JP2790573B2 - 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 a method in which a toner, which is a developer, is brought into contact with the surface of a photoreceptor to charge the surface of the photoreceptor and to perform exposure in accordance with a write signal to form a toner image on the surface of the photoreceptor. The present invention relates to an image forming apparatus to be formed.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic method using a Carlson process has been widely used for image formation using toner. As shown in FIG. 13, the apparatus employing the Carlson process includes a charger 32, an exposure unit 33, a developing unit 34, a transfer unit 35, a fixing unit 36, around a photosensitive drum 31 having a photosensitive layer on the surface. A cleaner 37 and a static eliminator 38 are sequentially provided.

In the above configuration, first, the surface of the photosensitive drum 31 is uniformly charged by the charger 32 in a dark place. Next, light is irradiated by the exposing device 33, and the charged charges on the irradiated portion are removed to form an electrostatic latent image. Next, a toner 39 charged with the opposite polarity to the charge on the photosensitive drum 31 in the developing device 34 adheres to the electrostatic latent image, thereby forming a visible image by the toner 39.

Thereafter, a recording material 40 is superimposed on this visible image,
The toner image is transferred to the recording material 40 by performing corona discharge from the back side of the recording material 40 by the transfer unit 35 to apply a charge having a polarity opposite to that of the toner 39. The transferred toner image is fixed on the recording material 40 by the heat and pressure of the fixing device 36 and becomes a permanent image. On the other hand, the residual toner 39 a remaining on the photosensitive drum 31 without being transferred to the recording material 40 is removed by the cleaner 37. After the electrostatic latent image on the photosensitive drum 31 is discharged by irradiating light from the static eliminator 38, the process starting from charging by the charger 32 is repeated again, and continuous image formation is performed. Will be

In the electrophotographic system to which the Carlson process is applied as described above, a corona discharger is usually used for charging the photosensitive drum 31 and transferring the toner 39 to the recording material 40. In this corona discharger, the applied voltage requires a high voltage of several kV and is easily affected by environmental changes such as a change in the amount of charge on the surface of the photosensitive drum 31 due to a change in temperature. In addition, ozone is generated during corona discharge, which causes environmental health problems.

[0006] For example, Japanese Patent Publication No. 2-4900 discloses an image forming method which does not require corona charging as described above. In this method, as shown in FIG. 14, a photoconductor 50 is formed by forming a transparent conductive layer 52 made of In ₂ O ₃ or the like, a photoconductive layer 53 made of Se or the like, a polyethylene An insulating layer 54 made of a late film, variylene, or the like is sequentially laminated.

A magnet 56 serving as a toner holder having a conductive toner 55 adhered to the surface of the photoreceptor 50 is provided.
When light is exposed from the transparent substrate 51 side in a state where a voltage is applied between the magnet 56 and the transparent conductive layer 52, the resistance of the photoconductive layer 53 is reduced in the light-irradiated portion, and electric charges are transferred to the insulating layer 52. Injected below 54. Thereby, the magnet 5
A strong electric field is applied between the photoconductor 6 and the photoconductor 50, and charges of opposite polarity are injected into the conductive toner 55 corresponding to the exposed area.

As a result, the conductive toner 55 charged with the insulating layer 54 interposed therebetween and the charge injected from the transparent conductive layer 52 form a pair of charges of opposite polarities, and thus are attracted to each other. Thereafter, even if the magnet 56 is moved away from the photoreceptor 50, only the conductive toner 55 in the above-described exposed area stops on the surface of the photoreceptor 50. Accordingly, a toner image can be formed on the surface of the photoconductor 50 without using corona charging. And, in this way, the photoconductor 50
A fixing device that transfers the toner image formed on the surface from the surface of the photoconductor 50 to the surface of the recording material 40 in the same manner as the Carlson process method, and heats and fixes the conductive toner 55 by fusing. , An image can be formed on the recording material 40 as a permanent image.

A specific apparatus using such an image forming method will be described with reference to FIG. 8, which is an explanatory view of the present invention. The photosensitive drum 1 as the photosensitive member 50 is provided on a transparent support 1a. And a transparent conductive layer 1b and a photoconductive layer 1c are formed on the substrate, and are configured to rotate in the A direction. Further, a magnet 5 arranged opposite to the photosensitive drum 1
The toner holding member 5 as the toner roller 6 extends in the longitudinal direction of the photosensitive drum 1 and has a magnetic roller 5a in which magnets of N polarity and S polarity are alternately arranged in the circumferential direction. And a developing sleeve 5b provided so as to cover the outer peripheral surface of the magnetic roller 5a, and an alternation generated with the rotation of the magnetic roller 5a in the B direction. The magnetic field holds the conductive magnetic toner T on the surface of the developing sleeve 5b and conveys the surface of the developing sleeve 5b in the direction C.

