JP3029852B2 - Development method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for carrying toner on a surface of a toner carrier and transporting the toner. The present invention relates to a developing method for electrostatically transferring toner on a toner carrier to an electrostatic line image formed on an image carrier to visualize an electrostatic latent image.

(Prior art)

In an image forming apparatus such as an electronic copying machine, a laser printer, or a facsimile that obtains a recorded image by visualizing an electrostatic latent image formed on a latent image carrier, a toner externally added with an auxiliary agent as necessary, The adoption of the above-mentioned type of developing method using a one-component developer is conventionally well known.

Such a development method can simplify the maintenance of the apparatus as compared with a development method using a two-component developer containing a carrier,
The advantage that the structure of the device can be miniaturized is obtained. In this developing method, for example, the toner contained in a toner container is carried on the surface of a toner carrier, and the toner is transported to a development area and used for development. At this time, as the amount of toner in the toner container decreases, the amount of toner supplied to the toner carrier also decreases. In addition, the amount of toner supplied to the toner carrier may decrease or increase abnormally due to the deterioration of each element of the developing device including the toner carrier with time or changes in environmental conditions.

When the amount of toner on the toner carrier changes as described above,
As a result, the density of the formed visible image changes, and it becomes impossible to obtain a visible image having a predetermined density. For example, if the amount of the toner carried on the toner carrier and conveyed to the developing area is smaller than a predetermined amount, the image density of the visible image is reduced, and the image quality is deteriorated.

Therefore, a reference pattern image is formed on the latent image carrier using the toner of the developing device, and the image density is detected by a sensor including a light emitting element and a light receiving element. It is conceivable to adjust the image density of the visible image by controlling the transfer amount of the toner. 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. When the sensor detects this, the voltage applied to the toner carrier is adjusted to adjust the voltage. By increasing the bias electric field between the photoconductor and the latent image carrier, the toner is easily transferred to the electrostatic latent image, thereby preventing the image density of the visible image from lowering.

[Problems to be solved by the invention]

However, according to the above-described method, first, a reference pattern image is formed on the latent image carrier, and thereafter, the image density is detected. However, since this operation must be performed at a time other than the actual development operation, the image Inevitably, the forming speed is reduced. If the detection operation can be performed in parallel with the actual developing operation, a decrease in the image forming speed can be prevented, but such detection cannot be performed by the above-described method.

An object of the present invention is to provide a developing method capable of eliminating the above-mentioned disadvantages with a simple configuration.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a developing method of the type described at the beginning, wherein the amount of the toner is larger than the amount of the toner carried on the toner carrier and conveyed. In this case, the toner is carried on the toner carrier so that large irregularities are formed on the surface of the toner layer, and the toner on the toner carrier has a light flux having a light beam diameter larger than the diameter of the toner particles. By irradiating the light of the
The amount of toner carried on the toner carrier is detected, and based on the result, the amount of toner transferred to the electrostatic latent image in the developing area is controlled to adjust the image density of the visible image. Is proposed.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view showing an example of a developing device for carrying out the method according to the present invention. First, the overall configuration and operation will be clarified.

In FIG. 1, a drum-shaped photoconductor 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 to face the photoconductor. In the toner container 3 of the developing device 2, a toner 4, to which an auxiliary agent is added as necessary, that is, a one-component developer is stored. The toner 4 may be a non-magnetic toner or a magnetic toner, but in the example of FIG. 1, a non-magnetic toner is used. Similarly, the specific volume resistivity of the toner shown in FIG.
It is assumed to be about ⁷ to 10 ¹² Ωcm.

On the front and rear side plates of the toner container 3, a developing roller 5 is supported in a state where a part thereof is exposed from an opening of the container, and the roller 5 is rotated counterclockwise in FIG. You. The developing roller 5 is an example of a toner carrier, but a belt-shaped toner carrier may be used instead of the roller 5.

A toner supply roller 6 as an example of a toner supply member is supported on front and rear side plates of the toner container 3.
Is rotated counterclockwise, for example, while contacting the developing roller 5.

The toner 4 in the toner container 3 is conveyed to the toner supply roller 6 while being stirred by the agitator 7 rotating clockwise, and then supplied to the developing roller 5 by the roller 6. During this supply, the toner is frictionally charged to a predetermined polarity, electrostatically adheres to the peripheral surface of the developing roller 5, and is carried on the developing roller 5. In the example of FIG. 1, the toner 4 is described as being charged to a positive polarity for convenience of explanation.

