JP2006091322A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with which transfer conditions are stabilized by holding transfer voltage and transfer current always constant, transferability is assured without impressing high voltage and an image failure (such as dust, roughness) is prevented. <P>SOLUTION: In the image forming apparatus which performs a primary transfer of a toner image formed on an image carrier 1 to an intermediate transfer body 6, performs a secondary transfer of the toner image on the intermediate transfer body 6 to transfer material 14 and forms an image, it has: a transfer part constituted of a transfer impression part including a transfer voltage/current impression part 12 and a transfer opposite part including a member 9 opposite to the transfer impression part; a variable register 17 provided between the transfer opposite part and a grounding; a temperature and humidity monitoring sensor 18 which detects transfer conditions and a variable resistor controller 19 which changes resistance of the variable resistor 17 according to a detection result of the temperature and humidity monitoring sensor 18. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine that forms a color image by secondary transfer of toner images of a plurality of colors onto a transfer material at once using an intermediate transfer member.

Conventionally, a transfer material (resistance variation due to temperature and humidity, longitudinal size, thickness, etc.) is used for stable transfer in transfer (primary transfer) and paper transfer (secondary transfer) from a photoreceptor to an intermediate transfer belt. It is known to employ constant current control that changes the transfer voltage in accordance with (see, for example, Patent Documents 1 and 2).
In the transfer device disclosed in Patent Document 1 and an image forming apparatus including the transfer device, a toner image on an intermediate transfer member is transferred by applying a transfer bias to a transfer material adsorbed on a transfer belt.
Further, in the disclosure of Patent Document 1, the transfer bias application power source is configured by connecting a constant voltage circuit and a constant current circuit in series. By changing the voltage value generated from the constant voltage circuit according to the properties of the transfer material, a good image can be obtained without causing a transfer image or a blurred image due to excessive transfer current.
In the image forming method and apparatus disclosed in Patent Document 2, a transfer current (or transfer voltage) that flows through a transfer portion immediately after the transfer of a toner image to a transfer material is started is an ammeter (or voltmeter). And the detected value is given to the CPU.
Then, based on the detected value of the ammeter (or voltmeter), transfer bias correction control is performed only when the transfer bias applied to the transfer material by the CPU exceeds the optimum range.
According to this disclosure, the toner image is transferred onto the transfer material with the optimum transfer bias corrected according to the state of the transfer material and the installation environment of the printer body. The problem that the transfer efficiency of the toner image onto the material is reduced is eliminated.
JP 2000-3101A JP 2000-330401 A

However, when the resistance value of the transfer part component (transfer roller or transfer belt) or transfer paper becomes high due to environmental conditions or the like, a high transfer voltage is required to keep the current constant.
By applying a high voltage, electric discharge easily occurs at the transfer portion, and image defects (such as dust and vomit) occur. In addition, the high voltage power supply is expensive.
In Patent Documents 1 and 2 described above, a voltage upper limiter is provided in order not to apply a high voltage. However, a voltage necessary for making the transfer current constant cannot be applied, and the transfer current Therefore, the optimum transferability cannot be obtained and image defects (such as a decrease in transfer rate) occur.
In view of the above-described circumstances, an object of the present invention is to achieve stable transfer conditions by always keeping the transfer voltage and transfer current constant, and to ensure transferability without applying a high voltage, resulting in image defects ( It is an object of the present invention to provide an image forming apparatus that does not generate dust or vomit.

In order to solve the above problems, the invention according to claim 1 is to primarily transfer a toner image formed on an image carrier onto an intermediate transfer member, and use the toner image on the intermediate transfer member as a transfer material. In an image forming apparatus that forms an image by secondary transfer, a transfer unit including a transfer application unit including a transfer voltage / current application member, and a transfer opposing unit including a member facing the transfer application unit; A variable resistor provided between the transfer facing portion and the ground, a transfer condition detecting means for detecting a transfer condition, and a control means for changing the resistance value of the variable resistor in accordance with a detection result of the transfer condition detecting means. And.
According to a second aspect of the present invention, the transfer condition detecting means is a temperature / humidity sensor for detecting temperature / humidity, and the control means is a resistance of the variable resistor according to the temperature / humidity detection result of the temperature / humidity sensor. It is characterized by changing the value.
Further, the transfer condition detecting means is a transfer material resistance detecting means for detecting a resistance value of the transfer material, and the control means changes the resistance value of the variable resistor in accordance with the resistance value of the transfer material. Features.
According to a fourth aspect of the present invention, the transfer condition detecting means is a counter ammeter disposed on the transfer facing portion to measure the counter current of the transfer facing portion, and the control means is The resistance value of the variable resistor is changed in accordance with the counter current measurement result of the counter ammeter.
The transfer condition detecting means may be configured such that the transfer condition detecting means measures a counter current of the transfer counter part and a counter ammeter disposed on the transfer counter part and an applied current of the transfer application part. An application ammeter disposed in the transfer application unit, and the control means determines the difference between the counter current measurement result of the counter ammeter and the application current measurement result of the application ammeter. It is characterized in that the resistance value of the variable resistor is changed.
The invention described in claim 6 is characterized in that a plurality of the variable resistors are provided in the main scanning direction.
The invention according to claim 7 is characterized in that the control means changes the resistance value of the variable resistor according to the width of the transfer material from the size information of the transfer material.
The invention according to claim 8 forms a color image by superimposing a plurality of color toner images on the intermediate transfer member and then transferring the plurality of color toner images to the transfer material in a lump. It is characterized by that.