The transparent conductive layer 1b and the developing sleeve 5
b, the surface of the photosensitive drum 1 is brought into contact with the conductive magnetic toner T while applying a voltage between the conductive magnetic toner T and the surface of the photosensitive drum 1. By exposing the contact area between the magnetic toner T and the photosensitive drum 1 from the transparent support 1a side with an exposure device (not shown), a toner image is formed on the surface of the photosensitive drum 1. The conductive magnetic toner T remaining on the surface of the photosensitive drum 1 after the transfer of the toner image is collected by the magnetic force of the developing sleeve 5b.

At this time, since the photosensitive drum 1 and the toner holder 5 are arranged close to each other, the conductive magnetic toner T in the contact area with the photosensitive drum 1 rotates Is conveyed naturally, and the opposing center point between the photosensitive drum 1 and the developing sleeve 5b, that is, the photosensitive drum 1
Are formed on the photosensitive member rotation direction side of the line connecting the center of the developing sleeve 5b and the center of the developing sleeve 5b.

Then, as described above, charging, exposure, development,
In an image forming apparatus that performs cleaning at the same time, the setting conditions of each unit are related to each other, and a difference in the setting conditions greatly affects a copied image. Therefore, each of them is usually set to the condition in the standard environment state. For example, the exposure position is determined by the charging characteristic of the conductive magnetic toner T under the standard environment, and the exposure position between the conductive magnetic toner T and the photosensitive drum 1. in view of relationships of disposed position it is set to the first exposure position L ₁ of the front position of the toner reservoir.

[0013]

However, in the above configuration, since each part is set to the condition in the standard environmental condition, it cannot cope with the change of the environmental condition, and the image quality becomes stable especially at high humidity. However, there is a problem that the copied image is blurred. This is because the potential difference between the exposed portion and the non-exposed portion on the surface of the photosensitive drum 1 is reduced. The cause of the decrease in the potential difference is that the conductive magnetic toner T in the toner pool, which has a sufficiently large resistance under a standard environment, has low charging characteristics to the photosensitive drum 1, and does not affect the exposed portion, has a high resistance. It is considered that in a humid environment, the resistance decreases, the charging characteristics of the photosensitive drum 1 increase, and the exposed portion is recharged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and moves an exposure position of a photoreceptor surface by an exposure apparatus in accordance with an environmental change, particularly, a humidity change, so that an exposure unit can be separated from an exposed portion due to an environmental change. It is possible to avoid a decrease in the potential difference from the exposed portion and obtain a clear image with stable image quality and without blurring. It is an object of the present invention to provide an image forming apparatus which can be configured without complicating the structure by performing based on a current value flowing between the image forming apparatus and the image forming apparatus.

[0015]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a transparent support having a transparent conductive layer and a photoconductive layer provided on a transparent support; A photosensitive member and a developing sleeve having a developer held on the surface thereof are opposed to each other, and the developer is brought into contact with the photosensitive member surface while applying a voltage between the transparent conductive layer and the developing sleeve. An image forming apparatus that charges the surface and performs exposure according to a write signal from the transparent support side of the photoreceptor with an exposure device in a contact area between the photoreceptor and the developer to form a toner image on the photoreceptor surface A current detecting means for detecting a current flowing between the photoconductor and the developing sleeve; and an exposure position changing means for moving an exposure position of the photoconductor by the exposure apparatus based on an output signal of the current detecting means. Have been It is characterized by a door.

According to a second aspect of the present invention, there is provided an image forming apparatus according to the first aspect, wherein the exposure position changing means includes a photosensitive member and a developing sleeve. The exposure position is moved in the rotational direction of the photoconductor from the center point where the photoconductor and the developing sleeve face each other, as the humidity increases, based on the correlation between the current flowing between the photoconductor and the humidity.

[0017]

According to the first aspect of the present invention, the current detecting means detects the current flowing between the photoconductor and the developing sleeve, which changes with the environmental change and has a correlation with the environmental change. From this detection output, an environmental change, for example, a change in humidity can be grasped. Therefore, for example, as in the configuration of claim 2, the exposure position changing means moves the exposure position in the rotational direction of the photoconductor from the center point where the photoconductor and the developing sleeve face each other with the increase in humidity. Even if the humidity becomes high and the charging characteristics of the developer to the photoconductor are improved, the amount of the developer contacting the photoconductor after the exposure is reduced, so that the recharge of the exposed portion is prevented and the exposure is performed. It is possible to avoid a decrease in the potential difference between the portion and the non-exposed portion.

[0018]

1 to 12 show an embodiment of the present invention.
This will be described below.

As shown in FIG. 2, the electrophotographic apparatus as the image forming apparatus of the present embodiment includes a cylindrical photosensitive drum (photoreceptor) 1 rotatable in the direction A in the apparatus. A developing device 2 is provided on the right side of the photosensitive drum 1, an exposure device 7 is provided in the photosensitive drum 1, and a transfer / fixing belt 8 is provided above the photosensitive drum 1.

