Image forming device

Abstract

To prevent a transfer unit from being excited.SOLUTION: An image forming apparatus comprises: a rotating transfer barrel that is supported by an image forming apparatus main body; a rotary member that is provided coaxially with the transfer barrel and rotates integrally with the transfer barrel; circulating members that are provided with a holding section that holds a leading end of a recording medium, are wound around the rotary member, and circulate in association with the rotation of the rotary member to convey the recording medium; a transfer unit that is supported by the image forming apparatus main body and has a transfer belt that sandwiches the recording medium conveyed by the circulating members with the transfer barrel at a sandwiching position to transfer an image; a first image forming section that is supported by the image forming apparatus main body and forms the image on the transfer belt; and a second image forming section that is supported at a position lower than the first image forming section in the image forming apparatus main body, and forms the image on the transfer belt. The mass of the second image forming section is larger than the mass of the first image forming section.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 discloses a transfer device having a belt-shaped image carrier that carries an image, a drive roller that moves the image carrier carrying the image while wrapping it around, a first tension roller that wraps the image carrier moved by the drive roller and applies tension to the image carrier, a first elastic support portion that has a first elastic member that generates the tension and supports one side of the rotation shaft of the first tension roller, a second elastic support portion that has a second elastic member that generates the tension and supports the other side of the rotation shaft of the first tension roller, a backup roller that wraps the image carrier wrapped around the tension roller, a transfer roller that has a recess on its peripheral surface and comes into contact with the image carrier wrapped around the backup roller to form a transfer nip, and a second tension roller that wraps the image carrier wrapped around the backup roller and applies tension to the image carrier.

[0003] Patent Document 2 discloses an image forming apparatus having a toner image carrier, a plurality of toner image forming means for forming a toner image of a corresponding color on the toner image carrier, and an intermediate transfer belt onto which the toner image of each color formed on each of the toner image carriers is transferred, and the toner image of each color transferred to the intermediate transfer belt is further transferred onto a recording medium. The image forming apparatus is characterized in that the image forming apparatus is provided with a plurality of tension rollers for tensioning the intermediate transfer belt in a shape having two or more flat portions opposed by the toner image carriers provided on the toner image forming means, and a displacement means for changing the position of at least one of the plurality of tension rollers to change the tension state of the intermediate transfer belt, and is arranged so that at least one of the toner image carriers and the intermediate transfer belt come into contact with each other or separate from each other due to the change in the tension state of the intermediate transfer belt. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-220812 A [Patent Document 2] JP 2002-108045 A Summary of the Invention [Problem to be solved by the invention]

[0005] The image forming apparatus may include a rotating transfer cylinder, a rotating member such as a sprocket that rotates integrally with the transfer cylinder, and a revolving member such as a chain that is wound around the rotating member and revolves with the rotation of the rotating member.The image reading device may include an image forming apparatus further including a transfer unit having a transfer belt that sandwiches a recording medium transported by the revolving member between the transfer cylinder and the transfer belt to transfer an image thereto, and a plurality of image forming units such as image forming units that form an image on the transfer belt.

[0006] In such an image forming apparatus, vibrations generated in the revolving member and the rotating member may propagate to a transfer unit having a transfer belt, with the lower end of the image forming apparatus main body serving as a fixed end, causing the transfer unit to vibrate.

[0007] The present invention aims to suppress vibration of the transfer unit compared to a configuration in which the mass of an image forming unit supported at a lower position among multiple image forming units is smaller than the mass of an image forming unit supported at a higher position than the image forming unit. [Means for solving the problem]

[0008] A first aspect includes a transfer cylinder supported by an image forming apparatus main body and rotating, a rotating member arranged coaxially with the transfer cylinder and rotating integrally with the transfer cylinder, a rotating member having a holding portion for holding a leading end of a recording medium, wrapped around the rotating member and transporting the recording medium by rotating with the rotation of the rotating member, a transfer unit supported by the image forming apparatus main body and having a transfer belt that transfers an image by sandwiching the recording medium transported by the rotating member between the transfer cylinder at a clamping position, a first image forming unit supported by the image forming apparatus main body and forming the image on the transfer belt, and a second image forming unit supported at a position lower than the first image forming unit in the image forming apparatus main body and forming the image on the transfer belt, wherein the mass of the second image forming unit is greater than the mass of the first image forming unit.

[0009] In a second aspect, the second image forming unit is disposed downstream of the first image forming unit in the rotation direction of the transfer belt and upstream of the nip position.

[0010] In a third aspect, the transfer belt has a first surface facing upward and a second surface located below the first surface and facing downward, the first image forming units are provided in plurality, the first image forming units form images on the first surface, the second image forming units are provided in plurality, the second image forming units form images on the second surface, and the mass of each of the second image forming units is greater than the mass of each of the first image forming units.

[0011] In a fourth aspect, the second surface is disposed downstream of the first surface in the rotation direction of the transfer belt and upstream of the nip position.

[0012] In a fifth aspect, the transfer cylinder has a recess formed on its outer peripheral surface, and the transfer unit has an opposing roll arranged opposite the transfer cylinder and pressed against the outer peripheral surface of the transfer cylinder via the transfer belt.

[0013] In a sixth aspect, the recess is a recess in which the holding portion is housed.

[0014] In a seventh aspect, a mass of a transport unit including the transfer cylinder, the rotating member, the holding portion, and the circulating member is equal to or greater than twice the mass of the transfer unit.

[0015] An eighth aspect includes an image forming unit that forms an image to be transferred to the transfer belt, and the mass of the image forming unit is 100 kg or more. Effect of the Invention

[0016] According to the configuration of the first aspect, vibration of the transfer unit is suppressed compared to a configuration in which the mass of a first image forming unit supported at a lower position among multiple image forming units is smaller than the mass of a second image forming unit supported at a higher position than the first image forming unit.

[0017] According to the second aspect of the configuration, image distortion occurring in the image transferred to the recording medium is less noticeable compared to a configuration in which the second image forming unit is located upstream of the first image forming unit in the rotational direction of the transfer belt and downstream of the pinch position.

[0018] According to the configuration of the third aspect, vibration of the transfer unit is suppressed compared to a configuration in which the mass of only one of the multiple second image forming units is greater than the mass of only one of the multiple first image forming units.

[0019] According to the fourth aspect of the configuration, image distortion occurring in the image transferred to the recording medium is less noticeable compared to a configuration in which the second surface is located upstream of the first surface in the rotational direction of the transfer belt and downstream of the pinch position.

[0020] According to the configuration of the fifth aspect, in a configuration in which there is a step due to a recess, vibration of the transfer unit is suppressed.

[0021] According to the configuration of the sixth aspect, in a configuration in which there is a step due to the recess in which the holding portion is housed, the transfer unit is prevented from being vibrated.

[0022] According to the seventh aspect, in a configuration in which the mass of the transport unit is at least twice the mass of the transfer unit, vibration of the transfer unit is suppressed.

[0023] According to the eighth aspect, in a configuration in which the mass of the image forming section is 100 kg or more, the transfer unit is prevented from being vibrated. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view showing the configuration of a chain, a sprocket, and a transfer cylinder in the image forming apparatus according to the first embodiment. [Diagram 3] 2 is a perspective view showing a state in which a recording medium is held by a gripper of the image forming apparatus according to the first embodiment. FIG. [Figure 4] FIG. 11 is a schematic diagram showing a configuration of an image forming apparatus according to a second embodiment. [Diagram 5] 13 is a table showing the evaluation results of the effects. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. First Embodiment (Image forming apparatus 10) First, a description will be given of the configuration of an image forming apparatus 10 according to the first embodiment. Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 10 according to the present embodiment.

