JPH027076A - Image forming device - Google Patents

Abstract

PURPOSE:To completely remove residual stuff generated by corona when an image is formed on a large transfer material and to prevent deterioration in a photosensitive body by changing the driving time of an air discharging means after the electrification by discharging means which forcibly discharges air in an image forming device to the outside of the device according to the size of a transfer material. CONSTITUTION:The title device employs two corona electrifiers i.e., a primary corona electrifier 5 and a transfer electrifier 11. Power is supplyed from one high voltage power source; electrification is simultaneously turned on and off. In the case of discharging by the corona electrifiers, stuff, such as ozon O3 and nitrogen oxide, which is generated by discharging and may deteriorate a photosensitive drum 1, is removed by an air discharging fan 13. The transfer material is detected by a paper feeding sensor 14 provided between paper feeding rollers 9 and resist rollers 10; according to the detected result, by the fan 13's driving starting time t1 and the detection of the leading edge of the transfer material/discharge start t2, the size of the transfer material is detected. The driving time of the fan 13 after the electrification has been completed is changed according to the size of the transfer material, whereby the stuff generated by discharging is effectively removed and a preferable image is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an image forming apparatus, and particularly to an image forming apparatus that applies corona discharge to the surface of a photoreceptor.

"Prior Art" This type of image forming apparatus has a configuration as shown in FIG. In the figure, the photosensitive drum 1 of the image carrier moves in the direction of arrow A in the figure, and the document on the document table 6 is illuminated by the illumination light source 6.
It rotates in synchronization with the optical scanning applied by the scanner, and is uniformly charged by a charger 5 and exposed through a lens 7 to form a latent image of the original image. Next, a developer is applied by the developing device 8, and the latent image is transferred to the visible state by the charging device 11.
A transfer charger 1 is applied to the transfer material sent between the photosensitive drum 1 and the photosensitive drum 1.
The transfer material is transferred by the action of a voltage etc. applied to the photosensitive drum 1, and the transfer material is separated from the photosensitive drum 1 by a separation charger (not shown).
The transfer material is fixed by the fixing device 12 and discharged outside the device. The photosensitive drum 1 further continues to rotate, has its previous history erased by a static eliminator (not shown), and has residual toner removed by an IJ-ning device 2, and is ready for the repeated image forming process. After the final image forming process, only the photosensitive drum 1 idles for a while and then rotates backward).The main motor that drives the photosensitive drum 1, etc. (not shown) stops, and the exhaust fan 16, which had been turned on after the image forming process, stops. It continues to drive, exhausts the internal air, and stops after a considerable amount of time.

The internal air discharge described above prevents the photosensitive drum 1 from deteriorating due to corona 1 discharge products. In this way, the image forming process goes through the processes of uniform charging, exposure, development, transfer separation, static elimination, and cleaning.
Generally, a corona charger is often used to eliminate static electricity, and the area of the photoreceptor to be exposed to light is controlled according to the size of the transfer material. These corona chargers generate discharge products such as ozone O and nitrogen oxides when performing corona discharge, which deteriorates the surface of the photosensitive drum 1. Therefore, the exhaust fan 16 is used to exhaust the air, and discharge products are generated in the exhaust passage. It is equipped with an object capturing filter 4.

However, as electrophotographic apparatuses have become smaller, it has become difficult to exhaust air in or near the primary charger 5 and transfer charger 11 around the photosensitive drum 1, and when the photosensitive drum 1 stops, accumulated discharge products cause the photosensitive drum 1 to This resulted in local deterioration of the photoreceptor layered around the outer periphery. As a countermeasure for this, in the conventional device, 1) the exhaust capacity of the exhaust fan 1S is increased;

2) Only the exhaust fan 13 is driven for a long time after stopping.

etc. were processed.

