JPH063901A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a distinct image having stable image quality and having no thinning under every environment by preventing an exposed part from being electrostatically charged again under the environment of high humidity. CONSTITUTION:While impressing voltage between a developing sleeve and a photosensitive drum, the photosensitive drum is electrostatically charged in a state where conductive magnetic toner is brought into contact with the photosensitive drum, and simultaneously exposure is performed by an exposing device and then, development is performed in an electrophotographic device. The electrophotographic device is provided with a humidity sensor 29, and a control circuit part 27 drives a motor 28 for changing a light irradiation position based on a detection signal from the sensor 29 so as to switch an exposing position for the surface of the photosensitive drum 1 to a 2nd exposing position being the rear position of toner reservoir under the environment of high humidity and to a 1st exposing position being the front position of the toner reservoir under standard environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention provides a toner image on the surface of a photosensitive member by contacting the surface of the photosensitive member with a toner as a developer to charge the surface of the photosensitive member and performing exposure according to a write signal. The present invention relates to an image forming apparatus to be formed.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic method based on the application of the Carlson process has been widely used for image formation using toner. As shown in FIG. 12, the apparatus adopting the above Carlson process has 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 its surface. A cleaner 37 and a static eliminator 38 are sequentially provided.

In the above structure, first, the surface of the photosensitive drum 31 is uniformly charged by the charger 32 in a dark place. Next, the exposure device 33 irradiates light to remove the charged charges in the light-irradiated portion, so that an electrostatic latent image is formed. Then, a visible image is formed by the toner 39 by adhering to the electrostatic latent image, the toner 39 charged to the opposite polarity to the charging charge on the photosensitive drum 31 in the developing device 34.

Then, the 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 device 35 and applying an electric 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. Further, the electrostatic latent image on the photoconductor drum 31 is irradiated with light from the static eliminator 38 to be neutralized, and then the process starting from the charging by the charger 32 is repeated again to perform continuous image formation. Be seen.

By the way, in the electrophotographic method 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. This corona discharger requires a high applied voltage of several kV, and is easily affected by environmental changes such as changes in the charge amount on the surface of the photosensitive drum 31 due to changes in temperature. Further, since ozone is generated during corona discharge, environmental hygiene problems also occur.

Therefore, for example, Japanese Patent Publication No. 2-4900 discloses an image forming method which does not require the above corona charging. In the method, as shown in FIG. 13, a photoreceptor 50 comprises a transparent base 51 such as glass, a transparent conductive layer 52 made of In ₂ O ₃ , etc., a photoconductive layer 53 such as Se, a polyethylene terephthalate. An insulating layer 54 made of a late film, a parylene, or the like is sequentially laminated and configured.

Then, a magnet 56 having a conductive toner 55 adhered to the surface of the photosensitive member 50 as a toner holding member.
And the voltage is applied between the magnet 56 and the transparent conductive layer 52. When the transparent substrate 51 is exposed to light, the resistance of the photoconductive layer 53 is lowered at the light irradiation portion, and the charge is changed to the insulating layer. Inject to the bottom of 54. This allows the magnet 5
A strong electric field is applied between 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 sandwiched therebetween and the charges injected from the transparent conductive layer 52 form a charge pair having opposite polarities, so that they are attracted to each other. After that, even if the magnet 56 is moved away from the photoconductor 50, only the conductive toner 55 in the exposed region remains on the surface of the photoconductor 50. As a result, a toner image can be formed on the surface of the photoconductor 50 without using corona charging. Then, 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 and heats and fixes the conductive toner 55 by melting, similarly to the Carlson process method. By feeding the sheet to the recording material 40, an image can be formed on the recording material 40 as a permanent image.

