JP3571954B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for forming an image on a sheet, and more particularly, to a grid plate arranged with corona charging means for charging an image carrier.
[0002]
[Prior art]
Conventionally, as an example of an image forming apparatus having a corona charger as a corona charger, an electrostatic latent image is formed on a photosensitive drum 1 as an image carrier, and the latent image is developed to form a recording material as a sheet. FIG. 17 shows an electrophotographic color image forming apparatus that forms a full-color image by transferring.
[0003]
In the image reading unit, the original 30 is placed on the original platen glass 31 and is exposed and scanned by the exposure lamp 32 so that the reflected light image from the original 30 is collected on the full color sensor 35 by the mirrors 33a, 33b, 33c and the lens 34. Illuminate to obtain a color separation image signal.
[0004]
The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown), and is sent to an image forming unit.
[0005]
In the image forming section, the photosensitive drum 1 serving as an image carrier is connected to a drum shaft 37 serving as a holding means, and is driven to rotate in a direction indicated by an arrow by driving means (not shown). Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3, which is an exposure means, a potential sensor 12, four developing units 4y, 4c, 4m, 4bk of different colors, and a light amount on the drum The detecting means 13, the transfer drum 5, and the cleaning device 6 are arranged.
[0006]
In the laser exposure optical system 3, an image signal from an image reading unit is converted into an optical signal by a laser output unit (not shown), and the converted laser light is reflected by a rotary polygon mirror 3a, and a lens 3b and a mirror 3c. And is projected on the cylindrical surface of the photosensitive drum 1.
[0007]
At the time of image formation, the photosensitive drum 1 is rotated in the direction of the arrow, the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly charged by the corona charger 2, and the light image E is irradiated for each of the separated colors. To form an electrostatic latent image.
[0008]
Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 using a resin as a base. The developing units 4y, 4c, 4m, and 4bk are selectively brought closer to the photosensitive drum 1 in accordance with each separation color by the operation of the eccentric cams 24y, 24c, 24m, and 24bk.
[0009]
Further, the toner image on the photosensitive drum 1 is transferred from a recording material cassette 7 to a recording material supplied to a position facing the photosensitive drum 1 via a conveyance system and a transfer drum 5.
[0010]
The transfer drum 5 includes a transfer charger 5b, an adsorption charger 5c for electrostatically adsorbing a recording material, and an inner static eliminator 5d, all of which are in urging contact with the photosensitive drum 1. The transfer drum 5 electrostatically adsorbing the recording material transfers the toner image on the photosensitive drum 1 onto the recording material by the transfer charger 5b as it rotates.
[0011]
In this manner, a desired number of color images are transferred to the recording material sucked and conveyed to the transfer drum 5 to form a full-color image.
[0012]
In the case of forming a full-color image, when the transfer of the toner images of four colors is completed in this way, the recording material is separated from the transfer drum 5 by the action of the separation claw 8a and the separation push-up roller 8b. 10 is discharged.
[0013]
After the transfer of the toner image, the photosensitive drum 1 is cleaned by the cleaning device 6 to remove the residual toner that is not transferred, that is, the residual toner, and is subjected to the image forming process again.
[0014]
As shown in FIGS. 15 and 16, the corona charger 2 includes a front block 40, a rear block 41 formed of an insulating member, and a shield plate 42 for regulating a charging area.
[0015]
A wire 43 is stretched between the front block 40 and the rear block 41, and the wire 43 is configured to receive a voltage from a contact portion of the rear block 41.
[0016]
Further, a grid plate 44 is attached so as to cover the opening of the shield plate 42 on the photosensitive drum 1 side.
[0017]
The grid plate 44 is a conductive thin plate in which mesh holes are formed in a control area for controlling the charging potential. The grid plate 44 receives a predetermined voltage or current from another contact portion of the rear block 41 and receives the charging potential of the photosensitive drum 1. Functions to control a desired value.
[0018]
The grid plate 44 is attached by hooking one end to a hook portion 45 of the front block 40 and the other end to a plate spring 46 attached to the rear block 41.
[0019]
In order to uniformly control the charged potential of the photosensitive drum 1, the grid plate 44 needs to have its positional accuracy within a predetermined range, and it is necessary to support the grid plate 44 with an appropriate tension so as not to hang down by its own weight. .
[0020]
For this reason, one end of the grid plate 44 is supported via a leaf spring 46, and an appropriate tension is held by the spring force.
[0021]
[Problems to be solved by the invention]
However, in the case of the above-described conventional technology, there is a problem that the size of the support mechanism itself increases when an elastic member such as a leaf spring is interposed in the support mechanism of the grid plate.
