JPH06230654A - Magnetic brush electrostatic charging device and image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of preventing excess mechanical actions from being executed or abnormality from being developed to the abnormality of an entire machine by controlling a magnetic brush electrostatic charging means capable of always accurately detecting electrostatic charging performance and a process means in accordance with the occurrence of the abnormality of the electrostatic charging performance. CONSTITUTION:The magnetic brush electrostatic charging means 20 uniformly electrostatically charging an image forming body 10 by a magnetic brush 21 in a oscillating electric field, a developing means obtaining a toner image by developing a latent image formed by an image exposing means, and a transfer means transferring the toner image on recording paper are provided, and then a control means 70 detecting a current flowing in the magnetic brush 21 in the midst of electrostatic charging in the means 20 and generating a control signal in accordance with the detected current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic brush charging device for uniformly charging an image forming body in an oscillating electric field and an image forming apparatus equipped with the same, and more particularly to a magnetic brush charging device for detecting the charging performance of the magnetic brush charging means. The present invention relates to an image forming apparatus that controls electrostatic photography process means and the like by detecting the charging performance of a brush charging device and a magnetic brush charging means.

[0002]

2. Description of the Related Art In order to eliminate defects caused by gas discharge of a corona charger, magnetic particles are adsorbed on a conductive cylinder (hereinafter referred to as a carrier) containing a magnet brush to form a magnetic brush. A so-called magnetic brush charging device has been proposed in which charging is performed by rubbing the surface of an image forming body with the magnetic brush (Japanese Patent Laid-Open No. 59-133569).

However, this device has a problem in charging performance. Specifically, since the state of the magnetic brush formed on the carrier is rough, even if the magnetic brush is charged while being vibrated by an electric field, unevenness is likely to appear on the magnetic brush, resulting in charging unevenness. Is.

In order to eliminate such drawbacks, the applicant of the present invention has proposed a magnetic brush charging means which improves the charging performance by defining the shape and particle size of the magnetic particles, the gap between the carrying carrier and the image forming body and the like. (Japanese Patent Laid-Open No. 4-116674).

Specifically, the spherical shape is such that at least the ratio of the major axis to the minor axis is 3 times or less, there are no protrusions such as needles and edges, and the resistivity is 10 ⁶ Ω · cm. ~ 10 ¹² Ω ・ cm
The magnetic particles or magnetic particles such as a magnet are dispersed in a resin and then subjected to a spheroidizing treatment, and a dispersed particle having a gap of 100 to 500 between the carrier and the image forming body is used.
It is specified to 0 μm.

The use of the above-mentioned magnetic particles has the following advantages.

(A) Since the magnetic particles are formed in a spherical shape, the particle layer formed on the carrier is made uniform, and a high bias voltage can be uniformly applied to the carrier. More specifically, magnetic particles are easily magnetized and adsorbed in the long axis direction, but since they become spherical and lose their directionality,
The layer is formed uniformly, and the occurrence of locally low resistance regions and unevenness of the layer thickness is prevented.

(B) Since the resistance of the magnetic particles is increased and the needle-like shape and the edge portion are eliminated, the electric field is not concentrated on the edge portion. Therefore, even if a high bias voltage is applied to the carrier, the image carrier surface is uniform. Even if the battery is discharged, uneven charging does not occur.

Furthermore, since the particle layer can be formed to have an appropriate thickness by forming the gap as described above, it is possible to prevent the occurrence of sweeps due to the rubbing of the brush.

Due to the above effects, the charging performance of the conventional magnetic brush charging means can be improved.

[0011]

However, the magnetic brush charging means proposed by the present applicant (Japanese Patent Laid-Open No. 4-116674) and the 雖 cannot prevent the deterioration of the charging performance due to the deterioration of the magnetic particles.

The term "deterioration of the magnetic particles" as used herein means that the resistance of the magnetic particles fluctuates due to the adhesion of toner or dirt remaining on the surface of the image forming body. If the toner component, which is an insulating or high-resistance substance, sticks to the surface of the magnetic particles, the resistance value of the magnetic particles becomes high. When the deterioration of the magnetic particles, which increases the resistance value, occurs, the charging performance of the magnetic brush charging means changes.

