JPH063972A - Transferring and carrying device - Google Patents

Abstract

PURPOSE:To perform good transferring action even though such an environmental condition as air pressure, temperature and humidity and the condition of a transferring paper are changed as to a transferring and carrying device without having a transferring and separation charger in which ozone is not produced. CONSTITUTION:As to the transferring and carrying device provided with a carrying means 13 in which a toner image formed on a photosensitive body 2 is superposed and carried by electrostatically attracting the transferring paper 15 to a dielectric belt 12, a contact electrode 10 directly applying a charge to the dielectric belt 12, and a bias power source 18 impressing a voltage on the contact electrode 10; a resistance value detecting means detecting the resistance value of the dielectric belt 12 which is seen from the contact electrode 10 is provided, a load condition is detected through the change of the resistance value, and a current Ip flowing in the photosensitive body 2 can be made constant so that uniform transferring can be always performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer / transport device applied to an electrophotographic device such as a copying machine, a printer or a facsimile.

[0002]

2. Description of the Related Art Generally, in an electrophotographic apparatus, an electrostatic latent image is formed on a photoconductor uniformly charged by a charging charger and then visualized by a developing apparatus to form a toner image. It is designed to be transferred to transfer paper. Here, the transfer unit transfers the toner image on the photoconductor by the action of the transfer charger to the transfer paper fed toward the photoconductor by the registration roller at a predetermined timing, and then transfers it by the action of the separation charger. It is configured to separate the paper from the photoconductor and convey it to a fixing unit or the like.

However, in such a structure, a transfer / separation charger is required in the transfer portion in addition to the indispensable charging charger, so that ozone, which has become an environmental problem in recent years, is generated. From this point of view, it is required to suppress the generation of ozone as much as possible in the structure of a transfer portion that does not include a transfer / separation charger.

Based on such a viewpoint, a transfer unit is provided in the transfer section for electrostatically adsorbing the transfer paper to the dielectric belt and superposing and transferring the toner images formed on the photoreceptor.
A transfer / conveyance device has been proposed in which electric charges are directly applied to the dielectric belt by a contact electrode to which a voltage is applied by a bias power source.

[0005]

However, in the case of the method using such a dielectric belt, when the environmental conditions such as atmospheric pressure, temperature and humidity, and the state of the transfer paper are changed, the current flowing to the photoconductor side is also changed. Instability may result in unstable transfer, but no measures have been taken to address this point.

[0006]

According to a first aspect of the present invention, there is provided a conveying unit that electrostatically attracts a transfer sheet to a dielectric belt and conveys toner images formed on a photoconductor in an overlapping manner. In a transfer / transport device including a contact electrode for directly applying an electric charge to the dielectric belt and a bias power source for applying a voltage to the contact electrode, a resistor for detecting a resistance value of the dielectric belt viewed from the contact electrode. A value detecting means is provided.

According to a second aspect of the present invention, the resistance value detecting means includes a current detecting means for detecting a current flowing through the contact electrode for applying an electric charge to the dielectric belt from the bias power source, and a bias voltage applied to the contact electrode. The voltage detecting means for detecting and the calculating means for calculating the resistance value of the dielectric belt based on the detected current value and voltage value.

Further, in the third aspect of the present invention, the dielectric belt is formed into an endless belt, and both inner ends are stretched by a roller which is applied with a bias voltage by a bias power source and serves as a contact electrode and a roller which is grounded and serves as an earth electrode. A resistance value by means of a ground current detecting means for mounting and detecting a current flowing through the ground electrode, and a calculating means for calculating the resistance value of the dielectric belt based on the detected ground current value and the bias voltage value by the bias power source. A detection means was provided.

Further, according to the invention of claim 4, there is provided a charge amount control means for varying the amount of charge applied to the dielectric belt according to the detected resistance value of the dielectric belt.

[0010]

According to the first aspect of the present invention, the resistance value of the dielectric belt is detected by the resistance value detecting means. Therefore, there are variations in the resistance value in manufacturing, variations in materials, fluctuations in resistance with time, Optimal image transfer in a transfer / separation chargerless configuration by detecting changes in environmental conditions such as changes in the resistance value of the dielectric belt, and taking necessary measures such as constant control of the photoconductor current according to the detection results. Is done.

