JPH02173774A - Image forming device - Google Patents

Abstract

PURPOSE:To keep the contacting state of a developing roller with a photosensitive body uniform and to accomplish an excellent developing action by allowing the developing roller to transmit the driving of rotation through a belt body stretched in a direction orthogonal to the reciprocating moving direction of a developing device and an intermediate rotor. CONSTITUTION:This device is provided with a supporting frame 10 which is mounted on a device main body side so as to freely reciprocate and fixes the developing device 2 in an immobile state, the intermediate rotor 25 which is supported on the supporting frame 10 side so as to constitute a rotation driving transmission mechanism and the belt body 27 stretched between the output part of a rotation driving source and the intermediate rotor 25 so that it may extend in the direction orthogonal to the reciprocating moving direction of the supporting frame 10. Therefore, driving component force which changes the contacting state of the developing roller 4 with the photosensitive body 1 is not generated from the belt body 27 in a driving state. The driving component force generated in the stretching direction of the belt body 27 is supported by the supporting frame 10 side through the intermediate rotor 25 and is not transmitted to the developing device 2 side. Thus, the contacting state of the developing roller 4 with the photosensitive body 1 is kept uniform.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an image forming system in which a developing device is installed so as to be movable back and forth so as to be close to and separated from a photoreceptor to perform contact development. Regarding equipment.

[Prior Art] In various image forming apparatuses such as copying machines, printers, and facsimile machines, the surface of a photoreceptor drum that is transported in a certain direction is uniformly charged (charging process), and this -like charging Exposure is performed on the photoreceptor drum to form an electrostatic latent image (n-light process), and toner is supplied from a developing device to the electrostatic latent image to develop the electrostatic latent image ( Development process) A visible image is obtained. This obtained visible image is copied onto recording paper (
(transfer step), thereby forming the final image.

The developing device that performs the above-mentioned developing process is provided with a developing roller that serves as a developer carrier that transports the developer stored in the device to a developing area while holding it in a layered manner.

In a developing device that employs a contact development method, the developing roller is placed in contact with the photoreceptor under constant pressure, and the toner transfer development operation is performed under constant pressure. ing.

However, in the contact development method described above, it is extremely important to maintain uniform contact between the photoreceptor and the developing roller in order to obtain a homogeneous image. That is, Fig. 4 (a), (b)
) and (C), if the developing roller's pressure is weak and causes poor contact, image dropouts and density unevenness are likely to occur, and if the developing roller's pressure is too strong, it will cause background stains. This tends to occur, and the amount of wear on the photoreceptor, especially the organic photoreceptor (OPC), increases, which greatly affects the life of the photoreceptor.

[Problems to be Solved by the Invention] As a means for maintaining a constant pressure force on a developing roller, there is a device described in, for example, Japanese Patent Laid-Open No. 61-290457. In this device, the point of action of the driving force from the rotating body (gear) on the driving side of the developing roller is set near the fulcrum of the developing device so that unnecessary rotational moment is not applied to the developing device. However, this device has a problem in that, on the input side of the driving force, a component force is generated in the direction in which the developing roller presses the photoreceptor or the developing roller is separated from the photoreceptor. Furthermore, JP-A-6
In the device described in Publication No. 3-146077, a floating rotating body such as a developing roller is arranged so as to be able to approach or separate from a fixed rotating body such as a photoreceptor that is pivotally supported at a predetermined position of the main body. The rotational driving force is transmitted through a coupling means such as an Oldham coupling. However, if the driving torque of the developing roller is large or if there is a large axial misalignment between the developing roller and the coupling means, a component force will be generated that changes the contact state between the developing roller and the photoreceptor, making it impossible to completely solve the problem. It has not become a means.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that can maintain a more even contact state between a developing roller and a photoreceptor in a contact developing method.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides that the developing device is placed close to the photoreceptor so that the developing roller provided in the developing device comes into contact with the photoreceptor. It is installed so as to be able to reciprocate in the direction of separation, and a predetermined rotational drive is transmitted from the output part of the rotational drive source provided on the device main body side 4! In the image forming apparatus, the rotational driving force is transmitted to the developing roller through a support frame, which is attached to the main body of the apparatus so as to be movable back and forth and fixes the developing unit in an immovable state; an intermediate rotary body supported by the support frame to form a drive transmission mechanism; and an output portion of the rotary drive source extending in a direction orthogonal to the reciprocating direction of the support frame. The belt body is stretched between the intermediate rotating body and the intermediate rotating body.

