Discharge device and image forming apparatus

Information

  • Patent Grant
  • 6411794
  • Patent Number
    6,411,794
  • Date Filed
    Thursday, June 15, 2000
    24 years ago
  • Date Issued
    Tuesday, June 25, 2002
    22 years ago
Abstract
A discharge device has a discharge wire for discharge in response to a voltage, a supporting block for supporting the discharge wire, an electric contact receiving an AC voltage, and a resistor element placed between the discharge wire and the electric contact. The discharge device serves particularly as a separation charger of an image forming apparatus.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a discharge device and image forming apparatuses, such as copying machines and printers, using a discharge device.




2. Description of the Related Art





FIG. 5

is a cross-sectional view of a copying machine of the electrophotographic type.




As

FIG. 5

shows, an electrostatic image is formed on the surface of a photosensitive drum


104


through the use of an optical unit


103


, an electrifying device


203


and other components and, subsequently, a toner serving as a developer is attached to the electrostatic image by means of a developing device


201


so that the electrostatic image develops into a visible image. Additionally, this visible image is transferred through a transferring device


111


onto a transfer material conveyed by feeding means


105


to


110


and the transfer material with the visible image on it is separated from the photosensitive drum


104


by a separating device


112


and subsequently conveyed by a conveying means


113


to a fixing device


114


where it is heated and pressurized to fix the visible image. The transfer material on which the visible image has been fixed is ejected outside of the copying machine through an ejecting device


116


.




Meanwhile, if a paper jam occurs during an image forming operation, the removal of the jammed paper becomes necessary. In addition, a need for periodical apparatus-interior maintenance exists. Therefore, for easy jam elimination and maintenance, there has been proposed a construction in which a section indicated by a broken line in

FIG. 5

is made as a single fixing/conveying unit


300


and this fixing/conveying unit


300


is drawable toward the front side of the image forming apparatus along a guide rail (not shown).




In this construction, the fixing/conveying unit


300


includes the transferring device


111


and the separating device


112


, which each require a high-voltage contact for its power supply. For the unit configuration, the high-voltage contact is disposed in the vicinity of either the transferring device


111


or the separating device


112


and at a position where the connection with the main body is facilitated. Taking this into consideration, the high-voltage contact is positioned on the rear surface of the transferring device


111


and the separating device


112


, that is, on the rear surface of the fixing/conveying unit


300


.




Furthermore, an AC voltage is to be applied to the separating device


112


. The electrifying device, thus designed to use an AC voltage, tends to generate radiation noise.





FIG. 6

is an enlarged cross-sectional view showing a high-voltage contact section for the separating device


112


in the image forming apparatus of FIG.


5


.




As

FIG. 6

shows, the high-voltage contact section for the separating device


112


in the image forming apparatus is composed of a separating device contact portion


51


, a separating device block


52


, a spring latching plate


55


, a main body contact


61


, a main body contact block


62


, a base plate contact


61


and a main body frame


70


.




The high-voltage contact section for the separating device


112


is constructed in a manner that the separating device contact portion


51


is inserted into a cylindrical portion


52




a


of the separating device block


52


and secured to a spring latch


55


. Additionally, an electrifying wire (not shown) is attached through a spring


56


to the spring latch


55


to establish the electrical connection.




On the other hand, in the contact section on the image forming apparatus main body side, the main body contact


61


and the base plate contact


63


are attached to the main body contact block


62


, with them being connected electrically to each other. Additionally, the base plate contact


63


is connected to a main body high-voltage base plate (not shown), while the main body contact block


62


is attached to the main body frame


70


.




The separating device contact portion


51


is brought into contact with the main body contact


61


, the latter made with an elastic material, thereby establishing electrical connection therebetween. A high AC voltage generated from a main body high-voltage base plate (not shown) is supplied to the base plate contact


63


, the main body contact


61


and the separating device contact portion


51


so that the electrifying wire (not shown) produces corona discharge, thereby accomplishing separation of a transfer material.




While the separating device


112


conducts the separating operation, a radiation noise may occur at the high-voltage contact section.




If a right-hand area of the main body frame


70


is exterior to the apparatus, the radiation noise tends to leak toward the exterior of the apparatus. For this reason, a shielding mechanism is required to prevent the leakage of the radiation noise.




