JPH0535111A - Development device - Google Patents

Abstract

(57) [Summary] [Object] To provide a developing device capable of forming an image having an appropriate density even in a high humidity or low humidity environment and suppressing the amount of toner scattering. [Structure] In a developing device 10 that supplies toner to a latent image formed on the image carrier 1 to visualize the latent image, the latent image is transferred to the image carrier 1 based on a signal from a temperature / humidity detecting unit 7. The developer carrying member 12 capable of changing the attack amount of the toner per unit time. The density of the image formed on the image carrier and the amount of toner scattered to the outside vary depending on the amount of water in the air, and also the amount of toner attack from the developer carrier 12 to the image carrier 1 per unit time. Also changes. Therefore, the temperature and humidity detecting means 7
The amount of toner attack is changed based on the signal from, so that an image having an appropriate density can be formed with the amount of toner scattering minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer and a facsimile which uses an electrophotographic system or an electrostatic recording system.

[0002]

2. Description of the Related Art For example, in an electrophotographic copying machine capable of forming a multicolor image, toner images of respective colors are formed on an image carrier through four developing devices having toners of respective colors such as yellow, magenta, cyan and black. A multicolor image is formed by multiple-transferring the toner images formed on the transfer paper held on the outer peripheral surface of the transfer drum.

A two-component developer consisting of toner and carrier is generally used in the color developing device, but among the developers adsorbed to the developing sleeve of the developing device by the action of magnetic force during the developing work, the toner is used. A toner image is formed by moving only the toner image toward the image carrier. In this case, the toner is electrostatically adsorbed on the carrier by frictional charging with the carrier, and is held on the developing sleeve via the carrier.

[0004]

However, although a developing device having the above-described two-component developer can form an extremely good image (toner image) under a specific environment, a sufficient image can be formed under a low humidity environment. There is a problem that an image having a density cannot be formed. This is because the charge amount of the toner tends to increase in a low humidity environment, and the attracting force between the toner and the carrier increases, so that the toner does not easily move to the image carrier side.

On the other hand, in a high humidity environment, on the contrary, the charge amount of the toner tends to decrease, so that the binding state between the toner and the carrier weakens, and the toner is removed from the developing sleeve by the centrifugal force due to the rotation of the developing sleeve. There is a disadvantage that the toner easily scatters and contaminates other devices with toner. That is, there is a problem in that toner is adhered to the transfer material carrier sheet of the transfer drum to cause transfer failure during durable use, or toner is adhered to the charging wire of the charger to cause image unevenness.

The present invention has been made in view of the above problems, and an object of the present invention is to form an image with an appropriate density even in an environment of high humidity or low humidity and to minimize toner scattering. It is to provide a developing device that can be suppressed.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a developing device for supplying toner to a latent image formed on an image carrier to visualize the latent image. It is characterized in that it has a developer carrier capable of changing an attack amount of toner to the image carrier per unit time based on a signal from the means.

[0008]

When the developing operation is performed, the charge amount of the toner changes due to the increase / decrease of the water content in the air (in a high humidity environment or a low humidity environment), the density of the image formed on the image carrier is changed, and the toner from the developing device is changed. The amount of splattering also changes. On the other hand, the light and shade of the image formed on the image carrier and the amount of toner scattering also change depending on the amount of attack of the toner from the developer carrier of the developing device to the image carrier per unit time.

Therefore, the attack amount of the toner from the developer carrying member to the image carrying member per unit time is changed based on the signal from the temperature and humidity detecting means, so that the image formed on the image carrying member has an appropriate density. In addition to holding the toner, the amount of toner scattered from the developing device was also minimized.

[0010]

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

First, a first embodiment of the present invention will be described with reference to FIGS.
Will be explained.

FIG. 1 shows the structure of a main part of an image forming apparatus capable of forming a multicolor image. In FIG. 1, reference numeral 1 denotes a photosensitive drum which is an image carrier rotated in the direction of the arrow in the figure. A primary charging device 2, a rotary developing device 3, a transfer drum 4, a cleaning device 5 and the like are arranged around the photosensitive drum 1.

The rotary developing device 3 is, as shown in FIG.
Four developing devices 10 having yellow, magenta, cyan, and black toners (specifically, yellow, magenta, cyan, and black developing devices 10A, 10B, 10C,
10D) is held in a rotatable cylindrical body 3a, and the desired developing device 10 can be positioned at the developing position of the photosensitive drum 1 by rotating the cylindrical body 3a.