The toner supplied and carried on the surface of the developing roller 5 is conveyed by the rotation of the roller 5, is leveled by a doctor blade 8 as an example of a layer thickness regulating member, and is regulated to a uniform thickness. Next, the toner is conveyed to a developing area 9 where the photoconductor 1 and the developing roller 5 are opposed to each other, where the toner is electrostatically transferred to an electrostatic latent image formed on the photoconductor 1 and the latent image is converted into a visible image. Become

As described above, in the developing method of the present embodiment, the toner is carried on the surface of the toner carrier composed of the developing roller 5 and transported, and the latent image carrier composed of the photoconductor 1 and the toner carrier are opposed to each other. In the area 9, the toner on the toner carrier is electrostatically transferred to the electrostatic latent image formed on the latent image carrier, and the electrostatic latent image is visualized.

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 carried on the development roller 5. Further, the visible image formed on the photoreceptor 1 is transferred to a transfer sheet (not shown) and fixed on the transfer sheet by a fixing device.

As shown in FIGS. 2 to 4, the developing roller 5 of the present embodiment has a structure in which a number of minute dielectrics 11 are dispersed and fixed on the peripheral surface of a conductive substrate 10 such as aluminum or stainless steel. The conductive surface 12 of the conductive substrate 10 itself and the surface of the dielectric 11 fixed thereto are exposed on the surface of the roller 5 in a regular or irregular state. Each dielectric 11
And the size thereof can be set as appropriate. If the shape of the dielectric exposed on the surface is, for example, circular, the diameter is set to, for example, about 10 to 500 μm, preferably about 50 to 300 μm.
Is set to, for example, about 30 to 70%. As the dielectric 11, a material having a polarity opposite to the charging polarity of the toner, that is, a material frictionally charged to a negative polarity in this example is selected.

On the other hand, the toner supply roller 6 in contact with the developing roller 5
For example, it is composed of a foam roller or a fur brush roller, and is made of a material that comes into contact with the surface of the dielectric 11 of the developing roller 5 and frictionally charges this to a negative polarity opposite to the charging polarity of the toner.

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 used for development receives scavenging zinc received from the toner supply roller. It is scraped off by force. At the same time, the dielectric 11 of the developing roller 5 is charged to a negative polarity opposite to the charging polarity of the toner by friction with the toner supply roller 6.

On the other hand, as described above, the toner carried to the developing roller 5 while being in contact with the peripheral 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 development roller 5. At this time, each dielectric 11 of the developing roller 4 is negatively triboelectrically charged, and a conductor surface is provided around each dielectric 11.
In the surface of the developing roller 5, negative charges are selectively applied only to a large number of dielectrics 11.
As a result, as shown in FIG.
A closed electric field E is formed between 11 and the conductor surface 12 around it. A minute closed electric field (microfield) is formed near the surface of the developing roller 5. At that time, each dielectric
Since the surface area of 11 is very small, the strength of each closed electric field is increased by the so-called edge effect. With such a closed electric field,
The positively charged toner is strongly pulled by the dielectric 11 and is held on the roller 5 in such a state that it hardly separates. Developing roller 5
When the layer thickness of the toner carried on the developing roller 5 is regulated by the doctor blade 8, a sufficiently charged toner is strongly held on the surface of the developing roller 5 by a minute closed electric field. As a result, only a large amount of toner having a large charge amount is conveyed to the developing area 9 to visualize the electrostatic latent image as described above.

The conductive base of the photoreceptor 1 is grounded, while a DC voltage or a voltage obtained by superimposing an AC voltage is applied to the conductive base 10 of the developing roller 5 by a power supply 50, and the photosensitive base is An electric field is formed between the body 1 and the developing roller 5, and the electrostatic latent image is visualized.

As described above, according to the developing device 2 illustrated, a large amount of toner is carried on the developing roller 5 and is conveyed to the developing area 9 so that a high-quality visible image can be formed. However, as described above, when the amount of the toner 4 in the toner container 3 decreases, the amount of the toner supplied to the developing roller 5 also runs short. And the image quality deteriorates. The amount of toner carried on the developing roller 5 and conveyed to the developing area 9 may also decrease due to a change in environmental conditions or the like. Alternatively, due to a change in environmental conditions or the like, an excessive amount of toner is carried on the developing roller 5 and may be transported to the developing area 9, in which case the image density of the visible image becomes abnormally high, Again, the image quality may be degraded.

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

As shown in FIGS. 1 and 4, for example, a sensor 32 having a light emitting element 30 and a light receiving element 31 is disposed opposite to a developing roller portion between the doctor blade 8 and the developing area 9. The light carried by the light emitting element 30 irradiates the toner carried on the developing roller 5, and the reflected light is reflected by the light receiving element 31.
Is detected, the amount of toner on the developing roller 5 is detected.

