JPH09244407A - Process unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize press-contact force between a photoreceptor drum and a developing roller though the quantity of developer housed in a developing housing is changed. SOLUTION: In this process unit, a drum unit 12 provided with the photoreceptor drum 24, a developing unit 16 provided with the developing housing 30 in which toner is housed and a developing roller 32 disposed in the housing 30, a supporting shaft 14 supporting the unit 16 so as to freely rock it with respect to the unit 12 and a spring 40 made to intervene between the units 16 and 12 and set for imparting an angular moment around the shaft 14 to the unit 16 so that the roller 32 is pressed in a direction toward the drum 24 are included. In such a case, the shaft center C of the shaft 14 is positioned on a vertical line passing within the moving range of a centroid between the centroid G1 of the unit 16 when the housing 30 is full of the toner and the centroid G2 of the unit 16 when the housing 30 is emptied of the toner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process unit detachably attached to an image forming apparatus such as an electrostatic copying machine or a laser printer.

[0002]

2. Description of the Related Art A drum unit having a photosensitive drum on which an electrostatic latent image is formed by an exposing unit, a developing housing containing a developer, and a developing unit provided in the developing housing to supply the developer to the drum unit. A process unit having a form including a developing device having a roller and a support shaft (fulcrum) for swingably supporting the developing device with respect to a drum unit is known (for example, see Japanese Patent Laid-Open No. 5-66662). In the process unit disclosed in the publication, the support shaft is arranged above the drum unit so that a gravity acting on the developing unit can generate a rotational moment that urges the developing roller toward the photosensitive drum. ing. A spring is interposed between the developing device and the drum unit. The spring is arranged to bias the developing device in a direction to reduce the rotational moment.

[0003]

In order to put the process unit of the above-mentioned form into practical use, it is necessary to solve the following technical problems. First, regardless of changes in the amount of developer contained in the developer housing,
By reducing the change in the pressure contact force between the photosensitive drum and the developing roller, the pressure contact force between the photosensitive drum and the developing roller is stabilized. In the above-mentioned conventional process unit, since the support shaft is arranged at a position apart from the upper side of the developing housing to the drum unit side,
As the amount of developer in the developing housing changes from a full state (so-called full state) to an empty state,
The rotation moment of the developing device around the support shaft changes greatly, and therefore the pressure contact force changes significantly. As a result, the supply amount of the developer from the developing roller to the photoconductor drum is largely changed in association with the change in the amount of the developer, and stable image formation may not be performed.

Second, when assembling the drum unit and the developing device, the developer can be easily assembled while preventing the developer from falling. In the above-mentioned conventional process unit, since the support shaft is arranged above the drum unit, the developing roller portion is directed downward to the developing device at the time of assembly, and there is a possibility that the developer may drop and pollute the surroundings. is there. In addition, handling is poor and assembly is poor.

The present invention has been made on the basis of the above facts, and a first technical problem thereof is that the photosensitive drum and the developing roller are irrespective of the change in the amount of the developer accommodated in the developing housing. The pressure contact force with can be stabilized,
It is to provide a new process unit.

A second technical object of the present invention is to provide a novel process unit which can be easily assembled while preventing the developer from falling when assembling the drum unit and the developing device.

[0007]

In order to achieve the first technical object, according to the present invention, a process unit detachably mounted on an image forming apparatus, in which an electrostatic latent image is formed. A drum unit having a photosensitive drum, a developing housing having a developer housed therein, a developing roller provided in the developing housing for supplying the developer to the photosensitive drum, and the developing device. Support shaft means for swingably supporting the drum unit, and the developing roller interposed between the developing device and the drum unit so as to urge the developing roller toward the photosensitive drum. Means for applying a rotational moment about the supporting shaft means to the developing device, and the shaft center of the supporting shaft means has a center of gravity of the developing device and a developing center in a full state of the developer housed in the developing housing. Agent Positioned on the vertical line passing through the range of movement of the gravity center between the centroid of the developing device in the empty state, a process unit, characterized in that, is provided.

