JPH11149204A - Contact charging device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of the charging failure and charging unevenness of a charged body resulting from the rise exceeding a permissible range of the whole or one part resistance of a contact charging member through the deterioration of the contact charging member by obtaining information on the deterioration degree in the contact charging device and an image formation device using the contact charging device, and to prevent the occurrence of image failure in the image formation device. SOLUTION: A voltage-applied charging member 20 is brought into contact with a charged body 1 so as to charge the charged body in a contact charging device. The contact charging device and an image formation device using the contact charging device are equipped with means 24 to 26 detecting the current value of a bias voltage applied to the contact charging member 20, and means 26 to 28 obtaining information on the deterioration of the contact charging member 20 from the detected current value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device for charging (including static elimination) an object to be charged by bringing a charging member to which a voltage is applied into contact with the object to be charged.

[0002] The present invention also relates to an image forming apparatus using a contact charging device as means for charging an image carrier.

[0003]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic system or an electrostatic recording system, an image bearing member such as an electrophotographic photosensitive member or an electrostatic recording dielectric or other charged member is charged to a predetermined polarity and potential. As a charging means, a corona charger has been widely used. In this method, a corona charger is disposed in a non-contact manner on a member to be charged, and the surface of the member is exposed to a corona emitted from the corona charger to charge the surface of the member to a predetermined polarity and potential.

Recently, a contact-type charging device (contact charging device) has been put to practical use because it has advantages such as low ozone and low power as compared with the non-contact type corona charger. In this method, a surface of a member to be charged is charged to a predetermined polarity and potential by bringing a contact charging member, to which a voltage is applied, into contact with the member to be charged.

[0005] The contact charging member has a magnetic brush portion in which magnetic particles are magnetically constrained, and a magnetic brush contact charging member for bringing the magnetic brush portion into contact with an object to be charged is preferably used in view of stability of charging contact. Have been.

[0006] The magnetic brush contact charging member has a magnetic brush portion formed by magnetically restraining conductive magnetic particles directly on a magnet or on a sleeve containing a magnet, and stops or rotates. Then, the magnetic brush portion is brought into contact with the member to be charged, and a voltage is applied to the member to start charging the member to be charged.

[0007] A brush provided with conductive fibers in the form of a brush (fur brush member contact charging member), or a conductive rubber roller formed by rolling conductive rubber (charging roller) is also preferably used as the contact charging member. ing.

In particular, using such a contact charging member, a member having a surface layer (charge injection layer) in which conductive fine particles are dispersed on a normal organic photoreceptor, or an amorphous silicon photoreceptor is used as a member to be charged. And a charging potential substantially equal to the DC component of the bias applied to the contact charging member can be obtained on the surface of the member to be charged (JP-A-6-392).
No. 1).

Such a charging method (charging of a member to be charged by direct injection of charges) is referred to as "injection charging". If this injection charging is used, the charging of the member to be charged does not use a discharge phenomenon that is performed using a corona charger.
Complete ozone-less and low power consumption type charging becomes possible,
It is getting attention.

In recent years, the size of an image forming apparatus has been reduced. However, if each unit and device for an image forming process such as charging, exposure, development, transfer, fixing, and cleaning are each reduced in size, the size of the image forming apparatus is reduced. There was a limit to the overall miniaturization.

The transfer residual toner on the image carrier after the transfer is collected by a cleaning means (cleaner) to become waste toner. It is preferable that the waste toner does not come out from the viewpoint of environmental protection.

In view of this, the cleaner-less system is constructed in such a manner that the cleaner is removed, and the untransferred toner on the image carrier is removed from the image carrier by "simultaneous development cleaning" by the developing means, and is collected and reused in the developing means. Has also appeared.

Simultaneous development cleaning refers to a fogging bias (a potential difference between the DC voltage applied to the developing means and the surface potential of the image carrier) at the time of development after the next step, in which toner slightly remaining on the image carrier after transfer is transferred. Fog removal potential difference Vba
ck). According to this method,
Since the transfer residual toner is collected by the developing means and used after the next step, waste toner can be eliminated and troublesome maintenance can be reduced. In addition, the cleaner-less system has a great advantage in terms of space, and can greatly reduce the size of the image forming apparatus.

[0014]

One of the problems in the contact charging device is that the contact charging member in contact with the member to be charged picks up dirt and foreign matter on the surface of the member to be charged and becomes contaminated by the accumulation thereof. If the contact member is easily contaminated (deterioration of the contact charging member) and becomes in an unacceptable contaminated state, the member to be charged cannot be charged to a desired potential or uneven charging occurs, resulting in a decrease in charging ability.

In an image forming apparatus using a contact charging device as a charging means for an image carrier such as a photoreceptor, an image forming apparatus having a dedicated cleaner for removing transfer residual toner on the image carrier after transfer. Even so, while the image formation is repeated, toner particles and so-called external additives such as silica contained in the developer, which somewhat pass through the cleaner, may cause the contact charging member to move due to the continuous movement of the image carrier. The contact charging member is likely to be contaminated because it is carried to the position and adheres to and mixes with the contact charging member to accumulate.

Normally, the electrical resistance of toner particles and silica is relatively high, so if such toner particles or silica adheres to or mixes with the contact charging member to cause an unacceptable contamination state, the contact charging member as a whole may be damaged. Alternatively, a part of the resistance increases, so that the image carrier cannot be charged to a desired potential, or charging unevenness occurs, resulting in an image defect.

The toner contamination of such a contact charging member,
The occurrence of image defects due to the above-mentioned problem is caused by the above-described “cleanerless method” which uses a contact charging means as a charging means for the photoconductor and does not have a dedicated cleaner for removing transfer residual toner on the image carrier after transfer. This is particularly noticeable in the image forming apparatus of the “system”.