A specific device using such an image forming method will be described with reference to FIG. 8 which is an explanatory view of the present invention. The photoconductor drum 1 as the photoconductor 50 is on the transparent support 1a. It has a structure in which a transparent conductive layer 1b and a photoconductive layer 1c are formed on the transparent conductive layer 1b and rotates in the A direction. Further, the magnet 5 arranged to face the photosensitive drum 1
The toner holder 5 as a member 6 extends along 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 non-magnetic material such as aluminum. And a developing sleeve 5b which is made of martensitic stainless steel and is provided so as to cover the outer peripheral surface of the magnetic roller 5a, and an alternation which occurs as the magnetic roller 5a rotates 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 C direction.

Then, the transparent conductive layer 1b and the developing sleeve 5
By applying a voltage between the surface of the photosensitive drum 1 and the conductive magnetic toner T while applying a voltage to the surface of the photosensitive drum 1, the surface of the photosensitive drum 1 is charged to the same polarity as the conductive magnetic toner T, and at the same time, conductive. By exposing the contact portion between the magnetic toner T and the photosensitive drum 1 from the transparent support 1a side by 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 toner image is transferred is collected by the magnetic force of the developing sleeve 5b.

Further, at this time, since the photosensitive drum 1 and the toner holding member 5 are disposed close to each other, the conductive magnetic toner T in the contact area with the photosensitive drum 1 rotates the photosensitive drum 1. Is naturally conveyed along with the photoconductor drum 1, and the photosensitive drum 1 and the developing sleeve 5b face each other, that is, the photoconductor drum 1
A toner reservoir is formed on the photosensitive member rotating direction side with respect to a line connecting the center of the developing sleeve and the center of the developing sleeve 5b.

Then, in this way, 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 the difference in the setting conditions greatly affects the copied image. Therefore, each is usually set to the condition in the standard environment state. For example, the exposure position is the charging characteristic of the conductive magnetic toner T in the standard environment, and the conductive magnetic toner T and the photosensitive drum 1. The first exposure position L ₁ is set at the front position of the toner reservoir in consideration of the arrangement position and the like.

[0013]

However, in the above configuration, since each part is set to the condition in the standard environmental condition, it is not possible to cope with the change in the environmental condition, and the image quality is stable especially in 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 decreases. 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 the standard environment, has a low charging characteristic to the photoconductor drum 1 and does not affect the exposed portion, is high. It is considered that in a humidity environment, the resistance is lowered, the charging characteristic of the photosensitive drum 1 is improved, and the exposed portion is recharged.

The present invention has been made in view of the above-mentioned problems, and by moving the exposure position of the surface of the photosensitive member by the exposure device in accordance with environmental changes, particularly humidity changes, it is possible to prevent the exposure portion from being exposed due to environmental changes. An object of the present invention is to provide an image forming apparatus capable of avoiding a decrease in the potential difference from the exposed portion and obtaining a clear image with stable image quality and no blurring.

[0015]

In order to solve the above-mentioned problems, an image forming apparatus according to a first aspect of the present invention is rotatable and has a transparent conductive layer and a photoconductive layer provided on a transparent support. A photosensitive member and a developer holding member holding the developer on the surface are arranged to face each other, and the developer is brought into contact with the surface of the photosensitive member while applying a voltage between the transparent conductive layer and the developer holding member. While charging the surface of the photoconductor, the contact area between the photoconductor and the developer is exposed by the exposure device from the transparent support side of the photoconductor in accordance with the write signal to form a toner image on the surface of the photoconductor. In the image forming apparatus, the environmental condition detecting means for detecting an environmental condition under the environment in which the image forming apparatus is disposed, and the exposure position of the photoconductor by the exposing device based on the output signal of the environmental condition detecting means. Exposure position changing means for moving It is characterized in that is provided.

According to a second aspect of the present invention, in order to solve the above problems, in the image forming apparatus according to the first aspect, the environmental condition detecting means is a humidity sensor. It has a feature.

