the normal printing operation. Then, as described above, when the sheet P (adjustment sheet) onto which the adjustment toner patterns RY, RM, RC, and RK are secondarily transferred and fixed passes the position of the second density detection sensor 96, the image densities of the adjustment toner patterns RY, RM, RC, and RK are detected, and transfer conditions such as the secondary transfer bias are determined based on the detection result, and the transfer conditions are stored in the memory of the control unit 90 in a form linked to the sheet type. When a sheet of the same type as that stored in the memory is set in the sheet feeder 26, the corresponding transfer conditions are read from the memory, and the secondary transfer process is carried out under those transfer conditions during printing. In addition, information on the type of sheet P used during printing can be grasped by the control unit 90 based on information about the sheet P input by the user to an operation display panel (not shown) installed on the exterior of the image forming apparatus 100.

[0041] Here, in the present embodiment, the image forming apparatus 100 is configured to be able to execute three control modes, namely, a "first adjustment mode," a "detection mode," and a "second adjustment mode," by the control unit 90, which functions as an image creation condition adjustment means and a transfer condition adjustment means. The "first adjustment mode" is performed in order to optimize the image creation conditions in advance when a printing operation is not being performed on the sheet P (when not printing). Specifically, the "first adjustment mode" is performed when the image forming apparatus 100 is started up (during warming up), between printing operations (jobs), between printing operations (jobs), etc. In contrast, the "second adjustment mode" is performed to optimize the image creation conditions when a printing operation is being performed on the sheet P (at the time of printing, during printing). Specifically, the "second adjustment mode" is performed during a series of printing operations (jobs). Moreover, the "detection mode" is performed immediately before the start of a printing operation, and is executed to correct the adjustment of the image-forming conditions made in the "second adjustment mode."

[0042] Specifically, in the "first adjustment mode", during non-printing when the printing operation on the sheet P is not being performed, the sheet P is not transported (passed), and the toner adhesion amounts of the detection toner patterns TY, TM, TC, and TK that are formed on the surface of the intermediate transfer belt 8 (image carrier) and then transferred to the secondary transfer belt 72 (transfer member) under predetermined transfer conditions are detected by the first concentration detection sensor 95 (detection means). Then, the image creation conditions are adjusted by the image creation condition adjustment means (controller 90) so that the detection result of the first concentration detection sensor 95 becomes a target value (target toner adhesion amount). Specifically, the detection toner patterns TY, TM, TC, and TK as shown in FIG. 4A are formed on the intermediate transfer belt 8 by the image forming process described above with reference to FIGS. 1 to 3, and the detection toner patterns TY, TM, TC, and TK are secondarily transferred to the secondary transfer belt 72 at the position of the secondary transfer nip under predetermined transfer conditions (secondary transfer conditions) without passing the sheet P. Then, the toner adhesion amount of the detection toner patterns TY, TM, TC, and TK secondarily transferred to the secondary transfer belt 72 is optically detected by the first density detection sensor 95. Then, based on the detection result of the first density detection sensor 95, the charging bias, exposure energy, development bias, toner concentration, and primary transfer bias are optimized by the control unit 90. Here, the transfer conditions (predetermined transfer conditions) used in the first adjustment mode are not optimized according to the type of sheet P, but are set to transfer conditions suited to, for example, a sheet P that is expected to be used frequently.

