JP2003057948A - Image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep an amount of charged toner constant by steadily charging toner regardless of a change in the resistance of a toner electrifying roller. SOLUTION: A developing roller 11 is in contact with a photoreceptor 1. A toner electrifying roller 17 is located upstream from a developing area where the developing roller 11 is in contact with the photoreceptor 1. A voltage applying means S2 is provided for applying a DC voltage to the toner 14, the DC voltage being equal to or higher than a discharge initiation voltage and having the polarity that is the same as the polarity of the toner 14. The voltage applying means is controlled in accordance with the detection result of a current detecting means 171.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device of an image forming apparatus such as an electrophotographic copying machine and an electrophotographic printer, and a process cartridge including at least the developing device.

[0002]

2. Description of the Related Art Conventionally, as a method of electrophotography, a photoconductive material is used, an electric latent image is formed on a photoconductor by various methods, and then the latent image is developed with a toner to form a visible image. According to the method, a toner image is transferred to a transfer material such as paper and then fixed by heat or pressure to obtain a copy.

At the present time, however, it is essential to develop a method for forming a thin layer of a toner and an apparatus therefor, which requires improvement in the resolution and definition of an image, and several measures have been proposed for this. ing.

In recent years, a toner on a semi-conductive developing roller or a developing roller having a dielectric layer formed on the surface thereof is charged by electric discharge from a toner charging roller, and then the toner is brought into contact with a surface layer of a photoreceptor. A non-magnetic one-component DC contact development method has been proposed in which development is performed by means of a non-magnetic method.

FIG. 10 shows a non-magnetic one-component DC contact developing system using a toner charging roller. This method
When the photoconductor 1 and the developing roller 81 come into contact with each other, arrows A and B respectively
Is rotating in the direction of. Photoconductor 1 by charging roller 2
Are charged, and a latent image is formed on the photoconductor 1 by the laser light from the exposure unit 5.

Then, the latent image is visualized by the developing device 80. After that, the developing roller 8 developed on the photoconductor 1
The toner 84 on 1 is transferred to the transfer material 9 by the transfer roller 6 and fixed by the fixing device 7.

The toner 84 that has not been transferred and remains on the photosensitive member 1 is stripped off by the cleaning blade 3 and stored in the cleaning container 4.

The developing device 80 has a developing container 86 containing a toner 84 as a one-component developer. The developing container 86 is arranged so that the elastic roller 82 is in pressure contact at a position on the upstream side in the rotation direction of the developing roller 81 with respect to the position at which the elastic blade 83 and the developing roller 81 abut. Therefore, by rotating the elastic roller 82 in the direction of arrow D, the toner 84 can be supplied onto the developing roller 81.

The toner 84 supplied onto the developing roller 81 is conveyed by the rotation of the developing roller 81, and is charged by friction at the contact portion between the elastic blade 83 and the developing roller 81 to be thinned. .

Further, the thinned toner 84 has a discharge starting voltage or more (here, “above” or more) having a large absolute value with respect to the toner layer. The same applies hereinafter unless otherwise specified. ) The toner charging roller 8 to which the voltage of
An electric charge is given by 5 and is uniformly charged.

Toner 84 having a uniform charge amount
Are conveyed by the developing roller 81 and supplied for developing the electrostatic latent image at the contact portion with the photoconductor 1.

Thereafter, the toner 84 left undeveloped at the contact portion between the photosensitive member 1 and the developing roller 81 is elastic roller 82.
Torn off. In addition, as described above, the elastic roller 8
2, new toner 84 is supplied to the developing roller 81, and the above operation is repeated.

By this developing method, the amount of charged electric charge of the toner that can make the toner height of the line image and that of the solid image the same can be controlled within an appropriate range, so that sharp lines and dots without scattering can be reproduced. Also,
Since the line image can be controlled to the minimum required toner height, the toner consumption amount can be reduced, the life of the developing device can be extended, and the running cost can be reduced.

