JP2006243067A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure yield by locking a fixing cover independently of a lock piece. <P>SOLUTION: When a fixing cover 55 is in a lock hold position, turning of the fixing cover 55 is suppressed because the fixing cover 55 has a lock projection 67 engaged with a portion 68 to be locked of a fixing frame 41. The fixing cover 55 is energized from the side of an opening/closing permission position side to the side of the lock hold position by a roll energizing spring 58. When the fixing cover 55 is slid from the lock hold position toward the opening/closing permission position, the lock projection 67 and the portion 68 to be locked are disengaged to allow the fixing cover 55 to turn around a cover shaft 62. The fixing cover 55 can be locked independently of a conventional lock piece, so that yield can be secured during forming because a conventional high dimensional precision is not required. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device and an image forming apparatus.

A fixing device used in an electrophotographic image forming apparatus such as a laser printer generally includes a heating roller having a heat source such as a halogen lamp in a frame and a pressure roller biased to the heating roller. The toner image is thermally fixed while the sheet on which the unfixed toner image is formed passes between both rollers. As such a fixing device, for example, a cover that can be opened and closed is provided on the frame as in the one described in Patent Document 1, and by opening the cover, operations such as replacement of each roller in the device and jamming (paper jam) processing are performed. There is something that can be configured. As a configuration for holding such a cover in a closed state with respect to the frame, one of the cover and the frame is integrally provided with a deformable lock piece, and a claw portion provided at the tip of the lock piece is provided. Some of them are designed to engage the other party.
JP 2002-202676 A

  Here, the frame and the cover of the fixing device are formed of, for example, a crystalline glass reinforced resin material. However, such a material has a large shrinkage after molding, and the dimensional accuracy cannot be increased very much. The above-mentioned lock piece is easy to come off when the engagement amount with respect to the member on the other side is small, and it becomes difficult to remove it when the engagement amount is large, so that relatively high dimensional accuracy is required at the time of molding. When the piece is molded from the above-mentioned material, there is a problem that the ratio of the molded product that does not meet the standard increases and the yield deteriorates.

  The present invention has been completed based on the above circumstances, and provides a fixing device and an image forming apparatus capable of securing a yield by locking a fixing cover without using a locking piece. For the purpose.

  As means for achieving the above object, a fixing device according to claim 1 is a frame, a heating roller rotatably provided in the frame, and heating the sheet material, and heating the sheet material. A pressure member that presses toward the roller, a cover that can be opened and closed with respect to the frame, a closed holding position that holds the cover in a closed posture with respect to the frame, and an openable and closable position that supports the openable and closable state. A support means that can slide between the cover and a slide restricting means that can restrict the sliding of the cover from the closed holding position to the open / close permitted position and that can be operated to release the restriction. Have

  According to a second aspect of the present invention, in the first aspect of the present invention, the support means is provided on the cover and includes a cover shaft serving as a rotation center during the opening / closing operation, and an engagement portion provided on the cover A slide groove provided on the frame and slidably engaged with the cover shaft between the closed holding position and the opening / closing allowable position; and provided on the frame, and the cover is in the closed holding position. An engaged portion that sometimes engages with the engaging portion to restrict the rotation of the cover and releases the engagement with the engaging portion when the cover is in the open / close permitted position; It has features where it is provided.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the slide restricting unit includes a biasing unit that biases the cover from the open / close permission position side to the closed holding position side. It has the characteristics in the place.

  According to a fourth aspect of the present invention, in the slide according to any one of the first to third aspects, the slide regulating means urges the cover from the open / close permitted position side to the closed holding position side by its own weight. It has the feature in the structure which is made.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the frame-side transport roller rotatably provided on the frame, and the cover is rotatably provided. A cover-side transport roller that forms a nip for transporting a sheet material to and from the frame-side transport roller when in the closed holding position and is separated from the frame-side transport roller when the cover is in an open position And has a feature.

  The invention according to claim 6 is the apparatus according to claim 5, further comprising roller urging means for urging one of the cover side conveying roller and the frame side conveying roller side to the other side, It is characterized in that it is biased from the open / close permission position side to the closed holding position side by the stress from the frame side transport roller.

  According to a seventh aspect of the present invention, the cover according to any one of the first to sixth aspects further comprises a fixing nip opening means for separating the pressure member from the heating roller in accordance with the opening operation. It has the characteristics in the place.

  According to an eighth aspect of the present invention, in the apparatus according to the seventh aspect, the cover is held in an open posture between the pressure member and the fixing nip opening means, and the pressure member is moved to the heating roller. It is characterized in that an open lock means is provided for holding it apart.

  An image forming apparatus according to a ninth aspect of the invention is characterized in that the fixing device according to any one of the first to eighth aspects is provided.

<Invention of Claims 1 and 9>
The cover in the closed holding position can be opened and closed by releasing the slide restricting means and sliding it to the open / close permitted position. According to this configuration, the cover can be locked without using a conventional lock piece, and a high dimensional accuracy is not required at the time of molding as in the conventional case, so that the yield can be ensured.

<Invention of Claim 2>
When the cover is in the closed holding position, the rotation of the cover is restricted by the engagement portion of the cover engaging the engaged portion of the frame. Further, when the cover shaft in the slide groove is slid from the closed holding position to the open / close permission position, the engagement between the engaging portion and the engaged portion is released, and the cover can be rotated. With this configuration, the cover locking mechanism can be realized with a relatively simple configuration.

