JPH07140809A - Image forming device - Google Patents

Abstract

PURPOSE:To apply appropriate transfer bias in accordance with a condition by causing a constant current to flow to a transfer electrode, measuring an applied voltage value and changing the transfer bias in accordance with the voltage value. CONSTITUTION:When an attracting roller 8 does not come into contact with a destaticizing roller 9 in the midst of prerotation at the time of turning on a power source, that is, when only a photoreceptor drum 3 is opposed to a transfer drum 2, a transfer constant-voltage power source 31 is switched to a transfer constant-current power source 32, and the specified constant current is made to flow to the drum 2, and the voltage at that time is measured. Since the rollers 8 and 9 do not abut on the drum 2, the current all flows from the drum 2 to the drum 3. Therefore, when the film thickness of the drum 3 and that of the dielectric layer 23 of the drum 2 are changed, the voltage value is changed. By previously preparing a transfer bias table corresponding to each voltage value, the transfer bias corresponding to the measured voltage value is impressed by the power source 31 through a control circuit 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a page printer. In particular, it relates to a multicolor image forming apparatus capable of forming a color image by using a developing device of a plurality of colors on an electrostatic latent image carrier, and more specifically, by transferring a transfer material around a transfer drum to perform multiple transfer, The present invention relates to a multicolor image forming apparatus provided with a means for forming a color image on a material.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus, an electrophotographic system for performing multiple transfer as shown in FIG. 18 has been widely used. Image carrier 1 used as an electrophotographic photosensitive drum
Reference numeral 03 rotates in the direction of the arrow, and is uniformly charged by the charging means 110, and thereafter, a laser exposure device 111 or the like irradiates a light image to form an electrostatic latent image on the photosensitive drum 103.
The latent image is developed by developing devices 101a and 101b, each of which stores a color developer such as yellow (Y), magenta (M), cyan (C), and black (Bk) carried by a rotatable support, A visible image, that is, a toner image is formed at 101c and 101d.

On the other hand, the transfer material 107 is fixed and conveyed by a gripper 105 on the surface of a transfer device 102 having a drum shape, for example, and electrostatically adsorbed by a suction device 108 to be held on the transfer drum 102. Photosensitive drum 103
The upper toner image is transferred onto the transfer device, that is, the transfer material 7 wound around the transfer drum 102 in this example.

To further explain, first, the electrostatic latent image formed on the photosensitive drum 103 by exposure determined by the image signal of the first color is visualized by, for example, a developing device 101a containing a yellow (Y) developer, The image is transferred onto the transfer material 7 held on the transfer drum 102. Then, the photosensitive drum 10
After cleaning the residual developer on No. 3 with the cleaner 112, an electrostatic latent image of the second color is formed on the photosensitive drum 103 by exposure based on the image signal of the second color, and for example, a magenta (M) developer is included. After being visualized by the developing device 101b, the yellow visible image of the first color is transferred onto the transfer material 107 on the transferred transfer drum 102 in an overlapping manner. Next, the same method as described above is repeated, and, for example, the toner images of cyan (C) as the third color and black (Bk) as the fourth color are superimposed and transferred onto the transfer material 107 on the transfer drum 102. Thereafter, the transfer material 107 is discharged by the separation charge-eliminator 106, separated from the transfer drum 102 by the separation claw 114, and fixed by the fixing device 104 to obtain a permanent image.

Transfer drum 102 after transfer material 107 is separated
The transfer cleaner 113 removes the developer adhering to the surface of the transfer body, and the charge removal device 109 removes the charge to electrically initialize it.

In the color image forming apparatus for carrying out the multiple transfer as described above, when the toner image on the photoconductor is transferred to the transfer material, the transfer drum is uniformly charged, and the toner is generated by the potential difference from the photoconductor. Is transferred to the transfer material. However, if the photoconductor is scraped off by a cleaning blade or the like and the film thickness is reduced, the electrostatic capacitance of the photoconductor becomes large, and if the surface of the transfer drum is scraped by passing paper, the electrostatic capacitance of the transfer drum becomes large and And the potential difference on the transfer drum increases. When the potential difference between the photoconductor and the transfer drum is too large, the transfer efficiency is deteriorated, and it becomes impossible to obtain a high-quality image such as the occurrence of jumping. For this reason, conventionally, constant current control has been performed so that the current flowing through the corona charger has a constant value.

[0007]

However, in the above-mentioned constant current control, the elastic layer 22 is provided on the aluminum core bar 21 as shown in FIG. 19, and the dielectric layer 23 is further coated on the elastic layer 22. There is a problem that it is difficult to apply it to a transfer drum having a structure (hereinafter referred to as a solid transfer drum). This is a structure in which a conventional transfer drum has a structure in which a dielectric sheet 102b is wound around a cylinder 102a whose central portion is cut out as shown in FIGS. 21 and 22, and transfer, adsorption, and static elimination bias are independent. On the other hand, in the solid transfer drum, since the dielectric layer 23 and the elastic layer 22 are supported by the aluminum core bar 21 as shown in FIGS.
The adsorption and static elimination bias cannot be made independent. For this reason, the adsorption bias and the static elimination bias may be superposed on the transfer bias, and the counter electrode of the transfer drum may not be only the photoconductor. Therefore, where the current actually flows even if the current is measured. Is unknown.

Therefore, an object of the present invention is to provide an image forming apparatus equipped with a solid transfer drum which can apply an appropriate transfer bias according to the conditions of the image carrier and the transfer means.