[0026] In addition, the arrow UP shown in the figure indicates the top of the device (vertically upward), and the arrow DO indicates the bottom of the device (vertically downward). Additionally, the arrow LH shown in the figure indicates the left of the device, and the arrow RH indicates the right of the device. Additionally, the arrow FR shown in the figure indicates the front of the device, and the arrow RR indicates the rear of the device. These directions are defined for the convenience of explanation, and the device configuration is not limited to these directions. In addition, in each direction of the device, the word "device" may be omitted. That is, for example, "above the device" may be simply indicated as "above".

[0027] In the following description, the "up-down direction" may mean "both above and below" or "either above or below". The "left-right direction" may mean "both right and left" or "either right or left". The "left-right direction" may also be referred to as the lateral direction or horizontal direction. The "front-rear direction" may also be referred to as "both forward and backward" or "either forward or backward". The front-rear direction corresponds to the axial direction of sprocket 25 described below, and may also be referred to as the lateral direction or horizontal direction. The up-down direction, left-right direction, and front-rear direction are directions that intersect with each other (specifically, directions that are perpendicular to each other).

[0028] In addition, the symbol "x" inside a "circle" in the figure means an arrow pointing from the front to the back of the page. In addition, the symbol "·" inside a "circle" in the figure means an arrow pointing from the back to the front of the page.

[0029] 1 is an inkjet type image forming apparatus that forms an ink image (one example of an image) on a recording medium P. Specifically, the image forming apparatus 10 includes an image forming apparatus main body 11, a medium storage section 12, a transport unit 16, and an image forming mechanism 14. Below, each section of the image forming apparatus 10 (the image forming apparatus main body 11, the medium storage section 12, the transport unit 16, and the image forming mechanism 14) will be described.

[0030] (Image forming device body 11) As shown in Fig. 1, the image forming device main body 11 is a portion in which each component of the image forming device 10 is provided. Specifically, as shown in Fig. 1, the image forming device main body 11 has a box-shaped housing 11A and legs 11B provided at the lower end of the housing 11A.

[0031] 1, for example, a medium container 12, an image forming mechanism 14, and a transport unit 16 are provided inside a housing 11A. A plurality of legs 11B are provided on the bottom surface of the housing 11A. A bottom surface 11C of each of the plurality of legs 11B is grounded on a floor surface 100 on which the image forming apparatus 10 is placed. The housing 11A is supported by the plurality of legs 11B. Note that the image forming apparatus main body 11 may be configured without the legs 11B.

[0032] (Medium storage section 12) The medium storage unit 12 is a portion of the image forming apparatus 10 that stores the recording medium P. The recording medium P stored in the medium storage unit 12 is supplied to a transport unit 16. Specifically, the recording medium P stored in the medium storage unit 12 is sent toward the transport unit 16 by a transport member 12A such as a transport roll.

[0033] For example, paper is used as the recording medium P. Note that the recording medium P is not limited to paper and may be, for example, a film or the like, as long as it is a medium on which an image can be formed.

[0034] (Transport unit 16) 1 is a unit that transports a recording medium P. The unit refers to a constituent unit in the image forming apparatus 10. Therefore, the unit is a constituent part that is handled as a single coherent unit in the image forming apparatus 10. In this embodiment, the unit is a unit that is detachably attached to the image forming apparatus main body 11. In other words, the unit is a unit that is moved as a unit relative to the image forming apparatus main body 11.

[0035] Specifically, as shown in Figures 1 and 2, the transport unit 16 has a transfer cylinder 50, a pair of sprockets 25, a pair of chains 22, and a gripper 24. Also, as shown in Figure 1, the transport unit 16 has a pair of sprockets 37 and a pair of sprockets 45. The pair of sprockets 25 is an example of a "rotating member." The pair of chains 22 is an example of a "rotating member." The gripper 24 is an example of a "holding portion."

[0036] Note that Fig. 1 shows one of the pair of chains 22, and one of the pair of sprockets 25, 37, 45. Fig. 1 also shows the sprockets 25, 37, 45, the chain 22, the gripper 24, etc. in a simplified manner. Fig. 2 also shows the gripper 24 in a simplified manner.

[0037] (Transfer cylinder 50) 2, the transfer cylinder 50 is formed in a substantially cylindrical shape with its axial direction extending in the front-rear direction. In other words, the transfer cylinder 50 is formed in a substantially circular shape when viewed from the rear.

[0038] The rear view refers to a view of the object (here, the transfer cylinder 50) from the front toward the rear of the object. In other words, the rear view refers to a view of the object toward the rear in one direction along the rotation axis direction of the pair of sprockets 25.

[0039] 1 and 2, a recess 54 is formed on the outer peripheral surface of the transfer cylinder 50. In this embodiment, one recess 54 is provided on a part of the outer peripheral surface of the transfer cylinder 50 in the circumferential direction. This recess 54 is elongated along the axial direction of the transfer cylinder 50 and has a depth along the radial direction of the transfer cylinder 50. Specifically, the recess 54 is formed from one end to the other end in the axial direction of the transfer cylinder 50. In other words, the recess 54 opens at one end and the other end in the axial direction of the transfer cylinder 50 and penetrates the transfer cylinder 50 in the axial direction.

[0040] 2, the recess 54 is a recess in which the gripper 24 is housed. Therefore, the depth of the recess 54 along the radial direction of the transfer cylinder 50 and the width along the circumferential direction of the transfer cylinder 50 are greater than the size of the gripper 24. In this manner, the recess 54 in this embodiment is different from a recess that is microscopically formed on the outer peripheral surface of the transfer cylinder 50. Note that, in this embodiment, one recess 54 is provided on a part of the outer peripheral surface of the transfer cylinder 50 in the circumferential direction, but a configuration in which multiple recesses are provided may also be used.

[0041] (A pair of sprockets 25, 37, 45, and a pair of chains 22) 2, the pair of sprockets 25 are provided on both axial ends of the transfer cylinder 50. The pair of sprockets 25 are provided coaxially with the transfer cylinder 50 and are configured to rotate integrally with the transfer cylinder 50. The transfer cylinder 50 and the pair of sprockets 25 are rotationally driven by a drive unit (not shown).

[0042] 1, the pair of sprockets 45 are disposed to the left (i.e., downstream in the conveying direction) of the pair of sprockets 25. The pair of sprockets 45 are disposed with a gap between them in the front-rear direction.

[0043] The pair of sprockets 37 are disposed below the pair of sprockets 25 and the pair of sprockets 45, and on the left side of the pair of sprockets 25 (i.e., on the side of the pair of sprockets 45). The pair of sprockets 37 are disposed with a gap between them in the front-rear direction.

[0044] The pair of chains 22 is formed in a loop as shown in Fig. 1. The pair of chains 22 is arranged at an interval in the front-rear direction as shown in Fig. 2. Each of the pair of chains 22 is wound around each of the pair of sprockets 25, 37, 45. That is, each of the pair of chains 22 meshes with each of the pair of sprockets 25, 37, 45.