More specifically, if the magnetic brush charging phenomenon is replaced with an equivalent circuit, a predetermined bias is applied to the gap between the carrier and the image forming body, and the magnetic brush shape existing in the gap is applied. Magnetic particles are equivalent to a resistance element having a resistance value R, and the dielectric layer of the image forming body has a capacitance C
It is considered to be equivalent to the capacitor. Further, the charging voltage of the image forming body is regarded as a transient response of the step voltage E.

Therefore, the charging potential is considered to be V ₀ (1-1 ^{-t / CR} ).

By analogy with this equation, the resistance of the above-mentioned magnetic particles fluctuates, so that a charging characteristic having another locus is generated. That is, the charging characteristics having a locus that cannot be drawn from the resistance of the initial magnetic particles are generated, and the initial charging performance cannot be obtained.

As described above, the magnetic brush charging means and the lid proposed by the present applicant have a problem that the charging performance cannot be maintained at a predetermined level because the resistance of the magnetic particles fluctuates.

On the other hand, when a metal material such as a chip or magnetic particles having high conductivity (hereinafter referred to as “highly conductive particles”) infiltrate into the magnetic particles, a magnetic brush containing the highly conductive particles is transferred by the carrier. When conveyed and rubbed against the image forming body, an electric current excessively flows toward the image forming body via the magnetic brush. As a result, the photosensitive layer on the image forming body may be destroyed. Further, the circuit system of the image forming apparatus may be destroyed. In this situation, even if the image forming operation is performed, the image forming body is not charged, is not partially or band-shaped, and the apparatus itself may not operate.

A first object of the present invention is to provide a magnetic brush charging means capable of always accurately detecting the charging performance.

A second object of the present invention is to prevent excessive machine operation or prevent abnormal development of the entire machine by controlling the process means depending on the occurrence of abnormal charging performance. It is to provide an image forming apparatus capable of

A third object of the present invention is to provide an image forming apparatus capable of preventing damage to the image forming body and damage to the circuit system due to overcurrent and preventing unnecessary image forming operation. To provide.

A fourth object of the present invention is to provide an image forming apparatus capable of detecting an abnormality of the magnetic brush charging device before executing the image forming operation and preventing unnecessary image forming operation. Especially.

[0022]

SUMMARY OF THE INVENTION The present invention has achieved the first object described above, in which a magnetic brush made of magnetic powder is formed on a rotatable magnetic powder carrier having magnetic field generating means, and an image forming body is formed under an oscillating electric field. Is a magnetic brush charging device for rubbing and charging the magnetic powder carrier, which has an electrode facing the magnetic powder carrier, detects a current flowing between them, and generates an output signal corresponding to the detected current value. It has a detection means.

In order to achieve the second object of the present invention, a magnetic brush charging means for uniformly charging an image forming body with a magnetic brush under an oscillating electric field and a latent image formed by the image exposing means are developed. An image recording apparatus having a developing means for obtaining a toner image by a transfer means and a transfer means for transferring the toner image onto a recording paper, wherein a current flowing through a magnetic brush being charged in the magnetic brush charging means is detected, It has a control means for generating a control signal according to the detected current.

To achieve the third object of the present invention, a magnetic brush charging means for uniformly charging an image forming body with a magnetic brush under an oscillating electric field and a latent image formed by the image exposing means are developed. An image forming apparatus comprising: a developing unit that obtains a toner image; and a transfer unit that transfers the toner image onto a recording sheet, the image forming apparatus having a detecting unit that detects a current flowing through the magnetic brush. It has a control means for stopping the toner image forming operation when an abnormality is detected by the detection means.

In order to achieve the fourth object of the present invention, magnetic brush charging means for uniformly charging an image forming body with a magnetic brush under an oscillating electric field, and a toner image on the image forming body are transferred onto a recording paper. After that, in the image forming apparatus having the fixing means for thermally fixing the recording paper, when the abnormality of the current flowing through the magnetic brush is detected during the warm-up of the fixing means, the abnormality display means is driven.

[0026]

EXAMPLES First, the particle size of the magnetic particles preferably used in the present invention will be described.

