Image forming apparatus

Abstract

To suppress increase in a positional deviation amount between images formed on a formation object body by an image formation body located on the downstream side with respect to a formation object body meander correction roll in comparison to a case where a distance between the plurality of formation object bodies located on the downstream side in the conveyance direction of the formation object body with respect to the formation object body meander correction roll is not the integral multiplication of the outer circumferential length of the formation object body meander correction roll.SOLUTION: An image formation apparatus comprises: a formation object body 52 which is conveyed along one direction; three or more image formation bodies 22, 32 which are arranged so as to be apart from each other along the one direction and form images on the formation object body; and a formation object body meander correction roll 45 which is in contact with the inner peripheral surface of the formation object body in a rotatable manner, is located on the downstream side with respect to the image formation body located on the uppermost stream side in the conveyance direction of the formation object body, the plurality of image formation bodies being located on the downstream side with respect to the roll. A distance 30B between the plurality of image formation bodies 32 located on the downstream side with respect to the formation object body meander correction roll is the integral multiplication of the outer circumferential length of the formation object body meander correction roll.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In the image forming apparatus of Patent Document 1, a plurality of image forming bodies that face the belt and form an image on the paper are provided around an annular belt that conveys the paper (object to be formed) on which the image is formed and is circulated by a driving roll.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, an object to be formed meandering correction roll for correcting meandering of the object to be formed may be provided in the image forming apparatus.

[0005] An object of the present invention is to suppress an increase in the amount of misalignment between images formed on the object to be formed by image forming bodies located downstream of the object to be formed meandering correction roll compared to a case where the distance between a plurality of image forming bodies located downstream of the object to be formed meandering correction roll in the conveyance direction of the object to be formed is not an integral multiple of the outer peripheral length of the object to be formed meandering correction roll.

Means for Solving the Problems

[0006] To achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a formed body conveyed along one direction, three or more image forming bodies arranged apart from each other along the one direction and forming an image on the formed body, and a formed body meandering correction roll rotatably contacting an inner peripheral surface of the formed body, located downstream of the image forming body located at the most upstream side in the conveyance direction of the formed body, and having a plurality of the image forming bodies located downstream of itself. Distances between the plurality of the image forming bodies located downstream of the formed body meandering correction roll are integer multiples of an outer peripheral length of the formed body meandering correction roll.

[0007] To achieve the above object, an image forming apparatus according to a second aspect of the present invention includes an annular belt circulating in one direction, three or more image forming bodies arranged apart from each other along the belt and forming an image on the belt and a formed body which is one of recording media conveyed by the belt, and a belt meandering correction roll rotatably contacting an inner peripheral surface of the belt, located downstream of the image forming body located at the most upstream side in the circulating direction, and having a plurality of the image forming bodies located downstream of itself. Distances between the plurality of the image forming bodies located downstream of the belt meandering correction roll are integer multiples of an outer peripheral length of the belt meandering correction roll.

[0008] Further, an image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the second aspect, and includes a driving roll rotatably contacting an inner peripheral surface of the belt and circulating the belt. The distances between the image forming bodies are integer multiples of an outer peripheral length of the driving roll.

[0009] Further, an image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the third aspect, in which the driving roll is located upstream of the belt meandering correction roll, a first distance which is the distance between the plurality of the image forming bodies located downstream of the driving roll and upstream of the belt meandering correction roll is an integer multiple of the outer peripheral length of the driving roll, and a second distance which is the distance between the plurality of the image forming bodies located downstream of the belt meandering correction roll is shorter than the first distance.

[0010] Further, the image forming apparatus according to the fifth aspect of the present invention is the image forming apparatus according to the fourth aspect, wherein three or more of the image forming members are arranged along a straight portion formed on the belt, downstream of the drive roll and upstream of the belt meander correction roll, and all the first distances are the same.

[0011] Further, the image forming apparatus according to the sixth aspect of the present invention is the image forming apparatus according to the fifth aspect, wherein three or more of the image forming members are arranged along another straight portion different from the one straight portion formed on the belt, downstream of the belt meander correction roll, and all the second distances are the same.

[0012] Further, the image forming apparatus according to the seventh aspect of the present invention is the image forming apparatus according to any one of the third to sixth aspects, and includes a winding roll that rotatably contacts the inner peripheral surface of the belt, and a pushing roll that is located between the drive roll and the winding roll and rotatably contacts the outer peripheral surface of the belt to push the belt inward.

[0013] Further, the image forming apparatus according to the eighth aspect of the present invention is the image forming apparatus according to any one of the first to seventh aspects, wherein the image forming member is a photosensitive drum that transfers a toner image to the object to be formed, and the distance is the distance between the rotation axes of adjacent photosensitive drums.

[0014] Further, the image forming apparatus according to the ninth aspect of the present invention includes an object to be formed that is conveyed along one direction, a plurality of image forming members that are arranged apart from each other along the one direction and form an image on the object to be formed, and an object to be formed meander correction roll that rotatably contacts the inner peripheral surface of the object to be formed and is located upstream of the plurality of image forming members in the conveyance direction of the object to be formed, and the distances between the plurality of image forming members are integer multiples of the outer peripheral length of the object to be formed meander correction roll.

