JP2008265930A - Paper feeder and image forming device provided with this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeder capable of attaining reduction in the number of parts, reduction in costs and miniaturization. <P>SOLUTION: In the paper feeder provided with a paper feed roller 5 intermittently rotated/driven; and a bottom plate 28 approaching/leaving from the paper feed roller 5 by lifting motion, rotation force is transmitted to the paper feed roller 5 through a tooth lacked gear 32 coaxially arranged to a cam shaft 31 for lifting the bottom plate 28 and a paper feed drive gear 27 engaged with this, an outer diameter of the paper feed roller 5 and a gear ratio of the tooth lack gear 32 and the paper feed drive gear 27 are set to a value that the paper can arrive at a registration roller, the subsequent roller arranged at a downstream side of the paper feed roller 5 by one rotation of the cam shaft 31. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet feeding device that supplies a recording material to a registration roller, and an image forming apparatus including the sheet feeding device.

  In an image forming apparatus such as a copying machine or a printer that employs an electrophotographic method, a plurality of sheets are stacked and accommodated in a sheet feeding cassette in advance, and the sheets are picked up one by one from the sheet feeding cassette and transferred to a registration roller. In addition to the cassette-type paper feeding device to be supplied, an MPF (Multi Purpose Feeder) paper feeding device is provided that feeds sheets set one by one on the manual feed tray to the registration rollers.

  The MPF paper feeder includes a paper feed roller that is driven to rotate intermittently and a bottom plate that moves up and down to come into contact with and separate from the paper feed roller. When an image forming signal is input, the bottom plate rises. The paper set on the bottom plate is pressed against the paper feed roller, and in this state, the paper feed roller is driven to feed the paper to the registration roller.

In such a sheet feeding device, the bottom plate is moved up and down and the sheet feeding roller is rotated using, for example, a missing gear. In addition, the raising / lowering movement of the bottom plate and the rotation of the paper feed roller are separately controlled (for example, see Patent Document 1).
JP-A-8-217265

  However, in the conventional MPF paper feeder, since the paper feed roller rotates only once for each up and down movement of the bottom plate, a relay transport roller is provided between the paper feed roller and the registration roller. It was necessary to provide it, which was a problem in terms of cost and space.

  In addition, when a method of separately controlling the raising / lowering movement of the bottom plate and the rotation of the paper feed roller is employed, there is a problem that the structure becomes complicated, resulting in an increase in the number of parts and an increase in cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet feeding device capable of reducing the number of parts, reducing the cost, and reducing the size, and an image forming apparatus including the sheet feeding device. It is in.

  In order to achieve the above object, the invention according to claim 1 is a paper feeding device comprising a paper feeding roller that is driven to rotate intermittently and a bottom plate that moves up and down to contact and separate from the paper feeding roller. A rotational force is transmitted to the paper feed roller through a gear arranged coaxially with a cam shaft for moving the bottom plate up and down and a drive gear meshing with the gear, and the outer diameter of the paper feed roller and the gear and the drive gear are transmitted. The gear ratio is set to a value that allows the sheet to reach the registration roller, which is the next roller disposed downstream of the sheet feeding roller, by one rotation of the cam shaft.

  According to a second aspect of the present invention, in the first aspect of the present invention, the gear ratio of the gear to the drive gear is set to 1: 1.7 or more.

  According to the third aspect of the present invention, the paper is fed to the registration roller by the paper feeding means, and the paper is conveyed to the transfer nip portion at an appropriate timing by the registration roller, and the toner image formed on the image carrier. In the image forming apparatus for fixing the toner image onto the sheet after the toner image is transferred onto the sheet, the sheet feeding unit is constituted by the sheet feeding apparatus according to claim 1.

  According to the present invention, the outer diameter of the paper feed roller and the gear ratio between the gear and the drive gear are set to the registration roller, which is the next roller disposed downstream of the paper feed roller by one rotation of the cam shaft. Since it is set to a value that can be reached, the sheet can be directly conveyed to the registration roller for one up and down movement of the bottom plate, and there is no need to provide a relay conveyance roller between the paper supply roller and the registration roller. In addition, the image forming apparatus can be reduced in space and can be reduced in size, and the number of parts can be reduced and the cost can be reduced.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[Image forming apparatus]
FIG. 1 is a side sectional view of a laser beam printer as an embodiment of an image forming apparatus according to the present invention.

  In the illustrated laser beam printer 1, an inclined concave discharge tray 3 is provided at the center of the upper surface of a box-shaped main body (housing) 2. Further, an openable / closable manual feed tray 4 is provided at the upper part of the front surface of the main body 2 (the right side in FIG. 1 is the front), and a feed roller 5 provided rotatably in the manual feed tray and the main body 2 at the back thereof. Constitutes the MPF paper feeder 6. Details of the paper feeding device 6 will be described later.