That is, in the case of the image forming apparatus of the cleanerless system, the transfer residual toner on the image carrier after the transfer is carried to the position of the contact charging member by the continuous movement of the image carrier, so that the contact charging member is moved. The contact charging member is liable to be deteriorated by adhering and mixing into the toner.

Accordingly, the present invention provides a contact charging device and an image forming apparatus using the contact charging device, by obtaining information on the degree of deterioration of the contact charging member, thereby obtaining the entire or one of the contact charging members due to the deterioration of the contact charging member. It is an object of the present invention to prevent the occurrence of poor charging and uneven charging of a member to be charged due to an unacceptable rise in the resistance of the image forming apparatus.

[0020]

SUMMARY OF THE INVENTION The present invention is a contact charging device and an image forming apparatus having the following constitutions.

(1) In a contact charging device for charging a member to be charged by contacting a member to which a voltage is applied with a member to be charged, means for detecting a current value of a bias voltage applied to the contact charging member, A contact charging device comprising means for obtaining information on the deterioration of the contact charging member from the measured current value.

(2) In a contact charging device for charging a member to be charged by bringing a charging member into which a voltage is applied into contact with the member to be charged, means for detecting a current value of a bias voltage applied to the contact charging member, and an environment A contact charging device comprising: means for detecting temperature and humidity; and means for obtaining information on deterioration of a contact charging member from detected current values and environmental temperature and humidity information.

(3) The information on the deterioration of the contact charging member obtained from the means for obtaining the information on the deterioration of the contact charging member is used as a signal for prompting replacement of the contact charging member (1) or (1). The contact charging device according to (2).

(4) The contact charging member has a magnetic brush portion in which magnetic particles are magnetically constrained, and is a magnetic brush contact charging member in which the magnetic brush portion contacts a member to be charged. The contact charging device according to any one of 1) to 3).

(5) The contact charging device according to any one of (1) to (4), wherein a bias in which an alternating voltage is superimposed on a DC voltage is used as a bias applied to the contact charging member. .

(6) The surface layer resistance of the member to be charged is 10 ⁹ to 1
0 ¹⁴ Ω · cm (1) to (5)
The contact charging device according to any one of the above.

(7) The contact charging device according to any one of (1) to (6), wherein the surface layer of the member to be charged is a resin dispersion layer of conductive fine particles.

(8) In an image forming apparatus in which an image is formed by an image forming process unit including a charging unit for charging the image carrier, any one of the charging units (1) to (7) for charging the image carrier. An image forming apparatus, comprising: the contact charging device according to any one of the above.

(9) Charging means for charging the image carrier, image information writing means for forming an electrostatic latent image corresponding to the target image information on the charged surface of the image carrier, and the electrostatic latent image In an image forming apparatus in which an image is formed by an image forming process unit including a developing unit that forms a toner image by developing the image carrier with a developer, a charging unit that charges the image carrier is any one of (1) to (7). An image forming apparatus, comprising: the contact charging device according to any one of the above.

(10) charging means for charging the image carrier;
Image information writing means for forming an electrostatic latent image corresponding to target image information on the charged surface of the image carrier; developing means for developing the electrostatic latent image with a developer to form a toner image; Image formation in which image formation is performed by image forming process means including transfer means for transferring a toner image to a recording material, and cleaning means for collecting transfer residual toner remaining on the image carrier after transfer of the toner image to the recording material An image forming apparatus, wherein the charging means for charging the image carrier is the contact charging device according to any one of (1) to (7).

(11) charging means for charging the image carrier;
Image information writing means for forming an electrostatic latent image corresponding to target image information on the charged surface of the image carrier; developing means for developing the electrostatic latent image with a developer to form a toner image; An image is formed by an image forming process unit including a transfer unit that transfers a toner image to a recording material, and the developing unit collects transfer residual toner remaining on the image carrier after transferring the toner image to the recording material. In the image forming apparatus which also serves as the means, the charging means for charging the image carrier is the contact charging device according to any one of (1) to (7).

(12) The image forming apparatus according to any one of (9) to (11), wherein the means for writing image information to the image carrier is an image exposing means.

(13) The image carrier according to any one of (8) to (12), wherein the image carrier has a photosensitive layer and a surface layer, and the surface layer is a resin dispersion layer of conductive fine particles. The image forming apparatus as described in the above.

<Operation> In the contact charging device, the resistance value of the contact charging member changes with the deterioration of the member. Accordingly, the degree of deterioration of the contact charging member can be determined from the resistance value of the contact charging member.

Accordingly, the present invention relates to a contact charging device and an image forming apparatus using the contact charging device, wherein a current value of a bias voltage applied to the contact charging member is detected, and from the detected current value, the contact charging member is detected. Deterioration information is obtained, or environmental temperature and humidity are further detected, and information on deterioration of the contact charging member is obtained from the detected current value and environmental temperature and humidity information, and the degree of the deterioration is out of tolerance. Sometimes, a signal to that effect is transmitted to urge the replacement of the contact charging member, etc., so that the charging failure of the member to be charged due to an unacceptable rise in the resistance of the entire or a part of the contact charging member due to the deterioration of the contact charging member. In an image forming apparatus, it is possible to prevent occurrence of image defects.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (FIGS. 1 to 6) (1) Schematic Configuration of Image Forming Apparatus (FIG. 1) FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention. . The image forming apparatus of the present embodiment is a laser beam printer using a transfer type electrophotographic process.

A is a laser beam printer, and B is an image reading device (image scanner) mounted on the printer.

A) Image Reading Device B In the image reading device B, reference numeral 31 denotes a platen glass fixedly arranged on the upper surface of the device, and is placed on the upper surface of the platen glass with the original G to be copied facing downward. Then, a document pressure plate (not shown) is placed over the document and set.

