This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2014-193370 filed on Sep. 24, 2014, the entire contents of which are incorporated herein by reference.
The present disclosure relates to an image forming apparatus that includes a discharge unit for discharging a sheet member after image formation to outside from a sheet discharge port.
There is known an image forming apparatus that performs image formation based on the electrophotography. The image forming apparatus includes a fixing device and a discharge unit. The fixing device fixes a toner image that has been transferred to a surface of a sheet member such as a print sheet, to the sheet member by causing the toner image to fuse. The discharge unit is disposed more in the downstream side in the sheet member conveyance direction than the fixing device. The discharge unit includes a discharge path inside, and the sheet member to which the toner image has been fixed passes through the discharge path and is discharged from a predetermined sheet discharge port to an external tray.
In this type of image forming apparatus, an electric field is generated between a sheet member and a photoconductor drum, and a potential difference in the electric field is used for the toner image to be transferred from the photoconductor drum to the sheet member. At this time, the sheet member is put in the electric field, and electric charges of positive or negative polarity are generated on the sheet member. In addition, while the sheet member is conveyed in a conveyance path, electric charges of positive or negative polarity are generated on the sheet member due to a friction between the sheet member and a conveyance guide surface. The phenomenon in which electric charges are generated on an object is called charging. When a sheet member such as a print sheet that is made of an insulator is charged, the generated charges do not flow, but are accumulated on the sheet member as static electricity. The sheet member contacts the conveyance guide surface and receives friction therefrom until immediately before being discharged from the sheet discharge port. As a result, the amount of static electricity charged on the sheet member becomes the largest immediately before the sheet member is discharged from the sheet discharge port. For this reason, conventionally, an electricity removing member, such as an electricity removing brush, is provided near the sheet discharge port, wherein the electricity removing member removes static electricity from the sheet member.
In addition, some conventional image forming apparatuses include a pressing member for giving stiffness (also called “toughness” or “rigidity”) to the sheet member before it is discharged. The pressing member is provided in the discharge path in the discharge unit. Specifically, the pressing member is provided near a discharge roller in the discharge path. The pressing member curves the sheet member by contacting and pressing the sheet member. With this configuration, the sheet member is stiffened when it is discharged, and thereby the sheet member is prevented from hanging down immediately after the discharge.
In addition, conventionally, there has been known a frame configuration for ensuring the rigidity of the image forming apparatus while realizing the downsizing thereof. Conventionally, reduction of the image forming apparatus in size and cost has been demanded, and downsizing of the discharge unit has been promoted. On the other hand, upsizing of the sheet member on which an image can be formed by the image forming apparatus is desired. In recent years, an image forming apparatus that can form an image on a sheet member of A3 size has been known.
An image forming apparatus according to an aspect of the present disclosure includes a discharge unit, a discharge roller, a pressing member, and a reinforcing frame. The discharge unit includes a guide member that forms a discharge path that guides a sheet member after image formation to a sheet discharge port. The discharge unit is attached to an apparatus main body. The discharge path is formed inside the discharge unit by the guide member. The discharge roller is disposed in a vicinity of the sheet discharge port of the discharge unit, and discharges the sheet member in the discharge path to outside from the sheet discharge port. The pressing member is attached to the guide member more in an upstream side than the sheet discharge port in a sheet member discharge direction, the pressing member projecting from the guide member toward the discharge path and configured to contact and press the sheet member that is passing through the discharge path. The reinforcing frame is made conductive with a reference potential portion of the apparatus main body and configured to reinforce the discharge unit by being, together with the discharge unit, fixed to the apparatus main body in a state of covering a part of the guide member to which the pressing member is attached. The reinforcing frame is formed from a metal plate material.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.
