JP3174306B2 - Transfer device and electrophotographic device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for transferring a toner image on paper in an electrophotographic apparatus.

[Conventional technology]

As a transfer device of an electrophotographic apparatus, a belt transfer or a roller transfer is known as a contact transfer method in which a charged member is brought into contact with a sheet in addition to a non-contact corona transfer. This belt transfer means that a sheet is conveyed to a photoreceptor portion on which a toner image is formed, and a dielectric charged to a polarity opposite to that of the toner from the back side (opposite side of the photoreceptor side) of the conveyed sheet. This is to transfer the toner image of the photoconductor portion against which the belt is pressed to the surface of the paper. Here, as a charging means for charging the belt, a corona charger arranged on the back side of the sheet is used. On the other hand, a transfer method that does not use a transfer belt, that is, on the back side of the paper on which the toner image is to be transferred,
There is also corona transfer in which a corona ion stream is directly irradiated. The belt transfer method has an advantage that the transferability to thick paper or rough paper is superior to the above-described corona transfer because the adhesion between the photoreceptor surface and the paper is good.

Related to the belt transfer device is U.S. Pat.
2, JP-A-54-58034 and JP-A-63-83765.

[Problems to be solved by the invention]

However, in the above technology, in a high humidity environment, the belt material and the paper become humid, and when the electric resistance value decreases, the electric field of the transfer portion (the contact portion between the paper and the photoconductor) becomes too high or the belt driving roller And the charging current flows through the paper guide, and the transfer image quality tends to deteriorate and the transfer efficiency tends to decrease. Further, when a corona discharge is applied to the dielectric belt for a long time, the belt surface layer is deteriorated and the electric resistance is reduced, so that the charge retention tends to be impaired.

That is, as shown in FIG. 21, there was a tendency that the transfer efficiency was lowered and the image density was lowered at the time of high humidity or printing for a long time.

 Note that the transfer efficiency η is defined by equation (1).

As a method for solving this problem, JP-A-60-57364 describes that the surface potential of the belt is measured before and after the transfer and the surface potential difference is set to a predetermined value. However, the surface potential of the belt is a physical quantity whose capacitance on the surface is dominant, and does not always correspond to a change in the resistance value of the belt or paper.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems, and to transfer an electrophotographic image without changing the transfer performance with respect to a change in environmental conditions around the apparatus or a change with time of a belt material, which enables stable printing. It is to provide a device.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, in a device for transferring an image by interposing a transfer member between a charged member charged by a charging unit and an image bearing member, the charging unit includes the charged unit. Arranged to apply corona charging to the back side opposite to the front side of the charging member that contacts the transferred member,
The charged member has a belt shape, a toner release layer containing a fluororesin is provided on the front side of the charged member, and a corona discharge degradation protection layer containing a fluororesin is provided on the back side of the charged member. It is the volume resistivity of the object to be charged member is a ¹⁰ 10 Ωcm~10 ¹⁴ Ωcm, controls the charge amount of the corona charging based on the electric resistance of the belt-shaped object charging member. Further, in the electrophotographic apparatus having a charging unit, a charged member charged by the charging unit, and a transfer device that transfers an image by interposing a transferred member between the image bearing member, the charged member Is a belt shape, the electrical resistance value of the charged member, a humidity sensor, a printed page or the operation time of the charging unit, and a predetermined humidity dependency of the charged member and the charged member. The current value of the charging unit is determined based on the aging characteristics, and based on the electric resistance value.

[Action]

The transfer device of the present invention operates so as to obtain a good transfer property by changing the current of a charging unit such as a transfer charger bias roll even when the electric resistance of the belt material and the paper changes.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a first embodiment of the present invention. The prerequisite configuration is that a charging device 2, an exposure unit 3, and a developing device 4 are arranged around a photoreceptor 1, and a transfer belt 5 is charged by a transfer charging device 6 to transfer a toner image onto paper. It is.
In this transfer device, (1) the bearing portion of the belt transport roller 14 on the paper supply side is insulated, and can be charged by the resistance measuring power supply 19, and the opposite roller grounded via the ammeter 20.
18 is pressed against the conveying roller 14 with the transfer belt 5 interposed therebetween,
(2) A control signal generator 21 for generating a control signal based on an output signal of the ammeter 20 is interposed in a stage preceding the high voltage power supply 22 of the transfer charger 6.

