JP2004245858A - Image forming apparatus and method of detecting its transfer material jamming - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a transfer material jamming detection method for reliably detecting, without installing a special member, a jamming over a long period of time even when a separation failure of transfer material occurs due to the state of the transfer material. <P>SOLUTION: The image forming apparatus is characterised in that application of transfer bias and application of destaticizing bias to a transfer means are carried out at the same time, at least when no image is being formed, and when the current value fed to a destaticizing means during bias application is represented by I<SB>1</SB>, the current value fed to the destaticizing means in actual transfer by I<SB>2</SB>and the variation threshold value of the destaticizing current by I<SB>0</SB>, the image forming action is stopped when a relationship of ¾I<SB>2</SB>-I<SB>1</SB>¾≤I<SB>0</SB>is established. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic method, such as a copying machine, a printer, and a facsimile.
[0002]
[Prior art]
In a conventional image forming apparatus, a toner image formed on a first image carrier (hereinafter, referred to as a photoconductor) is transferred to a second image carrier (hereinafter, referred to as a transfer material) such as paper, and then transferred. 2. Description of the Related Art There is known a method in which a toner image on a material is heated and pressed by a fixing device and fixed. In a conventional image forming apparatus for forming a full-color image, a transfer material is held on a transfer material carrier such as a transfer drum, and the developed yellow, magenta, cyan, and black colors are transferred to a photoconductor. There is known a method in which a transfer material is sequentially transferred to a transfer material on a material carrier, and then the transfer material peeled off from the transfer material carrier is heated and pressed by a fixing device and fixed to obtain a full-color image.
[0003]
On the other hand, instead of transferring the toner image to a transfer material on a transfer material carrier, each of yellow, magenta, cyan, and black colors developed on a photoreceptor is disclosed, for example, in JP-A-5-11562. Are successively superimposed on an intermediate transfer member (hereinafter, referred to as primary transfer), and the four color toner images formed on the intermediate transfer member are collectively transferred to a transfer material (hereinafter, referred to as secondary transfer), and then are fixed by a fixing device. An image forming apparatus for fixing has started to operate in the market. The feature of this color image forming apparatus is that it is not necessary to hold the transfer material on the transfer material carrier unlike the conventional image forming apparatus, and therefore, the thin paper (40 g / m²) And cardboard (200g / m²), Postcards, envelopes, and other types of transfer materials, and has the advantage of high transfer material versatility.
[0004]
In any of the above-described image forming apparatuses, the transfer material is once electrostatically attracted to the image carrier or the transfer material carrier, and then receives a high voltage at the time of transfer. Conveyed. If the transfer material is conveyed while maintaining the charged state in this way, a paper jam due to sticking of the transfer material to the conveyance path, an abnormal image of a lightning pattern generated when the charge on the transfer material moves along the surface, and the conveyance Leakage of charges to the protrusions or metal near the path may cause a circular abnormal image. Further, the larger the radius of the transfer portion of the image carrier is, the more difficult it is to separate the electrostatically attracted transfer material. Therefore, in order to prevent the above-mentioned paper jam, abnormal image, and poor separation from the image carrier, a static elimination member (hereinafter, referred to as a static elimination needle) is provided in the vicinity of the downstream side of the transfer unit (see, for example, Patent Document 1). reference).
[0005]
[Patent Document 1]
JP-A-8-76611
[0006]
[Problems to be solved by the invention]
However, even in an image forming apparatus using a static elimination needle, when the transfer material is curled along the image carrier, sufficient separation cannot be performed, and a separation failure may occur. Such a curl of the transfer material may cause the transfer material that has been left in the image forming apparatus for a long period of time, or a blank back surface portion of the transfer material on which an image has been formed once from the viewpoint of environmental protection, to be reloaded into the image forming apparatus. What happens when you do. When a paper jam (hereinafter, referred to as “jam”) occurs such that the transfer material wraps around the image carrier, if the transfer material enters cleaning means disposed around the image carrier, it is removed by the user. Therefore, when a jam is detected, it is necessary to stop the image forming operation at an early stage.
[0007]
In the prior art, the occurrence of a jam is detected by disposing a transfer material detecting means such as a reflection sensor on the downstream side of the transferring means. However, in such a configuration, if a sensor is provided in the vicinity of the transfer means, the toner scattered from the image carrier adheres to the above-described sensor. In some cases, the jam state is continuously detected even though there is no transfer material, and image formation cannot be continued in some cases. When a reflection sensor is provided near the fixing unit, the reflection sensor may be damaged by heat of the fixing unit.
