JP2007086814A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device capable of preventing void and insufficient transfer of a transfer image resulting from an environmental change and to provide an image forming apparatus equipped with the same. <P>SOLUTION: The transfer device includes: an intermediate transfer belt 101 moved in an endless manner; a secondary transfer bias roller 102 that applies a transfer current in contact with the belt 101; and a secondary transfer opposite roller 103 disposed on the face of the intermediate transfer belt 101 opposite to its contact face with the secondary transfer bias roller 102 and used to guide the transfer current in the direction of the thickness of the intermediate transfer belt 101, thereby defining a transfer position between the secondary transfer bias roller 102 and the secondary transfer opposite roller 103. In such a configuration, a secondary transfer nip current flowing from the intermediate transfer belt 101 to the secondary transfer opposite roller 103 is maintained at a prescribed range regardless of an environmental change by applying a secondary transfer bias to the intermediate transfer belt 101 from the secondary transfer bias roller 102. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transfer device for transferring a visible image such as a toner image from a visible image carrier belt such as a photosensitive member or an intermediate transfer belt to a transfer member such as transfer paper, and a facsimile, printer, copier, etc. provided with the transfer device The present invention relates to an image forming apparatus.

  Conventionally, a transfer device shown in FIG. 4 is known as this type of transfer device. In the figure, a transfer device 100 includes an intermediate transfer belt 101 as a visible image carrying belt, a secondary transfer bias roller 102 as a transfer current applying member, and a secondary transfer bias power source (not shown) for applying a secondary transfer bias thereto. A secondary transfer counter roller 103, a driving roller 104, a stretching roller 105, a primary transfer bias roller 106, a primary transfer earth roller 107, and the like are included.

  The intermediate transfer belt 101 is stretched between the secondary transfer counter roller 103, the drive roller 104, the stretching roller 105, the primary transfer bias roller 106, and the primary transfer ground roller 107, while the arrow in the drawing is drawn by the drive roller 104. It is driven to rotate in the B direction. A portion of the intermediate transfer belt 101 positioned between the primary transfer bias roller 106 and the primary transfer earth roller 107 is urged toward the photosensitive drum 1 of the image forming apparatus by both rollers, thereby causing a photosensitive effect. The primary transfer position is formed by positively adhering to the body drum 1.

  At the primary transfer position, a primary transfer electric field is formed between the primary transfer bias roller 106 and the intermediate transfer belt 101 by applying a primary transfer current. Most of the primary transfer current applied to the intermediate transfer belt 101 is guided to the ground via the primary transfer ground roller 107.

  The secondary transfer counter roller 103 and the secondary transfer bias roller 102 sandwich the intermediate transfer belt 101 therebetween to form a secondary transfer nip as a transfer position. In the secondary transfer nip, a secondary transfer electric field is formed by a secondary transfer bias having a polarity opposite to that of the toner applied from the secondary transfer bias roller 102 to the intermediate transfer belt 101.

  The driving roller 104 and the stretching roller 105 are in contact with the back surface of the intermediate transfer belt 101 on the downstream side and upstream side of the secondary transfer nip (hereinafter, simply referred to as nip downstream side and nip upstream side), respectively. The residual charge of the belt 101 is guided to the ground.

  When the intermediate transfer belt 101 passes through the primary transfer position as it rotates, the toner image is primarily transferred from the photosensitive drum 1 by the action of the primary transfer electric field. The primarily transferred toner image enters the secondary transfer nip as the intermediate transfer belt 101 rotates.

  On the other hand, a sheet feeding unit (not shown) of the image forming apparatus feeds the transfer sheet 10 toward the secondary transfer nip at a timing at which the transfer sheet 10 can be superimposed on the toner image. The toner image superimposed on the transfer paper 10 at the secondary transfer nip is secondarily transferred from the intermediate transfer belt 101 to the transfer paper 10 by the action of the pressure in the nip and the secondary transfer electric field.

  In the transfer device 100 having such a configuration, when the secondary transfer bias power source applies a secondary transfer bias having a predetermined voltage value to the secondary transfer bias roller 102, the electrical resistance of the intermediate transfer belt 101 is subject to environmental fluctuations. When the change occurs, the secondary transfer current flowing from the secondary transfer bias roller 102 to the intermediate transfer belt 101 changes. If the secondary transfer current changes in this way, the secondary transfer performance becomes unstable, and a secondary transfer image with a stable quality cannot be obtained.

