JP3343943B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in an electrophotographic recording apparatus such as a printer and a copying machine.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic recording apparatus, an image is formed by respective processes of charging, exposure, development, transfer, fixing and cleaning. In general, a corona charger is used as a charging device for the electrostatic latent image carrier. However, since it is necessary to apply a high voltage of 5 to 10 kV to the corona charger, it is not only dangerous but also requires a power supply for applying the high voltage, which increases the cost. . In addition, the corona charger has poor environmental stability, and the charge potential of the electrostatic latent image carrier changes particularly when affected by humidity.
Further, since the corona charger utilizes the corona discharge phenomenon, it generates ozone, which not only significantly deteriorates the characteristics of the electrostatic latent image carrier, but also adversely affects the human body. Therefore, in order to prevent adverse effects on the human body, an ozone absorption / decomposition filter is provided in the electrophotographic recording apparatus to prevent ozone from flowing out of the electrophotographic recording apparatus. However, the service life of the ozone absorption / decomposition filter capable of absorbing and decomposing ozone is short, and replacement work must be performed periodically.

In addition, the electrophotographic recording apparatus requires each process of charging, exposure, development, transfer, fixing and cleaning, so that not only the structure becomes complicated but also the size becomes large. Therefore, there has been provided a contact-type charging device in which a conductor is brought into contact with an electrostatic latent image carrier, and a direct current voltage is applied to the conductor to charge the electrostatic latent image carrier (Japanese Patent Application Laid-Open No. Sho 56-56). 165166). In addition, a conductive plate member made of an elastic metal (for example, phosphor bronze) or conductive rubber (for example, urethane rubber) is brought into contact with the electrostatic latent image carrier, and a DC voltage and an AC voltage are superimposed. There has been provided a contact-type charging device that applies a voltage to the conductive plate member to charge the electrostatic latent image carrier (Japanese Patent Application Laid-Open No. Sho 60/1985).
147756).

In these charging devices, since no corona charger is used, they are inexpensive, have good environmental stability, and do not generate ozone. In addition, since the charging blade and the cleaning blade are formed of the same member, and the charging process and the cleaning process are also used, the number of processes can be reduced, and the electrophotographic recording apparatus can be simplified and downsized.

[0005]

However, in the above-mentioned conventional electrophotographic recording apparatus, the size can be reduced by using both the charging process and the cleaning process. Is used, the transfer rate when transferring the toner image on the electrostatic latent image carrier to the final recording medium is 70 to 90.
[%] Will be low.

Therefore, the amount of toner developed in the developing process is 10 to 30 on the electrostatic latent image carrier after transfer.
[%] Remains, and the remaining toner must be collected by a cleaning process. In this case, in order to reduce the size of the electrophotographic recording apparatus, the capacity of the toner storage tank of the cleaner provided for the cleaning process must be reduced. However, since the amount of remaining toner is larger than the capacity of the toner storage tank, maintenance work for discarding the toner collected in the toner collection tank is required. And the toner scatters inside and outside the electrophotographic recording apparatus. Further, since the collected toner is discarded, 100% of the toner cannot be used, and the running cost increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of stably recording a good image over a long period of time by solving the problems of the conventional electrophotographic recording apparatus.

[0008]

For this purpose, in an image forming apparatus according to the present invention, an electrostatic latent image carrier for carrying an electrostatic latent image and a charging device for charging the surface of the electrostatic latent image carrier are provided. An exposure device that exposes the charged surface to form an electrostatic latent image, a developing device that attaches toner to the electrostatic latent image to form a toner image, and transfers the toner image to a recording medium Transfer device, a fixing device for fixing the toner image transferred to the recording medium on the recording medium, and an electric field forming means for controlling a voltage applied to the charging device.

Then, the electric field forming means, when not recording,
After generating an electric field between the electrostatic latent image carrier and the charging device to uniformly charge the surface of the electrostatic latent image carrier to a predetermined negative potential, switch the direction in which the electric field is generated, The potential of the charging device is set to 0 from the surface potential of the electrostatic latent image carrier.
By setting the potential to a predetermined potential up to [V], the toner attached to the charging device is transferred onto the electrostatic latent image carrier.

[0010]

[0011]

According to the present invention, in the image forming apparatus as described above, an electrostatic latent image carrier for carrying an electrostatic latent image, a charging device for charging the surface of the electrostatic latent image carrier, An exposure apparatus that exposes the charged surface to form an electrostatic latent image,
A developing device that forms a toner image by attaching toner to the electrostatic latent image, a transfer device that transfers the toner image to a recording medium, and a fixing device that fixes the toner image transferred to the recording medium to the recording medium And electric field forming means for controlling a voltage applied to the charging device.

[0012] The electric field forming means, when not recording,
After generating an electric field between the electrostatic latent image carrier and the charging device to uniformly charge the surface of the electrostatic latent image carrier to a predetermined negative potential, switch the direction in which the electric field is generated, The potential of the charging device is set to 0 from the surface potential of the electrostatic latent image carrier.
By setting the potential to a predetermined potential up to [V], the toner attached to the charging device is transferred onto the electrostatic latent image carrier.

