JP2006171521A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can output an image of high picture quality, even if paper sheets with a zero image area are fed continuously, and to provide a transfer device used for the apparatus. <P>SOLUTION: The image forming apparatus capable of continuously forming a toner image on a memory material by using toner has a toner consuming mode, by forming a toner consumption pattern between memory materials during continuous image formation. Fig.3 shows the process of writing a toner consumption pattern on an image carrier, a memory material conveyer, a transfer member or the like. By forming the toner consumption pattern between toner images formed on paper, the toner can be consumed (exchanged), even during continuous paper feeding. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an apparatus capable of forming a color image and a transfer apparatus used in the image forming apparatus.

Representative methods of color image formation include a direct transfer method in which toner images of different colors formed on a plurality of photoconductors are transferred while being superimposed directly on a transfer sheet, and toners of different colors formed on a plurality of photoconductors. There is an intermediate transfer method in which an image is transferred while being superimposed on an intermediate transfer member, and then transferred onto a transfer sheet at once. Since a plurality of photoconductors are arranged side by side facing the transfer paper or intermediate transfer body, this is called a tandem method, and yellow (Y), magenta (M), cyan (C), and black (K) for each photoconductor. For each color, an electrophotographic process such as formation and development of an electrostatic latent image is performed, and the image is transferred onto a running transfer sheet in the direct transfer method, or onto a running intermediate transfer member in the intermediate transfer method.

In the tandem color image forming apparatus using each of these methods, the direct transfer method receives an endless belt that runs while supporting transfer paper, and the intermediate transfer method receives an image from a photoconductor. Generally, an endless belt to be carried is employed. Then, an image forming unit including four photoconductors is installed side by side on one running side of the belt.
In the tandem color image forming apparatus, it is important to prevent the occurrence of color misregistration by accurately superimposing the toner images of the respective colors.

Patent Document 1 describes an image forming apparatus having a mode in which initial adjustment is performed in a toner sensor adjustment mode, and toner is replaced when the developer does not have a predetermined charge amount in the initial adjustment. Yes. However, in this method, if the toner charge amount is not intended during continuous paper feeding, it cannot be corrected.
Patent Document 2 describes an image forming apparatus that replaces toner in a developing device when executing process control such as color misregistration adjustment and development bias adjustment. However, in this case as well, the toner cannot be replaced during the continuous sheet passing, and therefore there is a possibility that the image is deteriorated when the continuous sheet passing through the low image area is performed.

JP 2001-100505 A JP 2004-271912 A

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of solving the above-described problems and capable of outputting a high-quality image even with continuous paper having a zero image area, and a transfer device used therefor.

As means for solving the above problems, the present invention has the following features.
The image forming apparatus according to claim 1, wherein the process of continuously forming a toner image on a storage material using toner can be performed continuously. It has a mode in which a toner consumption pattern is formed between the storage material and the storage material to consume the toner.
The image forming apparatus according to claim 2, wherein the image forming apparatus is a two-component developing method, and replenishes substantially the same amount of toner as the toner consumed in the toner consumption pattern into the developing apparatus. And
According to a third aspect of the present invention, the image forming apparatus further includes the inter-memory-material toner replacement mode only when outputting a low image area image.
According to a fourth aspect of the present invention, the image forming apparatus further includes a temperature / humidity detecting unit, and a toner replacement mode is inserted between the storage materials according to the detection result.
6. The image forming apparatus according to claim 5, further comprising a cleaning unit that collects the toner on the image carrier and the toner on the transfer member, the intermediate transfer member, and the transfer material transport member, and the toner consumption. The pattern is collected by any one or a plurality of cleaning means.
7. The image forming apparatus according to claim 6, wherein the image forming apparatus further transfers a toner consumption pattern from an image carrier to a transfer member, an intermediate transfer body, and a transfer material transport body, and a transfer current that flows at the time of an output pattern. It is characterized in that the transfer is performed with a smaller current.
The image forming apparatus according to claim 7, further comprising a toner having an average circularity of 0.90 to 0.99.
9. The image forming apparatus according to claim 8, wherein the image forming apparatus further uses toner having a shape factor SF-1 in the range of 120 to 180 and a shape factor SF-2 in the range of 120 to 190. It is characterized by.
The image forming apparatus according to claim 9, wherein the image forming apparatus further uses a toner having a volume average particle diameter to number average particle diameter ratio Dv / Dn in a range of 1.05 to 1.30. It is characterized by.

