JP5171202B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus capable of replenishing unused toner by attaching a toner replenishing unit to the image forming apparatus, and more particularly to control for adjusting a transfer voltage according to a stock leaving period of unused toner.

  2. Description of the Related Art A process cartridge type image forming apparatus that replaces a new process cartridge in which an image carrier, a developing device, a cleaning device, and the like are integrated and supplies toner to the image forming apparatus has been put into practical use. In addition, a toner cartridge type image forming apparatus that replaces a new toner cartridge or toner bottle that is detachable from the developing device and supplies toner to the image forming apparatus has been put into practical use.

  An image forming apparatus in which a storage device (for example, a wireless IC tag) capable of data writing / reading wirelessly is attached to these toner replenishing means and image forming conditions are adjusted according to read data has been put into practical use.

  Patent Document 1 discloses an image forming apparatus in which a memory element is attached to a process cartridge in which an image carrier, a developing device, a cleaning device, and the like are integrated. In the memory element, data of the manufacturing date and quality assurance date of the process cartridge are recorded. The image forming apparatus displays the number of days remaining until the quality assurance deadline based on the manufacturing date and quality assurance days read from the memory element.

  Japanese Patent Application Laid-Open No. 2004-228688 shows that after the start of use of the process cartridge, the charging performance of the toner in the process cartridge is lowered, and before the toner is completely consumed, it may not be able to withstand actual use. Here, a wireless IC tag is attached to the process cartridge, and the history information of the toner quality deterioration for each image formation is written, and the history information is read from the wireless IC tag every time it is activated, and the remaining life and replacement time are displayed. doing.

  Japanese Patent Application Laid-Open No. H10-228561 shows that if the inventory leaving period from the time of shipment from the factory to the actual charging of the developing device is long, the charging performance of the toner gradually decreases and the density of the toner image is excessive. Here, a one-drum type full-color image forming apparatus including a rotary developing device is shown, and toner is replenished by replacing an old toner bottle connected to the developer supply device with a new toner bottle. When a new toner bottle is connected and the date of manufacture is input, the toner image formation conditions (charging voltage and developing voltage) are automatically set according to the standing time.

JP-A-5-323716 JP 2005-178058 A JP 2006-251384 A

  For process cartridges, toner cartridges, and toner bottles, it has been found that image defects due to transfer defects are likely to occur if the inventory storage period from factory shipment to actual installation in the developing device is long.

  It has been found that the use of toners with different stock storage periods from the time of shipment from the factory until they are actually filled in the developing device causes the transfer efficiency of the toner images of each color to vary and the color balance of the output image to be easily lost.

  An object of the present invention is to provide an image forming apparatus in which an image defect due to a transfer defect is less likely to occur even when a toner replenishing unit has a long circulation period. It is another object of the present invention to provide an image forming apparatus in which image defects due to differences in transfer efficiency of toner images of each color are less likely to occur when toners of various colors whose distribution periods are long and short are used.

The image forming apparatus according to the present invention uses the first image carrier disposed along the intermediate transfer member and the toner supplied from the first toner replenishing unit provided with the first recording medium. A first toner image forming means for forming a toner image on one image carrier, and a first transfer part for forming a toner image by pressing the intermediate transfer member against the first image carrier. A transfer member; and a first power supply unit that applies a voltage to the first transfer unit and transfers a toner image from the first image carrier to the intermediate transfer member that passes through the first transfer unit. And a second image replenishing means provided with a second image carrier disposed downstream of the first image carrier in the rotation direction of the intermediate transfer member and a second recording medium. Second toner image forming means for forming a toner image on the second image carrier using toner; The intermediate transfer member is pressed against the second image bearing member to form a second transfer member for forming a second transfer portion of the toner image, and a voltage is applied to the second transfer portion to apply the second transfer member. A second power supply means for transferring the toner image from the second image carrier to the intermediate transfer member that passes through the transfer portion; and reading the first manufacturing time data from the first recording medium; Input means for reading the second manufacturing time data from the second recording medium, and setting the output voltage of the second power supply means based on the read first manufacturing time data and the second manufacturing time data. Setting means, and based on the read first production time data, the setting means sets the output voltage of the second power supply means as the toner production time of the first toner replenishing means is older. It is characterized by being set low .

  In the image forming apparatus of the present invention, the charging performance of the toner supplied from the toner replenishing means is indirectly detected based on the production time read from the recording medium. Then, it is assumed that the charging performance of the toner is lower as the manufacturing time is older, and the voltage output to the transfer unit is set lower.

  As a result, an appropriate transfer current can be ensured even for a toner whose charging performance is deteriorated due to a long stock leaving period. While preventing a decrease in transfer efficiency due to a shortage of transfer current, at the same time, a decrease in transfer efficiency caused by an increase in toner retransfer from the conveyance body to the image carrier due to an excess of the transfer current is also prevented.

  Therefore, even if the circulation period of the toner replenishing means is long, image defects due to transfer defects are unlikely to occur. In addition, when each color toner having a long and short distribution period is used, an image defect due to a transfer efficiency difference of each color toner image hardly occurs.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, as long as the charging performance of the toner taken out from the toner replenishing means is estimated and the transfer voltage is adjusted as a result, a part or all of the configuration of each embodiment is replaced with the alternative configuration. Other embodiments can also be implemented.

