JP2008076976A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-profile laser printer while preventing a flap. <P>SOLUTION: The laser printer 1 has: a curved guide 90 which is provided on the downstream side of a fixing unit 21 and provided with a guide surface 91 which curves a paper 3 and guides it in a direction different from a flow direction; a guide roller 60 which is disposed between the curved guide 90 and the fixing unit 21 and comes into contact with the paper 3, to guide it to the entrance of the curved guide 90; a roller support section 62 which moves the guide roller 60 between a separate position where the guide roller 60 guides the paper 3, so as to float the paper 3 from the guide surface 91 of the entrance of the curved guide 90 and a close position where the guide roller 60 guides the paper 3, so that the paper 3 is closer to the guide surface 91 of the entrance of the curved guide 90 than the separate position; and a solenoid section 80 which moves the guide roller 60 to the separate position, before the front edge of the paper 3 enters the entrance of the curved guide 90 and moves the guide roller 60 to the close position, before the rear edge of the paper 3 passes through the guide roller. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  As a general structure of an image forming apparatus, a conveyance path for conveying a sheet is provided, and a curved guide having a curved guide surface and reversing the sheet conveyance direction is provided in the middle of the conveyance path. . The front end of the sheet transported from the upstream side of the transport path to the entrance of the curved guide is set so as to be lifted from the guide surface of the entrance of the curved guide. This is to prevent the leading edge of the sheet from being caught at the entrance of the curved guide. However, when the trailing edge of the paper reaches the entrance of the curved guide, the trailing edge of the paper strikes the guide surface at the entrance of the curved guide due to the elastic reaction force, and a jumping sound is generated. On the other hand, in the market for image forming apparatuses, products with a lower profile are required. As the image forming apparatus is lowered in height, the curved guide is also lowered, and the curvature radius of the curved guide becomes smaller than before. Increased sound is an obstacle to low profile.

2. Description of the Related Art Conventionally, an image forming apparatus provided with a guide member for preventing a jumping sound is known from Patent Document 1 below. In this image forming apparatus, a guide member is provided between a paper feeding cassette that feeds paper and a curved guide disposed on the downstream side of the paper feeding cassette, and the rear end of the paper is bent by the guide member. It is designed to be guided by a guide surface.
JP-A-5-116800

  However, since this image forming apparatus is provided with a guide member in addition to the curved guide, if the curved guide is lowered, a space for installing the guide member cannot be secured, and the image forming apparatus is lowered. It becomes difficult to do. As described above, there is a situation in which the problem of preventing the bounce noise is incompatible with the problem of reducing the height of the image forming apparatus.

  The present invention has been completed based on the above-described circumstances, and an object thereof is to enable a reduction in the height of an image forming apparatus while preventing splashing noise.

  As means for achieving the above object, the invention of claim 1 is directed to a conveying means for conveying a recording medium along a conveying path, and an image for forming an image on the recording medium conveyed by the conveying means. Forming means, a curved guide provided in the middle of the transport path and having a guide surface that curves the recording medium and guides the recording medium in a direction different from the entry direction, and is arranged upstream of the entrance of the curved guide in the transport path. And a guide roller for contacting the recording medium and guiding it to the entrance of the curved guide, and the guide roller so that the recording medium floats from the guide surface at the entrance of the curved guide. A separation position for guiding the recording medium, and the recording surface of the recording medium in contact with the guide surface at the entrance of the curved guide or the guide surface at the entrance of the curved guide rather than the separation position. A roller support mechanism capable of moving between an approach position for guiding the recording medium so as to be in an approached state, and the guide roller before the front end of the recording medium enters the entrance of the curved guide. And a roller driving means for moving the recording medium to the approach position before the rear end of the recording medium passes through the guide roller.

  According to a second aspect of the present invention, in the first aspect, the roller driving unit is based on a sensor that detects that the recording medium is approaching the curved guide and a signal from the sensor. And a solenoid mechanism for moving the guide roller.

  According to a third aspect of the present invention, in the sensor according to the second aspect, the sensor is located upstream of the entrance of the curved guide, and when the front end of the recording medium enters the entrance of the curved guide. The solenoid mechanism is arranged downstream from the rear end of the recording medium, and is characterized in that the guide roller is moved to the separation position on condition that the sensor detects the recording medium.