[0014]

However, in the case of the prior art as described above, the resistance of the toner charging roller is increased by repeating the image formation, so that the toner on the developing roller is stabilized. There was a problem that charge cannot be applied. The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to enable a toner charging roller to stably apply an electric charge to toner on a developing roller for a long period of time. To provide a developing device, a process cartridge, and an image forming apparatus.

[0015]

In order to achieve the above object, in the image forming apparatus of the present invention, the electrostatic latent image is brought into contact with or in proximity to an image bearing member carrying an electrostatic latent image. A developer carrying member that conveys and visualizes the developer, and a regulating member provided on the upstream side of the developing region with respect to the rotation direction of the developer carrying member so as to come into pressure contact with the developer carrying member via the developer. And a developing device provided on the upstream side of the developing region with respect to the rotation direction of the developer carrying member and on the downstream side of the pressure contact portion between the developer carrying member and the regulating member so as to be close to or in contact with the developer. A developing device having a developer charging member is provided, and the developer charging member has an absolute value of discharge starting voltage or more,
And, it has a voltage applying means for applying a voltage having the same polarity as the charging polarity of the developer, and a current detecting means for detecting a current flowing to the developer charging member at the time of applying the voltage,
The voltage applying unit is controlled according to the detection result of the current detecting unit.

The developer charging member is preferably an elastic roller composed of a plurality of layers.

The developer charging member is preferably an elastic roller provided with a fluororesin on the surface layer.

It is preferable that the current detecting means operates during non-image formation.

Further, in the process cartridge of the present invention, a developer carrying member which comes into contact with or comes close to an image carrying member carrying an electrostatic latent image and conveys a developer to the electrostatic latent image to visualize the developer, and the developer. A regulating member provided on the upstream side of the developing region with respect to the rotating direction of the carrier so as to come into pressure contact with the developer bearing body via a developer, and on the upstream side of the developing region with respect to the rotating direction of the developer bearing body. A developing device having a developer charging member provided so as to be close to or in contact with the developer is provided on the downstream side of the pressure contact portion between the developer carrying member and the regulating member. A voltage that is equal to or higher than the absolute value of the discharge start voltage and has the same polarity as the charging polarity of the developer is applied to the member, and a current detection unit that detects a current flowing to the developer charging member when the voltage is applied, Characterized by .

The developer charging member is preferably an elastic roller composed of a plurality of layers.

The developer charging member is preferably an elastic roller provided with a fluororesin on the surface layer.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions of the components described in this embodiment,
Unless otherwise specified, the material, the shape, the relative arrangement, and the like are not intended to limit the scope of the present invention thereto. A developing device, a process cartridge, and an image forming apparatus according to an embodiment will be described with reference to FIGS. 1 and 2.

1 and 2 are cross-sectional views of the image forming apparatus and the developing apparatus in the embodiment. In FIG. 1, a photoreceptor 1 (φ30 mm) as a latent image carrier rotates in the direction of arrow A at 60 rpm (1 rps). The photoconductor 1 is uniformly charged to a dark part potential of -700V by the charging roller 2 applied to a DC voltage of -1300V, and the surface of the photoconductor 1 is statically irradiated by laser light from an exposure unit 5 that writes an electrostatic latent image on the photoconductor 1. A latent image is formed. The laser power is adjusted so that it becomes −150 V when the entire surface of the laser light is exposed.

This electrostatic latent image is developed by the developing device 10 arranged close to the photoconductor 1 and visualized as a toner image. In the present embodiment, the photoconductor 1 and the developing device 10 are configured as a process cartridge and can be attached to and detached from the image forming apparatus. In this embodiment, so-called reversal development is performed to form a toner image on the exposed portion.

The visualized toner image on the photosensitive member 1 is transferred onto the paper 9 as a recording medium by the transfer roller 6, and the transfer residual toner remaining on the photosensitive member 1 without being transferred is scraped off by the cleaning blade 3. And is stored in the waste toner container 4.