In such a configuration, the current when a certain potential difference is applied to the member (the transfer belt 5 or the transfer belt 5 and the paper) interposed between the pair of rollers 14 and 18 can be measured by the ammeter 20. It is possible to evaluate the electric resistance value of the member. The conversion circuit from the current value, which is the output signal of the ammeter, to the electric resistance value may be incorporated in the ammeter 20 or may be arranged in the control signal generator 21. Further, the control signal generator 21 generates a high-voltage power supply control signal for maintaining a predetermined relationship between the electrical resistance of the transfer unit and the corona discharge current value of the transfer charger 6, and controls the output current of the high-voltage power supply 22. Can be controlled.

On the other hand, according to the experiments of the inventors, as shown in FIG. 22, even in the initial stage, the transfer charger current at which the transfer efficiency is maximum in high humidity and low humidity is different, and after printing for about 100 hours, FIG. The transfer charger current value at which the transfer efficiency is maximized is different from the initial case (see FIG. 22), as shown in FIG.
It has been found that the above-mentioned causes are caused by the fact that the resistance value of the belt changes depending on the humidity as shown in FIG. 24, or that the surface layer is deteriorated by corona irradiation and the electric resistance value decreases.

Therefore, in this embodiment, the following (1) to (3)
In any case, it is possible to control the current value of the transfer charger to an appropriate value, and there is an effect that a good transfer property can be secured.

(1) When the electric resistance of the transfer belt and the paper changes due to a change in environmental conditions, (2) The electric resistance of the transfer belt changes over time due to corona charging, and the state of the surface layer changes due to toner contamination and abrasion, and the aging occurs (3) Printing conditions (single-sided or double-sided printing) even if the electrical resistance value of the paper is different for each type of paper used or the same paper
Or depending on storage conditions.

As an example, FIG. 25 shows the relationship between the relative humidity and the transfer efficiency when the present invention is carried out under the same conditions (belt material, transfer charger configuration, humidity, printing time) as those in FIG.
Compared to FIG. 21, it can be seen that the change width of the transfer efficiency due to the temporal change due to the humidity change and corona deterioration can be reduced, and there is an effect that the transferability can be stabilized.

The power supply 19 for electric resistance measurement can be used for pre-charging the belt 5 even when electric resistance measurement is not performed, so that there is an effect that the transportability and transferability of paper at high humidity can be further improved.

FIG. 2 is a diagram showing a second embodiment. The difference is that a humidity sensor 30 is used instead of providing the direct electric resistance value measuring means in the first embodiment. Here, the corona discharge current value of the transfer charger 6 is controlled by indirectly obtaining the resistance value of the member to be transferred by the following method. First, (1) the relationship between the humidity and the printing mode (single-sided printing or double-sided printing) and the electrical resistance of the paper are determined in advance for each paper quality,
When the humidity is measured and the information on the paper quality and the print mode are given, the electric resistance value of the corresponding paper can be specified. (2) The change in the electric resistance value of the transfer belt can be predicted by counting the operating time of the printed page or the transfer charger because the aging deterioration characteristic and the humidity dependency are measured in advance.

The data relating to the electrical resistance of the paper and the transfer belt may be input each time, but may be input to an external storage device such as a microcomputer, a ROM card, a floppy disk, or the like in the control signal generator 31. The print mode is determined by giving a print mode signal to the control signal generator 31.

Regarding the thickness of the paper, when the paper is set on the paper hopper or while the paper is running, the thickness of the paper is detected by a distance sensor, a displacement sensor, and the like, and a signal corresponding to the paper thickness is sent to the control signal generating unit 31. The thickness of a given sheet may be considered.

In the second embodiment, the evaluation accuracy of the electric resistance value of the transfer member tends to be slightly lower than in the first embodiment of FIG. However, since it is not necessary to provide the electric resistance measuring means around the transfer belt 5, there is an effect that the transfer unit can be downsized and the configuration can be simplified.

FIGS. 3 to 17 are views showing an embodiment relating to another electric resistance measuring means or electric resistance measuring method. Hereinafter, description will be made in order.

FIG. 3 shows a third embodiment, in which a transfer belt is charged and a resistance value is measured based on the surface potential of the belt surface. An auxiliary charger 41 corresponding to the transport roller 14 is provided, the transfer belt 5 is charged, the charging voltage is measured by a surface voltmeter 43, and the resistance value of the transfer belt is evaluated based on the measured voltage.

