JPH04253079A - electrophotographic equipment - Google Patents

Abstract

PURPOSE:To always obtain an image with stable density even in first copying after energization is started by changing the ratio of the power consumption of a photosensitive body heater to that of a fixing part heater according to the temp. of the surface of a photosensitive body and a fixing part. CONSTITUTION:The temperatures of the surface of the photosensitive body and the fixing part of a fixing unit are always monitored by respective temp. sensors 3 and 4. While keeping the sum of the power consumption of the photosensitive body heater 1 and the fixing part heater 2 constant, based on the monitored temperatures and a target temp., the ratio of the consumption power of the heaters 1 and 2, is changed. Therefore, the temperatures of the surface of the photosensitive body and the fixing part can almost simultaneously, reach the target temp. in a short time, regardless of external environment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus having a photoreceptor having a photosensitive layer containing silicon atoms on a conductive substrate.

0002

2. Description of the Related Art Conventionally, single-layer or multi-layer organic photoconductive materials using organic semiconductors such as polyvinylcarbazole have been widely used as photosensitive layers of electrophotographic photoreceptors. However, in recent years, amorphous silicon (hereinafter referred to as a-Si) semiconductors, which have excellent mechanical durability, moisture resistance, corona ion resistance, sensitivity, etc. and are also non-toxic, have been used as photoconductive materials. Electrophotographic photoreceptors are actively being developed and put into practical use.

A copying apparatus and an image forming process using such an a-Si photoreceptor are roughly as follows. FIG. 2 is a schematic diagram showing the image forming process of a copying machine using an a-Si photoreceptor, in which the photoreceptor rotates in the direction of arrow 11, as is well known, there are a main charger 12, an electrostatic latent image forming area 13, a developer 14, a transfer paper feeding system 15, a transfer charger 16a, a separation bander 16b, and a cleaner 17. , a transfer paper conveyance system 18, a static elimination light source 19, and the like are arranged.

The image forming process will be explained below using an example. The surface photosensitive layer of the photoreceptor 11 is uniformly charged by the main charger 12 to which a high voltage of +6 to 8 KV is applied. ~5000lm/
Light emitted by a light source 20 such as a W halogen lamp is irradiated onto the original 22 on the platen glass 21, and the reflected light is directed to the surface of the photoreceptor through a lens system 27 containing mirrors 23, 24, 25, 26 and a filter 28. The toner is guided upward and projected to form an electrostatic latent image, and a negative polarity toner is supplied to this latent image from the developing device 14 to form a toner image.

On the other hand, the transfer paper path 29 and the registration roller 3
The transfer material P is supplied toward the photoreceptor through the transfer paper supply system 15 consisting of 1, from the back side in the gap between the photoreceptor 11 and the transfer charger 16a to which a high voltage of +7 to 8 KV is applied.
A positive electric field having a polarity opposite to that of the toner is applied, whereby the negative polarity toner image on the surface of the photoreceptor is transferred to the transfer material P.

[0006]Also 12~14KVP-P, 300~60
The transfer material P passes through the transfer paper conveyance system 18 and is transferred to the fixing device (
(not shown), the toner image is fixed in the heated fixing section and is discharged from the apparatus. Note that residual toner that does not contribute to the transfer and remains on the surface of the photoreceptor at the transfer site is removed by Cleaner 1.
7 and is cleaned by the cleaning blade 30.

The surface of the photoreceptor renewed by the above-mentioned cleaning is further subjected to charge-eliminating exposure from the charge-eliminating light source 19 and subjected to the same cycle again. In addition, the image forming process on the photoreceptor 11 in electrophotography usually includes a step of charging and removing electricity from the surface of the photoreceptor, and the charge removal device used is a corona discharger (corotron), which has excellent uniform charge removal properties. Scorotron) is widely used.

However, corona dischargers generate ozone (O3) as a result of corona discharge. The generated ozone oxidizes nitrogen in the air to produce nitrogen oxides (NOX) and the like. Furthermore, the produced nitrogen oxides and the like react with moisture in the air to produce nitric acid (HNO3) and the like.