  Thus, the laser beam printer 1 conveys an image on a sheet based on image data transmitted from a terminal (not shown) while conveying a sheet as a recording material along a conveyance path L provided in the main body 2. The conveyance path L is substantially L-shaped in a side view and extends to the paper discharge tray 3.

  Further, the laser beam printer 1 includes a paper feeding unit 7 provided at a lower portion of the main body 2, an image forming unit 8 provided at a substantially central portion in the main body 2 above the paper feeding unit 7, and the image forming unit. A fixing unit 9 disposed behind the unit 8 and a concave paper discharge unit 10 provided on the upper surface of the main body 2 above the fixing unit 9 are provided.

  The sheet feeding unit 7 stacks and stores a plurality of sheets in a rectangular box-shaped sheet feeding cassette 11 having an open upper surface, and picks out a sheet in the sheet feeding cassette 11 one by one; A pair of paper feed rollers 13 for feeding the discharged paper to the transport path L is provided, and the transport path L temporarily stores the sent paper and then supplies it to the image forming unit 8 at a predetermined timing. A roller 14 is provided.

  The image forming unit 8 forms an image on a sheet supplied from the sheet feeding unit 7, and is a photosensitive drum 15 as an image carrier that is rotatably disposed at a substantially central portion in the main body 2; A primary charger 16, a developing device 17 serving as a developing unit, a transfer roller 18 serving as a transfer unit, and a cleaning device 19, and a laser scanner unit (LSU) 20 and a toner hopper 21 disposed above them are disposed around the primary charger 16. Etc.

  The fixing unit 9 is for fixing the toner image transferred to the sheet in the image forming unit 8 to the sheet, and includes a fixing roller 22 and a pressure roller 23 that are pressed against each other and rotated. Yes.

  Further, the paper discharge unit 10 is for discharging the paper on which the toner image is fixed in the fixing unit 9 to the outside of the main body 2, and a pair of paper discharge rollers 24 provided at the end of the conveyance path L. And a plurality of conveying guide ribs 25 in the form of longitudinal ribs for guiding the sheet conveyed through the conveying path L to the sheet discharge roller 24 and the sheet discharge tray 3 for stacking sheets discharged to the outside of the main body 2. I have.

  Next, an image forming operation of the laser beam printer 1 having the above configuration will be described.

  For example, when a print start signal is transmitted to the laser beam printer 1 from a terminal such as a personal computer (personal computer), the photosensitive drum 15 is moved in the direction of the arrow (clockwise) in FIG. ) And the surface thereof is uniformly charged to a predetermined potential by the primary charger 16. When a laser beam based on the image data transmitted from the terminal is output from the laser scanner unit 20 and irradiated onto the photosensitive drum 15, an electrostatic latent image is formed on the photosensitive drum 15. The electrostatic latent image formed on the photosensitive drum 15 is developed by the developing device 17 using toner as a developer to be visualized as a toner image.

  At the same time, in the paper feed unit 7, for example, the sheets stored in the paper feed cassette 11 are picked up one by one from the uppermost one by the pick roller 12, and the registration rollers are rotated by the paper feed roller 13 while the direction of 180 ° is reversed. 14 is conveyed.

  In the registration roller 14, the sheet is temporarily put into a standby state and then supplied to the image forming unit 8 at a predetermined timing synchronized with the toner image on the photosensitive drum 15.

  In the image forming unit 8, the sheet supplied to the transfer nip between the photosensitive drum 15 and the transfer roller 18 is conveyed while being pressed against the photosensitive drum 15 by the transfer roller 18, thereby its surface (transfer surface). ) Is transferred to the toner image on the photosensitive drum 15. The sheet onto which the toner image has been transferred is conveyed to the fixing unit 9, and is heated and pressed in the process of being sandwiched and conveyed by the fixing roller 22 and the pressure roller 23 in the fixing unit 9. Get fixed. The toner remaining on the surface of the photosensitive drum 15 (transfer residual toner) after the transfer of the toner image onto the paper is removed by the cleaning device 19.

  Thus, the sheet on which the toner image is fixed on the surface by the fixing unit 9 is conveyed upward along the conveyance path L, guided to the sheet discharge roller 24 along the conveyance guide rib 25, and is discharged by the sheet discharge roller 24. The paper is discharged and stacked on the paper discharge tray 3 at the top of the main body 2, and a series of image forming operations is completed.

When the user manually feeds the paper, the paper set on the manual feed tray 4 of the MPF paper feeder 6 is supplied to the registration roller 14 by the paper feed roller 5, and thereafter the same process as described above is performed. Then, an image is formed on the paper.
[MPF paper feeder]
Next, an embodiment of the MPF paper feeder 6 according to the present invention will be described with reference to the accompanying drawings.

