JPH0543157U - Charging device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a charging device capable of preventing deformation of a grid part fixed to a chassis part, and making it possible to make a surface potential of a photosensitive drum uniform and prevent printing trouble. The purpose is to A charging device for charging an image forming body 51, comprising:
The cross section is U-shaped and is formed to have a length corresponding to the image forming body 51.
It is a box type in which one side is opened with a length corresponding to the grid portion 7 and a grid portion 7 provided with U-shaped curved slit holes 16 on both sides, so that the opening surface fits between both sides of the grid portion 7. And a pressing plate 9 made of an elastic material is fixed at a position corresponding to the slit hole 16 with a pressing force in the opposite direction,
It is composed of a chassis portion 8 having a discharge wire 80 suspended in the center thereof, and when the grid portion 7 is fitted into the chassis portion 8, the tip of the holding plate 9 presses the curved inner portion of the slit hole 16 to form the grid portion. 7 is fixed to the chassis portion 8.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a charging device of an image forming apparatus such as an electrophotographic printer, and more particularly to a charging device capable of preventing deformation of a grid portion fixed to a chassis portion.

Recently, with the rapid spread of office automation equipment, electrophotographic printers are becoming widespread in copying machines, printers and the like. In such a device, the charger that charges the photosensitive drum prevents the grid surface from deforming because the surface potential of the photosensitive drum will not be uniform and printing defects will be induced unless the opposing gap between the photosensitive drum and the grid is uniform. A mechanism to do so is desired.

[0003]

[Prior Art]

 FIG. 5 illustrates an internal side view of the electrophotographic printing apparatus. In the figure, 1 is a cassette mounting portion, 2 is a cassette, 3 is a delivery roller, 4 is a conveying path, 5 is a printer section, and 6 is a stacker.

The printer unit 5 includes an optical unit 50, a photosensitive drum 51 a, a cleaner 52, a charger 53, a developing device 54, a transfer device 55, a charge eliminator 56, and a fixing device 57. A cassette 2 is set in the cassette mounting portion 1, and printing papers 2a of a desired size (hereinafter referred to as papers) 2a are accumulated in the cassette 2.

With such a configuration, when the power of the apparatus is turned on, the fixing unit 57 is heated to a predetermined temperature to be in a printable state, and then the sheet 2a is fed out from the cassette 2 in the direction of arrow A based on the print instruction signal. The sheet is conveyed along the conveying path 4 and is conveyed below the photosensitive drum 51a. By this time, the photosensitive drum 51a has been neutralized by the static eliminator 56, the residual toner has been cleaned by the cleaner 52, and has been recharged by the charger 53.

Optical data emitted from an optical unit 50 including a laser light source scans the photosensitive drum 51a, and the electrostatic image formed on the photosensitive drum 51a is developed into a toner image by a developing device 54, and a transfer device 55 is formed. After being transferred onto the sheet 2a by means of, the toner is fixed by the fixing device 57 and sent to the stacker 6.

Here, the structure of the charger 53 will be described in detail. As shown in FIG. 6, the charger 53 is composed of a grid portion 7a and a chassis portion 8a, and the grid portion 7a is made of a conductive material, For example, a stainless steel plate having a U-shaped cross section and having a length corresponding to the length of the photosensitive drum 51a is formed, and a mesh 70a is formed as a grid on the bottom surface of the U-shaped by pressing or etching.

Protrusions 71a to 71d are provided at both ends (outside the discharge area of the charger 53), holes 72a and 72b are provided in the protrusions 71a and 71b, and long holes 72c and 72d are provided in the protrusions 71c and 71d. Has been. The chassis portion 8a is made of a conductive material, for example, a stainless steel plate, and is formed in a box shape with one surface opened to a length corresponding to the grid portion 7a. The discharge wire 80a is arranged in the longitudinal direction at the center of the inside. ing. On the outside, one end is fixed to the back surface by welding or the like, and the other ends are provided with a plurality of leaf springs 9a and 9b that are bent and formed so as to press both side surfaces.

Further, projecting pins 82a to 82d are provided on both sides of the chassis portion 8a at positions corresponding to the holes 72a and 72b and the long holes 72c and 72d of the grid portion 7a. As shown in FIG. 7, when the grid portion 7a is fitted into the opening surface of the chassis portion 8a from the outside, the holes 72a and 72b and the long holes 72c and 72d of the grid portion 7a are fitted into the protruding pins 82a to 82d, and Both sides of the section 7a are inserted between both side surfaces of the chassis section 8a and the leaf springs 9a, 9b, and both sides of the grid section 7a are closely fixed to both side surfaces of the chassis section 8a by the elastic force of the leaf springs 9a, 9b. Is configured.