<Invention of Claim 3>
The cover is urged from the open / close permission position side to the closed holding position side by the urging means, so that the cover is prevented from sliding to the open / close permission position, so that the cover is surely prevented from being accidentally opened. Is done.

<Invention of Claim 4>
Since the cover is restricted from sliding to the open / close permission position by its own weight, other urging means can be omitted or simplified, and the cover can be prevented from being opened carelessly with a simple configuration.

<Invention of Claim 5>
As the cover is opened, the nip between the cover-side conveyance roller and the frame-side conveyance roller is opened, so that jamming can be easily performed.

<Invention of Claim 6>
Since the cover receives the urging force of the roller urging means and is urged from the open / close permission position side to the closed holding position side, the cover is prevented from being opened carelessly. Thereby, it is not necessary to provide a dedicated urging means for restricting the sliding of the cover to the open / close permission position, so that the configuration can be simplified.

<Invention of Claim 7>
By providing the fixing nip opening means, the nip between the heating roller and the pressure member is opened at the same time that the cover is opened, so that jamming or the like can be easily performed.

<Invention of Claim 8>
When the cover is opened, the cover is held in the open position by the opening lock means, and the nip between the heating roller and the pressure member is held in an open state, so that workability such as jam processing is further improved. To do.

Next, an embodiment of the present invention will be described with reference to FIGS.
(1) Overall Configuration of Laser Printer FIG. 1 is a side sectional view showing a schematic configuration of a laser printer 1 as an image forming apparatus of the present embodiment. The laser printer 1 is a direct tandem type color laser printer provided with photosensitive drums 33 as four image carriers corresponding to black, cyan, magenta, and yellow colors. In the following description, with respect to the front-rear direction, the right side in FIG. 1 and the left side in FIGS.

  As shown in FIG. 1, the laser printer 1 includes a box-shaped main body casing 2 as a whole, and a feeder unit 4 for feeding a sheet 3 as a sheet material therein or a fed sheet. 3 includes an image forming section 5 for forming an image. A top cover 6 that can be opened and closed is provided on the top surface of the main casing 2. By opening the top cover 6, the process cartridge 23 in the main casing 2 can be replaced. A paper discharge tray 7 on which the printed sheets 3 are stacked is formed on the upper surface of the upper cover 7.

(2) Feeder unit The feeder unit 4 includes a paper feed tray 10 that is detachably attached to the bottom of the main casing 2, a pickup roller 11 that is provided in front of and behind the front end of the paper feed tray 10, and a feed roller 11. The paper roller 12, the separation pad 14 that is pressed against the paper feed roller 12 by the bias of the spring 13, a pair of paper dust removing rollers 15 provided on the upper front side of the paper feed roller 12, and the paper dust removing roller 15 after And a pair of registration rollers 16 provided on the upper side.

  A paper pressing plate (not shown) that can be tilted so as to lift the front end side of the paper 3 is provided on the bottom surface of the paper feeding tray 10, and the paper 3 stacked on the top of the paper feeding tray 10 The sheet is pressed toward the pickup roller 11 by the urging force of the plate, and the conveyance is started between the sheet feeding roller 12 and the separation pad 14 by the rotation of the pickup roller 11. Then, when the sheet 3 is sandwiched between the sheet feeding roller 12 and the separation pad 14 by the rotation of the sheet feeding roller 12, the sheet 3 is rolled up one by one and sent obliquely forward and upward. After the paper dust is removed by the pair of paper dust removing rollers 15, the paper is conveyed to the registration roller 16. A paper feed port 17 for manually feeding the paper 3 is provided on the front surface of the main casing 2. The sheet 3 fed from here is also conveyed to the registration roller 16 by the manual sheet feeding roller 18. The registration roller 16 corrects the skew of the sheet 3 and sends the sheet 3 onto the transport belt 21 at a predetermined timing.

(3) Image Forming Unit The image forming unit 5 includes a conveyance belt 21, a scanner unit 22, a process cartridge 23, a fixing device 24, and the like.

(A) Conveying belt The conveying belt 21 is stretched between a pair of belt supporting rollers 26 that are spaced apart from each other in the front-rear direction so as to be inclined slightly toward the rear end. It is circulated by being driven to rotate. Inside the transport belt 21, four transfer rollers 27 arranged to be opposed to respective photosensitive drums 33 provided in a process cartridge 23 described later are provided at regular intervals in the front-rear direction. The conveyance belt 21 is sandwiched between the corresponding transfer rollers 27.

(B) Scanner Unit Four scanner units 22 as exposure means are arranged above and below the conveyance belt 21 at regular intervals. The scanner unit 22 reflects a laser beam L generated by a laser diode (not shown) so as to sequentially change the direction along a predetermined surface, and the process cartridge 23 receives the laser beam L reflected by the polygon mirror 28. A folding mirror 29 that is folded back toward the photosensitive drum 33, an fθ lens 30 provided in the optical path of the laser light L, and the like.

(C) Process Cartridge Four process cartridges 23 are provided corresponding to each color of magenta, yellow, cyan, and black, and are detachably mounted on the front side of each scanner unit 22 above the conveyor belt 21. . The process cartridge 23 includes a photosensitive drum 33 and a scorotron charger 34 at a lower portion of a frame-shaped cartridge frame 32, and a developing cartridge 35 as a developing unit above the cartridge frame 32.

  The photosensitive drum 33 has a cylindrical shape, and a drum body is formed by coating a metal drum shaft with a positively chargeable photosensitive layer whose outermost layer is made of polycarbonate or the like. The photosensitive drum 33 is rotationally driven by the input of power from a motor (not shown).

