JP2002148930A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of obtaining an image without a failure such as uneven pitch and uneven density. SOLUTION: In the developing device having a toner storage part in which toner being a developer is stored, a toner supply roller 5 and a development roller 6 and forming a toner image by supplying the toner to an electrostatic latent image on the surface of a photoreceptor, a compression spring constant of the toner supply roller consisting of a foam elastic body is 0.25 to 5.0 N/mm, smaller than the compression spring constant of the development roller, skin resistance of the toner supply roller is 0.4 to 1.2 N, deformation of the rollers when the toner supply roller is abutted on the development roller is substantially due to the deformation of the toner supply roller and the toner supply roller is arranged so that inroad quantity by the development roller is 0.5 to 2 mm and pressing force to the development roller is equal to or less than 6 N.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for a printer for electrophotography and electrostatic recording, and more particularly, to a developing device having a toner cartridge containing toner as a developer, a toner supply roller, and a developing roller. The present invention relates to a developing device that forms a toner image by supplying toner to an electrostatic latent image on the surface of a photoconductor.

[0002]

2. Description of the Related Art In recent years, a conductive roller system has been widely adopted as a developing roller and a toner supply roller used in a developing device arranged in a developing process in an electrophotographic apparatus such as an electrophotographic copying machine, a laser beam printer, and a facsimile. I have. In such a method, the toner is frictionally charged by rubbing the toner supply roller against the developing roller. Therefore, the toner supply roller has a stable friction property (pressing force) with the developing roller and a high toner supply to the frictional portion. Is required. Conventionally, a foamed elastic material obtained by foaming rubber, urethane, or the like is generally used for this type of toner supply roller.

[0003]

However, when the present inventors examined the performance of a conventional toner supply roller made of a foamed elastic body, the toner conveyed to the developing roller adhered to the toner regulating blade, Moreover, when this toner fixing layer gradually grows and eventually becomes a hindrance to the toner layer carried on the developing roller, a portion where the carried toner layer cannot pass occurs, and the toner is developed in a state where toner does not exist. As a result, it was found that a defect such as white spots due to non-supply of toner may occur in the developed image. The present invention has been made in view of such conventional circumstances, and provides a developing device equipped with a toner supply roller made of a foamed elastic material, which can obtain an image without a defect such as white spots due to non-supply of toner. The purpose is to do.

[0004]

The inventors of the present invention have studied the toner supply roller which has caused the above-described image defects, and have found the following. That is, the toner supply roller rubs the toner against the developing roller in order to charge the toner existing between the toner supply roller and the developing roller at the same time as the toner supply. To increase the damage of
It has been found that the toner is deteriorated and the deteriorated toner is easily fixed. As a result of further studies, it has been found that the rubbing force is greatly affected by the hardness and frictional resistance of the toner supply roller and the pressing force of the toner supply roller / developing roller. It has been found that when the hardness (compression spring constant) and the frictional resistance of the toner supply roller and the pressing force of the toner supply roller / developing roller are made suitable, an image without any trouble can be formed. The present invention has been made based on such findings.

That is, the present invention has a toner storage section storing toner as a developer, a toner supply roller and a development roller, and supplies toner to an electrostatic latent image on the surface of a photoreceptor to form a toner image. In the developing device, the compression spring constant of the toner supply roller made of a foamed elastic material is 0.25 to 5.
0 N / mm, smaller than the compression spring constant of the developing roller, and the surface frictional resistance of the toner supply roller is 0.4 to 1.2.
N, the deformation of the toner supply roller when the roller is brought into contact with the developing roller is substantially due to the deformation of the toner supply roller, and the amount of biting of the toner supply roller by the developing roller is 0.5. The present invention provides a developing device characterized by being arranged so that a pressing force against a developing roller is 6 N or less and an image forming apparatus equipped with the developer device.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The toner supply roller according to the present invention has a hardness (compression spring constant) of 0.25 to 5.0 N / mm, and the compression spring constant is 0.4 to 4.0 N. / Mm, particularly preferably 0.7 to 3.0 N / m.
m. If the compression spring constant is less than 0.25 N / mm, there is a disadvantage that the toner is not sufficiently triboelectrically charged, and if it exceeds 5.0 N / mm, there is a disadvantage that the toner is greatly damaged. Further, the compression spring constant of the toner supply roller according to the present invention needs to be smaller than the compression spring constant of the developing roller. If the compression spring constant of the toner supply roller is equal to or greater than the compression spring constant of the development roller, the development roller deforms when the toner supply roller comes into contact with the development roller, so that a certain amount of toner is not conveyed. The difference between the compression spring constant of the developing roller and the compression spring constant of the toner supply roller is preferably 30 N / mm or more.

