JP2002040876A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and economically prevent a picture flow phenomenon, which is caused by water adsorbed to electrically discharged materials sticking to the surface of a photosensitive drum, in various circumstances for use with respect to an image forming device using the a-Si photosensitive drum. SOLUTION: A drum heater to warm the surface of the photosensitive drum is provided in the photosensitive drum, and detection means which detect the temperature and the humidity of installation circumstances are provided in the image forming device, and a control means is provided which operates the drum heater only at the time of discriminating circumstances, in which a picture flow occurs, by using these detection values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, and the like. More specifically, it relates to heater control of an amorphous silicon (a-Si) photosensitive drum used therein.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a photosensitive layer is coated on a surface thereof, and a charging device, an exposing device, a developing device, a transfer device, a cleaning device, a neutralizing device, etc. are provided around a cylindrical photosensitive drum. Is provided, and the toner image formed on the photosensitive drum is copied onto a sheet to form an image.

The basic process of image formation in the image forming section will be described. First, the surface of a photosensitive drum is uniformly charged by corona discharge of a charging device while rotating in one direction at a constant speed. The charged surface is irradiated with exposure light for image information from the exposure device on the downstream side in the rotation direction, and an electrostatic latent image is formed. Further, the toner is adhered to the electrostatic latent image by a developing device disposed further downstream thereof to form a toner image. In the transfer device, the conveyed paper comes into contact with the drum surface, and the toner image is transferred onto the paper by imprint of the opposite potential. The toner remaining on the surface of the photosensitive drum without being transferred to the sheet by the transfer device is scraped off by a blade member and collected by a cleaning device. Thereafter, the surface of the photosensitive drum is uniformly irradiated with light by a static eliminator to eliminate the residual potential.

The above-mentioned photosensitive drum has a photosensitive layer of several tens of μm formed on the surface of a cylindrical base material. The photosensitive layer is made of an organic photosensitive member, a selenium arsenic photosensitive member, amorphous silicon ( (Hereinafter referred to as a-Si)). Organic photoreceptors are relatively inexpensive, but are prone to wear, have a short life, and require frequent replacement. Although the selenium arsenic photoconductor has a longer life than the organic photoconductor,
Since it is a toxic substance, it has a drawback that handling is troublesome. On the other hand, a-Si photoreceptors are more expensive than organic photoreceptors, but have attracted attention in recent years from the viewpoint of environmental measures and excellent in total cost because of their harmless substances, easy handling and long life. Demand is increasing.

An a-Si photosensitive member generally has a configuration and characteristics as shown in FIG. As shown in FIG. 3A, the a-Si photoreceptor has a plasma C on the surface of the cylindrical substrate 2a.
A-Si photoconductive layer 2b and a-S
The surface protection layer 2c of iC (amorphous silicon carbide) is formed by lamination. In the plasma CVD method, various gases are introduced into a reaction vessel into which silane gas, methane gas, hydrogen gas, diborane gas, and nitric oxide gas are injected as starting material gases according to an additive material of each film and reacted by plasma to be laminated. Form. 20 to 80 for the photoconductive layer 2b
This is a film having a thickness of about μm, and generates conductivity in response to light. The surface protective layer 2c is a high hardness film of about 0.3 to 1 μm made of an a-SiC-based inorganic high-resistance material, and has a function of maintaining the surface potential of the photoconductive layer and the potential distribution of the electrostatic latent image. .

The characteristics of the a-Si photoreceptor vary depending on the thickness of the photoconductive layer and the like as shown in FIG. When the thickness of the photoconductive layer is set to about 80 μm (A in the figure), a high surface potential can be obtained, but the influence of the temperature increases. When the thickness of the photoconductive layer is about 30 μm, it is hardly affected by temperature, but the film is thin, so that dark decay is fast, and the surface potential cannot be maintained high. .

