Image forming apparatus

Abstract

The present invention provides an image forming apparatus that can suppress the pulling of a sheet towards the pair of second rotating members between a pair of second rotating members and a pair of first rotating members, regardless of the length of the sheet in the conveying direction, and therefore can suppress misalignment of the sheet being conveyed by the pair of first rotating members. [Solution] The image forming apparatus 100 comprises a pair of first rotating members 91 and a pair of second rotating members 31. The pair of second rotating members 31 are movable in a pressure release direction T2 that releases the pressure contact of the second driven rotating member 312 with the second driving rotating member 311. The apparatus is configured to move the second driven rotating member 312 away from the second driving rotating member 311 in the pressure release direction T2 by utilizing the tensile force of the sheet P between the pair of first rotating members 91 and the pair of second rotating members 31 when they are being transported between the pair of first rotating members 91 and the pair of second rotating members 31.

Description

Technical Field

[0001] The present disclosure relates to image forming apparatuses such as copiers, multifunction peripherals, printers, and facsimile apparatuses.

Background Art

[0002] An image forming apparatus generally includes a transfer device, a fixing device, and a discharging device. The transfer device transfers a toner image formed on an image carrier onto a sheet such as a recording paper. The fixing device has a pair of fixing rotating members that fix the toner image on the sheet transferred by the transfer device. The discharging device has a pair of discharging rollers that discharge the sheet on which the toner image has been fixed by the fixing device to the outside.

[0003] In such an image forming apparatus, a pair of first rotating members in which a first driving-side rotating member and a first driven-side rotating member are in pressure contact to convey a sheet such as paper, and a pair of second rotating members in which a second driving-side rotating member and a second driven-side rotating member are in pressure contact to convey the sheet conveyed from the pair of first rotating members are provided, and the second conveyance speed of the sheet by the pair of second rotating members may be made greater than the first conveyance speed of the sheet by the pair of first rotating members.

[0004] For example, in an image forming apparatus, when a pair of first rotating members are a pair of fixing rotating members and a pair of second rotating members are a pair of discharging rollers, there are the following inconveniences.

[0005] FIG. 10 is a schematic cross-sectional view for explaining the inconvenience when the second conveyance speed V2 of the sheet P by the pair of second rotating members 31X is made greater than the first conveyance speed V1 of the sheet P by the pair of first rotating members 91X in a conventional image forming apparatus 100X.

[0006] As shown in Figure 10, in the image forming apparatus 100X, the transfer apparatus 8X transfers the toner image on the image carrier 23X to the sheet P while transporting the sheet P between the image carrier 23X (photoreceptor drum or intermediate transfer body) and the transfer member 81X (transfer roller). In the fixing apparatus 9X, the toner image is fixed to the sheet P while transporting the sheet P transported from the transfer apparatus 8X between a pair of first rotating members 91X (first drive-side rotating member 911X and first driven-side rotating member 912X) (in this example, a pair of fixing rotating members). In addition, the discharge apparatus 30X discharges the sheet P transported from the fixing apparatus 9X to the outside while transporting it between a pair of second rotating members 31X (second drive-side rotating member 311X and second driven-side rotating member 312X) (in this example, a pair of discharge rollers). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-62820 [Patent Document 2] Japanese Patent Application Publication No. 9-114153 [Overview of the project] [Problems that the invention aims to solve]

[0008] Incidentally, if the actual transport speed Vr1 of the sheet P by the pair of first rotating members 91X (the pair of fixing rotating members of the fixing device 9X) becomes faster than the original first transport speed V1 due to some influence, the sheet P will be pulled towards the pair of first rotating members 91X between the pair of first rotating members 91X and the upstream transport members (image carrier 23X and transfer member 81X of the transfer device 8X) (see the dashed line in Figure 10). As a result, the transport position of the sheet P transported by the upstream transport members (23X, 81X) will shift downstream in the transport direction W. In this example, the transfer position will shift downstream, which may lead to a deterioration in image quality.

[0009] Therefore, in the conventional image forming apparatus 100X, in addition to the first drive unit 210X (first drive motor) that drives the pair of first rotating members 91X, a second drive unit 220X (second drive motor) that drives the upstream transport members (23X, 81X) is provided, and the second transport speed V2 of the sheet P by the upstream transport members (23X, 81X) located upstream of the pair of first rotating members 91X is made greater than the first transport speed V1 of the sheet P by the pair of first rotating members 91X, thereby causing the sheet P to slacken between the upstream transport members (23X, 81X) and the pair of first rotating members 91X (see solid line in Figure 10). As a result, even if the actual transport speed Vr1 of the sheet P by the pair of first rotating members 91X becomes faster than the original first transport speed V1 due to some influence, it is possible to suppress the sheet P from being pulled towards the pair of first rotating members (23X, 81X), and therefore, it is possible to suppress the downstream shift in the transport direction W of the transport position of the sheet P transported by the upstream transport members (23X, 81X). In this example, it is possible to suppress the deterioration of image quality due to the downstream shift of the transfer position.

[0010] However, when the second drive unit 220X that drives the upstream transport members (23X, 81X) drives a pair of second rotating members 31X at the same second transport speed V2, the second transport speed V2 of the sheet P by the pair of second rotating members 31X downstream of the pair of first rotating members 91X becomes greater than the first transport speed V1 of the sheet P by the pair of first rotating members 91X. As a result, the sheet P is pulled towards the pair of second rotating members (discharge device) between the pair of second rotating members 31X and the pair of first rotating members 91X. Consequently, the transport position of the sheet P transported by the pair of first rotating members 91X shifts downstream in the transport direction W. In this example, the fixing position shifts downstream, which may lead to a deterioration in image quality. It may also cause damage to the sheet P.