[0008]
The present invention has been made in view of the above circumstances, and has as its object to dispose a special transfer member without disposing the transfer material depending on the state of the transfer material. The present invention provides an image forming apparatus and a transfer material jam detecting method for the image forming apparatus, which can realize accurate detection over a long period of time.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 provides an image carrier that carries a toner image, a transfer unit that transfers the toner image on the image carrier to a transfer material, and A transfer bias applying unit for applying a transfer bias, a charge eliminating unit provided in the vicinity of the transfer unit on the downstream side of the transfer unit and for eliminating charge from the transfer material, and a charge eliminating bias for applying a charge eliminating bias to the charge eliminating unit An application unit, and an image forming apparatus having a current value detection unit that detects a current value flowing through the charge removal unit, wherein the transfer bias application and the charge removal bias application to the transfer unit are performed simultaneously at least during non-image formation, At this time, the current value flowing through the static elimination means is represented by I₁The current value flowing through the neutralization means at the time of actual transfer is represented by I₂And the fluctuation threshold of the static elimination current is I₀Then | I₂−I₁| ≦ I₀The image forming operation is stopped when the relationship is established.
[0010]
According to the first aspect of the present invention, it is possible to detect the winding of the transfer material around the image carrier at an early stage and stop the image forming operation without adding a member such as a reflection sensor.
[0011]
According to a second aspect of the present invention, in the first aspect of the invention, the static elimination means is a static elimination needle provided so as to be in non-contact with the transfer material.
[0012]
According to the second aspect of the invention, the same operation and effect as those of the first aspect of the invention can be obtained, and at the same time, the charge of the transfer material is removed and the current flowing through the image carrier is changed by the fluctuation of the flowing current. The image forming operation can be stopped by detecting the winding of the transfer material at an early stage.
[0013]
According to a third aspect of the present invention, in the first aspect of the invention, the static elimination means is a static elimination brush provided so as to be in contact with the transfer material.
[0014]
According to the third aspect of the invention, the same operation and effect as those of the first aspect of the invention can be obtained, and at the same time, the charge of the transfer material is removed, and the current flowing through the image carrier is changed by the fluctuation of the flowing current. The image forming operation can be stopped by detecting the winding of the transfer material at an early stage.
[0015]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the transfer material jam is detected based on a value of a current flowing through the neutralizing unit. .
[0016]
According to the invention described in claim 4, the same operation and effect as the invention described in any one of claims 1 to 3 can be obtained, and without adding a member such as a reflection sensor. In addition, the winding of the transfer material around the image carrier can be detected at an early stage, and the image forming operation can be stopped.
[0017]
According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the polarity of the transfer bias applied to the transfer unit is equal to the polarity of the transfer bias applied to the transfer unit. The opposite polarity is applied.
[0018]
According to the invention described in claim 5, the same operation and effect as the invention described in any one of claims 1 to 4 can be obtained, and the charge of the transfer material is removed while removing the charge. The winding of the transfer material around the image carrier can be detected early by the fluctuation of the flowing current, and the image forming operation can be stopped.
[0019]
According to a sixth aspect of the present invention, in the first aspect of the present invention, the transfer bias applied to the transfer unit is controlled at a constant voltage. I do.
[0020]
According to the invention described in claim 6, the same operation and effect as the invention described in any one of claims 1 to 5 can be obtained, and the charge of the transfer material can be stably removed. In addition, it is possible to detect the winding of the transfer material around the image carrier at an early stage by the fluctuation of the flowing current, and to stop the image forming operation.
[0021]
According to a seventh aspect of the present invention, in the first aspect of the invention, the image carrier carries a plurality of color toner images to form a full-color image. Characterized in that it is an intermediate transfer member.
[0022]
According to the invention described in claim 7, the same operation and effect as those of the invention described in any one of claims 1 to 6 can be obtained, and a high-quality full-color image can be obtained. At the same time, even in the event that winding around the intermediate transfer member occurs, it is possible to detect it early and stop the image forming operation.