The difference between the case where the physical quantity underlying the control of the amount of corona discharge generated by the transfer charger is the surface potential and the case where the physical quantity is the electric resistance is as follows.

In other words, the surface potential depends on the amount of charge measured by the measuring unit and the electrostatic capacitance to the belt, whereas the electrical resistance depends on the amount of leakage of a part of the charge given by corona discharge. That is, the remaining charge that has not leaked is the charge amount measured by the measuring unit at the surface potential.

Therefore, in order to obtain the electric resistance value by measuring the surface potential, the leak must be calibrated. To perform this calibration, for example, for some transfer belts having different electric resistances, a corona discharge is applied to the transfer belt by a transfer charger to give a charge to the belt, and the belt has the same electrostatic capacitance with respect to the belt. A relationship between the electric resistance and the surface potential, that is, a calibration curve is obtained in advance. By inputting the data of the calibration curve to the control signal generator 21 in advance, the electrical resistance of the transfer belt 5 can be obtained based on the signal output from the surface voltmeter 43. The signal from the humidity sensor 30 is used for measuring or estimating the electric resistance of the sheet based on the surrounding humidity and the specification of the sheet (transferred member).

In the first embodiment, the electric resistance is measured in contact with the transfer belt, but in the present embodiment, the electric resistance is measured in a non-contact manner, so that there is an effect of preventing abrasion of the transfer belt 5 due to rubbing with the roller.

FIG. 4 shows a fourth embodiment in which a ground electrode 44 having an insulating film 45 is arranged so that the charging potential of the transfer belt 5 by the transfer charger 6 can be measured, and a surface voltmeter 43 is arranged at an opposite position. It is. Note that the insulating film 45 is not necessarily provided, and an air layer may be provided instead. In this embodiment, there is no need to provide the auxiliary charger 41 as compared with the third embodiment shown in FIG. 3, and there is an effect that the influence of the auxiliary charging on the transfer can be eliminated.

FIG. 5 shows a method of measuring the electric potential of the transfer belt 48 on the back surface of the transfer belt 48 to evaluate the electric resistance value of the belt.
FIG. 6 shows a transfer belt configuration used for this measurement. The transfer belt 48 connects the thin insulating layer 47 and the conductor 46 to the photosensitive member position 1 '.
The conductor 46 is grounded by grounding means 49 as shown in FIG. 5 to form a ground electrode. By arranging the surface voltmeter 43 at a position facing the conductor 46, the surface potential of the transfer belt 48 is measured from the back surface. In this embodiment, it is not necessary to add a member which comes into contact with the transfer belt 48 at a position (printing area) corresponding to the photoreceptor 1 ', so that the transfer belt can be removed from damage due to abrasion and electric discharge. Transfer charger 6
Can be provided in the vicinity of, so that there is an effect that the measurement accuracy is improved.

FIG. 7 shows the fourth embodiment shown in FIG. 4, in which at least two surface voltmeters 51 and 52 are provided, the potential decay rate is measured, and the current of the transfer charger 6 is determined based on the potential decay rate. It controls the value. Compared to the fourth embodiment shown in FIG. 4, even if the resistance and the capacitance of the insulating layer between the belt 5 and the ground electrode 44 change, there is an effect that the measurement can be performed with higher accuracy.

FIG. 8 shows a configuration in which the print signal pattern is input to the control signal generator 57 and the electric resistance is measured under predetermined printing conditions. As the electric resistance measuring means, instead of measuring the current flowing into the exit side transfer belt driving roller 15 as in this embodiment, the electric resistance measuring means shown in FIGS. 1 and 3 may be used. In this embodiment, the electrical resistance can be measured while the measurement conditions on the photosensitive member 1 side are kept constant, so that there is an effect that the measurement accuracy is improved as compared with the previous examples.

