JP2014111494A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of ensuring that a drawer unit is fixedly positioned on a slide rail.SOLUTION: A fitting portion 252 into which a first positioning pin 70 is fitted; and a guide groove 253 including a protruding portion 256 engaged with the first positioning pin 70 and restricting upward movement of a paper feed cassette, and a concave portion 255a provided at a position facing the protruding portion 256, and guiding the first positioning pin 70 to the fitting portion 252 are provided in a first engagement hole 251 of the paper feed cassette. A relief portion 257a allowing a second positioning pin 71 to move along a drawing direction of the second positioning pin 71 is provided in a second engagement hole 257 of the paper feed cassette. A protruding amount α of the protruding portion 256 of the first engagement hole 251, a relief amount γ of the first positioning pin 70 downstream in the drawing direction by the concave portion 255a, and a relief amount β of the second positioning pin 71 downstream in the drawing direction by the relief portion 257a of the second engagement hole 257 are set to satisfy a relation of α<β and α<γ.

Description

  The present invention relates to an image forming apparatus, and more particularly to an apparatus in which a drawer unit is removably attached to a housing portion formed in a main body of an image forming apparatus.

  In some conventional image forming apparatuses, a drawer unit such as a sheet conveying unit or a paper feed cassette is detachably attached to a housing portion formed in the main body of the image forming apparatus. For example, a drawer device that detachably mounts a paper feed cassette that is an example of a drawer unit is provided in a cassette housing portion that is an example of a storage unit, and when a sheet is stored in the paper feed cassette, the paper feed cassette is After pulling out from the storage unit, the sheet is stored.

  Such a drawer device includes a fixed rail provided facing the inner wall surface of the cassette housing portion and a slide rail slidably held by the fixed rail (see Patent Document 1). The paper feed cassette can be pulled out integrally with the slide rail by positioning and fixing the paper feed cassette with positioning pins provided on the slide rail.

  FIG. 9 is a diagram showing a configuration of a conventional drawer device. In FIG. 9, reference numeral 167 denotes a drawer device. The drawer device 167 includes a fixed rail 168 fixed to an inner wall surface of a cassette housing (not shown) formed in the image forming apparatus main body 1A, and a slide rail 169 slidably held on the fixed rail 168. It has. The two slide rails 169 are respectively provided with a first positioning pin 70 and a second positioning pin 71 for positioning the paper feed cassette. Then, as shown in FIG. 10, the paper feed cassette 500 is mounted on the slide rail 169 via the first and second positioning pins 70 and 71.

  Here, as shown in FIG. 11, a first engagement hole 501 that engages with the first positioning pin 70 is formed at the lower end on the upstream side in the drawing direction on both side surfaces in the width direction orthogonal to the drawing direction of the sheet feeding cassette 500. Has been. Further, a second engagement hole 503 that engages with the second positioning pin 71 is formed at the lower end on the downstream side in the pull-out direction of both side surfaces of the sheet feeding cassette 500 in the width direction.

  Then, by engaging the first engagement hole 501 and the second engagement hole 503 with the first positioning pin 70 and the second positioning pin 71, the sheet feeding cassette 500 is positioned with respect to the slide rail 169. The In FIG. 11, reference numeral 261 denotes a screw for fixing the slide rail 169 and the paper feed cassette 500, 262 is a screw hole formed in the slide rail 169, and B is a fastening margin that is a gap between the screw 261 and the screw hole 262.

  When the paper feed cassette 500 is mounted on the slide rail 169, the slide rail 169 is first pulled out. Then, the sheet cassette 500 is dropped toward the slide rail 169 from above so that the first and second engagement holes 501 and 503 engage with the first and second positioning pins 70 and 71, and then the screw 261. Thus, the slide rail 169 and the paper feed cassette 500 are fixed.

  By the way, assembling work of the paper cassette is performed in the assembly line of the factory, and in the market, a service man performs slides when, for example, exchanging the feeding roller or exchanging electrical components on the apparatus main body side behind the paper cassette. The operation of removing the paper cassette from the rail is performed. In order to reduce the work man-hours at this time, conventionally, as shown in FIG. 10, the screw fastening portion between the slide rail 169 and the paper feed cassette 500 is set to one place on one side (two places in total).