[0009]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
An electrostatic latent image is formed on the image carrier, and a visible image forming unit that visualizes the image with toner, and a transfer material is adsorbed on the surface dielectric layer, and the transfer material is brought into contact with the image carrier. In an image forming apparatus having a rotatable transfer means for electrostatically transferring a visible image on the image carrier onto a transfer material by means of a transfer electrode provided on the back surface of the dielectric layer, the transfer electrode of the transfer means is fixed. The image forming apparatus is characterized in that a current value is applied to measure an applied voltage value and a transfer bias is changed according to the voltage value.

According to another aspect of the present invention, a latent image forming means for forming an electrostatic latent image on the image bearing member and visualizing the latent image with toner, and a transfer material is adsorbed on the dielectric layer on the surface. And an image forming apparatus having a rotatable transfer unit that electrostatically transfers the visible image on the image carrier onto a transfer material by a transfer electrode provided on the back surface of the dielectric by contacting the image carrier with the image carrier. In the image forming apparatus, a constant voltage is applied to the transfer electrode of the transfer unit to measure a flowing current value, and the transfer bias is changed according to the current value.

The measurement is preferably performed during the pre-rotation.

Further, it is preferable that the measurement is performed after the printing operation is started and before the transfer material is held on the transfer means.

Further, it is preferable that the measurement is performed during a test print performed after the pre-rotation.

Further, it is preferable that the measurement is carried out while the margin portion of the front end of the transfer material passes through the image carrier.

Preferably, a toner image for density measurement is formed on the transfer drum or the transfer material for each color, and the density is detected by a density detection sensor for measuring reflected light, and the image density is determined by the detection result. Control and the measurement is performed during the concentration detection.

Preferably, the temperature and humidity of the atmosphere are detected, and the transfer bias is corrected based on the detection result.

Preferably, the thickness of the transfer material is detected, and the transfer bias is corrected based on the detection result.

[0018]

Embodiments of the image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIGS. 1 and 2 show an electrophotographic color image forming apparatus which is an embodiment of the image forming apparatus according to the present invention.
This color image forming apparatus has the same structure as the color image forming apparatus shown in the conventional example, except that the transfer apparatus has an elastic layer 22 also serving as a transfer electrode on an aluminum cored bar 21, and a transfer material on the surface. It is a solid transfer drum provided with a dielectric layer 23 for adsorption, and is different in that the adsorption device 8 and the static eliminator 9 are of a contact charging type.

This is because the use of a solid transfer drum extends the life of the dielectric layer, and the adsorption and neutralization device has a contact charging system, which is effective in ozone-less.

In this color image forming apparatus, the image bearing member 3, which is an electrophotographic photosensitive drum, rotates in the direction of the arrow and is uniformly charged by the charging means 10, and then the laser exposure device 1 is used.
The light image is irradiated by 1 or the like to form an electrostatic latent image on the photosensitive drum 3. The latent image is developed by developing devices 1a and 1b, each of which contains a color developer such as yellow (Y), magenta (M), cyan (C), and black (Bk) carried by a rotatable support. 1c, 1d visible image,
That is, it is a toner image.

On the other hand, the transfer material 7 is fixed and conveyed by the gripper 5 on the surface of the transfer device 2 having a drum shape, for example, and electrostatically adsorbed by the adsorbing device 8 to be held on the transfer drum 2. The toner image on the photosensitive drum 3 is transferred onto the transfer device, that is, the transfer material 7 wound around the transfer drum 2 in this example. After that, the transfer material 7 is discharged by the separation charge-eliminating device 6, separated from the transfer drum 2 by the separation claw 14, and a permanent image is obtained by the fixing device 4.

After the transfer material 7 has been separated, the transfer drum cleaner 13 removes the developer adhering to the surface of the transfer drum 2, and the charge removal device 9 removes the charge to electrically initialize the transfer drum 2.

In a color image forming apparatus for performing such multiple transfer, the photosensitive drum is scraped by a cleaning blade or the like to increase the electrostatic capacity of the photosensitive drum, or the surface of the transfer drum is scraped by passing a sheet of paper, resulting in electrostatic charge of the transfer drum. When the capacity becomes large, the potential difference between the photosensitive drum and the transfer drum becomes large, which causes a decrease in transfer efficiency and a flyback. Therefore, it is necessary to control the potential difference between the photosensitive drum and the transfer drum to a constant potential difference, but as described above, it is difficult to control the constant current with the solid transfer drum.

Therefore, the present inventors performed control as shown in FIG. In FIG. 1, a constant voltage transfer power source 31 and a constant current transfer power source 32 are selectively switchably connected to the transfer drum 2, and a voltage for measuring a voltage when a current flows in the constant current transfer power source 32. A total of V is connected. The measurement result of the voltmeter V is input to the control circuit 33, and the control circuit controls the constant voltage transfer power supply 31. An attraction power source 38 is connected to the attraction roller 8 and a charge elimination power source 39 is connected to the charge elimination roller 9.

More specifically, when the power supply is turned on and the adsorbing roller 8 and the discharging roller 9 are not in contact with each other during the pre-rotation, that is, when the transfer drum 2 faces only the photosensitive drum 3, the transfer constant voltage power supply 31 is set. The current source 32 is switched to, a specific constant current is passed through the transfer drum 2, and the voltage at that time is measured. The current passed here flows entirely from the transfer drum 2 to the photosensitive drum 3 because the attraction roller 8 and the discharging roller 9 are not in contact with the transfer drum 2. Therefore, if the film thickness of the photosensitive drum 3 or the film thickness of the dielectric layer 23 of the transfer drum 2 changes, the voltage value changes. Further, the voltage value also changes due to the resistance change of the dielectric layer 23 of the transfer drum 2 and the like due to the environment. Then, a transfer bias table corresponding to each voltage value is prepared in advance, and the transfer bias corresponding to the measured voltage value is supplied to the constant voltage power supply 31 via the control circuit 33.
Apply more.