The following describes an embodiment of the present disclosure with reference to the attached drawings. It should be noted that the following description is an example of a specific embodiment of the present disclosure and should not limit the technical scope of the present disclosure. It is noted that for the sake of explanation, an up-down direction 6 is defined based on the state (the state shown in
[Image Forming Apparatus 10]
The image forming apparatus 10 is shown in
The image forming apparatus 10 prints an image on a print sheet based on image data input from an external source via a network communication portion (not shown). As shown in
As shown in
The image forming portion 18 forms an image on a print sheet of a standard size such as an A series size (for example, A5 size, A4 size, or A3 size) or a B series size (for example, B5 size or B4 size), based on image data input from an external source. The image forming portion 18 transfers a toner image to a print sheet by using a print material such as toner. Specifically, as shown in
The fixing portion 19 is provided in the rear side of the image forming portion 18. The fixing portion 19 fixes the toner image that has been transferred to the print sheet, to the print sheet by heat. The fixing portion 19 includes a heating roller 41 and a pressure roller 42. The heating roller 41 is heated by a heating means such as an IH heater during a fixing operation. The pressure roller 42 is biased toward the heating roller 41 by an elastic member. When the print sheet passes through the fixing portion 19, the print sheet is pressed by the fixing portion 19 while the toner is heated and fused and adheres to the print sheet. This allows the toner image to be fixed to the print sheet, thereby an image is formed on the print sheet. At this time, the print sheet is heated to a high temperature.
A conveyance path 28 is provided more in the rear side than the fixing portion 19. The conveyance path 28 is formed by a pair of guide members (not shown). The conveyance path 28 is formed in the shape of extending rearward and then curving and extending upward along the rear surface of the image forming apparatus 10. The end of the conveyance path 28 is connected to a discharge path 61 formed inside the discharge unit 60, wherein the discharge path 61 is described below. A driven roller 38 is rotatably provided in the vicinity of the end of the conveyance path 28. The driven roller 38 is pressed against a conveyance roller 39 provided in the discharge unit 60, wherein the conveyance roller 39 is described below.
As shown in
[Discharge Unit 60]
The discharge unit 60 discharges, to the discharged-sheet stacking portion 21, a print sheet after image formation to which an image has been fixed by the fixing portion 19. As shown in
As shown in
As shown in
As shown in
The external guide member 71 and the internal guide member 72 are both insulators. Specifically, the external guide member 71 and the internal guide member 72 are resin molded products made of a synthetic resin having a low electric conductivity. The external guide member 71 and the internal guide member 72 constitute, together with the reinforcing frame 80, the housing of the discharge unit 60. An upper portion 71B of the external guide member 71 constitutes an upper part of the housing of the discharge unit 60, and a rear portion 71C of the external guide member 71 constitutes a rear side part of the housing of the discharge unit 60. In addition, the front surface of the internal guide member 72 constitutes a front side part of the housing of the discharge unit 60.
As shown in
The pair of discharge rollers 77 discharges a print sheet in the discharge path 61 to outside from the sheet discharge port 22. The pair of discharge rollers 77 is disposed near the sheet discharge port 22. Specifically, the pair of discharge rollers 77 is disposed more in the upstream side in the print sheet conveyance direction than the sheet discharge port 22. As shown in
Each pair of discharge rollers 77 is composed of a driving roller 77A and a driven roller 77B that are pressed against each other. The driving roller 77A and the driven roller 77B are disposed to face each other across the discharge path 61. The driving roller 77A is rotatably supported by an upper end portion 72B of the internal guide member 72. A rotational driving force is transmitted to the driving roller 77A from the discharge motor 64 (see
The conveyance roller 39 conveys a print sheet conveyed from the conveyance path 28 toward the discharge path 61. The conveyance roller 39 is rotatably supported by a lower end portion 72C of the internal guide member 72. A rotational driving force is transmitted to the conveyance roller 39 from the discharge motor 64 (see
As shown in
The pressing members 74 are supported by the upper portion 71B of the external guide member 71 so as to be displaced in a direction of separating from the upper portion 71B toward the discharge path 61 (separation direction). The separation direction is a downward direction in
Each of the pressing members 74 includes two arms 76. The arms 76 are provided on each of the projection portions 75 that are to contact a print sheet. The two arms 76 extend upward from opposite ends of the projection portion 75 in the front-rear direction 7. A hook 76A that is oriented downward is formed on each of the arms 76. The arms 76 and the base portions of the arms 76 are embedded in the opening 65. The upper portion 71B of the external guide member 71 is provided with a pair of support plates 53 and 54 that are separated from each other in the front-rear direction 7. The support plate 53 extends upward from a rear-side edge of the opening 65, and the support plate 54 extends upward from a front-side edge of the opening 65. A through hole 55 is formed in each of the support plates 53 and 54, wherein the through holes 55 pass through the support plates 53 and 54 in the front-rear direction 7. The through holes 55 are long holes that are elongated in the up-down direction 6. The hooks 76A are inserted through the through holes 55, thereby the pressing members 74 are supported so as to be displaced from the opening 65 in the up-down direction 6. It is noted that the length by which the pressing members 74 can be displaced in the up-down direction 6 is limited to the length of the through holes 55 in the up-down direction 6. That is, the amount of displacement of the pressing members 74 is determined by the length of the through holes 55 in the up-down direction 6. In addition, the amount of projection of the projection portions 75 toward the discharge path 61 is determined based on the extent to which a print sheet is curved.
