JP4944748B2 - Sheet cassette and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a paper feed cassette that is attached to and detached from a main body of an image forming apparatus in a paper transport direction, and an image forming apparatus including the same.

  An image forming apparatus such as a copying machine or a printer that forms an image on paper by an electrophotographic system is detachably mounted with a paper feed cassette that contains paper. It has a possible bottom plate.

  By the way, in the paper feed cassette, the bottom plate is lifted up as the paper on the bottom plate is consumed by the image forming operation. In particular, in the paper feed cassette that is attached and detached in the paper transport direction, a driven gear that drives the bottom plate is provided. There has been known one that employs a system in which a bottom plate is lifted up by receiving a driving force from a driving gear on the main body side that is provided on one side and meshes with the driven gear (for example, see Patent Documents 1 and 2).

In addition, as a measure for preventing the sheet cassette mounted on the image forming apparatus main body from being detached, an engagement member is provided on the left and right side walls of the sheet cassette, and the engagement convex portion of each engagement member is set to the engagement concave portion on the apparatus main body side. There has been proposed a method of engaging with (see Patent Document 3).
JP 2003-246468 A JP 2006-327706 A JP 2000-062970 A

  However, it can be attached to and detached from the image forming apparatus main body in the paper conveyance direction, and a driven gear for driving the bottom plate is provided on one side, and the bottom plate is received by receiving a driving force from a driving gear on the main body side meshing with the driven gear. In the paper feed cassette to be lifted up, if a locking mechanism for retaining the same locking force is provided on both left and right sides, it is necessary to simultaneously engage the locking mechanism and engage the drive transmission gear. There was a problem that the mounting operability of the paper cassette deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet feeding cassette with high mounting operability and an image forming apparatus including the same.

  In order to achieve the above object, the invention described in claim 1 is provided with a driven gear on one side, which is detachably attached to the image forming apparatus main body in a paper transport direction and drives a swingable bottom plate. In a paper feed cassette that lifts up the bottom plate by receiving a driving force from a driving gear on the main body side that meshes with the gear, a locking mechanism for retaining is provided only on the side opposite to the driving side where the driven gear is provided, or Is characterized in that there is a difference in the locking force of the locking mechanism provided on the driving side and the non-driving side.

  According to a second aspect of the present invention, in the first aspect of the present invention, a grounding angle-shaped wire spring is provided on the drive side where the driven gear is provided, and the lock mechanism is configured by the wire spring. The locking force is set to be smaller than the locking force of the locking mechanism on the counter drive side.

  According to a third aspect of the present invention, the image forming apparatus is configured by mounting the paper feed cassette according to the first or second aspect so as to be detachable from the image forming apparatus main body in the paper transport direction.

  According to the present invention, the locking mechanism for retaining is provided only on the side opposite to the driving side where the driven gear of the sheet feeding cassette is provided, or the locking mechanism for retaining is provided on the driving side and the non-driving side. Since there is a difference in the locking force, it is not necessary to perform both engagement of the locking mechanism and meshing of the drive transmission gear at the same time as in the conventional case, so that the mounting operability of the paper feeding cassette is improved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Image forming apparatus]
FIG. 1 is a cross-sectional view of a color laser printer as an embodiment of an image forming apparatus according to the present invention. The illustrated color laser printer is a tandem type, and a magenta image forming unit is provided at the center of the main body 100. 1M, a cyan image forming unit 1C, a yellow image forming unit 1Y, and a black image forming unit 1K are arranged in tandem at regular intervals.

  Each of the image forming units 1M, 1C, 1Y, and 1K is provided with photosensitive drums 2a, 2b, 2c, and 2d, and charging rollers 3a, 3b, 3c, and 3d are disposed around the photosensitive drums 2a to 2d. 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d and drum cleaning devices 6a, 6b, 6c, 6d are arranged, respectively.

  Here, the photosensitive drums 2a to 2d are drum-shaped photosensitive members, and are rotationally driven at a predetermined process speed in a direction indicated by an arrow (clockwise) by a variable speed stepping motor (not shown). The charging rollers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (K) toner, respectively, and are formed on the photosensitive drums 2a to 2d. In addition, the toner of each color is attached to each electrostatic latent image, and each electrostatic latent image is visualized as a toner image of each color.