  Therefore, the present invention is not limited to an image forming apparatus that uses a recording material conveyance belt, but can also be implemented by an intermediate transfer type image forming apparatus that transfers a toner image carried on an intermediate transfer belt to a recording material by a secondary transfer unit. Not only a tandem type image forming apparatus in which a plurality of photosensitive drums are arranged along the belt member, but also a single drum type image forming apparatus in which one photosensitive drum is arranged.

  In the present embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, a composite machine, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a machine.

  In addition, about the general matter regarding the image forming apparatus and wireless IC tag shown by patent documents 1-3, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted. In the description, the reference symbols in parentheses attached to the configuration names used in the claims are examples for assisting understanding of the invention, and the configuration is limited to the corresponding members in the embodiments. Is not.

<First Embodiment>
1 is an explanatory diagram of the configuration of the image forming apparatus according to the first embodiment, FIG. 2 is an explanatory diagram of the configuration of the image forming unit, and FIG. 3 is an explanatory diagram of the configuration of the developing device.

  As shown in FIG. 1, the image forming apparatus 100 according to the first embodiment employs a tandem direct transfer system in which a plurality of four image forming portions Pa, Pb, Pc, and Pd are arranged in a straight section of a recording material conveyance belt 21. An image forming apparatus.

  In the image forming portion Pa which is an example of the first toner image forming means, a yellow toner image is formed on the photosensitive drum 3 a and transferred to the recording material P carried on the recording material conveyance belt 21. In the image forming unit Pb, which is an example of the second toner image forming unit, a magenta toner image is formed on the photosensitive drum 3b and transferred onto the yellow toner image of the recording material P. In the image forming portions Pc and Pd as an example of the third toner image forming unit, a cyan toner image and a black toner image are formed on the photosensitive drums 3c and 3d, respectively, and are sequentially transferred to the recording material P in the same manner. .

  The recording material P onto which the four color toner images are sequentially transferred is separated from the recording material transport belt 21 and fed to the fixing device 9, where the toner image is fixed on the surface by being heated and pressurized. It is loaded on the discharge tray 20.

  The separation device 11 separates the recording material P drawn from the paper feed cassette 10 one by one and sends it out toward the registration roller 13.

  The registration roller 13 receives and waits for the recording material P in a stopped state, and delivers the recording material P to the recording material conveyance belt 21 in synchronization with the toner image carried on the photosensitive drum 3a.

In this embodiment, image formation is performed in an environment of a temperature of 23 ° C. and an absolute water content of 10.6 g / m ³ .

<Conveyor>
The recording material transport belt 21 is supported around the driven roller 15, the driving roller 14, the tension roller 16, and the transfer rollers 5a, 5b, 5c, and 5d, and is driven by the driving roller 14 to rotate in the direction of the arrow R2. .

As the recording material transport belt 21, an endless shape or a seamless belt (seamless) is used. The volume resistivity of the recording material transport belt 21 is adjusted to 1 × 10 ⁹ Ω · cm (using a probe conforming to JIS-K6911 method, applied voltage 100 V, applied time 60 sec, 23 degrees C50% RH).

  The recording material P is charged along with the transfer of the yellow toner image in the first image forming portion Pa, and is electrostatically attracted to the recording material conveyance belt 21. After the transfer of the black toner image in the final image forming unit Pd, the recording material P is decoupled from the recording material conveyance belt 21 by removing electricity by the separation charger 23 and attenuating the electrostatic adsorption force.

<Image carrier, toner image forming means>
The image forming portions Pa, Pb, Pc, and Pd are substantially the same except that the color of toner used in the attached developing devices 1a, 1b, 1c, and 1d is different from yellow, magenta, cyan, and black. Hereinafter, the image forming unit Pa will be described, and the other image forming units Pb, Pc, and Pd will be described by replacing “a” at the end of the reference numerals with “b”, “c”, and “d”.

  As shown in FIG. 2, the image forming unit Pa includes a charging device 2a, an exposure device 6a, a developing device 1a, a transfer roller 5a, and a cleaning device 4a around the photosensitive drum 3a.

  The photosensitive drum 3a is configured by applying an organic photoconductor (OPC) having a negative charging property to an outer peripheral surface of an aluminum cylinder having an outer diameter of 30 mm, and a process speed of 130 mm / sec centering on a central support shaft. To rotate in the direction of arrow R1.

  The charging device 2a is driven to rotate by pressing a charging roller against the photosensitive drum 3a. The power source D3 applies a voltage obtained by superimposing a DC voltage and an AC voltage to the charging roller, and charges the surface of the photosensitive drum 3a to a uniform negative potential VD (−500 V) having a negative polarity.

  The exposure device 6a scans the scanning line image data obtained by developing the yellow separated color image with a rotating mirror, and writes an electrostatic image of the image on the surface of the charged photosensitive drum 3a. The potential of the exposed portion becomes the bright portion potential VL (−200 to −500 V).

  The developing device 1a agitates a two-component developer in which a magnetic carrier is mixed with toner to charge the toner negatively. The charged toner is carried on the developing sleeve 101 rotating around the magnet 102 in a spiked state and rubs against the photosensitive drum 3a.

  The power source D4 applies a voltage obtained by superimposing an AC voltage on a negative DC voltage Vdev (−350 V) to the developing sleeve 101. As a result, the toner moves to the electrostatic image on the photosensitive drum 3a having a positive polarity relative to the developing sleeve 101, and the electrostatic image is reversely developed.