[0023]
According to another aspect of the present invention, there is provided an image carrier for carrying a toner image, transfer means for transferring the toner image on the image carrier to a transfer material, and transfer for applying a transfer bias to the transfer means. A bias applying unit, a discharging unit provided downstream of the transfer unit near the transfer unit and for discharging the transfer material, a discharging bias application unit for applying a discharging bias to the discharging unit, A transfer value jam detecting method for an image forming apparatus having a current value detecting means for detecting a current value flowing in the means, wherein a transfer bias application and a static elimination bias application to the transfer means are simultaneously performed at least during non-image formation, At this time, the current value flowing through the static elimination means is represented by I₁The current value flowing through the neutralization means at the time of actual transfer is represented by I₂And the fluctuation threshold of the static elimination current is I₀Then | I₂−I₁| ≦ I₀The image forming operation is stopped when the relationship is established.
[0024]
According to the invention described in claim 8, it is possible to detect the winding of the transfer material around the image carrier at an early stage without adding a member such as a reflection sensor and stop the image forming operation.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 shows a color image forming apparatus according to an embodiment of the present invention in which an image carrier is an intermediate transfer member (hereinafter, referred to as an intermediate transfer belt). Reference numeral 1 denotes a photoreceptor belt that rotates in the direction of the arrow in FIG. 1, and around the photoreceptor belt 1, a photoreceptor cleaning blade 2, a charger 4, an exposure unit 5, an intermediate transfer belt 10, and the like are arranged. The developing means is composed of four developing devices: a yellow developing device 6, a magenta developing device 7, a cyan developing device 8, and a black developing device 9. When a full-color image is formed, a visible image is formed in the order of a yellow developing device 6, a magenta developing device 7, a cyan developing device 8, and a black developing device 9, and the visible images of the respective colors are sequentially transferred onto the intermediate transfer belt 10 in an overlapping manner. Thus, a full-color image is formed.
[0027]
The intermediate transfer belt 10 is stretched by a drive roller 13, a primary transfer bias roller 11, a secondary transfer opposing roller 12, and a tension roller 3, and is driven by a drive motor (not shown). The primary transfer bias roller 11 is pressed in the direction of the photoreceptor belt 1 by a pressure spring 27. Each roller is supported from both sides of the intermediate transfer belt by an intermediate transfer belt unit side plate (not shown).
[0028]
The intermediate transfer belt 10 has a single layer or a plurality of layers made of PVDF (vinyldene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), or the like. Disperse a conductive material and set its volume resistivity to 10⁸-10¹²Ωcm and surface resistivity of 10⁸-10^FifteenIt is adjusted to be in the range of Ωcm.
[0029]
The surface of the intermediate transfer belt 10 may be coated with a release layer as needed. Materials used for the coating include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinyldene fluoride), PEA (perfluoroalkoxy fluororesin), and FEP (tetrafluoroethylene). Fluorinated resins such as ethylene fluoride-hexafluoropropylene copolymer) and PVF (vinyl fluoride) can be used, but are not limited thereto.
[0030]
The method of manufacturing the intermediate transfer belt 10 includes a casting method, a centrifugal molding method, and the like, and its surface may be polished as necessary.
[0031]
If the volume resistivity and the surface resistivity of the intermediate transfer belt 10 exceed the ranges described above, the bias required for the transfer increases, which undesirably increases the power supply cost. In addition, the charging potential of the intermediate transfer belt 10 becomes high in the transfer step and the transfer material peeling step, and self-discharge becomes difficult. When the volume resistivity and the surface resistivity are below the above ranges, the charge potential is rapidly attenuated, which is advantageous for static elimination by self-discharge.However, since the current at the time of transfer flows in the surface direction, toner scattering occurs. Would. Therefore, the volume resistivity and the surface resistivity of the intermediate transfer belt 10 in the present invention must be within the above ranges.
[0032]
The volume resistivity and the surface resistivity were measured by connecting a probe (inner electrode diameter: 50 mm, ring electrode inner diameter: 60 mm: JIS-K6911 compliant) to a digital ultra-high resistance microammeter (R8340A, manufactured by Advantest Corporation). A voltage of 500 V (surface resistivity: 500 V) was applied to the front and back of the transfer belt 10, and the measurement was performed with a discharge of 5 sec and a charge of 10 sec.
[0033]
Reference numeral 19 denotes a belt cleaning unit that can be brought into contact with and separated from the intermediate transfer belt 10, and is configured by a contact / separation mechanism 26 that comes into contact with and separates from the intermediate transfer belt 10, and the like. While the third, fourth, and fourth colors are being transferred by the belt, they are separated from the surface of the intermediate transfer belt 10 by the contact / separation mechanism 26, and when the secondary transfer is performed, they are pressed against each other at a predetermined timing to clean the remaining toner. A belt position detection mark 23 is provided at an end of the intermediate transfer belt 10, and by starting an image forming process of each color at a timing when the mark is detected by the mark sensor 24, accurate color superposition of each color image is performed. It becomes possible.