The cleaned photoconductor 1 is charged again and the above-mentioned operation is repeated. On the other hand, the paper 9 on which the toner image has been transferred is fixed by the fixing device 7, discharged to the outside of the device, and the printing operation ends.

Next, the developing device 10 according to the present embodiment.
Will be further described with reference to FIG.

In FIG. 2, the developing device 10 comprises a developing container 16 containing a non-magnetic toner 14 as a one-component developer,
A developing roller 11 having a diameter of 16 mm, which is located in an opening extending in the longitudinal direction in the developing container 16 and is installed to face the photoconductor 1.
And are equipped with. The electrostatic latent image on the photoconductor 1 is the photoconductor 1
And is developed in a developing area, which is an opposing portion of the developing roller 11, and visualized as a toner image. At this time, the developing roller 11 rotates in contact with the photosensitive member 1 in the direction of arrow B with a contact width and is in contact therewith.

In the developing device 10, the elastic roller 1
2 is abutted on the upstream side in the rotation direction of the developing roller 11 with respect to the abutting portion between the elastic blade 13 and the surface of the developing roller 11, and is rotatably supported. As this structure, a foam skeletal sponge structure or a fur brush structure in which fibers such as rayon and nylon are planted on a core metal is preferable from the viewpoint of supplying the toner 14 to the developing roller 11 and stripping the undeveloped toner. .

In the present embodiment, the elastic roller 12 has a diameter of 16 mm with polyurethane foam provided on the core metal.
Roller was used. The developing roller 1 of this elastic roller 12
The effective contact width for 1 is 1 to 6 mm,
Further, it is preferable that the elastic roller 12 has a relative speed with respect to the developing roller 11 at its abutting portion. In the present embodiment, the abutting width is set to 4 mm, and the developing speed is set as the peripheral speed of the elastic roller 12. The driving means (not shown) is rotationally driven in the direction of arrow D at a predetermined timing so that the speed becomes 80 mm / s.

By providing such a relative speed, it becomes possible to more efficiently supply the toner to the developing roller and strip the undeveloped toner from the developing roller.

The elastic blade 13 is supported by a blade supporting sheet metal, and is provided on the downstream side of the elastic roller 12 so that the vicinity of the tip on the free end side is brought into surface contact with the outer peripheral surface of the developing roller 11. The structure of the elastic blade 13 is a rubber material such as silicon or urethane, or a SU having spring elasticity.
The developing roller 11 has a thin metal plate such as S or phosphor bronze as a base.
It is made of a material such as a rubber material bonded to the contact surface side.

The contact direction is a so-called counter direction in which the tip end side is located upstream of the developing roller 11 in the rotation direction with respect to the contact portion.

In the present embodiment, the elastic blade has a structure in which a plate-shaped urethane rubber having a thickness of 1.0 mm is adhered to the blade supporting sheet metal. The contact pressure with respect to the developing roller 11 is 0.245 to 0.343 N / cm (2
5 to 35 gF / cm) (the linear pressure was measured by inserting three thin metal plates having a known friction coefficient into the abutting part and converting one of the central plates with a spring only).

The developing roller 11 has a right half-peripheral surface projecting into the developing container 16 at the opening, and a left substantially half-peripheral surface is exposed outside the developing container 16 and is horizontally provided. The surface exposed to the outside of the developing container 16 contacts and opposes the photoconductor 1 located on the left side of the developing device 10.

The developing roller 11 is driven to rotate in the direction of arrow B, and the surface thereof has appropriate irregularities for increasing the probability of rubbing against the toner 14 and favorably carrying the toner 14. .

In the present embodiment, the diameter is 16 mm,
A developing roller 11 having a length of 240 mm and a thickness of 4 mm coated with an acrylic / urethane-based silicone rubber layer is used.
Roller resistance 10 ⁴ to 10 ⁶ Ω, surface roughness Rz 0.5
.About.0.9 .mu.m, and the hardness was 45.degree. In Asker C hardness (weighted 9.8 N).