Further, in an electrophotographic image forming apparatus using an a-Si photosensitive member, a phenomenon called image deletion sometimes occurs depending on the use environment. The image deletion is a phenomenon in which an image is blurred or the periphery of the image is blurred. The cause of the image deletion is that the moisture in the air is adsorbed on the surface of the photoreceptor drum and the surface resistance is reduced, and the electric charge of the formed electrostatic latent image flows in the circumferential direction and the potential is reduced or the boundary is It is thought to be unclear.

[0008] One of the factors that causes moisture to be adsorbed on the surface of the photosensitive drum is that the molecular structure on the surface of the a-Si photosensitive member has a structure that easily adsorbs moisture. further,
When the image forming process is repeated on the photoconductor surface,
Ozone generated by corona discharge of the charging device reacts with paper powder and the like to generate a discharge product such as nitrate ion or ammonium ion, which may adhere to the surface of the photoreceptor and absorb moisture. If the drum is placed in a high-humidity environment under such conditions, a phenomenon occurs in which the surface resistance of the photoreceptor is reduced to a level at which a moisture image flows on the drum surface.

[0009]

In a conventional image forming apparatus using an a-Si photoreceptor, a drum heater is provided inside a photoreceptor drum to heat the surface of the photoreceptor drum in order to stabilize the performance and prevent image deletion. By always maintaining the temperature at a constant temperature, adsorption of moisture in the air has been prevented. However, as the necessity to deal with environmental problems increases, it is becoming increasingly necessary to reduce power consumption during standby and use of the image forming apparatus. In the control of the heater provided on the photoconductor drum, it is required to reduce the power consumption by effective control in consideration of environmental conditions and the characteristics of the a-Si photoconductor, instead of always operating the heater.

Accordingly, the present invention provides an image forming apparatus using an a-Si photoreceptor, which is provided with a temperature detecting means and a humidity detecting means to measure the temperature and humidity of the environmental atmosphere in which the image forming apparatus is placed, and It is an object of the present invention to provide an economical apparatus that operates a drum heater at a proper timing to reliably prevent image deletion and the like without lowering work efficiency and reduce power consumption.

[0011]

In the image forming apparatus of the present invention, an a-Si photosensitive drum is used in an image forming section, and a charging device, a developing device, a transfer device, a cleaning device, and a charge removing device are provided around the photosensitive drum. Are arranged to form an image. The photosensitive drum is formed in a cylindrical shape, and a drum heater is provided along an inner surface thereof. A humidity detecting unit and a temperature detecting unit are provided inside the image forming apparatus, and always detect the humidity and the temperature in the atmosphere of the environment where the image forming apparatus is installed. The signals from the respective detection units are sent to the control unit for controlling the operation of the image forming apparatus, and are judged, and control of the on / off operation of the drum heater is performed.

In the image forming apparatus according to the present invention, the humidity and the temperature are detected by the humidity detecting means and the temperature detecting means, and a necessary case is determined based on a result of the measurement. Since the heater device is operated, wasteful power consumption is suppressed, which is economical.

In the image forming apparatus according to the present invention, when it is determined that the environment is such that an image flow occurs in accordance with the detection results of the temperature detecting means and the humidity detecting means, the heater device is immediately activated to activate the photosensitive member. A control means is provided for permitting an image forming operation after operating for a predetermined time set to a time adjusted to a state where image flow does not occur even when moisture is adsorbed on the drum surface. When it is determined that the image deletion does not occur, the image forming operation is permitted as soon as the temperature of the fixing or the like is stabilized without operating the heater device. As a result, even at the start of use of the apparatus, it is possible to prevent the occurrence of image deletion and to form a good image. Further, when the apparatus is installed in a favorable environment in which image deletion does not occur, there is an effect that an image forming operation can be performed in a short time.

The image forming apparatus according to the third aspect determines the absolute humidity in accordance with the measurement result of the humidity by the humidity detecting means and the temperature measured by the temperature detecting means, confirms the temperature, and operates the heater device. And the power consumption can be reduced by minimizing the operation of the heater device. Further, since the heating device is stopped during the image forming operation that consumes a large amount of power, the maximum power consumption can be suppressed.

