JPS63163380A - Image forming device - Google Patents

Abstract

PURPOSE:To improve prevention effects for toner sticking on dustproof glass by using an electrode for toner scatter prevention and air flow generating means together. CONSTITUTION:The electrode 11 which produces an electric field in a constant range on the surface of the photosensitive body 5 of an image exposing device 6 is provided between the dustproof glass 4 and photosensitive body 5, so when toner is charged electrostatically to the negative polarity, such a voltage that the potential of the electrode 11 becomes lower than the potential of the photosensitive body 5 is applied to suppress the scattering of the toner and attract toner which is already scattered back to the surface of the photosensitive body 5 again. Further, air flow generating means 15 and 16 are provided and an air flow 17 is generated in the gap between the electrode 11 and the surface of the photosensitive body 5 to move much toner which is scattered at an exposed part and present on and nearby an optical path to a downstream side. Consequently, the effect which prevents the scattered toner from sticking on the dustproof glass 4 is improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention forms a multicolor toner image on the surface of a photoreceptor by repeating a series of steps of uniform charging, image exposure, and development multiple times on the photoreceptor. The present invention relates to an improvement in a means for preventing scattering of toner caused by image exposure of the second and subsequent colors in an image forming apparatus and a phenomenon in which the scattered toner adheres to the dust-proof glass of the image exposing apparatus.

(Conventional branch) In an image forming apparatus that repeats the steps of uniform charging, image exposure, and development multiple times on a photoconductor to form a plurality of color toner images overlappingly, and transfers this to a transfer material, The surface of the photoreceptor that has been developed for the first color is uniformly charged again by a charger, and then image exposure is performed using an image signal corresponding to the second color, and the latent image thus formed is transferred to the toner for the second color. Using the accommodated developing device, a second color toner image is formed so as to be superimposed on the surface of the photoreceptor on which a first color toner image has already been formed. Thereafter, when there is a third color and a fourth color, the same process is repeated to form toner images of each color so as to overlap each other.

After a superimposed toner image of a preset color is thus formed, this is transferred to a transfer material to form a color image.

As mentioned above, in a multiple toner image forming process in which charging, exposure, and development are repeated many times, the toner image formed in the first process (after charging, if there is exposure near the image, the Since the electric field distribution changes rapidly, the toner scatters due to the repulsive force between the toner particles and adheres to the area where the Coulomb force acts.This tendency is particularly noticeable in the case of reversal development.

FIG. 3 is an explanatory diagram of causes of toner scattering.

The vertical axis in FIGS. 3(a) to 3(e) indicates the negative potential of the surface of the photoreceptor. In the following description, uniform charging is assumed to be negative charging. ), the horizontal axis indicates the position of the photoreceptor surface. Figure (a) shows a state in which the surface of the photoreceptor is uniformly charged to a potential of -E volts by a charger.

Figure (b) shows that the area of the photoreceptor shown by is exposed to light, and the potential of that area becomes close to 0 volts. Figure (c) shows that when the exposed portion of the photoconductor passes through the developing device, negatively charged toner is transferred from the developing sleeve, which has approximately the same potential as the uniformly charged potential of the photoconductor, to the exposed portion of the photoconductor. It shows a state in which the particles fly toward the exposed area, adhere to the exposed area, and are developed. The surface of the photoreceptor on which the first color toner image is thus formed is uniformly charged for the second time by a charger while the toner image is still formed.

Figure (d) shows the potential during the second uniform charging.

Next, image exposure is performed using an image signal corresponding to the second color. In FIG.
In other words, the potential of the L' portion is higher than that of the L portion.

By the way, each toner particle of the first color toner image adheres to the surface of the photoreceptor due to Coulomb force between it and the photoreceptor, but since the toner particles are charged with the same polarity, they are not electrically charged. has a repulsive force acting on it. On the other hand, since toner particles are negatively charged, if there is a location where the potential is higher than the current location, a force acts to move the toner particles toward the higher potential along the direction of the electric field formed there. If the force used to move the toner is greater, the toner will fly out in the direction of higher potential.

Figure (f) is a diagram showing a situation where a part of the toner adhering to the area where the potential is -E volts tries to move to the area L' where the potential is close to 0 volts and scatters.

In this way, if toner scatters when image exposure corresponding to the next color is performed on a photoconductor on which a toner image has previously been formed, some of the scattered toner will adhere to the dust-proof glass in the image exposure device. As a result, there is a problem that the transmittance of the imagewise exposure light is lowered or unevenness is caused.