FIG. 6 and FIG. 7 are explanatory diagrams for clarifying the principle that the above-mentioned sensor 32 can detect the amount of toner on the developing roller. 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, in FIGS.
It becomes weaker as the distance in the direction indicated by Y in the figure increases. Therefore, when a small amount of toner 4 adheres to the surface X of the developing roller 5 as shown in FIG. 7, the toner 4 adheres to the surface of the developing roller 5 in a uniform layer, and the variation thereof is also small. When the amount of the toner 4 on the developing roller 5 is large, as shown in FIG. 6, the amount of the 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 conductor surface 12 are exposed on the surface of the developing roller 5 and a minute closed electric field is formed therebetween, the polarity is opposite to the charging polarity of the toner. Since a large amount of toner tends to adhere to the charged surface of the dielectric 11, if the amount of toner on the developing roller is large, unevenness on the surface becomes remarkable.

As described above, according to the developing method of the present embodiment, when the amount of the toner is larger than the amount of the toner carried and conveyed on the developing roller 5 which is an example of the toner carrier, The toner is carried on the toner carrier so that large irregularities are formed on the surface of the toner layer. At this time, when a large amount of the toner 4 is carried on the developing roller as shown in FIG. 6, when light is irradiated from the light emitting element 30 to the toner, there are many irregularities on the surface of the toner layer. Although the light is strongly scattered, if the amount of toner adhered is small as shown in FIG. 7, the scattering of the reflected light is extremely small. Therefore, when the amount of toner is large as in the former case, a small amount of light is 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 is incident on the light receiving element 31.
Therefore, 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.

In the developing method of the present embodiment, focusing on the above points, the light from the light emitting element 30 is irradiated on the toner 4 on the toner carrier composed of the developing roller 5 and the reflected light is incident on the light receiving element 31. Is configured to detect the amount of toner carried on the toner carrier. And the sensor
Based on the detection result of the toner amount by 32, the amount of transfer of the toner to the electrostatic latent image in the developing area 9 is controlled to adjust the image density of the visible image. For example, the output from the light receiving element 31 of the sensor 32 is input to the control device 33 as shown in FIG. 4, where the output of the sensor 32 is compared with a reference value. Thus, for example, when it is determined that the amount of toner adhered on the developing roller is smaller than a predetermined amount, the power supply 50 (see also FIG. 1) is controlled by the control device 33 and the developing roller 5
The voltage applied to the developing roller 5 is adjusted so that the electric field between the photoconductor 1 and the electrostatic latent image on the photoconductor 1 is increased. This makes it easier for the toner on the developing roller 5 to transfer to the electrostatic latent image, so that the shortage of the toner amount on the developing roller 5 can be compensated and a visible image having a predetermined density can be formed. When it is determined that the amount of toner on the developing roller 5 is too large, the voltage applied to the developing roller 5 is controlled so that the electric field between the electrostatic latent image on the photoconductor 1 and the developing roller 5 is weakened. Is difficult to transfer to a latent image, and control can be performed so that a visible image having a predetermined density can be obtained. In this way, a visible image of a predetermined density can always be formed.

At the time of detecting the amount of toner described above, if the luminous flux diameter of the light beam irradiating the toner layer is too small, light shines only on a very small part of the toner, and it becomes impossible to correctly detect the unevenness state of the toner layer surface. The light beam diameter is set to be larger than the diameter of the toner particles, and a relatively large area of the toner layer surface can be detected. For example, when the diameter of the toner particles is 5 to 20 μm, the light beam diameter of the light beam is set to about 100 to 150 μm. As described above, in the developing method of the present embodiment, the light from the light emitting element 30 having a light beam diameter larger than the diameter of the toner particles is applied to the toner on the toner carrier including the developing roller 5.

Further, the amount of toner adhered to the developing roller 5 and the light receiving element
The relationship between the amounts of received light at 31 will be further described. The relationship between them is as illustrated in FIG. In the range indicated by P where the toner adhesion amount is small, the toner adhesion amount and the received light amount change as indicated by a dotted line when only the toner layer is considered. However, the solid line actually changes due to the surface smoothness of the developing roller itself and the reflectance thereof. It changes like Further, in the range indicated by R where the amount of toner adhered to the developing roller is large, the curve approaches a constant value, and no significant change in the amount of received light is observed even when the amount of adhered toner increases. On the other hand, the toner adhesion amount on the developing roller 5 during the normal developing operation is in a range indicated by Q in FIG. 8, and the toner amount is detected in this range. The relationship between the amount of adhesion and the amount of received light is almost constant, and the amount of toner can be correctly detected.