Further, the developing roller 11 is brought into pressure contact with the photosensitive member 1 and
The invasion amount of the photosensitive member is 70 μm, and the peripheral speed of the developing roller 11 is 170 mm / s, whereas the peripheral speed of the photosensitive member 1 is 94.2 mm / s.

Here, the resistance value was measured by contacting an aluminum roller having a diameter of 30 mm and the developing roller with a contact load of 4.9 N (500 N).
gF) abuts the entire length and the aluminum tube is 30 rpm
Rotate at (0.5 rps). Next, apply 40 to the developing roller.
A DC voltage of 0V is applied. A resistance of 10 kΩ is arranged on the ground side, the voltage across the resistance is measured, the current is calculated, and the resistance of the developing roller 11 is calculated.

In this embodiment, the toner 14 is a non-magnetic one-component developer. It has a spherical shape as toner,
Further, it is preferable that the surface is smooth. Since such toner has a spherical shape, the adhesion to the photoconductor 1 is smaller than that of the conventional non-spherical toner, and the transferability to a transfer material such as paper is excellent.

Further, when the transfer residual toner which is not transferred and remains on the photoconductor 1 is cleaned by a cleaning means such as a blade or a fur brush, the photoconductor 1 is less worn due to its high lubricity. Have the advantage of.

In the present embodiment, the toner volume resistivity is 10 ¹⁴ Ω · cm or more.

The conditions for measuring the toner volume resistivity are as follows.

Measurement electrode plate area: φ6 mm = 0.238 cm ² , pressure: 1500 g, using a weight of 96.1 kPa (980
Pressure of gF / cm ² ), powder layer thickness during measurement: 0.5 to 1.0 mm, DC voltage of 400 V applied Micro ammeter (YHP4140)
pA METER / DCVOLTAGE SOURCE)
The current amount is measured with and the volume resistivity (specific resistance) is calculated from the resistance value.

As the toner in this embodiment, as the shape factor, SF-1 of 100 to 180 and SF-2 of 100 to 140 are used.

These SF-1 and SF-2 are Hitachi F
Randomly toner image 1 using E-SEM (S-800)
00 pieces were sampled, the image information was introduced into an image analysis device (Luzex3) manufactured by Nikole Co. through an interface and analyzed, and the image information was calculated from the definition of the following formula.

SF-1 = (MXLNG) ² / AREA ×
(Π / 4) × 100 SF-2 = (PERI) ² / AREA × (1 / 4π) ×
100 (AREA: toner projected area, MXLNG: absolute maximum length of toner particles, PERI: peripheral length of toner particles) The shape factor SF-1 of this toner indicates a spherical degree, and 10
As it increases from 0, it gradually changes from a spherical shape to an amorphous shape. SF-2 indicates the degree of unevenness of the toner surface, which is 1
As it increases from 00, the unevenness of the toner surface becomes more remarkable.

With respect to the method for producing the toner, in addition to the so-called pulverization method, if the toner has a shape factor within the above-mentioned range, it is also possible to use the method described in JP-A-36-10231 and JP-A-59-5.
A method of directly producing a toner using the suspension polymerization method described in Japanese Patent No. 3856, a dispersion polymerization in which a toner is directly produced using an aqueous organic solvent which is soluble in a monomer and in which the obtained polymer is insoluble. The toner can be produced by a method, an emulsion polymerization method represented by a soap-free polymerization method in which the toner is directly polymerized in the presence of a water-soluble polar polymerization initiator, or the like.

In this embodiment, the toner shape factor SF-1 is 100 to 180 and SF-2 is 100 to 1.
It can be easily controlled in the range of 40, and a suspension polymerization method under atmospheric pressure or under pressure is used to obtain a fine particle toner having a sharp particle size distribution and a particle size of 4 to 8 μm with relative ease. n-Butyl acrylate, a salicylic acid metal compound as a charge control agent, a saturated polyester as a polar resin, and a coloring agent were further added to produce colored suspension particles having a weight average particle diameter of 7 μm.

