JPH05289427A - Image forming device - Google Patents

Abstract

PURPOSE:To provide a miniaturized and inexpensive image forming device of which a whole ground circuit can be simplified and the sure connection of ground in can be stably obtained at the same time even in the case that the base of a machine is formed by an insulating material. CONSTITUTION:By making the ground circuit of a destaticization sheet 11 at a transfer and separation part TS through the shield case 5a of a transfer electrostatic charger and making the ground circuits from both members join with the ground circuit 34 of the photosensitive drum 1 by a drum shaft 1c, the ground circuits of the whole device are unified to one system. Thus, the constitution of the ground circuit is simplified and the number of contacts is reduced. Besides, the sure connection of the ground is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of simplifying a ground circuit of the entire apparatus and stably obtaining a reliable ground connection.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using electrophotography, a corona discharger has been widely used as a charging means and a transfer means. In the corona discharger, a high bias voltage is applied to the corona wire, and the shield case surrounding the corona wire is grounded to the grounding part of the apparatus body. When the shield case is grounded, a simple and reliable ground connection circuit is obtained by connecting the shield case and a sheet metal base as a casing of the main body of the device with a leaf spring or a conductor and grounding the base. be able to.

In recent years, however, in order to reduce the size of the machine body and reduce the number of parts, the base, which is the housing, is often formed of a resin material. In that case, since the resin base is an insulator and cannot serve as a ground circuit, the ground circuit of the transfer charger is configured to bypass the base. As a result, the grounding circuit becomes complicated and causes a cost increase, and the number of contacts increases, which easily causes a contact failure, which makes it difficult to secure a stable grounding connection.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. Even when the housing is made of an insulating material, the entire ground circuit can be simplified and a reliable ground connection can be made. It is an object of the present invention to provide a small-sized and inexpensive image forming apparatus that can stably obtain the image.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the main point of the present invention is to incorporate a power source for supplying electricity to a predetermined member and an insulating resin casing, and an image carrier so as to be circulatively movable. A process unit that is detachable from the apparatus main body and is electrically connected to at least the power source when mounted, and disposed in the insulating resin housing so as to face the surface of the image carrier when the process unit is mounted. In an image forming apparatus having a corona discharger, the corona discharger includes a corona wire and a shield case surrounding the corona wire, and the shield case is grounded to the grounding portion of the apparatus main body. It is at the point of ground connection through a circuit.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the embodiments shown in FIGS. FIG. 9 is a sectional view showing the overall configuration of an optical writing printer as an embodiment of the present invention. In the figure, a photosensitive drum 1 as an image bearing drum is provided in the approximate center of the printer so as to be rotatable in the direction of arrow A. Around the photosensitive drum 1, along the rotation direction thereof, a charging brush 2 for uniformly charging the peripheral surface of the photosensitive drum 1 to a predetermined potential, and for exposing the surface of the photosensitive drum 1 in accordance with input information and statically An optical recording head 3 that forms an electrostatic latent image, a developing device 4 that applies toner to the electrostatic latent image to visualize it as a toner image, and a toner image is electrostatically formed on a sheet sent from the right side in the drawing. A transfer charger 5 as a corona discharger for transferring the toner to the sheet, a cleaner 6 for removing the toner remaining on the photosensitive drum 1, and the like are sequentially arranged.

The developing device 4 of this embodiment adopts a non-magnetic one-component developing system, and includes a developing roll 4a for applying toner to the photosensitive drum 1, a toner supply roll 4b for supplying the toner contained therein, and a developing roll. A doctor blade 4c, etc., which contacts the upper peripheral surface of 4a and regulates the toner conveyance amount, is provided. A bias voltage having the same potential is applied to the developing roll 4a and the doctor blade 4c, and a bias voltage capable of forming an electric field for moving the toner to the developing roll 4a side is applied to the toner supply roll 4c.

At the bottom of the printer, a paper feed cassette 7 for stacking and storing paper, a paper feed roll 8 for feeding the stored paper one by one, a turn guide 9 for guiding the fed paper upward while reversing the fed paper, and a photoconductor. A sheet carry-in section including a pair of standby rolls 10 and the like for conveying the sheet to the image transfer section T in synchronization with the front end of the image on the drum 1 is formed.

The transfer charger 5 includes a shield case 5a extending in the axial direction of the photosensitive drum 1 and having a slender casing shape, and a corona wire 5b stretched along the longitudinal direction at the center of the internal space thereof. Become. On the downstream side wall surface of the shield case 5a, a static elimination sheet 11 as a static elimination separation means is fixed. Both the shield case 5a and the static elimination sheet 11 are grounded. The ground circuit configuration will be described later.

A transport guide member is provided on the downstream side of the static elimination sheet 11. In this example, a part of the upper surface of the base Bm, which is a casing formed of an insulating resin material, is horizontally formed as the transport guide portion 12. After the transfer, the charge removing sheet 11 removes the electric charge by the conveyance guide portion 12, and the paper separated from the surface of the photosensitive drum 1 by its elasticity is guided to the heating roll fixing device 13 on the downstream side.

