Roller unit and image forming apparatus

Abstract

To stably convey a recording medium with a simple structure.SOLUTION: The roller unit 170 includes a pickup roller 171p that picks up the recording media placed on the facing plate 156, a sheet feeding roller 171r that conveys the recording media, a separation roller 171r provided to face the sheet feeding roller 171q, and a conveyance guide 161 provided between the pickup roller 171p and the sheet feeding roller 171r, and when viewed from a direction parallel to a rotation axis of the sheet feeding roller 171r, a length between a first tangent 171r on a side of the facing plate 156 out of two tangents in contact with respective outer circumferences of the sheet feeding roller and the pickup roller 171p and a leading end of the conveyance guide 161 is equal to or less than a length of the first tangent. T1 161A 2mm, the gap between the 171r of the sheet feeding roller and the 161A of the leading end of the conveyance guide 161 is 0.2 mm or more and 2mm or less.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a roller unit and an image forming apparatus, and more particularly to a roller unit and an image forming apparatus that transports a recording medium. [Background technology]

[0002] In an image forming apparatus, a plurality of recording media such as paper sheets are placed in a stacked state in a paper feed tray. The image forming apparatus conveys the plurality of sheets one by one in order, starting with the topmost sheet, and forms an image on the recording media.

[0003] For example, Japanese Patent Application Laid-Open No. 2022-133665 describes a paper feed mechanism including: a tray for storing sheets; a first roller for removing the sheets from the tray and transporting them in a removal direction; a second roller for transporting the sheets removed by the first roller; a third roller facing the second roller and sandwiching the sheets between the second roller and the third roller; a first elastic body located between the first roller and a nip formed by the second roller and the third roller in a plane perpendicular to the rotation axis of the second roller, the first elastic body intercepting a first reference line along the removal direction and a second reference line connecting the contact position where the first roller contacts the sheet and the nip, the first elastic body forming an acute first angle with the first reference line; and a second elastic body located between the nip and the first elastic body, the second angle formed with the first reference line being smaller than the first angle.

[0004] However, the paper feed mechanism described in JP 2022-133665 A has the problem that it requires two elastic bodies, a first elastic body and a second elastic body, which makes the configuration complicated. Also, adjusting the positional relationship between the first elastic body and the second elastic body becomes complicated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-133665 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a roller unit that can stably transport a recording medium with a simple configuration.

[0007] Another object of the present invention is to provide an image forming apparatus that can stably transport a recording medium with a simple configuration. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, according to one aspect of the present invention, the roller unit comprises a pickup roller that picks up a recording medium placed on an opposing plate, a paper feed roller that transports the recording medium picked up by the pickup roller, a separation roller arranged opposite the paper feed roller, and a transport guide arranged between the pickup roller and the paper feed roller, and when viewed in a direction parallel to the rotation axis of the paper feed roller, a first line passing through the centers of rotation of the paper feed roller and the separation roller, and a second line passing through a first contact point where the first tangent on the opposing plate side of two tangents to the outer circumference of the paper feed roller and the pickup roller meets the paper feed roller, and the center of rotation of the paper feed roller, forms a first angle between 0 degrees and 15 degrees.

[0009] According to another aspect of the present invention, an image forming apparatus includes the above-described roller unit. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing an example of the appearance of an MFP according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view schematically illustrating a part of the internal configuration of the MFP. [Figure 3] FIG. 2 is an oblique view of the side door of the main body frame as seen from the inside. [Figure 4] FIG. 4 is a partially enlarged view of FIG. 3. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 2 is a first cross-sectional view of the roller unit. [Figure 9] FIG. 10 is a first diagram illustrating the position of the tip of the transport guide. [Figure 10] FIG. 10 is a second diagram illustrating the position of the tip of the transport guide. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same components are designated by the same reference numerals. The names and functions of these components are also the same. Therefore, detailed description thereof will not be repeated.

[0012] FIG. 1 is a perspective view showing an example of the exterior of an MFP according to an embodiment of the present invention. The MFP 100 includes an automatic document feeder 120, a document reading unit 130, an image forming unit 140, a paper feeder 150, and an operation panel 110. The document reading unit 130 reads a document. The automatic document feeder 120 transports the document to the document reading unit 130. The image forming unit 140 forms an image on paper or the like based on image data. The image data includes image data included in a print job received from a personal computer and image data output by the document reading unit 130 after reading the document. The paper feeder 150 supplies a recording medium to the image forming unit 140. Recording media include paper and sheet-like resin films such as overhead projector films. The following description will be given using a case where the recording medium is paper. The operation panel 110 is a user interface. The operation panel 110 provides information to the user. The operation panel 110 also accepts operations input by the user.

[0013] The automatic document feeder 120 automatically transports multiple documents set on a document tray one by one to a predetermined document reading position set on the platen glass of the document reading unit 130. The automatic document feeder 120 discharges the documents, from which the images formed on the documents have been read by the document reading unit 130, onto a document output tray. The document reading unit 130 includes a light source that irradiates light onto the documents transported to the document reading position, and a photoelectric conversion element that receives light reflected from the documents, and scans the document image according to the size of the documents. The photoelectric conversion element converts the received light into image data, which is an electrical signal, and outputs it to the image forming unit 140.

[0014] Paper feed unit 150 includes paper feed trays 151 to 153 and an openable / closable manual feed tray 154. In FIG. 1, manual feed tray 154 is shown in a closed state. Paper feed unit 150 transports paper stored in paper feed trays 151 to 153 or paper placed on manual feed tray 154 to image forming unit 140. Image forming unit 140 forms an image by a well-known electrophotographic method. Image forming unit 140 forms an image on paper transported by paper feed unit 150 and discharges the paper with the image formed on it to paper discharge tray 159.