[0013] In this case, the electric field forming means, when not recording,
After generating an electric field between the electrostatic latent image carrier and the charging device to uniformly charge the surface of the electrostatic latent image carrier to a predetermined negative potential, switch the direction in which the electric field is generated, The potential of the charging device is set to 0 from the surface potential of the electrostatic latent image carrier.
A predetermined potential up to [V] is set. Therefore, the toner attached to the charging device is electrostatically removed.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electrophotographic recording apparatus showing a first embodiment of the present invention. In the figure, an electrostatic latent image carrier 101 formed in a drum shape is rotated at a constant peripheral speed in the direction of arrow a by a driving unit (not shown). The electrostatic latent image carrier 101 includes a conductive support 101
In this embodiment, an organic photoreceptor having a diameter of 30 [mm] is used, but a selenium photoreceptor, a zinc oxide photoreceptor, an amorphous silicon photoreceptor, etc. Can also be used.

Next, an image forming process according to this embodiment will be described. First, in the charging process, the electrostatic latent image carrier 101 is charged uniformly and uniformly by a charging device 102 provided in contact with the surface thereof. The charging device 102 is configured such that the toner 106 remaining on the electrostatic latent image carrier 101 after the transfer passes between the charging device 102 and the electrostatic latent image carrier 101 or that the electrostatic latent image carrier after the transfer. The setting is such that the toner 106 remaining on the surface 101 is not removed (cleaned). In fact, toner 10
A small amount 6 remains just upstream of the contact portion between the electrostatic latent image carrier 101 and the charging blade 118, but does not increase thereafter, and passes between the charging blade 118 and the electrostatic latent image carrier 101. This was observed. The charging device 1
02 will be described later in detail.

In the exposure process, light corresponding to an image signal is exposed on the electrostatic latent image carrier 101 by the exposure device 103 to form an electrostatic latent image. As the exposure device 103, besides a combination of an LED array and a Selfoc lens (trade name), any combination of a laser and an image forming optical system can be used.

In the developing process, a developing device 104 closely attached to the electrostatic latent image carrier 101 or provided at a small distance attaches toner 106 on the toner carrier 105 to an arrow. And develops the electrostatic latent image formed on the electrostatic latent image carrier 101. In this embodiment, the electrostatic latent image carrier 101 is
Reversal development in which the toner 106 is developed on the portion of the electrostatic latent image carrier 101 that is exposed to light
01a and the toner carrier 105 are applied with a developing bias voltage.

By doing so, the toner carrier 10
In the space between 5 and the electrostatic latent image carrier 101, an electric field is generated by the electrostatic latent image formed on the electrostatic latent image carrier 101. Therefore, the charged toner 106 on the toner carrier 105 adheres to the electrostatic latent image carrier 101 by electrostatic force, and is developed to form a toner image. As the developing device 104, any of a two-component magnetic brush developing device, a one-component magnetic brush developing device, a one-component non-magnetic developing device, and the like can be used. The developing device 104 will be described later in detail.

On the other hand, the recording paper 108 as the final recording medium stored in the paper cassette 107 is taken out by the paper feeding roller 109 and the paper feeding roller 110 whose rotation is stopped.
And the skew of the recording paper 108 is corrected. Next, the paper feed roller 110 starts rotating, and the recording paper 108 is sent to the transfer unit. And in the transfer process,
The transfer device 111 transfers the toner image formed on the electrostatic latent image carrier 101 to the recording paper 108. The recording paper 108
Is transported to a fixing device 114 including a pressure roller 112 and a heat roller 113. In the subsequent fixing process, the heat of the heat generating roller 113 melts the toner 106, and the toner 106 penetrates between the fibers of the recording paper 108 by a pressing action, so that the toner image is fixed on the recording paper 108. The recording paper 108 on which the toner image has been fixed is discharged from a paper discharge roller 115.
Is sent out of the electrophotographic recording apparatus.

On the other hand, the toner 106 remaining on the electrostatic latent image carrier 101 after the transfer passes between the charging device 102 and the electrostatic latent image carrier 101 as the electrostatic latent image carrier 101 rotates. The toner is removed at the same time as the toner is developed by the toner carrier 105 of the developing device 104. For this reason, the developing device 10
4, the charging polarity of the electrostatic latent image carrier 101 and the toner 10
6, the non-magnetic one-component contact developing method in which the toner carrier 105 and the electrostatic latent image carrier 101 are in contact with each other, or the developer such as the toner 106 A contact developing method such as a magnetic brush developing method that contacts the carrier 101 is employed. In particular, the toner carrier 1
When the toner image 05 is rotated at a speed higher than the peripheral speed of the electrostatic latent image carrier 101, it is possible to perform good recording without causing an afterimage due to the remaining toner 106.

Incidentally, the amount of toner 106 passing between the charging blade 118 and the electrostatic latent image carrier 101 is 0.2 to 0.3 [mg / cm ² ] or less during normal operation. Recording could be continued without hindrance by the removal method. On the other hand, during an abnormal operation such as a jam of the recording paper 108, the entire amount of the toner 106 on the electrostatic latent image carrier 101 passes between the charging blade 118 and the electrostatic latent image carrier 101, Immediately thereafter, both charging and exposure are not sufficiently performed.