  According to the present invention, since the variable resistance is changed according to the transfer condition, the total resistance value in the transfer portion can be always constant, and the transfer voltage for securing the transfer current can also be constant. By performing transfer without applying a high voltage when the voltage fluctuates, it is possible to prevent the occurrence of transfer defects (such as dust and blurring).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of an image forming apparatus according to the present invention. In FIG. 1, an image forming apparatus applies a primary transfer bias from a primary transfer bias unit 15 to a back surface of an intermediate transfer body 6 by a primary transfer application roller 8 on a toner image formed on an image carrier 1. The toner image is transferred onto the intermediate transfer member 6.
Thereafter, the image forming apparatus is configured to transfer a toner image onto the transfer material 14 by applying a voltage from the secondary transfer power source 16 to the back surface of the transfer material 14 with the secondary transfer application roller 12. 2 is an image carrier, 3 is an image carrier driving roller, 4 is a primary transfer counter roller, 5 is an image carrier cleaning blade, 7 is an intermediate transfer body driving roller, 10 is a belt cleaning counter roller, and 11 is an intermediate. A transfer body tension roller 13 is a belt cleaning brush.
A variable resistance portion 17 is provided in the secondary transfer counter roller 9 configured on the side opposite to the secondary transfer application roller 12, and the environment (temperature, A temperature / humidity sensor 18 for measuring (humidity) is mounted. Based on the detection result of the temperature / humidity sensor 18, the resistance value of the variable resistance unit 17 is determined and changed by the variable resistance control unit 19 serving as a control means.
Chemical products (for example, PI (polyimide resin) or EP (ethylene propylene) rubber) are used for the intermediate transfer body 6, the secondary transfer application roller 12, and the secondary transfer counter roller 9, and the resistance value increases at low temperatures and low humidity. .
Therefore, the resistance value of the variable resistance unit 17 is controlled by the variable resistance control unit 19 so that the resistance value becomes low at low temperatures and low humidity, medium resistance at normal temperature, and high resistance at high temperature. Even when the environment changes and the resistance of the components of the transfer section changes, the total resistance in the transfer section set in advance can be obtained, and the transfer voltage and transfer current can always be fixed to the same condition.

FIG. 2 is a schematic view showing a second embodiment of the image forming apparatus according to the present invention. In FIG. 2, the same parts as those in FIG.
In the image forming apparatus shown in FIG. 2, a transfer condition detecting means for detecting a transfer condition is constituted by a transfer material resistance measuring unit 20, and the transfer material resistance measuring unit 20 transfers the transfer material 14 to roller pairs 23 and 24. The volume resistance value is calculated by measuring the current when the voltage is applied. Based on the calculation result, the variable resistance control section 19 changes the variable resistance section 17 so that the transfer section total resistance is set in advance, and the transfer condition is controlled to be the same even when the type of the transfer material 14 is changed.
FIG. 3 is a schematic view showing a third embodiment of the image forming apparatus according to the present invention. In FIG. 3, the same parts as those in FIG.
In the image forming apparatus shown in FIG. 3, the transfer condition detecting means is constituted by the counter ammeter 21. A variable resistance control unit 19 and a counter ammeter 21 are provided in the secondary transfer counter roller 9 to measure the current flowing to the counter side during transfer, and the variable resistance control unit 19 adjusts the counter current to a preset value. The resistance value of the variable resistance portion 17 is changed at.
FIG. 4 is a graph showing the current measurement value of the counter ammeter in FIG. 3 when the resistance value of the secondary transfer counter roller is changed. FIG. 4 shows the current measurement value of the counter ammeter 21 in FIG. 3 when the resistance value of the secondary transfer counter roller 9 is changed.
The counter current changes as the resistance of the secondary transfer counter roller 9 changes. By providing the variable resistance portion 17 in the secondary transfer counter roller 9, the resistance value is always constant, and the counter current can be stabilized.
FIG. 5 is a graph showing the relationship between the measured current value of the counter ammeter and the amount of mobile charge actually transferred. FIG. 5 shows the relationship between the current measurement value of the counter ammeter 21 and the amount of transferred charge actually transferred (transferred charge amount), and the relationship between the counter current and the amount of transferred charge indicating transferability. Therefore, it is possible to ensure transferability by stabilizing the counter current to an optimum value.
FIG. 6 is a schematic view showing a fourth embodiment of the image forming apparatus according to the present invention. In FIG. 6, the same parts as those in FIG.
In the image forming apparatus shown in FIG. 6, the transfer condition detecting means is constituted by an applied ammeter 22. An applied ammeter 22 is provided on the secondary transfer application roller 12 to measure the current flowing through the secondary transfer application roller 12 during transfer. Then, the counter current-applied current is calculated from the measured applied current value and the current measurement result of the counter ammeter 21. The resistance value of the variable resistance unit 17 is changed so as to become a preset value based on the calculated result.