  However, when the screw 261 is fastened to the downstream side in the pull-out direction of the paper feed cassette 500, when the paper feed cassette 500 is pulled out, the upstream side in the pull-out direction of the paper feed cassette 500 may be lifted. For this reason, conventionally, as shown in FIG. 11, a protruding portion 502 is formed in the first engagement hole 501 so that the upstream side in the pulling-out direction of the sheet feeding cassette 500 does not float.

  In FIG. 11, K is the amount of protrusion 502 of the first engagement hole 501 with respect to the first positioning pin 70, that is, the first of the protrusion 502 for the protrusion 502 to lock the first positioning pin 70. The amount of protrusion relative to one positioning pin 70. Ps is the pitch of the first and second positioning pins 70 and 71 of the slide rail 169, and Pc is the pitch of the first and second engagement holes 501 and 503 of the paper feed cassette 500.

JP 2002-154673 A

  However, in the conventional image forming apparatus having such a drawer device, the pitch Ps of the first and second positioning pins 70 and 71 and the pitch Pc of the first and second engagement holes 501 and 503 shown in FIG. Are set to approximately the same length. For this reason, when the paper feeding cassette 500 is dropped from above and attached to the slide rail 169, the paper feeding cassette 500 is attached in a state where the protruding portion 502 rides on the positioning pin 70 as shown in FIG. It may be fixed to the rail 169.

  Further, the amount K of the protrusion 502 of the first engagement hole 501 with respect to the first positioning pin 70 shown in FIG. 11 and the fastening margin B of the screw fastening portion are set to be substantially the same. Here, for example, due to an impact at the time of opening / closing operation of the paper feeding cassette 500, the paper feeding cassette 500 may be shifted in the direction opposite to the pulling direction by the fastening margin B of the screw fastening portion.

  When a load is applied in the vicinity of the front cover portion 505 in this state, the locking of the positioning pin 70 by the protruding portion 502 is released, and the paper feed cassette 500 rotates in a direction in which the upstream side in the pull-out direction is lifted with the screw fastening portion as a fulcrum. When the upstream side of the paper feeding cassette 500 in the pulling direction rises, the upstream side of the paper feeding cassette 500 in the pulling direction may interfere with the frame of the apparatus main body, and the paper feeding cassette 500 may be deformed or damaged.

  Accordingly, the present invention has been made in view of such a situation, and an object of the present invention is to provide an image forming apparatus capable of reliably positioning and fixing a drawer unit such as a paper feed cassette to a slide rail. It is.

  In the image forming apparatus, the image forming apparatus is fixed to a drawer unit that is retractably stored in a storage portion formed in the image forming apparatus main body, and an inner wall surface that is opposed to the width direction perpendicular to the pulling direction of the storage portion. A pull-out device provided with a fixed rail and a slide rail provided so that the pull-out unit can be attached from above; a first positioning pin provided on the upstream side in the pull-out direction of the slide rail; and the slide rail A second positioning pin provided on the downstream side in the pulling direction; a first engaging hole and a second engaging hole which are provided in the pulling unit and engage with the first positioning pin and the second positioning pin; and the second Fastening that is provided near the positioning pin and fastens the drawer unit to the slide rail A holding mechanism for the drawer unit, and the first engagement hole includes a fitting portion into which the first positioning pin enters, a first guide surface on the upstream side in the pull-out direction, and a downstream side in the pull-out direction. A second guide surface, a protrusion projecting from the first guide surface, engaging with the first positioning pin fitted to the fitting portion, and restricting upward movement of the drawer unit; and the second guide A recess having a recess provided at a position facing the protruding portion of the first guide surface, and a guide groove for guiding the first positioning pin to the fitting portion. An escape portion that allows movement of the second positioning pin in the pulling direction is provided, and the protrusion amount α of the protruding portion of the first engagement hole and the first positioning pin by the recess toward the downstream side in the pulling direction. The amount of relief γ and the front due to the relief portion of the second engagement hole The clearance amount of pull-out direction downstream side of the second positioning pins β, α <β, in which the relationship of alpha <gamma is characterized by being set to satisfy.

  As in the present invention, the projection amount α of the projection of the first engagement hole, the positioning pin escape amount γ in the first engagement hole, and the positioning pin relief amount β in the second engagement hole are expressed as α < By setting β and α <γ, the drawer unit can be reliably positioned and fixed to the slide rail.

