Sheet conveying device and image forming device

Abstract

To suppress sheet conveyance failures.SOLUTION: A sheet conveying device includes a first driven roller configured to pivot in accordance with changes in the inclination angle of a first drive roller, a second driven roller configured to pivot in accordance with changes in the inclination angle of a second drive roller, and a separation mechanism that switches between a contact state in which the first driven roller and the second driven roller are respectively in contact with the first drive roller and the second drive roller, and a separation state in which the first driven roller and the second driven roller are respectively separated from the first drive roller and the second drive roller. The separation mechanism has a swing member that supports the first driven roller and the second driven roller and is swingable about a first swing axis that extends along a sheet conveying direction, and the swing axis is located between the first driven roller and the second driven roller in a sheet width direction.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying device that conveys a sheet and an image forming apparatus that forms an image on a sheet. [Background technology]

[0002] Patent documents 1 and 2 disclose an image forming apparatus having a skew correction device that includes a pair of pre-registration rollers and a pair of registration rollers and corrects skew of a sheet, and a separation mechanism that transitions the pair of pre-registration rollers between a contact state and a separated state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-252918 [Patent Document 2] Japanese Patent Application Publication No. 2018-199572 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned Patent Document 1, the pre-registration driven roller of the pre-registration roller pair moves relative to the pre-registration drive roller, causing the pair of registration rollers to transition between a contact state and a separated state. When the pair of registration rollers has a plurality of nip portions in the width direction of the sheet, there is a demand for a sheet conveying device that reduces the difference in nip pressure at these plurality of nip portions and suppresses sheet conveyance failures.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet conveying device and an image forming apparatus that are capable of suppressing sheet conveyance failures. [Means for solving the problem]

[0006] One aspect of the present invention is a sheet conveying device including a first drive roller and a second drive roller that rotate by receiving a driving force and are arranged side by side in a sheet width direction perpendicular to a sheet conveying direction; a first steering means that changes the inclination angle of the rotation axis of the first drive roller with respect to the sheet width direction; a second steering means that changes the inclination angle of the rotation axis of the second drive roller with respect to the sheet width direction; a first driven roller that sandwiches and conveys a sheet together with the first drive roller, the first driven roller being configured to pivot about a first pivot axis that intersects both the sheet conveying direction and the sheet width direction in response to a change in the inclination angle of the first drive roller; and a second driven roller that sandwiches and conveys a sheet together with the second drive roller, the first driven roller being configured to pivot about a first pivot axis that intersects both the sheet conveying direction and the sheet width direction in response to a change in the inclination angle of the second drive roller. Therefore, the sheet conveying device is characterized in that it comprises a second driven roller configured to rotate around a second pivot axis that intersects both the sheet conveying direction and the sheet width direction, and a separation mechanism that switches between a contact state in which the first driven roller and the second driven roller abut against the first drive roller and the second drive roller, respectively, and a separation state in which the first driven roller and the second driven roller are separated from the first drive roller and the second drive roller, respectively, wherein the separation mechanism has a swing member that supports the first driven roller and the second driven roller and is swingable around a first swing axis that extends along the sheet conveying direction, and the swing axis is located between the first driven roller and the second driven roller in the sheet width direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress sheet conveyance failure. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing a sheet transport unit of the print module. [Figure 3] FIG. [Figure 4]FIG. 4A is an explanatory diagram of the operation of the registration rollers, and FIG. 4B is an explanatory diagram of the operation of the registration rollers. [Figure 5] 1A is a plan view showing the sheet conveying speed of the pair of registration rollers, FIG. 1B is a plan view showing the state in which the sheet is conveyed at an angle, and FIG. 1C is a plan view showing the state in which the lateral registration of the sheet is corrected. [Figure 6] FIG. 3 is a cross-sectional view of the register unit taken along a plane perpendicular to the sheet width direction. [Figure 7] FIG. 2 is a block diagram showing a control system according to the present embodiment. [Figure 8] 10 is a flowchart showing the control of a print module. [Figure 9] FIG. [Figure 10] (a) is a diagram showing the state immediately after the registration roller has rotated, (b) is a diagram showing the restoring force generated in the caster roller due to the rotation of the registration roller, and (c) is a diagram showing the state after the caster roller has rotated. [Figure 11] FIG. [Figure 12] FIG. [Figure 13] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] In this disclosure, the term "image forming apparatus" refers to a general device that forms an image on a sheet of recording material (recording medium), and includes at least a single-function printer, a copying machine, a multifunction machine, and a large commercial printing machine. Furthermore, the term "image forming apparatus" is not limited to the inkjet recording apparatus described in the following embodiments, but may also be an electrophotographic image forming apparatus equipped with an electrophotographic image forming engine as an image forming means, or may be one that uses another method (for example, offset printing).

[0011] (Schematic configuration of inkjet recording device) 1 is a schematic diagram showing an example of the general configuration of an inkjet recording apparatus 1 as an image forming apparatus according to the present embodiment. This inkjet recording apparatus 1 is a sheet-fed inkjet recording apparatus that produces a recorded matter by forming an ink image on a sheet S using two liquids, a reaction liquid and ink. The sheet S, which is the recording material (recording medium), can be a variety of sheet materials of different sizes and materials, including paper such as plain paper and cardboard, surface-treated sheet materials such as coated paper, specially shaped sheet materials such as envelopes and index paper, plastic film, cloth, etc.

[0012] 1, the inkjet recording apparatus 1 of this embodiment includes a feeding module 100, a printing module 200, a drying module 300, a fixing module 400, and a cooling module 500. The inkjet recording apparatus 1 of this embodiment also includes a reversing module 600 and a stacking module 700. A cut sheet S supplied from the feeding module 100 is transported along a transport path, processed in each module, and stacked in the stacking module 700.

[0013] The feeding module 100 includes three storage cabinets 212Ra, 212Rb, and 212Rc, each storing a sheet S. The storage cabinets 212Ra to 212Rc can be pulled out toward the front of the apparatus relative to the housing of the feeding module 100. The feeding module 100 feeds the sheets S stored in each of the storage cabinets 212Ra to 212Rc one by one using a separation belt and a conveyance roller, and conveys the sheets to the print module 200. The number of storage cabinets 212Ra to 212Rc is not limited to three, and may be one, two, four or more.

[0014] FIG. 2 is a plan view showing a sheet conveying section 200A of the print module 200. As shown in FIG. 2, the print module 200 includes a plurality of conveying roller pairs 208 and 209, a registration unit (hereinafter referred to as a registration unit 210), a print belt unit 220, and a recording section 230. Hereinafter, registration may be abbreviated to "registration." The sheet S conveyed from the feeding module 100 is conveyed to the print belt unit 220 after the registration unit 210 corrects any positional deviation of the sheet S. The recording section 230 is disposed opposite the print belt unit 220 across the conveyance path. The plurality of conveying roller pairs 208 and 209 and the registration unit 210 constitute the sheet conveying section 200A that conveys the sheet S to the recording section 230.

[0015] The registration unit 210 is an example of a sheet conveying device that conveys the sheet S. The print module 200 or the inkjet recording device 1 is an example of an image forming device (image forming system) that includes the registration unit 210 (sheet conveying device) and a recording unit 230 as an image forming means.

