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.