[0015] FIG. 2 is a side view schematically illustrating a portion of the internal configuration of the MFP. Referring to FIG. 2, a main transport path 41, indicated by a thick dotted line, is formed inside MFP 100 so as to extend essentially vertically. Main transport path 41 is a path for guiding paper transported from paper feed unit 150 through image forming unit 140 to paper output tray 159. In this example, main transport path 41 has a lower end 43 opposite to an upper end 13 located above image forming unit 140, which forms an inlet for receiving paper from paper feed unit 150. Furthermore, upper end 13 of main transport path 41 forms an outlet for discharging paper after image formation onto paper output tray 159. Paper output rollers 15 are provided at upper end 13 of main transport path 41. Lower end 43 of main transport path 41 is connected to multiple sub-transport paths SP1, SP2, and SP3 of paper feed unit 150, which will be described later.

[0016] The paper feed unit 150 includes three paper feed trays 151, 152, and 153 and a manual feed tray 154. One or more sheets of paper are placed in a stack on the manual feed tray 154. A counter plate 156 and a roller unit 170 are provided corresponding to the manual feed tray 154. The roller unit 170 includes a pickup roller 171p, a paper feed roller 171r, and a separation roller 171q. The paper feed roller 171r and the separation roller 171q are provided on the sub-transport path SP2. The counter plate 156 is biased upward by an elastic body such as a spring. The counter plate 156 pushes up multiple sheets of paper placed on the manual feed tray 154. The roller unit 170 sends the one or more sheets of paper placed on the manual feed tray 154 to the sub-transport path SP2, starting with the topmost sheet. The paper sent to the sub-transport path SP2 is supplied to the main transport path 41 by the paper feed roller 171r.

[0017] The three paper feed trays 151, 152, and 153 are stacked in this order, aligned from top to bottom. The manual feed tray 154 is provided on a side door 11A of the main body frame 11 of the MFP 100, and is located below the image forming unit 140. As indicated by the thick dashed line in FIG. 2, the paper feed unit 150 has a sub-transport path SP1 extending from the uppermost paper feed tray 151 of the three paper feed trays 151, 152, and 153 to the lower end 43 of the main transport path 41. A sub-transport path SP2 extends from the manual feed tray 154 to the lower end 43 of the main transport path 41. Furthermore, two sub-transport paths 152a and 153a are formed, extending from the middle and lowermost paper feed trays 152 and 153 of the three paper feed trays 151, 152, and 153, respectively, to the lower end 43 of the main transport path 41. A predetermined length of the main transport path 41 of each of the two sub transport paths 152a and 153a from the lower end 43 is a sub transport path SP3 shared by the two sub transport paths 152a and 153a.

[0018] A pickup roller 151p, a paper feed roller 151r, and a separation roller 151q are provided corresponding to paper feed tray 151. Paper feed roller 151r and separation roller 151q are provided on sub-transport path SP1. A pickup roller 152p, a paper feed roller 152r, and a separation roller 152q are provided corresponding to paper feed tray 152. Paper feed roller 152r and separation roller 152q are provided on sub-transport path 152a. A pickup roller 153p, a paper feed roller 153r, and a separation roller 153q are provided corresponding to paper feed tray 153. Paper feed roller 153r and separation roller 153q are provided on sub-transport path 153a. A roller unit 170 is provided corresponding to manual feed tray 154. Roller unit 170 is provided on sub-transport path SP2.

[0019] In MFP 100, during image formation, a tray that stores sheets of paper on which an image is to be formed is selected as a target tray from among three paper feed trays 151, 152, and 153 and manual feed tray 154. A pickup roller, paper feed roller, and separation roller corresponding to the tray selected as the target tray from three paper feed trays 151, 152, and 153 and manual feed tray 154 are operated. As a result, sheets are supplied from the tray selected as the target tray to main transport path 41 through one of sub-transport paths SP1, SP2, and SP3.

[0020] The image forming section 140 includes image forming units 21Y, 21M, 21C, and 21K for yellow, magenta, cyan, and black, respectively. An image is formed on paper by driving at least one of the image forming units 21Y, 21M, 21C, and 21K. A full-color image is formed when all of the image forming units 21Y, 21M, 21C, and 21K are driven. Print data for yellow, magenta, cyan, and black is input to the image forming units 21Y, 21M, 21C, and 21K, respectively. The image forming units 21Y, 21M, 21C, and 21K differ only in the color of the toner they use, so the following description focuses on the image forming unit 21Y for forming a yellow image.

[0021] The image forming unit 21Y includes an exposure head to which yellow printing data is input, a photosensitive drum, a main charger, a developing device, and a transfer roller 23Y. The exposure head emits laser light in response to the received printing data (electrical signal). The emitted laser light is scanned one-dimensionally by a polygon mirror provided in the exposure head, exposing the photosensitive drum. The direction of one-dimensional scanning of the photosensitive drum is the main scanning direction. The photosensitive drum is charged by the main charger, and then irradiated with laser light emitted by the exposure head. This forms an electrostatic latent image on the photosensitive drum. Next, the developing device applies toner to the electrostatic latent image to form a toner image. The toner image formed on the photosensitive drum is transferred onto the intermediate transfer belt 27 by the transfer roller 23Y.

[0022] Meanwhile, intermediate transfer belt 27 is suspended by drive roller 24 and roller 24A so as not to slacken. When drive roller 24 rotates counterclockwise in the drawing, intermediate transfer belt 27 rotates counterclockwise in the drawing at a predetermined speed. As intermediate transfer belt 27 rotates, roller 24A rotates counterclockwise.