According to a third aspect of the present invention, in order to solve the above-mentioned problems, in the image forming apparatus according to the first or second aspect, the exposure position changing means includes: It is characterized in that the exposure position is moved in the rotational direction of the photoconductor from the center point where the photoconductor and the developer holding member face each other as the humidity rises.

[0018]

According to the above-mentioned structure, the environmental condition detecting means detects the environmental condition in the environment where the image forming apparatus is installed, that is, the temperature, the humidity and the like. Therefore, for example, as in the configuration according to claim 2, the humidity can be detected by using the humidity sensor as the environmental condition detecting means. Then, based on this detection signal, for example, as in the configuration according to claim 3, the exposure position changing means determines the exposure position to the photoconductor and the developer holding member if the humidity rises based on the output signal of the humidity sensor. It is moved in the direction of rotation of the photoconductor from the center point facing it. This reduces the amount of developer that comes into contact with the photoconductor after exposure, resulting in high humidity, which prevents recharging of the exposed area even if the developer has high charging characteristics. Thus, it is possible to avoid a decrease in the potential difference between the exposed portion and the non-exposed portion.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIGS.
The explanation is based on the following.

As shown in FIG. 2, the electrophotographic apparatus which is the image forming apparatus of the present embodiment is provided with a cylindrical photosensitive drum (photosensitive member) 1 rotatable in the direction A in the apparatus. A developing device 2 is provided to the right of the photosensitive drum 1, an exposing device 7 is provided inside the photosensitive drum 1, and a transfer / fixing belt 8 is provided above the photosensitive drum 1.

As shown in FIG. 4, the photoconductor drum 1 has a surface of an optically transparent cylindrical transparent support 1a,
A transparent conductive layer 1b made of a sputtered film such as 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, the transparent conductive layer 1b has a film thickness of
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 has a developing tank 3 for storing a conductive magnetic toner T as a developer.
A stirring roller 4 that is rotatably provided in the developing tank 3 and stirs the conductive magnetic toner T; and an opening 3a of the developing tank 3.
A toner holder 5 as a developer holding member disposed at a position facing the photosensitive drum 1, and a doctor blade 6 fixedly provided below the toner holder 5 in the opening 3 a of the developing tank 3. It consists of

The toner holder 5 extends along the longitudinal direction of the photosensitive drum 1, and has N polarity and S 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, and is provided so as to cover the outer peripheral surface of the magnetic roller 5a. The sleeve 5b, which holds the conductive magnetic toner T on the surface of the developing sleeve 5b by the alternating magnetic field generated as the magnetic roller 5a rotates in the B direction, and rotates the magnetic roller 5a in the B direction. Is conveyed in the reverse C direction.

Further, the doctor blade 6 adjusts the carrying amount of the conductive magnetic toner T held on the surface of the developing sleeve 5b and carried in the C direction to a predetermined amount.

The conductive magnetic toner T is crushed by kneading resin such as styrene-acrylic copolymer with magnetic powder such as iron powder and ferrite, carbon black, etc.
It is composed of powder having a size of several μm to several tens of μm.

The exposure device 7 disposed in the photosensitive drum 1 is composed of an LED array in which a light-emitting diode and a short focus lens are combined, and it is responsive to a write signal from an exposure control means (not shown). The toner holding member 5 is irradiated with light, and the irradiation 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 is like this.

The exposure apparatus 7 is also provided with a light irradiation position displacement motor 28, which will be described later, that displaces the exposure apparatus 7 with the center of the photosensitive drum 1 as a fulcrum. The drive is a control circuit unit 27 described later.
Light irradiation position (exposure position)
Is the first exposure position L ₁ at the exposure position angle θ ₁ = 12 °, which is the front position of the toner pool shown in FIGS. 7A and 8.
And the second exposure position L ₂ at the exposure position angle θ ₂ = 17 °, which is the rear position of the toner reservoir shown in FIGS. 7B and 8.
It is designed to switch between and. The above exposure position angle means the center of the photosensitive drum 1 and the magnetic roller 5a.
Is an angle formed by a line connecting the center of the photosensitive drum 1 and a line connecting the center of the photoconductor drum 1 with the light irradiation position (exposure position).