  The transfer rollers 5a to 5d are arranged so as to be able to contact the photosensitive drums 2a to 2d via the intermediate transfer belt 7 in the respective primary transfer portions. Here, the intermediate transfer belt 7 is stretched between the secondary transfer counter roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The roller 8 is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7 in the secondary transfer portion. A belt cleaning device 11 is provided in the vicinity of the tension roller 9.

  Incidentally, toner containers 12a, 12b, 12c, and 12d for supplying toner to the developing devices 4a to 4d are arranged in a line above the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100. It is installed.

  In addition, a laser scanner unit (LSU) 13 is disposed below the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100, and a paper feed cassette 14 is detachably attached to the bottom of the main body 100 below the image forming units. is set up. A plurality of sheets (not shown) are stacked and accommodated in the paper feed cassette 14, and a pickup roller 15 for taking out the paper one by one from the paper feed cassette 14 is taken out in the vicinity of the paper feed cassette 14. A feed roller 16 and a retard roller 17 are provided for feeding the fed paper to the transport path L.

  In addition, the conveyance path L extending in the vertical direction on the side of the apparatus main body 100 includes a conveyance roller pair 18 that conveys the sheet, and the secondary transfer counter roller 8 and the second transfer opposing roller 8 at a predetermined timing after the sheet is temporarily held. A registration roller pair 19 is provided to be supplied to a secondary transfer portion which is a contact portion with the next transfer roller 10. Next to the transport path L, another transport path L ′ used for forming an image on both sides of the sheet is formed, and a plurality of transport roller pairs 20 are appropriately used in the transport path L ′. Are provided at regular intervals.

  By the way, the conveyance path L arranged in the vertical direction on one side in the apparatus main body 100 extends to the paper discharge tray 21 provided on the upper surface of the apparatus main body 100, and the fixing device 22 and the discharge path are in the middle. A paper roller pair 23 is provided.

  Next, an image forming operation by the color laser printer having the above configuration will be described with reference to FIG.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate at a predetermined process speed in the direction of the arrow in FIG. 1 (clockwise) in each of the image forming units 1M, 1C, 1Y, and 1K. The drums 2a to 2d are uniformly charged by the charging rollers 3a to 3d. The laser scanner unit 13 emits a laser beam modulated by a color image signal for each color, irradiates the surface of each photosensitive drum 2a to 2d with the laser beam, and each color is applied to each photosensitive drum 2a to 2d. An electrostatic latent image corresponding to the color image signal is formed.

  First, magenta toner is attached to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charged polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. This magenta toner image is transferred to the arrow shown in FIG. 1 by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied at the primary transfer portion (transfer nip portion) between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the intermediate transfer belt 7 which is rotationally driven in the direction.

  The intermediate transfer belt 7 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred to the magenta toner image on the intermediate transfer belt 7 in the primary transfer portion in the same manner as described above.

  Similarly, yellow and black toners respectively formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1K on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 7, respectively. The images are sequentially superimposed at each primary transfer portion, and a full-color toner image is formed on the intermediate transfer belt 7. The transfer residual toner which is not transferred onto the intermediate transfer belt 7 and remains on the photosensitive drums 2a to 2d is removed by the drum cleaning devices 6a to 6d, and the photosensitive drums 2a to 2d are prepared for the next image formation. It is done.

  Then, the pickup from the paper feed cassette 14 is performed in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 7 reaches the secondary transfer portion (transfer nip portion) between the secondary transfer counter roller 8 and the secondary transfer roller 10. The sheet fed to the conveyance path L by the roller 15, the feed roller 16 and the retard roller 17 is conveyed to the secondary transfer unit by the registration roller pair 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the sheet conveyed to the secondary transfer unit by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. .

  Thus, the sheet on which the full-color toner image has been transferred is conveyed to the fixing device 22, and the sheet on which the full-color toner image has been fixed by being heated and pressurized and thermally fixed on the surface of the sheet. The paper is discharged onto the paper discharge tray 21 by the paper discharge roller pair 23 to complete a series of image forming operations. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

[Paper cassette]
Next, details of the paper feed cassette 14 according to the present invention will be described with reference to FIGS.

  2 is a perspective view of the paper feed cassette according to the present invention, FIG. 3 is a partial perspective view of the right side (drive side) of the paper feed cassette, and FIG. 5 is a left partial perspective view of the paper feed cassette mounting portion, and FIG. 6 is a partial side view showing a locked state of the paper feed cassette by a lock mechanism provided on the non-driving side.

