Image reading apparatus and image forming system

An image reading apparatus includes a conveyance unit, a first reading unit, a first guide portion, a second reading unit, and a second guide portion. The second reading unit includes a rectangular transparent member, an optical reading unit, a housing, a first and a second contact portions, a first and a second pressing members, and a protruding portion. The first and the second contact portions are protruding from a facing surface of the housing. The protruding portion, when viewed from an upstream side in a conveyance direction of a recording material passing through a conveyance path between the second reading unit and the second guide portion, is disposed between the first contact portion and the second contact portion and protruding from the facing surface of the housing, a protruding amount of the protruding portion being smaller than protruding amounts of the first and the second contact portions.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to an image reading apparatus reading an image formed on a recording material and an image forming system including this image reading apparatus.

Description of the Related Art

In an image forming apparatus such as a printer and a copying machine, in a case forming images on both surfaces of a recording material, the image formation on a front surface (first surface) of the recording material and the image formation on a back surface (second surface opposite the first surface) are performed separately. That is, after the image formation on the front surface, the image formation on the back surface of the recording material is performed. Therefore, it is necessary to adjust image forming positions on the front and back surfaces of the recording material so that image forming positions (printing positions) are not relatively displaced (for example, does not cause a blur of a printed character and the like). Therefore, the image forming apparatus is configured to adjust the positions of the images to be formed on the front and back surfaces based on each of the images read on the front and back surfaces by reading the images formed on the front and back surfaces of the recording material.

Hitherto, an image reading apparatus in which, by disposing a contact glass on a side opposite an image forming surface of the recording material on a conveyance path on which the recording material is conveyed, the image formed on the recording material is read by an image sensor via the contact glass is suggested (Japanese Patent Application Laid-Open No. 2010-268058). As described in Japanese Patent Application Laid-Open No. 2010-268058, a reading reference member (also called as a backing roller) is rotatably disposed in the image reading apparatus. The backing roller is disposed opposite the contact glass so that a gap with the contact glass is formed correspondingly to a focal depth of the image sensor. When the recording material passes through this gap, the image on the recording material is read by the image sensor.

Incidentally, if it is possible to read the images on both surfaces in the single conveyance of the recording material, it is possible to perform an image reading efficiently. So as to achieve this, for example, a second image reading unit reading the image on the back surface (second surface) and a first image reading unit reading the image on the front surface (first surface) are disposed in sequence from upstream along the conveyance path of the recording material. In some cases, these first and second image reading units are constituted by common parts from viewpoints of maintenance and cost.

However, in a case where the first and second image reading units described in Japanese Patent Application Laid-Open No. 2010-268058 are used as the image reading unit, in some cases, the recording material blocks the gap between the contact glass and the backing roller opposite, and defective conveyance occurs. That is, in the image reading unit as described above, in some cases, the contact glass is fixed by pressing the contact glass onto an accommodating portion accommodating the image sensor by a pressing member. Then, in a case where the contact glass is disposed on an upper side in a vertical direction with respect to the recording material passing through the gap with the backing roller, in some cases, a part of the contact glass where the pressing member is not disposed bends in a vertically lower direction by the own weight of the contact glass. This is because, in the image reading apparatus hitherto, in a case where the contact glass bends, the gap formed between the backing roller and the contact glass becomes excessively narrow so that it becomes difficult for the recording material to pass through the gap.

So as to prevent the defective conveyance caused by the bending of the contact glass, a configuration to strengthen the pressing force of the pressing member holding the contact glass is considered. However, in a case where the first and the second image reading units are constituted by the common parts as described above, when the pressing force of the pressing member is determined corresponding to the image reading unit disposed on the upper side in the vertical direction, the contact glass of the image reading unit disposed on a lower side in the vertical direction becomes easy to bend. This is because, in the image reading unit disposed on the lower side in the vertical direction, the contact glass becomes easy to bend in a direction away from the backing roller by the pressing force of the pressing member onto the contact glass and the own weight of the contact glass. In a case where the contact glass of the image reading unit disposed on the lower side in the vertical direction bends as described above, a distance of the recording material, which is being conveyed, with respect to the image sensor changes so that the reading precision of the image is possibly lowered. As described above, in the case where the first and the second image reading units are constituted by the common parts, it has been difficult to compatibly achieve the suppression of the defective conveyance and the improvement in the reading precision of the image.

In view of a problem described above, purposes of this disclosure are to offer the image reading apparatus which is capable of compatibly suppressing the defective conveyance of the recording material caused by the bending of the contact glass and the improvement in the reading precision of the image, and an image forming system including this.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, an image reading apparatus configured to read an image formed by an image forming unit forming the image on a recording material and disposed downstream of the image forming unit in a conveyance direction of the recording material includes a conveyance unit configured to convey the recording material, a first reading unit configured to read the image on a first surface of the recording material from upward in a vertical direction, a first guide portion disposed interspatially lower in the vertical direction with respect to the first reading unit and forming a conveyance path of the recording material with the first reading unit, a second reading unit configured to read the image on a second surface opposite the first surface of the recording material from downward in the vertical direction, and a second guide portion disposed interspatially upper in the vertical direction with respect to the second reading unit and forming a conveyance path of the recording material with the second reading unit. The second reading unit includes a rectangular transparent member, an optical reading unit configured to read the image by irradiating light onto the second surface of the recording material via the transparent member, a housing comprising a facing surface facing the transparent member and accommodating the optical reading unit with the transparent member, a first contact portion protruding from the facing surface of the housing and coming into contact with the transparent member on a side of a first end separated from a center in a longitudinal direction of the transparent member, a second contact portion protruding from the facing surface of the housing and coming into contact with the transparent member on a side of a second end opposite the first end in the longitudinal direction of the transparent member, a first pressing member pressing an opposite surface opposite a contact surface of the transparent member toward the housing at a position closer to the center than the first contact portion in the longitudinal direction of the transparent member, the contact surface being a surface on which the first contact portion comes into contact with the transparent member, a second pressing member pressing the opposite surface of the transparent member toward the housing at a position closer to the center than the second contact portion in the longitudinal direction of the transparent member, and a protruding portion, in a case where viewed from an upstream side in the conveyance direction of the recording material passing through the conveyance path between the second reading unit and the second guide portion, disposed between the first contact portion and the second contact portion and protruding from the facing surface of the housing, a protruding amount of the protruding portion being smaller than protruding amounts of the first contact portion and the second contact portion.

