JP3506639B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by an electrophotographic system, and more particularly, to a method for forming an electrostatic latent image formed on a photosensitive drum by a toner. The present invention relates to an image forming apparatus that forms an image by causing a toner image to appear on an image and transferring the toner image to a sheet sandwiched between a photosensitive drum and a transfer roller. 2. Description of the Related Art An image forming apparatus for forming an image by an electrophotographic method has become widespread. In recent years, in addition to a single-function product such as a copying machine, a facsimile, and a printer, a plurality of these functions are provided. A multifunctional image forming apparatus that can be operated by one apparatus is also sold. As an example, in the case of a composite type image forming apparatus having a facsimile as a basic function and which can also be used as a copying machine and a printer, a document is passed over a reading device such as a line sensor fixedly arranged. A reading mechanism for reading the contents of the document is employed. The image forming mechanism includes an image forming unit (image forming unit), a transfer unit, and a fixing unit. A toner image is formed by the image forming unit, and the formed toner image is transferred to a sheet. Then, the toner image on the paper is fixed by a fixing unit and discharged. The image forming unit includes a photosensitive drum,
The developing device and the like are integrated, and the electrostatic latent image formed on the photoconductor drum by this image forming unit is made visible in a toner image. After the toner image has been transferred from the photosensitive drum to the paper, the light from the charge removing lamp is applied to the photosensitive drum to lower the potential of the photosensitive drum and to form the next electrostatic latent image. ing. Heretofore, the static elimination lamp has been arranged at the lower part of the transport path so as to pass through the paper from the back side of the transferred paper and hit the photosensitive drum. However, in the case of an image forming apparatus in which both sides of a sheet are provided with an image forming function, the static elimination performance may change depending on the original. For this reason, a configuration may be adopted in which the static elimination lamp is disposed above the transport path so that static elimination light is directly applied to the photosensitive drum. [0009] If the static elimination lamp is arranged above the conveyance path, the following problem occurs. At both ends of the photosensitive drum, there is a space that is not in contact with the transfer roller, and the toner scattered from the developing device is floating in this space. When the charge erasing light strikes the photosensitive drum, the light goes around both ends of the photosensitive drum to lower the potential of both ends of the photosensitive drum. For this reason, the floating toner is attracted to a portion where the potential of the photosensitive drum has dropped, and the toner rides there, and the edge of the paper is stained with the toner. Therefore, there has been a demand for a device that does not allow the floating toner to be put on the photosensitive drum. SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of preventing toner from being easily applied to both end portions of a photosensitive drum, thereby preventing stains at end portions of a sheet on which an image is formed. It is to provide. According to the first aspect of the present invention, there is provided an image forming apparatus comprising: a charge removing lamp for directly applying charge removing light to a photosensitive drum; An optical path regulating member is provided downstream of the drum to convey the paper and is provided with an optical path regulating member that regulates the neutralizing light from the neutralizing lamp from hitting both ends of the photosensitive drum.
The ends of the transfer roller where light exposure is restricted
If measured along the surface, the regulated part
The distance a to the inside of the end of the copying roller, and the distance
a is not less than 3 mm and not more than 9 mm . According to this configuration, since the discharge of the static elimination light on both ends of the photosensitive drum is restricted, the potential of both ends of the photosensitive drum does not decrease, and the adhesion of the floating toner can be prevented. Therefore, it is possible to prevent the toner on the sheet on which an image is formed from being stained. As described above, there is a space at both ends of the photosensitive drum that is not in contact with the transfer roller, and it is an object of the invention to prevent the toner floating in this space from adhering. In addition, it is reasonable to measure and evaluate the portion of the photosensitive drum that is restricted from being exposed to the charge removal light with reference to the surface of the transfer roller on the photosensitive drum side. In this case, in order to prevent the light from sneaking into this space, the light is not irradiated to the inside of the end of the transfer roller by a predetermined distance a on the front side of the transfer roller . Distance a is 3mm or more and 9mm or less.
You. Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing an external configuration of the image forming apparatus 1. The image forming apparatus 1 is a multifunctional device that is basically used as a facsimile and can also be used as a printer or a copier. The image forming apparatus 1 includes a main body housing 2 and a document reading unit 3 provided on an upper portion of the main body housing 2. On the upper surface of the document reading unit 3, an operation in which ten keys, function keys, a display, and the like are arranged is provided. A board 4 is provided. A document set table 5 projects from the front side of the document reading unit 3 (right front side in the figure). Documents placed on the document set table 5 are fetched one by one in a so-called sheet-through format, and the contents are read and received by a document tray 7 at the rear. The upper surface of the main body housing 2 located below the document setting table 5 is a discharge table 8 for receiving copied sheets. A paper cassette 10 that can be pulled out is fitted into the lower part of the front surface of the main body housing 2.