SUMMARY OF THE INVENTION




Accordingly, it is an object of the present invention to provide an image forming apparatus capable of reducing noises to be radiated to the external.




Another object of this invention is to provide a discharge device capable of reducing radiation noise at a high-voltage contact section.




In accordance with these objects, there is provided a discharge device comprising a discharging unit, a supporting member for supporting the discharging unit, and an electrifying device contact portion. A resistor element is placed between the discharging unit and the electrifying device contact portion.




In accordance with another aspect of the invention there is provided an image forming apparatus with an image forming unit having a high-voltage component. An AC base plate communicates power to the high-voltage component of the image forming unit thru a main body contact and an attachable/detachable high-voltage contact section. The high-voltage contact section includes a discharging unit, a supporting member for supporting the discharging unit, an electrifying device contact portion in contact with the main body contact and a resistor element placed between the discharging unit and the electrifying device contact portion.




Other objects of the present invention will become more readily apparent from the following description.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a plan view showing a fixing/conveying unit of an image forming apparatus according to a first embodiment of the present invention;





FIG. 2

is a cross-sectional view showing the fixing/conveying unit of the image forming apparatus according to the first embodiment of this invention;





FIG. 3

is an enlarged cross-sectional view showing a high-voltage contact section of the image forming apparatus according to the first embodiment of this invention;





FIG. 4

is an enlarged cross-sectional view showing a high-voltage contact section of an image forming apparatus according to a second embodiment of this invention;





FIG. 5

is a cross-sectional view showing an image forming apparatus; and





FIG. 6

is an enlarged cross-sectional view showing a high-voltage contact section of the image forming apparatus.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings.




(First Embodiment)





FIG. 1

is a plan view showing a fixing/conveying unit of an image forming apparatus according to a first embodiment of the present invention,

FIG. 2

is a cross-sectional view of the fixing/conveying unit of

FIG. 1

, and

FIG. 3

is an enlarged cross-sectional view showing a high-voltage contact section thereof.




In the image forming apparatus according to this embodiment, a photosensitive drum


1


carries a toner image developed by a developing device (not shown) and, subsequently, the toner image carried on the photosensitive drum


1


is transferred to a transfer material by an operation of a transfer electrifying device


3


. Furthermore, a pair of register rollers


2


convey the transfer material to the toner image on the photosensitive drum


1


, and the transfer electrifying device


3


transfers the toner image on the photosensitive drum


1


onto that transfer material.




The transfer material having thereon the toner image is separated from the photosensitive drum


1


by means of a separation rectifying device


4


and is then conveyed to a pair of fixing rollers


6


through a conveying belt


5


. The fixing roller r pair


6


fix the toner image on the transfer material, following which the transfer material is ejected to the external through the use of a pair of ejecting rollers


7


.




In this composition, the register roller pair


2


, the transfer electrifying device


3


, the separation electrifying device


4


, the conveying belt


5


, the fixing roller pair


6


and the ejecting roller pair


7


are all fixed on a unit base plate


8


, and are constructed as a fixing/conveying unit


9


to be attachable/detachable simultaneously to/from the main body of the image forming apparatus. The transfer electrifying device


3


and the separation electrifying device


4


of this fixing/conveying unit


9


are equipped with high-voltage contact sections


12




a


and


12




b


, respectively (see FIG.


1


). When the fixing/conveying unit


9


is mounted on the image forming apparatus main body, the high-voltage contact sections


12




a


and


12




b


are brought into contact with a main body contact section


13


so that the transfer electrifying device


3


and the separation electrifying device


4


receive a power supply.




In this embodiment, since radiation noise develops in the separation electrifying device


4


for supplying a high AC voltage, the high-voltage contact section for the separation electrifying device


4


in the image forming apparatus are constructed as shown in FIG.


3


.




As

FIG. 3

shows, the high-voltage contact section for the separation electrifying device


4


in the image forming apparatus is made up of a separation electrifying device contact portion


21


, a separation electrifying device block


22


, a resistor


23


, a connecting portion


24


, a spring latching plate


25


, a main body contact


31


, a main body contact block


32


, a base plate contact


33


and a main body frame


40


.