[0043] On the other hand, in the "detection mode", before printing begins immediately before the printing operation on the sheet P is performed, the toner adhesion amount of the detection toner patterns TY, TM, TC, TK which are formed on the intermediate transfer belt 8 (image carrier) and then transferred to the secondary transfer belt 72 (transfer member) under transfer conditions adjusted by the transfer condition adjustment means (control unit 90) under specified conditions is detected by the first concentration detection sensor 95 (detection means). In detail, the detection mode is a mode in which, before printing begins immediately before the printing operation on the sheet P is performed, the first concentration detection sensor 95 detects the toner adhesion amount of the detection toner patterns TY, TM, TC, and TK that are formed on the intermediate transfer belt 8 and then transferred to the secondary transfer belt 72 under transfer conditions adjusted by the transfer condition adjustment means for a sheet P of the same type as the sheet P. More specifically, by the image forming process as previously described with reference to Figures 1 to 3, the detection toner patterns TY, TM, TC, and TK as shown in Figure 4(A) are formed on the intermediate transfer belt 8, and the detection toner patterns TY, TM, TC, and TK are secondarily transferred to the secondary transfer belt 72 at the position of the secondary transfer nip under transfer conditions (secondary transfer conditions) suitable for the sheet P to be used in the printing to be performed immediately afterwards. Then, the toner adhesion amounts of the detection toner patterns TY, TM, TC, and TK secondarily transferred to the secondary transfer belt 72 are optically detected by the first density detection sensor 95. This detection result is used as a correction value in the second adjustment mode during the printing to be performed immediately afterwards.

[0044] In the "second adjustment mode", during printing, the toner adhesion amounts of the detection toner patterns TY, TM, TC, and TK that are formed outside the image area (outside the range of the image area M shown in FIG. 4(A)) on the intermediate transfer belt 8 (image carrier) and then transferred to the secondary transfer belt 72 (transfer member) under the same transfer conditions as in the detection mode are detected by the first concentration detection sensor 95 (detection means).Then, the image creation conditions are adjusted by the image creation condition adjustment means (controller 90) so that the correction value obtained by adding the difference between the detection result detected by the first concentration detection sensor 95 in the first adjustment mode and the detection result detected by the first concentration detection sensor 95 in the detection mode to the detection result of the first concentration detection sensor 95 becomes a target value. Specifically, by the image forming process as previously described with reference to Figures 1 to 3, the detection toner patterns TY, TM, TC, and TK as shown in Figure 4(A) are formed on the intermediate transfer belt 8. At this time, an image (toner image) related to printing desired by the user is formed on the intermediate transfer belt 8. Then, under transfer conditions (secondary transfer conditions) suitable for that sheet P, a desired image (toner image) is secondarily transferred onto the conveyed sheet P at the position of the secondary transfer nip, and the detection toner patterns TY, TM, TC, and TK formed outside the image area M are transferred onto the secondary transfer belt 72. Then, the toner adhesion amounts of the detection toner patterns TY, TM, TC, and TK secondarily transferred onto the secondary transfer belt 72 are optically detected by a first density detection sensor 95. 5, a correction value (toner adhesion amount) is added to the detection result (toner adhesion amount) of the first concentration detection sensor 95, which is obtained by subtracting the detection result (toner adhesion amount) detected by the first concentration detection sensor 95 in the detection mode before the start of printing from the detection result (toner adhesion amount) detected by the first concentration detection sensor 95 in the first adjustment mode when not printing.Then, the control unit 90 optimizes the charging bias, exposure energy, development bias, toner concentration, and primary transfer bias so that the value (toner adhesion amount) to which the correction value is added becomes a target value. The image area M is defined as a range in the main scanning direction through which a sheet P of the maximum size that can be passed is passed.

[0045] The detection results of the first concentration detection sensor 95 are corrected in this manner in the second adjustment mode because, if the transfer conditions (secondary transfer conditions) are different, the amount of toner adhesion of the detection toner patterns TY, TM, TC, and TK transferred to the secondary transfer belt 72 also changes, as shown in Figure 6. That is, the transfer conditions in the first adjustment mode and the transfer conditions in the second adjustment mode may differ, and in such a case, the toner adhesion amounts of the detection toner patterns TY, TM, TC, and TK also differ, and the image creation conditions adjusted based on the detection results do not become constant, and the image density does not become the target. In particular, this phenomenon becomes more noticeable due to external environments such as temperature and humidity, in addition to the usage environment such as the type of sheet P. Therefore, in this embodiment, the detection mode is performed immediately before printing begins, and the toner adhesion amount of the detection toner patterns TY, TM, TC, and TK is detected using the same transfer conditions as during printing. The difference between this detection result and the detection result in the first adjustment mode is used as a correction value and added to the detection result in the second adjustment mode to offset the difference in the detection results due to the different transfer conditions described above. Therefore, there is less variation between the adjustment of image-making conditions in the first adjustment mode performed when not printing and the adjustment of image-making conditions in the second adjustment mode performed during printing, and the problem of not being able to obtain the target image density is less likely to occur.

