JPH0486858A - Developing device - Google Patents

Abstract

PURPOSE:To prevent drastic escape from the home position of a press-contact part and o stabilize the formation of a developer thin layer by providing spring leaf material whose one end is supported and a weight which presses the upper press-contact part of the spring leaf material toward a developing roller in a developer thin layer forming means. CONSTITUTION:Toner A supplied to the developing roller 12 is formed to be a thin layer by a blade 16 and electrostatically charged and transferred to an electrostatic latent image on the surface of a photosensitive drum 11. The blade 16 is constituted by mounting a chip 162 in a longitudinal direction at the tip part of a leaf spring 161, and supported to a device main body by a 1st blade holder 16a, a spacer 16b and a 2nd blade holder 16c. A foaming material 20 is interposed between a baffle plate 19 and the back surface of the blade 16 so as to prevent the leakage of the toner A and the vibration of the blade 16. The blade 16 is pressed by plural compression springs 22 with a rotary shaft 21 as fulcrum. Furthermore, the weight 16d for pressing the chip 162 toward the roller 12 at the press-contact position of the chip 162 with the roller 12 is attached to a surface reverse to the surface where the chip 162 is mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device for visualizing an electrostatic latent image in an electrophotographic device, an electrostatic recording device, or the like.

(Prior Art) One of the developing methods using a one-component developer is the pressure development method.
)It has been known.

This pressure development method attaches the toner to the surface of the developing roller by applying an electric charge to the toner through friction with the developing roller and friction with a blade for forming a thin toner layer that is pressed against the surface of the developing roller. One of its characteristics is that it can be transported. Therefore, there are many advantages such as no magnetic material is required, the device can be simplified and miniaturized, and the toner can be made into colored toner products. Resin or rubber elastic material is usually used for the pressure contact part of the blade in order to ensure a predetermined nip width with the developing roller, and the tip of the pressure contact part is rounded to ensure a uniform thickness of the toner layer. It is desirable to have a shape. Further, in order to uniformly press the pressure contact portion against the surface of the developing roller, it is preferable to employ a blade having a structure in which the pressure contact portion is mounted on a thin plate spring. Furthermore, in order to stabilize the pressure applied by the blade to the developing roller, there are many methods in which the blade is rotatably supported in the main body of the apparatus and a compression spring is used to bias the pressure contact part of the blade in the direction of pressing it against the developing roller. It is taken.

However, even if the pressure contact part of the blade is pressed against the developing roller in this way, there is a risk that the blade will largely escape from its fixed position due to the repulsive force received when the toner passes between the developing roller and the developing roller. As a result, the toner layer becomes thick and the amount of charge becomes insufficient, which may result in defective images with uneven density, background fog, etc.

(Problems to be Solved by the Invention) As described above, in the conventional developing device, the pressure contact portion of the developer thin layer forming means is significantly moved from the normal position due to the repulsive force received when forming the developer thin layer on the surface of the developing roller. There is a risk of the developer escaping, resulting in the problem that a thin developer layer with a stable thickness cannot be obtained.

The present invention is intended to solve these problems, and it is possible to prevent the pressing part from significantly escaping from the fixed position when forming a thin layer of developer on the surface of the developing roller, and to form a thin layer of developer with a uniform thickness. An object of the present invention is to provide a developing device capable of forming a layer on the surface of a developing roller.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the developing device of the present invention includes a developing roller disposed facing the electrostatic latent image holder, and a developing roller disposed opposite to the electrostatic latent image holder. and a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, and the electrostatic latent image is formed by bringing the developer thin layer formed on the surface of the developing roller close to or in contact with the electrostatic latent image holder. In a developing device that visualizes an electrostatic latent image held by a holder, a developer thin layer forming means includes a spring plate member whose one end is supported, and is provided on the spring plate member, and the developer thin layer forming means is provided on the spring plate member with one end supported. The present invention is characterized in that it includes a pressure contact portion that is pressed against the developing roller with the layer in between, and a suppressing means that presses the pressure contact portion toward the developing roller at or near a position where the pressure contact portion comes into pressure contact with the developing roller.

(Function) In the developing device of the present invention, the suppressing means presses the pressing portion toward the developing roller at or near the position where the pressing portion is pressed against the developing roller. It is possible to prevent the pressing part from escaping from its fixed position to a large extent when forming a thin layer of developer, thereby stabilizing the formation of a thin layer of developer on the surface of the developing roller.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the overall structure of a contact type component nonmagnetic developing device (hereinafter simply referred to as a developing device) according to an embodiment of the present invention.