According to a second aspect of the present invention, an image forming system includes an image forming apparatus comprising the image forming unit, and the image reading apparatus according to claim1coupled to the image forming apparatus and configured to read the image on the recording material discharged from the image forming apparatus.

DESCRIPTION OF THE EMBODIMENTS

Image Forming System

UsingFIG.1, a schematic configuration of an image forming system including an image reading apparatus of this embodiment will be described. The image forming system1X shown inFIG.1includes an image forming apparatus100, the image reading apparatus200, and a finisher apparatus300. The image forming apparatus100, the image reading apparatus200, and the finisher apparatus300are connected in a manner capable of receiving and delivering a recording material S. In this embodiment, the image reading apparatus200and the finisher apparatus300are post-process units which are freely retrofittable to the image forming apparatus100for function enhancement and capable of performing post-processes of the recording material S on which a toner image has been formed by the image forming apparatus100, as described later.

These image forming apparatus100, image reading apparatus200, and finisher apparatus300are coupled in a manner capable of transmitting and receiving data to and from each other via a communication interface capable of performing serial and parallel communications. Thus, the image forming apparatus100is capable of monitoring, while controlling, operating states, including the failure, of the image reading apparatus200and the finisher apparatus300.

Image Forming Apparatus

At first, the image forming apparatus100will be described. The image forming apparatus100is a tandem type full color printer of an electrophotographic system. The image forming apparatus100includes image forming units Pa, Pb, Pc, and Pd which respectively form images of yellow, magenta, cyan, and black. The image forming apparatus100forms the toner image on the recording material S in accordance with an image signal transmitted from a document reading apparatus190coupled to an apparatus body100A or an external apparatus such as a personal computer, not shown, communicably coupled to the apparatus body100A.

To be noted, in a case of this embodiment, an image forming unit700forming the toner image on the recording material S is constituted by the image forming units Pa to Pd, primary transfer rollers24ato24d, an intermediate transfer belt130, a plurality of rollers13to15, and a secondary transfer outer roller11. Further, the recording material S includes various kinds of recording materials S cut beforehand (so-called cut sheet) such as a paper including a standard paper, cardboard, a rough paper, an uneven paper, a coated paper, and the like, a plastic film, and a cloth.

As shown inFIG.1, the image forming units Pa, Pb, Pc, and Pd are disposed inside the apparatus body100A in a line along a moving direction of the intermediate transfer belt130. The intermediate transfer belt130is stretched over the plurality of rollers13,14, and15, and moved in a clockwise direction in the figure. Further, the intermediate transfer belt130bears and conveys the toner image that has been primarily transferred as described later. The secondary transfer outer roller11is disposed at a position opposite a secondary transfer inner roller14stretching the intermediate transfer belt130across the intermediate transfer belt130, and forms a secondary transfer portion T2transferring the toner image on the intermediate transfer belt130onto the recording material S. A fixing unit800is disposed downstream of the secondary transfer portion T2in a conveyance direction of the recording material S.

A plurality (in this embodiment, two cassettes) of cassettes10accommodating the recording material S are disposed below the image forming unit700. The recording materials S different in sizes and thicknesses are accommodated in the cassettes10, and the recording material S is selectively conveyed from either one of the cassettes10. The recording material S is conveyed from the cassette10by a conveyance roller16toward a registration roller12via a conveyance path. Thereafter, the recording material S is conveyed toward the secondary transfer portion T2by rotating the registration roller12in synchronization with the toner image formed on the intermediate transfer belt130. To be noted, it is not limited to the recording material S accommodated in the cassette10, and acceptable to convey the recording material S placed on a manual sheet feed portion (not shown).

The image forming units Pa, Pb, Pc, and Pd are substantially the same in a configuration except for a developing color of the toner image. Therefore, the image forming unit Pa of yellow will be described as a representative herein, and descriptions of the other image forming units Pb, Pc, and Pd will be omitted.

In the image forming unit Pa, a photosensitive drum3aof a cylindrical type is disposed as a photosensitive member. The photosensitive drum3ais rotatably driven in a counter clockwise direction in the figure. A charge unit2a, an exposing unit La, a developing unit1a, the primary transfer roller24a, and a drum cleaning unit4aare disposed around the photosensitive drum3a.

A process to form, for example, a full color image by the image forming apparatus100will be described. At first, when an image forming operation is started, a surface of the photosensitive drum3a, which is rotating, is uniformly charged by the charge unit2a. The charge unit2ais, for example, a corona charger charging the photosensitive drum3ain a dark potential of a uniform negative polarity by irradiating a charged particle accompanying corona discharge, and the like. Next, the photosensitive drum3ais scanned and exposed with a laser beam irradiated from the exposing unit La in accordance with the image signal. Herewith, an electrostatic latent image in accordance with the image signal is formed on the surface of the photosensitive drum3a. The electrostatic latent image formed on the photosensitive drum3ais developed to the toner image, which is a visible image, by the developer containing a toner and a carrier accommodated inside the developing unit1a. In the case of this embodiment, the developing units1ato1duse the two-component developer containing a non-magnetic toner and a magnetic carrier as the developer.