[0015] Further, the image forming apparatus according to the tenth aspect of the present invention includes an annular belt that circulates in one direction, a plurality of image forming units that are arranged side by side along the belt and are spaced apart from each other, and form an image on a to-be-formed object that is one of the belt and the recording medium conveyed by the belt, and a belt meandering correction roll that rotatably contacts the inner peripheral surface of the belt and is located upstream of the plurality of image forming units in the circumferential direction. The distance between the plurality of image forming units is an integer multiple of the outer peripheral length of the belt meandering correction roll.

Advantages of the Invention

[0016] According to the first aspect, compared with the case where the distance between a plurality of image forming units located downstream of the to-be-formed object meandering correction roll in the conveyance direction of the to-be-formed object is not an integer multiple of the outer peripheral length of the to-be-formed object meandering correction roll, the amount of misalignment between the images formed on the to-be-formed object by the image forming units located downstream of the to-be-formed object meandering correction roll is suppressed from increasing.

[0017] According to the second aspect, compared with the case where the distance between a plurality of image forming units located downstream of the belt meandering correction roll in the circumferential direction of the belt is a length different from an integer multiple of the outer peripheral length of the belt meandering correction roll, the amount of misalignment between the images formed on the to-be-formed object by the image forming units located downstream of the belt meandering correction roll is suppressed from increasing.

[0018] According to the third aspect, compared with the case where the distance between the image forming units is a length different from an integer multiple of the outer peripheral length of the drive roll, the amount of misalignment between the images formed on the to-be-formed object by the image forming units located downstream of the belt meandering correction roll is suppressed from increasing.

[0019] According to the fourth aspect, compared with the case where the second distance is the same as the first distance, the amount of misalignment between the images formed on the to-be-formed object by a plurality of image forming units located downstream of the belt meandering correction roll is suppressed from increasing.

[0020] According to the fifth aspect, it is possible to reduce the horizontal dimension of the image forming apparatus as compared with the case where at least one of the first distances is different from the other first distances.

[0021] According to the sixth aspect, it is possible to reduce the horizontal dimension of the image forming apparatus as compared with the case where at least one of the second distances is different from the other second distances.

[0022] According to the seventh aspect, the wrap angle of the drive roll and the belt increases as compared with the case where the belt is linear between the drive roll and the winding roll.

[0023] According to the eighth aspect, in a configuration in which each image forming member forms a toner image on a member to be formed, the distance between a plurality of image forming members located downstream of the belt meander correction roll is different from an integer multiple of the outer peripheral length of the belt meander correction roll. Compared with the case of the length, it is possible to suppress an increase in the amount of misalignment between the images formed on the member to be formed by the image forming members located downstream of the belt meander correction roll.

[0024] According to the ninth aspect, compared with the case where the distance between a plurality of image forming members located downstream of the member to be formed meander correction roll in the conveyance direction of the member to be formed is not an integer multiple of the outer peripheral length of the member to be formed meander correction roll, It is possible to suppress an increase in the amount of misalignment between the images formed on the member to be formed by the image forming members located downstream of the member to be formed meander correction roll.

[0025] According to the tenth aspect, compared with the case where the distance between a plurality of image forming members located downstream in the circumferential direction of the belt from the belt meander correction roll is a length different from an integer multiple of the outer peripheral length of the belt meander correction roll, It is possible to suppress an increase in the amount of misalignment between the images formed on the member to be formed by the image forming members located downstream of the belt meander correction roll.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

[0027] Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In the following, the upstream side in the conveyance direction of the recording paper P as an example of the recording medium may be simply referred to as the "upstream side", and the downstream side in the conveyance direction may be simply referred to as the "downstream side". Similarly, the upstream side in the circumferential direction (conveyance direction) of the transfer belt (belt) (object to be formed) 52 may be simply referred to as the "upstream side", and the downstream side in the circumferential direction (conveyance direction) may be simply referred to as the "downstream side".

[0028] As shown in FIG. 1, the image forming apparatus 10 is, for example, an electrophotographic system that forms a toner image (an example of an image) on the recording paper P. And this image forming apparatus 10 is provided with an image forming part 12, a storage part 14, a conveyance part 16, and a fixing device 18 in an apparatus main body (not shown). Hereinafter, each part (image forming part 12, storage part 14, conveyance part 16, and fixing device 18) of the image forming apparatus 10 will be described.

[0029] Furthermore, in the following description, the width direction (horizontal direction) of the apparatus main body is defined as the X direction, the vertical direction (vertical direction) of the apparatus main body is defined as the Y direction, and the direction orthogonal to the X direction and the Y direction (the direction orthogonal to the paper surface) is defined as the Z direction.

[0030] <Image Forming Part> The image forming part 12 has a function of forming a toner image on the recording paper P. Specifically described, the image forming part 12 has a first photoreceptor unit 20, a second photoreceptor unit 30, and a transfer device 50.

[0031] [Photoreceptor Unit] As shown in FIG. 1, two first photoreceptor units 20 and two second photoreceptor units 30 are provided. Each first photoreceptor unit 20 and each second photoreceptor unit 30 are detachable from the apparatus main body. The image forming apparatus 10 of the present embodiment has two first photoreceptor units 20Y and 20M of two colors, yellow (Y) and magenta (M), and two second photoreceptor units 30C and 30K of two colors, cyan (C) and black (K).