In the above invention, even if the rotational moment of the developing device around the support shaft changes with the change of the amount of the developer in the developing housing from the full state to the empty state, the shaft of the support shaft means changes. Since the center of gravity is located on the vertical line passing through the range of movement of the center of gravity of the developing device in the developing housing full state and the center of gravity of the developing device in the empty state of the developing device, Regardless of the change in the amount, it is possible to suppress the change in the pressure contact force between the photosensitive drum and the developing roller to be small, and to stabilize the pressure contact force between the photosensitive drum and the developing roller.
As a result, it is possible to reduce the change in the supply amount of the developer from the developing roller to the photosensitive drum, regardless of the change in the amount of the developer, and always perform stable image formation. The present invention is also applicable to the process unit in which the support shaft means is positioned above as in the conventional example.

In order to achieve the first technical object, according to the present invention, a process unit detachably mounted on an image forming apparatus, in which an electrostatic latent image is formed, is a photosensitive drum. A drum unit provided with a developing housing containing a developer and a developing roller disposed in the developing housing to supply the developer to the photosensitive drum; and the developing unit with respect to the drum unit. Supported by the developing device so that the developing roller is urged in the direction toward the photoconductor drum by being interposed between the supporting shaft means for swingably supporting the developing roller and the developing device and the drum unit. Spring means for imparting a rotational moment about the shaft means, and the axis of the support shaft means is positioned on a vertical line passing through the center of gravity of the developing device in the full state of the developer housed in the developing housing. Is, the process unit, characterized in that, is provided.

In the present invention, the shaft center of the support shaft means is positioned on the vertical line passing through the center of gravity of the developing device in the full state of the developer housed in the developing housing. As the amount of developer in the developing housing changes from the full state to the empty state, the center of gravity of the developing device moves,
Even if the rotational moment of the developing device around the support shaft increases, it is offset by the decrease in the weight of the developing device itself. As a result, it is possible to reduce the change in the supply amount of the developer from the developing roller to the photosensitive drum, regardless of the change in the amount of the developer, and always perform stable image formation. The present invention is also applicable to the process unit in which the support shaft means is positioned above as in the conventional example.

In order to achieve the second technical object, according to the present invention, there is provided a process unit detachably mounted on an image forming apparatus, the process unit including a photosensitive drum on which an electrostatic latent image is formed. A drum unit, a developing housing containing a developer and a developing roller disposed in the developing housing to supply the developer to the photosensitive drum, and the developing unit is shaken with respect to the drum unit. A support shaft means that is movably supported, and is interposed between the developing device and the drum unit, and the support shaft means is provided in the developing device so that the developing roller is biased in the direction toward the photosensitive drum. And a spring means for imparting a rotational moment around the support shaft means, the support shaft means being disposed below a bottom portion of the developing housing.

In the above invention, since the supporting shaft means is disposed below the bottom of the developing housing, the drum unit and the developing device can be assembled without directing the developing roller portion downward, so that the developing agent It is possible to prevent falling and contamination of the surroundings. Further, since the support shaft means is positioned below the above, the handling is good and the assembling property is improved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a process unit constructed according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 schematically shows a printer 4 equipped with an embodiment of a process unit 2 constructed according to the present invention. In this embodiment, the printer 4 is a small-sized low-speed laser printer used as a printing device such as a word processor, and has a main body 6
And the cover 1 mounted so as to be rotatable around the axis 8 of the main body 6.
0 is included. The process unit 2 includes a main body 6
It is installed inside to be detachable.

As shown in FIG. 2, the process unit 2 is provided with a drum unit 12 and a developing device 16 which is swingably supported by the drum unit 12 via a support shaft 14. The drum unit 12 includes a pair of metallic side wall members 18 arranged at intervals in the front-back direction of the drawing, and a horizontal frame member (not shown) arranged between the side wall members 18 so as to connect the side wall members 18 to each other. ing. A support arm 20 extending parallel to the same direction is formed at the lower portion of each of the side wall members 18. A bearing portion 22 is provided at the tip of each of the support arms 20. Each of the bearing portions 22 is arranged so as to have a common axis. A ring-shaped handle 23 extending parallel to the upper side is provided on each upper portion of the side wall members 18.
Are formed. Although not clearly shown in the drawing, each of the handles 23 is formed of a synthetic resin, and
Is attached to each.