Generally, when the average particle size of magnetic particles is large,
Since the state of the magnetic brush formed on the carrier is rough, even if the magnetic brush is charged while being vibrated by the electric field, unevenness is likely to appear on the magnetic brush, which causes a problem of uneven charging. To solve this problem, the average particle size of the magnetic particles should be reduced. As a result of the experiment, the effect begins to appear when the average particle size is 150 μm or less, and particularly when it is 100 μm or less, no substantial problem occurs. It has been found. However, if the particles are too fine, they will adhere to the surface of the image forming body during charging,
It may easily scatter. These developments are also related to the strength of the magnetic field acting on the particles and the strength of the magnetization of the particles due to the strength, but generally, the average particle size of the particles becomes prominent at 30 μm or less.

From the above, the average particle size of the magnetic particles is
It is preferably 150 μm or less, particularly preferably 100 μm or less and 30 μm or more. The magnetic strength of the magnetic particles is 20
To 200 emu / g are preferably used.

Such a magnetic particle is used as a magnetic material for a conventional carrier in a magnetic carrier particle of a conventional component developer,
Metals such as iron, chromium, nickel and cobalt, or compounds and alloys thereof, such as ferric tetroxide, γ-ferric oxide,
Chromium dioxide, manganese oxide, ferrite, manganese-
Resin such as styrene-based resin, vinyl-based resin, ethylene-based resin, rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, etc. on the surface of ferromagnetic particles such as copper-based alloy or those magnetic particles Or particles made by a resin containing magnetic fine particles dispersed therein are subjected to particle size selection by a conventionally known average particle size selection means.

The spherical shape of the magnetic particles means that
The particle layer formed on the carrier is uniform, and a high bias voltage can be uniformly applied to the carrier. That is, magnetic particles are generally spherical, which means that magnetic particles are easily magnetized and adsorbed in the long-axis direction, but the spherical particles lose their directionality. It is possible to prevent the occurrence of unevenness in the region of low thickness and layer thickness. With the increase in the resistance of the magnetic particles, the edges seen in conventional particles are eliminated, and the concentration of the electric field on the edges does not occur. As a result, even if a high bias voltage is applied to the magnetic particle carrier, the image The effect that uniform charging is not generated on the surface of the formed body and uneven charging does not occur.

The spherical particles having the above-mentioned effects include conductive magnetic particles such that the magnetic particles have a resistivity of 10 ³ Ω · cm or more and 10 ¹² Ω · cm or less, particularly 10 ⁴ Ω · cm or less. It is preferable to form the above. The resistivity after tapping putting particles in a container having a sectional area of 0.50 cm ^2, a load of 1 kg / cm ² on packed particles, 1,000 V between the load part and a bottom electrode / It is a value obtained by reading the current value when a voltage that causes an electric field of cm is applied.If this resistivity is low, when a bias voltage is applied to the carrier, the charge is injected into the magnetic particles and the image Magnetic particles tend to adhere to the surface of the image forming body, or dielectric breakdown of the image forming body due to the bias voltage easily occurs. If the resistivity is high, charge injection is not performed and charging is not performed.

Further, the magnetic particles used in the present invention are those having a small specific gravity and an appropriate maximum magnetization so that the magnetic brush constituted by the particles moves lightly by the oscillating electric field and external scattering does not occur. desirable. Specifically, it was found that good results can be obtained by using a material having a true specific gravity of 6 or less and a maximum magnetization of 30 to 100 emu / g.

In summary, the magnetic particles are spherical so that at least the ratio of the major axis to the minor axis is 3 times or less, there are no protrusions such as needles and edges, and the resistivity is high. The appropriate condition is preferably 10 ⁴ Ω · cm or more and 10 ⁹ Ω · cm or less. Then, such spherical magnetic particles should be selected as spherical as possible for the magnetic particles, and in the particles of the magnetic material fine particle dispersion system, the fine particles of the magnetic material should be used as much as possible to perform the spherical treatment after the formation of the dispersed resin particles. Or by forming dispersed resin particles by a spray drying method.

Embodiment 1 FIG. 1 is an explanatory view showing an embodiment of the magnetic brush charging device of the first invention.