  Therefore, a transfer device is known in which the secondary transfer bias power source is controlled at a constant current so that the secondary transfer current flowing from the secondary transfer bias roller 102 to the intermediate transfer belt 101 is constant. In such a transfer device, a constant secondary transfer current can be applied to the intermediate transfer belt 101 regardless of fluctuations in the electrical resistance of the intermediate transfer belt 101.

  However, even if the secondary transfer current is controlled at such constant current, the secondary transfer performance may become unstable depending on the temperature and humidity environment.

  Therefore, as a result of earnest research on the cause of unstable secondary transfer performance due to temperature and humidity environments, the present inventors have found the following phenomenon. That is, in the transfer device shown in FIG. 4, the secondary transfer current supplied to the intermediate transfer belt 101 is transmitted to the downstream side of the nip in the belt and flows into the drive roller 104 as shown in FIG. Then, the current is split into a nip current A2 that flows in the belt thickness direction in the nip and flows into the secondary transfer counter roller 103, and an upstream current A3 that travels in the belt to the upstream side of the nip and flows into the stretching roller 105. The downstream resistance R1, the nip resistance R2, and the upstream resistance R3 act on the downstream current A1, the nip current A2, and the upstream current A3, respectively. As shown in FIG. 6, the downstream resistance R <b> 1 is an electric resistance in a length L <b> 1 from the secondary transfer nip of the intermediate transfer belt 101 to a contact position with the driving roller 104, and an electric resistance of the driving roller 104. Is the sum of The nip resistance R <b> 2 is the sum of the electrical resistance corresponding to the thickness of the intermediate transfer belt 101 and the electrical resistance of the secondary transfer counter roller 103. The upstream resistance R3 is the sum of the electrical resistance in the length L2 from the secondary transfer nip of the intermediate transfer belt 101 to the contact position with the stretching roller 105 and the electrical resistance of the stretching roller 105. It is.

  Changes in electrical resistance due to environmental fluctuations occur not only in the intermediate transfer belt 101 but also in the secondary transfer counter roller 103, the driving roller 104, and the stretching roller 105. When at least one of these rollers changes its electrical resistance at a different rate of change from the others, the ratio of the nip resistance R2 to the total resistance R0, which is the sum of the electrical resistances R1 to R3, changes. To do. As the environment changes to increase this rate, the nip current A2 will naturally decrease. When this reduction amount reaches a predetermined value, it is understood that the electrostatic force for moving the toner from the intermediate transfer belt 101 to the transfer paper 10 at the secondary transfer nip is insufficient and the transfer amount becomes insufficient. It was. In particular, in a portion having a relatively large amount of toner adhering, such as a solid portion of an image, the image tends to become dull due to insufficient transfer amount due to insufficient electrostatic force. Further, when the environment changes so as to increase the nip current A2, and the amount of increase reaches a predetermined value, a charge having a polarity opposite to the normal polarity is injected into the toner. As a result, it has been found that the image appears as white spots without being partially transferred. In particular, in a portion where the toner adhesion amount is relatively small, such as a halftone portion, the charge injection amount per toner particle tends to be larger than the solid portion, and white spots tend to occur.

  The transfer device that applies the secondary transfer bias having the opposite polarity to the toner to the transfer surface of the intermediate transfer belt 101 has been described with reference to FIGS. 4 to 6. However, the secondary transfer bias having the same polarity as the toner is used. The same blur (transfer amount shortage) may occur in the transfer device that applies to the back surface of the intermediate transfer belt 101. Similar blurring or white spots may occur even in a transfer device in which only one of the rollers is connected to the ground instead of the transfer device in which the driving roller 104 and the stretching roller 105 are connected to the ground. In addition, a transfer position forming roller instead of the secondary transfer counter roller 103 is not a transfer device that forms the secondary transfer nip, and contacts the intermediate transfer belt 101 at a position not facing the secondary transfer bias roller 102. Similar blurring and white spots may occur in the transfer device that forms the next transfer position. Furthermore, the blurring and white spots that occur when the toner image is secondarily transferred from the intermediate transfer belt 101 to the transfer paper 10 have been described. However, when the toner image is primarily transferred from the photosensitive belt to a transfer body such as transfer paper, When transferring a visible image from a visible image carrying belt to a transfer body, similar blurring or white spots may occur.