Reference numeral 32 denotes an image reading unit provided with a document irradiation lamp 32a, a short focus lens array 32b, a CCD sensor 32c, and the like. When a copy button (not shown) is pressed, the unit 32 opens the platen glass 3.
1 is moved forward from the home position indicated by the solid line on the left side of the glass to the right side along the lower surface of the glass, and is driven backward when the predetermined forward end point is reached, and the first home position indicated by the solid line Is returned to.

In the forward drive of the unit 32,
The downward image surface of the set original G on the original platen glass 31 is sequentially illuminated and scanned from the left side to the right side by the original irradiation lamp 32a of the unit 32, and the original surface reflected light of the illumination scanning light is a short focal length lens. An image is incident on the CCD sensor 32c by the array 32b.

The CCD sensor 32c includes a light receiving section, a transfer section,
It consists of an output unit. The light signal is converted into a charge signal in the CCD light receiving unit, and the transfer unit sequentially transfers the light signal to the output unit in synchronization with the clock pulse. The output unit converts the charge signal into a voltage signal, amplifies the signal, reduces the impedance, and outputs the voltage signal. The analog signal thus obtained is subjected to well-known image processing, converted into a digital signal, and sent to the printer A.

That is, the image information of the document G is photoelectrically read by the image reading device B as a time-series electric digital pixel signal (image signal).

B) Printer A In the printer A, reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (photosensitive drum) as an image carrier. The photoreceptor of this example has a negative charge OPC having a charge injection layer on the surface.
It is a photoconductor. This photoreceptor will be described in detail in section (2) below.

The photosensitive drum 1 has a predetermined peripheral speed in the counterclockwise direction indicated by an arrow about the center support shaft, and a rotation speed of 100 m in this embodiment.
m / sec, and in the rotation process, the entire memory is subjected to the pre-exposure by the pre-exposure device (eraser lamp) 9 to erase the electric memory remaining in the previous image forming process. In the case of (1), a uniform charge treatment of negative polarity is applied.

The charging means 2 in this embodiment is a contact charging type magnetic brush charging device. The charging device 2 will be described later in detail in (3).

In response to the image signal output from the laser scanning unit (laser scanner) 3 and sent from the image reading device B to the printer A, the uniformly charged surface of the rotating photosensitive drum 1 By performing the scanning exposure L with the modulated laser beam, the rotating photosensitive drum 1 is rotated.
On the surface, an electrostatic latent image corresponding to the image information of the document G photoelectrically read by the image reading device B is sequentially formed.

The laser scanning section 3 comprises a light emitting signal generator, a solid laser element, a collimator lens system, a rotating polygon mirror (polygon mirror) and the like.

When the laser scanning unit 3 performs laser scanning exposure L on the surface of the rotating photosensitive drum, first, the solid-state laser element is turned on and off at a predetermined timing by a light emission signal generator based on the input image signal (ON / OFF). ). The laser light emitted from the solid-state laser element is converted into a substantially parallel light beam by a collimator lens system, scanned by a rotating polygon mirror rotating at a high speed, and spotted on the photosensitive drum surface 1 by an fθ lens group. It is imaged. By such laser beam scanning, an exposure distribution for one image scan is formed on the photosensitive drum surface 1, and the rotation of the photosensitive drum 1 causes the photosensitive drum surface to be positioned perpendicular to the scanning direction for each scan. By scrolling by a fixed amount, an exposure distribution according to the image signal is obtained on the rotating photosensitive drum surface.

The electrostatic latent image formed on the surface of the rotating photosensitive drum 1 is sequentially developed as a toner image by the developing device 4 in the case of the present embodiment, and is reversely developed. The developing device 4 of this embodiment is a two-component contact developing type device. This developing device 4 will be described later (4)
It will be described in detail in the section.

On the other hand, the transfer material P as a recording medium stored in the paper feed cassette 5 is fed out one by one by the paper feed roller 5a and fed into the printer A, and the registration roller 5b
Thus, at a predetermined control timing, the sheet is fed to a transfer portion T which is a contact nip portion between the photosensitive drum 1 and a transfer belt type transfer device 6 as a transfer unit.

The toner image on the side of the rotating photosensitive drum 1 is sequentially electrostatically transferred to the surface of the transfer material P fed to the transfer portion T by the transfer charging blade 6 d disposed inside the transfer belt 6. This transfer device 6 will be described later in detail in (5).

The transfer material P having received the transfer of the toner image through the transfer portion T is sequentially separated from the surface of the photosensitive drum 1, and is conveyed to the fixing device 7 by an extension of the transfer belt type transfer device 6,
The toner image is thermally fixed and output as a copy or print.

After the transfer material is separated, the surface of the rotating photosensitive drum 1 is subjected to removal of transfer residual toner by a cleaning device (cleaner) 8 and is repeatedly provided for image formation.

(2) Photoreceptor Drum 1 (FIG. 2) As the photoreceptor drum 1 as an image carrier, a commonly used organic photoreceptor or the like can be used. Also, C
A photoreceptor using an inorganic semiconductor such as dS, Si, or Se can also be used. Preferably, when an organic photoreceptor having a surface layer having a material having a resistance of 10 ² to 10 ¹⁴ Ω · cm or an amorphous silicon photoreceptor is used, charge injection charging can be realized and ozone generation can be prevented. , And power consumption. Further, the chargeability can be improved.

The photosensitive drum 1 used in this embodiment is a negatively charged organic photosensitive member having a charge injection layer on the surface thereof.
The first to fifth five layers described below are provided in order from the bottom on a 30 mm-diameter aluminum drum base (hereinafter, referred to as an aluminum base). FIG. 2 is a model diagram of the layer structure.

The first layer 12 is a subbing layer and has a thickness of 20 μm provided for smoothing out defects or the like of the aluminum base 11.
m of the conductive layer.