[0045] Then, the transfer cylinder 50 and the pair of sprockets 25 are rotated integrally in a rotation direction B (the direction of the arrow B in FIGS. 1 and 2), whereby the pair of sprockets 37, 45 rotate while the pair of chains 22 revolves in a circumferential direction C (the direction of the arrow C in FIGS. 1 and 2). That is, the pair of chains 22 revolves in accordance with the rotation of the pair of sprockets 25, 37, 45.

[0046] (Gripper 24) As shown in Fig. 3, the gripper 24 functions as a holding section that holds the leading end of the recording medium P. As shown in Fig. 2, the gripper 24 is attached to a mounting member 23 that is provided along the front-rear direction between the pair of chains 22. That is, the gripper 24 is provided to the pair of chains 22 via the mounting member 23.

[0047] The mounting members 23 are arranged at predetermined intervals along the circulating direction C of the chain 22. One end and the other end of the mounting members 23 in the longitudinal direction are attached to each of the pair of chains 22.

[0048] As shown in Fig. 2, a plurality of grippers 24 are attached to the mounting member 23 at predetermined intervals along the front-rear direction. As shown in Fig. 3, the gripper 24 has a claw 24A and a claw base 24B. The gripper 24 is configured to hold the recording medium P by pinching the tip of the recording medium P between the claw 24A and the claw base 24B. For example, the gripper 24 has the claw 24A pressed against the claw base 24B by a spring or the like, and the claw 24A is opened and closed relative to the claw base 24B by the action of a cam or the like.

[0049] In the present embodiment, the gripper 24 as an example of a holding portion holds the leading end of the recording medium P from the downstream side in the transport direction of the recording medium P, but is not limited to this. An example of the holding portion may be, for example, a holding portion that holds the leading end of the recording medium P from both lateral sides of the recording medium P, and may be any holding portion that holds the leading end of the recording medium P.

[0050] In the transport unit 16, the leading end of the recording medium P supplied from the medium storage section 12 in which the recording medium P is stored is held by the gripper 24 as shown in Fig. 3. With the gripper 24 holding the leading end of the recording medium P, the chain 22 rotates in the circumferential direction C to transport the recording medium P and pass through a transfer position TA described below. At this time, the gripper 24 passes through the transfer position TA (i.e., between the transfer cylinder 50 and the opposing roll 65) described below while being accommodated in the recess 54 of the transfer cylinder 50.

[0051] (Image forming mechanism 14) 1 has a function of forming an image on a recording medium P. Specifically, the image forming mechanism 14 forms an image using ink on the recording medium P transported by a transport unit 16. More specifically, the image forming mechanism 14 has ejection units 15A, 15B, 15C, 15D, 15E, and 15F (hereinafter referred to as 15A to 15F) and a transfer unit 60 having a transfer belt 62, as shown in FIG.

[0052] (Discharge unit 15A~15F) Each of the ejection units 15A to 15F has a function of forming an image to be transferred from the transfer belt 62 to the recording medium P. Specifically, each of the ejection units 15A to 15F is a unit that ejects ink droplets of a predetermined color onto the transfer belt 62 to form an image of the respective color on the outer circumferential surface of the transfer belt 62. The predetermined colors include yellow (Y), magenta (M), cyan (C), and black (K).

[0053] (Transfer unit 60) As described above, the transfer unit 60 is a unit having the transfer belt 62 that transfers an image onto the recording medium P. Specifically, the transfer unit 60 has the transfer belt 62, an opposing roll 65, a plurality of support rolls 64, and a cleaning unit 70.

[0054] (Transfer belt 62, opposing roll 65, and multiple support rolls 64) The transfer belt 62 is formed in a ring shape (specifically, endless shape), and is wound around an opposing roll 65 and a plurality of supporting rolls 64, and is supported by the opposing roll 65 and the plurality of supporting rolls 64.

[0055] The opposing roll 65 is disposed opposite the transfer cylinder 50 with the transfer belt 62 disposed between the opposing roll 65 and the transfer cylinder 50. Specifically, the opposing roll 65 is disposed on the upper right side with respect to the transfer cylinder 50. The opposing roll 65 is pressed against the outer circumferential surface of the transfer cylinder 50 via the transfer belt 62 by, for example, the elastic force of an elastic member (not shown).

[0056] In this embodiment, the opposing position where the opposing roll 65 faces the transfer cylinder 50 is the transfer position TA where an image is transferred to the recording medium P. The transfer position TA is an example of a "sandwich position." In addition, since the image is transferred to the recording medium P and formed on the recording medium P at the transfer position TA, it can also be called an image forming position.

[0057] Specifically, four of the multiple support rolls 64 are provided on the inner circumferential side of the transfer belt 62, as indicated by the reference characters (A), (B), (C), and (D) in the figure. The support rolls 64(A) and 64(B) are arranged side by side in the left-right direction below and to the right of the transfer position TA. The support roll 64(C) is arranged above and to the right of the transfer position TA. The support roll 64(D) is arranged above and to the left of the transfer position TA. The support rolls 64(C) and 64(D) are arranged side by side in the left-right direction.

[0058] The transfer belt 62 is wound around an opposing roll 65 and four support rolls 64, so that when viewed from behind, it has an approximately pentagonal shape formed by five surfaces, including a first surface 91, a second surface 92, and a third surface 93.

[0059] The first surface 91 of the transfer belt 62 faces upward between the support roll 64(C) and the support roll 64(D). On the other hand, the second surface 92 and the third surface 93 of the transfer belt 62 face downward. Specifically, the second surface 92 of the transfer belt 62 faces diagonally downward to the right between the support roll 64(B) and the support roll 64(C). The third surface 93 of the transfer belt 62 faces diagonally downward to the left between the opposing roll 65 and the support roll 64(D). The second surface 92 and the third surface 93 are disposed below (i.e., at a lower position) than the first surface 91. In addition, the second surface 92 is disposed downstream of the first surface 91 and upstream of the transfer position TA in the rotation direction A of the transfer belt 62.

[0060] Of the four support rolls 64, the support roll 64(D) is a drive roll that transmits a driving force to the transfer belt 62. The support roll 64(D) is rotated by a drive motor (not shown). The support roll 64(D) is a solid support roll. On the other hand, the support rolls 64(A), 64(B), and 64(C) are hollow support rolls and are driven rolls. For this reason, the mass of the support roll 64(D) is greater than the mass of each of the support rolls 64(A), 64(B), and 64(C). The hollow support roll refers to a support roll having a cavity inside, and the solid support roll refers to a support roll having no cavity inside.

[0061] Then, the transfer belt 62 rotates in a rotation direction A (the direction of the arrow A in FIG. 1) as the support roll 64 (D) is rotated. This rotating transfer belt 62 sandwiches the recording medium P transported by the transport unit 16 between itself and the transfer cylinder 50 at the transfer position TA, and transfers the image formed on its outer circumferential surface onto the recording medium P. As a result, the image is formed on the recording medium P.

[0062] (Cleaning Department 70) The cleaning unit 70 has a function of cleaning the transfer belt 62. Specifically, the cleaning unit 70 has a function of removing foreign matter adhering to the transfer belt 62. Examples of foreign matter include paper dust generated from paper as an example of the recording medium P, and ink.

[0063] 1, the cleaning unit 70 is disposed to face the third surface 93 of the transfer belt 62. The cleaning unit 70 has a blade 72 and a housing 74 in which the blade 72 is disposed.

