JP4732149B2 - Charging device - Google Patents

Description

  The present invention relates to a charging device used in an image forming apparatus or the like, and more particularly to a so-called scorotron charging device.

  2. Description of the Related Art In image forming apparatuses such as copying machines, printers, and facsimiles, apparatuses that apply a high voltage to a discharge wire to generate corona discharge have been widely used as devices for uniformly charging the surface of a photoreceptor. Furthermore, in order to make the corona discharge distribution more uniform, a scorotron charging device having a grid is often used.

  FIG. 7 shows an example of a conventional scorotron charging device. A pair of grid holders 3a '(only one of the grid holders in this figure) are attached to both sides of the shield case 1, and a discharge wire (not shown) is stretched in the shield case 1 in the longitudinal direction. A single grid wire 11 is folded and stretched around the opening 12 of the shield case 1 by a plurality of pins 31 formed on the pair of grid holders 3a '.

When the grid wire 11 is stretched over the opening 12 of the shield case 1, first, the starting end of the grid wire 11 is wound around and fixed to a projection (not shown) of one grid holder. Next, the grid wires 11 are alternately hooked on the pins 31 of the grid holder attached to both ends of the shield case 1 so that the plurality of grid wires 11 straddle the openings 11 of the shield case 1. Stretch. Then, the end of the grid wire 11 is wound around the screw 4 and the screw 4 is screwed into the screw hole 35 formed in the grid holder 3a ′ to fix the end of the grid wire 11.
JP-A-5-011568 JP-A-6-130785 JP 2003-177595 A

  However, when the end of the grid wire 11 is fixed, it is necessary to fix the grid wire 11 in a state where tension is applied, and an operation requiring skill such as tightening the fixing screw 4 while pulling the grid wire 11 is required. It was.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a charging device that can easily fix the end of a grid wire while applying tension.

  According to the present invention, an elongated substantially rectangular parallelepiped shield case having an opening, a discharge wire disposed in the shield case, and a plurality of wire hooks are formed and attached to both ends of the shield case. In the charging device including a pair of grid holders and a grid wire that is folded back and stretched between the wire hanging portions so as to straddle the opening, an end portion of the grid wire is fixed to at least one of the grid holders A charging device is provided in which a fixing portion is provided, and a winding portion around which a grid wire is wound is formed between the opening of the shield case and the fixing portion.

  Here, from the viewpoint of further improving workability, it is preferable that the winding portion is a protrusion formed on a side portion of the grid holder. Moreover, it is preferable to form the groove part which winds a grid wire in the outer periphery of the said winding part.

  Furthermore, the fixing portion may be configured such that a screw around one end of the grid wire is screwed into a screw hole formed in the grid holder to fix the wire.

  In the charging device of the present invention, the tension applied to the grid wire is held here by winding the grid wire around the winding portion formed between the opening of the shield case and the fixed portion of the grid wire. There is no need to pull the grid wires when fixing the wire ends. Thereby, the attachment workability of the grid wire is significantly improved.

  Further, when the winding part is a protrusion formed on the side part of the grid holder, the workability can be further improved. Furthermore, if a groove portion around which the grid wire is wound is formed on the outer periphery of the winding portion, workability and tension retention can be improved.

  And, if the end of the grid wire is fixed by screwing the screw wound around the end of the grid wire into the screw hole formed in the grid holder, the wire is fixed without increasing the number of parts compared to the conventional one. become able to.

  Hereinafter, a charging device according to the present invention will be described with reference to the drawings. The present invention is not limited to these embodiments.

  FIG. 1 is a schematic view of an image forming apparatus provided with a charging device according to the present invention. The image forming apparatus in this figure is a so-called in-body discharge type image forming apparatus. A paper discharge space 6 having an opening on the front side is formed at a substantially central portion in the vertical direction of the apparatus body M. On the bottom surface of the paper discharge space 6, a tray 87 for placing paper to be discharged is integrally formed with the casing. On the other hand, a reading mechanism 91 for reading a document is built in the upper side of the paper discharge space 6, and an image forming mechanism is built in the lower side of the paper discharge space 6.