In this case, a voltage is applied to the charging blade 118 and the toner carrier 105, the exposure device 103 is turned off, and the electrostatic latent image carrier 101 is rotated several times as an initialization operation. The body 101 can be sufficiently charged. In this manner, an electric field is generated by the surface potential of the electrostatic latent image carrier 101 and the developing bias voltage, and the toner force is applied to the toner 106 remaining on the electrostatic latent image carrier 101 by the electrostatic force at that time. Collect. Therefore, since a cleaner is not required, the size of the image forming apparatus can be reduced, and the collected toner does not need to be discarded, thereby simplifying the maintenance work. Further, since almost 100% of the toner can be used, the running cost can be reduced.

Next, the charging device 102 will be described.
FIG. 2 is a schematic diagram of a charging device employed in the image forming apparatus according to the first embodiment of the present invention. In the figure, reference numeral 102 denotes a charging device, which is a charging blade 11 constituting a charging member.
8 is supported by a metal guide 119,
Toner 10 having a belly or edge remaining on the free end side
6 is contacted or weakly pressed against the electrostatic latent image carrier 101 so that the carrier 6 can pass therethrough. A DC power supply 120 is provided between the guide 119 and the conductive support 101a of the electrostatic latent image carrier 101.
Is connected, and the charging blade 118 is connected via the guide 119.
Is applied with a DC voltage.

In this embodiment, the polarity of the voltage (hereinafter referred to as "applied voltage") applied by the DC power supply 120 to the charging blade 118 is negative, but this is a negative charging type electrostatic latent. This is because the image carrier 101 is used, and the positively charged electrostatic latent image carrier 101 is used.
Is used, the polarity of the applied voltage is positive.

In the following description, the value of the applied voltage is -1.4 [kV], but the value of the applied voltage is set to -1 to -1.6 [kV] and applied to the charging blade 118. As a result, the electrostatic latent image carrier 101 is
It can be charged at 0 to -900 [V]. In this embodiment, the charging blade 118 has a short side length of 25.
[Mm] and the length of the long side was 250 [mm]. The length of the long side of the charging blade 118 is determined by the electrostatic latent image carrier 101.
Of the photoconductive layer 101b in the longitudinal direction. Due to the manufacture of the electrostatic latent image carrier 101, it is difficult to form the photoconductive layer 101b on the circumference of both ends in the longitudinal direction. Therefore, the length of the long side of the charging blade 118 is slightly shorter than the length of the photoconductive layer 101b in the longitudinal direction so that current does not leak from the DC power supply 120 to the electrostatic latent image carrier 101.

The charging blade 118 is fixed to the guide 119 by a conductive double-sided tape.
It is not limited to the conductive double-sided tape, but may be any as long as it can electrically conduct. The charging blade 118 is made of a rubber material such as butyl rubber, chloroprene rubber, urethane rubber, silicone rubber, nitrile rubber, styrene rubber, butadiene rubber, or carbon,
It is formed by adding a conductive powder such as graphite, ferrite, aluminum powder, copper powder, bronze powder, stainless steel powder, titanium oxide, tin oxide, metal powder, metal fiber, etc., and has a volume resistance value of 10 ⁶ to 10 ¹³ [ Ω-cm] can be used.

The charging blade 118 is preferably an elastic body so as to be able to uniformly contact the electrostatic latent image carrier 101, and the thickness of the rubber material when a rubber material is used. Is preferably in the range of 0.5 to 5 [mm]. Next, a description will be given of a second embodiment in which the charging blade has a two-layer structure of a conductive layer and a resistance layer.

FIG. 3 is a schematic diagram of a charging device employed in an image forming apparatus according to a second embodiment of the present invention. In the figure, reference numeral 102 denotes a charging device, and a charging blade 123 constituting a charging member is formed by a conductive layer 121 and a resistance layer 122. The charging blade 123 is supported by an insulating guide 124, and is contacted or weakly pressed against the electrostatic latent image carrier 101 at the free end side of the resistance layer 122 so that the toner 106 having the antinode or edge can pass through. .
A DC power supply 120 is connected between the conductive layer 121 of the charging blade 123 and the conductive support 101 a of the electrostatic latent image carrier 101, and a DC voltage is applied to the charging blade 118 via a guide 119. The polarity of the voltage applied to the conductive layer 121 of the DC power supply 120 is negative because the negatively charged electrostatic latent image carrier 101 is used, and the positively charged electrostatic latent image carrier 101 is used. When the body 101 is used, the conductive layer 12 of the DC power supply 120 is used.
The polarity of the applied voltage with respect to 1 is positive.

As the conductive layer 121 of the second embodiment, any conductive layer having a volume resistance of 1.0 × 10 ⁴ [Ω-cm] or less can be used. For example, S
K-steel, stainless steel, phosphor bronze, copper, nickel silver, beryllium copper, etc., a thin metal plate having a thickness of 10 to 1000 [μm] or a volume resistivity of 1.0 × 10 ⁴ [Ω-cm] or less In order to obtain a uniform contact width in the longitudinal direction with the electrostatic latent image carrier 101, a conductive rubber having a rubber hardness of 90 ° [JIS A] or less, for example, butyl rubber, chloroprene rubber, urethane rubber, silicone Rubber, nitrile rubber, styrene rubber, butadiene rubber, etc.
A blade formed by adding conductive powder such as graphite, ferrite, aluminum powder, copper powder, bronze powder, stainless steel powder, titanium oxide, tin oxide, metal powder, metal fiber, and the like, polyimide, polyamide, polyester, polystyrene, Carbonate, graphite, ferrite, aluminum powder, copper powder, bronze powder,
Conductive powders such as stainless steel powder, titanium oxide and tin oxide,
What added metal powder, metal fiber, etc. can be used.