1 is a diagram illustrating a schematic configuration of a color laser printer which is an example of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a configuration of a drawer rail of a drawer device provided in the color laser printer. The figure explaining the position of the 1st positioning pin provided in the said drawer rail, the 2nd positioning pin, and the 1st engagement hole provided in the paper feed cassette, and the 2nd engagement hole. The figure explaining the said 1st positioning pin, the 2nd positioning pin, and the pitch of a 1st engagement hole and a 2nd engagement hole. The figure explaining the state of the said 1st positioning pin and 2nd positioning pin, and a 1st engagement hole and a 2nd engagement hole when a paper feeding cassette is attached to the said drawer rail. FIG. 6 is a first diagram illustrating a state of the first positioning pin and the second positioning pin, the first engagement hole, and the second engagement hole in the middle of attaching the sheet feeding cassette to the drawer rail. FIG. 6 is a second diagram illustrating a state of the first positioning pin and the second positioning pin, the first engagement hole, and the second engagement hole in the middle of attaching the sheet feeding cassette to the drawer rail. The figure which shows the state by which the paper feed cassette was mounted | worn with the said slide rail. The figure which shows the structure of the conventional drawer | drawing-out apparatus. The figure which shows the state which mounted | wore with the paper feed cassette to the drawer rail of the said drawer | drawing-out apparatus. The figure explaining the structure for mounting | wearing with the paper feed cassette in the said drawer rail. The figure explaining the state where the paper feed cassette is not normally attached to the drawer rail.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a color laser printer which is an example of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a color laser printer, and 1A denotes a color laser printer main body (hereinafter referred to as a printer main body) which is an image forming apparatus main body. The printer main body 1A is provided with an image forming unit 1B that forms an image on the sheet S, an intermediate transfer unit 1C, a paper feeding unit 1D that feeds the sheet S to the image forming unit 1B, and the like. The color laser printer 1 is capable of forming an image on the back surface of the sheet. For this reason, the sheet S on which the image is formed on the front surface (one surface) is reversed and is again formed in the image forming unit 1B. A re-conveying section 1E is provided for conveying the sheet.

  Here, the image forming unit 1B is arranged in a substantially horizontal direction, and each of the four process stations 20 forms four color toner images of yellow (Y), magenta (M), cyan (C), and black (Bk). (20Y, 20M, 20C, 20K). The process station 20 carries toner images of four colors of yellow, magenta, cyan and black, and is a photosensitive drum 11 (11Y, 11M, 11C, 11K) which is an image carrier driven by a stepping motor (not shown). ). Further, a charger 12 (12Y, 12M, 12C, 12K) for uniformly charging the surface of the photosensitive drum is provided. Further, a scanner 13 (13Y, 13M, 13C, 13K) is provided that forms an electrostatic latent image on a photosensitive drum that rotates at a constant speed by irradiating a laser beam based on image information. In addition, a developing device 14 (14Y, 14M, 14C, 14K) is provided that visualizes a toner image by attaching yellow, magenta, cyan, and black toner to the electrostatic latent image formed on the photosensitive drum. Yes. The charger 12, the scanner 13, the developing device 14 and the like are arranged around the photosensitive drum 11 along the rotation direction.

  In the lower part of the printer main body, sheet feeding cassettes 61 to 64 for storing sheets S and sheet feeding units 201 to 204 for feeding sheets S stacked and stored in the sheet feeding cassettes 61 to 64 are provided. When the image forming operation is started, the sheet S is separated and fed one by one from the sheet feeding cassettes 61 to 64 by the sheet feeding units 201 to 204, and then passes through the conveyance vertical path 81, and the pre-registration roller. After passing through 75, it is conveyed to the registration roller 76. Here, the registration roller 76 has a function of correcting skew by following the leading edge of the sheet S by forming a loop by the sheet S being abutted. Further, it has a function of conveying the sheet S to the secondary transfer unit at a predetermined timing in accordance with the timing of image formation on the sheet S, that is, a toner image carried on an intermediate transfer belt described later. .

  The intermediate transfer unit 1 </ b> C includes an intermediate transfer belt 31 that is driven to rotate along the arrangement direction of the process stations 20 indicated by arrows in synchronization with the outer peripheral speed of the photosensitive drum 11. Here, the intermediate transfer belt 31 applies an appropriate tension to the intermediate transfer belt 31 by the urging force of the driving roller 33, the driven roller 32 that forms the secondary transfer region with the intermediate transfer belt 31 interposed therebetween, and a spring (not shown). The tension roller 34 is stretched. The intermediate transfer belt 31 includes four primary transfer rollers 35 (35Y, 35M, 35C, and 35K) that constitute the primary transfer unit by sandwiching the intermediate transfer belt 31 together with the photosensitive drum 11 inside. ing. Then, by applying a transfer bias from the primary transfer roller 35 to the intermediate transfer belt 31, each color toner image on the photosensitive drum is sequentially transferred to the intermediate transfer belt 31 and a full color image is formed on the intermediate transfer belt 31. Is done.