[0032] In the following, when it is necessary to distinguish each color of yellow (Y), magenta (M), cyan (C), and black (K), English letters Y, M, C, and K are attached after the reference numerals of each member, and when it is not necessary to distinguish each color, the English letters Y, M, C, and K may be omitted.

[0033] The transfer belt 52 formed of an elastic material of the transfer device 50 described later has two linear portions that are linear when viewed from the Z direction. These two linear portions are the upper portion 52A and the lower portion 52B. When viewed from the Z direction, the upper portion 52A is along the X direction, and the lower portion 52B is inclined with respect to the X direction. That is, when viewed from the Z direction, the angle θB (see FIG. 1) formed by the lower portion 52B and the X direction is an acute angle, and the angle θB is larger than the angle θA (not shown) formed by the upper portion 52A and the X direction. The angle θA is 0° or an acute angle slightly larger than 0°. When viewed from the Z direction, the upper portion 52A and the lower portion 52B are arranged side by side in the Y direction. Note that the "linear portion" in this specification and the claims is not limited to a completely linear shape. For example, the upper portion 52A located between the steering roll 45 and the winding roll 48 described later is slightly recessed at the portion pressed by the two first photoreceptor drums 22 and the primary transfer roll 41, but the upper portion 52A corresponds to the "linear portion". Similarly, the lower portion 52B located between the steering roll 45 and the winding roll 47 is slightly recessed at the portion pressed by the two second photoreceptor drums 32 and the primary transfer roll 41, but the lower portion 52B corresponds to the "linear portion".

[0034] The two first photoreceptor units 20 face the outer peripheral surface (upper surface) of the upper portion 52A and are arranged in the X direction along the upper portion 52A. In particular, when the two first photoreceptor units 20 are arranged such that the lower surface formed by the plane of the support plate 28 (to be described later) of each first photoreceptor unit 20 is parallel to the outer peripheral surface (upper surface) of the upper portion 52A, the length of the apparatus main body in the Y direction is suppressed as compared with the case where they are arranged so as to be non-parallel to the outer peripheral surface. Further, when the lower surface of the support plate 28 and the outer peripheral surface of the upper portion 52A face each other in the Y direction, if the distance between the lower surface of the support plate 28 and the outer peripheral surface of the upper portion 52A is shortened, the length of the apparatus main body in the Y direction is suppressed. Each first photoreceptor unit 20 has a first photoreceptor drum 22 that rotates in one direction (for example, the counterclockwise direction in FIG. 1). Each first photoreceptor drum 22 is rotatable about a rotation axis 20X extending in the Z direction. The distance (adjacent distance) between the rotation axes 20X of the two first photoreceptor units 20 when viewed from the Z direction is the first distance 20B. Further, each first photoreceptor unit 20 has, in order from the upstream side in the rotation direction of the first photoreceptor drum 22, a first charging portion 24, a first exposure portion 25, a first developing portion 26, and a first removing portion 27. Further, each first photoreceptor unit 20 has a pair of support plates 28 that are separated from each other in the Z direction. Note that in FIG. 1, the illustration of one of the support plates 28 is omitted. The first charging portion 24, the first exposure portion 25, the first developing portion 26, and the first removing portion 27 are members extending in the Z direction. Both end portions in the Z direction of the first charging portion 24, the first exposure portion 25, the first developing portion 26, and the first removing portion 27 are respectively supported by the pair of support plates 28. Further, the relative movement of the pair of support plates 28 is restricted. As shown in FIG. 1, the dimension of each first photoreceptor unit 20 in the X direction is the horizontal dimension 20L.

[0035] The two second photoreceptor units 30 face the outer peripheral surface (lower surface) of the lower part 52B and are arranged along the lower part 52B. Each second photoreceptor unit 30 has a second photoreceptor drum 32 that rotates in one direction (for example, the counterclockwise direction in FIG. 1). Each second photoreceptor drum 32 is rotatable about a rotation axis 30X extending in the Z direction. The distance (adjacent distance) between the rotation axes 30X of the two second photoreceptor units 30 when viewed from the Z direction is the second distance 30B. Further, each second photoreceptor unit 30 has, in order from the upstream side in the rotation direction of the second photoreceptor drum 32, a second charging unit 34, a second exposure unit 35, a second developing unit 36, and a second removing unit 37. Furthermore, each second photoreceptor unit 30 has a pair of second support plates 38 that are separated from each other in the Z direction. Note that in FIG. 1, the illustration of one of the second support plates 38 is omitted. The second charging unit 34, the second exposure unit 35, the second developing unit 36, and the second removing unit 37 are members extending in the Z direction. Both end portions in the Z direction of the second charging unit 34, the second exposure unit 35, the second developing unit 36, and the second removing unit 37 are respectively supported by the pair of second support plates 38. Furthermore, the relative movement of the pair of second support plates 38 is restricted. As shown in FIG. 1, the dimension of each second photoreceptor unit 30 in the X direction is the horizontal dimension 30L.

[0036] In this specification and the claims, the "image forming body" refers to something that attaches toner or ink to the object to be formed (for example, the transfer belt 52). That is, the first photoreceptor drum 22 of the first photoreceptor unit 20 corresponds to the "image forming body", and the second photoreceptor drum 32 of the second photoreceptor unit 30 corresponds to the "image forming body". That is, the first charging unit 24, the first exposure unit 25, the first developing unit 26, and the first removing unit 27 do not correspond to the "image forming body". Similarly, the second charging unit 34, the second exposure unit 35, the second developing unit 36, and the second removing unit 37 do not correspond to the "image forming body". Note that as will be described later, when the image forming apparatus 10 is an inkjet type, the inkjet head corresponds to the "image forming body".

