JPH0566657A - Developing device - Google Patents

Abstract

(57) [Abstract] [Purpose] In the one-component development used in an electrophotographic apparatus, the supply amount of the developer is reduced and the image density is reduced due to the accumulation of the toner in the conveying roll that supplies the developer to the developing roll. It is an object of the present invention to provide an excellent one-component developing device that solves the above problem and has the characteristics of uniform and stable image density. [Structure] 5 is a scraping member set so as to abut on the transport roll 3, and 6 is a developing roll.
Is set to abut. The scraping member 5 is a rigid body, and the amount of bite into the transport roll 3 is 0.3.
By setting the peripheral speed ratio of the transport roll 3 to the developing roll 6 to be 1.8 or more, the holding amount of the developer in the transport roll 3 is always constant, The amount of the developer supplied from the roll 3 to the developing roll 6 is larger than the amount of the developer developed from the developing roll 6, and a uniform developing device with stable image density can be obtained.

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 electrophotographic apparatus or the like, and more specifically, a developer is supplied from a carrying roll onto the developing roll and carried to an electrostatic latent image to form an electrostatic latent image. The present invention relates to a one-component developing device for developing a visible image.

[0002]

2. Description of the Related Art Conventionally, in this type of developing device, a developer stored in a hopper is conveyed to a developing roll by a conveying roll which comes into contact with the developing roll and rotates in the same direction or in the opposite direction. Then, by the layer forming member that is in contact with the developing roll at a uniform linear pressure, the developer conveyed to the developing roll is made into a developer layer having a predetermined thickness, and this developer layer is held on the holder. It is known that an electrostatic latent image is moved to a visible image so that the electrostatic latent image becomes a visible image. As the transfer roll, an elastic roll made of urethane foam or rubber or a fur brush roll made of nylon or rayon is used.

In such a developing device, the developer gradually accumulates in the carrying roll, the amount of the developer supplied to the developing roll is reduced, and the thickness of the developer layer on the carrying roll is reduced.
As a result, it is known that there is a problem that the image density decreases. In particular, in the case of an image with a high black image ratio (so-called solid image), the amount of developer developed from the developing roll to the latent image holding member (hereinafter referred to as the developing amount) is large, so that the development supplied from the transport roll to the developing roll is large. There is a problem in that the amount of the agent (hereinafter referred to as the supply amount) cannot be kept up, the image becomes thin, and uneven image density occurs. Especially when the entire image is solid, the developing roll 1
The image density is high up to the first round, and light after the first round. The density of the leading edge of the image becomes high because the developing roll and the transport roll rotate before the development starts, and the developer is supplied from the transport roll to the developing roll several times, so that the developer layer on the developing roll becomes thick. This is because the image density becomes high. However, after the first roll of the developing roll, the developer on the developing roll is almost undeveloped,
After that, since the developer is supplied from the transport roll to the developing roll only once, the thickness of the developer layer on the developing roll becomes thin. In such a state, it was difficult to obtain a uniform and stable image.

For this reason, the scraping member that comes into contact with the transport roll removes the developer accumulated on the transport roll. However, there is a problem that if the amount of the scraping member intruded into the transport roll is too large, the transport roll is deformed and the supply of the developer is reduced.
Further, JP-A 1-130175 discloses a scraping member having elasticity as a means for preventing a difficult change in the amount of dust, but since the transport roll also has elasticity, it is difficult to set the elastic force of the scraping member. I couldn't get enough effect.

[0005]

SUMMARY OF THE INVENTION In the present invention, the developer is accumulated in the conveying roll, the supply amount of the developer to the developing roll is reduced, and the image density is lowered, as described above. This is to solve the problem that the density difference and the density unevenness occur between the front end of the image and the first rotation of the developing roll.

[0006]

In order to solve the above problems, the present invention provides a developing roll that carries a developer and conveys it to a developing area, and a conveyer that presses the developer roll and supplies the developer to the developing roll. A roll, a developer layer thickness regulating member for thinning the developer supplied to the developing roll, and a scraping member abutting on the conveying roll on the downstream side of the pressure contact portion between the developing roll and the conveying roll. In the one-component developing device, the amount of the developer supplied from the transport roll to the developing roll is greater than the amount of the developer developed from the developing roll to the latent image holding member holding the latent image. The scraping member is a rigid body, the amount of biting into the transport roll is in the range of 0.3 to 1.0 mm, and the peripheral speed of the transport roll is the developing roll with the rotation direction of the transport roll and the developing roll being opposite to each other. Lap It is characterized in that it is 1.8 times or more.