The toner image formed on the photosensitive drum3ais primarily transferred to the intermediate transfer belt130at a primary transfer portion T1formed with the primary transfer roller24adisposed opposite the photosensitive drum3aacross the intermediate transfer belt130. At this time, a primary transfer bias is applied to the primary transfer roller24a. A residual toner remained on the surface of the photosensitive drum3aafter the primary transfer is collected by the drum cleaning unit4a.

After these operations have been performed at each of the image forming units Pa, Pb, Pc, and Pd of yellow, magenta, cyan, and black in sequence, the toner images of four colors are superimposed on the intermediate transfer belt130. Thereafter, the recording material S accommodated in the cassette10is conveyed to the secondary transfer portion T2in a timing synchronizing with the formation of the toner image. Further, by applying the secondary transfer bias to the secondary transfer outer roller11, the full color toner image formed on the intermediate transfer belt130is collectively transferred to the recording material S. A residual toner remained on the intermediate transfer belt130after the secondary transfer is collected by a belt cleaning unit22.

The recording material S onto which the toner image has been transferred is conveyed to the fixing unit800. The fixing unit800fixes the toner image on the recording material S by providing the recording material S, onto which the toner image has been transferred, with heat and pressure. In the case of this embodiment, after the heat and pressure have been provided by a first fixing device81, it is possible to selectively provide the heat and pressure by a second fixing device91. In the fixing unit800, it is possible to switch, by a fixing switch flapper95, between conveying the recording material S to the second fixing device91after passed through the first fixing device81and conveying the recording material S by circumventing the second fixing device91after passed through the first fixing device81.

The second fixing device91is disposed downstream of the first fixing device81in the conveyance direction of the recording material S. The second fixing device91is selectively used for a purpose of such as further providing gloss on the toner image on the recording material S fixed by the first fixing device81. For example, in a case where the recording material S is the coated paper such as a glossy paper and a synthetic paper, the recording material S passed through the first fixing device81is conveyed on a fixing route30aso that the fixing is performed at both of the first and second fixing devices81and91. On the other hand, in a case where the recording material S is a non-coated paper such as the standard paper, the recording material S passed through the first fixing device81is conveyed on a fixing bypass route30bcircumventing the second fixing device91so that the fixing is not performed at the second fixing device91while performing the fixing at the first fixing device81.

Since it is acceptable that the first and second fixing devices81and91above are the same in a configuration, descriptions will be provided by taking the first fixing device81as an example herein. The first fixing device81includes a fixing roller82(or a fixing belt) coming into contact with the surface of the recording material S, onto which the toner image has been transferred, in a rotatable manner, and a pressing belt83(or pressing roller) forming a fixing nip portion with the fixing roller82by coming into pressure contact with the fixing roller82. The fixing roller82is heated by a heater84, and the pressing belt83is heated by a heater, not shown. The first fixing device81fixes the toner image on the recording material S by heating and pressing the recording material S, on which the toner image has been formed, at the fixing nip portion formed by the fixing roller82and the pressing belt83, while nipping and conveying the recording material S at the fixing nip portion. Thus, the toner of the toner image formed on the recording material S is melted and mixed by the heat and pressure, and is fixed on the recording material S as the full color image.

In the case of this embodiment, the image forming apparatus100is capable of performing duplex printing. In a case of one-side printing, the recording material S on which the toner image has been fixed is conveyed to a discharge conveyance path150and discharged to an outside of the apparatus body100A (outside the apparatus body) from a sheet discharge port of the apparatus body100A. In a case of the duplex printing, the recording material S on which the toner image has been fixed is conveyed to a duplex inverse conveyance path600. On the duplex inverse conveyance path600, the recording material S is inverted by a switchback action, and front and back surfaces of the recording material S are inverted. The inverted recording material S is conveyed toward the registration roller12, and conveyed to the secondary transfer portion T2by the registration roller12in a state where the back surface, on which the toner image has not been printed, faces a side of the intermediate transfer belt130. At the secondary transfer portion T2, the full color toner image formed on the intermediate transfer belt130is secondarily transferred to the recording material S (on the back surface side) collectively. Thereafter, the toner image on the recording material S is fixed by the fixing unit800, and then the recording material S is discharged outside the apparatus body100A from the sheet discharge port in a state where the surface on which the image has been formed immediately before faces upwards. To be noted, switching between the discharge conveyance path150and the duplex inverse conveyance path600is performed by a conveyance switch flapper160.

In the case of this embodiment, the recording material S discharged from the image forming apparatus100is conveyed by the image reading apparatus200. In the case of this embodiment, the image reading apparatus200is disposed so as to read the images (toner images) formed on both surfaces of the recording material S by the image forming apparatus100. The image reading apparatus200of this embodiment will be described later (refer toFIG.2).

Further, the finisher apparatus300is coupled to the image reading apparatus200in a manner capable of receiving the recording material S. The finisher apparatus300performs post-process processing, such as a punching process punching a hole in the recording material S and a stapling process bundling and stapling a plurality of sheets of the recording material S, of the recording material S conveyed from the image reading apparatus200to the finisher apparatus300. In the finisher apparatus300, the recording material S, which has been punched, and a bundle of the recording material S, which has been stapled, are separately discharged to an upper sheet discharge tray301and a lower sheet discharge tray302, respectively.