[0016] In this embodiment, the "positional deviation" of the sheet S includes both the positional deviation of the sheet S in the sheet width direction (hereinafter referred to as "lateral deviation") and the positional deviation of the sheet S in the rotational direction when viewed in the thickness direction of the sheet S (hereinafter referred to as "skew"). Correcting the skew of the sheet S is called skew correction. Correcting the lateral deviation of the sheet S and aligning it to a desired position in the sheet width direction is called lateral registration. As will be described later, the registration unit 210 of this embodiment performs a correction operation to simultaneously correct both the skew and lateral deviation of the sheet S. This correction operation may be performed multiple times for one sheet S. Note that the registration unit 210 may also correct only either the lateral deviation or the skew.

[0017] The print belt unit 220 includes a breathable print belt 25 stretched over multiple rollers and a pump unit that generates negative pressure in the space inside the print belt 25. The recording section 230 is a sheet processing section (image forming section) that performs recording (printing) on ​​the conveyed sheet S from above using a recording head 230H to form an image on the sheet S. The sheet S is conveyed while being attracted to the print belt 25 by the print belt unit 220, thereby ensuring clearance between the recording head 230H and the sheet S. A plurality of recording heads 230H are arranged along the conveyance direction. In this embodiment, in addition to the four colors of Y (yellow), M (magenta), C (cyan), and Bk (black), a total of five line-type recording heads corresponding to the reaction liquids are provided.

[0018] The number of colors and recording heads is not limited to five. The inkjet method can employ a method using a heating element, a piezoelectric element, an electrostatic element, a MEMS (microelectromechanical system) element, or the like. Each color of ink is supplied to the recording head 230H from an ink tank via an ink tube. The sheet S on which an image is formed by the recording unit 230 is transported by the print belt unit 220, and an in-line scanner located downstream of the recording unit in the transport direction detects misalignment and color density of the image formed on the sheet S, allowing the printed image to be corrected.

[0019] The drying module 300 includes a decoupling section 320, a drying belt unit 330, and a hot air blowing section 340. The drying module 300 reduces the liquid content of the ink applied to the sheet S by the recording section 230, thereby improving the fixation of the ink to the sheet S. The sheet S on which an image has been formed by the recording section 230 of the print module 200 is transported to the decoupling section 320 located within the drying module 300. The decoupling section 320 transports the sheet S using air pressure from above and belt friction, and by loosely holding and transporting the sheet S on the belt, it prevents the sheet S from shifting on the print belt unit 220 where the ink image is formed. The sheet S transported from the decoupling section 320 is adsorbed and transported by the drying belt unit 330, and at the same time, hot air is blown from the hot air blowing section 340 located above the belt to dry the ink-applied surface of the sheet S. In addition to the method of applying hot air, the drying method may be a combination of a method of irradiating the surface of the sheet S with electromagnetic waves (ultraviolet rays, infrared rays, etc.) or a conductive heat transfer method using contact with a heating element.

[0020] The fixing module 400 has a fixing belt unit 410 equipped with an upper belt unit and a lower belt unit. The fixing module 400 fixes the ink onto the sheet S by passing the sheet S conveyed from the drying module 300 between the heated upper belt unit and lower belt unit.

[0021] The cooling module 500 has multiple cooling units 510 and cools the high-temperature sheet S transported from the fixing module 400. The cooling units 510 use a fan to draw in outside air into the cooling box, increasing the pressure inside the cooling box, and then blow air from nozzles formed in the transport guide onto the sheet S, thereby cooling the sheet S. The cooling units 510 are arranged on both sides of the transport path, allowing the sheet S to be cooled from both sides. A transport path switching unit is also arranged within the cooling module 500. The transport path switching unit switches the transport path of the sheet S between a path for transporting the sheet S to the inversion module 600 and a double-sided transport path used during double-sided printing. During double-sided printing, the sheet S with an image formed on its first side is transported to the transport path below the cooling module 500 and then transported through each of the double-sided transport paths of the fixing module 400, the drying module 300, the print module 200, and the feeding module 100. Then, the sheet S is conveyed again to the registration unit 210, print belt unit 220 and recording section 230 of the print module 200, where an image is formed on the second side opposite to the first side.

[0022] The double-sided conveying section of the fixing module 400 is provided with a first reversing section 420 that reverses the front and back of the sheet S. The reversing module 600 also has a second reversing section that can reverse the front and back of the sheet S being conveyed, and can freely change the front and back orientation of the sheet S being discharged.

[0023] The stacking module 700 has a top tray 720 and a stacking section 750, and stacks the sheets S conveyed from the reversing module 600 while aligning them.

[0024] (Register unit) Next, the outline of the registration unit 210 will be described with reference to Figures 2, 3 and 6. Figure 3 is a perspective view showing the registration unit 210. Figure 6 is a cross-sectional view of the registration unit 210 in a plane perpendicular to the sheet width direction.

[0025] In the following description and drawings, the conveying direction of the sheet S in the registration unit 210 is referred to as the sheet conveying direction, and is represented by an arrow (X) in the drawings. The sheet width direction perpendicular to the sheet conveying direction is represented by an arrow (Z) in the drawings. With respect to the sheet width direction (Z), the left side (the tip side of the arrow (Z), the +Z side) when viewed toward the sheet conveying direction (X) is represented as the "left," and the right side (the opposite side of the arrow (Z), the -Z side) is represented as the "right." Furthermore, the direction perpendicular to both the sheet conveying direction (X) and the sheet width direction (Z) is represented by an arrow (Y) in the drawings (see FIG. 3).

[0026] In the registration unit 210, the pair of registration rollers (240L, 240R) may be used to skew the sheet S in order to correct the sheet position in the sheet width direction. The "sheet conveying direction (X)" is a fixed direction regardless of whether the sheet S is skewed or not. Specifically, the sheet conveying direction (X) in this embodiment is parallel to the conveying direction of the sheet S by conveying members that convey the sheet S without skew on the upstream and downstream sides of the pair of registration rollers (240L, 240R). An example of a conveying member on the upstream side of the pair of registration rollers (240L, 240R) is the below-described pair of conveying rollers (208, 209), and an example of a conveying member on the downstream side is the below-described print belt 25.

[0027] 2, 3, and 6, the registration unit 210 includes conveyance roller pairs 208 and 209, registration rollers 212L and 212R, caster rollers 252L and 252R, conveyance drive motors M1L and M1R, and steering motors M2L and M2R. The registration unit 210 also includes image sensors SN1L and SN1R, registration sensors SN2L and SN2R, and home position sensors SN3L and SN3R.

[0028] The registration rollers 212L, 212R are both examples of drive rollers that rotate by receiving a driving force. The caster rollers 252L, 252R are both examples of driven rollers that sandwich and transport a sheet together with the drive roller. If the registration roller 212L and caster roller 252L on one side in the sheet width direction (Z) are referred to as the first drive roller and first driven roller, the registration roller 212R and caster roller 252R on the other side can be referred to as the second drive roller and second driven roller.

[0029] The registration rollers 212L, 212R, caster rollers 252L, 252R, transport drive motors M1L, M1R, and steering motors M2L, M2R are arranged on the left and right sides, respectively. Similarly, the image sensors SN1L, SN1R, pre-registration sensors 131, 132, registration sensors SN2L, SN2R, second registration sensors 122, 123, and home position sensors SN3L, SN3R are arranged on the left and right sides, respectively.

[0030] In the sheet conveying direction (X), a conveying roller pair 209 is disposed downstream of the conveying roller pair 208, a registration roller pair 240L, 240R is disposed downstream of the conveying roller pair 209, and a print belt unit 220 is disposed downstream of the registration roller pair. Each of the conveying roller pairs 208, 209 is formed by an upper roller, which is a rubber roller made of, for example, EPDM (ethylene propylene diene rubber), and a lower roller made of, for example, urethane that abuts against the upper roller. The upper rollers are rotated by motors. More specifically, the left registration roller 212L is rotated by a left conveying drive motor M1L, and the right registration roller 212R is rotated by a right conveying drive motor M1R. The lower rollers (caster rollers 252L, 252R) are biased toward the upper rollers by springs and rotate following the upper rollers.

