JP4516198B2 - Electrophotographic image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus.
[0002]
[Prior art]
In general, an electrophotographic image forming apparatus receives print data, develops it into image data, first irradiates a photosensitive member with a light beam such as a laser to form an image by charge, a so-called latent image, and then develops it. A colored particle (toner) is selectively adhered by a container to visualize it, thereby forming an image. On the other hand, a medium such as paper is conveyed to a photosensitive member by a conveying unit such as a roller, and an image formed on the photosensitive member is transferred. Then, the image is printed (printed) by fixing the image on a sheet by a fixing device. In such an electrophotographic image forming apparatus, in order to perform a stable printing operation, a sheet that guarantees printing quality is usually defined. Therefore, it is necessary for the user to prepare a sheet defined by the apparatus. If the sheet is easily available, there is no problem. If not, the user must be prepared to deteriorate the print quality. In some cases, not only the print quality is deteriorated but also a so-called paper jam phenomenon in which the paper is wound around the drum may be derived. Therefore, conventionally, when paper other than those specified is used, the paper is supplied from the manual tray so that the paper transport path is as straight as possible, and the printing operation is performed. Winding around the drum cannot be solved. Even if the paper is stipulated, the paper may not always behave as expected in consideration of the storage state of the paper and changes in the surrounding environment. Further, the sheet conveyed at high speed vibrates and contacts the parts in the sheet conveying path due to its instantaneous behavior, thereby disturbing the unfixed image. In addition to the plain paper called so-called copy paper, various paper may be used for electrophotographic image forming apparatuses such as OHP paper, label paper, envelopes and postcards. In this way, it is conceivable that media with different thickness, rigidity, paper curling, etc. may be used, so it is necessary to make the device compatible with a wide range of paper types. became.
[0003]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic image forming apparatus having a mechanism for stabilizing the behavior of the leading edge of a sheet that is generated when a sheet having unfixed colored particles (toner) attached thereto is conveyed to a fixing device.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, the colored particle (toner) adhering surface side is brought into contact with the end of the paper in the conveyance path of the paper to which the unfixed colored particles (toner) adhere. A paper guide is provided to regulate the paper behavior when the fixing device is loaded.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIG.
[0006]
The printer main body 25 includes a developing device 1 to a developing device 4, an optical unit 5, a charger 8, a photosensitive belt 22, a transfer drum 21, a paper feeding roller 10, a registration roller 12, a transfer roller 13, a static eliminator 15, a fixing device 19, The paper discharge roller 18 and the paper feed cassette 6 are the main components. The control block diagram is shown in FIG. The control block is roughly divided into two blocks, that is, a printing apparatus main body control unit 100 and an anti-transfer paper apparatus control unit 101. The printer main body control unit 100 is an I / F unit for exchanging data with the host, exposure, development, fixing unit, motor as a power source, solenoid drive unit, operation / display unit, paper feed control unit , A sequence control unit for controlling several detectors and the like, and a sheet reversal control unit. The anti-transfer paper device control unit 101 includes a motor that is a power source, a solenoid drive unit, several detectors, and the like, and operates according to a signal from the paper reverse control unit.
[0007]
The operation of the printing device 25 will be described.
