JP2622990B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic recording process, such as an electrostatic copying machine and the same printer.

(Problems to be Solved with Conventional Technique) After forming an electrostatic latent image on the surface of an image carrier, toner is supplied to the electrostatic latent image to visualize the latent image, and a sheet-like transfer material such as paper is applied to the toner image. An image forming apparatus including a step of abutting and electrostatically transferring the toner image to the transfer material has been conventionally known.

FIG. 3 schematically shows a typical configuration of such an image forming apparatus. The surface photosensitive layer of the photoreceptor 1 extending in the direction perpendicular to the paper and rotating in the direction of arrow A has a primary photosensitive layer. It is uniformly charged by the charger 2, and is subjected to image exposure 4 using reflected light of light irradiating the original surface, an image-modulated laser beam, and the like to form an electrostatic latent image.

When the latent image comes to the position of the developing device 5 as the photoreceptor rotates, toner is supplied from the latent image to visualize the latent image to form a toner image.

Further, when the toner image reaches a transfer portion having the transfer charger 7, a transfer material (not shown) is supplied from the transport path 6 to the transfer portion at the same timing as the toner image. After the toner image is transferred to the transfer material, the transfer material is conveyed to a fixing portion (not shown) while carrying the toner image.

At the time of transfer, residual toner remaining on the photoreceptor without transferring to the transfer material reaches the cleaning device 8 and is scraped off by the elastic cleaning blade 8a attached thereto, and further, the residual charge is removed by the pre-discharge lamp 9 As a result, the photoconductor is ready for the next image forming step.

By the way, in the image forming apparatus having the above-described configuration, it has been found that it is preferable that an appropriate amount of toner is always present at a blade edge portion of the cleaning blade that comes into contact with the photoconductor.

Of course, if the amount of the toner is too large, the accumulated toner runs laterally in the longitudinal direction of the edge, overflows from the cleaning device, and the transfer material may contaminate various parts in the image forming apparatus. Conversely, for example, when a large number of originals with a small amount of toner and a large white portion are continuously copied, the generation of residual toner is reduced, and as a result, the amount of toner collected at the blade edge becomes too small, and the blade and the The friction between the photoconductor and the photoconductor increases, and cleaning failure and blade turn-up due to blade edge swelling tend to occur.

In the case of paper that is often used as a transfer material,
The amount of hard-to-clean substances such as fine paper powder, rosin, and talc that will be generated will be relatively large compared to the amount of toner, which may damage the photoreceptor or cause poor cleaning. is there.

In the image forming apparatus as described above, the blank exposure lamp 3 is provided in order to prevent the toner from adhering to the outside of the image area due to the image exposure of the back scan or the frame portion of the document table. It is well known that a means is provided for turning on the light at the sheet interval to prevent toner from adhering to the non-image area.

Therefore, as described above, when the amount of toner generated from the image portion is too small, the lamp is turned off and the toner is adhered to this portion in a belt shape, and the toner is transported to the cleaning device as it is. Further, there has been proposed an apparatus which supplies toner to a blade edge portion.

By such means, a certain effect can be expected to avoid the problem of insufficient toner to be stored in the blade edge portion. However, in the conventional method, in consideration of various conditions, the above-mentioned belt-like shape is most used. Normally, it is assumed that toner is required and the amount of toner is set so as to meet the condition.

Originally, the appropriate amount of toner to be stored in the blade edge should differ depending on the copy mode, the type of transfer material, environmental characteristics such as temperature and humidity, the type of document, etc. It is unavoidable that toner is consumed more than necessary because it is gradual.

For this reason, for example, in a cartridge type device, the toner storage amount is limited, so that the toner runs out before the life of the photoconductor comes to end, thereby limiting the life of the cartridge itself. Things will happen.

Further, as described above, the amount of the belt-like toner in the space between sheets is
Generally speaking, the amount of toner is often larger than the required amount, so that the amount of toner stored at the blade edge tends to be excessive, which tends to cause the above-mentioned inconvenience.

Further, since the formation of the belt-shaped toner portion is performed in the same manner as in the image forming process, it is influenced by the environmental conditions as in the image portion.

Therefore, in a low humidity environment, when a large number of copies with low toner consumption are taken and the charge of the toner in the developing device becomes abnormally high, the toner is less likely to be transferred to the photoconductor. Tends to cause density reduction and fogging, the amount of toner to be supplied to the blade edge tends to be insufficient, and in such an environment, the electrostatic attraction between the photoconductor and the toner is strong, so that Cleaning becomes difficult. At high humidity, frictional charging of the toner hardly occurs at the developing site, so only the easily charged portion of the toner component is transferred to the photoreceptor, the balance of the toner component is different, the density tends to decrease, and the cleaning is difficult. Only the components tend to go to the cleaning blade. As described above, when the humidity is high or low, a state in which the cleaning is difficult occurs, and the amount of toner in the toner band formed between the papers tends to be small, which tends to cause a cleaning failure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and adjusts the amount of toner in a toner band formed at a sheet interval including a pre-rotation and a post-rotation in accordance with changes in environmental conditions. It is an object of the present invention to provide an image forming apparatus capable of avoiding wasteful consumption of toner without causing the problem and performing stable cleaning at all times.

