Image forming device

Abstract

To provide an image forming apparatus that can suppress deformation of a sheet pressing member and can also suppress incidence of external light from a sheet ejection port to an image carrier.SOLUTION: An image forming apparatus comprises: an image forming unit; a sheet ejection port; an ejection roller pair; a sheet pressing member; a sheet ejection tray; and an eaves part. The image forming unit includes an image carrier, an electrifying device that electrifies the image carrier, an exposure device that exposes a surface of the electrified image carrier to form an electrostatic latent image, and a developing device that supplies toner to the image carrier on which the electrostatic latent image is formed. The sheet ejection port is arranged above the image forming unit and ejects a sheet on which an image is formed. The sheet pressing member presses both ends of a sheet passing through the sheet ejection port at both left and right ends of the sheet ejection port. The eaves part is provided by extending an end edge in a sheet ejection direction of an upper cover that constitutes an upper part of the sheet ejection port. A straight line passing through a leading end of the eaves part and a lower end edge of the sheet ejection port passes through above the image carrier.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile, and more particularly to an image forming apparatus having a sheet discharge port for discharging a sheet on which an image has been formed onto a discharge tray. [Background technology]

[0002] In image forming devices using electrophotography, such as copiers, printers, facsimiles, and combination machines thereof, when performing an image forming operation, a photoconductor drum (image carrier) is uniformly charged by a charging device, an electrostatic latent image is formed on the photoconductor drum by a laser beam from an exposure device (laser scanning unit, etc.) based on document image data, and a toner image is formed by attaching a developer (toner) to the electrostatic latent image by a developing device. The toner image is transferred to paper (recording medium) in the transfer section, and then heated and pressed by the fixing section to be fixed on the paper. The paper with the fixed image is discharged to the outside from a sheet discharge port.

[0003] In such an image forming apparatus, the sheet heated and pressurized by the fixing unit may curl significantly on both the left and right sides depending on the conditions. When the sheet curls locally in this way, it blocks the sheet discharge port, significantly impairs the alignment and stackability of the sheets discharged onto the discharge tray, and there is also a risk that previously stacked sheets will be pushed out in the discharge direction and fall off the discharge tray.

[0004] Therefore, as disclosed in Patent Documents 1 and 2, a sheet pressing member is extended from the top of the sheet discharge port in a substantially vertical downward direction relative to the sheet transport direction, and the curled sheet is pressed down to improve the alignment and stackability of the sheet. This sheet pressing member is disposed at two locations, on the left and right sides of the sheet discharge port, and is configured to press both left and right ends of the sheet, which are particularly prone to curling. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-194192 A [Patent Document 2] JP 2007-199652 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the discharge tray is generally formed on the top surface of the image forming apparatus, and the sheet discharge outlet is provided at the top of the image forming apparatus where the user can easily access (touch) in order to discharge the sheet onto the discharge tray. Also, due to the miniaturization in the height direction of image forming apparatuses in recent years, the discharge tray has become shallower, and the discharge tray and the sheet discharge outlet are disposed close to each other in the height direction. Therefore, when removing a sheet discharged onto the discharge tray, there is a risk that the sheet pressing member disposed at the sheet discharge outlet may be touched and the sheet pressing member may be inadvertently deformed.

[0007] Furthermore, due to the miniaturization of image forming devices, the photosensitive drum may be placed close to the sheet discharge port, resulting in a layout in which external light is directly incident on the photosensitive drum from the sheet discharge port, which may adversely affect the formation of an electrostatic latent image on the photosensitive drum and cause image defects.

[0008] SUMMARY OF THE PRESENT DISCLOSURE In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of suppressing deformation of a sheet pressing member and also suppressing incidence of external light from a sheet discharge port onto an image carrier. [Means for solving the problem]