The drum unit 12 is also provided with a photosensitive drum 24 having a photosensitive layer formed on its peripheral surface, a paper dust removing brush 26, and a charging corona discharger 28. The photosensitive drum 24 is rotatably supported between the side wall members 18. The paper dust removing brush 26 and the charging corona discharger 28 are mounted between the side wall members 18. The upper and left sides of the photosensitive drum 24 are open.

The developing device 16 contains a developing housing 30 containing a developer consisting of a one-component toner, and a developer housed in the developing housing 30 to hold the developer. The developing roller 32 for supplying the electrostatic latent image, the replenishing roller 34 for supplying the developer to the peripheral surface of the developing roller 32, and the stirring means 36 for stirring the developer are provided. The developing roller 32 is the developing housing 30.
It is made of conductive solid synthetic rubber such as urethane rubber fixed to the outer peripheral surface of a rotating shaft (not shown) rotatably supported between both side walls. Supply roller 3
Reference numeral 4 is made of foam such as foamed silicone or foamed urethane fixed to the outer peripheral surface of a rotary shaft (not shown) rotatably supported between both side walls of the developing housing 30. The supply roller 34 is pressed against the developing roller 32. The stirring means 36 is composed of a stirring member fixed to a rotating shaft (neither is shown) rotatably supported between both side walls of the developing housing 30.

The support shafts 14 are fixed so as to project laterally outward from a pair of support members formed so as to extend downward from the bottoms of both side walls of the developing housing 30. Each of the support shafts 14 is arranged so as to have a common axis. The distance between the support arms 20 of the drum unit 12 is larger than the distance between the side walls of the developing housing 30. Therefore, both side walls of the developing housing 30 are positioned between the support arms 20, and the support shafts 14 are swingably supported by the bearing portions 22 of the corresponding support arms 20. Each of the bearing portions 22 and the support shaft 1
Each of 4 constitutes a support shaft means.

Coil springs 40, which are spring means, are interposed between both side walls of the developing housing 30 and the corresponding side wall members 18 of the drum unit 12. Each coil spring 40 imparts a rotational moment about the support shaft 14 to the developing device 16 so that the developing roller 32 is biased in the direction toward the photosensitive drum 24. As a result, the developing roller 32 is pressed against the photosensitive drum 24.

The axis C of the support shaft 14 is in a full state of the developer accommodated in the developing housing 30 (state of FIG. 2).
Is positioned on the vertical line passing through the moving range of the center of gravity G1 of the developing device 16 and the center of gravity G2 of the developing device 16 in the empty state (not shown) of the developer. In this embodiment, the axis C of the support shaft 14 is positioned on a vertical line passing through substantially the middle of the moving range between the center of gravity G1 and the center of gravity G2.

The process unit 2 configured as described above is detachably mounted on the printer 4, as shown in FIG. That is, the process unit 2 includes the printer 4
The upper part of the cover 10 is opened by rotating the cover 10 around the axis 8 in the counterclockwise direction in FIG. Next, the process unit 2 is mounted in the printer 4 from above. In the printer 4, the drum unit 12 of the process unit 2
There is provided a positioning means (not shown) that can place the device at a predetermined position. By turning the cover 10 of the printer 4 around the axis 8 in the clockwise direction in FIG. 1, the upper side of the cover 10 is closed. A holding member (not shown) is provided in the cover 10 at a position corresponding to each of the grips 23 of the drum unit 12, and when the cover 10 is closed, each holding member has a predetermined upper portion of the grip 23. The drum unit 12 is held in the printer 4 by pressing it with pressure. Each of the handles 23 is made of a synthetic resin having elasticity, and when pressed down by the pressing member of the cover 10, the handles 23 are elastically deformed downward. This allows the drum unit 1
2 is held securely in the printer 4.

