JPH08682Y2 - Image forming device developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a developing device such as an electrophotographic copying machine or a printer.

2. Description of the Related Art Developing methods for developing an electrostatic latent image formed on a photosensitive drum are roughly classified into a wet developing method and a dry developing method. Most of the recent copying machines adopt the dry developing method because of the convenience of handling or the developing characteristics, and even in the dry developing method, the developing device can be designed compactly and the solid black reproducibility and gradation reproducibility are excellent. The magnetic brush developing method that is used is becoming the mainstream. In the magnetic brush development method, the non-magnetic sleeve is fixed and the magnet is rotated inside the sleeve, or the non-magnetic sleeve is rotated around the fixed magnet, the developer is conveyed on the sleeve, and the brush is erected. Is a developing method of developing the electrostatic latent image by contacting it with the photosensitive drum.

Since the gap between the photosensitive drum and the developing roll (sleeve) greatly affects the developing characteristics, a tracking roll is rotatably provided on the housing supporting the developing roll.
The gap is kept constant by bringing the tracking roll into contact with the photosensitive drum.

FIG. 3 is a schematic configuration diagram of a conventional developing device. Reference numeral 10 denotes a photoconductor drum, and the photoconductor drum 10 is rotationally driven in the direction of arrow A by a driving means (not shown),
A gear 12 is integrally mounted on the same axis of the photosensitive drum 10.

Reference numeral 14 is a housing of the developing device, and long holes 16, 16 are formed in the housing 14, and the long holes 16, 16 are loosely fitted to support pins 18, 18 formed on a frame of a main body of a copying machine or the like. And is slidably supported. Reference numeral 20 denotes a developing roll. The developing roll 20 is rotatably supported by the housing 14, and tracking rolls 22 are rotatably provided on the shafts at both ends thereof. A gear 24 is integrally attached to the shaft of the developing roll 20. Reference numeral 26 denotes a developer transport mechanism that supplies the developer such as toner stored in the housing 14 to the vicinity of the developing roll 20, and 28
Is a trimming blade that regulates the developer adsorbed on the developing roll 20 to a constant layer thickness.

Reference numeral 30 denotes a spring attached to the frame 32 of the main body of the copying machine or the like, and the spring 30 biases the housing 14 in the direction of arrow B. The tracking roll 22 axially supported by the housing 14 is a photosensitive member. The developing roller 20 and the photosensitive drum 10 face each other at a predetermined gap while being pressed against the drum 10, and the gear 12 of the photosensitive drum 10 and the gear of the developing roller 20 are opposed to each other.
24 meshes with each other, and the rotational force of the photosensitive drum 10 is transmitted to the developing roller 20.

However, the toner stored in the housing 14 is conveyed by the developer conveying mechanism 26 and is rotated by the developing roll.
Adsorbed on 20. The toner adsorbed on the developing roll 20 is
The layer thickness is regulated to a certain amount by the trimming blade 28, and the electrostatic latent image formed on the photoconductor drum 10 is contacted and attracted to the photoconductor drum 10 at the portion facing the photoconductor drum 10. It is supposed to be visualized.

The biasing force of the spring that biases the housing is greater than the force acting in the direction of arrow C in FIG. 3 when the rotational force of the photosensitive drum is transmitted to the developing roll through the gear. It needs to be set large. In particular, in a wide-width machine capable of copying (printing) of A2 size or larger, a large force is required for the rotation of the developing roll, and therefore the biasing force of the spring is considerably large. However, if the biasing force of this spring is large, the force is not transmitted by the gear when the operation is stopped, so that the force does not act in the direction of arrow C, and almost all the biasing force of the spring is applied to the photosensitive drum via the tracking roll. Will work. Therefore, there is a problem in that the pressure contact force between the photoconductor drum and the tracking roll is too large when the rotation of the developing roll is stopped, and the life of the photoconductor drum is shortened due to abrasion. Further, since the spring itself has a large biasing force, there is a problem that the life of the spring is shortened due to plastic deformation or the like.