``Problems to be Solved by the Invention'' However, in an image forming apparatus that controls the area of the photoreceptor to be charged according to the size of the transfer material, when forming an image on a transfer material smaller than the maximum transfer material size, the corona discharge time is Despite the short length, driving the exhaust means for a long time after image formation has the disadvantage of poor power efficiency. Further, there are problems such as noise from the exhaust fan and wear of each bearing.

Therefore, if the drive time of the exhaust fan is set in accordance with the minimum transfer material, residual corona products cannot be removed sufficiently when an image is formed on a large transfer material, resulting in deterioration of the photoreceptor.

"Means for Solving the Problems" The present invention includes a photoreceptor in the apparatus, a corona charger that discharges to the photoreceptor, an exhaust means for forcibly discharging the air inside the apparatus to the outside of the apparatus, and a means for detecting the size of the transfer material. The image forming apparatus is characterized in that the driving time of the exhaust means after charging is completed is changed depending on the size of the transfer material.

"Example" Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

The points already explained with respect to FIG. 1 will not be repeated to avoid duplication. The transfer material is inserted from the right side of the main body, and when the image forming process starts, it is sent to the registration rollers 10 by the paper feed roller 9. The registration rollers 10 begin to move so that the image formed on the photosensitive drum 1 and the transfer material are synchronized.

A paper feed sensor 14 is disposed between the paper feed roller 9 and the registration roller 10. This paper feed sensor 14 is located on the path that also passes the minimum amount of transfer material that can pass through, and is comprised of a guard detection lever and a photosensor so that an on signal is issued if there is transfer material, and it is turned off if there is no transfer material. ing. If the paper feed sensor 14 is on when the main switch of the main body is turned on, it is determined that there is a paper jam in the paper feed section, and image formation is not performed.

As shown in the timing chart of FIG. 2, the start switch for the image forming process is turned on (tl), and the paper feed roller 9
The charger 5.11 starts discharging the photosensitive drum 1 only when the transfer material conveyed by the transfer material activates the paper feed sensor 14 (tl). In addition, the exhaust fan 13 has a drive means dedicated to the fan, and when the start switch is turned on (tl)
Start working at

The transfer material is conveyed by the registration rollers 10 in synchronization with the image on the photosensitive drum 1. The image forming process on the photosensitive drum 1 has been described in detail in the description of the conventional technology, so it will not be repeated. After the image is transferred from the photosensitive drum 1, it is transported to the fixing device 12. When the trailing edge of the transfer material passes the paper feed sensor 14 (tl)%, the same sensor 14
After a certain period of time (ta-t s
) That is, after the image is transferred from the photoreceptor to the rear end of the transfer paper, the discharge of the chargers 5 and 11 is stopped.

In this embodiment, two of the primary charger 5 and the transfer charger 11 are used.
A corona charger is used for this purpose, but since electricity is supplied from one high-voltage power source, charging is turned on and off at the same time. As is well known, when discharging with a corona charger, discharge products such as ozone 05 and nitrogen oxides are generated, which deteriorates the photoconductor.
Although the charger is removed from the vicinity, the internal space is narrow, especially in small machines, and the placement of other components is related to the charger 5.1.
If the air path from the exhaust fan 1 to the exhaust fan 16 is complicated, it is difficult to remove discharge products. In particular, if an upper limit is set on the size and rotational speed of the exhaust fan 13, that is, the exhaust capacity due to the structure of the apparatus, the longer the charging time is, the more discharge products remain in the vicinity of the photosensitive drum 1.

The relationship between the charging time (ta-tz) and the amount of discharge products remaining near the photoreceptor depends on the exhaust capacity of the exhaust fan 1δ and the exhaust fan 1.
Although it cannot be generalized because it is closely related to the air path from the chargers 5 and 11 to the charger 6, it has been found that in the image forming apparatus of this embodiment, it is almost proportional. That is, the charging time (b-
The rate of increase in tz) and the rate of increase in residual discharge products were approximately equal. Of the charging time (ta-tz), (ta
-tg) is constant regardless of the size of the transfer material, so the increase in charging time is proportional to the size of the transfer material when the paper feed sensor 14 is turned on (bb). Therefore, in the present invention, in order to efficiently remove the residual discharge products, the driving time (ts-ta) of the exhaust fan 13 after the completion of charging is regulated in accordance with the size of the transfer material.