In this case, according to the invention of claim 2,
Since the voltage value and the current value supplied to the dielectric belt are detected, and the resistance value detecting means for detecting the resistance value of the dielectric belt by performing arithmetic processing based on these detected values, a special detecting means is provided. There is no need for a simple configuration.

Similarly, in the invention according to claim 3,
One roller that stretches the dielectric belt is used as the ground electrode, and the ground current flowing through this ground electrode is detected, and the resistance value detecting means for detecting the resistance value of the dielectric belt using the bias voltage value is used. The configuration is sufficient.

Further, in the invention according to claim 4,
Since the amount of electric charge supplied to the dielectric belt is changed according to the detected resistance value of the dielectric belt, relatively good transfer can be performed for a certain period even when the dielectric belt is deteriorated. Will be maintained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. First, FIG. 2 shows a configuration example of an image forming unit and a transfer / conveyance device in a copying machine. The image forming unit 1 is mainly composed of a drum-shaped photoconductor 2, around which a charging corona discharger 3, an exposure optical system 4, a developing device 5, a pre-transfer charge eliminator 6, a transfer device are formed in accordance with an electrophotographic process. The transport device 7, the cleaning device 8, the static eliminator 9 and the like are arranged in this order.

Here, in the transfer / transport device 7, first,
An endless belt-shaped dielectric belt 1 between a pair of rollers 10 and 11.
A transport means 13 in which 2 is stretched is provided. The dielectric belt 12 is arranged such that the roller 10 side portion thereof contacts the transfer position of the photoconductor 2, and the flatness at the contact position is maintained by the auxiliary roller 14. Further, the registration roller 1 for feeding the transfer paper 15 toward the nip portion between the photoconductor 2 and the dielectric belt 12 at a predetermined timing.
6 and a guide 17 are provided.

The roller 10 serves as a contact electrode and is electrically connected to a bias power source 18 so as to directly apply an electric charge to the dielectric belt 12 through the roller 10. On the other hand, the roller 11 serves as a ground electrode and is grounded via a ground current detecting means 19. The bias power supply 18 and the ground current detecting means 19 function as a CP detecting means.
It is connected to U20. The CPU 20 is also connected to a photoconductor voltage detection means 21 for detecting the voltage of the photoconductor 2. In addition, the roller 11 with respect to the dielectric belt 12
The cleaning blade 22 is in contact with the downstream side position of the.

In such a structure, the photosensitive member 2 has a negative polarity (about -8) due to corona discharge by the charging corona discharger 3.
00V). Then, the exposure optical system 4 irradiates the image information to form an electrostatic latent image on the photoconductor 2. Next, in the developing device 5, the toner charged to the positive polarity adheres to the photoconductor 2 in accordance with the latent image potential, so that a toner image is formed. This toner image passes through the pre-transfer charge eliminator 6 to weaken the electrostatic attraction force with the photoconductor 2. On the other hand, the transfer paper 15 is sent out from the registration roller 16 and electrostatically attracted to the dielectric belt 12 to which a bias voltage is applied. The transfer paper 15 is superposed on the toner image at the nip portion, and the toner image to which an electric field having a polarity opposite to the electric charge (positive polarity) of the toner is applied from the back surface of the transfer paper 15 via the dielectric belt 12 is the transfer paper 15. Is transcribed to. Paper dust and a small amount of toner that has not been transferred are adhered to the photosensitive body 2 after the transfer, and thus are removed by the cleaning device 8. Then, the photoconductor 2 is photo-erased by the static eliminator 9 to return to the initial state, and the series of image forming processes is completed.