The present invention has been made in view of these points,
It is an object of the present invention to provide a developing device for an image forming apparatus, which can reduce wear of a photosensitive drum and the like and can perform good development for a long period of time.

Means for Solving the Problems FIG. 1 is an explanatory view of the principle of the present invention. Developing roll 1
And a gear 2 for transmitting power to the developing roll 1 and a tracking roll 4 for bringing the electrostatic latent image carrier 3 and the developing roll 1 into contact with each other with a predetermined gap by abutting against the electrostatic latent image carrier 3. And are supported on the housing 5. The housing 5 is biased by the spring means 6, and the electrostatic latent image carrier 3
The tracking roll 4 is brought into pressure contact with the developing roll 1 and a driving means having a gear 7 meshing with the gear 2 of the housing 5 is provided outside the housing 5 to
Is rotatively driven so that the electrostatic latent image formed on the electrostatic latent image carrier 3 is developed with the toner that stands on the developing roll 1.

The housing 5 is rotatably supported by a shaft 8, and the dimension from the rotation center 8 of the housing 5 to the meshing portion between the gear 2 of the housing 5 and the gear 7 of the driving means is L1, the electrostatic latent image When the dimension up to the pressure contact portion between the carrier 3 and the tracking roll 4 is L2, and the dimension up to the urging portion of the spring means 6 to the housing 5 is L3, L1 <L2 <L3 is configured. Deploy.

Action The rotation moment applied to the housing 5 by the spring means 6 acts on the housing 5 in a direction against the biasing force of the spring means 6 when the driving means transmits the rotation force to the gear 2 of the housing 5. Although it must be larger than the moment, according to the present invention, since L3> L1 is set, the urging force F3 of the spring means 6 can be sufficiently small due to the lever principle.

Further, when the driving by the driving means is stopped, all the rotational moment of the spring means 6 to the housing 5 acts as a pressure on the electrostatic latent image carrier 3 via the tracking roll 4, but L2> L1. Because I am doing
Pressure contact force F2 of the tracking roll 4 to the electrostatic latent image carrier 3
Is smaller than the force F1 that acts on the housing 5 in the direction against the biasing force of the spring means 6 when the rotational force is transmitted to the gear 2 of the housing 5 by the driving means.

In this way, the biasing force of the spring means can be significantly reduced, the plastic deformation of the spring is reduced, and the contact pressure of the tracking roll against the electrostatic latent image carrier is reduced, so that the electrostatic latent image carrier is carried. The life of the body and the spring means can be extended.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a structural explanatory view of a developing device to which the present invention is applied, in which 40 is a photosensitive drum, and the photosensitive drum 40 is rotationally driven in the direction of arrow D by a driving means (not shown). Reference numeral 42 is a housing of the developing device, and the housing 42 is rotatably supported by a shaft 44 on a frame of a main body of a copying machine or the like.

A developing roll 46 is rotatably supported on the housing 42. The developing roll 46 is constructed by rotatably providing a cylindrical non-magnetic sleeve around a fixed magnet, and a gear 50 is integrally attached to the rotary shaft of the sleeve.
Tracking rolls 48 are rotatably provided on the shafts of both ends of the developing roll 46. Reference numeral 52 is an idle gear that is rotatably supported by the housing 42 and is provided so as to mesh with the gear 50.

Reference numeral 54 is a developer supplying means such as toner, 56 is a blender roll for stirring the developer, and 58 is a paddle wheel for transporting the developer frictionally charged by the stirring of the blender roll 54 to the vicinity of the developing roll 46. A trimming blade 60 regulates the developer adsorbed on the surface of the developing roll 46 to a constant layer thickness.

62 is an external drive gear attached to the drive means provided in the main body of the copying machine, and the external drive gear 62 is an idle gear.
Meshed with 52.

