JP2007308212A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of securely detecting the presence or absence of a paper in a paper feeding cassette at all times. <P>SOLUTION: In this image forming device provided with a paper feeding cassette 7 for feeding papers loaded on a bottom plate 10 one by one in an image forming device main body detachably and having a detection means for detecting the presence or absence of a paper in the paper feeding cassette 7 by an actuator 36 capable of passing through a cut-out part 10a formed in one end part in the direction of width of the bottom plate 10 of the paper feeding cassette 7, a projection 39 protruding upward is formed on an upper face in the vicinity of the cut-out part 10a of the bottom plate 10. The projection 39 is formed to be vertically long along the direction of paper conveyance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a detection unit that detects the presence or absence of paper in a paper feed cassette by an actuator that can pass through a notch formed in one end portion in the width direction of a bottom plate of the paper feed cassette. is there.

  Image forming apparatuses such as copying machines, printers, and facsimile machines are provided with a paper cassette that can be attached to and detached from the apparatus main body. FIG. 7 shows a conventional example of this paper cassette.

  FIG. 7 is a perspective view of a paper feed cassette 107 provided in a conventional image forming apparatus. As shown in FIG. 7, the paper feed cassette 107 has a rectangular box shape with an open top surface. The bottom plate 110 in which the left and right of the rear end portion (front side in FIG. 7) are pivotally mounted by the shaft 112 so as to be pivotable up and down is housed inside. The bottom plate 110 is moved up and down by a lift plate (not shown) that rotates up and down around a front end portion by a drive shaft (not shown), and rises to a predetermined height position corresponding to the number of sheets stacked on the bottom plate 110. By doing so, the uppermost sheet is fed one by one by a pickup roller (not shown) provided on the main body side.

  By the way, when the paper feed cassette 107 can also store a small size paper, the range of movement in the width direction of the pair of left and right side cursors 135 for pressing the paper in the horizontal direction becomes large. The left and right sides of the plate 110 are greatly cut away to avoid interference with the side cursor 135, and the width thereof is narrowed.

  On the other hand, an arm-shaped actuator 136 for detecting the presence or absence of paper in the paper feed cassette 107 hangs down from the main body side above the paper feed cassette 107, and an actuator in the width direction one end of the bottom plate 110 A notch portion 110a that allows 136 to pass therethrough is formed. Here, the upper end of the actuator 136 is attached to one end of a shaft 137 that extends horizontally in the width direction, and the other end of the shaft 137 that extends outward from the paper feed cassette 107 has an arm-shaped detection member 138. Is attached.

  Thus, when sheets are stacked on the bottom plate 110 in the sheet cassette 107, the actuator 136 does not rotate by contacting the upper surface of the sheet, and therefore the detection member 138 does not rotate. , It is detected that there is a sheet in the sheet feeding cassette 107.

  When the paper is used and no paper is left on the bottom plate 110, there is no support for the actuator 136, so the actuator 136 rotates through the notch portion 110 a of the bottom plate 110 and rotates. Is also transmitted to the detection member 138 via the shaft 137, and the detection member 138 also rotates integrally, so that the rotation of the detection member 138 is optically detected, thereby eliminating the sheet in the paper feed cassette 107. Is detected.

Patent Document 1 discloses a configuration in which a sheet is bent by curving the bottom plate of a sheet feeding cassette so that the center is convex with respect to the width direction of the sheet.
JP 2000-168964 A

  However, the following problems occur in the paper feed cassette 107 provided in the conventional image forming apparatus.

  That is, FIG. 8 shows an enlarged cross-sectional view taken along the line C-C of FIG. 7, and as shown in FIG. 8, a small-size paper P having a small width dimension is stacked on the bottom plate 110, and When the remaining number of sheets P decreases, one end in the width direction of the sheet P bends downward at the notch 110a portion of the bottom plate 110 and escapes from the actuator 136. Therefore, the actuator 136 cuts off the bottom plate 110. There is a problem in that it passes through the notch portion 110a and erroneously detects that there is no paper P even though there is paper P in the paper feed cassette 107. Such a problem cannot be solved even by the configuration described in Patent Document 1.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus that can always reliably detect the presence or absence of paper in a paper cassette.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a paper feed cassette that detachably attaches to the apparatus main body and feeds the paper stacked on the bottom plate one by one, and the width of the bottom plate of the paper feed cassette. In the image forming apparatus having detection means for detecting the presence or absence of paper in the paper feed cassette by an actuator that can pass through the notch formed at one end in the direction, on the upper surface in the vicinity of the notch of the bottom plate, A protruding protrusion is formed.