  2 is a perspective view of the MPF paper feeding device according to the present invention, FIG. 3 is a perspective view of the main part of the MPF paper feeding device, FIG. 4 is a side view showing the operation of the MPF paper feeding device, and FIG. It is.

  As shown in FIG. 2, the paper feed roller 5 of the MPF paper feed mechanism 6 is rotatably arranged at the approximate center in the paper passing width direction, and is connected to one axial end of the paper feed drive shaft 26 arranged in the paper passing width direction. A paper feed drive gear 27 is attached to the other axial end of the paper feed drive shaft 26.

  A bottom plate 28 is provided below the paper feed roller 5 so as to be movable up and down. One end of the bottom plate 28 in the width direction (the end on the side where the paper feed drive gear 27 is provided (the left end in FIG. 2)). )) Is provided with a lift arm 29 and a bottom bracket 30.

  Further, a cam shaft 31 is arranged below the paper feed drive gear 27 in parallel with the paper feed drive shaft 26, and a missing gear 32 and a control cylinder 33 are attached to the cam shaft 31. A cam 34 that engages with the lower surface of the lift arm 29 is attached to the end of the cam shaft 31.

  On the outer peripheral portion of the toothless gear 32, toothless portions 32a and 32b are formed in two rows in the width direction. The paper feeding drive gear 27 and the input gear 35 are selectively connected to the toothless gear 32. To mesh. The input gear 35 is rotationally driven by a motor (not shown). Further, a locking claw 33a projects from a part of the outer periphery of the control cylinder 33.

Thus, in the present embodiment, the outer diameter of the paper feed roller 5 and the gear ratio between the toothless gear 32 and the paper feed drive gear 27 are such that the paper can reach the registration roller 14 by one rotation of the cam shaft 31. Is set to a value. Specifically, in the present embodiment, the outer diameter D of the paper feed roller 5 is set to φ30 mm, and the gear ratio (tooth ratio) r _G between the paper feed drive gear 27 and the missing gear 32 is set to 1.7. Therefore, the distance X by which the paper is conveyed by one rotation of the cam shaft 31 is
X = π × D × r _G = 3.14 × 30 × 1.7≈160 mm
It becomes.

  Therefore, in the present embodiment, the registration roller 14 is disposed at a position downstream of the sheet feeding roller 5 by (160−10) = 150 mm, assuming that the amount of bending of the sheet is 10 mm.

  A solenoid 36 is disposed below the control cylinder 33, and the tip of the actuator 37 of the solenoid 36 bent in an L shape is selectively with respect to the locking claw 33 a of the control cylinder 33. Disengage. Here, when the actuator 37 is energized by the spring 38 and the solenoid 36 is not energized, the tip of the actuator 37 is engaged with the engaging claw 33a of the control cylinder 33 as shown in FIGS. As a result, the control cylinder 33, the toothless gear 32, and the cam 34 are stationary at the illustrated positions.

  As shown in FIG. 3, a spring 39 is stretched on the back surface of the cam 34, and the cam 34, the toothless gear 32, and the control cylinder 33 are moved in the direction of arrow A in FIGS. 4 and 5 by the spring 39. It is biased (clockwise).

  Thus, the toothless gear 32 is rotationally driven in the counter arrow A direction (counterclockwise direction) in FIGS. 4 and 5 against the biasing force of the spring 39 by the input gear 35 that is rotationally driven by a motor (not shown). Accordingly, the toothless gear 32, the control cylinder 33 and the cam 34 are returned to the positions shown in FIGS. 2 and 4, and at this time, the operation of the solenoid 36 on the locking claw 33a of the control cylinder 33 is performed as described above. Since the tip end portion of the child 37 is engaged, the toothless gear 32, the control cylinder 33 and the cam 34 are stationary without rotating. In this state, the spring 39 accumulates rotational energy for rotating the missing gear 32, the control cylinder 33, and the cam 34 in the direction of arrow A in FIGS.

  Thus, when the user manually feeds paper using the MPF device 6, when the paper is set on the manual feed tray 4 and a print start signal is input, the solenoid 36 is energized and activated. The child 37 operates against the urging force of the spring 38, and the tip portion thereof is detached from the locking claw 33 a of the control cylinder 33. Then, since the rotational energy accumulated in the spring 39 is released, the toothless gear 32, the control cylinder 33, and the cam 34 are integrally rotated in the direction of the arrow in FIG.