As shown in FIGS. 1 and 2, the transfer drum 4 is a transfer material carrier sheet 4a-1 made of polyethylene terephthalate, polyvinylidene fluoride resin film or the like.
A rotatable cylindrical cylinder 4a, a transfer charger 4b arranged inside the cylinder 4a so as to face the photosensitive drum 1 in a fixed state, and a fixed state facing the inner and outer surfaces of the cylinder 4a. And a gripper 4d for positioning and holding the transfer material P on the outer peripheral surface of the cylinder 4a. The transfer drum 4 rotates while adsorbing and holding the transfer material P on the transfer material carrying sheet 4a-1 of the cylinder 4a,
The toner images on the photosensitive drum 1 are transferred onto the transfer material P in multiple layers via the transfer charger 4b.

That is, the image light L of yellow image information is exposed on the outer peripheral surface of the photosensitive drum 1 uniformly charged by the primary charger 2 through a scanner unit (not shown) or the like, and the photosensitive drum 1 is electrostatically charged. When the latent image is formed, the yellow developing device 10A of the rotary developing device 3 is positioned on the photosensitive drum 1 side, and this electrostatic latent image is rotated by the yellow developing device 10A as the photosensitive drum 1 rotates. Is visualized as. Then, this toner image is formed on the photosensitive drum 1.
Is transferred to the transfer material P held on the outer peripheral surface of the cylinder 4a of the transfer drum 4 which rotates in synchronization with the photosensitive drum 1.

After the transfer of the photosensitive drum 1 is completed, the residual toner is cleaned by the cleaning device 5, and the primary charging device 2 uniformly charges the photosensitive drum 1 again to expose it with the image light L of magenta image information. An electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image is magenta developing device 10 of the rotary developing device 3 positioned to face the photosensitive drum 1.
The toner image is visualized as a toner image by B, and the toner image is multiple-transferred onto the transfer material P of the cylinder 4a of the transfer drum 4 which rotates in synchronization with the toner image. Similarly, the toner images formed on the photosensitive drum 1 via the cyan and black 10C and 10D based on the image light L of the cyan and black image information are multi-transferred onto the transfer material P.

On the other hand, after the transfer material P is positioned and held on the outer peripheral surface of the cylinder 4a of the transfer drum 4 via the gripper 4d, the transfer material P is transferred onto the transfer material P via the transfer charger 4b as the cylinder 4a rotates. As described above, the toner images of the respective colors are transferred in a multiple manner. Then, the transfer material P, which has been transferred, is discharged by the discharging charger 4c, separated from the cylinder 4a of the transfer drum 4, and conveyed to the fixing device 6, where the toner image is heated by the fixing device 6. It is pressed, melted and mixed to fix as a permanent image.

The structure of the developing device 10 of the rotary developing device 3 will be described with reference to FIG. 3. The developing device main body 11 of the developing device 10 has a fixed magnet 13 therein, and the magnet 13 is fixed. By the action of 13, the developer T
Developing sleeve 12 which holds and rotates, and developing sleeve 12 for regulating the layer thickness of the developer on the developing sleeve 12.
And the developing blade 14 arranged so as to have a predetermined gap
And screw type first and second stirring members 15 and 16 which rotate in the direction of the arrow in the drawing and circulate while stirring the developer.
Etc. are arranged. Incidentally, the first and second stirring members 15, 1
Both ends of the partition plate 17 for partitioning between 6 are cut out.

The developer T used in the developing device 10 is a two-component developer composed of non-magnetic toner and magnetic carrier, and is developed while being agitated and circulated by the first and second agitating members 15 and 16. The toner in the agent T is frictionally charged with the carrier, and the toner is electrostatically adsorbed and held by the carrier. Therefore, as the developing sleeve 12 rotates, the developer T is transported to the photosensitive drum 1 side while being adsorbed and held on the developing sleeve 12 via the carrier at the position of the scooping pole S2 of the magnet 13. Then, the developer on the developing sleeve 1 is separated from the carrier by the action of the developing bias voltage applied to the developing sleeve 12 at the position of the main developing pole N1 of the magnet 13 and is moved to the photosensitive drum 1 side.

By the way, although the developing work by the developing device 10 as described above is extremely properly performed under a specific environment,
Changes in environmental conditions, especially the amount of water in the air, cause various problems in the developing work.