Image Reading Apparatus

Next, usingFIG.2, a schematic configuration of the image reading apparatus200of this embodiment will be described. As shown inFIG.2, the image reading apparatus200includes a plurality of conveyance roller pairs (201,202,203,204,205,215,216,217, and218) for conveying the recording material S discharged from the image forming apparatus100, and a duplex image reading unit400. An inlet conveyance roller pair201conveys the recording material S discharged from the image forming apparatus100toward the duplex image reading unit400. The duplex image reading unit400is a so-called document feeding-reading apparatus which reads the image while conveying the recording material S in the conveyance direction (in an arrow X direction). In this embodiment, the duplex image reading unit400reads the image on the front surface (the first surface) of the recording material S and thereafter the image on the back surface (the second surface) in a single conveyance. The duplex image reading unit400will be described in detail later.

The images on both surfaces read by the duplex image reading unit400are used as image data for adjustments of positions of the images formed on the front and back surfaces of the recording material S so that relative positions of the images on the front and back surfaces are not misaligned with respect to the recording material S. So as to obtain the image data, test images (test pattern) are formed on both surfaces of the recording material S, and are read by the duplex image reading unit400. Further, since it is necessary to form the test images on a plurality of sheets of the recording material S in succession and read such images, the time required for reading the image is shortened by the document feeding-reading. To be noted, it is acceptable to perform the reading of the image by the duplex image reading unit400in a case where the test image is formed on the recording material S, and not to perform the reading of the image in a case where any image of a user request other than the test image is formed.

In a case where the punching process or the stapling process is performed as the post-process processing, the recording material S passed through the duplex image reading unit400is conveyed to the finisher apparatus300by an exit conveyance roller pair205via a through path230. On the other hand, in a case where the punching process or the stapling process is not performed, the recording material S is discharged to a fixed tray223disposed on an upper surface of the image reading apparatus200by the plurality of discharge conveyance roller pairs (215,216,217, and218) via a discharge path232. Switching between the through path230and the discharge path232on which the recording material S is conveyed as described above is performed by a branch flapper222.

Duplex Image Reading Unit

Next, usingFIGS.3and4, a configuration of the duplex image reading unit400will be described. To be noted, illustrations of an abutment member409and a compression spring410(refer toFIG.4) are omitted inFIG.3. As shown inFIG.3, the duplex image reading unit400includes a plurality of reading conveyance roller pairs (202,203, and204), serving as conveyance units to convey the recording material S, a first CIS (contact image sensor) unit400a, and a second CIS unit400b. By the rotation of the plurality of reading conveyance roller pairs (202,203, and204), the recording material S is conveyed in the conveyance direction (arrow X direction).

In this embodiment, the first and second CIS units400aand400bare disposed sequentially from downstream at two separated positions facing a recording material conveyance path H through which the recording material S passes. The first (downstream side) CIS unit400a, serving as a first reading unit, is disposed on the side in the vertically upper direction of the recording material S conveyed on the recording material conveyance path H so as to read the front surface (the first surface) of the recording material S. That is, the first CIS unit400ais configured to read the image on the front surface of the recording material S from above in the vertical direction. On the other hand, the second (upstream side) CIS unit400b, serving as a second reading unit, is disposed on the side in the vertically lower direction of the recording material S conveyed on the recording material conveyance path H so as to read the back surface (the second surface) of the recording material S. That is, the second CIS unit400bis configured to read the image on the back surface of the recording material S from below in the vertical direction.

In this embodiment, the first and second CIS units400aand400bare the same in a configuration, and are disposed in a state vertically opposite each other across the recording material conveyance path H. That is, while arrangements of the first and second CIS units400aand400bwith respect to the image reading apparatus200are different from each other, the first and second CIS units400aand400bare constituted by common parts. At this point, the common parts are, for example, parts which are formed or fabricated by the same dies. Therefore, so as to facilitate understanding of descriptions, the descriptions below will be provided by taking the second CIS unit400bas an example unless otherwise specifically stated.

As shown inFIG.4, the second CIS unit400bincludes an accommodating case407, serving as a housing, a CIS401which is, for example, a contact image sensor of a unit-magnification optical system, and a reading glass (contact glass)403. The CIS401, serving as an optical reading unit, irradiates light from an LED (light emitting diode) array401a, that is a light source, to the recording material S conveyed on the recording material conveyance path H, and reads the image on the recording material S by forming the image on a sensor element401b(such as a photoelectric conversion element) from the reflected light reflected in the recording material S. The LED array401ais disposed in a width direction intersecting with the conveyance direction of the recording material S in a vertical direction, and irradiates the light so that the intensity of light irradiation is approximately uniform in the width direction. Further, the sensor element401bis a plurality of line sensors disposed in the width direction, and reads the image formed on the recording material S, which is conveyed, by one line at a time. The CIS401is accommodated inside the accommodating case407. The width direction above is an arrangement direction of the LED array401aand a line direction of the sensor element401b.

The reading glass403, serving as a transparent member, is mounted on a side facing the recording material S conveyed on the recording material conveyance path H in the accommodating case407, and transmits the irradiated light irradiated from the LED array401atoward the recording material S and the reflected light reflected in the recording material S in response to the irradiation of the light. That is, in the second CIS unit400b, the image on the recording material S conveyed on the recording material conveyance path H is read via the reading glass403. A mounting configuration of the reading glass403with respect to the accommodating case407will be described later (refer toFIGS.5to7). In this embodiment, the CIS401and the reading glass403are disposed detachably from the accommodating case407so that a worker such as a service person is able to detach the reading glass403from the accommodating case407and replace the reading glass403, which has been damaged, or the CIS401, which has been broken.