  The image forming mechanism will be described. The surface of the photosensitive drum 70 is uniformly charged positively or negatively by the charging device C. As will be described later, in the charging device C, a high voltage is applied to the discharge wire to generate corona discharge to charge the surface of the photoconductive drum 70, and at the same time, a predetermined voltage is applied to the grid wire to apply the surface of the photoconductive drum 70. To suppress uneven charging.

  On the other hand, a document (not shown) is placed on the document placing table 90, and the image data is read by the reading device 91. The read image data is written on the surface of the photosensitive drum 70 by a laser scanner (exposure device) 72, and an electrostatic latent image is formed on the surface of the photosensitive drum 70. Specifically, in the case of the reverse development method, the charge corresponding to the image is removed, and in the case of the regular development method, the charge corresponding to the background is removed to form an electrostatic latent image. Next, the electrostatic latent image on the photosensitive drum 70 is visualized with toner by the developing device 73. At this time, the charging polarity of the toner is the same as the charging polarity of the photosensitive drum 70 in the case of the reversal development method, and is opposite to the charging polarity of the photosensitive drum 70 in the case of regular development.

  On the other hand, the paper P stored in the paper feed cassette 81 is pulled out by the pickup roller 82, sandwiched between the paper feed roller 83 and the separating roller 84, and sent to the conveyance path. Then, the registration roller pair 80 feeds the paper P to the transfer unit at the timing when the toner image on the photosensitive drum 70 reaches the transfer unit. In the transfer portion, the sheet P is sandwiched between the photosensitive drum 70 and the transfer roller 74, and a charge having a polarity opposite to the toner charging polarity is applied to the transfer roller 74. Toner image moves onto the paper P. The toner remaining on the photosensitive drum 70 without moving onto the paper P is removed and collected by the cleaning roller 75. On the other hand, the paper P on which the toner image is placed is conveyed to the fixing roller pair 85. Here, the toner image is heated and pressurized by the fixing roller pair 85 and fixed on the paper P. Then, the paper P is sent to the discharge roller pair 86 and discharged to the tray 87.

  FIG. 2 is a perspective view of the charging device C used in the image forming apparatus of FIG. The charging device C includes a shield case 1 and a charger case 2, and the shield case 1 is engaged with the charger case 2. A discharge wire 21 is stretched in the longitudinal direction on the charger case 2. On the inner bottom surface, a screw 23 having a spiral wing portion 232 formed on the outer periphery of the rod-shaped member 231 is rotatably attached, and the cleaning member 22 for cleaning the discharge wire 21 and the grid wire 11 serves as the screw. 23 is screwed to the wing portion 232. When the screw 23 is rotated by a motor (not shown), the cleaning member 22 moves in the longitudinal direction, and the discharge wire 21 and the grid are cleaned by the cleaning tool 221 made of felt or the like that is in contact with the discharge wire 21 and the grid wire 11 respectively. The wire 11 is cleaned.

  On the other hand, the shield case 1 is formed by forming a conductive material such as stainless steel into an elongated and substantially rectangular parallelepiped shape, and a pair of grid holders 3a and 3b are attached to both ends thereof. A plurality of pins (wire hooking portions) 31 are formed on the grid holders 3a and 3b, respectively, and a screw 4 for fixing the terminal end of the grid wire 11 is further screwed into one grid holder 3a. A screw hole 35 is formed. A projection (winding portion) 33 is formed on the side of the grid holder 3 a between the opening 12 of the shield case 1 and the screw hole 35. An enlarged perspective view of this portion is shown in FIG.

  As shown in FIG. 3, the protrusion 33 is formed so as to protrude outward from a notch 32 formed on the side of the grid holder 3 a, and a groove 34 is formed along the side surface of the notch 32 on the back side. Formed (see FIG. 5). The protrusion 33 is integrally formed with the grid holder 3a.

  As shown in FIG. 4, the end of the grid wire 11 folded and stretched around the opening 12 of the shield case 1 by a plurality of pins 31 formed on the pair of grid holders 3a, 3b After being wound about 33 times around 33, it is wound around the male thread portion of the screw 4. Then, the screw 4 is screwed into the screw hole 35 formed in the grid holder 3a, whereby the grid wire 11 is sandwiched and fixed between the head of the screw 4 and the grid holder 3a.