  The present invention has been made in view of the above background, and a first object of the present invention is to provide a transfer device capable of suppressing the blurring of a transfer image due to environmental fluctuations.

  In addition to the first object, the second object is to provide a transfer device that can suppress white spots of a transferred image due to environmental fluctuations, and an image forming apparatus including the transfer device. is there.

The inventor uses a transfer device similar to the transfer device 100 shown in FIG. 4 to generate the nip current A2 that flows from the secondary transfer bias roller 102 to the secondary transfer counter roller 103 via the intermediate transfer belt 101. The relationship between the amount and the secondary transfer performance was investigated. Specifically, the amount of the nip current A2 is adjusted while the ratio of the nip resistance R2 and the total resistance R0 is adjusted by sequentially exchanging the driving roller 104 and the stretching roller 105 with ones each exhibiting a specific electric resistance. Was adjusted to various values. Then, it was investigated whether the halftone portion of the secondary transfer image when the nip current A2 of each value flows or the solid portion was blurred. The results of this investigation are shown in Table 1 below.

  In Table 1, “◯” in the halftone transfer property and solid portion transfer property indicates that no white spots or blurs were visually recognized, “Δ” indicates that a slight amount was visually recognized, and “×” indicates Indicates that it was easily viewed. As shown in Table 1, it can be seen that if the nip current A2 is maintained at 4.8 [μA] or more, it can be suppressed to a level at which the blur of the solid portion is not visually recognized.

  In order to achieve the first object, the invention of claim 1 is directed to a visible image carrying belt carrying a visible image and moving in a predetermined direction, and a transfer in contact with the visible image carrying belt. A transfer current applying member for applying an electric current and a surface of the visible image carrying belt opposite to a contact surface of the transfer current applying member, and contacting the transfer current with a thickness of the visible image carrying belt; A transfer position forming member that guides in the direction to form a transfer position with the transfer current applying member, and contacts the visible image carrying belt at a position different from the transfer position forming member to be electrically grounded And a grounding member for transferring a visible image on the visible image carrying belt to a transfer member conveyed to the transfer position. Maintain the amount above 4.8 [μA] regardless of environmental changes. Is characterized in that so as to.

  In this transfer apparatus, the amount of current flowing from the visible image carrying belt to the transfer position forming member is maintained at 4.8 [μA] or more regardless of environmental changes. Specifically, with respect to the combination of the visible image carrying belt, the transfer position forming member, and the grounding member, if a transfer current of a predetermined value is applied to the visible image carrying belt, the amount of current flowing through the transfer position forming member is changed to the environment. Regardless, a material that exhibits a resistance change characteristic that maintains 4.8 [μA] or more is used. Further, by controlling the output value of the transfer current based on the detection result of the amount of current flowing through the transfer position forming member, the amount of current flowing through the transfer position forming member is 4.8 [μA] or more regardless of environmental fluctuations. You may make it maintain. In such a configuration, the condition “transfer nip current A2 ≧ 4.8 [μA]” in Table 1 is satisfied, and it is possible to suppress the blurring of the transfer image due to environmental fluctuations to a level where it is not visually recognized. it can.

  In order to achieve the second object, according to a second aspect of the present invention, in the transfer device according to the first aspect, the amount of current flowing through the transfer position forming member is 4.8 [ [mu] A] to 27.0 [[mu] A] or less.

  In this transfer apparatus, the amount of flow from the visible image carrying belt to the transfer position forming member is maintained in the range of 4.8 to 27.0 [μA] regardless of environmental fluctuations, resulting in environmental fluctuations. In addition to the blurring of the transferred image, it can be suppressed to a level at which white spots in the transferred image due to environmental changes are not visually recognized.