[0011] In this regard, Patent Document 1 describes an image forming apparatus in which, as the tension of the roll paper increases, the roll paper transport path becomes a path in which the wrapping angle of the roll paper with respect to the register roller increases, and in which case the guide member is pushed and displaced by the roll paper against the biasing force from the biasing means.

[0012] Furthermore, Patent Document 2 describes an image forming apparatus in which a guide means is provided between the fixing roller of the heat roll fixing device and the paper discharge roller located downstream of the transport path of the fixing roller, to absorb the difference in paper feeding speed between the fixing roller and the paper discharge roller by varying the transport path.

[0013] However, while the image forming apparatus described in Patent Documents 1 and 2 can increase the retraction width of the transport path (roll paper transport path in Patent Document 1, transport path in Patent Document 2) when the sheet is pulled, the limit of the retraction width may be reached depending on the length of the sheet in the transport direction. In that case, it is not possible to prevent the sheet from being pulled beyond the limit of the retraction width.

[0014] Therefore, the present disclosure aims to provide an image forming apparatus that can suppress the pulling of the sheet towards the pair of second rotating members between the pair of second rotating members and the pair of first rotating members, regardless of the length of the sheet in the conveying direction, even if the second conveying speed of the sheet by the pair of second rotating members is greater than the first conveying speed of the sheet by the pair of first rotating members, and thus can suppress misalignment of the sheet conveyed by the pair of first rotating members. [Means for solving the problem]

[0015] To solve the aforementioned problems, the image forming apparatus according to the present disclosure comprises a pair of first rotating members, a first drive-side rotating member and a first driven-side rotating member, which press against each other to transport a sheet, and a pair of second rotating members, a second drive-side rotating member and a second driven-side rotating member, which press against each other to transport the sheet transported from the pair of first rotating members, wherein the second transport speed of the sheet by the pair of second rotating members is greater than the first transport speed of the sheet by the pair of first rotating members, and the pair of second rotating members are movable in a pressure release direction that releases the pressure contact of the second driven-side rotating member from the second drive-side rotating member, and the second driven-side rotating member is moved away from the second drive-side rotating member in the pressure release direction by utilizing the tensile force of the sheet between the pair of first rotating members and the pair of second rotating members when the sheet is transported between them. [Effects of the Invention]

[0016] According to this disclosure, even if the second conveying speed of the sheet by the pair of second rotating members is greater than the first conveying speed of the sheet by the pair of first rotating members, it is possible to suppress the sheet from being pulled towards the pair of second rotating members between the pair of second rotating members and the pair of first rotating members, regardless of the length of the sheet in the conveying direction, and therefore it is possible to suppress misalignment of the sheet being conveyed by the pair of first rotating members. [Brief explanation of the drawing]

[0017] [Figure 1] This is a cross-sectional view showing an image forming apparatus according to this embodiment. [Figure 2] This is a schematic cross-sectional view showing a pair of first rotating members and a pair of second rotating member portions in the image forming apparatus according to this embodiment. [Figure 3] This is a schematic cross-sectional view showing a pair of first rotating members, a pair of second rotating members, and a sheet guide member in an image forming apparatus according to the first embodiment. [Figure 4]It is a schematic cross-sectional view showing a pair of first rotating members, a pair of second rotating members, and a sheet guide member in an image forming apparatus according to a second embodiment. [Figure 5] It is a schematic cross-sectional view showing a pair of first rotating members, a pair of second rotating members, and a sheet guide member in an image forming apparatus according to a third embodiment. [Figure 6] It is a plan view of a sheet guide member according to a fourth embodiment. [Figure 7] It is a schematic cross-sectional view showing a state in which a sub-sheet guide member is located at a protruding position in a sheet guide member according to a fourth embodiment. [Figure 8] It is a schematic cross-sectional view showing a state in which a sub-sheet guide member is located at a retracted position in a sheet guide member according to a fourth embodiment. [Figure 9] It is a schematic cross-sectional view showing a sheet guide member according to a fifth embodiment. [Figure 10] It is a schematic cross-sectional view for explaining the inconvenience when the second conveyance speed of a sheet by a pair of second rotating members is made higher than the first conveyance speed of the sheet by a pair of first rotating members in a conventional image forming apparatus.

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0019] (Image Forming Apparatus) FIG. 1 is a cross-sectional view showing an image forming apparatus 100 according to the present embodiment. In the figure, the left-right direction is X, the right side is X1, the left side is X2, the direction orthogonal to the left-right direction X is the depth direction Y, the front side is Y1, the back side is Y2, and the vertical direction orthogonal to the left-right direction X and the depth direction Y is Z. The following description will be made based on these definitions.

[0020] The image data handled by the main body 101 of the image forming apparatus 100 corresponds to either a color image using black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (e.g., black). For this reason, four photoreceptor drums 1 (an example of an image carrier), chargers 2, print heads 3 (an example of an exposure device), developing devices 4, primary transfer devices 5, and drum cleaning devices 6 are provided to form four types of toner images corresponding to each color, and these are associated with black, cyan, magenta, and yellow, respectively, forming four image stations Pa, Pb, Pc, and Pd. Note that the image forming apparatus 100 may also be a monochrome image forming apparatus.