The transfer / fixing belt 8 is formed in an endless belt shape by 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 includes a transfer roller 9 formed of a conductive elastic member disposed above the photosensitive drum 1, and a transfer roller 9 disposed on the left side of the transfer roller 9 and slightly above the transfer roller 9. A heating device 10 to be described later, which is provided, and a tension roller 11, which is arranged on the lower left side of the heating device 10, are wound so as to surround them from the outside. The transfer / fixing belt 8 is
The photosensitive drum 1 and the transfer roller 9 are sandwiched between the photosensitive drum 1 and the transfer roller 9, and move in the arrow direction.

A film-shaped polyimide resin is used as the material of the transfer / fixing belt 8, but the material is not particularly limited to this material, and at least the conductive magnetic toner will be described later. As long as the surface on which T is transferred has an insulating property, it is composed of, for example, a metal belt such as an electroformed nickel belt as a base material, which is coated with fluorine, or other member of polyamide resin. It may be one. 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 to 200 μm, and the surface may be formed as a rough surface in order to obtain an appropriate gloss of the image.

The heating device 10 has a conductive magnetic toner T transferred onto the surface of the transfer / fixing belt 8 as described later.
Is for heating and melting, and a planar Mo-based heating resistor 10a is printed on an alumina ceramic substrate, and
It is composed of a ceramic heater in 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 10a, and this heating surface is in direct contact with the surface of the transfer / fixing belt 8. It is located in.

Further, a pressure roller 12 which is rotated while applying a pressing force in the direction of the heating device 10 via the transfer / fixing belt 8 is arranged at the upper portion of the heating device 10. The pressure roller 12 is configured to sandwich the transfer sheet P conveyed by the recording material conveying unit 14 described later at a pressure contact portion with the transfer / fixing belt 8.

Further, in the electrophotographic apparatus, as shown in FIG. 3, a cooling fan 24 for cooling the transfer / fixing belt 8 from the lower side, and a main motor 13 which is a drive source of the apparatus.
And the above-mentioned recording material conveying means 14 for conveying the transfer paper P to the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12,
Paper output means 21 for discharging the transfer paper P from inside the apparatus, a humidity sensor 29 for detecting humidity in the environment where the electrophotographic apparatus is arranged, and a light irradiation position displacement motor provided in the exposure apparatus 7. Control circuit section 27 for controlling the driving of 28
And are provided.

The recording material conveying means 14 is arranged above the photosensitive drum 1, the developing device 2 and the transfer / fixing belt 8 and has a transfer paper supply opening (not shown) as its constituent member. To a pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12, a pair of conveyance guide plates 15, a paper feed actuator 16 and a paper feed roller 18 arranged near the transfer paper supply opening.・ 18
Registration rollers 19 and 19 arranged in the middle of the path of the conveyance guide plate 15 and a sheet feeding solenoid 20 for controlling the rotation of the registration rollers 19 and 19 are provided.

The paper output means 21 is a transfer / fixing belt 8
It is disposed on the left side of the pressure contact portion between the pressure roller 12 and the pressure roller 12, and as its constituent member, connects the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12 to a transfer paper discharge opening (not shown). A pair of paper ejection guide plates 22 forming a paper path, a paper ejection actuator 23 arranged in the vicinity of a pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12, and a paper ejection guide plate 22.
Transport rollers 25, 25 disposed on the terminal side of the.

The humidity sensor 29 as an example of the environmental condition detecting means is connected to the control circuit section 27 as shown in FIG. 1, and outputs the detection result to the control circuit section 27. .