[0064] The blade 72 functions as an example of a contact portion that comes into contact with the transfer belt 62 and removes foreign matter from the transfer belt 62. Specifically, the blade 72 comes into contact with a portion of the transfer belt 62 that is wound around the support roll 64(D). That is, the blade 72 is disposed opposite the support roll 64(D) with the transfer belt 62 disposed between the blade 72 and the support roll 64(D). In this embodiment, the blade 72 comes into contact with the portion of the transfer belt 62 that is wound around the support roll 64(D) and scrapes off foreign matter adhering to the transfer belt 62, thereby removing the foreign matter from the transfer belt 62.

[0065] The housing 74 has an opening 74A on the third surface 93 side of the transfer belt 62 (that is, on the support roll 64(D) side), and receives the foreign matter removed by the blade 72 through the opening 74A.

[0066] Note that an example of a contact portion that contacts the transfer belt 62 is not limited to the blade 72. An example of a contact portion may be a brush or the like, and may be anything that can remove foreign matter from the transfer belt 62. Furthermore, the blade 72 as an example of a contact portion may be configured to contact a portion of the transfer belt 62 that is not wound around the support roll 64. In this case, a member such as a roll is disposed facing the blade 72 with the transfer belt 62 disposed between the blade 72 and the transfer belt 62.

[0067] (Support structure of each part of image forming apparatus 10) The transport unit 16 has a support 26 that supports each part of the transport unit 16 (specifically, the transfer cylinder 50 and the pair of sprockets 25, 37, 45, etc.). The support 26 has support plates 27 that are arranged on both the front and rear sides of the transfer cylinder 50. The support 26 supports each part of the transport unit 16 by means of the support plates 27. As a result, each part of the transport unit 16 is integrated. And, the transport unit 16 is supported by the image forming apparatus main body 11 by, for example, attaching the support 26 to the image forming apparatus main body 11.

[0068] The transfer unit 60 has a support 66 that supports each part of the transfer unit 60 (specifically, the transfer belt 62, the opposing roll 65, the multiple support rolls 64, the cleaning unit 70, etc.). The support 66 has support plates 67 that are disposed on both the front side and the rear side of the transfer belt 62. The support 66 supports each part of the transfer unit 60 by means of the support plates 67. As a result, each part of the transfer unit 60 is integrated.

[0069] In this embodiment, the transfer unit 60 and the discharge units 15A to 15F are supported by, for example, support members 81, 82, 83, 84, 85, and 86 (hereinafter referred to as 81 to 86) on the image forming apparatus main body 11. Specifically, the support members 81 to 86 are formed in a plate shape extending in one direction.

[0070] Each of the support members 81, 82, and 83 is formed in a plate shape extending in the vertical direction. One end (specifically, the lower end) of each of the support members 81, 82, and 83 is attached to the support plate 67 of the transfer unit 60, and the other end (specifically, the upper end) is attached to the image forming apparatus main body 11. Discharge units 15A, 15B, and 15C are attached to the intermediate portions between the one end and the other end of each of the support members 81, 82, and 83, respectively.

[0071] Each of the support members 84, 85, and 86 is formed in a plate shape extending diagonally upward to the left. One end (specifically, the upper end) of each of the support members 84, 85, and 86 is attached to the support plate 67 of the transfer unit 60, and the other end (specifically, the lower end) is attached to the image forming apparatus main body 11. Discharge units 15D, 15E, and 15F are attached to the intermediate portion between the one end and the other end of each of the support members 84, 85, and 86. As described above, the transfer unit 60 and each of the discharge units 15A to 15F are supported by the image forming apparatus main body 11.

[0072] (Positional relationship of discharge units 15A to 15F) As described above, the ejection units 15A, 15B, and 15C and the ejection units 15D, 15E, and 15F supported by the image forming apparatus main body 11 have the following positional relationship.

[0073] In this embodiment, the ejection units 15A, 15B, and 15C face a first surface 91 facing the upward side of the transfer belt 62, and eject ink droplets onto the first surface 91 to form an image. The ejection units 15D, 15E, and 15F face a second surface 92 facing the downward side (specifically, the diagonally downward right side) of the transfer belt 62, and eject ink droplets onto the second surface 92 to form an image.

[0074] As described above, the second surface 92 is disposed below (i.e., at a lower position) than the first surface 91. The discharge units 15D, 15E, and 15F facing the second surface 92 are supported at a lower position than the discharge units 15A, 15B, and 15C facing the first surface 91.

[0075] As described above, the second surface 92 is disposed downstream of the first surface 91 and upstream of the transfer position TA in the rotation direction A of the transfer belt 62. The discharge units 15D, 15E, and 15F facing the second surface 92 are disposed downstream of the discharge units 15A, 15B, and 15C facing the first surface 91 in the rotation direction A of the transfer belt 62 and upstream of the transfer position TA.

[0076] The ejection units 15A, 15B, and 15C are an example of a "first image forming portion," and the ejection units 15D, 15E, and 15F are an example of a "second image forming portion."

[0077] (Weight of each part of the image forming apparatus 10) The mass of the transport unit 16, which includes the transfer cylinder 50, the pair of sprockets 25, 37, 45, the pair of chains 22, and the gripper 24, is more than twice the mass of the transfer unit 60. Specifically, the mass of the transfer unit 60 is 300 kg, and the mass of the transport unit 16 is, for example, 600 kg.

[0078] The mass of each of the discharge units 15A to 15F is set to 100 kg or more. Specifically, the mass of each of the discharge units 15A to 15F is set to, for example, in the range of more than 115 kg and not more than 135 kg. Note that the mass of each of the discharge units 15A to 15F includes the mass of the ink filled in each of the discharge units 15A to 15F.

[0079] Furthermore, the mass of each of the discharge units 15D, 15E, and 15F is greater than the mass of each of the discharge units 15A, 15B, and 15C. For example, the mass of each of the discharge units 15A, 15B, and 15C is in the range of more than 115 kg and not more than 125 kg. For example, the mass of each of the discharge units 15D, 15E, and 15F is in the range of more than 125 kg and not more than 135 kg.

[0080] (Operation of the first embodiment) Next, the operation of the first embodiment will be described.

[0081] In the image forming apparatus 10, the leading end of the recording medium P supplied from the medium storage unit 12 in which the recording medium P is stored is held by the gripper 24 as shown in Fig. 3. With the gripper 24 holding the leading end of the recording medium P, the chain 22 rotates in the rotation direction C to transport the recording medium P and pass the transfer position TA. At this time, the gripper 24 passes between the transfer cylinder 50 and the opposing roll 65 while being stored in the recess 54 of the transfer cylinder 50.

[0082] Then, the transfer belt 62 sandwiches the recording medium P between itself and the transfer cylinder 50 at the transfer position TA, and transfers the image formed on its outer circumferential surface onto the recording medium P. In this way, the image is formed on the recording medium P.

[0083] In the image forming apparatus 10, vibrations generated in the chain 22, the sprocket 25, etc. during the transport of the recording medium P are transmitted to the lower end (specifically, the leg portion 11B) of the image forming apparatus main body 11. The vibrations may further be transmitted to the transfer unit 60 having the transfer belt 62 with the lower end of the image forming apparatus main body 11 as a fixed end, causing the transfer unit 60 to vibrate.