  The scorotron charger 34 is disposed opposite to the photosensitive drum 33 at a predetermined interval so as not to come into contact with the photosensitive drum 33 in the obliquely upper rear side of the photosensitive drum 33. The scorotron charger 34 uniformly charges the surface of the photosensitive drum 33 to positive polarity by generating corona discharge from a charging wire such as tungsten.

  The developing cartridge 35 has a box shape opened downward, and is detachably attached to the cartridge frame 32. In the upper part of the developing cartridge 35, a toner storage chamber 36 filled with a positively chargeable non-magnetic one-component toner is provided as a developer. Examples of the toner include polymerizable monomers such as styrene monomers such as styrene, and acrylic monomers such as acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4) methacrylate. Polymerized toner obtained by copolymerization by suspension polymerization or the like is used. Such a polymerized toner has a substantially spherical shape, has extremely good fluidity, and can achieve high-quality image formation. Below the toner storage chamber 36, a supply roller 37, a developing roller 38, a layer thickness regulating blade (not shown), and the like are provided.

  The supply roller 37 is rotatably supported by the developing cartridge 35 and is rotationally driven by input of power from a motor (not shown). The supply roller 37 is configured by covering a metal roller shaft with a roller made of a conductive foam material.

  The developing roller 38 is rotatably supported by the developing cartridge 35 in a state in which the developing roller 38 is in contact with the supply roller 37 so as to be compressed with each other below and obliquely below the supply roller 37. Further, the developing roller 38 faces and contacts the photosensitive drum 33 in a state where the developing cartridge 35 is mounted on the cartridge frame 32. The developing roller 38 is configured by covering a metal roller shaft with a roller body made of a conductive rubber material. The developing roller 38 is rotationally driven by power input from a motor (not shown).

  The layer thickness regulating blade includes a pressing portion made of insulating silicone rubber at the tip of a metal leaf spring material. The layer thickness regulating blade is supported above the developing roller, and the pressing portion is pressed against the developing roller 38 by the elastic force of the leaf spring material.

  The toner discharged from the toner storage chamber 36 is supplied to the developing roller 38 by the rotation of the supply roller 37, and at this time, the toner is positively frictionally charged between the supply roller 37 and the developing roller 38. The toner supplied onto the developing roller 38 enters between the pressing portion of the layer thickness regulating blade and the developing roller as the developing roller 38 rotates, and is carried on the developing roller 38 as a thin layer having a constant thickness. Is done.

  As the surface of the photosensitive drum 33 rotates, the surface of the photosensitive drum 33 is first uniformly charged positively by the scorotron charger 34 and then exposed by high-speed scanning of the laser light L from the scanner unit 22 to form on the paper 3. An electrostatic latent image corresponding to the image to be formed is formed.

  Next, when the developing roller 38 rotates, the positively charged toner carried on the developing roller 38 is formed on the surface of the photosensitive drum 33 when it comes into contact with the photosensitive drum 33. It is supplied to the electrostatic latent image. As a result, the electrostatic latent image on the photosensitive drum 33 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 33.

  Thereafter, the toner image carried on the surface of the photosensitive drum 33 is transferred to the transfer roller 27 while the paper 3 conveyed by the conveyance belt 21 passes through the transfer position between the photosensitive drum 33 and the transfer roller 27. Is transferred to the sheet 3 by a transfer bias voltage applied to the sheet 3. The sheet 3 on which the toner image corresponding to each color is transferred is then conveyed to the fixing device 24. In the fixing device 24, the toner image is thermally fixed on the paper surface by heating the paper 3. Then, the heat-fixed sheet 3 is sent along one of the three transport paths R1 to R3 as described later, and is discharged or re-conveyed to the image forming unit 5.

(4) Fixing Device Next, the structure of the fixing device 24 will be described in detail. 2 is a rear view of the fixing device 24 in a state in which the fixing cover 55 is closed, FIG. 3 is a sectional view taken along line AA in FIG. 2, and FIG. 4 is a line AA in FIG. 5 is a cross-sectional view taken along the line AA of FIG. 2 when the fixing cover 55 is in the open posture. 6 is a cross-sectional view taken along the line BB of FIG. 2, FIG. 7 is a cross-sectional view taken along the line BB of FIG. 2 showing the middle of opening the fixing cover 55, and FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2.

  The fixing device 24 is disposed on the downstream side (rear side) of the transfer position between the photosensitive drum 33 and the transfer roller 27. As shown in FIG. 3 and the like, the fixing device 24 includes a fixing frame 41 as a housing, and includes a heating roller 42 and a pressure roller 43 as a pressure member on the inside thereof. The fixing frame 41 is formed of crystalline glass reinforced resin or the like, and is configured to substantially cover the periphery of the heating roller 42 and the pressure roller 43.

  The heating roller 42 is formed in a cylindrical shape from a metal such as aluminum, and a halogen lamp 44 is provided therein as a heat source. Both ends of the heating roller 42 in the axial direction are rotatably supported by the fixing frame 41, and are driven to rotate counterclockwise in FIG. 3 by the input of power from a motor (not shown).