The control circuit section 27 comprises an amplifier 30, a differential amplifier 33 to which an upper limiter 31 and a lower limiter 32 are connected, a duty conversion circuit 34 into which a triangular wave is input, and an inverter 35. It is connected to the light irradiation position displacement motor 28 described above. Then, the DC signal input from the humidity sensor 29 is input to the duty conversion circuit 34 via the amplifier 30 and the differential amplifier 31, and the duty conversion circuit 34 performs duty conversion using a triangular wave. The AC signal is converted by the inverter 35. By the AC signal, the light irradiation position displacement motor 28 is driven as follows.

That is, if the value detected by the humidity sensor 29 is within the range indicating the standard environment, the exposure position by the exposure device 7 is the _first position with the exposure position angle θ ₁ = 12 °.
Motor 28 for displacing the light irradiation position so that the exposure position is L _1.
If the value detected by the humidity sensor 29 is within a range indicating a high humidity environment, the motor 28 for displacing the light irradiation position by the exposure device 7 causes the exposure position angle θ ₂ = The light irradiation position displacement motor 28 is driven so as to reach the second exposure position L _{2 of} 17 °. That is, the control circuit section 27 and the light irradiation position displacement motor 28 constitute the exposure position changing means of the present invention.

The signal for driving the light irradiation position displacement motor 28 is output at times other than the time when the writing 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 according to the environmental conditions will be described after the explanation of the operation. .

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

First, the transfer paper feeding 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 feed detection switch (not shown) detects the supply of the transfer paper P and sends a paper feed detection signal to the main motor 13 to drive it. The main motor 13 is driven to rotate. Next, the rotation of the main motor 13 is transmitted to the sheet feeding rollers 18 through a rotation transmission mechanism (not shown), whereby the sheet feeding rollers 18 are rotated, and the rotation of the sheet feeding roller 18 is accompanied. , The transfer paper P is the registration roller 1
Transported on September 19th.

As described above, the registration roller 19.1
The transfer paper P conveyed to the sheet 9 is transferred to the registration rollers 19 and 19
Since the rotation is stopped by the control of the paper feeding solenoid 20, the transportation is temporarily stopped. At this time, the sheet feeding rollers 18, 18 are in a state of sandwiching the rear end side of the transfer sheet P, and the resistance of the roller surface is small. It is slipped on both sides.

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

Next, the developing process of the conductive magnetic toner T will be described with reference to FIGS. 4 to 6, 8 and 9.

First, as shown in FIG. 4, 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 B direction. At the same time, it is conveyed on the surface of the developing sleeve 5b in the C direction, which is the opposite direction to the A direction, which is the rotation direction of the photosensitive drum 1. At this time, at the contact portion between the conductive magnetic toner T held on the surface of the developing sleeve 5b and the photoconductor drum 1, a voltage of several tens of V applied between the developing sleeve 5b and the transparent conductive layer 1b. The charged conductive magnetic toner T is naturally conveyed in the rotation direction of the photoconductor to form a toner pool.

Then, the photoconductive layer 1c on the surface of the photoconductor drum 1 is passed through the conductive magnetic toner T from the developing sleeve 5b.
Charge is injected into the developing sleeve 5
It is charged to approximately the same potential as b. That is, as shown in the schematic view of FIG. 9A, the photosensitive drum 1 and the developing sleeve 5b.
It can be considered that the conductive magnetic toner T and the conductive magnetic toner T form a kind of capacitor, and an equivalent circuit thereof is as shown in FIG. In this case, in the part where the conductive magnetic toner T and the photoconductive layer 1c are separated, the conductive magnetic toner T is predominantly acted on by the magnetic force generated by the magnetic roller 5a, and therefore 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 installed in advance, that is, in the standard environment, the toner pool shown in FIG. Of the write signal from the exposure device 7 at the first exposure position L ₁ at the front position of the toner reservoir and at the second exposure position L ₂ at the rear position of the toner pool shown in FIG. 8 under the high humidity environment. 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 that of 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 shown in FIG.
As shown in FIG.
The magnetic force of the magnetic roller 5a is shaken off by the action of the electric field acting between b and the surface of the photoconductor drum 1 and the van der Waals force acting between the photoconductor drum 1 and the conductive magnetic toner T. A toner image that adheres to the surface of the photosensitive drum 1 and that corresponds to the write signal is formed on the surface of the photosensitive drum 1.