Even if an image having a low image area is continuously output, a high-quality image can be continuously output.
The toner in the developing device can be replaced efficiently, and high-quality images can be output continuously.
High-quality images can be output continuously even when outputting a low image area image.
A high-quality image can be continuously output by entering the toner replacement mode even in a temperature and humidity environment where the toner is likely to deteriorate.
By dividing the toner consumption pattern into a plurality of cleaning means, it is possible to reduce the load on the cleaning means and prevent the occurrence of defective cleaning.
The toner consumption pattern can be divided into the image carrier cleaning means and the other cleaning means, and the load on each cleaning means can be reduced.

One embodiment in which the present invention is applied to an electrophotographic direct color transfer color laser printer (hereinafter referred to as “laser printer”) as an image forming apparatus will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of a laser printer according to the present embodiment. This laser printer has four sets of toner image forming units 1Y, 1M, 1C, 1K (hereinafter referred to as yellow) (Y), magenta (M), cyan (C), and black (K). , Subscripts Y, M, C, and K of the respective symbols indicate yellow, magenta, cyan, and black members, respectively, indicating the moving direction of the transfer paper 100 (along the arrow A in the figure). 60 in the traveling direction) are arranged in order from the upstream side. Each of the toner image forming units 1Y, 1M, 1C, and 1K includes photosensitive drums 11Y, 11M, 11C, and 11K as image carriers and a developing unit. In addition, the arrangement of the toner image forming units 1Y, 1M, 1C, and 1K is set so that the rotation axes of the photosensitive drums are parallel and arranged at a predetermined pitch in the transfer paper moving direction. .

In addition to the toner image forming units 1Y, 1M, 1C, and 1K, the laser printer carries the optical writing unit 2, the paper feed cassettes 3 and 4, the registration roller pair 5, and the transfer paper 100, and each toner image forming unit. A transfer unit 6 as a belt driving device having a transfer conveyance belt 60 as a transfer conveyance member that conveys the sheet so as to pass through the transfer position, a belt fixing type fixing unit 7, a paper discharge tray 8, and the like. In addition, a manual feed tray MF and a toner supply container TC are provided, and a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like (not shown) are also provided in a space S indicated by a two-dot chain line.
The optical writing unit 2 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each of the photosensitive drums 11Y, 11M, 11C, and 11K while scanning the laser beam based on the image data. To do.

FIG. 2 is an enlarged view showing a schematic configuration of the transfer unit 6. The transfer conveyance belt 60 used in the transfer unit 6 is a high-resistance endless single-layer belt having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm, and the material thereof is PVDF (polyvinylidene fluoride). The transfer conveyance belt 60 is wound around support rollers 61 to 68 so as to pass through the transfer positions that are in contact with and face the photosensitive drums 11Y, 11M, 11C, and 11K of the toner image forming units.
Among these support rollers, the entrance roller 61 on the upstream side in the transfer sheet moving direction is disposed on the outer peripheral surface of the transfer conveyance belt 60 so that the electrostatic adsorption roller 80 to which a predetermined voltage is applied from the power source 65a is opposed. Yes. The transfer paper 100 that has passed between the two rollers 61 and 65 is electrostatically attracted onto the transfer conveyance belt 60.
A roller 63 is a drive roller that frictionally drives the transfer conveyance belt 60, and is connected to a drive source (not shown) and rotates in the direction of the arrow.

As a transfer electric field forming means for forming a transfer electric field at each transfer position, transfer bias applying members 67Y, 67M, 67C, and 67K are provided at positions facing the photosensitive drum so as to be in contact with the back surface of the transfer conveyance belt 60. ing. These are bias rollers provided with a sponge or the like on the outer periphery, and a transfer bias is applied to the roller core from each transfer bias power source 9Y, 9M, 9C, 9K. Due to the action of the applied transfer bias, a transfer charge is applied to the transfer conveyance belt 60, and a transfer electric field having a predetermined strength is formed between the transfer conveyance belt 60 and the surface of the photosensitive drum at each transfer position. In addition, a backup roller 68 is provided to keep the contact between the transfer paper and the photoconductor in the area where the transfer is performed, and to obtain the best transfer nip.

The transfer bias applying members 67Y, 67M, and 67C and the backup roller 68 disposed in the vicinity thereof are integrally held by the swing bracket 93 so as to be rotatable, and can be rotated around a rotation shaft 94. This rotation is clockwise when the cam 96 fixed to the cam shaft 97 is rotated in the direction of the arrow.
The entrance roller 61 and the suction roller 80 are integrally supported by the entrance roller bracket 90, and can be rotated clockwise from the state shown in FIG. A hole 95 provided in the swing bracket 93 and a pin 92 fixed to the entrance roller bracket 90 are engaged with each other, and rotate in conjunction with the rotation of the swing bracket 93. By the clockwise rotation of these brackets 90, 93, the bias applying members 67Y, 67M, 67C and the backup roller 68 disposed in the vicinity thereof are separated from the photoreceptors 11Y, 11M, 11C, and the entrance roller 61 and the suction roller 80 also moves downward. It is possible to avoid contact between the photoconductors 11Y, 11M, and 11C and the transfer conveyance belt 60 when forming a black-only image.