  According to a second aspect of the present invention, in the first aspect of the present invention, the protrusions are formed in a vertically long shape along the paper conveyance direction.

  According to the first aspect of the present invention, even when a small-sized sheet having a small width dimension is stacked on the bottom plate and the remaining number of sheets is reduced, the sheet actuator Since the end portion in the vicinity is bent upward by the protrusion formed in the vicinity of the notch portion of the bottom plate, it does not hang down at the notch portion portion of the bottom plate and escape from the actuator as in the prior art. For this reason, the conventional problem that the actuator passes through the notch portion of the bottom plate and erroneously detects that there is no paper in spite of the presence of paper in the paper feed cassette is eliminated. Thus, the presence or absence of paper in the paper feed cassette is always reliably detected.

  According to the second aspect of the present invention, since the protrusion is formed vertically in the paper transport direction, only the end portion near the actuator of the paper is partially bent upward, and the drooping of that portion is reliably prevented. False detection of the presence or absence of paper in the paper cassette is reliably prevented.

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

  FIG. 1 is a perspective view of a laser beam printer as an embodiment of an image forming apparatus according to the present invention, and FIG. 2 is a side sectional view of the laser beam printer.

  First, the basic configuration of the laser beam printer 1 will be described with reference to FIGS. 1 and 2. The laser beam printer 1 includes a box-shaped apparatus main body 1a. As shown in FIG. An inclined concave paper discharge tray 32 is provided at the center of the upper surface of the paper, and an operation display section 34 is disposed beside it. In addition, an openable and closable manual feed tray 8 (shown in an open state is shown in FIG. 2) is provided at the upper part of the front surface of the apparatus main body 1a (the front side in FIG. 1 is the front), and at the lower part of the apparatus main body 1a. A rectangular box-shaped paper feed cassette 7 that can be pulled out to the front side is provided.

  Next, the internal structure of the laser beam printer 1 will be described with reference to FIG.

  The laser beam printer 1 forms an image on a sheet based on image data transmitted from a terminal (not shown) while conveying the sheet along a conveyance path L provided in the apparatus main body 1a. The transport path L includes a horizontal portion L1 extending substantially horizontally from the front to the rear (right to left in FIG. 2) in the apparatus main body 1a, and a vertical portion L2 rising substantially vertically from the end of the horizontal portion L1. It is comprised by the side view substantially L-shape.

  Further, the laser beam printer 1 includes a paper feeding unit 2 provided at a lower portion of the apparatus main body 1a, an image forming unit 3 provided at a substantially central portion in the apparatus main body 1a above the paper feeding unit 2, The fixing unit 4 disposed behind the image forming unit 3, the concave paper discharge unit 5 provided on the upper surface of the apparatus main body 1 a above the fixing unit 4, the horizontal unit L 1 of the conveyance path L, and the supply unit A switchback unit 6 provided between the paper cassette 7 is provided.

  The paper feed unit 2 stores paper and feeds the paper toward the image forming unit 3 and includes the paper feed cassette 7 and the manual feed tray 8.

  Here, the paper feed cassette 7 has a rectangular box shape with an open upper surface, and fulfills a function of feeding sheets (not shown) stacked and accommodated therein, one by one, as shown in FIG. As shown, in the state where it is mounted in the apparatus main body 1a, it is located below the horizontal portion L1 of the transport path L as shown.