[0046] As previously described with reference to Figures 1 and 3, the image forming apparatus 100 in this embodiment has four photoconductor drums 1Y, 1M, 1C, and 1K (photoconductors) corresponding to the four colors of yellow, magenta, cyan, and black, which are arranged in parallel to face an intermediate transfer belt 8 (intermediate transfer body). As previously described with reference to Figure 4(A), during full-color printing (a printing operation using four colors), detection toner patterns TY, TM, TC, and TK of four colors corresponding to yellow, magenta, cyan, and black, respectively, are formed in the first adjustment mode, detection mode, and second adjustment mode. Here, the image forming apparatus 100 in this embodiment is configured to perform monochrome printing using only the imaging unit 6K related to black (printing without using the color imaging units 6Y, 6M, and 6C). During monochrome printing, the image forming apparatus 100 is configured to form only the detection toner pattern TK corresponding to black in the first adjustment mode, detection mode, and second adjustment mode. Then, only the imaging conditions of the black imaging unit 6K are adjusted. With this configuration, during monochrome printing, it is possible to avoid unnecessary toner consumption by the color image forming units 6Y, 6M, and 6C that are not involved in monochrome printing.

[0047] Here, referring to FIG. 4(A), in the first adjustment mode, detection mode, and second adjustment mode, the four color detection toner patterns TY, TM, TC, and TK formed, respectively, are all set so that the length H in the sub-scanning direction is equal to or greater than the length (πD) of one revolution of the photosensitive drums 1Y, 1M, 1C, and 1K (having a diameter D) (H≧πD). When the length H of the detection toner patterns TY, TM, TC, and TK in the sub-scanning direction is short (H<πD), the toner adhesion amount is likely to vary, and the detection results of the first density detection sensor 95 also vary, making it difficult to optimize the image formation conditions. Therefore, it is preferable to make the above-mentioned relationship H≧πD hold. 4A, the four color detection toner patterns TY, TM, TC, and TK formed in the first adjustment mode, detection mode, and second adjustment mode are set to be at the same position in the main scanning direction (the up-down direction in FIG. 4). This makes it possible to detect each of the four color detection toner patterns TY, TM, TC, and TK by installing one first density detection sensor 95 at the same position in the main scanning direction. Also, it is possible to eliminate factors that cause differences in the amount of toner adhesion due to differences in the position in the main scanning direction.

[0048] As described above, the image forming apparatus 100 in this embodiment is provided with the secondary transfer belt 72 (transfer member) for transferring the toner image formed on the surface of the intermediate transfer belt 8 (image carrier) to the sheet P, and the first concentration detection sensor 95 (detection means) for detecting the toner adhesion amount of the detection toner patterns TY, TM, TC, and TK formed on the surface of the intermediate transfer belt 8 and then transferred to the surface of the secondary transfer belt 72. Also provided are an image creation condition adjustment means (control unit 90) for adjusting the image creation conditions for forming the toner image on the surface of the intermediate transfer belt 8, and a transfer condition adjustment means (control unit 90) for adjusting the transfer conditions of the secondary transfer belt 72 during printing. During non-printing times when no printing operation is being performed on the sheet P, a first adjustment mode is configured to be executable in which, without transporting the sheet P, the toner adhesion amount of the detection toner patterns TY, TM, TC, and TK which are formed on the surface of the intermediate transfer belt 8 and then transferred to the secondary transfer belt 72 under predetermined transfer conditions is detected by a first concentration detection sensor 95, and the image creation conditions are adjusted by an image creation condition adjustment means so that the detection result becomes a target value. In addition, before printing begins immediately before the printing operation on the sheet P is performed, a detection mode is configured to be executable in which the first concentration detection sensor 95 detects the amount of toner adhesion of the detection toner patterns TY, TM, TC, and TK that are formed on the intermediate transfer belt 8 and then transferred to the secondary transfer belt 72 under transfer conditions adjusted by a transfer condition adjustment means under specified conditions. Furthermore, during printing, the first concentration detection sensor 95 detects the amount of toner adhesion of the detection toner patterns TY, TM, TC, and TK that are formed outside the image area M on the intermediate transfer belt 8 and then transferred to the secondary transfer belt 72 under the same transfer conditions as in the detection mode, and a second adjustment mode is configured to be executable in which the image creation conditions are adjusted by the image creation condition adjustment means so that a correction value obtained by adding the difference between the detection result detected by the first concentration detection sensor 95 in the first adjustment mode and the detection result detected by the first concentration detection sensor 95 in the detection mode to the detection result becomes the target value. This makes it possible to prevent the occurrence of a problem in which a target image density cannot be obtained.

