JP3200945B2 - Image forming device - Google Patents

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 an electrophotographic technique, a corona discharger is frequently used as a charging means and a transfer means. In the corona discharger, a high bias voltage is applied to the corona wire, and a shield case surrounding the corona wire is grounded to a ground portion of the apparatus main body. When connecting the shield case to the ground, a simple and reliable ground connection circuit is obtained by connecting the shield case and a sheet metal base as a casing of the apparatus body with a leaf spring or a lead wire and connecting the base to the ground. be able to.

However, in recent years, in order to reduce the size of the body and reduce the number of parts, the base serving as the housing is often formed of a resin material. In this case, since the resin base is an insulator and cannot be 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 an increase in cost. In addition, the number of contacts increases, and conduction failure of the contacts easily occurs, making it difficult to secure a stable ground connection.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art, and can simplify the entire ground circuit and reliably connect the ground even when the housing is formed of an insulating material. It is an object of the present invention to provide a small and inexpensive image forming apparatus capable of stably obtaining the image.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the main point of the present invention is to provide an apparatus main body having a power supply for supplying electricity to predetermined members and an insulating resin housing, and a built-in image carrier which is circulatingly movable. A process unit detachable from the apparatus main body and electrically connected to at least the power supply at the time of mounting; and a process unit disposed in the insulating resin housing so as to be able to face the surface of the image carrier under the mounted state of the process unit. The corona discharger, the corona discharger includes a corona wire and a shield case surrounding the corona wire, and the shield case is provided for the process unit.
In the mounted state, it is provided so as to be connectable to a grounding circuit of the process unit connected to a grounding part of the apparatus main body, and the grounding circuit is provided.
The point is that it is connected to ground via a road .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiments shown in FIGS. FIG. 9 is a sectional view showing the overall configuration of an optical writing printer as one embodiment of the present invention. In FIG. 1, a photosensitive drum 1 as an image carrier drum is provided at substantially the center of the printer so as to be rotatable in the direction of arrow A. Around the photosensitive drum 1, a charging brush 2 that uniformly charges the peripheral surface of the photosensitive drum 1 to a predetermined potential along the rotation direction, and exposes the surface of the photosensitive drum 1 according to input information to perform static exposure. An optical recording head 3 for forming an electrostatic latent image, a developing device 4 for applying toner to the electrostatic latent image and developing the toner image into a toner image, and electrostatically applying the toner image on a sheet sent from the right side in FIG. A transfer charger 5 as a corona discharger for transferring the toner to the photosensitive drum 1, 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 employs a non-magnetic one-component developing method, and includes a developing roll 4a for applying toner to the photosensitive drum 1, a toner supply roll 4b for supplying toner stored therein, and a developing roll. A doctor blade 4c and the like which come into contact with the upper peripheral surface of 4a and regulate the toner conveyance amount are provided. A bias voltage having the same potential is applied to the developing roll 4a and the doctor blade 4c, respectively, and a bias voltage capable of forming an electric field for moving the toner toward the developing roll 4a is applied to the toner supply roll 4c.

At the lower part of the printer, a paper feed cassette 7 for loading and storing papers, a paper feed roll 8 for feeding out stored papers one by one, a turn guide 9 for inverting the fed out papers and guiding them upwards, a photoconductor A paper loading section is formed by a pair of standby rolls 10 for transporting the paper to the image transfer section T in synchronization with the leading edge of the image on the drum 1.

The transfer charger 5 is composed of an elongated housing-shaped shield case 5a extending in the axial direction of the photosensitive drum 1, and a corona wire 5b extending along the longitudinal direction at the center of the internal space. Become. A static elimination sheet 11 as static elimination and separation means is fixed to the downstream side wall surface of the shield case 5a. The shield case 5a and the static elimination sheet 11 are both grounded. The ground circuit configuration will be described later.

A transport guide member is provided downstream of the charge removing sheet 11. In this example, a part of the upper surface of a base Bm as a housing molded using an insulating resin material is formed horizontally as a transport guide portion 12. After the transfer, the transfer guide unit 12 removes the charge on the charge removing sheet 11 and separates the paper from the surface of the photosensitive drum 1 by its own elasticity. The sheet is guided to the heating roll type fixing device 13 on the downstream side.