Corona products have strong hygroscopicity, and the surface of the photoreceptor and the image carrier surface to which they have adhered have a lower resistance due to the moisture absorption of the adhered corona products, and the charge retention ability (surface resistance) of the surface has decreased completely or partially. This tends to result in a state in which the surface area is substantially reduced, resulting in blurring of the output image,
The phenomenon of so-called image deletion, in which charges on the surface of the photoreceptor move (leak) in the in-plane direction, causing the electrostatic charge latent image pattern to collapse or not be formed, is observed.

In order to prevent such image blurring, a heater is provided on the inner surface of the photoreceptor to heat or keep the surface of the photoreceptor in a dry state, thereby reducing moisture absorption of adhered corona products. This suppresses the substantial reduction in resistance of the photoreceptor surface due to this.

In the recent office automation market, the demand for ultra-high-speed heavy-duty machines is increasing as the amount of copies taken in offices increases, and a-Si, which has excellent stability and wear resistance, is being used. The photoreceptor system is considered to be the most suitable for this ultra-high-speed electrophotographic device, and the current situation is that development is progressing to install it in even higher-speed devices.

[0012] Also, like a normal power supply of 100V, 15A,
At the same time, it is also required that the equipment can be used within 1.5KW, and further performance improvement of low power consumption high speed electrophotographic equipment must be achieved in order to meet the strong demands of the market. be.

[0013]

[Problems to be Solved by the Invention] Although good electrophotographic images can be obtained by the above-mentioned conventional method, there is a strong demand in the market for further improvement in the image quality of electrophotographic images due to strong demands for safety such as fire prevention. Power off on holidays
Immediately after the power is turned on, the aforementioned photoreceptor heater does not function sufficiently and the density of the image gradually changes, which has even been pointed out as a problem to be solved.

Normally, even when the main switch of an electrophotographic apparatus using an a-Si photoreceptor is turned off, when power is supplied to the electrophotographic apparatus, the surface of the photoreceptor is kept at an appropriate temperature. The photoconductor heating heater is configured to be energized to maintain the temperature. When the main switch is turned on in this state, the heater of the fixing device is energized to raise the temperature of the fixing section, and when the temperature reaches the appropriate temperature, it becomes possible to make a copy. In other words, the wait-up is completed. At this time, since the surface temperature of the photoreceptor is always at an appropriate temperature, no change in image density occurs.

On the other hand, power is not supplied to the electrophotographic apparatus by turning off the power circuit breakers for the entire floor at night, and the electrophotographic apparatus is not supplied with power to the electrophotographic apparatus when both the photoreceptor and the fixing section of the fixing device have cooled to about room temperature. If power is supplied and the main switch is turned on at almost the same time,
The temperature of the photoconductor and the fixing section start rising at the same time, and there is a difference in the time it takes to reach the appropriate temperature.

This time not only varies depending on the power consumption of the photoreceptor heating heater and the fuser heater, the material of the fuser, the material of the substrate used for the photoreceptor, but also the ambient temperature (inside the electrophotographic apparatus). temperature).
It has been impossible to make the surface temperature of the photoreceptor and the temperature of the fixing section reach appropriate temperatures at the same time.

Therefore, if the wait-up is completed when the temperature of the fixing section reaches the appropriate temperature, the surface of the photoconductor will change as shown in the fixing section temperature curve a and the photoconductor surface temperature curve b in FIG. The temperature continues to rise until it reaches the appropriate temperature (section B in FIG. 3).

In the a-Si photoconductor, the temperature dependence of the dark potential and bright potential is -4 to -9 V/deg and -1 V/deg, respectively.
．． Since it is about 5 to 4 V/deg, the surface temperature of the photoreceptor is 10°C lower than the appropriate temperature at the end of the weight-up.
If it is low, after the wait-up, the dark potential will be -
Since a potential change of 40 to -90 V and a bright potential of -15 to -40 V occurs, the electrophotographic image gradually becomes thinner, and no density change occurs for the first time in the region C in FIG. 3.