  When the cam 34 rotates, the lift arm 29 engaged with the cam 34 pushes up the bottom plate 28, so that the paper placed on the bottom plate 28 is pressed against the paper feed roller 5. In this state, when the paper feed drive gear 27 meshes with the toothless gear 32, the rotation of the toothless gear 27 is transmitted to the paper feed drive shaft 26 via the paper feed drive gear 27, and the paper feed drive shaft 26 and this The sheet feeding roller 5 bound to the sheet rotates, and the sheet on the bottom plate 28 is nipped between the bottom plate 28 and the sheet feeding roller 5 and fed to the registration roller 14 shown in FIG. At this time, the input gear 35 is stationary without rotating because it faces the missing tooth portion 32b of the missing gear 32.

  By the way, in this embodiment, as described above, the outer diameter of the paper feed roller 5 and the gear ratio between the toothless gear 32 and the paper feed drive gear 27 are set so that the paper reaches the registration roller 14 by one rotation of the cam shaft 31. Since it is set to a possible value, the sheet can be directly conveyed to the registration roller 14 with respect to one rotation of the cam shaft 31 (one up and down movement of the bottom plate 28). For this reason, as shown in FIG. 1, there is no need to provide a relay conveying roller between the paper feed roller 5 and the registration roller 14, and the space saving of the laser beam printer 1 is realized and the size can be reduced. The number of parts can be reduced and the cost can be reduced.

  In the present embodiment, the rotation of the paper feed roller 5 and the vertical movement of the bottom plate 28 are performed by the rotation of a single segment gear 32 having a pair of segment teeth 32a and 32b. Costs can be reduced by reducing the number of parts.

  As described above, when the feeding of the sheet to the registration roller 14 is completed, the input gear 35 is rotationally driven by a motor (not shown), and the toothless gear 32 meshed with the input gear 35 is connected to the control cylinder 33 and the cam 34. 2 and 4 are returned to the initial positions shown in FIG. 2 and FIG. Is stopped. Thereafter, the same operation is repeated, and the paper is manually fed from the MPF paper feed mechanism 6.

  In the above description, the present invention has been described with respect to a laser beam printer and an MPF paper feeder provided therein. However, the present invention is not limited to a printer, and other arbitrary images such as a copying machine and a facsimile machine. Of course, the present invention can be similarly applied to the forming apparatus and the paper feeding apparatus provided therein.

1 is a side sectional view of an image forming apparatus (laser beam printer) according to the present invention. 1 is a perspective view of an MPF paper feeder according to the present invention. It is a perspective view of the principal part of MPF paper feeder concerning the present invention. It is a side view which shows the effect | action of the MPF paper feeder which concerns on this invention. It is a sectional side view which shows the effect | action of the MPF paper feeder which concerns on this invention.

Explanation of symbols

1 Laser beam printer (image forming device)
DESCRIPTION OF SYMBOLS 2 Printer main body 3 Paper discharge tray 4 Manual feed tray 5 Paper feed roller 6 MPF paper feeder 7 Paper feed part 8 Image forming part 9 Fixing part 10 Paper discharge part 11 Paper feed cassette 12 Pick roller 13 Paper feed roller 14 Registration roller 15 Photosensitive Drum 16 Primary charger 17 Developing device 18 Transfer roller 19 Cleaning device 20 Laser scanner unit (LSU)
DESCRIPTION OF SYMBOLS 11 Toner hopper 22 Fixing roller 23 Pressure roller 24 Paper discharge roller 25 Conveying guide rib 26 Paper feed drive shaft 27 Paper feed drive gear 28 Bottom plate 29 Lift arm 30 Bottom bracket 31 Cam shaft 32 Missing gear 32a, 32b Missing gear 33 Control Cylinder 33a Control cylinder locking claw 34 Cam 35 Input gear 36 Solenoid 37 Solenoid actuator 38, 39 Spring L Conveyance path

Claims (3)

In a paper feeding device comprising a paper feeding roller that is driven to rotate intermittently, and a bottom plate that moves up and down and contacts and separates from the paper feeding roller,
A rotational force is transmitted to the paper feed roller through a gear arranged coaxially with a cam shaft that moves the bottom plate up and down and a drive gear meshing therewith, and the outer diameter of the paper feed roller and the gear are driven. The gear ratio with respect to the gear is set to a value that allows a sheet to reach a registration roller that is the next roller disposed downstream of the paper feed roller by one rotation of the cam shaft. .   2. The paper feeding device according to claim 1, wherein a gear ratio of the gear to the driving gear is set to 1: 1.7 or more. After the paper is fed to the registration roller by the paper feeding means, the paper is conveyed to the transfer nip portion at an appropriate timing by the registration roller, and the toner image formed on the image carrier is transferred onto the paper. In an image forming apparatus for fixing the toner image on a sheet,
3. An image forming apparatus, wherein the paper feeding means is constituted by a paper feeding device according to claim 1.

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