On the downstream side of the fixing device 13, a paper transport path switching plate 14 is arranged. An FD (face-down) is provided in an upward direction on the downstream side of the sheet transport path switching plate 14.
A discharge path 15 and a FU (face-up) discharge path 16 are formed horizontally. The FD discharge route 15 is
The curved sheet extends upward, and the sheet on which the toner image has been fixed is reversed and guided upward. At the end of the FD discharge path 15, a paper discharge roller pair 17 is arranged. The sheet conveyed while being reversed is discharged by the sheet discharge roller pair 17 onto a sheet discharge tray portion 18 formed by denting the upper surface of the printer in a face-down state with the image surface facing downward.

The above-mentioned optical writing printer employs a roof open structure so that maintenance work such as internal inspection and replacement of consumable members can be easily performed. That is, the roof 19 which is the upper case of the machine body is divided from the lower case 20 and is hingedly connected so as to be freely opened and closed. The roof 19 has an optical writing head 3 and an FD.
A part of the guide member forming the discharge path 15 is integrally rotatably installed. The photoconductor drum 1, the charging brush 2, and the cleaner 6 are used as a drum unit U1, and the developing device 4 is used as a toner unit U2. Each unit U1, U2
When replacing, the roof 19 is rotated as shown by the chain double-dashed line. As a result, substantially the entire upper part of the machine body is opened, and the units U1 and U2 can be easily replaced.

The base Bm of this example is formed in a housing shape with its upper surface closed, and is arranged between the insertion portion of the paper feed cassette 7 and the paper transport path via the transfer portion T and the fixing device 13. is there. The upper surface of the base Bm is used as the transport guide portion 12 as described above, and the other portions are formed in a concavo-convex shape corresponding to each member arranged above the base. Inside the base Bm thus formed, an electric circuit such as a control unit for controlling the operation of the entire printer is arranged.

Here, each circuit configuration of power supply and ground and each connection structure in the optical writing printer of this example will be described. FIG. 1 is a block diagram showing a circuit configuration of power feeding and grounding in the optical writing printer of this example. In this example, from the high-voltage unit 22 which is the power supply for the entire printer, power supply circuits for supplying three systems of bias voltage, that is, the power supply circuit 23a to the drum unit U1, the power supply circuit 23b to the toner unit U2, and the transfer separation unit. Power supply circuit 23c to TS,
Have been pulled out respectively.

The specific circuit connection structure of the drum unit power supply circuit 23a is as shown in FIG. One end of the coil spring 24 is brought into contact with one end of the feeding circuit pattern formed on the substrate 22a of the high voltage unit 22, and the other end of the coil spring 24 is connected to the charging brush 2.
In this case, a metal plate spring 25 is fixed to one end of the conductive substrate 2b in which the brush bristles 2a of the charging brush 2 are planted, and the plate spring 25 and the other end of the coil spring 24 are elastically contacted. In this way, by adopting the elastic connection structure via the coil spring 24 and the leaf spring 25, a reliable conductive connection can be stably ensured even for a drum unit that can be freely attached and detached.

The connection structure of the toner unit power supply circuit 23b to the developing roll 4a is constructed as shown in FIG. A leaf spring 27 is provided at a proper position of the power supply pattern of the high-voltage unit 22 so as to straddle a support base 26 supporting the toner unit.
One end of is elastically contacted. The other end of the leaf spring 27 is elastically contacted with the tip of a mounting reference shaft 28 that is projected from a toner unit case (not shown). The end of the mounting reference shaft 28 on the inner side of the unit is connected to a conductive bearing 4e, which is externally inserted on the rotation shaft 4d of the developing roller 4a, via a leaf spring 29, a resistor 30, and a leaf spring 31. Further, as shown in FIG. 6, one end of the leaf spring 31 in the power supply circuit to the developing roller 4a is elastically contacted to the doctor blade 4b in a conductive support member 4f of the doctor blade 4b. .. Furthermore,
As shown in FIG. 5, with respect to the toner supply roll 4b, the other end of the leaf spring 29 elastically contacted with the inner end of the unit of the mounting reference shaft 28 described above is provided outside the rotary shaft 4g of the toner supply roll 4b. It is electrically connected to the inserted conductive bearing 4h. As shown in FIG. 1, the power supply circuit 23c for the transfer / separation unit TS also has an elastic connection structure via the leaf spring 32 and the pin 33.