  As shown in FIG. 3, the developing device 1a (1b, 1c, 1d) includes a two-component developer in which yellow (magenta, cyan, black) nonmagnetic toner and a magnetic carrier are mixed at a predetermined mixing ratio. 106 is filled with a predetermined amount.

  The developing device 1a is roughly divided into a developing container 104 that stores toner, and a developing sleeve 101 that carries and transports the stored toner to the surface of the photosensitive drum 3a. In the developing container 104, a two-component developer 106 is contained, and an agent agitating screw 105 for agitating and charging the toner and the magnetic carrier by friction is provided.

The magnetic carrier has a resistance of about 10 ¹³ Ω · cm and a volume average particle size of about 40 μm. The volume average particle diameter was measured by dividing the range of 0.5 to 350 μm into 32 logarithms using a laser diffraction particle size distribution analyzer HEROS (manufactured by JEOL Ltd.), and was defined as a 50% median diameter.

  The toner was made into a powder having a volume average particle size of about 9 μm by dispersing a colorant, a charge control agent and the like in a resin mainly composed of polyester and pulverizing and classifying. The toner is triboelectrically charged to a negative polarity by sliding with the magnetic carrier in the developing container 104.

The charge amount of the toner immediately after production is about −25 μC / g in an environment of a temperature of 23 ° C. and an absolute water content of 10.6 g / m ³ (hereinafter, unless otherwise noted, the toner is immediately after production. ).

  The developing sleeve 101 carries the two-component developer 106 adjusted to a uniform layer thickness by the regulating member 103 and is conveyed to a portion (developing nip) facing the photosensitive drum (3a: FIG. 2).

  The toner conveyed to the developing nip by the developing sleeve 101 receives an electric force due to the potential difference between the electrostatic latent image potential of the photosensitive drum 3a and the developing sleeve 101, and flies from the developing sleeve 101 toward the photosensitive drum 3a. The flying toner reciprocates between the developing sleeve 101 and the photosensitive drum 3a by an AC voltage applied to the developing sleeve 101. While having such reciprocating motion, the toner having negative charge moves according to the potential difference between the DC voltage Vdev applied to the developing sleeve 101 and the electrostatic image. In the dark portion potential VD region, the toner returns onto the developing sleeve 101, and in the bright portion potential VL region, an amount of toner corresponding to the potential adheres to the photosensitive drum (3a: FIG. 2).

<Transfer means>
As shown in FIG. 2, the transfer roller 5a is brought into pressure contact with the photosensitive drum 3a with a predetermined pressing force at the transfer portion Ta of the image forming portion Pa. The transfer roller 5a faces the photosensitive drum 3a via the recording material conveyance belt 21, and forms a transfer portion Ta for the recording material P between the recording material conveyance belt 21 and the photosensitive drum 3a.

The transfer roller 5a is formed of an elastic material such as a rubber mixed with a cored bar and an ion conductive material such as sodium perchlorate, a polymer elastomer material such as urethane, or a polymer foam material, and has a volume resistance of 1 ×. 10 ⁶ Ω · cm.

  The power source Da applies a positive direct current voltage to the roller shaft of the primary transfer roller 5a, and moves the toner image carried on the photosensitive drum 3a charged negatively to the recording material P passing through the transfer portion Ta. Let

  The cleaning device 4a rubs the cleaning blade against the photosensitive drum 3a, and removes the transfer residual toner remaining on the surface of the photosensitive drum 3a after passing through the transfer portion Ta.

  The belt cleaning device 22 rubs the cleaning blade against the intermediate transfer belt 21 to remove the toner adhering to the recording material conveyance belt 21.

<Toner supply means>
A toner cartridge 11a, which is an example of a first toner supply unit, is connected to the developing device 1a. The toner cartridge 11a is formed in a rectangular parallelepiped appearance with a length substantially equal to the length of the developing device 1a. The toner cartridge 11a is detached from the developing device 1a by sliding to the near side along the developing device 1a, and is attached to the developing device 1a by sliding to the back side.

  On the bottom surface of the toner cartridge 11a and the ceiling surface of the developing device 1a, an opening having a shutter (not shown) that slides and opens as the toner cartridge 11a and the developing device 1a move relative to each other is formed. In a state where the toner cartridge 11a is mounted on the developing device 1a, both shutters are opened and the mutual openings are in communication. However, when the toner cartridge 11a is pulled out, both the shutters are closed to prevent toner scattering.

  The supply screw Na disposed on the opening prevents the toner from dropping to the developing device 1a through the opening in the stopped state. Along with the rotation of the supply screw Na, unused toner in the toner cartridge 11a is cut out in an amount corresponding to the number of rotations and falls into the developing device 1a from the opening.

  On the back side of the toner cartridge 11a, a wireless IC tag 30a, which is a storage device capable of reading / writing data without power supply, is attached. The wireless IC tag 30a stores fixed information such as a manufacturer name, a product number, a corresponding image forming apparatus model, and a manufacturing date.

< Setting means>
FIG. 4 is a block diagram of a control system of the image forming apparatus, FIG. 5 is a flowchart of control of a transfer voltage, and FIG. 6 is a flowchart of work related to use of a wireless IC tag.