[0021] At each image station Pa, Pb, Pc, and Pd, the chargers 2-2 uniformly charge the surface 1a of the photoreceptor drums 1-1, which are rotated in a predetermined rotation direction R, to a predetermined potential. The print heads 3-3 expose the surface 1a of the photoreceptor drums 1-1, forming an electrostatic latent image on the surface 1a of the photoreceptor drums 1-1. The developing device 4 develops the electrostatic latent image on the surface 1a of the photoreceptor drums 1-1, forming a toner image on the surface 1a of the photoreceptor drums 1-1. As a result, toner images of each color are formed on the surface 1a of each photoreceptor drum 1-1. The drum cleaning devices 6-6 remove and recover residual toner from the surface 1a of the photoreceptor drums 1-1. The primary transfer devices 5-5 sequentially transfer the toner images of each color on the surface 1a of each photoreceptor drum 1-1 onto the intermediate transfer belt 23 (an example of an image carrier or upstream transport member) which is moved around by the drive roller 21 and driven roller 22 of the belt drive device 20, thereby forming a color toner image on the intermediate transfer belt 23. The belt cleaning device 7 removes and recovers any residual toner from the intermediate transfer belt 23.

[0022] A transfer nip section TN is formed between the intermediate transfer belt 23 and the transfer roller 81 (an example of a transfer member, an upstream transport member) of the secondary transfer device 8. The transfer roller 81 of the secondary transfer device 8 traps the sheet P, such as recording paper, that has been transported through the sheet transport path 11 in the transfer nip section TN and transports it together with the intermediate transfer belt 23, while transferring the color toner image on the surface of the intermediate transfer belt 23 onto the sheet P. The fixing device 9 traps the sheet P between a pair of fixing rotating members (an example of a pair of first rotating members 91), heats and pressurizes it, and fixes the color toner image on the sheet P. The pair of fixing rotating members (91) consist of a fixing member that heats and melts the toner on the sheet P, and a pressurizing member that presses the sheet P between itself and the fixing member. The fixing member acts as a first driving rotating member 911 or a first driven rotating member 912 (in this example, the first driven rotating member 912, specifically the fixing belt). The pressurizing member acts as either a first driven rotating member 912 or a first driving rotating member 911 (in this example, the first driving rotating member 911, specifically a pressurizing roller).

[0023] The sheet P is pulled out from the paper feed cassette 13 by the pickup roller 12, transported through the sheet transport path 11, and delivered to the discharge tray 15 via a pair of discharge rollers (an example of a pair of second rotating members 31) after passing through the secondary transfer device 8 and the fixing device 9. The sheet transport path 11 is equipped with a registration roller 16, etc. The registration roller 16 temporarily stops the sheet P, aligns the leading edge of the sheet P, and then starts transporting the sheet P in accordance with the timing of toner image transfer at the transfer nip section TN between the intermediate transfer belt 23 and the transfer roller 81.

[0024] (Regarding this embodiment) Figure 2 is a schematic cross-sectional view showing a pair of first rotating members 91 and a pair of second rotating members 31 in the image forming apparatus 100 according to this embodiment.

[0025] As shown in Figure 2, the image forming apparatus 100 includes a pair of first rotating members 91 (a pair of fixed rotating members in this example) and a pair of second rotating members 31 (a pair of discharge rollers in this example). The pair of first rotating members 91 transport the sheet P by pressing a first drive-side rotating member 911 (a pressure roller in this example) and a first driven-side rotating member 912 (a fixed belt in this example) into contact. The pair of second rotating members 31 transport the sheet P transported from the pair of first rotating members 91 by pressing a second drive-side rotating member 311 (a drive-side discharge roller in this example) and a second driven-side rotating member 312 (a driven-side discharge roller in this example) into contact.

[0026] In the image forming apparatus 100, the second transport speed V2 of the sheet P by the pair of second rotating members 31 is greater than the first transport speed V1 of the sheet P by the pair of first rotating members 91.

[0027] The pair of second rotating members 31 are movable in a pressure release direction T2 that releases the pressure contact of the second driven rotating member 312 with respect to the second driving rotating member 311.

[0028] The configuration utilizes the tensile force F of the sheet P between the pair of first rotating members 91 and the pair of second rotating members 31 when they are being transported between the pair of first rotating members 91 and the pair of second rotating members 31 to move the second driven rotating member 312 away from the second driving rotating member 311 in the direction of release of pressure T2.

[0029] In this example, as shown in Figure 2, the image forming apparatus 100 further includes a discharge device 30, a first drive unit 210 (first drive motor), a second drive unit 220 (second drive motor), and a control unit 120, in addition to a transfer device (secondary transfer device 8 in this example) and a fixing device 9. The transfer device (8) transfers the toner image formed on the image carrier (intermediate transfer belt 23 in this example) onto the sheet P. The fixing device 9 has a pair of fixing rotating members (91) that fix the toner image on the sheet P transferred by the transfer device (8). The discharge device 30 has a pair of discharge rollers (an example of a pair of second rotating members 31) that discharge the sheet P on which the toner image has been fixed by the fixing device 9 to the outside. The first drive unit 210 drives the conveyance of the sheet P by the fixing device 9 (first drive-side rotating member 911). The second drive unit 220 drives both the transport of the image carrier (23) and the sheet P of the transfer device (8), and the transport of the sheet P of the discharge device 30. The pair of first rotating members 91 are a pair of fixing rotating members, and the pair of second rotating members 31 are a pair of discharge rollers.

[0030] The control unit 120 controls the entire image forming apparatus 100. As shown in Figure 2, the control unit 120 realizes various functions by reading and executing various programs stored in the storage unit 122 (for example, storage or ROM). The control unit 120 may be implemented by one or more control devices / arithmetic units [CPU (Central Processing Unit), SoC (System on a Chip)]. Alternatively, the control unit 120 may be composed of one or more control circuits. The control unit 120 has a processing unit 121 consisting of a microcomputer such as a CPU, and a storage unit 122 including non-volatile memory such as ROM and volatile memory such as RAM. The control unit 120 controls the operation of various components by having the processing unit 121 load control programs pre-stored in the ROM of the storage unit 122 onto the RAM of the storage unit 122 and execute them.