[0007] In the toner supply roller according to the present invention, the frictional resistance of the foamed elastic body forming the surface is 0.4 to 1.2N, preferably 0.4 to 0.8N. If the frictional resistance is less than 0.4 N, there is a disadvantage that the toner cannot be transported because the slip is too large. If the frictional resistance exceeds 1.2 N, the toner is greatly damaged, and the toner is liable to be deteriorated. Occurs. The number of cells of the foamed elastic body is preferably 6 to 260 cells per 1 mm ² , and more preferably 10 to 100 cells. In the developing device of the present invention, the deformation of the roller when the toner supply roller is brought into contact with the development roller is substantially due to the deformation of the toner supply roller, and the amount of bite of the toner supply roller by the development roller is 0. It is arranged such that the pressing force against the developing roller is 5 to 2 mm, preferably 0.5 to 1.5 mm, and 6 N or less, preferably 5.0 N or less. The amount of bite by the developing roller of the toner supply roller is
When the thickness is less than 0.5 mm, there is a disadvantage that the toner remaining on the developing roller cannot be sufficiently scraped off.
When m exceeds m, there is a disadvantage that damage to the toner is increased. Further, when the pressing force of the toner supply roller against the developing roller exceeds 6N, there is a disadvantage that damage to the toner is increased.

The foamed elastic body forming such a toner supply roller may be any foamed elastic body having the above characteristics, such as ester-based polyurethane foam, ether-based polyurethane foam, nitrile rubber, ethylene propylene rubber, and ethylene propylene diene. Examples include foams of rubber materials such as rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, silicone rubber, acrylic rubber, chloroprene rubber, butyl rubber, and epichlorohydrin rubber. These may be used alone or in combination of two or more to form a foam. Of these, ester polyurethane foam, ether polyurethane foam, nitrile rubber foam, ethylene propylene rubber foam, ethylene propylene diene rubber foam, and silicone rubber foam are particularly preferred. For the purpose of controlling frictional resistance, the foam raw material can be mixed with silicone oil or the foam surface can be coated with silicone oil.

Further, the toner supply roller according to the present invention comprises:
It may be conductive, and can be produced by forming a conductive foamed elastic layer on the outside of a good conductive shaft in the same manner as conventionally used as a conductive toner supply roller. For metal shafts, steel materials such as sulfur free-cutting steel plated with zinc, aluminum,
Examples include stainless steel and phosphor bronze.
For the conductive foamed elastic layer, a foamed elastic material obtained by adding a conductive agent to an appropriate foamed elastic body and imparting conductivity is used. Also in the case of the conductive foamed elastic body, the number of cells is preferably 6 to 260 cells per 1 mm ² , and more preferably 10 to 100 cells.

As the conductive agent to be added when imparting conductivity to the foamed elastic body, an ionic conductive agent or an electronic conductive agent is used. Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (eg, lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (eg, stearyltrimethylammonium), benzyltrimethylammonium, and a modified fatty acid dimethylethylammonium. Ammonium salts such as perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, ethyl sulfate, carboxylate and sulfonate, lithium and sodium Perchlorates of alkali metals and alkaline earth metals such as, potassium, calcium, magnesium,
Chlorate, hydrochloride, bromate, iodate, borofluoride, trifluoromethyl sulfate, sulfonate and the like can be mentioned.