In this embodiment, the photosensitive drum is a negatively charged OP.
A transfer drum having a thickness of 25 μm and a charge transfer layer (hereinafter referred to as CT layer) provided on the charge generation layer is used as a transfer drum. Elastic body 2 with 5 mm and volume resistance of 10 ⁴ Ω · cm or less
2 is sprinkled on it, and the thickness is 75 μm and the volume resistance is 10 ¹⁴ -1.
The one coated with the dielectric substance 23 of 0 ¹⁶ Ω · cm was used.
At this time, when a constant current of 10 μA was applied to the transfer drum and the above voltage was measured, V = 1320V, and the optimum transfer bias for the first color was Vbest = 1050V. If a photosensitive drum having a CT layer thickness of 23 μm is used, V
= 1110V, Vbest = 960V, and if the CT layer thickness of the photosensitive drum is 17 μm, V = 950
V, Vbest = 820V. Also, CT of the photosensitive drum
When the layer thickness is 25 μm and the dielectric thickness is 60 μm, the voltage is V = 1040V, the optimum transfer bias for the first color is Vbest = 900V, and the dielectric film thickness is 50.
If the one with μm is used, V = 900V, Vbest = 790
It was V.

FIG. 3 is a graph showing the voltage and the optimum transfer bias for the first color based on the above measurement results.
It can be seen that there is a correlation between the voltage and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

As a result, the same transferability can always be obtained even if the film thickness of the dielectric layer of the photosensitive drum or the transfer drum changes.

It is preferable that the temperature and humidity sensor detect the atmosphere and the table is changed according to the detection result. This makes it possible to correct the resistance change of the transfer material due to the temperature and humidity of the atmosphere.

Further, it is more preferable that the thickness of the transfer material is detected by a conventionally known means and the table is corrected based on the detection result. Accordingly, it is possible to correct the difference in resistance value between the transfer materials.

Second Embodiment A second embodiment according to the present invention will be described with reference to FIG. This embodiment has the same configuration as that of the first embodiment, and those having the same operations as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 4, a constant voltage transfer power source 31 is connected to the transfer drum 2, and an ammeter A for measuring the current flowing when a specific constant voltage is applied to the constant voltage transfer power source 31.
Are connected. The measurement result by the ammeter A is input to the control circuit 33, and the control circuit 34 controls the constant voltage transfer power source 3
1 is controlled. Further, the suction roller 38 has a suction power source 38.
However, the static elimination power source 39 is connected to the static elimination roller 9.

More specifically, when the adsorption and charge eliminating rollers 8 and 9 are not in contact with each other during the pre-rotation when the power is turned on, that is, when the transfer drum 2 faces only the photosensitive drum 3, a specific voltage is applied to the transfer drum 2. Is applied and the current flowing at that time is measured. As for the current measured here, only the current flowing from the photosensitive drum 3 to the transfer drum 2 is measured because the attraction and charge eliminating rollers 8 and 9 are not in contact with each other. Therefore, when the film thickness of the photosensitive drum 3 or the film thickness of the dielectric layer 23 of the transfer drum 2 changes, the current value thereof changes. Further, the current value also changes due to the resistance change of the dielectric layer or the like due to the environment. And
A transfer bias table corresponding to each current value is prepared in advance, and a transfer bias corresponding to the measured current value is applied.

In this embodiment, the photosensitive drum is a negatively charged OP.
A transfer drum having a thickness of 25 μm and a CT layer provided on the charge generation layer is used. The transfer drum is made of an aluminum cored bar 21 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less. The body 22 is wound, the thickness is 75 μm, and the volume resistance is 10 ¹⁴ 〜.
The one coated with the dielectric 23 of 10 ¹⁶ Ω · cm was used. At this time, when a constant voltage of 1 KV was applied to the transfer drum and the above current was measured, it was I = 7.5 μA, and the optimum transfer bias for the first color was Vbest = 1050V. When a photosensitive drum having a CT layer thickness of 23 μm is used, I = 8.8 μA and Vbest = 960 V, and when a photosensitive drum CT layer having a thickness of 17 μm is used,
I = 12.8 μA and Vbest = 820V. Also,
When the CT layer of the photosensitive drum has a thickness of 25 μm and the dielectric has a thickness of 60 μm, the current is I = 9.9 μA, 1
The optimum transfer bias for the color is Vbest = 900V, and if the dielectric film thickness is 50 μm, I = 13.5.
μA and Vbest = 790V.

From the above measurement results, FIG. 5 shows a graph of the current and the optimum transfer bias for the first color, and it can be seen that there is a correlation between the current and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

As a result, the same transferability can be always obtained even if the film thickness of the dielectric layer of the photosensitive drum or the transfer drum changes. Further, since only one constant voltage power source is required as the transfer power source, the cost can be reduced.

Further, it is preferable that the atmosphere is detected by the temperature and humidity sensor and the table is changed according to the detection result. This makes it possible to correct the resistance change of the transfer material due to the temperature and humidity of the atmosphere.

Further, it is more preferable that the thickness of the transfer material is detected by a conventionally known means and the table is corrected based on the detection result. Accordingly, it is possible to correct the difference in resistance value between the transfer materials.