Here, the vicinity of the transfer / transport device 7 will be described in detail with reference to FIG. First, an electrostatic latent image of image information and a toner image electrostatically attracted to the electrostatic latent image are formed on the photosensitive layer 2b on the surface of the photosensitive member 2 with the conductive substrate 2a grounded. On the other hand, from the back surface of the transfer paper 15, the bias power source 18
As a result, electric charges are applied to the dielectric belt 12 via the rollers 10 and 14. Here, on the surface of the transfer paper 15 interposed in the nip portion between the photoconductor 2 and the dielectric belt 12,
The negative charge is induced, and the toner image is transferred to the transfer paper 15 at the contact surface with the toner image. Due to the strong electric field on the side of the dielectric belt 12, the transfer paper 15 on which the toner image is transferred passes through the separation point of the photoconductor 2 while being attracted to the dielectric belt 12, and is conveyed to the next process (fixing) side. The potential of the dielectric belt 12 gradually decreases from the contact electrode (roller 10) to which the bias is applied toward the ground electrode (roller 11) side, and is almost 0 V at the contact portion with the roller 11. For this reason, the electrostatic attraction between the dielectric belt 12 and the transfer paper 15 is almost eliminated in the vicinity of the roller 11, so the transfer paper 15 is separated from the dielectric belt 12 due to its rigidity and waist, and the fixing unit side. Head to. After this, since untransferred toner, paper dust, and the like have adhered to the surface of the dielectric belt 12, the blade 22 scrapes it off.

Next, the control relating to such a transfer / transport device 7 will be described. First, in the bias power source 18 that applies an electric charge to the dielectric belt 12, its output voltage Vo
The output current Io and the output current Io are respectively detected by a voltage detecting means and a current detecting means (not shown), and input to the A / D converter in the CPU 20. Here, the output current Io is the dielectric belt 12 and the current Ip flowing to the side of the photoconductor 2 and the roller 1
It is shunted to the ground current Ia flowing through 1 to the ground.
The ground current Ia flowing to the ground is the ground current detecting means 19
Is detected by and is input to the A / D converter in the CPU 20.

Therefore, the CPU 20 calculates the difference between the output current Io and the ground current Ia, and the current I flowing through the photoconductor 2 is calculated.
p is obtained, and the output of the bias power source 18 is controlled by constant current so that the current Ip becomes a predetermined value. As a result, even if the resistance value of the dielectric belt 12 fluctuates due to manufacturing variations or the like, the current Ip flowing through the photoconductor 2 is constant, so that uniform transfer can always be performed.

By the way, when the transfer / transport device 7 is electrically viewed, it is as shown in FIG. First, the load from the bias power source 18 of the voltage V _B branches in two directions. One is a serial connection of the resistance Z ₁ of the dielectric belt 12 in the thickness direction, the resistance Z ₃ of the transfer paper 15, and the average resistance Z ₄ of the photoconductor 2 in the direction of the photoconductor 2. The other is two rollers 1 that bridge the dielectric belt 12 in the circumferential direction of the dielectric belt 12.
It is a resistance Z ₂ between 0 and 11.

In the present embodiment, the voltage V _B applied to the dielectric belt 12, the output current Io and the earth current Ia are directly detected, converted into digital data by the CPU 20, and further the output current Io and the earth current Ia. Since the current Ip flowing through the photoconductor 2 is detected by calculating the digital data of and, the resistance value of the load can be obtained by calculating these digital data. Incidentally, the circumferential resistance value Z ₂ of the dielectric belt 12 is obtained by dividing the voltage V _B by the ground current Ia.

Since the load condition is detected in this manner, the resistance value of the dielectric belt 12 fluctuates (manufacturing variation,
Variation in resistance from the beginning due to variation in materials, etc.
Variation of resistance with time, environmental variation such as temperature and humidity) Variation of resistance value of the transfer paper 15 (variation of resistance value from the beginning, difference due to paper type such as carbon amount and thickness, moisture absorption variation due to environmental change) 15 size change Even if there is a change in image density (transferred toner), a good transfer operation can be performed.