[0034]
Reference numeral 15 denotes a secondary transfer unit, which includes a secondary transfer bias roller (transfer unit) 14 and a contact / separation mechanism 16 for bringing the secondary transfer bias roller 14 into and out of contact with the belt 10. The secondary transfer bias roller 14 is formed of a conductive material on a metal core such as SUS.⁶-10¹⁰It is constituted by coating an elastic body such as urethane adjusted to a resistance value of Ω. Here, if the resistance value of the secondary transfer bias roller 14 exceeds the above-mentioned range, it becomes difficult for the current to flow. Therefore, it is necessary to apply a higher voltage in order to obtain the necessary transferability. Invite. In addition, since a high voltage is applied, a discharge occurs in a gap before and after the transfer portion nip, so that white spots occur due to the discharge on the halftone image. Conversely, if the resistance value of the secondary transfer bias roller 14 falls below the above range, transferability between a multi-color image portion (for example, a three-color superimposed image) and a single-color image portion existing on the same image cannot be compatible. This is because although the resistance value of the secondary transfer bias roller 14 is low, a sufficient current flows to transfer a single-color image portion at a relatively low voltage, but is optimal for a single-color image portion to transfer a multi-color image portion. Since a voltage value higher than the minimum voltage is required, if the voltage is set to a value at which the multi-color image portion can be transferred, the transfer current becomes excessive for a single-color image, resulting in a reduction in transfer efficiency.
[0035]
The resistance value of the secondary transfer bias roller 14 was measured by placing the secondary transfer bias roller 14 on a conductive metal plate and applying a load of 4.9 N on one side (a total of 9.8 N on both sides) to both ends of the cored bar. Was calculated from the value of the current flowing when a voltage of 1000 V was applied between the cored bar and the metal plate in a state where.
[0036]
A driving force is applied to the secondary transfer bias roller 14 by a driving gear (not shown), and the peripheral speed thereof is adjusted to be substantially the same as the peripheral speed of the intermediate transfer belt 10.
[0037]
The secondary transfer bias roller 14 is normally separated from the surface of the intermediate transfer belt 10, but is contacted in a timely manner when the four-color superimposed images formed on the surface of the intermediate transfer belt 10 are collectively transferred to the transfer material 22. The transfer to the transfer material 22 is performed by being pressed by the separation mechanism 16 and applying a predetermined bias voltage.
[0038]
Further, the static elimination needle (static elimination means) 40 performs static elimination of the charged transfer material 22 by applying a predetermined bias voltage when the leading end of the transfer material reaches the static elimination needle position. The polarity of the bias applied to the static elimination needle is opposite to the polarity applied to the secondary transfer bias roller 14, and in the present embodiment, a negative polarity is applied. In the present embodiment, the static elimination needle 40 is obtained by processing SUS301 having a thickness of 0.2 mm into a saw-tooth shape as shown in FIG. 2 and having an adjacent tooth tip pitch of 3 mm.
[0039]
The transfer material 22 is fed by the feed roller 25 and the registration roller 21 at the timing when the leading end of the four-color superimposed image on the surface of the intermediate transfer belt 10 reaches the secondary transfer position. The four-color superimposed image transferred to the transfer material 22 is discharged after being fixed by the fixing unit 17.
[0040]
Here, full-color image formation will be described in detail. First, the photoreceptor belt 1 is uniformly charged to a surface potential of -500 V by a charger 4 and thereafter is exposed by an exposing unit 5 to form an electrostatic latent image, thereby writing an image. The electrostatic latent image on the image No. 1 is visualized by a yellow developing device 6 with a one-component developer composed of a yellow toner, and becomes a yellow image (yellow toner image). At this time, the developing bias applied to the yellow developing device 6 is -300V. The primary transfer bias roller 11 transfers a yellow image on the photoreceptor belt 1 to the intermediate transfer belt 10 by applying a secondary transfer bias from a high-voltage power supply (not shown) to contact the back surface of the intermediate transfer belt 10 and apply a charge. Let it. At this time, the primary transfer bias was set to 700V. The photoconductor belt 1 is cleaned by the photoconductor cleaning unit 2 after the transfer of the yellow image.