[0031] The registration rollers 212L, 212R and the caster rollers 252L, 252R form a registration roller pair 240L, 240R that sandwich and transport the sheet S. In this embodiment, the left registration roller 212L and the left caster roller 252L form a left registration roller pair 240L, and the right registration roller 212R and the right caster roller 252R form a right registration roller pair 240R.

[0032] Furthermore, the steering angle of the left registration roller 212L is changed by the left steering motor M2L. The steering angle of the right registration roller 212R is changed by the right steering motor M2R. By changing the steering angles of the registration rollers 212L and 212R, a component in the sheet width direction (Z) is generated in the conveying force applied to the sheet S by the registration rollers 212L and 212R, so that the sheet S can be conveyed (skewed) obliquely with respect to the sheet conveying direction (X).

[0033] The steering angle of the registration rollers 212L, 212R is the inclination angle of the rotation axis of the roller with respect to the sheet width direction (Z) when viewed in the Y direction, which is perpendicular to both the sheet conveyance direction (X) and the sheet width direction (Z). The steering angle can also be referred to as the angle between the sheet conveyance direction (X) and the direction of movement of the roller surface at the contact point with the sheet S, or the inclination angle of the vector of the force (conveyance force) applied to the sheet S by the registration rollers 212L, 212R with respect to the sheet conveyance direction (X). In the following description, the "pivot" of the roller refers to the movement in which the steering angle of the roller changes as the rotation axis of the roller rotates around an axis that intersects both the sheet width direction (Z) and the sheet conveyance direction (X). The above "intersecting axis" is, for example, an axis parallel to the Y direction, but it does not necessarily have to be parallel to the Y direction.

[0034] The left caster roller 252L is a driven roller that rotates following the left registration roller 212L. The right caster roller 252R is a driven roller that rotates following the right registration roller 212R. The caster roller 252L can rotate following the rotation of the registration roller 212L. The caster roller 252R can rotate following the rotation of the registration roller 212R. In other words, the caster rollers 252L, 252R (driven rollers) are configured to rotate around a rotation axis that intersects with both the sheet conveyance direction and the sheet width direction, following changes in the inclination angle of the registration rollers 212L, 212R (drive rollers). In this embodiment, the rotation axis is parallel to the Y direction.

[0035] The home position sensors SN3L and SN3R are disposed near the registration rollers 212L and 212R. The home positions of the registration rollers 212L and 212R are detected by the home position sensors SN3L and SN3R, respectively. The home positions of the registration rollers 212L and 212R are positions where the inclination of the rotation axis of the rollers is parallel to the sheet width direction (Z), that is, where the steering angle is 0 degrees. The registration rollers 212L and 212R are configured so that they can be returned to their home positions when the home positions are detected by the home position sensors SN3L and SN3R.

[0036] (Drive turning mechanism) Next, the drive turning mechanisms 211L and 211R provided in the registration unit 210 will be described with reference to Figures 2 and 3. The drive turning mechanisms 211L and 211R rotate and turn the registration rollers 212L and 212R, respectively. As shown in Figures 2 and 3, the drive turning mechanism 211L has a conveyance drive motor M1L, a steering motor M2L, a motor gear 213L, a drive input gear 214L, a steering shaft 215L, and a frame 216L. Similarly, the drive turning mechanism 211R has a conveyance drive motor M1R, a steering motor M2R, a motor gear 213R, a drive input gear 214R, a steering shaft 215R, and a frame 216R.

[0037] The left frame 216L is fixed to the steering shaft 215L and supports the registration roller 212L and the conveyor drive motor M1L. Similarly, the right frame 216R is fixed to the steering shaft 215R and supports the registration roller 212R and the conveyor drive motor M1R. Fan-shaped drive input gears 214L and 214R are attached to the steering shafts 215L and 215R, respectively, and motor gears 213L and 213R of the steering motors M2L and M2R are in mesh with the drive input gears 214L and 214R, respectively.

[0038] Therefore, the rotation of the steering motors M2L, M2R causes the left and right registration rollers 212L, 212R to rotate integrally with the frames 216L, 216R, respectively, changing the steering angles of the registration rollers 212L, 212R (see FIGS. 4(a) and 4(b)). Note that, because the conveyance drive motors M1L, M1R are also supported by the frames 216L, 216R, they rotate around the steering shafts 215L, 215R together with the corresponding registration rollers 212L, 212R.

[0039] By configuring the drive turning mechanisms 211L and 211R in this way, the registration rollers 212L and 212R can change the conveying speed of the sheet S independently of each other, and can also change the conveying direction of the sheet S independently of each other.

[0040] The steering motor M2L is an example of a steering means (first steering means) that changes the inclination (steering angle) of the rotation axis of the registration roller 212L with respect to the sheet width direction (Z). The steering motor M2R is an example of a steering means (second steering means) that changes the inclination (steering angle) of the rotation axis of the registration roller 212R with respect to the sheet width direction (Z).

[0041] (Skew detection unit) A set of two or more sensors arranged at different positions in the sheet width direction (Z) can function as a skew detection unit for detecting the amount of skew of the sheet S. The "amount of skew" corresponds to the angle of inclination of the leading edge of the sheet S (the downstream end in the sheet conveying direction) relative to the sheet width direction (Z).

[0042] The pair of left and right registration sensors SN2L and SN2R is a skew detection unit that detects skew, which is a positional deviation in the rotational direction of the sheet S. The skew detection unit can also be said to be a posture detection unit that detects the posture of the sheet S. The posture of the sheet S is the angle of inclination of the leading edge of the sheet S relative to the sheet width direction (Z).

[0043] A controller 50 (see FIG. 7), which will be described later, calculates the amount of skew of the sheet S at the positions of the registration sensors SN2L and SN2R based on the time difference between the detection of the leading edge of the sheet by the left and right registration sensors SN2L and SN2R and the conveying speed of the sheet S. Note that instead of a set of two or more sensors, for example, an image sensor that captures an image may be used to analyze the image and detect the skew of the sheet S.

[0044] (Lateral deviation detection unit) The pair of image sensors SN1L and SN1R is an example of a detection means for detecting positional misalignment of the sheet S. In this embodiment, the pair of image sensors SN1L and SN1R is a lateral misalignment detection unit that detects lateral misalignment, which is positional misalignment of the sheet S in the sheet width direction (Z).

[0045] The image sensors SN1L and SN1R are disposed near the pair of registration rollers 240L and 240R. More specifically, in the sheet conveying direction X, the image sensor SN1L is disposed upstream of the pair of registration rollers 240L, and the image sensor SN1R is disposed downstream of the pair of registration rollers 240R.

[0046] The image sensors SN1L and SN1R are optical sensors (line sensors) such as CIS sensors that have an imaging area extending in the sheet width direction (Z). The left image sensor SN1L detects the position of the left edge of the sheet S, and the right image sensor SN1R detects the position of the right edge of the sheet S. The image sensors SN1L and SN1R are arranged so that they can detect the side edges of the largest and smallest size sheets on which the inkjet recording apparatus 1 can form an image. The controller 50 can calculate the amount of lateral deviation based on the detection results of the side edge positions by the left and right image sensors SN1L and SN1R.