A guide rail 81 is provided on the rear surface of the chassis portion 8a for inserting the charger 53 into the guide groove 11 when the charger 53 is mounted on the device frame 10 described later. Referring again to FIG. 6, blocks 83 and 84 made of an insulating material attached to both ends of the chassis portion 8a support both ends of the discharge wire 80a, and the block 83 is electrically connected to the discharge wire 80a and is detachable from the device. A power supply terminal 85 composed of a banana plug is provided. A handle 86 is formed on the block 84. Although not shown, the handle 86 includes a positioning metal piece 87 having a positioning hole 88. (See FIG. 7) Further, as shown in FIGS. 7 and 8, when the guide rail 81a of the charger 53 is inserted into the guide groove 11 of the device frame 10 and mounted, the device frame 10 shown by the two-dot chain line in FIG. The power supply terminal 85 of the chassis portion 8a is inserted into the electrode 13 of the provided socket 12, and the positioning pin 88 of the mounting frame 10 is fitted into the positioning hole 88 of the positioning metal piece 87 of the handle 86, so that the photosensitive drum 51a , A predetermined gap G 1 is set.

Therefore, as shown in FIG. 9, the grid portion 7a is electrically connected to the chassis portion 8a and is grounded through the varistor 15, and the photosensitive drum 51a is also grounded. Therefore, by biasing the discharge wire 80a to -VC with a high voltage power source, the surface of the photosensitive drum 51a can be charged by corona discharge from the discharge wire 80a.

[0012]

[Problems to be solved by the device]

 According to the above-mentioned conventional method, in order to control the grid voltage by using a conductor in the chassis part and keeping the same potential as the grid part, it is necessary to strengthen the coupling in order to establish conduction between the chassis part and the grid part. Therefore, the pressing force of the leaf spring is strong, and when the grid part is attached to the chassis part, the bottom of the grid part is originally horizontal as shown by the solid line in Fig. 8 and the gap between the grid part and the photosensitive drum is large. Should be G, but as shown by the chain double-dashed line in the figure, the grid portion is deformed by the pressing of the leaf spring and the bottom surface is curved, and the gap G is not uniform and the vicinity of the position pressed by the leaf spring is There is a problem that the gap becomes g and the surface potential of the photosensitive drum becomes non-uniform, which causes printing defects such as white spots in printing and fog.

An object of the present invention is to provide a charging device capable of making the surface potential of a photosensitive drum uniform to prevent printing trouble and to obtain stable printing quality.

[0014]

[Means for Solving the Problems]

 FIG. 1 is a principle view of the present invention, in which (a) is a perspective view and (b) is a sectional front view of an essential part. In the figure, 51 is an image forming body, 70 is a mesh, 7 is a U-shaped section and is formed to have a length corresponding to the length of the image forming body 51. The mesh 70 is formed on the bottom surface of the U-shaped, and at least one pair is formed. The grid part having the slit holes 16 of 16 is a pair of curved slit holes provided on both sides of the grid part 7 so as to face each other, and 8 is a box type having one surface open to the length corresponding to the grid part 7, An opening surface is fitted between both sides of the grid portion 7 so that the inner sides of both sides of the grid portion 7 are in close contact with the side surfaces, and a chassis portion having at least a pair of holding plates 9 and a discharge wire 80, A pair of pressing plates provided on both sides of the chassis portion 8 and formed of elastic materials that are fixed to the slit holes 16 on both sides of the grid portion 7 so as to have biasing forces in opposite directions at positions corresponding to the slit holes 16. , 80 are provided on the chassis 8 and Is Kakahari substantially between the center of the longitudinal ends of the over sheet portion 8, a discharge wire Ya to which a voltage is applied between the side surfaces being insulated from the sides of the box-shaped.

Therefore, when the grid portion 7 is fitted into the opening surface of the chassis portion 8, the tip of the pressing plate 9 presses the curved inner portion of the slit hole 16 to fix the grid portion 7 to the side surface of the chassis portion 8. Is configured to.

[0016]

[Action]

 When the grid portion 7 is fitted on the opening surface of the chassis portion 8, at least the tips of the holding plates 9 press the curved inner portions of the slit holes 16 to fix the grid portion 7 to the chassis portion 8. Since the pressing force of the pressing plate 9 does not reach the outer portion of the slit hole 16, the grid portion 7 can be prevented from being deformed, and the gap between the bottom surface of the grid portion 7 and the image forming body 51 does not become uneven. As the surface potential of the image forming body 51 becomes uniform and the charging is uniformly performed, it is possible to prevent white spots in printing, printing troubles such as fog, and obtain stable printing quality.

[0017]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. The same reference numerals indicate the same objects throughout the drawings.

