JP5177473B2 - Image forming apparatus, process cartridge - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer using an electrophotographic process, and a process cartridge used therefor.

  Currently, in the image forming apparatus as described above, downsizing, high image quality, and ecology are indispensable conditions. When aiming for miniaturization, "cleaner-less" that eliminates the need for cleaning means as a dedicated device by using as a developing means a cleaning means that cleans the toner remaining on the surface of the photoreceptor after toner image transfer. A so-called image forming apparatus has also appeared.

  For example, developing means for forming a latent image on a uniformly charged image carrier and developing the latent image with a developer containing spherical toner and carrier carried on the developer carrier to form a toner image. And the developing means has a toner selected from the group consisting of yellow toner, cyan toner, magenta toner and black toner, and the developing means transfers the toner image onto a transfer material. Later, it also serves as a simultaneous development cleaning unit that collects residual toner remaining on the image carrier at the same time as the development. The simultaneous development cleaning unit forms an image forming unit, and a plurality of the image forming units are arranged along the conveyance belt. The present invention relates to a cleanerless image forming apparatus that is arranged in a row and conveys a transfer material by the conveying belt and passes a plurality of the image forming units to form a color image. The ratio of the area covered with the spherical toner particles by the external additive externally added to the spherical toner particles of the spherical toner is 15% or more and 50% or less. The shape factor SF-1 of the spherical toner is 100 to 140. A cleanerless type image forming apparatus characterized in that SF-2 is in the range of 100 to 120 has been proposed (see, for example, Patent Document 1).

  However, a plurality of image forming units are provided, toner images of different colors are formed in each image forming unit, and the toner images are sequentially superimposed and transferred onto the intermediate transfer member and used as a transfer material in the secondary transfer unit. When trying to achieve a cleaner-less color image forming apparatus that performs batch transfer, if toner on the transfer medium is reversely transferred onto the photosensitive drum, another color toner is mixed in the developing unit, and development There is a problem that the hue in the vessel changes.

  Therefore, the image forming apparatus includes a photoreceptor on which a toner image is formed and an intermediate transfer body that receives the transfer of the toner image from the surface of the photoreceptor, and finally transfers the toner image on the intermediate transfer body onto a recording medium. And a scraping member for scraping off residual toner from the surface of the photoconductor after the toner image is transferred to the intermediate transfer body in an image forming apparatus for forming an image composed of a fixed toner image on a recording medium by fixing. There has also been proposed an image forming apparatus including a cleaning device having a housing that opens toward the surface of the intermediate transfer member and accommodates the scraping member (see, for example, Patent Document 2).

  Furthermore, the technique of Patent Document 4 includes a cleaning device having a scraping member that scrapes residual toner from the surface of the photosensitive member, and a housing that opens toward the surface of the intermediate transfer member and accommodates the scraping member. This prevents toner color mixture and charger contamination. However, having an open housing on the intermediate transfer member takes up space and is expensive.

  Patent Document 3 discloses a contact charging method used in an electrophotographic apparatus, in which a plurality of charging members are arranged, at least one of which applies a bias having a polarity opposite to the charging polarity of the photoreceptor, and the remaining at least One method has been proposed in which a bias having the same polarity as the charging polarity of the photosensitive member is applied and finally the photosensitive member is charged to a predetermined potential required by a plurality of charging members. However, in the system using a plurality of charging devices, the photosensitive member is charged by the plurality of charging devices, so that the photosensitive member receives an electrostatic hazard at two or more locations. For this reason, the electrostatic hazard given to the photoconductor is large, and the influence of the discharge product on the photoconductor is likely to increase, and the electrostatic chronological deterioration gradually deteriorates as the photoconductor is repeatedly charged and discharged. I will do it. In particular, this contact charging method has a drawback in that the hazard to the photoreceptor is too great because the photoreceptor is once charged to a polarity opposite to the predetermined charging polarity and then charged to the predetermined charging polarity.

Japanese Patent No. 3248047 JP 2003-186364 A JP-A-4-310980

  The present invention has been made in view of the above-described conventional problems, and prevents a change in color tone due to the mixture of toner remaining on the surface of the image carrier after the primary transfer in the developing device. To provide an image forming apparatus and a process cartridge used therefor that can achieve miniaturization, reduction of toner consumption by increasing toner use efficiency, and elimination of waste toner or elimination of waste toner, and ecology compatibility without problems. With the goal.

An image forming apparatus according to claim 1 of the present invention includes:
An image carrier and toner image forming means for forming a toner image having a predetermined polarity on the image carrier;
An intermediate transfer member provided opposite to the image carrier;
Primary transfer means for transferring a toner image of the image carrier onto the intermediate transfer member;
Secondary transfer means for transferring the toner image on the intermediate transfer member to a recording medium;
In an image forming apparatus comprising:
Bias applying means for applying a bias voltage having the same polarity as the predetermined polarity to a contact member that contacts the image carrier;
Delivery means for delivering residual toner remaining on the image carrier after the primary transfer to the intermediate transfer body by the contact member to which a bias voltage having the same polarity as the predetermined polarity is applied by the bias application means. ,
A plurality of pairs of the image carrier and the toner image forming means;
The toner image forming means forms toner images of different colors on the corresponding image carrier,
The intermediate transfer member moves in a predetermined direction;
A plurality of the primary transfer means are provided to face the plurality of image carriers through the intermediate transfer member, and sequentially transfer toner images of different colors on the intermediate transfer member,
The secondary transfer means collectively transfers the color toner images formed on the intermediate transfer member to a recording medium,
Residual toner transferred from the image carrier to the intermediate transfer member by the transfer unit is located at the most downstream side in the moving direction of the intermediate transfer member, and forms a black toner image. you recovered,
It is characterized by that.

  An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the bias voltage value is −300V to −700V.

  The image forming apparatus according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the bias voltage is applied before the residual toner reaches a position where the contact member contacts the image carrier. It is characterized by applying.

  An image forming apparatus according to a fourth aspect is the image forming apparatus according to any one of the first to third aspects, wherein the contact member is a sheet-like member, and the material is 6 nylon, 12 nylon, or vinylon. , Saran, rayon, polyethylene, acrylic, and fluorine (PVDF, PFA, PTFE) resin.

  An image forming apparatus according to a fifth aspect is the image forming apparatus according to any one of the first to fourth aspects, wherein the image carrier is rotatable in a predetermined direction, and the contact member is a rotation of the image carrier. It abuts in the counter direction with respect to the direction.

An image forming apparatus according to claim 6
The image forming apparatus according to claim 1.
The image carrier is rotatable in both forward and reverse directions;
The contact member of the delivery means temporarily holds the residual toner,
A bias voltage having the same polarity as the predetermined polarity is applied to the contact member by the bias applying means during a predetermined period in which the image carrier rotates in a direction opposite to the rotation direction at the time of primary transfer. The residual toner held on the toner is transferred to the intermediate transfer member.

According to a seventh aspect of the present invention , in the image forming apparatus according to the sixth aspect , the timing at which the image carrier is reversely rotated corresponds to a non-image portion where the image carrier has no toner image. Features.

An image forming apparatus according to an eighth aspect is the image forming apparatus according to the sixth or seventh aspect , wherein the predetermined period is a process control execution interval.

An image forming apparatus according to a ninth aspect is the image forming apparatus according to the sixth or seventh aspect , wherein the predetermined period is determined in accordance with a cumulative rotational speed of the image carrier.

The image forming apparatus according to claim 1 0, in the image forming apparatus according to claim 6 or 7, the predetermined time period, wherein the determined according to the accumulated number of rotations of said image bearing member.

The image forming apparatus according to claim 1 1, in the image forming apparatus according to claim 6 1 0, the abutment member is a member of the sheet, and the image bearing member, the image bearing member The abutting in the forward direction with respect to the rotational direction during the primary transfer.

An image forming apparatus according to claim 1 2, in the image forming apparatus according to claim 6 1 0, the abutment member is a member of the sheet-like, smooth or curved substantially smooth, wherein The image carrier is in contact with the middle or almost the middle of the curved portion in the rotation direction of the image carrier at the time of the primary transfer.

  According to the present invention, the toner reversely transferred onto the image carrier can be efficiently transferred onto the intermediate transfer member by the abutting member to which a bias is applied. Therefore, the toner should be originally transferred from the image carrier. It is possible to more effectively prevent the toner and the reversely transferred toner from being mixed.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a diagram showing an entire image forming apparatus as an example of an object of the present invention. In the figure, reference numeral 1 denotes a photosensitive drum as an image carrier having a cylindrical shape with a diameter of φ24 mm (hereinafter simply referred to as a photosensitive member unless otherwise required), for example, rotating at a peripheral speed of 120 mm / second. . A brush-shaped charger 2 as a charging unit is pressed against the surface of the photosensitive member 1 and is rotated by the rotation of the photosensitive member 1. A bias in which AC is superimposed on DC or DC by a high voltage power source (not shown). The photoreceptor 1 is uniformly charged by applying a voltage. The surface potential of the photoreceptor 1 due to this charging is, for example, −500V.

  The photosensitive member 1 is exposed to image information by an exposure unit 3 which is a latent image forming unit to form an electrostatic latent image. This exposure step is performed using a laser beam scanner using a laser diode, an LED, or the like.

  In the figure, reference numeral 4 denotes a one-component contact developing device which is a developing means which is a toner image forming means, and a predetermined developing bias (voltage value is negative but supplied from a high voltage power source not shown). Good). Thus, the electrostatic latent image on the photoreceptor 1 is visualized as a toner image. The developing device 4 initially stores about 180 g of one-component toner, for example.

  In the figure, reference numeral 10 denotes a process unit in which a photoconductor, a charger, and a developer are integrated. Four process units 10 are arranged in parallel. When a full-color image is formed, a visible image is formed in the order of yellow, magenta, cyan, and black, and a visible image of each color is always in contact with each other. A full color image is formed by sequentially superimposing and transferring onto the transfer belt 15.

  An intermediate transfer belt 15 as an intermediate transfer member is stretched around a drive / secondary transfer counter roller 21, a metal cleaning counter roller 16, a primary transfer roller 5, and a tension roller 20, and is not shown. Is driven to rotate via the driving and secondary transfer counter roller 21. Note that the tension roller 20 is biased by springs on both sides so as to apply tension to the intermediate transfer belt 15. The tension roller 20 is an aluminum pipe having a diameter of, for example, φ20 mm. The tension roller 20 is a regulating member that presses a collar having a diameter of, for example, φ24 mm at both ends, but regulates the behavior so that the intermediate transfer belt 15 does not meander.

  The driving / secondary transfer counter roller 21 may be, for example, a polyurethane rubber (for example, a thickness of 0.3 to 1 mm) or a thin layer coating roller (for example, a thickness of 0.03 to 0.1 mm). A urethane coating roller (thickness 0.05, φ20) or the like with a small diameter change due to is preferable. Below, it demonstrates as what uses this.

  As the primary transfer member 5, a conductive blade, a conductive sponge roller, a metal roller, or the like can be used. In this example, for example, a metal roller having a diameter of 8 mm is used, and the moving direction of the intermediate transfer belt 15 with respect to the photoreceptor 1 is used. 8 mm, for example, 1 mm offset in the vertical upward direction, and a predetermined transfer bias, for example, +500 to +1000 V is applied to the primary transfer roller 5 by a single high voltage power source (not shown) in common with respect to the photoreceptor 1. A transfer electric field is formed through the transfer belt 15 to transfer the toner image on the photoreceptor 1 to the intermediate transfer belt 15.

  In the figure, reference numeral 17 denotes a toner mark sensor (TM sensor), which measures the toner image density and each color position on the belt 15 by a regular reflection type or diffusion type sensor, and adjusts the image density and color matching.

  In the figure, reference numeral 32 denotes an intermediate transfer belt cleaning unit, which performs cleaning by scraping off transfer residual toner on the intermediate transfer belt 15 with a cleaning blade 31. As the cleaning blade 31, for example, urethane rubber having a thickness of 1.5 to 3 mm and a rubber hardness of 65 to 80 ° can be used, and the counter blade can be brought into contact with the intermediate transfer belt 15. The transfer residual toner scraped off by the cleaning blade 31 is stored in the intermediate transfer member waste toner storage section 33 through a toner conveyance path (not shown). At least one of the part corresponding to the cleaning nip part of the belt 15 or the edge part of the cleaning blade 31 is coated with a coating agent such as a lubricant, toner, zinc stearate or the like at the time of assembly, and the blade swells in the cleaning nip part. While preventing the rise, a dam layer is formed in the cleaning nip portion to improve the cleaning performance.

  Each roller that stretches the intermediate transfer belt 15 is supported from both sides of the intermediate transfer belt 15 by an intermediate transfer belt unit side plate (not shown).

  Materials used for the intermediate transfer belt 15 include PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), TPE (thermoplastic elastomer), and carbon black. A resin film-like endless belt can be used by dispersing a conductive material such as, but in this example, for example, a structure of a single layer structure in which carbon black is added to TPE having a tensile modulus of 1000 to 2000 MPa and a thickness of 100 to A belt having a width of 200 μm and a width of 230 mm can be used.

Further, the resistance value of the intermediate transfer belt 15 is, for example, a volume resistivity of 10 ⁸ to 10 ¹¹ Ω · cm and a surface resistivity of 10 ⁸ to 10 ¹¹ Ω / □ in an environment of 23 ° C. and 50% RH (both Mitsubishi Chemical Corporation). Manufactured by product name: HIRESTAUP MCP-HT450, preferably applied voltage 500V, application time 10 seconds. If the volume resistivity and surface resistivity of the intermediate transfer belt 15 exceed the above-described ranges, the intermediate transfer belt 15 is charged. Therefore, it is necessary to take a measure such as setting the set voltage value higher as it goes downstream in the image forming order. Therefore, it becomes difficult to use a single power supply for the primary transfer unit. This is because the electric charge generated on the surface of the intermediate transfer belt 15 is increased by the discharge generated in the transfer process, the transfer material peeling process, and the like, and self-discharge becomes difficult. It is necessary to provide it. Also, if the volume resistivity and surface resistivity are below the above ranges, the charge potential decays faster, which is advantageous for static elimination by self-discharge, but toner scattering occurs because the current during transfer flows in the surface direction. End up. Therefore, the volume resistivity and the surface resistivity of the intermediate transfer belt 15 in the present invention are preferably within the above ranges.

In the figure, reference numeral 25 denotes a secondary transfer roller. The secondary transfer roller 25 is configured by coating a metal core such as SUS with an elastic body such as urethane adjusted to a resistance value of 10 ⁶ to 10 ¹⁰ Ω with a conductive material. For example, an ion conductive roller (urethane + carbon dispersion, NBR, hydrin), an electronic conductive type roller (EPDM), or the like can be used as the material. In this example, the diameter is, for example, φ20 mm, Asker C hardness of 35 to 50 °. The urethane roller can be used. Here, when the resistance value of the secondary transfer roller 25 exceeds the above range, it becomes difficult for the current to flow. Therefore, in order to obtain a required transfer property, it is necessary to apply a higher voltage, thereby reducing the power supply cost. Incurs an increase. In addition, since it is necessary to apply a high voltage, discharge occurs in the gap before and after the nip of the transfer portion, and white spots are lost on the halftone image due to the discharge. This is remarkable in a low-temperature and low-humidity environment (for example, 10 ° C. and 15% RH). On the other hand, if the resistance value of the secondary transfer roller 25 falls below the above range, the transferability between the multi-color image portion (for example, three-color superimposed image) and the single-color image portion existing on the same image cannot be achieved. This is because the resistance value of the secondary transfer roller 25 is low, so that a sufficient current flows to transfer the monochrome image portion at a relatively low voltage. However, it is optimal for the monochrome image portion to transfer the multiple color image portion. This is because a voltage value higher than the voltage is required, and setting a voltage that can transfer a plurality of color image portions causes an excessive transfer current in a single color image, resulting in a decrease in transfer efficiency.

  The resistance value of the secondary transfer roller 25 is measured by installing the roller 25 on a conductive metal plate and applying a load of 4.9 N on one side to both ends of the core metal and the metal core and the metal. For example, it can be calculated from the value of the current that flows when a voltage of 1 kV is applied to the plate.

  The transfer material 22 is fed by the paper feeding / conveying roller 23 and the registration roller pair 24 at the timing when the leading edge of the toner image on the surface of the intermediate transfer belt 15 reaches the secondary transfer position, and is transferred to a predetermined level by a high voltage power source (not shown). By applying a bias voltage, the toner image on the intermediate transfer belt 15 is transferred to the transfer material 22. The transfer material 22 is separated from the intermediate transfer belt 15 by the curvature of the driving and secondary transfer counter roller 21, and the toner image transferred to the transfer material 22 is fixed by the fixing unit 26 and then discharged.

In this embodiment, the process speed at the time of fixing is changed depending on the type of the transfer material 22. Specifically, for example, when a transfer material having a basis weight of 100 g / m ² or more is used, the process speed is set to half speed, and the transfer material is twice the normal process speed in the fixing nip formed by the fixing roller pair. It is possible to ensure the fixing property of the toner image by passing through the time.

<Experimental example>
An experimental example in which a test machine having the same configuration as that of the image forming apparatus shown in FIG. 1 (shown as a printer in the figure) is prepared will be described below. The sheet member was brought into contact with the photoreceptor upstream of the charging brush, and a monochrome half chart (halftone gradation image) was continuously printed on 3000 sheets of A4 paper at an image area ratio of 5% (photosensitive temperature 22 to 25 ° C.). , Environmental humidity 50-70%). Subsequently, the afterimage level of the 3000th print image was evaluated by rank for each sheet member. With respect to the rank criteria, ◯ indicates that the afterimage is not visible visually, Δ indicates that the afterimage is thin, and × indicates that the image is clearly visible. Further, as an index indicating how much untransferred toner and reverse transfer toner are scraped off by the sheet member, the evaluation was made based on the number of black streaks on the image due to the contamination of the charging brush. Specifically, in the process unit for black (Bk), Bk reversely charged toner is applied to a local portion of the charging brush roller (a portion corresponding to the toner fixing to the sheet) due to the fixing of the Bk toner to the sheet member. As it accumulates, it is known that black stripes occur in the above-mentioned half chart. Accordingly, the number of black stripes in the 3000th printed image was confirmed, and 0 was evaluated as ◯, 1-2 were evaluated as Δ, and three or more were evaluated as ×. As a comparison object, a urethane rubber blade was brought into contact with the photoreceptor, and the same experiment was performed. As the cleaning blade, a 100 μm SUS plate having a mounting angle of 17 ° and a bite of 0.5 mm was used.

As the black (Bk) toner, a spherical toner having an average particle diameter adjusted to 6 [μm] and having an external additive added thereto was used. As the photoreceptor (3Bk), an undercoat layer having a thickness of 3 [μm], a charge generation layer having a thickness of 0.2 [μm], and a charge transport layer having a thickness of 23 [μm] are sequentially laminated on a drum. The one having an electrostatic capacity of 110 [pF / cm ² ] was used. During printing, the photoconductor having such a configuration was rotationally driven at a linear speed of 120 [mm / sec].

  As the charging brush roller, one having an outer diameter (φ) of 11 [mm] formed by brushing a plurality of conductive flocked fibers on a rotating shaft member having a diameter of 5 [mm] was used. The charging bias applied to the charging brush roller includes a peak-to-peak voltage Vpp 1.0 [kV], a printing frequency 300 [Hz], a non-printing (inter-paper) frequency 10 [Hz], and a duty 45 [ %] With a DC voltage Vdc of −500 [V] superimposed on it. By dropping 300 [Hz] at the time of printing to 10 [Hz] in the inter-paper area, it is possible to discharge the transfer residual toner captured by the charging brush roller onto the photosensitive member. As described above, the discharged toner is collected from the photoreceptor to the developing roller. However, it is difficult to collect the low charge amount toner. Even when the frequency is lowered to 10 [Hz], the reversely charged toner is not discharged from the charged brush roller, and therefore gradually accumulates on the charged brush roller.

As the sheet member, a conductive sheet having a thickness of 0.1 [mm] made of a material obtained by dispersing carbon powder as a conductive material in polyvinylidene fluoroethylene (PVDF) was used. The volume resistance of this conductive sheet is 105 to 107 [Ω · cm]. The surface resistance is 102 [Ω / □]. The results of the above experiment are shown in Table 1 below as Experimental Examples 1 to 3 and Comparative Examples 1 to 4.

  A bias having the same polarity as the charging polarity of the toner is applied. As shown in Table 1, voltages of -300 V and -500 V are applied to the sheet members of Experimental Examples 1 and 2, which are examples of the present invention. There was no afterimage on the image and no black streak irregularities. However, afterimages were seen at voltages of −300 V or less, and black streak unevenness occurred. This is considered to be because the unevenness of the surface potential of the photoreceptor immediately after transfer cannot be made uniform because the applied bias is too small. Further, since the mechanical rigidity of the sheet member itself is weak, the adsorption force between the toner and the sheet member itself does not work in a state where almost no bias is applied, and the untransferred toner and the reverse transfer toner easily slip through. It is thought that black streaks occurred on the image because the charging brush was contaminated.

  Furthermore, when a large bias of −500 V or higher was applied, no afterimage was observed, but black streak irregularities occurred frequently at −700 or higher. The reason for this is considered that when the applied bias is too large, the toner of the opposite polarity is fixed at the front end of the sheet member, and the rigidity of the fixed portion changes, so that the toner slips through and contaminates the charging brush.

  As an example for comparison, the result of using a blade member instead of a sheet member (shown as Comparative Example 4 in Table 1) resulted in an afterimage and 2-3 black streaks. Regarding the afterimage, it is considered that the unevenness of the photoreceptor surface potential cannot be made uniform because no bias is applied to the blade. Also, residual toner and reverse transfer toner could not be prevented

  From the above points, when the applied bias voltage V is in the range of −300 <V <−700, the unevenness of the photoreceptor surface potential that causes afterimages is alleviated, and the transfer residual toner on the photoreceptor is reversely transferred. It can be said that the toner can be efficiently transferred onto the intermediate transfer member. Further, since the residual toner is dropped onto the intermediate transfer belt by gravity dropping by the sheet member in contact with the photosensitive member, the low-cost cleanerless development system can be realized with a minimum configuration.

  FIG. 2 shows a second embodiment. In FIG. 2, sheet members 202 a to 202 d (hereinafter referred to as “sheet member 202” unless otherwise necessary) that scrape toner remaining on the photoreceptors 201 a to 201 d (hereinafter referred to as “photosensitive member 201” unless otherwise required) after the primary transfer. 1 (referred to as “A” in FIG. 1) is in contact with the photosensitive member 201, is not in contact with the intermediate transfer belt 203, and transfers the residual toner to the intermediate transfer belt 203 by gravity drop. That is, the image is not disturbed by non-contact delivery. Further, the sheet member 202 that is a contact member curves smoothly or substantially smoothly (in the figure, it is curved in an arc shape, but is not limited to this), so to speak in the rotation direction at the time of primary transfer with the photosensitive member 201. It is in the state of contact at the middle or almost the middle of the portion curved in the forward direction (the direction opposite to the counter direction). The material of the sheet member 202 is preferably conductive 12 nylon. By adopting such a configuration, a cleaner-less system that does not include a device for collecting residual toner can be realized, and toner remaining on the photoconductor 201 after the primary transfer is not collected in the developing unit, and thus cleaner-less. It is possible to prevent a change in hue, which is a problem in the method. In the figure, reference numerals 211a to 211d denote primary transfer rollers. Since other configurations can be variously configured such as the same as the image forming apparatus of FIG. 1, illustration and description are omitted.

  FIG. 3 shows a third embodiment. In this embodiment, if the sheet member 302 that is a delivery member is always in contact (particularly in contact in the counter direction), the photosensitive member 301 continues to be worn and the characteristics of the photosensitive member 301 are deteriorated. A contact / separation mechanism 321 is provided on the sheet member 302, and the sheet member 302 is separated from the photosensitive member 301 to prevent wear of the photosensitive member 301 while the transfer is not performed. That is, while the sheet is not transferred, the sheet member is separated from the photosensitive member 301 as the image carrier, thereby suppressing the wear of the image carrier and preventing the life of the image carrier from being reduced.

  FIG. 4 shows a fourth embodiment. In this embodiment, the most upstream color in the rotation direction of the intermediate transfer belt 403 is Y, and the primary transfer rollers 411a to 411d (hereinafter referred to as the primary transfer roller 411 unless otherwise required) run the intermediate transfer belt 403. 5 to 10 mm offset (the rotation axis of the photosensitive member and the rotation shaft of the primary transfer roller are shifted to the downstream side of each of the photosensitive members 401a to 401d (hereinafter referred to as the photosensitive member 401 if not particularly required) correspondingly contacting with the direction. )). Further, the amount of biting between the primary transfer roller 411 and the photosensitive member 401 during color image formation is arranged to be 0.5 mm. By offsetting and biting the primary transfer roller 411, the primary transfer roller 411 does not directly apply a load to the photoconductor 401 via the intermediate transfer belt 403, and the intermediate transfer belt 403 is applied to the photoconductor 401. Since the transfer nip can be formed, the hardness of the primary transfer roller 411 can be set without participating in the transfer failure. That is, since the winding amount of the photoreceptor 401 and the intermediate transfer belt 403 can be increased by offset transfer, the pre-nip discharge can be reduced by increasing the nip width and increasing the distance from the center of the nip. The occurrence of + polar toner that is easy to copy can be reduced. In addition, when the primary transfer roller 411 is located immediately below, image quality degradation can be prevented by dispersing the pressure in the primary transfer nip. The offset amount and the amount of biting can be arbitrarily set so that the gap between the photosensitive member 401 and the primary transfer roller 411 is larger than the thickness of the intermediate transfer belt 403.

  In this embodiment, the most downstream color is black (Bk), and only the intermediate magenta photosensitive member 401c and cyan photosensitive member 401b are sheet members 402b and 402c (hereinafter referred to as a sheet member 402 unless particularly required). ). This is because the most upstream color toner does not mix in the developing device, and the most downstream color black photoreceptor 401a collects the upstream transfer magenta and cyan reverse transfer toners. To do. In the case of black, even if other colors are mixed, the change in hue can be suppressed to a minimum, and the toner consumption can be suppressed by increasing the use efficiency of the toner, which is compatible with ecology. Further, since the sheet member 402 only needs to be arranged with respect to the two photoconductors, it is possible to reduce the size and cost of the apparatus.

  FIG. 5 shows a fifth embodiment. In this embodiment, by providing the sheet member 502 integrally with the process cartridge 500, the contact position accuracy between the sheet member 502 and the photosensitive member 501 can be increased. Further, since the process cartridge 500 can be replaced as a unit, the replacement becomes easy. In the figure, reference numeral 503 denotes an intermediate transfer belt.

  FIG. 6 shows a sixth embodiment of the invention relating to reverse rotation. In this embodiment, immediately after the execution of the alignment density adjustment program for every 200 sheets, the photosensitive member 601 that has been rotated as indicated by the arrow in FIG. 3A is reversely rotated as shown in FIG. At the time of reverse rotation, a bias voltage is applied from an AC power source 604 by a high voltage output (not shown), and the residual toner 631 temporarily collected on the sheet member 602 is dropped onto a non-image portion on the intermediate transfer belt 603. Thus, the sheet member 602 can prevent the reverse transfer toner from being cleaned and the afterimage due to the unevenness of the potential without using a large cleaner unit. That is, the reverse polarity toner or the high adhesion toner temporarily collected on the sheet member 602 serving as the cleaning member is obtained by performing control to apply a bias to the sheet member 602 serving as the cleaning member with the AC power source 604 when the photosensitive member 601 rotates in the reverse direction. Is easily dropped on the intermediate transfer belt 603. An image carrier such as a photosensitive member can be rotated in both forward and reverse directions, and the toner is delivered by dropping onto the intermediate transfer belt 603 as described above, and the toner is collected by a cleaning device for the intermediate transfer belt 603. Of course it is good.

  In each of the embodiments described above, the bias voltage is applied before the residual toner reaches the position where the sheet member or the like as a contact member contacts the photoconductor as the image carrier. It is preferable to control the operation. Further, the sheet member is described as being pre-charged by applying a bias, but the present invention is not limited to the pre-charging configuration, and may be used as a charging unit. Furthermore, the contact member is not limited to the sheet member as in each of the above embodiments, and may be a brush or a blade. However, a sheet member that is not rigid is optimal. Further, as described above, the sheet member that is a contact member that temporarily holds the residual toner is in contact with the rotation direction of the photosensitive member that is the image carrier in the forward direction that is opposite to the counter direction. It is preferable that the configuration be such that However, depending on the conditions such as the material of the image carrier such as the photoconductor, the sheet member as a contact member is brought into contact with the rotation direction of the image carrier in the counter direction, and the remaining toner on the image carrier is efficiently used. It can also be configured to scrape well or temporarily hold.

  In addition, as a material of the sheet member used in the above-described embodiments, 6 nylon, 12 nylon, vinylon, saran, rayon, polyethylene, acrylic, a fluorine-based resin material (PVDF, PFA, PTFE) or the like can be used.

  As another possible embodiment of the image forming apparatus according to the present invention, for example, an apparatus that is composed of an image carrier and a developing device and that cleans residual toner on the image carrier after transfer is used. A cleaner-less process cartridge is provided for each color, and a process for forming a toner image on the image carrier by the developing device is collectively performed for a plurality of developing devices at the time of printing, and each color is provided on the intermediate transfer member. The process cartridge has a process of performing primary transfer in a lump so that the images of the image are overlapped, and primary transfer of the formed color toner image onto the transfer material, and the process cartridge is positioned vertically above the intermediate transfer member. In the image forming apparatus, the toner remaining on the latent image carrier after transfer by the transfer device is applied to at least one image carrier on a member in contact with the image carrier. Thus, it is possible to provide a mechanism for transferring the image onto the intermediate transfer member on the upstream side of the charging mechanism, and further, a predetermined bias voltage is applied to the member. By transferring the toner reversely transferred onto the body onto the intermediate transfer member, it is possible to prevent the toner to be transferred from the photosensitive member from being mixed with the reversely transferred toner, and to the member within the above range. By applying a bias, toner transfer efficiency is improved, and afterimages can be prevented by reducing potential irregularities on the surface of the photoreceptor immediately after transfer.

  Further, in the apparatus according to another aspect described above, the member in contact with the image carrier is not in contact with the intermediate transfer member, so that the image is not disturbed by non-contact delivery. A cleaner-less development system with a minimum configuration and a low-cost by installing a mechanism to transfer residual toner onto the intermediate transfer member by gravity drop by a member that is configured or contacted on the image carrier. In addition, the image carrier and the primary transfer unit indirectly apply a bias only through the intermediate transfer belt, so that the image carrier and the intermediate transfer can be performed by offset transfer. By increasing the contact length of the body, that is, the nip width and increasing the distance from the center of the nip, the pre-nip discharge is reduced, the occurrence of + polar toner that is easy to reverse transfer is reduced, and directly below If there is a roller can also be dispersed pressure in the primary transfer nip prevent image quality degradation.

  In the apparatus according to the other aspect described above, the process cartridge is composed of an image carrier and a developing device, and is a cleanerless process that does not include a device for collecting residual toner on the image carrier after transfer. A cartridge is provided for each color, and at the time of printing, a process of forming a toner image on the image carrier by the developing device is collectively performed for a plurality of developing devices, and the images of the respective colors are collectively stacked on the intermediate transfer member. A process cartridge having a process of performing a primary transfer and a secondary transfer of the formed color toner image onto a transfer material, and using a process cartridge disposed vertically above the intermediate transfer member, and at least one of the process cartridges To the image carrier, toner remaining on the image carrier after the primary transfer is provided in the process cartridge, and is applied to the downstream side of the primary transfer nip of the image carrier. It can be configured to include a mechanism to pass on the intermediate transfer member by the member.

  As another possible embodiment of the image forming apparatus according to the present invention, the image forming apparatus has a plurality of process cartridges composed of an image carrier and a developing device, and is printed on the image carrier by the developing device during printing. The process of forming a toner image is collectively performed for a plurality of developing devices, and primary transfer is performed collectively so that the images of the respective colors are superimposed on an intermediate transfer member disposed at an angle with respect to the bottom surface of the apparatus main body. And a step of primarily transferring the formed color toner image onto the intermediate transfer member, the process cartridge is positioned vertically above the intermediate transfer member, and the at least one image carrier has the above-mentioned after the primary transfer. It has a cleaning member in which the toner remaining on the image carrier abuts against the image carrier, and the residual toner is temporarily collected by the abutting member, and the image carrier rotates in reverse every predetermined period. Do The image forming apparatus is characterized in that the residual toner temporarily collected in step 1 is moved onto the intermediate transfer member. In this aspect, the toner reversely transferred onto the image carrier is temporarily collected by a cleaning member on the belly. In addition, a space-saving and low-cost cleaner mechanism can be realized by dropping it onto the middle roller by reverse rotation, and by dropping it onto the intermediate transfer member, the toner that is reversely transferred from the toner to be transferred from the image carrier can be obtained. Mixing can be prevented.

  In this aspect, the image carrier can be prevented from being disturbed by setting the timing of the reverse rotation of the image carrier as the non-image portion and dropping the primary collected residual toner onto the non-image portion on the intermediate transfer member. . Further, the predetermined period described above is a process control execution interval, and by performing reverse rotation control before and after the process control, the primary collected residual toner can be periodically dropped on the non-image portion. The predetermined period may be determined according to the cumulative number of rotations of the image carrier, or determined according to the cumulative number of rotations of the intermediate transfer member. Further, when the image carrier rotates in the reverse direction, a predetermined bias voltage is controlled, and the bias applied to the cleaning member is controlled to make it easy for residual toner collected primarily during the reverse rotation to fall on the intermediate transfer member. You can also.

  In the claims and the description of the present application, process control refers to control for adjusting various characteristic values that affect image quality such as alignment adjustment, toner density adjustment, gamma correction, and fixing temperature control. Say.

The figure which shows the whole image forming apparatus which is an example of the implementation object of invention Conceptual sectional view showing the main part of the second embodiment of the present invention A conceptual sectional view showing an important section of a 3rd example of the present invention. A conceptual sectional view showing an important section of a 4th example of the present invention. A conceptual sectional view showing an important section of a 5th example of the present invention. Conceptual sectional view showing the main part of a sixth embodiment of the present invention

Explanation of symbols

1: Photosensitive drum 2: Charger 3: Exposure means 4: Development means 5: Primary transfer roller 10: Process unit 15: Intermediate transfer belt 16: Metal cleaning counter roller 17: Toner mark sensor (TM sensor)
20: Tension roller 21: Driving / secondary transfer counter roller 22: Transfer material 23: Paper feed roller 24: Registration roller pair 25: Secondary transfer roller 26: Fixing means 31: Cleaning blade 32: Intermediate transfer belt cleaning unit 33 : Waste toner storage unit for intermediate transfer member 201a to 201d: Photoconductors 202a to 202d, A: Sheet member 203: Intermediate transfer belt 211a to 211d: Primary transfer roller 301: Photoconductor 302: Sheet member 321: Contact / separation mechanism 401a ˜401d: photoconductors 402b, 402c: sheet member 403: intermediate transfer belt 411a-411d: primary transfer roller 500: process cartridge 501: photoconductor 502: sheet member 503: intermediate transfer belt 601: photoconductor 602: sheet member 603 : Intermediate transfer bell 604: AC power 631: residual toner

Claims (12)

An image carrier and toner image forming means for forming a toner image having a predetermined polarity on the image carrier;
An intermediate transfer member provided opposite to the image carrier;
Primary transfer means for transferring a toner image of the image carrier onto the intermediate transfer member;
Secondary transfer means for transferring the toner image on the intermediate transfer member to a recording medium;
In an image forming apparatus comprising:
Bias applying means for applying a bias voltage having the same polarity as the predetermined polarity to a contact member that contacts the image carrier;
Delivery means for delivering residual toner remaining on the image carrier after the primary transfer to the intermediate transfer body by the contact member to which a bias voltage having the same polarity as the predetermined polarity is applied by the bias application means. ,
A plurality of pairs of the image carrier and the toner image forming means;
The toner image forming means forms toner images of different colors on the corresponding image carrier,
The intermediate transfer member moves in a predetermined direction;
A plurality of the primary transfer means are provided to face the plurality of image carriers through the intermediate transfer member, and sequentially transfer toner images of different colors on the intermediate transfer member,
The secondary transfer means collectively transfers the color toner images formed on the intermediate transfer member to a recording medium,
Residual toner transferred from the image carrier to the intermediate transfer member by the transfer unit is located at the most downstream side in the moving direction of the intermediate transfer member, and forms a black toner image. to recover,
An image forming apparatus.   The image forming apparatus according to claim 1, wherein the bias voltage value is −300 V to −700 V.   3. The image forming apparatus according to claim 1, wherein the bias voltage is applied before the residual toner reaches a position where the abutting member abuts on the image carrier. .   4. The image forming apparatus according to claim 1, wherein the contact member is a sheet-like member, and the material thereof is 6 nylon, 12 nylon, vinylon, saran, rayon, polyethylene, acrylic, fluorine. An image forming apparatus characterized by being one of a series (PVDF, PFA, PTFE) resin.   5. The image forming apparatus according to claim 1, wherein the image carrier is rotatable in a predetermined direction, and the contact member is in contact with the rotation direction of the image carrier in a counter direction. An image forming apparatus. The image forming apparatus according to claim 1.
The image carrier is rotatable in both forward and reverse directions, the contact member of the transfer means temporarily holds the residual toner, and the image carrier is in a direction opposite to the rotational direction at the time of primary transfer. During a predetermined period of rotation, the bias applying means applies a bias voltage having the same polarity as the predetermined polarity to the contact member, and passes the residual toner held on the contact member to the intermediate transfer member. An image forming apparatus . The image forming apparatus according to claim 6 .
The timing to reversely rotate the image carrier,
An image forming apparatus characterized in that in correspondence with the non-image area no toner image before Kizo carrier. 8. The image forming apparatus according to claim 6 , wherein the predetermined period is a process control execution interval . The image forming apparatus according to claim 6 or 7, the predetermined time period, the image forming apparatus according to claim Rukoto determined according to the accumulated number of rotations of said image bearing member. The image forming apparatus according to claim 6 or 7, the predetermined time period, the image forming apparatus characterized by determined according to the accumulated number of rotations of the intermediate transfer body. The image forming apparatus according to claim 6 , wherein the contact member is a sheet-like member, and the image carrier and a rotation direction of the image carrier at the time of the primary transfer. an image forming apparatus comprising that you contact in the forward direction. The image forming apparatus according to claim 6 1 0, wherein a member of the contact member is a sheet-like, smooth or substantially smoothly curved, and the image bearing member, said image bearing member An image forming apparatus, wherein a middle portion or a substantially middle portion of the curved portion is in contact with a rotation direction at the time of primary transfer.