[Function] In the means having such a configuration, first, the belt member constituting the rotational drive transmission mechanism is extended in a direction perpendicular to the reciprocating direction of the support frame, that is, the reciprocating direction of the developing unit. Since the belt member is stretched, a driving force that changes the contact state between the developing roller and the photoreceptor is not generated from the belt member in the driving state.

In addition, the driving force generated in the tensioning direction of the belt body, which is a direction perpendicular to the direction of reciprocating movement of the developing device, is supported by the support frame via the intermediate rotating body, and therefore the driving force generated by the developing device is It is no longer transmitted.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

As shown in FIGS. 1 and 2, a photosensitive drum 1
A developing device 2 is arranged near the. A developing roller 4 serving as a developer carrier is pivotally supported within the developing casing 3 of the developing device 2. The developing roller 4 is provided so that a portion of the surface of the developing roller 4 is exposed through the opening of the developing casing 3, and the exposed surface portion is placed on the surface of the photoreceptor drum 1 at a predetermined location. It is designed to be contacted with a pressure of . Further, on the surface of the developing roller 4, there is a toner supply roller 5 that pumps up the toner stored in the developing casing 3 onto the developing roller 4, and a toner regulating roller that forms the toner supplied onto the developing roller 4 into a thin layer. 6 are provided in contact with each other. Further, an agitator 7 is installed in the rear region of the toner supply roller 5 to agitate the accumulated toner.

A front reference pin 8 and a rear reference pin 9 are provided on the front side plate 3a of the developer casing 3 and the rear side plate 3b of the developer casing 3 so as to protrude toward the outside of the developer 2, respectively. On the other hand, a support frame 10 having a substantially U-shaped cross section is disposed above the developing device 2 with its open portion facing toward the developing device 2. Reference holes are formed through both side plate portions of the support frame 10, and the front reference pin 8 and the rear reference pin 9 are inserted into each of these reference holes, respectively. As a result, the entire developing device 2 is immovably fixed at a fixed position on the support frame 1o.

Further, a plurality of support shafts 11 and 12 projecting outward from the support frame 10 are provided upright on the front side plate 10a and the rear side plate 10b, which constitute both sides of the support frame 1o, respectively. And each of these supporting shafts 11.12
Rollers 13 and 14 made of ball bearings are rotatably attached to the protruding tip portions of the rollers 13 and 14, respectively. On the other hand, the main body front side plate 15 and the main body rear side plate 16 are attached to the main body base 1 so as to sandwich the support frame 1o from both the front side and the back side.
7 with a certain precision. A front guide rail 18 and a rear guide rail 19 each having an opening-shaped cross section are provided at the upper portions of the inner facing surfaces of the main body front side plate 13 and the main body rear side plate 14, with their open portions facing toward the support frame 10. They are mounted so that they face each other. These front guide rail 18 and rear guide rail 1
The rollers 13 and 14 are rotatably mounted on each inner bottom wall surface of the roller 9. Roller 1 next to the support frame 10
3 and 14, the entire developing device 2 is supported so as to be movable back and forth in the horizontal direction so as to approach and move away from the photosensitive drum 1.

At the rear end of the support frame 10 (right end in FIG. 2),
A pressure spring 20 is attached to press the developing device 2 against the photosensitive drum 1. The biasing force of the pressure spring 2o causes the developing roller 4 of the developing device 2 to come into contact with the surface of the photosensitive drum 1 with a predetermined pressure.

Further, as shown in FIG. 3, the main body rear side plate 16
A drive motor 21 is fixed to the lower part of the
A motor pulley 22 is attached to the output shaft 21a of the drive motor 21. In addition, the support frame 1
An intermediate bearing 23 is mounted on the rear side plate 10b of 0,
An intermediate drive shaft 24 is rotatably supported through the intermediate bearing 23 so as to pass therethrough. Further, an intermediate pulley 25 and a driving gear 26 are fixed to both end portions of the intermediate shaft drive shaft 24, respectively. Above intermediate pulley 25
is arranged directly above the motor pulley 22, and these intermediate pulleys 25 and motor pulley 22
A drive belt 27 is stretched between the two. The drive belt 27 is stretched so as to extend in the vertical direction, and is oriented in a direction perpendicular to the horizontal direction, which is the reciprocating direction of the developing device 2 described above.

Furthermore, the developing gear 28 meshed with the driving gear 26 is fixed to the support shaft 4a of the developing roller 4, thereby completing a rotational drive transmission mechanism, and the developing roller 4 is rotationally driven from the driving motor 21. power is transmitted.