(2) Configuration of the Invention (Technical Means for Solving the Problems, Action of the Invention) In order to achieve the above object, the present invention provides an image carrier,
After the transfer, a cleaning blade that removes residual toner remaining on the image carrier, an environmental humidity detecting unit, and a toner amount to be attached to the outside of the image forming area of the image carrier, based on a detection result of the environmental humidity detecting unit, An image forming apparatus comprising: an amount-of-adhered-toner variable unit that changes the amount of toner to be increased when the humidity is high, compared to when the humidity is low.

With this configuration, it is possible to always hold a proper amount of toner on the edge portion of the cleaning blade and perform a stable cleaning operation.

(Explanation of Example) An example described below is an image forming apparatus configured to convey toner adhered to a portion outside an image area to a cleaning blade. It is provided with means for changing. Here, the environmental condition refers to humidity or / and temperature.

The following tables show the results of performing image forming experiments under various conditions using the above-described image forming apparatus.

Table 1 shows the toner band formation width when the image formation was performed in such a manner that the domestic transfer paper was repeatedly subjected to “single continuous”, that is, a pause of several seconds after copying one sheet, at normal humidity, at room temperature. This is a conventional example in which the control of the number of times, that is, how many times a copy of the toner band is inserted once is examined.

In the above table, a circle indicates a good result, and a cross indicates a failure. In the right area of the dotted line, cleaning failure occurred due to insufficient toner. Further, in the area on the left side of the chain line, the toner was dropped in the transfer paper transport portion and the vicinity of the transfer portion due to excessive toner. The meaning of the dotted line and the chain line is the same hereinafter.)

Table 2 shows the transfer paper made in Northern Europe (size 11 ×
An embodiment in which the number and width of toner band formation are controlled under the same conditions, such as environmental conditions, copy mode, and copy density, except that a 17-inch type is used.

Since the transfer paper is made of a foreign material, it is difficult to clean the transfer paper because it is a large amount of paper powder. Therefore, it is understood that a large amount of toner is required in the toner band, and the boundary is indicated by a dotted line.

Table 3 shows the results of a single continuous copy test using domestic paper in a low humidity environment (25 ° C., 10% RH). In such a case, as described above, the copy density is low (0.9), and the range in which good cleaning can be performed (part marked with a circle)
However, it can be seen that a good cleaning action can be obtained by supplying a large amount of toner to the inter-sheet toner band, that is, shifting to the left as compared with the case of Table 1 above. Further, even if the amount of toner is increased, overflow of toner is less likely to occur than in the case of Table 1.

Table 4 shows the results of a test performed under the same conditions as in Table 3 except that foreign transfer paper was used as the transfer paper.

Transfer paper contains a lot of paper dust and low copy density (0.9)
It can be seen that cleaning is difficult and a larger amount of toner is required than in the case of Table 3.

Note that the range in which the toner overflows and falls does not differ from the previous example.

Table 5 shows test results under the same conditions as in Table 1 except that continuous copying was performed.

As can be seen from the above table, since the paper is domestically produced, there is little paper dust and there is no pre-rotation or post-rotation for each copy operation for continuous copying, so that sufficient toner is supplied and cleaning failure does not occur. The required amount of toner is also small, as indicated by the dotted line.

On the other hand, it can be seen that the overflow and fall of the toner can be sufficiently made even if the toner band is controlled so as to form the toner band with a small width because the amount of toner per operation is large.

FIG. 1 shows an embodiment of the present invention in which the amount of toner in a toner band between sheets is controlled according to environmental conditions. In the embodiment shown in FIG. 1, it is configured to cope with a change in humidity. .

A mode in which the environment changeover switch controls the toner amount of the toner band by the humidity sensor is selected as shown in Table 6.

Then, the output signal controls the toner band forming means so as to obtain the number and width of the toner band.

As the toner band forming means, for example, a blank exposure, a developing bias and the like can be used, and by controlling these, the number of times and the width of the toner band are set.

Although the description has been given above of the case of responding to humidity, it is easy to respond to various external conditions as necessary, such as other factors, such as temperature or the state of the document, the type of transfer material. It will be understandable.

In the case where the temperature, humidity and the like greatly change as a whole, as in summer and winter, as shown in FIG. 2, the toner band forming means such as blank exposure is controlled by switching the environment changeover switch. It can also be set to match the environment.

(3) Effects of the Invention As described above, according to the present invention, in an image forming apparatus provided with a cleaning device using a cleaning blade, it is possible to always supply an appropriate amount of toner to the blade edge so that cleaning failure and blade In addition to avoiding the occurrence of turning over and maintaining a stable cleaning function, for example, it is possible to prevent the occurrence of fog, which reduces the density of the image in a low-humidity environment, such as a document with a low toner consumption, thereby contributing to obtaining a high-quality image. However, it is big.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment, and FIG. 3 is a schematic side view showing a configuration of an image forming apparatus suitable for applying the present invention. is there. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Primary charger, 3 ... Blank exposure lamp, 4 ... Image signal provision means, 6 ... Convey path, 7 ...
... Transfer charger, 8 ... Cleaning device, 8a ... Cleaning blade.

Claims (1)

(57) [Claims] An image carrier, a cleaning blade for removing residual toner remaining on the image carrier after transfer, an environmental humidity detector, and an amount of toner adhering to the outside of the image forming area of the image carrier. An image forming apparatus, comprising: an amount-of-adhered-toner changing unit that changes the detection result of the environmental humidity detection unit so that the amount of toner increases in a high humidity state compared to a low humidity state.