[0022]
In other words, a corona charger having a grid plate needs to be provided with two systems of high voltage applying mechanisms, that is, a charging wire and a grid plate. Since the mechanism is provided in the charging block, more insulating walls and the like are required, and the configuration of the charger is complicated, and the size of the charger is further increased. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the related art, and an object of the present invention is to provide an image forming apparatus that holds the grit plate itself in tension to reduce the number of parts and reduce the size of the apparatus. To provide.
[0023]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a corona charging means for charging an image carrier, and a corona charging means mounted between the corona charging means and the image carrier, for controlling a charging potential on the image carrier. And a grid plate for controlling the value of the grid plate, wherein a bent portion formed on a part of the grid plate and elastically deformed and stretched when the grid plate is attached is provided. And
[0024]
It is preferable that the bent portion is formed outside a control region where the grid plate controls a charged potential on the image carrier to a desired value.
[0025]
Preferably, the bent portion is bent at a substantially right angle.
[0026]
It is preferable that a warp preventing means for preventing a warp generated in the grid plate near the bent portion is provided.
[0027]
The warpage prevention means includes an opening provided on the control region side of the bent portion of the grid plate, and a projection provided on a mounting member to which the grid plate is mounted, and engaging with the opening. It is preferable that the configuration is provided.
[0028]
It is preferable that the warp prevention means is provided on the control region side of the bending portion of the mounting member to which the grid plate is mounted, and has a plurality of parallel ribs abutting on the grid plate.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto unless otherwise specified. Absent.
[0030]
(First Embodiment)
FIG. 17 shows a schematic configuration diagram of an electrophotographic color image forming apparatus having a corona charger as a corona charging means according to the first embodiment, similarly to the prior art.
[0031]
In the image reading unit, the original 30 is placed on the original platen glass 31 and is exposed and scanned by the exposure lamp 32 so that the reflected light image from the original 30 is collected on the full color sensor 35 by the mirrors 33a, 33b, 33c and the lens 34. Illuminate to obtain a color separation image signal.
[0032]
The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown), and is sent to an image forming unit.
[0033]
In the image forming section, the photosensitive drum 1 serving as an image carrier is connected to a drum shaft 37 serving as a holding means, and is driven to rotate in a direction indicated by an arrow by driving means (not shown). Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3, which is an exposure means, a potential sensor 12, four developing units 4y, 4c, 4m, 4bk of different colors, and a light amount on the drum The detecting means 13, the transfer drum 5, and the cleaning device 6 are arranged.
[0034]
In the laser exposure optical system 3, an image signal from an image reading unit is converted into an optical signal by a laser output unit (not shown), and the converted laser light is reflected by a rotary polygon mirror 3a, and a lens 3b and a mirror 3c. And is projected on the cylindrical surface of the photosensitive drum 1.
[0035]
At the time of image formation, the photosensitive drum 1 is rotated in the direction of the arrow, the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly charged by the corona charger 2, and the light image E is irradiated for each of the separated colors. To form an electrostatic latent image.
[0036]
Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 using a resin as a base. The developing units 4y, 4c, 4m, and 4bk are selectively brought closer to the photosensitive drum 1 in accordance with each separation color by the operation of the eccentric cams 24y, 24c, 24m, and 24bk.
[0037]
Further, the toner image on the photosensitive drum 1 is transferred from a recording material cassette 7 to a recording material supplied to a position facing the photosensitive drum 1 via a conveyance system and a transfer drum 5.
[0038]
The transfer drum 5 includes a transfer charger 5b, an adsorption charger 5c for electrostatically adsorbing a recording material, and an inner static eliminator 5d, all of which are in urging contact with the photosensitive drum 1. The transfer drum 5 electrostatically adsorbing the recording material transfers the toner image on the photosensitive drum 1 onto the recording material by the transfer charger 5b as it rotates.
[0039]
In this manner, a desired number of color images are transferred to the recording material sucked and conveyed to the transfer drum 5 to form a full-color image.
[0040]
In the case of forming a full-color image, when the transfer of the toner images of four colors is completed in this way, the recording material is separated from the transfer drum 5 by the action of the separation claw 8a and the separation push-up roller 8b. 10 is discharged.
[0041]
After the transfer of the toner image, the photosensitive drum 1 is cleaned by the cleaning device 6 to remove the residual toner that is not transferred, that is, the residual toner, and is subjected to the image forming process again.
[0042]
Next, the corona charger 2 and the grid plate 44 of the present embodiment will be described with reference to FIGS.
[0043]
As shown in FIGS. 1 and 2, the corona charger 2 includes a front block 40, a rear block 41 formed of an insulating member, and a shield plate 42 for regulating a charging area. A wire 43 is stretched between the front block 40 and the rear block 41, and the wire 43 is configured to receive a voltage from a contact portion of the rear block 41.