Returning toFIG.3, the duplex image reading unit400further includes a first backing roller405, serving as a first guide portion, and a second backing roller406, serving as a second guide portion. The first backing roller405is disposed by leaving a space (gap) with the first CIS unit400ain the vertically lower direction, and the second backing roller406is disposed by leaving a space (gap) with the second CIS unit400bin the vertically upper direction. The first CIS unit400areads the image on the front surface of the recording material S when the recording material S passes through the gap formed between the reading glass403and the first backing roller405. The second CIS unit400breads the image on the back surface of the recording material S when the recording material S passes through the gap formed between the reading glass403and the second backing roller406.

The first and second backing rollers405and406are driven by a backing motor, not shown, and rotatably driven at the same peripheral speed as the reading conveyance roller pairs (202,203, and204). Thus, by not causing differences in the speeds among the first and second backing rollers405and406, which rotate, and the recording material S, which is conveyed, it is possible to prevent the image on the recording material S from falling into a rubbing state. Further, since rubbing does not occur on the image, it is possible to reduce the soiling by the toner caused by the rubbing of the image. To be noted, the gap mentioned above, through which the recording material S passes, is set at an appropriate size so as to pass through the recording material S depending on a type of the recording material S as described later, so that the first and second backing rollers405and406do not actively convey the recording material S.

In this embodiment, the first and second backing rollers405and406are the same in a configuration. Therefore, descriptions will be provided by taking the second backing roller406as an example herein. As shown inFIG.4, at the second backing roller406rotatably supported by bearings, not shown, abutment members409and409for a gap adjustment are disposed on the bearings at both ends in a rotational axis direction (width direction). The abutment member409is urged toward the reading glass403by the compression spring410so as to abut on the reading glass403. Thus, it is possible to move the second backing roller406toward the reading glass403with the bearing along with a movement of the abutment member409, which is caused by the urging. Then, when the abutment member409abuts on the reading glass403, the second backing roller406is positioned at a position to form the gap G, which becomes a conveyance path of the recording material S, with the reading glass403. To be noted, it is acceptable that the first and second backing rollers405and406are guide members that do not rotate.

The abutment member409, serving as a change unit, is rotatably disposed on the bearing so that it is possible to change the size of the gap G, that is, a space of the conveyance path formed between the second backing roller406and the reading glass403. For example, the abutment member409is formed in an elliptical shape or in an eccentric polygonal shape in which a length from the center to each side is different. By rotating the abutment member409around the bearing, the second backing roller406, together with the bearing, approaches to and is separated from the reading glass403so that the size of the gap G changes. The abutment member409is, for example, formed in a shape which is capable of changing the size of the gap G in ten steps. To cite an example, the abutment member409is formed to have different radii of ten steps, for example, 10.25, 10.35, 10.45, 10.65, . . . , and 11.50 mm (millimeter).

The size of the gap G above is determined by a focal depth of the CIS401and the type of the recording material S (more particularly, the thickness determined depending on grammage). That is, the size of the gap G is set at larger than the thickness of the recording material S so that the recording material S does not block (so-called jam) the gap G by the thickness of the recording material S during conveyance and, further, the recording material S is able to enter the gap G smoothly. However, the size of the gap G is limited to a level of a size at which the recording material S is not conveyed in a manner deviating from the focal depth of the CIS401so that the CIS401is able to read the image on the recording material S even if the recording material S flaps during the conveyance. That is, the size of the gap G is set at a size at which the size of the gap G is larger than the thickness of the recording material S and is smaller than a sum of the thickness of the recording material S and the focal depth of the CIS401.

For example, in a case where the CIS401with the focal depth of 0.45 mm is used, if the thickness of the recording material S is less than 0.1 mm (grammage is less than 100 g/m2(grams per square meter)), the size of the gap G is set at 0.3 mm. In this case, when the recording material S enters the gap G between the second backing roller406and the reading glass403, since a gap of 0.2 mm (difference between the size of the gap G and the thickness of the recording material S) is produced, the recording material S enters the gap G smoothly, and is conveyed without blocking the gap G.

Mounting Configuration of Reading Glass

Next, usingFIGS.5to7, a mounting configuration of the reading glass403onto the accommodating case407will be described. As shown inFIG.5, the reading glass403is fixed to the accommodating case407by 4 pieces of plate springs501disposed on sides of both ends from the center in the width direction (longitudinal direction of the reading glass403) and upstream and downstream sides in the conveyance direction of the accommodating case407. The reading glass403also serves as a conveyance guide, and the recording material S is conveyed on a surface of the reading glass403. Therefore, if the plate spring501is disposed in a conveyance area L where a maximum conveyable size of the recording material S in the longitudinal direction of the reading glass403is conveyed, there is a risk of causing the damage to the recording material S by the plate spring501. Accordingly, it is not possible to dispose the plate spring501in the conveyance area L, where the recording material S is conveyed, in the width direction (longitudinal direction of the reading glass403). Therefore, 4 pieces of plate springs501are disposed outside the conveyance area L of the accommodating case407(on the sides of the ends in the width direction).

As shown inFIG.6, each of the plate springs501includes a fixed portion501afixed to the accommodating case407, a pressing portion501bpressing the reading glass403, and an urging portion501cbending from the fixed portion501aand urging the pressing portion501btoward the reading glass403. The accommodating case407includes a bottom surface portion407c, a first wall portion407astanding on an upstream side of the bottom surface portion407c, and a second wall portion407bstanding on a downstream side of the bottom surface portion407copposite the first wall portion407a. Each of the plate springs501disposed on the upstream side of the accommodating case407is fixed to the first wall portion407aby a screw or the like via the fixed portion501a, and each of the plate springs501disposed on the downstream side of the accommodating case407is fixed to the second wall portion407bby the screw or the like via the fixed portion501a. To be noted, this is not limited to this, and it is acceptable to fix the plate springs501to each of both end wall portions407dand407d(refer toFIG.5) standing at both ends of the accommodating case407opposite each other in the width direction via the fixed portions501a.