The resistance layer 122 of the charging blade 123
For example, a rubber sheet such as butyl rubber, chloroprene rubber, urethane rubber, silicone rubber, nitrile rubber, styrene rubber, butadiene rubber, fluoro rubber, ethylene propylene rubber, vinyl chloride, cellulose, polyimide, polyamide, polyester, polystyrene, polycarbonate, Soft oily polymer film made of resin such as fluororesin, conductive powder such as carbon, graphite, ferrite, aluminum powder, copper powder, bronze powder, stainless steel powder, titanium oxide, tin oxide, metal powder, metal fiber, etc. And the volume resistivity is 10 ⁶ to 1
Any one of 0 ¹³ [Ω-cm] can be used. In order to obtain a uniform contact width in the longitudinal direction with the electrostatic latent image carrier 101, the rubber hardness is set to 90.
° [JIS A] or less.

In the experiment, a thin stainless steel plate having a thickness of 100 μm was used as the conductive layer 121.
Carbon is added to urethane rubber, and the volume resistance is 1.0
× 10 ⁸ [Ω-cm], rubber hardness 60 ° [JIS
A], thickness 2.0 [mm], short side length 25 [m]
m], and a conductive rubber sheet having a long side of 250 [mm] was used as the resistance layer 122.

In addition, aluminum foil (foil), copper foil, etc.
1.0 × 10 for metal foil and volume resistance ^Four[Ω-cm] or less
A conductive tape or the like was bonded to the resistance layer 122.
The resistance layer 122 is plated with various metals,
Conductive layer 121 is formed by performing puttering, thick film printing, etc.
May be. Further, the charging blade 123 carries an electrostatic latent image.
Small enough to make contact or weak pressure contact with body 101
At least one of the conductive layer 121 and the resistive layer 122
Any body is acceptable.

Next, a third embodiment of the present invention will be described. FIG. 4 is a schematic diagram of a charging device employed in an image forming apparatus according to a third embodiment of the present invention. In the figure, 1
02 is a charging device, 101 is an electrostatic latent image carrier, 101a is a conductive support, 101b is a photoconductive layer, 120 is a DC power supply, 121 is a conductive layer, 122 is a resistive layer, 123 is a charging blade, and 124 is a guide. It is.

In the second embodiment, the charging blade 123 is attached to the electrostatic latent image carrier 101 by changing the mounting direction of the charging blade 123 from the trailing direction as shown in FIG. 3 to the counter direction as shown in FIG. The same charging characteristics as described above can be obtained. Next, a fourth embodiment of the present invention will be described. FIG. 5 is a schematic view of a charging device employed in an image forming apparatus according to a fourth embodiment of the present invention.

In the figure, reference numeral 102 denotes a charging device. In this case, a conductive rubber roller 126 is used as a charging member. The conductive rubber roller 126 is formed by covering a conductive shaft 127 with a rubber resistance layer 128. The conductive shaft 127 is a metal shaft made of stainless steel, steel, aluminum, or the like.
A DC power supply 120 is connected between the charging blade 7 and the conductive support 101 a of the electrostatic latent image carrier 101, and a DC voltage is applied to the charging blade 118 via a guide 119.

The rubber resistance layer 128 is made of a rubber material such as butyl rubber, chloroprene rubber, urethane rubber, silicone rubber, nitrile rubber, styrene rubber, butadiene rubber, fluorine rubber, ethylene propylene rubber, carbon, graphite, ferrite, or the like. A conductive powder such as aluminum powder, copper powder, bronze powder, stainless steel powder, titanium oxide and tin oxide, a conductive powder such as a metal powder and a metal fiber, etc. are added, and the volume resistance value is 10 ⁶ to 10 ¹³ [Ω− cm]
Any of these can be used.
In order to obtain a uniform contact width in the longitudinal direction with the electrostatic latent image carrier 101, the rubber hardness is set to 90 ° [JIS A].
The following is assumed.

Further, as in the first to third embodiments, the electrostatic latent image carrier 101 and the conductive rubber roller 126 are brought into contact with each other or weakly pressed to such an extent that the residual toner 106 can pass through. Also, the conductive rubber roller 126
Indicates a copying direction (direction of arrow b) with respect to the rotation direction of the electrostatic latent image carrier 101 by a driving system (not shown);
Or, the same direction as the rotation direction of the electrostatic latent image carrier 101 (arrow c)
Direction). Further, it can be fixed so as not to rotate. When the conductive rubber roller 126 is rotated in the copying direction, the peripheral speed of the electrostatic latent image carrier 101 and the conductive rubber roller 126
May be different or the same. In particular, when the peripheral speed of the electrostatic latent image carrier 101 and the peripheral speed of the conductive rubber roller 126 are the same, the conductive rubber roller 126 does not become a rotational load of the electrostatic latent image carrier 101.