[0023] As a result, image forming units 21Y, 21M, 21C, and 21K sequentially transfer toner images onto intermediate transfer belt 27. The timing at which each of image forming units 21Y, 21M, 21C, and 21K transfers a toner image onto intermediate transfer belt 27 is adjusted by detecting a reference mark on intermediate transfer belt 27. As a result, yellow, magenta, cyan, and black toner images are superimposed on intermediate transfer belt 27.

[0024] In main transport path 41, timing roller 45, transfer roller 47, and fixing roller 49 are arranged in this order at intervals from bottom end 43 to top end 13. Paper supplied from paper feed unit 150 to main transport path 41 is sent to timing roller 45.

[0025] Timing roller 45 adjusts the transport state of the paper on main transport path 41 so that the paper reaches transfer roller 47 at the same time as the toner image formed on intermediate transfer belt 27 reaches transfer roller 47. The paper transported by timing roller 45 is pressed against intermediate transfer belt 27 by transfer roller 47. By charging transfer roller 47, the yellow, magenta, cyan, and black toner images formed in superimposition on intermediate transfer belt 27 are transferred to the paper. The amount of charge on transfer roller 47 is adjusted to a value appropriate for the basis weight of the paper by controlling the voltage applied to transfer roller 47 by the CPU.

[0026] The paper with the transferred toner image is transported to the fixing roller 49 and heated by the fixing roller 49. This melts the toner and fixes it to the paper. The paper with the image formed on it is then ejected by the paper ejection roller 15 from the upper end 13 of the main transport path 41 onto the paper ejection tray 159. The temperature of the fixing roller 49 is controlled by the CPU and adjusted to a value appropriate for the basis weight of the paper.

[0027] Paper discharge tray 159 and manual feed tray 154 are arranged on either side of main transport path 41. Paper discharge tray 159 and manual feed tray 154 are arranged on two opposite side surfaces of the main body of MFP 100. Here, manual feed tray 154 is arranged on the left side surface of MFP 100, and paper discharge tray 159 is arranged on the right side surface.

[0028] Fig. 3 is a perspective view of the side door of the main body frame as seen from the inside. Fig. 4 is a partial enlarged view of Fig. 3. Referring to Figs. 3 and 4, roller unit 170 is disposed inside side door 11A of main body frame 11 at a position corresponding to manual feed tray 154. One of paper guide pair 155 is disposed below roller unit 170. Paper guide pair 155 forms part of each of sub-transport path SP2 and sub-transport path SP3. Figs. 3 and 4 show the surface of paper guide pair 155 that forms sub-transport path SP3.

[0029] Because roller unit 170 is disposed inside side door 11A, when side door 11A is open, the user can see and touch roller unit 170. This allows roller unit 170 to be easily removed from side door 11A and a new roller unit 170 to be attached to side door 11A. This allows the user to easily replace roller unit 170.

[0030] FIG. 5 is a perspective view of the roller unit. Referring to FIG. 5, roller unit 170 includes an upper unit part 170A and a lower unit part 170B. FIG. 6 is a perspective view of the upper unit part. FIG. 7 is a perspective view of the lower unit part. Referring to FIGS. 5 to 7, upper unit part 170A is disposed above lower unit part 170B. Upper unit part 170A and lower unit part 170B are separate bodies. For this reason, it is possible to replace roller unit 170, but it is also possible to replace upper unit part 170A and lower unit part 170B separately.

[0031] The unit upper part 170A includes an upper case 179A, a pickup roller 171p, a paper feed roller 171r, and a gear 176. The upper case 179A is fixed to the side door 11A. The pickup roller 171p is cylindrical. In this embodiment, the cross-sectional diameter of the pickup roller 171p is 20 mm. The pickup roller 171p is attached to a pick roller shaft 173p. The symmetrical rotation axis of the pickup roller 171p and the axis of the pick roller shaft 173p are parallel. The pick roller shaft 173p is rotatably supported by the upper case 179A. A pick gear 175p is coupled to the pick roller shaft 173p.

[0032] The paper feed roller 171r has a cylindrical shape. In this embodiment, the cross-sectional diameter of the paper feed roller 171r is 20 mm. The paper feed roller 171r is attached to a paper feed roller shaft 173r. The paper feed roller shaft 173r is connected to the rotation shaft of a gear 176. The driving force of a motor is transmitted to the gear 176. The symmetrical rotation shaft of the paper feed roller 171r and the axis of the paper feed roller shaft 173r are parallel. The paper feed roller shaft 173r is rotatably supported by the upper case 179A. The paper feed roller shaft 173r is supported by the upper case 179A in a state parallel to the pick roller shaft 173p. A paper feed gear 175r is coupled to the paper feed roller shaft 173r.

[0033] The pickup roller 171p and the paper feed roller 171r are connected via another gear. Therefore, the paper feed roller 171r and the pickup roller 171p rotate in conjunction with each other. In this embodiment, the rotational force of the gear 176 is transmitted to the paper feed roller shaft 173r. The number of teeth of the pick gear 175p and the paper feed gear 175r is set so that the peripheral speed of the pickup roller 171p is slower than that of the paper feed roller 171r. After the paper P reaches the paper feed roller 171r, a one-way limiter is provided on the pickup roller 171p to transport the paper at the peripheral speed of the paper feed roller 171r.