As shown in the figure, this developing device 10 uses non-magnetic toner (hereinafter simply referred to as toner) as a developer on an electrostatic latent image formed on the surface of a photoreceptor drum 11, which is an electrostatic latent image holder. ) A developing roller 12 for transferring toner A to visualize the electrostatic latent image, and a toner container 13 containing toner A.
, a mixer 14 that stirs the toner A in the toner container 13 , a toner supply roller 15 that supplies the toner A in the toner container 13 to the developing roller 12 , and a developing roller 1
The main part thereof is composed of a blade 16 which is a developer thin layer forming means for forming a thin toner layer on the surface of the developer.

Next, the developing process in this developing device 10 will be explained.

The toner A contained in the toner container 13 is transferred to the mixer 1.
4, the toner is sent toward the toner supply roller 15, and further supplied to the developing roller 12 by the toner supply roller 15. Here, the toner A is negatively charged due to friction with the surface of the rotating developing roller 12, is electrostatically attracted to the surface of the developing roller 12, and is transported. After this,
The toner A attached to the surface of the developing roller 12 is removed by the blade 1.
6 regulates the amount of toner conveyed and becomes a thin layer, and at the same time, it is charged again by friction with the developing roller 12 and blade 16 and is conveyed as a dense toner layer. After this,
The toner A attached to the surface of the developing roller 12 is sufficiently charged by contact with the photoreceptor drum 11 and then transferred onto the electrostatic latent image on the surface of the photoreceptor drum 11 . This makes the electrostatic latent image visible. The toner A on the surface of the developing roller 12 that has not been transferred is scraped through the recovery blade (Mylar film) 17 and returned to the toner container 14 .

By the way, in this embodiment, since a reversal development method using a negatively charged organic photoreceptor drum 11 is adopted, a negatively charged toner is used as the toner A, and the blade 1
6 is made of a material that easily charges the toner A negatively. Further, the surface potential of the photosensitive drum 11 is -55
On the other hand, a developing bias potential of -200 V is applied to the metal shaft 12a of the developing roller 12 via a protective resistor. Further, the developing roller 12 is always 1 to 4 m away from the surface of the photoreceptor drum 11.
It rotates at a speed of about 1.2 to 4 times the rotational speed of the photosensitive drum 11 while having a contact width (developing nip) of about m.

Note that if toner A falls off the developing roller 12 for some reason during the above-mentioned development process, it will stain the inside of the main unit or the transfer paper, so in this embodiment, a plasticizer that reacts with toner A and dissolves it A toner welding member 18 made of a toner or the like is attached to the lower part of the developing device 10. Furthermore, this makes it possible to prevent the toner A from scattering even when the developing device 10 is placed upside down.

The blade 16 is constructed by mounting a chip 162 made of urethane resin in the longitudinal direction on the tip of a thin plate spring 161 made of urethane resin, which is brought into pressure contact with the surface of the developing roller 12 .

This blade 16 is supported by the main body of the apparatus by a first blade holder 16a, a spacer 16b, and a second blade holder 16c. Reference numeral 19 denotes a baffle plate attached to the first blade boulder 16a to sandwich a foam material 20 made of maltbrene or the like between it and the back surface of the blade 16. By sandwiching the foamed material 20 between the baffle plate 19 and the back surface of the blade 16 in this manner, leakage of toner A from the toner container 13 and vibration of the blade 16 are prevented.

Moreover, this blade 16 has a tip 1 provided at its tip.
At 62, the developing roller 12 is biased by a plurality of compression springs 22 with the rotating shaft 21 as a fulcrum so that the surface of the developing roller 12 can be suppressed with an appropriate force.

In addition, in the developing device of this embodiment, the chip 162 and the developing roller 12 are arranged so that the chip 162 of the blade 16 does not largely escape from the fixed position due to the repulsive force received when forming a thin toner layer on the surface of the developing roller 12. A weight 16d for pressing the chip 162 toward the developing roller 12 at a pressure contact position with the chip 162 is bonded to the surface of the thin plate spring 161 that is exactly opposite to the surface on which the chip 162 is mounted.

Note that in order not to damage the elastic force of the thin plate spring 161, it is necessary to make the pressing force applied to the blade 16 by the compression spring 22 larger than the pressing force applied to the vibration 16 by the weight 16d.

In this embodiment, the blade 16 is compressed by the compression spring 22.
Blade 1 with a pressure of 1200g and a weight of 16d
The pressurizing force to 6 is set to 60g, respectively.