[0009] In order to achieve the above object, the first configuration of the present invention is an image forming apparatus including an image forming section, a sheet discharge port, a pair of discharge rollers, a sheet pressing member, a sheet discharge tray, and a eaves portion. The image forming section includes an image carrier having a photosensitive layer formed on its surface, a charging device that charges the image carrier to a predetermined surface potential, an exposure device that exposes the surface of the image carrier charged by the charging device to form an electrostatic latent image by attenuating the charge, and a developing device that supplies toner to the image carrier on which the electrostatic latent image is formed, and forms an image on a sheet. The sheet discharge port is disposed above the image forming section and discharges the sheet on which the image is formed in the image forming section. The pair of discharge rollers is provided near the sheet discharge port. The sheet pressing members are provided at both left and right ends of the sheet discharge port, extending obliquely downward toward the downstream side in the sheet discharge direction, and press both ends of the sheet passing through the sheet discharge port. The sheet discharge tray is stacked with the sheets discharged from the sheet discharge port. The eaves portion is provided by extending an edge of the top cover constituting the upper portion of the sheet discharge outlet in the sheet discharge direction from an upper edge of the sheet discharge outlet that faces the lower edge of the sheet discharge outlet. A straight line passing through the tip of the eaves portion and the lower edge of the sheet discharge outlet passes above the image carrier.

[0010] According to the first configuration of the present invention, when removing a sheet discharged onto the discharge tray, the eaves make it difficult for a user to touch the sheet pressing member, thereby suppressing deformation of the sheet pressing member. Also, since the layout is such that external light entering from the sheet discharge port does not directly enter the image carrier, there is no risk that the external light entering from the sheet discharge port will adversely affect the formation of an electrostatic latent image on the image carrier. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a front perspective view of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a side cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 3] FIG. 1 is an exploded perspective view of a top cover 60 of an image forming apparatus 1 according to an embodiment of the present invention and a sheet pressing member 50 attached to the top cover 60. [Figure 4] FIG. 1 is a partial cross-sectional view of an image forming apparatus 1 showing the relationship between the optical path of incident light from a sheet discharge port 14 and a photosensitive drum 31. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an external perspective view of an image forming apparatus 1 according to an embodiment of the present invention, as viewed from the front side (the right side in Fig. 2). Fig. 2 is a side cross-sectional view showing a schematic configuration of the image forming apparatus 1 of this embodiment.

[0013] The image forming apparatus 1 (here, a monochrome printer) includes a main housing 10 having a substantially rectangular parallelepiped casing structure, a paper feed section 20, an image forming section 30, and a fixing section 40, which are housed within the main housing 10. A front cover 11 is provided on the front side of the main housing 10, and a rear cover 12 is provided on the rear side. Each unit of the image forming section 30 and the fixing section 40 can be inserted or removed from the rear side of the main housing 10 by opening the rear cover 12. In addition, an ejection tray 13 onto which sheets after image formation are ejected is provided on the top surface of the main housing 10.

[0014] The paper feed section 20 includes a paper feed cassette 21 that stores sheets on which an image forming process is to be performed. A part of the paper feed cassette 21 protrudes further forward from the front surface of the main body housing 10. The paper feed cassette 21 is provided with a lift plate 21U that lifts up the stack of sheets for feeding, in a paper storage space in which the stack of sheets is stored. A paper feed section 21A is provided at the top of the rear end side of the paper feed cassette 21. A paper feed roller 21B is disposed in the paper feed section 21A to feed the topmost sheet of the stack of sheets in the paper feed cassette 21 one by one.

[0015] The image forming unit 30 performs an image forming operation to form a toner image (developer image) on a sheet sent from the paper feed unit 20. The image forming unit 30 includes a photoconductor drum 31, and a charging unit 32, an exposure unit 35, a developing unit 33, and a transfer roller 34 arranged around the photoconductor drum 31.

[0016] The photosensitive drum 31 (image carrier) has a rotating shaft and an outer peripheral surface (drum body) that rotates around the rotating shaft. The outer peripheral surface of the photosensitive drum 31 is made of, for example, a known organic (OPC) photoreceptor, and a photosensitive layer made of a charge generation layer, a charge transport layer, etc. is formed on the outer peripheral surface. The photosensitive layer is uniformly charged by a charging section 32 (described later), and then irradiated with light by an exposure section 35 to form an electrostatic latent image in which the charge is attenuated, and a toner image in which the electrostatic latent image is visualized by a developing section 33 is carried on the photosensitive drum 31.