  As shown in FIG. 4, the communication unit 40 wirelessly communicates with the wireless IC tags 30a, 30b, 30c, and 30d and inputs data such as the date of manufacture of the toner. In addition, after the start of use of the toner cartridges 11a, 11b, 11c, and 11d, the communication unit 40 displays the estimated supply amount of each color toner and the estimated remaining amount of each color toner recorded in the wireless IC tags 30a, 30b, 30c, and 30d as needed. Update.

  The control unit 41 includes hardware having a calculation function and software defining the calculation operation, and controls the image forming units Pa, Pb, Pc, and Pd to execute toner image formation / transfer. The control unit 41 controls the power sources Da, Db, Dc, and Dd to perform transfer voltage control, and processes information from the communication unit 40, the time management unit 42, and the storage unit 43.

  The time management unit 42 has a calendar function and outputs the current date and time.

  The storage unit 43 is configured by a semiconductor memory, a hard disk, or the like, and stores various data and programs such as an environment table of target transfer current values in transfer voltage control.

As shown in FIG. 5 with reference to FIG. 4, when the image forming apparatus 100 is turned on, the control unit 41 determines whether or not the door that always opens and closes when the toner cartridge 11 a is replaced. Is discriminated (S10).

  When the door is closed and operation is possible (YES in S10), the control unit 41 reads the manufacturing date recorded in the wireless IC tags 30a, 30b, 30c, and 30d (S11).

  The control unit 41 sets a target transfer current according to the read manufacturing date (S12). In other words, the control unit 41 uses the date of manufacture of the toner cartridge 11a acquired through the communication unit 40 and the current date stored in the time management unit 42, and the date of manufacture of the toner. Calculate the number of days elapsed from. Then, the control unit 41 refers to the data table of the storage unit 43 by the number of days elapsed, determines a target transfer current offset value, and stores the target transfer current offset value in the storage unit 43.

  The control unit 41 executes transfer voltage control (ATCV: Auto Transfer Voltage Control) using the set target transfer current (S13). Prior to image formation, transfer voltage control is performed independently for each color in order at the image forming portions Pa, Pb, Pc, and Pd.

  The reason why the transfer voltage control is performed is that the volume resistance of the material constituting the transfer roller 5a (5b, 5c, 5d) and the transfer belt 21 changes depending on the temperature change or usage history, and is necessary for securing the target transfer current. This is because the voltage value changes. In the first embodiment, since the resistance value of the transfer roller 5a (5b, 5c, 5d) is adjusted using an ion conductive material, the change in the voltage value is remarkable.

The transfer voltage control at idle state of the recording material conveying belt 21 and the photosensitive drum 3a, during image formation and is charged in the same manner as the photosensitive drum 3 a, an exposure without the transfer voltage of the plurality of levels from the power supply Da roller 5a To output. Then, each of the currents flowing through the transfer roller 5a to which a plurality of levels of voltages are applied is detected, and the target transfer voltage at which the target transfer current flows is calculated and stored in the recording unit 43 from the relationship between the plurality of levels of voltage and the detected current. .

  At this time, the control unit 41 adds a target transfer current offset value corresponding to the number of days elapsed to an ideal target transfer current designed on the assumption that image formation is performed using new toner immediately after manufacture. Use target transfer current.

  When the control unit 41 receives the job (YES in S14), it executes image formation using the target transfer voltage (constant voltage) set in the transfer voltage control (S15). The target transfer voltage set by the most recent transfer voltage control is read from the recording unit 43, the power source Da is controlled, and the target transfer voltage is output to the transfer roller 5a.

  When the job is finished (YES in S16), the control unit 41 turns off the power of the image forming apparatus (S17).

  The control unit 41 reads the date of manufacture of each color toner from the wireless IC tags 30a, 30b, 30c, and 30d attached to the toner cartridges 11a, 11b, 11c, and 11d through the communication unit 40.

  As shown in FIG. 6 with reference to FIG. 4, when the toner cartridge 11a is manufactured, the wireless IC tag 30a stores information related to the manufacturing date and other manufacturing lots (S21).

  Thereafter, the toner cartridge 11a is sealed and packed and shipped as a product (S22).

  When using the new toner cartridge 11a, the user of the image forming apparatus 100 or the maintenance manager unpacks the toner cartridge 11a and attaches it to the image forming apparatus 100 (S23).

  At this time, when the power of the image forming apparatus 100 is ON, it is confirmed that the door is closed as described above (S25), and the date of manufacture of the toner is transmitted from the wireless IC tag 30a through the communication unit 40. Read (S26).

  However, when the power of the image forming apparatus 100 is OFF, when the power is turned ON (S24), the date of toner manufacture is read from the wireless IC tag 30a through the communication unit 40 (S26).

  When the power is turned on, the date of manufacture of the toner is read from the wireless IC tag 30a through the communication unit 40 regardless of whether or not a new toner cartridge 11a has been installed immediately before (S26).

<Problems with retransfer toner>
In the image forming apparatus 100, a toner ratio in the developer in the developing device 1a is detected using a magnetic permeability sensor (not shown). When the toner ratio in the developer falls below a specified value, the toner cartridge 11a develops the toner. Toner is supplied to the device 1a. However, if the distribution period of the toner cartridge 11a is long and the toner is left for a long time, the charging performance of the toner decreases during this period (see FIG. 10), and even if the stirring operation is performed in the developing device 1a, It becomes difficult to obtain a sufficient charge amount for appropriate image formation. For this reason, when the replaced toner cartridge 11a happens to be an old one with a long circulation period, a sufficient amount of toner charge cannot be obtained when the replenishment of the toner having a lowered charging performance is started. Retransfer problems are likely to occur.