Examples of the electronic conductive agent include conductive carbon such as Ketjen black and acetylene black;
SAF, ISAF, HAF, FEF, GPF, SRF,
Rubber carbon such as FT and MT; carbon for oxidation-treated ink, pyrolytic carbon, natural graphite, artificial graphite; conductive metal oxides such as tin oxide, titanium oxide and zinc oxide; nickel, copper, silver, Examples thereof include metals such as germanium.

These conductive agents may be used alone or in combination of two or more. The amount of addition is not particularly limited, but in the case of the ionic conductive agent, usually 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the foamed elastic body. Selected by range. On the other hand, in the case of the electronic conductive agent, it is selected in the range of 1 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of the rubber-based elastic body. Note that, in addition to the conductive agent, other rubber additives such as a known filler and a crosslinking agent can be appropriately added to the conductive elastic layer as needed.

Further, in the present invention, when the conductive foamed elastic body of the toner supply roller is formed of polyurethane foam, the acetone foam of the polyurethane foam is used so that the deposit on the surface of the roller does not fuse the toner. Since the extraction rate is preferably 5% by weight or less, it is necessary to sufficiently examine the amount of the conductive agent to be added.
That is, if a large amount of carbon black (for example, channel black) having a large amount of volatilization is blended, the acetone extraction ratio is increased, and if a carbon black having a large oil absorption (for example, acetylene black or high-structure oil furnace black) is blended, the acetone extraction ratio is increased. Can be reduced.

In the developing device of the present invention, as described above, the compression spring constant of the developing roller needs to be equal to or greater than the compression spring constant of the toner supply roller. The developing roller used in the developing device of the present invention is conductive, and has a conductive elastic layer formed on the outside of a good conductive shaft, similarly to those conventionally used as a conventional conductive developing roller. . The conductive elastic layer is made of an elastic material obtained by adding a conductive agent as described above to an appropriate rubber-like elastic body to impart conductivity. Here, the rubber-like elastic body is not particularly limited, and can be arbitrarily selected from those conventionally used in conductive developing rollers. Examples of the rubbery elastic body include nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, silicone rubber, urethane rubber, acrylic rubber, chloroprene rubber, butyl rubber, and epichlorohydrin rubber. And the like. These may be used alone or in combination of two or more. Among them, nitrile rubber, urethane rubber, epichlorohydrin rubber, ethylene propylene rubber, ethylene propylene diene rubber, and silicone rubber are particularly preferable.

In the developing roller according to the present invention, in order to control frictional resistance and prevent contamination of the photosensitive member, etc.
For example, a thickness 1 made of a crosslinkable resin such as an alkyd resin, a phenol resin, a melamine resin and a mixture thereof.
It is preferable that a resin coating layer having a thickness of 100 μm is provided on the roller surface. These crosslinkable resins may contain various additives such as a charge control agent, a lubricant, a conductive agent, and other resins, if desired. The resin coating layer is usually
A dipping method, a roll coater method, a doctor blade method, using a coating liquid obtained by dissolving or dispersing a cross-linkable resin, a cross-linking agent, and various additives (using an alcohol-based solvent such as methanol or a ketone-based solvent such as methyl ethyl ketone as a solvent). After being applied on the elastic layer by a spray method or the like, it can be formed by drying at room temperature or at a temperature of about 50 to 170 ° C. and curing by crosslinking.

FIG. 1 is a schematic view of a developing section of a laser printer which is an example of the developing apparatus of the present invention. Reference numeral 1 in the figure denotes a photoconductor, whose surface is uniformly charged by a primary charger 2, and then an image signal transmitted from a control unit (not shown) is converted into an optical signal using an LED array print head 3. After conversion, this is exposed on the surface of the photoreceptor 1 to form an electrostatic latent image. This electrostatic latent image is stored in a toner cartridge 4 and is developed by toner supplied to the photoconductor 1 via a toner supply roller 5 and a developing roller 6 to form a toner image. The toner image formed on the surface of the photoreceptor 1 is transferred to a paper surface supplied from a paper magazine 7 by a transfer charger 8 and fixed by a thermal fixing device 9, and the paper is transported and discharged in the direction of the arrow. The photoreceptor 1 after the transfer is returned to the initial state by the cleaning unit 10.

