JP2544078Y2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The invention relates to an electrophotographic image forming apparatus, which is suitable for a printer, a facsimile, a copying machine, and the like of a computer.

[Prior Art] In an image forming apparatus using an electrophotographic process, there is a problem that toner wraps around and attaches to an exposure device such as an LED printer head, a laser head, or a liquid crystal shutter. When the toner adheres, the light output of the exposure device decreases, and the uneven toner output causes uneven light output. For this reason, the adhesion of the toner deteriorates the printing quality.

As a countermeasure against this, Japanese Utility Model Laid-Open No. 61-41,220 discloses a self-focusing lens array (SL
It is proposed to provide a cover around A). FIG. 6 shows such an image forming apparatus. In the figure, 2 is a photosensitive drum, 4 is a charger, 6 is an LED printer head, 8 is a developing device, and 10 is toner. In this technology, LED head 6
An enclosure 12 is provided around to prevent toner 10 from entering.
However, the toner 10 is a very fine particle,
The LED head 6 penetrates through the opening at the tip of the LED 10. Therefore, it is not sufficient as a measure against the adhesion of the toner 10.

[Problem of the Invention] The problem of the present invention is to prevent scattered toner from adhering to the exposure device and improve the printing quality.

[Constitution of the Invention] The image forming apparatus of the present invention is an image forming apparatus in which a photosensitive drum is exposed by irradiating light from an exposure device, and a cover having an opening at a tip portion is attached to the exposure device. Means for maintaining at least a tip portion of the cover at a predetermined potential is provided, and an opening width Wg of the opening is set to a width of mm with respect to a beam width W1 of light from an exposure device, W1 < Wg ≦ W1 + 1, and the gap between the photosensitive drum and the tip of the cover of the exposure device is 1 mm or less.

Here, the toner scattered from the developing device is attracted to the outer surface of the photosensitive drum or the cover using the charge of the toner,
Prevent toner from reaching the opening at the top of the shroud.

[Operation of the Invention] In the invention, a narrow opening is provided by narrowing the tip of the cover to prevent toner from entering through the opening. The width of the opening is larger than the beam width and equal to or less than the beam width + 1 mm. In this invention, the gap between the cover and the photosensitive drum is reduced to 1 mm or less to reduce the amount of toner reaching the opening.

Further, utilizing the fact that the toner is charged, the toner is repelled by an electric field before reaching the opening, or the toner is attracted to a place other than the opening by the electric field, thereby further reducing the amount of the toner reaching the opening. .

[Effects of the Invention] In the invention, the toner scattered from the developing device is prevented from entering the inside of the exposure device, and the printing quality is prevented from being lowered. The aperture is slightly larger than the light beam width,
It also prevents the covering from scattering the beam.

[Embodiment] Figs. 1 to 3 show a first embodiment. In FIG.
Reference numeral 2 denotes a photosensitive drum, 4 denotes a charger, 6 denotes an LED printer head, 8 denotes a developing device, and 10 denotes toner. Instead of the LED printer head 6, a printer head using a liquid crystal shutter may be used. In the embodiment, the toner 10 from the developing device 8 is used.
A case where the LED head 6 is provided outside the photosensitive drum 2, in which scattering is particularly serious, is shown, but the same applies to a case where the LED head 6 is provided inside the photosensitive drum 2. Reference numeral 14 denotes a layer forming member for feeding the toner 10 to the photosensitive drum 2 with a uniform thickness.
Is a collection member for the toner 10, and 18 is a transfer corotron. 20
Is a cover provided at the tip of the LED head 6, 22 is a power supply for the charger 4, and 24 is a power supply for applying a voltage of the same polarity as the toner 10 to the tip of the cover 20.

FIG. 2 shows the cover 20 in an enlarged manner. Inside the LED head 6, there are a light emitting diode array 30 and a self-focusing lens array 32, which are positioned and held by a housing 34. The cover 20 is provided so as to cover the front end of the self-focusing lens array 32, and the front end of the cover 20 has a narrow opening. The cover 20 is provided in two layers of an insulating inner member 36 and a metal tip member 38.
To the power supply 24. The cover 20 may be integrated with the housing 34.