[0017] The charging section 32 (charging device) is disposed at a predetermined distance from the outer peripheral surface of the photoconductor drum 31, and uniformly charges the outer peripheral surface of the photoconductor drum 31 in a non-contact state. Specifically, the charging section 32 has a charge wire and a grid electrode (neither shown). The charging section 32 generates a corona discharge by passing a current of a predetermined current value through the charge wire, and applies a predetermined voltage to the grid electrode, thereby uniformly charging the outer peripheral surface of the photoconductor drum 31 facing the grid electrode to a predetermined surface potential.

[0018] Exposure section 35 (exposure device) has a laser light source and optical devices such as mirrors and lenses, and irradiates the outer peripheral surface of photoconductor drum 31 with light modulated based on image data provided from an external device such as a personal computer. In this way, exposure section 35 forms an electrostatic latent image on the outer peripheral surface of photoconductor drum 31 that corresponds to an image based on the image data.

[0019] The developing section 33 (developing device) is detachable from the main housing 10, and develops the electrostatic latent image formed on the outer peripheral surface of the photoconductor drum 31 by supplying non-magnetic single-component toner (developer) to the outer peripheral surface of the photoconductor drum 31. Developing the electrostatic latent image means forming a toner image (developer image) that visualizes the electrostatic latent image.

[0020] The transfer roller 34 is a roller for transferring the toner image formed on the outer peripheral surface of the photoreceptor drum 31 onto a sheet. Specifically, the transfer roller 34 rotates around its axis, and has an outer peripheral surface facing the outer peripheral surface of the photoreceptor drum 31 at a position downstream of the developing device 33 in the rotation direction of the photoreceptor drum 31. The transfer roller 34 transfers the toner image carried on the outer peripheral surface of the photoreceptor drum 31 onto a sheet passing through a nip portion between the transfer roller 34 and the outer peripheral surface of the photoreceptor drum 31. During this transfer, a transfer voltage of the opposite polarity to that of the toner is applied to the transfer roller 34.

[0021] The fixing unit 40 performs a fixing process to fix the toner image transferred to the sheet onto the sheet. The fixing unit 40 has a fixing roller 41 and a pressure roller 42. The fixing roller 41 has an internal heating source and heats the toner transferred to the sheet to a predetermined temperature. The pressure roller 42 is pressed against the fixing roller 41 to form a fixing nip between the fixing roller 41 and the pressure roller 42. When the sheet onto which the toner image has been transferred is passed through the fixing nip, the toner image is fixed onto the sheet by the heating by the fixing roller 41 and the pressure by the pressure roller 42.

[0022] A main transport path 22F and a reverse transport path 22B for transporting a sheet are provided inside the main housing 10. The main transport path 22F extends from the paper feed section 21A of the paper feed section 20, via the image forming section 30 and the fixing section 40, to a sheet discharge port 14 provided opposite the discharge tray 13 on the upper surface of the main housing 10. The reverse transport path 22B is a transport path for returning a sheet that has been printed on one side to the upstream side of the image forming section 30 on the main transport path 22F when double-sided printing is performed on the sheet.

[0023] The main transport path 22F extends from below to above the transfer nip formed by the photoconductor drum 31 and the transfer roller 34. A pair of registration rollers 23 is disposed upstream of the transfer nip on the main transport path 22F. The sheet is temporarily stopped by the pair of registration rollers 23, and after skew correction is performed, the sheet is sent to the transfer nip at a predetermined timing for image transfer. A plurality of transport rollers for transporting the sheet are disposed at appropriate positions on the main transport path 22F and the reverse transport path 22B.

[0024] The reverse conveying path 22B is formed between the outer surface of the reversing unit 25 and the inner surface of the rear cover 12 of the main housing 10. The transfer roller 34 and one of the pair of registration rollers 23 are mounted on the inner surface of the reversing unit 25. The rear cover 12 and the reversing unit 25 are each rotatable about a fulcrum 121 provided at the lower end thereof. When a jam (paper jam) occurs in the reverse conveying path 22B, the rear cover 12 is opened. When a jam occurs in the main conveying path 22F, or when the photoconductor drum 31 unit or the developing unit 33 is taken out to the outside, the reversing unit 25 is also opened in addition to the rear cover 12.