The magnetic brush charging device 20 of the present embodiment is a case
By arranging 25 openings so as to face the image forming body 10 and enclosing the magnetic powder carrier 23, the magnetic powder 21 and the like therein, the magnetic brush made of the magnetic powder 21 on the magnetic powder carrier 23. Is formed, and the photosensitive layer 12 of the image forming body 10 is rubbed under an oscillating electric field to perform charging, and the charging performance can be detected by including a deterioration detecting unit that detects deterioration of the magnetic powder 21. It was made possible. The configuration and function of the magnetic brush charging device of this embodiment will be described below.

First, the structure and function for charging the magnetic brush device 20 will be described.

The image forming body 10 covers the surface of the conductive substrate 11 with O
This is a drum composed of the PC photosensitive layer 12.

The magnetic powder 21 is a spherical ferrite particle coated with a conductive coating, or a conductive magnetic resin particle obtained by crushing magnetic particles and a resin as main components after proficiency, Outer diameter is spherical, particle diameter is 50μm, specific resistance is 10
It is adjusted to ³ Ω · cm.

The magnet 22 has S poles and N poles magnetized on a cylindrical rod as shown in the figure, and both ends of the magnet 22 are fixed to the inner wall of the housing 25. The magnetic powder carrier 23 has a conductive cylindrical shape formed of a non-magnetic metal, and the magnet 23 is included in the cylinder. As a result, the magnetic powder carrier 23 rotates in the same direction as the image forming body 10 at a peripheral speed of 1.2 to 2.0 times. The gap between the magnetic powder carrier 23 and the image forming body 10 varies depending on the charging potential or the like, but in the present embodiment, it is 0.1-5 mm, preferably 0.3-1.5 m.
held in m. This gap varies depending on the charging voltage and the like.

The power supply 24 is V _PP 200 to 3500 as shown in FIG.
The same value as the voltage to be charged with the AC voltage source 24a of V, for example, −
This is equivalent to a series connection of a variable DC voltage source 24b set to 500 to -1000V. One output terminal of the DC voltage source 24b is connected to the conductive base 11, and the conductive base 11 is grounded. On the other hand, the output terminal of the AC voltage source 24a is connected to the magnetic powder carrier 23. The layer of magnetic particles 21 attached to and conveyed by the magnetic powder carrier 23 is a regulation plate provided in the opening of the housing 25.
The gap thickness is regulated by 26. This makes the magnetic particles
The 21st layer connects the magnetic powder carrier 23 and the photosensitive layer 12. Therefore,
The power supply 24 applies the above-described voltage in the gap of 0.1 to 5 μm between the magnetic powder carrier 23 and the conductive substrate 11 of the image forming body 10. Since the charge is directly injected into the image forming body 10, a low voltage is applied. In addition, the generation of ozone is reduced and the AC component is included, so that extremely stable uniform charging can be performed. The DC component controls the constant voltage, and the AC component V _PP controls the constant current.

Next, the structure and function of the deterioration detecting means will be described.

The deterioration detecting means comprises an electrode 27 embedded in a casing 25 facing the magnetic powder carrier 23, an ammeter 28 and a process CPU 70 connected in series with the electrode 27, and the charging of the magnetic brush charging device 20 is performed. It is intended to detect performance fluctuations. An equivalent circuit including deterioration detecting means will be considered below.

The deterioration detecting means for varying the -500-1000V and an AC voltage source 24a of the V _PP 200~3500V DC voltage source 24b
Are connected in series, and one output terminal of the DC voltage source 24b is grounded via the conductive base 11. On the other hand, AC voltage source 24
By connecting the output terminal of a to the magnetic powder carrier 23 and connecting to the electrode 27 with magnetic particles that can be regarded as a resistance component, it can be regarded as an equivalent circuit forming a loop connected to the DC power supply 24b via the ammeter 28. Here, since the DC power source 24a is variable, the ammeter 28 detects the AC current conducted through the magnetic particles 21 and outputs an output corresponding to the detected AC current value to the process CPU 70.
Send to. This allows the process CPU 70 to
It is possible to detect a change in charging performance due to a change in impedance of 21.

FIG. 2 is a graph showing the relationship between the value of current flowing through the magnetic brush composed of magnetic particles and the surface potential V _s of the image forming body.