[0041]
Next, the photoreceptor belt 1 is uniformly charged to a surface potential of -500 V by the charger 4 and then exposed by the exposure means 5 to form an electrostatic latent image, thereby writing an image. The electrostatic latent image on the body belt 1 is visualized by a magenta developing device 7 with a one-component developer composed of magenta toner to form a magenta image (magenta toner image). The developing bias applied to the magenta developing device 7 is -300V. The primary transfer bias roller 11 transfers a magenta image on the photoreceptor belt 1 to the intermediate transfer belt 10 by applying a transfer bias from a high-voltage power supply and contacting the back surface of the intermediate transfer belt 10 to apply a charge. At this time, the primary transfer bias was set to 800V. The photoconductor belt 1 is cleaned by the photoconductor cleaning unit 2 after the transfer of the magenta image.
[0042]
Next, the photoreceptor belt 1 is uniformly charged to a surface potential of -500 V by the charger 4 and then exposed by the exposure means 5 to form an electrostatic latent image, thereby writing an image. The electrostatic latent image on the photoreceptor belt 1 is visualized by a cyan developing device 8 with a one-component developer composed of cyan toner to be a cyan image (cyan toner image). At this time, the developing bias applied to the cyan developing device 8 is -300V. The primary transfer bias roller 11 is applied with a transfer bias from a high voltage power supply and contacts the back surface of the intermediate transfer belt 10 to apply an electric charge, thereby converting the cyan image on the photoreceptor belt 1 to a yellow image and a magenta image on the intermediate transfer belt 10. And transfer it. At this time, the primary transfer bias was set to 900V. The photoconductor belt 1 is cleaned by the photoconductor cleaning unit 2 after the transfer of the cyan image.
[0043]
Further, the photoreceptor belt 1 is uniformly charged to a surface potential of -500 V by the charger 4 and thereafter is exposed by the exposure means 5 to form an electrostatic latent image, thereby writing an image. The electrostatic latent image on the body belt 1 is visualized by a black developing device 9 with a one-component developer composed of black toner to become a black image (black toner image). At this time, the developing bias applied to the black developing device 9 is -300V. The primary transfer bias roller 11 is applied with a transfer bias from a high voltage power supply and contacts the back surface of the intermediate transfer belt 10 to apply an electric charge. , And superimposed and transferred to the cyan image. At this time, the primary transfer bias was set to 900V. The photoconductor belt 1 is cleaned by the photoconductor cleaning unit 2 after the transfer of the black image.
[0044]
The full-color image (four-color superimposed image) on the intermediate transfer belt 10 is transferred by the secondary transfer bias roller 14 to the transfer material 22 fed from the sheet feeding device by the feed roller 25 and the registration roller 21, and the transfer material 22 The sheet is discharged after the image transferred from the intermediate transfer belt 10 is fixed by the transfer unit 17.
[0045]
In addition, the present embodiment employs a single-color mode for forming an image of any one of yellow, magenta, cyan, and black, a two-color mode for forming an image of any two colors of yellow, magenta, cyan, and black, and a yellow mode. , Magenta, cyan, and black, and a full-color mode for forming a four-color superimposed image as described above. These modes can be specified by the operation unit. is there.
[0046]
When one of the single-color mode, the two-color mode, and the three-color mode is designated, in the above-described full-color mode, images of each color of yellow, magenta, cyan, and black are formed on the photoreceptor belt 1 and intermediately transferred. Instead of the operation of transferring to the belt 10, an image is formed on the photosensitive belt 1 in a single color corresponding to the single color mode and transferred to the intermediate transfer belt 10, or a two-color image corresponding to the two-color mode is exposed. An operation of forming the image on the body belt 1 and transferring the image to the intermediate transfer belt 10 or an operation of forming an image of three colors according to the three-color mode on the photosensitive belt 1 and transferring the image to the intermediate transfer belt 10 is performed; After the single-color image, the two-color superimposed image, or the three-color superimposed image on the intermediate transfer belt 10 is transferred to the transfer material 22 by the secondary transfer bias roller 14 and fixed by the fixing unit 17 It is discharged.