[0037] As shown in FIG. 1, inside the first developing unit 26, a developing roll 26A, a recovery auger 26B, a supply auger 26C, and a stirring auger 26D are provided. Similarly, inside the second developing unit 36, a developing roll 36A, a recovery auger 36B, a supply auger 36C, and a stirring auger 36D are provided. The supply auger 26C and the stirring auger 26D are arranged in the X direction. On the other hand, the supply auger 36C and the stirring auger 36D are arranged in the Y direction. Therefore, the horizontal dimension of the second developing unit 36 is shorter than the horizontal dimension of the first developing unit 26. For this reason, the horizontal dimension 30L is shorter than the horizontal dimension 20L.

[0038] As shown in FIG. 1, when viewed from the Z direction, the two first photoreceptor units 20 are arranged in the X direction. That is, the two first photoreceptor units 20 are not arranged in the Y direction. On the other hand, when viewed from the Z direction, a part of the two second photoreceptor units 30 are arranged in the Y direction. The horizontal dimension 30V shown in FIG. 1 is the X-direction dimension of the said part of the two second photoreceptor units 30. 30E shown in FIG. 1 is the horizontal dimension of the part composed of the two second photoreceptor units 30. 30G shown in FIG. 1 is the horizontal dimension of the part composed of the lower part 52B and the two second photoreceptor units 30.

[0039] In each first photoreceptor unit 20, the first charging unit 24 charges the outer peripheral surface of the first photoreceptor drum 22. Then, the first exposure unit 25 exposes the outer peripheral surface of the first photoreceptor drum 22 charged by the first charging unit 24 to form an electrostatic latent image on the outer peripheral surface of the first photoreceptor drum 22. Further, the first developing unit 26 develops the electrostatic latent image formed on the outer peripheral surface of the first photoreceptor drum 22 by the first exposure unit 25 to form a toner image. Then, after the transfer of the toner image to the transfer belt 52, the first removing unit 27 removes the toner remaining on the outer peripheral surface of the first photoreceptor drum 22.

[0040] In each second photoreceptor unit 30, a second charging unit 34 charges the outer peripheral surface of the second photoreceptor drum 32. Then, a second exposure unit 35 exposes the outer peripheral surface of the second photoreceptor drum 32 charged by the second charging unit 34 to form an electrostatic latent image on the outer peripheral surface of the second photoreceptor drum 32. Further, a second developing unit 36 develops the electrostatic latent image formed on the outer peripheral surface of the second photoreceptor drum 32 by the second exposure unit 35 to form a toner image. And a second removing unit 37 removes the toner remaining on the outer peripheral surface of the second photoreceptor drum 32 after the transfer of the toner image to the transfer belt 52.

[0041] [Transfer device] As shown in FIG. 1, the transfer device 50 includes four primary transfer rolls 41 as an example of a primary transfer member, a transfer belt 52 as an example of an intermediate transfer member, and a transfer cylinder 60 as an example of a secondary transfer member. That is, the transfer device 50 performs primary transfer by overlapping the toner image formed on the outer peripheral surface of each first photoreceptor drum 22 on the transfer belt 52, and performs secondary transfer of the overlapped toner image onto the recording paper P.

[0042] (Primary transfer roll) As shown in FIG. 1, each primary transfer roll 41 facing the upper portion 52A transfers the toner image formed on the outer peripheral surface of each first photoreceptor drum 22 to the outer peripheral surface of the transfer belt 52 at the primary transfer position T1 between the first photoreceptor drum 22 and the primary transfer roll 41. Each primary transfer roll 41 facing the lower portion 52B transfers the toner image formed on the outer peripheral surface of each second photoreceptor drum 32 to the outer peripheral surface of the transfer belt 52 at the primary transfer position T1 between the second photoreceptor drum 32 and the primary transfer roll 41. The distance between the primary transfer positions T1 of the two first photoreceptor drums 22 corresponds to the first distance 20B. Similarly, the distance between the primary transfer positions T1 of the two second photoreceptor drums 32 corresponds to the second distance 30B. In the present embodiment, a primary transfer voltage is applied between the primary transfer roll 41 and the first photoreceptor drum 22, whereby the toner image formed on the outer peripheral surface of the first photoreceptor drum 22 is transferred to the outer peripheral surface of the transfer belt 52 at the primary transfer position T1. Similarly, a primary transfer voltage is applied between the primary transfer roll 41 and the second photoreceptor drum 32, whereby the toner image formed on the outer peripheral surface of the second photoreceptor drum 32 is transferred to the outer peripheral surface of the transfer belt 52 at the primary transfer position T1.

[0043] (Transfer Belt) As shown in FIG. 1, the transfer belt 52 is annular such that the toner image is transferred to the outer peripheral surface, and is wound around a driving roll 44, a steering roll 45, a backup roll 46, a winding roll 47, a winding roll 48, and a pushing roll 49 to determine its posture. The steering roll 45 is an example of a belt meandering correction roll (a formed body meandering correction roll).