  According to a third aspect of the present invention, in the transfer device according to the second aspect, an environmental condition suitable for use is specified, and as long as the environmental condition is used, the amount of current in the transfer position forming member is within the above range. The visible image carrying belt, the transfer position forming member, and the grounding member are made of a material that exhibits resistance change characteristics that can be maintained.

  In this transfer apparatus, environmental conditions suitable for use are specified by clearly specifying a temperature range and a humidity range suitable for use in a sticker attached to the apparatus and an instruction manual. On the other hand, a visible image carrying belt such as an intermediate transfer belt, a transfer position forming member such as a secondary transfer counter roller, and a grounding member such as a driving roller and a stretching roller are each transferred under this environmental condition. It exhibits resistance change characteristics that maintain the amount of current flowing in the range of 4.8 to 27.0 [μA]. With such a configuration, under specified environmental conditions, it is possible to suppress the blurring and white spots of the transferred image due to environmental fluctuations to a level at which they cannot be visually recognized.

  According to a fourth aspect of the present invention, there is provided the transfer device according to the second aspect, wherein the amount of current flowing through the transfer position forming member regardless of temperature fluctuations in the range of 10 [° C.] to 40 [° C.] in the above range. Or a material exhibiting a resistance change characteristic that maintains the amount of the current in the above range regardless of humidity fluctuations under a humidity condition of 15% to 80%. A visual image carrying belt, a transfer position forming member, and a grounding member are configured.

  In this transfer apparatus, regardless of temperature fluctuations or humidity fluctuations under the general functional guarantee temperature conditions (10 to 40 [° C.]) or the functional guarantee humidity conditions (15 to 80 [%]) of the transfer apparatus, It is possible to reduce the level of blurring and white spots in the transferred image due to environmental fluctuations to a level at which they cannot be visually recognized.

  According to a fifth aspect of the present invention, in the transfer device according to the second aspect, a transfer power source that supplies the transfer current to the transfer current applying member and a current detection unit that detects the amount of the current are provided, and the current detection unit detects the transfer current. The transfer power supply is configured to control the output current so that the amount of current applied falls within the above range.

  In this transfer apparatus, the amount of upstream current can be controlled by controlling the transfer voltage power source without controlling the resistance change characteristics of the visible image carrying belt, transfer position forming member, and grounding member. By maintaining it within the range of 27.0 [μA], it is possible to reduce the level of blurring and whitening of the transferred image due to environmental fluctuations to a level where they cannot be visually recognized.

  The invention of claim 6 comprises a visible image forming means for forming a visible image on a visible image carrying belt, and a transfer device for transferring the visible image from the visible image carrying belt to a transfer body. In the image forming apparatus for forming an image on the transfer body, the transfer apparatus according to claim 2, 3, 4, or 5 is provided.

  In this image forming apparatus, by the same operation as that of the transfer apparatus according to the second aspect, it is possible to suppress the blurring and white spots of the transfer image caused by environmental fluctuations in the transfer apparatus to a level at which they cannot be visually recognized.

  According to the first, second, third, fourth, or fifth invention, there is an excellent effect that the blur of the transferred image due to the environmental change can be suppressed to a level where it is not visually recognized.

In particular _, according to the invention of claim 2, 3, 4 or 5, in addition to the blurring of the transferred image due to the environmental fluctuation, the level of the transferred image due to the environmental fluctuation is suppressed to a level where it is not visually recognized. There is an excellent effect of being able to.

  In particular, according to the invention of claim 3, it is possible to suppress the blurring and white spots of the transferred image caused by environmental fluctuations to a level at which they cannot be visually recognized under specified environmental conditions. effective.

  In particular, according to the fourth aspect of the present invention, the environmental fluctuation is not affected by the temperature fluctuation or humidity fluctuation under the general functional guarantee temperature condition or the functional guarantee humidity condition (15 to 80 [%]) of the transfer device. There is an excellent effect that it is possible to suppress the blurring and white spots of the transferred image caused by the above to a level at which they are not visually recognized.

  In particular, according to the fifth aspect of the present invention, there is no need to finely adjust the resistance change characteristics of the visible image carrying belt, the transfer position forming member, and the grounding member. There is an excellent effect that it can be suppressed to a level at which it is impossible to visually recognize the white spots and white spots.