Third Embodiment A third embodiment according to the present invention will be described with reference to FIGS. The present embodiment has the same configuration as that of the previous embodiment, and those having the same operations as those of the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

More specifically with reference to the image forming sequence diagram of FIG. 6, the transfer constant voltage power supply 31 is switched to the constant current power supply 32 from the start of the printing operation to the contact of the suction roller 8 with the transfer drum 2. A specific constant current is applied to the transfer drum 2, and the voltage at that time is measured by a voltmeter V. Here, since the attraction and charge eliminating rollers 8 and 9 are not in contact with each other, only the photosensitive drum 3 faces the transfer drum 2, and all the current flowing at this time flows from the transfer drum 2 to the photosensitive drum 3. Therefore, if the film thickness of the photosensitive drum 3 or the film thickness of the dielectric layer 23 of the transfer drum 2 changes, the voltage value changes. Further, the voltage value also changes due to the resistance change of the dielectric layer or the like due to the environment. Then, a transfer bias table corresponding to each voltage value is prepared in advance, and the transfer bias corresponding to the measured voltage value is applied from the constant voltage power supply 31.

In this embodiment, the photosensitive drum 3 is a negatively charged O
A transfer drum 2 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less is formed on an aluminum cored bar 21 by using a PC having a CT layer having a thickness of 25 μm provided on the charge generation layer. An elastic body 22 is sprinkled, and a thickness of 75 μm and a volume resistance of 10
^The one coated with a dielectric layer 23 of ¹⁴ to 10 ¹⁶ Ω · cm was used. At this time, when a constant current of 10 μA was applied to the transfer drum 2 and the above voltage was measured, V = 1300V, and the optimum transfer bias for the first color was Vbest = 1050V. When the photosensitive drum has a CT layer thickness of 23 μm, V = 1120V and Vbest = 960V, and when the photosensitive drum has a thickness of 17 μm, V = 93V.
It was 0V and Vbest = 820V. In addition, C of the photosensitive drum
When the thickness of the T layer is 25 μm and the thickness of the dielectric layer is 60 μm, the voltage is V = 1040V, the optimum transfer bias for the first color is Vbest = 900V, and the thickness of the dielectric layer is 50 μm. If one is used, V = 860V, Vbest =
It was 790V.

From the above measurement results, FIG. 7 shows a graph of the voltage and the optimum transfer bias of the first color, and it can be seen that there is a correlation between the voltage and the optimum transfer bias of the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

As a result, even if the film thickness of the dielectric layer of the photosensitive drum or the transfer drum changes, the same transferability can always be obtained. Since this control is performed each time printing is performed, it is possible to cope with a slight change. However, during continuous printing, the suction or static elimination roller may be in contact with the second and subsequent sheets, so only the first sheet is used and this data is used for the second and subsequent sheets.

Further, it is preferable that the atmosphere is detected by the temperature and humidity sensor and the table is corrected according to the detection result. This makes it possible to correct the resistance change of the transfer material due to the temperature and humidity of the atmosphere.

Further, it is more preferable that the thickness of the transfer material is detected by a conventionally known means and the table is corrected based on the detection result. Accordingly, it is possible to correct the difference in resistance value between the transfer materials.

Fourth Embodiment A fourth embodiment according to the present invention will be described with reference to FIGS. The present embodiment has the same configuration as that of the previous embodiment, and those having the same operations as those of the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

Explaining in detail with reference to FIG. 8, a specific constant voltage is applied to the transfer drum 2 from the start of the printing operation to the contact of the suction roller 8 with the transfer drum 2.
The current flowing at that time is measured. Here, since the attraction and charge eliminating rollers 8 and 9 are not in contact with each other, only the photosensitive drum 3 faces the transfer drum 2, and all the current flowing at this time flows from the transfer drum 2 to the photosensitive drum 3. Therefore, the film thickness of the photosensitive drum 3 and the dielectric layer 23 of the transfer drum 2 are
When the thickness of the film changes, the current value changes. Further, the current value also changes due to the resistance change of the dielectric layer or the like due to the environment. Then, a transfer bias table corresponding to each current value is prepared in advance, and the transfer bias corresponding to the measured current value is applied from the constant voltage power supply 31.

In this embodiment, the photosensitive drum 3 is a negatively charged O
A transfer drum 2 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less is formed on an aluminum cored bar 21 by using a PC having a CT layer having a thickness of 25 μm provided on the charge generation layer. An elastic body 22 is sprinkled, and a thickness of 75 μm and a volume resistance of 10
^The one coated with a dielectric layer 23 of ¹⁴ to 10 ¹⁶ Ω · cm was used. At this time, when a constant voltage of 1 KV was applied to the transfer drum 2 and the above current was measured, I = 7.0 μA,
The optimum transfer bias for the first color was Vbest = 1050V. When the CT layer of the photosensitive drum 3 has a thickness of 23 μm, I = 8.5 μA and Vbest = 960 V, and when the CT layer of the photosensitive drum 3 has a thickness of 17 μm, I = 13.2 μA and Vbest = 820V. When the CT layer of the photosensitive drum has a thickness of 25 μm and the dielectric has a thickness of 60 μm, the current is I = 9.
8 μA, the optimum transfer bias for the first color is Vbest = 900V
And using a dielectric having a film thickness of 50 μm, I
= 13.8 μmA and Vbest = 790V.