[0031] The control unit 120 controls the first drive unit 210 and the second drive unit 220 so that the second transport speed V2 of the second drive unit 220 is greater than the first transport speed V1 of the first drive unit 210.

[0032] In this embodiment, the control unit 120 sets the second transport speed V2 of the sheet P by the upstream transport member (23,81) located upstream of the pair of first rotating members 91 to be greater than the first transport speed V1 of the sheet P by the pair of first rotating members 91, thereby slackening the sheet P between the upstream transport member (23,81) and the pair of first rotating members 91. As a result, even if the actual transport speed Vr1 of the sheet P by the pair of first rotating members 91 becomes faster than the original first transport speed V1 due to some influence, it is possible to suppress the sheet P from being pulled towards the pair of first rotating members (23,81), and therefore, it is possible to suppress the downstream shift in the transport direction W of the transport position of the sheet P transported by the upstream transport member (23,81). In this example, it is possible to suppress the deterioration of image quality due to the downstream shift of the transfer position.

[0033] Furthermore, in this embodiment, the second transport speed V2 of the sheet P by the pair of second rotating members 31 is greater than the first transport speed V1 of the sheet P by the pair of first rotating members 91. The sheet P is pulled towards the pair of second rotating members 31 between the pair of second rotating members 31 and the pair of first rotating members 91. However, by using the tensile force F of the sheet P to move the second driven rotating member 312 away from the second driving rotating member 311 in the direction of release T2, the pressure force of the second driven rotating member 312 against the second driving rotating member 311 can be reduced.

[0034] Thus, according to this embodiment, regardless of the length of the sheet P in the conveying direction W, the tensile force F of the sheet P moves the second driven rotating member 312 away from the second driving rotating member 311 in the pressure release direction T2, thereby reducing the pressure force of the second driven rotating member 312 against the second driving rotating member 311 to a degree that ensures reliable conveyance of the sheet P. This prevents the sheet P from being pulled towards the pair of second rotating members 31 between the pair of second rotating members 31 and the pair of first rotating members 91, and therefore prevents misalignment of the sheet P being conveyed by the pair of first rotating members 91.

[0035] Figures 3 to 5 are schematic cross-sectional views showing a pair of first rotating members 91, a pair of second rotating members 31, and a sheet guide member 40 in the image forming apparatus 100 according to the first to third embodiments, respectively.

[0036] As shown in Figures 3 to 5, the image forming apparatus 100 according to this embodiment further comprises a sheet guide member 40 and a biasing member 60 (a coil spring in this example), as shown in Figure 3. The sheet guide member 40 constitutes a transport path L that guides the sheet P, which is transported by a pair of first rotating members 91, to a pair of second rotating members 31. The sheet guide member 40 supports the second driven rotating member 312 so as to be rotatable around the rotation axis α, and is movable in a pressure contact direction T1 in which the second driven rotating member 312 is pressed against the second driving rotating member 311 and in a pressure release direction T2. ​​The biasing member 60 biases the sheet guide member 40 in the pressure contact direction T1. The sheet guide member 40 has a curved portion 40a that is curved so that the sheet P side (the side of the opposing sheet guide member 50 that constitutes the transport path L) is convex in the transport direction W. In the image forming apparatus 100, the sheet P comes into contact with the sheet guide member 40 due to the tensile force F when it is conveyed between a pair of first rotating members 91 and a pair of second rotating members 31, causing the sheet guide member 40 to move in the release direction T2 against the biasing force of the biasing member 60.

[0037] In this configuration, when the second driven rotating member 312 is in contact with the second driving rotating member 311, as the sheet P is conveyed by the pair of second rotating members 31, the tensile force F of the sheet P increases. As the tensile force F of the sheet P increases, the second driven rotating member 312 moves in the direction T2 in which contact is released from the second driving rotating member 311. That is, the contact force of the second driven rotating member 312 with respect to the second driving rotating member 311 decreases, and as a result, the tensile force F of the sheet P decreases. On the other hand, as the contact force of the second driven rotating member 312 with respect to the second driving rotating member 311 decreases, the conveying force of the sheet P by the pair of second rotating members 31 decreases, and as the tensile force F of the sheet P decreases, the second driven rotating member 312 moves in the direction T1 in which contact is released from the second driving rotating member 311. In other words, the pressure force of the second driven rotating member 312 against the second driving rotating member 311 increases, and as a result, the tensile force F of the sheet P increases.

[0038] In other words, the tensile force F of the sheet P increases, which reduces the pressure force of the second driven rotating member 312 against the second driving rotating member 311, thus decreasing the tensile force F of the sheet P. This process is repeated, and the pressure force of the second driven rotating member 312 against the second driving rotating member 311 increases as the tensile force F of the sheet P decreases, thus increasing the tensile force F.

[0039] Thus, in this embodiment, the sheet P can autonomously suppress being pulled towards the pair of second rotating members 31 between the pair of second rotating members 31 and the pair of first rotating members 91.

[0040] More specifically, the curved portion 40a is provided on the sheet guide member 40 upstream of the central portion in the transport direction W. The sheet guide member 40 transports the sheet P, which has been transported in the vertical direction Z or diagonally upward close to the vertical direction Z (in this example, diagonally upward close to the vertical direction Z), in a direction intersecting the vertical direction Z (for example, horizontal direction H or diagonally upward close to the horizontal direction H; in this example, diagonally upward close to the horizontal direction H).

[0041] The curvature angle θa of the sheet guide member 40 (the angle between the virtual tangent of the upstream end and the virtual tangent of the downstream end in the conveying direction W) (see Figure 3) is not limited to this, but for example, it can be 90 to 160 degrees, preferably 90 to 140 degrees, more preferably 90 to 120 degrees, and even more preferably 90 to 100 degrees. In this example, the curvature angle θa is set to about 96 degrees.