  According to the sixth aspect of the invention, there is an excellent effect that it is possible to suppress the blurring and white spots of the transferred image due to environmental fluctuations in the transfer device to a level at which they cannot be visually recognized.

  Hereinafter, an embodiment in which the present invention is applied to an electrophotographic full-color copying machine (hereinafter simply referred to as “copying machine”) as an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram showing an overall configuration of a copying machine according to the present embodiment, and FIG. 2 is a schematic configuration diagram showing a configuration around a transfer unit of the copying machine.

  First, the basic configuration of the copying machine of this embodiment will be described with reference to FIGS. In each figure, the photosensitive drum 1 is rotated in the direction of arrow A in the figure, and its surface is uniformly charged by a charging charger 2 as charging means, and then laser light emitted from the laser optical device 3 is emitted. By being guided in a predetermined direction by the mirror 3a, scanning exposure is performed based on image information, and an electrostatic latent image is formed on the surface.

  The image information is obtained by performing appropriate image processing in accordance with the document information read by the scanner 4 serving as an image reading unit. A desired full-color image is obtained by using yellow, magenta, cyan, and black colors. This is monochrome image information that has been decomposed into information. On the photosensitive drum 1, electrostatic latent images based on the image information of these colors are sequentially formed. The electrostatic latent images corresponding to these colors are sequentially moved to a position facing the photosensitive drum 1 by the rotation of the rotary developing device 5, and the yellow developing unit 5Y, the magenta developing unit 5M, the cyan developing unit 5C, and the black developing unit. 5B develops toner images of yellow, magenta, cyan, and black, respectively.

  Below the photosensitive drum 1 in the figure, there are an intermediate transfer belt 101, a secondary transfer bias roller 102, a secondary transfer counter roller 103, a driving roller 104, a stretching roller 105, a primary transfer bias roller 106, and a primary ground. A transfer device 100 including a roller 107, a primary transfer bias power source and a secondary transfer bias power source (not shown) is provided.

The intermediate transfer belt 101 as a visible image carrying belt is stretched around the five rollers denoted by reference numerals 103 to 107 and is synchronized with the photosensitive drum 1 by the rotation of the driving roller 104 in the drawing. It is driven to rotate in the direction of arrow B. The intermediate transfer belt 101 is made of a material such as PVdF (polyvinylidene fluoride) having a thickness of 150 [μm] and has a volume resistivity of 10 ⁸ to 10 ¹⁴ [Ωcm] (100 V by the measuring method described in JISk6911). A belt having a surface resistivity of 10 ⁸ to 10 ¹⁴ [Ω / □] (measured with resistance meter Hiresta IP manufactured by Mitsubishi Chemical Corporation, 10 seconds value) is used. These resistivities are exhibited under environmental conditions of a temperature of 23 [° C.] and a humidity of 50 to 60 [%], respectively.

  A portion of the intermediate transfer belt 101 located between the primary transfer bias roller 106 and the primary transfer earth roller 107 is positively brought into close contact with the photosensitive drum 1 to form a primary transfer position. A primary transfer electric field is formed between the primary transfer position by applying a primary transfer current to the intermediate transfer belt 101 from the primary transfer bias roller 106. Most of the primary transfer current applied to the intermediate transfer belt 101 is guided to the ground via the primary transfer ground roller 107.

  A primary transfer bias power source that supplies a primary transfer bias to the primary transfer bias roller 106 performs differential constant current control on the primary transfer bias as described in JP-A-8-314285. Regardless of environmental fluctuations, the primary transfer current flowing from the primary transfer bias roller 106 to the intermediate transfer belt 101 is maintained at a constant value.

  The secondary transfer counter roller 103, which is a transfer position forming member, comes into contact with the secondary transfer bias roller 102 formed of an elastic member via the intermediate transfer belt 101 to bite into the second transfer transfer roller. Next transfer nip is formed. This bite is realized as follows. That is, when the copying machine is in a standby state, the secondary transfer bias roller 102 is in a state of being separated from the intermediate transfer belt 101 as illustrated. When the copying operation is started, it is moved upward in the drawing by a raising clutch (not shown) at a predetermined timing, and comes into contact with the secondary transfer counter roller 103 via the intermediate transfer belt 101, so that the secondary transfer counter The roller 103 is bitten. The secondary transfer bias roller 102 is configured such that the parallelism with the secondary transfer counter roller 103 is kept constant by positioning means (not shown). The contact pressure with the secondary transfer counter roller 103 is kept constant by a positioning roller (not shown) provided on the secondary transfer bias roller 102.