  As shown in FIG. 6, the pressure roller 43 is formed by covering a metal roller shaft 43A with a roller made of a rubber material, and both ends of the roller shaft 43A are attached to flat arm portions 45, respectively. The roller shaft 43A is supported so as to be driven to rotate. Each arm portion 45 is rotatably supported on the fixing frame 41 by an arm shaft 45A provided at an obliquely upper front position of the roller shaft 43A of the pressure roller 43, and both arm portions 45 are supported by the arm shaft 45A. The pressure roller 43 can be displaced so as to approach and separate from the heating roller 42. Further, an upper end portion of a spring member 46 that is elastically deformable in the vertical direction is attached to the upper rear surface of the fixing frame 41, and a lower end of the spring member 46 is attached to an obliquely rear upper position of the roller shaft 43A in the arm portion 45. ing. As a result, the pressure roller 43 is pressed against the heating roller 42 by the urging force of the spring member 46, and a fixing nip portion 47 is formed between the rollers 42 and 43.

  As shown in FIG. 3, the fixing frame 41 is provided with a heat insulating wall portion 49 in a portion covering the front from the upper side of the heating roller 42. The heat insulating wall 49 has a double structure including an inner wall 49A and an outer wall 49B, and includes a hollow portion 49C between the inner wall 49A and the outer wall 49B. By providing the heat insulating wall 49 having the hollow portion 49C for heat insulation in the fixing frame 41 in this way, it is possible to suppress the release of heat due to radiation from the heating roller 42 to the outside of the fixing device 24. It is possible to reduce the heat loss of the heating roller 42 as well as to suppress the temperature rise inside. The heat insulating wall 49 of the present embodiment is formed hollow by gas injection molding. However, the present invention is not limited to this. For example, a separate cover is attached to the outside of the fixing frame to form a hollow between the two. Alternatively, the hollow portion may be formed by foam molding.

  In the front surface of the fixing frame 41, a paper entry hole 51 for allowing the paper 3 to enter the front position of the fixing nip portion 47 is opened. A heat insulating cover 52 extends from the lower end of the heat insulating wall 49 toward the inside of the paper entry hole 51. Since the heat insulating cover portion 52 is curved so as to be spaced apart from the outer peripheral surface of the heating roller 42, it does not come into contact with the outer peripheral surface of the heating roller 42. In addition, the front end of the heat insulating cover 52 is above the straight line connecting the fixing nip 47 and the transfer position between the most downstream photosensitive drum 33 and the transfer roller 27 (substantially coincides with the position through which the paper 3 passes). Therefore, the sheet 3 entering the fixing nip 47 does not come into contact with the sheet. The heat insulating cover portion 52 suppresses the release of radiant heat and the like forward from the paper entry hole 51 by the heating roller 42, so that the temperature rise in the apparatus can be suppressed.

  As shown in FIGS. 2 and 3, a shaft portion 53A of the fixing paper discharge roller 53 is supported at the rear upper end position of the fixing frame 41 so as to be rotatable in the left-right direction. Four fixing paper discharge rollers 53 as frame-side conveyance rollers are attached to the shaft portion 53A at intervals in the length direction thereof. Each fixing paper discharge roller 53 is rotated in the forward direction (counterclockwise direction in FIG. 3) or the reverse direction (clockwise direction in FIG. 3) by driving the shaft portion 53A with power from a motor (not shown). The

  A fixing cover 55 (corresponding to the cover of the present invention) is attached to the rear surface of the fixing frame 41 so as to be openable and closable below the fixing paper discharge roller 53. 3 and 6, the fixing cover 55 has a closed posture that covers the rear of the fixing nip portion 47 in a vertical posture, and a posture in which the upper end portion is tilted backward from the closed posture as shown in FIGS. Therefore, the fixing nip 47 can be held in an open posture in which the rear of the fixing nip 47 is opened. In the following description of the fixing cover 55, the direction in the closed position is used as a reference unless otherwise specified.

  As shown in FIGS. 2 and 3, the fixing cover 55 is attached with a first roller holding portion 57 that holds a first pinch roller 56 as a cover-side conveying roller at a position corresponding to each fixing paper discharge roller 53. . The first roller holding portion 57 can be displaced in the vertical direction and is biased upward by a roller biasing spring 58 as a roller biasing means. The first pinch roller 56 is held so as to be driven and rotated so as to protrude upward from the upper end of the fixing cover 55, and when the fixing cover 55 is in the closed position, the first pinch roller 56 is biased by the roller biasing spring 58. Thus, the first nip portion 59 is formed in pressure contact with the lower outer peripheral surface of the fixing paper discharge roller 53. The first nip portion 59 is located on the downstream side of the fixing nip portion 47 and obliquely rearward and upward.

  As shown in FIGS. 2 and 6, a pair of side plates 61 elongated in the substantially vertical direction are provided on the left and right ends of the fixing cover 55. On the outer surface of each side plate 61, a columnar cover shaft 62, which serves as a rotation center of the fixing cover 55, protrudes outward in the vicinity of the lower end. On the other hand, the fixing frame 41 is provided with a pair of left and right opposing walls 63 that face each side plate 61 of the fixing cover 55 with a predetermined interval. Each opposing wall 63 is formed with a cylindrical bearing portion 64 protruding inward, and a cover shaft 62 is rotatably fitted in a slide groove 65 formed inside the bearing portion 64. Yes. The slide groove 65 extends in a substantially vertical direction (precisely, an oblique direction upward from the rear end), and the fixing cover 55 is in a closed holding position where the cover shaft 62 is located at the lower end of the slide groove 65 (see FIG. 6). And an open / close permission position (see FIGS. 7 and 8) located at the upper end of the slide groove 65 along the length direction.