On the other hand, if the wait-up is completed when the surface temperature of the photoconductor reaches the appropriate temperature, the temperature of the fixing section may not reach the appropriate temperature, as shown in FIG. The toner transferred onto the paper is not fixed and is ejected from the apparatus.

As a means of solving these problems, there is a method in which the weight-up is terminated when both the surface temperature of the photoreceptor and the temperature of the fixing section reach appropriate temperatures. In the area B in FIG. 4, a loss of time and power consumption occurs. Another way to shorten the time during weight-up is to use a heater with a higher power rating, but in this case, the rated power consumption of the electrophotographic device increases, and it is commonly used in offices. This poses a problem in that it becomes difficult to install.

The present invention aims to solve the above problems. That is, an object of the present invention is to provide an electrophotographic apparatus that can always obtain images with stable density regardless of usage conditions or external environment.

[0022]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a photoreceptor having a photosensitive layer containing silicon atoms on a conductive substrate, a temperature sensor for measuring the surface temperature of the photoreceptor, In an electrophotographic apparatus, the electrophotographic apparatus includes a temperature control means for adjusting the surface temperature of the photoreceptor, a temperature sensor for measuring the temperature of a fixing section of a fixing device, and a temperature control means for adjusting the temperature of the fixing section. The difference between the surface temperature of the photoreceptor and the target temperature is compared with the difference between the temperature of the fixing section and the target temperature, and the ratio of the amount of power supplied for heating the photoconductor and the amount of power supplied for heating the fixing section is determined accordingly. It is assumed that there is a means to change it.

[0023]

[Operation] According to the present invention, the surface temperature of the photoconductor and the temperature of the fixing section of the fixing device are constantly monitored, and the power consumption of the heater for heating the photoconductor and the heating of the fixing section are determined based on these values and the target temperature. By keeping the sum of the power consumption of the heater constant and changing their ratio, the surface temperature of the photoconductor and the temperature of the fusing part can be adjusted.
Regardless of the external environment, the target temperature can be reached almost simultaneously and in the shortest possible time.

[0024]

[Embodiment] Figure 1 shows a first embodiment of the present invention.
FIG. 3 is an explanatory diagram schematically showing a mechanism for heating a photoreceptor and a heating unit. In FIG. 1, 1 is a heater for heating the photoconductor, 2 is a heater for heating the fixing section, 3 is a temperature sensor for measuring the temperature of the surface of the photoconductor, and 4 is a temperature sensor for measuring the temperature of the fixing section. A sensor, 5, a photoconductor power supply control circuit for comparing the temperatures of the photoconductor and the fixing section to determine and control the power supplied to the heater 1 for warming the photoconductor; 6, the photoconductor and the fixing section; 7 is an AC power source that supplies power to both the heaters 1 and 2. .

The heating mechanism shown in FIG. 1 was installed in a copying machine NP-6150 manufactured by Canon Inc., and a first experiment was conducted to examine the temperature rise of the photoreceptor and fixing section. however,
The heater 1 for heating the photoreceptor had a maximum rating of 200 W, and the heater 2 for heating the fixing section had a maximum rating of 2000 W. Further, the total power consumption of both heaters 1 and 2 was set to within 1300W.

[0026] Figures 5 and 6 show room temperature of 23°C and humidity of 60%.
5 shows the temperature changes of the photoconductor and the fixing section, and FIG. 6 shows the power consumption of the heater 1 for warming the photoconductor (curve d) and the temperature change of the fixing section. It shows the power consumption (curve c) of the heater 2 for heating.

The surface temperature of the photoreceptor and the temperature of the fixing section are as follows:
Both reached the target temperature in 4 minutes, and then maintained the target temperature. In this experiment, the heating mechanism was controlled according to the flow shown in FIG. 7, but this is just an example.
You may change it as appropriate.