The high-voltage contact section


12


b of the separation electrifying device


4


is constructed with the separation electrifying device contact portion


21


, the resistor


23


and the connecting portion


24


embedded in the separation electrifying device block


22


, and the separation electrifying device contact portion


21


, the resistor


23


and the connecting portion


24


are connected electrically to each other. Additionally, the spring latching plate


25


is attached through a screw


27


to the connecting portion


24


. Incidentally, it is also appropriate that the connecting portion


24


and the spring latching plate


25


are constructed as an integrated unit.




In addition, an electrifying wire (not shown) is attached through a spring


26


to the spring latching plate


25


to establish an electrical connection.




On the other hand, in the main body high-voltage contact section


13


of the image forming apparatus, the main body contact


31


made from a metallic elastic material and the base plate contact


33


are attached to the main body contact block


32


, with the main body contact


31


and the base plate contact


33


connected electrically to each other. The base plate contact


33


is also connected to a main body high-voltage base plate (not shown), while the main body contact block


32


is fit into an opening portion


40




a


, made in a rear surface of the main body frame


40


, to be set thereat.




The separation electrifying device contact portion


21


is inserted into the opening portion


40




a


made in the rear surface of the main body frame


40


and is brought into contact with the main body contact


31


, situated on the rear surface of the main body frame


40


, to establish electrical connection between separation electrifying device contact portion


21


and main body contact


31


. A high AC voltage generated from a main body pressing base plate (not shown) is supplied to the base plate contact


33


, the main body contact


31


and the separation electrifying device contact portion


21


in this order so that the electrifying wire (not shown) performs the corona discharge, that is, conducts the transfer material separating operation. The separation electrifying device contact portion


21


is formed into a conical configuration. The reason for a conical configuration is that when the fixing/conveying unit


9


is mounted in the image forming apparatus in a state where the transfer material is left in error after a jam handling operation or the like, there is the possibility of a fire if the transfer material is put between the separation electrifying device contact portion


21


and the main body contact


31


. Accordingly, to prevent this, the separation electrifying device contact portion


21


is made pointed so as to break through the transfer material and, further, to come into contact with the main body contact


31


for securing the electrical connection.




While the separation electrifying device


4


conducts the separating operation, a radiation noise occurs in the high-voltage contact section and, if the right-hand area of the main body frame


40


is designed to be exterior of the apparatus, then this creates an apparatus radiation noise problem. However, in this embodiment, the resistor


23


is placed in the left-hand area (the front side of the opening portion


40




a


of the main body frame


40


) with respect to the vicinity of the main body frame


40


and the power load such as the corona discharge is disposed downstream, which reduces the radiation noise occurring in the high-voltage contact section so that the radiation noise occurring on the right side of the main body frame


40


is reduced. That reduction effect was as much as 10 dB or more, and it was confirmed that this arrangement functions sufficiently as a countermeasure against the radiation noise.




(Second Embodiment)




Referring to

FIG. 4

, a description will be given hereinbelow of a second embodiment of this invention.





FIG. 4

is an enlarged cross-sectional view showing a high-voltage contact section for a separation electrifying device


4


in an image forming apparatus according to this embodiment.




In this embodiment, the high-voltage contact section


12




b


for the separation electrifying device


4


in the image forming apparatus is composed of a separation electrifying device contact portion


21


′, a separation electrifying device block


22


′, a resistor


23


, a connecting portion


24


′, a spring latching plate


25


, a main body contact


31


′, a main body contact block


32


′, a base plate contact


33


′ and a main body frame


40


.




In the high-voltage contact section


12




b


for the separation electrifying device


4


, the separation electrifying device contact portion


21


′ and the spring latching plate


25


are fit through the connecting portion


24


′ to the separation electrifying device block


22


′. The connecting portion


24


′ is constructed such that metallic ping


24





a


and


24





b


are connected to the resistor


23


and a mold


24





c


is put around them to form a cylindrically embedded configuration.




The separation electrifying device contact portion


21


′, the resistor


23


and the spring latching plate


25


are connected electrically to each other, and an electrifying wire (not shown) is attached through a spring


26


to the spring latching plate


25


to establish electrical connection.




On the other hand, in the main body high-voltage contact section


13


of the image forming apparatus, the main body contact


31


′ made from a metallic elastic material is attached to the base plate contact


33


′, and the base plate contact


33


′ is attached to the main body contact block


32


′. The main body contact


31


′ and the base plate contact


33


′ are connected electrically to each other, while the base plate contact


33


′ is connected to a main body high-voltage base plate (not shown). Additionally, the main body contact block


32


′ is fitted in an opening portion


40




a


, made in a rear surface of the main body frame


40


, to be set thereat.