  Further, each side plate 61 of the fixing cover 55 is formed with a locking projection 67 as an engaging portion protruding outward at a position closer to the upper end than the cover shaft 62. The lock protrusion 67 has a substantially rectangular parallelepiped shape elongated in the rear end rising direction, and a tapered surface 67A is formed by dropping one corner of the front lower end. On the other hand, on each opposing wall 63 of the fixing frame 41, a locked portion 68 as an engaged portion is formed inwardly projecting inwardly and upwardly from the bearing portion 64. The locked portion 68 has a substantially U-shape that opens obliquely rearward and upward, and the lock protrusion 67 enters the locked portion 68 along the longitudinal direction thereof, whereby both 67 and 68 are formed. Is engaged, and the rotation of the fixing cover 55 around the cover shaft 62 from the closed position to the open position is restricted. Further, the lock protrusion 67 and the locked portion 68 are engaged when the fixing cover 55 is in the closed holding position, and are not engaged when the fixing cover 55 is in the open / close permission position. Further, when the fixing cover 55 is in the closed holding position, the elastic restoring force of the roller urging spring 58 that biases the first pinch roller 56 toward the fixing paper discharge roller 53 side closes and holds the fixing cover 55 from the opening / closing allowable position side. It is comprised so that it may act on the direction (downward direction) urged | biased to the position side. That is, the roller urging spring 58 functions as a slide restricting means that can restrict the slide of the fixing cover 55 from the closed holding position to the open / close permitted position and can perform a release operation. In addition, in this configuration, the fixing cover 55 functions as a slide restricting unit by being urged from the closed holding position to the open / close permitted position side by its own weight. The cover shaft 62, the lock protrusion 67, the slide groove 65, and the locked portion 68 described above correspond to the support means of the present invention.

  Further, as shown in FIGS. 2 and 3, the fixing cover 55 is opened at the lower end position on the inner surface of the left and right side plates 61 as a fixing nip opening means and an opening lock means having a substantially cylindrical shape along the left-right direction. A lock unit 70 is provided. On the other hand, the arm portion 45 is provided with a pressed portion 71 that extends obliquely rearward and downward with respect to the roller shaft 43A of the pressure roller 43. When the fixing cover 55 is opened, the release lock portion 70 is provided. The arm portion 45 is configured to be pressed down in contact with the rear edge of the pressed portion 71. In addition, a lock recess 72 serving as an open lock means that is recessed in an arc shape is formed at the rear edge of the pressed portion 71, and when the pressed portion 71 pushes down the arm portion 45 by a predetermined amount, The release lock portion 70 is engaged (see FIG. 5). Further, a shaft hole 74 to which a chute 73 (see FIGS. 9 and 10) described later is attached is provided at the lower end portion of the side plate 61 in the fixing cover 55. 2 to 8 show a state in which the chute 73 is removed from the shaft hole 74 for convenience of explanation.

  Further, as shown in FIG. 3, an intermediate roller 75 that can be driven and rotated is attached to the fixing frame 41 at an intermediate position between the fixing nip portion 47 and the first nip portion 59. The intermediate roller 75 is disposed on the side opposite to the first pinch roller 56 with respect to the sheet 3 conveyed between the fixing nip portion 47 and the first nip portion 59, and a contact point with respect to the sheet 3 is provided. It arrange | positions so that it may become the position of the 1st pinch roller 56 side rather than the common tangent C of the heating roller 42 and the 1st pinch roller 56.

(5) Transport Path after Fixing FIG. 9 is a cross-sectional view showing the rear part of the laser printer 1 with the rear cover 77 closed, and FIG. 10 shows the rear part of the laser printer 1 with the rear cover 77 opened. It is sectional drawing shown.
The main casing 2 is provided with a rear opening 76 behind the fixing device 24, and a rear cover 77 that covers the rear opening 76 so as to be opened and closed is attached. The rear cover 77 is rotatable between the closed posture shown in FIG. 9 and the open posture shown in FIG. 10 around the vicinity of the lower end. On the inner surface of the rear cover 77, a second roller holding portion (not shown) that holds a second pinch roller 78 that can be driven and rotated at a position corresponding to each fixing paper discharge roller 53 is attached. The second roller holding portion can swing back and forth and is urged forward by a spring member (not shown). When the rear cover 77 is closed, the second pinch roller 78 is pressed against the rear side of the fixing paper discharge roller 53 by the urging force of the spring member, thereby forming the second nip portion 79. The second nip portion 79 is located on the downstream side of the first nip portion 59 and obliquely rearward and upward.

  An arc-shaped path 81 extending in a substantially arc shape from the second nip portion 79 obliquely upward and upward is provided at the rear portion in the main body casing 2, and a discharge port 82 is provided at the upper end thereof. The discharge port 82 is provided with a pair of upper and lower upper discharge rollers 83, and the sheet 3 sent from the arcuate path 81 is discharged onto the discharge tray 7 by the upper discharge roller 83. Yes. Further, as shown in FIG. 1, a re-conveying path 84 is provided at the lower part in the main body casing 2, going downward from the second nip portion 79 and going forward. In this re-conveying path 84, relay rollers 85 for conveying the paper 3 to two places are arranged. The re-conveying path 84 is folded upward at the front portion of the main body casing 2 and continues to the position immediately before the registration roller 16.