As shown in FIG. 4, the photosensitive drum 1 is provided on the surface of an optically transparent cylindrical transparent support 1a.
A transparent conductive layer 1b made of a sputtered film of In ₂ O ₃ or SnO ₂ ,
A photoconductive layer 1c made of a photoconductive material such as Se, ZnO, CdS, or amorphous Si is sequentially laminated.
In this embodiment, as the transparent conductive layer 1b, a film thickness
An In ₂ O ₃ layer having a thickness of 0.5 μm is formed, and an amorphous Si layer having a thickness of 3 μm is formed as the photoconductive layer 1c.

As shown in FIG. 2, the developing device 2 includes a developing tank 3 for storing a conductive magnetic toner T as a developer.
A stirring roller 4 rotatably provided in the developing tank 3 for stirring the conductive magnetic toner T; and an opening 3a of the developing tank 3
And a doctor blade 6 fixed at a position below the toner holding member 5 in the opening 3a of the developing tank 3 at a position opposed to the photosensitive drum 1.

The toner holder 5 extends in the longitudinal direction of the photosensitive drum 1 and has N polarity and S polarity in the circumferential direction.
A magnetic roller 5a in which magnets having polarities are alternately arranged, and a non-magnetic conductive member such as aluminum or martensitic stainless steel, which is provided so as to cover the outer peripheral surface of the magnetic roller 5a The conductive magnetic toner T is held on the surface of the developing sleeve 5b by an alternating magnetic field generated by the rotation of the magnetic roller 5a in the direction B, and the B direction is the rotation direction of the magnetic roller 5a. Are transported in the reverse C direction.

As shown in FIG. 1, the developing sleeve 5b is connected to a developing sleeve voltage applying power source E,
Thus, as described later, a voltage is applied between the developing sleeve 5b and the transparent conductive layer 1b of the photosensitive drum 1. Further, between the developing sleeve 5b and the developing sleeve voltage application power source E, the developing sleeve 5
b and developing sleeve current I flowing between photosensitive drum 1
Split resistor R ₁ is a current sensing means for sensing is provided, and the voltage of the voltage drop was point A current flows through the dividing resistor R _1, a signal corresponding to the current flowing through the developing sleeve 5b , To a control device 27 described later. Then, as the dividing resistors R _1, so as not to affect the developing sleeve current I is 10～100Myuei, resistance is used having a resistance value of 1～10Keiomega. The variable resistor R _d is provided between the developing sleeve 5b and the split resistor R ₁ is a toner resistance R _d of the conductive magnetic toner T that varies with environmental conditions.

The doctor blade 6 adjusts the transport amount of the conductive magnetic toner T held on the surface of the developing sleeve 5b and transported in the direction C to a predetermined amount.

The conductive magnetic toner T is obtained by kneading a resin such as a styrene-acryl copolymer with a magnetic powder such as iron powder or ferrite, carbon black, or the like.
It is composed of powder having a size of several μm to several tens μm.

The exposure device 7 arranged in the photosensitive drum 1 is constituted by an LED array in which a short-focus lens is combined with a light emitting diode, and responds to a write signal from exposure control means (not shown). Light is emitted toward the toner holding member 5, and the emitted light is focused on the photoconductive layer 1c via the transparent support 1a and the transparent conductive layer 1b of the photosensitive drum 1. It has become.

The exposing device 7 is rotated about the center of the photosensitive drum 1 as a fulcrum.
The exposure device moving motor 28 is provided, and the exposure position on the surface of the photosensitive drum 1 is moved by driving the exposure device moving motor 28. The exposure positions in the present embodiment are, as shown in FIGS. 7A and 8, a first exposure position L ₁ at an exposure position angle θ ₁ = 12 °, which is a front position of a toner pool described later. As shown in FIG. 7B and FIG. 8, the second exposure position L where the exposure position angle θ ₂ = 17 °, which is the rear position of the toner pool,
₂ and the first and second exposure positions L ₁ and L ₂
Is performed based on an output signal from the control device 27 described later. That is, the exposure apparatus moving motor 2
8 and the control device 27 constitute an exposure position changing means of the present invention. The above-mentioned exposure position angle is a line connecting the center of the photosensitive drum 1 with the center of the photosensitive drum 1 facing the developing sleeve 5b, that is, the line between the center of the photosensitive drum 1 and the center of the magnetic roller 5a. And the line connecting the light irradiation position (exposure position) and the center of the photosensitive drum 1.

The transfer / fixing belt 8 is formed in an endless belt shape using a film material mainly composed of a polyimide resin having excellent mechanical strength and high heat resistance. As shown in FIG. 2, the transfer / fixing belt 8 is provided with a transfer roller 9 made of a conductive elastic member provided above the photoreceptor drum 1 and at a position slightly above the transfer roller 9 on the left side thereof. It is wound around a heating device 10 to be described later, which is provided, and a tension roller 11 disposed on the lower left side of the heating device 10 from the outside. Then, the transfer / fixing belt 8
The photosensitive drum 1 and the transfer roller 9 are sandwiched between the photosensitive drum 1 and the transfer roller 9.