FIG. 9 shows a method of measuring electric resistance when the photosensitive drum 60 of the sheet winding type is used in the ninth embodiment. The current flowing into the photoconductor cap 61 disposed at the winding port is measured, and the resistance value is measured in advance to evaluate the resistance value from the relationship between the electric resistance value of the transfer belt 5 and the current flowing into the cap 61. The current of the transfer charger 6 is controlled based on this. The cap unit 61 has a switching switch 66 connected to the dashed line during normal printing, and is held by a potential holding means 64 so as to be substantially equal to the surface charging potential of the photoreceptor 60. Is connected via a switching switch. In this embodiment, the transfer belt 5 in the transfer unit
Or, since the electrical resistance between the transfer belt 5 and the paper can be measured,
There is an effect that not only the measurement accuracy is improved but also the printing quality can be further improved.

In the embodiment of FIG. 9, the current flowing into the photosensitive member was directly measured. However, the corona discharge current of the transfer charger and the current flowing into the shield case were also measured. May be requested. In this case, since there is no need to ground the photoconductor cap, there is an effect that the switching switch 66 and the grounding means are not required.

As another embodiment of the method of providing the measurement electrode near the photoconductor, there is a method of providing disk-shaped electrodes 67 and 68 having the same diameter and different diameter as the photoconductor as shown in FIGS. In addition, as shown in FIG. 12, a part of the photoconductor is made of a transparent conductive material 70, and the photoconductor is made conductive by irradiating light with a light emitter 72 at the time of measuring electric resistance, and this is used as a measurement electrode. There are ways. Further, as shown in FIG. 13, a push-up roller 75 for bringing the transfer belt 5 into close contact with the photoconductor 1 may be used as a measurement electrode.

FIG. 14 shows a configuration in which the current flowing into the opposing roller 16 of the bias cleaner 17 is measured to control the current of the transfer charger 6. Compared to the above-described embodiment, there is an effect that the electric resistance of the transfer belt 5 can be measured without adding any new member.

In the embodiment of FIG. 15, a resistor 85 is provided between the paper suction and resistance measurement roll 84 and the ammeter 20 so that the resistance value is changed between normal printing and electric resistance measurement. It was done. In the present embodiment, there is an effect that the sheet suction means and the resistance measuring means can be shared.

In FIG. 15, a bias roll 81 connected to an additional resistor 82 is used as a charging means, but a transfer charger 6 for performing corona discharge as in the above-described example may be used.

In the embodiment shown in FIG. 16, a charger is provided on the drive roller 15 side of the transfer belt 5 to measure the electric resistance. For details, an AC static eliminator 88 is arranged to face the drive roller 15 and is used for static elimination of paper during normal printing.When measuring electric resistance, reset to a predetermined AC discharge current value or set to a DC discharge current value. The current flowing into the driving roller 15 is measured, and the current value of the transfer charger 6 is controlled based on the measured current. In this embodiment, the power source 89 of the resistance measuring charger 88 is slightly large, but there is an effect that the electric resistance can be measured without adding a new component around the transfer belt 5.

In the embodiment of FIG. 17, a resistor is interposed between the transport roller 14 and the drive roller 15 which are the support rollers of the transfer belt, and the electrical resistance of the transport roller and the drive roller with respect to the ground is set to a predetermined value. Things. A resistance member 95 having a resistance value R1 is interposed between the conveyance rollers 14 and grounded, and a driving roll 15 forming an electric resistance measuring means is grounded via a resistance member 93 having a resistance value R2 and an ammeter 20. Further, the electric resistance value of the resistor is set to R1> R2, preferably R1> 10R2. In order to further enhance the effect, the transfer belt 5 is separated from the photoconductor 1 at the time of measuring the electric resistance so that the electric resistance value and the charged state of the photoconductor 1 do not affect the transfer belt 5.
In the present embodiment, the charge charged on the transfer belt 5 by the transfer charger 6 can be prevented from leaking from the transport roller 14, and the influence of the photoconductor 1 can be eliminated, so that the measurement accuracy of the electric resistance can be improved. effective.

FIG. 18 is a modification of the embodiment of FIG. The difference from the example of FIG. 1 is that the transport roll 105 on the paper feed side is made of an insulating material, and a pair of conductor electrodes 106 and 107 are provided in the longitudinal direction. One is a charged electrode 106 for measuring electric resistance, and the other is a current characteristic. Electrode 1
07.

In the case of this example, the surface resistance can be measured without providing the first counter electrode 18, and the electric resistance state of the belt can be ascertained based on the measurement, and the transfer current that gives good transferability can be set.