  In the secondary transfer nip, a secondary transfer electric field is formed by the influence of a secondary transfer bias having a polarity opposite to that of the toner applied to the intermediate transfer belt 101 from the secondary transfer bias roller 102 serving as a transfer current applying member. .

  The secondary transfer bias power source for applying a secondary transfer bias to the secondary transfer bias roller 102 flows from the secondary transfer bias roller 102 to the intermediate transfer belt 101 by controlling the secondary transfer bias at a constant current. The value of the secondary transfer current is kept constant.

  The driving roller 104 and the stretching roller 105 are disposed on the downstream side and the upstream side of the secondary transfer nip, respectively, and are connected to the ground, and guide residual charges held on the intermediate transfer belt 101 to the ground. Therefore, the driving roller 104 and the stretching roller 105 each function as a grounding member.

  The toner images of the respective colors sequentially developed on the photosensitive drum 1 are transferred onto the intermediate transfer belt 101 by yellow, magenta, cyan and black toners by the action of the primary transfer electric field at the primary transfer position. Each image is sequentially superimposed and primarily transferred. When the primary transfer of all the toner images is completed, a full-color primary transfer image is formed on the intermediate transfer belt 101.

  As described above, the copying machine includes a toner image forming unit that forms a full-color primary transfer image as a visible image on the intermediate transfer belt 101 that is a visible image carrying belt.

  The above-described lifting clutch is used after the three-color transfer image in which the three color toner images of yellow, magenta, and cyan pass through the position facing the secondary transfer bias roller 102 as the intermediate transfer belt 101 rotates. The secondary transfer nip is formed by the upward movement of the secondary transfer bias roller until the full-color primary transfer image moves to the facing position.

  On the other hand, a sheet feeding registration unit 9 disposed on the right side of the secondary transfer nip in the drawing feeds a transfer sheet 10 as a transfer member from the sheet feeding cassette 8 or the manual feed tray toward the registration roller pair 9a. The registration roller pair 9a feeds the transfer paper 10 between the intermediate transfer belt 101 and the secondary transfer bias roller 102 in the secondary transfer nip at a timing at which the transfer paper 10 can be superimposed on the full-color primary transfer image.

  The full-color primary transfer image superimposed on the transfer paper 10 at the secondary transfer nip is secondarily transferred collectively from the intermediate transfer belt 101 to the transfer paper 10 by the action of the pressure in the nip and the secondary transfer electric field. The The transfer paper 10 on which a full-color secondary transfer image is formed by this secondary transfer is separated from the intermediate transfer belt 101 by the paper discharger 12 and then sent to the fixing device 13. Then, after the full-color secondary transfer image is fixed here, it is discharged out of the copying machine.

  The primary transfer residual toner slightly remaining on the photoreceptor drum 1 after the primary transfer onto the intermediate transfer belt 101 is cleaned by the photoreceptor cleaning device 15 in preparation for the reuse of the photoreceptor drum 1.

  Further, the secondary transfer residual toner on the intermediate transfer belt 101 that has not been secondarily transferred onto the transfer paper 10 is intermediately transferred by the intermediate transfer belt cleaning device 16 that can be brought into contact with and separated from the intermediate transfer belt 101. It is removed from the transfer belt 101. In this intermediate transfer belt cleaning device 16, a cleaning blade 16a that abuts on the intermediate transfer belt 101 to remove residual toner and a coating bar 16b made of a lubricant formed in a plate shape are polished to perform intermediate transfer. A lubricant application brush 16c to be applied on the belt 101 is provided.

  Further, the adhering matter adhering to the secondary transfer bias roller 102 is removed by the cleaning blade 17 in contact with the secondary transfer bias roller 102 and then stored in the paper transfer collection case 18. A lubricant is applied by a coating bar 19 to the surface of the secondary transfer bias roller 102 after cleaning.