The transfer / fixing belt 8 is made of a film-like polyimide resin as a material. However, the material is not particularly limited to this material. If the surface to which T is to be transferred has an insulating property, for example, a metal belt such as an electroformed nickel belt as a substrate is coated with fluorine, or is composed of another member of polyamide resin. May be done. The thickness of the transfer / fixing belt 8 is not particularly limited, but is 10 μm in consideration of thermal conductivity and mechanical strength.
The thickness is preferably about 200 μm, and the surface may be formed as a rough surface to make the gloss of the image appropriate.

The heating device 10 includes a conductive magnetic toner T transferred to the surface of the transfer / fixing belt 8 as described later.
Is heated and melted, and a planar Mo-based heat generating resistor 10a is printed on an alumina ceramic substrate.
It is composed of a ceramic heater on which a glass coat is printed and laminated. The heating device 10 is configured to quickly raise the temperature to a predetermined heating temperature by energizing the heating resistor 10 a so that the heating surface directly contacts the surface of the transfer / fixing belt 8. Are located in

A pressing roller 12 which rotates while applying a pressing force in a direction toward the heating device 10 via the transfer / fixing belt 8 is provided on an upper portion of the heating device 10.
The pressure roller 12 sandwiches a transfer sheet P conveyed by a recording material conveying unit 14 described below at a pressure contact portion with the transfer / fixing belt 8. .

Further, as shown in FIG. 3, the electrophotographic apparatus has a cooling fan 24 for cooling the transfer / fixing belt 8 from below, and a main motor 13 which is a driving source of the apparatus.
The above-described recording material transporting means 14 for transporting the transfer paper P to a pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12;
The paper output means 21 for discharging the transfer paper P from the inside of the apparatus, and the control means 27 for driving the exposure apparatus moving motor 28 of the exposure apparatus 7 to switch the exposure position on the surface of the photosensitive drum 1 as described above. Is provided.

The recording material conveying means 14 is disposed above the photosensitive drum 1, the developing device 2, and the transfer / fixing belt 8, and includes a transfer paper supply opening (not shown) as a constituent member thereof. , A transfer guide plate 15 forming a transfer path connecting the transfer / fixing belt 8 and the pressure roller 12 with the pressure roller 12, a sheet feed actuator 16 and a sheet feed roller 18 arranged near the transfer sheet supply opening. And the registration rollers 19, which are arranged in the middle of the path of the conveyance guide plate 15.
19, and a paper feed solenoid 20 for controlling the rotation of the registration rollers 19.

The paper output means 21 is provided for the transfer / fixing belt 8.
The pressure roller 12 is disposed on the left side of the pressure contact portion between the pressure roller 12 and the pressure roller 12, and as a component thereof, an outlet connecting the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12 to a transfer paper discharge opening (not shown). A paper output guide plate 22 forming a paper path, a paper output actuator 23 disposed near a pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12, and a transport disposed at an end of the paper output guide plate 22. Rollers 25 are provided.

The control device 27 includes a CPU (not shown)
Includes a microcomputer and a storage unit comprising a Central Processing Unit) or the like, as shown in FIG. 1, the split resistor R ₁ which is provided between the developing sleeve 5b and the developing sleeve voltage source E, an exposure device 7 is connected to a motor 28 for moving the exposure apparatus.

Here, first, the correlation between the developing sleeve current I detected from the divisional resistor R ₁ and the humidity in the environment where the electrophotographic apparatus is provided will be described. FIG.
(A) is a schematic diagram of a developing unit when a voltage is applied between the photosensitive drum 1 and the developing sleeve 5b and the photosensitive magnetic drum 1 is brought into contact with the conductive magnetic toner T at the time of non-exposure. (B) is an equivalent circuit thereof. C ₁ is the electrostatic capacity of the toner, C ₂ is the capacitance of the photosensitive drum 1, the R _d toner resistance of the conductive magnetic toner T as described above, R _p is representative of the dark resistance of the photoconductor drum 1 I have.

A current flowing through the developing sleeve 5b after the conductive magnetic toner T and the photosensitive drum 1 are sufficiently charged;
That is, the developing sleeve current I is as follows: I = V _s / (R _d + R _p ) V _s = developing sleeve applied voltage R _d = toner resistance R _p = photosensitive drum dark resistance. In this case, the photosensitive drum 1 is so unexposed, dark resistance R _p photosensitive drum is constant, the developing sleeve current I is determined by the toner resistor R _d. Toner resistance R
_d , as shown in FIG. 10, as the humidity increases,
Since the conductive magnetic toner T absorbs moisture, it has a characteristic that its resistance value decreases. Accordingly, a relationship is established between the humidity and the developing sleeve current I, as the humidity increases, the developing sleeve current I increases. By identifying the developing sleeve current I, the humidity can be grasped.