  According to a fourth aspect of the present invention, there is provided the method according to any one of the first to third aspects, wherein the conveyance unit forms a conveyance path for the recording medium between the guide roller and an entrance of the curved guide. It is characterized by the fact that it has a driving roller that is opposed to it.

  A fifth aspect of the present invention is characterized in that, in any one of the first to fourth aspects, a guide member having a curved shape corresponding to the guide surface is disposed opposite to the curved guide. Have

<Invention of Claim 1>
According to the first aspect of the present invention, the guide roller can be moved to the separated position by the roller driving means before the front end of the recording medium enters the entrance of the curved guide. Thereby, it is possible to prevent the front end of the recording medium from being caught at the entrance of the curved guide. Thereafter, the guide roller can be moved to the approach position by the roller driving means before the rear end of the recording medium passes through the guide roller. Thereby, there is no possibility that the rear end of the recording medium will bounce and hit the guide surface at the entrance of the curved guide to generate a bounce sound. Therefore, it is possible to cope with a reduction in the height of the image forming apparatus by preventing splashing noise by using a guide roller that is essentially necessary.

<Invention of Claim 2>
According to the second aspect of the present invention, the sensor detects that the recording medium is approaching the curved guide and transmits a signal. Based on this signal, the solenoid mechanism generates a driving force to move the guide roller. be able to.

<Invention of Claim 3>
According to the invention of claim 3, the guide roller can be moved to the separation position before the front end of the recording medium enters the entrance of the curved guide. As a result, the recording medium can be reliably guided by the guide roller. The guide roller can be moved to the approach position after the front end of the recording medium has entered the entrance of the curved guide. Thereby, it is possible to reliably prevent the recording medium from being caught at the entrance portion of the curved guide.

<Invention of Claim 4>
According to the fourth aspect of the present invention, the recording medium can be sandwiched between the guide roller and the driving roller in the separated position and conveyed to the curved guide. That is, the guide roller can function as a driven roller for the drive roller. Therefore, it is not necessary to provide a driven roller separately from the guide roller.

<Invention of Claim 5>
According to the invention of claim 5, when the recording medium enters the curved guide, the recording medium can be transported between the guide surface and the guide member. Therefore, the recording medium can be stably conveyed along the guide surface in the curved guide.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
[Overall configuration of laser printer]
FIG. 1 is a side sectional view of an essential part showing an embodiment of a laser printer (an example of an “image forming apparatus” of the present invention) 1. In FIG. 1, the laser printer 1 includes a main body casing 2, a paper feed mechanism unit 4 for feeding paper (an example of “recording medium” of the present invention) 3 in the main body casing 2, An image forming unit (an example of the “image forming unit” of the present invention) 5 for forming an image on the formed paper 3, and a paper discharge mechanism unit for discharging the paper 3 with the image formed (“ An example) 6 of “conveying means”. In the following description, the right side in FIG.

  An attachment / detachment opening 7 for attaching / detaching a process cartridge 20 described later is formed on the front side wall of the main casing 2, and a front cover (not shown) for opening / closing the attachment / detachment opening 7 is provided. When the front cover is opened, the attachment / detachment opening 7 is opened, and the process cartridge 20 can be attached / detached to / from the main body casing 2 via the attachment / detachment opening 7. A paper feed tray 9 on which paper 3 for forming an image is loaded is attached to the lower portion of the main body casing 2 so as to be drawn forward.

  The paper feed tray 9 has a box shape with an open upper surface that can accommodate the sheets 3 in a stacked form, and a sheet pressing plate 15 is provided at the lower part thereof. The paper pressing plate 15 is configured such that the paper 3 can be placed in a stacked form, and supported at the rear end thereof so as to be swingable, so that the front end can be moved in the vertical direction according to the amount of the paper 3 to be stacked. Is done.

  A lever 17 for lifting the front end of the paper pressing plate 15 upward is provided at the front end of the paper feed tray 9. The lever 17 is formed in a substantially L-shaped cross section so as to go from the front side to the lower side of the paper pressing plate 15, and its upper end is attached to a lever shaft 18 provided at the front end of the paper feed tray 9. The rear end portion is in contact with the lower surface of the front end portion of the paper pressing plate 15. Thus, when the lever shaft 18 is driven to rotate clockwise in the drawing, the lever 17 rotates with the lever shaft 18 as a fulcrum, and the rear end portion of the lever 17 lifts the front end portion of the paper pressing plate 15. When the paper feed tray 9 is detached from the main casing 2, the paper pressing plate 15 moves downward due to its own weight.