  The laser printer 1 is configured such that the sheet 3 after being thermally fixed is sent to one of the following three transport paths. That is, the laser printer 1 includes a first transport path R1 (see FIG. 9) from the second nip 79 to the discharge tray 7 through the arc-shaped path 81 and the rear cover in a state where the rear cover 77 is closed. The second conveyance path R2 (see FIG. 10) from the first nip portion 59 toward the rear cover 77 in the state where the 77 is opened, and the re-conveyance path 84 from the second nip portion 79 in the state where the rear cover 77 is closed. A third transport path R3 (see FIG. 9) that passes through the image forming section 5 again is provided.

  A flapper 86 that can be rotated at a position below the second pinch roller 78 is attached to the rear cover 77. The flapper 86 has a plate shape with a sharp cross-sectional shape at the tip, and when the rear cover 77 is closed, the tip is arranged at an intermediate position between the first nip portion 59 and the second nip portion 79. As shown in FIG. 3, the flapper 86 also has a leading end that is in contact with the outer peripheral surface of the fixing paper discharge roller 53 and a forward guide position that is separated from the outer peripheral surface of the fixing paper discharge roller 53. It can be displaced to a direction guide position (dashed line), and is biased counterclockwise in FIG. 3 by a spring member (not shown) so that the tip is pressed against the outer peripheral surface of the fixing paper discharge roller 53. Yes.

  Below the flapper 86, a chute 73 included in the above-described fixing device 24 is disposed. The chute 73 has an arcuately curved plate shape, and a shaft portion (not shown) provided near the lower end is engaged with the shaft hole 74 of the fixing cover 55 described above, so that the shaft hole 74 is centered. Is pivotally attached to the. When the rear cover 77 is closed, as shown in FIG. 9, the rib 87 projecting from the inner surface of the rear cover 77 is brought into contact with the vicinity of the side end of the outer surface of the chute 73 so that the chute 73 stands up. Supported. In this guide position, a part of the re-transport path 84 (third transport path R3) is formed between the outer surface of the chute 73 and the inner surface of the rear cover 77. When the rear cover 77 is opened, as shown in FIG. 10, the chute 73 is supported at the intrusion prevention position where the chute 73 has fallen to the rear side. At this intrusion prevention position, the chute 73 closes the gap between the rear cover 77 and the fixing device 24, thereby preventing the sheet 3 from entering the reconveying path 84.

  In addition, an air flow path 88 extending upward from the fixing device 24 is provided at the rear portion in the main body casing 2. The upper part of the air flow path 88 communicates with the arcuate path 81 and the discharge port 82, and the air around the fixing device 24 heated by heat radiation from the upper part of the fixing frame 41 passes through the air flow path 88. Then, it is guided upward and discharged from the discharge port 82 to the outside. A duct 89 extending substantially in the vertical direction is provided between the air flow path 88 and the most downstream process cartridge 23 and the scanner unit 22, and a fan 90 is provided at the left end position of the upper end of the duct 89. It has been. The outside air taken in by the fan 90 is discharged from the duct 89 into the main casing 2, thereby cooling the main casing 2. A partition wall 91 provided between the duct 89 and the air flow path 88 extends in the vertical direction as a whole, and has a shape in which a lower half portion protrudes to the front side so as to escape the fixing frame 41. If the duct covers the fixing device, the air in the duct is heated by the heat from the fixing device, which may adversely affect the cooling function. Since the upper portion is an air flow path 88 for releasing heat to the outside, the air in the duct 89 is suppressed from being heated by heat radiation from the fixing device 24, and the cooling efficiency of the device is improved.

(6) Operation and Effect of Laser Printer During the printing operation, the sheet 3 is moved from the fixing nip portion 47 by the rotational driving of the heating roller 42 and the fixing discharge roller 53 in the forward direction (counterclockwise direction in FIG. 3). 1 nip portion 59 is conveyed. Here, since the sheet 3 is bent so as to protrude toward the first pinch roller 56 by contacting the intermediate roller 75 between the fixing nip portion 47 and the first nip portion 59, the intermediate roller 75 is provided. Compared to the case where there is no sheet, the amount of winding of the sheet 3 around the first pinch roller 56 increases. When the sheet 3 passes through the fixing nip portion 47, the sheet 3 may be curled (warped) toward the heating roller 42. As described above, the sheet 3 is formed on the outer peripheral surface of the first pinch roller 56. The curl is corrected by being warped in the opposite direction to the curl. Since the intermediate roller 75 rotates following the transported paper 3, the printing surface is less rubbed than when the paper 3 is wound around the first pinch roller 56 using a member other than a roller. Therefore, it is possible to prevent the paper 3 from being stained or jammed.

  When face-down paper discharge is performed after printing, printing is performed with the rear cover 77 closed. As shown in FIGS. 3 and 9, the leading edge of the sheet 3 that has passed through the first nip portion 59 hits the front surface of the flapper 86 (two-dot chain line in FIG. 3) at the reverse guide position, and the flapper 86 is moved in the forward direction. It is displaced to the guide position (one-dot chain line in FIG. 3). Then, the leading edge of the sheet 3 goes to the second nip portion 79 through a gap opened between the leading edge of the flapper 86 and the outer peripheral surface of the fixing paper discharge roller 53. Then, the sheet 3 is discharged from the second nip portion 79 through the arc-shaped path 81 and the discharge port 82 onto the sheet discharge tray 7 (first conveyance path R1), and the surface printed on the image forming section 5 is directed downward. It is loaded in a facing position.