In the first to third embodiments, the charging device 10
The charging blades 118 (FIG. 1) and 12
3 (FIG. 3) and the conductive rubber roller 126 (FIG. 5)
Has been described, but is limited to only these shapes
Instead, a charging brush or charging belt may be used.
The volume resistance value of the portion in contact with the latent image carrier 101 is 10 ⁶
-10¹³If it is composed of [Ω-cm]
Good. Also, the arrangement method is not limited to this.
In addition, various changes are possible.

Various modifications are possible as long as they can be brought into contact with or weakly pressed against the electrostatic latent image carrier 101 so that the remaining toner 106 can pass therethrough. In the case of this embodiment, the polarity of the toner 106 is negative, and a negative voltage is applied to the charging blades 118 and 123 and the conductive rubber roller 126. Therefore, the toner 106 having the negative polarity is electrically charged to the charging member. This makes it difficult for the toner 106 to adhere to the charging member and prevents the toner 106 from sticking to the charging member, so that good charging characteristics of the charging member can be maintained for a long period of time.

If recording is performed for a long period of time, foreign matter may adhere to the charging member, and the electrostatic latent image carrier 101 may not be charged. Examination of the foreign matter attached to the charging member reveals that the toner 106 charged to the positive polarity and the external additives, the charge control agent, the internal additives, etc. contained in the toner 106 charged to the positive polarity (hereinafter, referred to as “ Plus charged toner ”).

If the positively-charged toner or the like adheres to the area A in FIG. 2 where the toner is in contact with the electrostatic latent image carrier 101 of the charging member and before and after the area A, the charging member removes the electrostatic latent image carrier 101 from the area. Although it can be charged, if the positively charged toner or the like is fixed to the area A, the electrostatic latent image carrier 101 cannot be charged. Next, the cause of the formation of the positively charged toner and the like will be described.

FIG. 6 is a sectional view of a non-magnetic one-component contact type developing device. In the figure, 105 is a toner carrier, 13
0 is a toner layer thickness regulating member, 131 is a toner supply roller,
132 is a toner hopper. The toner 106 is stored in the toner hopper 132.
A toner supply roller 131 is provided below the inside of the roller 32. The toner supply roller 131 is formed by coating a foaming agent such as urethane foam around a conductive support such as a metal core to form an elastic surface layer. The surface of the toner supply roller 131 is always covered with the toner 106. Covered.

When the toner supply roller 131 is rotated in the direction of arrow d (counterclockwise), the toner 106 is conveyed to the toner carrier 105 provided in contact with the toner supply roller 131 with the rotation. Is done. The transported toner 106 comes into contact with the toner carrier 105 and the toner supply roller 131, and is charged by friction and charged.
The toner 10 is transferred to the toner carrier 105 by electrostatic force generated by a developing bias voltage of a DC power supply 134 connected between the toner carrier 105 and the toner supply roller 131, and the toner 10
6 and the toner carrier 105
Is conveyed via the toner carrier 105 rotating in the direction of arrow e (counterclockwise).

A toner layer thickness regulating member 130 is provided on the downstream side where the toner 106 is conveyed, and has a uniform thickness of about one to two layers of toner 106 particles on the toner carrier 105. The toner 106 is further charged by friction with the toner layer thickness regulating member 130 at this time. The toner 106 attached to the toner carrier 105 is transported to the electrostatic latent image carrier 101 provided in contact with the toner carrier 105, and
The toner image corresponding to the electrostatic latent image on the
Developing is performed by a developing bias voltage of a DC power supply 133 connected between the image carrier 05 and the conductive support 101a of the electrostatic latent image carrier 101. The toner 106 that does not contribute to the development is again conveyed to the toner supply roller 131 and collected.

In this embodiment, the electrostatic latent image carrier 101 has a uniform pressing force over the entire length in the longitudinal direction.
, And also have properties as a developing electrode near the surface layer. Therefore, for example, a conductive rubber or the like is coated around a conductive support such as a metal core to form an elastic electric resistance layer, and a thin insulating layer is further applied thereon.

As the conductive rubber, any rubber material such as chloropyrene rubber, nitrile rubber and urethane rubber can be used, and a conductive additive such as conductive carbon black is added thereto. Further, the toner carrier 105 is brought into contact with the electrostatic latent image carrier 101 with a uniform pressing force over the entire length in the longitudinal direction, and the rubber hardness is set to 60 ° [JIS A] or less because a certain contact width is required. .

Since the insulating layer is applied on the conductive rubber, the insulating layer has an elasticity enough to follow the displacement of the conductive rubber when pressed against the electrostatic latent image carrier 101. Urethane-based paints, silicone rubber-based paints, and the like correspond to this. Toner carrier 10
Explaining the example of No. 5 in specifications, a metal core having a diameter of 8 [mm] is coated with chloroprene rubber having a rubber hardness of 30 [JIS A] and a volume resistance of 10 ⁴ [Ω-cm], A urethane-based paint is applied thereon to a thickness of about 20 to 100 [μ], the final finished outer diameter is about 20 [mm], and the roughness of the surface layer is 0.5 to 5 [μRZ]. In this case,
Although the toner carrier 105 has a three-layer configuration, the toner carrier 105 may have a two-layer configuration in which an elastic electric resistance layer of a conductive support is covered.