A second layer 13; a positive charge injection preventing layer, which serves to prevent positive charges injected from the aluminum substrate 11 from canceling out negative charges charged on the surface of the photoreceptor; 1 × 1
0 is the resistance layer in the ⁶ Omega · cm about the resistance adjusted thickness 1 [mu] m.

Third layer 14: a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and which generates positive and negative charge pairs upon exposure to light.

Fourth layer 15: a charge transport layer, in which hydrazone is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer 14 can be transported to the surface of the photoreceptor.

Fifth layer 16: a charge injection layer, which is a coating layer of a material in which ultrafine SnO ₂ particles as conductive particles 16a are dispersed in a binder of an insulating resin. Specifically, a particle diameter of about 0.03 μm obtained by doping an insulating resin with antimony, which is a light-transmitting insulating filler, to reduce the resistance (to make it conductive).
This is a coating layer of a material in which m SnO ₂ particles are dispersed in a resin by 70% by weight.

The thus prepared coating liquid was applied to a thickness of about 3 μm by a suitable coating method such as dipping coating method, spray coating method, roll coating method, beam coating method, etc. to form a charge injection layer.

The surface resistance is 10 ¹³ Ω · cm. By controlling the surface resistance in this manner, the chargeability is directly improved and a high-quality image can be obtained. Photoreceptor is O
It can be realized not only with a PC but also with an a-Si drum, and further high durability can be realized.

Here, the volume resistance of the surface layer was measured by arranging metal electrodes at an interval of 200 μm, flowing a preparation liquid for the surface layer during the film formation, and applying a voltage of 100 V between the electrodes. Value. The measurement is a value measured under the conditions of a temperature of 23 ° C. and a humidity of 50% RH.

(3) Charging Device 2 (FIG. 3) The charging device 2 in this example is a contact charging type magnetic brush charging device. FIG. 3 is a schematic configuration diagram thereof. Reference numeral 20 denotes a magnetic brush charger as a contact charging member disposed in contact with the photosensitive drum 1.

The magnetic brush charger 20 of this embodiment is of a rotary sleeve type, and has a magnet roll 21 fixed and supported non-rotatably, and an outer diameter which is concentrically and rotatably fitted around the outside of the magnet roll. A 16-mm non-magnetic sleeve (non-magnetic, conductive, charging electrode sleeve) 22;
A magnetic brush portion 23 of conductive magnetic particles (magnetic carrier for charging) and the like formed by being attracted and held on the outer peripheral surface of the non-magnetic sleeve 22 by the magnetic force of the magnet roll 21 inside the sleeve.

The magnetic brush charger 20 is brought into contact with the photosensitive drum 1 by bringing the magnetic brush portion 23 into contact with the surface of the photosensitive drum 1.
It is arranged almost in parallel. In this case, the magnetic brush charger 20 was arranged such that the contact nip width (charging area) n of the magnetic brush portion 23 formed on the photosensitive drum 1 was about 5 mm.

The charging magnetic particles constituting the magnetic brush portion 23 have an average particle diameter of 10 to 100 μm, a saturation magnetization of 20 to 250 emu / cm ³ , and a resistance of 1 × 10 ² to 1 × 10 ^2.
It is preferably ¹⁰ Ω · cm. Considering the presence of insulation defects such as pinholes in the photosensitive drum 1, it is preferable to use a photosensitive drum having a resistance of 1 × 10 ⁶ Ω · cm or more. In order to improve the charging performance, it is better to use one having as small a resistance as possible. In this example, the average particle diameter is 25 μm, the saturation magnetization is 200 emu / cm ³ , and the resistance is 5 × 10 ^6.
Ω · cm magnetic particles were used.

The resistance value of the magnetic particles is such that the bottom area is 228 mm.
After placing 2g of the magnetic particles in the ^second metal cell, 6.6kg /
The weight was measured in cm ² and a voltage of 100 V was applied for measurement.

The average particle size of the magnetic particles is represented by the maximum chord length in the horizontal direction. The measurement was performed by microscopically selecting 300 or more particles at random, measuring the diameter, and taking the arithmetic average.

For the measurement of the magnetic characteristics of the magnetic particles, a DC magnetization BH characteristic automatic recording device BHH-50 manufactured by Riken Denshi Co., Ltd. can be used. At this time, the diameter (inner diameter) is 6.5 m
m, magnetic particles in a cylindrical container with a height of 10 mm
The filling is carried out at about g weight, and the saturation magnetization is measured from the BH curve while keeping the particles from moving in the container.

As the magnetic particles, a resin carrier formed by dispersing magnetite as a magnetic material in a resin and dispersing carbon black for conductivity and resistance adjustment;
Alternatively, a material in which the surface of a single magnetite such as ferrite is oxidized and reduced to adjust the resistance, or a material in which the surface of a single magnetite such as ferrite is coated with a resin and the resistance is adjusted may be used. In the present embodiment, a ferrite surface whose resistance has been adjusted by oxidizing and reducing is used.

Non-magnetic sleeve 2 of magnetic brush charger 20
No. 2 was rotated at a speed of 150 mm / sec against a rotational peripheral speed of 100 mm / sec in a counterclockwise direction of an arrow opposite to the rotation direction of the photoconductor drum 1 (counter direction) in the charging area n. .

A predetermined charging bias was applied to the non-magnetic sleeve 22 from a charging bias application power source S1.

In this example, as a charging condition, a DC bias was applied under constant voltage control of -550V.

With the rotation of the non-magnetic sleeve 22, the magnetic brush portion 23 rotates in the same direction and rubs the surface of the photosensitive drum 1 in the charging area n, so that the electric charge is removed from the charging magnetic particles constituting the magnetic brush portion 23. Is provided on the photosensitive drum 1,
The surface of the photosensitive drum 1 is uniformly contact-charged to a predetermined polarity and potential.