In the graph, the vertical axis represents the photosensitive layer surface potential V _s of the image forming body 10, and the horizontal axis represents the current value I detected by the ammeter of this embodiment. The surface potential V _s1 shown by the dotted line shows the minimum required charging potential for forming a good latent image. The current I ₁ required to obtain the surface potential V _s1 is the current value flowing through the magnetic brush 21 made of magnetic particles 21.

FIG. 3 is a graph showing the change over time in the current value for conducting the magnetic particles when the magnetic brush charging device of FIG. 1 was inserted into the image forming apparatus and running was performed.

The graph shows how the conductivity of the magnetic particles 21 decreases as the number of prints is accumulated. In other words, it indicates the durable print number of the magnetic particles 21. In the graph, the vertical axis represents the current value I detected by the ammeter of this embodiment, and the horizontal axis represents the number of prints. The detection current I ₁ shown by the dotted line is a current value corresponding to the electric conductivity of the magnetic particles 21 required to obtain the minimum surface potential V _s1 required for forming a good latent image. The graph shows that the magnetic particles 21 become I ₁ before and after 27,000 prints.

FIG. 4 is an explanatory view showing another embodiment of the magnetic brush charging device of the first invention.

The structure for charging the magnetic brush device 20 is almost the same as in FIG. The difference is that the number of magnetic poles of the magnet 22 is increased, which allows the magnetic brush to have uniform and short ears. Thin layer forming member
Although the location of the 121 is different, the layer of the magnetic particles 21 attached to the magnetic powder carrier 23 and conveyed is functionally used.
It regulates the thickness of the gap between the magnetic powder carrier 23 and the magnetic powder carrier 23, and is the same as the regulation member 26.

The magnetic brush charging device 20 is provided with a scraper 27b for peeling the magnetic particles 21 adhering to the magnetic powder carrier 23 from the magnetic powder carrier 23 and replacing the magnetic particles 21 with new magnetic particles 21. An agitating means 122 is provided for agitating 21 and the magnetic particles 21 in the apparatus to homogenize the magnetic brush 21 made of magnetic particles.

The exchange of magnetic particles is performed by a structure in which a magnet 22 provided with two S poles adjacent to each other and a scraper disposed opposite to each other at a position where the two S poles are adjacent to each other. The magnet 22 is fixed to the housing 25, and the magnetic powder carrier 23 is a conductive cylinder made of a non-magnetic metal, and the magnet 22 is enclosed in the cylinder. The magnetic powder carrier 23 rotates in the opposite direction in the same direction as the image forming body 10 at a peripheral speed of 1.2 to 2.0 times. The gap between the magnetic powder carrier 23 and the image forming body 10 varies depending on the charging potential and the like, but in the present embodiment, it is 0.1-5 mm, preferably 0.3-1.1 m.
held in m. The magnetic particles 21 charge the image forming body 10 while rubbing with the magnetic brush adsorbed on the magnetic powder carrier 21. After that, the magnetic particles 21 are peeled off between the S and S pole portions of the magnet 22 by the scraper 27b. After that, the new magnetic particles 21 will be attached to the magnetic powder carrier 23, so that the image-formed body 10 can be charged by forming brush-shaped ears with the homogenized magnetic particles 21 after stirring. .

The magnetic brush charging 20 of this embodiment can maintain stable charging performance. Furthermore, since the magnetic brush charging device has the original characteristics, it is possible to perform stable and uniform charging at a low voltage while reducing the generation of ozone.

Next, the structure and function of the deterioration detecting means will be described.

The deterioration detecting means detects the deterioration of the magnetic particles by detecting the current passing through the magnetic particles 21 peeled off from the magnetic powder carrier 21, and the scraper 27b.
The electrode 27a is composed of a DC power supply 29 and an ammeter 28 connected in series to these. The scraper 27b has a portion in contact with the magnetic particle carrier 23 with an insulating material or has a portion made of an insulating material, and also has an electrode member.

With this configuration, the ammeter 28 detects the direct current flowing through the magnetic particles 21, and sends the output corresponding to the detected current value to the process CPU 70. This allows
The process CPU 70 can detect a change in charging performance due to a change in impedance of the magnetic particles 21.