FIG. 2 is a perspective view showing details of this blade 16.

As described above, this blade 16 has a tip 162 made of urethane resin mounted in the longitudinal direction on the tip of a thin plate spring 161 made of urethane resin, and a sealing material 163 made of urethane foam or the like on both ends of the thin plate spring 161. It is constructed by pasting the . However, here chip 1
The urethane resin 62 has a higher rubber hardness according to JIS-A standards than the urethane resin of the thin plate spring 161. Thereby, the chip 162 can be brought into pressure contact with the developing roller 12 with uniform force over the entire area without impairing the elasticity of the thin plate spring 161.

Further, the sealing material 163 is thicker than the height of the chip 162, and is attached to the thin plate spring 161 so that its leading end protrudes from the leading end surface of the chip 162 toward the developing roller 12. Thereby, when the chip 162 is in pressure contact with the surface of the developing roller 12, it is possible to reliably seal off toner from flowing out from both ends. Furthermore, since the sealing material 163 is attached so as to sandwich the ends of the thin plate spring 161, there is no fear that it will peel off even under the pressure of conveying the toner.

In addition, in the blade 16 of this embodiment, as shown in FIG.
It is mounted from a distance of l. That is,
The tip portion of the thin plate spring 161 is used for holding and positioning when mounting the chip 162 on the thin plate spring 161 by adhesive. Thereby, it is possible to improve the mounting accuracy of the chip 162 and the accuracy in the tangential direction between the developing roller 12 and the chip 162. In addition, dl
If it is too large, the pressure caused by the flow of toner will cause
0.5mm due to the risk of toner layer formation failure.
~5 mm is appropriate. Desirably 0.5mm~2
Approximately mm is optimal.

In addition, chips 162 are provided at both ends of the thin plate spring 61 in the longitudinal direction.
There are parts that are not mounted.

A seal member 163 is attached to this portion. In other words, the length Lp of the chip 162 in the longitudinal direction is shorter than the length Lc of the thin plate spring 161 by d2 + d3. The length d2 + d3 needs to be at least about 3 mm on one side considering sealing performance, but if it is too long, the developing device 10 itself will become large, so it is preferably about 4 to 30 mm, preferably about 4 to 20 mm. Further, the length Lp of the chip 162 at this time is larger than the effective development width, and the length Lc of the thin plate spring 161 is set to be equal to the width of the developing roller 12 or to the extent that it covers the side seal (not shown) of the developing roller 12. do.

Further, in this embodiment, the blade 16 has a weight of 50 g/
Although the toner layer was pressed against the developing roller 12 with a linear pressure of 5 g/cm to 250 g/cm, it was confirmed through experiments that a good toner layer could be formed.

Next, the developing roller 12 will be explained. FIG. 4 is a perspective sectional view of the developing roller 12.

The characteristics required of the developing roller 12 are that it has "conductivity and elasticity".

The simplest configuration that satisfies this requirement is, for example, one in which the outer periphery of a metal shaft is covered with a conductive rubber roller. Surface smoothness is required. Therefore, in this embodiment, an elastic layer 12b made of, for example, conductive silicone rubber or urethane rubber is provided around the outer periphery of the metal shaft 12a, and a conductive layer 12c made of conductive polyurethane is further provided on the surface of this elastic layer 12b. It has a two-layer structure.

The elastic layer 1.2b may be either conductive or non-conductive, but it is preferable to use a conductive layer in consideration of the possibility of peeling or scratches on the conductive layer 12c. In addition, due to packaging or long-term storage, JIS standard 6301
Regarding the permanent strain shown in , if it exceeds 10%, uneven rotation period of the developing roller will occur in the image, so the compressive strain of the elastic layer 12b must be 1096 or less, preferably 5% or less. Regarding the relationship between rubber hardness and permanent set, there is generally a tendency that the higher the rubber hardness, the smaller the permanent set, so the balance between the materials and each other is important. Further, after the developing roller 12 is deformed by the blade 16,
Since development is performed by directly contacting the photoreceptor drum 11, if the deformation is not nearly recovered by the time the development starts, image quality will deteriorate. Therefore, the overall rubber hardness (JIS-A standard) of the developing roller 12 is 35'' or less, the elastic layer 12b is 30'' or less, and furthermore, each of the rubber hardness is 30'' or less.
The angle is preferably 25° or less.