Then, 1.5 wt% of hydrophobic silica is added to this.
% By external addition, a negative-polarity toner 14 having excellent transferability as described above and less wear during cleaning of the photoconductor 1 was manufactured.

In the developing device 10 as described above, the toner 14 in the developing container 16 is agitated during the developing operation.
5 is fed in the direction of the elastic roller 12 as the arrow C rotates. Next, in the toner 14, the elastic roller 12 has an arrow D.
When the developing roller 11 is rotated in the direction, it is carried to the vicinity of the developing roller 11 and is rubbed against the abutting portion between the developing roller 11 and the elastic roller 12, so that the developing roller 11 is frictionally charged and adheres to the developing roller 11. After that, as the developing roller 11 rotates in the direction of arrow B, it is sent under pressure contact with the elastic blade 13,
A thin layer is formed on the developing roller 11.

In the present embodiment, a good charge amount is −60 to −20 μC / g, a good toner coat amount is 0.4 to 1.0 mg / cm ² , and a toner layer thickness is 10 to 20 μm. Is set so that the value of can be obtained. In order to stabilize the charge amount of the toner 14 described above, the toner charging roller 17 contacts the developing roller 11 and charges the toner by discharging.

The toner charging roller 17 is a rubber roller having a diameter of 7 mm, and is composed of a plurality of layers, in particular, an elastic roller having a surface layer made of fluororesin or the like for reducing toner adhesion on the surface layer. preferable. By comprising a plurality of layers, it is possible to adjust the resistance to a desired value while providing a surface layer that reduces toner adhesion. As a result, the developer is not contaminated, and it is possible to stably apply the charge to the developer by the toner charging roller, and it is possible to stably maintain the charge amount of the developer.

The contact load on the developing roller 11 by the pressing member (not shown) is 0.49 to 1.96 N (50 to 200 g).
F). The toner is closely packed and uniformly coated by the contact of the toner charging roller 17. The longitudinal positional relationship between the elastic blade 13 and the toner charging roller 17 is preferably arranged so as to surely cover the entire contact area of the elastic blade 13 on the developing roller 11.

Next, a method of applying charges will be described below.

As shown in FIG. 3, when the resistance of the toner charging roller 17 is 10 ⁸ Ω, the behavior shown by the solid line is exhibited. However, the toner surface potential has a surface potential of about -20V even when the applied voltage is 0V. This is an elastic blade 1
This is because it was subjected to triboelectric charging in No. 3.

If the surface potential due to this frictional charging is excluded, as shown by the solid line in FIG. 3, the discharge to the toner is started when the voltage applied to the toner charging roller 17 reaches about -600 V, and thereafter. The inclination of the toner surface potential is about 1 with respect to the change of the voltage applied to the toner charging roller 17.
The behavior is similar to DC discharge charging of the photoconductor.

Here, the void voltage Vg between the toner charging roller 17 which is the developer charging member and the toner 14 which is the developer at the time when the discharge starts is expressed by the following equations (1) and (2). The voltage Va applied to the toner charging roller at that time is defined as the discharge start voltage.

However, since the approximate expression (1) of the Paschen's rule is assumed only for a positive voltage, in the expression (2), Vg is calculated by considering only the absolute value of Va-Vc.
Therefore, although the case where the applied voltage is negative is described in detail in this embodiment, the discharge start voltage can be obtained from the equations (1) and (2) even when the applied voltage is positive.

[0060] Vb = 312 + 6.2g (1) Vg = g (│Va-Vc│) / {(Lt / Kt) + g} ... (2) In the above formula, g: Gap distance Approximate expression of Paschen's law when Vb: g> 8 μm Vg: Void voltage on toner charging roller and toner layer surface Va: voltage applied to the toner charging roller Vc: toner layer surface potential Lt: toner layer thickness Kt: relative permittivity of toner layer Is.