[0025] A pair of discharge rollers 24, a sheet pressing member 50, and a transport guide 63 are disposed near the sheet discharge outlet 14. The pair of discharge rollers 24 discharges a sheet from the sheet discharge outlet 14 onto the discharge tray 13. A pair of sheet pressing members 50 are provided on both the left and right sides of the sheet discharge outlet 14 (see FIG. 1), and press both left and right ends of a sheet that is particularly prone to curling. The transport guide 63 is attached to the rear surface of the top cover 60, and guides a sheet transported along the main transport path 22F to the sheet discharge outlet 14.

[0026] 3 is an exploded perspective view of the top cover 60 of the image forming apparatus 1 of this embodiment and the sheet pressing member 50 attached to the top cover 60. The sheet pressing member 50 is formed of a single sheet material and has a fixed portion 50a and a pressing portion 50b. The fixed portion 50a is fixed to the rear surface of the top cover 60 that constitutes the upper portion of the sheet discharge outlet 14. The pressing portion 50b protrudes obliquely downward from the fixed portion 50a toward the downstream side in the sheet discharge direction (the right side in FIG. 2), and contacts both the left and right side portions of the sheet discharged from the sheet discharge outlet 14 to press it downward. A positioning hole 50c is formed in the fixed portion 50a.

[0027] The material of the sheet pressing member 50 is not particularly limited as long as it is a film of a flexible synthetic resin or the like, but a film having a strength sufficient to suppress curling of the sheet is preferable. For example, a film (lumiror film) made of polyethylene terephthalate (PET) is preferably used as such a film. There is also no particular limit to the size or thickness of the sheet pressing member 50, and it may be appropriately set depending on the size of the sheet discharge port 14 and the size of the sheet to be conveyed, but it is necessary for the sheet pressing member 50 to have a certain degree of elasticity in order to suppress curling of the sheet. Therefore, for example, in the case of a PET film, the thickness of the film is preferably 0.1 mm or more.

[0028] When attaching the sheet pressing member 50, first, the fixing portion 50a of the sheet pressing member 50 is fixed to the back surface of the top cover 60. More specifically, the positioning hole 50c formed in the fixing portion 50a of the sheet pressing member 50 is fitted into the positioning boss (not shown) formed on the back surface of the top cover 60. In this state, the transport guide 63 (see FIGS. 2 and 4) is attached to the back surface of the top cover 60, whereby the fixing portion 50a is sandwiched and fixed between the top cover 60 and the transport guide 63. Then, the top cover 60 to which the sheet pressing member 50 and the transport guide 63 are attached is attached to the main body housing 10.

[0029] Here, since the sheet discharge outlet 14 is located at a place that is easily accessible (easy to touch) by the user, there is a risk of the sheet pressing member 50 being deformed by mistake. More specifically, the sheet pressing member 50 is flexible and elastically deforms to prevent excessive pressing when the sheet comes into contact with it. If the user touches it, there is a risk of deformation (plastic deformation) occurring that exceeds the range of elastic deformation. Therefore, in this embodiment, the edge of the top cover 60 that constitutes the upper surface of the sheet discharge outlet 14 in the sheet discharge direction is extended to form the eaves portion 61. Specifically, the eaves portion 61 is formed by extending the edge of the top cover 60 in the sheet discharge direction downstream from the upper edge 14b of the sheet discharge outlet 14 that faces the lower edge 14a of the sheet discharge outlet 14.

[0030] Furthermore, due to the effect of miniaturization of the height direction size of the image forming apparatus 1, the distance between the photoconductor drum 31 and the sheet discharge opening 14 becomes shorter, and the layout may result in a situation where external light entering from the sheet discharge opening 14 directly hits the photoconductor drum 31. As a result, this may adversely affect the formation of an electrostatic latent image on the photoconductor drum 31 by the exposure unit 35, resulting in image defects.

[0031] 4 is a partial cross-sectional view of the image forming apparatus 1 showing the relationship between the optical path of incident light from the sheet discharge outlet 14 and the photoconductor drum 31. Of the incident light entering the main body housing 10 from the sheet discharge outlet 14, the optical path of the incident light that reaches the lowest point inside the main body housing 10 is represented by a straight line F that passes through the tip 61a of the eaves portion 61 and the lower edge 14a of the sheet discharge outlet 14.