[0044] The driving roll 44 having a circular cross-section is configured to be rotationally driven about an axis 44X extending in the Z direction by a driving unit (not shown), and circulates the transfer belt 52 in a circulating direction indicated by an arrow A at a predetermined speed.

[0045] The diameter of the steering roll 45 with a circular cross-section is the same as the diameter of the drive roll 44 within the tolerance range. In other words, the outer peripheral length 45C of the steering roll 45 and the outer peripheral length 44C of the drive roll 44 are the same within the tolerance range. The steering roll 45 is rotatable about an axis 45X extending in the Z direction. Further, the steering roll 45 is swingable about the central portion in the direction of the axis 45X. Therefore, the meandering of the transfer belt 52 is suppressed by the steering roll 45.

[0046] The first distance 20B between the two first photoreceptor drums 22 and the second distance 30B between the two second photoreceptor drums 32 are set to be integer multiples of the outer peripheral length 44C of the drive roll 44 and the outer peripheral length 45C of the steering roll 45. The second distance 30B is shorter than the first distance 20B. For example, in this embodiment, the first distance 20B is set to be 4 times the outer peripheral length 44C and the outer peripheral length 45C, and the second distance 30B is set to be 3 times the outer peripheral length 44C and the outer peripheral length 45C.

[0047] The distance along the transfer belt 52 between the primary transfer position T1 of the downstream first photoreceptor drum 22 and the primary transfer position T1 of the upstream second photoreceptor drum 32 is a distance different from the first distance 20B and the second distance 30B. That is, the distance along the transfer belt 52 between the primary transfer position T1 of the downstream first photoreceptor drum 22 and the primary transfer position T1 of the upstream second photoreceptor drum 32 does not correspond to the "adjacent distance (first distance, second distance)" in the claims. The distance along the transfer belt 52 between the primary transfer position T1 of the downstream first photoreceptor drum 22 and the primary transfer position T1 of the upstream second photoreceptor drum 32 is also set to be an integer multiple of the outer peripheral length 44C of the drive roll 44 and the outer peripheral length 45C of the steering roll 45.

[0048] Also, the backup roll 46 faces the transfer cylinder 60 with the transfer belt 52 interposed therebetween. And the contact region where the transfer cylinder 60 and the transfer belt 52 contact is the nip region Np (see FIG. 1). This nip region Np is the secondary transfer position T2 where the toner image is transferred from the transfer belt 52 to the recording paper P.

[0049] The winding roll 47, which is located downstream of the second photoreceptor unit 30K and upstream of the backup roll 46, is rotatably in contact with the inner peripheral surface of the transfer belt 52. The winding roll 48, which is located upstream of the first photoreceptor unit 20Y and downstream of the drive roll 44, is rotatably in contact with the inner peripheral surface of the transfer belt 52. Further, the pushing roll 49, which is located upstream of the winding roll 48 and downstream of the drive roll 44, is rotatably in contact with the outer peripheral surface of the transfer belt 52 and presses the transfer belt 52 toward the inner peripheral side. When the pushing roll 49 is not provided, the portion of the transfer belt 52 located between the drive roll 44 and the winding roll 48 has the shape indicated by the phantom line in FIG. 2. In this case, the wrap angle between the transfer belt 52 and the drive roll 44 is θI. On the other hand, in the present embodiment, since the pushing roll 49 is provided, the wrap angle between the transfer belt 52 and the drive roll 44 is θ. As is apparent from FIG. 2, the wrap angle θ is larger than the wrap angle θI.

[0050] <Transport unit> As shown in FIG. 1, the transport unit 16 has a transport device (not shown) that transports the recording paper P sent out from the storage unit 14 in the direction of arrow B. By the transport device, the recording paper P sent out from the storage unit 14 is transported to the transfer cylinder 60. The recording paper P onto which the toner image has been secondarily transferred by passing through the transfer cylinder 60 (secondary transfer position T2) is transported to the fixing device 18 by the transport device.

[0051] <Fixing device> As shown in FIG. 1, the fixing device 18 includes a heating roll 42 as an example of a heating member and a pressure roll 43 as an example of a pressure member. The fixing device 18 heats and presses the recording paper P by sandwiching it between the heating roll 42 and the pressure roll 43, thereby fixing the toner image transferred onto the recording paper P by the transfer cylinder 60 to the recording paper P.

[0052] Next, the operation and effects of the image forming apparatus 10 having the above-described configuration will be described in detail.

[0053] In the image forming apparatus 10 of the present embodiment, a second distance (adjacent distance) 30B, which is the distance between the rotation axes 30X of two second photoreceptor drums 32 (image forming members) located downstream of the steering roll 45 and upstream of the transfer position to the recording paper P, is an integral multiple of the outer peripheral length 45C of the steering roll 45. Therefore, compared with the case where the second distance 30B is a length different from an integral multiple of the outer peripheral length 45C, an increase in the amount of deviation in the registration of the toner image formed on the transfer belt (formed body) 52 by the two second photoreceptor drums 32 located downstream of the steering roll 45 is suppressed.