  A secondary transfer roller 41 is disposed so as to face the driven roller 32, and the secondary transfer roller 41 contacts the lowermost surface of the intermediate transfer belt 31 and is conveyed by the registration roller 76. The sheet S is nipped and conveyed together with the intermediate transfer belt 31. When the sheet S passes through the nip portion between the secondary transfer roller 41 and the intermediate transfer belt 31, a bias is applied to the secondary transfer roller 41, so that the toner image on the intermediate transfer belt is transferred to the sheet S on the secondary side. Transcribed. In FIG. 1, reference numeral 51 denotes a control unit that controls operations necessary for image formation of the printer main body 1A.

  Next, an image forming operation of the color laser printer 1 configured as described above will be described. When the image forming operation is started, first, a latent image is formed on each photosensitive drum 11 at each process station 20 arranged along the intermediate transfer belt 31. Thereafter, each developing device 14 develops the latent image to form a toner image.

  Next, the toner images formed on the photosensitive drums in this way are sequentially primary-transferred onto the intermediate transfer belt 31 in the primary transfer region. As a result, the four-color toner images are primarily transferred on the intermediate transfer belt 31, and a full-color image is formed on the intermediate transfer belt. Further, the sheets S accommodated in the paper feed cassettes 61 to 64 in parallel with the toner image forming operation are separated and fed one by one by the paper feed units 201 to 204 and then passed through the pre-registration roller 75. It is conveyed to the registration roller 76. At this time, the skew of the sheet S is corrected by the registration roller 76.

  In addition, after the skew is corrected, the sheet S is intermediated with the secondary transfer roller 41 by the registration roller 76 which starts rotating at the timing when the leading edge of the sheet and the toner image formed on the intermediate transfer belt 31 coincide. It is conveyed to the nip portion with the transfer belt 31. Then, the sheet is nipped and conveyed by the secondary transfer roller 41 and the intermediate transfer belt 31 and, at the same time, passes through the nip portion between the secondary transfer roller 41 and the intermediate transfer belt 31, the sheet biased by the bias applied to the secondary transfer roller 41. The toner image on the intermediate transfer belt is secondarily transferred to S.

  Next, the sheet S on which the toner image is secondarily transferred is conveyed to the fixing device 5 by the pre-fixing conveying device 42. Here, the fixing device 5 fixes the toner image formed on the sheet on the sheet S via the intermediate transfer belt 31, and the sheet S holding the toner image passes through the fixing device 5. The toner image is fixed by applying heat and pressure. Then, the sheet S having the fixed image obtained in this way is conveyed to the paper discharge conveyance path 82 when discharged onto the paper discharge tray 66 as it is, and to the reverse guide path 83 when double-sided image formation is performed. Route selection is performed as possible.

  When images are formed on both sides, the sheet S is pulled from the reverse guide path 83 to the switchback path 84, and the leading and trailing edges are moved by performing a switchback operation in which the rotation direction of the second reverse roller pair 91 is forward and reverse. It is exchanged and conveyed to the double-sided conveyance path 85. Thereafter, the sheets are recombined in time with the sheet S of the subsequent job conveyed from the sheet feeding units 201 to 204, and are similarly sent to the secondary transfer unit via the registration roller 76. The subsequent image forming process for the back surface (second surface) is the same as that for the front surface (first surface) described above.

  By the way, in FIG. 1, 1F is a cassette housing part provided in the lower part of the printer main body 1A. When sheets are stored, replenished, etc., the sheet feeding cassettes 61 to 64 as an example of a drawer unit stored in the cassette storage portion 1F are pulled out to the front side of the printer main body 1A.

  As shown in FIG. 2, a drawer provided with a fixed rail 68 and a drawer rail 69 which is a slide rail is provided on both inner wall surfaces 86 in the width direction perpendicular to the drawer direction of the cassette accommodating section 1F as an example of the accommodating section. A device 67 is provided. The fixed rails 68 are respectively fixed to the opposing inner wall surfaces 86, and the pull-out rails 69 are supported by the fixed rails 68 so as to be freely drawn out.