[0034] The unit lower part 170B includes a lower case 179B, a separation holder 179C, and a separation roller 171q. The unit lower part 170B has bearing fulcrum holes 177B formed on each of two opposing side surfaces. A swinging rotation shaft 177A fixed to the separation holder 179C is inserted into the fulcrum holes 177B, and the swinging rotation shaft 177A is rotatably supported. Therefore, the separation holder 179C is supported by the lower case 179B in a state where it can rotate around the axis of the swinging rotation shaft 177A. The swinging rotation shaft 177A is parallel to the paper feed roller shaft 173r.

[0035] The separation roller 171q has a cylindrical shape. The separation roller 171q is attached to a separation roller shaft 173q. The symmetrical rotation axis of the separation roller 171q and the axis of the separation roller shaft 173q are parallel to each other. The separation roller shaft 173q is rotatably supported by a separation holder 179C. The separation roller shaft 173q is supported by the separation holder 179C in a state parallel to the swing rotation axis 177A. A load resistor 175q is coupled to the separation roller shaft 173q. The load resistor 175q restricts the rotation of the separation roller shaft 173q. Therefore, the separation roller shaft 173q stops without rotating as long as the external force applied to the separation roller shaft 173q is smaller than the force with which the load resistor 175q restricts the separation roller shaft 173q.

[0036] With the fulcrum hole 177B supporting the swingable rotation shaft 177A, the unit lower part 170B is positioned so that the separation roller 171q faces the paper feed roller 171r. The unit lower part 170B is rotatable around the axis of the swingable rotation shaft 177A. The unit lower part 170B is biased by an elastic body such as a coil spring in the direction in which the separation roller 171q faces the paper feed roller 171r. Therefore, the separation roller 171q is biased in the direction in which it faces the paper feed roller 171r. When no paper is present between the separation roller 171q and the paper feed roller 171r, the separation roller 171q comes into contact with the paper feed roller 171r.

[0037] Fig. 8 is a first cross-sectional view of the roller unit. Fig. 8 shows the area around roller unit 170 in a cross section taken along a plane perpendicular to the direction from the front to the rear of MFP 100. Referring to Fig. 8, manual feed tray 154 is plate-shaped and has a loading surface on which one or more stacks of paper are placed. Manual feed tray 154 has an opposing plate 156 on its upper surface, near side door 11A. A plurality of sheets of paper P placed on manual feed tray 154 are partially placed on opposing plate 156.

[0038] A pair of paper guides 155 is attached to the loading surface of the manual feed tray 154. The paper guides 155 have positioning surfaces that are perpendicular to the loading surface and parallel to the paper transport direction. The paper transport direction is perpendicular to the paper feed roller shaft 173r of the pickup roller 171p and runs from the outside to the inside of the side door 11A. The paper guides 155 are arranged on the manual feed tray 154 with their positioning surfaces facing each other. The paper guides 155 are movable in one direction, and their positioning surfaces can move toward and away from each other. By moving the paper guides 155, the user can align the width direction of one or more stacks of paper placed on the manual feed tray 154. The width direction is perpendicular to the paper transport direction.

[0039] Opposing plate 156 is a plate-shaped member and has a rotation axis that is parallel to the loading surface of manual feed tray 154 and perpendicular to the paper transport direction. The rotation axis of opposing plate 156 is supported by manual feed tray 154, and opposing plate 156 is attached to manual feed tray 154 so as to be rotatable around the rotation axis. An elastic member that urges opposing plate 156 upward is provided between opposing plate 156 and manual feed tray 154. Therefore, when opposing plate 156 is urged upward by the elastic member, one or more sheets of paper placed on manual feed tray 154 move upward. The first cross-sectional view shown in FIG. 8 shows a state in which opposing plate 156 of manual feed tray 154 is pushed upward.

[0040] A pickup roller 171p is disposed opposite the opposing plate 156. The axis of the pickup roller 171p is perpendicular to the direction in which the sheets of paper placed on the manual feed tray 154 are transported. In a plan view of the opposing plate 156 seen from above, the opposing plate 156 and the pickup roller 171p overlap. When the opposing plate 156 is raised, the uppermost surfaces of the multiple sheets of paper P come into contact with the pickup roller 171p. Therefore, with the pickup roller 171p in contact with the uppermost surface of the sheet of paper P, the pickup roller 171p presses the sheet of paper P downward with a predetermined force. In this state, when the pickup roller 171p rotates, the uppermost sheet of paper P is transported toward the paper feed roller 171r due to the frictional force generated between the pickup roller 171p and the uppermost sheet of paper P. The pickup roller 171p rotates clockwise in FIG. 8. The paper transport direction is from right to left in FIG. 8.

[0041] A paper feed roller shaft 173r of the paper feed roller 171r and a separation roller shaft 173q of the separation roller 171q are parallel to each other. The separation roller 171q is biased toward the paper feed roller 171r. When no paper is present between the paper feed roller 171r and the separation roller 171q, the separation roller 171q comes into contact with the paper feed roller 171r.

[0042] Because separation holder 179C rotates around swing rotation shaft 177A, the distance between separation roller shaft 173q of separation roller 171q and paper feed roller shaft 173r of paper feed roller 171r can be adjusted. Separation holder 179C is biased by an elastic member such as a spring in a direction that separation roller shaft 173q approaches paper feed roller shaft 173r. Separation roller 171q is biased toward paper feed roller 171r. As a result, the distance between separation roller 171q and paper feed roller 171r can be adjusted to accommodate multiple types of paper P with different thicknesses.

[0043] The paper feed roller 171r is rotatable around the axis of the paper feed roller shaft 173r. The rotational force of the gear 176 is transmitted to the paper feed roller shaft 173r. Therefore, the rotational force of the gear 176 is transmitted to the paper feed roller 171r via the paper feed roller shaft 173r, and the paper feed roller 171r rotates around the axis of the paper feed roller shaft 173r. The direction in which the paper feed roller 171r rotates is clockwise in FIG. 8.