On the other hand, the transfer bias applying member 67K and the backup roller 68 adjacent to the transfer bias applying member 67K are rotatably supported by the outlet bracket 98, and are rotatable about a shaft 99 coaxial with the outlet roller 62. When attaching / detaching the transfer unit 6 to / from the main body, the transfer unit 6K is rotated clockwise by operating a handle (not shown), and the transfer bias applying member 67K and the backup roller 68 adjacent thereto are moved from the black image forming photosensitive member 11K. They are separated.
A cleaning device 85 composed of a brush roller and a cleaning blade is disposed on the outer peripheral surface of the transfer conveyance belt 60 wound around the driving roller 63. The cleaning device 85 removes foreign matters such as toner adhering to the transfer conveyance belt 60.
A roller 64 is provided downstream of the driving roller 63 in the traveling direction of the transfer conveyance belt 60 in a direction to push the outer peripheral surface of the transfer conveyance belt, and a winding angle around the drive roller 83 is ensured. A tension roller 65 that applies tension to the belt with a pressing member (spring) 69 is provided in the loop of the transfer conveyance belt 60 further downstream from the roller 64.

The one-dot chain line in FIG. 1 shown above indicates the conveyance path of the transfer paper 100. The transfer paper 100 fed from the paper feed cassettes 3 and 4 or the manual feed tray MF is transported by transport rollers while being guided by a transport guide (not shown), and is transported to a temporary stop position where the registration roller pair 5 is provided. The transfer paper 100 delivered at a predetermined timing by the registration roller pair 5 is carried on the transfer conveyance belt 60, conveyed toward the toner image forming units 1Y, 1M, 1C, and 1K, and passes through the transfer nips. .
The toner images developed on the toner drums 11Y, 11M, 11C, and 11K of the toner image forming units 1Y, 1M, 1C, and 1K are superimposed on the transfer paper 100 at the transfer nips, respectively. It is transferred onto the transfer paper 100 under the action of pressure. By this superposition transfer, a full-color toner image is formed on the transfer paper 100.
The surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K after the toner image transfer are cleaned by a cleaning device, and are further discharged to prepare for the formation of the next electrostatic latent image.

On the other hand, the transfer paper 100 on which the full-color toner image is formed is fixed in the first paper discharge direction B or the second in accordance with the rotation posture of the switching guide G after the full-color toner image is fixed by the fixing unit 7. In the paper discharge direction C. When the paper is discharged from the first paper discharge direction B onto the paper discharge tray 8, it is stacked in a so-called face-down state with the image surface down. On the other hand, when the paper is discharged in the second paper discharge direction C, it is conveyed toward another post-processing device (such as a sorter or a binding device) (not shown), or is registered again for double-sided printing via a switchback unit. It is conveyed to the roller pair 5.

Next, the characteristic part of this embodiment is demonstrated.
FIG. 3 is a diagram in which a toner consumption pattern is written on an image carrier, a storage material conveyance body, a transfer member, and the like. A toner image consumption pattern is formed between toner images to be formed on paper, and toner consumption (replacement) can be performed even during continuous paper feeding.

Next, a process for deteriorating the toner and a defect caused by the process will be described with reference to FIGS.
FIG. 4 is a schematic view of a portion where the toner is stressed (toner charging portion). The toner is charged at the member 150 by applying stress. (In the case of two-component development, the friction between the toner and the carrier and the one component are charged by the friction between the toner and the friction member.) However, if excessive stress is applied, the additive is buried and the toner aggregates.
The following states can be considered as a state in which the stress on the toner becomes excessive.

1) In the case of one-component development The toner that is not developed in the one-component development rotates many times on the developing roller. For this reason, if an image with a small amount of toner consumption continues to be produced, the same toner passes through the member 150 many times, resulting in excessive stress. When the stress becomes excessive in one-component development, the additive on the toner surface is buried (or released). In some cases, the toner is broken into fine particles.

2) In the case of two-component development If an image with low toner consumption is continuously produced even in two-component development, the number of times the toner and the carrier are rubbed increases, resulting in excessive stress on the toner. When the stress on the toner is excessive, the additive on the toner surface is buried (or released) as in the one-component development method, or the toner is cracked and fine powder is formed.