  The paper feed cassette 7 includes a lift plate 9 that contacts and separates from the inner bottom surface, a bottom plate 10 that moves up and down in conjunction with the contact and separation operation of the lift plate 9, and a front end of the lift plate 9 (paper feeding direction). A lift drive shaft 11 that is attached in the vicinity of the downstream end) and rotates the lift plate 9 in the direction of the arrow in FIG. 2 and a shaft that can rotate in the vicinity of the rear end (upstream end in the sheet feeding direction) of the bottom plate 10. A supporting shaft 12 is provided.

  Further, the paper feed unit 2 includes a pickup roller 13 that takes out the paper in the paper feed cassette 7 one by one, a feed roller 14 that sends out the taken paper to the horizontal part L1 of the transport path L, a retard roller 15, and a plurality of rollers. Pick-up rollers 16, 17, and 18, and a pickup that picks up the paper placed on the manual feed tray 8 in addition to the registration rollers 19 that supply the image forming unit 3 to the image forming unit 3 at a predetermined timing after temporarily waiting the fed paper. A roller 20 is provided.

  The image forming unit 3 forms an image on a sheet supplied from the sheet feeding unit 2, and is an image carrier that is rotatably disposed at a substantially central portion in the front-rear direction of the horizontal portion L 1 of the transport path L. A photosensitive drum 21, a primary charger 22, a developing device 23, a transfer roller 24 and a cleaning device 25 disposed around the photosensitive drum 21, a laser scanner unit (LSU) 26, a toner hopper 27, and the like disposed above them. I have.

  The fixing unit 4 is for fixing the toner image transferred onto the paper in the image forming unit 3 to the paper, and includes a heating roller 28 and a pressure roller 29 that rotate while being pressed against each other. Yes.

  Further, the paper discharge unit 5 is for discharging the paper on which the toner image has been fixed in the fixing unit 4 to the outside of the apparatus main body 1a, and is provided in the middle of the vertical portion L2 of the transport path L. And a paper discharge roller 31 provided at the end of the vertical portion L2 and a paper discharge tray 32 for stacking paper discharged outside the apparatus main body 1a.

  The switchback unit 6 is used when images are formed on both sides of a sheet. The switchback unit 6 is provided in another conveyance path L ′ disposed below the horizontal portion L1 of the conveyance path L and its proper position. A plurality of transport rollers 33 are provided.

  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), in the image forming unit 3, the photosensitive drum 21 is driven in a direction indicated by an arrow (clockwise) in FIG. ) And the surface thereof is uniformly charged to a predetermined potential by the primary charger 22. When a laser beam based on the image data transmitted from the terminal is output from the laser scanner unit 26 and irradiated onto the photosensitive drum 21, an electrostatic latent image is formed on the photosensitive drum 21. Then, the electrostatic latent image formed on the photosensitive drum 21 is developed by the developing device 23 using toner as a developer to be visualized as a toner image.

  At the same time, in the paper feeding unit 5, for example, the sheets stored in the paper feeding cassette 7 are picked up one by one from the uppermost one by the pickup roller 13, and the feed roller 14, the retard roller 15, and the paper feeding rollers 16, 17. , 18 are sent to the horizontal portion L1 of the conveying path L, and after being temporarily put into a standby state by the registration roller 19, are supplied to the image forming portion 3 at a predetermined timing synchronized with the toner image on the photosensitive drum 21. . In the paper feed cassette 7, the bottom plate 10 is raised to a predetermined height position corresponding to the number of sheets stacked on the lift plate 9 by rotating the lift plate 9 away from the inner bottom surface. The uppermost one of the sheets stacked on the bottom plate 10 is picked up by the pickup roller 13. Further, when an image is formed on the paper loaded on the manual feed tray 8, the paper is taken out one by one by the pickup roller 20, and sent to the horizontal portion L1 of the transport path L by the paper feed rollers 16 and 18. .