[0047] Instead of the two image sensors SN1L and SN1R, a single image sensor that covers the area in the sheet width direction (Z) through which the largest size sheet S passes (maximum paper passing area) may be used. Also, only one of the left and right image sensors SN1L and SN1R may be used to detect the amount of lateral deviation and correct the lateral deviation based on the detection result of the side edge position on one side.

[0048] (controller) 7 is a block diagram showing a configuration related to control of the registration unit 210. The operation of the registration unit 210 is controlled by a controller 50 serving as a control means. The controller 50 is connected to a ROM 51 and a RAM 52 serving as storage units. The controller 50 controls the operation of the registration unit 210 by reading a program stored in the ROM 51 based on an instruction from, for example, an external computer 201, and executing the program while using the RAM 52 as a work memory. The controller 50 may be a control unit that oversees the operation of the entire print module 200. Note that some or all of the functions of the controller 50 described below may be executed by another control unit provided in the inkjet recording apparatus 1.

[0049] The controller 50 receives detection signals from the image sensors SN1L and SN1R, the registration sensors SN2L and SN2R, and the home position sensors SN3L and SN3R. The controller 50 also issues instructions to the feed motor 54, the steering motors M2L and M2R, the conveyance drive motors M1L and M1R, and the separation motor M4 (described later) to control the start / stop, rotation amount, angular velocity, etc. of each motor. The feed motor 54 is a drive source for the separation belt, etc. in the feed module 100.

[0050] The controller 50 is also communicably connected to an operation unit 202, which is a user interface of the inkjet recording apparatus 1. The operation unit 202 includes a display unit such as a liquid crystal panel that displays information to the user by means of images, and an input unit such as buttons and a touch panel function of the liquid crystal panel that accepts input from the user.

[0051] As will be described below, the controller 50 executes a correction operation to correct the positional deviation of the sheet S based on the detection results of the skew detection unit and the lateral deviation detection unit. The controller 50 performs the lateral deviation correction of the sheet S by controlling the rotation amount of the steering motors M2L and M2R mainly based on the detection results of the image sensors SN1L and SN1R. The controller 50 also performs the skew correction of the sheet S by controlling the angular velocities of the left and right conveyance drive motors M1L and M1R mainly based on the detection results of the registration sensors SN2L and SN2R.

[0052] The controller 50 also uses a separation motor M4 as a drive source to bring the left and right caster rollers 252L, 252R into contact with and separate from the registration rollers 212L, 212R. The controller 50 also detects the home positions of the left and right registration rollers 212L, 212R based on the detection results of the left and right home position sensors SN3L, SN3R.

[0053] (Print module operation) The operation of the print module 200, including skew correction and lateral misalignment correction by the registration unit 210, will be described with reference to Figures 4(a) to 5(c) and 8. Figures 4(a) to 5(c) are explanatory diagrams relating to the operation of the registration rollers 212L and 212R. Figure 8 is a flowchart describing the control of the print module 200, focusing particularly on the operation of the registration unit 210.

[0054] The flowchart shown in FIG. 8 will be described taking as an example the procedure of a print job (single-sided print job) in which an image is formed only on one side (first side) of a sheet S. An image forming operation is a series of operations in which the inkjet recording apparatus 1, which serves as an image forming apparatus, forms an image on a sheet S while transporting the sheet S. A print job is a series of tasks including an image forming operation on at least one sheet S. Each step of the flowchart is executed by the controller 50. Note that in a print job in which images are formed on both sides (first side and second side) of a sheet S (double-sided print job), the control shown in FIG. 7 is performed twice.

[0055] 7, in step S1, when the controller 50 receives an instruction to execute an image forming operation (print job), it starts a single-sided print job. The controller 50 receives the print job when the user operates the operation unit 202 (for example, by pressing the print execution button) or from an external computer 201 to which the controller 50 is connected directly or via a network. The print job received by the controller 50 includes setting information (job information) such as the number of copies to be printed and the size of the sheets S to be used for printing, which are specified by the user. The controller 50 analyzes the received print job and executes the image forming operation in accordance with the job information.

[0056] During the execution of a print job in which images are successively formed on a plurality of sheets S, the following steps S2 to S13 are executed in parallel with a time lag for each sheet S. In the following explanation, a series of processes (S2 to S17) for one sheet S (the current sheet) in the print job will be explained. A sheet S fed after the current sheet in the print job is called a subsequent sheet. In particular, the sheet S fed after the current sheet in the print job may be called the next sheet.

[0057] Next, the controller 50 selects a sheet S of a size specified by the print job from, for example, one of the storages 110a, 110b, or 110c. Then, the controller 50 rotates the feed motor 54 to feed the sheet S of the size specified in the job information from the feed module 100. Next, the controller drives the drive motor and the like to convey the sheet S toward the registration unit 210 using the conveyance roller pair 208, 209 (see FIG. 2), and causes the sheet S to reach the registration roller pair 240L, 240R (S2). The controller 50 can detect that the sheet S has reached the registration rollers 212L, 212R, for example, based on detection of the leading edge of the sheet by the registration sensors SN2L, SN2R.

[0058] In step S3, the controller 50 acquires the skew amount ΔX of the sheet S based on the detection results of the registration sensors SN2L and SN2R. Specifically, the controller 50 calculates the skew amount ΔX of the sheet S based on the time difference between the timings at which the left and right registration sensors SN2L and SN2R detect the leading edge of the sheet S and the sheet conveying speed of the conveying roller pairs 208 and 209.

[0059] In step S4, the controller 50 creates skew correction profiles for the conveyance drive motors M1L, M1R and the steering motors M2L, M2R based on the skew amount ΔX acquired in step S3. Then, in S5, the controller 50 executes skew correction by controlling the operation of the conveyance drive motors M1L, M1R and the steering motors M2L, M2R in accordance with the skew correction profile created in S4. The series of operations from steps S3 to S5 is sometimes referred to as active operation.

[0060] Specifically, the transport drive motors M1L and M1R are driven according to the skew correction profile based on instructions from the controller 50, thereby independently controlling the rotational speeds of the registration roller pairs 240L and 240R. For example, in the states shown in FIGS. 4A and 5A, the transport drive motors M1L and M1R are controlled so that the sheet transport speeds of the registration roller pairs 240L and 240R are VL and VR, respectively. As shown in FIG. 5B, the skew angle (skew amount ΔX) of the skewed sheet S is detected, a skew correction profile is created, and the transport drive motors M1L and M1R are independently controlled according to the skew correction profile. The controller 50 then controls the transport speed VR of the registration roller pair 240R to be greater than the transport speed VL of the registration roller pair 240L. As a result, the sheet S is rotated as indicated by the arrow ω in FIG. 5B, and the skew of the sheet S is corrected as indicated by the dashed line in the figure. In other words, the controller 50 corrects the skew of the sheet S by controlling the difference in conveying speed between the registration rollers 212L and 212R.

[0061] Next, in step S6, the controller 50 acquires the lateral deviation amount ΔZ of the sheet S based on the detection results of the image sensors SN1L and SN1R. The controller 50 detects the positions of both ends of the sheet S in the sheet width direction Z by detecting how much of the image sensors SN1L and SN1R are covered by the sheet S, and calculates the lateral deviation amount ΔZ from the positions of both ends. In step S7, the controller 50 creates a lateral registration correction profile for the conveying drive motors M1L and M1R and the steering motors M2L and M2R based on the lateral deviation amount ΔZ acquired in step S6. Then, in step S8, the controller 50 performs lateral registration correction by controlling the operation of the conveying drive motors M1L and M1R and the steering motors M2L and M2R in accordance with the lateral registration correction profile created in step S7. The series of operations from step S6 to S8 is sometimes referred to as active registration.