From the above measurement results, the current and the optimum transfer bias for the first color are shown in the graph of FIG. 9, and it can be seen that there is a correlation between the current and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

As a result, the same transferability can always be obtained even when the film thickness of the dielectric layer of the photosensitive drum or the transfer drum changes. Since this control is performed every time printing is performed, it is possible to cope with a slight change. However, during continuous printing, the second or subsequent sheets may be in contact with the adsorption or static elimination roller, so only the first sheet is used and this data is used for the second and subsequent sheets.

It is preferable that the temperature and humidity sensor detect the atmosphere and the table is changed according to the detection result. This makes it possible to correct the resistance change of the transfer material due to the temperature and humidity of the atmosphere.

Further, it is more preferable that the thickness of the transfer material is detected by a conventionally known means and the table is corrected based on the detection result. Accordingly, it is possible to correct the difference in resistance value between the transfer materials. Further, since the transfer power source may be only one constant voltage power source, the cost can be reduced.

Fifth Embodiment A fifth embodiment according to the present invention will be described with reference to FIGS. The present embodiment has the same configuration as that of the previous embodiment, and those having the same operations as those of the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

This will be described in detail with reference to FIG. 10. After the pre-rotation when the power is turned on, test printing is performed, and particularly when the adsorption and charge eliminating rollers 8 and 9 are not in contact, that is, the transfer drum 2 faces only the photosensitive drum 3. At that time (for the first color, the current flowing from the rear end of the transfer material after passing the attraction roller 8 to the photosensitive drum 3 or the second, third, and fourth colors) is measured. The current measured here is the attraction and static elimination roller 8,
Since 9 is not in contact, only the current flowing from the photosensitive drum 3 through the transfer material to the transfer drum 2 is measured. Therefore, the film thickness of the photosensitive drum 3 and the dielectric layer 23 of the transfer drum 2 are
When the thickness of the film changes, the current value changes. Further, the current value also changes due to the resistance change of the transfer material, the dielectric layer, etc. due to the environment. Then, a transfer bias table corresponding to each current value is prepared in advance, and the transfer bias corresponding to the measured current value is applied during the subsequent image formation.

In this embodiment, the photosensitive drum 3 is a negatively charged O
A transfer drum 2 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less is formed on an aluminum cored bar 21 by using a PC having a CT layer having a thickness of 25 μm provided on the charge generation layer. An elastic body 22 is sprinkled, and a thickness of 75 μm and a volume resistance of 10
^The one coated with a dielectric layer 23 of ¹⁴ to 10 ¹⁶ Ω · cm was used. Transfer bias is 1050V for the first color and 12 for the second color
50V, 1450V for the third color, and 1650V for the fourth color were applied. Then, when the temperature and humidity of the atmosphere are 25 ° C. and 60%, the above current is measured from when the trailing edge of the transfer material of the first color passes through the attraction roller 8 to when it passes through the photosensitive drum 3.
I = 5.2 μA, the optimum transfer bias for the first color is V
best = 1050V. And CT of the photosensitive drum
If the layer thickness is 23 μm, I = 7.2 μ
A, Vbest = 960V, and using a photosensitive drum having a CT layer thickness of 17 μm, I = 9.8 μA, Vbe
st = 820V. When the CT layer of the photosensitive drum has a thickness of 25 μm and the dielectric layer has a thickness of 60 μm, the current is I = 8.6 μA, the optimum transfer bias for the first color is Vbest = 900V, and the dielectric is Layer thickness is 50μ
m = 1, I = 10.8 μA, Vbest = 79
It was 0V. Further, the thickness of the photosensitive drum and the thickness of the dielectric are 25 μm and 75 μm, respectively, and the temperature and humidity of the atmosphere are 15 μm.
At ℃, 10%, I = 3.7μA, Vbest = 1210V
Met. Further, when the temperature and humidity of the atmosphere were 30 ° C. and 80%, I = 14.2 μA and Vbest = 720V.

From the above measurement results, FIG. 11 is a graph showing the current and the optimum transfer bias for the first color, and it can be seen that there is a correlation between the current and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

As a result, not only the change in the film thickness of the dielectric layer of the photosensitive drum or the transfer drum but also the change in the resistance of the transfer material due to the environment can be corrected, and the same transfer property can be obtained more strictly. Therefore, it is not necessary to separately check the atmosphere information and the transfer material information by the environment sensor, and the apparatus is simple and the cost can be reduced.

In this embodiment, a constant voltage is applied and the current is measured, but the same effect can be obtained by supplying a constant current and measuring the voltage.

Sixth Embodiment A sixth embodiment according to the present invention will be described with reference to FIGS. The present embodiment has the same configuration as that of the previous embodiment, and those having the same operations as those of the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

This will be described in detail with reference to FIG. 12. During a normal printing operation, the transfer constant voltage power supply 31 is switched to the constant current power supply 32 to flow a constant current while the margin of the transfer material tip passes through the photosensitive drum 3. Measure the applied voltage. However,
Since the suction operation is still performed in the first rotation, the suction roller 8 is in contact with the transfer drum 2. Therefore,
Strictly speaking, the current passed is not only the current flowing between the photosensitive drum 3 and the transfer drum 2. However, if the film thickness of the dielectric layer 23 of the photosensitive drum 3 or the transfer drum 2 changes or the resistance of the transfer material or the like changes depending on the temperature and humidity of the atmosphere, the measured voltage also changes. Contributes to transferability. Therefore, a transfer bias table corresponding to each voltage value is prepared in advance, and the transfer bias corresponding to the measured voltage value is applied.