Thus, the ground circuit in the optical writing printer of this example is grouped into one system of the ground circuit 34 via the drum unit U1 as shown in FIG. 1 and connected to the ground circuit pattern on the substrate in the high voltage unit 22. It is configured to do. FIG. 4 is a schematic cross-sectional view showing the ground connection structure of the photosensitive drum 1. In the figure, resin holders 1b are fitted on both ends of a cylindrical tube 1a made of a conductive material such as aluminum (only one end is shown). A photosensitive layer (not shown) is applied to the peripheral surface of the cylindrical tube 1a. The drum shaft 1c is inserted in the center of the holder 1b. In this example, a recess 1d is formed in the center of the inside of the holder 1b, and the tapered end of the drum shaft 1c formed in a tapered shape is projected into the recess 1d. A leaf spring 1f fixed to the inner surface of the holder 1b is attached to the tapered tip surface.
The central part of the is contacted. Both ends of the leaf spring 1f are elastically contacted with the inner peripheral surface of the cylindrical shell 1a. Drum shaft 1
One end of a coil spring 35 penetratingly inserted into the side wall of the main body base is elastically contacted with the tip end surface of the end portion of the c projecting to the outer surface of the holder. The other end of the coil spring 35 is elastically contacted with the ground circuit pattern on the substrate 22a of the high voltage unit. That is, the ground circuit of the photoconductor drum 1 is the cylindrical tube 1a.
→ leaf spring 1f → drum shaft 1c → coil spring 35 →
It is formed along the path of the ground circuit pattern of the substrate 22a (see FIG. 1).

2 and 3 show a ground connection structure of the static elimination sheet 11 and the transfer shield case 5a. In FIG.
The static elimination sheet 11 has a length extending over substantially the entire area of the downstream side surface 5a1 of the shield case 5a, and is attached to the downstream side surface 5a1 with a conductive double-sided tape in this example. As shown in FIG. 2, one end of a leaf spring 37 fixed to the inner surface of the side wall 36 of the main body base is elastically contacted with the bottom surface of the shield case 5a. This leaf spring 37
The other end of is elastically contacted with the peripheral surface of the drum shaft 1c of the photosensitive drum 1 described above.

As described above, the static elimination sheet 11 is conductively connected to the leaf spring 37 through the shield case 5a, and the ground circuits of both are combined into one system. The drum shaft 1c merges with the grounding circuit of the photosensitive drum described above. As a result, the ground circuits of the three parts are integrated into one system. As a result, the grounding circuit is simplified, the number of contacts is reduced, and reliable conductive connection can be stably obtained.

The present invention should not be limited to the preferred embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, the above embodiment is an example in which the lower case 20 side of the machine body is configured by the base Bm of the insulating resin material, and the transfer charger 5 is disposed as a corona discharger on the base Bm. The present invention can be applied to the case where the base is made of an insulating resin material and a corona discharger such as a charger or a static eliminator is arranged on the base. Further, although the photosensitive drum is used as the image bearing member in the above embodiment, the present invention is not limited to this, and when the dielectric other than the photosensitive member is formed into an endless belt shape instead of a drum shape,
The present invention can be effectively applied.

[0021]

As described above in detail, according to the present invention, in the image forming apparatus which uses the corona discharger while forming the housing constituting the apparatus main body with the insulating material such as resin, the corona discharger is used. A simple ground circuit with a small number of contacts can be easily configured by connecting the shield case to the ground via the ground circuit of the process unit containing the image carrier and integrating the ground circuit of the entire device into one system. You can As a result, it is possible to promote the downsizing and provide the image forming apparatus, which can obtain a reliable ground connection stably, at a low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a power supply circuit and a ground circuit of an optical writing printer as an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a relationship between a transfer charger and a photoconductor drum in the optical writing printer.

FIG. 3 is a perspective view showing a configuration of a transfer separation unit in the optical writing printer.

FIG. 4 is a schematic cross-sectional view showing a drum ground circuit structure in the optical writing printer.

FIG. 5 is a schematic cross-sectional view showing a power supply circuit connection structure to a toner supply roll in the optical writing printer.

FIG. 6 is a schematic cross-sectional view showing a power supply circuit connection structure to a doctor blade in the optical writing printer.

FIG. 7 is a schematic cross-sectional view showing a structure for connecting a power supply circuit to a developing roll in the optical writing printer.

FIG. 8 is a schematic cross-sectional view showing a power supply circuit connection structure to a drum unit in the optical writing printer.

FIG. 9 is a schematic cross-sectional view showing the overall configuration of the optical writing printer.

[Explanation of symbols]

 1 Photoconductor Drum 2 Charging Brush 1a Cylindrical Element Tube 1c Drum Shaft 4 Developer 4a Developing Roll 4b Toner Supply Roll 4c Doctor Blade 5 Transfer Charger 5a Shield Case 5b Corona Wire 11 Electrification Sheet 22 High Voltage Unit 34 Ground Circuit (Photoconductor) Drum) Bm Base TS Transfer / separation unit U1 Drum unit U2 Toner unit

Claims (1)

[Claims] 1. An apparatus main body having a power source for supplying electricity to a predetermined member and an insulating resin casing, and an image carrier which is rotatably incorporated and is detachably attached to the apparatus main body. An image forming apparatus comprising: a process unit electrically connected to the process unit; and a corona discharger disposed in the insulating resin casing so as to face the surface of the image bearing member in a mounted state of the process unit. The discharger comprises a corona wire and a shield case surrounding the corona wire, and the shield case is grounded via a ground circuit of the process unit connected to a ground portion of the apparatus body. apparatus.