Since the toner 14 used in this embodiment has an excellent particle size distribution and a spherical shape, the ratio of toner to air in the toner layer is constant, and the value of Kt in the equation (2) is Is stable.

Injection charging is another method for imparting a charge to the toner. In this case, the voltage applied to the toner charging roller and the toner surface potential behave as shown in FIG. From the above results, it is considered that the method of applying charges in the present embodiment uses discharge.

The above experiment is for the case where the entire length of the toner charging roller 17 is in contact with the toner coat portion.

Next, the range of roller resistance at which the toner charging roller 17 can discharge the toner was examined. When the roller resistance of the toner charging roller 17 is 10 ⁷ Ω or less, the voltage between the toner charging roller 17 and the toner coat portion capable of discharging the toner cannot be obtained, and when it is 10 ¹² Ω or more, the toner charging roller is changed from the developing bias. In the configuration of this embodiment in which the bias of 17 is obtained, the discharge starting voltage is too large and is not suitable. Therefore, the proper range of the roller resistance of the toner charging roller 17 is 10 ⁷ to 10 ¹² Ω · cm.

The resistance measuring method is as follows. Diameter 16
φmm aluminum roller and toner charging roller are brought into contact with the entire area in the longitudinal direction with a contact load of 1.67N (170gF), and the diameter is 1
A 6 mm aluminum roller is rotated at 30 rpm (0.5 rps).

Next, a DC voltage of -400 V is applied to the toner charging roller. A resistance of 100 kΩ is arranged on the ground side, the voltage across the resistance is measured, the current is calculated, and the resistance of the toner charging roller is calculated. The length in the longitudinal direction is 2
It was set to 20 mm.

FIG. 5 shows the relationship between the voltage between the developing roller 11 and the toner charging roller 17 and the toner charge amount on the developing roller 11.

When the toner charge amount of the toner 14 that has passed through the elastic blade 13 is -30 μC / g, the applied voltage is saturated to -60 μC / g when the applied voltage is -1300 V or more.

When the toner charge amount of the toner 14 passing through the elastic blade 13 is −60 μC / g, the toner saturated charge amount is −60 μC / g regardless of the applied voltage.
It is constant in g. Therefore, by using the toner charging roller 17, it is possible to stabilize the charge amount even when the charge amount of the toner is different under high temperature and high humidity and under low temperature and low humidity.

However, as shown in FIG. 6, the relationship between the toner charge amount on the toner charging roller 17 and the developing roller 11 varies due to the resistance variation due to the durability of the toner charging roller 17.

The control of the present embodiment will be described.

In order to accurately measure the resistance of the toner charging roller 17, a constant voltage power source S2 is applied to the toner charging roller 17.
From the constant voltage power source S1 to the developing roller 11, and the current detection circuit 1
The current is detected by 71, a voltage that makes the current constant is determined, and the voltage applied from the constant voltage power source S2 is controlled.

Here, during image formation, the toner surface potential on the upstream side of the toner charging roller 17 on the developing roller 11 fluctuates due to toner consumption, so that the current detected by the current detection circuit 171 becomes unstable and the accuracy decreases. There are cases.
Therefore, it is preferable to detect the current during non-image formation without consuming the toner.

Next, the case where the current is detected by the current detection circuit 171 and the current value is controlled to 20 μA will be described.

In the initial stage of the developing device, a voltage of -1300V is applied to the toner charging roller 17 from the constant voltage power source S2, a voltage of 0V is applied to the developing roller 11 from the constant voltage power source S1, and the current detection circuit 171 causes the current to flow. Is 20 μA (resistance of toner charging roller 17: 6.5
× 10 ⁷ Ω).