[0084] In particular, in this embodiment, since the opposing roll 65 is pressed against the outer peripheral surface of the transfer cylinder 50 via the transfer belt 62, when the recess 54 of the transfer cylinder 50 passes through the transfer position TA, vibrations are likely to occur at the transfer position TA due to the step of the recess 54 (hereinafter referred to as factor A).

[0085] Furthermore, in this embodiment, the mass of the transport unit 16 is more than twice the mass of the transfer unit 60, so that the transfer unit 60 is likely to vibrate due to vibrations generated in the transport unit 16 (hereinafter, referred to as factor B).

[0086] Furthermore, in this embodiment, the mass of each of the ejection units 15A to 15F is set to 100 kg or more, so that the image forming apparatus 10 becomes large and the transfer unit 60 is easily vibrated (hereinafter, referred to as factor C). When the transfer unit 60 is vibrated, image disturbance such as banding occurs in the image transferred from the transfer belt 62 to the recording medium P. Note that banding is an image disturbance in which striped shading appears in the image.

[0087] In this embodiment, the mass of each of the discharge units 15D, 15E, and 15F supported at a lower position than the discharge units 15A, 15B, and 15C is set to be greater than the mass of each of the discharge units 15A, 15B, and 15C.

[0088] For this reason, even if vibrations generated by the chain 22, sprocket 25, etc. are transmitted to the transfer unit 60 having the transfer belt 62 with the lower end of the image forming device main body 11 as a fixed end, the transfer unit 60 is less likely to vibrate than in a configuration (hereinafter referred to as configuration A) in which the masses of each of the ejection units 15D, 15E, and 15F are smaller than the masses of each of the ejection units 15A, 15B, and 15C.

[0089] As a result, according to this embodiment, in a configuration in which the transfer unit 60 is likely to vibrate due to the aforementioned factors A, B, and C, vibration of the transfer belt 62 is suppressed compared to configuration A, and image distortion of the image formed on the recording medium P is suppressed.

[0090] In addition, in this embodiment, as described above, the mass of each of the multiple discharge units (specifically, discharge units 15D, 15E, and 15F) that face the second surface 92 of the transfer belt 62 is greater than the mass of each of the multiple discharge units (specifically, discharge units 15A, 15B, and 15C) that face the first surface 91 of the transfer belt 62.

[0091] As a result, vibration of the transfer unit 60 is suppressed compared to a configuration in which the mass of only one of the multiple discharge units (specifically, discharge units 15D, 15E, 15F) facing the second surface 92 is greater than the mass of only one of the multiple discharge units (specifically, discharge units 15A, 15B, 15C) facing the first surface 91.

[0092] In this embodiment, the discharge units 15D, 15E, and 15F are disposed downstream of the discharge units 15A, 15B, and 15C in the rotation direction A of the transfer belt 62, and upstream of the transfer position TA.

[0093] In other words, the second surface 92 on which an image is formed by the ejection units 15D, 15E, and 15F is located downstream of the first surface 91 on which an image is formed by the ejection units 15A, 15B, and 15C in the rotational direction A of the transfer belt 62, and upstream of the transfer position TA.

[0094] Here, the mass of each of the discharge units 15D, 15E, and 15F, which are supported at a lower position than the discharge units 15A, 15B, and 15C, is made larger than the mass of each of the discharge units 15A, 15B, and 15C, so that the discharge units 15D, 15E, and 15F are less likely to vibrate than the discharge units 15A, 15B, and 15C.

[0095] Therefore, in this embodiment, vibration is suppressed in the ejection units 15D, 15E, and 15F, which form images on the transfer belt 62 later in the sequence, so that image disturbances such as banding are less noticeable in the images formed on the transfer belt 62.

[0096] As a result, image disturbances such as banding that occur in the image transferred to the recording medium P are less noticeable compared to a configuration in which the ejection units 15D, 15E, and 15F are arranged upstream of the ejection units 15A, 15B, and 15C in the rotational direction A of the transfer belt 62 and downstream of the transfer position TA.

[0097] Therefore, it can be said that image disturbances such as banding that occur in the image transferred to the recording medium P are less noticeable compared to a configuration in which the second surface 92 is positioned upstream of the first surface 91 in the rotational direction A of the transfer belt 62 and downstream of the transfer position TA.

[0098] <Second embodiment> (Image forming apparatus 200) In the first embodiment, the image forming apparatus 10 is an inkjet type image forming apparatus that forms an image on a recording medium P using ink, but the image forming apparatus is not limited to this. An example of the image forming apparatus may be, for example, an electrophotographic image forming apparatus, and any apparatus that forms an image will do. In the second embodiment, an electrophotographic image forming apparatus 200 will be described. FIG. 4 is a schematic diagram showing the configuration of the image forming apparatus 200 according to this embodiment. Note that parts having the same functions as those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0099] (Image forming mechanism 214) The image forming apparatus 200 has an image forming mechanism 214 instead of the image forming mechanism 14. The image forming mechanism 214 has a function of forming a toner image (one example of an image) on a recording medium P by an electrophotographic method. More specifically, the image forming mechanism 214 has toner image forming units 222A, 222B, 222C, 222D, 222E, and 222F (hereinafter referred to as 222A to 222F) that form toner images, and a transfer unit 60 having a transfer belt 62, as shown in FIG.

[0100] (Toner image forming units 222A to 222F) 4 has a function of forming an image to be transferred from the transfer belt 62 to the recording medium P. Specifically, each of the toner image forming units 222A to 222F is a unit that forms an image of each color using toner of a predetermined color. The predetermined colors include yellow (Y), magenta (M), cyan (C), and black (K).

[0101] In this embodiment, the toner image forming units 222A to 222F are configured similarly except for the toner that they use, so in FIG. 4, the components of the toner image forming unit 222C are denoted by reference numerals as a representative of the toner image forming units 222A to 222F.

[0102] Specifically, each of the toner image forming units 222A to 222F has a photoconductor 224 that rotates in one direction (for example, the counterclockwise direction in FIG. 4). Each of the toner image forming units 222A to 222F also has a charger 223, an exposure device 240, and a developing device 238.

[0103] In each of the toner image forming units 222A to 222F, the charger 223 charges the photoconductor 224. Furthermore, the exposure device 240 exposes the photoconductor 224 charged by the charger 223 to light, thereby forming an electrostatic latent image on the photoconductor 224. Furthermore, the development device 238 develops the electrostatic latent image formed on the photoconductor 224 by the exposure device 240, thereby forming a toner image.

[0104] Each of the toner image forming units 222A to 222F further has a support (not shown) that supports each part of the toner image forming units 222A to 222F (specifically, the photoconductor 224, the charger 223, the exposure device 240, the developing device 238, etc.). The support has a support frame (not shown) disposed on each of the front and rear sides of the photoconductor 224. Also, the toner image forming units 222A to 222F may be any unit that has at least the photoconductor 224.

[0105] (Transfer unit 60) 4 has a function of transferring the toner images formed by the toner image forming units 222A to 222F onto a recording medium P. Specifically, the transfer unit 60 performs primary transfer of the toner images of the photoconductors 224 of each color onto a transfer belt 62 serving as an intermediate transfer body, and performs secondary transfer of the superposed toner images onto the recording medium P. As shown in FIG. 4, the transfer unit 60 has a primary transfer roll 226 in addition to the transfer belt 62, an opposing roll 65, a plurality of support rolls 64, and a cleaning unit 70.