Therefore, based on the correlation between the developing sleeve current I and the humidity, the storage section of the control device 27 stores in advance the developing sleeve current corresponding to the humidity separating the standard environment and the high humidity environment. I flows through the dividing resistor R ₁ ,
It stored a voltage drop value in the divided resistor R ₁ by the current as a voltage drop the reference value. Thereby, the control device 2
7, the input signal from the A point, detects a voltage drop in the divided resistor R _1, and compares the voltage drop value and the voltage drop the reference value, the voltage drop value in the divided resistor R ₁ is a voltage drop If it is equal to or more than the reference value, it is determined that the environment is in a high-humidity environment, and if it is within the voltage drop reference value, it is determined that it is in a standard environment.

When it is determined that the environment is the standard environment, the control device 27 drives the exposure device moving motor 28 so that the exposure position of the exposure device 7 is changed to the exposure position angle as described above. First exposure position L ₁ at θ ₁ = 12 °
(FIG. 7 (a)).
See), if it is determined that the high-humidity environment, by driving the exposure device movement motor 28, the exposure position by the exposure device 7 is a second exposure position L ₂ of the exposure position angle theta ₂ = 17 ° The exposure device 7 is moved as described above (see FIG. 7B).

The movement of the exposure device 7 is as follows.
This is performed at a time other than the time when the write signal from the exposure control means is generated.

The reason why the exposure position is switched between the first exposure position L ₁ and the second exposure position L ₂ in accordance with the environmental conditions will be described after the description of the operation. .

Next, the operation of the electrophotographic apparatus having the above configuration will be described.

First, 1 is supplied by transfer paper supply means (not shown).
When a sheet of transfer paper P is fed from the transfer paper supply opening,
When the leading end of the transfer paper P pushes up the paper feed actuator 16, a paper input detection switch (not shown) detects the supply of the transfer paper P, transmits a paper input detection signal to the main motor 13, and Is driven to rotate. Next, the rotation of the main motor 13 is transmitted to the paper feed rollers 18 via a rotation transmission mechanism (not shown) so that the paper feed rollers 18 are rotated. , The transfer paper P is a registration roller 1
It is transported to 9/19.

As described above, the registration rollers 19.
Transfer paper P conveyed to registration rollers 19
Is stopped under the control of the sheet feeding solenoid 20, so that the conveyance is temporarily stopped. At this time, the paper feed rollers 18 are in a state where the rear end side of the transfer paper P is sandwiched, and the resistance of the roller surface is small. Both sides have slipped.

Here, the electrophotographic apparatus enters a standby state,
If the print start signal is not generated within the predetermined time, the main motor 13 stops. On the other hand, when the print start signal is generated in the standby state, all the rotating parts except the registration rollers 19 are rotated by the rotation transmitting mechanism.

Next, the developing process of the conductive magnetic toner T will be described with reference to FIGS.

First, the conductive magnetic toner T stored in the developing tank 3 is held on the surface of the developing sleeve 5b by the alternating magnetic field generated by the rotation of the magnetic roller 5a in the direction B, as shown in FIG. At the same time, the photosensitive drum 1 is transported on the surface of the developing sleeve 5b in a direction C which is a direction opposite to the direction A which is the rotation direction of the photosensitive drum 1. At this time, a voltage of several tens of volts applied between the developing sleeve 5b and the transparent conductive layer 1b is applied to a contact portion between the conductive magnetic toner T held on the surface of the developing sleeve 5b and the photosensitive drum 1. Then, the charged conductive magnetic toner T is naturally conveyed in the rotation direction of the photoconductor to form a toner reservoir.

Then, the photoconductive layer 1c on the surface of the photosensitive drum 1 is passed through the conductive magnetic toner T from the developing sleeve 5b.
Charge is injected into the photoconductive layer 1c and the developing sleeve 5
It is charged to substantially the same potential as b. For this reason, in a portion where the conductive magnetic toner T and the photoconductive layer 1c are separated, the conductive magnetic toner T is dominantly acted on by the magnetic force generated by the magnetic roller 5a, and does not adhere to the photosensitive drum 1. .

Next, as shown in FIG. 5, in a predetermined exposure position L corresponding to the humidity of the environment in which the electrophotographic apparatus is previously disposed, that is, in a standard environment, the toner accumulation shown in FIG. of in the first exposure position L ₁ of the front position, whereas, in the high humidity environment, at a second exposure position L ₂ of the rear position of the toner reservoir 8, the write signal from the exposure device 7 When the corresponding LEDs are sequentially selected and exposed, the charges injected into the photoconductive layer 1c are neutralized, and the surface potential of the photoconductive layer 1c becomes substantially the same as the transparent conductive layer 1b, A potential difference occurs between the photoconductive layer 1c and the developing sleeve 5b.