The push-up roller 18 shown in FIG. 1 may be configured as shown in FIG. 18, or the surface resistance measuring means shown in FIG. 18 may be juxtaposed with the volume resistance measuring means shown in FIG. 1 or FIG. good.

FIG. 19 shows another embodiment of the present invention. The difference from the example of FIG. 1 is that the current flowing into the transfer belt is measured using a charged photosensitive member as a charging electrode without providing a power supply for measuring electric resistance. In this example, the method of using the opposing roll 18 contacting on the surface of the belt was shown as an electrode for measuring the inflow current, but a push-up roll 75 contacting on the back surface of the belt or the bias roller 81 in FIG. 15 may be used. it can. When the bias roller 81 is used, it may be separated from the high voltage power supply by a switching switch and grounded via an ammeter.

In this embodiment, there is an advantage that it is not necessary to newly provide an electrode for measuring electric resistance and a power supply for measurement.
At the time of measuring the electric resistance, the exposure means 3 has a predetermined exposure pattern (including a non-operating state), and the developing device 4 is retracted so that the developer and the photoreceptor are in a non-contact state (FIG. 19). (Refer to the position indicated by the broken line in FIG. 3) is desirable in order to maintain the charged electric charge and to improve the measurement accuracy.

FIG. 20 shows a configuration in which the electrical resistance value of the transfer belt 5 and the sheet is measured by the electrical resistance value measuring means, and when the electrical resistance value becomes equal to or less than a predetermined value, the resistance value recovering means 99 is operated. Any means may be used as the resistance value recovery means 99, as long as the factor that changed the electrical resistance value is changed or removed. A far-infrared ray generator, a microwave generator, or the like can be used in addition to the dehumidifier 99 shown in the figure. In this embodiment, since the change width of the electric resistance value of the transfer belt 5 can be made smaller than that in the above-described example, there is an effect that the change width can be made smaller when controlling the charging current of the transfer charger 6.

Further, when the electric resistance value does not recover even if the resistance value recovery means 99 is operated, or when the electric resistance value becomes equal to or less than a predetermined value in an apparatus having no resistance value recovery means 99,
It is preferable to output a display indicating the necessity of belt replacement or output information. Thereby, there is an advantage that character omission due to transfer failure can be prevented.

Further, after outputting the output information indicating that the belt should be replaced, the subsequent operation may be suspended or stopped. Furthermore, the output information from the electrophotographic apparatus may be transmitted to another apparatus. With this, it is possible to notify other devices and system systems that a serious situation such as the need to replace the belt has occurred, thereby preventing an accident such as a printing failure.

FIG. 26 shows another embodiment of the present invention. This embodiment is different from the previous examples in that a bias roll is used as a charged member.
108 is used. The bias roll 108 includes a cylindrical base 110 and an elastic body 109 coated on the outer periphery thereof. The high voltage power supply 22 for charging and the bias roll 108 are electrically connected by a power supply brush 111. Also in this example, the elastic body 109
Since the current value of the charging high-voltage power supply 22 can be controlled based on the electric resistance of the elastic body 109, the transferability can be stabilized even if the electric resistance value of the elastic body 109 changes with time or changes with environmental conditions.
Further, in this embodiment, there is an advantage that the entire transfer apparatus can be configured to be smaller than when a belt-shaped member is used as the charged member.

FIG. 27 is another embodiment of the present invention. In this example, a sheet 114 as a member to be transferred and a bias roll 108 as a charging unit are used.
The electric resistance of the sample can be measured as follows. (1) A disk-shaped electrode 68 is arranged, and (2) a charging power supply 11
5 is configured to be able to operate as a constant current source whose current value can be set during transfer and as a voltage source when measuring electric resistance. Another difference between this embodiment and the previous embodiment is that the developing machine 4
The point is that a light neutralization lamp 116 is interposed between the transfer portion and the transfer portion. In this example, the electric charge (-)
When there is a sheet, the charge (+) generated on the back side of the sheet 114 due to the transfer may cause the sheet to be wound around the photosensitive member. However, the charge on the surface of the photosensitive member can be erased by irradiating the light with the light discharging lamp 116. This has the effect of preventing winding. Note that an AC static eliminator may be arranged downstream of the bias roll 108 in order to reduce the electric charge (+) on the back side of the sheet.