[0044]
Further, a grid plate 44 is attached so as to cover the opening of the shield plate 42 on the photosensitive drum 1 side.
[0045]
The grid plate 44 is a conductive thin plate in which a mesh-shaped hole 60 as shown in FIG. 3 is formed in a control region for controlling the charging potential, and a bent portion 61 is formed in a part thereof in advance.
[0046]
The grid plate 44 is attached to the corona charger 2 as follows. First, the front hook holes 62 of the grid plate 44 shown in FIG. 3 are engaged with the hook dowels 63 formed integrally with the front block 40. After that, the rear hook holes 64 of the grid plate are engaged with the hook portions 66 of the grid tension plate 65.
[0047]
The grid tension plate 65 is rotatable in a direction indicated by an arrow in FIG. 4 around a support protrusion 67 formed integrally with the rear block 41. In the state of FIG. The bent portion 61 of the plate 44 is maintained at a substantially right angle formed in advance. From this state, the grid tension plate 65 is rotated, brought into contact with the rear block 41 as shown in FIG. When the grid plate 44 shown in FIG. 5 is attached, the hook portion 66 of the grid tension plate 65 moves outward relative to the state shown in FIG. 4, and the grid plate 44 is stretched in the longitudinal direction. become.
[0048]
At this time, since the bent portion 61 of the grid plate 44 is elastically deformed and stretched as shown in FIG. 5, the grid plate 44 is held in a state where an appropriate tension is applied. Further, due to this tension, the grid plate 44 is pressed against the height regulating ribs 70 and 71 provided on the front block 40 and the rear block 41, and can maintain its position in the direction of the photosensitive drum 1 with high accuracy. .
[0049]
As described above, by the elastic deformation of the bent portion 61 of the grid plate 44 itself, an appropriate tension can be generated on the grid plate 44 without using an elastic member such as a spring separately. The grid plate 44 can be fixed, and the number of components can be reduced and the size of the device can be reduced.
[0050]
The shape of the bent portion 61 formed in advance is not limited to being bent at substantially a right angle as in the present embodiment, but may be applied to the bent portion 61 if the shape can be elastically deformed such as step folding, bending, or bellows. can do.
[0051]
In the present embodiment, the grid plate 44 is attached to the corona charger 2, but the present invention can also be effectively applied to a case where the grid plate 44 is attached to an attachment member such as a process cartridge or an apparatus body. The corona charging means can be used not only as a charger for charging the photosensitive drum 1 but also as a charger for neutralization, transfer, separation, and the like, to which the present invention can be similarly applied.
[0052]
(Second embodiment)
7 and 8 show a second embodiment. This is a configuration in which the manner of attaching the grid plate 44 and elastically deforming the bent portion are changed from those of the first embodiment.
[0053]
Other configurations and operations are the same as those of the first embodiment, and therefore, the same components will be denoted by the same reference characters and description thereof will be omitted.
[0054]
7 and 8 show a corona charger of the image forming apparatus according to the present embodiment. The corona charger 2 includes a front block 40, a rear block 41 formed of an insulating member, and a shield plate 42 for regulating a charging area.
[0055]
A wire 43 is stretched between the front block 40 and the rear block 41, and the wire 43 is configured to receive a voltage from a contact portion of the rear block 41.
[0056]
Further, a grid plate 44 is attached so as to cover the opening of the shield plate 42 on the photosensitive drum 1 side.
[0057]
The mounting of the grid plate 44 is shown in FIG. As shown in FIG. 8A, the grid plate 44 is provided with a bent portion 80 on the other end side in advance.
[0058]
When one end of the grid plate 44 is hooked on the hook 45 of the front block 40 and the other end is fixed at a predetermined position of the rear block 41 with a screw 81, as shown in FIG. , Elastic deformation occurs due to the attachment, and an appropriate tension is applied to the grid plate 44. Further, a predetermined voltage is applied to the grid plate 44 using the screw 81 as a contact.
[0059]
As described above, also in the present embodiment, similar to the first embodiment, appropriate tension can be generated on the grid plate 44 without separately using an elastic member such as a spring, and a high accuracy can be achieved with a simple configuration. Of the grid plate 44 can be realized.
[0060]
(Third embodiment)
9 to 14 show a third embodiment. In the first embodiment, a local warp in the short direction of the grid plate 44 occurs near the bent portion 61 of the grid plate 44, and this warp impairs the positioning of the grid plate 44, and the photosensitive drum 1 is charged. There is a problem that the potential changes from a desired value and a partial image thinning occurs. Therefore, the present invention includes a warp preventing means for correcting the grid plate 44 so as to prevent the warp.