That is, FIG. 4 shows the relationship between the amount of water in the air (g / m ³ ) and the image density (Dmax) on the photosensitive drum 1 when the contrast potential is constant. As shown, when the amount of water in the air increases (high humidity state), the image density on the photosensitive drum 1 monotonically increases, and an image having a density higher than the actual density is formed. And when the amount of water in the air decreases (low humidity),
The opposite effect occurs. Therefore, an image having an appropriate density cannot be formed in the high humidity condition or the low humidity condition. This is because as the amount of water in the air increases, the amount of water absorbed by the toner in the developer T increases, and the toner's tribo (charge amount per unit weight μ
C / g) decreases, the electrostatic attraction between the toner and the carrier weakens, and the toner excessively moves to the photosensitive drum 1 side. If the water content in the air decreases, the water absorption amount of the toner decreases. Is decreased and tribo of the toner is increased, so that it becomes difficult for the toner to move to the photosensitive drum 1 side.

Further, FIG. 5 shows the relationship between the amount of water in the air and the amount of toner scattering (ΔW) due to the durability from the developing sleeve 12. As shown in this figure, the amount of toner scattering is the amount of air. It increases monotonically as the amount of water in it increases. Therefore, in a high humidity state, the amount of toner scattered to the outside of the developing device 10 increases, and the inside of the image forming apparatus is contaminated with the toner, which is not preferable. This is because when the humidity is high, the tribo of the toner is lowered and the electrostatic attraction between the toner and the carrier is lowered, so that the toner is easily scattered to the outside by the action of the centrifugal force of the developing sleeve 10.

On the other hand, FIG. 6 shows the peripheral speed (v) of the developing sleeve 12 of the developing device 10 and the image density (Dmax) on the photosensitive drum 1 when the contrast potential and the environmental conditions (water content in the air) are constant. As is clear from this figure, the image density monotonically increases as the peripheral speed of the developing sleeve 12 increases. This is the developing sleeve 12
This is because the amount of toner attack (movement amount) per unit time on the electrostatic latent image on the photosensitive drum 1 increases as the peripheral speed of the photosensitive drum 1 increases.

Therefore, from the relationship between FIGS. 4 and 5 and FIG. 6, when the water content in the air increases, the developing sleeve 12
By lowering the peripheral speed of the developing sleeve 12 and decreasing the amount of toner attack from the developing sleeve 12 to the photosensitive drum 1 side, an image having an appropriate density can be formed on the photosensitive drum 1 and the peripheral speed of the developing sleeve 12 decreases. Since the centrifugal force is weakened, the amount of toner scattering due to durability is also reduced. When the amount of water in the air decreases, the peripheral speed of the developing sleeve 12 is increased,
If the attack amount of toner from the developing sleeve 12 to the photosensitive drum 1 side is increased, an image having an appropriate density can be formed on the photosensitive drum 1, and the toner scattering amount does not increase so much.

FIG. 7 shows the above relationship, and if the peripheral speed of the developing sleeve 12 is monotonically decreased with an increase in the amount of water in the air, an image with an appropriate image density is obtained in the air. Regardless of the water content of the toner, it can be always formed, and the scattering of the toner can be minimized. Specifically, under high temperature and high humidity (water content in air is 21 g / m ³ ).
Then, the peripheral speed of the developing sleeve 12 may be set to be the same as the peripheral speed of the photosensitive drum 1 (both rotate in the same direction), and under medium temperature and low humidity (water content in air is 1.4 g / m ³ ) The peripheral speed may be 2.5 times that of the photosensitive drum 1.

Therefore, a temperature / humidity sensor 7 is provided in the image forming apparatus as shown in FIG.
If the rotation speed of the developing sleeve 12 of the developing device 10 is controlled on the basis of the signal from, the image of high quality and proper density is kept on the photosensitive drum 1 for a long period of time with the amount of toner scattering due to the durability being suppressed to the minimum. It can be formed over.
Note that, as shown in FIG. 8, even if the amount of water in the air is divided into a plurality of regions (zones) and the peripheral speed of the developing sleeve 12 is changed stepwise, the same effect as above can be obtained. Of course you can.

Here, as described above, the toner tribo is related to the amount of water absorption of the toner, but since there is hysteresis in the water absorption and water discharge of the toner, the detection value of the temperature and humidity sensor 7 and the toner tribo are Can't always be said to be correlated. Therefore, it is also effective to prepare a table considering the above-mentioned hysteresis and correct the signal value from the temperature / humidity sensor 7 to determine the peripheral speed of the developing sleeve 12.

Next, a second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to 0. The same reference numerals are given to those having the same functions as those according to the first embodiment, and the description thereof will be omitted.