FIG. 5 is an explanatory view showing another embodiment of the magnetic brush charging device of the first invention.

In the magnetic brush charging device 20 of this embodiment, the magnet 22 is rotated as a magnetic field for arranging the poles so that the magnetic particles 21 are directly attached to the magnet 22 to form the image forming body 10 by the magnetic brush. It is designed to be charged. The power supply 24 is equivalent to an AC voltage limit 24a of V _PP 200 to 3500V and a variable DC voltage limit 24a set to the same value as the voltage to be charged, for example, -500 to -1000V, connected in series. One output terminal of the DC voltage source 24b is connected to the conductive base 11, and the conductive base 11 is grounded. On the other hand, the output terminal of the AC voltage limit 24a is grounded to the magnet 22. The layer of magnetic particles 21 attached to and conveyed by the magnet 22 connects the magnet 22 and the photosensitive layer 12. Therefore, the power source 24 is 0.1 to 5 m between the magnet 22 and the conductive substrate 11 of the image forming body 10.
The above-mentioned voltage is applied to the image forming body 10 at intervals of m.
Since the electric charge is directly injected into, the generation of ozone is prevented at a low voltage, and since the AC component is included, extremely stable uniform charging can be performed.

As shown in FIG. 5, the deterioration detecting means has a plurality of electrodes 27 fixed to a casing 25 covering the brush-like magnetic particles 21 attached to the magnet 22 so as to be close to each other. An ammeter 28 and a DC power supply 29 are connected in series between the two. The process CPU 70 detects fluctuations in the charging performance of the magnetic brush charging device 20 based on the detection value from the ammeter 28.

Embodiment 2 FIG. 6 is an explanatory view showing an embodiment of the image forming apparatus of the second invention.

The image forming apparatus 100 according to the present embodiment includes the image forming body 10.
A magnetic brush charging device 20 that uniformly charges the toner with a magnetic brush under an oscillating electric field, a developing device 40 that develops the latent image formed by the image exposing means 30 to obtain a toner image, and the toner image is transferred to a recording sheet. An image is reproduced by including the transfer device 50. The image forming apparatus 100 includes a process CPU 70 that detects a current flowing through the magnetic brush that is being charged in the magnetic brush charging device 20 and generates a control signal according to the detected current. Since it is possible to control the process means 30, 40, 50 and the like, it is possible to prevent an extra machine operation from being performed and prevent the machine from developing into an abnormality.

The outline of the configuration and function of each member of the image forming apparatus 100 of this embodiment will be described below.

The image forming body 10 covers the surface of the conductive substrate 11 with O
This is a drum composed of the PC photosensitive layer 12. The magnetic brush charging device 20 applies a predetermined voltage from the power supply 24 between the magnetic powder carrier 23 and the image forming body 10 to uniformly charge the surface potential of the image forming body 10 before latent image formation. Any of the configurations shown in FIGS. 1, 4 and 5 described above may be used.
The ammeter 28 detects the alternating current or the direct current that conducts the magnetic particles 21 as described above, and sends it to the process CPU 70. As a result, the process CPU 70 detects the change in the charging performance due to the change in the impedance of the magnetic particles 21.

The image exposure means 30 is composed of a laser modulator 31 and a laser optical system 31, and forms a latent image on the image forming body 10 by the image light modulated based on the image signal.

The developing device 40 carries a so-called two-component or one-component developer for electrostatic photography on the sleeve 41 to visualize the electrostatic latent image formed on the image forming body 10.
The developing method may be either a contact developing method or a non-contact developing method. The power supply 43 applies a voltage to the sleeve 41.

The transfer device 50 is a belt transfer device that transfers a visible image from the image forming body 10 to a recording sheet by a voltage from a power source 54. The transfer device is not limited to this, and a corona discharger or a scorotron discharger may be adopted.

The cleaning device 60 is for removing the developer, toner and fine particles remaining on the surface of the image forming body 10.

The main body display section 82 displays the number of copy settings, error message, etc. by the driver 81.