  However, the conventional techniques described in Patent Documents 1 and 2 can display the quality guarantee time limit and the remaining printable number of sheets by grasping the deterioration of the toner cartridge, but cannot solve the image defect due to the deterioration. .

  Further, in the conventional technique described in Patent Document 3, the density of the toner image carried on the image carrier is kept constant by adjusting the charging voltage and the development voltage when forming an image using toner having a reduced charge amount. It is described that keep it. However, since the transfer voltage and transfer current are not optimized with respect to the decrease in the charge amount of the toner image formed on the image carrier, the toner image formed on the image transfer medium and the recording material can be transferred with high transfer efficiency. Cannot be transferred to.

  From recent studies, it has been found that toner used or left for a long period of time has a significantly reduced charging performance (charged ability) of the toner due to changes over time as compared with new toner. When an image forming operation is performed on the assumption of a toner having a decreased charging performance and a toner with little change over time (a small decrease in charging performance), an excessive transfer current flows with respect to the charge amount of the toner. In this case, toner retransfer is likely to occur.

  In toner retransfer, a portion of toner transferred from the image carrier to the recording material or intermediate transfer member at the transfer portion is charged by discharge at the downstream side of the transfer portion to reverse the charge polarity and electrically This is a phenomenon that is pulled back to the carrier. In addition, a phenomenon in which a part of the toner carried on the recording material or the intermediate transfer member and passing through the transfer portion is charged by discharge on the upstream side of the transfer portion to reverse the charge polarity and electrically pulled back to the image carrier. But there is. Toner retransfer is likely to occur when a toner whose charging performance is reduced and the charging polarity is easily reversed is used. Even if a plurality of image carriers are arranged in tandem, toner retransfer is likely to occur.

  In this way, in the situation where toner retransfer occurs, the amount of toner formed on the recording material decreases, so the image density decreases, or the amount of toner that is not imaged increases, resulting in an increase in waste toner. To do. For this reason, in order to continue normal image formation using toner after many years, it is necessary to perform image formation control different from when toner with little deterioration with time is supplied.

Therefore, in the first embodiment, the transfer voltage (target transfer current) is set to reflect the deterioration with time of the charging performance of each color toner. In the setting means (41), the input means (40) reads the output voltage applied to the second and subsequent transfer members (5b, 5c, 5d) arranged in plurality from the upstream side in the rotation direction of the transport body (21). It is set between the lower limit voltage value and the upper limit voltage value based on the manufacturing time data.

  For example, the output voltage includes the lower limit voltage value based on the production time data read from the recording medium (30d) of the toner replenishing means (11d) of the toner transferred at the transfer portion (Td), and the upstream of the transfer portion (Td). Is set to the middle of the upper limit voltage value based on the production time data read from the recording medium (30a, 30b, 30c) of the toner replenishing means of the toner transferred on the side.

The setting means (41) sets the target transfer current value based on the manufacturing time data read by the input means (40). Prior to the formation of the toner image, a temporary output voltage is output from the power supply means (Da) to detect the current flowing through the transfer means (5a).

  Then, the constant voltage obtained based on the current detection result is set as the output voltage of the power supply means (Da) at the time of image formation.

  According to the image forming apparatus of the first embodiment, it is possible to set an appropriate target transfer current corresponding to the number of days elapsed even when using a toner having a large number of days elapsed from the time of manufacture and having reduced charging performance during stock storage. . The adverse effect of increasing the amount of residual toner and re-transfer toner and reducing the amount of toner imaged on the recording material, resulting in a lighter image density, and increasing the amount of toner that is not imaged, resulting in an increase in waste toner. Is prevented.

<Comparative Example 1>
7 is a diagram showing the relationship between the transfer current and the residual transfer toner concentration, FIG. 8 is a diagram showing the relationship between the transfer current and the retransfer toner concentration, and FIG. 9 is a graph showing the relationship between the transfer residual toner concentration and the retransfer toner concentration. It is explanatory drawing of the target transfer current considered. FIG. 10 is an explanatory diagram of the relationship between the number of days of toner elapsed and the charging performance of the toner.

  In Comparative Example 1, the toner remaining on the photosensitive drum 3b after passing through the transfer portion Tb will be described by paying attention to the image forming portion Pb.

  FIG. 7 shows a result of measuring the toner (transfer residual toner) remaining on the photosensitive drum 3b when the magenta toner image carried on the photosensitive drum 3b is transferred onto the recording material P by the transfer roller 5b, with different transfer currents. It is. Here, the horizontal axis represents the transfer current passed through the transfer roller 5b, and the vertical axis represents the residual toner density.

  As a method of measuring the transfer residual toner density, A3 size magenta single color is output at the maximum density, and the magenta toner remaining on the surface of the photosensitive drum 3b downstream of the transfer portion Tb is peeled off and collected, and the reflection density is measured. did. For the reflection density measurement, a reflection densitometer (X-Rite 500 series) manufactured by X-Rite was used (hereinafter, in this embodiment, the method for measuring the transfer residual toner density and the retransfer toner density is as follows. The same).