[0015]

Next, embodiments of the present invention will be described in detail with reference to the drawings. Although the embodiment is a copying apparatus as an image forming apparatus, the present invention is not limited to this, and various images such as a laser beam printer, an LED printer, and a facsimile that employ an a-Si photosensitive member as an electrophotographic process. Applicable to forming equipment.

FIG. 1 is a schematic view showing an entire copying apparatus employing the present invention. At the lower part, a plurality of paper storage stages 11 for storing paper for image formation are arranged. Above it is a double-sided device 6 for temporarily stacking and reversing sheets on which images are formed on one side when forming images on both sides of the sheet. Above this, the image forming unit 12 and the fixing device 8 are arranged. The sheet fed from the storage stage is conveyed along the conveyance path and contacts the surface of the photosensitive drum 2 when passing through the image forming unit 12 to copy a toner image.
The toner image is conveyed further downstream, and the toner image on the sheet is thermally fused by the fixing device 8. Above the image forming unit 12, an image reading device 10 and an image output device 9 are arranged. An operation panel 18 for setting copying conditions, starting a copying operation, and the like is provided in front of the uppermost portion, and a document feeder 7 is provided behind the operation panel 18. Further, a temperature detecting means 20 and a humidity detecting means 22 are provided in a gap portion between the side plate of the sheet storage stage 11 opposite to the sheet feeding direction and the exterior cover. These devices and electronic members are controlled by main body control means 40 (not shown).

Here, the position of the temperature detecting means 20 and the humidity detecting means 22 will be additionally explained. The upper part of the copier 1 radiates heat from the heat source of the fixing device and the light source of the document reading unit, and the surrounding air moves in a complicated manner by the cooling fan. It is difficult to measure correctly. The installation location of the temperature detecting means 20 and the humidity detecting means 22 in FIG. 1 does not have a heat source nearby, and no air flows from the fan. Also, it is just covered with a resin cover,
Because there is a gap in some parts, circulation with outside air is also made,
A measured value with small deviation following changes in the temperature and humidity of the external environment can be obtained.

Next, the image forming section 12 will be described in more detail with reference to FIG. In the image forming section 12, a charging device 13, a developing device 4, a transfer device 5, a cleaning device 3, and a charge removing device 14 are arranged around the photosensitive drum 2. Further, a potential sensor 16 for measuring the potential of the surface of the photosensitive drum is provided upstream of the developing device 4.

A charging wire for corona discharge is stretched over the charging device 13, and a cleaning member made of felt is slidably supported in the length direction of the charging device 13 in contact with the charging wire. . The cleaning member reciprocates while contacting along the charge wire by a driving mechanism using a small motor and a rope or the like, and removes toner, paper powder, and the like attached to the wire.

The developing device 4 contains a two-component developer in which a carrier and a toner are mixed, and charges the toner while stirring. A part of the developer is in contact with the surface of the rotating developing sleeve 4a, which is arranged opposite to the photosensitive drum 2 and is held by a magnetic force, and the toner is applied to the electrostatic latent image on the surface of the photosensitive drum 2 here. Adhere to. The toner ratio in the developer (hereinafter referred to as toner concentration) is a toner control sensor 4b.
(Not shown), and while monitoring the output value, the toner that has adhered to the surface of the photosensitive drum and has been consumed is supplied from the toner tank. The toner sensor 4b measures the magnetic permeability of the developer to determine the toner concentration. However, the detection value slightly changes due to the influence of temperature and humidity, and thus needs to be corrected. Further, the electrical characteristics of the image forming process such as charging and transfer slightly change depending on the temperature and humidity, and the toner density is changed in order to correct the change of the image transferred on the paper due to the influence. These corrections are performed based on the correction values stored in the main body control means in advance by detecting the temperature and humidity of the atmosphere by the temperature detection means 20 and the humidity detection means 22.

A transfer belt 5 a is stretched over the transfer device 5 and is moved at the same speed as the peripheral speed of the photosensitive drum 2. A transfer roller 5b is disposed inside the transfer belt 5a, and presses the transfer belt 5a in the direction of the photosensitive drum 2. When an image is formed, a high voltage is applied to the transfer belt 5a. The toner image is transferred to a sheet passing through the gap.