  As shown in FIG. 2, the paper feed cassette 14 has a flat rectangular box-shaped base cassette 24 having an open top surface, and a bottom plate 26 that swings up and down around a fulcrum 25 inside thereof. A pair of left and right side cursors 27 for aligning the left and right sides of a plurality of sheets stacked on the bottom plate 26, an end cursor 28 for aligning the rear ends of the sheets, a lift plate (not shown) that pushes up the bottom plate 26, A lift mechanism 29 that drives the lift plate to push up the bottom plate 26 is provided. Here, the lift mechanism 29 is provided on the right side of the base cassette 24 (hereinafter referred to as “drive side”), and includes a driven gear 30 and a sector gear (not shown) that meshes with the driven gear 30. Has been. Although not shown, the sector gear is connected to a lift shaft that supports the lift plate.

  Further, as shown in detail in FIG. 3, a wire spring 31 constituting a drive-side locking mechanism is provided near the lift mechanism 29 on the right side (drive side) of the paper feed cassette 14. . The wire spring 31 is for grounding and has a mountain shape that is pointed toward the side.

  Thus, the paper feed cassette 14 is attached to and detached from the image forming apparatus main body 100 in the paper transport direction (the arrow direction in FIGS. 2 to 5). As shown in FIG. 5, a rectangular concave cassette mounting portion 102 formed of a sheet metal main body frame 101 is formed, and the paper feed cassette 14 is directed in the paper transport direction with respect to the cassette mounting portion 102 (arrow shown in the figure). Direction).

  As shown in FIG. 4, a guide projection 103 and a guide rail 104 project from the inner surface of the right side (drive side) of the main body frame 101 constituting the cassette mounting portion 102, and these guide projections 103. An engagement recess 105 is formed between the guide rail 104 and the guide rail 104. When the paper feed cassette 14 is mounted on the cassette mounting portion 102, the wire spring 31 serving as a drive side locking mechanism provided on the right side (drive side) of the paper feed cassette 14 is engaged with the engagement recess 105. Accordingly, a locking force for fixing the paper feeding cassette 14 to the apparatus main body 100 side works, and this locking force prevents the paper feeding cassette 14 from coming off.

  On the other hand, as shown in FIG. 5, a non-removing side locking mechanism 32 for retaining is provided on the inner surface on the left side (reverse driving side) of the main body frame 101 constituting the cassette mounting portion 102. The counter-drive side lock mechanism 32 includes a lock member 34 whose intermediate portion is rotatably supported by the main body frame 101 by a shaft 33, and both ends of the lock member 35 are circles formed on the main body frame 101. It fits into arc-shaped guide holes 101a and 101b. Accordingly, the lock member 34 can be rotated around the shaft 33 within an angular range in which both ends thereof can move within the guide holes 101a and 101b, and an arrow shown in FIG. 5 is applied by a biasing means such as a torsion spring (not shown). When the paper feed cassette 14 is not mounted on the cassette mounting portion 102 as shown in FIG. 5, the lock member 34 has one end engaged with the end of the guide hole 101a. It is stationary while maintaining a substantially horizontal state.

  In addition, a hook-shaped engagement protrusion 34A that is pointed downward is integrally provided at one end of the lock member 34 (the front side in the mounting direction of the paper feed cassette 14).

  Thus, when the paper feed cassette 14 is mounted in the cassette mounting portion 102 on the apparatus main body 100 side, when the paper feed cassette 14 is moved in the direction of the arrow in FIG. The lock member 34 is engaged with the inclined surface 34a of the engagement protrusion 34A of the lock member 34, and the lock member 34 is rotated counterclockwise in FIG. 6 about the shaft 33 against the urging force of the urging means. Although the movement of the sheet feeding cassette 14 in the direction of the arrow is allowed by the rotation of the locking member 34, the convex portion 14A of the sheet feeding cassette 14 gets over the engaging protrusion 34A of the locking member 34 as shown in FIG. At that time, the lock member 34 is rotated in the clockwise direction in FIG. 6 by the urging force of the urging means, and the engaging projection 34A is engaged with the convex portion 14A of the sheet feeding cassette 14 as shown in the drawing. As a result, a locking force for fixing the sheet feeding cassette 14 to the apparatus main body 100 side works, and this locking force prevents the sheet feeding cassette 14 from coming off. It is set larger than the locking force of the mechanism.