As described above, the toner image formed on the surface of the photosensitive drum 1 is applied with a voltage having a polarity opposite to the injected charge of the toner image to the transfer roller 9, as shown in FIG. Then, it is transferred onto 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, at the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12 on the heating device 10, the toner image on the surface of the transfer / fixing belt 8 and the transfer paper P are transferred.
In response to the output of a signal from the CPU of the engine controller (not shown) to the paper feeding solenoid 20, the rotation stop state of the registration rollers 19 is released, and the transfer paper P has its leading end. And the transfer / fixing belt 8 at the same timing as the front end of the transfer / fixing belt 8.
It is conveyed to the pressure contact portion between the fixing belt 8 and the pressure roller 12.

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

After that, the transfer paper P on which the toner image is transferred and fixed is pushed up by the paper output actuator 23, and is discharged from the apparatus through the transfer paper discharge opening by the rotation of the conveying rollers 25. Then, after a predetermined time has passed since the transfer paper P was discharged to the outside of the device, the heating device 10
When the heating resistor 10a is energized and the driving of the main motor 13 is stopped, the series of operations as described above ends.

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

As described above, an electrophotographic apparatus which conducts charging, exposure, and development simultaneously by bringing the conductive magnetic toner T into contact with the photosensitive drum 1 in a state where voltage is applied to the photosensitive drum 1 and the developing sleeve 5b. In high humidity, the amount of the conductive magnetic toner T that comes into contact with the photosensitive drum 1 after exposure is
It is considered to affect the 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 exposure, the exposure position is changed, and environmental conditions, particularly humidity are changed stepwise at each exposure position. The surface potential of the photoconductor drum 1 was measured under each condition, and the images obtained under each condition were compared. Specifically, the electrophotographic apparatus whose exposure position is set to the first exposure position L ₁ shown in FIG. 7A and the exposure position to the second exposure position L ₂ shown in FIG. 7B. It was performed using the set electrophotographic apparatus. The electrophotographic apparatus has the same structure as the electrophotographic apparatus of this embodiment except that the exposure position is fixed.

In this case, the photosensitive drum 1 is an amorphous silicon photosensitive member having a drum diameter of 30 mm and a film thickness of 3 μm, and the light source is L having an exposure amount of 2 μJ / cm ² .
An ED head is used, a toner roller 5 of the developing device 2 is a magnetic roller with a magnetic force of about 700 gauss, which has a non-magnetic conductive sleeve and 8 magnetic poles, and a toner resistance of 1. 0 × 10 ¹² Ωcm, developer resistance 1.
7 × 10 ³ Ωcm, toner particle size 12μ, 2 component developer, development bias 70V, process speed 5
It was set to 0 cm / sec.

The results of measuring the surface potential of the photosensitive drum 1 under each condition are shown in FIG. Curve A represents the potential of the non-exposed portion, curve B represents the potential of the exposed portion exposed at the first exposure position L ₁ , and curve C represents the potential of the exposed portion exposed at the second exposure position L ₂ . Shows.

When exposure is performed at the first exposure position L ₁ , the standard environment is 24 ° C. 42% to the high humidity environment 35 ° C. 90
%, When the temperature and humidity, especially the humidity are increased, about 1
The potential, which was V, increased to about 30 V, and a remarkable increase in potential was observed. On the other hand, when the exposure is performed at the second exposure position L ₂ ,
Standard environment is 24 ℃ 42% to high humidity environment 35
Even if the temperature is changed to 90%, the increase is limited to about 1 V to about 5 V, and the increase in the potential of 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 in the rotation direction side of the photosensitive drum 1, the conductive material contacting the exposed photosensitive drum 1 is obtained. It was found that the amount of the magnetic toner T can be reduced and a large potential difference between the exposed portion and the non-exposed portion can be obtained in a high humidity environment.