  Here, as shown in FIG. 2, a first positioning pin 70 is provided at the upstream lower end of both side surfaces in the width direction orthogonal to the pull-out direction of the pull-out rail 69, that is, at the tip of the pull-out rail 69. A second positioning pin 71 is provided on the downstream side of both side surfaces in the width direction of the drawer rail 69, that is, on the rear end portion of the drawer rail 69.

  In FIG. 2, 72 is a screw hole which is a through hole formed in the vicinity of the downstream side of the pull-out rail 69 in the pull-out direction of the second positioning pin 71. As shown in FIG. Screws 261 are attached to the. The screw hole 72, a screw hole 259 of the paper feed cassette 61 described later, and a screw 261 constitute a fastening portion 90 that fastens the paper feed cassette 61 to the drawer rail 69.

  On the other hand, as shown in FIG. 3, a first engagement hole 251 that engages with the first positioning pin 70 is provided at the lower end of the rear end portion on both side surfaces in the width direction of the cassette body 65 of the paper feed cassette 61. A second engagement hole 257 that engages with the second positioning pin 71 is formed at the lower end of the second positioning hole 71. When the paper feed cassette 61 is mounted on the drawer rail 69, the first engaging hole 251 and the second engaging hole 257 are engaged with the first positioning pin 70 and the second positioning pin 71, thereby pulling out the paper cassette 61. The paper feed cassette 61 is positioned with respect to the rail 69.

  The first and second positioning pins 70 and 71, the first and second engagement holes 251 and 257, and the fastening portion 90 constitute a drawer unit holding mechanism 92. The same applies to the other paper feed cassettes 62 to 64. In the present embodiment, the cassette body 65 is formed of a low-resistance material, and the first engagement holes 251 and the second engagement holes 257 are finished smoothly.

  FIG. 4 is a view showing a state in which the paper feed cassette 61 is mounted on the drawer rail 69. In FIG. 4, Pc represents the pitch between the first engagement holes 251 and the second engagement holes 257, and Ps represents the pitch between the first positioning pins 70 and the second positioning pins 71 of the drawer rail 69. In FIG. 4, reference numeral 259 denotes screw holes provided on both side surfaces of the cassette main body 65, and the positions of the screw holes 259 are closer to the second engagement hole 257 and away from the first engagement hole 251. It has become a position.

  Here, as shown in FIG. 5, the first engagement hole 251 includes a fitting portion 252 that fits the first positioning pin 70, and a guide groove 253 that guides the first positioning pin 70 to the fitting portion 252. ing. The guide groove 253 includes a first guide surface 254 on the upstream side in the pulling direction having a ridge line far from the second engagement hole 257, and a second guide surface on the downstream side in the pulling direction having a ridge line close to the second engagement hole 257. 255.

  On the first guide surface 254, a protrusion 256 that engages with the first positioning pin 70 and restricts the upward movement of the paper feed cassette 61 protrudes downstream in the pull-out direction. The first guide surface 254 has a ridge line that gently continues toward the apex of the protrusion 256. In other words, the surface of the protrusion 256 that contacts the first positioning pin 70 is formed with a gentle low friction surface. In FIG. 5, α is the amount of protrusion that is the protrusion amount at which the protrusion 256 overlaps the first positioning pin 70 in the vertical direction.

  Further, a clearance portion for making the interval between the first guide surface 254 and the protrusion 256 at the portion of the second guide surface 255 facing the protrusion 256 of the first guide surface 254 wider than the outer diameter of the positioning pin 70. The recessed part 255a which forms is provided. In FIG. 5, when γ passes through the protrusion 256 of the guide surface 254, an amount by which the first positioning pin 70 can move toward the second guide surface along the pull-out direction by the escape portion formed by the recess 255a. Is the amount of escape.

  On the other hand, the second engagement hole 257 has a horizontal ridge line 258 that restricts the upward movement of the second positioning pin 71. Further, the second engagement hole 257 is formed with a relief portion 257 a that allows movement of the second positioning pin 71 along the pulling direction. In FIG. 5, β is an escape amount that is an amount by which the second positioning pin 71 can be moved by the escape portion 257 a when the first positioning pin 70 moves toward the second guide surface along the pulling direction.