[0047]
Here, when the image forming operation for forming the multi-color superimposed images on the transfer material 22 is continuously performed by the number of sheets set by the operation unit, the rear end of the transfer material 22 sufficiently passes through the secondary transfer bias roller 14. At a timing, the secondary transfer bias voltage from the high voltage power supply (transfer bias applying means) 100 to the secondary transfer bias roller 14 is turned off, and then the toner image of the next page on the intermediate transfer belt 10 is attached to the secondary transfer bias roller 14. To prevent this, the secondary transfer bias roller 14 is separated from the intermediate transfer belt 10 by the contact / separation mechanism 16.
[0048]
Incidentally, the toner particle diameter is desirably in the range of 4 to 10 μm in volume average particle diameter. If the particle diameter is smaller than this, it may cause background contamination during development, or the fluidity may be deteriorated. Conversely, if the particle diameter is larger than this, a high-definition image cannot be obtained due to toner scattering or deterioration of resolution.
[0049]
In this embodiment, a toner having a volume average particle diameter of 7.5 μm is used.
(Example 1)
Next, specific examples of the present invention will be described in detail.
[0050]
FIG. 3 is a schematic diagram of the secondary transfer unit. When the transfer material 22 is conveyed to a secondary transfer section composed of the intermediate transfer belt 10 and the secondary transfer bias roller 14 in accordance with the toner image formed on the intermediate transfer belt 10, the high voltage power supply 100 and the transfer bias A predetermined bias voltage is applied by the value control unit 101.
[0051]
On the other hand, FIG. 4 is a schematic diagram of the static elimination needle 40 part. The static elimination needle 40 is connected to a high-voltage power supply 102 and a static elimination bias control means 103, and an ammeter (current value detection means) 104 is arranged between the static elimination needle 40 and the high-voltage power supply 102. The high voltage power supply (static elimination bias applying means) 102 is controlled so that an appropriate voltage is applied to the static elimination needle 40 by the static elimination bias control means 103. The voltage value applied to the static elimination needle 40 is set in advance according to the type of transfer material, the number of times of transfer to the same transfer material as in double-sided printing, the atmosphere environment, and the like.
[0052]
As shown in FIG. 5, when the transfer material 22 passes near the static elimination needle 40, a change occurs in the current flowing through the static elimination needle 40. This is because the transfer material 22 has a positive charge due to the secondary transfer bias roller 14, and a current flows due to the combination of the positive charge and the negative charge of the discharging bias. When the resistance of the transfer material is low (for example, the surface resistance of the transfer material is 9 Ω or less), a current flows through the transfer material, so that more current fluctuation occurs.
[0053]
On the other hand, as shown in FIG. 6, when the transfer material 22 cannot be separated from the intermediate transfer belt 10 and is wrapped around the surface thereof, the distance between the static elimination needle 40 and the transfer material 22 becomes longer, and the fluctuation of the current increases. Has been shown to be very small.
The present invention focuses on this point, and detects the winding of the transfer material 22 around the intermediate transfer belt 10 from the current flowing through the static elimination needle 40.
[0054]
Here, FIG. 7 shows a flowchart of this control. First, at the start of image formation (step S2), the secondary transfer bias roller 14 is brought into contact with the intermediate transfer belt 10, and a predetermined secondary transfer bias and a static elimination bias are applied (steps S3 and S4). The value of the current flowing through 40 is measured.₁(Step S1).
[0055]
Next, the current I flowing into the static elimination needle 40 at the start of the secondary transfer₂Is measured (step S5) and is substituted into the following equation to obtain the static elimination current variation threshold I.₀Is obtained (step S6). Note that I₀Is a value obtained from an experiment in which conditions such as environment and transfer material are varied. I₀FIG. 8 shows the experimental results obtained when.
｜ I₂−I₁| ≦ I₀
If the above relationship is not satisfied, the secondary transfer is continued as it is (step S8). If the above relationship is satisfied, the transfer material 22 has not reached the secondary transfer nip, or the intermediate transfer belt It is determined that the image has been wound around the image forming apparatus 10, and the image forming operation is stopped (step S7).
[0056]
As a result of verifying each value described above in the present embodiment, when the separation is performed normally,
I₀= 0.8 [μA]
I₁= 1.2 [μA]
I₂= 2.6 [μA]
It became.
[0057]
Substituting each of these values into the above equation gives
｜ I₂−I₁| = | 2.6-1.2 | = 1.4 [μA]> 0.8 [μA]
Since the above expression is not satisfied, the image forming operation is continued without stopping.
[0058]
Next, a case will be described in which the transfer material 22 in which an image is formed in advance and in which the front end portion in the transport direction is curled and whose curl is further intentionally increased is used.