In this embodiment, as described above, the first and second CIS units400aand400bthat are the same in the configuration are disposed vertically opposite each other across the recording material conveyance path H (refer toFIG.3). Therefore, especially for the first CIS unit400a, fixing the reading glass403to the accommodating case407by adhesive, double-sided tape, or the like so as to prevent the reading glass403from falling down is considered. However, in a case where the reading glass403is fixed by the adhesive, the double-sided tape, or the like, it becomes difficult for the worker to detach the reading glass403from the accommodating case407and perform a maintenance work such as the replacement of the reading glass403or the CIS401. Therefore, it is appropriate to fix the reading glass403to the accommodating case407by the plate spring501as describe above so that the worker is able to detach the reading glass403from the housing case407easily. To be noted, in the case of this embodiment, the plate springs501serve as a first pressing member and a second pressing member (third pressing member, fourth pressing member) pressing the reading glass403outside the conveyance area L of the accommodating case407.

As shown inFIG.6, the reading glass403is detachably nipped by the plate springs501with the first wall portion407a(similar also on a side of the second wall portion407b). In this embodiment, 4 pieces of contact supporting portions411supporting the reading glass403by coming into contact with the reading glass403are disposed on the sides of both ends of each of the first and second wall portions407aand407bin the width direction. As shown inFIG.7, similar to the plate springs501, the contact supporting portions411are disposed outside the conveyance area L (on the side of the end) of the accommodating case407. Therefore, the plate springs501press the reading glass403from a side of an opposite surface403b(opposite surface side) opposite a contact surface403awith which the contact supporting portions411come into contact. However, the plate springs501are disposed to press the reading glass403inside contact positions at which the contact supporting portions411come into contact with the reading glass403(refer toFIG.9B). In the case of this embodiment, at a first end of the reading glass403in the longitudinal direction, the plate springs501on one side press the reading glass403toward the accommodating case407inside the contact supporting portions411and from a side of the opposite surface403bopposite the contact surface403awith which the contact supporting portions411come into contact. Further, at a second end of the reading glass403in the longitudinal direction, the plate springs501on the other side press the reading glass403toward the accommodating case407inside the contact supporting portions411and from the side of the opposite surface403b.

As shown inFIGS.6and7, the contact supporting portions411are, for example, integrally formed by drawing at a time of manufacturing the accommodating case407from a galvanized steel sheet by presswork so as to protrude from an opposite glass surface4701of each of the first and second wall portions407aand407b. The reading glass403is not supported on whole surfaces of the opposite glass surface4701(frame surface) of each of the first and second wall portions407aand407b, but supported by four pieces of the contact supporting portions411protruding from the frame surfaces on the first and second wall portions407aand407b(four-point supporting). Thus, it is possible to more accurately define a mounting position of the reading glass403with respect to the accommodating case407(in more particular, with respect to the CIS401mounted to the accommodating case407), which affects the reading of the image by the CIS401. To be noted, the opposite glass surface4701is a portion opposite the reading glass403at a distance in comparison with the contact supporting portions411and an opposite supporting portion412described later.

That is, in a case where the second CIS unit400bis manufactured by mounting the reading glass403with a length of 400 mm in the width direction onto the accommodating case407, it is difficult to confine an error of a height position of the reading glass403with respect to the accommodating case407within 0.1 mm. This is, for example, because of a difficulty to confine the flatness of the frame surfaces of the first and second wall portions407aand407bof the accommodating case407within 0.1 mm. Therefore, the reading glass403is partially supported by the contact supporting portions411, not by the whole surface of the frame surfaces, and pressed by the plate springs501from the opposite surface403b. Herewith, the reading glass403is mounted onto the accommodating case407at a height corresponding to the focal depth of the CIS401. Thus, the contact supporting portions411on one side protrude from the opposite glass surface4701opposite the reading glass403of the accommodating case407, and come into contact with the reading glass403on one side outside the conveyance area L, in which the recording material S is conveyed, in the longitudinal direction of the reading glass403. The contact supporting portions411on the other side protrude from the opposite glass surface4701opposite the reading glass403of the accommodating case407, and come into contact with the reading glass403on the other side outside the conveyance area L, in which the recording material S is conveyed, in the longitudinal direction of the reading glass403. In the case of this embodiment, the contact supporting portions411serve as a first contact portion and a second contact portion (third contact portion, fourth contact portion) coming into contact with both end portions of the reading glass403outside the conveyance area L of the accommodating case407.

Further, in this embodiment, as shown inFIG.7, each of the opposite supporting portions412is disposed in the center of each of the first and second wall portions407aand407bin the longitudinal direction as a protruding portion protruding from each end of the first and second wall portions407aand407b. That is, the opposite supporting portion412is disposed inside the conveyance area L (within the conveyance area) of the reading glass403in the longitudinal direction opposite the reading glass403, and includes an opposite surface412aopposite the contact surface403a(refer toFIG.3) of the reading glass403, with which the contact supporting portion411comes into contact. The opposite surface412aof the opposite supporting portion412comes into contact with the contact surface403awith the reading glass403bending, and does not come into contact with the contact surface403awith the reading glass403not bending. Details of this opposite supporting portion412will be described later (refer toFIG.9B).