The cleaning device 3 is provided with a cleaning brush 3a made of a bristle member and a cleaning blade 3b made of urethane rubber in contact with the surface of the photosensitive drum 2. The cleaning brush 3a is rotationally driven to sweep off toner remaining on the surface of the photosensitive drum, and the cleaning blade 3b scrapes remaining toner.

Next, the photosensitive drum 2 has an a-Si conductive photosensitive layer 2b and an a-SiC surface protective layer 2C formed on the surface of an aluminum alloy cylindrical substrate 2a, and is rotatably supported. In FIG. 1, it rotates clockwise. The thickness of the photosensitive layer is about 30 μm, and the characteristics of voltage and temperature are shown in FIG.
It is almost the same as C in (b). The outer dimensions of the photoreceptor drum 2 are about 100 mm in diameter, and have a length in the width direction capable of forming an image on A3 size paper.

As shown in FIGS. 2 and 4, a drum heater 17 is provided inside the cylindrical base 2a of the photosensitive drum 2. In the drum heater 17, heating coils 17a are arranged at appropriate intervals on a heat-resistant insulating sheet having elasticity, and a heater temperature sensor 17b is arranged near the center. The drum heater 17 is rolled and inserted into the cylindrical base material of the photosensitive drum 2, spreads by the elasticity of the sheet, and adheres along the inner surface thereof and is fixed by frictional force. Further, flanges 30 are press-fitted at both ends of the photosensitive drum 2, and bearings 31 are mounted on bosses thereof, and are rotatably supported by bearings provided in the image forming unit. Flange 3 on one end
1 is provided with a terminal 32 for supplying power to the drum heater 17 and an output signal reading terminal 33 for the temperature sensor. The heating coil 17a and the heater temperature sensor 17b are connected to one end of the terminals 32 and 33, and the common electrode plate 36 grounded to the disk-shaped electrode plates 34 and 35 fixed to the external boss portion at the other end. It is connected to. Electrode plate 34,
Electrodes 37, 38, 39 are always in contact with the peripheral surfaces of 35, 36, and are electrically connected even while the photosensitive drum 2 is rotating.
Also,

The drum heater 17 is operated as needed as will be described later. When the drum heater 17 is operated, it is supplied to the heating coil 17a so as to maintain the photosensitive drum 2 at a constant temperature based on the temperature detected by the heater temperature sensor 17a. Is turned on and off. The control temperature is in the range of about 40 to 50 ° C. in view of the characteristics of the a-Si photoreceptor and the purpose of removing moisture, and is preferably about 45 ° C. near the center of the range. And the copier 1
Is set to 43 ° C.

Next, the operation control of the drum heater 17 will be described. FIG. 5 is a block diagram showing an electrical configuration relating to the operation control of the copying apparatus 1. The control means 40 for controlling each electronic member in the copying apparatus 1 to execute image formation includes a central processing unit (CPU) 41 and a program storage device (R
OM) 42, a variable storage device (RAM) 43, and the like. The CPU 41 reads each control program stored in the ROM 42 in response to a power-on signal or an input signal from the operation panel 18, issues an operation instruction to various electronic devices according to the command, reads an output value of the detection means, and reads a specified value. Judge by comparing with. Further, if necessary, data such as settings on the operation panel 18, output values of the detection means, the number of processed sheets, and the count number of the timer are temporarily stored in the RAM 43. The control program includes a power-on control 44, a standby state control 45, a copy operation control 46, and a drum heater control 4.
7, potential correction control 48, fixing temperature control 49, toner density control 50, environment monitor control 51, and the like.