On the downstream side of the fixing device 13, a paper transport path switching plate 14 is provided. An FD (face down) is provided on the downstream side through the sheet transport path switching plate 14 in the upward direction.
A discharge path 15 and a FU (face-up) discharge path 16 are formed in the horizontal direction. The FD discharge path 15 is
The paper that extends upward while curving and guides the paper on which the toner image has been fixed is turned upside down. At the end of the FD discharge path 15, a pair of paper discharge rollers 17 is provided. The paper conveyed while being inverted is discharged by a discharge roller pair 17 onto a discharge tray portion 18 formed by recessing the upper surface of the printer in a face-down state with the image surface facing down.

The above-described 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 fuselage, is divided from the lower case 20, and connected by a hinge 21 so as to be freely openable and closable. The roof 19 has an optical writing head 3 and an FD
A part of a guide member forming the discharge path 15 and the like are installed so as to be integrally rotatable. The photosensitive drum 1, the charging brush 2, and the cleaner 6 are a drum unit U1, and the developing unit 4 is a toner unit U2. Each unit U1, U2
Is replaced, the roof 19 is rotated as shown by a two-dot chain line. As a result, substantially the entire area of the upper part of the fuselage is opened, and the units U1 and U2 can be easily replaced.

The base Bm of the present embodiment is formed in a housing shape having a closed upper surface, and is disposed 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 an uneven shape corresponding to each member disposed 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 provided.

The power supply and ground circuit configurations and connection structures in the optical writing printer of the present embodiment will now be described. FIG. 1 is a block diagram showing a circuit configuration of power supply and ground in the optical writing printer of the present embodiment. In the present embodiment, a power supply circuit for supplying a bias voltage of three systems, that is, a power supply circuit 23a to the drum unit U1, a power supply circuit 23b to the toner unit U2, and a transfer separation unit Power supply circuit 23c to TS,
Have been drawn out respectively.

The specific circuit connection structure of the drum unit power supply circuit 23a is as shown in FIG. One end of a coil spring 24 is in contact with one end of a power supply circuit pattern formed on a substrate 22 a 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 leaf spring 25 is fixed to one end of the conductive substrate 2b on which the brush bristles 2a of the charging brush 2 are planted, and the other end of the leaf spring 25 and the other end of the coil spring 24 are elastically contacted. With the elastic connection structure via the coil spring 24 and the leaf spring 25 in this manner, a reliable conductive connection can be stably secured even to a freely detachable drum unit.

The connection structure of the toner unit power supply circuit 23b to the developing roll 4a is configured as shown in FIG. A leaf spring 27 straddling a support 26 supporting the toner unit at an appropriate position of the power supply pattern of the high voltage unit 22
One end is elastically contacted. The other end of the leaf spring 27 is elastically contacted with the tip of a mounting reference shaft 28 protruding from a toner unit case (not shown). The inner end of the mounting reference shaft 28 is connected to a conductive bearing 4e extrapolated to the rotating shaft 4d of the developing roll 4a via a leaf spring 29, a resistor 30, and a leaf spring 31. As shown in FIG. 6, one end of the leaf spring 31 in the power supply circuit for the developing roller 4a is elastically connected to the doctor blade 4b so as to be conductive with the 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 plate spring 29 elastically contacting the unit inner end of the mounting reference shaft 28 is attached to the rotation shaft 4g of the toner supply roll 4b. It is conductively connected to the inserted conductive bearing 4h. In addition, 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.