Incidentally, the reading glass403is, in comparison with a length in the width direction, short in the conveyance direction of the recording material S. In this embodiment, the reading glass403in a rectangular shape with a length of 400 mm in the width direction (longitudinal direction) and a length of 100 mm in the conveyance direction (short direction) is used. At this point, in this embodiment, the rectangular shape does not necessarily include a square corner portion. For example, even if the reading glass is an approximately rectangular shape with a chamfered corner portion, or even if any of sides is slanting, a shape having a long side and a short side is considered to be the rectangular shape. Since the reading glass403in the rectangular shape is used as described above, the reading glass403easily bends in the longitudinal direction in a case where the reading glass403is supported partially not by whole surface of the frame surface but by the contact supporting portions411as described above. Further, since the thickness of the reading glass403is formed thin (for example, 3 mm), the reading glass403more easily bends in the longitudinal direction. UsingFIGS.8A and8B, the suppression of possible bending in the reading glass403in the first CIS unit400awill be described.FIG.8Ashows a comparative example, andFIG.8Bshows this embodiment. Further, usingFIGS.9A and9B, the restriction of the possible bending in the reading glass403in the second CIS unit400bby the opposite supporting portion412will be described.FIG.9Ashows the comparative example without the opposite supporting portion, andFIG.9Bshows this embodiment with the opposite supporting portion.

In a case of the comparative example shown inFIG.8A, the reading glass403receives the pressing force by the abutment member409and the pressing force by the plate spring501at positions on the opposite surface403bof the reading glass403opposite the contact supporting portions411. That is, the reading glass403receives the pressing force by the abutment member409and the pressing force by the plate spring501at positions close to both ends in the width direction. In this case, the bending occurs in the center portion of the reading glass403in the width direction by own weight. While the resultant force of the pressing force by the abutment member409and the pressing force by the plate spring501described above acts in an opposite direction of a direction in which the reading glass403bends by the own weight, it is because the resultant force does not adequately suppress the bending by the own weight in the center portion in the width direction. In a case where the length of the reading glass403in the width direction is 400 mm, approximately 0.3 mm level of the bending at most occurs by the own weight in the center portion of the reading glass403in the width direction.

In a state where approximately 0.3 mm level of the bending occurs in the reading glass403, even if the size of the gap G is set at 0.3 mm, a size of a gap becomes 0 mm in the center portion. That is, since the gap formed between the reading glass403and the first backing roller405disappears, the gap is blocked by the recording material S. Therefore, for example, so as to prevent the recording material S from blocking, an increase in the size of the gap G (for example, 0.6 mm) based on an assumption of the bending of the reading glass403is considered. However, in such a case, there is a risk that the recording material S flaps on the sides of both ends, where an amount of the bending of the reading glass400is small, and the defective reading of the image by the CIS401occurs. That is, in general, the focal depth of the CIS401is 0.3 to 0.5 mm level. Therefore, in a case where the size of the gap G is set at 0.6 mm, the recording material S in the conveyance easily deviates from the focal depth at both ends in the width direction, and the image read by the CIS401becomes in a so-called blurred state (unfocused state).

Taking into consideration the above, in this embodiment, as shown inFIG.8B, the reading glass403receives the pressing force by the abutment member409and the pressing force by the plate spring501at positions on the opposite surface403binside the contact supporting portions411. Herewith, since the bending by the own weight is canceled by the resultant force of the pressing force by the abutment member409and the pressing force by the plate spring501, it is possible to suppress the occurrence of the bending in the reading glass403. To be noted, since it is acceptable if the bending in the reading glass403produced by the own weight is canceled, it is acceptable if the resultant force of the pressing force by the abutment member409and the pressing force by the plate spring501is received at the positions on the opposite surface403binside the contact supporting portions411. For example, it is not limited to the example shown inFIG.8B, and it is acceptable that, while the pressing force by the abutment member409is received at the positions inside the contact supporting portions411, the pressing force by the plate spring501is received at positions opposite the contact supporting portions411. To be noted, in the case of the first CIS unit400a, since the bending is not produced in the reading glass403, the opposite supporting portion412does not come into contact with the contact surface403aof the reading glass403.

However, as described above, in this embodiment, the first and second CIS units400aand400bconstituted by the common parts are disposed vertically opposite each other across the recording material conveyance path H (refer toFIG.3). That is, the reading glass403and the accommodating case407constituting each of the first and second CIS units400aand400buse the common parts of the same shape in the first and second CIS units400aand400b. Therefore, as shown inFIG.9A, in the second CIS unit400b, a bending direction of the reading glass403by the own weight is the same as a bending direction of the reading glass403by the resultant force of the pressing force by the abutment member409and the pressing force by the plate spring501(downward in the gravity direction). As a result, since a bending amount of the reading glass403becomes larger than a bending amount by the own weight, there is a risk that the size of the gap G accordingly becomes larger than a size corresponding to the focal depth (for example, 0.5 mm) of the CIS401so that the defective reading of the image by the CIS401occurs.

Therefore, in this embodiment, as shown inFIG.9B, the opposite supporting portion412restricting the bending of the reading glass403is disposed in the accommodating case407so that the size of the gap G does not become larger than the size corresponding to the focal depth of the CIS401. The opposite supporting portion412includes the opposite surface412awhich is, when viewed from an upstream side in the conveyance direction, opposite the contact surface403aand closer to the accommodating case407than contact positions (height) at which the contact supporting portions411come into contact with the reading glass403. For example, a protruding amount of the opposite supporting portion412from the frame surface is formed smaller than protruding amounts of the contact supporting portions411so that a difference between the contact positions of the contact supporting portions411coming into contact with the reading glass403and the opposite surface412abecomes equal to or more than 0.1 mm and equal to or less than 0.2 mm. That is, in a case where the second CIS unit400bis viewed from the upstream side in the conveyance direction, the opposite surface412aserving as a top of the opposite supporting portion412is disposed at a position lower than the contact surfaces (top) of the contact supporting portions411coming into contact with the reading glass403. In other words, the opposite surface412aof the opposite supporting portion412is disposed lower than an imaginary line connecting two contact points of the contact supporting portions411on the reading glass403.