Therefore, in order to set the current value to 20 μA, the potential difference between the developing roller 11 and the toner charging roller 17 needs to be 1300 V, and -300 V is applied to the developing roller 11 to secure the developing contrast by the constant voltage power source S1. The toner charging roller 17 is applied with -1600 V from the power source S2 under constant voltage control.

After printing 5000 pages in A4 size,
A voltage of -1300V is applied from the constant voltage power source S2, a voltage of 0V is applied to the developing roller 11 from the constant voltage power source S1, and the current value detected by the current detection circuit 171 is 10 μA (as shown in FIG. The resistance of the toner charging roller 17 is 1.3 × 10 ⁷ Ω). In this case, in order to set the current value to 20 μA, −2100 V is applied from the power source S2 by constant voltage control from FIG.

Here, in the case of constant current control as shown in FIG. 8, for example, if the toner surface potential is unstable depending on the rotation direction of the developing roller before the charge is applied by the toner charging roller 17, the charge is applied by the toner charging roller 17. The toner surface potential becomes unstable depending on the rotation direction of the developing roller. Therefore, in this embodiment, the constant voltage control is optimal as shown in FIG.

If the above control is not performed, A4 size is 5
When 000 pages are printed, as shown in FIG. 6, the toner charge amount on the developing roller after being charged by the toner charging roller 17 is reduced to 40 μC / g.

On the other hand, by performing the above control,
Even after printing 5000 pages in A4 size, the toner charge amount on the developing roller after being charged by the toner charging roller 17 is 60 μC / g, which is the same as in the initial stage of the developing device.

Therefore, under this condition, the toner charged by the toner charging roller 17 is made uniform to −60 μC / g and is uniformly transported to the developing section, which is the section facing the photoconductor 1. At the contact portion, the thin toner layer formed on the developing roller 11 is developed as a toner image on the electrostatic latent image on the photoconductor 1 by the −300V DC voltage applied from the power source S1 to the developing roller 11. It

The undeveloped toner that is not consumed in the developing section is rotated by the rotation of the developing roller 11 and the developing roller 11
Will be collected from the bottom. This collected developing roller 11
The undeveloped toner on the upper side is the elastic roller 12 and the developing roller 11
Is peeled off from the surface of the developing roller 11 at the contact portion with. Most of the peeled toner is conveyed along with the rotation of the elastic roller 12 and the toner 14 in the developing container 16 is conveyed.
And the charge of the toner 14 is dispersed. At the same time, new toner is supplied onto the developing roller 11 by the rotation of the elastic roller 12, and the above-described operation is repeated.

As described above, the current detection circuit 171 is provided upstream of the power source S2, the current of the toner charging roller 17 is detected, and the voltage from the power source S2 is controlled by the constant voltage control of the toner charging roller 17 according to the resistance of the toner charging roller. By applying the voltage, even if the resistance is increased by energizing the toner charging roller 17, it is possible to stabilize the charge amount of the toner 14 and reduce the reversal fog, thereby significantly improving the toner use efficiency and the line, A clear image quality of dots can be obtained.

Further, in the present embodiment, the process cartridge is composed of the developing device which is attachable to and detachable from the carrying device main body, but it is used as the developing device which is fixed in the carrying device main body and supplies only the toner. Alternatively, the developing device, the photoconductor, the cleaning blade, the waste toner container, and the charging device may be integrally formed and used as a process cartridge that is attachable to and detachable from the carrying device body.
This results in an excellent user-friendly handling structure.

[0085]

As described above, in the developing device of the present invention, by detecting the current flowing to the developer charging member and controlling the voltage applied to the developer charging member from the detection result, long-term It is possible to provide an image forming apparatus and a process cartridge capable of stably providing an electric charge to the developer by the developer charging member and stably maintaining the charged amount of the developer.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus using a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of the developing device according to the embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the voltage applied to the toner charging roller and the toner surface potential when the roller resistance of the toner charging roller is 10 ⁸ Ω.