Furthermore, since the surface of the conductive layer 12c is the surface that comes into contact with the blade 16 and the photoreceptor drum 11, plasticizers, sulfurizers, etc.
Regarding the surface smoothness, it is desirable that the maximum surface roughness is 3 μm or less, as long as it does not contaminate the toner A or the surface of the photoreceptor drum 11 by seeping out process oil or the like. If it is more than that, uneven patterns on the surface tend to appear in the image.

A method for achieving the smoothness of the conductive layer 12c with a maximum surface roughness of 3 μm or less is to apply the conductive layer 12c with a sufficient thickness on the elastic layer 12b, and then use post-processing (polishing) to obtain a predetermined surface roughness. One possible method is to finish the outer diameter and surface roughness, but this method is expensive. Therefore, a method of finishing without requiring post-processing is desired, and for this purpose, the surface roughness of the elastic layer 12b, the film thickness of the conductive layer 12c, and the viscosity of the paint for forming the conductive layer 12c are optimally selected. Must. That is, the lower the viscosity of the paint and the greater the surface roughness of the elastic layer 12b,
The thickness of the conductive layer 12c must be increased. Furthermore, as for the paint for forming the conductive layer 12c, the viscosity of the same paint must be changed by changing the amount of dilution depending on the method of applying the paint to the surface of the elastic layer 12b.

FIGS. 5 to 7 show typical methods of applying the conductive layer paint.

FIG. 5 shows a spray coating method, FIG. 6 shows a dipping coating method, and FIG. 7 shows a knife coating method.

The viscosity of the paint in each method is in the order of the spray method <dipping method ≦ the knife method, and the paint film thickness T required to achieve the above-mentioned surface smoothness (maximum surface roughness of 3 μm) of the conductive layer 12c. (μm
) is possible if the maximum surface roughness of the elastic layer 12b is Rz (μm), and T≧10XRz in the spray method, and T≧5XRz in the dipping method and the knife method.

Furthermore, the elongation of the material itself of the conductive layer 12c cannot be ignored here. In other words, if this is less than 100%,
The conductive layer 12c cannot follow the elastic deformation of the elastic layer 12b, and cracks are likely to occur particularly at both ends where the elastic deformation is large.

Furthermore, regarding the ratio of the elongation (%) of the rubber material of the elastic layer 12b to the elongation (%) of the conductive layer 12c, unless this is 0.5 or more and 5 or less, the conductive layer 12c is similarly It was also confirmed through experiments that the elastic deformation of 12b could not be followed and cracks were generated. Note that this will be explained in detail later. Furthermore, if the above values are not satisfied, the recovery speed of the developing roller 12 after deformation will be slow, and the overall rubber hardness of the developing roller 12 will be high.
Density unevenness is likely to occur in the rotation period of the developing roller 12. Furthermore, in this embodiment, since the toner is negatively charged, the conductive layer 12c is required to be made of a material that is easily positively triboelectrically charged, and must also have excellent transportability.

In view of the above, in this embodiment, conductive silicone rubber is used as the elastic layer 12b of the developing roller 12, and conductive polyurethane paint is used as the conductive layer 12c. Further, the conductive silicone rubber used for the elastic layer 12b has a hardness of 28'' with a type A hardness needle of 6301 according to the JIS standard, and an elongation of 425%.The outer diameter is 18 mm. The electrical resistance value of the silicone rubber was measured when the developing roller 12 was arranged parallel to a stainless steel roller with a diameter of 60 mm so that the contact width was 2 mm, and a potential difference of 100 V was established between the metal shafts of each roller. The result calculated from the current value was 3.4 x 10' Ω·cm. The permanent set was 1.8% as measured using the measurement method of JIS standard 6301.

On the other hand, conductive polyurethane paint is made by dispersing conductive carbon particles in polyurethane resin.
The conductive layer 12 is applied to the surface of the elastic layer 12b using this paint in the following steps.
c was established.

First, a conductive polyurethane paint called "Subarex DH2023] 3" manufactured by Nippon Miractron ■ was used, and a diluting solvent containing methyl ethyl ketone (MEK) and tetrahydrofuran (THF) mixed at a ratio of 1:1 was added thereto. do. “Sparex DH202313”
is a solution-type conductive polyurethane paint based on thermoplastic polyurethane. After thoroughly stirring this diluted paint, it is applied onto the surface of the elastic layer 12b washed with a solvent using a dipping method. At this time, the pulling speed of the treated material was 3.5 mm/sec. Approximately 30 minutes after application
It was dried in air for a minute, and then heat-treated at 100°C for 20 minutes.