In the case of this embodiment, as described above, since the photosensitive drum 1 has the charge injection layer 16 on its surface, the photosensitive drum 1 is charged by charge injection charging. That is, by applying a predetermined charging bias voltage to the non-magnetic sleeve 22, charges are given to the photosensitive drum 1 from the magnetic particles constituting the magnetic brush portion 23, and the surface of the photosensitive drum 1 is charged with the charging bias voltage. Is charged to a potential corresponding to. The non-magnetic sleeve 22 tends to have better charging uniformity as the rotation speed is higher.

Reference numerals 24 to 28 denote block circuits for a deterioration information detection / warning system of the magnetic brush charger 20 as a contact charging member. This will be described in detail in section (6).

(4) Developing Device 4 (FIG. 4) As a toner developing method for an electrostatic latent image, generally, the following a to d
Are roughly divided into four types.

A. Non-magnetic toner is coated on the sleeve with a blade or the like, and magnetic toner is coated by magnetic force, transported, and developed in a non-contact state with the photoreceptor (one-component non-contact development). B. A method in which the toner coated as described above is developed in contact with the photoreceptor (one-component contact development). C. A method in which a mixture of toner particles and a magnetic carrier is used as a developer and conveyed by magnetic force to develop in contact with a photoreceptor (two-component contact development). D. Method of Developing the Two-Component Developer in a Non-Contact State (Two-Component Non-Contact Development) Among these, the two-component contact development method of c is often used from the viewpoint of high image quality and high stability. ing.

FIG. 4 shows a schematic configuration of the developing device 4 used in this embodiment. The developing device 4 of the present embodiment uses a mixture of non-magnetic toner particles and magnetic carrier particles as a developer, causes the developer to be held as a magnetic brush layer by a magnetic force on a developer carrying member, and This is a two-component magnetic brush contact development type apparatus that transports and contacts the surface of the photosensitive drum 1 to develop an electrostatic latent image as a toner image.

Reference numeral 41 denotes a developing container; 42, a developing sleeve as a developer carrier; 43, a magnet roller as magnetic field generating means fixedly disposed in the developing sleeve 42;
44 is a developer layer thickness regulating blade for forming a thin layer of the developer on the surface of the developing sleeve, 45 is a developer stirring and conveying screw, 46 is a two-component developer housed in the developing container 41, and is a non-magnetic developer. Toner particles t and magnetic carrier particles c
Are mixed.

The developing sleeve 42 is arranged so that the closest distance (gap) to the photosensitive drum 1 is about 500 μm at least during development.
The developer magnetic brush thin layer 46a carried on the outer surface of the photosensitive drum 1 is set in contact with the surface of the photosensitive drum 1. The contact nip m between the developer magnetic brush layer 46a and the photosensitive drum 1 is a developing area (developing section).

The developing sleeve 42 is driven around the fixedly disposed magnet roller 43 at a predetermined rotation speed in the counterclockwise direction indicated by an arrow, and the developer 46 is applied to the outer surface of the sleeve in the developing container 41 by the magnetic force of the magnet roller 43. A magnetic brush is formed. The developer magnetic brush is sleeve 4
2, is carried out of the developing container as a thin layer of developer magnetic brush 46a having a predetermined thickness under the regulation of the layer thickness by the blade 44, is conveyed to the developing section, and comes into contact with the surface of the photosensitive drum 1, With the subsequent rotation of the sleeve 42, it is returned and transported into the developing container 41 again.

That is, first, the developer 46 pumped up by the N ₃ pole of the magnet roller 43 with the rotation of the developing sleeve 42 is transported from the S ₂ pole to the N ₁ pole in the process of being perpendicular to the developing sleeve 42. The thin layer 46 a of the developer 46 is formed on the developing sleeve 42 by being regulated by the regulating blade 44 disposed at the position. Developer layer 46a which is a thin layer formed brush is formed by the conveyed to the developing main pole S ₁ of the developing unit magnetic force. An electrostatic latent image on the photosensitive drum 1 by the developing agent layer 46a formed on the spikes is developed as a toner image, then the developer on the developing sleeve 42 by a repulsive magnetic field of the N ₃ pole · N ₂ pole developer container 4
Returned to 1

A developing bias of a DC voltage (DC) and an alternating voltage (AC, AC voltage) is applied between the developing sleeve 42 and the conductive drum substrate of the photosensitive drum 1 by a developing bias applying power source S2.

In this example, DC voltage: -480 V alternating voltage; amplitude Vpp = 1500 V, frequency Vf = 30
A developing bias of 00 Hz is applied, and the toner t in the developer magnetic brush thin layer 46 a on the developing sleeve 42 side selectively adheres to the electrostatic latent image on the photosensitive drum 1 side in the developing section, so that the electrostatic latent image is formed. It is developed as a toner image.

In general, in the two-component developing method, when an alternating voltage is applied, the developing efficiency is increased and the quality of the image is high, but on the contrary, there is a risk that fogging is likely to occur. For this reason, fogging is generally prevented by providing a potential difference between the DC voltage applied to the developing device 4 and the surface potential of the photosensitive drum 1.

The potential difference for preventing fog is called a fog removal potential (Vback), and the potential difference prevents toner from adhering to the non-image area of the photosensitive drum 1 during development.

The toner concentration (mixing ratio with the carrier) of the developer 46 in the developing container 41 gradually decreases as the toner is consumed for developing the electrostatic latent image. The toner concentration of the developer 46 in the developing container 41 is detected by a detection unit (not shown), and when the toner concentration falls to a predetermined allowable lower limit concentration, the toner replenishing unit 47.
Then, the toner t is supplied to the developer 46 in the developing container 41, and the toner replenishment is controlled so that the toner concentration of the developer 46 in the developing container 41 is always kept within a predetermined allowable range.