The process CPU 70 is the above-mentioned process means 1
The image forming process is controlled by driving and controlling 0, 20, 30, 40, 50, 60. The process CPU 70 stores the limiting current value corresponding to the environmental condition, and detects the fluctuation of the charging performance of the magnetic brush charging device 20 by comparing the limiting current value with the detected current value. On the basis of the fluctuation of the process conditions, the process conditions such as the applied voltage, the number of rotations of the motor, the emission intensity of the semiconductor laser and the developing bias are changed, or an abnormal display is made.

Since the image forming apparatus 100 of the present embodiment is provided with the above-mentioned members, it detects a current value lower than the limit current value I ₁ after performing the printing operation about 30,000 times as shown in FIG. By doing so, the process CPU 70 stops each of the process means 10 to 70, and displays a message such as "charge not possible" on the main body display section.

Therefore, since the image forming apparatus 100 of this embodiment can control the process means 30, 40, 50, etc. in accordance with the occurrence of the abnormal charging performance, no extra machine operation is performed and the entire machine is prevented. It is possible to prevent the abnormal development.

Embodiment 3 FIG. 7 is an illustration of an embodiment of the image forming apparatus of the third and fourth inventions of the present application.

The image forming apparatus 100 according to the present embodiment includes the image forming body 10.
A magnetic brush charging device 20 that uniformly charges the toner with a magnetic brush under an oscillating electric field, a developing device 40 that develops the latent image formed by the image exposing means 30 to obtain a toner image, and the toner image is transferred to a recording sheet. An image is reproduced by including the transfer device 50. The image forming apparatus 100 includes a process CPU 70 that detects a current flowing through the magnetic brush that is being charged in the magnetic brush charging device 20 and generates a control signal according to the detected current. By detecting it during warming up, the abnormalities caused by highly conductive particles, metal pieces such as Chirico mixed in the magnetic brush charging device 20 can be detected, and thus the image forming body 10 can be detected.
It is possible to prevent damage to the circuit system and damage to the circuit system due to overcurrent, and prevent unnecessary image forming operation.

Further, the image forming apparatus 100 detects an abnormality of the magnetic brush charging device before performing an image forming operation, for example, during power-on and during warming up for heating the heat fixing roll to a predetermined temperature, and performs an unnecessary image forming operation. Try not to.

Constituent requirements of the image forming apparatus 10, 20, 30, 40,
Since 60 is the same as that in FIG. 6, its explanation is omitted. M ₁ drives the image forming body 10 and the transfer belt 50. M ₂ drives the developing device.

The image forming apparatus 100 may perform the detecting operation during the warm-up or during the image forming process.

The image forming apparatus 100 includes the magnetic brush charging device 2
0 is driven to rotate the image forming body 10 to detect the current flowing through the magnetic brush or the magnetic brush charging device 20.
The current may be detected via an electrode inside.

When the above-mentioned abnormality occurs and an overcurrent flows, an electric hole is formed in the image forming body 10, and the detected value from the ammeter 28 becomes excessive. On the contrary, if the magnetic brush 21 is deteriorated in the magnetic brush charging device, the value detected by the ammeter 28 fluctuates and falls outside the allowable range. Here, the permissible range is a range with diagonal lines shown in FIG.

When the image forming apparatus 100 detects an excessive current or about 0 during warming up, it displays a message indicating the occurrence of an abnormality and turns off the main body power. This prevents the magnetic brush charging device 20 from being started until the magnetic brush charging device 20 is replaced or other abnormal parts are repaired.

If the image forming apparatus 100 detects the abnormality by the deterioration detecting means during the image forming process, at least the power source 24
Is turned off, the laser exposure, the developing bias, the developing drive, the transfer bias, and the transfer belt drive are turned off to stop the image forming process. However, if the recording paper passes through the registration rollers, the image forming apparatus 100 drives the conveying system such as the image forming body 10, the transfer belt 50, and the fixing roller to eject the paper, and then stops.

[0080]

According to the first invention of the present application, it is possible to provide the magnetic brush charging means capable of always accurately detecting the charging performance.

According to the second invention of the present application, by controlling the process means in accordance with the occurrence of the abnormality in the charging performance, it is possible to prevent an extra mechanical operation from being performed or prevent the machine from developing into an abnormality. It was possible to provide an image forming apparatus capable of doing so.