  Thus, as described above, when the paper feed cassette 14 is mounted on the cassette mounting portion 102 on the apparatus main body 100 side, the driven gear 30 constituting a part of the lift mechanism 29 of the paper feed cassette 14 is moved to the apparatus main body 100. Meshes with a drive gear (not shown) on the side. When the paper stacked on the bottom plate 26 of the paper cassette 14 is consumed by the image forming operation, a driving force from a driving motor (not shown) provided on the apparatus main body 100 side is supplied to the paper cassette through the driving gear. The driven gear 30 and the lift drive shaft (not shown) that are transmitted to the driven gear 30 on the 14 side and mesh with the driven gear 30 are rotationally driven. Then, a lift plate (not shown) is driven, and the lift plate swings the bottom plate 26 upward about the fulcrum 25 and pushes it up, so that the paper loaded on the bottom plate 26 is brought into the pickup roller 15 shown in FIG. As a result, the sheet can be continuously fed.

  As described above, in the present embodiment, there is a difference in the locking force between the driving side locking mechanism (wire spring 31) and the non-driving side locking mechanism 32 of the paper feed cassette 14, and the driving side locking mechanism (wire spring 31) has a difference. Since the locking force is set to be smaller than the locking force of the non-driving side locking mechanism 32, it is not necessary to perform both engagement of the locking mechanism having the same locking force and meshing of the drive transmission gear as in the prior art. The mounting operability of 14 is improved.

  In this embodiment, a lock mechanism with a small locking force is provided on the drive side, but the same effect can be obtained by providing a lock mechanism only on the counter drive side.

  Although the present invention has been described with respect to a mode in which the present invention is applied to a color laser printer and a paper cassette attached to and detached from the color laser printer, the present invention is applied to a monochrome image forming apparatus and a paper cassette attached to and detached from it. Is also applicable to a copying machine other than a printer, a facsimile machine, and the like.

1 is a cross-sectional view of a color laser printer according to the present invention. It is a perspective view of the paper feed cassette concerning the present invention. It is a right side (drive side) partial perspective view of the paper feed cassette concerning the present invention. FIG. 4 is a partial perspective view on the right side of the sheet cassette mounting portion on the apparatus main body side. FIG. 4 is a left partial perspective view of a paper cassette mounting unit on the apparatus main body side. It is a partial side view which shows the locked state by the lock mechanism provided in the non-driving side of the paper feed cassette which concerns on this invention.

Explanation of symbols

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1K Black image forming unit 2a to 2d Photosensitive drum 3a to 3d Charging roller 4a to 4d Developing device 5a to 5d Transfer roller 6a to 6d Drum cleaning device 7 Intermediate transfer belt 8 Secondary transfer counter roller 9 Tension roller 10 Secondary transfer roller 11 Belt cleaning device 12a to 12d Toner container 13 Laser scanner unit (LSU)
DESCRIPTION OF SYMBOLS 14 Paper feed cassette 14A Projection part of paper feed cassette 14a Slope of paper feed cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Transport roller pair 19 Registration roller pair 20 Transport roller pair 21 Paper discharge tray 22 Fixing device 23 Paper discharge roller pair 24 base cassette 25 fulcrum of bottom plate 26 bottom plate 27 side cursor 28 end cursor 29 lift mechanism 30 driven gear 31 wire spring (drive side lock mechanism)
32 Anti-drive side lock mechanism 33 Lock member shaft 34 Lock member 34A Lock member engagement protrusion 34a Engagement protrusion slope 100 Image forming apparatus main body 101 Main body frame 101a Main body frame guide hole 101b Main body frame guide hole 102 Cassette mounting Part 103 Guide protrusion 104 Guide rail 105 Engaging recess L, L 'Conveyance path

Claims (3)

A driven gear that can be attached to and detached from the image forming apparatus main body in the paper conveyance direction and drives a swingable bottom plate is provided on one side, and receives a driving force from a driving gear on the main body side that meshes with the driven gear. In the paper feed cassette that lifts up the bottom plate,
The locking mechanism for retaining is provided only on the side opposite to the driving side where the driven gear is provided, or the locking force of the locking mechanism for retaining is provided on the driving side and the non-driving side. A paper cassette characterized by   A grounding angle-shaped wire spring is provided on the driving side where the driven gear is provided, and the locking mechanism is configured by the wire spring, and the locking force of the locking mechanism is smaller than the locking force of the locking mechanism on the non-driving side. 2. The paper feed cassette according to claim 1, wherein the paper feed cassette is set. 3. An image forming apparatus comprising: the paper feeding cassette according to claim 1 or 2 detachably attached to a main body of the image forming apparatus in a paper transport direction.

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