[0044] When the separation roller 171q is in contact with the paper feed roller 171r, the separation roller 171q rotates in accordance with the rotation of the paper feed roller 171r. However, a load resistor 175q that regulates the rotation of the separation roller 171q is provided on the separation roller shaft 173q of the separation roller 171q.

[0045] Two or more overlapping sheets of paper may be picked up by pickup roller 171p from multiple sheets placed on manual tray 154. In this case, a stack of two or more sheets enters between paper feed roller 171r and separation roller 171q. The topmost sheet of the two or more sheets contacts paper feed roller 171r, and the bottommost sheet contacts separation roller 171q. Here, we will explain the case where two sheets Pa1 and Pa2 overlap. The coefficient of dynamic friction between paper feed roller 171r and the topmost sheet Pa1 is μ1, the coefficient of static friction between separation roller 171q and the bottommost sheet Pa2 is μ2, and the coefficient of static friction between the topmost sheet Pa1 and the bottommost sheet Pa2 is μ3. The outer circumferential surfaces of paper feed roller 171r and separation roller 171q are formed of a material that satisfies the relationships μ1 > μ3 and μ2 > μ3, and are surface-treated.

[0046] A load resistor 175q that regulates rotation is provided on separation roller shaft 173q of separation roller 171q. When multiple sheets of paper Pa1 and P2 enter between paper feed roller 171r and separation roller 171q, a force in the direction opposite to the conveyance direction is generated on paper Pa2. Because μ2 > μ3, separation roller 171q stops without rotating while in contact with paper Pa2. Also, because μ1 > μ3, the frictional force that paper Pa1 receives from paper feed roller 171r overcomes the frictional force that paper Pa1 receives from paper Pa2, and paper Pa1 is conveyed by paper feed roller 171r.

[0047] A transport guide 161 is disposed between the pickup roller 171p and the paper feed roller 171r. The transport guide 161 guides the paper P transported by the pickup roller 171p to the nip between the paper feed roller 171r and the separation roller 171q. The transport guide 161 also functions to separate multiple sheets of paper P when multiple sheets of paper P are transported overlapping each other by the pickup roller 171p. There are multiple types of paper P with different thicknesses or hardnesses. The transport guide 161 can accommodate multiple types of paper P. The hardness of the paper is determined by the basis weight of the paper. The basis weight of thin plain paper is 60 g / m 2 The basis weight of thick cardboard is 300 g / m 2 is.

[0048] The transport guide 161 has a flat plate shape that is elongated in a direction perpendicular to the transport direction. The transport guide 161 is formed of a flexible material that has elasticity. The flexible material is, for example, a polyethylene-based material. In this embodiment, the transport guide 161 is formed of a PET resin sheet. The thickness of the tip 161A of the transport guide 161 is 0.15 mm or more and 0.35 mm or less. This allows the amount of elastic deformation of the transport guide 161 to be adjusted to an appropriate value. Therefore, even if the thickness or hardness of the paper P varies, the tip 161A of the transport guide 161 can be positioned appropriately corresponding to the thickness or hardness of the paper. Note that the tip 161A of the transport guide 161 may have a pointed shape in a cross section perpendicular to the transport direction. Only the tip portion of the transport guide 161, including the tip 161A, may be formed of a flexible material.

[0049] The conveying guide 161 elastically deforms when the paper P comes into contact with its tip 161A. The conveying guide 161 is fixed to the side door 11A so that the position of the tip 161A is appropriate. The position of the tip 161A of the conveying guide 161 is determined by the relative positions of the paper feed roller 171r, separation roller 171q, and pickup roller 171p.

[0050] FIG. 9 is a first diagram illustrating the position of the tip of the conveyance guide. Referring to FIG. 9, a first straight line L1, a second straight line L2, and a first tangent line T1 are defined. The first tangent line T1 is one of two tangent lines tangent to the outer peripheries of the sheet feed roller 171r and the pickup roller 171p, and is the tangent line on the opposing plate 156 side. The first straight line L1 is a line passing through the rotation center Cr of the sheet feed roller 171r and the rotation center Cq of the separation roller 171q. The second straight line L2 is a line passing through the first contact point P1 where the first tangent line T1 contacts the outer periphery of the sheet feed roller 171r and the rotation center Cr of the sheet feed roller 171r.

[0051] The first angle θa between the first line L1 and the second line L2 is between 0 and 15 degrees. Preferably, the first angle θa is between 5 and 15 degrees. When the first angle is less than 0 degrees, the second contact point P2 where the paper feed roller 171r and the separation roller 171q meet is located upstream of the first contact point P1 in the rotation direction of the paper feed roller 171r. When the first angle is less than 0 degrees, the contact area between the paper feed roller 171r and the paper feed roller 171r is reduced. This increases the likelihood of slippage between the paper P and the paper feed roller 171r, making the conveyance speed of the paper P unstable. When the first angle is greater than 15 degrees, the leading edge of the paper P that is thick or hard is more likely to collide with the paper feed roller 171r, increasing the likelihood of damage to the paper feed roller 171r. Therefore, by appropriately determining the first angle θa, the transport speed of the paper P is stabilized and damage to the paper feed roller 171r is suppressed.

[0052] The value obtained by subtracting the sum of the radii of paper feed roller 171r and pickup roller 171p from the distance between first contact point P1 and third contact point P3 is between 0 mm and 10 mm. The first contact point is the point where first tangent line T1 contacts the outer periphery of paper feed roller 171r. The third contact point P3 is the point where first tangent line T1 contacts the outer periphery of pickup roller 171p. The sum of the radii of paper feed roller 171r and pickup roller 171p is the sum of radius Rr of paper feed roller 171r and radius Rp of pickup roller 171p. This results in a relatively large contact area between paper P and paper feed roller 171r. This reduces slippage between paper P and paper feed roller 171r, stabilizing the transport speed of paper P.