  Next, when performing double-sided printing, the printing operation is performed with the rear cover 77 closed. First, after printing is performed on one side of the sheet 3 by the image forming unit 5, the leading end of the sheet 3 passes through the first nip part 59 and the second nip part 79 in the same manner as in face-down paper discharge, and is arcuate. It is sent out to the path 81. Then, when the trailing edge of the sheet 3 passes between the flapper 86 and the fixing paper discharge roller 53, the reverse guide position where the flapper 86 contacts the fixing paper discharge roller 53 by the biasing force of the spring member (two points in FIG. 3). It is displaced to the chain line). Subsequently, before the rear end 3A (see FIG. 3) of the sheet 3 passes through the second nip portion 79, the fixing paper discharge roller 53 is rotated in the reverse direction (clockwise direction in FIG. 3). As a result, the rear end 3A of the sheet 3 descends and comes into contact with the rear surface of the flapper 86, and the sheet 3 is guided to the re-transport path 84 (third transport path R3). Then, the sheet 3 reaches the image forming unit 5 again from the re-conveying path 84 via the registration roller 16, and printing is performed on the surface opposite to the previous printing surface.

  Next, when face-up paper discharge is performed after printing, printing is performed with the rear cover 77 opened as shown in FIG. By opening the rear cover 77, the second pinch roller 78 and the flapper 86 are separated from the fixing paper discharge roller 53, and the second nip 79 is opened. For this reason, the sheet 3 that has passed through the first nip portion 59 does not go to the first transport path R1, but proceeds rearward as it is, is discharged onto the rear cover 77 (second transport path R2), and is printed. It is loaded with the top up. When the rear cover 77 is opened, the chute 73 falls outside due to its own weight, and the re-transport path 84 is closed. For this reason, the sheets 3 stacked on the rear cover 77 are prevented from slipping into the reconveying path 84. In this way, in the laser printer 1, the sheet 3 is transferred to the three transport paths R1 by one drive roller (fixing discharge roller 53) and two driven rollers (first pinch roller 56, second pinch roller 78). ~ R3 can be sent separately. Thus, only one roller driving mechanism is required, and the apparatus can be prevented from becoming complicated. Therefore, it is possible to prevent an increase in the size of the apparatus and suppress an increase in cost.

  Next, when the fixing cover 55 of the fixing device 24 is opened, the rear cover 77 is first opened, and the fixing cover 55 in the closed holding position shown in FIGS. Slide to. At this time, the first roller holding portion 57 that holds the first pinch roller 56 is displaced downward with respect to the fixing cover 55, and the roller urging spring 58 is compressed. When the fixing cover 55 reaches the open / close permission position, the cover shaft 62 reaches almost the upper end of the slide groove 65, and the engagement between the lock projection 67 and the locked portion 68 is released. Therefore, when the fixing cover 55 is rotated so as to be tilted rearward, as shown in FIGS. 4 and 7, the release lock portion 70 of the fixing cover 55 comes into contact with the rear edge of the pressed portion 71 in the arm portion 45. . When the fixing cover 55 is further rotated from this state, the pressed portion 71 is lowered accordingly, the pressure roller 43 is separated from the heating roller 42, and the fixing nip portion 47 is opened. When the fixing cover 55 reaches the opening posture shown in FIGS. 5 and 8, the opening lock portion 70 engages with the lock recess 72 of the pressed portion 71, and the displacement between the arm portion 45 and the fixing cover 55 is restricted. The In this state, even if the arm portion 45 tries to rotate counterclockwise due to the bias of the spring member 46, the fixing cover 55 is covered by the positional relationship between the cover shaft 62, the open lock portion 70, and the lock recess 72. Since the component force to rotate counterclockwise around the shaft 62 does not act, both the first nip portion 59 and the fixing nip portion 47 are held open.

  5 and 8, when the fixing cover 55 in the opened posture is closed, if the fixing cover 55 is pushed diagonally forward and rotated in the counterclockwise direction, the opening lock portion 70 and the lock recess 72 may The engagement is released, the arm portion 45 is raised by the biasing force of the spring member 46, and the pressure roller 43 comes into pressure contact with the heating roller 42. Subsequently, the taper surface 67A of the lock projection 67 abuts on the lower side portion 68A of the locked portion 68, and the lock projection 67 rides on the lower side portion 68A. On the other hand, the first pinch roller 56 contacts the fixing paper discharge roller 53 and the roller urging spring 58 is compressed. When the fixing cover 55 reaches the closed position, the lock projection 67 gets over the lower side portion 68A of the locked portion 68, and the fixing cover 55 is moved from the open / close permitted position to the closed holding position by the elastic restoring force of the roller biasing spring 58. While sliding, the lock protrusion 67 engages the inside of the locked portion 68 (see FIGS. 3 and 6). As a result, the fixing cover 55 is locked in the closed posture.

  As described above, according to the present embodiment, the fixing cover 55 in the closed holding position can be freely opened and closed by performing the compression (release) operation of the roller urging spring 58 as the slide regulating means and sliding it to the open / close permission position. It becomes. According to this configuration, the fixing cover 55 can be locked without using a conventional locking piece, and high dimensional accuracy is not required at the time of molding as in the conventional case, so that the yield can be ensured.

  When the fixing cover 55 is in the closed holding position, the lock protrusion 67 of the fixing cover 55 engages with the locked portion 68 of the fixing frame 41, so that the rotation of the fixing cover 55 is restricted. When the cover shaft 62 in the slide groove 65 is slid from the closed holding position to the open / close permitted position, the engagement between the lock protrusion 67 and the locked portion 68 is released, and the fixing cover 55 can be rotated. With this configuration, the lock mechanism of the fixing cover 55 can be realized with a relatively simple configuration.