On the other hand, looking at the obtained image, in the case of the image obtained by exposing at the first exposure position L ₁ , the standard environment is 24 ° C.
At 42%, it is clear, but with increasing humidity,
Blurred portions were generated, and the image quality was extremely low at a high humidity environment of 35 ° C. and 90%. On the contrary, in the case of the image obtained by exposing at the second exposure position L ₂ , it is clear in the high humidity environment of 35 ° C. 90%,
Blurring occurred in the standard environment at 42 ° C. and 42%. This is the photosensitive drum 1 of the conductive magnetic toner T.
Charging characteristics, the photoconductor drum 1 and the conductive magnetic toner T
It is considered that this is due to the influence of the positional relationship with

From the above, the image quality is more stable when exposed to the conductive magnetic toner T after exposure in a standard environment, and the conductive magnetic toner T is exposed after exposure in a high humidity environment. It was found that the image quality is more stable if it does not come into contact with.

From these results, in the electrophotographic apparatus of this embodiment, the exposure position is switched between the first exposure position L ₁ under the standard environment and the second exposure position L ₂ under the high humidity environment. There is.

As described above, in the electrophotographic apparatus of this embodiment, the humidity sensor 29 detects the humidity in the environment where the electrophotographic apparatus is installed, and the control circuit section 27
The exposure device 7 is based on the output signal from the humidity sensor 29.
The light irradiation position by the second exposure position L ₂ which is the rear position of the toner reservoir in the high humidity environment, and the first exposure position L which is the front position of the toner reservoir in the standard environment.
Since it is switched to _1, the exposure is always performed at the exposure position corresponding to the humidity.

As a result, in a high-humidity environment, the amount of the conductive magnetic toner T that contacts the photosensitive drum 1 after exposure is reduced, so that the charging characteristic of the conductive magnetic toner T to the photosensitive drum 1 is improved. Even if the temperature rises, it prevents recharging of the exposed area and maintains a large potential difference between the non-exposed area and the exposed area, so there is no blurred image and a stable and clear image is obtained. Obtainable. On the other hand, under the standard environment, the exposure is performed under the set conditions as before, so the image quality is not affected by the correction for the high humidity environment, etc., and the clear and stable image is obtained. can get.

That is, it is possible to obtain a clear image without blurring under any environment regardless of the environment in which the electrophotographic apparatus is installed.

Further, according to the above construction, the toner melted on the surface of the transfer belt 8 due to heating is transferred by pressing the transfer paper P on top of it. Therefore, a transfer device such as a corona discharger is not required, and further, the entire apparatus can be downsized, and transfer fixing is performed at the same time, so that the dirt of the toner image is eliminated,
This can also improve the image quality.

Furthermore, since it is not necessary to provide a charger such as a corona discharger for charging the surface of the photosensitive drum 1, there is no fear of generating ozone in the charging step. Moreover, since the exposure device 7 is disposed inside the photoconductor drum 1, the entire device can be made extremely small, and the exposure device 7 can be prevented from being contaminated with dirt. It is possible to maintain the amount of irradiation light from the laser beam stably over a long period of time, and this also makes it possible to obtain a high quality image.

Further, in the above embodiment, the exposure position is switched to the two exposure positions of the first exposure position L ₁ and the second exposure position L _2. However, the present invention is not limited to this, and more fine exposure is possible. By switching the position, it is possible to obtain a clear image with stable image quality even in any environment. Similarly, the exposure position angle used in this embodiment is not limited to these.