[0106] The primary transfer roll 226 is a roll that transfers the toner image on each of the photoconductors 224 of the toner image forming units 222A to 222F onto the transfer belt 62 at a primary transfer position T1 between the photoconductor 224 and the primary transfer roll 226. Specifically, each of the primary transfer rolls 226 and each of the photoconductors 224 sandwich the transfer belt 62 at the primary transfer position T1.

[0107] In this embodiment, a primary transfer electric field is applied between the primary transfer roll 226 and the photoconductor 224, so that the toner image formed on the photoconductor 224 is transferred to the transfer belt 62 at a primary transfer position T1. Furthermore, a secondary transfer electric field is applied between the opposing roll 65 and the transfer cylinder 50, so that the toner image transferred to the transfer belt 62 is transferred to the recording medium P sandwiched between the transfer belt 62 and the transfer cylinder 50 at a transfer position TA. The transfer unit 60 in this embodiment is configured similarly to the transfer unit 60 in the first embodiment, except that it has the primary transfer roll 226.

[0108] (Fixing device 280) The image forming apparatus 200 further includes a fixing device 280 that fixes the toner image transferred onto the recording medium P to the recording medium P. As shown in FIG. 4, the fixing device 280 includes a pressure roll 281 and a heating roll 282.

[0109] In this embodiment, the pair of sprockets 45 are provided on both axial ends of the pressure roll 281. The pair of sprockets 45 are arranged coaxially with the pressure roll 281 and are configured to rotate integrally with the pressure roll 281. In addition, a recess 284 is formed on the outer periphery of the pressure roll 281 in which the gripper 24 and the mounting member 23 are housed.

[0110] In the fixing device 280, a heating roll 282 is disposed above the pressure roll 281. The heating roll 282 has a heat source 282A such as a halogen lamp inside the roll.

[0111] Then, in the fixing device 280, the recording medium P is conveyed while being sandwiched between a heating roll 282 and a pressure roll 281, and the recording medium P is heated and pressurized, thereby fixing the toner image transferred to the recording medium P to the recording medium P.

[0112] In the image forming apparatus 200, the transport unit 16 rotates the chain 22 in the rotation direction C with the gripper 24 holding the leading end of the recording medium P, thereby passing the recording medium P through the transfer position TA and the fixing position NP between the pressure roll 281 and the heating roll 282. Then, the toner images that have been primarily transferred and superimposed on the transfer belt 62 at the primary transfer positions T1 of each of the toner image forming units 222A to 222F are secondarily transferred onto the recording medium P at the transfer position TA. The toner images secondarily transferred onto the recording medium P are fixed onto the recording medium P at the fixing position NP.

[0113] (Support structure of each part of image forming apparatus 200) The transport unit 16 has a support 26 that supports each part of the transport unit 16 (specifically, the transfer cylinder 50 and the pair of sprockets 25, 37, 45, etc.). The support 26 has support plates 27 that are arranged on both the front and rear sides of the transfer cylinder 50. The support 26 supports each part of the transport unit 16 by means of the support plates 27. As a result, each part of the transport unit 16 is integrated. And, the transport unit 16 is supported by the image forming apparatus main body 11 by, for example, attaching the support 26 to the image forming apparatus main body 11.

[0114] The transfer unit 60 has a support 66 that supports each part of the transfer unit 60 (specifically, the transfer belt 62, the opposing roll 65, the multiple support rolls 64, the cleaning unit 70, etc.). The support 66 has support plates 67 that are disposed on both the front side and the rear side of the transfer belt 62. The support 66 supports each part of the transfer unit 60 by means of the support plates 67. As a result, each part of the transfer unit 60 is integrated.

[0115] In this embodiment, the transfer unit 60 and the toner image forming units 222A to 222F are supported by, for example, support members 81, 82, 83, 84, 85, and 86 (hereinafter referred to as 81 to 86) on the image forming apparatus main body 11. Specifically, the support members 81 to 86 are formed in a plate shape extending in one direction.

[0116] Each of the support members 81, 82, and 83 is formed in a plate shape extending in the vertical direction. One end (specifically, the lower end) of each of the support members 81, 82, and 83 is attached to the transfer unit 60, and the other end (specifically, the upper end) is attached to the image forming apparatus main body 11. As an example, the transfer unit 60 is attached to each of the support members 81, 82, and 83 at the shaft portion of each primary transfer roll 226.

[0117] Further, toner image forming units 222A, 222B, and 222C are attached to the intermediate portions between one end and the other end of each of the support members 81, 82, and 83. Each of the toner image forming units 222A, 222B, and 222C is attached to each of the support members 81, 82, and 83 at the shaft portion of each of the photoconductors 224, for example.

[0118] Each of the support members 84, 85, and 86 is formed in a plate shape extending diagonally upward to the left. One end (specifically, the upper end) of each of the support members 84, 85, and 86 is attached to the transfer unit 60, and the other end (specifically, the lower end) is attached to the image forming apparatus main body 11. As an example, the transfer unit 60 is attached to each of the support members 84, 85, and 86 at the shaft portion of each primary transfer roll 226.

[0119] Further, toner image forming units 222D, 222E, and 222F are attached to the intermediate portions between one end and the other end of each of the support members 84, 85, and 86. Each of the toner image forming units 222D, 222E, and 222F is attached to each of the support members 84, 85, and 86 at the shaft portion of each photoconductor 224, for example. As described above, the transfer unit 60 and each of the toner image forming units 222A to 222F are supported by the image forming apparatus main body 11.

[0120] (Positional Relationship of Toner Image Forming Units 222A to 222F) As described above, the toner image forming units 222A, 222B, and 222C and the toner image forming units 222D, 222E, and 222F supported by the image forming apparatus main body 11 have the following positional relationship.

[0121] In this embodiment, the toner image forming units 222A, 222B, and 222C face a first surface 91 facing the upward side of the transfer belt 62. Specifically, the photoconductors 224 of the toner image forming units 222A, 222B, and 222C are in contact with the first surface 91 of the transfer belt 62 and form a toner image on the first surface 91. The toner image forming units 222D, 222E, and 222F face a second surface 92 facing the downward side (specifically, the right diagonally downward side) of the transfer belt 62. Specifically, the photoconductors 224 of the toner image forming units 222D, 222E, and 222F are in contact with the second surface 92 of the transfer belt 62 and form a toner image on the second surface 92.

[0122] As described above, the second surface 92 is disposed below (i.e., at a lower position) than the first surface 91. The toner image forming units 222D, 222E, and 222F facing the second surface 92 are supported at a lower position than the toner image forming units 222A, 222B, and 222C facing the first surface 91.

[0123] As described above, the second surface 92 is disposed downstream of the first surface 91 and upstream of the transfer position TA in the rotation direction A of the transfer belt 62. The toner image forming units 222D, 222E, and 222F facing the second surface 92 are disposed downstream of the toner image forming units 222A, 222B, and 222C facing the first surface 91 in the rotation direction A of the transfer belt 62 and upstream of the transfer position TA.

[0124] The toner image forming units 222A, 222B, and 222C are an example of a "first image forming portion," and the toner image forming units 222D, 222E, and 222F are an example of a "second image forming portion."