  The paper feed mechanism unit 4 includes a paper feed roller 10 located above the front end of the paper feed tray 9 and a pickup roller 12 that is behind the paper feed roller 10 and contacts the uppermost paper 3 of the paper feed tray 9. ing. A reversing guide 37 having a guide surface 16 that reverses and guides the conveyance direction of the paper 3 is provided at a position facing the front half of the outer peripheral surface of the paper feeding roller 10. And the guide surface 16 pass through the sheet 3. A separation pad 11 that presses against the paper feed roller 10 by a biasing force of a spring is provided at an inlet portion of the reversing guide 37. Further, during the conveyance of the reversing guide 37, the pinch roller 13 located on the downstream side of the separation pad 11 and the paper dust removing roller 8 located on the downstream side of the pinch roller 13 are respectively arranged opposite to the paper feed roller 10. ing.

  The uppermost sheet 3 in the sheet feeding tray 9 is pressed toward the pickup roller 12 by the sheet pressing plate 15, and is sent out to the entrance of the reversing guide 37 by the rotation of the pickup roller 12. Are separated one by one when sandwiched between them. Then, the sheet 3 fed out between the pickup roller 12 and the separation pad 11 is sandwiched between the sheet feeding roller 10 and the pinch roller 13 and between the sheet feeding roller 10 and the paper dust removing roller 8 to be a reverse guide. The sheet is discharged from the outlet 37 and conveyed to the registration roller 14 disposed obliquely above and behind the sheet feeding roller 10.

The registration roller 14 is composed of a pair of rollers, corrects the skew of the sheet 3, and sends the sheet 3 to an image forming position (a contact portion between a photosensitive drum 29 and a transfer roller 32 described later).
The image forming unit 5 includes a scanner unit 19, a process cartridge 20, a fixing device 21, and the like.

  The scanner unit 19 is provided in the upper part of the main casing 2 and includes a laser light source (not shown), a polygon mirror 22 that is rotationally driven, an fθ lens 23, a reflecting mirror 24, a lens 25, a reflecting mirror 26, and the like. . The laser beam based on the image data emitted from the laser light source is deflected by the polygon mirror 22 as shown by a chain line, passes through the fθ lens 23, and then the optical path is bent downward by the reflecting mirror 24. Irradiation is performed on the surface of a drum body 34 of a photosensitive drum 29 described later of the process cartridge 20.

  The process cartridge 20 is arranged below the scanner unit 19 and includes an upper frame 27 and a lower frame 28 that is formed separately from the upper frame 27 and combined with the upper frame 27 as a casing. Further, the process cartridge 20 includes a photosensitive drum 29, a scorotron charger 30 as a charger (hereinafter also simply referred to as a charger 30), a developing cartridge 31, a transfer roller 32, and a cleaning brush 33 in a casing. Yes.

  The photosensitive drum 29 has a cylindrical shape, the outermost layer is formed of a positively chargeable photosensitive layer made of polycarbonate or the like, and an axial center of the drum main body 34 along the longitudinal direction of the drum main body 34. And an extending metallic drum shaft 35. The drum shaft 35 is supported by the upper frame 27, and the drum main body 34 is rotatably supported by the drum shaft 35, so that the photosensitive drum 29 is rotatable about the drum shaft 35 in the upper frame 27. Is provided.

  The scorotron charger 30 is disposed opposite to the photosensitive drum 29 at a predetermined interval so as not to come into contact with the photosensitive drum 29 at an obliquely upper rear side of the photosensitive drum 29. The scorotron charger 30 uniformly charges the surface of the photosensitive drum 29 to positive polarity by generating corona discharge from a charging wire (not shown) such as tungsten.

  The developing cartridge 31 has a box shape with the rear side opened, and is detachably attached to the lower frame 28. In the developing cartridge 31, a toner storage chamber 39, a supply roller 40, a developing roller 41, and a layer thickness regulating blade 42 are provided.

  The toner storage chamber 39 is formed as an internal space on the front side of the developing cartridge 31 partitioned by the partition plate 43. The toner storage chamber 39 is filled with positively charged non-magnetic one-component toner 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.

  Such a toner is blended with a colorant such as carbon black, wax, and the like, and an external additive such as silica is added to improve fluidity. The average particle size of the toner is about 6 to 10 μm.