  The copying machine according to the present embodiment starts image forming processing based on the timing at which a position detection mark (not shown) provided in a non-image area on the intermediate transfer belt 101 is detected by the belt mark sensor 14. Is configured to do. When a monochrome copy image is formed by this copying machine, the image forming process may be started without detecting the position detection mark by the belt mark sensor 14.

Next, a characteristic configuration of the copying machine according to the present embodiment will be described.
In this copying machine, the amount of secondary transfer nip current flowing from the secondary transfer bias roller 102 to the secondary transfer counter roller 103 via the intermediate transfer belt 101 is 4.8 [μA] or more regardless of environmental changes. It is configured to be maintained in a range of 27.0 [μA] or less. As a method for maintaining the amount of the secondary transfer nip current in this way, the following two methods are conceivable.

  In the first method, for the combination of the driving roller 104, the secondary transfer counter roller 103, the stretching roller 105, and the intermediate transfer belt 101, the amount of the secondary transfer nip current is reliably set to 4 under a predetermined condition. And a combination of materials exhibiting resistance change characteristics that are maintained in the range of 0.8 to 27.0 [μA]. The predetermined conditions include an appropriate temperature range and an appropriate humidity range specified in a sticker attached to the apparatus main body and an instruction manual, and a general function guarantee temperature range of the transfer apparatus 100 of 10 [° C.] or more and 40 This is a condition that has either a temperature range of [° C.] or less, or a humidity range of 15 [%] or more and 80 [%] or less, which is a general function-guaranteed humidity range of the transfer apparatus 100.

  The second method is a method for causing the secondary transfer bias power source to perform output control that maintains the amount of the secondary transfer nip current in the range of 4.8 to 27.0 [μA]. FIG. 3 is a configuration diagram showing a main configuration of a copying machine adopting this method. In the figure, the transfer device 100 includes a current detection unit 108 that detects the value of a secondary transfer nip current flowing from the intermediate transfer belt 101 to the secondary transfer counter roller 103. The current value detected by the current detection means is converted into a predetermined electrical signal and output to the secondary transfer bias power source 109 as a current value signal. A secondary transfer bias power source 108, which is a transfer power source for supplying a secondary transfer bias to the secondary transfer bias roller 102, basically sets an output current value to the secondary transfer bias roller 102 to a predetermined value regardless of environmental fluctuations. The constant current control is performed to change the output voltage value so as to maintain the current value. However, when the current value signal from the current detection means 108 is a signal indicating that the current value signal exceeds 27.0 [μA], the output current value is changed until the current value signal of 27.0 [μA] is detected. Lower than the value that should be maintained. Further, when the current value signal is a signal indicating that the current value signal is lower than 4.8 [μA], the output current value is higher than the value to be maintained until the current value signal of 4.8 [μA] is detected. Make it high.

  The copying machine according to the present embodiment maintains the amount of the secondary transfer nip current in the range of 4.8 to 27.0 [μA] by the first method or the second method regardless of environmental fluctuations. It is configured as follows. Therefore, as shown in Table 1 above, it is possible to reduce the level of blurring and white spots in the transferred image due to environmental fluctuations to a level where they cannot be visually recognized. When the second method is adopted, the resistance change characteristics of the driving roller 104, the secondary transfer counter roller 103, the stretching roller 105, and the intermediate transfer belt 101 are finely adjusted. Even if it is not, it becomes possible to suppress the blurring and white spots of the transferred image due to environmental fluctuations to a level where they are not visually recognized.

  Although the copying machine of the embodiment has been described above, the embodiment of the present invention is not limited to this copying machine.

  For example, it goes without saying that the present invention can also be applied to an image forming apparatus that includes only one developing device and forms a monochrome image on a transfer body such as transfer paper.

  Further, for example, an image in which the positions of the secondary transfer bias roller 103 and the secondary transfer bias roller are reversed and the secondary transfer bias roller applies a secondary transfer bias having the same polarity as the toner to the back surface of the intermediate transfer belt. The present invention can also be applied to a forming apparatus.