FIG. 4 is a diagram showing a relationship between a voltage applied to a toner charging roller and a toner surface potential in the case of injection charging.

FIG. 5 is a diagram showing the relationship between the voltage between the developing roller and the toner charging roller and the amount of charge in the embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the voltage between the developing roller and the toner charging roller and the amount of charged electric charge at the initial stage of the developing device and after printing 5000 pages in the embodiment of the present invention.

FIG. 7 is a diagram showing the relationship between the voltage between the developing roller and the toner charging roller and the value of the current flowing in the current detection circuit at the initial stage of the developing device and after printing 5000 pages in the embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the developing roller rotation direction in the toner coat area and the toner surface potential when constant current control is performed in the embodiment of the present invention.

FIG. 9 is a diagram showing the relationship between the developing roller rotation direction in the toner coat area and the toner surface potential when constant voltage control is performed in the embodiment of the present invention.

FIG. 10 is a schematic sectional view of an image forming apparatus using a conventional developing device.

[Explanation of symbols]

1,21 photoconductor 2.22 charging roller 3 cleaning blade 4 Waste toner container 5 Exposure unit 6 Transfer roller 7 Fixing device 9 Paper (transfer material) 10,80 Development device 11, 81 Development roller 12, 82 Elastic roller 13,83 Elastic blade 14,84 toner 15 Stirring member 16 developer container 17,85 toner charging roller 171 Current detection circuit S1, S2 power supply

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H073 AA01 BA01 BA13 BA22 BA45                       CA02                 2H077 AD06 AD13 AD35 AE02 DA24                       DA42 DB08 DB14 EA11 EA15                       EA16 FA13 FA22

Claims (7)

[Claims] 1. A developer carrying body which is in contact with or close to an image carrying body carrying an electrostatic latent image and which conveys a developer to the electrostatic latent image to visualize the developer, and a rotational direction of the developer carrying body. And a regulating member provided on the upstream side of the developing area so as to be in pressure contact with the developer carrying body via the developer, and on the upstream side of the developing area with respect to the rotation direction of the developer carrying body, and the developer. A developing device having a developer charging member provided so as to be close to or in contact with the developer is provided on the downstream side of the pressure contact portion between the carrier and the regulating member, and the absolute value of the discharge start voltage is provided to the developer charging member. A value or more, and a voltage applying means for applying a voltage having the same polarity as the charging polarity of the developer, and a current detecting means for detecting a current flowing to the developer charging member at the time of applying the voltage, and According to the detection result of the current detection means, Image forming apparatus and controls the applying means. 2. The image forming apparatus according to claim 1, wherein the developer charging member is an elastic roller including a plurality of layers. 3. The image forming apparatus according to claim 1, wherein the developer charging member is an elastic roller provided with a fluororesin on a surface layer. 4. The image forming apparatus according to claim 1, wherein the current detecting unit operates during non-image formation. 5. A developer carrying member which is in contact with or in close proximity to an image carrying member carrying an electrostatic latent image and conveys a developer to the electrostatic latent image to visualize the developer, and a developer carrying member with respect to a rotation direction of the developer carrying member. And a regulating member provided on the upstream side of the developing area so as to be in pressure contact with the developer carrying body via the developer, and on the upstream side of the developing area with respect to the rotation direction of the developer carrying body, and the developer. A developing device having a developer charging member provided so as to be close to or in contact with the developer is provided on the downstream side of the pressure contact portion between the carrier and the regulating member, and the absolute value of the discharge start voltage is provided to the developer charging member. A process cartridge to which a voltage equal to or more than a value and having the same polarity as the charging polarity of the developer is applied, and a current detecting unit that detects a current flowing to the developer charging member when the voltage is applied. . 6. The process cartridge according to claim 5, wherein the developer charging member is an elastic roller including a plurality of layers. 7. The process cartridge according to claim 5, wherein the developer charging member is an elastic roller having a surface layer made of fluororesin.