[0053] Furthermore, the distance between the first tangent line T1 and the tip 161A of the conveying guide 161 is 2 mm or less. Preferably, the distance between the first tangent line T1 and the tip 161A of the conveying guide 161 is 1 mm or less. More preferably, the distance between the first tangent line T1 and the tip 161A of the conveying guide 161 is 0 mm.

[0054] Furthermore, the distance between the surface of the paper feed roller 171r and the tip 161A of the conveyance guide 161 is 0.2 mm or more and 2 mm or less. Preferably, the distance between the surface of the paper feed roller 171r and the tip 161A of the conveyance guide 161 is 0.2 mm or more and 1 mm or less. The conveyance guide 161 is provided between the pickup roller 171p and the paper feed roller 171r. The conveyance guide 161 guides the paper P conveyed by the pickup roller 171p to the paper feed roller 171r. When paper P with a small thickness or hardness contacts the conveyance guide 161, the amount of elastic deformation of the conveyance guide 161 is relatively small, and the degree to which the paper P bends is relatively large. When paper P with a large thickness or hardness contacts the conveyance guide 161, the amount of elastic deformation of the conveyance guide 161 is relatively large, and the degree to which the paper P bends is relatively small.

[0055] The distance between first tangent T1 and tip 161A of conveyance guide 161 is set to an appropriate value. Of the two tangents that touch the outer peripheries of paper feed roller 171r and pickup roller 171p, first tangent T1 is the tangent on the opposing plate 156 side. The distance between the surface of paper feed roller 171r and tip 161A of conveyance guide 161 is set to an appropriate value. Therefore, conveyance guide 161 elastically deforms in response to the thickness or hardness of paper P, so that the tip of paper P can enter the nip portion where paper feed roller 171r and separation roller 171q contact each other regardless of the thickness or hardness of paper P.

[0056] FIG. 10 is a second diagram illustrating the position of the tip of the conveyance guide. Referring to FIG. 10, a third line L3, a fourth line L4, and a second tangent line T2 are defined. The third line L3 is a line passing through the second contact point P2 where the sheet feed roller 171r and the separation roller 171q meet and the rotation center Cs of the swing rotation shaft 177A. The fourth line L4 is a line passing through the second contact point P2 and perpendicularly intersecting the first line L1. The second tangent line T2 is a line passing through a point P4 on the outer periphery of the pickup roller 171p that is closest to the opposing plate 156 and is tangent to the outer periphery of the pickup roller 171p.

[0057] The conveyance guide 161 is disposed at a position intersecting the second tangent line T2, so that the probability that the paper P conveyed by the pickup roller 171p will come into contact with the conveyance guide 161 can be increased.

[0058] The second angle θb formed by the third line L3 and the fourth line L4 is between 0 and 15 degrees. When the leading edge of the paper P contacts the separation roller 171q, the separation roller 171q receives a force that rotates the separation roller 171q around the rotation center Cq of the sliding rotation shaft in a direction away from the paper feed roller 171r. The smaller the second angle θb, the smaller the force acting to rotate the separation roller 171q in a direction away from the paper feed roller 171r. The second angle θb is determined so that the separation roller 171q does not separate from the paper feed roller 171r even when the leading edge of a thick or hard recording medium contacts the separation roller 171q. If the second angle θb is too small, the separation roller 171q will separate from the paper feed roller 171r when a thick or hard paper P contacts the separation roller 171q. In this case, it will be impossible to separate one sheet of paper P from two or more overlapping sheets of paper P. Conversely, if the second angle θb is too large, the contact area between the paper P with a low thickness or hardness and the paper feed roller 171r becomes small. This makes it easier for slippage to occur between the paper P and the paper feed roller 171r, making the conveyance speed of the paper P unstable. The second angle θb is between 0 degrees and 15 degrees. This makes it possible to efficiently separate one sheet of paper P from two or more sheets of paper with a high thickness or hardness that are piled up, and stabilize the conveyance speed of the paper with a low thickness or hardness.

[0059] <Modification> (1) In the above-described embodiment, roller unit 170 provided in paper feed tray 153 has been described. The present invention can also be applied to mechanisms for removing paper from paper feed trays 151, 152, and 153, similar to roller unit 170. The operations for removing and transporting paper from paper feed trays 151, 152, and 153 are the same, so paper feed tray 151 will be described here as an example.

[0060] Referring to FIG. 2, one or more sheets of paper are stored in a stack in paper feed tray 151. Paper feed tray 151 has a lift-up mechanism, which serves as a member equivalent to opposing plate 156, that pushes up one or more sheets of paper stored in paper feed tray 151. When pickup roller 151p rotates, the frictional force between the pickup roller 151p and the sheets of paper causes the topmost sheet of paper to be sent to sub-transport path SP1. The sheet sent to sub-transport path SP1 is supplied to main transport path 41 by paper feed roller 151r.

[0061] There are cases where two or more overlapping sheets of paper are picked up from paper feed tray 151 by pickup roller 151p. In this case, the stack of two or more sheets of paper enters between paper feed roller 151r and separation roller 151q. The topmost sheet of the two or more sheets contacts paper feed roller 151r, and the bottommost sheet contacts separation roller 151q. The force biasing separation roller 151q is adjusted so that the frictional force between paper feed roller 151r and the topmost sheet and the frictional force between separation roller 151q and the second sheet are greater than the frictional force between the topmost sheet and the second sheet. A member similar to conveyance guide 161 is arranged between pickup roller 151p and paper feed roller 151r.