  As shown in FIG. 5, when the grid wire 11 is wound around the protrusion 33, the tension applied to the grid wire 11 is maintained by the frictional resistance between the grid wire 11 and the protrusion 33 and between the grid wires 11. Even when the grid wire 11 is not pulled with a strong force at the time of fixing with 4, the grid wire 11 is not loosened and can be easily screwed.

  There is no particular limitation on the number of windings of the grid wire 11 around the protrusions 33. Increasing the number of windings of the grid wire 11 increases the frictional resistance and makes it easier to maintain the tension applied to the grid wire 11, but it is usually sufficient to wind it once.

  The projection 33 formed on the grid holder 3a is not particularly limited as long as the grid wire 11 can be wound around it. However, the grid wire 11 is prevented from being detached from the projection 33 by vibration or impact, and the contact area is increased. From the viewpoint of increasing the frictional resistance, it is desirable to form the groove 34 in the portion where the grid wire 11 is wound. FIG. 6 shows another form of the protrusion 33 formed on the grid holder 11. 6 has a substantially cylindrical shape, and a groove portion 34 is formed along the side surface of the notch portion 32 on the back surface side.

  The formation position of the protrusion 33 is not particularly limited as long as it is between the opening 12 of the shield case 1 and the fixed portion. However, if the protrusion 33 protrudes from the surface of the grid holder 3a, the projection 33 may be broken due to contact with other members, etc. Therefore, the notch 32 formed on the side of the grid holder 3a as in the above-described embodiment. It is preferable to form inside.

  For fixing the end of the grid wire 11, a conventionally known fixing method can be used in addition to fixing with a screw. For example, the end of the grid wire 11 is pushed together with a pin into a hole formed in the grid holder. There may be.

  Although the material of the grid wire 11 used in the present invention is not particularly limited, a material that is not easily corroded by corona discharge from the discharge wire 21 is preferable. For example, stainless steel is exemplified. As a diameter of the grid wire 11, the range of 30-350 micrometers is preferable, for example. Further, when the grid wire 11 is stretched over the opening 12 of the shield case 1, the distance between adjacent grid wires is preferably in the range of 0.5 to 1.5 mm. If the distance exceeds 1.5 mm, it is difficult to control charging, and if it is less than 0.5 mm, it is difficult to attach the grid wire. The number of grid wires 11 stretched around the opening 12 of the shield case 1 may be determined as appropriate so as to satisfy the above conditions while taking into account the size of the photosensitive member to be charged. On the other hand, as the discharge wire 21 used in the present invention, for example, a tungsten wire plated with gold is exemplified.

1 is a schematic diagram illustrating an example of an image forming apparatus using a charging device according to the present invention. It is a perspective view which shows an example of the charging device which concerns on this invention. It is an expansion perspective view of a grid holder. It is an expansion perspective view of the grid holder which shows the fixed state of a grid wire. It is a perspective view of the state where a grid wire was wound around a projection. It is a perspective view which shows the other form of protrusion. It is a fragmentary perspective view which shows the fixed state of the conventional grid wire.

Explanation of symbols

1 Shield case 2 Charger case 3a, 3b Grid holder 4 Screw (fixed part)
C Charging Device 11 Grid Wire 21 Discharge Wire 31 Pin (Wire Hook)
32 Notch 33 Protrusion (winding part)
34 Groove 35 Screw hole (fixed part)

Claims (4)

An elongated, substantially rectangular parallelepiped shield case with an opening, a discharge wire disposed in the shield case, a pair of grid holders formed with a plurality of wire hooks and attached to both ends of the shield case; In a charging device comprising a grid wire folded back and stretched between the wire hanging portions so as to straddle the opening,
A fixing portion for fixing an end portion of the grid wire is provided on at least one of the grid holders,
A charging device, wherein a winding portion around which a grid wire is wound is formed between the opening of the shield case and the fixed portion.   The charging device according to claim 1, wherein the winding portion is a protrusion formed on a side portion of the grid holder.   The charging device according to claim 1, wherein a groove portion around which the grid wire is wound is formed on an outer periphery of the winding portion.   The charging device according to any one of claims 1 to 3, wherein the fixing unit is configured to screw a screw wound around one end of the grid wire into a screw hole formed in the grid holder and fix the wire. .

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