In this embodiment, the photosensitive drum 3 is a negatively charged O
A transfer drum 2 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less is formed on an aluminum cored bar 21 by using a PC having a CT layer having a thickness of 25 μm provided on the charge generation layer. An elastic body 22 is sprinkled, and a thickness of 75 μm and a volume resistance of 10
^The one coated with a dielectric layer 23 of ¹⁴ to 10 ¹⁶ Ω · cm was used. When the temperature and humidity of the atmosphere are 25 ° C. and 60% and a constant current of 10 μA is applied to the transfer drum 2 to measure the above voltage, V = 1210 V, and the optimum transfer bias for the first color is Vbest = 1050 V. Met. When the photosensitive drum 3 has a CT layer thickness of 23 μm, V = 1000 V and Vbest = 960 V, and when the photosensitive drum CT layer has a thickness of 17 μm, V = 820 V , Vbest = 820V. If the photosensitive drum has a CT layer thickness of 25 μm and a dielectric layer thickness of 60 μm, the current is V = 950.
V, the optimum transfer bias for the first color is Vbest = 900V, and if the dielectric layer having a thickness of 50 μm is used, V =
It was 800V and Vbest = 790V. Furthermore, the thickness of the photosensitive drum and the thickness of the dielectric layer are 25 μm and 75 μm, respectively.
When the temperature and humidity of the atmosphere are 15 ° C and 10% at m, V = 141
It was 0V and Vbest = 1210V. When the temperature and humidity of the atmosphere are 30 ° C. and 80%, V = 680V, Vbest = 7
It was 20V.

From the above measurement results, FIG. 13 is a graph showing the voltage and the optimum transfer bias for the first color, and it can be seen that there is a correlation between the voltage and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

According to this, it is possible to correct the difference in the resistance value depending on the paper type and the resistance change of the transfer material due to the environment. Therefore, the environmental sensor and the thickness detection of the transfer material are not required, and the apparatus is simplified and the cost can be reduced.

Embodiment 7 A seventh embodiment according to the present invention will be described with reference to FIGS. The present embodiment has the same configuration as that of the previous embodiment, and those having the same operations as those of the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

This will be described in detail with reference to FIG. 14. During the normal printing operation, the current flowing during the first rotation while the transfer material front end margin passes through the photosensitive drum is measured. However, since the suction operation is still performed in the first rotation, the suction roller 8 is in contact with the transfer drum 2. Therefore, strictly speaking, the measured current is not only the current flowing between the photosensitive drum 3 and the transfer drum 2. However, if the film thickness of the dielectric layer 23 of the photosensitive drum 3 or the transfer drum 2 changes or the resistance of the transfer material changes due to the temperature and humidity of the atmosphere, the measured current also changes. Contributes to transferability. Therefore, a transfer bias table corresponding to each current value is prepared in advance, and the transfer bias corresponding to the measured current value is applied.

In this embodiment, the photosensitive drum is a negatively charged OP.
A transfer drum having a thickness of 25 μm and a CT layer provided on the charge generation layer is used. The transfer drum is made of an aluminum cored bar 21 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less. The body 22 is sprinkled, and the thickness is 75 μm and the volume resistance is 10 ¹⁴ 〜.
The one coated with a dielectric layer 23 of 10 ¹⁶ Ω · cm was used. When the temperature and humidity of the atmosphere are 25 ° C. and 60%, a constant voltage of 1 KV is applied to the transfer drum and the above current is measured, I = 8.0 μA, and the optimum transfer bias for the first color is Vbest. = 1050V. If a photosensitive drum having a CT layer thickness of 23 μm is used, I
= 9.9 μA, Vbest = 960 V, and using a photosensitive drum having a CT layer thickness of 17 μm, I = 12.
It was 5 μA and Vbest = 820V. The CT layer of the photosensitive drum has a thickness of 25 μm and the dielectric layer has a thickness of 60 μm.
Current is I = 11.4 μA, the optimum transfer bias for the first color is Vbest = 900 V, and when the thickness of the dielectric layer is 50 μm, I = 13.6 μ
A, Vbest = 790V. Further, the thickness of the photosensitive drum and the thickness of the dielectric layer are 25 μm and 75 μm, respectively, and when the temperature and humidity of the atmosphere are 15 ° C. and 10%, I = 6.3 μA,
Vbest = 1210V. Further, when the temperature and humidity of the atmosphere are 30 ° C. and 80%, I = 16.9 μA and Vbest = 72
It was 0V.

From the above measurement results, FIG. 15 shows a graph of the current and the optimum transfer bias for the first color, and it can be seen that there is a correlation between the current and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

According to this, it is possible to correct the difference in the resistance value depending on the paper type and the resistance change of the transfer material due to the environment. Therefore, the environment sensor and the thickness detection of the transfer material are not required, and the transfer power source may be one constant voltage power source, so that the apparatus is simple and the cost can be reduced.

Embodiment 8 An eighth embodiment according to the present invention will be described with reference to FIG.

This embodiment has the same structure as the previous embodiment,
The same elements as those in the previous embodiment are designated by the same reference numerals, and the description thereof will be omitted. In particular, this embodiment is characterized in that the density is controlled.

More specifically, in the color image forming apparatus, if the image density varies depending on various conditions such as the number of environmental prints to be used, the original correct color tone cannot be obtained. Therefore, in order to judge the condition of the image during image formation, a toner image for each color density detection is experimentally formed on the transfer drum or transfer material, the density is automatically detected, and this detection result is exposed. The density is controlled to feed back the image forming conditions such as the amount and the developing bias to form an original color image.