  As shown in FIG. 7, the transfer residual toner density decreases as the transfer current is increased. When the amount of transfer residual toner increases, the amount of magenta toner transferred to the recording material P decreases accordingly, the image density decreases, and the amount of waste toner collected by the cleaning device (4b: FIG. 1) increases. For this reason, when attention is paid only to the amount of residual toner, it is preferable that the transfer current flowing through the transfer roller 5b is large.

  FIG. 8 shows the retransfer toner density at which the yellow toner image transferred to the recording material P at the upstream image forming portion Pa is injected with the charge at the transfer portion Tb and retransferred to the photosensitive drum 3b. This is the result of measurement. Here, the horizontal axis represents the transfer current passed through the transfer roller 5b, and the vertical axis represents the retransfer toner density.

  As a method for measuring the retransfer toner amount, a yellow toner image in which a single yellow color was output at the maximum density in A3 size was carried on the recording material P by the image forming portion Pa and passed through the transfer portion Tb. Then, the yellow toner attached to the surface of the photosensitive drum 3b downstream of the transfer portion Tb was collected by peeling off the tape, and the reflection density was measured. The reflection density was measured in the same manner as the measurement of the transfer residual toner density described above.

  As shown in FIG. 8, the retransfer toner density increases as the transfer current increases. When the amount of retransfer toner increases, the amount of yellow toner remaining on the recording material P decreases accordingly, the image density decreases, and the amount of waste toner collected by the cleaning device (4b: FIG. 1) increases. For this reason, when attention is paid only to the retransfer toner amount, it is preferable that the transfer current flowing through the transfer roller 5b is small.

  From the characteristics of FIGS. 7 and 8, it is desirable that the target transfer current is set to a value that minimizes the total amount of residual transfer toner and retransfer toner. FIG. 9 is a diagram in which FIGS. 7 and 8 are superimposed, and shows the relationship between the magenta transfer residual toner density and the yellow retransfer toner density at the transfer portion Tb with respect to the transfer current.

  As shown in FIG. 9, in Comparative Example 1, it is assumed that the toner has just been manufactured, and 12 to 18 μA where both the transfer residual toner density and the retransfer toner density are 0.025 or less is an appropriate range of the transfer current value. It becomes. For this reason, 15 μA, which is the center value of 12 to 18 μA, is set as the design value.

  Actually, when the transfer voltage control (ATVC) is performed by using the toner immediately after manufacture and the target transfer current is 15 μA, stable image formation is possible without decreasing the image density and increasing the waste toner. Become.

  However, when the same image formation is performed using toner that has passed many years from the date of manufacture, the amount of residual transfer toner and retransfer toner with respect to the transfer current is smaller than when using toner immediately after manufacture. It turns out to change.

  This is because the toner left in the toner cartridges 11a and 11b in the unused state causes a change with time, and the charging performance (charged ability) is lowered.

  As shown in FIG. 10, the toner charge amount decreases according to the number of days that have been left in the toner cartridges 11a and 11b in an unused state. Here, the number of days elapsed is the number of days since the manufacture of the toner, and the charge amount of the toner is a measurement result of the charge amount of the toner frictionally charged by rubbing with the magnetic carrier in the developing device 1b.

  The toner charge amount after 3,000 days has been reduced to about half of the toner charge amount of 0 days (immediately after production). Specifically, the toner charge amount, which was about −25 μC / g immediately after manufacture, was about −10 μC / g after 3000 days.

  Although the specific mechanism by which the toner charge amount decreases with the number of days elapsed is not well understood, the cause may be a deterioration in charging performance due to oxidation of the external additive mixed with the toner or the toner itself. Also, the oil component inside the toner may deposit on the toner surface, burying the external additive with the oil component, or the toner may easily adhere to the magnetic carrier surface, making it impossible to create a normal friction state. It is done.

<Comparative example 2>
FIG. 11 is a diagram of the relationship between the transfer current and the residual transfer toner concentration for toners having different ages. FIG. 12 is a diagram of the relationship between the transfer current and the retransfer toner concentration for toners having different ages. FIG. 13 is an explanatory diagram of the target transfer current for the toner with 1500 days elapsed.

  In Comparative Example 2, the relationship between the transfer residual toner concentration and the retransfer toner concentration with respect to the transfer current in the transfer portion Tb is compared for the toner (new toner) with approximately 0 days elapsed, the toner for 1500 days, and the toner for 3000 days. did.

  In the experiment, the toners used in the image forming portions Pa, Pb, Pc, and Pd are arranged with the same number of days elapsed, and the transfer residual toner density and the retransfer toner density on the surface of the photosensitive drum 3b are measured as in Comparative Example 1. doing. In the output image, the transfer residual toner density is an A3 size magenta single color output at the maximum density, and the retransfer toner density is an A3 size yellow single color output at the maximum density.

  As shown in FIG. 11, it can be seen that the amount of residual toner for the same transfer current decreases as the elapsed time of the toner advances to 0 days, 1500 days, and 3000 days.

  As shown in FIG. 12, it can be seen that the amount of retransfer toner for the same transfer current increases as the elapsed time of the toner advances to 0 days, 1500 days, and 3000 days.

  FIG. 13 is a diagram obtained by superimposing the time-lapsed 1500 days diagrams of FIG. 11 and FIG. 12, and shows the magenta transfer residual toner density and the yellow retransfer toner density in the transfer portion Tb.