[0049] In this embodiment, the present invention is applied to an image forming apparatus 100 that uses a secondary transfer belt 72 as a transfer member (secondary transfer member). However, the present invention can also be applied to an image forming apparatus that uses a secondary transfer roller as a transfer member (secondary transfer member). In this embodiment, the present invention is applied to an image forming apparatus 100 using an intermediate transfer belt 8 (intermediate transfer body) as an image carrier and a secondary transfer belt 72 as a transfer member. In contrast, the present invention can also be applied to an apparatus that does not include an intermediate transfer body such as an intermediate transfer belt or intermediate transfer drum, but includes a developing device that develops toner, a photosensitive drum (photosensitive body) as an image carrier on which a toner image developed by the developing device is formed, and a transfer member that contacts the photosensitive drum to form a transfer nip and transfers the toner image on the photosensitive drum to a sheet transported to the transfer nip, that is, a so-called direct transfer type image forming apparatus. In this case, the "imaging conditions" adjusted by the image forming adjustment means are at least one of the charging bias, the exposure energy of the exposure light, the developing bias, and the toner concentration of the developer. In the present embodiment, the present invention is applied to the image forming apparatus 100 that forms color images. However, the present invention can also be applied to an image forming apparatus that forms only monochrome images. Even in such cases, the same effects as those of this embodiment can be obtained.

[0050] It is clear that the present invention is not limited to the present embodiment, and that the present embodiment may be modified as appropriate within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and may be any number, position, shape, etc. suitable for implementing the present invention. [Explanation of symbols]

[0051] 1Y, 1M, 1C, 1K photoconductor drum (photoconductor), 4Y charging device, 5Y developing device, 7 Exposure equipment, 8 Intermediate transfer belt (image carrier, intermediate transfer body), 9Y Primary transfer roller (primary transfer member), 50 Fixing device, 70 Secondary transfer roller, 72 Secondary transfer belt (transfer member, secondary transfer member), 80 secondary transfer opposing roller (secondary transfer opposing member), 90 control unit (imaging condition adjustment means, transfer condition adjustment means), 95 first concentration detection sensor (detection means, first detection means), 96 second concentration detection sensor (second detection means), 100 Image forming apparatus (image forming apparatus main body), TY, TM, TC, TK detection toner patterns, RY, RM, RC, RK adjustment toner patterns, M image area, P sheet (recording medium).