  An agitator 44 is provided in the toner storage chamber 39. The toner in the toner storage chamber 39 is agitated by the agitator 44 and discharged toward the supply roller 40 from the opening 45 communicating in the front-rear direction below the partition plate 43.

  The supply roller 40 is disposed behind the opening 45 and is rotatably supported by the developing cartridge 31. The supply roller 40 is configured by covering a metal roller shaft with a roller made of a conductive foam material. The supply roller 40 is rotationally driven by power input from a motor (not shown).

  The developing roller 41 is rotatably supported by the developing cartridge 31 in a state where the developing roller 41 is in contact with the supplying roller 40 so as to be compressed with respect to the rear side of the supplying roller 40. The developing roller 41 is opposed to and contacts the photosensitive drum 29 in a state where the developing cartridge 31 is mounted on the lower frame 28. The developing roller 41 is configured by covering a metal roller shaft 38 with a roller made of a conductive rubber material. Both end portions of the roller shaft 38 protrude outward from the side surface of the developing cartridge 31 in the width direction perpendicular to the front-rear direction.

  In the roller of the developing roller 41, the surface of a roller body made of conductive urethane rubber or silicone rubber containing carbon fine particles or the like is coated with a coating layer of urethane rubber or silicone rubber containing fluorine. A developing bias is applied to the developing roller 41 during development. The developing roller 41 is rotationally driven in the same direction as the supply roller 40 by the input of power from a motor (not shown).

  The layer thickness regulating blade 42 includes a pressing portion 47 having a semicircular cross section made of insulating silicone rubber at the tip of a blade body 46 made of a metal leaf spring material. The layer thickness regulating blade 42 is supported by the developing cartridge 31 above the developing roller 41, and the pressing portion 47 is pressed onto the developing roller 41 by the elastic force of the blade body 46.

  The toner discharged from the opening 45 is supplied to the developing roller 41 by the rotation of the supply roller 40, and at this time, the toner is positively frictionally charged between the supply roller 40 and the developing roller 41. The toner supplied onto the developing roller 41 enters between the pressing portion 47 of the layer thickness regulating blade 42 and the developing roller 41 as the developing roller 41 rotates, and is further charged here to have a constant thickness. It is carried on the developing roller 41 as a thin layer.

  The transfer roller 32 is rotatably supported by the lower frame 28. When the upper frame 27 and the lower frame 28 are combined, the transfer roller 32 is opposed to and contacts the photosensitive drum 29 in the vertical direction. They are arranged to form a nip therebetween. The transfer roller 32 is configured by covering a metal roller shaft 36 with a roller made of a conductive rubber material. A transfer bias is applied to the transfer roller 32 during transfer. The transfer roller 32 is rotationally driven in the opposite direction to the photosensitive drum 29 by the input of power from a motor (not shown).

  The cleaning brush 33 is attached to the lower frame 28, and is arranged to face and contact the photosensitive drum 29 on the rear side of the photosensitive drum 29 in a state where the upper frame 27 and the lower frame 28 are combined. ing.

  The surface of the photosensitive drum 29 is first uniformly charged positively by the scorotron charger 30 as the photosensitive drum 29 rotates, and then exposed by high-speed scanning of the laser beam from the scanner unit 19. An electrostatic latent image corresponding to the image to be formed is formed.

  Next, when the toner carried on the developing roller 41 and positively charged toner contacts the photosensitive drum 29 by the rotation of the developing roller 41, an electrostatic latent image formed on the surface of the photosensitive drum 29 is formed. Of the surface of the image, that is, the surface of the photosensitive drum 29 that is uniformly positively charged, the image is supplied to an exposed portion exposed to a laser beam and having a lowered potential. As a result, the electrostatic latent image on the photosensitive drum 29 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 29.

Thereafter, the toner image carried on the surface of the photosensitive drum 29 is transferred to the transfer roller 32 while the sheet 3 conveyed by the registration roller 14 passes through the transfer position between the photosensitive drum 29 and the transfer roller 32. The image is transferred to the paper 3 by the applied transfer bias. The sheet 3 on which the toner image is transferred is conveyed to the fixing device 21.
The transfer residual toner remaining on the photosensitive drum 29 after the transfer is collected by the developing roller 41. Further, paper dust from the paper 3 adhering to the photosensitive drum 29 after the transfer is collected by the cleaning brush 33.