[0042] <First Embodiment> As shown in Figure 3, the sheet guide member 40 is mounted on the image forming apparatus body 101 so as to be able to swing around a pivot axis β(βa) along the rotation axis α. The pivot axis β(βa) is located on the side of the pair of first rotating members 91 of the sheet guide member 40. The biasing member 60 biases the side of the pair of second rotating members 31 of the sheet guide member 40.

[0043] In this configuration, the sheet guide member 40 swings around the oscillation axis β (βa) of the pair of first rotating members 91, so that the interaxial distance per unit oscillation angle between the rotation axis α of the second driven rotating member 312 and the rotation axis γ of the second driving rotating member 311 can be increased, i.e., the pressure force of the second driven rotating member 312 against the second driving rotating member 311 per unit oscillation angle. This makes it easier to change the pressure force of the second driven rotating member 312 against the second driving rotating member 311 due to the tensile force F of the sheet P.

[0044] Incidentally, as the installation position of the biasing member 60 moves further away from the oscillation axis β(βa) on the pair of first rotating members 91, the second driven rotating member 312 can be pressed against the second driving rotating member 311 with a smaller biasing force (pressing it so that the sheet P can be transported).

[0045] In this respect, in this embodiment, since the biasing member 60 biases the pair of second rotating members 31 on the sheet guide member 40, the second driven rotating member 312 can be pressed against the second driving rotating member 311 (pressed against so that the sheet P can be transported) with a smaller biasing force.

[0046] More specifically, the sheet guide member 40 has a downstream end in the transport direction W that rotatably supports the second driven rotating member 312 around the rotation axis α, and an upstream end in the transport direction W that is pivotably mounted on the image forming apparatus body 101 around the pivot axis β(βa). The pivot axis 47(47a) of the pivot axis β(βa) provided at the upstream end of the sheet guide member 40 in the transport direction W is located near the downstream side of the pair of first rotating members 91 in the transport direction W.

[0047] The biasing member 60 is located downstream of the center of the sheet guide member 40 in the transport direction W (in this example, near the upstream side of the pair of second rotating members 31). The biasing member 60 is held at one end by a guide-side first holding portion 41 provided on the back surface of the sheet guide member 40, and at the other end by a body-side first holding portion 111 provided on the image forming apparatus body 101 opposite the guide-side first holding portion 41, so as to bias the sheet guide member 40 toward the second drive-side rotating member 311. The guide-side first holding portion 41 is a projection that protrudes toward the image forming apparatus body 101, and the body-side first holding portion 111 is a projection that protrudes toward the sheet guide member 40.

[0048] <Second Embodiment> In the image forming apparatus 100 according to the second embodiment, the same reference numerals are used for components identical to those in the image forming apparatus 100 according to the first embodiment, and their descriptions are omitted.

[0049] As shown in Figure 4, the sheet guide member 40 is mounted on the image forming apparatus body 101 so as to be able to swing around a pivot axis β(βb) along the rotation axis α. The pivot axis β(βb) is located on the side of the pair of second rotating members 31 of the sheet guide member 40. The biasing member 60 biases the side of the pair of first rotating members 91 of the sheet guide member 40.

[0050] In this configuration, the sheet guide member 40 swings around the swing axis β (βb) on the pair of second rotating members 31. If the swing axis β is the fulcrum, the curved portion 40a on the upstream side in the conveying direction W of the sheet guide member 40 is the point of force application, and the contact portion 31a of the second driven rotating member 312 against the second driving rotating member 311 is the point of application, then by the "lever principle," a tensile force F is applied to the point of force application (40a), and the swinging motion around the fulcrum [β (βb)] allows a greater force to be applied to the point of application (31a) than the tensile force F applied to the point of force application (40a). As a result, even with a tensile force F smaller than the tensile force F of the sheet P in the first embodiment, the contact force of the second driven rotating member 312 against the second driving rotating member 311 can be changed.

[0051] Incidentally, as the installation position of the biasing member 60 moves further away from the oscillation axis β (βb) on the pair of second rotating members 31, the first driven rotating member 912 can be pressed against the first driving rotating member 911 with a smaller biasing force (pressing it so that the sheet P can be transported).

[0052] In this respect, in this embodiment, since the biasing member 60 biases the pair of first rotating members 91 on the sheet guide member 40, the second driven rotating member 312 can be pressed against the second driving rotating member 311 (pressed against so that the sheet P can be transported) with a smaller biasing force.

[0053] More specifically, the sheet guide member 40 has a downstream end in the transport direction W that rotatably supports the second driven rotating member 312 around the rotation axis α, and an extension portion 32 extends from the downstream end in the transport direction W to the side opposite to the second driven rotating member 311. The tip of the extension portion 32 of the sheet guide member 40 is pivotably mounted on the image forming apparatus body 101 around the pivot axis β (βb). The angle λ (the angle on the upstream side in the transport direction W with respect to the first virtual line δa and on the sheet guide member 40 side with respect to the second virtual line δb) is not limited to this, but is set to approximately 80 to 90 degrees (approximately 96 degrees in this example). The distance between the rotation axis α and the oscillation axis β(βb) of the sheet guide member 40 is smaller than the distance between the rotation axis α and the installation position of the biasing member 60 of the sheet guide member 40. The oscillation axis 47(47b) of the oscillation axis β(βb) provided in the extension 32 is located approximately below the rotation axis α.