FIG. 4 is a diagram showing a situation in which scattered toner adheres to the dustproof glass. That is, when the toner 7 of the toner image formed on the surface of the photoreceptor 5 is exposed to the image by the laser beam 3, a part of the toner scattered as shown in the figure is transferred to the frame 8.
or even reach the dustproof glass 4 and adhere thereto.

In this way, there is a problem in that not only the interior of the machine gets dirty, but also the toner adhering to the dustproof glass prevents the laser beam 3 from passing through.

As a means to solve this problem, there is a method of suctioning the scattered toner using an air current, or a method of using a toner scattering prevention electrode, which is currently being applied for by the applicant of the present application (Japanese Patent Application No. 61-255336).

FIG. 5 is a diagram showing an example of a means configuration using the toner scattering prevention electrode. In this example, a slit electrode 9 having a slit 14 is provided as a toner scattering prevention electrode. By applying a larger voltage, an electric field is formed between the photoreceptor 5 and the surface of the photoreceptor 5 to suppress toner scattering. This electric field suppresses toner scattering, and when a voltage whose absolute value is larger than the absolute value of the charged potential of the photoconductor 5 is applied, a force is generated to pull the scattered toner back toward the photoconductor 5. acts.

Further, since the slit 14 is a narrow passage, there is an effect that scattered toner is difficult to reach the dustproof glass 4.

(Problem to be Solved by the Invention) However, the method of suctioning scattered toner using airflow requires special fans, ducts, filters, etc. to be effective, and generates noise. There are problems such as the problem of increasing the size of the equipment, and the problem of increasing costs.

Further, in the case of using a toner scattering electrode, the slit 14 of the slit electrode 9 is located just above the area where the largest amount of toner scatters due to image exposure.

However, since this slit 14 is where the electrode is cut, it is where the electric field strength is the weakest. In the end, the most amount of toner is scattered where the force that tries to pull the scattered toner back toward the photoreceptor 5 is the weakest, so it is not possible to completely prevent the scattered toner from entering into the slit 14. There is a problem.

The purpose of the present invention is to use both of the above means in combination.
To provide an image forming apparatus which solves the problems of each means and can form high-quality images without causing scattered toner to adhere to the dust-proof glass of an image exposure device and without causing a decrease in exposure amount or uneven exposure. There is a particular thing.

(Means for Solving the Problems) The present invention has the following means configuration to achieve the above object. That is, the image forming apparatus of the present invention is an image forming apparatus that forms a multicolor toner image on the surface of a photoreceptor by repeating a series of steps of uniform charging, image exposure, and development multiple times on the photoreceptor. , has an electrode (referred to as a toner scattering prevention electrode) that forms an electric field between the dust-proof glass of the image exposure device and the photoreceptor and a certain range of the photoreceptor surface, and a gap between the electrode and the photoreceptor surface. The image forming apparatus is characterized in that it has an airflow generating means that generates an airflow.

(Function) The image forming apparatus of the present invention has an electrode between the dust-proof glass of the image exposure device and the photoreceptor, which forms an electric field between a certain range of the surface of the photoreceptor. Depending on the charging polarity of the toner, for example, when the toner is negatively charged, by applying a voltage that makes the potential of the electrode lower than the potential of the photoreceptor, an electric field is formed in the direction from the photoreceptor to the electrode, resulting in toner scattering. At the same time, the toner that has once been scattered is also subjected to a force that pulls it back toward the surface of the photoreceptor.

When the toner is positively charged, by applying a voltage that makes the potential of the electrode higher than the potential of the photoreceptor, toner scattering is suppressed and the scattered toner is pulled back. As a result, an air current is generated in the gap between the electrode and the surface of the photoconductor, and the scattered toner, which is scattered in the exposed area and is present in large quantities in the optical path and its vicinity, is moved to the downstream side of the air current. By removing a large portion of the scattered toner from the optical path and its vicinity in this way, the effect of preventing the scattered toner from reaching and adhering to the dustproof glass can be greatly improved.

As described above, in the image forming apparatus of the present invention, toner scattering is suppressed using the toner scattering prevention electrode, and while the scattered toner is directed toward the surface of the photoreceptor, the areas with high density of the scattered toner are Since the air current is used to move the scattered toner from the optical path and its vicinity, it is sufficient to use a small-scale air flow generating means compared to the case where the scattered toner is sucked and collected using the air current alone. However, problems such as noise, large size, and high cost do not arise.

(Example) Hereinafter, an example of the image forming apparatus of the present invention will be described based on the drawings. FIG. 1 is a diagram showing the configuration of main parts of an embodiment of an image forming apparatus according to the present invention.