[0059]
In this case, due to the curl of the transfer material 22, the transfer material 22 could not be separated from the intermediate transfer belt 10, and separation failure occurred. I at this time₀, I₁, I₂Are
I₀= 0.8 [μA]
I₁= 1.2 [μA]
I₂= 1.8 [μA]
It became.
[0060]
Substituting each of these values into the above equation gives
｜ I₂−I₁| = | 1.8-1.2 | = 0.6 [μA] ≦ 0.8 [μA]
Then, since the above expression is satisfied, it is determined that a jam has occurred, and the image forming operation is stopped.
[0061]
As described above, by performing this control, the winding of the transfer material around the intermediate transfer belt can be detected without adding a reflection sensor or the like, and the image forming operation can be stopped.
(Example 2)
In the present embodiment, a static elimination brush 41 as shown in FIG. 9 is used instead of the static elimination needle. FIG. 10 is a cross-sectional view of the secondary transfer portion when the charge removing brush 41 is used.
[0062]
As in Example 1, I₀FIG. 11 shows the experimental results obtained when.
[0063]
Embodiment 1 of this static elimination brush 41 is also used. As a result of verifying each value in the same way as
I₀= 1.2 [μA]
I₁= 2.2 [μA]
I₂= 4.5 [μA]
It became.
[0064]
Substituting each of these values into the above equation gives
｜ I₂−I₁| = | 4.5-2.2 | = 2.3 [μA]> 1.2 [μA]
Since the above expression is not satisfied, the image forming operation is continued without stopping.
[0065]
Next, the transfer material 22 in which an image has been formed in advance and in which the front end portion in the transport direction is curled and further curled intentionally is used, and the transfer material 22 cannot be separated from the intermediate transfer belt 10 and a separation failure occurs. I at the time₀, I₁, I₂Are
I₀= 1.2 [μA]
I₁= 2.2 [μA]
I₂= 2.6 [μA]
It became.
[0066]
Substituting each of these values into the above equation gives
｜ I₂−I₁| = | 2.6-2.2 | = 0.4 [μA] ≦ 1.2 [μA]
Then, since the above expression is satisfied, it is determined that a jam has occurred, and the image forming operation is stopped.
[0067]
As described above, even in the case of using the static elimination brush as in the present embodiment, by performing this control, it is possible to detect the winding of the transfer material around the intermediate transfer belt without adding a reflection sensor and the like, and The formation operation can be stopped.
[0068]
The embodiments described above are described for the purpose of facilitating the understanding of the present invention, and do not limit the present invention. For example, in the above-described embodiment, the description has been made using the intermediate transfer belt as the image carrier. However, the present invention is not limited to this. The present invention is applicable to all image carriers such as a transfer drum, a photosensitive drum as a latent image carrier, and a photosensitive belt. Furthermore, transfer rollers were used as the primary transfer means and the secondary transfer means, but not only rotary contact transfer methods such as a rotary transfer brush, but also contact transfer methods such as a transfer belt, a transfer brush, a transfer blade, and a transfer plate. The present invention can be applied to an image forming apparatus using the image forming apparatus.
[0069]
【The invention's effect】
According to the first aspect of the present invention, it is possible to detect the winding of the transfer material around the image carrier at an early stage and stop the image forming operation without adding a member such as a reflection sensor.
[0070]
According to the second aspect of the invention, the same operation and effect as those of the first aspect of the invention can be obtained, and at the same time, the charge of the transfer material is removed, and the variation of the flowing current causes the transfer to the image carrier. The image forming operation can be stopped by detecting the winding of the transfer material at an early stage.
[0071]
According to the third aspect of the invention, the same operation and effect as those of the first aspect of the invention can be obtained, and while the charging of the transfer material is removed, the variation of the flowing current causes the transfer to the image bearing member. The image forming operation can be stopped by detecting the winding of the transfer material at an early stage.
[0072]
According to the invention described in claim 4, the same operation and effect as the invention described in any one of claims 1 to 3 can be obtained, and without adding a member such as a reflection sensor, The image forming operation can be stopped by detecting the winding of the transfer material around the image carrier at an early stage.
[0073]
According to the fifth aspect of the invention, the same operation and effect as those of the first aspect of the invention can be obtained, and the flow of the transfer material can be removed while removing the charge. The winding of the transfer material around the image carrier can be detected at an early stage by the fluctuation of the current, and the image forming operation can be stopped.