[0062] Specifically, the steering motors M2L and M2R are driven in accordance with a lateral registration correction profile based on instructions from the controller 50, whereby the rotation angles of the registration roller pairs 240L and 240R are independently controlled. For example, in the states shown in Figures 4(a) and 5(a), the steering motors M2L and M2R control the steering angles of the registration rollers 212L and 212R so that they are positioned as detected by the home position sensors SN3L and SN3R. Therefore, the registration roller pairs 240L and 240R are positioned so as to face straight in the sheet conveying direction V.

[0063] As shown in FIG. 5(c), the lateral registration position of the sheet S that has been conveyed with a lateral deviation is detected, a lateral registration correction profile is created, and the steering motors M2L and M2R are independently driven and controlled in accordance with the lateral registration correction profile. The pair of registration rollers 240L and 240R are then rotated, and the pair of registration rollers 240L conveys the sheet S in the direction of the rotation at a conveying speed VL, while the pair of registration rollers 240R conveys the sheet S in the direction of the rotation at a conveying speed VR. As a result, the sheet S is conveyed while moving in the sheet width direction W as indicated by the arrow VB in FIG. 5(c), and the lateral registration position of the sheet S is corrected to a reference position (a position that coincides with the conveying center) as indicated by the dashed line in the figure. During this lateral registration correction, when skew correction is not performed, the conveying speeds VL and VR of the pair of registration rollers 240L and 240R are controlled to be the same, and the rotation angles of the pair of registration rollers 240L and 240R are controlled to be the same.

[0064] In step S9, the sheet S is transferred from the registration rollers 212L and 212R to the print belt 25. In step S10, the controller 50 separates the caster rollers 252L and 252R from the registration rollers 212L and 212R using a separation mechanism 270, which will be described in detail later. That is, the controller 50 changes the registration rollers 240L and 240R from a contact state to a separation state after the leading edge of the sheet S reaches the print belt 25, which is a conveying member downstream of the registration rollers 240L and 240R. In this embodiment, the controller 50 changes the registration rollers 240L and 240R from a contact state to a separation state before the trailing edge of the sheet S passes through the registration rollers 240L and 240R.

[0065] In step S11, the controller 50 starts the recording process by the recording unit 230. Note that the separation of the caster rollers 252L and 252R (S10) may occur after the start of the recording process (S11). Next, in step S12, after the trailing edge of the sheet S passes through the nip (registration nip) of the pair of registration rollers 240L and 240R, the controller 50 causes the caster rollers 252R and 252L to abut against the registration rollers 212R and 212L, respectively, using the separation mechanism 270, which will be described in detail later. Then, in step S13, the controller 50 ejects the sheet S on which the image has been formed onto the stacking unit 750 of the stacking module 700, thereby completing the print job.

[0066] In the case of an image forming operation (double-sided printing) in which images are formed on both sides of the sheet S, the controller 50, after S11, causes the sheet S with the image formed on the first side to be conveyed to the double-sided conveying path. The controller 50 then inverts the sheet S at the inverting section 420 and conveys it again toward the registration unit 210. Thereafter, the controller 50 executes the processes from step S2 onwards on the inverted sheet S, thereby forming an image on the second side of the sheet S.

[0067] In the above explanation, skew correction and lateral deviation correction are described separately, but the registration unit 210 can simultaneously perform skew correction and lateral deviation correction using the registration roller pair 240L, 240R. That is, the controller 50 can simultaneously perform control to correct skew of the sheet S mainly by controlling the speed difference between the registration roller pair 240L, 240R (active registration), and control to correct lateral deviation of the sheet S mainly by controlling the tilt angle of the registration roller pair 240L, 240R (steering operation). Note that correcting skew and lateral deviation "simultaneously" means that the period during which the sheet S is turned for skew correction and the period during which the sheet S is moved in the sheet width direction for lateral deviation correction at least partially overlap.

[0068] (Caster roller configuration) Next, the configuration of the caster rollers 252L, 252R will be described using Figures 9 and 10. Figure 9 is a front view showing the pair of registration rollers 240R, 240L. Figure 10(a) is a diagram showing the state immediately after the registration roller 212R has turned, and Figure 10(b) is a diagram showing the restoring force RF generated in the caster roller 252R due to the turning of the registration roller 212R. Figure 10(c) is a diagram showing the state after the caster roller 252R has turned.

[0069] As shown in FIG. 9, the registration unit 210 (see FIG. 2) has caster roller units 251L and 251R. The caster roller unit 251R has a holding portion 256R as a second holding portion including a swivel rotation shaft 255R and a frame 253R fixed to the tip of the swivel rotation shaft 255R. The swivel rotation shaft 255R as the second shaft portion is supported by a swing member 271 (see FIG. 11), which will be described later, to be rotatable about the center line (second pivot axis) of the swivel rotation shaft 255R. The caster roller unit 251R also has a roller shaft 254R rotatably supported by the frame 253R, and a caster roller 252R fixed to the roller shaft 254R.

[0070] Similarly, the caster roller unit 251L has a holding portion 256L as a first holding portion including a swivel shaft 255L and a frame 253L fixed to the tip of the swivel shaft 255L. The swivel shaft 255L as a first shaft portion is supported by a swing member 271 (see FIG. 11) described below so as to be rotatable about the center line (first pivot axis) of the swivel shaft 255L. The caster roller unit 251L also has a roller shaft 254L rotatably supported by the frame 253L, and a caster roller 252L fixed to the roller shaft 254L.

[0071] In the present embodiment, the caster rollers 252L, 252R are fixed to the rotatable roller shafts 254L, 254R, respectively, but this is not limiting. For example, the roller shafts 254L, 254R may be fixed to the frames 253L, 253R, respectively, and the caster rollers 252L, 252R may be supported rotatably with respect to the roller shafts 254L, 254R.

[0072] Since the caster roller units 251L and 251R have the same configuration, only the caster roller unit 251R will be described below. As described above, the caster roller 252R is configured to be able to turn (rotate) about the swivel rotation shaft 255R via the frame 253R and the roller shaft 254R. The swivel rotation shaft 255R is disposed upstream of the nip portion between the registration roller 212R and the caster roller 252R by a distance X1 in the sheet conveying direction X. This distance X1 is referred to as the caster rail.

[0073] Next, the pivoting operation of the caster roller 252R will be described in detail. The caster roller 252R is urged toward the registration roller 212R by a spring 273R of a separation mechanism 270, which will be described in detail later. When the registration roller 212R is driven by the conveyance drive motor M1R, the caster roller 252R receives a frictional force at the nip portion with the registration roller 212R and rotates in accordance with the registration roller 212R. At this time, as shown in FIG. 9(a), the caster roller 252R receives a force F from the registration roller 212R in the direction indicated by the arrow.

[0074] As described above, the pivot shaft 255R of the caster roller unit 251R is disposed upstream in the sheet conveying direction X from the nip portion of the registration roller pair 240R by a distance X1. Therefore, when the registration roller 212R starts the steering operation (lateral deviation correction operation), a force F acts on the caster roller 252R as shown in FIG. 10(a). That is, the force F acts in a direction inclined with respect to the angle of the caster roller 252R.