  The fixing device 21 is provided on the rear side of the process cartridge 20, and includes a fixing frame 48, a heating roller 49, a pressure roller 50, and a paper passage sensor (an example of the “sensor” of the present invention) 51. . The heating roller 49 and the pressure roller 50 are provided in the fixing frame 48. The paper passage sensor 51 is disposed on the downstream side of the heating roller 49 and the pressure roller 50, and is attached to the support member 52 that is connected to the fixing frame 48 so as to be rotatable.

The heating roller 49 includes a metal tube whose surface is coated with a fluororesin, and a halogen lamp for heating in the metal tube, and is rotated by input of power from a motor (not shown).
The pressure roller 50 is disposed below the heating roller 49 so as to press the heating roller 49. The pressure roller 50 is configured by covering a metal roller shaft with a roller made of a rubber material, and is driven in accordance with the rotational drive of the heating roller 49.

  In the fixing device 21, the toner transferred onto the paper 3 at the transfer position is thermally fixed while the paper 3 passes between the heating roller 49 and the pressure roller 50. The sheet 3 on which the toner is fixed is sent to the sheet passage sensor 51.

  The sheet passage sensor 51 is disposed on the upstream side of the entrance (upstream end portion) of the curved guide 90, which will be described later, and on the downstream side of the rear end of the sheet 3 when the front end of the sheet 3 enters the entrance of the curved guide 90. Has been. The paper passage sensor 51 is an actuator that detects the passage of the paper 3, and has a base end portion 53 that is pivotally supported by a support member 52, and is provided so as to be rotatable about the base end portion 53. Yes. Further, the paper passage sensor 51 includes a contact portion 56 that protrudes from the base end portion 53 in a direction intersecting the conveyance path of the paper 3, and a shielding plate that protrudes in the opposite direction to the direction in which the contact portion 56 protrudes from the base end portion 53. 54. Further, on both sides of the shielding plate 54, a photo interrupter 55 is provided in which a light emitting plate having a light emitting element and a light receiving plate having a light receiving element are arranged to face each other.

  The paper passage sensor 51 is pressed against the heating roller 49 while the contact portion 56 is held at a non-detection position where the paper 3 passes through the conveyance path of the paper 3 by a spring force of a spring (not shown) when the paper 3 is not passing. When the leading edge of the sheet 3 conveyed from between the rollers 50 contacts the contact portion 56, it is detected that the contact portion 56 is in sliding contact with the lower surface of the sheet 3 by rotating counterclockwise around the base end portion 54. To the position. When the rear end of the sheet 3 passes through the contact portion 56, the sheet passage sensor 51 is rotated in the clockwise direction in the figure by the spring force and returns to the non-detection position. When the paper passage sensor 51 is in the detection position, it is positioned so as not to block (intersect) the optical path from the light emitting element to the light receiving element of the photo interrupter 55, and is in an ON state (state shown in FIGS. 1 and 2). Part (an example of the “solenoid mechanism” of the present invention) is sent to 80, but when it is in the non-detection position, it is positioned so as to block the optical path of the photo interrupter 55 and enters the OFF state (state in FIG. 3). Sending is stopped.

[Configuration of paper discharge mechanism]
The paper discharge mechanism 6 includes a guide roller 60 disposed on the downstream side of the paper passage sensor 51, a drive roller 70 disposed above the guide roller 60 and opposed to the guide roller 60, and a solenoid that moves the guide roller 60 up and down. A section 80, a curved guide 90 that has a curved shape and reverses the conveyance direction of the paper 3, and a paper discharge roller 110 that discharges the paper 3 to the paper discharge tray 100 are provided.

The guide roller 60 is configured by covering the roller shaft 61 with a roller made of a rubber material. The roller shaft 61 is rotatably supported by a roller support portion (an example of the “roller support mechanism” of the present invention) 62.
The drive roller 70 is configured by covering a roller shaft 71 with a roller made of a rubber material, and is driven to rotate clockwise by the input of power from a motor (not shown). The guide roller 60 is driven according to the rotational drive of the drive roller 70. The sheet 3 conveyed from between the heating roller 49 and the pressure roller 50 is sandwiched between the guide roller 60 and the driving roller 70 and conveyed downstream.

  The curved guide 90 has an inlet disposed on the downstream side of the guide roller 60 and the driving roller 70, and an outlet (downstream end) connected to the paper discharge roller 110. The curved guide 90 has a guide surface 91 that guides forward by sliding and reversing the sheet 3 conveyed backward from between the guide roller 60 and the drive roller 70. Further, a guide member 92 having a curved shape corresponding to the guide surface 91 is opposed to the curved guide 90.