Here, in the present embodiment, β, Pc, and Ps are set so that the relationship β = Pc−Ps is established. Further, the magnitude relationship between α, β, and γ is set as shown in the following formula (including dimensional tolerance).
α <β and α <γ (1)

  Next, the mounting operation of the paper feed cassette 61 to the drawer rail 69 will be described. When the paper feed cassette 61 is mounted on the drawer rail 69, first, the pair of drawer rails 69 are pulled out from the cassette housing portion 1F. Next, the paper feed cassette 61 is moved from the upper side of the pulled-out pull-out rail 69 toward the first positioning pin 70 and the second positioning pin 71, and the first engagement holes 251 and the second engagement on both side surfaces of the cassette body 65. The holes 257 are put together and dropped.

  FIG. 6 shows a state in the middle of dropping the paper feed cassette 61. At this time, the first positioning pin 70 is in contact with the first guide surface 254 of the first engagement hole 251, and the second positioning pin 71 is in contact with the horizontal ridge line 258 of the second engagement hole 257. Here, as described above, the first guide surface 254 has a ridge line that continues gently toward the apex of the protrusion 256. Thus, thereafter, the paper feed cassette 61 is smoothly guided vertically downward by the first engagement hole 251 and the first positioning pin 70 due to the weight of the paper feed cassette 61. Further, the paper feed cassette 61 is smoothly guided in the back side direction indicated by the broken-line arrow by the second engagement hole 257 and the second positioning pin 71.

  Thereafter, as shown in FIG. 7, the apex of the protruding portion 256 of the first engagement hole 251 contacts the first positioning pin 70, whereby the first positioning pin 70 moves in the direction of the second guide surface 255. To do. Here, as shown in the equation (1), the escape amount γ is larger than the applied amount α. Therefore, even if the first positioning pin 70 moves in the direction of the second guide surface 255, the second guide surface 255 is not in the first position. The guide of the positioning pin 70 is not hindered.

  When the first positioning pin 70 moves in the direction of the second guide surface 255, the second positioning pin 71 also moves in the same direction. Here, even if the second positioning pin 71 moves in this way, the escape amount β is larger than the applied amount α as shown in the equation (1). Therefore, even in the second engagement hole 257, the second positioning pin 71 There is no hindrance to movement.

  Next, when the apex of the protrusion 256 of the first engagement hole 251 exceeds the center of the first positioning pin 70, the first positioning pin 70 is guided by the fitting portion 252. Further, in the second engagement hole 257, the paper feed cassette 61 moves in the downstream direction with respect to the drawing direction while the horizontal ridge line 258 is in contact with the second positioning pin 71. When the fitting portion 252 and the first positioning pin 70 are fitted, the sheet feeding cassette 61 is engaged with the drawer rail 69 at the correct attachment position.

  Next, as shown in FIG. 8, the paper feed cassette 61 is fixed to the drawer rail 69 by fastening both sides of the drawer rail 69 and the cassette body 65 with screws 261. Here, in a state in which the drawer rail 69 is correctly mounted, the front side of the paper feed cassette 61 is fastened with screws 261, and the rear side is the first positioning pin 70 with the protruding portion 256 of the first engagement hole 251. Therefore, the paper feed cassette 61 does not lift up.

In the present embodiment, if the difference between the inner diameter of the screw hole 72 of the drawer rail 69 and the inner diameter of the screw hole 259 of the paper feed cassette 61 shown in FIG. 2 is δ, the difference δ is related to the magnitude of α. Is set as follows (including dimensional tolerances).
α> δ (2)

  Thus, by setting α and δ, even if the screw 261 is loosened, the first positioning pin 70 does not get over the protruding portion 256 in the first engagement hole 251, and the The back side does not float up.

  As described above, in the present embodiment, the amount α of the protrusion 502, the amount of relief β that the second positioning pin 71 can move by the relief portion 257a, the amount of relief γ of the first positioning pin 70 by the recess 255a, The relationship is set as shown in Equation (1). That is, the applied amount α (projection amount α) of the protrusion 256 of the first engagement hole 251, the escape amount γ of the first positioning pin 70 by the recess 255 a in the first engagement hole 251, and the second engagement hole 257. Is set such that α <β and α <γ.