On the other hand, the toner 106 is
Since the charge polarity of No. 01 is negative, a non-magnetic one having a diameter of about 9 to 12 [μm] was used by filling a styrene-based or polyester-based resin with a negative charge-type charge control agent. . Then, due to friction between the toner supply roller 131 and the toner carrier 105, the toner 106 interposed therebetween is charged to a negative polarity and adheres to the toner carrier 105. Further, as the toner 106, a toner having magnetism obtained by adding a magnetic powder such as iron or ferrite to a resin can be used.

As the toner layer thickness regulating member 130, urethane rubber is used, and the thickness of the toner 106 on the toner carrier 105 is made uniform and uniform, and further charged. In addition to rubber, stainless steel, a thin metal plate made of phosphor bronze, a material of a high molecular compound such as nylon or polyester, or a material obtained by applying the above high molecular compound on rubber, metal, etc. is used to obtain good recording. be able to.
When rubber is used, a thin layer of the toner 106 is uniformly and uniformly attached on the toner carrier 105, and the rubber hardness is set to 40 to 9 in order to perform optimal charging by friction.
Preferably, it is 0 ° [JIS A].

When the charging polarity of the electrostatic latent image carrier 101 is positive, the toner 106 that is positively charged is used. Since the developing device 104 has such a configuration, the toner 106 in the developing device 104 is initially charged with the toner carrier 105 and the toner layer thickness regulating member 1.
30 and the toner supply roller 131 is charged to a negative polarity.

In an image forming apparatus which does not use a cleaner like the image forming apparatus of the present invention, the toner 106 remaining after the transfer is collected by the developing device 104, and the collected toner 106 is used for effective use of the toner 106. The development is performed again. Thus, the toner 1
06 is recycled, a part of it is
4, toner layer thickness regulating member 130, toner supply roller 1
31, the electrostatic latent image carrier 101, the charging member and the like are in contact for a long period of time. Such a toner 106 is subjected to mechanical stress, and the external additives, the charge control agent, the internal additives and the like constituting the toner 106 are separated from the toner 106, and a positive polarity opposite to the desired polarity is generated. It is charged to a polarity, and the positively charged toner and the like are generated.

Then, the positively charged toner or the like is applied to the electrostatic latent image carrier 1 not irradiated with light from the exposure device 103 (FIG. 1).
The image is transferred from the developing device 104 to the non-image area on the image No. 01 and is normally developed. Further, the positively charged toner and the like are transported to the charging device 102 as the electrostatic latent image carrier 101 rotates. In the charging device 102, the electrostatic latent image carrier 1
Since a negative voltage is applied to the charging member in order to charge 01, an electric field is generated between the electrostatic latent image carrier 101 and the charging member.

As a result, it is considered that the positively charged toner or the like adheres electrostatically to the charging member, and eventually becomes fixed because it becomes a foreign substance and rubs against the electrostatic latent image carrier 101 for a long period of time. . The number of recording sheets, that is, the life, until the above-mentioned positively charged toner or the like is fixed to the charging member and a charging failure occurs varies depending on the composition and configuration of the toner 106 to be used. However, there are some which do not cause charging failure.

Next, a refresh operation for removing the positively charged toner and the like attached to the charging member from the charging member and extending the life of the charging member will be described. This refresh operation is performed during non-recording. In performing the refresh operation, an electric field for electrostatically transferring the positively charged toner or the like to the electrostatic latent image carrier 101 is formed between the electrostatic latent image carrier 101 and the charging member. Further, an electric field for electrostatically transferring the positively charged toner or the like transferred to the electrostatic latent image carrier 101 to the toner carrier 105 is formed between the electrostatic latent image carrier 101 and the toner carrier 105. An electric field for electrostatically transferring the positively charged toner or the like transferred to the toner carrier 105 to the toner supply roller 131 is applied to the electrostatic latent image carrier 101 and the toner carrier 105.
Form between.

In this state, the electrostatic latent image carrier 10
1. Toner carrier 105 and toner supply roller 131
Between the area A where the electrostatic latent image carrier 101 is in contact with the charging member (FIG. 2) and the development area B where the electrostatic latent image carrier 101 is in contact with the toner carrier 105 or the toner 106. Is rotated by an angle equal to or more than the rotation direction distance L between them. By doing so, the positively charged toner or the like adhering to the charging member can be electrostatically transferred from the electrostatic latent image carrier 101 to the toner supply roller 131 via the toner carrier 105 and collected.

Next, a specific refresh operation will be described with reference to FIG. FIG. 7 is an explanatory diagram of the potential.
First, the voltage applied from the DC power supply 120 to the charging member is changed, and the potential of the charging member is changed from -1.4 [kV] at the time of recording to a higher positive potential (for example, +1 [kV]).
Further, the voltage applied from the DC power source 133 to the toner carrier 105 is changed, and the potential of the toner carrier 105 is changed by -4 during recording.
00 [V] to a high potential on the negative side (for example, -1.1
[KV]).

Then, the voltage applied from the DC power supply 134 to the toner supply roller 131 is changed, and the toner supply roller 13
The potential of No. 1 is changed from -200 [V] at the time of recording to a higher potential on the negative side (for example, -600 [V]). And
The electrostatic latent image carrier 101, the toner carrier 105, and the toner supply roller 131 were rotated by one rotation of the electrostatic latent image carrier 101.

