JP3084128B2 - Electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus which can be used as a printer or a facsimile, and more particularly, to effectively utilize a reversal development method to prevent toner contamination of an LED head and other exposure heads for a long time. The present invention relates to an electrophotographic apparatus capable of forming a clear image over a wide range.

[0002]

2. Description of the Related Art Conventionally, an exposure image corresponding to image information is formed on a uniformly charged photosensitive drum using an LED head or other linear exposure head, and then a toner is applied to the exposure image from a developing sleeve side. Printers and facsimile machines which are configured to allow the toner image to be adhered and then transferred to a plain paper or other recording material guided to a transfer position via a registration roller are known. In the LED head constituting the exposure head, a selfoc lens array made of glass or resin is arranged on the front surface of a head array in which LED chips are arranged in a row, and these are integrally formed by a resin or metal support. It has a holding structure.

[0003]

Now, in the above device,
Cells in order to perform development while rotating the developing sleeve in the current image unit, the floating toner and toner scattering easily occurs, whereas exposure head adjacent to the developing sleeve is positioned on the side, especially facing the photosensitive drum Since the Fock lens array is formed of a material having a different charging sequence from that of the toner, the toner easily adheres to the lens array electrostatically. If the toner adheres to the front surface (output surface) of the lens array, Affects image quality.

[0004] Therefore, in the conventional apparatus, there is a problem that the cleaning of the exposure head is required periodically, and the maintenance work is complicated. For this reason, in the electrophotographic apparatus, it is difficult to achieve free maintenance. For this reason, for example, it has become a major obstacle to spread to individual users on the premise that free maintenance is required by lowering sales costs.

In view of the above-mentioned drawbacks of the prior art, the present invention provides an electrophotograph capable of obtaining a stable image quality without toner adherence to the exit surface of a lens array or the like even after long-term use.
The purpose is to provide a device .

[0006]

In order to achieve the object of the present invention is sensitive light drum on
Unrealized said the corotron wire to a static-the corotron wire
And a charging grid on the side facing the photosensitive drum.
A charging unit having a shield case formed with the front
A linear exposure head for exposing the charged photosensitive drum with a lens array disposed on its surface to form a non-latent image portion corresponding to image information ; and a charge having the same polarity as the charged potential on the photosensitive drum. A developing unit for applying a developer to the non-latent image portion by using a developer injected with the developer, and arranging the exposure head adjacently to the charging unit adjacent to the charging unit without grounding, and at least forming an image. Sometimes the emission surface of the exposure head is configured to be chargeable to the same polarity as the charging potential .
An electrophotographic apparatus.

[0007] The first invention is directed to the photosensitive drum.
In a cross section orthogonal to the axis of
An intersection connecting the extension surface of each of the emergent surface and the exit surface of the lens array.
Point at least the lens array and the shield case.
Position in the space between
It is characterized by being placed. That is, in order to smoothly charge to the same polarity as that of the charging unit at the time of image formation , it is necessary to use FIG.
As shown in (A), the surface of the shield case 43 on which the charging grid 42 is formed and the exit surface 3 of the SELFOC lens 31.
1a, the intersection X connecting the respective extension lines is located on the space between the exposure head 3 and the charging unit 4 or further on the shield case 43 side, so that the charging grid 4
The two surfaces directly face the emission surface 31a or the lens side surface of the SELFOC lens 31, which facilitates smooth charging of the emission surface 31a and the lens side surface.

However, as shown in FIG. 3B, the fact that the intersection X is located outside the lens means that the exit surface 31a of the SELFOC lens does not directly face the charging grid 42, but only faces the side of the shield case 43. Therefore, it is difficult to smoothly charge the emission surface 31a.

In addition, it is close to the shield case.
Electrical conduction between the resin frame and the exposure head,
It is also an effective method according to the first aspect of the present invention to charge both to the same polarity.
It is a step. Further, the present second invention, without taking the configuration of the first invention, were electrically conduction between the sheet Rudokesu the resin frame in proximity to the exposure head, so as to charge both the same polarity arrangement It was done. The electrical continuity can be easily achieved by connecting the shield case or a frame supporting the case and the exposure head with a conductive wire. Further, the third aspect of the present invention provides
Supports LED head array in the head and the lens array
The supporting member is formed of an insulating material.