FIG. 7 is a schematic diagram illustrating the relationship between the calculation result of the counter current-applied current calculated from the applied ammeter and the counter ammeter and the amount of mobile charge. FIG. 7 shows the relationship between the calculation result of the counter current-applied current calculated from the applied ammeter 22 and the counter ammeter 21 in FIG.
Since the difference between the counter current and the applied current is related to the amount of mobile charge representing transferability, the transferability can be secured by changing the resistance of the variable resistance portion 17 to an optimum current.
FIG. 8 is a schematic view showing a fifth embodiment of the image forming apparatus according to the present invention.
The image forming apparatus shown in FIG. 8 is provided with a plurality (A, B, C, D) of variable resistance portions 17 in the main scanning direction. Although not shown, a control means for controlling each variable resistor 17 is also provided for each variable resistor unit 17, thereby eliminating a resistance difference in the main scanning direction of the transfer unit. The transfer material 14 is shown between the secondary transfer counter roller 9 and the secondary transfer application roller 12.
The arrangement position and the number of arrangement of the variable resistance parts 17 (A, B, C, D) in FIG. 8 are determined from the transfer material size, and the resistance value is higher in the area where the transfer material 14 does not pass in the transfer part than the passing part. In this way, a transfer current is not applied to a portion where there is no transfer material.
For example, in the variable resistance portions A, B, C, and D, when A is arranged in the A4 width, B and C are arranged in the postcard width, and the postcard is passed through, B, C <A, B Change the resistance so that A and B are set so that the resistance difference becomes extremely larger than the resistance values of postcard resistance + B and C, taking into account the resistance of the postcard.
In the above configuration, when the voltage application direction of the secondary transfer is the back surface of the intermediate transfer body 6, the application side and the opposite side are arranged oppositely, and the variable resistance portion 17 is provided on the back surface side roller of the transfer material 14. It is possible to respond by connecting.

According to the present invention, since the transfer condition is detected using the temperature / humidity sensor, even when the resistance of the transfer material or the transfer part component (belt, roller, etc.) changes due to environmental fluctuations, the resistance value in the transfer part. Can always be constant.
In addition, by making the transfer voltage for securing the transfer current constant, the transfer is performed without applying a high voltage when the voltage fluctuates, thereby preventing the occurrence of transfer defects (such as dust and vomit).
In the present invention, since the resistance of the transfer material is detected by the transfer material resistance detection means, even when the transfer material (transfer paper thickness, type, etc.) changes, the resistance value in the transfer portion can be always constant. In addition, the voltage and current can be stabilized, and the occurrence of transfer defects (such as dust and blurring) can be prevented.
According to the present invention, it is possible to calculate the total resistance and transfer transfer charge amount in the transfer portion by arranging an ammeter on the transfer opposite side and measuring the current during transfer. By changing the variable resistance value based on the result, it is possible to make the total resistance and the amount of moving charges constant. Therefore, even when the environmental change or the transfer material changes, the transferability can be stabilized, and the occurrence of transfer defects (such as dust and blurring) can be prevented.
According to the present invention, ammeters are arranged on the transfer application side and the transfer opposite side, and the amount of moving charge can be calculated from the difference between them, and the variable resistance value is changed so as to make the amount of moving charge constant from the result. This makes it possible to stabilize the transferability and prevent the occurrence of transfer defects (such as dust and blurring) even when the environmental change or the transfer material changes.
Further, according to the present invention, by providing a plurality of variable resistors in the main scanning direction, the resistance value in the main scanning direction can be kept constant, and the transferability deviation of the transfer material in the main scanning direction can be reduced. In addition, it is possible to prevent the occurrence of transfer defects (such as dust and vomit).
Furthermore, according to the present invention, since the resistance value of the variable resistor is changed according to the transfer material width from the size information of the transfer material, an excessive current is not passed to a portion where there is no transfer material, and transfer failure ( Occurrence of dust and soot) can be prevented.
The image forming apparatus of the present invention is applicable to an image forming apparatus that forms a color image. When applied to an image forming apparatus that forms a color image, a toner image is formed on the image carrier 1, After the primary transfer onto the intermediate transfer body 6 and the multiple color toner images are repeatedly superimposed on the intermediate transfer body 6, the multiple color toner images are collectively transferred onto the transfer material 14. A color image may be formed by transfer.