  The paper discharge tray 100 is formed by recessing the upper surface of the main casing 2 downward. The bottom surface of the discharge tray 100 is provided with a mounting surface 101 that has an upward slope toward the front, and the rear surface of the mounting surface 101 has a shape that stands vertically toward the discharge roller 110. A sheet trailing edge receiving portion 102 is provided. When the paper 3 is discharged from the paper discharge roller 110 to the paper discharge tray 100, the paper 3 is placed on the placement surface 101 and the rear end of the paper 3 is supported by the paper rear end receiving portion 102. .

  The paper discharge roller 110 is configured by covering the roller shaft 111 with a roller made of a rubber material, and is driven to rotate counterclockwise by the input of power from a motor (not shown). An auxiliary roller 112 is disposed opposite to the paper discharge roller 110 at an obliquely lower front side of the paper discharge roller 110. The auxiliary roller 112 is driven according to the rotational drive of the paper discharge roller 110. The sheet 3 conveyed from the downstream end of the curved guide 90 is sandwiched between the sheet discharge roller 110 and the auxiliary roller 112 and sent out to the placement surface 101 of the sheet discharge tray 100.

  The roller support portion 62 is directly connected to the movable shaft 81 of the solenoid portion 80 and can move up and down in conjunction with the movable shaft 81. As a result, the guide roller 60 moves away from the guide position 91 at the entrance of the curved guide 90 and the separation position for guiding the paper 3 so that the paper 3 is lifted from the guide surface 91 at the entrance of the curved guide 90. It can move between the approaching position for guiding the sheet 3 so as to be closer to the guide surface 91 at the entrance of the curved guide 90 than the contacted or separated position.

  The solenoid unit 80 includes a movable shaft 81 that can move up and down in the axial direction based on a signal sent from the paper passage sensor 51. Specifically, in a state where the signal is not sent from the paper passage sensor 51 (OFF state), the movable shaft 81 is held at the lower position and the guide roller 60 is held at the approach position. In the state in which is sent (ON state), the movable shaft 81 is moved upward to bring the guide roller 60 into pressure contact with the drive roller 70, and the guide roller 60 is held at the separated position. That is, the solenoid unit 80 moves the guide roller 60 to the separated position on condition that the paper passage sensor 51 detects the paper 3.

  The solenoid unit 80 that moves the guide roller 60 up and down is provided with a shock absorbing buffer pad (not shown) made of a rubber material. This buffer pad alleviates the impact by a part of the movable part coming into contact with the buffer pad immediately before the guide roller 60 reaches the approach position when the guide roller 60 in the separated position moves to the approach position. This is to restrict the impact sound from being generated when the lower end portion of the movable shaft 81 and the bottom surface of the concave portion (not shown) that accommodates the movable shaft 81 come into contact with each other vigorously inside the solenoid portion 80.

  The leading edge of the sheet 3 conveyed between the heating roller 49 and the pressure roller 50 contacts the contact portion 56 of the sheet passage sensor 51 at the non-detection position, and the sheet passage sensor 51 is moved in the counterclockwise direction in the drawing. Rotate to reach the detection position. As a result, a signal is sent from the paper passage sensor 51 toward the solenoid unit 80, and based on this signal, the movable shaft 81 at the lower position is moved to the upper position, and the guide roller 60 at the approach position is moved to the separated position. And move. The guide roller 60 is driven as the drive roller 70 is driven to rotate, and when the leading edge of the paper 3 is sandwiched between the guide roller 60 and the drive roller 70, the paper 3 is conveyed toward the entrance of the curved guide 90. .

  The leading edge of the sheet 3 conveyed from between the guide roller 60 and the drive roller 70 enters the curved guide 90 in a state of floating from the guide surface 91 at the entrance of the curved guide 90, and along the guide surface 90. Guided upward. The leading edge of the sheet 3 gradually changes from the top to the front along the guide surface 90, and advances between the guide surface 91 and the guide member 92. And the paper is discharged to the paper discharge tray 100.