[0062] (2) In the above embodiment, MFP 100 that forms images using toner has been described as an example of an image forming apparatus, but it may also be an inkjet printer that forms images using ink.

[0063] <Summary of implementation form> (Item 1) A pickup roller that picks up a recording medium placed on an opposing plate; a paper feed roller that conveys the recording medium picked up by the pickup roller; a separation roller provided opposite the paper feed roller; a conveyance guide provided between the pickup roller and the paper feed roller, When viewed from a direction parallel to the rotation axis of the paper feed roller, the distance between a first tangent line on the opposing plate side of the two tangent lines that contact the outer peripheries of the paper feed roller and the pickup roller and the tip of the conveyance guide is 2 mm or less; The roller unit has a distance between the surface of the paper feed roller and the tip of the transport guide of 0.2 to 2 mm.

[0064] According to this aspect, a transport guide is provided between the pickup roller and the paper feed roller to guide the recording medium transported by the pickup roller. When a recording medium with a low thickness or hardness contacts the transport guide, the recording medium curves. A comparison is made between a case where a recording medium with a high thickness or hardness contacts the transport guide and a case where a recording medium with a low thickness or hardness contacts the transport guide. The amount of elastic deformation of the transport guide is greater for a recording medium with a high thickness or hardness than for a recording medium with a low thickness or hardness. Furthermore, the degree of curvature of the recording medium is smaller for a recording medium with a high thickness or hardness than for a recording medium with a low thickness or hardness. The distance between the first tangent line on the opposing plate side of the two tangent lines contacting the outer peripheries of the paper feed roller and the pickup roller and the tip of the transport guide is 2 mm or less, and the distance between the surface of the paper feed roller and the tip of the transport guide is 0.2 mm or more and 2 mm or less. Therefore, regardless of the thickness or hardness of the recording medium, the tip of the recording medium can be properly inserted between the paper feed roller and the separation roller. As a result, a roller unit capable of stably transporting recording media with a simple configuration can be provided.

[0065] (Item 2) A roller unit as described in Item 1, wherein, when viewed from a direction parallel to the rotation axis of the paper feed roller, a first angle formed by a first line passing through the rotation centers of the paper feed roller and the separation roller and a second line passing through a first contact point where the first tangent line meets the paper feed roller and the rotation center of the paper feed roller is greater than or equal to 0 degrees and less than 15 degrees.

[0066] According to this aspect, a first angle formed by the first line and the second line is defined. The first line is a line passing through the rotation centers of the paper feed roller and the separation roller. The second line is a line passing through the rotation center of the paper feed roller and the first tangent where the first tangent line meets the paper feed roller. The first tangent line is the tangent on the opposing plate side of the two tangent lines that meet the outer periphery of the paper feed roller and the pickup roller. If the first angle is less than 0 degrees, the contact area between the paper feed roller and a recording medium with a small thickness or hardness is reduced. This makes slippage more likely to occur between the recording medium and the paper feed roller, resulting in unstable recording medium transport speed. If the first angle is greater than 15 degrees, the leading edge of a recording medium with a large thickness or hardness is more likely to collide with the paper feed roller, increasing the probability of damage to the paper feed roller. The first angle formed by the first line and the second line is between 0 degrees and 15 degrees. This stabilizes the recording medium transport speed and reduces damage.

[0067] (Item 3) The rotation shaft of the separation roller is rotatable around a swing rotation shaft, Item 3. The roller unit according to item 1 or 2, wherein, when viewed from a direction parallel to the rotation axis of the paper feed roller, a second angle formed by a third line passing through the oscillating rotation axis and a second contact point where the paper feed roller and the separation roller meet, and a fourth line passing through the second contact point and intersecting the first line perpendicularly is between 0 degrees and 15 degrees.

[0068] According to this aspect, a second angle is defined between a third line passing through the second contact point where the feed roller and the separation roller meet and the oscillating rotation axis, and a fourth line passing through the second contact point and perpendicular to the first line. When the leading edge of a recording medium contacts the separation roller, the separation roller receives a force that rotates the separation roller around the sliding rotation axis in a direction away from the feed roller. The magnitude of the force that rotates the separation roller in a direction away from the feed roller decreases as the second angle decreases. It is preferable to increase the second angle so that the separation roller does not move too far away from the feed roller even when the leading edge of a thick or hard recording medium contacts the separation roller. If the second angle is too small, the separation roller will move away from the feed roller when a thick or hard recording medium contacts the separation roller. In this case, it will be impossible to separate one recording medium from two or more overlapping recording media. Conversely, if the second angle is too large, the contact area between a thin or hard recording medium and the feed roller will be small. This makes it easier for slippage to occur between the recording medium and the paper feed roller, resulting in unstable conveyance speed for the recording medium. The second angle is between 0 degrees and 15 degrees. This allows for efficient separation of a single recording medium from a stack of two or more recording media that are thick or hard, while stabilizing the conveyance speed for recording media that are thin or hard.

[0069] (Item 4) A roller unit described in any one of items 1 to 3, wherein, when viewed from a direction parallel to the rotation axis of the paper feed roller, the value obtained by subtracting the sum of the radius of the paper feed roller and the radius of the pickup roller from the distance between the first tangent point and a third tangent point where the first tangent line meets the pickup roller is between 0 mm and 10 mm.