FIG. 2 is a schematic view showing a state of toner supply and frictional charging by the toner supply roller 5 and the developing roller 6, and FIG. 2B is an enlarged view of a portion indicated by a symbol A in FIG. It is. Since the contact portion 60 of the developing roller 6 with the toner supply roller 5 and the contact portion 50 of the toner supply roller 5 with the development roller 6 move in the directions of the arrows, the toner sandwiched between them is in contact. Due to the frictional force with the part 50, as shown in FIG. 2B, the toner is frictionally charged by sliding on the contact part 60 in the direction opposite to the traveling direction. Slip occurs between the toner and the contact portion 60 to charge the toner, and the charged toner is supplied onto the developing roller. Therefore, by using a toner supply roller having an appropriate frictional resistance with the toner, both the frictional force between the toner supply roller and the toner (toner holding property) and the frictional force between the developing roller and the toner (toner slipping property) are improved. To be
The toner can be supplied and the toner charged with little damage to the toner, and as a result, development without image defects can be performed.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention. Examples 1 to 3 and Comparative Examples 1 to 8 In the printer shown in FIG.
Toner supply rollers C, D, E having a roller diameter of 13.0 mm
F, G, H or I, or the developing roller A and toner supply rollers J, K,
Combine with L or M and install at constant temperature / humidity (2
An image was formed in an environment of 5 ° C. and 50% RH), and the image quality of the image was evaluated.

The developing rollers A and B used here were produced by the following method. Glycerin is added with propylene oxide and ethylene oxide, and has a molecular weight of 5000.
Polyether polyol (OH value: 33 mg KO)
H / g) per 100 parts by weight of 1,4-butanediol 1.0
Parts by weight, 0.5 parts by weight of nickel acetylacetonate, 0.01 parts by weight of dibutyltin dilaurate and 0.2 parts by weight of sodium perchlorate were added and mixed using a mixer to prepare a polyol composition. After stirring and defoaming the polyol composition under reduced pressure, 17.5 parts by weight of urethane-modified MDI (diphenylmethane diisocyanate) was added, and the mixture was stirred for 2 minutes. Next, this was cast into a mold in which the metal shaft was heated to 110 ° C. in advance, and cured at 110 ° C. for 2 hours to form a conductive elastic layer on the outer periphery of the metal shaft to obtain a roller. Polish the surface of the obtained roller and apply the surface to JIS
The 10-point average roughness was adjusted to 4.0 μmRz.

Next, as a resin for forming the resin coating layer,
Oil-free alkyd resin (manufactured by Dainippon Ink, M6
402) and a melamine resin (manufactured by Dai Nippon Ink Co., Ltd., Super Beckamine L-145-60, solid content ratio 60% by weight) so that the oil-free alkyd resin and the melamine resin have a solid content weight ratio of 80/20. Mixed with methyl ethyl ketone as a solvent, and the solid concentration is 20% by weight.
It was adjusted to be. 20 parts by weight (20 phr) of carbon (De) per 100 parts by weight of the solid content of this mixture
Gussa, Printex L6: average particle size 18
nm) and dispersed using a paint shaker to prepare a coating solution. The roller was immersed in the coating solution, pulled up, and heated at 130 ° C. for 3 hours to produce a developing roller A having a cured resin coating layer. The outer diameter of the obtained developing roller A was 16.0 mm, and the compression spring constant was 45 N / mm. The method of measuring the compression spring constant will be described later. Further, by applying silicone oil to the surface of the produced developing roller A, a developing roller B having silicone fine particles adhered to the roller surface was produced.