Through the above steps, the metal shaft 12a and the conductive layer 12c
The resistance value between is 5X103Ω・cm.

Rubber hardness is 36° with A type hardness needle of 6301 according to JIS standard.
A developing roller 12 having a surface roughness of 3 μmRz was obtained. In addition, the elastic layer 12b and the developing roller 12 elongate (
%) was 0.83.

Now, such a developing device 10 is installed in a laser printer, and the image area potential, that is, the exposed area potential is 80V, the non-image area potential, that is, the unexposed area potential is 500V, the developing bias is -200V, and the photoreceptor drum 11 and the developing When reversal development was performed with the contact width of the roller 12 being 1.5 mm, it was possible to obtain a printed sample with an image density of 1.4 and an extremely sharp line image with no fogging and a uniform solid image with no unevenness. . Further, as a result of carrying out a life test of 10,000 sheets, it was possible to obtain an extremely good image equivalent to the initial image even after the life test was completed.

FIG. 8 is a graph showing changes in image density and toner band 71 from the initial stage to 10,000 sheets. Note that a solid image was used to measure the image density here.

The amount of charge on the toner was determined by measuring the amount of charge over 10 rotations of the developing roller 12 using a charge amount measuring device.

From this graph, it can be seen that the image density hardly changes even after 10,000 sheets are printed, and the amount of charge also hardly changes. Furthermore, when we visually checked the shape of the chip 162 after 10,000 sheets had been printed, we found that the height of the chip 162 was approximately 0.
．． Shape of pressure contact surface of 5mm worn developing roller 12
No change was observed in the contact width.

For comparison, remove the weight 16d attached to the blade 16,
When we conducted a life test of 10,000 sheets using a developing device in which the compression force of the compression spring 22 was set to 1480 g, we were able to obtain good image samples at the initial stage, but after 10,000 sheets were printed, the image sample was solid. Image unevenness appeared on the image due to poor toner transport.

Next, another embodiment of the present invention will be described.

FIG. 9 is a sectional view showing the structure of a developing device according to another embodiment of the present invention.

As shown in the figure, in this embodiment, a spring 16e is used as a means for pressing the blade 16 against the developing roller 12. This spring 16e is connected to the baffle plate 19
A plurality of chips 162 are fixed at equal intervals along the longitudinal direction of the chip 162 on the surface facing the thin plate spring 161 . The pressing force applied by the spring 16e is set to a value that does not impair the elastic force of the thin plate spring 161, for example, 100 g.

In the embodiment described above, the blade 16 is supported at a position opposite to the rotational direction of the developing roller 12, but it may be supported at a position with respect to the rotational direction.

[Effects of the Invention] As explained above, according to the developing device of the present invention, the suppressing means presses the pressing portion toward the developing roller at or near the position where the pressing portion is pressed against the developing roller. By doing this, it is possible to prevent the pressing part from escaping significantly from the fixed position when forming a thin layer of developer on the surface of the developing roller, and to stabilize the formation of a thin layer of developer on the surface of the developing roller. Become.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the overall configuration of a developing device according to an embodiment of the present invention, FIG. 2 is a perspective view showing details of the blade in the developing device shown in FIG. 1, and FIG. 3 is a blade shown in FIG. 2. FIG. 4 is a perspective sectional view showing details of the developing roller in FIG. 1, FIGS. 5 to 7 are diagrams for explaining the method of forming the conductive layer of the developing roller, and FIG. 8 is a front view of the developing roller. 9 is a graph showing the results of a life test conducted using the developing device shown in FIG. 1 to examine changes in image density and charge amount, and FIG. 9 is a cross-sectional view of the developing device for explaining another embodiment of the present invention. It is. 10...Developing device, 11...Photosensitive drum, 12.
・Developing roller, 16... Blade, 161... Thin spring, 162... Chip, 16d... Weight, 6e...
··spring.

Claims (1)

[Claims] A developing roller disposed opposite to the electrostatic latent image holder;
a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, and bringing the developer thin layer formed on the surface of the developing roller close to or in contact with the electrostatic latent image holder. In the developing device for visualizing the electrostatic latent image held by the electrostatic latent image holding member, the developer thin layer forming means is provided on a spring plate member whose one end is supported, and on the spring plate member, a pressure contact portion that is in pressure contact with the surface of the developing roller with a thin developer layer sandwiched therebetween; and a pressing means that presses the pressure contact portion toward the development roller at or near a pressure contact position between the pressure contact portion and the development roller. A developing device comprising: