JP3689573B2 - Image forming apparatus - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer.
[0002]
[Prior art]
In image forming apparatuses such as copying machines and laser beam printers, color needs are increasing. As a color image forming method, a sublimation type, a thermal transfer type, an ink jet method, an electrophotographic method, and the like are known, but the electrophotographic method is said to be most excellent in terms of image forming speed.
[0003]
In recent years, the intermediate transfer system is becoming the mainstream among the electrophotographic systems. This method has advantages such as no choice of transfer material and excellent color registration (low color misregistration).
[0004]
FIG. 1 shows a schematic configuration of an image forming apparatus using a drum-type intermediate transfer member. In the image forming apparatus shown in the drawing, yellow, magenta, cyan, and black single color toner images formed on a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 are sequentially transferred to an intermediate transfer member 2. The toner images of these four colors are collectively transferred onto the transfer material in a lump after the primary transfer and superimposing on them.
[0005]
In this method, since there is no need to wrap the transfer material P around the intermediate transfer body 2, it can be used for envelopes and cardboard, and is highly versatile and the color registration does not change depending on the thickness of the transfer material. Therefore, there is an advantage that high image quality can be obtained.
[0006]
In the intermediate transfer system, the intermediate transfer member 2 is formed by removing toner (secondary transfer residual toner) remaining on the surface of the intermediate transfer member 2 without being transferred onto the transfer material P from a cleaning member such as a cleaning blade made of polyurethane elastomer, rayon, or the like. The collected image is collected by a fur brush or a winding type cleaning web, and is prepared for the next image formation.
[0007]
As another cleaning method, the tribo of the transfer residual toner is changed by the charging means 4 that is placed in contact with the surface of the intermediate transfer body 2 and charges the secondary transfer residual toner, and the secondary transfer is performed simultaneously with the primary transfer of the next image. A technique for electrostatically collecting the transfer residual toner on the photosensitive drum 1 has been developed.
[0008]
Specifically, a solid roller (charging member) 41 or a brush roller (collecting member) 42 is used as a recharging means for secondary transfer residual toner, and the transfer residual toner tribo is the reverse of the toner tribo charged in the developing unit. At the same time as the primary transfer of the toner image from the photosensitive drum 1 to the intermediate transfer body 2 by charging to the polarity, the secondary transfer residual toner is transferred from the intermediate transfer body 2 to the photosensitive drum 1, and the cleaning unit ( Collective collection is performed by a cleaning device 8.
[0009]
By using this method, toner that does not contribute to the final image formation can be collected all at once, so that compared with the case where a separate cleaning unit is provided in the intermediate transfer body 2, the waste toner transport unit and the waste toner collection box are used. There is no need to provide a plurality of devices, and there are advantages such as downsizing of the device, cost reduction, and simplification of maintenance.
[0010]
By the way, as the cleaning unit 8 for the photosensitive drum 1, a method using a cleaning blade 81 made of an elastic material such as rubber has been widely used. However, the structure of the blade-type cleaning unit 8 is simple and compact. This is because it is advantageous in terms of cost.
[0011]
As the material of the cleaning blade 81, polyurethane rubber, which is a kind of thermoplastic elastomer, is mainly used in terms of chemical resistance, wear resistance, moldability, mechanical strength, and the like.
[0012]
In the cleaning unit 8 having the cleaning blade 81, a method in which the cleaning blade 81 is pressed against the surface of the traveling photosensitive drum 1 from the counter direction is the mainstream. The cleaning mechanism in this method is that when the cleaning blade 81 is brought into pressure contact with the surface of the photosensitive drum 1 with a force (5 to 40 gf / cm) necessary for removing the residual toner on the surface of the photosensitive drum 1, the cleaning blade 81. At the contact portion between the edge portion and the photosensitive drum 1, first, the edge portion of the cleaning blade 81 that is in close contact with the surface of the photosensitive drum 1 by the frictional force acting on the contact portion is deformed (shear deformation) in the traveling direction of the photosensitive drum 1 (arrow R1 direction). , Compression deformation), and then the energy accumulated in the edge portion of the cleaning blade 81 due to the stress acts as a restoring force (repulsive elastic force) to return to the original state, which is considered to be due to a so-called Stick-Slip motion. . Therefore, in order to obtain stable cleaning performance in the cleaning unit 8 using the cleaning blade 81, it is necessary to optimize the amplitude and frequency of the Stick-Slip motion. In order to optimize the amplitude and frequency of the stick-slip motion, the frictional force of the contact portion between the edge of the cleaning blade 81 and the surface of the photosensitive drum 1, the shape of the cleaning blade 81, the material properties of the cleaning blade 81 (Young's modulus, Poisson) By adjusting the ratio, modulus (stress-strain curve), etc.
[0013]
However, with the long-term use of the apparatus, for example, NO on the surface of the photosensitive drum 1_X When the toner resin or the like adheres, the friction coefficient of the surface of the photosensitive drum 1 increases, and the frictional force between the edge portion of the cleaning blade 81 and the photosensitive drum 1 (contact portion) naturally increases. For this reason, the energy accumulated in the edge portion of the cleaning blade 81 in the stick state increases, and the stick-slip motion has amplitude> proper value and frequency <proper value (the appropriate value is a range in which the cleaning operation is stabilized). . As this phenomenon progresses, the edge portion of the cleaning blade 81 jumps up without following the surface of the photosensitive drum 1, slipping out of the toner, and rubbing the toner (toner fusion, filming) on the surface of the photosensitive drum 1, Furthermore, abnormal noise (blade squealing) and abnormal vibration (chatter) occur, so-called blade turning occurs in which the edge portion is reversed so as to follow the rotation direction of the photosensitive drum 1, and the edge portion of the cleaning blade 81 and the photosensitive portion are also exposed. There is a possibility that the surface of the drum 1 is damaged (blade edge chipping, photosensitive drum surface scratch).
[0014]
In order to solve this problem, conventionally, an inorganic material such as graphite, boron nitride, molybdenum disulfide, tungsten disulfide, or silicon dioxide, a fluorine resin, silicon, or the like is provided at the contact portion between the tip of the cleaning blade 81 and the photosensitive drum 1. Means have been taken to reduce the frictional force by applying solid powder (lubricant) of organic substances such as resin, polyamide (nylon resin), polyacetal, polyethylene, and polyimide.
[0015]
However, as the apparatus is used, the lubricant disappears from the edge portion of the cleaning blade 81, and the frictional force increases again. Therefore, this is not a fundamental solution for reducing the frictional force between the edge portion of the cleaning blade 81 and the photosensitive drum 1. . Further, although various devices for constantly supplying the lubricant to the edge portion of the cleaning blade 81 have been devised, the device configuration of the cleaning unit 8 becomes complicated and the cost is greatly increased, so that it has not been put into practical use. .
[0016]
Furthermore, conventionally, an OPC (organic photo semiconductor) photosensitive drum 1 composed of a surface layer using polycarbonate as a binder resin has been widely used as the photosensitive drum 1, but in order to solve the above-described problems. A protective layer (OCL) in which an appropriate amount (3 to 40 wt%) of Teflon resin is dispersed in a polycarbonate binder resin may be provided on the surface of the OPC photosensitive drum 1. By using the photosensitive drum 1 having the OCL as a surface layer, and adding inorganic fine particles having a particle size of 2 μm or less whose surface has been hydrophobized, such as strontium titanate, cerium oxide, alumina, and zirconia, to the toner, These inorganic fine particles are accumulated in the contact portion between the edge portion of the cleaning blade 81 and the photosensitive drum 1, and the Teflon resin contained in the OCL is supplied to the contact portion by polishing the OCL surface to promote a lubricating effect.
[0017]
However, in the case where a large amount of images with extremely low toner consumption are continuously copied, the above polishing effect is brought about at the contact portion between the edge of the cleaning blade 81 and the photosensitive drum 1 as the number of copies increases. Inorganic fine particles are extremely reduced, and problems such as toner fusing, abnormal vibration, and blade turning may occur.
[0018]
Further, as a method for reducing the frictional force between the cleaning blade 81 and the photosensitive drum 1, a method using a cleaning blade (hereinafter referred to as “nylon-coated blade”) in which a nylon resin layer is disposed on the contact surface with the photosensitive drum 1 is used. is there. When this nylon coat blade is used, the frictional force between the edge portion and the photosensitive drum 1 can be sufficiently reduced.
[0019]
However, since the nylon resin does not have an elastomeric property unlike polyurethane, the cleaning action of the residual toner due to the stick-slip movement of the edge portion of the cleaning blade 81 is not seen, and the residual toner is blocked and scraped off. It is thought that. Therefore, in order to completely eliminate the residual toner, the pressure contact force of the cleaning blade to the surface of the photosensitive drum 1 needs to be considerably higher than that of the polyurethane blade (about twice that of the polyurethane blade). There arises a problem that the life of the photosensitive drum 1 is reduced, for example, the amount of abrasion on the surface of the photosensitive drum 1 is increased or the surface is damaged.
[0020]
As another means, a solid or halftone Obi image having a width of the whole of the main scanning direction or a width close to that in the main scanning direction at a fixed timing other than the time of image formation is formed on the photosensitive drum 1 in the sub-scanning direction. In the transfer area, a method of utilizing the toner polishing and lubricating action by causing the toner that forms an Obi image to reach the edge of the cleaning blade 81 without being subjected to the transfer action in the transfer area has been widely used (Black Obi Sequence). ). In this black obi sequence, the adhering matter on the surface of the photosensitive drum 1 is polished, and the cleaning action can be stabilized by the effect of keeping the state of the surface of the photosensitive drum 1 constant and the effect of increasing the lubricity of the edge of the cleaning blade 81.
[0021]
However, in this black obi sequence, toner is consumed at times other than during image formation, which increases the running cost and increases the amount of waste toner, so it is necessary to enlarge the waste toner container or shorten the container replacement time.
[0022]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and after the residual toner on the intermediate transfer member is returned onto the image carrier (photosensitive drum) by using a recharging unit, the cleaning blade type image carrier cleaning is performed. In an image forming apparatus that performs batch cleaning with the apparatus, the image carrier surface scratches on the surface of the image carrier due to a change in the pressing load of the cleaning blade on the surface of the image carrier caused by the use of the image forming apparatus An object of the present invention is to provide an image forming apparatus capable of preventing toner fusion, abnormal noise, abnormal vibration, blade turning, and the like, and guaranteeing a high image and high quality.
[0023]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention according to claim 1 transfers the toner image formed on the surface of the image carrier to the transfer material at the transfer nip portion, and does not transfer the toner image to the transfer material. Cleaning device for residual toner remaining on the surfaceA cleaning blade in contact with the surface of the image carrierIn the image forming apparatus to be removed by the step, the transfer nip portion along the moving direction of the surface of the image carrier and theCleaning bladeA recharging unit disposed between the recharging member and the recharging member disposed on the downstream side of the recharging member. A collecting member for temporarily collecting the residual toner recharged by the recharging means.The residual toner temporarily collected by the collecting member is discharged from the rotating member to the image carrier at regular intervals, and is supplied between the image carrier and the cleaning blade.
  It is characterized by that.
[0024]
  According to the second aspect of the present invention, toner images of different colors sequentially formed on the surface of the image bearing member are primarily transferred onto the intermediate transfer member sequentially at the primary transfer nip, and the toner image is transferred onto the intermediate transfer member. After superimposing a plurality of color toner images, the plurality of color toner images on the intermediate transfer body are secondarily transferred collectively onto a transfer material at a secondary transfer nip portion, and at the time of primary transfer, the intermediate transfer body Residual toner remaining on the surface of the image carrier without being transferred to the surface, and residual toner remaining on the surface of the intermediate transfer body without being transferred to the transfer material during the secondary transfer, and transferred onto the image carrier The cleaning deviceA cleaning blade in contact with the surface of the image carrierIn the image forming apparatus to be removed by the step, recharging means provided between the secondary transfer nip portion and the primary transfer nip portion along the moving direction of the surface of the intermediate transfer member is provided. The means includes a recharging member for recharging residual toner remaining on the surface of the intermediate transfer member without being transferred to the transfer material at the time of the secondary transfer, and a recharging member disposed on the downstream side of the recharging member. A recovery member that temporarily recovers the recharged residual toner.The residual toner temporarily collected by the collecting member is discharged from the rotating member to the intermediate transfer member at a constant interval, and is supplied between the image carrier and the cleaning blade via the image carrier. ,It is characterized by that.
[0032]
  Claim3The present invention relates to claim 1.Or 2In the image forming apparatus, the collection member is a conductive brush.
[0038]
  Claim4The present invention relates to claim 1.3In the image forming apparatus, the recharging member recharges the residual toner collected by the collecting member.
[0039]
  Claim5The present invention according to claim4In the image forming apparatus, the recharging member contacts and separates from the collecting member.
[0040]
[Action]
According to the above-described configuration, the residual toner is temporarily collected inside the recharging unit that returns the residual toner on the intermediate transfer member onto the image carrier, and before the residual toner collecting capability in the recharging unit becomes insufficient. The toner collected inside the recharging means is charged back to the reverse polarity of the toner tribo charged in the developing unit by the tribo and returned electrostatically onto the intermediate transfer member, and further from the intermediate transfer member to the image carrier. By changing the position, it is possible to achieve the same effect as the above-mentioned Obi image while maintaining low cost and space saving.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0042]
<Embodiment 1>
FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in the figure is a laser beam printer using an intermediate transfer member, and the figure is a longitudinal sectional view showing a schematic configuration thereof.
[0043]
The image forming apparatus shown in FIG. 1 uses a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier, and a drum-type intermediate transfer drum having a two-layer structure as an intermediate transfer member 2. Is used.
[0044]
The image forming apparatus in FIG. 1 will be described more specifically. The image forming apparatus uses an intermediate transfer drum having a diameter of 186 mm as the intermediate transfer body 2, and is a four-color full-color electrophotographic system having a maximum sheet passing size A3, a process speed of 117 mm / sec, image exposure, and reverse development. An image forming apparatus. In order to form a full-color image, yellow (Y), magenta (M), cyan (C), and black (Bk) toner images are sequentially formed on the photosensitive drum 1 that is rotationally driven in the direction of the arrow R1. The toner images of the respective colors are sequentially transferred onto the surface of the intermediate transfer body 2 and the toner images for four colors are superimposed on the surface of the intermediate transfer body 2. This transfer is performed through a primary transfer nip portion N1 formed between the photosensitive drum 1 and the intermediate transfer body 2. The transfer of the toner image from the photosensitive drum 1 to the intermediate transfer body 2 is called primary transfer, and the toner image for four colors is superimposed on the surface of the intermediate transfer body 2 by rotating the intermediate transfer body 2 four times. This completes the primary transfer.
[0045]
Next, the toner images for four colors on the intermediate transfer body 2 are collectively transferred onto a transfer material P such as paper. This transfer is a transfer performed through a secondary transfer nip portion N2 formed between the intermediate transfer body 2 and the transfer unit 3, and is called secondary transfer. The transfer unit 3 serving as a transfer unit is a unit in which a transfer belt 31 is stretched between two rollers 32 and 33, and the transfer belt 31 is intermediately transferred by a transfer roller 32 on the upstream side with respect to the conveying direction of the transfer material P. The toner image is subjected to secondary transfer while being brought into contact with the body 2, and at the same time, the transfer material P is attracted to the transfer belt 31 to be separated from the intermediate transfer body 2. The other roller is a drive roller 33, which drives the unit so that the peripheral speed of the intermediate transfer body 2 and the peripheral speed of the transfer belt 31 at the secondary transfer nip portion N2 are equal. The transfer unit 3 is supported so that the transfer roller 32 side can swing around the drive roller 33 side, and the transfer belt 31 can be brought into and out of contact with the intermediate transfer body 2. Yes.
[0046]
The toner image secondarily transferred onto the transfer material P is transferred onto the surface of the transfer material P by a heat fixing roller unit 11 as a fixing device disposed downstream of the secondary transfer nip portion N2 in the transport direction of the transfer material P. To be established. The transfer material P after the toner image is fixed is discharged to the outside of the image forming apparatus main body.
[0047]
Next, each member and each unit will be described in detail.
[0048]
The photosensitive drum 1 is a negatively chargeable OPC (organic optical semiconductor) drum having a diameter of 62 mm. First, the surface thereof is uniformly charged by a charging roller 7 as a primary charger. Here, the bias applied to the charging roller 7 is a bias in which a DC component and an AC component are superimposed.
[0049]
Next, the surface of the photosensitive drum 1 is exposed by the laser exposure device 5. In this embodiment, an infrared laser diode having a wavelength of 760 nm and a polygon scanner are combined, and an exposure apparatus having a lens and a mirror is used to perform image exposure.
[0050]
Next, the electrostatic latent image formed by laser exposure is developed with toner by a developing device. In the image forming apparatus of the present embodiment, toners of four colors Y, M, C, and Bk are used. Specifically, a fixed black developing device 9 and a rotary color developing as shown in FIG. Unit 10 is used.
[0051]
The black developing device 9 employs a jumping development method using magnetic one-component toner. A conductive non-magnetic developing sleeve 91 having a diameter of 16 mm enclosing a fixed magnet roll is coated with a toner having a particle diameter of about 6 μm with an elastic blade 92, and the DC component applied to the developing sleeve 91 and the AC component of a rectangular wave are used for photosensitivity. Reverse development is performed by jumping to and from the drum 1.
[0052]
The color developing unit 10 incorporates three yellow, magenta, and cyan developing devices into a rotary rotary, and rotates the rotary developer in the direction of arrow R10 for the color toner developer to be developed. Development is performed at the development position facing the photosensitive drum 1. Each color developer performs development by a jumping development method using non-magnetic one-component toner. The toner is a polymer toner having a core / shell structure with a particle size of about 7 μm and containing wax inside. The toner is coated on the developing sleeve 101 by the application roller 103, and the layer thickness is regulated by the elastic blade 102 and sent to the developing position. The development is performed under the same bias condition as that of the black developing device 9.
[0053]
The primary transfer is performed by applying a voltage to the intermediate transfer member 2, and the primary transfer residual toner on the photosensitive drum 1 is scraped off by a cleaning unit (cleaning device) 8 having a polyurethane elastomer cleaning blade 81, The toner is fed to the waste toner box via the waste toner conveyance roller 82 and the waste toner conveyance screw 83.
[0054]
In the case of monochromatic printing (monochromatic image formation), after performing primary transfer, the toner image is conveyed as it is to the secondary transfer nip portion N2 on the intermediate transfer body 2 and undergoes secondary transfer. In the case of four-color full-color printing (four-color full-color image formation), the intermediate transfer body 2 rotates four times to primarily transfer Y, M, C, and Bk toner images, and then performs a secondary transfer nip portion. Secondary transfer is received at N2. In the image forming apparatus according to the present embodiment, by applying an appropriate voltage to the recharging unit 4, the secondary transfer residual toner on the intermediate transfer body 2 is temporarily collected inside the recharging unit 4, or The waste toner collected inside the recharging means 4 is discharged onto the intermediate transfer member 2 and then transferred to the photosensitive drum 1. Further, the waste toner transferred to the photosensitive drum 1 is scraped off by the cleaning blade 81 and collected in the waste toner box.
[0055]
The recharging means 4 used in the present embodiment is a solid roller (recharging roller) 41 as a recharging member having a diameter of 20 mm mainly made of acrylic rubber and a collecting member having a diameter of 20 mm made of rayon conductive yarn. The brush roller (collecting roller) 42 is configured to be detachable from the intermediate transfer body 2.
[0056]
The solid roller 41 has a three-layer structure of a low resistance sponge layer made of acrylic sponge, a resistance layer made of acrylic urethane resin, and a surface release layer made of fluororesin. The volume resistance value is 10 for the resistance layer.^Five -10⁹ Ω, 10 for the surface release layer¹²-10¹⁶Ω. Further, it can be detached from the intermediate transfer member 2 alone. The contact force is a total pressure of 100 to 300 g, rotates in the counter direction with respect to the rotation direction of the intermediate transfer body 2 (the direction of the arrow R2), and recharges the secondary transfer residual toner on the intermediate transfer body 2.
[0057]
The fineness of the pile material of the brush roller 42 is 100 to 500 denier (preferably 300 denier) per 100 filaments, and the fiber density is 100 to 300 KF / inch.² (Preferably 200KF / inch² ). Further, the intrusion amount with respect to the intermediate transfer member 2 is 0.5 ± 0.3 mm, and rotates in the counter direction with respect to the rotation direction of the intermediate transfer member 2 to collect the secondary transfer residual toner on the intermediate transfer member 2 or Recharge.
[0058]
In the case of monochrome printing, the primary transfer bias is + 200V. When four-color full-color printing is performed, if the first-color toner is further superimposed on the intermediate transfer body 2 where the first-color toner is already present and primary transfer is attempted, the transfer contrast is substantially reduced by the previous toner potential. In order to compensate for this, it is necessary to increase the transfer bias. On the other hand, if the primary transfer bias is too high, a discharge occurs between the photosensitive drum 1 and the intermediate transfer body 2, and image degradation and toner tribo on the intermediate transfer body 2 change. Can not. In view of these circumstances, the primary transfer bias at the time of multicolor printing was set to 200 V, 300 V, 300 V, and 200 V sequentially for each rotation of Y, M, C, and Bk.
[0059]
In the present embodiment, the pre-secondary transfer corona charger 12 disposed on the right side of the intermediate transfer member 2 in FIG. 1 is used for the toner on the intermediate transfer member 2 in order to improve the secondary transfer efficiency. Perform corona charging. The corona charger 12 in the figure is of the scorotron type, and a DC current is passed through the corona wire and an AC component is superimposed to prevent the corona wire from being stained. The shield potential is grounded. Due to the corona charging, the toner tribo on the intermediate transfer member 2 is black toner, and the negative charge increases from about −10 μC / g to about −20 μC / g. At the time of secondary transfer, the transfer material P is supplied from a paper feeding unit (not shown), and the transfer belt 31 that can be separated from and brought into contact with the intermediate transfer body 2. The secondary transfer bias performs constant current control. Electric charges are supplied from the transfer belt 31 to the transfer material P, and the toner image on the intermediate transfer member 2 is secondarily transferred to the transfer material P.
[0060]
The secondary transfer residual toner on the intermediate transfer body 2 is first charged positively by the solid roller 41, and then a negative bias is applied to the brush roller 42 on the downstream side to recharge the toner in the recharging means 4 (mainly the brush roller 42). Collected on the brush). When the print counter reaches a certain number (100 sheets in the present embodiment), the solid roller 41 is separated from the intermediate transfer member 2 and brought into contact with the brush roller 42, and the toner (brush) collected in the recharging means 4 is recovered. The toner adhering to the roller 42 is recharged positively. Further, by making the bias (plus) of the brush roller 42 larger than the bias applied to the intermediate transfer member 2, the primarily collected waste toner is discharged onto the intermediate transfer member, and the contact between the photosensitive drum 1 and the intermediate transfer member 2 is discharged. The toner is collected on the photosensitive drum 1 at the primary transfer nip portion N1 which is a contact portion.
[0061]
The mechanism for charging the secondary transfer residual toner on the intermediate transfer body 2 by the solid roller 41 is due to discharge. In the discharge (small) gap between the solid roller 41 to which the voltage is applied and the intermediate transfer body 2, the discharge is excited according to Paschen's law. In general, the charging roller 7 of the photosensitive drum 1 is well known as a charging means based on such discharge. In this case, all of the DC current supplied from the charging roller 7 becomes the charging current of the photosensitive drum 1. .
[0062]
However, since both the intermediate transfer member 2 and the solid roller 41 are medium resistance members in the above-described method, the DC current supplied to the solid roller 42 does not all contribute to charging, and most of the injected current flows directly in ohmic fashion. It is. For this reason, if the solid roller 41 is controlled at a constant current, when the resistance value of the member fluctuates due to environmental fluctuations or manufacturing fluctuations, the ratio between the direct injection current and the current that contributes to toner charging changes. The toner tribo is not stable. Therefore, by adjusting the contact nip between the solid roller 41 and the intermediate transfer body 2 that directly contributes to the injection current, the discharge gap of 5 to 500 μm is maintained and the toner charging property is ensured.
[0063]
The bias applied to the solid roller 41 performs constant current control as a DC component (plus), and the AC component is 2 kHz, 3 kV._PPThe rectangular wave is superimposed. The reason for superimposing the AC bias is that the discharge with only the DC bias occurs only in one direction and the charge amount is small. However, when the AC is superimposed, the toner is discharged from both the intermediate transfer member 2 and the solid roller 41. For this reason, the chargeability is improved by increasing the discharge gap.
[0064]
When the secondary transfer residual toner is collected with respect to the brush roller 42, the bias applied to the brush roller 42 is controlled as a DC component (minus) like the solid roller 41, and the AC component is 2 kHz, 3 kV._PPThe rectangular wave is superimposed. The reason for superimposing the AC bias is to make the tribo of the secondary transfer residual toner that could not be collected by the brush roller 42 uniform and return it all to the photosensitive drum 1. Further, when the waste toner temporarily collected by the recharging means 4 is discharged onto the intermediate transfer body 2, the bias applied to the brush roller 42 is a constant current as a DC component (plus) as in the case of the solid roller 41. Control, AC component is 2kHz, 3kV_PPThe rectangular wave is superimposed. The reason for superimposing the AC bias is that the toner tribo discharged onto the intermediate transfer body 2 is made uniform by the AC component, so that all of the toner bias is returned to the photosensitive drum 1.
[0065]
The operation sequence of the recharging means 4 described above will be described with reference to FIG.
[0066]
Usually, the recharging means 4 (solid roller 41, brush roller 42) is separated from the intermediate transfer body 2 (see FIG. 2A). When the primary transfer image is formed on the intermediate transfer body 2, the recharging means 4 (just before the primary transfer of the final color (Bk at the time of four-color full color printing or the designated color at the time of single color printing) is performed. The solid roller 41 and the brush roller 42) are brought into contact with the intermediate transfer body 2 (see FIG. 2B). At the same time as the secondary transfer of the leading edge of the toner image formed on the intermediate transfer body 2 is started, a predetermined bias is applied to the solid roller 41 and the brush roller 42, and the counter direction is applied to the intermediate transfer body 2, respectively. The toner is rotated in the directions of arrows R41 and R42, and the secondary transfer residual toner is collected in the recharging unit 4. This secondary transfer residual toner collection sequence is repeated for each print.
[0067]
Next, when the secondary transfer residual toner collection mode is repeated 100 times (full color printing is counted once for one print, and single color printing is counted once for 4 prints), the recharging means 4 is transferred to the next printing sequence. The collected waste toner discharging mode is executed. As shown in FIG. 2C, the state of the recharging means 4 at this time is such that the unit of the recharging means 4 is in contact with the intermediate transfer body 2, and the brush roller 42 is also the secondary transfer residual toner. Similar to the recovery mode, the intermediate transfer member 2 is in contact with the intermediate transfer member 2. On the other hand, the solid roller 41 is separated from the intermediate transfer member 2 and is in contact with the brush roller 42. The contact condition at this time is set so that the brush tip of the brush roller 42 enters the surface of the solid roller 41 at 0.5 ± 0.3 mm. Then, after performing the waste toner discharging mode once in accordance with the bias condition previously set, the secondary transfer residual toner collecting mode is entered again, and thereafter the same operation is repeated.
[0068]
However, if the image forming apparatus is abnormally stopped due to a density control sequence or a jam of the transfer material P, the solid DC roller 41 and the brush roller 42 both have a positive DC component of 2 kHz, 3 kV._PPA bias on which the AC component of the rectangular wave is superimposed is applied, and the toner on the intermediate transfer member 2 is returned directly onto the photosensitive drum 1 without being collected inside the recharging means 4 (actually, the brush roller 42), and photosensitive The drum 1 is collected by the cleaning unit 8.
[0069]
As described above, in the present embodiment, the configuration of the recharging unit 4 includes the solid roller 41 for recharging the waste toner and the brush roller 42 for collecting the waste toner downstream thereof. This eliminates the need for providing a separate cleaning means for the intermediate transfer body 2 and also allows the waste toner to be reused to execute a black obi sequence for stabilizing the cleaning of the photosensitive drum 1 for a long period of time. Stable images can be supplied while maintaining space saving and low running cost.
[0070]
In the first embodiment described above, the case where the recharging unit 4 is applied to a four-color full-color image forming apparatus has been described as an example. However, the present invention is not limited to this and may be applied to a single-color image forming apparatus. Can do. In this case, the recharging unit 4 is disposed opposite to the surface of the photosensitive drum 1 between the transfer nip portion that transfers the toner image on the photosensitive drum 1 to the transfer material P and the cleaning unit. The function and effect in this case are the same as those in the first embodiment.
[0071]
【The invention's effect】
As described above, according to the present invention, the charging roller for recharging the residual toner on the intermediate transfer member and the recharging means including the charging brush for collecting the residual toner on the intermediate transfer member are provided on the intermediate transfer member. The residual toner is temporarily collected inside the recharging means (charging brush), and the collected toner tribo is developed before the residual toner collecting ability of the recharging means (charging brush) becomes insufficient. The toner tribo charged at the surface is charged to the opposite polarity and electrostatically returned to the intermediate transfer member, and the collected toner is transferred from the intermediate transfer member to the image carrier, and is collected in a batch by the image carrier cleaning device. This prevents problems such as scratches on the surface of the image carrier, toner fusing on the surface of the image carrier, abnormal noise, abnormal vibration, and turning of the blade while maintaining low cost and space saving. Long-term cleaning It has become possible to maintain a stable state.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.
FIGS. 2A, 2B, and 2C are schematic views illustrating an operation state of a recharging unit in the image forming apparatus according to the present invention.
[Explanation of symbols]
1 Image carrier (photosensitive drum)
2 Intermediate transfer body (intermediate transfer drum)
3 Secondary transfer unit
4 Recharging means
8 Cleaning device (cleaning unit)
41 Recharging member (solid roller)
42 Collection member (brush roller)
81 Cleaning blade

Claims (5)

A toner image formed on the surface of the image carrier is transferred to a transfer material at a transfer nip portion, and residual toner remaining on the surface of the image carrier without being transferred to the transfer material is used as a cleaning blade of the cleaning device. In an image forming apparatus that is removed by contacting the surface ,
Recharging means disposed between the transfer nip portion and the cleaning blade along the moving direction of the image carrier surface;
The recharging means includes
A recharging member for recharging residual toner remaining on the surface of the image carrier;
The residual toner recharged possess a recovery member for temporarily recovered by being disposed on the downstream side of the該再charging member該再charging means,
Residual toner temporarily collected by the collecting member is discharged from the rotating member to the image carrier at regular intervals, and is supplied between the image carrier and the cleaning blade.
An image forming apparatus. Toner images of different colors sequentially formed on the surface of the image carrier are primarily transferred onto the intermediate transfer member sequentially at the primary transfer nip, and a plurality of color toner images are superimposed on the intermediate transfer member. Thereafter, the toner images of a plurality of colors on the intermediate transfer member are secondarily transferred onto the transfer material at the secondary transfer nip portion, and the surface of the image carrier is not transferred to the intermediate transfer member during the primary transfer. The residual toner remaining on the intermediate transfer member and the residual toner not transferred to the transfer material during the secondary transfer but remaining on the surface of the intermediate transfer member, and transferred onto the image carrier, are cleaned with the cleaning blade of the cleaning device. In the image forming apparatus that is removed by contacting the surface of the carrier ,
Recharging means disposed between the secondary transfer nip portion and the primary transfer nip portion along the moving direction of the surface of the intermediate transfer member,
The recharging means includes
A recharging member that recharges residual toner remaining on the surface of the intermediate transfer member without being transferred to the transfer material during the secondary transfer;
The residual toner recharged possess a recovery member for temporarily recovered by being disposed on the downstream side of the該再charging member該再charging means,
Residual toner temporarily collected by the collecting member is discharged from the rotating member to the intermediate transfer member at regular intervals, and is supplied between the image carrier and the cleaning blade via the image carrier.
An image forming apparatus. The collection member is a conductive brush,
The image forming apparatus according to claim 1 or 2, characterized in that. The recharging member recharges residual toner collected by the collecting member;
The image forming apparatus according to any one of claims 1 to 3, characterized in that. The recharging member contacts and separates from the recovery member;
The image forming apparatus according to claim 4 .

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