[0075] Then, as shown in FIG. 10(b), a moment indicated by arrow Y is generated around the pivot shaft 255R in the caster roller 252R, and a restoring force RF is generated so that the caster roller 252R is at the same angle as the registration roller 212R. This moment indicated by arrow Y increases or decreases depending on the deviation between the orientation of the caster roller 252R around the pivot shaft 255R (the sheet conveying direction X in FIG. 10(b)) and the vector direction of the force F, and decreases as the deviation decreases. Therefore, when the vector direction of the force F and the orientation of the caster roller 252R coincide, the moment indicated by arrow Y becomes zero. Due to this mechanism, the caster roller 252R pivots in accordance with the registration roller 212R, as shown in FIG. 10(c), and the registration roller 212R and the caster roller 252R are aligned.

[0076] As described above, in this embodiment, in a configuration in which the registration roller 212R is rotated by the driving force of the steering motor M2R, a caster rail (distance X1) is provided between the rotation shaft 255R of the registration roller 212R and the nip portion of the registration roller pair 240R. This causes the caster roller 252R to rotate automatically following the steering operation of the registration roller 212R, and the rotation angles of the registration roller 212R and the caster roller 252R become the same. Note that the distance X1 of the caster rail may be set arbitrarily.

[0077] (separation mechanism) Next, the spacing mechanism 270 will be described with reference to Figures 11 to 13. Figure 11 is a perspective view showing the spacing mechanism 270. Figure 12 is a side view showing the spacing mechanism 270. Figure 13 is a front view showing the spacing mechanism 270. Note that Figures 11 to 13 only show the side of the conveyance path for the sheet S where the caster rollers 252L and 252R are located, and omit the side where the registration rollers 212L and 212R are located and the guides that form the conveyance path.

[0078] 11 to 13, the spacing mechanism 270 includes frames 290 and 291 fixed to support members (not shown) provided inside the print module 200, a support frame 292 connecting the frames 290 and 291, and a drive unit 280. The frames 290 and 291 each have side surfaces 290a and 291a extending upward. The spacing mechanism 270 also includes a swing shaft 272 fixed to the side surfaces 290a and 291a and extending in the sheet width direction Z, and a swing member 271 supported by the swing shaft 272. The center line of the swing shaft 272 is shown as a swing axis AX2, which serves as a second swing axis, in FIG. 11.

[0079] A swing support member 274 is attached to the swing member 271, and the swing member 271 is swingably supported with respect to the swing shaft 272 via the swing support member 274. That is, the swing member 271 is provided swingably in the Z1 direction and the Z2 direction opposite to the Z1 direction, centered on a swing axis AX2, which is the center line of the swing shaft 272 extending in the seat width direction Z.

[0080] Furthermore, the swinging member 271 has side walls 271L and 271R provided at both ends in the sheet width direction Z and extending upward. Support holes 271La and 271Ra are provided in the side walls 271L and 271R, respectively. A swinging shaft 272 passes through the support holes 271La and 271Ra, and a gap is provided between at least the swinging shaft 272 and the support holes 271La and 271Ra in the Y direction (up-down direction, vertical direction, gravity direction). For example, the inner diameter of the support holes 271La and 271Ra is approximately equal to the outer diameter of the swinging shaft 272 in the sheet conveying direction X and is larger than the outer diameter of the swinging shaft 272 in the Y direction.

[0081] The swing support member 274 is configured to be thin in the sheet width direction Z. As described above, a gap is provided in the Y direction between the swing shaft 272 and the support holes 271La, 271Ra. Therefore, the swing member 271 is configured to be swingable about a swing axis AX1 as a first swing axis that passes through the swing support member 274 and extends in the sheet conveying direction X. In other words, the swing member 271 is provided to be swingable in the Z3 direction and the Z4 direction opposite to the Z3 direction about the swing axis AX1.

[0082] The pivoting shafts 255L and 255R are pivotally (rotatably) supported on the pivoting member 271. Therefore, the caster rollers 252L and 252R, which can pivot about the pivoting shafts 255L and 255R, move in conjunction with the pivoting member 271. In other words, the caster rollers 252L and 252R can pivot in the Z1 and Z2 directions about the pivoting shaft 272 extending in the sheet width direction Z, and can also pivot in the Z3 and Z4 directions about the pivoting axis AX1 extending in the sheet conveying direction X.

[0083] In the following description, the swing member 271 will be described by referring to one end 271A as the downstream side in the sheet conveying direction X and the other end 271B as the upstream side across the swing shaft 272. Therefore, when the swing member 271 swings around the swing shaft 272, the one end 271A and the other end 271B move in opposite directions in the Y direction.

[0084] Furthermore, the caster rollers 252L, 252R are both disposed upstream in the sheet conveying direction X with respect to the swing shaft 272, i.e., on the other end 271B side. Therefore, when the swing member 271 swings around the swing shaft 272, the caster rollers 252L, 252R swing in the same direction in the up-down direction. On the other hand, the caster rollers 252L, 252R are disposed on opposite sides of the swing axis AX1 in the sheet width direction Z. Therefore, when the swing member 271 swings around the swing axis AX1, the caster rollers 252L, 252R swing in opposite directions in the up-down direction.

[0085] The other end 271B of the swinging member 271 is biased upward (in the Y direction) by springs 273L and 273R via a pressing portion 277. More specifically, one end of the springs 273L and 273R is fixed to a fixing member (not shown), and the other end is connected to the pressing portion 277. The biasing force of the springs 273L and 273R, which are, for example, compression springs, is transmitted to the other end 271B of the swinging member 271 via the pressing portion 277.

[0086] As a result, the caster rollers 252L, 252R are biased by the springs 273L, 273R toward the registration rollers 212L, 212R and come into contact with the registration rollers 212L, 212R with a predetermined nip pressure. At this time, the pair of registration rollers 240L, 240R are in contact with each other. The springs 273L, 273R are arranged on approximately the same line in the sheet width direction Z. In other words, the springs 273L, 273R are arranged so that at least a portion of each spring overlaps with each other when viewed in the sheet width direction Z. Furthermore, the springs 273L, 273R are arranged on opposite sides of the swing axis AX1 in the sheet width direction Z. Therefore, the springs 273L, 273R are balanced so that the pressing forces with which the caster rollers 252L, 252R press the registration rollers 212L, 212R are approximately equal.

[0087] The other end 271B of the swinging member 271 presses the caster rollers 252L, 252R via the swivel rotation shafts 255L, 255R and the frames 253L, 253R, but is configured not to interfere with the swivel movement of the caster rollers 252L, 252R around the swivel rotation shafts 255L, 255R.

[0088] Meanwhile, bent portions 271a, 271a that bend downward are provided at one end 271A of the swinging member 271. The bent portions 271a, 271a may be formed integrally with the swinging member 271, or may be provided separately from the swinging member 271 and fixed to the swinging member 271. A support shaft 286 is fixed to the bent portions 271a, 271a, and driven rollers 285, 285 are rotatably supported on both ends of the support shaft 286.

[0089] The drive unit 280 described above has a spacing motor M4, an output pulley 281, a belt 287, an input pulley 282, a rotating shaft 283, and cams 284, 284. The spacing motor M4 is attached to a support frame 292, and the output pulley 281 is fixed to the output shaft of the spacing motor M4. The rotating shaft 283 is rotatably supported by the support frame 292, and the input pulley 282 and the cams 284, 284 are fixed to the rotating shaft 283.