FIG. 2 is a configuration diagram in which the present invention is applied to the charger of the electrophotographic printing apparatus described in the conventional example. The leaf springs 9a and 9b in FIG. 2 correspond to the holding plate 9 in FIG. 1, respectively. As shown in the perspective view of FIG. 2, when the mesh 70a of the grid portion 7b is on the lower surface, U-shaped slits 15a and 15b having a width of, for example, about 0.5 mm are provided on both sides of the U-shape.

The slits 16a and 16b are provided at positions where the tip ends of the leaf springs 9a and 9b of the chassis portion 8a come inside the curve when the grid portion 7b is fitted into the opening surface of the chassis portion 8a. Other configurations are the same as those in FIGS. 6 and 7 described in the conventional example.

With such a configuration, when the grid 7b is fitted into the chassis portion 8a as shown in FIG. 3, the tip ends of the leaf springs 9a, 9b are curved in the U-shaped slit holes 16a, 16b of the grid 7b. The grid 7b can be fixed to the chassis portion 8a by hitting against the inside and pressing.

At this time, the pressing force of the leaf springs 9a, 9b deforms only the inside of the curvature of the slit holes 16a, 16b to press the chassis portion 8a, and the pressing force does not reach the outside of the slit holes 16a, 16b. As a result, the grid 7b is prevented from being deformed, and as shown in FIG. 4, the gap between the surface of the mesh 70a and the photosensitive drum 51a is maintained at a predetermined dimension G, and as a result, the surface potential in the longitudinal direction of the photosensitive drum 51a becomes uniform. , Stable print quality can be obtained.

In the above example, a case was described in which a pair of opposed slit holes 16a, 16b and a pair of corresponding leaf springs 9a, 9b were provided, but a plurality of pairs may be provided, and slit holes 16a Although the case where the curvature of 16b is convex in the plane direction of the mesh 70a has been described, it may be concave in another curve direction, for example, the plane direction of the mesh 70a.

[0023]

[Effect of the device]

 As described above, according to the present invention, at least a pair of curved slit holes are provided on both sides of the grid portion, and when the grid portion is fitted to the outside of the chassis portion, the slits are formed by at least a pair of holding plates. By pressing the inside of the curve of the hole, the grid part can be fixed to the chassis part, and since the pressing force of the holding plate does not reach the outside part of the slit hole, deformation of the grid part can be prevented, The gap between the bottom surface of the grid and the image forming body becomes uniform, so that the surface potential of the image forming body becomes uniform and the charging is performed uniformly, and white spots in printing, fog, and other printing problems are prevented. The effect is that stable printing quality can be obtained.

[Brief description of drawings]

FIG. 1 Principle diagram of the present invention

FIG. 2 is an exploded perspective view showing an embodiment of the present invention.

FIG. 3 is a side view of the embodiment.

FIG. 4 is a sectional view taken along the line BB ′ of FIG.

FIG. 5 is a side view of the inside of the electrophotographic printing apparatus.

FIG. 6 is an exploded perspective view showing a conventional charger.

FIG. 7 is a side view of a conventional example.

8 is a sectional view taken along the line AA ′ in FIG.

FIG. 9 is an explanatory diagram of a charger

[Explanation of symbols]

7, 7a and 7b are grid portions, 8 and 8a are chassis portions, 9 is a holding plate, 9a and 9b are leaf springs, 16, 16a and 16b are slit holes, 51 is an image forming body, 51a is a photosensitive drum, 8
0,80a is the discharge wire,

Claims (1)

[Scope of utility model registration request] 1. A charging device, which is arranged to face an outer peripheral surface of a rotatable image forming body (51) with a predetermined gap therebetween, and charges the image forming body (51) by corona discharge.
(7) and a chassis part (8), wherein the grid part (7) has a U-shaped cross section and the image forming body (51).
Is formed in a length corresponding to the length of the U-shape, a mesh (70) is formed on the bottom surface of the U-shape, and at least a pair of curved slit holes (16) are provided on both sides of the U-shape so as to face each other. The chassis part (8) has a box shape with one surface open at a length corresponding to the grid part (7), and the opening surface is the grid part.
Fitted between both sides of (7), the side surface is the grid part.
At least a pair of holding plates (9) made of elastic material are formed in close contact with the inside of both sides of (7) and respectively correspond to the slit holes (16) of the grid part (7) in opposite directions. The discharge wires (80), which are fixed to each other so as to have a pressing force, are suspended between the centers of both ends in the longitudinal direction, are insulated from the side surface of the box shape, and a voltage is applied between the side surface and the side surface. ), And when the opening surface of the chassis portion (8) is fitted between both sides of the grid portion (7), the tip of the holding plate (9) has the slit hole (16). By pressing the inner part of the curve, the grid part (7)
The charging device is characterized in that is fixed to the side surface of the chassis part (8).