[0054] Furthermore, in the image forming apparatus 10, a first distance 20B between two first photoreceptor drums 22 and a second distance 30B between two second photoreceptor drums 32 are set to be integral multiples of the outer peripheral length 44C of the drive roll 44. Therefore, compared with the case where the first distance 20B and the second distance 30B are set to lengths different from integral multiples of the outer peripheral length 44C, an increase in the amount of deviation in the registration of the toner image formed on the transfer belt (formed body) 52 by the two second photoreceptor drums 32 located downstream of the steering roll 45 is suppressed.

[0055] Furthermore, the second distance 30B between the two second photoreceptor drums 32 located downstream of the first photoreceptor drum 22 is shorter than the first distance 20B. By the way, in the case of a comparative example (not shown) where the first distance 20B and the second distance 30B are the same, the second distance 30B is adjusted to match the first distance 20B. Therefore, the distance along the transfer belt 52 from the drive roll 44 to the second photoreceptor unit 30K is shorter in this embodiment than in the comparative example. The longer this distance, the greater the speed variation of the transfer belt 52 and the cumulative amount of errors in the adjacent distances. Accordingly, in the comparative example, the amount of misregistration of the toner image between the second photoreceptor unit 30C and the second photoreceptor unit 30K is likely to be larger than the amount of misregistration of the toner image between the first photoreceptor unit 20Y and the first photoreceptor unit 20M. On the other hand, in the embodiment, since the distance (second distance 30B) between the second photoreceptor unit 30C and the second photoreceptor unit 30K is shorter than in the comparative example, the cumulative amount of speed variation and errors in the adjacent distances is smaller than in the comparative example. Therefore, in this embodiment, compared with the case where the first distance 20B and the second distance 30B are the same, it is suppressed that the amount of misregistration of the toner image increases as the position of the photoreceptor drum is located downstream of the transfer belt 52.

[0056] Furthermore, a push-in roll 49 is located between the drive roll 44 and the winding roll 48 and rotatably contacts the outer peripheral surface of the transfer belt 52 to push the transfer belt 52 inward. Therefore, the wrap angle (θ) between the drive roll 44 and the transfer belt 52 increases compared to the case where the transfer belt 52 is linear between the drive roll 44 and the winding roll 48.

[0057] As described above, the image forming apparatus 10 according to this embodiment has been described with reference to the drawings. However, the image forming apparatus 10 according to this embodiment is not limited to the one shown, and can be appropriately designed and changed without departing from the gist of the present invention.

[0058] For example, the transfer belt 52 of the image forming apparatus 10 of the first modification shown in FIG. 3 has only one straight portion 52E. In FIG. 3, the illustration of the developing roll 26A, the recovery auger 26B, the supply auger 26C, the agitation auger 26D, the developing roll 36A, the recovery auger 36B, the supply auger 36C, and the agitation auger 26D is omitted. The upstream end of the straight portion 52E is wound around the steering roll 45, and the downstream end of the straight portion 52E is wound around the driving roll 44. That is, the steering roll 45 is located upstream of the driving roll 44. This image forming apparatus 10 has two first photoreceptor units 20 and two second photoreceptor units 30 arranged along the straight portion 52E. That is, all the photoreceptor units (the first photoreceptor unit 20 and the second photoreceptor unit 30) included in the image forming apparatus 10 are located downstream of the steering roll 45 and upstream of the driving roll 44.

[0059] The adjacent distance 23B between the rotation axis 20X of the downstream first photoreceptor drum 22 and the rotation axis 30X of the upstream second photoreceptor drum 32 is set to an integral multiple of the outer peripheral length 44C of the driving roll 44 and the outer peripheral length 45C of the steering roll 45. Further, the relationship of the first distance 20B > adjacent distance 23B > second distance 30B holds. For example, the first distance 20B is set to 4 times the outer peripheral length 44C and the outer peripheral length 45C, the adjacent distance 23B is set to 3.5 times the outer peripheral length 44C and the outer peripheral length 45C, and the second distance 30B is set to 3 times the outer peripheral length 44C and the outer peripheral length 45C.

[0060] In the image forming apparatus 10 of this first modification, the first distance 20B, the adjacent distance 23B, and the second distance 30B are set to integral multiples of the outer peripheral length 45C of the steering roll 45 and the outer peripheral length 44C of the driving roll 44. Therefore, compared with the case where the first distance 20B, the adjacent distance 23B, and the second distance 30B are set to lengths different from the integral multiples of the outer peripheral length 45C and the outer peripheral length 44C, the registration deviation of the toner images of different colors formed on the transfer belt 52 by each first photoreceptor unit 20 and each second photoreceptor unit 30 is less likely to occur.

[0061] Furthermore, the adjacent distance 23B is shorter than the first distance 20B, and the second distance 30B is shorter than the adjacent distance 23B. Therefore, compared with the case where the first distance 20B, the adjacent distance 23B, and the second distance 30B are the same as each other, the amount of deviation in the registration of the toner image is suppressed from increasing as the position of the photoreceptor drum is located more downstream of the transfer belt 52.