[0090] A belt 287 is wound around the output pulley 281 and the input pulley 282, and the rotation of the output pulley 281 is transmitted to the input pulley 282 via the belt 287. When the input pulley 282 rotates, a rotary shaft 283 rotates, and cams 284, 284 attached to the rotary shaft 283 rotate. The cams 284, 284 abut against driven rollers 285, 285 that swing integrally with one end 271A of the swinging member 271. In addition, the distance from the outer circumferential surfaces of the cams 284, 284 to the center of rotation is not constant. Therefore, when the cams 284, 284 rotate, one end 271A of the swinging member 271 moves in the Y direction (up and down direction) via the driven rollers 285, 285.

[0091] That is, when the separation motor M4 is driven to rotate the cams 284, 284, the swinging member 271 swings in the Z1 direction and the Z2 direction around the swing shaft 272. When the swinging member 271 swings in the Z2 direction around the swing shaft 272 against the biasing force of the springs 273L, 273R, the nip between the registration rollers 212L, 212R is released, and the caster rollers 252L, 252R are separated from the registration rollers 212L, 212R. At this time, the pair of registration rollers 240L, 240R is in a separated state. That is, the separation motor M4 in this embodiment is a common drive source (actuator) for switching the left and right pairs of registration rollers 240L, 240R between a contact state and a separated state. The mechanism for bringing the pair of registration rollers 240L and 240R into contact with and separating from each other is not limited to one that uses a motor and a cam, and the swinging member 271 may be moved by a solenoid, for example.

[0092] 8, after the registration unit 210 has performed skew correction and lateral deviation correction, the sheet S is further conveyed by the print belt unit 220. Here, after the sheet S is attracted to the print belt 25, the caster rollers 252L, 252R are separated from the registration rollers 212L, 212R by driving the separation motor M4. As a result, the sheet S is conveyed without receiving conveyance resistance from the registration rollers 212L, 212R, and therefore a high-precision image can be formed on the sheet S by the recording unit 230.

[0093] Furthermore, when the pair of registration rollers 240L, 240R are in contact with each other, the swinging member 271 is configured to be swingable about the swing axis AX1, so that the caster rollers 252L, 252R can be brought into contact with the registration rollers 212L, 212R in a well-balanced manner.

[0094] (Summary of this embodiment) As described above, the spacing mechanism 270 of this embodiment has a swinging member 271 that can swing about a swing axis AX1 extending along the sheet conveying direction X and a swing axis 272 extending along the sheet width direction Z. The swing axis AX1 and the swing axis AX2, which is the center line of the swing axis 272, are perpendicular to each other. The swinging member 271 swings about the swing axis 272 by the driving force of the spacing motor M4, so that the caster rollers 252L, 252R can be in an abutting state and a separated state.

[0095] Furthermore, when the caster rollers 252L, 252R are in contact with the registration rollers 212L, 212R, respectively, the swinging member 271 can swing about the swing axis AX1 in the Z3 and Z4 directions and supports the caster rollers 252L, 252R. The swing axis AX1 is located between the caster rollers 252L and 252R in the sheet width direction Z. Therefore, when the swinging member 271 swings about the swing axis AX1, the caster rollers 252L, 252R come into contact with the registration rollers 212L, 212R in a balanced manner. For example, even if the registration rollers 212L, 212R are misaligned in the Y direction due to assembly tolerances of the components, the swinging member 271 swings about the swing axis AX1, thereby reducing the difference in nip pressure between the registration roller pairs 240L, 240R. This improves the accuracy of the correction operation for correcting the positional deviation of the sheet, and can suppress sheet conveyance failure.

[0096] The separating mechanism 270 also has a spring 273L as a first biasing member and a spring 273R as a second biasing member. The spring 273L is disposed on one side of the swing axis AX1 in the sheet width direction Z and biases the swing member 271 toward the registration roller 212L. The spring 273R is disposed on the other side of the swing axis AX1 in the sheet width direction Z and biases the swing member 271 toward the registration roller 212R. Furthermore, the spring 273L is disposed so that at least a portion thereof overlaps the spring 273R when viewed in the sheet width direction Z. These springs 273L and 273R allow the caster rollers 252L and 252R to abut against the registration rollers 212L and 212R in a balanced manner.

[0097] The swing axis AX1 is preferably located at the center between the caster rollers 252L, 252R in the sheet width direction Z. However, even if the swing axis AX1 is shifted from the center, the springs 273L, 273R can bring the caster rollers 252L, 252R into contact with the registration rollers 212L, 212R in a balanced manner.

[0098] The springs 273L and 273R are disposed on the same side (upstream side) of the swing shaft 272 in the sheet conveying direction X. Therefore, the springs 273L and 273R also function as springs for bringing the caster rollers 252L and 252R into contact with each other.

[0099] Furthermore, the spacing mechanism 270 has cams 284, 284 arranged on the opposite side of the swing axis AX1 from the caster rollers 252L, 252R in the sheet conveying direction X. A drive unit 280 including the cams 284, 284 and spacing motor M4 is arranged on one end 271A side of the swing member 271, with the swing axis AX1 between them. Furthermore, the caster rollers 252L, 252R and springs 273L, 273R are arranged on the other end 271B side of the swing member 271, with the swing axis AX1 between them. By arranging them in this manner, the registration unit 210 can be made more compact.

[0100] Furthermore, the caster roller 252L can rotate around the center line of the pivot shaft 255L, but this center line is offset by a distance X1 (caster rail) from the nip portion of the registration roller pair 240L in the sheet conveying direction X. Similarly, the caster roller 252R can rotate around the center line of the pivot shaft 255R, but this center line is offset by a distance X1 from the nip portion of the registration roller pair 240R in the sheet conveying direction X. Therefore, the caster rollers 252L, 252R can rotate following the pivoting motion of the registration rollers 212L, 212R. Note that, although both the caster rollers 252L, 252R have the caster rail distance X1, the caster rails of the left and right caster rollers 252L, 252R do not necessarily have to be the same.

[0101] In this embodiment, the caster rollers 252L, 252R are configured to be rotatable about independent pivot axes. Meanwhile, the caster rollers 252L, 252R are supported by a single swinging member 271 via the pivot axis. This allows the swinging member 271 to swing about the swing axis 272, switching both of the two caster rollers 252L, 252R between abutting and swinging states, thereby reducing the size of the device and enabling the caster rollers 252L, 252R to be positioned with precision.

[0102] (Other embodiments) In this embodiment, the swing member 271 can swing about the swing axis AX1 and the swing shaft 272, but the swing axis AX1 does not necessarily have to be parallel to the sheet conveying direction X and may be offset within a range of ±15° from the sheet conveying direction X. Similarly, the swing shaft 272 does not necessarily have to be parallel to the sheet width direction Z and may be offset within a range of ±15° from the sheet width direction Z. In other words, it is sufficient that the swing axis AX1 extends along the sheet conveying direction X, and it is sufficient that the swing shaft 272 extends along the sheet width direction Z.

[0103] In the present embodiment, the caster rollers 252L and 252R are disposed upstream of the swing shaft 272 in the sheet conveying direction X, but this is not limiting. For example, the caster rollers 252L and 252R may be disposed downstream of the swing shaft 272 in the sheet conveying direction X. In addition, the springs 273L and 273R are disposed upstream of the swing shaft 272 in the sheet conveying direction X, but this is not limiting. For example, the springs 273L and 273R may be disposed downstream of the swing shaft 272 in the sheet conveying direction X.

[0104] In addition, in the present embodiment, the cams 284, 284 and the spacing motor M4 are disposed downstream of the swing shaft 272 in the sheet conveying direction X, but this is not limiting. For example, the cams 284, 284 and the spacing motor M4 may be disposed upstream of the swing shaft 272 in the sheet conveying direction X.