Then, in the white background portion (portion where no patch is written) during the density detection, the transfer power supply is set to a constant current power supply, a constant current is supplied to the transfer drum, and the voltage applied at that time is measured. Since the attraction roller 8 and the charge eliminating roller 9 are not in contact with the transfer drum 2 during the density detection, all the electric current that has been flown flows from the transfer drum 2 to the photosensitive drum 3. Therefore, if the film thickness of the photosensitive drum 3 or the film thickness of the dielectric layer 23 of the transfer drum 2 changes, the voltage value changes. Further, the voltage value also changes due to the resistance change of the dielectric layer or the like due to the environment. Then, a transfer bias table corresponding to each voltage value is prepared in advance, and the transfer bias corresponding to the measured voltage value is applied from the constant voltage power supply 31.

In this embodiment, the photosensitive drum 3 is a negatively charged O
A transfer drum 2 having a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less is formed on an aluminum cored bar 21 by using a PC having a CT layer having a thickness of 25 μm provided on the charge generation layer. An elastic body 22 is sprinkled, and a thickness of 75 μm and a volume resistance of 10
^The one coated with a dielectric layer 23 of ¹⁴ to 10 ¹⁶ Ω · cm was used. At this time, when a constant current of 10 μA was applied to the transfer drum 2 and the above voltage was measured, V = 1260V, and the optimum transfer bias for the first color was Vbest = 1050V.
When the photosensitive drum has a CT layer thickness of 23 μm, V = 1150 V and Vbest = 960 V, and when the photosensitive drum has a CT layer thickness of 17 μm, V = 900 V, Vbest = 820V. When the CT layer of the photosensitive drum has a thickness of 25 μm and the dielectric layer has a thickness of 60 μm, the voltage is V = 1060.
V, the optimum transfer bias for the first color is Vbest = 900V, and if the dielectric layer having a thickness of 50 μm is used, V =
840V and Vbest = 790V.

From the above measurement results, FIG. 16 is a graph showing the voltage and the optimum transfer bias for the first color, and it can be seen that there is a correlation between the voltage and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

As a result, the same transferability can always be obtained even if the film thickness of the dielectric layer of the photosensitive drum or the transfer drum changes.

It is preferable that the temperature and humidity sensor detect the atmosphere and the table is changed according to the detection result. This makes it possible to correct the resistance change of the transfer material due to the temperature and humidity of the atmosphere.

Further, it is more preferable that the thickness of the transfer material is detected by a conventionally known means and the table is corrected based on the detection result. Accordingly, it is possible to correct the difference in resistance value between the transfer materials.

Embodiment 9 A ninth embodiment according to the present invention will be described with reference to FIG. The present embodiment has the same configuration as that of the previous embodiment, and those having the same operations as those of the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

The present embodiment is characterized in that the density control is performed as in the eighth embodiment. Then, a constant voltage is applied to the transfer drum on the white background portion (portion where no patch is written) during the density detection, and the current flowing at that time is measured. Since the attraction roller 8 and the static elimination roller 9 are not in contact with the transfer drum 2 during the density detection, all the current is transferred from the transfer drum 2 to the photosensitive drum 3.
Flow to. Therefore, the film thickness of the photosensitive drum 3 and the transfer drum 2
When the film thickness of the dielectric layer 23 changes, the voltage value changes. Further, the voltage value changes due to the resistance change of the dielectric layer or the like due to the environment. Then, a transfer bias table corresponding to each current value is prepared in advance, and the transfer bias corresponding to the measured current value is applied from the constant voltage power supply 31.

In this embodiment, the photosensitive drum 3 is a negatively charged O
The transfer drum is a PC with a 25 μm-thick CT layer provided on the charge generation layer. The transfer drum is made of an aluminum cored bar 21 with a thickness of 5.5 mm and a volume resistance of 10 ⁴ Ω · cm or less. The body 22 is sprinkled, and the thickness is 75 μm and the volume resistance is 10 ¹⁴ on the body 22.
What was coated with a dielectric layer 23 of -10 ¹⁶ Ω · cm was used. At this time, when a constant voltage of 1 KV was applied to the transfer drum and the above current was measured, it was I = 7.4 μA, and the optimum transfer bias for the first color was Vbest = 1050V.
Then, when the CT layer of the photosensitive drum having a thickness of 23 μm is used, I = 8.6 μA and Vbest = 960 V,
If the CT layer of the photosensitive drum has a thickness of 17 μm, I = 13.4 μA and Vbest = 820V, and if the CT layer of the photosensitive drum has a thickness of 17 μm,
= 13.4 μA and Vbest = 820V. The CT layer of the photosensitive drum has a thickness of 25 μm and the dielectric has a thickness of 6 μm.
When the one having a thickness of 0 μm is used, the current is I = 9.7 μA, the optimum transfer bias for the first color is Vbest = 900 V, and when the one having a dielectric film thickness of 50 μm is used, I = 14.2 μA.
A, Vbest = 900V, the film pressure of the dielectric is 50 μm
Of the above, I = 14.2 μA and Vbest = 790
It was V.

From the above measurement results, FIG. 17 is a graph showing the current and the optimum transfer bias for the first color, and it can be seen that there is a correlation between the current and the optimum transfer bias for the first color. Then, the optimum transfer bias for the second and subsequent colors is calculated from the optimum transfer bias for the first color.

As a result, the same transferability can always be obtained even if the film thickness of the dielectric layer of the photosensitive drum or the transfer drum changes.

It is preferable that the temperature and humidity sensor detect the atmosphere and the table is changed according to the detection result. This makes it possible to correct the resistance change of the transfer material due to the temperature and humidity of the atmosphere.

