JPH07152244A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of preventing the developing efficiency from largely fluctuating due to the reduced toner charge rate, thereby stably uniformizing the toner supply quality to the image transporting body such as a photoreceptor drum and obtained the excellent quality of the development, in respect of the image forming device developing the latent image formed on the surface of the image transporting body such as the photoreceptor drum by the toner transported with the toner transporting body such as the developing roller. CONSTITUTION:The image forming device is provided with the image carrier 1 driven to rotate and on which the latent image is formed, and the toner carrier 21 which is driven to rotate in contact with the image carrier 1 so as to transport the toner to the image carrier while sticking the toner 50 for developing the latent image on the surface, and constituted so that the toner 50 on the surface of the toner carrier 21 is charged at -16muC/g to -19umuC/g.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image formation in which a latent image formed on the surface of an image carrier such as a photosensitive drum is developed with toner carried by a toner carrier such as a developing roller. Regarding the device.

As a developer for such an image forming apparatus,
A so-called one-component developer consisting only of toner containing no carrier particles is widely used, but in order to obtain good development quality, the toner supply amount from the toner carrier to the image carrier should be kept constant. There is a need to.

Particularly in an electrophotographic apparatus in which toners of a plurality of colors are overlapped to form a full-color image, if the toner supply amount varies depending on the color, the color reproducibility deteriorates and the image quality remarkably deteriorates. Will end up.

[0004]

2. Description of the Related Art In an electrophotographic apparatus or the like, a layer thickness regulating blade arranged so as to come into pressure contact with the surface of a developing roller while the toner adheres to the surface of a developing roller as a toner carrier and is conveyed. The toner layer is formed to have a predetermined uniform thickness.

Then, the toner layer is conveyed by the rotation of the developing roller to the surface of the photosensitive drum, which is an image carrier, and the latent image on the surface of the photosensitive drum is developed. At this time, the peripheral speed of the developing roller is set to be higher than the peripheral speed of the photosensitive drum to secure the toner amount necessary for the development.

The toner amount M supplied from the developing roller to the photosensitive drum can be expressed by the following equation. M = (Vd / Vp) Dt.a.P.nd, where Vd / Vp: peripheral speed ratio (developing roller peripheral speed / photosensitive drum peripheral speed) Dt: toner layer thickness a: toner density P: toner filling rate nd: development efficiency (ratio of toner transferred from the development roller to the photosensitive drum).

Therefore, conventionally, from the above equation, if the peripheral speed ratio is set large when the toner layer thickness is thin, and conversely, when the toner layer thickness is large, the peripheral speed ratio is set small, the toner supply amount to the photosensitive drum. It is considered that the toner layer thickness and the peripheral speed ratio are set to an appropriate relationship at the time of designing.

[0008]

However, the developing efficiency, that is, the ratio of the toner adhering to the developing roller to the photosensitive drum side varies depending on the difference in the charge amount of the toner.

Therefore, even if the apparatus is designed in consideration of only the relationship between the toner layer thickness and the peripheral speed ratio, unless the charge amount of the toner moving to the photosensitive drum is always set to an appropriate value, the fog on the photosensitive drum is caused. Occurs and the image quality deteriorates.

Particularly in the case of a color image forming apparatus, since the toner charge amount differs for each color toner, the charge amount must be set to an appropriate value for each color toner to prevent fog from occurring. The color shade changes greatly, and the image quality significantly deteriorates.

Even with the same color toner, fog may occur due to a slight difference in the charge amount of the toner for each replacement unit. Therefore, it is necessary to check the image quality every time the toner is replaced and adjust the developing process section of the apparatus so that the fog does not occur. This problem also applies to monochrome devices.

Therefore, in the present invention, the deviation of the toner charge amount is small and the developing efficiency does not largely change. As a result, the toner supply amount to the image carrier such as the photosensitive drum becomes stable and uniform, and good developing quality is obtained. It is an object of the present invention to provide an image forming apparatus that can obtain the image forming apparatus, and further to provide an image forming apparatus that uses a one-component developer and that can obtain high-quality image regardless of the difference in toner material. To aim.

[0013]

In order to achieve the above object, the image forming apparatus of the present invention is rotationally driven with a latent image formed on the surface thereof as shown in FIG. 1 for explaining the embodiment. An image carrier, a toner carrier that is rotatably driven in contact with the image carrier so that toner for developing the latent image is adhered to the surface and is conveyed to the image carrier; A toner layer thickness regulating body arranged in pressure contact with the surface of the toner transport body to regulate the layer thickness of the toner attached to the surface of the toner transport body and transported on the surface of the toner transport body. Toner of -16 μC / g to -1
It is characterized in that it is charged to 9 μC / g.