[0054] The biasing member 60 is provided upstream of the center of the sheet guide member 40 in the transport direction W (in this example, the center of the curved portion 40a in the transport direction W). The biasing member 60 is held at one end by a guide-side second holding portion 42 provided on the back surface of the sheet guide member 40, and at the other end by a body-side second holding portion 112 provided on the image forming apparatus body 101 opposite the guide-side second holding portion 42, so as to bias the sheet guide member 40 toward the transport path L. The guide-side second holding portion 42 is a protruding portion that projects toward the image forming apparatus body 101, and the body-side second holding portion 112 is a protruding portion that projects toward the sheet guide member 40.

[0055] <Third Embodiment> In the image forming apparatus 100 according to the third embodiment, the same reference numerals are used for components identical to those in the image forming apparatus 100 according to the first and second embodiments, and their descriptions are omitted.

[0056] In this embodiment, the sheet guide member 40 is provided on the image forming apparatus body 101 so as to be swingable so as to change the transport width of the transport path L (the transport width between the sheet guide member 40 and the opposing sheet guide member 50 that constitute the transport path L opposite to the sheet guide member 40). Here, the transport width of the transport path L refers to the distance of the transport path L in a direction perpendicular to the surface of the sheet P being transported (the distance between the sheet guide member 40 and the opposing sheet guide member 50).

[0057] The biasing member 60 includes a first biasing member 61 (a first coil spring in this example) and a second biasing member 62 (a second coil spring in this example). The first biasing member 61 biases the pair of first rotating members 91 of the sheet guide member 40 toward the transport path L (opposing sheet guide member 50). The second biasing member 62 biases the pair of second rotating members 31 of the sheet guide member 40 toward the transport path L (opposing sheet guide member 50).

[0058] The first biasing force exerted by the first biasing member 61 on the seat guide member 40 is greater than the second biasing force exerted by the second biasing member 62 on the seat guide member 40.

[0059] In this configuration, without providing a pivot axis 47, the sheet guide member 40, which is provided on the image forming apparatus body 101 so as to be able to pivot so as to change the transport width of the transport path L, can be pivoted around the pivot axis β (βc) on the side of the pair of first rotating members 91 along the rotation axis α relative to the image forming apparatus body 101 by two biasing members 60 (61, 62).

[0060] More specifically, the sheet guide member 40 has a downstream end in the conveying direction W that rotatably supports the second driven rotating member 312 around the rotation axis α.

[0061] The main body 101 of the image forming apparatus is provided with a sheet guide member housing section 101a. The sheet guide member 40 is housed in the sheet guide member housing section 101a so as to be movable between a close position, where it is close to the opposing sheet guide member 50, and a distanced position, where it is farther away from the opposing sheet guide member 50. Here, when the sheet guide member 40 is in the close position, the transport width of the transport path is set to the standard transport width, and when it is in the distanced position, the transport width of the transport path is made larger than the standard transport width. The opposing sheet guide member 50 is fixed to the main body 101 of the image forming apparatus.

[0062] The first biasing member 61 is located downstream of the center of the sheet guide member 40 in the transport direction W (in this example, near the upstream side of the pair of second rotating members 31). The biasing member 60 is biased toward the transport path L, with one end held by a guide-side first holding portion 41 provided on the back surface of the sheet guide member 40, and the other end held by a body-side first holding portion 111 provided on the image forming apparatus body 101 opposite the guide-side first holding portion 41. The guide-side first holding portion 41 is a projection that protrudes toward the image forming apparatus body 101, and the body-side first holding portion 111 is a projection that protrudes toward the sheet guide member 40.

[0063] The second biasing member 62 is provided upstream of the center of the sheet guide member 40 in the transport direction W (in this example, the center of the curved portion 40a in the transport direction W). The biasing member 60 is held at one end by a guide-side second holding portion 42 provided on the back surface of the sheet guide member 40, and at the other end by a body-side second holding portion 112 provided on the image forming apparatus body 101 opposite the guide-side second holding portion 42, so as to bias the sheet guide member 40 toward the transport path L. The guide-side second holding portion 42 is a protruding portion that projects toward the image forming apparatus body 101, and the body-side second holding portion 112 is a protruding portion that projects toward the sheet guide member 40.

[0064] In this example, the first biasing force of the first biasing member 61 and the second biasing force of the second biasing member 62 are set such that the oscillation axis β(βc) is located at or near the contact point between the seat guide member 40 and the first biasing member 61.

[0065] <Formation of the 4th Implementation> In the image forming apparatus 100 according to the fourth embodiment, the same reference numerals are used for components identical to those in the image forming apparatus 100 according to the first to third embodiments, and their descriptions are omitted.

[0066] Figure 6 is a plan view of the sheet guide member 40 according to the fourth embodiment. Figures 7 and 8 are schematic cross-sectional views showing the state in which the sub-sheet guide member 45 is in the protruding position and the retracted position in the sheet guide member 40 according to the fourth embodiment, respectively. Note that biasing members 60, 61, 62, etc. are omitted from the illustration in Figures 7 and 8.

[0067] The sheet guide member 40 according to the fourth embodiment can be applied to the configurations according to the first to third embodiments.

[0068] In this embodiment, the sheet guide member 40 includes a sheet guide member body 44, a sub-sheet guide member 45, and a sub-biasing member 46 (a coil spring in this example) (see Figures 7 and 8). The sheet guide member body 44 is provided with a plurality of ribs 441 to 441 extending along the conveying direction W, and through holes 442 to 442 (see Figure 6) extending along the conveying direction W between adjacent ribs 441, 441. The sub-sheet guide member 45 is provided with sub-ribs 451 to 451 extending along the conveying direction W on the side of the sheet guide member body 44 away from the sheet P, so as to penetrate the through holes 442 to 442 in the sheet guide member body 44. The sub-biasing member 46 biases the sub-sheet guide member 45 toward the sheet guide member body 44.