Therefore, the conductive magnetic toner T is the same as that shown in FIG.
As shown in FIG.
b and the action of the van der Waals force acting between the photosensitive drum 1 and the conductive magnetic toner T, and shakes off the magnetic force of the magnetic roller 5a. The toner image adheres to the surface of the photosensitive drum 1 and is formed on the surface of the photosensitive drum 1 according to the write signal.

As described above, in the toner image formed on the surface of the photosensitive drum 1, as shown in FIG. 3, a voltage having a polarity opposite to the charge injected into the toner image is applied to the transfer roller 9. Is transferred to the surface of the transfer / fixing belt 8 at the pressure contact portion between the photosensitive drum 1 and the transfer roller 9. On the other hand, the toner image on the surface of the transfer / fixing belt 8 and the transfer paper P are pressed by the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12 on the heating device 10.
In response to this, a signal is output from the CPU of the engine controller (not shown) to the paper feed solenoid 20, so that the above-described rotation stop state of the registration rollers 19 is released, and the transfer paper P is moved to its leading end. Transfer and fixing at a timing that coincides with the leading end of the transfer and fixing belt 8.
The sheet is conveyed to a pressure contact portion between the fixing belt 8 and the pressure roller 12.

Then, the transfer of the toner image
The fixing belt 8 and the transfer paper P are conveyed while being superposed between the heating device 10 and the pressure roller 12,
The transfer and fixing of the toner image onto the transfer paper P are performed simultaneously. That is, when the transfer paper P is pressed out between the transfer / fixing belt 8 and the pressure roller 12 and sent out, the releasability of the conductive magnetic toner T heated and melted by the heating device 10 is determined by the transfer paper P Since the surface of the transfer / fixing belt 8 is better than the surface of the transfer / fixing belt 8, most of the conductive magnetic toner T on the surface of the transfer / fixing belt 8 is transferred and fixed on the transfer paper P.
The conductive magnetic toner T remaining on the surface of the photosensitive drum 1
Is again caused by the magnetic force of the developing sleeve 5b and the like.
Will be collected.

Thereafter, the transfer paper P on which the toner image has been transferred and fixed is pushed up by the paper ejection actuator 23, and is discharged from the apparatus through the transfer paper discharge opening by the rotation of the transport rollers 25. After a predetermined time has passed since the transfer paper P was discharged out of the apparatus, the heating device 10
And the drive of the main motor 13 is stopped, and the above-described series of operations ends.

Next, the reason why the exposure is performed at the first exposure position L ₁ in a standard environment and at the second exposure position L ₂ in a high humidity environment will be described.

As described above, with the voltage applied between the photosensitive drum 1 and the developing sleeve 5b, the conductive magnetic toner T is brought into contact with the photosensitive drum 1 to perform charging, exposure and development simultaneously. In high humidity, the amount of the conductive magnetic toner T contacting the exposed photosensitive drum 1 at high humidity is
It is thought to affect image quality. Therefore, as a means for changing the amount of the conductive magnetic toner T that comes into contact with the photosensitive drum 1 after the exposure, the exposure position is changed. At each exposure position, environmental conditions, particularly humidity, are changed stepwise. The surface potential of the photosensitive drum 1 was measured under each condition, and images obtained under each condition were compared. Specifically, the electrophotographic apparatus in which the exposure position is set to the first exposure position L ₁ shown in FIG. 7 (a), the exposure position to the second exposure position L ₂ shown in FIG. 7 (b) The measurement was performed using the set electrophotographic apparatus. The electrophotographic apparatus has the same configuration as the electrophotographic apparatus of this embodiment except that the exposure position is fixed.

In this case, an amorphous silicon photosensitive member having a drum diameter of 30 mm and a film thickness of 3 μm is used as the photosensitive drum 1, and a light source having an exposure amount of 2 μJ / cm ² is used as a light source.
An ED head is used, and a magnetic roller having a magnetic force of about 700 gauss having a nonmagnetic conductive sleeve and eight magnetic poles is used as the toner holding member 5 of the developing device 2. 0 × 10 ¹² Ωcm, developer resistance 1.
Using a two-component developer having a density of 7 × 10 ³ Ωcm and a toner particle diameter of 12 μm, a developing bias is 70 V, and a process speed is 5
0 cm / sec.

FIG. 11 shows the results of measuring the surface potential of the photosensitive drum 1 under each condition. Curve A, the potential of the non-exposed portion, the curve B, and potential of the exposed portion was exposed in the first exposure position L _1, curve C, the potential of the exposed portion was exposed in the second exposure position L ₂ Each is shown.