Reference numeral 64 is a spring attached to the frame 66 of the main body of the copying machine or the like. The spring 64 urges the housing 42 in the direction of arrow E, and both ends of the developing roll 46 axially supported by the housing 42. The tracking roll 48 provided on the pressure roller is pressed against the photoconductor drum 40, and the developing roll is rotated at a predetermined gap.
46 and the photoconductor drum 40 face each other.

The dimension from the rotation center 44 of the housing 42 to the meshing portion of the idle gear 52 and the external drive gear 62 is L1, the photosensitive drum 40
Let L2 be the dimension up to the pressure contact portion between the tracking roller 48 and the tracking roll 48, and L3 be the dimension up to the urging portion of the housing 42 by the spring 64, and L1 <L2 <L3, respectively.

However, the developer supplied by the developer supply means 54 is triboelectrically charged by the blender roll 56 and then conveyed by the paddle wheel 58 to reach the vicinity of the developing roll 46. The developing roll 46 is rotationally driven in the direction of arrow F by the driving means via the gears 62, 52, 50, and the developer is the developing roll 46.
Is adsorbed on the surface of the photosensitive drum 40, regulated to a constant layer thickness by the trimming blade 60, and reaches the portion facing the photosensitive drum 40. Here, the developer is brought into contact with and adsorbed to the photoconductor drum 40 so that the electrostatic latent image formed on the photoconductor drum 40 is visualized.

According to the present embodiment, the housing 42 is rotatably provided, and the dimension from the rotation center 44 of the housing 42 to the meshing portion of the idle gear 52 and the external drive gear 62 is L
1, L1 <L2 <L3, where L2 is the dimension of the photosensitive drum 40 and the tracking roll 48 to the pressure contact portion and L3 is the dimension of the spring 64 to the urging portion of the housing 42・ It is arranged. Due to the relationship of L3> L1, the housing 42 via the idle gear 52 by the external drive gear 62
Than the force acting in the direction to rotate the counterclockwise direction.
It is possible to reduce the biasing force of 64. Also, L2>
Due to the relationship of L1, the tracking roll 48 and the photosensitive drum 40
Also, the pressure contact force between and is smaller than the force for rotating the housing 42 in the counterclockwise direction by the rotational force transmission from the external drive gear 62 to the idle gear 52.

As a result, the urging force of the spring 64 can be reduced, the plastic deformation of the spring 46 is reduced, the pressing force of the tracking roll 48 to the photosensitive drum 40 is reduced, and the abrasion of the photosensitive drum 40 is reduced. Therefore, the life of the photoconductor drum 40 and the spring 64 can be extended.

Effect of the Invention Since the present invention is configured as described above in detail, the urging force of the spring means for urging the housing can be reduced by the lever principle, and the pressing force of the tracking roll against the electrostatic latent image carrier is also small. Therefore, it is possible to provide the developing device of the image forming apparatus which prevents the spring means and the electrostatic latent image bearing member from being short-lived and can perform good development for a long period of time.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a diagram illustrating the configuration of an embodiment of the present invention, and FIG. 3 is a diagram illustrating the configuration of a conventional technique. 1 ... Developing roll, 2, 7 ... Gear, 3 ... Electrostatic latent image carrier, 4
... tracking roll, 5 ... housing, 6 ... spring means.

Claims (1)

[Scope of utility model registration request] 1. A developing roll, a gear for transmitting power to the developing roll, and a tracking for contacting the electrostatic latent image carrier with the developing roll by abutting against the electrostatic latent image carrier. The roll is supported by the housing, and the housing is biased by spring means to press the tracking roll against the electrostatic latent image carrier, and drive means having a gear meshing with the gear of the housing is provided outside the housing. In the developing device of the image forming apparatus in which the developing roll is driven to rotate, the housing is rotatably supported so that the gear of the housing and the gear of the driving unit mesh with each other from the rotation center of the housing. The dimension up to the part is L1, the dimension up to the pressure contact part between the electrostatic latent image carrier and the tracking roll is L2, and the dimension up to the urging part of the housing by the spring means. The when and L3,
A developing device for an image forming apparatus, which is configured and arranged so that L1 <L2 <L3.