FIG. 5 is a diagram in which the additive and additive on the toner surface are buried (or released). When an excessive stress is applied to the toner, the additive that should be attached to the toner surface is buried in the toner (buried) or separated from the toner (release of the additive).
In particular, since the low-temperature fixing has progressed in recent years, the glass transition temperature of the resin used for the toner tends to decrease. A substance having a low glass transition temperature often has a soft toner surface, and the additive is easily buried.

FIG. 6 is a diagram showing the embedding of the additive and the adhesion force of the toner image carrier. When the additive is attached to the toner, the toner and the image carrier are not in direct contact with each other. Therefore, the non-electrostatic adhesion force of the toner image carrier is small. However, when the additive is buried (or released), the toner and the image carrier are in direct contact with each other, so that the non-electrostatic adhesion between the toner image carriers is increased. As a result, problems such as poor transferability occur.

FIG. 7 is a flowchart showing an algorithm for the toner replacement mode off and on. After continuous paper passing, the temperature / humidity environment is first detected. As a result, when it is determined that the humidity is high, the toner replacement mode is turned on during continuous paper passing.
When the temperature / humidity detection result is not a high humidity environment, the image area at the time of image formation is detected. As a result, in the case of an output with a low image area, a toner replacement mode is inserted after the paper. When the image area is large, the toner replacement mode is not set and the paper is continuously passed.

In the above embodiment, the present invention is applied to the transfer unit 6 in the tandem printer in which a plurality of the photosensitive drums 11Y, 11M, 11C, and 11K are arranged on the transfer conveyance belt 60. However, the present invention is applied. Possible printers and belt drives are not limited to this configuration.
For example, the toner replacement mode can also be adopted in a quadruple tandem intermediate transfer system as shown in FIG. In the quadruple tandem intermediate transfer system, as described in claims 5 and 6, the toner consumption pattern is collected not only by the image carrier cleaning means but also by the intermediate transfer body and (secondary) transfer member cleaning means. To do. In this way, by dividing the toner consumption pattern into several cleaning means, the load on the cleaning means can be reduced.

  The toner used in the image forming apparatus of the present invention has an average circularity of 0.90 to 0.99. An average circularity of the toner of 0.90 to 0.99 is excellent in dot reproducibility and good transferability, so that high image quality can be obtained. When the average circularity is less than 0.90 and the toner is separated from the spherical shape, it is difficult to obtain a high-quality image having sufficient transferability or no dust. The circularity of the toner is a value obtained by optically detecting particles and dividing by the perimeter of an equivalent circle having the same projected area. Specifically, the measurement is performed using a flow type particle image analyzer (FPIA-2000; manufactured by Sysmex Corporation). In a predetermined container, 100 to 150 mL of water from which impure solids are removed in advance is added, 0.1 to 0.5 mL of a surfactant is added as a dispersant, and about 0.1 to 9.5 g of a measurement sample is further added. The suspension in which the sample is dispersed is subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the shape and distribution of the toner are measured at a dispersion concentration of 3,000 to 10,000 pieces / μL.

The toner has a shape factor SF-1 in the range of 100 to 180, and a shape factor SF-2 in the range of 100 to 190.
FIG. 9 is a diagram schematically showing the shape of the toner for explaining the shape factor SF-1 and the shape factor SF-2.
The shape factor SF-1 indicates the ratio of the roundness of the toner shape, and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the shape factor SF-1 of the toner is close to 100, the shape of the toner is close to a sphere, and the contact between the toner and the toner or the contact between the toner and the photosensitive member becomes a point contact. -Adhesive force between each other becomes weak, and hence the fluidity becomes high. Also, the adhesive force between the toner and the photosensitive member becomes weak, and the transfer rate becomes high. On the other hand, if the value of the shape factor SF-1 is greater than 180, the shape factor SF-1 becomes indefinite, which is not preferable because developability and transferability deteriorate.

The shape factor SF-2 indicates the ratio of the uneven shape of the toner, and is represented by the following formula (2). This is a value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (2)
The closer the value of SF-2 is to 100, the smoother the unevenness of the toner surface. In order to improve the cleaning property, it is preferable that the surface has moderate unevenness. However, when the shape factor SF-2 is larger than 190, the unevenness becomes conspicuous so that the toner is scattered on the image. This is not preferable because the image quality is lowered.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.) and introducing it into an image analyzer (LUSEX 3: manufactured by Nireco). Analyzed and calculated.