FIG. 8 shows the temperature changes of the photoreceptor and fixing section when the second experiment was conducted in an environment with a room temperature of 15.degree. C. and a humidity of 10%. FIG. 9 shows the power consumption of the heater 1 (curve d) and the power consumption of the heater 2 (curve c) when an experiment was conducted under the same environment as FIG. 8. In FIG. 8, the surface temperature of the photoreceptor and the temperature of the fixing section both reached the target temperature in 5 minutes, and thereafter maintained the target temperature.

As a third experiment, when copying was started immediately after the temperature of the photoreceptor and fixing section reached the target temperature under the same conditions as in FIGS. 8 and 9, at a room temperature of 15° C. and a humidity of 10%. FIG. 10 shows the temperature changes of the photoreceptor and the fixing section, and FIG. 11 shows the changes of the power consumption of both heaters 1 and 2.

Copying was performed at a speed of one A4 sheet of paper every 2 seconds. Until the end of the wait-up, the surface temperature of the photoreceptor, the temperature of the fixing section, and the power consumption of each heater 1 and 2 all show the same changes as shown in FIGS. 8 and 9, but after the start of copying, Since the heat of the photoreceptor and the fixing section is absorbed by the copy paper, the power consumption of each heater 1 and 2 increases. However, the temperatures of the photoconductor and the fixing section maintain the target temperature and are stable.

[0031] Also, at this time, in the copied image,
A fourth experiment was conducted to examine changes in reflection density. Figure 12
The figure shows the change in the density of the copy image that corresponds to the part where the reflection density is 0.3 on the original paper chart. The reflection density of the copy image is 0.35-0.
It varied within the range of 42.

As a fifth experiment, a copying machine NP-6150 manufactured by Canon Inc. was used without the heating mechanism shown in FIG. After turning on the power, immediately turn on the main switch.
After the wait-up is finished, start copying immediately.
The reflection density of the copied image was measured. Copy A every 2 seconds
This was done at the speed of 4 sheets per sheet. At the start of copying, the temperature of the fixing section had reached the target value of 190°C, but the surface temperature of the photoreceptor was 35°C, which was 10°C lower than the target value of 45°C.

FIG. 13 shows the measurement of the density of the copy image at a portion corresponding to a reflection density of 0.3 on the original paper chart.
This shows the changes. At the start of copying, the reflection density was 0.47, but after that, the density gradually decreased, and the decrease in density stopped after about the 100th copy. copy 20
The density change at the 0th sheet was in the range of 0.30 to 0.47.

FIG. 14 shows a second embodiment of the invention. That is, the figure schematically shows the heating mechanism shown in FIG. 1 in which the development potential adjustment mechanism according to the present invention, which adjusts the development potential based on the temperature dependence of the photoreceptor surface temperature and the photoreceptor surface potential, is added. It is something.

In FIG. 14, 8 is a memory for storing the temperature dependence of the surface potential of the photoreceptor, and 9 is a developing device for adjusting the development potential from the temperature dependence of the photoreceptor and the surface temperature of the photoreceptor. The potential control section 10 is a developing device. The heating mechanism and developing potential control mechanism shown in FIG. 14 were installed in a copying machine NP-6150 manufactured by Canon Inc. The development potential control section 9 incorporates a program that adjusts the development potential using the following equation.

(Development potential) = (Reference development potential) - {(Photoconductor target temperature) - (Photoconductor temperature)} x (Temperature dependence of the bright potential of the photoconductor) The bright potential of the photoconductor used in the experiment Temperature dependence is -2.4V
/deg, this value was input into the memory 8 in FIG.

The copying machine NP- modified as described above
6150 in an environment with a room temperature of 15°C and a humidity of 10%, immediately turn on the main switch and turn on the main switch.
After the wait-up is finished, start copying immediately.
The reflection density of the copied image was measured. Copy A every 2 seconds
This was done at a speed of 4 sheets per sheet. At the start of copying, the temperature of the fixing section had reached the target value of 190°C, and the surface temperature of the photoreceptor was the target value of 45°C.