FIG. 28 and FIG. 29 show another embodiment of the present invention, and are explanatory diagrams relating to another example of the embodiment relating to the printing mode reflecting the printing process through which the printed material has passed, that is, the printing mode. In the embodiment shown in FIG. 2 described above, the case of single-sided printing and double-sided printing of the paper is described as a printing mode. However, when the control of the charging means of the present invention is performed, the following effects are obtained in terms of transferability and image quality. There are (1) to (4).

(1) Black toner printing and color toner printing (2) Image density setting (3) Single color printing and color printing by color superposition (4) Blank paper printing (1) Especially when the electrical resistance values of black toner and color toner are different This is because (2) and (3) are because the optimal current value of the charging means is different due to the difference in the amount of toner adhesion as shown in FIG. Further, as shown in FIG. 29, when blank paper is printed or when there is no paper, the charging means is turned off or the current value of the charging means is reduced, or a current of the opposite polarity is set as shown by a broken line. This can prevent transfer of the toner remaining on the photoconductor,
This has the effect of removing white paper stains and toner stains on the charged member.

Further, in the present invention, the following (1) to (3) may be performed.

(1) A display for displaying the current value of the charging means is provided.

(2) When the current value of the charging means becomes larger than a predetermined value and affects the life of the charged member, the user gives priority to the print image quality and continues the current control of the charging means, or gives priority to the life of the charged member. Then, it is possible to select whether the current value of the charging means is within a predetermined value. According to the above (1) and (2), there is an effect that the electrophotographic apparatus can be operated according to the user's needs.

(3) When the use environment conditions of the electrophotographic apparatus can be grasped in advance, for example, in the case of the electrophotographic apparatus having a maintenance cycle in which the environmental conditions relating to the season can be predicted, according to the winter season when the humidity is low and the summer when the humidity is high. By changing the electrical resistance specification of the charged member, a member having a lower electric resistance value in a low humidity season and a member having a higher electric resistance value in a high humidity season are used. Here, the season varies depending on the country or region, and many types of charged members can be used. For example, in the Tokyo region as a standard region in Japan, the low humidity season ( November to April) humidity is 50-60% RH
(Relative Humidity: Percentage of the ratio of the amount of water vapor actually contained in the air to the maximum amount of water vapor that the air can contain at that humidity), the volume resistivity is approximately A material of 10 ¹¹ Ωcm has a volume resistivity of approximately 10 ¹³ Ω when the humidity in the high humidity season (May to October) is 70 to 80% RH.
It is better to use cm material.

In a printer that performs high-speed printing, the maintenance cycle is usually set to 3 to 6 months, so that it is possible to cope with the low and high humidity seasons. By selecting and using a plurality of charged members having different electric resistance values as described above,
Since the range of humidity conditions that can be handled by one type of charged member can be narrowed, the following effects can be obtained.

The material selection and production of the charged member are facilitated, and the production cost can be reduced.

By setting the central value of the control current of the charging means in correspondence with the low humidity environment belt and the high humidity environment belt, the control width of the corona current of the transfer charger can be narrowed, so that the control accuracy is further improved. Printing quality can be improved.

The transfer belt of the present invention has a two-layer structure in which a fluorine resin layer is provided on the surface of the elastic layer to facilitate toner cleaning, or more desirably, a three-layer structure in which a fluorine resin layer is provided on the back surface. It is better to use the one in which the degree of the change with time due to aging is reduced. Further, in the above-described embodiment, a configuration as described in (1) to (4) above may be adopted.

(1) The transfer belt is charged using a bias roll instead of the transfer charger.

(2) The electric resistance measurement is performed with the photoconductor separated.

(3) The resistance between the belt drive roller and the ground is 5 × 10 ^{7 to} 5
A resistor is interposed so as to be × 10 ⁹ Ω. (A) The charge leakage during high humidity is kept low. (B) The distance between the drive roller and the transfer belt when removing electricity by the belt drive roller. The discharge in the minute gap is alleviated to reduce the deterioration of the belt.

(4) Use a dew condensation sensor instead of a humidity sensor.

Further, in the above-described embodiments, the case of the back charging system in which charging is performed from the back side (inside) of the belt has been described as an example. It goes without saying that you can do it. In the case of the front charging system, a two-layer belt having an insulator on the front surface and a conductor on the back surface is generally used. In this case, the structure shown in FIG. 1 (where the transfer charger 6 faces the drive roller 14) is used. In order to measure the electric resistance, the members in contact with the inner surface of the belt such as the drive roll 15 and the opposing roll 16 should be insulated, or the surface resistance measuring means shown in FIG. 18 should be in contact with the outer surface of the belt. What is necessary is just to arrange it.