The two-component developer 46 used in this example is composed of toner particles t; a negatively charged toner having an average particle diameter of 6 μm and titanium oxide having an average particle diameter of 20 nm externally added by 1% by weight. Carrier c; saturation magnetization Is a mixture of 205 emu / cm ³ of magnetic carrier having an average particle diameter of 35 μm in a weight ratio of 6 to 94. At this time, the toner in the developer has a triboelectric charge amount of about 25 × 10 ⁻³ c / kg.
Met.

For the volume average particle diameter of the toner, for example, the one measured by the following measuring method is used.

As the measuring device, Coulter Counter T
Using an A-II type (manufactured by Coulter), an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution and a CX-i personal computer (manufactured by Canon) are connected, and primary electrolyte is sodium chloride. 1% NaC
Adjust the aqueous solution.

The measuring method is as follows.
In 150 ml, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the particle size distribution of 2 to 40 μm particles was measured using the Coulter Counter TA-II using an aperture of 100 μm. Is measured to determine the volume distribution. From these determined volume distributions, the volume average particle size of the sample is obtained.

(5) Transfer Device 6 (FIG. 1) The transfer device 6 is of the transfer belt type in this embodiment as described above. Reference numeral 6a denotes an endless transfer belt.
The photosensitive drum 1 is rotated in a forward direction in the direction of rotation of the photosensitive drum 1 at a peripheral speed substantially equal to the rotational peripheral speed of the photosensitive drum 1. 6d is a transfer belt 6a
A transfer charging blade disposed inside the transfer belt 6a, the ascending belt portion of the transfer belt 6a is pressed against the photosensitive drum 1 to form a transfer nip portion T, and a transfer bias is applied from a transfer bias applying power source S3. The transfer material P
Is charged from the back surface of the toner with the polarity opposite to that of the toner. As a result, the toner image on the rotating drum 1 side is sequentially electrostatically transferred onto the surface of the transfer material P passing through the transfer portion T.

In this embodiment, the belt 6a has a thickness of 75
A resin made of a μm polyimide resin was used.

The material of the belt 6a is not limited to a polyimide resin, but may be a polycarbonate resin,
Plastics such as polyethylene terephthalate resin, polyvinylidene fluoride resin, polyethylene naphthalate resin, polyetheretherketone resin, polyethersulfone resin, and polyurethane resin, and fluorine-based and silicon-based rubbers can be suitably used. The thickness is not limited to 75 μm, but is
000 μm, preferably 50 to 150 μm can be suitably used.

Further, as the transfer charging blade 6d, one having a resistance of 1 × 10 ⁵ to 1 × 10 ⁷ Ω, a plate thickness of 2 mm, and a length of 306 mm was used. This transfer charging blade 6d
Was transferred by applying a bias of +15 μA under constant current control.

(6) Deterioration information detection of contact charging member 20
Warning system (FIGS. 3, 5, and 6) The transfer unit T transfers the toner image on the photosensitive drum 1 side to the transfer material P side after transferring the toner image on the photosensitive drum 1 side. In this embodiment, in which the remaining toner that cannot be completely removed is the contact charging member, the magnetic brush charger 20 is gradually contaminated by being mixed into the magnetic brush portion 23 of the magnetic brush charger 20 (deterioration of the contact charging member). Depending on the resistance value of the toner and the like, if a certain amount or more (predetermined amount or more) of toner is mixed into the magnetic brush portion 23 of the magnetic brush charger 20, the charging ability is reduced, and as a result, image deterioration is caused.

ΔV, which is the difference between the first-turn potential and the saturation potential at which the photosensitive drum 1 as a member to be charged is charged by the magnetic brush charger 20, is a constituent member of the magnetic brush portion 23 of the magnetic brush charger 20. The lowering of the charging ability caused by the increase in the resistance of the magnetic particles (or the magnetic brush portion) due to the incorporation of toner having a higher resistance than the magnetic particles (magnetic carrier for charging).

FIG. 5 shows the relationship between the resistance value of the magnetic particles and ΔV. Here, the resistance value of the magnetic particles is such that the bottom area is 228 mm ²
After putting 2 g of magnetic particles into the metal cell of 6.6 kg / c
The measurement is performed by applying a voltage of 100 V with a weight of m ² . According to this, the resistance value of the magnetic particles and ΔV are in a proportional relationship.

FIG. 6 shows the environmental dependence of the resistance value of the magnetic particles. This shows that the resistance value of the magnetic particles is high at low temperature and low humidity and low at high temperature and high humidity, and the resistance value of the magnetic particles also changes with environmental changes. Therefore, when information on deterioration is obtained from the resistance value of the magnetic particles, it is necessary to consider factors depending on such environmental conditions.

In this embodiment, the magnetic brush charger 20
The current value Idc of the DC component of the applied voltage to
When the value of Idc becomes equal to or less than the predetermined current value Ith, FIG.
It is determined that the charging capability of the magnetic brush charger 20 has decreased in accordance with the characteristics shown in FIG. At this time, the reference current value Ith is defined in advance depending on the environmental temperature and humidity.

That is, in FIG. 3, the current value _Idc of the DC component of the voltage applied to the magnetic brush charger 20 detected by the ammeter 24 is input to the CPU 26 through the analog / digital converter 25, and
Based on the temperature and humidity information obtained by the environment sensor 27 input to the CPU 6, a comparison is made with a replacement prescribed current value Ith preset in the CPU 26. CPU2 if less
6 issues an information signal that the magnetic brush charger 20 has deteriorated. The charger deterioration signal activates the warning / display 28 as a charger replacement signal urging the user to replace the charger, for example.