  With this configuration, if the first and second engagement holes 251 and 257 are aligned with the first and second positioning pins 70 and 71 of the pull-out rail 69 and dropped, the sheet feeding cassette 61 can be attached to the drawer rail 69. When the paper feeding cassette 61 is dropped, the paper feeding cassette 61 is positioned while guiding the positioning pin 70 from the guide groove 253 provided in the first engagement hole 251 to the fitting portion 252 by its own weight. As described above, the sheet feeding cassette 61 is dropped by aligning the first and second engagement holes 251 and 257 with the first and second positioning pins 70 and 71 of the pull-out rail 69, so that only one operation is required. The paper feed cassette 61 can be accurately mounted on the drawer rail 69.

  Further, as described above, the number of fastening by screws 261 is one on each side, and two in total, thereby reducing the number of man-hours for attaching and detaching service personnel and assembly work in factory assembly. Can be realized. In the present exemplary embodiment, the sheet feeding cassettes 62 to 64 are described as examples of the drawer unit. However, the drawer unit may be applied to a sheet conveyance unit such as the fixing conveyance unit 301 illustrated in FIG.

DESCRIPTION OF SYMBOLS 1 ... Color laser printer 1A ... Color laser printer main body, 1B ... Image formation part, 1F ... Cassette accommodating part, 61-64 ... Paper feed cassette, 67 ... Drawer apparatus, 68 ... Fixed rail, 69 ... Drawer rail, 70 ... 1st positioning pin, 71 ... 2nd positioning pin, 72 ... Screw hole, 86 ... Both-side inner wall surface, 90 ... Fastening part, 92 ... Holding mechanism of drawer unit, 251 ... 1st engagement hole, 252 ... Fitting part, 253 ... Guide groove, 254 ... First guide surface, 255 ... Second guide surface, 255a recess, 256 ... Projection portion, 257 ... Second engagement hole, 257a ... Escape portion, 259 ... Screw hole, 261 ... Bis, α ... Projection amount of the projecting portion, .beta...., Escape amount of the second positioning hole in the second engagement hole, .gamma.... Escape amount of the first positioning pin in the first engagement hole. Cassette screw holes Allowance of the inner diameter

Claims (5)

A drawer unit that is retractably housed in a housing portion formed in the image forming apparatus main body;
A fixed rail fixed to opposing inner wall surfaces in the width direction orthogonal to the pull-out direction of the storage portion, a pull-out device provided so as to be able to be pulled out to the fixed rail, and a slide rail to which the pull-out unit is attached from above;
A first positioning pin provided on the upstream side of the slide rail in the pulling direction and a second positioning pin provided on the downstream side of the slide rail in the pulling direction;
A first engagement hole and a second engagement hole which are provided in the drawer unit and engage with the first positioning pin and the second positioning pin;
And a holding part for the drawer unit, which is provided in the vicinity of the second positioning pin, and has a fastening part for fastening the drawer unit to the slide rail,
The first engagement hole is
A fitting portion into which the first positioning pin enters;
A first guide surface upstream in the pull-out direction, a second guide surface downstream in the pull-out direction, and a first guide pin that projects from the first guide surface and engages with the fitting portion to engage the pull-out unit A protrusion that restricts the upward movement of the first guide surface, and a recess provided at a position facing the protrusion of the first guide surface of the second guide surface, and guides the first positioning pin to the fitting portion. A guide groove,
The second engagement hole includes an escape portion that allows movement along the pull-out direction of the second positioning pin,
The amount of protrusion α of the protrusion of the first engagement hole, the amount of escape γ of the first positioning pin toward the downstream side in the pull-out direction of the first positioning pin, and the second positioning by the escape portion of the second engagement hole. An image forming apparatus characterized in that a relief amount β on the downstream side in the pin drawing direction is set so that a relationship of α <β and α <γ is established. The fastening portion is formed in the slide rail, and includes a through hole to which a screw is attached, and a screw hole provided in the drawer unit,
2. The image forming apparatus according to claim 1, wherein a difference δ between the inner diameter of the through hole and the inner diameter of the screw hole is set so that a relationship of α> δ is established.   When the drawer unit is attached from above, the surface of the protruding portion that comes into contact with the first positioning pin is gently lowered so that the drawer unit is attached while its first weight causes the first positioning pin to enter the fitting portion. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed with a friction surface.   The image forming apparatus according to claim 1, wherein the drawer unit is a paper feed cassette that stores sheets.   The image forming apparatus according to claim 1, wherein the drawer unit is a sheet conveying unit that conveys a sheet.

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