[0007]

With this configuration, the accumulation of the developer in the carrying roll and the deformation of the carrying roll can be prevented, and the supply amount becomes larger than the developing amount. Therefore, the developer is stably supplied from the carrying roll to the developing roll, It is possible to obtain a developing device having a uniform and stable image density.

[0008]

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

FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 1 denotes a hopper that stores a developer 2, and a transport roll 3 is disposed in an opening 1a of the hopper 1 so as to be rotatable in a direction of an arrow 3a. 4 is a conveyance roll 3 for passing the developer 2 in the hopper 1 through the opening 1a.
It is a feed blade for supplying to and is rotatable in the direction of arrow 4a. Reference numeral 5 is a rigid scraping member set so as to abut against the transport roll 3, and 6 is a developing roll, which is indicated by an arrow 6a.
It is rotatable in the direction of and is set so as to come into contact with the transport roll 3. The free end of the blade 7 is in contact with the developing roller 6 with a predetermined pressure. On the other hand, at a position facing the developing roll 6, the holding roll 9 holding the electrostatic latent image 8 is
It is arranged rotatably in the direction of arrow 9a. Further, a bias power source of a DC voltage is applied to the developing roll 6 by a bias power source 10.

The scraping member 5 is arranged so that the amount of bite into the transport roll 3 is 0.3 to 1.0 mm, and the peripheral speed of the transport roll is set to the peripheral speed of the developing roll by a driving device (not shown). It is set to be 1.8 times the speed.

That is, the inventor of the present invention investigated the relationship between the amount of developer held in the transport roll and the amount of development and supply by changing the bite amount of the scraping member and the peripheral speed ratio of the transport roll to the developing roll. As a result, the amount of bite is 0.3 m
If the peripheral speed ratio of the transport roll to the developing roll is 1.8 or more within the range of m to 1.0 mm, the amount of the developer retained is kept constant even when used for a long period of time.
It has been found that the supply amount is always larger than the developing amount, so that the image density is constant and uneven image density does not occur.

FIGS. 2 and 3 show the experimental results when the scraping amount of the scraping member is 0 mm, 0.5 mm, and 1.3 mm by curves A, B, and C, respectively.
FIG. 2 shows the change in the amount of developer held in the transport roll.
Indicates a change in image density. The peripheral speed ratio of the transport roll to the developing roll was 1.8. In addition, a change in holding amount when a scraping member having elasticity disclosed in JP-A-1-130175 is used as a conventional example is added to FIG. 2 (curve D). As is clear from FIG. 2 and FIG. 3, when the bite amount is 0.5 mm (curve B), the developer holding amount in the transport roll and the image density are almost constant even after long-term operation. However, unlike the other cases (curve A, curve C), it does not change gradually. Further, as shown in FIG. 2, even when an elastic scraping member (curve D) is used, the amount of developer retained in the transport roll changes significantly, and although not shown, the image density also greatly decreases. In addition, Fig. 4 shows that when the scraping amount of the scraping member is 0 mm and 0.5 mm,
The results of examining the change in the ratio of the supply amount to the development amount (supply amount / development amount) with 3000 copies are shown in curve A, respectively.
And B. At this time, the peripheral speed ratio of the transport roll to the developing roll is 1.5. When the bite amount is 0 mm (curve A), the supply amount is gradually reduced and the ratio of the supply amount to the developing amount is less than 1, resulting in significant image unevenness. Biting amount 0.5 mm (curve B)
In this case, the decrease width is small, the ratio never falls below 1, and uneven image density does not occur.

However, even at this time, if the toner is used for a longer period of time, the supply amount will gradually decrease due to the deterioration of the developer, and the ratio of the supply amount to the developing amount may fall below 1 to cause uneven density. .. Therefore, in order to withstand longer-term use, the peripheral speed of the transport roll was changed and the supply amount was examined. FIG. 5 shows the ratio of the supply amount to the development amount (supply amount / development amount) when the peripheral speed ratio of the transport roll to the developing roll is changed. The curve A is the initial stage, and the curve B is after copying 9000 sheets. Indicates. At this time, the scraping amount of the scraping member was 0.5 mm. As shown in FIG. 5, when the peripheral speed ratio was 1.8 or more, the supply amount exceeded the development amount both at the initial stage and after copying, and image unevenness and density difference did not appear, and a uniform copy image was obtained.