[0008]
The charger 8 uniformly charges the photosensitive belt 22 in response to a print start signal from a host not shown here. The optical unit 5 draws a latent image on the photosensitive belt 22 by print data sent from the host. The drawn latent image is developed by any one of the developing devices 1 to 4, and the colored particles (toner) in the developing device are applied onto the photosensitive belt 22. The photosensitive belt 22 is rotated by a driving source not shown here, and the colored particles (toner) on the photosensitive belt 22 are transferred onto the transfer drum 21. The photosensitive belt 22 is neutralized by an erase lamp 160, and excess colored particles (toner) remaining on the photosensitive belt 22 are removed by a belt cleaner 23 and charged by the charger 8 again. In the case of color printing, this process is repeated several times while switching the developing device. On the transfer drum 21, a visible image is formed by single-colored or multiple-colored colored particles (toner), and when the desired transfer is completed or in advance, the paper 27 is fed from the paper cassette 6 to the paper feed roller 10. And waits at the registration roller 12. After the paper is detected by the detector 161, the paper feed roller 10 stops after a predetermined time. At the timing when the position of the visible image formed on the transfer drum 21 coincides with the transfer position on the sheet, the sheet waiting at the registration roller 12 starts to be conveyed again, and the transfer roller 13 The visible image is transferred to the paper side. The sheet is peeled off from the transfer drum 21 by the static eliminator 15, and the colored particles (toner) are fixed on the sheet 27 by the fixing unit 19 and discharged to the sheet discharge tray 28. Further, excess colored particles (toner) remaining on the transfer drum 21 are removed by the drum cleaner 20. FIG. 3 is a cross-sectional view of a fixing device showing an embodiment of the present invention. The fixing device 19 includes a pressure roller 19a, a fixing roller 19b, a cleaning roller c, a peeling claw 19d, a paper guide 19e, a guide 182, an oil bottle 181, and an oil tray 178 as main components. Oil bottles 181 and oil pans 178 are made up of roll paper impregnated with oil and those in which oil components are contained in colored particles (toner) according to recent techniques, and are so-called oil-less. It's not always necessary. The sheet on which unfixed colored particles (toner) conveyed along the guide 182 adheres is pressurized and heated by the pressure roller 19a and the fixing roller 19b, and the colored particles (toner) are melted and fixed to the sheet. FIG. 4 is a cross-sectional view showing the arrangement of the transfer drum 21 and the fixing device 19 in the conventional example. The paper 27 on which the colored particles (toner) are transferred from the transfer drum 21 is ideally conveyed along a straight ideal locus 183 connecting the contact portions of the transfer drum 21, the fixing roller 19b, and the pressure roller 19a. Although there is no problem, the sheet is actually deviated from the ideal trajectory 183 due to a change in the type of paper or environment. FIG. 5 shows the contact of the paper 27 with the fixing roller 19b in the conventional example. The leading end of the paper 27 conveyed along the guide 182 contacts the pressure roller 19a, and is caught in the contact portion between the fixing roller 19b and the pressure roller 19a by the rotation of the pressure roller 19a in the arrow direction. Depending on the collision angle between the pressure roller 19a and the front end of the paper 27, the front end of the paper 27 is instantaneously vibrated and deformed toward the fixing roller 19b. Therefore, colored particles (toner) in an unfixed state adhere to the surface of the fixing roller 19b, and then the sheet 27 and the fixing roller 19b come into contact again to be transferred and fixed to the sheet 27 side again. Therefore, the image is disturbed at a portion of about 7 to 8 mm at the front end of the sheet. 6 and 7 are perspective views showing the relationship between the paper guides 179a and 179b and the paper 27 according to one embodiment of the present invention. The deformation of the sheet caused by the contact of the sheet 27 with the pressure roller 19a already described is not only in contact with the fixing roller 19b, but depending on the type of sheet to be conveyed, the deformation may be repeated with the transfer drum 21. It can lead to contact. In this case, the colored particles (toner) once transferred to the paper 27 return to the transfer drum 21 side again, and after the fixing, the image of the contacted part is lost and the image quality is remarkably lowered. become. The paper guides 179a and 179b are arranged so as to contact only the end portion of the paper 27 so as to avoid recontact with the transfer drum 21 without contacting the surface to which the colored particles (toner) adhere. The colored particles (toner) are not affected. Further, when the deformation amount of the paper 27 is not large, the paper guides 179a and 179b and the paper 27 do not contact each other. FIG. 8 shows the relationship between the paper 27 and the paper guides 179a and 179b. When the amount of deformation of the sheet increases, the edge of the sheet 27 comes into contact with the slopes of the sheet guides 179a and 179b, so that further deformation of the sheet 27 is restricted at the time of contact, so colored particles (toner) It is avoided that the surface on which the toner adheres contacts the transfer drum 21 again. The slopes of the paper guides 179a and 179b may be either straight lines or curved lines, and the shape is determined along the transport path of the paper 27. Although not described here, it can be easily assumed that the interval between the sheet guide A 179a and the sheet guide B 179b is automatically changed in accordance with the size of the sheet 27 to be used.