In the embodiment, the minimum size of the transfer material that can be passed is a postcard lengthwise feed (t48m), and the maximum size that can be passed is the Japanese Industrial Standard paper size B4 lengthwise feed (364jul). Also, the surface speed (process speed) of photosensitive drum 1 v = 72 m
/second. The time (1, -16) is the time required for the transfer material to pass from the paper feed sensor 14 to the transfer section, and is 1.1 seconds in this embodiment.

Therefore, if the transfer material size is x (m), the corona discharge time (ta-t2) is ta-
tz = (ta - ts) 10% + a = 1.1 + "- + a te. Here, α is the time for the leading edge of the transfer material to reach the transfer section after being detected by the paper feed sensor 14, and This depends somewhat on the startup time of the fixing device 12, but normally the paper feed roller 9 does not operate until these times reach predetermined values.
It can be considered that α=1.1 seconds. Therefore, the shortest discharge time is 4.3 seconds and the longest is 7.3 seconds. It is amazing that each corresponds to one size when a postcard is fed vertically and one when paper size B4 is fed vertically.

In contrast, the exhaust fan 1 after charging is completed according to the present invention.
6 drive time (ts-ta) from a minimum of 2 seconds to a maximum of 3.5 seconds.
I set it to seconds. These relationships are shown in the graph of FIG. These were determined based on the time required to remove residual discharge material near the photoreceptor in this example.

In addition, in this embodiment, all the chargers are supplied with electricity from one high-voltage power supply, so they are turned on and off at the same time, but in the case of chargers that have multiple high-voltage power supplies and are turned on and off at different times, the charger turns on and off at the same time. What is necessary is to change the fan drive time from the time the fan is turned off.

In addition, if the relationship between the charging time (ta-tz) and the residual discharge products near the photoreceptor is not proportional, and the device has a configuration expressed by another relational expression, the fan drive time should be set based on that relationship. Of course it's good.

The present invention is particularly effective when forming an image on one sheet of transfer material, but when images are formed continuously on multiple sheets of transfer material, and the distance between the two transfer materials is narrow, residual discharge may occur. If it is shorter than the time equivalent to the time required to remove the transfer material, the drive time (ts-ta) may be taken into account when setting the drive time (ts-ta) of the exhaust fan after charging based on the number of sheets of transfer material. G ~ [Effects of the Invention] As explained above, by changing the exhaust fan drive time after the completion of discharge to the photoreceptor depending on the size of the transfer material 1, it is possible to efficiently remove discharge products and stabilize the process. It is possible to obtain good images.

In addition, by optimizing the drive time of the exhaust means, the noise of the exhaust means can be reduced.
There is a tradition of reducing vibration and wear of mechanical parts such as bearings, and as a result, prolonging the life of the image forming apparatus body.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an image forming apparatus implementing the present invention, and FIG. 2 is a timing chart showing the sequence of the present invention.
FIG. 6 is a graph showing the relationship between paper passing size and exhaust fan driving time in an embodiment of the present invention. 1. Photosensitive drum 5.--forming charger 9. Paper feed roller 10.. Registration roller 11.. Transfer charger 1
3. Exhaust fan 14. Paper feed sensor. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. In an image forming apparatus that includes a photoreceptor, a corona charger that discharges electricity to the photoreceptor, an exhaust means that forcibly exhausts air inside the apparatus to the outside of the apparatus, and a means that detects the size of a transfer material,
An image forming apparatus characterized in that the driving time of the exhaust means after charging is completed is changed depending on the size of the transfer material.