The operation of this embodiment configured as described above will be described. First, the developer 2 in the hopper 1 is supplied from the opening 1 a to the outer peripheral portion of the transport roll 3 by the rotation of the feed blade 4. The supplied developer 2 is transported to the developing roll 6 by the transport roll 3. At the contact portion between the two rolls 3 and 6, the developer moves from the transport roll 3 to the outer peripheral surface of the carrier roll 6. The developer remaining on the carrying roll without moving to the developing roll is scraped off by the scraping member 5.
And an appropriate amount of developer is newly supplied to the outer peripheral portion of the transport roll 3.

In the present embodiment, as described above, the scraping amount of the scraping member 5 to the transport roll 3 is 0.3 to.
Since it is 1.0 mm, even in long-term use,
The amount of developer held on the transport roll 3 is constant, and the image density is also constant.

Moreover, since the peripheral speed of the transport roll is 1.8 times the peripheral speed of the developing roll, the supply amount is larger than the developing amount, and a uniform image is always obtained.

The developer is triboelectrically charged by the rubbing of the transport roll 3 and the developing roll 6, and a sufficient electric charge is applied. By the rotation of the developing roll 6, the developer on this roll moves to the contact position of the blade 7 and
As a result, a developer layer having a predetermined thickness is obtained. Then, it reaches a position facing the holding body 9. The holder 9 is rotating in the direction of the arrow 9a, and when the electrostatic latent image 8 held on the outer peripheral surface reaches the facing position, the developing roller 6 is rotating while being applied with a bias voltage. Due to the electric field between the electrostatic latent image 8 and the developing roller 6, the developer on the developing roller 6 is attracted to the electrostatic latent image 8 and adheres to the latent image 8. In this way, the latent image is developed.

Although the scraping member is attached to the hopper in the above embodiment, the scraping member and the hopper may of course be integrated.

Further, in the above embodiment, as the transport roll 3,
Although a fur brush roll made of rayon fiber is used, an elastic roll made of urethane foam or rubber or a fur brush roll made of nylon fiber or acrylic fiber may be used.

If the peripheral speed ratio of the conveying roll to the developing roll is too large, the developer may spill or scatter out of the developing device. Therefore, the peripheral speed ratio is preferably 3 or less.

[0021]

As described above, according to the present invention,
The scraping member that comes into contact with the transport roll that supplies the developer to the developing roll is made of a rigid body, and the dent amount is 0.3 to 1.
Since the peripheral speed ratio of the carrying roll to the developing roll was set to 1.8 or more in the range of 0 mm, the amount of developer held in the carrying roll was always constant, and the amount of developer supplied from the carrying roll to the developing roll was constant. Can be always larger than the amount of the developer developed on the latent image carrier from the developing roll, and uniform and stable image density development can be performed for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing changes in the amount of developer retained in the transport roll due to the difference in the amount of scraping of the scraping member in the example of the present invention.

FIG. 3 is a characteristic curve diagram showing a change in image density due to a difference in the amount of scraping of the scraping member in the embodiment of the present invention.

FIG. 4 is a characteristic curve diagram showing changes in the ratio of the supply amount to the development amount (supply amount / development amount) due to the difference in the bite amount of the scraping member in the embodiment of the present invention.

FIG. 5 is a characteristic curve diagram showing a change in a ratio of a supply amount and a development amount (supply amount / development amount) due to a difference in peripheral speed ratio of a transport roll with respect to a developing sleeve in an example of the present invention.

[Explanation of symbols]

 2 developer 3 transport roll 5 scraping member 6 development roll

Claims (4)

[Claims] 1. A developing roll that carries a developer and conveys it to a developing area; a conveying roll that presses the developing roll to supply the developer to the developing roll; and a press contact portion between the developing roll and the conveying roll. On the downstream side, a developer layer thickness regulating member for thinning the developer supplied to the developing roll, and a scraping member abutting on the carrying roll are provided, and the amount of the developer supplied from the carrying roll to the developing roll. Is more than the amount of developer developed from the developing roll to the latent image holding member that holds the latent image,
A one-component developing device characterized by a large number. 2. The one-component developing device according to claim 1, wherein the scraping member is a rigid body, and the amount of biting into the conveying roll is in the range of 0.3 to 1.0 mm. 3. The one-component developing device according to claim 2, wherein the conveying roll and the developing roll rotate in opposite directions, and the peripheral velocity of the conveying roll is 1.8 times or more the peripheral velocity of the developing roll. 4. The one-component developing device according to claim 2, wherein the conveying roll is a fur brush having a fiber density of 20000 filaments / inch ² or more.