In the first embodiment, the peripheral speed of the developing sleeve 12 of the developing device 10 is changed according to the increase or decrease of the water content in the air,
The amount of toner scattering is minimized and the photosensitive drum 1
Although an image having an appropriate density is formed on the upper surface, in the present embodiment, the layer thickness of the developer on the developing sleeve 12 (hereinafter referred to as the agent coat amount (mg / cm ² )) is changed to the air. I tried to deal with the increase and decrease of water content.

FIG. 9 shows the relationship between the agent coating amount of the developing sleeve 12 and the image density (Dmax) on the photosensitive drum 1. As shown in FIG. It increases monotonically due to the increase in layer thickness). This is because the amount of toner attack per unit time on the electrostatic latent image formed on the photosensitive drum increases as the amount of agent coating increases.

Therefore, as shown in FIG.
If the amount of water increases, the amount of developer coating on the developing sleeve 12
Decrease (decrease the amount of toner attack), moisture in the air
If the amount decreases, the amount of developer coating on the developing sleeve 12 increases.
If you increase the amount of toner attack, the photosensitive drum 1
A high-quality image with proper density can be formed on it for a long time
It will be. Also, if the amount of water in the air increases, it will be durable
The amount of toner scattering due to
Since the amount of agent coat on the tube 12 is reduced, this toner
The amount of scattering of is suppressed. Specifically, the developing sleeve 12
When the peripheral speed of is 1.5 times that of the photosensitive drum 1,
High temperature and high humidity (water content in the air is 21 g / m³) In development
The amount of agent coating on the sleeve 12 is 20 mg / cm²age,
Under moderate temperature and low humidity (water content in the air is 1.4g / m³) Now
The amount of agent coating on the image sleeve is 60 mg / cm²given that
Good.

Here, in order to change the amount of agent coating on the developing sleeve 12, the developing blade 14 shown in FIG. 3 is moved to change the gap between the developing blade 14 and the developing sleeve 12, or the developing blade 14 is changed. As shown in FIG. 3, it has a double structure consisting of a magnetic plate 14a and a non-magnetic plate 14b, the non-magnetic plate 14b is fixed, the magnetic plate 14a is movable, and the gap between the magnetic plate 14a and the developing sleeve 12 is It should be changed.

In the above first and second embodiments, the attack amount of toner from the developing sleeve 12 to the photosensitive drum 1 side is changed according to the change of the water content in the air. However, the relative humidity in the air is detected. Then, even if the attack amount is changed, the effect of the present invention can be substantially maintained. Further, in the first and second embodiments, the developing device 10 using the two-component developer is used.
However, it goes without saying that the present invention can be applied to a developing device that uses a single-component magnetic toner.

[0034]

As is apparent from the above description, according to the present invention, the attack amount of the toner from the developer carrier to the image carrier per unit time is changed based on the signal from the temperature and humidity detecting means. Therefore, an image having an appropriate density is always formed on the image carrier, and the amount of toner scattered from the developing device can be minimized.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of an image forming apparatus incorporating a developing device according to a first embodiment.

FIG. 2 is a perspective view of a transfer drum incorporated in the image forming apparatus.

FIG. 3 is a sectional view of the developing device and the like.

FIG. 4 is a diagram showing the relationship between the density of an image formed by the developing device and the amount of water in the air.

FIG. 5 is a diagram showing the relationship between the amount of toner scattered from the developing device and the amount of water in the air.

FIG. 6 is a diagram showing the relationship between the density of an image formed by the developing device and the peripheral speed of the developing sleeve.

FIG. 7 is a diagram showing a relationship between a peripheral speed of a developing sleeve and an amount of water in the air for forming an image having an appropriate density by the developing device.

FIG. 8 is another relationship diagram showing the relationship between the peripheral speed of the developing sleeve and the amount of water in the air for forming an image having an appropriate density with the developing device.

FIG. 9 is a diagram showing the relationship between the density of an image formed by the developing device according to the second embodiment and the amount of agent coating on the developing sleeve.

FIG. 10 is a diagram showing the relationship between the amount of agent coating and the amount of water in the air for forming an image having an appropriate density with the developing device.

[Explanation of symbols]

 1 Photosensitive Drum (Image Carrier) 7 Temperature and Humidity Detection Sensor 10 Developing Device

Claims (1)

Claim: What is claimed is: 1. A developing device for supplying a toner to a latent image formed on an image carrier to visualize the latent image, based on a signal from a temperature and humidity detecting means. A developing device having a developer carrier capable of changing an attack amount of toner to the image carrier per unit time.