As a result, the positively charged toner and the like attached to the charging member were electrostatically removed from the charging member, and then transferred to the toner supply roller 131 and collected. The potential difference between the member to which the positively charged toner or the like is attached and the member to which the positively charged toner or the like is transferred is at least 200 [V] from various experiments.
This was necessary.

The refresh operation is performed by the exposure apparatus 1
03 was not operated, but the entire surface of the electrostatic latent image carrier 101 was exposed by the exposure device 103, and the electrostatic latent image carrier 101 was exposed.
Of the toner carrier 105 by lowering the surface potential of
In addition, the refresh operation could be performed with the voltage applied to the toner supply roller 131 being the same voltage as during recording. Further, the means for forming an electric field for electrostatically removing the positively charged toner or the like attached to the charging member is not limited to the above-described one. For example, instead of changing the potential of the charging member to a positive potential (for example, +1 [kV]), the potential of the charging member was set to -1.4 [kV] to uniformly charge the electrostatic latent image carrier 101. Thereafter, even when the potential of the charging member was changed from -1.4 [kV] to 0 [V] (GND), the same was obtained.

As described above, in order to remove the positively charged toner and the like adhering to the charging member, an electric field having a polarity opposite to that during recording is generated between the charging member and the electrostatic latent image carrier 101.
A positively charged toner or the like is charged from the charging member to the electrostatic latent image carrier 10.
What is necessary is just to transfer to 1. Further, a method and a place for collecting the positively charged toner and the like removed from the charging member are not limited to those described above. For example, a conductive roller is brought into contact with the electrostatic latent image carrier 101 to be provided as a roller transfer device, and the toner image on the electrostatic latent image carrier 101 is recorded on a recording paper 108.
And a negative voltage is applied to the roller transfer device to transfer the positively charged toner and the like removed from the charging member to a transfer roller, which can be collected by a blade or the like. As described above, the collection method and collection place of the positively charged toner and the like can be variously changed.

By the way, the positively charged toner or the like removed from the charging member is applied to the toner supply roller 131 of the developing device 104.
When the potential of the toner carrier 105 is changed to a higher potential on the minus side, the positively charged toner and the like can be removed from the electrostatic latent image carrier 101, but at the same time, Is transferred to the electrostatic latent image carrier 101.

Therefore, as in the case of the abnormal operation such as the jam of the recording paper 108 as described above, a voltage at the time of recording is applied to the charging member and the toner carrier 105 to thereby expose the exposure device 103.
When the electrostatic latent image carrier 101 is rotated several times as an initialization operation in a state where the toner 106 is not operated, the toner 106 transferred onto the electrostatic latent image carrier 101 is sufficiently charged while the electrostatic latent image carrier 101 is sufficiently charged. To the toner carrier 10
5 can be recovered.

In this case, when the electrostatic latent image carrier 101 is rotated several times, the electrostatic latent image carrier 101 is charged by the charging member, while the toner is higher than the surface potential of the electrostatic latent image carrier 101. Since the potential of the carrier 105 is increased to the positive side, the negatively charged toner 106 is transferred to the toner carrier 105. Next, the timing of performing the refresh operation and the initialization operation will be described.

Generally, in the electrophotographic recording apparatus, various sensors are checked when the main power supply is turned on, so that the refresh operation and the initialization operation can be performed after the check operation is completed. Further, the refresh operation and the initialization operation can be performed before the recording is started or after the recording is completed.

Since the electrophotographic recording apparatus generally has a function of counting the number of recordings, for example, 500
The refresh operation and the initialization operation can be performed for each set recording number such as 2,000, 5,000, or 5,000. Further, the refresh operation and the initialization operation can be performed by combining these timings.

The refresh operation and the initializing operation are not limited to the one performed only once, and for example, the refreshing operation, the initializing operation, the refreshing operation, and the initializing operation are repeated four times in total.
The refresh operation, the refresh operation, and the initialization operation may be repeated three times in total, or the refresh operation, the initialization operation, and the initialization operation may be repeated three times in total.

In recording, only a DC voltage is applied to the charging member, but the DC voltage and the AC voltage can be applied to the charging member in a superimposed manner. It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made based on the gist of the present invention.
They are not excluded from the scope of the invention.

[0068]

As described above in detail, according to the present invention, in an image forming apparatus, an electrostatic latent image carrier for carrying an electrostatic latent image and a surface of the electrostatic latent image carrier are provided. A charging device for charging, an exposure device for exposing a charged surface to form an electrostatic latent image, a developing device for attaching toner to the electrostatic latent image to form a toner image, and The image forming apparatus includes a transfer device that transfers the toner image transferred onto the recording medium, a fixing device that fixes the toner image transferred onto the recording medium onto the recording medium, and an electric field forming unit that controls a voltage applied to the charging device.

The electric field forming means, when not recording,
After generating an electric field between the electrostatic latent image carrier and the charging device to uniformly charge the surface of the electrostatic latent image carrier to a predetermined negative potential, switch the direction in which the electric field is generated, The potential of the charging device is set to 0 from the surface potential of the electrostatic latent image carrier.
By setting the potential to a predetermined potential up to [V], the toner attached to the charging device is transferred onto the electrostatic latent image carrier.