A double-sided guide member 11 that can be pulled out and detached from the front is fitted on the top of the reference numeral 0. FIG. 2 is a longitudinal sectional view for explaining the internal structure of the image forming apparatus 1. With reference to FIG. 2, the movement of the original and the paper in image forming apparatus 1 will be described. An original is set on the original setting table 5 with the original surface facing down. Document set (not shown)
Are fed by a feed roller 21 in order from the bottom, are separated one by one by a separating roller 22 to prevent double feed, and are sent to the reading sensor 24 at a predetermined speed by a guide roller pair 23. In this embodiment, the reading sensor 24 is a CIS (Conta
ct Image Sensor), and sequentially reads the image on the original surface one line at a time in the direction perpendicular to the paper surface. The document that has passed through the reading sensor 24 is discharged to the document tray 7 by the discharge roller pair 25. An actuator 27 of a micro switch 26 protrudes upstream of the reading sensor 24 in the document conveying path. When the leading edge of the document enters, the actuator 27 falls, and when the document passes, the actuator 27 rises, and the leading edge and the trailing edge of the fed document can be detected. As described above, a paper cassette 10 that can be pulled out from the front surface (right side in FIG. 2) is accommodated below the main body housing 2. Paper cassette 1
The sheets (not shown) put in the sheet No. 0 are taken out one by one by the feeding roller 31, sent by the conveying roller pair 32, and given to the registration roller pair 33 through the passage 46 and the reversing path 41. The paper whose transport timing has been adjusted by the pair of registration rollers 33 is sent to the transfer roller 34. The transfer roller 34 is arranged near the photosensitive drum 35 of the image forming unit 13. In the image forming unit 13, in addition to the photosensitive drum 35, a main charger 36 for charging the surface of the photosensitive drum 35, and the surface of the photosensitive drum 35 charged by the main charger 36 are exposed by the laser unit 14. When the electrostatic latent image is thus formed, a developing roller 37 for developing the electrostatic latent image with toner, a toner cartridge 38 for replenishing toner to the developing roller 37, and a transfer remaining on the photosensitive member A cleaning device 39 for scraping and collecting the toner is included. The image forming unit 13 is detachable from the image forming apparatus main body. The toner image on the surface of the photosensitive drum 35 is transferred to the sheet by passing the sheet between the photosensitive drum 35 and the transfer roller 34. The sheet on which the toner image has been transferred is transferred to the main transport path 51.
Along the line to the fixing device 52. The fixing device 52 includes a heat roller 53 and a pressure roller 54. When the sheet passes between these roller pairs, the toner image transferred to the sheet is heated and pressed to be melted, and the toner image is transferred onto the sheet. Be established. The sheet on which the toner image is fixed is conveyed by a pair of intermediate rollers 55 and sent to a discharge path 56. In the discharge path 56, a curl removing and switchback roller pair 57 is disposed near the upstream end thereof.
The roller pair 57 functions to correct the curl generated in the sheet sent to the discharge path 56, and switches back the sheet when forming an image on both sides of the sheet. More specifically, when the sheet passes through the fixing device 52, the upper surface of the sheet (the surface on which the image is transferred and which is in contact with the heat roller 53) is thermally contracted mainly by the action of the heat roller 53. Then, the paper curls so as to curve downward. Thus, the roller pair 57 conveys the paper while handling it lightly so as to be convexly curved in the direction opposite to the curl.
Thereby, the curl of the sheet is corrected, and the almost straightened sheet is discharged from the pair of discharge rollers 58 onto the discharge table 8 through the discharge path 56. When performing double-sided copying on a sheet, the curl removing and switchback roller pair 57
When the paper is sent to the
9 is detected. This detection switch 59 is a roller pair 57
, The detection output is derived immediately before the trailing edge of the sheet sent to the roller pair 57 finishes passing through the roller pair 57. Based on the output of the detection switch 59, the curl removing / switchback roller pair 57 is reversed, and the pawl 60 is displaced, so that the paper can enter the double-sided path 61. Then, the sheet is sent to the duplex path 61. The two-sided path 61 is formed below the main transport path 51, and the introduction path 40, the horizontal path 42 that guides the sheet to the front side of the apparatus 1 substantially horizontally, and the sheet sent from the horizontal path 42. It has a reversing path 41 for reversing 180 degrees.
The sheet inverted in the reversing path 41 is sent from the register 33 to the transfer roller 34 in the same manner as described above. FIG. 3 is an enlarged vertical sectional view showing the structure of the image forming unit 13 of the image forming apparatus 1 and the vicinity thereof.
A static elimination lamp 61 for directly irradiating the static elimination light to the photosensitive drum 35 is arranged and fixed downstream of the photosensitive drum 35 in the sheet conveyance. Reference numeral 62 denotes a substrate on which the static elimination lamp 61 is installed. The substrate 62 is fixed to a predetermined position of the main body of the image forming apparatus 1. FIG. 4 shows the discharge lamp 61 and the photosensitive drum 3.