[0069] The sub-sheet guide member 45 is movable between a protruding position and a retracted position. The protruding position is the position where the sub-ribs 451-451 are driven by the sub-biasing member 46 through the through holes 442-442 in the sheet guide member body 44 and protrude towards the sheet P side beyond the multiple ribs 441-441. The retracted position is the position where the sub-ribs 451-451 are retracted from the protruding position against the biasing force of the sub-biasing member 46. The biasing force of the sub-biasing member 46 is smaller than the swinging force of the sheet guide member 40, which swings due to the tensile force F of the sheet P.

[0070] In this configuration, when there is no tensile force F on the sheet P or when it is less than the reference tensile force F, the sub-sheet guide member 45 is positioned in a protruding position by the sub-biasing member 46, and the sub-ribs 451-451 protrude more than the multiple ribs 441-441. Therefore, when the sheet P is transported along the transport path L, only the sub-ribs 451-451 of the multiple ribs 441-441 and sub-ribs 451-451 come into contact with each other, and the sheet P can be transported with a small sliding resistance with the sub-ribs 451-451. Consequently, the sheet P can be transported stably.

[0071] As the tensile force F of the sheet P gradually increases and exceeds the reference tensile force (the force that balances the biasing force of the sub-biasing member 46), the sub-ribs 451-451 first retract from their protruding position to their retracted position against the biasing force of the sub-biasing member 46. As a result, the sheet P being transported along the transport path L is in sliding contact with both the multiple ribs 441-441 and the sub-ribs 451-451. When the tensile force F of the sheet P increases further, the sheet guide member 40, composed of the sheet guide member body 44 and the sub-sheet guide member 45, swings around the swing axis β such that the second driven-side rotating member 312 moves in the direction T2 of release from the second driven-side rotating member 311. At this time, the sheet P can be transported with a greater sliding resistance with the sub-ribs 451-451 than when only the sub-ribs 451-451 are present. Therefore, the sheet guide member 40 can be made easier to swing.

[0072] More specifically, the sub-sheet guide member 45 is located upstream of the center of the sheet guide member body 44 in the transport direction W (in this example, the center of the curved portion 40a in the transport direction W).

[0073] The curvature angle θb of the sub-sheet guide member 45 (the angle between the virtual tangent at the upstream end and the virtual tangent at the downstream end in the conveying direction W) (see Figure 7) is set to be smaller than the curvature angle θa of the sheet guide member 40. In this example, the curvature angle θb is set to approximately 67 degrees.

[0074] The sheet guide member body 44 is provided with a sub-sheet guide member housing section 44a (see Figures 7 and 8). The sub-sheet guide member 45 is housed in the sub-sheet guide member housing section 44a so as to be movable between a close position, which is close to the opposing sheet guide member 50, and a separated position, which is further away from the opposing sheet guide member 50.

[0075] The sub-biasing member 46 is biased towards the transport path L by having one end held by a guide-side third holding portion 43 provided on the back surface of the sheet guide member body 44, and the other end held by a body-side third holding portion 113 provided on the sheet guide member body 44 so as to face the guide-side third holding portion 43. The guide-side third holding portion 43 is a protrusion that projects toward the sheet guide member body 44, and the body-side third holding portion 113 is a protrusion that projects toward the sub-sheet guide member 45. The sub-biasing member 46 is provided in the center of the sub-sheet guide member 45 in the transport direction W.

[0076] <Fifth Implementation Formation> In the image forming apparatus 100 according to the fifth embodiment, the same reference numerals are used for components identical to those in the image forming apparatus 100 according to the first to fourth embodiments, and their descriptions are omitted.

[0077] Figure 9 is a schematic cross-sectional view showing the sheet guide member 40 according to the fifth embodiment. Note that biasing members 60, 61, 62, etc. are omitted from the illustration in Figure 9.

[0078] The sheet guide member 40 according to the fifth embodiment can be applied to the configurations according to the first to fourth embodiments.

[0079] Incidentally, as the installation position of the biasing members 60 (61, 62) moves further away from the oscillation axis β, the seat guide member 40 can be oscillated with a smaller biasing force.

[0080] In this regard, in this embodiment, the installation position of the biasing members 60 (61, 62) can be changed.

[0081] In this configuration, the installation position of the biasing members 60 (61, 62) can be changed according to the biasing force of the biasing members used. Therefore, instead of being limited to parts with a specific biasing force, it is possible to select a part that can perform optimally while being low-cost from among multiple types of parts with different biasing forces, taking into consideration cost and functionality.

[0082] More specifically, the number of possible installation locations for the guide-side first holding portion 41 and the main body-side first holding portion 111 according to the first and third embodiments, as well as the number of possible installation locations for the guide-side second holding portion 42 and the main body-side second holding portion 112 according to the second and third embodiments, are two or more.

[0083] This disclosure is not limited to the embodiments described above, and can be implemented in a variety of other ways. Therefore, these embodiments are merely illustrative in all respects and should not be constrained. The scope of this disclosure is defined by the claims and is not restricted by the text of the specification. Furthermore, any variations or modifications falling within the equivalent scope of the claims are all within the scope of this disclosure. [Explanation of Symbols]