This difference in the position between the opposite surface412aand the contact positions of the contact supporting portions411coming into contact with the reading glass403is set at a different value depending on the focal depth of the CIS401. Further, so as to reduce the variance among sheets of the recording material S, the first CIS unit400aon the downstream side is disposed by bringing the first CIS unit400aclose to the second CIS unit400bon the upstream side as much as possible. In such a case, when the reading glass403bends upwards in the second CIS unit400b, the conveyance path from the second CIS unit400bto the first CIS unit400ais narrowed, and affects the conveyance in the first CIS unit400a. So as to avoid this, the protruding amount of the opposite supporting portion412from the frame surface is formed smaller than the protruding amounts of the contact supporting portions411. However, since there is a risk that the reading of the image by the CIS401is not performed appropriately if the difference in the positions between the opposite surface412aand the contact positions at which the contact supporting portions411come into contact with the reading glass403is larger than 0.2 mm, the difference above is set at equal to or more than 0.1 mm and equal to or less than 0.2 mm.

As described above, while the reading glass403bends downwards in the gravity direction in the second CIS unit400b, the reading glass403that has bent is supported by coming into contact with the opposite supporting portion412. In a case where the difference above is, for example, set at 0.2 mm, since the bending of the reading glass403is restricted to 0.2 mm, while the size of the gap G becomes 0.5 mm (in the center portion) at most, this is within a range (0.3 mm to 0.5 mm) of the focal depth of the CIS401. Therefore, the reading of the image by the CIS401is not affected.

As described above, in this embodiment, the bending of the reading glass403by the own weight is canceled by the abutment member409and the plate spring501in the first CIS unit400a. Further, in the second CIS unit400b, the bending of the reading glass403is restricted by supporting the reading glass403, which is bent by the own weight, the abutment member409, and the plate spring501, by the opposite supporting portion412so that the reading glass403does not bend further. Herewith, it is possible to suppress narrowing of the gaps G formed between the first backing roller405and the reading glass403in the first CIS unit400aand formed between the second backing roller406and the reading glass403in the second CIS unit400b. Therefore, even in a case where the first and second CIS units400aand400bconstituted by the common parts are disposed vertically opposite each other across the recording material conveyance path H, it is possible to read the images on both surfaces of the recording material S appropriately by each of the CIS401.

By this disclosure, it is possible to provide the image reading apparatus capable of compatibly achieving suppression of defective conveyance due to the bending of the transparent member and improvement in precision of the reading of the image.

OTHER EMBODIMENTS

In this embodiment, for example, the accommodating case407is manufactured by performing the presswork of the galvanized steel sheet with a thickness of 0.8 mm, and the contact supporting portions411and the opposite supporting portion412are formed by the drawing. Theoretically, it is possible to obtain the effect described above by setting the protruding amount of the contact supporting portion411at 0.1 mm and setting the protruding amount of the opposite supporting portion412at 0 mm, that is, without forming the opposite supporting portion412. However, since, even if processed with high accuracy, the protruding amount of the contact supporting portion411becomes a level of 0.1 mm±0.1 mm and, in addition, it is difficult to bring the flatness of the frame surface to less than 0.1 mm, the formation of the opposite supporting portion412is preferred.

Further, as shown inFIG.10, it is preferable that the difference of the positions between the opposite surface412aand the contact positions at which the contact supporting portions411come into contact with the reading glass403becomes adjustable at equal to more than 0.1 mm and equal to or less than 0.2 mm by stacking one or a plurality of pieces of a spacer480having a predetermined thickness on each of the opposite surface412aand the contact supporting portions411. In this case, it is preferable to change a number of pieces of the spacer480stacked on each of the opposite surface412aand the contact supporting portions411taking into consideration a variance in the flatness of the frame surface. To be noted, while it is acceptable to manufacture the accommodating case407by resin molding, properties of the frame surface manufactured by the resin molding is likely to cause variations in comparison with a case made of a plate shaped metal member. Therefore, in a case of the accommodating case407manufactured by the resin molding, especially, it is preferable that the difference mentioned above is adjustable by changing the number of pieces of the spacer480stacked on each of the opposite surface412aand the contact supporting portions411.

To be noted, it is preferable that a gap between the accommodating case407and the reading glass403is covered in a manner encircling the gap by a sponge and the like so that foreign substances such as the paper dust produced by the conveyance of the recording material S does not enter inside the accommodating case407.

To be noted, in the embodiment described above, the descriptions have been provided by taking the configuration, in which the image reading apparatus200is coupled to the image forming apparatus100, as an example, it is not limited to this. For example, a configuration in which, inside the apparatus body100A of the image forming apparatus100, the duplex image reading unit400(refer toFIG.2) is disposed on the discharge conveyance path150downstream of the fixing unit800in the conveyance direction is acceptable. Further, it is acceptable that a conveyance apparatus including the other casing is coupled to between the image forming apparatus100and the image reading apparatus200.

To be noted, while, in the embodiment described above, the descriptions are provided using the image forming apparatus100of the electrophotographic system, in place of this, for example, it is acceptable to use an image forming apparatus of a thermal drying system such as an ink jet printer and a sublimation type printer.

This application claims the benefit of Japanese Patent Application No. 2020-201382, filed Dec. 3, 2020, which is hereby incorporated by reference herein in its entirety.