As a result, a reduction in the charging ability of the charging device 20 caused by mixing of the remaining transfer toner remaining on the photosensitive drum 1 that has not been removed by the cleaning device 8 into the charging device 20 can be prevented. By detecting the deterioration of the charger and notifying the deterioration of the charger, it is possible to prevent the image deterioration caused by the increase in the resistance of the magnetic particles in the charger 20 and to always obtain a stable image.

<Embodiment 2> (FIGS. 7 and 8) The image forming apparatus of FIG. 7 of the present embodiment is similar to the image forming apparatus of Embodiment 1 described above except that the cleaning device 8 is omitted, and the transfer residual toner is removed. This is a cleaner-less system in which the developing device 4 collects the developer by simultaneous cleaning.

After the transfer, the transfer residual toner is left on the photosensitive drum 1. Here, the transfer residual toner on the photosensitive drum 1 often has both positive and negative polarities due to peeling discharge at the time of transfer. The transfer residual toner having the mixed polarity reaches the magnetic brush charger 20 and mixes with the magnetic particles in the magnetic brush portion 23 of the charger 20, and is discharged to the photosensitive drum 1 after all the polarity is negatively charged.
At this time, the toner is not sufficiently taken into the charger 20 by only applying the DC voltage to the magnetic brush charger 20, but when the alternating voltage is applied to the magnetic brush charger 20, the photosensitive drum 1 The toner is easily taken into the charger 20 by the vibration effect of the electric field between the two. In FIG. 8, Sac is a power supply for applying an alternating voltage to the charger 20.

The untransferred toner discharged on the photosensitive drum 1 after the polarity is uniformed by the charger 20 reaches the developing section m, and is transferred into the developing apparatus by the fog removing electric field during development by the developing apparatus 4 at the same time as development. Collected.

When the image area in the rotation direction is longer than the circumferential length of the photosensitive drum 1, these simultaneous development and recovery are performed simultaneously with other image forming processes such as charging, exposure, development, and transfer. Done.

As a result, the transfer residual toner is collected in the developing device 4 and used after the next process, so that waste toner can be eliminated. Further, there is a great advantage in terms of space, and the size of the image forming apparatus can be significantly reduced.

However, in the case of performing the above-mentioned simultaneous cleaning with development, the toner is taken into the charger 20 in order to make the polarity of the untransferred toner uniform. It is remarkable compared to the case of the device.

In the present embodiment, in a cleaner-less image forming apparatus that performs simultaneous development and cleaning, as shown in FIG.
A DC component current value Idc of a bias applied by superimposing a DC voltage and an alternating voltage with ac is detected by an ammeter 24, and the detected value is analog-to-digital converted as in the case of the image forming apparatus of the first embodiment. Input to the CPU 26 through the container 25,
When the value of Idc becomes equal to or less than the predetermined current value Ith, it is determined that the charging capability of the charger 20 has decreased, and a signal indicating deterioration of the charger is generated.

It is also possible to stop the alternating voltage superimposed as the applied bias at a specific timing, and to detect the DC component current value Idc when only the DC voltage is applied.

With this configuration, simultaneous development and cleaning is performed by the developing device 4, and even when a bias in which a DC voltage is superimposed on an alternating voltage is applied to the charger 20, the magnetic particles in the charger have a high resistance. Image deterioration can be prevented, and a stable image can always be obtained.

<Embodiment 3> (FIG. 9) The image forming apparatus of the present embodiment also has a configuration in which simultaneous cleaning is performed by the developing device 4 similarly to the image forming apparatus of Embodiment 2 described above. An image forming apparatus of a cleanerless system for applying a bias in which a DC voltage is superimposed on an alternating voltage.

FIG. 9 shows a change in ΔV with respect to the number of durable sheets when the DC voltage and the alternating voltage are superimposed on the magnetic brush charger 20 as an applied bias, and a change in the AC component current value at that time. According to this, ΔV and the AC component current value show almost the same changes.

Therefore, in this embodiment, the AC component current value Iac of the bias applied by superimposing the DC voltage and the alternating voltage on the magnetic brush charger 20 is detected, and the value of the Iac becomes equal to or less than the predetermined current value. In such a case, it is determined that the charging ability of the charger 20 has decreased, and a signal indicating deterioration of the charger is issued.

The other structure is the same as that of the second embodiment.

Thus, the same effect can be obtained by detecting the AC component current value Iac of the bias applied by superimposing the DC voltage and the alternating voltage on the charger 20.

<Others> 1) The configuration of the present invention is not limited to the first, second and third embodiments. For example, the contact charging member may be a fur brush charger, a conductive rubber or a conductive sponge. The used charging roller or the like may be used, or a non-rotating contact charging member or the like may be used.

2) The photosensitive member as the member to be charged (image carrier) also has a surface resistance of 10 ⁹ to 10 ¹⁴ Ω · cm.
It is desirable to have a low-resistance layer in order to realize charge injection charging and to prevent generation of ozone, but an organic photoreceptor other than the above may be used. That is, the contact charging is not limited to the charge injection charging system of the embodiment, but may be a contact charging system in which a discharge phenomenon is dominant.

3) As the developing device, only the two-component developing method has been described in Embodiments 1, 2, and 3, but other developing methods are also effective. Preferably, one-component contact development or two-component contact development in which a developer is brought into contact with a photoreceptor to develop a latent image is effective in further enhancing the simultaneous recovery effect of the developer.

When a polymerized toner is used as the toner particles in the developer, other developing methods such as one-component non-contact development and two-component non-contact development as well as one-component contact development and two-component contact development described above are used. , A sufficient recovery effect can be obtained.

4) As a waveform of the alternating voltage (AC voltage), a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Further, there may be a rectangle formed by periodically turning on / off the DC power supply. As described above, a bias whose voltage value periodically changes can be used as the waveform of the alternating voltage.