  In the image forming unit 3, the sheet supplied to the transfer nip between the photosensitive drum 21 and the transfer roller 24 is conveyed while being pressed against the photosensitive drum 21 by the transfer roller 24, thereby its surface (transfer surface). ), The toner image on the photosensitive drum 21 is transferred. The sheet on which the toner image has been transferred is conveyed to the fixing unit 4, and is heated and pressed in the process of being sandwiched and conveyed by the heating roller 28 and the pressure roller 29 in the fixing unit 4. Get fixed. The toner remaining on the surface of the photosensitive drum 21 after transfer of the toner image onto the sheet (transfer residual toner) and electric charge are removed by the cleaning device 25.

  Thus, the sheet on which the toner image is fixed on the surface by the fixing unit 4 is conveyed upward by the conveying roller 30 along the vertical portion L2 of the conveying path L, and is provided on the upper portion of the apparatus main body 1a by the discharge roller 31. The paper is discharged and stacked on the discharged paper discharge tray 32.

  The above is a series of operations when an image is formed on one side of a sheet. When an image is formed on both sides of a sheet, a sheet on which a toner image is fixed on one side by a fixing unit 4 is conveyed by a conveyance roller 30. After the sheet is fed to the vertical portion L2 of the conveyance path L, the sheet is switched back by feeding the conveyance roller 30 in the reverse direction to be fed to another conveyance path L ′. Then, the paper is transported forward (to the right in FIG. 2) along the transport path L ′ by the plurality of transport rollers 33 provided in the transport path L ′, and the paper is transported by the paper feed rollers 16, 17, 18. When the sheet is fed again to the horizontal portion L1 of the conveyance path L, the front and back of the sheet are reversed, and thereafter, the toner image on the photosensitive drum 21 is transferred to the surface of the sheet (the other side on which no image is formed) by the same operation as described above. ) And the toner image is fixed on the paper in the fixing unit 4, images are formed on both sides of the paper. The sheet on which images are formed on both sides in this way is conveyed upward along the vertical portion L2 of the conveyance path L by the conveyance roller 30 and is discharged to the discharge tray 32 by the discharge roller 31 as described above.

  Next, the gist of the present invention will be described with reference to FIGS.

  3 is a perspective view of the paper feed cassette, FIG. 4 is a partial perspective view of the bottom plate of the paper feed cassette, FIG. 5 is an enlarged detail view of part A in FIG. 4, and FIG. 6 is a view in FIG. FIG.

  The paper feed cassette 7 can accommodate a plurality of sizes of paper from a small size to a large size. As shown in FIG. 3, the paper feed cassette 7 includes a pair of left and right for pressing the paper in the lateral direction. Side cursors 35 are provided so as to be movable along the width direction so as to be separable from each other. Since the small size paper can be stored in the paper feed cassette 7, the range of movement of the side cursor 35 in the width direction is increased. For this reason, the left and right sides of the bottom plate 10 interfere with the side cursor 35. To avoid it, it is greatly cut out and its width is narrowed.

  By the way, the apparatus main body 1a is provided with a detecting means for optically detecting the presence / absence of paper in the paper feed cassette 7. As shown in FIG. An arm-shaped actuator 36 that constitutes a part of the means hangs down from the main body side, and a notch 10 a that allows passage of the actuator 36 is formed at one end in the width direction of the bottom plate 10. Here, the actuator 36 has an upper end attached to one end of a shaft 37 extending horizontally in the width direction, and an arm-shaped detection member 38 at the other end of the shaft 37 extending outward from the paper feed cassette 7. Is attached.

  Thus, when the paper is stacked on the bottom plate 10 in the paper feed cassette 7, the actuator 36 does not contact the upper surface of the paper and does not rotate, and therefore the detection member 38 does not rotate. Then, it is detected that there is a sheet in the sheet feeding cassette 7.

  When paper is used and no paper is left on the bottom plate 10, there is no support for the actuator 36, so the actuator 36 rotates through the notch 10 a of the bottom plate 10 and rotates. Is also transmitted to the detection member 38 via the shaft 37, and the detection member 38 is also rotated integrally, so that the rotation of the detection member 38 is optically detected, thereby eliminating the sheet in the paper feed cassette 7. Is detected.