[0052] The present invention can also be embodied in the following combinations of Supplementary Notes 1 to 7. (Appendix 1) a transfer member for transferring a toner image formed on the surface of the image carrier onto a sheet; a detection means for detecting an amount of toner adhesion of a detection toner pattern formed on the surface of the image carrier and then transferred to the surface of the transfer member; an image forming condition adjusting unit that adjusts image forming conditions for forming a toner image on the surface of the image carrier; a transfer condition adjusting means for adjusting the transfer conditions of the transfer member during printing; Equipped with a first adjustment mode is configured to be executable in which, during a non-printing time when a printing operation on a sheet is not being performed, the detection means detects an amount of toner adhesion of the detection toner pattern that has been formed on the surface of the image carrier and then transferred to the transfer member under predetermined transfer conditions, without conveying a sheet, and the image creation conditions are adjusted by the image creation condition adjustment means so that the detection result becomes a target value, a detection mode is configured to be executable in which, before the start of printing immediately before a printing operation on a sheet is performed, the detection means detects an amount of toner adhesion of the detection toner pattern that has been formed on the image carrier and then transferred to the transfer member under transfer conditions adjusted by the transfer condition adjustment means under predetermined conditions, the image forming apparatus being configured to be capable of executing a second adjustment mode in which, during printing, the detection means detects an amount of toner adhesion of the detection toner pattern that has been formed outside the image area on the image carrier and then transferred to the transfer member under the same transfer conditions as in the detection mode, and the image forming conditions are adjusted by the image forming condition adjustment means so that a correction value obtained by adding to the detection result a difference between the detection result detected by the detection means in the first adjustment mode and the detection result detected by the detection means in the detection mode becomes the target value. (Appendix 2) The transfer member is a secondary transfer member for secondary transferring the toner image, which has been primarily transferred onto the surface of an intermediate transfer body, onto a sheet, The transfer conditions are: a secondary transfer bias applied to at least one of the secondary transfer member and a secondary transfer opposing member that is in contact with the secondary transfer member via the intermediate transfer body; a secondary transfer pressure when the secondary transfer member contacts the intermediate transfer body; and a linear velocity difference of the secondary transfer member with respect to the intermediate transfer body at a secondary transfer nip where the secondary transfer member contacts the intermediate transfer body; 2. The image forming apparatus according to claim 1, characterized in that the image forming apparatus is at least one of the above. (Appendix 3) The intermediate transfer body is an intermediate transfer belt, 3. The image forming apparatus according to claim 2, wherein the secondary transfer member is a secondary transfer belt. (Appendix 4) The imaging conditions are a charging bias applied to a charging device in order to charge the surface of a photoconductor facing the intermediate transfer body as the image carrier; an exposure energy of exposure light irradiated onto the photoconductor to form a latent image on the surface of the photoconductor charged by the charging device; a developing bias applied to a developing device that develops the latent image formed on the surface of the photoconductor; a toner concentration of a developer contained inside the developing device; a primary transfer bias applied to a primary transfer member for transferring the toner image formed on the surface of the photoconductor to the surface of the intermediate transfer member; The image forming apparatus according to any one of claims 1 to 3, characterized in that the image forming apparatus is at least one of the above. (Appendix 5) Four photoconductors corresponding to four colors, yellow, magenta, cyan, and black, are arranged in parallel so as to face the intermediate transfer body, During monochrome printing, only the detection toner pattern corresponding to black is formed in each of the first adjustment mode, the detection mode, and the second adjustment mode; The image forming device described in Appendix 4, characterized in that during full-color printing, in the first adjustment mode, the detection mode, and the second adjustment mode, four detection toner patterns corresponding to yellow, magenta, cyan, and black, respectively, are formed. (Appendix 6) The image forming device according to claim 4 or 5, wherein in the first adjustment mode, the detection mode, and the second adjustment mode, the four color detection toner patterns formed respectively have a length in the sub-scanning direction that is equal to or greater than the length of one circumference of the photoconductor, and are positioned at the same position in the main scanning direction. (Appendix 7) a second detection unit that detects an image density of the adjustment toner pattern that is formed on the surface of the image carrier and then transferred to the surface of the sheet by the transfer member; The transfer condition adjusting means adjusts a transfer condition of the transfer member during printing based on a detection result of the second detection means, The image forming apparatus according to any one of Appendix 1 to Appendix 6, characterized in that the detection mode is a mode in which, before printing begins immediately before a printing operation is performed on a sheet, the detection means detects the amount of toner adhesion of the detection toner pattern that is formed on the image carrier and then transferred to the transfer member under transfer conditions adjusted by the transfer condition adjustment means for a sheet of the same type as the sheet. [Prior art documents]

Patent Document

[0053]