  On the other hand, when the rear end of the sheet 3 passes through the contact portion 56 of the sheet passage sensor 51 at the detection position, the sheet passage sensor 51 rotates in the clockwise direction in the drawing to reach the non-detection position and to the solenoid unit 80. The transmission of the directed signal is stopped. When the transmission of the signal from the paper passage sensor 51 is stopped, the solenoid unit 80 moves the movable shaft 81 to the lower position and moves the guide roller 60 at the separated position to the approach position. At this time, the sheet 3 moves while being in contact with the surface of the guide roller 60 due to its elastic force, and the guide 3 is not in contact with the guide surface 91 at the entrance of the curved guide 90 or when the guide roller 60 is in the separated position. The state is close to the surface 91. Therefore, the rear end of the sheet 3 enters the curved guide 90 along the guide surface 91 without hitting the guide surface 91 at the entrance of the curved guide 90 and generating a jumping sound. Then, when the rear end of the paper 3 moves along the guide surface 91 and passes between the paper discharge roller 110 and the auxiliary roller 112, the paper 3 is placed on the placement surface 101 of the paper discharge tray 100. .

As described above, this embodiment can provide the following effects.
1. The guide roller 60 can be moved to the separated position by the paper passage sensor 51 and the solenoid unit 80 before the front end of the paper 3 enters the entrance of the curved guide 90. Thereby, it is possible to prevent the front end of the sheet 3 from being caught at the entrance of the curved guide 90. Thereafter, the guide roller 60 can be moved to the approach position by the paper passage sensor 51 and the solenoid unit 80 before the rear end of the paper 3 passes the guide roller 60. Thereby, there is no possibility that the rear end of the sheet 3 will bounce and hit the guide surface 91 at the entrance of the curved guide 90 to generate a bounce sound. Therefore, it is possible to cope with the reduction in the height of the laser printer 1 by preventing the splashing noise by using the guide roller 60 that is inherently necessary.

  2. The paper passing sensor 51 detects that the paper 3 is approaching the curved guide 90 and transmits a signal. Based on this signal, a driving force can be generated by the solenoid unit 80 to move the guide roller 60. .

  3. The guide roller 60 can be moved to the separation position before the front end of the sheet 3 enters the entrance of the curved guide 90. Thereby, the paper 3 can be reliably guided by the guide roller 60. Then, the guide roller 60 can be moved to the approach position after the front end of the sheet 3 enters the entrance of the curved guide 90. Thereby, it is possible to reliably prevent the sheet 3 from being caught at the entrance of the curved guide 90.

  4). The sheet 3 can be sandwiched between the guide roller 60 and the driving roller 70 located at the separated positions and conveyed to the curved guide 90. That is, the guide roller 60 can function as a driven roller for the drive roller 70. Accordingly, it is not necessary to provide a driven roller separately from the guide roller 60.

  5. When the sheet 3 enters the curved guide 90, the sheet 3 can be conveyed between the guide surface 91 and the guide member 92. Therefore, the sheet 3 can be stably conveyed along the guide surface 91 in the curved guide 90.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the present embodiment, an example applied to the paper discharge mechanism unit 6 is illustrated, but according to the present invention, it may be applied to the paper feed mechanism unit 4. Specifically, the pinch roller 13 (an example of the “guide roller” of the present invention) 13 is supported on a member (an example of the “roller support mechanism” of the present invention) by the pinch roller 13 and the paper feed roller (an “drive” of the present invention). A solenoid unit (an example of a “solenoid mechanism” according to the present invention) that is moved toward and away from 10 is provided, and a paper passage sensor (an example of a “sensor” according to the present invention) is disposed upstream of the solenoid unit. What is necessary is just to provide.

  (2) In the present embodiment, the contact type paper passage sensor 51 is used as an example of the sensor. However, according to the present invention, a configuration using a non-contact type transmission optical sensor may be used. For example, the light emitting side sensor and the light receiving side sensor may be arranged so as to cross the conveyance path of the paper 3 and the guide roller 60 may be moved to the separated position on condition that the paper 3 is detected.

  (3) In the present embodiment, an example using a solenoid mechanism is illustrated. However, according to the present invention, for example, a stepping motor or the like is used and the rotation shaft of the motor is used as a pinion shaft, and a rack is provided on the roller support portion 62. Thus, the roller support unit 62 may be moved up and down by rotating the motor on condition that the sheet is detected.