  By the way, in this embodiment, as shown in detail in FIGS. 4 and 5, a protrusion 39 protruding upward is formed on the upper surface in the vicinity of the notch portion 10 a of the bottom plate 10 of the sheet feeding cassette 7 in the sheet conveying direction. It is formed vertically long along. The protrusion 39 may be formed integrally when the bottom plate 10 is molded, or a separate member from the bottom plate 10 may be attached to the bottom plate 10 by adhesion or the like.

  Thus, in the present embodiment, the protrusion 39 protruding upward is formed on the upper surface in the vicinity of the notch 10a of the bottom plate 10 of the paper feed cassette 7 as described above. When a small-sized paper P having a small width dimension is stacked on the bottom plate 10 and the remaining number of sheets P is reduced (FIG. 6 shows a state where one sheet P remains). 8), the end of the paper P near the actuator 36 is bent upward by a protrusion 39 formed in the vicinity of the notch 10a of the bottom plate 10, so that the bottom as shown in FIG. The plate 110 does not hang down at the notch 110a and escape from the actuator 136.

  For this reason, the conventional problem that the actuator 36 does not pass through the notch 10a of the bottom plate 10 and erroneously detects that the sheet P is present even though the sheet P is present in the sheet cassette 7 is solved. Thus, up to the last sheet P is detected, and the presence or absence of the sheet P in the sheet feeding cassette 7 is always reliably detected.

  Further, in the present embodiment, since the protrusions 39 are formed vertically in the paper transport direction, only the end portion of the paper P near the actuator 36 is partially bent upward, and the drooping of that portion is reliably prevented. Thus, erroneous detection of the presence or absence of the paper P in the paper feed cassette 7 is reliably prevented.

  In the above, the embodiment in which the present invention is applied to a laser beam printer has been described. However, the present invention can be similarly applied to other arbitrary image forming apparatuses such as a copying machine and a facsimile machine in addition to a printer. Of course.

1 is a perspective view of an image forming apparatus (laser beam printer) according to the present invention. 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 a paper feed cassette of an image forming apparatus (laser beam printer) according to the present invention. FIG. 3 is a partial perspective view of a bottom plate of a paper feed cassette of the image forming apparatus (laser beam printer) according to the present invention. It is the A section enlarged detail drawing of FIG. FIG. 6 is an enlarged sectional view taken along line B-B in FIG. It is a perspective view of a paper feed cassette of a conventional image forming apparatus. FIG. 8 is an enlarged cross-sectional view taken along the line C-C in FIG.

Explanation of symbols

1 Laser beam printer (image forming device)
DESCRIPTION OF SYMBOLS 1a Apparatus main body 2 Paper feed part 3 Image formation part 4 Fixing part 5 Paper discharge part 6 Switchback part 7 Paper feed tray 8 Manual feed tray 9 Lift plate 10 Bottom plate 10a Bottom plate notch part 11 Lift drive shaft 12 Shaft 13 Pickup Roller 14 Feed roller 15 Retard roller 16-18 Feed roller 19 Registration roller 20 Pickup roller 21 Photosensitive drum 22 Primary charger 23 Developing device 24 Transfer roller 25 Cleaning device 26 Laser scanner unit (LSU)
27 Toner Hopper 28 Heating Roller 29 Pressure Roller 30 Conveying Roller 31 Discharge Roller 32 Discharge Tray 33 Conveying Roller 34 Operation Display Unit 35 Side Cursor 36 Actuator (Detecting Unit)
37 axis 38 detection member (detection means)
39 Protrusion L, L 'Conveying path L1 Conveying path horizontal part L2 Conveying path vertical part P Paper

Claims (2)

An actuator capable of detachably attaching to the apparatus main body a paper cassette that feeds sheets stacked on the bottom plate one by one, and that can pass through a notch formed at one end in the width direction of the bottom plate of the paper cassette. In the image forming apparatus having detection means for detecting the presence or absence of paper in the paper feed cassette,
An image forming apparatus, wherein a protrusion projecting upward is formed on an upper surface in the vicinity of the notch portion of the bottom plate.   The image forming apparatus according to claim 1, wherein the protrusion is formed vertically long along a sheet conveyance direction.

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