In the apparatus in such an embodiment, first, the frame 10 (supported by the moving belt 27) constituting the rotational drive transmission mechanism is
Since the rack is stretched so as to extend in a direction perpendicular to the reciprocating direction of the developing device 2, that is, the reciprocating direction of the developing device 2,
The driving component force that changes the contact state between the developing roller 4 and the photosensitive drum 1 when the driving belt 27 is driven is much smaller than that in the case of using conventional gear means and compressing means. That is, when the amount of positional deviation that occurs in conventional gears and couplings is E, and the outer diameter of the gear or coupling is d, the drive that causes the developing roller 4 to act so that the photoreceptor drum l presses against or separates from the photoreceptor drum b. The component force will change corresponding to ε/d. On the other hand, the rotating belt 27 having the above-mentioned arrangement corresponds to an extremely large apparent d, and therefore, in this case, the driving force corresponding to the above-mentioned ε/d can be almost ignored.

Further, the driving force in the stretching direction of the drive belt 27, that is, the direction perpendicular to the reciprocating direction of the developing device 2, is transmitted to the support frame 10 via the intermediate pulley 25, the intermediate drive shaft 24, and the intermediate bearing 23. Supported. Therefore, the driving force in this case is hardly transmitted to the developing unit 2 and can be ignored.

When the apparatus according to this embodiment was tested, almost no effect was found due to the driving of the developing roller 4, and the contact pressure between the photosensitive drum 1 and the developing roller 4 maintained a uniform distribution in the axial direction of the roller. It was confirmed that the developing operation was performed while It was also confirmed that high-quality images could be obtained with almost no image omissions, image density differences, or background stains due to pressure deviation of the developing roller 4.

Further, the developing device 2 in this embodiment is positioned beside the support frame 10 by a front reference pin 8 and a rear reference pin 9. Therefore, parallelism of the developing device 2 with respect to the photoreceptor drum 1 can be easily achieved, and the front reference pin 8 and the rear reference pin 9 can be connected to the support frame 1o.
The entire developing unit 2 can be easily and accurately attached and detached by pulling it out from the reference hole in the sidewall or attaching it again. Therefore, it is convenient when performing maintenance, replenishing toner, or changing the color of toner. Further, according to this embodiment, there is no need to provide a motor exclusively for the developing unit, and a small and low-cost image forming apparatus can be obtained.

[Effects of the Invention] As described above, the present invention eliminates the generation of the developing roller driving force in the direction of the photoreceptor, and also prevents the driving force in the orthogonal direction from being transmitted to the developing device. The developing device is attached to the apparatus main body through a support frame that is reciprocally movable, and is supported by a belt body stretched in a direction orthogonal to the reciprocating direction of the developing device and the support frame. Since the rotational drive is transmitted to the developing roller via the intermediate rotary body, it is possible to eliminate the influence on the contact state based on the driving force of the developing roller in the contact developing method, and the relationship between the developing roller and the photoconductor can be eliminated. It is possible to maintain a more even contact state and perform a good developing operation.

[Brief explanation of the drawing]

1 and 2 are a front explanatory view and a side explanatory view showing a support and drive mechanism for a developing device in an embodiment of the present invention, and FIG. 3 is a side view corresponding to FIG. 2 showing a state in which the developing device is removed. Explanatory diagram, FIG. 4(a). (b) and (C) are diagrams showing the relationship between the pressing force of the developing roller and the state of the formed image in contact development. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Developing device, 4... Developing roller 10... Support frame, 18... Front guide rail, 19... Rear guide rail, 25... Intermediate pulley 27 ...Active movement belt. Chi7 2 squares 4 squares

Claims (1)

[Scope of Claims] The developing device is installed so that it can freely reciprocate toward and away from the photoreceptor so that a developing roller provided in the developer comes into contact with the photoreceptor, and In an image forming apparatus configured to transmit rotational driving force to the developing roller from an output part of a rotational drive source provided on the apparatus main body side via a predetermined rotational drive transmission mechanism, the image forming apparatus is capable of reciprocating to the apparatus main body side. a support frame that is attached to the support frame and fixes the developing device in an immovable state; an intermediate rotating body that is supported by the support frame so as to constitute the rotational drive transmission mechanism; An image forming apparatus comprising: a belt stretched between the output section of the rotational drive source and the intermediate rotating body so as to extend in orthogonal directions.