[0062] Also, the present invention may be implemented in the aspect of the second modification example shown in FIG. 4. The acute angle formed by the upstream portion 52C, which is a straight portion located upstream of the steering roll 45 and downstream of the winding roll 48 of the transfer belt 52 of the image forming apparatus 10 of this second modification example, and the X direction is θ1. The acute angle formed by the downstream portion 52D, which is a straight portion located downstream of the steering roll 45 and continuous with the upstream portion 52C, and the X direction is θ2, which is larger than θ1. As is clear from FIG. 4, the upstream portion 52C and the downstream portion 52D are not arranged in the Y direction but are arranged in the X direction. Further, two first photoreceptor units 20 are provided along the upper surface (outer peripheral surface) of the upstream portion 52C, and two second photoreceptor units 30 are provided along the upper surface (outer peripheral surface) of the downstream portion 52D. The first photoreceptor unit 20 of the second modification example has the same specifications as the first photoreceptor unit 20 of the embodiment, and the second photoreceptor unit 30 of the second modification example has the same specifications as the second photoreceptor unit 30 of the embodiment.

[0063] The distance (adjacent distance) between the rotation axes 20X of the two first photoreceptor units 20 when viewed from the Z direction is the first distance 20B. The distance (adjacent distance) between the rotation axes 30X of the two second photoreceptor units 30 when viewed from the Z direction is the second distance 30B. As shown in FIG. 4, the horizontal dimension of each first photoreceptor unit 20 is 20HL, and the horizontal dimension of each second photoreceptor unit 30 is 30HL. The horizontal dimension 30HL is shorter than the horizontal dimension 20HL.

[0064] When viewed from the Z direction, a part of each of the two second photoreceptor units 30 is arranged in the Y direction. The horizontal dimension 30P shown in FIG. 4 is the X-direction dimension of the relevant part of the two second photoreceptor units 30. 30F shown in FIG. 4 is the X-direction dimension of the part composed of the two second photoreceptor units 30. The horizontal dimension 30P is larger than the horizontal dimension 30V in FIG. 1. Therefore, the horizontal dimension 30F is smaller than the horizontal dimension 30E in FIG. 1.

[0065] In the image forming apparatus 10 of the second modification shown in FIG. 4, the angle θ2 is larger than the angle θ1. And the two second photoreceptor units 30 are provided along the downstream portion 52D. Further, the second distance 30B is shorter than the first distance 20B. Therefore, compared with the case where the downstream portion 52D is parallel to the horizontal direction and the second distance 30B is the same as the first distance 20B, the horizontal dimension of the part composed of the downstream portion 52D and the two second photoreceptor units 30 is smaller. Accordingly, compared with the case where the downstream portion 52D is parallel to the horizontal direction and the second distance 30B is the same as the first distance 20B, the horizontal dimension of the image forming apparatus 10 of the second modification when viewed from the Z direction is smaller.

[0066] Furthermore, the horizontal dimension 30HL of the second photoreceptor unit 30 is shorter than the horizontal dimension 20HL of the first photoreceptor unit 20. Therefore, compared with the case where the horizontal dimension 30HL is equal to or greater than the horizontal dimension 20HL, the horizontal dimension of the image forming apparatus 10 of the second modification when viewed from the Z direction is smaller.

[0067] Furthermore, when viewed from the Z direction, a part of each of the two second photoreceptor units 30 is arranged in the Y direction. Therefore, compared with the case where the two second photoreceptor units 30 are arranged side by side while being separated in the X direction when viewed from the Z direction, the horizontal dimension 30F of the part composed of the two second photoreceptor units 30 is smaller. Accordingly, compared with the case where the two second photoreceptor units 30 are arranged side by side while being separated in the X direction when viewed from the Z direction, the horizontal dimension of the image forming apparatus 10 of the second modification is smaller.

[0068] Also, the number of photoreceptor drums (image forming bodies) arranged along the transfer belt 52 may be any number as long as it is three or more.

[0069] Further, the number of image forming members provided in a region downstream of the steering roll 45 and upstream of the transfer position onto the recording paper P may be any plural number.

[0070] Further, the image forming apparatus 10 may be configured such that each first photoreceptor unit 20 and each second photoreceptor unit 30 form a toner image on a recording paper P (object to be formed) conveyed by a conveyance belt (not shown) provided instead of the transfer belt 52.

[0071] Also, a toner image is given as an example of the image, and here it is a toner image formed by a dry electrophotographic method, but the present invention is not limited thereto. For example, it may be a toner image formed by a wet electrophotographic method or an image formed by an inkjet method.

[0072] Further, an ink image or a toner image is formed on a long and non-annular continuous paper (object to be formed) wound around a plurality of rotators including the drive roll 44 and conveyed by the drive roll 44 and the rotators while having at least one straight portion, and a steering roll (object to be formed meandering correction roll) 45 rotatably contacts the inner peripheral surface of the continuous paper, and the image forming apparatus 10 may be configured.

[0073] When the image forming apparatus 10 is of an inkjet type, a first distance that is the distance between the centers of inkjet heads (image forming members) corresponding to the first photoreceptor units 20 and a second distance that is the distance between the centers of inkjet heads (image forming members) corresponding to the second photoreceptor units 30 are set to be integer multiples of the outer circumferences 44C and 45C.

[0074] When the image forming apparatus 10 includes the first photoreceptor unit 20 and the second photoreceptor unit 30, each adjacent distance may be the same within the tolerance range. Similarly, when the image forming apparatus 10 includes an inkjet, each adjacent distance may be the same within the tolerance range.

[0075] When the image forming apparatus 10 includes either the first photoreceptor unit 20 and the second photoreceptor unit 30 or an inkjet, each adjacent distance does not have to be an integral multiple of the outer circumferences 44C and 45C.