[0125] (Weight of Each Part of Image Forming Apparatus 200) The mass of the transport unit 16, which includes the transfer cylinder 50, the pair of sprockets 25, 37, 45, the pair of chains 22, and the gripper 24, is more than twice the mass of the transfer unit 60. Specifically, the mass of the transfer unit 60 is 300 kg, and the mass of the transport unit 16 is, for example, 600 kg.

[0126] The mass of each of the toner image forming units 222A to 222F is set to 100 kg or more. Specifically, the mass of each of the toner image forming units 222A to 222F is set to, for example, in the range of more than 115 kg and not more than 135 kg.

[0127] Furthermore, the mass of each of the toner image forming units 222D, 222E, and 222F is greater than the mass of each of the toner image forming units 222A, 222B, and 222C. For example, the mass of each of the toner image forming units 222A, 222B, and 222C is in the range of more than 115 kg and not more than 125 kg. For example, the mass of each of the toner image forming units 222D, 222E, and 222F is in the range of more than 125 kg and not more than 135 kg.

[0128] (Operation of the second embodiment) Next, the operation of the second embodiment will be described.

[0129] In the image forming apparatus 200, similarly to the image forming apparatus 10, vibrations generated in the chain 22, the sprocket 25, etc. during the transport of the recording medium P propagate to the lower end (specifically, the leg portion 11B) of the image forming apparatus main body 11. The vibrations may further propagate to the transfer unit 60 having the transfer belt 62, with the lower end of the image forming apparatus main body 11 serving as a fixed end, causing the transfer unit 60 to vibrate. In the present embodiment as well, the transfer unit 60 is likely to be vibrated due to the factors A, B, and C described above.

[0130] In this embodiment, the mass of each of toner image forming units 222D, 222E, and 222F supported at a position lower than toner image forming units 222A, 222B, and 222C is greater than the mass of each of toner image forming units 222A, 222B, and 222C.

[0131] For this reason, even if vibrations generated by the chain 22, sprocket 25, etc. are transmitted to the transfer unit 60 having the transfer belt 62 with the lower end of the image forming device main body 11 as a fixed end, the transfer unit 60 is less likely to vibrate compared to a configuration (hereinafter referred to as configuration B) in which the mass of each of the toner image forming units 222D, 222E, and 222F is smaller than the mass of each of the toner image forming units 222A, 222B, and 222C.

[0132] As a result, according to this embodiment, in a configuration in which the transfer unit 60 is likely to vibrate due to the aforementioned factors A, B, and C, vibration of the transfer belt 62 is suppressed compared to configuration B, and image distortion of the image formed on the recording medium P is suppressed.

[0133] In addition, in this embodiment, as described above, the mass of each of the multiple toner image forming units (specifically, toner image forming units 222D, 222E, 222F) facing the second surface 92 of the transfer belt 62 is made greater than the mass of each of the multiple toner image forming units (specifically, toner image forming units 222A, 222B, 222C) facing the first surface 91 of the transfer belt 62.

[0134] As a result, vibration of the transfer unit 60 is suppressed compared to a configuration in which the mass of only one of the multiple toner image forming units (specifically, toner image forming units 222D, 222E, 222F) facing the second surface 92 is greater than the mass of only one of the multiple toner image forming units (specifically, toner image forming units 222A, 222B, 222C) facing the first surface 91.

[0135] In this embodiment, the toner image forming units 222D, 222E, and 222F are disposed downstream of the toner image forming units 222A, 222B, and 222C in the rotation direction A of the transfer belt 62, and upstream of the transfer position TA.

[0136] In other words, the second surface 92 on which an image is formed by the toner image forming units 222D, 222E, and 222F is located downstream of the first surface 91 on which an image is formed by the toner image forming units 222A, 222B, and 222C in the rotational direction A of the transfer belt 62, and upstream of the transfer position TA.

[0137] Here, since the mass of each of toner image forming units 222D, 222E, and 222F, which are supported at a lower position than toner image forming units 222A, 222B, and 222C, is greater than the mass of each of toner image forming units 222A, 222B, and 222C, toner image forming units 222D, 222E, and 222F are less likely to vibrate than toner image forming units 222A, 222B, and 222C.

[0138] Therefore, in this embodiment, vibration is suppressed in the toner image forming units 222D, 222E, and 222F, which form images on the transfer belt 62 later, so that image disturbances such as banding are less noticeable in the images formed on the transfer belt 62.

[0139] As a result, image disturbances such as banding that occur in the image transferred to the recording medium P are less noticeable compared to a configuration in which toner image forming units 222D, 222E, and 222F are arranged upstream of toner image forming units 222A, 222B, and 222C in the rotational direction A of transfer belt 62 and downstream of transfer position TA.

[0140] Therefore, it can be said that image disturbances such as banding that occur in the image transferred to the recording medium P are less noticeable compared to a configuration in which the second surface 92 is positioned upstream of the first surface 91 in the rotational direction A of the transfer belt 62 and downstream of the transfer position TA.

[0141] (evaluation) In the evaluation, in the configuration of the second embodiment, the mass of each of the toner image forming units 222A, 222B, and 222C and the mass of each of the toner image forming units 222D, 222E, and 222F were changed, an image was formed on a recording medium P, and the presence or absence of banding occurring in the image was evaluated.

[0142] In this evaluation, a monochromatic halftone image (image density 20%) was formed on the recording medium P using each of the toner image forming units 222A to 222F, and the occurrence of banding was visually confirmed.

[0143] (Evaluation Criteria) A: No banding is observed B: Banding can be seen

[0144] Example 1 The mass of each of the toner image forming units 222A, 222B, and 222C was set to 125 kg, and the mass of each of the toner image forming units 222D, 222E, and 222F was set to 128 kg.

[0145] Comparative Example 1 The mass of each of the toner image forming units 222A, 222B, and 222C was set to 128 kg, and the mass of each of the toner image forming units 222D, 222E, and 222F was set to 125 kg.

[0146] (Evaluation Results) As shown in Fig. 5, the occurrence of banding was confirmed in Comparative Example 1. In contrast, the occurrence of banding was not confirmed in Example 1. It is considered that the banding occurs due to vibration of the transfer unit 60. Therefore, from the results shown in Fig. 5, it is considered that vibration of the transfer unit 60 is suppressed in Example 1 compared to Comparative Example 1.

[0147] (Modification) In the first embodiment, the mass of each of the multiple discharge units (specifically, discharge units 15D, 15E, 15F) facing the second surface 92 of the transfer belt 62 is larger than the mass of each of the multiple discharge units (specifically, discharge units 15A, 15B, 15C) facing the first surface 91 of the transfer belt 62, but this is not limited to the above. For example, the mass of a portion (one or more) of the multiple discharge units (specifically, discharge units 15D, 15E, 15F) facing the second surface 92 may be larger than the mass of a portion (one or more) of the multiple discharge units (specifically, discharge units 15A, 15B, 15C) facing the first surface 91.

[0148] In the first embodiment, the discharge units 15D, 15E, and 15F are disposed downstream of the discharge units 15A, 15B, and 15C in the rotation direction A of the transfer belt 62 and upstream of the transfer position TA, but this is not limited thereto. For example, the discharge units 15D, 15E, and 15F may be configured to be disposed upstream of the discharge units 15A, 15B, and 15C in the rotation direction A of the transfer belt 62 and downstream of the transfer position TA.