According to the third invention of the present application, there is provided an image forming apparatus capable of preventing damage to the image forming body and damage to the circuit system due to overcurrent and preventing unnecessary image forming operation. Could be provided.

According to the fourth invention of the present application, there is provided an image forming apparatus capable of detecting an abnormality of the magnetic brush charging device before executing the image forming operation and preventing unnecessary image forming operation. I was able to.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a magnetic brush charging device of the first invention.

FIG. 2 is a graph showing a relationship between a current value conducted through a magnetic brush made of magnetic particles and a surface potential V _{s for} image formation.

FIG. 3 is a graph showing a change over time in a current value for conducting magnetic particles when running is performed by inserting the magnetic brush charging device of FIG. 1 into an image forming apparatus.

FIG. 4 is an explanatory view showing another embodiment of the magnetic brush charging device of the first invention.

FIG. 5 is an explanatory view showing another embodiment of the magnetic brush charging device of the first invention.

FIG. 6 is an explanatory diagram showing an embodiment of the image forming apparatus of the second invention.

FIG. 7 is an explanatory diagram of an embodiment of the image forming apparatus according to the third and fourth aspects of the present invention.

[Explanation of symbols]

 10 Image forming body 11 Conductive substrate 12 Photosensitive layer 20 Magnetic brush charging device 21 Magnetic particles 22 Magnet 23 Magnetic particle carrier 24 Power source 24a AC voltage source 24b DC voltage source 25 Enclosure 26 Regulator plate 27 Electrode 27a Electrode 27b Scraper 28 Ammeter 29 DC power supply 30 Exposure means 31 Laser modulator 32 Laser optical system 40 Developing device 41 Sleeve 43 Power supply 50 Transfer device 51 Transfer roller 52 Transfer roller 54 Power supply 60 Cleaning device 70 Process CPU 81 Driver 82 Main unit display 90 Fixing device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kunio Shigeta, Konica stock company, 2970 Ishikawa-cho, Hachioji, Tokyo (72) Inventor, Yukie Hososhizawa, 2970 Ishikawa-machi, Hachioji, Tokyo (72) invention Noriyuki Hiroshi Nomori 2970 Ishikawa-cho, Hachioji City, Tokyo Konica Stock Company

Claims (6)

[Claims] 1. A magnetic brush charging device for forming a magnetic brush of magnetic powder on a rotatable magnetic powder carrier having magnetic field generating means, and rubbing an image forming body under an oscillating electric field for charging. An electrode facing the magnetic powder carrier,
A magnetic brush charging device comprising: a detection unit that detects a current flowing between them and generates an output signal corresponding to the detected current value. 2. A magnetic brush charging device in which the electrode is provided in a regulating means for regulating the thickness of the magnetic brush. 3. A magnetic brush charging means for uniformly charging an image forming body with a magnetic brush under an oscillating electric field, a developing means for developing a latent image formed by an image exposing means to obtain a toner image, and the toner image. An image recording apparatus having a transfer means for transferring the image onto a recording paper, and a control means for detecting a current flowing through the magnetic brush being charged in the magnetic brush charging means and generating a control signal according to the detected current. An image recording device characterized by the above. 4. A magnetic brush charging means for uniformly charging an image forming body with a magnetic brush under an oscillating electric field, a developing means for developing a latent image formed by an image exposing means to obtain a toner image, and the toner image. An image forming apparatus having a transfer means for transferring a toner image to a recording sheet, and a detecting means for detecting a current flowing through the magnetic brush, and a toner image forming operation is performed when an abnormality is detected by the detecting means during toner image formation. An image forming apparatus having a control means for stopping the operation. 5. A magnetic brush charging means for uniformly charging an image forming body with a magnetic brush under an oscillating electric field, and a fixing means for fixing the recording sheet after the toner image on the image forming body is transferred onto the recording sheet. In the image forming apparatus having the above-mentioned, when the abnormality of the current flowing through the magnetic brush is detected during the warm-up of the fixing means, the abnormality display means is driven. 6. An image forming apparatus, wherein the abnormality display means is driven and the warming up is stopped to disable image formation.