The toner supply rollers C,
D, E, F, G, H, I, J, K, L and M were prepared by the following method. 20 wt. Parts of a polymer polyol having a solid content of about 28% made of a polyether polyol having a molecular weight of 5,000, which is obtained by adding 15 wt.% Of ethylene oxide and 85 wt.% Of propylene oxide to glycerin, and 75 wt. Molecular weight 3 with addition of 25% by weight of oxide
40 parts by weight of a hydrophilic polyether polyol having a molecular weight of 400, 40 parts by weight of a polyether polyol having a molecular weight of 4800 obtained by adding 15% by weight of ethylene oxide and 85% by weight of propylene oxide to glycerin, and 21 parts by weight of tolylene diisocyanate (TDI-80) After sufficiently stirring, the mixture was kept at 60 ° C., and the stirring was repeated every 12 hours to obtain a polyether polyol prepolymer after 48 hours. Next, with respect to 100 parts by weight of the prepolymer, 27 parts by weight of water-dispersed carbon (carbon content: 8% by weight) containing conductive carbon was added with bis-catalyst as a catalyst.
A mixture prepared by dissolving 0.1 part by weight of a 70% dipropylene glycol solution of (dimetalaminoethyl) ether and 2.5 parts by weight of a polyether-modified silicone foam stabilizer comprising 70% by weight of a polyoxyethylene of an ether chain ( Total 2
9.6 parts by weight). This mixture is filled into a cylindrical mold, the inner surface of which is coated with Teflon and the end is sealed by a removable cap, the cap is closed and the cap is closed and adjusted to 70 ° C. It was left in a hot-air oven for 8 to 10 hours to obtain polyurethane foams of various hardnesses (compression spring constants) which were foam-cured.

The cured polyurethane foam was removed from the mold by removing the cap at the end of the mold, and passed through a roll to be subjected to a glassing treatment. Next, a hole having an inner diameter of 5 mm was formed at the center of the circle at the end face of the cylinder, and a zinc-coated shaft coated with an adhesive and having an outer diameter of 6.0 mm and a length of 240 mm was press-fitted. After heating and bonding for 15 minutes in an open at 60 ° C, the outer diameter of the cylinder is 11.4m
m (roller L), 13.0 mm (rollers C, D, E, F,
G, H, I), 15.0 mm (rollers J, M) and 16.
It was polished with a grindstone so as to have a thickness of 0 mm (roller K) to produce a toner supply roller. The prepared toner supply roller C,
The number of cells for D, E, F, G, J, K and L are all 1
12 to 36 cells per mm ^{2, the} number of cells of the toner supply roller H is 10 to 26 cells per mm ² ,
Was 16 to 36 cells per 1 mm ^{2, and the} number of cells of the toner supply roller M was 12 to 30 cells per 1 mm ² . The number of cells was determined by taking a photograph at a magnification of 40 to 60 times using a CCD video camera manufactured by Hilox Corporation, and measuring the number of cells in the image in accordance with JIS K6402.

As shown in FIG. 3, the toner supply rollers C to M are foamed elastic rollers in which a foamed elastic roller 12 is arranged around a metal rotating shaft 11, and in this embodiment, This toner supply roller was arranged as the toner supply roller 5 of the printer shown in FIG. 1, and an image forming test was performed. In this printer, the axial distance between the developing roller 6 and the toner supply roller 5 is fixed at 13.5 mm, and the outer diameter of the developing roller A is 16.0 mm, so that the outer diameter is 11.4 mm, 13.0 mm, and 15 mm. 0.0mm and 16.0m
m, the amount of biting of the developing roller A into the toner supply roller is 0.2 mm,
1.0 mm, 2.0 mm and 2.5 mm. In this embodiment, the compression spring constants of the developing roller and the toner supply roller were measured in the circumferential direction of the roller and in the longitudinal direction of the roller by the measuring method shown in FIG. As shown in FIG. 4, the rotation shaft 1 of the toner supply roller 5 or the developing roller 6
1 is horizontally identified by a V block 13 and a force gauge 14 installed above the roller 12 is moved downward at a constant speed (0.
1 mm / sec) and compressed to a depth of about 1.0 mm by a disc-shaped compression jig (disc indenter) 15 having a diameter of 13 mm provided at the tip of the force gauge 14, and measured stress-distortion. It was performed by a method of calculating the spring constant from the line. This measurement was performed at intervals of 30 mm in the longitudinal direction of the roller and at 30 degrees in the circumferential direction of the roller, and was calculated as an average value.