[0009]
【The invention's effect】
According to the present invention, in an electrophotographic image forming apparatus provided with a deformation amount restriction guide for deformation of paper on the unfixed colored particle (toner) adhering side of the paper, the deformation amount of the paper can be restricted regardless of the type of paper. The printing quality can be kept good.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a printing apparatus when a paper guide is attached according to an embodiment of the present invention.
FIG. 2 is a control block diagram of the printing apparatus according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a fixing device showing an embodiment of the present invention.
FIG. 4 is a cross-sectional view showing the arrangement of a transfer drum and a fixing device in a conventional example.
FIG. 5 is a diagram illustrating contact of a sheet with a fixing roller in a conventional example.
FIG. 6 is a perspective view showing a paper posture correction protrusion according to an embodiment of the present invention.
FIG. 7 is a perspective view illustrating a relationship between a sheet guide and a sheet according to an embodiment of the present invention.
FIG. 8 is a cross-sectional view showing a relationship between a paper guide and a paper, showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Developer 1,2 ... Developer 2,3 ... Developer 3,4 ... Developer 4,5 ... Optical unit, 6 ... Paper feed cassette a, 8 ... Charger, 10 ... Feed roller a, 12 ... Registration roller, 13: Transfer roller, 15: Static eliminator, 18 ... Paper discharge roller, 19 ... Fixing device, 19a ... Pressure roller, 19b ... Fixing roller, 19c ... Cleaning roller, 19d ... Separation claw, 19e, 179 ... Paper Guide, 19f, 179a ... Paper guide A, 19, 179b ... Paper guide B, 19h ... Protrusion, 19i ... Support body joint, 20 ... Drum cleaner, 21 ... Transfer drum, 22 ... Photosensitive belt, 23 ... Belt cleaner, 25 ... Printer main body, 27 ... Paper a, 28 ... Discharge tray, 100 ... Printer main body control unit, 101 ... Non-transfer paper device control unit, 160 ... Erase lamp, 161 ... Detector, 178 ... Oil receiving Dish, 180 ... support plate 181 ... oil bottles, 182 ... guide, 183 ... ideal track, 184 ... contact portion, 185 ... sheet posture correction projection.

Claims (2)

In an electrophotographic image forming apparatus, comprising: a paper cassette for storing paper; a transfer body on which an image is formed; a transport unit that transports the paper to the transfer body; and a fixing device that fixes a transfer image of the paper. The leading edge of the paper to which unfixed colored particles (toner) adhere is separated from the transfer body and is conveyed to the fixing device, and is unfixed in the vicinity of the transfer body and in the axial direction of the transfer body. It provided the paper guide attached sheet surface of the colored particles (toner), the paper guides, at both ends of the support plate provided in the axial direction of the transfer body, adhered portion of the colored particles (toner) and are arranged so as not to contact, has an inclined surface portion along the transport path of the sheet abutting said inclined surface portion of the paper guide only paper end of the unfixed colored particles (toner) is adhered surface sheet Recontacts the transfer body Electrophotographic image forming apparatus characterized by avoiding.   2. The electrophotographic image forming apparatus according to claim 1, wherein the electrophotographic image forming apparatus is arranged in the order of the paper cassette, the transfer body, and the fixing device from below, and the fixed paper is placed on an upper paper discharge tray. An electrophotographic image forming apparatus which discharges.

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