FIG. 5 is a plan view showing a positional relationship with the fifth embodiment. The static elimination lamp 61 is provided opposite to the photosensitive drum 35. The x-axis is taken in parallel with the central axis of the photosensitive drum 35, and the y-axis is taken in a direction perpendicular thereto. The static elimination lamp 61 is specifically composed of a plurality (six in FIG. 4) of LEDs (light emitting diodes) arranged on a substrate 62. The substrate is provided with an optical path regulating member 63 for regulating the optical path of each LED, corresponding to each LED. The light path restricting members 63 provided corresponding to these LEDs correspond to the "light path restricting members for restricting the discharge light from the discharge lamp from hitting both ends of the photosensitive drum" in the present invention. . The symbol a in FIG. 4 represents the distance from the end of the transfer roller 34 to the end of the light whose emission is restricted. The distance a is
The measurement is performed along the surface 34a of the transfer roller 34 on the side of the charge removing lamp. As described above, at both ends of the photosensitive drum 35, there is a space that is not in contact with the transfer roller 34, and it is an object of the invention to prevent the adhesion of toner floating in this space. Surface 3 on the static elimination lamp side
This is because it is rational to measure the distance a along 4a. FIG. 5 is a perspective view of a substrate 62 on which LEDs are arranged. An optical path restricting member 63 provided corresponding to each LED is provided with a light shielding plate 63a. Is regulated to hit both ends. Due to the above-described optical path restriction, the region inside the distance a shown in FIG. 4 is irradiated with the static elimination light, and the region outside the distance a is not irradiated with the static elimination light. FIG. 6 is a graph showing the result of measuring the surface potential of the photosensitive drum 35 by changing the distance a from 3 mm to 9 mm by adjusting the position of the optical path regulating member 63. The end face of the sheet is set at a position x = −1 mm slightly protruding from the end of the transfer roller 34. The surface potential of the photosensitive drum 35 is approximately 7 in the region of x <a.
The voltage is sufficiently high at 50 V, and the effect of the static elimination light regulation appears. When the position of the optical path regulating member 63 is adjusted, if the distance a is too long, an area having a high surface potential extends to the inside of the sheet, which is not preferable. Conversely, distance a
Is too short, the effect of preventing toner scattering is weakened. In practice, it has been confirmed that there is no problem if the distance a is set to 3 mm or more and 9 mm or less. The embodiment of the present invention has been described above.
The implementation of the present invention is not limited to the above embodiment. For example, the shape of the optical path restricting member 63 may be any shape as long as it can restrict the discharge light from the discharge lamp from hitting both ends of the photosensitive drum. In the above embodiment, the light path regulating member 6
3 blocks an area where the angle θ of the static elimination light is larger than 90 degrees, but the angle of 90 degrees as the threshold value is determined by the relative positional relationship between the extreme end LED and the photosensitive drum 35. And is not fixed at 90 degrees. FIG. 7 shows a configuration example in which an angle larger than 90 degrees is selected as a threshold value. In the case of FIG. 7, one end LED
The distance between the LED and the other end LED is smaller than that in the case of FIG.
Slightly larger than 0 degrees. In addition, various design changes can be made within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view illustrating an external configuration of an image forming apparatus. FIG. 2 is a longitudinal sectional view for explaining the internal structure of the image forming apparatus 1. FIG. 3 is an enlarged vertical cross-sectional view showing a configuration of an image forming unit 13 of the image forming apparatus 1 and its vicinity. FIG. 4 is a plan view showing a positional relationship between a static elimination lamp 61 and a photosensitive drum 35. FIG. 5 is a perspective view of a substrate 62 on which LEDs are arranged. FIG. 6 is a graph showing the results of measuring the surface potential of the photosensitive drum while varying the distance a from the end of the light whose radiation is restricted to the end of the transfer roller. FIG. 7 is a diagram illustrating an example of a configuration in which a threshold value of the optical path regulation is an angle larger than 90 degrees. [Description of Signs] 1 Image forming apparatus 34 Transfer roller 35 Photoreceptor drum 61 LED constituting a discharging lamp 62 Substrate 63 Optical path regulating member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-76662 (JP, A) JP-A-60-140287 (JP, A) JP-A-60-168172 (JP, A) JP-A-11-116 84912 (JP, A) Japanese Utility Model 2-100273 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 21/08 G03G 15/16

Claims (1)

(57) Claims 1. An electrostatic latent image formed on a photosensitive drum is made visible in a toner image, and the toner image is transferred to a sheet sandwiched between the photosensitive drum and a transfer roller. In the image forming apparatus that forms an image by performing the above operation, a discharge lamp for directly applying the discharge light to the photosensitive drum is disposed downstream of the photosensitive drum in the sheet conveyance, and the discharge light from the discharge lamp is used as the photosensitive member. An optical path regulating member is provided to regulate the contact of the photosensitive drum with both ends of the photosensitive drum.
Minute along the surface of the transfer roller,
The part to be controlled must be within the distance a from the end of the transfer roller.
The distance a is 3 mm or more and 9 mm or less .