A conductive electrode member 11, which is an electrode for forming an electric field (toner scattering prevention electrode), is provided between the dust-proof glass 4 and the photoreceptor 5 of the image exposure device 6, and is held by a resin slit member 10. A duct 15 and a fan 16 are provided as airflow generating means for generating an airflow 17 in the gap between the conductive electrode member 11 and the photoreceptor 5.

Toner scattering due to imagewise exposure occurs most strongly at the currently exposed portion (exposure point a) on the photoreceptor.

Naturally, no electrode can be provided directly above this portion because of the optical path of the image exposure light.

That is, since there is no electrode at a position corresponding to the part where toner scattering is most intense, the electric field in this part is weak and the toner that has reached the opening of the slit 14 cannot be sufficiently prevented from entering the slit 14 by the electric field alone. Hard to stop.

In this embodiment, a duct 15 and a fan 16 are provided to increase the air flow.
7, the toner scattered from the exposure point a is not directed toward the opening of the slit 14, but directed downstream (to the right in the figure).

That is, the peak point of the amount of toner scattering is removed from the opening of the slit 14. In this case, even if the scattered toner is not sucked into the duct 15, it is possible to sufficiently prevent the scattered toner from reaching and adhering to the dustproof glass. The airflow generation means may be considerably smaller than the airflow generation means used when the airflow is sucked by the airflow.

FIG. 2 shows an apparatus configuration as shown in FIG. 1, in which the width of the slit 14 is 2IIm, the distance between the conductive electrode member 11 and the surface of the photoreceptor 5 is 5III11, and the potential of the photoreceptor is -470m.
V, the potential of the conductive electrode member 11 is -500■, the duct 1
5 opening is 350mm x 10mm, fan motor output is I
In Figure 0, which is a diagram showing the toner scattering distribution situation when the flow velocity is 0.4+a/S or more in OW, the vertical axis indicates the amount of scattered toner below the conductive electrode member 11, and the horizontal axis indicates the amount of toner scattered under the conductive electrode member 11. Point a on the horizontal axis, which indicates the position on the body in the rotational direction, indicates the exposure position. The upper part of the figure shows the positions of the electrode members. The solid line curve shows the toner scattering situation when there is no electrode member or airflow, and the dotted line curve shows the situation when the potential of the electrode member is -500
In the case of (2), it is shown that the amount of toner scattering is suppressed.

The curve represented by a series of O marks is for the case of only airflow, and the solid curve is in a state where it is almost parallel to the downstream direction of the airflow. The curve represented by a series of X marks is the state when the potential of the electrode member is -300V and an airflow of 0.4■/S or more is generated, and the dotted line curve is almost parallel to the downstream direction of the airflow. The situation is as follows.

This shows that the peak position of the amount of toner scattering can be moved away from the slit opening due to the airflow.

(Effects of the Invention) As explained above, in the image forming apparatus of the present invention, the amount of scattered toner itself is suppressed and the peak point of the amount of scattered toner is is removed from the optical path space, so
It has the advantage of being able to prevent toner from adhering to the dust-proof glass, which cannot be achieved with either method alone, and as a result, it is possible to form high-quality images without lowering the exposure amount or causing uneven exposure. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main components of an embodiment of the device of the present invention;
Figure 2 is a diagram explaining the influence of electrodes and airflow on toner scattering, Figure 3 is a diagram explaining the causes of toner scattering, Figure 4 is a diagram explaining the situation of toner scattering, and Figure 5 is an example of a configuration using a toner scattering prevention electrode. This is a diagram. 1... Charger, 2... Mirror, 3
...Laser light, 4...Dust-proof glass,
5... Photoreceptor, 6... Image exposure device,
7... Toner, 8... Frame, 9
...... Slit electrode, 10... Resin slit member, 11... Conductive electrode member, 1
2...Rail, 13...Groove, 14
...Slit, 15...Duct,
16...Fan, 17...Airflow,
a...Exposure point. Agent: Patent Attorney Yoshihiro Yahata No. 1 Illustration rate 2 Figure 4 shows 1-2 Figure 3

Claims (1)

[Claims] An image forming apparatus that forms a multicolor toner image on the surface of a photoreceptor by repeating a series of steps of uniform charging, image exposure, and development multiple times on the photoreceptor, and includes a dust-proof glass of the image exposure device and a photoreceptor. Image formation characterized by having an electrode that forms an electric field between the body and a certain range of the surface of the photoreceptor, and an airflow generating means that generates an airflow in the gap between the electrode and the surface of the photoreceptor. Device.