  (4) In the present embodiment, the guide roller 60 is moved to the separation position on the condition that the paper 3 is detected. However, according to the present invention, the paper passage sensor is provided downstream of the paper discharge roller 110. And the guide roller 60 may be moved to the approach position on condition that the paper passage sensor detects the paper 3. In such a configuration, the guide roller 60 and the sheet pass so that the rear end of the sheet 3 does not pass between the guide roller 60 and the drive roller 70 when the leading edge of the sheet 3 passes the sheet passage sensor. It is necessary to set the conveyance distance to the sensor.

  (5) In the present embodiment, the guide roller 60 is illustrated as functioning as a driven roller for the drive roller 70. However, according to the present invention, the drive roller 70 may not be provided, or what is the guide roller 60? Alternatively, a driven roller for the driving roller 70 may be provided.

  (6) In this embodiment, the guide roller 60 is provided separately from the pressure roller 50 to move the paper 3 from the separation position to the approach position. However, according to the present invention, the pressure roller 50 is provided. It is also possible to function as a guide roller.

(7) In the present embodiment, the guide member 92 is illustrated. However, according to the present invention, the guide member 92 is not necessarily provided.
(8) In the present embodiment, at the timing when the rear end of the sheet 3 passes the sheet passage sensor, the pressure roller 60 is released from the pressure contact with the driving roller 70 and close to the guide surface 91 at the entrance of the curved guide 90. After that, the guide roller 60 is brought into pressure contact with the driving roller 70 at the timing when the leading edge of the next sheet 3 comes into contact with the sheet passage sensor and is moved to the detection position. However, according to the present invention, if the rear end of the sheet 3 is moved so as to contact the guide surface 91 at the entrance of the curved guide 90, the following is performed. Before the leading edge of the sheet 3 comes into contact with the sheet passage sensor and is moved to the detection position, the guide roller 60 is brought into pressure contact with the driving roller 70 and moved to a position away from the guide surface 91 at the entrance of the curved guide 90. It may be allowed to.

The principal part sectional side view which shows one Embodiment of the laser printer in this embodiment. The principal part expanded side sectional view which shows the state which the guide roller exists in a separation position The principal part expanded side sectional view which shows the state which the guide roller exists in an approach position

Explanation of symbols

1. Laser printer (an example of the “image forming apparatus” of the present invention)
3. Paper (an example of the “recording medium” of the present invention)
4. Paper feed mechanism (an example of “conveying means” in the present invention)
5... Image forming section 6... Paper discharge mechanism section (an example of “conveying means” in the present invention)
51... Paper passage sensor (an example of the “sensor” of the present invention)
DESCRIPTION OF SYMBOLS 60 ... Guide roller 62 ... Roller support part 70 ... Drive roller 80 ... Solenoid part (an example of the "solenoid mechanism" of this invention)
90 ... curved guide 91 ... guide surface 92 ... guide member

Claims (5)

Conveying means for conveying the recording medium along the conveying path;
Image forming means for forming an image on the recording medium transported by the transport means;
A curved guide having a guide surface that is provided in the middle of the transport path and guides the recording medium in a direction different from the entering direction;
A guide roller arranged on the upstream side of the entrance of the curved guide in the transport path and for contacting the recording medium and guiding it to the entrance of the curved guide;
The guide roller is separated from the guide position of the recording medium so that the recording medium floats from the guide surface at the entrance of the curved guide, and the recording medium is located at the entrance of the curved guide. A roller support mechanism that is movable between an approach position that guides the recording medium so as to be in a state of being in contact with the guide surface or closer to the guide surface of the entrance of the curved guide than the separated position;
The guide roller is moved to the separation position before the front end of the recording medium enters the entrance of the curved guide, and the rear end of the recording medium is moved to the approach position before passing the guide roller. An image forming apparatus comprising: a roller driving unit. 2. The roller driving unit includes a sensor that detects that the recording medium is approaching the curved guide, and a solenoid mechanism that moves the guide roller based on a signal from the sensor. The image forming apparatus described. The sensor is disposed upstream of the entrance of the curved guide and downstream of the rear end of the recording medium when the front end of the recording medium enters the entrance of the curved guide. The solenoid mechanism 3. The image forming apparatus according to claim 2, wherein the guide roller is moved to the separated position on condition that the sensor detects the recording medium. 4. The image forming apparatus according to claim 1, wherein the conveyance unit includes a driving roller that is opposed to the guide roller with a conveyance path of the recording medium interposed therebetween at an entrance of the curved guide. apparatus. The image forming apparatus according to claim 1, wherein a guide member having a curved shape corresponding to the guide surface is disposed to face the curved guide.

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