FIG. 6 is a flowchart for explaining the flow of the power-on control 44 when power is supplied to the apparatus main body. FIG. 7 is a timing chart showing the operation state of the apparatus from when the power is turned on to when the apparatus becomes stable until the copy becomes possible. When the power switch of the copying machine 1 is turned on, the output value of the temperature detecting means 20 is read in step S1, and the output value is set to a predetermined value (set temperature of the drum heater 17: 43).
° C). If it is smaller (temperature lower than 43 ° C.), the process proceeds to step S2, where the output value of the humidity detecting means 22 is read, and the magnitude of the output value determined in advance according to the output value of the temperature detecting means 20 is confirmed. If the output value of the humidity detecting means 22 is high (humidity is high), the drum heater 17 is operated and the timer TM1 is started in step S3.

In step S4, the timer TM1 counts until the time t1 has elapsed. The time t1 is the time when the photosensitive drum is operated by the operation of the drum heater 17 even when the photosensitive drum is left for a long time in an environment in which image deletion is most likely to occur under the assumed environmental conditions (assuming about 35 ° C. and about 85%). The time is set to be sufficient for the surface resistance of the surface to be restored to a level that does not cause image deletion. In the copying apparatus 1, the time is set to about 10 minutes. When the timer TM1 reaches t1, the timer TM1 is cleared in step S5, and the process proceeds to the potential correction in step S6.

When the power is turned on, step S10 is started in parallel with the temperature and humidity detection. In step S10, cleaning of the charge wire of the charging device 13 is started, and the fixing lamp 8b for heating the fixing roller 8a provided in the fixing device 8 is turned on. A fixing temperature sensor 8c is arranged close to the surface of the fixing roller 8a, and measures the surface temperature of the fixing roller 8a. In step 11, it is monitored whether the fixing roller 8a reaches a primary stable temperature TR1 (about 165 ° C.) at which the toner melts. Next, in step S12, it is confirmed whether the timer TM1 is operating. If the drum heater 17 is not operating due to the temperature and humidity conditions, TM1 is in a cleared state, and at that time, the process proceeds to step S6, and the potential correction is started.

In the potential correction in step S6, each device of the image forming unit 12 is driven. Here, the motor M1 that drives the image forming unit 12 also drives the fixing device 8, and the fixing roller 8a also rotates at the same time. Further, a voltage is applied to the charging device 13, and the potential of the surface of the photosensitive drum 2 charged by the corona discharge is measured by the potential sensor 16. Here, when the measured surface potential is out of the optimum value, the potential correction control 48 predicts the adjustment amount of the voltage value applied to the charging device to correct the deviation amount, and issues an instruction to the voltage control device. Soup The measured value of the potential sensor 16 is read again to confirm the deviation from the optimal value. If the deviation is out of the range, the adjustment is performed again, and the potential correction is repeated until the optimal value is within a certain range.

Further, even after the fixing device has reached the primary stable temperature TR1, the fixing roller is continuously heated, and the process proceeds to step S.
The process proceeds to step 20, where it is monitored whether or not the temperature reaches the secondary stable temperature TR2 (about 195 ° C.) which is the optimum temperature for fixing the toner image on the sheet. When the temperature reaches the secondary stable temperature TR2, the process proceeds to step S21, and the on / off control of the fixing lamp is started so as to maintain TR2. In step S22, it is confirmed whether the timer TM1 is cleared. If the timer TM1 is cleared, the fixing device is driven in steps S23 and S24 for a predetermined time t2. t2 is performed to make the temperature distribution of the fixing roller uniform. Here, it is set to about 30 seconds. When this is completed, a copy-enabled state is established. The image forming section 12 and the fixing device 8 may be driven by independent motors, respectively, and may be independently rotated only when necessary.

FIG. 8 is a flowchart showing the control of the drum heater 17 after the copying is enabled. The main body control means 40 executes the environmental monitor control 49 at regular time intervals, checks the output values of the temperature detection means 20 and the humidity detection means 22, and according to the preset temperature T1 and each temperature in the case of T1 or less. The operation of the drum heater is determined by comparing the set value of the humidity H1 and the signal is transmitted to the drum heater control 47 according to the result. In the copy operation control, signals at the start and end of copying are transmitted to the drum heater control means. The drum heater control 47 operates the drum heater 17 based on these signals.