In this embodiment, a friction tester “HEIDON Tribogear” manufactured by Shinto Kagaku Co., Ltd. is used, and FIG.
The surface frictional resistance of the roller was measured according to the method described in (1). As shown in FIG. 5, the toner supply roller 5 was fixed to the movable stage 16 and moved in the direction of the arrow at a friction speed of 100 mm / min. The mating member of the friction was an acrylic round bar 17 having a diameter of 12 mm, which was arranged in a direction perpendicular to the toner supply roller 5 and was rubbed by a load 19 with a load of 1N. The friction resistance at this time was measured by the load cell 18. The reason why the acrylic material was selected as the friction partner material is that the main component of the toner is similar to the acrylic material, and the friction by this combination simulates the friction between the toner supply roller and the toner. The toner supply roller used in this embodiment is formed by the method shown in FIG.
After measuring the compression spring constant and measuring the frictional resistance by the method shown in FIG. 5, the image forming test was performed by arranging it as the toner supply roller 5 of the printer shown in FIG. Further, as the developing roller 6, a developing roller A or B was disposed. In the image evaluation and the image forming test, the A4 size paper is fed in the vertical direction and the temperature and humidity (2
(5 ° C., 50% RH) environment. Image evaluation was performed by printing 10 dark gray solid images and then printing 1000 continuous 7% gray solid images as a continuous image formation test. The results are shown in Tables 1 and 2. In the following table, the image quality was evaluated by forming a solid dark gray image and setting the case where the image quality was uniform and good (○), and the case where the image quality was uneven due to uneven density and the like (x). The occurrence of a defect in a blank image in continuous image formation is indicated as "none" when no image has been generated up to 1000 sheets, and the number of images formed up to that time is described when an image has been generated.

[0025]

[Table 1]

[0026]

[Table 2]

From the results shown in Table 1, the following can be understood. Even when the frictional resistance of the toner supply roller is 0.4 to 1.2 N, the hardness (compression spring constant) of the toner supply roller is 0.25.
If it is less than N / mm, no white spot image defect due to toner deterioration occurs, but image defects such as uneven density in image quality have occurred. Even if the frictional resistance of the toner supply roller is 0.4 to 1.2 N, the hardness (compression spring constant) of the toner supply roller is 5.0 N
/ Mm, image defects such as white spot image defects due to toner deterioration and density unevenness in image quality have occurred. Hardness (compression spring constant) of toner supply roller is 0.25 ~
Even at 5.0 N / mm, if the frictional resistance of the toner supply roller is less than 0.4 N, there is no white spot image defect due to toner deterioration, but image defect such as uneven density in image quality. It has occurred. Hardness (compression spring constant) of toner supply roller is 0.25 ~
Even at 5.0 N / mm, if the frictional resistance of the toner supply roller exceeds 1.2 N, image defects such as blank image defects due to toner deterioration and uneven density in image quality occur. I have.