  As shown in FIG. 13, the transfer current range in which the magenta transfer residual toner density and the yellow retransfer toner density are less than or equal to the reflection density of 0.025 when the toner with the elapsed time of 1500 days is used is 12 in Comparative Example 1. It becomes 10-16 μA which is different from ˜18 μA. An appropriate transfer current range of 10 to 16 μA in Comparative Example 2 includes 15 μA of Comparative Example 1 assuming a new toner, but the center value is not 15 μA.

  Under the conditions of Comparative Example 2, when image formation was performed with the transfer voltage control (ATVC) target transfer current set to 15 μA of Comparative Example 1, yellow retransfer toner increased slightly. Similarly, in the image forming portions Pc and Pd, the retransfer toner of the toner image transferred on the upstream side slightly increased.

  Further, when the fixed output image was observed, no image defect due to the transfer defect occurred, but the image density was slightly reduced and output, and the color tone slightly changed.

  Accordingly, when a target transfer current of 15 μA having a design value assuming a new toner is used in image formation using toner having an age of 1500 days, the image quality deteriorates.

<Comparative Example 3>
FIG. 14 is an explanatory diagram of the target transfer current in the toner having a time elapsed of 3000 days.

  FIG. 14 is a diagram obtained by superimposing the time-lapse days of 3000 in FIGS. 11 and 12 and shows the magenta transfer residual toner density and the yellow retransfer toner density in the transfer portion Tb.

  As shown in FIG. 14, when using a toner with a lapse of 3000 days, the transfer current range in which the magenta transfer residual toner density and the yellow retransfer toner density are less than or equal to the reflection density of 0.025 is 12 in Comparative Example 1. It becomes 8-14 μA which is different from ˜18 μA. The appropriate transfer current range of 8 to 14 μA in Comparative Example 3 does not include 15 μA of Comparative Example 1 assuming a new toner.

  When image formation was performed with the target transfer current of transfer voltage control (ATVC) set to 15 μA of Comparative Example 1 under the conditions of Comparative Example 3, the yellow retransfer toner increased compared to Comparative Example 2 using 1500 days of elapsed time. . Similarly, also in the image forming portions Pc and Pd, the retransfer toner of the toner image transferred on the upstream side increased from that in Comparative Example 2 in which the toner was used for 1500 days.

  Further, when the fixed output image was observed, the image density was remarkably thin, and image defects in which the color tone of the color changed due to transfer defects occurred in many places.

  Therefore, when a target transfer current of 15 μA having a design value assuming a new toner is used for image formation using an old toner having an elapsed time of 3000 days, an image defect occurs.

<Example 1>
FIG. 15 is an explanatory diagram of a aging coefficient in the first embodiment, FIG. 16 is an explanatory diagram of a target transfer current set by the control of the first embodiment, and FIG. 17 is an explanatory diagram of a result of experimenting on the control of the first embodiment.

  As shown in FIG. 4, in Example 1, the target transfer current 15 μA having a design value assuming a new toner is not uniformly applied, and the number of days of toner aging is determined for each of the image forming portions Pa, Pb, Pc, and Pd. The target transfer current is set.

  Here, assuming that the number of days of aging of the toner immediately after production is t days, the aging coefficient k is defined as follows:

k (t) = 1/3000 × t (0 ≦ t <3000)
k (t) = 1 (t ≧ 3000)

  As shown in FIG. 15, the aging coefficient k is k = 0 in the case of a new toner, and changes to a maximum k = 1 as the number of days elapsed. The horizontal axis in FIG. 15 is the elapsed time t, and the vertical axis is the time coefficient k.

  The reason for this definition is that the charge amount of each color toner used in the image forming apparatus 100 of the first embodiment gradually decreased from 0 days to about 3000 days. However, after about 3000 days, the charge amount decreased. Because it was almost stable. The aging coefficient k is preferably set according to the characteristics of the toner, the sealed state of the toner cartridge, various conditions of the image forming apparatus, and the like, and is confirmed by experiments.

  The target transfer current Itr (t) when the elapsed time of the toner is t days is calculated by the following equation (1).

Itr (t) = Itr (0) + k (t) × α (1)
Itr (0) = 15 μA: target transfer current assuming a new toner in Example 1
α = −4 μA: target transfer current offset value in Example 1

  In the first exemplary embodiment, the target transfer current offset value α is common to all image forming units, but can be set for each image forming unit.

  By substituting the aging coefficient k (t) determined according to the number of days elapsed from the data table of FIG. 15 into the equation (1), the target transfer current corresponding to the number of days of toner aging is set as shown in FIG.

  As shown in FIG. 16, the target transfer current when t = 1500 days is 13 μA, and the target transfer current when t = 3000 days or more is 11 μA.

  As shown in FIG. 9, if the number of days of toner elapsed is 0 days, the proper transfer current range is 12 to 18 μA, and the center value is 15 μA.

  As shown in FIG. 13, when the elapsed time of the toner is 1500 days, the proper transfer current range is 10 to 16 μA, and the center value is 13 μA.

  As shown in FIG. 14, if the number of days of toner elapsed is 3000 days, the proper transfer current range is 8 to 14 μA, and the center value is 11 μA.

  The three circles plotted in FIG. 16 are these central values corresponding to the days elapsed time of 0 days, 1500 days, and 3000 days.