Thus, when the power is turned on, the amount of moisture in the environment is always checked, and the drum heater 1 is turned on only when necessary.
7 is activated to prevent image deletion and wasteful power consumption is suppressed. Further, during copying, the drum heater 17 is stopped in consideration of the fact that the photosensitive drum 2 rises due to frictional heat of the cleaning blade 3b or heat of the lamp of the static eliminator 14, so that waste of power consumption is further reduced.

FIG. 9 shows the results of experiments conducted under several environmental conditions on the occurrence of image deletion in the copying apparatus 1 of the embodiment and the effect of preventing image deletion according to the present invention.
The photoreceptor used is a-Si, and its film thickness is about 3
0 μm. Based on past experience, it was predicted that image deletion would occur due to the relationship between temperature and humidity. Therefore, the absolute humidity calculated from the temperature and humidity was set as a reference for image deletion. FIG. 10 is a graph showing the relationship between temperature, relative humidity, and absolute humidity. First, the situation of occurrence of image deletion in the copying apparatus 1 was confirmed in a case where some environments were set and the drum heater was not operated. Based on the results and past empirical knowledge, the absolute humidity at which the occurrence of image deletion was assumed to be a generation limit was predicted to be 17.8 g / m ³ . Then, a value of a criterion of the environmental monitor control 51 is set based on the value,
Using the outputs of the temperature detecting means 20 and the humidity detecting means 22, the above-described control of the drum heater 17 at the time of turning on the power and transition to the copying enabled state was performed, and an experiment for confirming the occurrence of image deletion in each environment was performed again. As a result, although some effects were obtained, image deletion sometimes occurred in some environments.

It is predicted from the experimental results that a difference occurs between the actual environmental temperature and humidity and the measured value of the temperature / humidity detecting means provided in the copying apparatus 1 due to a time delay to the change. And so on. Therefore, it is conceivable that the absolute humidity of the outside air flowing around the photoconductor drum is higher than the predicted value when the power is turned on to the copying machine 1 in the idle state and the fan or the like is operated to flow around the photosensitive drum. In addition, it is considered that the influence of the binding characteristics of the a-Si photoconductor surface with moisture and the influence of the state of adhesion of the discharge product to the photoconductor surface interact with each other. Due to these factors, it is considered that a certain degree of variation in the relationship between the occurrence of image deletion and the absolute humidity is unavoidable depending on the configuration of the image forming apparatus and the usage conditions.

It is conceivable to provide the temperature detecting means and the humidity detecting means in the vicinity of the photoreceptor drum. Is predicted. Therefore, the position shown in FIG. 1 is considered to be an effective position in which the space is easily secured and the design is convenient, and the external environment temperature is most approximately reflected as the installation location of the temperature and humidity detecting means. .
However, it is difficult to predict the delay and some differences with respect to changes in the temperature and humidity in the real environment. Therefore, when the absolute humidity at which the drum heater 17 is operated is set, the effect of reducing the power consumption may slightly decrease, but it is understood that it is necessary to set a lower value in consideration of an error in the measured value.

Therefore, the boundary value of the operation of the drum heater was reexamined. Most image forming apparatuses are used in air-conditioned offices and the like, and it is empirically known that no image deletion occurs in such a comfortable environment. The environmental conditions there are generally 60
% Is expected. From FIG. 10, the absolute humidity at 25 ° C./60% is 13.4 g / m ³ . Then, the operating condition of the drum heater 17 was set to an absolute humidity of 13.5 g / m ³ , the control of the present invention was performed, and an environmental experiment was performed again.