[0149] In the first embodiment, the second surface 92 on which an image is formed by the discharge units 15D, 15E, and 15F is disposed downstream of the first surface 91 on which an image is formed by the discharge units 15A, 15B, and 15C in the rotation direction A of the transfer belt 62 and upstream of the transfer position TA, but is not limited thereto. For example, the second surface 92 may be configured to be disposed upstream of the first surface 91 in the rotation direction A of the transfer belt 62 and downstream of the transfer position TA.

[0150] In the first embodiment, six discharge units 15A to 15F are provided, but the number is not limited to this. At least two discharge units having different heights may be provided, and the mass of the discharge unit at the lower position among these discharge units may be made larger than the mass of the other discharge units.

[0151] In the first embodiment, the mass of each of the discharge units 15A to 15F is set to 100 kg or more, but this is not limited to this. For example, the mass of each of the discharge units 15A to 15F may be less than 100 kg.

[0152] In the second embodiment, the mass of each of the multiple toner image forming units (specifically, toner image forming units 222D, 222E, 222F) facing the second surface 92 of the transfer belt 62 is larger than the mass of each of the multiple toner image forming units (specifically, toner image forming units 222A, 222B, 222C) facing the first surface 91 of the transfer belt 62, but this is not limited to the above. For example, the mass of a part (one or more) of the multiple toner image forming units (specifically, toner image forming units 222A, 222B, 222C) facing the second surface 92 may be larger than the mass of a part (one or more) of the multiple toner image forming units (specifically, toner image forming units 222A, 222B, 222C) facing the first surface 91.

[0153] In the second embodiment, the toner image forming units 222D, 222E, and 222F are disposed downstream of the toner image forming units 222A, 222B, and 222C in the rotation direction A of the transfer belt 62 and upstream of the transfer position TA, but this is not limited thereto. For example, the toner image forming units 222D, 222E, and 222F may be configured to be disposed upstream of the toner image forming units 222A, 222B, and 222C in the rotation direction A of the transfer belt 62 and downstream of the transfer position TA.

[0154] In the first embodiment, the second surface 92 on which the image is formed by the toner image forming units 222D, 222E, and 222F is disposed downstream of the first surface 91 on which the image is formed by the toner image forming units 222A, 222B, and 222C in the rotation direction A of the transfer belt 62, and upstream of the transfer position TA, but is not limited thereto. For example, the second surface 92 may be configured to be disposed upstream of the first surface 91 in the rotation direction A of the transfer belt 62, and downstream of the transfer position TA.

[0155] In the second embodiment, six toner image forming units 222A to 222F are provided, but the present invention is not limited to this. At least two toner image forming units having different heights may be provided, and the mass of the toner image forming unit at the lower position among the toner image forming units may be made larger than the mass of the other toner image forming units.

[0156] In the second embodiment, the mass of each of the toner image forming units 222A to 222F is set to 100 kg or more, but is not limited to this. For example, the mass of each of the toner image forming units 222A to 222F may be less than 100 kg.

[0157] In the first and second embodiments, the recesses 54 are formed on the outer peripheral surface of the transfer cylinder 50, but this is not limited thereto. For example, a transfer cylinder 50 without the recesses 54 may be used. In this case, for example, a configuration is adopted in which the leading end of the recording medium P is held from both lateral sides of the recording medium P by holding portions disposed on both axial ends of the transfer cylinder 50. In other words, a holding portion that does not need to be accommodated in the recesses 54 is used. In addition, the recesses 54 formed on the outer peripheral surface of the transfer cylinder 50 may be a recess that is used for purposes other than accommodating the gripper 24 as an example of a holding portion.

[0158] In the first and second embodiments, the chain 22 is used as an example of a circumferential member, and the sprocket 25 is used as an example of a rotating member, but the present invention is not limited to this. For example, a timing belt having an uneven inner circumference may be used as an example of a circumferential member, and a timing pulley (i.e., a pulley having an uneven outer circumference) may be used as an example of a rotating member. Also, a belt may be used as an example of a circumferential member, and a pulley that rotates the belt by friction may be used as an example of a rotating member.

[0159] In the first and second embodiments, the mass of the transport unit 16 is set to be twice or more the mass of the transfer unit 60, but this is not limited thereto. For example, the mass of the transport unit 16 may be less than twice the mass of the transfer unit 60.

[0160] The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements are possible without departing from the spirit and scope of the present invention. For example, the above-described modified examples may be combined in combination as appropriate. [Explanation of symbols]

[0161] 10, 200 Image forming device 11 Image forming device main body 15A, 15B, 15C: Discharge units (examples of first image forming units) 15D, 15E, 15F Discharge unit (an example of a second image forming unit) 22 Chain (an example of a rotating component) 24 Gripper (an example of a holding part) 25 Sprocket (an example of a rotating part) 50 Transfer cylinder 54 Recess 60 Transcription Unit 62 Transfer belt 91 Front page 92 Second side 222A, 222B, 222C toner image forming units (examples of the first image forming unit) 222D, 222E, 222F toner image forming units (examples of the second image forming unit) P Recording medium TA transcription position (an example of clamping position)

Claims

1. a transfer cylinder supported by the image forming apparatus body and rotating; a rotating member provided coaxially with the transfer cylinder and rotating integrally with the transfer cylinder; a rotating member that is provided with a holding portion that holds a leading end of a recording medium, is wound around the rotating member, and rotates with the rotation of the rotating member to transport the recording medium; a transfer unit supported by the image forming apparatus body and including a transfer belt for transferring an image to the recording medium conveyed by the rotating member by sandwiching the recording medium between the transfer cylinder and the transfer belt at a sandwiching position; a first image forming unit supported by the image forming apparatus body and configured to form the image on the transfer belt; a second image forming unit supported at a position lower than the first image forming unit in the image forming apparatus body and configured to form the image on the transfer belt; Equipped with The image forming apparatus, wherein the mass of the second image forming unit is greater than the mass of the first image forming unit.

2. The second image forming unit is disposed downstream of the first image forming unit in a rotation direction of the transfer belt and upstream of the pinch position. The image forming apparatus according to claim 1 .

3. the transfer belt has a first surface facing upward and a second surface disposed below the first surface and facing downward; The first image forming unit is provided in plurality, and the plurality of first image forming units form images on the first surface; The second image forming unit is provided in plurality, and the plurality of second image forming units form an image on the second surface, The mass of each of the second image forming units is greater than the mass of each of the first image forming units.

3. The image forming apparatus according to claim 1 or 2.

4. The second surface is disposed downstream of the first surface in the rotation direction of the transfer belt and upstream of the pinch position. The image forming apparatus according to claim 3 .

5. The transfer cylinder has a recess formed on an outer circumferential surface thereof, The transfer unit has an opposing roll disposed opposite the transfer cylinder and pressed against the outer circumferential surface of the transfer cylinder via the transfer belt. The image forming apparatus according to any one of claims 1 to 4.

6. The recess is a recess in which the holding portion is accommodated. The image forming apparatus according to claim 5 .

7. The mass of a transport unit including the transfer cylinder, the rotating member, the holding portion, and the rotating member is equal to or greater than twice the mass of the transfer unit. The image forming apparatus according to any one of claims 1 to 6.

8. an image forming unit that forms an image to be transferred onto the transfer belt; The mass of the image forming unit is 100 kg or more. The image forming apparatus according to any one of claims 1 to 7.

Images