In the above description, the dielectric belt 1
The current I flowing through the photoconductor 2 with respect to the variation of the resistance value of 2
Although uniform transfer can be performed by keeping p constant, the electric charge supplied to the dielectric belt 12 may be changed when the detected resistance value is equal to or higher than a predetermined value.
For example, a rubber-based medium-resistance dielectric belt 12
It has been experimentally confirmed that the resistance value increases with the use of weakened bonds between the molecules constituting the belt over time.
In this case, the voltage applied to the dielectric belt 12 also rises, but on the contrary, an abnormal image may occur due to the peeling discharge due to the high voltage. Therefore, when the resistance value of the dielectric belt 12 becomes a predetermined value or more, if the current supplied to the dielectric belt 12 is reduced, it is possible to secure a relatively good transfer for a certain period even with the deteriorated belt. Further, in parallel with this, the fact that the belt replacement time has been reached may be displayed.

[0025]

According to the first aspect of the present invention, by providing the resistance value detecting means for detecting the resistance value of the dielectric belt as viewed from the contact electrode, there are variations in the resistance value in manufacturing and in the materials. Since it is possible to detect the load status through resistance value fluctuations of the dielectric belt due to changes in resistance and environmental conditions over time, necessary measures such as constant control of the photoconductor current according to the detection results. By adopting the above, optimum image transfer can be performed in the transfer / separation chargerless configuration.

In this case, according to the second aspect of the present invention, the voltage value and the current value supplied to the dielectric belt are detected, and the resistance value of the dielectric belt is detected by performing arithmetic processing based on these detected values. Since the resistance value detecting means is provided, the resistance value of the dielectric belt can be detected with a simple structure without providing any special detecting means.

Similarly, according to the third aspect of the invention, one of the rollers that stretches the dielectric belt is used as the ground electrode, and the ground current flowing through this ground electrode is detected, and the dielectric belt is used by using the bias voltage value. Since the resistance value detecting means for detecting the resistance value is used, the resistance value of the dielectric belt can be detected with a simple configuration.

Further, according to the invention as set forth in claim 4, since the amount of electric charge supplied to the dielectric belt is made variable according to the detected resistance value of the dielectric belt, the dielectric belt is deteriorated. Even in such a case, relatively good transfer can be maintained for a certain period.

[Brief description of drawings]

FIG. 1 is an enlarged front view of the vicinity of a transfer portion showing an embodiment of the present invention.

FIG. 2 is a schematic front view showing the vicinity of an image forming unit and a transfer / transport device.

FIG. 3 is an electrical circuit diagram in the vicinity of a transfer / transport device.

[Explanation of symbols]

 2 Photoreceptor 10 Roller = Contact Electrode 11 Roller = Ground Electrode 12 Dielectric Belt 13 Conveying Means 15 Transfer Paper 18 Bias Power Supply 19 Earth Current Detecting Means 20 Resistance Detecting Means, Charge Amount Means

Claims (4)

[Claims] 1. A transfer device for electrostatically adsorbing a transfer paper to a dielectric belt to transfer toner images formed on a photoconductor in a superposed manner, and a contact electrode for directly applying an electric charge to the dielectric belt. And a bias power supply for applying a voltage to the contact electrode, wherein a transfer value is provided to detect the resistance value of the dielectric belt as viewed from the contact electrode. Transport device. 2. The resistance value detection means includes a current detection means for detecting a current flowing from a bias power source to a contact electrode for applying an electric charge to the dielectric belt, and a voltage detection means for detecting a bias voltage applied to the contact electrode. 2. The transfer / conveyance apparatus according to claim 1, further comprising a calculation unit that calculates a resistance value of the dielectric belt based on the detected current value and voltage value. 3. The endless belt is used as the dielectric belt, and both inner ends are stretched by a roller serving as a contact electrode by applying a bias voltage by a bias power source and a roller serving as a ground electrode and flowing to the ground electrode. A resistance value detecting means for detecting a current and a resistance value detecting means for calculating a resistance value of the dielectric belt based on the detected ground current value and the bias voltage value by the bias power source are provided. The transfer conveyance device according to claim 1. 4. The charge amount control means for varying the amount of charge applied to the dielectric belt according to the detected resistance value of the dielectric belt. Transfer transport device.