4, 6 and 7, 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 detection accuracy, light from the light emitting element 30 is perpendicularly incident on the surface of the developing roller 5 and the reflected light is reflected by the light receiving element
It is desirable to arrange both elements 30 and 31 so that light can be received by 31.

Further, a He-Ne laser or the like can be used as a light source of the light emitting element 1. However, when such light hits the photosensitive pair 1 and may adversely affect the electrostatic latent image, the light receiving element 30 receives light. It is preferable to provide a light shielding member (not shown) that covers the light beam up to the element 31 so that the light does not irradiate the photosensitive pair 1.

The doctor blade 8 shown in FIG. 1 is made of a conductor such as a metal, and a voltage having the same polarity as the charged polarity of the toner on the developing roller 5 is applied thereto by a power source 51 as shown by a broken line. By injecting charge into the toner, the charge amount of the toner can be increased.However, when such a configuration is employed, the power supply 51 is controlled by the control device 33 based on the output of the sensor 32, The voltage applied to the doctor blade 8 can also be adjusted. 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 to increase the amount of charge injected into the toner. Make it easier to move to the upper electrostatic latent image,
This prevents a reduction in the image density of the visible image. If the amount of toner on the developing roller 5 is too large, the voltage applied to the doctor blade 8 is reduced to reduce the amount of charge injected into the toner, and this toner transfers to the electrostatic latent image in the developing area 9. It is also possible to make control so as to prevent the problem that the image density of the visible image becomes abnormally high.

In any case, in the illustrated configuration, since the amount of toner on the developing roller 5 is directly detected, this detecting operation can be performed during a normal developing operation, and a measure can be taken. Therefore, the time for performing only the detection operation can be eliminated, and the entire image forming speed can be increased as compared with the method of once forming a reference pattern image on the photoconductor and detecting the image density.

In the above, a specific example in which the present invention is applied to a developing method in which a minute closed electric field is formed near the surface using the developing roller 5 in which the surfaces of the conductor surface 12 and the dielectric 11 are exposed has been described. The present invention can be widely applied to a developing method using a conventionally known toner carrier of various types. For example, using a toner carrier formed by laminating an insulating layer on the surface of a conductive substrate,
In the developing method in which the insulating layer on the surface is charged by friction with the toner supply roller 6 as shown in FIG. 1, for example, and the toner adheres to the surface of the toner carrier by the charge, the toner on the toner carrier is also used. 6 and 7, the surface of the toner layer has severe irregularities depending on the amount of adhesion, or the surface of the toner layer becomes smooth. Conversely, this is detected by a sensor, and the toner amount is detected. Can be detected.

〔The invention's effect〕

According to the present invention, since the amount of toner on the toner carrier is directly detected, the detection operation can be performed during a normal developing operation, and wasteful time can be saved. As a result, it is possible to prevent a decrease in image forming speed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a developing device for carrying out the method according to the present invention. FIG. 2 is an explanatory diagram schematically showing an enlarged view of a dielectric material of a developing roller and toner attached to the roller. 3
FIG. 4 is an enlarged view of the surface of the developing roller also schematically showing the surface of the dielectric, FIG. 4 is a perspective view of the developing roller and a sensor opposed thereto, and FIG. 5 is formed near the surface of the developing roller. FIGS. 6 and 7 are explanatory views showing the state of toner adhesion on the surface of the developing roller, and FIGS.
The figure shows an example of the relationship between the toner adhesion amount on the developing roller and the light reception amount of the light receiving element. 4 ... toner, 9 ... development area 30 ... light emitting element, 31 ... light receiving element

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigekazu Enoki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Naoki Iwata 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (56) References JP-A-64-40965 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08 G03G 21/00 370

Claims (1)

(57) [Claims] An electrostatic latent image formed on the latent image carrier in a developing area where the latent image carrier and the toner carrier are opposed to each other; In a developing method of electrostatically transferring toner on a carrier to visualize an electrostatic latent image, the toner may be smaller than the amount of toner carried and conveyed on the toner carrier. When the amount is large, the surface of the toner layer has large irregularities,
Carrying the toner on the toner carrier, irradiating the toner on the toner carrier with light from a light emitting element having a light beam diameter larger than the diameter of the toner particles, and causing the reflected light to enter the light receiving element By detecting the amount of toner carried on the toner carrier, the amount of toner transfer to the electrostatic latent image in the development area is controlled based on the result, and the image density of the visible image is adjusted. A developing method characterized by the above-mentioned.