In the present invention, in order to ensure the current control of the charging unit, a member having a volume resistivity of the charged member (transfer belt) having the following value may be selected and used.

10 ¹² Ωcm to 10 ¹⁶ Ωcm for the front charging system, and 10 ¹² Ωcm for the back charging system
It is desirable to be in the range of 10 ¹⁰ Ωcm to ^{10 14} Ωcm. However, the lower limit of humidity is 15 ℃, 20% RH, the upper limit is 30 ℃, 80% RH
The volume resistivity is set on condition that the applied voltage is 1 kV.

In the above, the embodiment in the printer device of black printing has been described, but the present invention is not limited to this embodiment, and can achieve the objects and effects of the present invention.
It can be applied to a transfer device relating to all modifications, improvements and applications. For example, it is also used as a transfer device of a single-drum multi-transfer color printer, a transfer device of a multi-drum color printer, a transfer device of a color-overlay color printer on a drum, and an intermediate transfer device of a printer using an intermediate transfer body. be able to.

[Effects of the Invention] According to the present invention, stable transfer characteristics can be obtained even when ambient conditions such as changes over time, environmental changes, and paper specifications occur, and the effect of significantly improving print quality can be obtained. is there.

[Brief description of the drawings]

1 is a longitudinal sectional view of an embodiment of the present invention, FIGS. 2 to 4 are cross-sectional views of another embodiment of the present invention, and FIG. 5 is a description of a transfer belt used in the embodiment of FIG. FIGS. 6 to 17 and FIGS. 19 and 20 are longitudinal sectional views of another embodiment of the present invention.
FIG. 18 is a perspective view of another embodiment of the present invention, FIG. 21 is an explanatory view showing the relationship between relative humidity and transfer efficiency of a conventional example, FIGS.
FIG. 23 is an explanatory diagram showing the relationship between the transfer charger current and the transfer efficiency after initial printing for about 100 hours, and FIG. 24 is an explanatory diagram showing the relationship between the relative humidity and the electrical resistivity of the transfer belt.
FIG. 25 is an explanatory view showing the relationship between the relative humidity and the transfer efficiency of the embodiment of the present invention, FIGS. 26 and 27 are longitudinal sectional views of another embodiment of the present invention, and FIG. FIG. 29 is a schematic diagram of a printing section and a blank section on a sheet and an explanatory diagram of a current control method of the charging means corresponding thereto. 1 photoreceptor, 2 charger, 3 exposure unit, 4
…… Developer, 5… Transfer belt, 6… Transfer charger, 7
... heat roll, 8 ... cleaner, 9 ... paper hopper, 10 ... paper stacker, 11 ... paper pick roller, 12 and 13 ... paper feed roller, 14 ... belt transport roller, 15 ... belt drive roller , 16: Belt cleaner facing roller, 17: Belt cleaner, 18: Facing roller, 19: Bias power supply for resistance measurement, 20: Ammeter, 21
…… Control signal generator, 22 …… High voltage power supply for charging, 23 ……
Inverting path switching member, 24 ... Switching member drive control unit, 25 ...
Return path switching member, 26: Return path switching member drive control unit, 27: Forward / reverse rotation roller, 28: Paper return unit, 29
…… Reversal path, 30 …… Humidity sensor, 31 …… Control signal generator, 33 …… Print signal, 34 …… Print signal converter, 35…
Printed page counter, 36 Print mode signal, 37 Print mode signal converter, 41 Auxiliary charger, 42 Current for auxiliary charger, 43 Surface voltmeter, 44 Ground electrode, 45 …
... insulating film, 46 ... conductor, 47 ... insulating layer, 48 ... transfer belt, 49 ... ground means, 50 ... potential decay rate determination means, 51 and 52 ... surface voltmeter, 55 ... contact member , 56 …… Ammeter,
57: control signal generator, 60: photosensitive sheet, 61: photosensitive cap, 62: draw-out roller, 63: take-up roller, 64: potential holding means, 65: ammeter, 66 ... ... Switching switch, 67 ... Disc electrode, 68 ... Disc electrode, 69 ...
... opaque conductive substrate, 70 ... transparent conductive member, 71 ... reflective mirror, 72 ... luminous body, 75 ... push-up roller, 76 ...
Belt cleaning brush, 77 ... Toner collection roll,
78 Contact means 79 Toner recovery bias 80 Toner cleaning bias 81 Bias roller 82 Additional resistance 83 Bias roll charging voltage power supply 84 Paper suction and resistance measurement Roll, 85: Variable resistor, 86: Variable resistance value control unit, 87: Print sequence signal, 88: AC
Static eliminator, 89 High voltage power supply, 90 High voltage power supply control unit, 91
... Printing sequence signal generator 92 ... Contact member 93 ...
Resistor, 95: Resistor, 96: Contact member, 97: Grounding member, 98: Tension adjusting roll, 99: Resistance value recovery means, 10
0: resistance value recovery means control unit, 101: dry air, 102:
… Hygroscopic air, 103… measurement bias roll, 104… measurement power supply, 105… insulation roll, 106… charged electrode, 107
… Current measuring electrode, 108… bias roll, 109… elastic body, 110… substrate, 111… power supply brush, 112… photoconductive layer, 113… photoconductor base, 114… paper, 115… ... Charging power supply, 116 ... Light elimination lamp, 117 ... Toner, 118 ...
... Bias roll core, 119 ... Elastic body, 120 ... Printing section, 122 ... Tension adjustment roller, L _W ...
_{I: a} printing section, curve A: showing the relationship between the initial relative humidity and the transfer efficiency, curve B: showing the relationship between the relative humidity after about 100 hours of printing and the transfer efficiency, d, m ... … Subscripts indicating low and high humidity, respectively, R, r… indicate volume resistivity and surface resistivity, respectively, A, B… each initial, about 1
Subscript indicating 00 hours later.