The toner has a volume average particle size of 3.0 to 8.0 μm and a ratio Dv / Dn of the volume average particle size Dv to the number average particle size Dn of 1.05 to 1.30. By using a toner having such a particle size and particle size distribution, it is excellent in all of heat-resistant storage stability, low-temperature fixability, and hot offset resistance, and particularly when used in a full color image forming apparatus. High glossiness is obtained. In general, it is said that the smaller the toner particle size, the more advantageous it is to obtain a high-resolution and high-quality image, but conversely with respect to transferability and cleaning properties. Is disadvantageous. Further, when the volume average particle size is smaller than the above range, in the two-component developer, the toner is fused to the surface of the magnetic carrier in the developing device for a long period of time, and the charging ability of the magnetic carrier is lowered. When used as a developer, toner filming on the developing roller and toner fusion to a member such as a blade for thinning the toner are likely to occur. On the contrary, when the volume average particle size of the toner is larger than the above range, it becomes difficult to obtain a high-resolution and high-quality image, and the balance of the toner in the developer is performed. In many cases, the variation in the particle size of the toner becomes large.
On the other hand, if Dv / Dn exceeds 1.30, the charge amount distribution becomes wide and the resolving power decreases, which is not preferable. The average particle size and particle size distribution of the toner can be measured using a Coulter Counter TA-II and a Coulter Multisizer II (both manufactured by Coulter). In the present invention, a counter-counter type TA-II is used, connected to an interface (manufactured by Nikka Giken) and PC9801 personal computer (manufactured by NEC) that outputs number distribution and volume distribution, and measurement is performed. did.

1 is a schematic configuration diagram of a laser printer according to an embodiment. It is an enlarged view showing a schematic configuration of a transfer unit. It is an image figure of a toner consumption pattern. FIG. 3 is a conceptual diagram (how to apply stress) of charging at a developing unit. FIG. 4 is a diagram for explaining an additive on the toner surface and the burying of the additive. It is a figure which shows the relationship between the burying of an additive and the adhesive force between a toner and an image carrier. FIG. 6 is a diagram illustrating an algorithm for toner replacement mode on and off. It is a figure which shows the example of adoption with a 4 tandem intermediate transfer system. It is the figure which represented typically the shape of the toner in order to demonstrate shape factor SF-1 and shape factor SF-2.

Explanation of symbols

1Y, 1M, 1C, 1K toner image forming unit
2 Optical writing unit 3, 4 Paper cassette
5 Registration roller pair 6 Transfer unit
7 Fixing unit 8 Output tray
9 Transfer bias power supply 11Y, 11M, 11C, 11K Photosensitive drum 60 Transfer conveyance belt
61-68 support rollers
80 Electrostatic adsorption roller
80a power supply
90 Entrance roller bracket
91 axes
92 pins
93 Swing bracket
94 Rotating shaft
95 holes
96 cams
97 Camshaft
98 outlet bracket
99 axes
100 Transfer paper A Belt running direction
B First paper discharge direction
C Second paper discharge direction S Space
MF bypass tray
G switching guide

Claims (9)

In an image forming apparatus capable of continuously performing a process of forming a toner image on a storage material using toner,
The image forming apparatus has a mode in which a toner consumption pattern is formed between a storage material and a storage material during continuous image formation to consume the toner. The image forming apparatus according to claim 1.
The image forming apparatus is a two-component developing system,
An image forming apparatus comprising: a developing device that replenishes substantially the same amount of toner as consumed in a toner consumption pattern. The image forming apparatus according to claim 1, wherein
The image forming apparatus is characterized in that the inter-memory-material toner replacement mode is set only when a low image area image is output. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus includes a temperature / humidity detecting unit, and a toner replacement mode is set between storage materials according to a detection result. The image forming apparatus according to claim 1,
The image forming apparatus includes a cleaning unit that collects toner on an image carrier and toner on a transfer member, an intermediate transfer member, and a transfer material transport member, and collects a toner consumption pattern by one or a plurality of cleaning units. An image forming apparatus. The image forming apparatus according to claim 5.
The image forming apparatus is characterized in that when transferring a toner consumption pattern from an image carrier to a transfer member, an intermediate transfer body, and a transfer material transport body, a current smaller than a transfer current that flows at the time of an output pattern is transferred. Image forming apparatus. The image forming apparatus according to claim 1,
The image forming apparatus uses toner having an average circularity of 0.90 to 0.99. The image forming apparatus according to claim 1,
The image forming apparatus uses toner having a shape factor SF-1 in the range of 120 to 180 and a shape factor SF-2 in the range of 120 to 190. The image forming apparatus according to claim 1,
The image forming apparatus uses a toner having a ratio Dv / Dn of a volume average particle diameter to a number average particle diameter in a range of 1.05 to 1.30.

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