Other than the above, various changes can be made within the scope of the present invention. For example, as shown in FIG. 11, it remains on the photosensitive drum 1 after contact with 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 provided on the transparent support 1a from the surface side. Instead of the photosensitive drums 1 that are sequentially stacked, a photosensitive member 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. Is.
Further, in addition to the conductive magnetic toner T, the present invention can be applied to a mechanism for developing with other toner as long as it is a toner for an electrophotographic apparatus.

[0068]

As described above, the image forming apparatus according to the first aspect of the present invention detects the environmental conditions of the environment in which the image forming apparatus is installed, and the environmental condition detecting means. Exposure position changing means for moving the exposure position of the photoconductor by the exposure device based on the output signal of the means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the environmental condition detecting means is a humidity sensor.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the exposure position changing means changes the exposure position to a photoconductor as the humidity increases. It is configured to move in the rotation direction of the photoconductor from the center point facing the developer holding member.

As a result, when the humidity rises, the exposure position moves and the amount of the developer that comes into contact with the exposed photoreceptor decreases, so that, for example, the charging characteristics of the developer to the photoreceptor become high. Even in this case, recharging of the exposed portion can be prevented, and reduction of the potential difference between the exposed portion and the non-exposed portion can be avoided.
As a result, the image quality is stable regardless of environmental changes,
The effect is that a clear image without blurring can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a control circuit unit that controls a light irradiation position of an exposure device in an electrophotographic apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a photosensitive drum, a developing device, an exposing 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 where the surface of the photosensitive drum is neutralized by exposure.

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

FIG. 7 is a view showing a light irradiation position (exposure position) by an exposure device provided in the electrophotographic apparatus, FIG.
FIG. 6 is an explanatory diagram showing a second exposure position under a high humidity environment.

FIG. 8 is an explanatory diagram showing a positional relationship between 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 showing a photosensitive drum, a developing sleeve and a conductive magnetic toner in the electrophotographic apparatus, and FIG. 9B is an equivalent circuit diagram thereof.

FIG. 10 is a graph showing the environmental dependence of the surface potential on the photosensitive drum.

FIG. 11 shows a developing device provided in the electrophotographic apparatus,
It is a block diagram at the time of providing a scraper.

FIG. 12 is a schematic diagram showing a configuration of an image forming apparatus adopting a conventional Carlson process.

FIG. 13 is a schematic cross-sectional view showing a main part of an image forming apparatus adopting a conventional image forming process using conductive toner.

[Explanation of symbols]

 1 Photoreceptor Drum (Photoreceptor) 1a Transparent Support 1b Transparent Conductive Layer 1c Photoconductive Layer 5b Developing Sleeve 7 Exposure Device 27 Control Circuit Unit (Exposure Position Changing Means) 28 Light Irradiation Position Displacement Motor (Exposure Position Changing Means) 29 Humidity sensor (environmental condition detection means) T Conductive magnetic toner (developer)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsumi Adachi 22-22 Nagaike-cho Naganocho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Yukito Nishio 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within the corporation

Claims (3)

[Claims] 1. A transparent support having a transparent conductive layer and a photoconductive layer provided on a transparent support, and a developer holding member having a developer held on the surface thereof are arranged to face each other. While applying a voltage between the conductive layer and the developer holding member, the developer is brought into contact with the surface of the photoconductor to charge the surface of the photoconductor, and the contact area between the photoconductor and the developer is exposed by an exposure device. In an image forming apparatus that forms a toner image on the surface of a photoconductor by performing exposure according to a writing signal from the transparent support side of the photoconductor, environmental conditions that detect environmental conditions under the environment in which the image forming apparatus is installed. An image forming apparatus comprising: a detection unit and an exposure position changing unit that moves an exposure position of a photoconductor by the exposure device based on an output signal of the environmental condition detection unit. 2. The image forming apparatus according to claim 1, wherein the environmental condition detecting means is a humidity sensor. 3. 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 developer holding member face each other as the humidity rises. The image forming apparatus according to claim 1 or claim 2.