[0076] The diameter of the steering roll 45 and the diameter of the drive roll 44 may be different from each other. However, also in this case, it is preferable to set the diameter of the steering roll 45 and the diameter of the drive roll 44 so that each adjacent distance becomes an integral multiple of the outer circumferences 45C and 44C.

[0077] The number of types of colors of the image (toner image, ink image) formed on the object to be formed (transfer belt 52, recording medium P) does not have to be four. For example, the number of types of colors of the image may be six.

[0078] For example, when three or more first photoreceptor units 20 are arranged along the upper part 52A or the upstream part 52C, all of the plurality of first distances may be the same within the tolerance range of each other, or at least one first distance may be different from the other first distances. Note that "all the first distances are the same" in the claims means that all of the plurality of first distances are the same within the tolerance range of each other. For example, the first distance between the rightmost first photoreceptor unit 20 and the first photoreceptor unit 20 adjacent to the first photoreceptor unit 20 may be shorter than the first distance between the leftmost first photoreceptor unit 20 and the first photoreceptor unit 20 adjacent to the first photoreceptor unit 20. When all of the plurality of first distances are the same within the tolerance range of each other, the horizontal dimension of the image forming apparatus 10 can be made smaller than when at least one first distance is different from the other first distances. That is, by setting all the first distances to the same distance as the shortest first distance when each first distance is different, the horizontal dimension of the image forming apparatus 10 can be made smaller than when at least one first distance is different from the other first distances.

[0079] For example, when three or more second photoreceptor units 30 are arranged along the lower part 52B or the downstream part 52D, all of the plurality of second distances may be the same within the tolerance range of each other, or at least one second distance may be different from the other second distances. Note that "all the second distances are the same" in the claims means that all of the plurality of second distances are the same within the tolerance range of each other. For example, the second distance between the rightmost second photoreceptor unit 30 and the second photoreceptor unit 30 adjacent to the second photoreceptor unit 30 may be shorter than the second distance between the leftmost second photoreceptor unit 30 and the second photoreceptor unit 30 adjacent to the second photoreceptor unit 30. When all of the plurality of second distances are the same within the tolerance range of each other, the horizontal dimension of the image forming apparatus 10 can be made smaller than when at least one second distance is different from the other second distances.

Explanation of Signs

[0080] 10 Image forming apparatus 22 First photoreceptor drum (image forming body) 32 Second photoreceptor drum (image forming body) 44 Driving roll 45 Steering roll (belt meandering correction roll) (formed body meandering correction roll) 49 Pushing roll 52 Transfer belt (belt) (formed body) P Recording paper (recording medium) (formed body)

Claims

1. A workpiece to be formed that is conveyed along one direction, Three or more image forming units that are arranged side by side along the one direction with a space therebetween and form an image on the workpiece, A workpiece meandering correction roll that rotatably contacts an inner peripheral surface of the workpiece, is located downstream of the image forming unit that is located on the most upstream side in the conveyance direction of the workpiece, and has a plurality of the image forming units located downstream of itself, Comprising: An image forming apparatus, wherein distances between the plurality of image forming units located downstream of the workpiece meandering correction roll are integer multiples of an outer peripheral length of the workpiece meandering correction roll.

2. An annular belt that circulates in one direction, Three or more image forming units that are arranged side by side along the belt with a space therebetween and form an image on the belt and a workpiece that is one of the recording media conveyed by the belt, A belt meandering correction roll that rotatably contacts an inner peripheral surface of the belt, is located downstream of the image forming unit that is located on the most upstream side in the circulation direction, and has a plurality of the image forming units located downstream of itself, Comprising: An image forming apparatus, wherein distances between the plurality of image forming units located downstream of the belt meandering correction roll are integer multiples of an outer peripheral length of the belt meandering correction roll.

3. Comprising a driving roll that rotatably contacts an inner peripheral surface of the belt and circulates the belt, The image forming apparatus according to claim 2, wherein the distances between the image forming units are integer multiples of an outer peripheral length of the driving roll. The image forming apparatus according to claim 2.

4. The driving roll is located upstream of the belt meandering correction roll, A first distance that is a distance between the plurality of image forming units located downstream of the driving roll and upstream of the belt meandering correction roll is an integer multiple of an outer peripheral length of the driving roll, A second distance that is a distance between the plurality of image forming units located downstream of the belt meandering correction roll is shorter than the first distance, The image forming apparatus according to claim 3.

5. Three or more of the image forming units located downstream of the driving roll and upstream of the belt meandering correction roll are arranged along a straight portion formed on the belt, All the first distances are the same, The image forming apparatus according to claim 4.

6. Three or more of the image forming units located downstream of the belt meandering correction roll are arranged along another straight portion different from the one straight portion formed on the belt, All the second distances are the same, The image forming apparatus according to claim 5.

7. A winding roll that rotatably contacts the inner peripheral surface of the belt, A pushing roll that is positioned between the driving roll and the winding roll, rotatably contacts the outer peripheral surface of the belt, and pushes the belt inward, having The image forming apparatus according to any one of claims 3 to 6.

8. The image forming member is a photosensitive drum that transfers a toner image to the object to be formed, The distance is the distance between the rotation axes of adjacent photosensitive drums, The image forming apparatus according to any one of claims 1 to 7.

Images