[0105] In addition, in the present embodiment, the springs 273L, 273R bias the caster rollers 252L, 252R to be in contact with each other, but this is not limiting. For example, the springs 273L, 273R may be configured to bias the caster rollers 252L, 252R to be in a spaced-apart state, and to be brought into contact with each other by the drive unit 280.

[0106] Furthermore, in the present embodiment, the springs 273L and 273R press the swing member 271 via the pressing portion 277, but this is not limiting. For example, the springs 273L and 273R may directly press the other end 271B of the swing member 271 without using the pressing portion 277.

[0107] In addition, in the present embodiment, the registration unit 210 that performs skew correction upstream of the recording unit 230 in the sheet conveying direction X has been described as an example, but the present invention is not limited to this. For example, the registration unit 210 may be disposed upstream in the sheet conveying direction X of a reading unit that reads an image on a sheet, a punching unit that punches holes in a sheet, a folding unit that folds a sheet, or the like.

[0108] In addition, in the present embodiment, the swinging member 271 is configured to be swingable around the swinging shaft 272, but the present invention is not limited to this. For example, the swinging member 271 may be configured to be slidable in the Y direction (up and down direction) so as to switch the caster rollers 252L, 252R between a contact state and a separated state.

[0109] Furthermore, in this embodiment, the cams 284 are used to oscillate the oscillating member 271 around the oscillating shaft 272, but this is not limiting. For example, a link mechanism or the like may be used to convert the rotation of the spacing motor M4 into reciprocating motion to move the oscillating member 271. Furthermore, the cams 284 press the oscillating member 271 via the driven rollers 285, but this is not limiting. For example, the cams 284 may press the oscillating member 271 directly. In this case, a coating that reduces sliding resistance may be applied to the contact position between the cam 284 and the oscillating member 271, or a member with low sliding resistance may be attached.

[0110] In addition, in the present embodiment, the caster rollers 252L, 252R are pressed against the registration rollers 212L, 212R by the biasing force of the springs 273L, 273R, but this is not limiting. For example, the weight of one end 271A of the swinging member 271 may be made greater than the weight of the other end 271B, so that the swinging member 271 is biased in the Z1 direction by its own weight.

[0111] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0112] 1...inkjet recording apparatus (image forming apparatus) / 50...control means (controller) / M2L...first steering means (steering motor) / M2R...second steering means (steering motor) / 200...image forming apparatus (print module) / 210...sheet conveying device (registration unit) / 212L...first driving roller (registration roller) / 212R...second driving roller (registration roller) / 230...image forming means (recording unit) / 252L...first driven roller (caster roller) / 252R ...Second driven roller (caster roller) / 256L...First holding portion (holding portion) / 255L...First shaft portion (swivel rotation shaft) / 255R...Second shaft portion (swivel rotation shaft) / 256R...Second holding portion (holding portion) / 270...Separating mechanism / 271...Oscillating member / 272...Oscillating shaft / 273L...First biasing member (spring) / 273R...Second biasing member (spring) / 284...Cam / AX1...First swing axis (swing axis) / AX2...Second swing axis (swing axis) / M4...Drive source (separating motor) / X...Sheet conveying direction / Z...Sheet width direction

Claims

1. a first driving roller and a second driving roller that rotate by receiving a driving force and are arranged side by side in a sheet width direction perpendicular to a sheet conveying direction; a first steering means for changing an inclination angle of a rotation axis of the first drive roller with respect to the sheet width direction; a second steering means for changing an inclination angle of a rotation axis of the second drive roller with respect to the sheet width direction; a first driven roller that sandwiches and conveys a sheet together with the first drive roller, the first driven roller being configured to rotate around a first rotation axis that intersects both the sheet conveying direction and the sheet width direction in accordance with a change in the inclination angle of the first drive roller; a second driven roller that sandwiches and conveys a sheet together with the second drive roller, the second driven roller being configured to rotate around a second rotation axis that intersects both the sheet conveying direction and the sheet width direction in accordance with a change in the inclination angle of the second drive roller; a separation mechanism that switches between a contact state in which the first driven roller and the second driven roller are in contact with the first drive roller and the second drive roller, respectively, and a separation state in which the first driven roller and the second driven roller are separated from the first drive roller and the second drive roller, respectively; the separating mechanism includes a swinging member that supports the first driven roller and the second driven roller and is swingable about a first swing axis that extends along the sheet conveying direction; The swing axis is located between the first driven roller and the second driven roller in the sheet width direction. A sheet conveying device characterized by:

2. The swinging member is configured to be swingable about a second swing axis extending along the seat width direction, the spacing mechanism switches the first driven roller and the second driven roller between the contact state and the spacing state by the swinging member swinging about the second swing axis.

2. The sheet transport device according to claim 1.

3. the first driven roller and the second driven roller are disposed on the same side of the second swing axis in the sheet conveying direction; 3. The sheet transport device according to claim 2.

4. The spacing mechanism includes a drive source and a cam that rotates by a drive force from the drive source and swings the swing member around the second swing axis.

4. The sheet transport device according to claim 3.

5. the cam is located on the opposite side of the second swing axis from the first driven roller and the second driven roller in the sheet conveying direction; 5. The sheet transport device according to claim 4.

6. The first swing axis and the second swing axis are perpendicular to each other.

3. The sheet transport device according to claim 2.

7. The separating mechanism includes a first biasing member that is disposed on one side of the first swing axis in the sheet width direction and biases the swing member toward the first drive roller, and a second biasing member that is disposed on the other side of the first swing axis in the sheet width direction and biases the swing member toward the second drive roller.

3. The sheet transport device according to claim 2.

8. the first biasing member and the second biasing member are disposed on the same side as the first driven roller and the second driven roller with respect to the second pivot axis in the sheet conveying direction; 8. The sheet transport device according to claim 7.

9. the first biasing member and the second biasing member bias the swinging member so that the first driven roller and the second driven roller are in the contact state; 8. The sheet transport device according to claim 7.

10. The first biasing member is disposed so as to overlap at least a portion of the second biasing member when viewed in the seat width direction.

8. The sheet transport device according to claim 7.

11. the spacing mechanism has a swing shaft supported by a fixed member and having the second swing axis as a center line; the swinging member is supported with a gap between it and the swinging shaft in a direction intersecting both the sheet conveying direction and the sheet width direction; 3. The sheet transport device according to claim 2.

12. a first holding portion having a first shaft portion rotatably supported about the first pivot axis with respect to the swing member, the first holding portion rotatably supporting the first driven roller; a second holding portion having a second shaft portion rotatably supported about the second pivot axis with respect to the swing member, and rotatably supporting the second driven roller; 2. The sheet transport device according to claim 1.

13. the first pivot axis is disposed offset with respect to a nip portion between the first drive roller and the first driven roller in the sheet conveying direction; the second pivot axis is disposed offset with respect to a nip portion between the second drive roller and the second driven roller in the sheet conveying direction; 13. The sheet transport device according to claim 12.

14. The sheet conveying device further includes a control unit that corrects a positional deviation of the sheet in the sheet width direction by controlling an inclination angle of the first drive roller and the second drive roller.

2. The sheet transport device according to claim 1.

15. a conveying speed of the second driving roller is controlled independently of that of the first driving roller; the control unit corrects skew of the sheet by controlling a difference in conveying speed between the first drive roller and the second drive roller.

15. The sheet transport device according to claim 14.

16. a sheet conveying device according to any one of claims 1 to 15; an image forming means for forming an image on the sheet conveyed by the sheet conveying device; An image forming apparatus comprising:

Images