FIG. 15 shows the measurement of the density of the copy image in a portion corresponding to a reflection density of 0.3 on the original paper chart.
This shows the changes. The density change of the copied image was within the range of 0.39 to 0.42, confirming the effect of the heat development potential adjustment mechanism shown in FIG. 14.

As a sixth experiment, a heating mechanism shown in FIG. 1 was attached to a copying machine NP-7550 manufactured by Canon Inc.
The heater 1 for heating the photoconductor has a maximum rating of 200 W, and the heater 2 for heating the fixing section has a maximum rating of 2000 W. Immediately after turning on the power to the copying machine in an environment with a room temperature of 15° C. and a humidity of 10%. An experiment was conducted in which the main switch was turned on, copying was started immediately after the wait-up was completed, and the reflection density of the copied image was measured. The first 200 copies are made at a speed of 30 A4 sheets per minute, then 500 copies are made at a speed of 50 A4 sheets per minute.
After that, 200 copies were made again at a speed of 30 A4 sheets per minute. The total power consumption of both heaters 1 and 2 was set to be within 1300W.

FIG. 16 shows the changes in the density of the copy image measured in areas corresponding to reflection densities of 0.3 and 1.1 on the original paper chart. Changes in reflection density are 0.34-0.42 and 1.36-1.42, respectively.
It was within the range of. Further, the image characteristics such as image blurring and fogging were also good without any problems.

In order to compare with the sixth experimental example, as a seventh experiment, changes in copy density were investigated using a copying machine NP-7550 manufactured by Canon Inc. without any modification under the same conditions as in the above experimental example. FIG. 17 shows the changes in the density of the copy image measured on the original paper chart in areas corresponding to reflection densities of 0.3 and 1.1. The changes in reflection density were 0.33 to 0.50 and 1.36 to 1.46, respectively. In particular, changes in reflection density depending on usage conditions were clearly evident, such as a monotonous drop in reflection density immediately after copying started, and an increase in reflection density during continuous copying.

As an eighth experiment, a copying machine NP-8580 manufactured by Canon Inc. was equipped with the heating and developing potential regulator shown in FIG.
0W, and the heater 2 for heating the fixing section has a maximum rating of 2.
000W, and turn on the main switch immediately after turning on the power to the copier in an environment with a room temperature of 15°C and a humidity of 10%.
Immediately after the wait-up was completed, copying was started and the reflection density of the copied image was measured. For the first 200 copies, single-sided copying was performed at a speed of 30 A4 sheets per minute, followed by continuous double-sided copying of 500 sheets at a speed of 50 A4 sheets per minute. In this eighth experiment as well, the total power consumption of both heaters 1 and 2 was kept within 1300W.

FIG. 18 shows the changes in the density of the copy image measured in areas corresponding to reflection densities of 0.3 and 1.1 on the original paper chart. Changes in reflection density are 0.37-0.41 and 1.38-1.44, respectively.
It was within the range of. Further, the image characteristics such as image deletion and fogging were also good without any problems.

In order to compare with the above-mentioned 8th experiment, as a 9th experiment, changes in the density of a copied image were investigated under the same conditions as in the above-mentioned 8th experiment without making any modifications to a copying machine NP-8580 manufactured by Canon Inc. FIG. 19 shows the changes in the density of the copy image measured on the original paper chart in areas corresponding to reflection densities of 0.3 and 1.1. The changes in reflection density were 0.34-0.52 and 1.38-1.
It was 48. In particular, immediately after the start of copying, the reflection density monotonically decreased, and during double-sided copying, the reflection density increased, which clearly showed changes in reflection temperature depending on usage conditions.