[0010]

According to the above technical means, the exposure head is substantially in a floating electrode state, and the exit surface of the selfoc lens facing the exposure head, particularly the photosensitive drum, has the same polarity as the toner due to the discharge current from the charging unit side. Thus, even if the floating toner and the scattered toner come close to the lens surface, they repel each other, and the possibility of toner adhesion is greatly reduced. In particular, in the present embodiment, which will be described later, an experimental result was obtained that cleaning was unnecessary even after 300,000 sheets were printed, and as a result, stable image quality was obtained without toner adherence to the exit surface of the lens array even after long-term use. Can be obtained.

Maintaining the same polarity of the exposure head as that of the charging unit makes it difficult for noise or the like to be generated in the signal current in the LED head. In particular, the LED head array and the selfoc lens array in the exposure head are supported. By forming the supporting member made of an insulating material, it is possible to completely prevent noise from being applied to the signal current flowing through the LED head array, which leads to prevention of image distortion and the like. Further, the present invention does not require a special member and can be achieved with a simple layout configuration, so that it is possible to avoid a cost increase and a complicated configuration of the apparatus.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just. FIG.
Is a photosensitive drum unit incorporated in the image forming apparatus according to the embodiment of the present invention. The photosensitive drum 1 including the heater 2 is configured to be rotatable in the direction of an arrow, and a developing sleeve is arranged on the right side in the drawing along the rotating direction. A transfer unit 8 is disposed below the developing unit 10 via a recording paper conveyance path, and a cleaning mechanism 5, an eraser 7 made of an optical fiber, a charging unit 4, And an LED unit 3.

A cleaning mechanism 5 is provided with a cleaning roller 50 and a cleaning blade 51 on the side facing the peripheral surface of the photosensitive drum 1 along the rotation direction thereof, and the peripheral surface and the tip of the blade 51 can be pressed against the drum. And the frame 52 that supports or supports them is substantially
A screw 53 is formed on the back side of the frame 52 and extends in parallel with the drum axis together with the cleaning roller 50. The residual toner scraped off by the cleaning roller 50 and the cleaning blade 51 is removed by the screw 53. send transportable to the collection container side (not shown).

The charging unit 4 is a main body frame ( not shown) on the drum shaft end side (more precisely, a drum unit frame ).
It comprises a corotron wire 41 stretched therebetween , and a metal shield case 43 having a U-shaped cross section and having a charging grid 42 formed on the side surrounding the corotron wire 41 and facing the photosensitive drum 1. The shield case 43 is supported by the main body frame made of an insulating resin at both ends in the axial direction.

On the other hand, the LED unit 3 has a selfoc lens array 31 on the side facing the photosensitive drum 1, an LED chip array 32 in which LED chips are arranged in a line on the incident surface side, and supports these integrally. A support 33 made of insulating resin and a metal lens support frame 34 for holding the lens array 31 in cooperation with the support 33. In the cross section orthogonal to the axis of the photosensitive drum 1 , the selfoc lens array 31 has an intersection X connecting an extension line of the surface on which the charging grid 42 is formed and an output surface of the selfoc lens array 31 with the lens. A
The length and the focal length are set so as to be located on the space between the ray 31 and the shield case 43.

As shown in FIG. 2, the support 33 made of an insulating resin extends at both ends in the longitudinal direction, and a screw mounting hole 35a is formed in the extending portion 35 by screwing. Utilizing LED frame 36 and L
The spaces between the ED heads 3 are fixed with LED mounting screws 37.
The LED mounting screws 37, the head 3 / LED frames coil spring 37a between 36 and also the mounting screw 37 of the tip body frame in the axial direction on both sides of the housing frame 16 from the extended was received surface 17 on inward Contact.

[0017] with this result, adjusting the gap between the main body off <br/> bus and SELFOC lens array of the photosensitive drum which is rotatably supported by the laser beam 31 is made possible by the screw 37 adjusts, via the screw 37 body frame and the LED head 3, even while the LED head 3 and the shield case 43 is able to electrically conduct through the body frame. The present embodiment is further said between body frame which supports the support 33 and the shield case 43 is connected via conductor 39, aiming to further ensure the electrical continuity.

On the other hand, the developing unit 10 carries on the developing sleeve 11 an insulating toner charged to the same potential as the charging potential of the charging unit, in other words, the same potential as the surface potential of the photosensitive drum. The toner is configured to be able to adhere to the non-latent image portion.