As shown in FIG. 1, when the drum unit 12 is mounted in the printer 4, a laser unit 40 is disposed around the photosensitive drum 24, downstream of the charging corona discharger 28. A non-contact type transfer roller 42 is disposed downstream of the developing roller 32. The laser unit 40 is arranged at the bottom of the printer 4.
A paper feed tray 44 on which the transfer paper is placed is provided on the upper left side of the cover 10, and a paper feed roller 46 is provided on the downstream side of the paper feed tray 44 and a paper separating roller is provided at a position facing the paper feed roller 46. Friction pads 48 are provided respectively. A fixing roller pair 50 is arranged downstream of the photosensitive drum 24 and the transfer roller 42, and a discharge roller pair 52 is arranged downstream of the fixing roller pair 50. Discharge roller pair 5
A discharge tray 54 is provided on the downstream side of 2. The rollers provided on the printer 4 side and the rotating members such as the photosensitive drum 24 provided on the process unit 2 side are rotationally driven in directions indicated by arrows by a driving device (not shown). Further, the driving device for each rotating member such as the photosensitive drum 24 provided on the process unit 2 side is connected to and removed from the driving device provided on the printer 4 side by mounting and releasing the process unit 2 on and from the printer 4. Is configured.

In the printer 4 constructed as described above, when the photoconductor drum 24 is rotationally driven by the driving device for printing, the surface photosensitive layer of the photoconductor drum 24 is specified by the charging corona discharger 28. It is charged substantially uniformly in polarity. Next charged photosensitive drum 2
The surface of the photosensitive layer 4 is irradiated with laser light based on print information from a laser unit 40 as an exposure unit that forms an electrostatic latent image, and an electrostatic latent image is formed. Then, the electrostatic latent image formed on the surface of the photosensitive layer of the photosensitive drum 24 is transferred to the developing device 1.
6 develops a toner image. On the other hand, paper feed tray 4
The transfer papers placed on the sheet 4 are fed one by one by the action of the paper feed roller 46 and the friction pad 48. Then, the transfer sheet is conveyed between the photoconductor drum 24 and the transfer roller 42 through the guide path 56, and the toner image attached to the photoconductor drum 24 is transferred to the surface thereof. The transfer sheet on which the toner image is transferred passes through the guide path 58 and the fixing roller pair 50.
Transported to The transfer paper on which the toner image is heated and fixed by the fixing roller pair 50 is discharged onto the discharge tray 54 by the discharge roller pair 52.

By printing approximately a predetermined number of transfer sheets by the printer 4, the toner amount in the developing housing 30 changes from the full state to the empty state.
With the decrease in the toner amount, the center of gravity of the developing device 16 and the rotation moment of the developing device 16 around the support shaft 14 change. However, the axis C of the support shaft 14 passes within the range of movement of the center of gravity between the center of gravity G1 of the developing device 16 when the developer in the developing housing 30 is full and the center of gravity G2 of the developing device 16 when the developer is empty. Since it is positioned on the vertical line, the photosensitive drum 24 and the developing roller 32 are irrespective of the change in the toner amount.
It is possible to suppress a small change in the pressure contact force between the photosensitive drum 24 and the developing roller 32 and stabilize the pressure contact force between the photosensitive drum 24 and the developing roller 32. As a result, it is possible to reduce the change in the amount of toner supplied from the developing roller 32 to the photosensitive drum 24, regardless of the change in the amount of toner, so that stable image formation is always performed. In addition, in this embodiment, the axis C of the support shaft 14 is positioned on the vertical line passing through substantially the middle of the moving range between the center of gravity G1 and the center of gravity G2. The range of change can be reduced.

When the axis C of the support shaft 14 is positioned on the vertical line passing through the center of gravity G1 of the developing device 16 in the full state of the toner accommodated in the developing housing 30,
As the toner amount in the developing housing 30 changes from the full state to the empty state, the center of gravity G1 of the developing device 16 becomes G.
When the developing device 16 moves to 2, the rotation moment of the developing device 16 around the support shaft 14 increases, but this change is offset by the decrease in the weight of the developing device 16 itself. As a result, it is possible to reduce the change in the amount of toner supplied from the developing roller 32 to the photosensitive drum 24, regardless of the change in the amount of toner, so that stable image formation is always performed.