The separation electrifying device contact portion


21


′ is inserted into the opening portion


40




a


made in the rear surface of the main body frame


40


and is brought into contact with the main body contact


31


′ situated on the rear surface of the main body frame


40


to establish an electrical connection therebetween. A high AC voltage generated from a main body pressing base plate (not shown) is supplied to the base plate contact


33


′, the main body contact


31


′ and the separation electrifying device contact portion


21


′ so that the electrifying wire (not shown) performs the corona discharge to conduct the transfer material separating operation.




This embodiment is characterized in that the connecting portion


24


′ is made to be attachable/detachable with respect to the separation electrifying device block


32


′. This is because, taking into consideration a radiation noise countermeasure in the image forming apparatus, easy changing of the resistor


23


allows a wider range of applications. The frequency of the radiation noise can vary according to the using condition of the image forming apparatus. At this time, if the resistor


23


is embedded in the separation electrifying device block


32


′ as well an the above-described first embodiment, the image forming apparatus requires a new mold for the separation electrifying device block


32


at every specification.




Accordingly, in this embodiment, since the connecting portion


24


′ is detachable, when a need for changing of the type of the resistor


23


arises, the alteration can be confined to a minimum. Thus, this construction can flexibly cope with various specifications. Also in this embodiment, it was confirmed that sufficient effects are attainable for the reduction of radiation noise.




It should be understood that the foregoing relates to only preferred embodiments of the present invention, and that it is intended to cover all changes and modifications of the embodiments of the invention herein used for the purpose of the disclosure, which do not constitute departures from the spirit and scope of the invention. For example, although the above description of the embodiments have been made in conjunction with a separation electrifying device of an image forming apparatus, this invention is also applicable to other discharge devices receiving supply of an AC voltage.



Claims
  • 1. A discharge device comprising:a discharging wire; a supporter member for supporting said discharging wire; an electrifying device contact portion; and a resistor element placed between said supporter member and said electrifying device contact portion.
  • 2. A discharge device according to claim 1, wherein an AC voltage is applied to said electrifying device contact portion.
  • 3. A discharge device according to claim 1, wherein said electrifying device contact portion has a conical shape and is adapted for contact with a conductive elastic member.
  • 4. A discharge device according to claim 1, wherein said resistor element is attachable to and detachable from said supporter member.
  • 5. An image forming apparatus comprising:an AC base plate; a main body contact connected to said AC base plate; a frame installed on a rear side of a main body of said image forming apparatus; and an attachable/detachable discharging means, comprising: a discharging member; a supporter member for supporting said discharging member; an electrifying device contact portion in contact with said main body contact; and a resistor element placed between said discharging member and said electrifying device contact portion, wherein said main body contact is disposed exterior to said frame.
  • 6. An image forming apparatus according to claim 5, wherein said frame has an opening portion for enabling contact of said electrifying device contact portion with said main body contact with said discharging means is mounted.
  • 7. An image forming apparatus according to claim 5, wherein said resistor element is disposed interior of said frame.
  • 8. An image forming apparatus according to claim 5, further comprising a separation rectifying device, wherein an AC voltage is applied to the separation rectifying device through a discharge wire.
  • 9. An image forming apparatus according to claim 5, wherein said main body contact is a conductive elastic member.
  • 10. An image forming apparatus according to claim 5, wherein said resistor element is attachable to and detachable from said supporter member.
  • 11. An image forming apparatus according to claim 5, wherein an image forming unit is contained within the frame and said image forming unit comprises an image carrier for carrying a toner image and transfer means for transferring said toner image on said image carrier to a transfer material, and wherein said attachable/detachable discharging means conducts electrification elimination of said transfer material after the transferring.
Priority Claims (1)
Number Date Country Kind
11-171045 Jun 1999 JP
US Referenced Citations (4)
Number Name Date Kind
2863063 Schulze Dec 1958 A
4307431 Sone et al. Dec 1981 A
4466729 Iwata Aug 1984 A
5381216 Osaka et al. Jan 1995 A
Foreign Referenced Citations (1)
Number Date Country
59-102258 Jun 1984 JP