Next, the operation of this embodiment will be described. First, a high voltage positive polarity charging voltage is applied to the corotron of the charging unit, and the charging grid 42 is
, A grid voltage having a positive polarity lower than the charging voltage is applied, and the photosensitive drum is uniformly charged. At this time, the L
Since the exit surface side of the SELFOC lens array 31 of the ED head is disposed adjacent to and facing the charging grid 42, a discharge current from the charging grid 42 is applied to the lens array 31 side, and the same as the charging potential. It is charged to a positive polarity. Is the charged, SELFOC lens array 31 and the support 33 also + because of the conductive shield case 43 body frame side and electrically for supporting via lead 39 even while in the resin support 33 side .

As a result, the entire LED head 3 is charged to +. If an image is formed in this state, even if floating toner or toner scattering occurs due to rotation of the developing sleeve, the toner is charged to +. Even if the toner comes close to the LED head 3, the toner repels each other, greatly reducing the possibility of toner adhesion. In this embodiment, no deterioration in image quality due to toner adhesion occurred even after 300,000 sheets were printed. Further, since the LED head 3 is substantially in a floating electrode state, stable image quality can be obtained without toner adhesion even after the image forming operation is stopped.

[0021]

As described above, according to the present invention, a stable image quality can be obtained without toner adherence to the exit surface of the lens array even after long-term use. And so on.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the LED head shown in FIG.

3 (A) and 3 (B) show the positional relationship between intersections connecting extensions of the charging grid forming surface of the shield case and the emission surface of the SELFOC lens, respectively. FIG. 3 (A) shows the present invention, and FIG.
Indicates a comparative example.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor drum 3 LED unit 4 charging unit 10 developing unit 41 corotron wire 42 charging grid 43 shield case 31 selfoc lens array 32 LED chip array 33 support 34 support frame

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/04-15/04 120 G03G 21/00 530-540 B41J 2/44-2/455 H04N 1 / 23-1/31

Claims (4)

(57) [Claims] 1. On a photosensitive drumObiCorotronwa to be electrified
Including earThe photoconductor drum surrounding the corotron wire.
Screen with a charging grid on the side facing the
HaveWith charging unitWith a lens array on the front
ElectrificationLetSaidExposure on photoreceptor drum
A linear exposure head for forming a corresponding non-latent image portion,Said
On the photoconductor drumInjected charge of the same polarity as the charged potential
A developing unit for attaching a developer to the non-latent image portion using an image agent;
And without the grounding of the exposure head
Adjacent to the charging unit and placed close to
At least during image formation, the emission surface of the exposure head is charged with a charging potential.
And chargeable to the same polarity asElectrophotographic equipment, In a cross section orthogonal to the axis of the photosensitive drum,
The charging grid forming surface and the exit surface of the lens array, respectively.
The intersection connecting the extension lines of at least the lens array
In the space between the shield cases or the sea
Located on the case side Electrophotographic equipment characterized by
Place. 2. A resin close to said shield case.
The frame and the exposure head are electrically connected to each other.
The electrophotographic apparatus according to claim 1, wherein the electrophotographic apparatuses are charged to the same polarity . (3)Corotronwa that charges the photosensitive drum
A charging unit including an ear, and a charged photosensitive drum.
To expose a non-latent image area corresponding to the image information
Line-shaped exposure head and charging potential on the photosensitive drum
The non-latent image portion using a developer into which a charge having the same polarity as that of the non-latent image is injected.
And a developing unit for applying a developer to the substrate.
Adjacent to the charging unit without grounding the head
It is placed in close proximity so that it can face each other.
The emission surface of the optical head can be charged to the same polarity as the charging potential
Electrophotographic equipment Close to the shield case surrounding the corotron wire
Between the exposed resin frame and the exposure head.
And both are charged to the same polarity. Electric
Child photographic equipment. (4)Corotronwa that charges the photosensitive drum
And a photoconductor drum surrounding the corotron wire.
Screen with a charging grid on the side facing the
Charging unit with a lens and a lens array on the front
The charged photosensitive drum is exposed to light, and
A linear exposure head for forming a corresponding non-latent image portion,
Injecting a charge of the same polarity as the charged potential on the photoreceptor drum
A developing unit for attaching a developer to the non-latent image portion using an image agent;
And without the grounding of the exposure head
Adjacent to the charging unit and placed close to
At least during image formation, the emission surface of the exposure head is charged with a charging potential.
In an electrophotographic apparatus configured to be chargeable to the same polarity as  An LED head array in the exposure head;SaidLentua
That the support that supports the ray is made of insulating materialFeatures and
DoElectrophotographic equipment.