As described above, the support shaft 14 is arranged below the bottom of the developing housing 30. Therefore, since the drum unit 12 and the developing device 14 can be assembled without directing the developing roller 32 downward, it is possible to prevent the toner from falling and the surroundings from being contaminated. Further, since the support shaft 14 is positioned on the lower side, the handling is good and the assemblability is improved.

Although the embodiment of the process unit according to the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various modifications or modifications can be made without departing from the scope of the present invention. Is.

[0028]

According to the process unit constructed in accordance with the present invention, the pressure contact force between the photosensitive drum and the developing roller can be stabilized regardless of the change in the amount of toner contained in the developing housing. Further, when the drum unit and the developing device are assembled, it is possible to easily assemble them while preventing the toner from dropping.

[Brief description of drawings]

FIG. 1 is a front view schematically showing a printer equipped with an embodiment of a process unit configured according to the present invention.

FIG. 2 is a schematic front view of the process unit shown in FIG.

[Explanation of symbols]

2 Printer 4 Process Unit 6 Main Body 10 Cover 12 Drum Unit 14 Support Shaft 16 Developer 24 Photoreceptor Drum 30 Developing Housing 32 Developing Roller 40 Laser Unit 42 Transfer Roller G1 Center of Gravity of Developing Device 16 in Full State of Developer G2 Developer Empty Center of gravity of the developing device 16 in the state C Axial center of the support shaft 14

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukishi Terada 1-2-2, Tamatsukuri, Chuo-ku, Osaka City Mita Engineering Co., Ltd. (72) Hiromitsu Ogawa 1-228 Tamatsukuri, Chuo-ku, Osaka City Within Mita Engineering Co., Ltd.

Claims (3)

[Claims] 1. A process unit detachably attached to an image forming apparatus, the drum unit including a photosensitive drum on which an electrostatic latent image is formed, a developing housing containing a developer, and the developing housing. A developing device having a developing roller disposed therein for supplying a developer to the photosensitive drum, a supporting shaft means for supporting the developing device so as to be swingable with respect to the drum unit, the developing device and the drum unit And a spring means which is interposed between the developing roller and the developing roller so as to bias the developing roller in the direction toward the photosensitive drum, and which applies a rotational moment to the developing device about the supporting shaft means. The axis of the means is a lead passing through the center of gravity of the developing device in the full state of the developer contained in the developing housing and the moving range of the center of gravity between the center of gravity of the developing device in the empty state of the developer. Positioned on the line, the process unit, characterized in that. 2. A process unit detachably mounted on an image forming apparatus, the drum unit including a photosensitive drum on which an electrostatic latent image is formed, a developing housing containing a developer, and the developing housing. A developing device having a developing roller disposed therein for supplying a developer to the photosensitive drum, a supporting shaft means for supporting the developing device so as to be swingable with respect to the drum unit, the developing device and the drum unit And a spring means which is interposed between the developing roller and the developing roller so as to bias the developing roller in the direction toward the photosensitive drum, and which applies a rotational moment to the developing device about the supporting shaft means. A process unit, wherein the axis of the means is positioned on a vertical line passing through the center of gravity of the developing device in the full state of the developer accommodated in the developing housing. 3. A process unit detachably attached to an image generating apparatus, the drum unit including a photosensitive drum on which an electrostatic latent image is formed, a developing housing containing a developer, and the developing housing. A developing device having a developing roller disposed therein for supplying a developer to the photosensitive drum, a supporting shaft means for supporting the developing device so as to be swingable with respect to the drum unit, the developing device and the drum unit And a spring means which is interposed between the developing roller and the developing roller so as to bias the developing roller in the direction toward the photosensitive drum, and which applies a rotational moment to the developing device about the supporting shaft means. A process unit, wherein the means is disposed below a bottom portion of the developing housing.