The toner carrier is preferably driven to rotate at a peripheral speed 1.2 to 2.5 times the peripheral speed of the image carrier, and the toner layer thickness on the surface of the toner carrier is good. Is
11 μm to 18 μm depending on the toner layer thickness regulator
It is good to be regulated by the thickness of. Further, it is preferable not to apply a bias voltage to the toner layer thickness regulator.

In the multicolor image forming apparatus of the present invention, an image carrier on which an electrostatic latent image is formed, a plurality of toner carriers for carrying toner for each color to the image carrier, and the image carrier. Driving means for rotationally driving the body, driving means for rotationally driving each of the toner transport bodies, and toner layer thickness regulating body provided in each of the toner transport bodies for regulating the layer thickness of the toner on each of the toner transport bodies In the multicolor image forming apparatus, the toner transport bodies each have a peripheral speed of 1.
The toner layer is rotatably driven at a peripheral speed of 2 to 2.5 times, and the thickness of the toner layer on each of the toner conveying bodies is regulated to 11 μm to 18 μm by each of the toner layer thickness regulating bodies. A bias voltage may not be applied to each of the toner layer thickness regulators.

[0016]

[Function] The charge amount of the toner on the surface of the toner carrier is reduced by
By making the range from μC / g to −19 μC / g, even if the peripheral speed ratio between the toner carrier and the image carrier and the toner layer thickness on the toner carrier vary within the design range, Since the toner charge amount does not vary so much, the developing efficiency does not change significantly. As a result, a stable and uniform toner supply amount from the toner carrier to the image carrier is maintained.

[0017]

EXAMPLES The inventor conducted experiments by paying attention to the fact that the charge amount of toner is related to the toner layer thickness on the developing roller and the peripheral speed ratio between the developing roller and the photosensitive drum.

As a result, the charge amount of the toner is stable when the value of the toner layer thickness on the developing roller is 11 μm to 18 μm and the charge amount of the toner is -16 μC / g to −19 μC / g. , The charge amount of toner is -16μ even when the peripheral speed ratio of the developing roller / photosensitive drum is 1.2 times to 2.5 times.
It was found to be stable between C / g and −19 μC / g (FIGS. 3 and 4).

It was confirmed that by keeping the toner layer thickness and the peripheral speed ratio of the developing roller / photosensitive drum within this range, the charge amount of the toner can be stabilized and the occurrence of fog can be prevented (FIG. 5).

Embodiments will be described below with reference to the drawings.
FIG. 2 shows an electrophotographic full-color printer to which the present invention is applied. However, the present invention can be applied to various image forming apparatuses that develop a latent image with toner in addition to a monochrome printer.

The developing unit 10 of this printer device has four sets of developing units 11, 12, 1 for recording four colors of black, which is added to the three primary colors yellow, magenta, and cyan.
3, 14 are provided.

When recording, first, the surface of the photosensitive drum 1 (image carrier) is charged to a negative voltage by the charger 2. Then, the surface of the photosensitive drum 1 is exposed by the laser optical unit 3 to form an electrostatic latent image of an image to be recorded on the surface of the photosensitive drum 1.

The photosensitive drum 1 is rotationally driven in the arrow direction,
In the developing unit 10, color toner is selectively attached to the latent image on the photosensitive drum 1. Here, the yellow toner is used first.

In the transfer section 4, the toner image on the photosensitive drum 1 is transferred onto the transfer belt 5. After the transfer, the cleaner drum 6 cleans the photosensitive drum 1 to remove residual toner, and the image forming process is repeated.

In the next step, magenta is used in place of yellow for development, and the magenta toner image is superposed on the transfer belt 5 while being aligned with the yellow toner image. In the same manner, the cyan toner image and the black toner image are sequentially superposed on the transfer belt 5.

When the four color toner images are overlaid,
In the second transfer portion 7, the toner images are collectively transferred from the transfer belt 5 onto the recording paper 100. Then, the recording paper 100 is heated by the fixing device 8 to melt the toner, and the recording paper 100 is melted.
Fix it on.

After the transfer belt 5 is transferred onto the recording paper 100, the cleaner 9 removes the residual toner and uses it again for recording. The above operation is repeated to record a full-color image on the recording paper 100.

FIG. 1 shows the developing unit 12 for magenta among the four developing units of the developing unit 10 as an example. Developing unit 1 using other color toner
The configurations of 1, 13, and 14 are the same.