FIG. 3 shows an enlarged view of the opening 40 at the tip of the cover 20. The width Wg of the opening 40 is slightly larger than the beam width W1 of the light from the lens array 32, and specifically, W1 <Wg ≦ W1 + 1 in mm units. This is because if Wg is equal to W1 or Wg is smaller than W1, the light from the lens array 32 will be scattered by the cover 20, and if Wg is larger than W1 by more than 1 mm, the penetration of the toner 10 will be remarkable. Because it becomes. 1m change width of Wg
m is a tolerance (± 0.5m) smaller than 1mm
This is because it is difficult to achieve a tolerance of less than m.

Gap gd between tip member 38 of cover 20 and photosensitive drum 2
Is smaller, the opening between the photosensitive drum 2 and the cover 20 is smaller.
The amount of toner 10 wrapping around 40 decreases. But the gap
It is difficult to make gd too small, and is set to 1 mm or less here. Also, empirically reducing gd from 2mm to 1mm,
The amount of wraparound toner 10 was significantly reduced.

The operation of the embodiment will be described. A part of the toner 10 sent from the developing device 8 scatters and goes around the LED head 6 side. However, the opening width Wg of the opening 40 is such that the beam width W1 has a play of 1 mm or less, and the width of the opening is small, so that the penetration of the toner 10 into the cover 20 is slight. The photosensitive drum 2
The gap gd between the cover 10 and the cover 20 is 1 mm or less, and the toner 10 rarely enters the opening 40 through the gap gd.

If the toner 10 is negatively charged, the voltage -V2 of the power supply 24 is set to, for example, about -800V. The surface potential -V1 of the photosensitive drum 2 is usually about -100 to 500 V, and the surface potential of the photosensitive drum 2 is higher than the potential of the tip member 38. As a result, the negatively charged toner 10 is repelled by the tip member 38 and is drawn to the photosensitive drum 2 side. It is rare that the toner 10 reaches the opening 40 against the electric field in the narrow gap gd, and the contamination of the lens array 32 hardly occurs. Of course, the toner 10 adheres to the photosensitive drum 2 as a result, but the photosensitive drum 2 is for attaching the toner 10 originally, and the adhesion of the scattered toner 10 causes only a slight stain of the image.

FIG. 4 shows a second embodiment. In this embodiment, the covering
A metal member 42 is provided on the side surface and the end of the developing device 8 on the side of 120, and a positive power supply 44 is connected to the metal member 42. As a result,
The scattered toner is collected by the metal member 42, and the amount reaching the opening 40 becomes small.

FIG. 5 shows a third embodiment. In this embodiment, the metal member 42 is grounded, for example. Then, the toner 10 is negatively charged, and the surface potential of the photosensitive drum 2 is negative.
Is attracted to the metal member 42. 4 and 5, the metal member 42 is provided only on the side of the developing device 8, but may be provided on the entire surface of the cover 120.

[Brief description of the drawings]

1 is a configuration diagram of an image forming apparatus according to an embodiment, FIG. 2 is an enlarged cross-sectional view of a main part of the embodiment, FIG. 3 is a cross-sectional view further enlarging a main part of the embodiment, and FIG. 5 is an enlarged sectional view of a main part of the third embodiment, and FIG. 6 is a configuration diagram of a conventional example. In the figure, 2 ... a photosensitive drum, 4 ... a charger, 6 ... a LED printer head, 8 ... a developing device, 10 ... a toner, 20,120 ... a cover, 22,24,44 ... a power supply, 30 ... Light emitting diode array,
32 self-focusing lens array, 34 housing, 36 internal member, 38 tip member, 40 opening, 42 metal member, Wg opening width, W1 beam width
gd …… the gap.

Claims (1)

(57) [Scope of request for utility model registration] An image forming apparatus configured to irradiate a photosensitive drum with light from an exposing device to perform exposure, wherein the exposing device is provided with a cover having an opening at a front end thereof; Means for maintaining the tip at a predetermined potential are provided, and the opening width Wg of the opening is provided.
An image, wherein W1 <Wg ≦ W1 + 1, and the gap between the photosensitive drum and the tip of the cover of the exposure device is 1 mm or less, in mm with respect to the beam width W1 of light from the exposure device. Forming equipment.