In this confirmation experiment, no image deletion occurred, and almost satisfactory results were obtained. The set value of the absolute humidity at which the drum heater is operated and the control temperature at the time of operation are affected by the characteristics of the photoconductor and the configuration of the machine, and may be set higher than this value. However, in consideration of the fact that the environment in which the image forming apparatus is used is generally an air-conditioned office, economical effects such as reduction in power consumption can be achieved even when the drum heater is operated only when the environment deviates from the environment. It is thought that we can obtain enough. In particular, a great effect can be obtained in a season in which the humidity decreases. In addition, in consideration of the risk of image deletion and economics, the setting values of the absolute humidity and temperature for optimal operation of the drum heater may be changed in accordance with the environment and season of the room where the room is installed. It is also possible to provide a setting mode in which optimum setting values corresponding to the respective settings are set in advance, and allow the user to select the setting mode.

The power consumption of the drum heater 17 is affected by the size of the photosensitive drum and the environmental temperature. In the copying apparatus 1 of the embodiment, the wattage when energized is about 70 W.
Therefore, according to the drum heater control of the present invention, the maximum power consumption during copying can be reduced, and the power consumption can be reduced.

[0040]

From the experiments described above, in the electrophotographic image forming apparatus using the a-Si photoreceptor, the drum heater is always turned on in order to keep the photoreceptor temperature constant and to prevent image deletion. However, in the case of a thin film type a-Si photoreceptor that is hardly affected by temperature characteristics, it is possible to predict an environment where there is a risk of image deletion from temperature and humidity. It can be activated. Further, it can be seen that there is no problem even if the drum heater is stopped because heat is applied to the photosensitive drum during the copying operation. Therefore, by using the drum heater control of the present invention, it is possible to reliably prevent image deletion and reduce power consumption.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a main configuration of a copying apparatus using the present invention.

FIG. 2 is a schematic diagram showing a configuration of a photosensitive drum and an image forming unit around the photosensitive drum of the copying apparatus shown in FIG.

FIG. 3A is a schematic diagram illustrating a configuration of an a-Si photosensitive member. (B) is a graph showing characteristic data in the relationship between the temperature and the surface potential of the a-Si photoconductor.

FIG. 4 is a schematic cross-sectional view in the drum axis direction for explaining the configuration of a drum heater provided inside the photosensitive drum.

FIG. 5 is a block diagram illustrating an electrical configuration related to operation control in the copying apparatus of FIG. 1;

FIG. 6 is a flowchart for describing control in the copying apparatus of FIG. 1 from power-on to a copy enabled state.

7 is a timing chart showing an operation state of a drum heater and the like in the copying apparatus shown in FIG.

FIG. 8 is a flowchart illustrating control of a drum heater after a copy enabled state in the copying apparatus of FIG. 1;

FIG. 9 shows an experimental result of confirming occurrence of an image deletion phenomenon in each environment using the control unit of the present invention in the copying apparatus of FIG.

FIG. 10 is a psychrometric chart showing absolute humidity values at temperature and relative humidity.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming device 2 photoreceptor drum 3 cleaning device 4 developing device 5 transfer device 12 image forming unit 13 charging device 14 static eliminator 15 transfer unit 16 potential sensor 17 drum heater 20 temperature detecting means 22 humidity detecting means

Claims (4)

[Claims] An image forming apparatus of a type in which an electrostatic image formed on the surface of an a-Si photosensitive drum is formed into a toner image by a developing device and then transferred onto a sheet, wherein the electrostatic image is formed in the image forming device. Is provided with respective detecting means for detecting the ambient temperature and humidity of the environment in which the image forming apparatus is placed, and a drum heater device for increasing the surface temperature is provided for the photosensitive drum. An image forming apparatus comprising: a control unit that operates the drum heater device based on a detection result by the temperature detection unit and the humidity detection unit in a power-on state of the apparatus. 2. The control means activates the drum heater device for a predetermined time when it is determined from the detection results of the humidity detection device and the temperature detection device that the heater device needs to be activated when the power is turned on. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus shifts to an image formable state after the image formation. 3. The method according to claim 1, wherein the control means determines the absolute humidity from the detection results of the temperature detecting means and the humidity detecting means, and activates the drum heater device when the absolute humidity is equal to or more than a predetermined value. The image forming apparatus according to claim 1. 4. An image forming apparatus according to claim 1, wherein said control means keeps said drum heater device in a stopped state during image forming processing.