The developing unit 12 is of a so-called one-component developer type which uses only non-magnetic toner 50 which does not mix magnetic carrier particles as a developer, for example, a volume resistivity of 4 × 10 ^-14 Ω. cm, average particle size 12μ
m, a polyester type toner containing 0.5% of a silica external additive is used.

The developing roller 21 (toner carrier) is made of a conductive urethane foam material having conductivity, and is pressed against the surface of the photosensitive drum 1 to be faster than the peripheral speed of the photosensitive drum 1. At the peripheral speed, the contact portion is rotationally driven in the same direction as the photosensitive drum 1.

The reset roller 22 which is rotationally driven while being in contact with the developing roller 21 in the developing unit 12 is formed of a conductive urethane foam material or the like.

Toner 5 stored in the developing unit 12
0 is sent to the developing roller 21 by the reset roller 22. Then, the toner 50 on the surface of the developing roller 21 is moved by the layer thickness regulating blade 23 made of a leaf spring-shaped stainless steel plate pressed against the surface of the developing roller 21 by a tension coil spring 24 at a predetermined pressure (for example, 35 gf / cm).
Is conveyed to the photosensitive drum 1 side in a state where the layer thickness is regulated to a constant value.

The toner remaining on the developing roller 21 side without moving to the photosensitive drum 1 side at the contact portion with the photosensitive drum 21 is collected in the developing unit 12 by the reset roller 22.

Reference numerals 26 and 27 denote bias power sources for applying a bias voltage to the developing roller 21 and the reset roller 22, for example, a voltage of -300V is applied to the developing roller 21 and a voltage of -400V is applied to the reset roller 22.

Reference numeral 28 denotes a bias power source for applying a bias voltage to the layer thickness regulating blade 23, which applies a voltage of, for example, -400V. However, the power supply 28 can be removed.

Using the apparatus of the above embodiment, the developing roller 2
1 and the peripheral speed ratio of the photosensitive drum 1 and the thickness of the toner layer on the developing roller 21 were changed, and the difference in the charge amount of the toner was measured.

The peripheral speed ratio between the developing roller 21 and the photosensitive drum 1 was determined by fixing the peripheral speed of the photosensitive drum 1 to 70 mm / s and changing the peripheral speed of the developing roller 21. As shown in FIG. 7, the peripheral speed is controlled by the developing roller 21.
A control signal is output from a controller 30 including a CPU (not shown) to the drive circuits 21b and 1b of the motor 21a that rotationally drives the motor 1a and the motor 1a that rotationally drives the photosensitive drum 1, respectively.

The toner layer thickness on the developing roller 21 is
It was adjusted by changing the protrusion length e which is the tip portion of the layer thickness regulating blade 23 shown in FIG. As shown in FIG. 9, the toner layer thickness is reliably changed by changing the protrusion amount e of the layer thickness regulating blade 23.

The charging of the toner is caused by friction when the toner passes through the layer thickness regulating blade 23, and the charging amount can be controlled by the peripheral speed ratio between the developing roller 21 and the photosensitive drum 1 and the toner layer thickness.

FIG. 3 shows changes in the toner layer thickness on the developing roller 21 and the toner charge amount when the developer supply amount is set to a predetermined condition. In the range where the toner layer thickness is 11 μm or less, a rapid change in the charge amount occurs, so even a slight variation in the toner layer thickness causes a large change in the developing efficiency, which is a condition that the developing quality is likely to deteriorate. I understand. Therefore, it is preferable to select the toner layer thickness of 11 μm or more.

FIG. 4 shows changes in the peripheral speed ratio between the developing roller 21 and the photosensitive drum 1 and the toner charge amount when the toner supply amount is set to a predetermined condition. It can be seen that in the range of the peripheral speed ratio of 2.5 or more, the development amount is likely to be deteriorated because the charge amount rapidly increases due to the slight variation in the peripheral speed ratio. Therefore, it is preferable to select the peripheral speed ratio of 2.5 or less.

In this experiment, the print density, which is almost proportional to the amount of toner adhering to the photosensitive drum 1, was examined. The result is as shown in FIG. 5, and in the range of the peripheral speed ratio of 1.2 or less, the charge amount was in a good condition. Even if there is, the print density is remarkably reduced, and it cannot be used. Therefore, the peripheral speed ratio is 1.2
You should choose the above.

FIG. 6 is an experimental result showing the relationship between the toner layer thickness on the developing roller 21 and the print density. Considering the decrease in print density, the toner layer thickness is preferably in the range of 18 μm or less.

Further, as shown in FIGS. 3 to 6, when a voltage is applied to the layer thickness regulating blade 23, the print density is remarkably reduced even with the same charge amount. It is better not to apply a voltage to the blade 23.