[0032] 4, in the image forming apparatus 1 of this embodiment, the protrusion amount of the overhanging portion 61 in the sheet discharge direction is defined so that the straight line F passes above the photosensitive drum 31. This results in a layout in which external light entering from the sheet discharge outlet 14 does not directly enter the photosensitive drum 31, and therefore there is no risk that the external light entering from the sheet discharge outlet 14 will adversely affect the formation of an electrostatic latent image on the photosensitive drum 31.

[0033] Furthermore, the tip 61a of the eaves portion 61 protrudes downstream in the sheet discharge direction (to the right in FIG. 4) beyond the tip 50d of the sheet pressing member 50 when no external force is applied to the sheet pressing member 50. This makes it difficult for a user to touch the sheet pressing member 50 due to the eaves portion 61 when removing a sheet discharged onto the discharge tray 13, thereby suppressing deformation of the sheet pressing member 50.

[0034] In addition, the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the present invention. For example, in the above embodiment, the sheet pressing member 50 is sandwiched and fixed between the top cover 60 and the conveying guide 63, but the method of fixing the sheet pressing member 50 is not limited to this, and it may be fixed using a double-sided adhesive tape, adhesive, screws, etc.

[0035] In the above embodiment, a monochrome printer has been described as an example of the image forming apparatus 1, but the present invention can also be applied to, for example, a tandem color printer. The present invention can also be applied to image forming apparatuses such as copiers, facsimiles, and digital multifunction machines equipped with these functions. [Industrial Applicability]

[0036] The present invention can be used in an image forming apparatus having a sheet discharge port that discharges a sheet on which an image is formed onto a discharge tray. By using the present invention, it is possible to provide an image forming apparatus that can suppress deformation of a sheet pressing member provided at the sheet discharge port and also suppress the incidence of external light from the sheet discharge port onto an image carrier. [Explanation of symbols]

[0037] 1. Image forming device 13 Output tray 14 Sheet outlet 14a Lower edge 14b Top edge 24 Discharge Roller Pair 30 Image forming section 31 Photoconductor drum (image carrier) 32 Charging section (charging device) 33 Development section (developing device) 35 Exposure section (exposure device) 50 Sheet pressing member 50a Fixed part 50b Pressing part 60 Top cover 61 Eaves 63 Transport guide

Claims

1. an image carrier having a photosensitive layer formed on its surface; a charging device for charging the image carrier to a predetermined surface potential; an exposure device that exposes the surface of the image carrier charged by the charging device to light and forms an electrostatic latent image by attenuating the charge; a developing device that supplies toner to the image carrier on which the electrostatic latent image is formed; an image forming section for forming an image on a sheet; a sheet discharge port disposed above the image forming unit and configured to discharge the sheet on which an image has been formed by the image forming unit; a pair of discharge rollers provided in the vicinity of the sheet discharge port; a sheet pressing member extending obliquely downward toward a downstream side in a sheet discharge direction at both left and right ends of the sheet discharge outlet and pressing both ends of the sheet passing through the sheet discharge outlet; a sheet discharge tray on which the sheets discharged from the sheet discharge port are stacked; In an image forming apparatus comprising: a top cover that constitutes an upper portion of the sheet discharge outlet has an end edge in the sheet discharge direction extended from an upper end edge of the sheet discharge outlet that faces a lower end edge of the sheet discharge outlet to provide a visor portion, and a straight line passing through a tip of the visor portion and the lower end edge of the sheet discharge outlet passes above the image carrier, the sheet pressing member has a fixed portion fixed to a rear surface of the top cover, and a pressing portion protruding obliquely downward from the fixed portion toward a downstream side in the sheet discharge direction, The fixing portion is formed with a positioning hole that fits into a positioning boss formed on the back surface of the top cover, An image forming apparatus characterized in that the sheet pressing member is fixed to the top cover by clamping the fixing portion between the top cover and a conveying guide attached to the back surface of the top cover with the positioning hole engaged with the positioning boss.

2. 2. The image forming apparatus according to claim 1, wherein a tip of the overhanging portion protrudes downstream in the sheet discharging direction further than a tip of the sheet pressing member when no external force is applied.

Images