[0061]
Other configurations and operations are the same as those of the first embodiment, and therefore, the same components will be denoted by the same reference characters and description thereof will be omitted.
[0062]
In the present embodiment, a projection 72 is provided on the height regulating rib 70 of the front block 40, and is engaged with the laterally inner end face of the opening 73 provided on the grid plate 44.
[0063]
For this reason, when a tension is applied to the grid plate 44, the grid plate 44 is likely to be warped in the short direction near the bent portion 61 due to the elastic deformation of the bent portion 61, but the projection 72 moves inward of the opening 73. In order to prevent shrinkage, the amount of warpage in the short direction can be significantly reduced.
[0064]
Further, a warp preventing rib 74 having substantially the same height as the height restricting rib 70 is formed in parallel on the control region side of the height restricting rib 70. The prevention rib 74 abuts against the grid plate 44 with light pressure to perform the correction.
[0065]
As described above, the deformation that shrinks the opening 73 in the short direction is prevented by stretching the protrusion 72 to prevent local warp in the short direction, and the warp preventing rib 74 contacts the grid plate 44. As a result, slight warpage is prevented, so that local warpage of the grid plate 44, which adversely affects image formation, does not occur. It is possible to improve the image quality of the formed image by uniformly setting the charging potential to a desired value.
[0066]
【The invention's effect】
As described above, by providing the bent portion, the grid plate itself can hold the tension by elastic deformation, the highly accurate grid plate support can be realized with a simple configuration, and good image formation can be performed. Can be.
[0067]
Further, the warpage preventing means can prevent the warpage occurring in the grid plate, and prevent the highly accurate positioning of the grid plate from being impaired.
[Brief description of the drawings]
FIG. 1 is a side view showing a corona charger according to a first embodiment.
FIG. 2 is a diagram illustrating a corona charger viewed from a photosensitive drum side according to the first embodiment.
FIG. 3 is a diagram showing a grid plate according to the first embodiment.
FIG. 4 is a diagram illustrating how the grid plate according to the first embodiment is mounted.
FIG. 5 is a view showing a state where the grid plate according to the first embodiment is mounted.
FIG. 6 is an enlarged perspective view showing the vicinity of a bent portion of the grid plate according to the first embodiment.
FIG. 7 is a side view showing a corona charger according to a second embodiment.
FIG. 8 is a diagram illustrating how to attach a grid plate according to a second embodiment.
FIG. 9 is a side view showing a corona charger according to a third embodiment.
FIG. 10 is a diagram illustrating a corona charger viewed from a photosensitive drum side according to a third embodiment.
FIG. 11 is a diagram showing a grid plate according to a third embodiment.
FIG. 12 is a diagram illustrating a grid plate according to a third embodiment.
FIG. 13 is a view showing a state where a grid plate according to a third embodiment is mounted.
FIG. 14 is an enlarged perspective view showing the vicinity of a bent portion of a grid plate according to a third embodiment.
FIG. 15 is a side view showing a conventional corona charger.
FIG. 16 is a view showing a corona charger viewed from the photosensitive drum side according to the related art.
FIG. 17 is a schematic sectional view showing an image forming apparatus.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 photosensitive drum 2 corona charger 3 laser exposure optical system 4 y, 4 c, 4 m, 4 bk developing device 5 transfer drum 6 cleaning device 7 recording material cassette 9 heat roller fixing device 10 tray 11 pre-exposure lamp 12 potential sensor 13 light amount detection on drum Means 40 Front block 41 Rear block 42 Shield plate 43 Wire 44 Grid plate 45 Hook portion 60 Hole 61, 80 Bend portion 62 Front hook hole 63 Hanging dowel 64 Rear hook hole 65 Grid tension plate 66 Hanging portion 67 Support projection 68, 81 Screw 70, 71 Height regulating rib 72 Projection 73 Opening 74 Warpage prevention rib

Claims (2)

An image carrier;
Corona charging means for charging the image carrier,
Mounted between said corona charging means and the image bearing member, a charging potential on the image bearing member is a grid plate having a control region facing the site to be controlled to a desired value, the image bearing member surface A grid plate having a bent portion bent at a substantially right angle outside a control region near at least one end in a direction orthogonal to the moving direction of the image forming apparatus,
The grid plate has an opening outside the control region, between the control region and the bending portion in a direction orthogonal to the moving direction of the image carrier surface,
The image forming apparatus according to claim 1, wherein the corona charging unit has a protrusion that engages with an inner end surface of the opening in a moving direction of the image carrier surface . 2. The corona charger according to claim 1, further comprising a height regulating rib for holding a position of the grit plate with respect to the image carrier, wherein the protrusion is provided on the height regulating rib. Image forming apparatus.

Images