[0084] 1. Photosensitive drum (an example of an image carrier) 100 Image forming apparatus 101 Image forming apparatus main unit 101a Seat guide member housing 111 Main body side first holding part 112 Main unit side second holding part 113 Third holding part on main body side 120 Control Unit 121 Processing Unit 122 Storage section 21 Drive rollers 210 First drive unit 22 Driven roller 220 Second drive unit 23. Intermediate transfer belt (an example of an upstream conveying member) 30 Ejector 31 A pair of second rotating members (a pair of discharge rollers) 311 Second drive-side rotating member 312 Second driven rotating member 31a Press-fit portion 32 Extension section 40. Seat guide member 40a Curved section 41 Guide side first retaining part 42 Guide-side second retaining part 43 Guide-side third retaining part 44. Seat guide component body 441 Rib 442 Through hole 44a Sub-seat guide member housing section 45 Sub-seat guide member 451 Subrib 46 Sub-biasing member 47. Oscillating axis 50 Opposing Seat Guide Member 60 biasing member 61 First biasing member 62 Second biasing member 81 Transfer roller (an example of an upstream conveying member) 9. Fixing device 91 A pair of first rotating members (a pair of fixed rotating members) 911 First drive-side rotating member (pressure roller) 912 First driven rotating member (fixing belt) F Tensile force H horizontal direction L Transport route P Sheet R rotation direction T1 Pressure contact direction T2 Pressure release direction V1 First transport speed V2 Second transport speed Vr1 Actual transport speed W Conveying direction X Left / right direction Y (depth direction) Z vertical direction α rotation axis β oscillation axis γ Rotation axis δa First virtual line δb Second virtual line δc Third virtual line θa Curve angle θb curvature angle λ angle

Claims

1. A pair of first rotating members, a first driving rotating member and a first driven rotating member, press against each other to transport a sheet, A pair of second rotating members, the second driving rotating member and the second driven rotating member, press against each other to transport the sheet being transported from the pair of first rotating members, Equipped with, An image forming apparatus in which the second transport speed of the sheet by the pair of second rotating members is greater than the first transport speed of the sheet by the pair of first rotating members, The pair of second rotating members are movable in a pressure release direction that releases the pressure contact of the second driven rotating member with respect to the second driving rotating member. An image forming apparatus characterized in that it is configured to move the second driven rotating member away from the second driving rotating member in the direction of release of pressure contact by utilizing the tensile force of the sheet between the pair of first rotating members and the pair of second rotating members when they are being transported between the pair of first rotating members and the pair of second rotating members.

2. An image forming apparatus according to claim 1, A conveying path is configured to guide the sheet, which is conveyed by the pair of first rotating members, to the pair of second rotating members, and a sheet guide member is provided which supports the second driven rotating member so as to be rotatable around the axis of rotation, and which is movable in the direction in which the second driven rotating member is pressed against the second driving rotating member and in the direction in which the pressure is released. A biasing member that biases the sheet guide member in the pressure contact direction, Furthermore, The sheet guide member has a curved portion that is curved such that the sheet side is convex in the direction of sheet transport, An image forming apparatus characterized in that, when the sheet is conveyed between the pair of first rotating members and the pair of second rotating members, the tensile force causes the sheet guide member to abut against the sheet guide member, and the sheet guide member moves in the direction of release of pressure against the biasing force of the biasing member.

3. An image forming apparatus according to claim 2, The sheet guide member is provided on the image forming apparatus body so as to be able to swing around a pivot axis along the rotation axis, The pivot axis is provided on the side of the pair of first rotating members of the seat guide member, The image forming apparatus is characterized in that the biasing member biases the pair of second rotating members of the sheet guide member.

4. An image forming apparatus according to claim 2, The sheet guide member is provided on the image forming apparatus body so as to be able to swing around a pivot axis along the rotation axis, The pivot axis is provided on the side of the pair of second rotating members of the seat guide member, The image forming apparatus is characterized in that the biasing member biases the pair of first rotating members of the sheet guide member.

5. An image forming apparatus according to claim 2, The sheet guide member is provided on the image forming apparatus body so as to be swingable so as to change the transport width of the transport path. The biasing member comprises a first biasing member that biases the pair of first rotating members of the sheet guide member toward the transport path, and a second biasing member that biases the pair of second rotating members of the sheet guide member toward the transport path. An image forming apparatus characterized in that the first biasing force of the first biasing member on the sheet guide member is greater than the second biasing force of the second biasing member on the sheet guide member.

6. An image forming apparatus according to claim 2, The sheet guide member comprises a sheet guide member body having a plurality of ribs extending in the direction of conveying the sheet and through holes extending in the direction of conveying between adjacent ribs; a sub-sheet guide member having sub-ribs extending in the direction of conveying on the side of the sheet guide member body opposite to the sheet, so as to penetrate the through holes in the sheet guide member body; and a sub-biasing member that biases the sub-sheet guide member toward the sheet guide member body. The sub-sheet guide member is movable between a protruding position in which the sub-ribs are driven by the sub-biasing member to pass through the through-holes in the sheet guide member body and protrude toward the sheet side beyond the plurality of ribs, and a retracted position in which the sub-ribs are retracted from the protruding position against the biasing force of the sub-biasing member. An image forming apparatus characterized in that the biasing force of the sub-biasing member is smaller than the swinging force of the sheet guide member that swings due to the tensile force of the sheet.

7. An image forming apparatus according to any one of claims 2 to 6, An image forming apparatus characterized in that the installation position of the biasing member can be changed.

8. An image forming apparatus according to claim 1, A transfer device for transferring a toner image formed on an image carrier onto the aforementioned sheet, A fixing device having a pair of fixing rotating members for fixing the toner image on the sheet transferred by the transfer device, A discharge device having a pair of discharge rollers for discharging the sheet on which the toner image has been fixed by the aforementioned fixing device to the outside, A first drive unit that drives the transport of the sheet in the fixing device, A second drive unit that drives both the transport of the image carrier and the sheet in the transfer apparatus and the transport of the sheet in the discharge apparatus, Equipped with, The pair of first rotating members are the pair of fixed rotating members, and the pair of second rotating members are the pair of discharge rollers. An image forming apparatus characterized by controlling the first drive unit and the second drive unit so that the second transport speed of the second drive unit is greater than the first transport speed of the first drive unit.

Images