[0058] When exposed with the first exposure position L _1, 35 ° C. is a high humidity environment from 24 ° C. 42% is a standard environment 90
%, The temperature and humidity, especially when the humidity is increased, about 1 V
Was increased to about 30 V, and a remarkable potential increase was observed. On the other hand, when exposed in the second exposure position L _2, 35 ° C. is a high humidity environment from 24 ° C. 42% is a standard environment
Even if the voltage is changed to 90%, the voltage rises only from about 1 V to about 5 V, and the potential rise in the exposed portion is suppressed.

From this, by moving the exposure position on the surface of the photosensitive drum 1, that is, by moving the exposure position to the rotation direction side of the photosensitive drum 1, the conductive contact with the photosensitive drum 1 after the exposure is made. It has been found that the amount of the magnetic magnetic toner T can be reduced and the potential difference between the exposed part and the non-exposed part in a high humidity environment can be increased.

[0060] On the other hand, looking image obtained when the image obtained by exposure in the first exposure position L _1, 24 ° C., which is a standard environment
At 42%, it is clear, but with increasing humidity,
A sharpened portion occurred, and the image quality was extremely low in a high humidity environment of 35 ° C. and 90%. On the contrary, when the image obtained by exposure in the second exposure position L _2, in 35 ° C. 90% is a high-humidity environment, is a clear,
At a standard environment of 24 ° C. and 42%, flaring occurred. This is a photosensitive drum 1 made of conductive magnetic toner T.
To the photosensitive drum 1 and the conductive magnetic toner T
It is thought to be due to the influence of the positional relationship and the like.

Therefore, in a standard environment, the image quality is more stable when there is some contact with the conductive magnetic toner T after exposure, and in a high humidity environment, the conductive magnetic toner T is exposed after exposure. It was found that the image quality was more stable when no contact was made.

From these results, in the electrophotographic apparatus of this embodiment, the exposure position is switched between the first exposure position L _{1 in} the standard environment and the second exposure position L _{2 in} the high humidity environment. I have.

As described above, in the electrophotographic apparatus of this embodiment, the developing sleeve flowing between the photosensitive drum 1 and the developing sleeve changes with the environmental change, for example, increases with an increase in humidity. the current I, and detected split resistor R _1, and outputs to the controller 27, the control device 27 based on this signal, drives the exposure unit moving motor 28, in a high-humidity environment, the toner reservoir the second exposure position L ₂ is a rear position of, in a standard environment, in the first exposure position L ₁ is a front position of the toner reservoir, the exposure device 7
The exposure position on the surface of the photosensitive drum 1 is switched.

As a result, in a high humidity environment, the amount of the conductive magnetic toner T that comes into contact with the photosensitive drum 1 after exposure is reduced, so that the charging characteristic of the conductive magnetic toner T to the tourist drum 1 is improved. Even if it becomes high, re-charging of the exposed part is prevented, and the potential difference between the non-exposed part and the exposed part is maintained in a large state. Obtainable. On the other hand, in the standard environment, the exposure is performed under the setting conditions as before, so that the image quality is not affected by the correction corresponding to the high humidity environment, and the image quality is stable, and the clear image without blur is obtained. can get. In other words, regardless of the environment in which the electrophotographic device is installed, in any environment,
A clear image without blurring can be obtained.

Further, since the humidity is detected by a simple configuration of detecting the current, the image forming apparatus having the excellent performance as described above can be configured without complicating the structure. .

Further, according to the above configuration, the toner melted on the surface of the transfer belt 8 by heating is transferred by the transfer paper P being pressed thereon. Therefore, a transfer device such as a corona discharge device is not required, and further, the entire device can be reduced in size, and the transfer and fixing are performed at the same time.
This can also improve the image quality.

Further, since there is no need to provide a charger such as a corona discharger for charging the surface of the photosensitive drum 1, there is no danger of generating ozone in the charging step. In addition, since the exposure device 7 is disposed in the photosensitive drum 1, the entire device can be configured to be extremely small, and the attachment of dirt to the exposure device 7 can be avoided. It is possible to stably maintain the amount of irradiation light from the light source for a long period of time, and thereby, it is possible to obtain high quality image quality.

In the above embodiment, the exposure position is switched between the first exposure position L ₁ and the second exposure position L _2. However, the present invention is not limited to this. By switching the position, a clear image with stable image quality and without blurring can be obtained even in any environment. Similarly, the exposure position angle used in this embodiment is not limited to these.

In addition to the above, various modifications are possible within the scope of the present invention. For example, as shown in FIG. 12, the toner remains on the photosensitive drum 1 after contacting the transfer belt 8. A scraper 26 made of rubber or the like for collecting the conductive magnetic toner T may be provided above the developing sleeve 5b, and the photoconductive layer 1c and the transparent conductive layer 1b are placed on the transparent support 1a from the front side. Instead of the photoconductor drums 1 provided one after another, a photoconductor having a configuration in which a blocking layer is provided between the photoconductive layer 1c and the transparent conductive layer 1b can be used in order to improve charge retention characteristics. It is.
Further, in addition to the conductive magnetic toner T, the present invention can be applied to a mechanism for developing with another toner as long as the toner is for an electrophotographic apparatus.