Patent Document 1

Claims

1. a transfer member for transferring a toner image formed on the surface of the image carrier onto a sheet; a detection means for detecting an amount of toner adhesion of a detection toner pattern formed on the surface of the image carrier and then transferred to the surface of the transfer member; an image forming condition adjusting unit that adjusts image forming conditions for forming a toner image on the surface of the image carrier; a transfer condition adjusting means for adjusting the transfer conditions of the transfer member during printing; Equipped with a first adjustment mode is configured to be executable in which, during a non-printing time when a printing operation on a sheet is not being performed, a toner adhesion amount of the detection toner pattern that is formed on the surface of the image carrier and then transferred to the transfer member under predetermined transfer conditions is detected by the detection means without transporting a sheet, and the image creation conditions are adjusted by the image creation condition adjustment means so that the detection result becomes a target value, a detection mode is configured to be executable in which, before the start of printing immediately before a printing operation on a sheet is performed, the detection means detects an amount of toner adhesion of the detection toner pattern that has been formed on the image carrier and then transferred to the transfer member under transfer conditions adjusted by the transfer condition adjustment means under predetermined conditions, an image forming apparatus configured to be capable of executing a second adjustment mode in which, during printing, the detection means detects the amount of toner adhesion of the detection toner pattern that is formed outside the image area on the image carrier and then transferred to the transfer member under the same transfer conditions as in the detection mode, and the image forming conditions are adjusted by the image forming condition adjustment means so that a correction value obtained by adding the difference between the detection result detected by the detection means in the first adjustment mode and the detection result detected by the detection means in the detection mode becomes the target value.

2. The transfer member is a secondary transfer member for secondary transferring a toner image, which has been primarily transferred onto a surface of an intermediate transfer body, onto a sheet, The transfer conditions are: a secondary transfer bias applied to at least one of the secondary transfer member and a secondary transfer opposing member that is in contact with the secondary transfer member via the intermediate transfer body; a secondary transfer pressure when the secondary transfer member contacts the intermediate transfer body; a linear velocity difference of the secondary transfer member with respect to the intermediate transfer body at a secondary transfer nip where the secondary transfer member contacts the intermediate transfer body; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is at least one of the above.

3. The intermediate transfer body is an intermediate transfer belt, 3. The image forming apparatus according to claim 2, wherein the secondary transfer member is a secondary transfer belt.

4. The imaging conditions are a charging bias applied to a charging device in order to charge the surface of a photoconductor facing the intermediate transfer body as the image carrier; an exposure energy of exposure light irradiated onto the photoconductor to form a latent image on the surface of the photoconductor charged by the charging device; a developing bias applied to a developing device that develops the latent image formed on the surface of the photoconductor; a toner concentration of a developer contained inside the developing device; a primary transfer bias applied to a primary transfer member for transferring a toner image formed on the surface of the photoreceptor to the surface of the intermediate transfer member; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is at least one of the above.

5. Four photoconductors corresponding to four colors, yellow, magenta, cyan, and black, are arranged in parallel so as to face the intermediate transfer body, During monochrome printing, only the detection toner pattern corresponding to black is formed in each of the first adjustment mode, the detection mode, and the second adjustment mode, 5. The image forming apparatus according to claim 4, wherein, during full-color printing, in the first adjustment mode, the detection mode, and the second adjustment mode, the detection toner patterns are formed in four colors, corresponding to yellow, magenta, cyan, and black, respectively.

6. 6. The image forming apparatus according to claim 5, wherein in the first adjustment mode, the detection mode, and the second adjustment mode, the four color detection toner patterns formed respectively have a length in the sub-scanning direction that is equal to or greater than the length of one circumference of the photosensitive body, and are positioned in the same position in the main scanning direction.

7. a second detection unit for detecting an image density of the adjustment toner pattern formed on the surface of the image carrier and then transferred to the surface of the sheet by the transfer member; The transfer condition adjusting means adjusts a transfer condition of the transfer member during printing based on a detection result of the second detection means, The image forming apparatus according to claim 1 or claim 2, characterized in that the detection mode is a mode in which, before printing begins immediately before the printing operation on the sheet is performed, the detection means detects the amount of toner adhesion of the detection toner pattern that is formed on the image carrier and then transferred to the transfer member under transfer conditions adjusted by the transfer condition adjustment means for a sheet of the same type as the sheet.

Images