Each of the pressing members 74 is elastically biased downward by an elastic member 56 such as a spring. By being elastically biased by the elastic member 56, a force that presses the conveyed print sheet is generated in each of the pressing members 74. Specifically, each of the plurality of pressing members 74 is biased by the elastic member 56 in a direction of separating from the upper portion 71B of the external guide member 71 downward. As shown in
In the present embodiment, a coil spring formed from a metal wire having conductivity, or a plate spring formed from a metal plate having conductivity, is used as the elastic member 56. It is noted that the elastic member 56 is not limited to a spring as far as it can elastically biases the pressing member 74 downward. In addition, the elastic member 56 is not limited to a metal material as far as it has conductivity.
[Reinforcing Frame 80]
The reinforcing frame 80 is provided for the purpose of increasing the rigidity of the discharge unit 60 to increase the strength. The reinforcing frame 80 is formed from a metal plate material. As shown in
The reinforcing frame 80 and the internal guide member 72 are fixed to the side frames 14A and 14B of the housing 14, wherein the reinforcing frame 80 is fixed in the state of covering the external guide member 71 from outside (from the rear side in
The following describes the reinforcing frame 80. As shown in
The upper plate 81 is a thin and long plate member that extends in the left-right direction 8 in the state where the discharge unit 60 is attached to the housing 14. As shown in
The base plate 82 is connected to the rear end portion of the upper plate 81, and is a plate member that extends downward in the vertical direction from the rear end portion of the upper plate 81. As shown in
The side plate 83 is formed at each of opposite ends of the reinforcing frame 80 in the left-right direction 8. A side plate 83A is formed at the left end of the reinforcing frame 80, and a side plate 83B is formed at the right end of the reinforcing frame 80. The side plates 83A and 83B are each connected to the upper plate 81 and the base plate 82. The side plate 83A is formed to be larger in size than the side plate 83B. The side plate 83A covers the discharge motor 64 in the state where the discharge motor 64 is attached to the supported portion 67. In the present embodiment, the side plate 83A is, together with the supported portion 67 of the discharge unit 60, fixed to the side frame 14A of the housing 14 in the state where it covers the discharge motor 64. In addition, the side plate 83B is, together with the supported portion 68, fixed to the side frame 14B of the housing 14 in the state where it covers the supported portion 68.
Two through holds 84A are formed in the side plate 83A at positions that correspond to the two bosses 69A of the supported portion 67. In addition, two through holds 84B are formed in the side plate 83B at positions that correspond to the two bosses 69B of the supported portion 68.
As shown in
As shown in
It is noted that, as shown in
As shown in
The reinforcing frame 80 and the discharge unit 60 configured as described above are attached to the side frames 14A and 14B of the housing 14, as follows. First, the reinforcing frame 80 is temporarily fixed to the discharge unit 60. Specifically, the reinforcing frame 80 is attached to the rear surface of the discharge unit 60 in the state where the side plates 83A and 83B of the reinforcing frame 80 are spread. At this time, the bosses 69A of the supported portion 67 are inserted through the through holes 84A of the side plate 83A, and the bosses 69B of the supported portion 68 are inserted through the through holes 84B of the side plate 83B. Next, opposite end portions of the discharge unit 60 are fixed to the side frames 14A and 14B in the state where the reinforcing frame 80 is temporarily fixed. Specifically, the bosses 69A and 69B of the supported portions 67 and 68 are inserted through the attachment holes of the side frames 14A and 14B, respectively. Subsequently, fixtures such as screws are inserted through the bosses 69A and 69B from outside the side frames 14A and 14B. In this way, the reinforcing frame 80 and the discharge unit 60 are fixed to the side frames 14A and 14B.