Continued on the front page (72) Inventor Yuzuru Shimazaki 4026 Kuji-cho, Hitachi City, Ibaraki Pref.Hitachi, Ltd.Hitachi Laboratory, Hitachi, Ltd. Inventor Masato Yamada 2-6-1, Otemachi, Chiyoda-ku, Tokyo Hitachi Koki Co., Ltd. (56) References JP-A-2-163778 (JP, A) JP-A-62-284376 (JP, A) JP-A-1-109384 (JP, A) JP-A-53-87738 (JP, A) JP-A-61-185066 (JP, U) JP-A-63-20172 (JP, U) JP-A-3-35563 (JP, U)

Claims (3)

(57) [Claims] 1. An apparatus for transferring an image by interposing a transfer member between a charged member charged by a charging unit and an image bearing member, wherein the charging unit is connected to the transferred member of the charged member. The charged member is arranged in a belt shape on the back side opposite to the contacting front side, and a toner release layer containing a fluorine resin is provided on the front side of the charged member. corona discharge deterioration protective layer comprising a fluororesin is provided on the back side of the charging member, wherein a volume resistivity of the charging member is ¹⁰ 10 Ωcm~10 ¹⁴ Ωcm, the electric resistance of the belt-shaped object charging member A transfer device for controlling a charge amount of the corona charge based on the charge amount. 2. An electrophotographic apparatus comprising: a charging unit; and a transfer device that transfers an image by interposing a transfer member between a charged member charged by the charging unit and an image bearing member. A charging member having a belt shape, an electric resistance value of the charged member, a humidity sensor, an operation time of a printed page or the charging unit, a predetermined humidity dependency of the charged member, and the charging; An electrophotographic apparatus that determines the current value of the charging unit based on the electrical resistance value and determines the current value based on the electrical resistance value. 3. An image carrier, a charger for uniformly charging the image carrier, an exposure device for forming an electrostatic latent image on the image carrier, and a toner image on the image carrier. A transfer belt provided with a toner release layer containing a fluororesin on the front side and a corona discharge degradation protection layer containing a fluororesin on the back side; and A transfer charger configured to transfer the toner image onto a transfer member or the transfer belt interposed between the transfer belt and the image carrier by corona charging the back side, and measure an electric resistance of the transfer belt An electrophotographic apparatus, wherein the transfer belt has a volume resistivity of 10 ¹⁰ Ωcm to ^{10 14} Ωcm, the control unit controlling the current of the transfer charger based on the measured electric resistance.