The ground circuit in the optical writing printer of this embodiment is integrated into one system of a ground circuit 34 via the drum unit U1 as shown in FIG. 1, and is connected to the ground circuit pattern on the substrate in the high voltage unit 22. Configuration. FIG. 4 is a schematic cross-sectional view illustrating a ground connection structure of the photosensitive drum 1. In the figure, resin holders 1b are fitted to both ends of a cylindrical base tube 1a made of a conductive material such as aluminum (only one end is shown). A photosensitive layer (not shown) is provided on the peripheral surface of the cylindrical tube 1a. A drum shaft 1c is inserted into the center of the holder 1b. In this example, a concave portion 1d is formed in the center of the inside of the holder 1b, and the tapered end of the tapered drum shaft 1c is projected into the concave portion 1d. A leaf spring 1f fixed to the inner surface of the holder 1b is attached to the tapered tip surface.
The center of the abutment is in contact. Both ends of the leaf spring 1f are in elastic contact with the inner peripheral surface of the cylindrical tube 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 protruding from the holder outer surface c. The other end of the coil spring 35 is in elastic contact with a ground circuit pattern on the substrate 22a of the high voltage unit. That is, the grounding circuit of the photosensitive drum 1 has a cylindrical tube 1a.
→ leaf spring 1f → drum shaft 1c → coil spring 35 →
It is formed over the path of the ground circuit pattern on the substrate 22a (see FIG. 1).

FIGS. 2 and 3 show a ground connection structure between the charge removing sheet 11 and the transfer shield case 5a. In FIG.
The static elimination sheet 11 has a length that extends over substantially the entire downstream side surface 5a1 of the shield case 5a, and is affixed 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
Is in elastic contact 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 via the shield case 5a to combine the grounding circuits of the two into one system. The drum shaft 1c joins the ground circuit of the photosensitive drum described above. As a result, the ground circuits at three locations are integrated into one system. As a result, the ground circuit is simplified, the number of contacts is reduced, and a reliable conductive connection can be stably obtained.

It should be noted that the present invention is not limited to the preferred embodiment described above, and it is needless to say 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 fuselage is formed of a base Bm of an insulating resin material, and the transfer charger 5 is disposed as a corona discharger on the base Bm. The present invention can also be applied to a case where a base is made of an insulating resin material and a corona discharger such as a charger and a static eliminator is disposed on the base. Further, in the above embodiment, the photosensitive drum is used as the image carrier. However, the present invention is not limited to this. Even when the dielectric other than the photosensitive member is formed in an endless belt shape instead of a drum shape,
The present invention can be effectively applied.

[0021]

As described in detail above, according to the present invention, a corona discharge device is provided in an image forming apparatus using a corona discharge device in which a housing constituting the apparatus main body is formed of an insulating material such as resin. By connecting the shield case to the ground via the ground circuit of the process unit incorporating the image carrier, and integrating the ground circuit of the entire device into one system, a simple ground circuit with a small number of contacts can be easily configured. Can be. As a result, it is possible to promote downsizing and to provide an inexpensive image forming apparatus capable of stably obtaining a reliable ground connection.

[Brief description of the 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 one embodiment of the present invention.

FIG. 2 is a sectional view showing a relationship between a transfer charger and a photosensitive 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 sectional view showing a drum ground circuit structure in the optical writing printer.

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

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

FIG. 7 is a schematic cross-sectional view showing a power supply circuit connection structure 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 sectional view showing the entire configuration of the optical writing printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging brush 1a Cylindrical tube 1c Drum shaft 4 Developing device 4a Developing roll 4b Toner supply roll 4c Doctor blade 5 Transfer charger 5a Shield case 5b Corona wire 11 Static elimination sheet 22 High voltage unit 34 Grounding circuit (Photoconductor) Drum) Bm base TS Transfer separation unit U1 Drum unit U2 Toner unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-67172 (JP, A) JP-A-64-65573 (JP, A) JP-A-1-250966 (JP, A) 43359 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 G03G 15/02 G03G 15/14-15/16 G03G 21/16-21/18 H05K 3/02

Claims (1)

(57) [Claims] 1. An apparatus main body having a power supply for supplying electricity to a predetermined member and an insulating resin housing, and an image carrier circulatingly built therein and detachably attached to the apparatus main body, and at least the power supply at the time of mounting. An image forming apparatus, comprising: a process unit electrically connected to the image forming apparatus; and a corona discharger disposed in the insulating resin housing so as to be able to face the image carrier surface when the process unit is mounted. discharger has a shield case surrounding the corona wire and the corona wire, wherein the shield case
Ground circuit and connectable to said process unit under the mounted state of the process unit is connected to the ground portion of the apparatus main body
And an image forming apparatus connected to the ground via the ground circuit .