Meanwhile, a conventional discharge unit includes an electricity removing brush (electricity removing member) for removing static electricity from print sheets. In such a conventional discharge unit, when the pair of discharge rollers 77 are supported by metal shafts, a discharge of static electricity may be generated between the metal shafts and a print sheet before the print sheet reaches the electricity removing brush. In addition, not limited to the metal shafts, when conductive members such as metal frames and screws are disposed in such a way as to be exposed to the discharge path 61, static electricity of a print sheet may be discharged to the conductive members. In particular, in a configuration where the pressing members 74 are provided, the pressing members 74 are positively contacted with the print sheet, and due to the charging generated by the contact friction, the amount of charges of static electricity increases prominently on both the print sheet and the pressing members 74. As a result, the print sheet immediately after passing through the pressing members 74 has the largest amount of charges of static electricity and is in the state where a discharge is likely to occur. In addition, since static electricity is also charged on the pressing members 74, when the next print sheet approaches the pressing members 74, a discharge may be generated between the pressing members 74 and the print sheet. The static electricity discharged near the sheet discharge port may generate a noise that may cause the peripheral equipment to malfunction, as well as electronic devices mounted in the image forming apparatus 10. In addition, when the print sheet on which an image can be formed is upsized while the discharge unit is being downsized, the discharge unit becomes thinner and longer in the width direction. This decreases the rigidity of the discharge unit. In these circumstances, realizing both the downsizing and improvement of the rigidity of the discharge unit is desired.
With the above-described configuration of the reinforcing frame 80 and the discharge unit 60, it is possible to reduce the amount of charges on the pressing members 74 by causing the charges to move from the pressing members 74 in the state where the reinforcing frame 80 and the discharge unit 60 are attached to the housing 14. This prevents a discharge from occurring to the pressing members 74. In addition, in a case where a print sheet being conveyed in the discharge path 61 has been charged with static electricity, the print sheet reaches and contacts the pressing members 74, which allows electric charges that have been charged on the contact part of the pressing members 74, to move to the ground from the pressing members 74 via the elastic members 56, reinforcing frame 80, and side frame 14A. This allows the amount of charges on the print sheet to be reduced. In addition, with the configuration where the reinforcing frame 80 covers the discharge unit 60 in such a manner that the upper plate 81, base plate 82, and side plate 83 surround the discharge unit 60, the rigidity and strength of the discharge unit 60 are increased. In addition, if a discharge of static electricity occurs near the sheet discharge port 22, the reinforcing frame 80 formed from a metal plate plays a role of an electromagnetic shield, thereby it is possible to prevent an irradiation of electric wave noise from occurring due to a discharge of static electricity to outside of the reinforcing frame 80. That is, according to the image forming apparatus 10 of the present embodiment, it is possible to improve the rigidity of the discharge unit 60, reduce the amount of charges of static electricity near the sheet discharge port 22, and prevent troubles from occurring due to a noise that would be generated by a discharge of static electricity.
Furthermore, the discharge motor 64 is attached to the supported portion 67 of the internal guide member 72 via the bracket 87, and the side plate 83A of the reinforcing frame 80 is further provided outside thereof. As a result, it is possible to effectively dissipate the heat that has been generated in the discharge motor 64, through the side plate 83A. In addition, since the bracket 87 and the side plate 83A are connected to each other, static electricity accumulated in the discharge motor 64 can be moved to the ground.
In the above-described embodiment, a print sheet passes through the fixing portion 19, the conveyance path 28, and the discharge path 61, and is discharged from the sheet discharge port 22. As a result, the heat that is generated in the heating roller 41 of the fixing portion 19 rises together with the surrounding air and passes through the conveyance path 28 and the discharge path 61. At this time, the heat is transmitted to the reinforcing frame 80 directly or indirectly via the external guide members 71 and 72. This allows a high dissipation effect to be gained, and makes it possible to prevent the peripheral of the discharge path 61 from having high temperature.
In the above-described embodiment, the pressing members 74 indirectly contact the reinforcing frame 80 via the elastic member 56. However, not limited to this, the pressing members 74 may directly contact the reinforcing frame 80.
In the above-described embodiment, the pressing members 74 have conductivity. However, the present disclosure is not limited to the configuration. The pressing members 74 may not have conductivity. In this case, movement of electric charges charged on the pressing members 74 cannot be expected, but when a discharge of static electricity occurs in the peripheral of the pressing members 74, the electric wave noise generated by the discharge can be blocked by the reinforcing frame 80.
It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.
Number | Date | Country | Kind |
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2014-193370 | Sep 2014 | JP | national |