Under the condition that no voltage is applied to the layer thickness regulating blade 23, the toner layer thickness is set to 11 μm or more and the peripheral speed ratio is set to 2.5 or less so that a rapid change of the toner charge amount does not occur. The toner charge amount of
It is in the range of -16 μC / g to -19 μC / g.

Therefore, the toner charge amount is -16 μC / g
A printing test was conducted by changing the temperature in the range of −19 μC / g and its vicinity, and the states of fogging and print density were judged. As a result, as shown in FIG. 10, the toner charge amount is −16 μC.
Fog and print density were good in the range of / g to -19 μC / g.

[0047]

According to the present invention, only by setting the peripheral speed ratio between the toner carrier and the image carrier or the toner layer thickness on the toner carrier, fogging can be prevented regardless of the difference in toner material. Therefore, high quality image can be obtained.

This means that it is not necessary to precisely define the peripheral speed ratio between the toner carrier and the image carrier or the toner layer thickness on the toner carrier at the time of designing the device, and the number of manufacturing steps can be reduced. It is possible to reduce the price.

In the color image forming apparatus, the peripheral speed ratio between the toner carrier and the image carrier or the toner layer thickness on the toner carrier is set to a rough range regardless of the difference in the material of the color toner used. Therefore, even if there are considerable variations, the occurrence of fog can be prevented, and high-quality image quality can be obtained.

Further, even with the same color toner, it is not necessary to check the image quality due to a slight difference in the charge amount of the toner for each replacement unit due to each toner replacement. Therefore, even in a monochrome device, the peripheral speed ratio between the toner carrier and the image carrier or the toner layer thickness on the toner carrier is set to a rough range to prevent fog even if there is considerable variation. It is possible to prevent this, and it is possible to obtain a high quality image.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus according to an embodiment.

FIG. 2 is a configuration diagram of a color printer device according to an embodiment.

FIG. 3 is a diagram showing an experimental result of an example.

FIG. 4 is a diagram showing an experimental result of an example.

FIG. 5 is a diagram showing an experimental result of an example.

FIG. 6 is a diagram showing an experimental result of an example.

FIG. 7 is a partial configuration diagram of an example.

FIG. 8 is an explanatory diagram of a relationship between a blade protrusion amount and a toner layer thickness.

FIG. 9 is an explanatory diagram of a relationship between a blade protrusion amount and a toner layer thickness.

FIG. 10 is a chart showing experimental results of Examples.

[Explanation of symbols]

 1 Photosensitive Drum (Image Conveying Body) 21 Developing Roller (Toner Conveying Body) 23 Layer Thickness Control Blade (Toner Layer Thickness Controlling Body) 50 Toner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshimi Takizawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (6)

[Claims] 1. An image carrier on which a latent image is formed and which is rotatively driven, and a toner for developing the latent image, which adheres to the surface and is conveyed to the image carrier. A toner carrier that is rotationally driven in contact with the toner carrier, and a toner that is placed in pressure contact with the surface of the toner carrier to regulate the layer thickness of the toner that adheres to the surface of the toner carrier and is carried. An image forming apparatus having a layer thickness regulator, wherein the toner on the surface of the toner carrier is charged to −16 μC / g to −19 μC / g. 2. The image forming apparatus according to claim 1, wherein the toner carrier is rotationally driven at a peripheral speed of 1.2 to 2.5 times the peripheral speed of the image carrier. 3. The toner layer thickness on the surface of the toner carrier is 11 μm to 18 depending on the toner layer thickness regulator.
The image forming apparatus according to claim 1, wherein the image forming apparatus is regulated to have a thickness of μm. 4. The image forming apparatus according to claim 1, wherein a bias voltage is not applied to the toner layer thickness regulator. 5. An image carrier on which an electrostatic latent image is formed, a plurality of toner carriers that carry toner for each color to the image carrier, drive means for rotatably driving the image carrier, and A multi-color image forming apparatus including: a drive unit that rotationally drives each toner transport body; and a toner layer thickness regulator that is provided on each toner transport body and regulates the layer thickness of the toner on each toner transport body. The toner carrier is rotatably driven at a peripheral speed 1.2 to 2.5 times the peripheral speed of the image carrier, and the toner layer thickness on the toner carrier is 1 depending on the layer thickness regulator
A multicolor image forming apparatus, characterized in that the thickness is regulated to 1 μm to 18 μm. 6. The multicolor image forming apparatus according to claim 5, wherein a bias voltage is not applied to each toner layer thickness regulator.