[0074]
According to the invention described in claim 6, the same operation and effect as the invention described in any one of claims 1 to 5 can be obtained, and the charge of the transfer material can be stably removed. In addition, the winding of the transfer material around the image carrier is detected at an early stage based on the fluctuation of the flowing current, and the image forming operation can be stopped.
[0075]
According to the invention described in claim 7, it is possible to obtain the same operation and effect as the invention described in any one of claims 1 to 6, and to obtain a high-quality full-color image. At the same time, even if the winding around the intermediate transfer member occurs, it can be detected early and the image forming operation can be stopped.
[0076]
According to the invention described in claim 8, it is possible to detect the winding of the transfer material around the image carrier early without adding a member such as a reflection sensor and stop the image forming operation.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a laser printer using an intermediate transfer belt according to an embodiment of the present invention.
FIG. 2 is a perspective view of the static elimination needle of the present invention.
FIG. 3 is a schematic diagram of a secondary transcription site of the present invention.
FIG. 4 is a schematic view of a static elimination needle part of the present invention.
FIG. 5 is a diagram illustrating a transfer material passing state when no jam occurs.
FIG. 6 is a diagram illustrating a transfer material passing state when a jam occurs.
FIG. 7 is a flowchart illustrating control according to an embodiment of the present invention.
FIG. 8 is a diagram showing the results of a current measurement experiment with and without paper jam in Example 1.
FIG. 9 is a perspective view of a discharging brush according to a second embodiment.
FIG. 10 is a diagram illustrating a transfer material passing state according to the second exemplary embodiment.
FIG. 11 is a diagram showing the results of an experiment for measuring current with and without paper jam in Example 2.
[Explanation of symbols]
10. Intermediate transfer belt (image carrier)
14 Secondary transfer bias roller (transfer means)
40 ... static elimination needle (static elimination means)
100: High voltage power supply (transfer bias applying means)
102 high-voltage power supply (static bias applying means)
104: ammeter (current value detecting means)

Claims (8)

An image carrier that carries the toner image; a transfer unit that transfers the toner image on the image carrier to a transfer material; a transfer bias application unit that applies a transfer bias to the transfer unit; A static eliminator provided in the vicinity of the transfer means for eliminating static from the transfer material; a static elimination bias applying means for applying a static elimination bias to the static elimination means; and a current value detecting means for detecting a current value flowing through the static elimination means. an image forming apparatus having the bets, performs said transfer bias application and discharge bias applied to the transfer means during at least a non-image forming at the same time, the current flowing through the charge eliminating means when the the I _1, when the actual transfer to the Assuming that the current value flowing through the static elimination means is I ₂ and the fluctuation threshold of the static elimination current is I ₀ ,
| I ₂ −I ₁ | ≦ I ₀
Wherein the image forming operation is stopped when the relationship of The image forming apparatus according to claim 1, wherein the discharging unit is a discharging needle provided so as not to contact the transfer material. The image forming apparatus according to claim 1, wherein the discharging unit is a discharging brush provided so as to contact a transfer material. 4. The image forming apparatus according to claim 1, wherein a transfer material jam is detected based on a current value flowing through the charge removing unit. 5. The image forming apparatus according to claim 1, wherein a polarity opposite to a polarity of a transfer bias applied to the transfer unit is applied to the charge removing unit. The image forming apparatus according to claim 1, wherein a transfer bias applied to the transfer unit is controlled at a constant voltage. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer body that forms a full-color image by carrying a plurality of color toner images. An image carrier that carries the toner image; a transfer unit that transfers the toner image on the image carrier to a transfer material; a transfer bias application unit that applies a transfer bias to the transfer unit; A static eliminator provided in the vicinity of the transfer means for eliminating static from the transfer material; a static elimination bias applying means for applying a static elimination bias to the static elimination means; and a current value detecting means for detecting a current value flowing through the static elimination means. A method for detecting a jam of a transfer material of an image forming apparatus, comprising: simultaneously applying a transfer bias to a transfer unit and applying a charge removing bias to the transfer unit at least during non-image formation, and setting a current value flowing to the charge removing unit to I ₁ and then, the actual current value flowing to the discharging means when the transfer and I _2, the variable threshold of the static eliminating current When I _0,
| I ₂ −I ₁ | ≦ I ₀
Wherein the image forming operation is stopped when the relationship of (1) is established.

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