  In addition, the fixing cover 55 is urged from the opening / closing permission position side to the closing holding position side by the roller urging spring 58 as the urging means, so that the fixing cover 55 is restricted from sliding to the opening / closing permission position. Therefore, the fixing cover 55 is reliably prevented from being opened carelessly.

  In addition, since the fixing cover 55 is restricted from sliding to an openable / closable position by its own weight, other urging means can be omitted or simplified, and the fixing cover 55 is inadvertently configured with a simple configuration. Can be prevented from opening.

  Further, as the fixing cover 55 is opened, the first nip portion 59 between the first pinch roller 56 and the fixing paper discharge roller 53 is opened, so that jam processing can be easily performed.

  Further, since the fixing cover 55 receives the urging force of the roller urging spring 58 and is urged from the open / close permission position side to the closed holding position side, the fixing cover 55 is prevented from being opened carelessly. Accordingly, it is not necessary to provide a dedicated urging unit for restricting the fixing cover 55 from sliding to the open / close permission position, so that the configuration can be simplified.

  Further, by providing an opening lock portion 70 as a fixing nip opening means, the fixing cover 55 is opened, and at the same time, the fixing nip portion 47 between the heating roller 42 and the pressure roller 43 is opened. Can be easily performed.

  When the fixing cover 55 is opened, the fixing cover 55 is held in an open posture by an opening lock portion 70 and a lock recess 72 as an opening lock means, and a fixing nip portion between the heating roller 42 and the pressure roller 43. Since 47 is held in an open state, workability such as jam processing is further improved.

  The present invention is not limited to the embodiments described with reference to the above description and drawings, and various modifications can be made without departing from the scope of the invention.

1 is a side sectional view showing a schematic configuration of a laser printer according to an embodiment of the present invention. Rear view of the fixing device with the fixing cover closed AA line sectional view of FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 2 showing the middle of opening the fixing cover. 2 is a cross-sectional view taken along line AA in FIG. 2 when the fixing cover is in an open posture. BB sectional view of FIG. 2 is a cross-sectional view taken along the line BB in FIG. 2 showing the way of opening the fixing cover. 2 is a cross-sectional view taken along the line BB in FIG. 2 when the fixing cover is in an open posture. Sectional view showing the rear of the laser printer with the rear cover closed Sectional view showing the rear of the laser printer with the rear cover open

Explanation of symbols

1. Laser printer (image forming device)
3 ... paper (sheet material)
24. Fixing device 41 ... Fixing frame (frame)
42 ... heating roller 43 ... pressure roller (pressure member)
53. Fixing paper discharge roller (frame side conveyance roller)
55. Fixing cover (cover, slide regulating means)
56 ... 1st pinch roller (cover side transport roller)
58 ... Roller biasing spring (slide regulating means, biasing means, roller biasing means)
62 ... Cover shaft (support means)
65 ... Slide groove (support means)
67 ... Lock protrusion (support means, engaging portion)
68: Locked part (support means, engaged part)
70... Opening lock part (fixing nip opening means, opening lock means)
72: Lock recess (open lock means)

Claims (9)

Frame,
A heating roller that is rotatably provided in the frame and heats the sheet material;
A pressure member that presses the sheet material toward the heating roller;
A cover that can be opened and closed with respect to the frame;
A support means for allowing the cover to slide between a closed holding position for holding the cover in a closed posture in an unopenable state and an open / close permission position for supporting the cover so as to be opened and closed;
A slide regulating means capable of regulating sliding of the cover from the closed holding position to the opening / closing allowable position and capable of releasing the regulation;
A fixing device comprising: The supporting means includes
A cover shaft provided on the cover and serving as a rotation center at the time of opening and closing;
An engaging portion provided on the cover;
A slide groove provided on the frame, the cover shaft being slidably engaged between the closed holding position and the open / close permitted position;
The frame is provided on the frame, engages with the engaging portion when the cover is in the closed holding position, and restricts the rotation of the cover, and engages when the cover is in the open / close permitted position. An engaged part for releasing engagement with the part;
The fixing device according to claim 1, further comprising: The fixing device according to claim 1, wherein the slide restricting unit includes an urging unit that urges the cover from the open / close permission position side to the closed holding position side. 4. The slide control means according to claim 1, wherein the cover is biased from the open / close permission position side to the closed holding position side by its own weight. 5. The fixing device described. A frame-side conveying roller rotatably provided on the frame;
When the cover is rotatably provided and forms a nip for conveying the sheet material with the frame-side conveying roller when the cover is in the closed holding position, and when the cover is in an open posture A cover-side transport roller spaced from the frame-side transport roller;
The fixing device according to claim 1, further comprising: Roller urging means for urging one of the cover side conveying roller and the frame side conveying roller side to the other side, and the cover from the open / close permitted position side by the stress from the frame side conveying roller. The fixing device according to claim 5, wherein the fixing device is biased toward the closed holding position. The fixing device according to claim 1, wherein the cover includes a fixing nip opening unit that separates the pressure member from the heating roller in accordance with the opening operation. An opening lock means is provided between the pressure member and the fixing nip opening means to hold the cover in an open posture and hold the pressure member in a state separated from the heating roller. The fixing device according to claim 7, wherein the fixing device is a fixing device. An image forming apparatus comprising the fixing device according to claim 1.

Images