[0070] According to this aspect, the value obtained by subtracting the sum of the radius of the paper feed roller and the radius of the pickup roller from the length of the line segment connecting the first tangent line to the third tangent line where the first tangent line contacts the pickup roller is between 0 mm and 10 mm. This results in a relatively large contact area between the recording medium and the paper feed roller. This reduces slippage between the recording medium and the paper feed roller, stabilizing the recording medium transport speed.

[0071] (Item 5) A roller unit according to any one of Items 1 to 4, wherein, when viewed from a direction parallel to the rotation axis of the pickup roller, a tangent line passing through a point on the outer periphery of the pickup roller closest to the opposing plate and tangent to the outer periphery of the pickup roller intersects with the conveying guide.

[0072] In this aspect, a tangent line passing through the point on the outer periphery of the pickup roller closest to the opposing plate and tangent to the outer periphery of the pickup roller intersects with the transport guide, so that the storage medium picked up by the pickup roller can be reliably brought into contact with the transport guide before it reaches the paper feed roller.

[0073] (Item 6) The roller unit according to any one of Items 1 to 5, wherein the tip of the transport guide is made of a flexible resin material.

[0074] In this aspect, the tip of the transport guide is made of a flexible resin material, and therefore the tip of the transport guide is elastically deformed when the recording medium comes into contact with the tip, thereby allowing the recording medium to be properly guided to the paper feed roller.

[0075] (Item 7) The roller unit according to Item 6, wherein the tip of the transport guide is made of a polyethylene-based material.

[0076] (Item 8) The roller unit according to item 6 or 7, wherein the thickness of the tip of the transport guide is 0.15 mm or more and 0.35 mm or less.

[0077] According to this aspect, the amount of elastic deformation of the transport guide can be appropriately adjusted, and therefore, even if the thickness or hardness of the recording medium varies, the tip of the transport guide can be positioned at an appropriate position corresponding to the thickness or hardness of the recording medium.

[0078] (Item 9) An image forming apparatus comprising the roller unit according to any one of items 1 to 8.

[0079] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0080] 100 MFP, 11 main body frame, 11A side door, 120 automatic document feeder, 130 document reading unit, 140 image forming unit, 150 paper feed unit, 154 manual feed tray, 155 paper guide pair, 156 opposing plate, 159 paper output tray, 161 transport guide, 161A tip, 170 roller unit, 170A upper unit, 170B lower unit, 171p pickup roller, 171q separation roller, 171r paper feed roller, 173p pick roller shaft, 173q separation roller shaft, 173r paper feed roller shaft, 175p pick gear, 175q load resistor, 175r paper feed gear, 176 gear, 177A swing rotation shaft, 177B fulcrum hole, 179A upper case, 179B lower case, 179C Separation holder, Cq rotation center, Cr rotation center, Cs rotation center, L1 first line, L2 second line, L3 third line, L4 fourth line, P1 first tangent point, P2 second tangent point, P3 third tangent point, Rp radius, Rr radius, SP1 sub-transport path, SP2 sub-transport path, SP3 sub-transport path, T1 first tangent line, T2 second tangent line, θa first angle, θb second angle.

Claims

1. a pickup roller for picking up the recording medium placed on the opposing plate; a paper feed roller that conveys the recording medium picked up by the pickup roller; a separation roller provided opposite the paper feed roller; a conveyance guide provided between the pickup roller and the paper feed roller, a distance between a first tangent line on the opposing plate side of two tangent lines that contact the outer peripheries of the paper feed roller and the pickup roller and a tip of the conveyance guide when viewed from a direction parallel to the rotation axis of the paper feed roller and the pickup roller is 2 mm or less; A roller unit in which the distance between the surface of the paper feed roller and the tip of the transport guide is 0.2 mm or more and 2 mm or less.

2. 2. The roller unit of claim 1, wherein, when viewed from a direction parallel to the rotation axis of the paper feed roller, a first angle formed by a first line passing through the rotation centers of the paper feed roller and the separation roller and a second line passing through a first contact point where the first tangent line meets the paper feed roller and the rotation center of the paper feed roller is greater than or equal to 0 degrees and less than 15 degrees.

3. The rotation shaft of the separation roller is rotatable around a swing rotation shaft, 2. The roller unit of claim 1, wherein, when viewed from a direction parallel to the rotation axis of the paper feed roller, a second angle formed by a third line passing through the second contact point where the paper feed roller and the separation roller meet and the oscillating rotation axis, and a fourth line passing through the second contact point and intersecting perpendicularly with a first line passing through the rotation centers of the paper feed roller and the separation roller, is greater than or equal to 0 degrees and less than 15 degrees.

4. A roller unit as described in any one of claims 1 to 3, wherein, when viewed from a direction parallel to the rotation axis of the paper feed roller, the value obtained by subtracting the sum of the radius of the paper feed roller and the radius of the pickup roller from the distance between a first point of contact where the first tangent line meets the paper feed roller and a third point of contact where the first tangent line meets the pickup roller is greater than or equal to 0 mm and less than or equal to 10 mm.

5. 4. The roller unit according to claim 1, wherein, when viewed from a direction parallel to the rotation axis of the pickup roller, a tangent line passing through a point on the outer periphery of the pickup roller closest to the opposing plate and tangent to the outer periphery of the pickup roller intersects with the conveying guide.

6. 4. The roller unit according to claim 1, wherein the tip of the transport guide is made of a flexible resin material.

7. 7. The roller unit according to claim 6, wherein the tip of said transport guide is made of a polyethylene-based material.

8. 7. The roller unit according to claim 6, wherein the thickness of the tip of the transport guide is 0.15 mm or more and 0.35 mm or less.

9. An image forming apparatus comprising the roller unit according to any one of claims 1 to 3.

Images