[0070]

As described above, according to the image forming apparatus of the first aspect of the present invention, the current detecting means for detecting the current flowing between the photosensitive member and the developing sleeve, and the output signal of the current detecting means And an exposure position changing means for moving an exposure position of the photoconductor by the exposure apparatus.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the exposure position changing means determines the correlation between the current flowing between the photosensitive member and the developing sleeve and the humidity. The exposure position is moved in the direction of rotation of the photoconductor from the center point where the photoconductor and the developing sleeve face each other as the humidity rises.

Accordingly, the current detecting means detects a current flowing between the photosensitive member and the developing sleeve which changes with the environmental change and which is correlated with the environmental change. For example, a change in humidity can be grasped. Then, the exposure position changing means moves the exposure position to the rotation direction side of the photoconductor relative to the opposing center point between the photoconductor and the developing sleeve, for example, as the humidity increases,
Even if the amount of developer in contact with the photoreceptor after exposure is reduced, for example, the humidity becomes high and the charging characteristics of the developer to the photoreceptor are improved, re-charging of the exposed portion is prevented and the exposed portion is not contacted. It is possible to avoid a decrease in the potential difference from the exposed portion. As a result,
The effect is that a clear image with stable image quality and without blurring can be obtained without being affected by environmental changes.

Further, since an environmental change can be detected without using a sensor or the like, an effect that the structure can be formed at low cost without complicating the structure can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a circuit for detecting a developing sleeve current and identifying a toner resistance in an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a photosensitive drum, a developing device, an exposure device, and a transfer / fixing belt in the electrophotographic apparatus.

FIG. 3 is a schematic configuration diagram showing various components constituting the electrophotographic apparatus.

FIG. 4 is an explanatory diagram showing a state where the surface of the photosensitive drum is charged by contact with a conductive magnetic toner.

FIG. 5 is an explanatory diagram showing a state in which the surface of the photosensitive drum is neutralized by exposure.

FIG. 6 is an explanatory diagram showing a state where a toner image is formed on the surface of the photosensitive drum.

7A and 7B are diagrams illustrating a light irradiation position (exposure position) by an exposure device provided in the electrophotographic apparatus, wherein FIG. 7A is an explanatory diagram illustrating a first exposure position under a standard environment, and FIG.
FIG. 4 is an explanatory diagram showing a second exposure position in a high humidity environment.

FIG. 8 is an explanatory diagram illustrating a positional relationship among a toner pool formed on the surface of the photosensitive drum, a first exposure position, and a second exposure position.

FIG. 9A is a schematic diagram of a developing unit in the electrophotographic apparatus, and FIG. 9B is an equivalent circuit diagram of the developing unit.

FIG. 10 is a graph showing a relationship between humidity and toner resistance of a conductive magnetic toner T used in the electrophotographic apparatus.

FIG. 11 is a graph showing the environmental dependence of the surface potential of the photosensitive drum.

FIG. 12 shows a developing device provided in the electrophotographic apparatus.
FIG. 3 is a configuration diagram when a scraper is provided.

FIG. 13 is a schematic diagram showing a configuration of an image forming apparatus employing a conventional Carlson process.

FIG. 14 is a schematic sectional view showing a main part of an image forming apparatus employing an image forming process using a conventional conductive toner.

[Explanation of symbols]

Reference Signs List 1 photoconductor drum (photoconductor) 1a transparent support 1b transparent conductive layer 1c photoconductive layer 5b developing sleeve 7 exposure device 27 control device (exposure position changing device) 28 exposure device moving motor (exposure position changing device) R ₁ division Resistance (current detection means) T Conductive magnetic toner (developer)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/05 G03G 21/00 530 G03G 21/20

Claims (2)

(57) [Claims] A rotatable photoreceptor having a transparent conductive layer and a photoconductive layer provided on a transparent support, and a developing sleeve having a developer held on a surface thereof are disposed to face each other; A developer is brought into contact with the surface of the photoreceptor while applying a voltage between the photoreceptor and the developing sleeve to charge the surface of the photoreceptor. Perform exposure according to the write signal from the support side,
In an image forming apparatus for forming a toner image on the surface of a photoconductor, current detection means for detecting a current flowing between the photoconductor and the developing sleeve, and a photoconductor by the exposure device based on an output signal of the current detection means. An image forming apparatus, comprising: an exposure position changing unit that moves an exposure position. 2. The apparatus according to claim 1, wherein the exposure position changing means changes the exposure position between the photosensitive member and the developing sleeve as the humidity increases, based on the correlation between the current flowing between the photosensitive member and the developing sleeve and the humidity. 2. The image forming apparatus according to claim 1, wherein the photosensitive member is moved in a rotation direction of the photosensitive member from a center point facing the photosensitive member.