Furthermore, it is more preferable to detect the thickness of the transfer material by a conventionally known means and correct the table based on the detection result. Accordingly, it is possible to correct the difference in resistance value between the transfer materials. Further, since the transfer power source may be only one constant voltage power source, the cost can be reduced.

[0086]

As is apparent from the above description, the image forming apparatus equipped with the solid transfer drum according to the present invention measures the voltage value applied by applying a constant current to the transfer electrode of the transfer means and measuring the applied voltage value. By adopting a configuration in which the transfer bias is changed in accordance with the above, it is possible to apply an appropriate bias according to the conditions of the image carrier and the transfer means, the transfer efficiency is good, and it is possible to always obtain a high quality image.

An image forming apparatus equipped with a solid transfer drum according to another aspect of the present invention applies a constant voltage to a transfer electrode of a transfer means, measures a flowing current value, and sets a transfer bias according to the current value. By changing the configuration,
The same action and effect as above can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view of essential parts of an embodiment of a transfer device in an image forming apparatus according to the present invention.

FIG. 2 is a configuration diagram of an embodiment of an image forming apparatus according to the present invention.

FIG. 3 is a graph showing the relationship between the measured voltage V and the optimum transfer bias Vbest according to the first embodiment of the present invention.

FIG. 4 is a main part explanatory view of an embodiment of a transfer device in the image forming apparatus according to the present invention.

FIG. 5 is a graph showing the relationship between the measured current I and the optimum transfer bias Vbest according to the second embodiment of the present invention.

FIG. 6 is a timing chart showing an image forming sequence according to a third embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the measured voltage V and the optimum transfer bias Vbest according to the third embodiment of the present invention.

FIG. 8 is a timing chart showing an image forming sequence according to a fourth embodiment of the present invention.

FIG. 9 is a graph showing the relationship between the measured current I and the optimum transfer bias Vbest according to the fourth embodiment of the present invention.

FIG. 10 is a timing chart showing an image forming sequence according to a fifth embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the measured current I and the optimum transfer bias Vbest according to the fifth embodiment of the present invention.

FIG. 12 is a timing chart showing an image forming sequence according to a sixth embodiment of the present invention.

FIG. 13 is a graph showing the relationship between the measured voltage V and the optimum transfer bias Vbest according to the sixth embodiment of the present invention.

FIG. 14 is a timing chart showing an image forming sequence according to a seventh embodiment of the present invention.

FIG. 15 is a graph showing the relationship between the measured current I and the optimum transfer bias Vbest according to the seventh embodiment of the present invention.

FIG. 16 is a graph showing the relationship between the measured voltage V and the optimum transfer bias Vbest in Example 8 according to the present invention.

FIG. 17 is a graph showing the relationship between the measured current I and the optimum transfer bias Vbest in Example 9 according to the present invention.

FIG. 18 is a configuration diagram of a conventional color image forming apparatus.

FIG. 19 is a configuration diagram of a solid transfer drum.

FIG. 20 is an explanatory view of a main part of a transfer device having a solid transfer drum.

FIG. 21 is a configuration diagram of a transfer drum of a conventional example.

FIG. 22 is an explanatory view of a main part of a transfer device of a conventional example.

[Explanation of symbols]

 2 Transfer Drum (Transfer Means) 3 Photosensitive Drum (Image Carrier) 8 Adsorption Roller 9 Electrification Roller 23 Dielectric Layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Moto Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Nobuaki Kamiya, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Toshiaki Miyashiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (9)

[Claims] 1. A visible image forming means for forming an electrostatic latent image on an image carrier and developing the image with toner, and a transfer material is adsorbed on a dielectric layer on the surface of the image carrier. And a rotatable transfer means for electrostatically transferring the developed image on the image carrier onto a transfer material by a transfer electrode provided on the back surface of the dielectric layer in contact with the image forming apparatus. An image forming apparatus, wherein a constant current is applied to the transfer electrode, the voltage value applied is measured, and the transfer bias is changed according to the voltage value. 2. An image forming means for forming an electrostatic latent image on an image carrier and developing the image with toner, and a transfer material is adsorbed on a surface dielectric layer, and the image carrier is used as the image carrier. An image forming apparatus having a rotatable transfer means for electrostatically transferring a visible image on an image carrier onto a transfer material by a transfer electrode provided on the dielectric back surface of the transfer electrode of the transfer means. An image forming apparatus characterized in that a constant voltage is applied to the substrate to measure a flowing current value, and a transfer bias is changed according to the current value. 3. The image forming apparatus according to claim 1, wherein the measurement is performed during pre-rotation. 4. The image forming apparatus according to claim 1, wherein the measurement is performed after the printing operation is started and before the transfer material is held on the transfer unit. 5. The image forming apparatus according to claim 1, wherein the measurement is performed during a test print performed after the pre-rotation. 6. The image forming apparatus according to claim 1, wherein the measurement is performed while a margin of a transfer material front end passes through the image carrier. 7. A toner image for density measurement is formed on the transfer drum or the transfer material for each color, the density is detected by a density detection sensor that measures reflected light, and the image density is controlled by the detection result. The image forming apparatus according to claim 1, wherein the measurement is performed during the density detection. 8. The image forming apparatus according to claim 1, wherein the temperature and humidity of the atmosphere are detected, and the transfer bias is corrected based on the detection result. 9. The image forming method according to claim 1, wherein the thickness of the transfer material is detected, and the transfer bias is corrected based on the detection result. apparatus.