The results shown in Table 2 show the following. The frictional resistance of the toner supply roller is 0.4 to 1.2 N;
And the hardness (compression spring constant) of the toner supply roller is 0.25
If the pressing force exceeds 6 N when pressing against the developing roller even at ~ 5.0 N / mm, image defects such as white image defects due to toner deterioration and uneven density in image quality occur. ing. The frictional resistance of the toner supply roller is 0.4 to 1.2 N;
And the hardness (compression spring constant) of the toner supply roller is 0.25
Even if it is up to 5.0 N / mm, if the amount of bite exceeds 2.0 mm in pressing against the developing roller, there will be no white spot image defect due to toner deterioration, but density unevenness in image quality And other image defects have occurred. The frictional resistance of the toner supply roller is 0.4 to 1.2 N;
And the hardness (compression spring constant) of the toner supply roller is 0.25
Even if it is up to 5.0 N / mm, if the bite amount is less than 0.5 mm in pressing against the developing roller, there will be no white spot image defect due to toner deterioration, but unevenness in image quality, etc. Image failure has occurred.

From the above, it can be seen that a large frictional resistance and a large pressing force cause damage to the toner and cause deterioration of the toner, which in turn leads to a defective white image. Conversely, with a small frictional resistance and a small pressing force, the damage to the toner is small, but sufficient electrification due to friction is not obtained, and the toner remaining on the developing roller is sufficiently scraped off. It can be seen that this is not the case, which leads to a problem such as uneven density in the image.

[0030]

According to the present invention, since the toner supply roller presses the toner against the developing roller, supplies the toner to the developing roller, and frictionally charges the supplied toner, the toner deterioration is caused. It is possible to perform development without image defects such as white spots, and to scrape off the toner remaining on the developing roller in a favorable manner, so that a good image free from defects such as uneven pitch and uneven density can be obtained for a long time. It can be formed over a period.

[Brief description of the drawings]

FIG. 1 is a schematic view of a developing unit of a laser printer which is an example of a developing device of the present invention.

FIG. 2 is a schematic diagram showing a state of toner frictional charging by a toner supply roller and a developing roller according to the present invention.

FIG. 3 is a schematic perspective view of a toner supply roller according to the present invention.

FIG. 4 is a schematic diagram illustrating a method of measuring the compression spring constant of the developing roller and the toner supply roller described in the embodiment.

FIG. 5 is a schematic diagram showing a method for measuring the surface frictional resistance of the toner supply roller shown in the example.

[Explanation of symbols]

 1: Photoreceptor 2: Primary charger 3: LED array print head 4: Toner cartridge 5: Toner supply roller 6: Developing roller 7: Paper magazine 8: Transfer charger 9: Thermal fixing device 10: Cleaning unit 11: Rotation Shaft 12: Foam elastic roller 13: V block 14: Force gauge 15: Compression jig (disc indenter) 16: Movable stage 17: Acrylic round bar 19: Load load

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H077 AC04 AD06 FA13 FA14 FA22 FA27 3J103 AA02 AA13 AA32 BA31 BA41 FA02 FA05 FA18 GA02 GA58 GA73 HA03 HA05 HA11 HA12 HA15 HA18 HA20 HA32 HA33 HA36 HA37 HA48 HA52 HA53 HA54

Claims (5)

[Claims] 1. A developing device, comprising: a toner accommodating section accommodating a toner as a developer; a toner supply roller; and a developing roller; The compression spring constant of the toner supply roller made of a foamed elastic material is 0.25 to 5.0 N / mm, smaller than the compression spring constant of the developing roller, and the surface friction resistance of the toner supply roller is 0.4 to 1.2 N. The deformation of the toner supply roller when the roller is brought into contact with the developing roller is substantially due to the deformation of the toner supply roller,
The amount of bite by the developing roller of the toner supply roller is 0.
A developing device, wherein the developing device is disposed so that the pressing force against the developing roller is 6 N or less. 2. The developing device according to claim 1, wherein a difference between a compression spring constant of the toner supply roller and a compression spring constant of the developing roller is 30 N / mm or more. 3. The developing device according to claim 1, wherein the toner supply roller has a conductive foamed elastic layer formed outside a good conductive shaft. 4. The developing device according to claim 3, wherein the good conductive shaft is a metal shaft, and the conductive foamed elastic layer is provided with conductivity by conductive carbon. 5. An image forming apparatus equipped with the developing device according to claim 1.