JPH0481871A - Development method - Google Patents

Abstract

PURPOSE:To control the transfer rate of a toner to an electrostatic latent image and to adjust the image density of a visible image by irradiating the toner with light and detecting the amt. of the toner from the reflected light. CONSTITUTION:The toner on a developing roller 5 is irradiated by a light emitting element 30 and the reflected light thereof is made incident on a light receiving element 31. The output from the element 31 is inputted to a controller 33 where the output of a sensor 32 and a reference value is compared. A power source 50 is controlled by the controller 33 when judgment is made that the amt. of adhesion of the toner on the roller 5 is little. The voltage impressed to the roller 5 is then regulated so as to intensify the electric field between the roller 5 and the electrostatic latent image. The easier transfer of the toner on the roller 5 to the electrostatic latent image is assured in this way and the deficiency of the toner amt. on the roller 5 is made up.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention carries toner on the surface of a toner carrier and conveys the toner, and in a development area where a latent image carrier and a toner carrier face each other, The present invention relates to a developing method in which toner on a toner carrier is electrostatically transferred to an electrostatic latent image formed on an image carrier to visualize the latent image.

[Conventional technology]

In an image forming apparatus such as an electronic copying machine, a laser printer, or a facsimile machine that obtains a recorded image by visualizing an electrostatic latent image formed on a latent image carrier, a toner to which an adjuvant is externally added as necessary, i.e. -Ingredients! i! It is well known in the art to employ the above-mentioned type of development method using a developer.

This development method has the advantage that maintenance and management of the device can be simplified and the structure of the device can be made smaller, compared to a development method using a two-component developer containing a carrier. This developing method is configured such that, for example, toner contained in a toner container is electrostatically adhered to the surface of a toner carrier, and the toner is transported to a developing area for development. At this time, when the amount of toner in the toner container decreases, the amount of toner supplied to the toner carrier also decreases. Furthermore, the amount of toner supplied to the toner carrier may decrease or increase abnormally due to deterioration over time of various elements of the developing device including the toner carrier or changes in environmental conditions.

When the amount of toner on the toner carrier changes in this way, the density of the visible image formed thereby changes, making it impossible to obtain a visible image with a predetermined density.

For example, if the amount of toner carried on the toner carrier and conveyed to the development area decreases below a predetermined amount, the image density of the visible image decreases and the image quality deteriorates.

Conventionally, a standard pattern image is formed on a latent image carrier using toner from a developing device, the image density is detected by a sensor consisting of a light emitting element and a light receiving element, and the electrostatic latent image in the developing area is detected based on the result. The image density of the visible image was adjusted by controlling the amount of toner transferred to the surface. For example, when the amount of toner on the toner carrier decreases below a predetermined amount, the image density of the reference pattern image decreases, so when a sensor detects this, it adjusts the voltage applied to the toner carrier and The bias electric field between and the latent image carrier is strengthened,
By making it easier for the toner to transfer to the electrostatic latent image, a decrease in the image density of the visible image is prevented.

[Problem to be solved by the invention]

However, according to the conventional method described above, a reference pattern image is first formed on the latent image carrier, and then the image density is detected, but this operation must be performed at a time other than the actual developing operation. Therefore, the problem that the image forming speed decreases cannot be avoided. If the detection operation could be performed in parallel with the actual developing operation, it would be possible to prevent a decrease in the speed of forming one image, but conventional methods have not been able to perform such detection.

An object of the present invention is to provide a developing method that eliminates the above-mentioned conventional drawbacks with a simple structure.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention, in the developing method of the type described at the beginning, irradiates light from a light-emitting element to the toner on a toner carrier and makes the reflected light enter a light-receiving element. We propose a configuration that detects the amount of toner carried on a toner carrier, controls the amount of toner transferred to the electrostatic latent image in the development area, and adjusts the image density of the visible image based on the result. .

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of a developing device for carrying out the method according to the present invention, and first the overall structure and operation thereof will be explained.

In FIG. 1, a drum-shaped photoreceptor 1, which is an example of a latent image carrier, is driven in the direction of arrow A, and a developing device 2 is provided opposite to it. A toner container 3 of the developing device 2 contains a toner 4 to which an auxiliary agent is externally added as necessary, that is, a -component developer. The toner 4 may be a non-magnetic toner or a magnetic toner, but
In the example shown in FIG. 1, it is assumed that non-magnetic toner is used.

Similarly, the volume resistivity of the toner shown in Figure 1 is 107
It is assumed that the resistance is about 1012 ΩG.

A developing roller 5 is supported on the front and rear side plates of the toner container 3 with a portion exposed from the opening of the container.
is opposed to the photoreceptor 1 and rotated counterclockwise in the figure. Although the developing roller 5 constitutes an example of a configuration of a toner carrier, a belt-shaped toner carrier may be used instead of the roller 5.

Further, a toner supply roller 6, which is an example of a toner supply member, is supported on the front and rear side plates of the toner container 3.

The roller 6 is rotated counterclockwise, for example, while being in contact with the developing roller 5.

The toner 4 in the toner container 3 is conveyed to a toner supply roller 6 while being agitated by an agitator 7 that rotates clockwise, and then supplied to a developing roller 5 by this roller 6. During this supply, the toner is frictionally charged to a predetermined polarity, electrostatically adheres to the circumferential surface of the developing roller 5, and is carried by the developing roller 5. In the example shown in FIG. 1, for convenience of explanation, it is assumed that the toner 4 is positively charged.

The toner supplied and supported on the circumferential surface of the developing roller 5 is conveyed by the rotation of the roller 5, and is leveled by a doctor plate 18, which is an example of a layer thickness regulating member, and is regulated to have a uniform thickness. This toner is then conveyed to a developing area 9 where the photoreceptor 1 and the developing roller 5 face each other, where it is electrostatically transferred to the electrostatic latent image formed on the photoreceptor 1, converting the latent image into a visible image. become

The toner that has passed through the development area 9 without being subjected to development is returned to the toner supply roller 6 while being supported on the development roller 5, and the visible image formed on the photoreceptor 1 is not shown. The image is transferred to transfer paper and fixed onto the transfer paper by a fixing device.

As shown in FIGS. 2 to 4, the developing roller 5 is made up of a large number of minute dielectrics 11 dispersed and fixed on the circumferential surface of a conductive base 10 made of, for example, aluminum or stainless steel. A conductive substrate 10 is placed on the surface of this roller 5.
Its conductive surface 12 and the surface of the dielectric 11 fixed thereto are exposed in a regular or irregular manner. Each dielectric 1
The shape and size of 1 can be set as appropriate. If the shape of the dielectric exposed on the surface is, for example, circular, its diameter is, for example, 10 to 500 μm, preferably 50 to 30 μm.
The surface area ratio of the dielectric material 11 to the total surface area of the developing roller 5 is set to about 30 to 70%, for example. The dielectric 11 is selected from a material that is triboelectrically charged to have a polarity opposite to that of 1 to ner, in this example, to a negative polarity.

On the other hand, the toner supply roller 6 that is in contact with the developing roller 5 is made of, for example, a foam roller or a fur brush roller, and contacts the surface of the dielectric 11 of the developing roller 5 to make it have a negative polarity opposite to the charged polarity of the toner. Constructed from a triboelectrically charged material.

As described above, the portion of the developing roller that has passed through the developing area 9 moves to the toner supply roller 6 and comes into contact with the roller 6, and the toner that has not been subjected to development is scavenged by the toner supply roller 6. scraped off by a spider. At the same time, the dielectric member 11 of the developing roller 5 is charged to a negative polarity opposite to the charging polarity of the toner due to friction with the toner supply roller 6.

On the other hand, as described above, the toner conveyed to the developing roller 5 while in contact with the circumferential surface of the toner supply roller 6 is frictionally charged to a positive polarity by the friction between the toner supply roller 6 and the developing roller 5. At this time, each dielectric material 11 of the developing roller 4 is frictionally charged to a negative polarity, and a conductive surface 12 exists around each dielectric material 11, and the surface of the developing roller 5 is A negative charge is selectively applied only to the As a result, as shown in FIG. 5, a closed field E is created between each negatively charged dielectric material 11 and the surrounding conductor surface 12.
are formed, and a large number of minute closed fields (microfields) are formed near the surface of the developing roller 5. Since the surface area of each dielectric 11 is very small, the strength of each closed field becomes very strong due to the so-called edge effect. Due to this closed field, the positively charged toner is strongly attracted to the dielectric 11 and held on the roller 5 in a large amount in a state where it is difficult to separate. When the layer thickness of the toner carried on the developing roller 5 is regulated by the doctor blade 8, the sufficiently charged toner is strongly held on the surface of the developing roller 5 by the micro closed field, but the toner with a small amount of charge is is removed by the contact pressure with the doctor blade 8, resulting in a large amount of charge! - Only a large amount of toner is transported to the developing area 9, and the electrostatic latent image is visualized as described above.

The conductive base of the photoreceptor 1 is grounded, whereas the conductive base 10 of the developing roller 5 is applied with a DC voltage or a voltage obtained by superimposing AC on it by a power source 50.
In this state, an electric field is formed between the photoreceptor 1 and the developing roller 5, and the latent image is visualized.

As described above, according to the illustrated fI;l image device 2, a large amount of toner can be carried on the developing roller 5 and conveyed to the developing area 9, thereby forming a high-quality visible image. However,
As explained earlier, when the amount of toner 4 in the I/toner container 3 decreases, the amount of toner supplied to the developing roller 5 also becomes insufficient, and if this is left untreated, the image density of the visible image will decrease. and its image quality deteriorates. The amount of hener carried by the developing roller 5 and transported to the developing area 9 may decrease due to changes in environmental conditions. Alternatively, due to changes in environmental conditions, an excessive amount of toner may be carried on the developing roller 5 and transported to the developing area 9. In this case, the image density of the visible image becomes abnormally high. After all, there is a risk that the image quality will deteriorate.

In order to avoid such problems, conventionally a standard pattern image visualized by a developing device was formed on a photoreceptor, and this was detected by a sensor to adjust the image density of the visible image. However, as mentioned above, this has inevitably resulted in the problem of a reduction in image forming speed.

Therefore, in this embodiment, the amount of toner on the developing roller 5 is detected by a sensor, and the image density of the visible image is adjusted based on this. A specific example of its configuration will be clarified below.

As shown in FIGS. 1 and 4, for example, facing the developing roller portion between the doctor blade 8 and the developing area 9,
A sensor 32 having a light emitting element 30 and a light receiving element 31 is arranged. The amount of toner on the developing roller 5 is detected by irradiating the toner carried on the developing roller 5 with light from the light emitting element 30 and making the reflected light enter the light receiving element 31.

FIGS. 6 and 7 are explanatory diagrams illustrating the reason why the amount of toner on the developing roller can be detected by the sensor 32 described above. The electric field in the space near the developing roller 5 increases as the distance from the surface X of the developing roller 5 increases, that is, as shown in FIGS.
The larger the distance in the direction indicated by Y in the figure, the weaker it becomes. Therefore, when a small amount of toner 4 adheres to the surface X of the developing roller 5 as shown in FIG. Although it is small, when the amount of toner 4 on the developing roller 5 is large as shown in FIG. 6, the amount of toner decreases as the distance from the surface of the developing roller 5 in the Y direction increases, and the surface becomes uneven. In particular, as in this example, when the surface of the dielectric 11 and the conductive surface 12 are exposed on the surface of the developing roller 5 and a minute closed electric field is formed between them, the charged polarity of the toner is opposite to that of the toner. Since a large amount of toner tends to adhere to the surface of the charged dielectric 11, when the amount of toner on the developing roller is large, the surface becomes noticeably uneven.

As mentioned above, the shape of the surface of the toner layer varies depending on the amount of toner carried on the developing roller. The present invention has been made with attention to this point. That is, when a large amount of toner 4 is carried on the developing roller as shown in FIG. 6, when light is irradiated from the light emitting element 30 onto the developing roller, the reflected light is intense due to the many irregularities on the surface of the toner layer. However, when the amount of attached toner is small as shown in FIG. 7, the scattering of reflected light becomes extremely small.

Therefore, when the amount of toner is large as in the former case, the light receiving element 31
A small amount of light will be incident on the light receiving element 31, and when the amount of toner is small as in the latter case, a large amount of light will be incident on the light receiving element 31. In this way, the amount of toner on the developing roller 5 can be detected based on the difference in the amount of light incident on the light receiving element 31.

The processing after detecting the amount of toner by the sensor 32 is the same as in the past, and based on the detection result, the amount of toner transferred to the electrostatic latent image in the development area 9 is controlled and the image density of the visible image is adjusted. . That is, the output from the light receiving element 31 of the sensor 32 is input to the control device 33 as shown in FIG.
Here, the output of the sensor 32 is compared with a reference value, and if it is determined that the amount of toner adhering to the developing roller is less than a predetermined amount, the controller 33 controls the power supply 50 (see also FIG. 1). ) is controlled, and the voltage applied to the developing roller 5 is adjusted so that the electric field between the developing roller 5 and the electrostatic latent image on the photoreceptor 1 is strengthened. This makes it easier for the toner on the developing roller 5 to transfer to the electrostatic latent image, making it possible to compensate for the lack of toner on the developing roller 5 and forming a visible image with a predetermined density. Developing roller 5
When it is determined that the amount of toner on the photoreceptor 1 is too large,
The voltage applied to the developing roller 5 is controlled so that the electric field between the electrostatic latent image and the developing roller 5 is weakened, the toner is difficult to transfer to the latent image, and a visible image with a predetermined density is obtained. You can also. In this way, a visible image of a predetermined density can always be formed.

Further, the doctor blade 8 shown in FIG. 1 is made of a conductor such as metal, and a voltage of the same polarity as the charged polarity of 1 to 3 on the developing roller 5 is applied to it by a power source 51 as shown by the broken line. It is also possible to increase the amount of charge on the toner by injecting charge into the toner.
When such a configuration is adopted, based on the output of the sensor 32.

It is also possible to control the power supply 51 by the control device 33 and adjust the voltage applied to the lid plate 8. For example, when it is determined that the amount of toner on the developing roller 5 is too small, the voltage applied to the doctor blade 8 is increased.
- The amount of charge injected into the toner is increased, and this toner is easily transferred to the electrostatic latent image on the photoreceptor 1 in the development area 9, thereby preventing a decrease in the image density of the visible image. Furthermore, when the amount of toner on the developing roller 5 is too large, the voltage applied to the doctor blade 8 is lowered to reduce the amount of charge injected into the toner, and this toner is transferred to an electrostatic latent image in the developing area 9. However, it is also possible to perform control to prevent the problem of abnormally high image density of the visible image.

In any case, in the illustrated configuration, (
- Since the amount of toner is directly detected, this detection operation can be performed during normal developing operation, and countermeasures can be taken accordingly. Therefore, it is possible to eliminate the time required to perform only the detection operation, and the overall image forming speed can be increased compared to the conventional method of once creating a reference pattern image on a photoreceptor and then detecting the image density. .

4, 6, and 7, for convenience, the light emitting element 30 and the light receiving element 31 are shown as being inclined with respect to the surface of the developing roller 5. In order to increase the accuracy of detecting the uneven state of the surface, the pixel element 30 is arranged so that the light from the light emitting element 30 is perpendicularly incident on the surface of the developing roller 5 and the reflected light is received by the light receiving element 31.
, 3] is desirable.

Further, an I-(e-N e laser or the like can be used as a light source for the light emitting element 1, but such light does not reach the photoreceptor 1.
If there is a risk of adversely affecting the electrostatic latent image, a light shielding member (not shown) is provided to cover the light beam from the light emitting element 30 to the light receiving element 31 to prevent the light from irradiating the photoreceptor 1. It is recommended to configure it as follows.

Furthermore, if the diameter of the light beam of the light beam that irradiates the toner layer is too small, the light will hit only a small portion of the toner, making it impossible to accurately detect the uneven state of the surface of the toner layer. It is advantageous to have a size that is much larger than the diameter so that a relatively large area of the surface of the toner layer can be detected. For example, when the diameter of the toner particles is 5 to 20 μm, the diameter of the light beam is set to about 100 to 150 μm.

Also, the amount of toner attached to the developing roller 5 and the light receiving element 3
To further explain the relationship between the amount of light received in 1, the relationship between 1 and 1 is as illustrated in FIG.

1. In the range indicated by P where the amount of henna adhesion is small.

Considering the toner layer, the amount of toner adhesion and the amount of light received change as shown by the dotted line, but they actually change as shown in the solid line due to the influence of the surface smoothness of the developing roller itself and its reflectance. In the range indicated by R, where the amount of toner adhesion is large, the curve approaches a constant value, and there is no significant change in the amount of light received even if the amount of toner adhesion increases.On the other hand, during normal development The amount of henna deposited on the roller 5 falls within the range shown by Q in FIG. It becomes constant, and toner drop can be detected correctly.

Above, a specific example in which the present invention is applied to a developing device that uses the developing roller 5 in which the conductive surface 12 and the surface of the dielectric 11 are exposed and forms a minute closed field near the surface has been described. The present invention can be widely applied to developing devices that use various types of toner carriers that are conventionally known. For example, a toner carrier formed by laminating an insulating layer on the surface of a conductive substrate is used, and the insulating layer on the surface is charged by friction with, for example, a toner supply roller 6 as shown in FIG. Even in a developing device that attaches toner to the surface of a toner carrier, severe unevenness may occur on the surface of the toner layer, as shown in FIGS. 6 and 7, depending on the amount of toner attached to the toner carrier. On the other hand, since the surface becomes smooth, this can be detected by a sensor and the amount of toner can be detected.

〔Effect of the invention〕

According to the present invention, since the amount of toner on the toner carrier is directly detected, the detection operation can be performed during normal developing operation, and wasted time can be saved.

Thereby, it is possible to increase the image forming speed compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a developing device for carrying out the method according to the present invention, FIG. 3
The figure is an enlarged view of the surface of the developing roller that also schematically represents the surface of the dielectric, FIG. 4 is a perspective view of the developing roller and the sensor placed opposite it, and FIG. FIGS. 6 and 7 are diagrams illustrating the state of adhesion of toner on the surface of the developing roller. FIG. 8 is a diagram showing an example of the relationship between the amount of toner adhering to the developing roller and the amount of light received by the light receiving element. 4...Toner 9...Development area 30...Light emitting element 31...Light receiving element Representative Patent attorney Norio Hoshino Husband? Figure 3 Figure O Figure 4 Figure 5

Claims (1)

[Scope of Claims] Toner is carried on the surface of a toner carrier and transported, and in a development area where the latent image carrier and the toner carrier face each other, an electrostatic latent image formed on the latent image carrier is processed. In a developing method in which a latent image is visualized by electrostatically transferring toner on a toner carrier, the toner on the toner carrier is irradiated with light from a light emitting element and the reflected light is received. The amount of toner carried on the toner carrier is detected by entering the element, and based on the result, the amount of toner transferred to the electrostatic latent image in the development area is controlled, and the image density of the visible image is adjusted. A developing method characterized by adjustment.