[0045]

[Effects of the Invention] As explained above, according to the present invention,
The power consumption ratio of the heater for heating the photoconductor and the heater for heating the fusing section is changed according to the surface temperature of the photoconductor and the temperature of the fusing section, and the surface temperature of the photoconductor and the temperature of the fusing section are simultaneously targeted. Since this value can be reached, an image with stable density can always be obtained even in the first copy after the electrophotographic apparatus starts to be energized.

Furthermore, by adjusting the developing potential based on the temperature dependence of the surface temperature and surface potential of the photoreceptor, it is possible not only to obtain an image with a more stable density, but also to ensure that the photoreceptor is Since image forming rotation starts after reaching a predetermined temperature, there is no chance of the cleaner blade tipping over due to increased frictional resistance on the surface of the photoreceptor due to dew condensation, etc.
The average life of the blade is also increased.

Furthermore, since electricity can be cut off at night or on holidays, it is possible to ensure the safety of offices in high-rise buildings and the like.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a heating mechanism in a first embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a conventional electrophotographic apparatus.

FIG. 3 is an explanatory diagram showing one example of an increase in the photoconductor surface temperature and the fixing unit temperature.

FIG. 4 is an explanatory diagram showing another example of increase in photoreceptor surface temperature and fixing unit temperature.

FIG. 5 is an explanatory diagram showing the photoreceptor surface temperature and fixing unit temperature in the first experiment.

FIG. 6 is an explanatory diagram showing the power consumption of a heater for heating a photoconductor and the power consumption of a fixing section heater in the first experiment.

FIG. 7 is an explanatory diagram of the flow in the first experiment.

FIG. 8 is an explanatory diagram showing the photoreceptor surface temperature and fixing unit temperature in a second experiment.

FIG. 9 is an explanatory diagram showing power consumption of a heater for heating a photoconductor and power consumption of a heater for heating a fixing section in a second experiment.

FIG. 10 is an explanatory diagram showing the surface temperature of the photoreceptor and the temperature of the fixing section in the third experiment.

FIG. 11 is an explanatory diagram showing the power consumption of a heater for heating a photoreceptor and the power consumption of a heater for heating a fixing section in a third experiment.

FIG. 12 is an explanatory diagram showing reflection density in a fourth experiment.

FIG. 13 is an explanatory diagram showing reflection density in a fifth experiment.

FIG. 14 is an explanatory diagram showing a heating mechanism and a developing potential adjustment mechanism in a second embodiment of the present invention.

FIG. 15 is an explanatory diagram of the effect of the apparatus of FIG. 14;

FIG. 16 is an explanatory diagram showing reflection density in a sixth experiment.

FIG. 17 is an explanatory diagram showing reflection density in a seventh experiment.

FIG. 18 is an explanatory diagram showing reflection density in an eighth experiment.

FIG. 19 is an explanatory diagram showing reflection density in a ninth experiment.

[Explanation of symbols]

1: Heater for heating the photoreceptor 2
: Heater for heating the fixing section 3: Temperature sensor for measuring the surface temperature of the photoconductor 4: Temperature sensor for measuring the temperature of the fixing section 5: Supply power control circuit for the photoconductor 6: Supply power control circuit for the fixing section

Claims (2)

[Claims] 1. A photoreceptor having a photoreceptor layer containing silicon atoms on a conductive substrate, a temperature sensor for measuring the surface temperature of the photoreceptor, a temperature control means for adjusting the surface temperature of the photoreceptor, and a fixing device. In an electrophotographic apparatus having a temperature sensor that measures the temperature of a fixing section of a device, and a temperature control means that adjusts the temperature of the fixing section, the difference between the surface temperature of the photoreceptor and a target temperature and the temperature of the fixing section An electrophotographic apparatus, comprising means for comparing a difference in target temperature and changing the ratio of the amount of power supplied for heating the photoreceptor and the amount of power supplied for heating the fixing section accordingly. 2. Claim 1, further comprising memory means for storing the temperature dependence of the surface potential of the photoreceptor, and means for adjusting the developing potential based on the surface temperature and temperature dependence of the photoreceptor. The electrophotographic device described.