1 is a schematic view showing an embodiment of an image forming apparatus according to the present invention. It is the schematic explaining the transfer material resistance measurement part in the image forming apparatus by this invention. FIG. 3 is a schematic diagram illustrating a counter ammeter provided on a secondary transfer counter roller in the image forming apparatus according to the present invention. It is a figure which shows the electric current measured value of the counter ammeter in FIG. 3 with a graph when changing the resistance value of a secondary rolling opposing roller. It is a figure which shows the relationship between the electric current measurement value of a counter ammeter, and the amount of mobile charges actually transferred. FIG. 3 is a schematic diagram illustrating an applied ammeter provided on a secondary transfer application roller in the image forming apparatus according to the present invention. It is the schematic which shows the relationship between the calculation result of the counter current-applied current calculated from the applied ammeter and the counter ammeter and the amount of mobile charge. It is the schematic which shows the variable resistance part provided with two or more in the main scanning direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Image carrier, 6 Intermediate transfer body, 9 Transfer part (transfer opposing part, member, secondary transfer opposing roller), 12 Transfer part (transfer application part, transfer voltage / current application member, secondary transfer application roller), 14 Transfer material, 16 Secondary transfer power supply, 17 Variable resistor (variable resistor unit), 18 Transfer condition detection means (temperature / humidity sensor), 19 Variable resistance control unit, 20 Transfer material resistance detection means (transfer material resistance measurement unit) , 21 Opposing ammeter, 22 Applied ammeter

Claims (8)

  In an image forming apparatus in which a toner image formed on an image carrier is primarily transferred onto an intermediate transfer member, and the toner image on the intermediate transfer member is secondarily transferred to a transfer material to form an image. A transfer unit including a transfer application unit including an application member, a transfer counter unit including a member facing the transfer application unit, a variable resistor provided between the transfer counter unit and the ground, and transfer conditions An image forming apparatus comprising: a transfer condition detection unit that detects a change in resistance; and a control unit that changes a resistance value of the variable resistor in accordance with a detection result of the transfer condition detection unit.   The transfer condition detecting means is a temperature / humidity sensor for detecting temperature / humidity, and the control means changes a resistance value of the variable resistor in accordance with a temperature / humidity detection result of the temperature / humidity sensor. The image forming apparatus according to 1.   The transfer condition detecting means is a transfer material resistance detecting means for detecting a resistance value of the transfer material, and the control means changes the resistance value of the variable resistor in accordance with the resistance value of the transfer material. The image forming apparatus according to claim 1.   The transfer condition detecting means is a counter ammeter disposed in the transfer counter part for measuring the counter current of the transfer counter part, and the control means is responsive to the counter current measurement result of the counter ammeter. The image forming apparatus according to claim 1, wherein a resistance value of the variable resistor is changed.   The transfer condition detecting means is disposed in the transfer application unit for measuring a counter ammeter disposed in the transfer counter unit for measuring the counter current of the transfer counter unit and in the transfer application unit. And the control means changes the resistance value of the variable resistor from the difference between the opposing current measurement result of the opposing ammeter and the applied current measurement result of the applied ammeter. The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 1, wherein a plurality of the variable resistors are provided in the main scanning direction.   The image forming apparatus according to claim 6, wherein the control unit changes a resistance value of the variable resistor according to a width of the transfer material from size information of the transfer material.   The color image is formed by superimposing a plurality of color toner images on the intermediate transfer member and then transferring the plurality of color toner images to the transfer material at a time. 8. The image forming apparatus according to any one of items 7.

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