5) The image exposing means for forming an electrostatic latent image is not limited to the laser scanning exposing means for forming a digital latent image as in the embodiment, but is a general analog type. Other light-emitting elements such as an image exposure or LED may be used, and any device that can form an electrostatic latent image corresponding to image information, such as a combination of a light-emitting device such as a fluorescent lamp and a liquid crystal shutter, may be used.

The image carrier may be an electrostatic recording dielectric or the like. In this case, after the dielectric surface is uniformly charged to a predetermined polarity and potential, the charge is selectively removed by a charge removing means such as a charge removing needle head or an electron gun to write and form a desired electrostatic latent image.

6) The recording medium for receiving the transfer of the toner image from the image carrier may be an intermediate transfer member such as a transfer drum.

[0128]

As described above, according to the present invention, for a contact charging device and an image forming apparatus using the contact charging device, information on the degree of deterioration of the contact charging member can be obtained.
Prevents poor charging of the member to be charged and uneven charging caused by an unacceptable increase in the resistance of the entire or a part of the contact charging member due to deterioration of the contact charging member. Can be prevented, and the intended purpose is well achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic diagram of a layer configuration of a photoreceptor.

FIG. 3 is a schematic diagram of a configuration of a magnetic brush charger, and a block circuit of a deterioration information detection-warning system of the charger.

FIG. 4 is a structural model diagram of a developing device part.

FIG. 5 is a relationship diagram between a change in the resistance value of the magnetic particles and a change in ΔV.

FIG. 6 is a diagram showing the relationship between the resistance value of magnetic particles and the environment.

FIG. 7 is a schematic diagram of an image forming apparatus (cleanerless) according to a second embodiment.

FIG. 8 is a schematic diagram of a configuration of a magnetic brush charger and a block circuit of a deterioration information detection / warning system of the charger.

FIG. 9 is a relationship diagram between a change in ΔV and a change in an AC component current value.

[Explanation of symbols]

 Reference Signs List A laser beam printer B image reading device (image scanner) 1 member to be charged (image carrier, photosensitive drum) 2 contact charging means 20 magnetic brush charger (contact charging member) 3 laser scanning unit (laser scanner) 4 developing device Reference Signs List 5 paper cassette 6 transfer device 7 fixing device 8 cleaning device 9 pre-exposure lamp 24 ammeter 25 analog / digital converter 26 CPU 27 environment sensor 28 charger deterioration warning / display

Claims (13)

[Claims] 1. A contact charging device for charging a member to be charged by contacting a charging member to which a voltage is applied with the member to be charged, means for detecting a current value of a bias voltage applied to the contact charging member; A contact charging device comprising means for obtaining information on the deterioration of the contact charging member from the current value obtained. 2. A contact charging device for charging a member to be charged by bringing a member to which a voltage is applied into contact with the member to be charged, comprising: means for detecting a current value of a bias voltage applied to the member to be charged; A contact charging device comprising: means for detecting humidity; and means for obtaining information on deterioration of a contact charging member from detected current values and environmental temperature / humidity information. 3. The method according to claim 1, wherein the information on the deterioration of the contact charging member obtained from the means for obtaining the information on the deterioration of the contact charging member is used as a signal for prompting replacement of the contact charging member. 4. The contact charging device according to claim 1. 4. A magnetic brush contact charging member having a magnetic brush portion in which magnetic particles are magnetically constrained, and wherein the magnetic brush portion is brought into contact with an object to be charged. 4. The contact charging device according to any one of 1 to 3. 5. The contact charging device according to claim 1, wherein a bias in which an alternating voltage is superimposed on a DC voltage is used as a bias applied to the contact charging member. 6. The surface layer resistance of the member to be charged is 10 ⁹ to 10 ^14.
The contact charging device according to claim 1, wherein the resistance is Ω · cm. 7. The contact charging device according to claim 1, wherein the surface layer of the member to be charged is a resin dispersion layer of conductive fine particles. 8. An image forming apparatus in which an image is formed by an image forming process means including a charging means for charging an image carrier, wherein the charging means for charging the image carrier is any one of claims 1 to 7. An image forming apparatus, comprising: 9. A charging unit for charging an image carrier, an image information writing unit for forming an electrostatic latent image corresponding to target image information on a charged surface of the image carrier, and 8. An image forming apparatus in which an image is formed by an image forming process means including a developing means for developing a toner image by developing with a developer, wherein the charging means for charging the image carrier is any one of claims 1 to 7. An image forming apparatus, comprising: 10. A charging unit for charging an image carrier, an image information writing unit for forming an electrostatic latent image corresponding to target image information on a charging-processed surface of the image carrier, and Developing means for developing a toner image by developing with a developer, transfer means for transferring the toner image to a recording material, and cleaning means for collecting transfer residual toner remaining on the image carrier after transferring the toner image to the recording material An image forming apparatus in which an image is formed by an image forming process means including: a contact charging device according to any one of claims 1 to 7, wherein the charging means for charging the image carrier is provided. Image forming device. 11. A charging unit for charging an image carrier, an image information writing unit for forming an electrostatic latent image corresponding to target image information on a charged surface of the image carrier, and An image is formed by image forming process means including developing means for developing a toner image by developing with a developer and transfer means for transferring the toner image to a recording material, and the developing means transfers the toner image to the recording material. 8. A contact charging device according to claim 1, wherein the charging device for charging the image carrier is a cleaning device that also serves as a cleaning device for recovering transfer residual toner remaining on the image carrier. An image forming apparatus comprising: 12. An image exposure means according to claim 9, wherein said means for writing image information to said image carrier is an image exposure means.
2. The image forming apparatus according to claim 1, wherein: 13. An image carrier having a photosensitive layer and a surface layer,
The image forming apparatus according to claim 8, wherein the surface layer is a resin dispersion layer of conductive fine particles.