  For example, instead of forming the secondary transfer nip, a transfer position forming roller instead of the secondary transfer counter roller 103 comes into contact with the intermediate transfer belt 101 at a position not facing the secondary transfer bias roller 102 and 2 The present invention can also be applied to an image forming apparatus that forms a next transfer position.

  Also, for example, an image forming apparatus that performs primary transfer from a visible image carrying belt such as a photosensitive belt to a transfer body such as transfer paper and does not perform secondary transfer, or an image forming apparatus that performs transfer beyond tertiary transfer. The present invention can be applied.

  Further, it is not an image forming apparatus for forming an image by an electrophotographic process but an image forming apparatus of a direct recording system called toner projection as described in Japanese Patent Laid-Open No. 9-254430, and a visible image carrying belt. The present invention can also be applied to a belt that transfers a visible image from a belt such as a counter electrode belt to a transfer body such as transfer paper.

1 is a schematic configuration diagram showing an overall configuration of a copier according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating a configuration around a transfer unit of the copier. FIG. 2 is a configuration diagram showing an example of a main configuration of the copier. 1 is a schematic configuration diagram showing a conventional transfer device together with a photosensitive drum of an image forming apparatus. The schematic diagram explaining downstream electric current A1, nip electric current A2, and upstream electric current A3. The schematic diagram explaining downstream resistance R1, nip resistance R2, and upstream resistance R3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging charger 3 Laser optical apparatus 4 Scanner 5 Rotating type developing device 8 Paper feed cassette 9 Paper feed resist part 100 Transfer device 101 Intermediate transfer belt (visible image carrying belt)
102 Secondary transfer bias roller (transfer current applying member)
103 Secondary transfer counter roller (transfer position forming member)
104 Drive roller (grounding member)
105 Tension roller (grounding member)
108 Current detection means 109 Secondary transfer bias power supply (transfer power supply)

Claims (6)

A visible image carrying belt that carries a visible image and moves in a predetermined direction, a transfer current applying member that contacts the visible image carrying belt and applies a transfer current, and the visible image carrying belt A transfer position that contacts a surface opposite to the contact surface with the transfer current application member, guides the transfer current in the thickness direction of the visible image carrying belt, and forms a transfer position with the transfer current application member A forming member and a grounding member that contacts the visible image carrying belt at a position different from the transfer position forming member and is electrically grounded, and transfers the visible image on the visible image carrying belt to the transfer member. In a transfer device that transfers to a transfer body conveyed to a position,
A transfer apparatus characterized in that the amount of current flowing through the transfer position forming member by applying the transfer current is maintained at 4.8 [μA] or more regardless of environmental changes. The transfer device according to claim 1.
A transfer apparatus characterized in that the amount of current flowing through the transfer position forming member is maintained in a range of 4.8 [μA] or more and 27.0 [μA] or less regardless of environmental changes. The transfer device according to claim 2,
As long as environmental conditions suitable for use are specified, and the material is used under these environmental conditions, the visible image is formed of a material that exhibits resistance change characteristics so that the transfer position forming member maintains the amount of current in the above range. A transfer device comprising a carrier belt, a transfer position forming member, and a grounding member. The transfer device according to claim 2,
Under the temperature condition of 10 [° C.] to 40 [° C.], the amount of current flowing through the transfer position forming member is maintained in the above range regardless of temperature fluctuation, or 15 [%] to 80 [%]. The visible image carrying belt, the transfer position forming member, and the grounding member are made of a material that exhibits a resistance change characteristic that maintains the amount of the current in the above range regardless of humidity fluctuations under the above humidity conditions. A transfer device characterized by that. The transfer device according to claim 2.
A transfer power source for supplying the transfer current to the transfer current applying member and a current detection means for detecting the amount of the current are provided, and the output current is controlled so that the current amount detected by the current detection means falls within the above range. A transfer apparatus, wherein the transfer power supply is configured to perform the above. Visible image forming means for forming a visible image on a visible image carrying belt, and a transfer device for transferring the visible image from the visible image carrying belt to a transfer body, the visible image being provided on the transfer body. In an image forming apparatus that forms an image by transferring an image,
An image forming apparatus comprising the transfer device according to claim 2, 3, 4, or 5.

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