In this case, the electric field forming means does not
After generating an electric field between the electrostatic latent image carrier and the charging device to uniformly charge the surface of the electrostatic latent image carrier to a predetermined negative potential, switch the direction in which the electric field is generated, The potential of the charging device is set to 0 from the surface potential of the electrostatic latent image carrier.
A predetermined potential up to [V] is set. Therefore, the toner attached to the charging device is electrostatically removed and collected on the electrostatic latent image carrier, so that a good image can be stably recorded over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic recording apparatus showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a charging device used in the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a schematic view of a charging device employed in an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram of a charging device employed in an image forming apparatus according to a third embodiment of the present invention.

FIG. 5 is a schematic diagram of a charging device used in an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of a non-magnetic one-component contact developing device.

FIG. 7 is an explanatory diagram of a potential.

[Explanation of symbols]

 Reference Signs List 101 electrostatic latent image carrier 102 charging device 103 exposure device 104 developing device 106 toner 108 recording paper 111 transfer device 114 fixing device

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-34566 (JP, A) JP-A-3-4277 (JP, A) JP-A-2-259784 (JP, A) JP-A-4- 371972 (JP, A) Actually open 58-54644 (JP, U)

Claims (4)

(57) [Claims] (A) an electrostatic latent image carrier for carrying an electrostatic latent image; (b) a charging device for charging a surface of the electrostatic latent image carrier; and (c) a charged surface. An exposure apparatus for exposing the electrostatic latent image to form an electrostatic latent image; (d) a developing apparatus for forming a toner image by attaching toner to the electrostatic latent image; and (e) transferring the toner image to a recording medium. A transfer device; (f) a fixing device for fixing the toner image transferred to the recording medium to the recording medium; and (g) an electric field forming means for controlling a voltage applied to the charging device. The electric field forming means generates an electric field between the electrostatic latent image carrier and the charging device during non-recording to uniformly charge the surface of the electrostatic latent image carrier to a predetermined negative potential. and then switches the direction generated in the electric field, the surface of the potential of the charging device the latent electrostatic image bearing member Position from up to 0 [V]
An image forming apparatus, wherein the toner attached to the charging device is transferred onto an electrostatic latent image carrier by setting a predetermined potential therebetween. 2. An electrostatic latent image carrier for carrying an electrostatic latent image, (b) a charging device for charging a surface of the electrostatic latent image carrier, and (c) a charged surface. An exposure apparatus for exposing the electrostatic latent image to form an electrostatic latent image; (d) a developing apparatus for forming a toner image by attaching toner to the electrostatic latent image; and (e) transferring the toner image to a recording medium. A transfer device; (f) a fixing device for fixing the toner image transferred to the recording medium to the recording medium; (g) an electric field forming means for controlling a voltage applied to the charging device; with a means for counting, (i) the electric field forming means, based on the counted number of recording sheets, performs a refresh operation during a non-recording, in the refresh operation, the front Kisei latent image bearing member charged apparatus to generate an electric field between the by the electrostatic latent image bearing member Uniform surface
After charging to a predetermined negative potential, an electric field
Switching the direction that, by <br/> the potential of the charging device to a predetermined potential between the surface potential of the latent electrostatic image bearing member to 0 V, the toner adhering to the charging device An image forming apparatus, wherein the image is transferred onto an electrostatic latent image carrier. 3. An electrostatic latent image carrier for carrying an electrostatic latent image; (b) a charging device for charging a surface of the electrostatic latent image carrier; and (c) a charged surface. An exposure apparatus for exposing the electrostatic latent image to form an electrostatic latent image; (d) a developing apparatus for forming a toner image by attaching toner to the electrostatic latent image; and (e) transferring the toner image to a recording medium. A transfer device; (f) a fixing device for fixing the toner image transferred to the recording medium to the recording medium; and (g) an electric field for controlling a voltage applied to the charging device and a voltage applied to the developing device. together and a forming means, (h) electric field forming means, at the time of non-recording, electrostatic image bearing by generating an electric field between the front Kisei latent image bearing member and the charging device
The body surface was uniformly charged to a predetermined negative potential
After switching the direction of generation of the electric field, the potential of the charging device from the surface potential of the latent electrostatic image bearing member to 0 [V]
By a predetermined potential between, it is transferred to the electrostatic latent image bearing member onto a preparative toner adhering to the charging device, further,
An image forming apparatus, wherein the image is transferred to a developing device. 4. An electrostatic latent image carrier for carrying an electrostatic latent image, (b) a charging device for charging a surface of the electrostatic latent image carrier, and (c) a charged surface. An exposure apparatus for exposing the electrostatic latent image to form an electrostatic latent image; (d) a developing apparatus for forming a toner image by attaching toner to the electrostatic latent image; and (e) transferring the toner image to a recording medium. A transfer device; (f) a fixing device for fixing the toner image transferred to the recording medium to the recording medium; and (g) an electric field for controlling a voltage applied to the charging device and a voltage applied to the developing device. (H) the electric field forming means generates an electric field having a polarity opposite to that of an electric field generated between the electrostatic latent image carrier and the charging device during recording during non-recording, In addition, at the time of non-recording, it is generated between the electrostatic latent image carrier and the developing device. By switching the electric field, the oppositely charged toner adhered to the charging device is transferred onto the electrostatic latent image carrier, and further transferred to the developing device. (I) The developing device includes a toner carrier. And (j) an electric field generated between the toner carrying member and the toner supplying member is switched during non-recording.