  The plotted center value is in good agreement with the target transfer current based on the control of the first embodiment, and by performing the control of the first embodiment, the target transfer current is appropriately set according to the number of days of the toner. I understand that I can do it.

  FIG. 17 shows the transitions of the residual transfer toner and the retransfer toner amount with respect to the number of days of toner aging when the target transfer current is set by the control of the first embodiment.

  As shown in FIG. 17, the reflected toner density does not exceed 0.025 for the remaining transfer toner and the retransfer toner with respect to the toner of 0 to 3500 days, and the transfer voltage is set using an appropriate target transfer current. It was confirmed that control (ATVC) was performed.

  According to the control of the first embodiment, an appropriate target transfer current corresponding to the number of elapsed days can be set even when toner having a large number of elapsed days is used. As a result, it is possible to output a high-quality image with high density and high color tone reproducibility while keeping the residual transfer toner and re-transfer toner low. The transfer residual toner and the retransfer toner increase, and the amount of toner remaining on the recording material does not decrease to reduce the image density and increase the waste toner.

  Although the image forming unit Pb has been described here, the same control is performed in the image forming units Pc and Pd, and even when the toner cartridge 11b is replaced, the continuity of density and color tone is higher than before. High quality images can be output stably.

<Example 2>
FIG. 18 is an explanatory diagram of the time coefficient in the second embodiment. FIG. 19 is an explanatory diagram of the control when both the yellow toner and the magenta toner are new toners, and FIG. 20 is an explanatory diagram of the control when the elapsed time of the yellow toner is 3000 days and the magenta toner is a new toner. FIG. 21 is an explanatory diagram of the control when the yellow toner is a new toner and the elapsed time of the magenta toner is 3000 days. FIG. 22 is an explanatory diagram of the control when the elapsed time is 3000 days for both the yellow toner and the magenta toner.

  In the first embodiment, the control suitable for the case where the toner having the same number of days elapsed is used in the yellow image forming portion Pa and the magenta image forming portion Pb has been described.

  In the second embodiment, control suitable for a more general case in which toners having different aging days are used in the yellow image forming portion Pa and the magenta image forming portion Pb will be described.

  The target transfer current of the magenta image forming unit Pb is set in consideration of the age of the yellow toner filled in the toner cartridge 11a and the age of the magenta toner filled in the toner cartridge 11b.

  The target transfer current of the cyan image forming unit Pc is set in consideration of the age of yellow and magenta toners filled in the toner cartridges 11a and 11b and the age of cyan toner filled in the toner cartridge 11c.

  The target transfer current of the black image forming portion Pd takes into account the age of the yellow, magenta, and cyan toners filled in the toner cartridges 11a, 11b, and 11c and the age of the black toner filled in the toner cartridge 11d. Is set.

  In the second embodiment, similarly to the first embodiment, the target transfer current is set between the lower limit value of the transfer current at which the transfer residual toner becomes a specified value or less and the upper limit value of the transfer current at which the retransfer toner becomes a specified value or less. Set. Further, the lower limit value of the transfer current at which the transfer residual toner becomes a specified value or less is set based on the date of manufacture read from the wireless IC tag of the toner cartridge connected to the image forming unit.

  However, the upper limit value of the transfer current at which the retransfer toner becomes equal to or less than the specified value is set based on the date of manufacture read from the wireless IC tag of the toner cartridge connected to the upstream image forming unit. When there are a plurality of image forming units on the upstream side, the setting is made based on the date of manufacture read from the wireless IC tags of a plurality of toner cartridges connected to the plurality of image forming units.

  Here, assuming that the toner aging days immediately after the production are tx days, the aging coefficient k is expressed by the following equation for the yellow, magenta, cyan, and black toner aging days ta, tb, tc, and td days. Define as follows.

k (tx) = 1/3000 × tx (0 ≦ t <3000)
k (tx) = 1 (tx ≧ 3000)
x = a, b, c, d

  As shown in FIG. 18, the aging coefficient k is k = 0 in the case of a new toner, and changes to a maximum k = 1 as the number of days elapsed. In FIG. 15, the horizontal axis represents the number of days elapsed with time tx, and the vertical axis represents the aging coefficient k.

  In the second embodiment, the relationship of the aging coefficient with respect to the number of days elapsed is the same in all image forming units, but a different relationship may be set for each image forming unit. The time coefficient k is preferably set according to the characteristics of the toner, the sealed state of the toner cartridge, various conditions of the image forming apparatus, and the like.

  First, setting of the target transfer current in the image forming unit Pb will be described.

  When the age of yellow toner is ta and the time of magenta toner is tb, the target transfer current Itrb (ta, tb) of the image forming portion Pb is calculated by the following equation (2).

Itrb (ta, tb) = Itrb (0, 0) + [{k (ta) + k (tb)} / 2] × α ′ (2)
Itrb (0, 0) = 15 μA: target transfer current value of image forming portion Pb when new toner (yellow, magenta) is used
α ′ = − 4 μA: target transfer current offset value of the image forming portion Pb

  By substituting the aging coefficient k (tx) determined according to the number of days elapsed from the data table of FIG. 18 into Equation (2), a target transfer current corresponding to the number of days of toner aging is set.

  With reference to FIGS. 19 to 22, the case where the elapsed time ta of yellow toner and the elapsed time tb of magenta toner are the following combinations (1) to (4) will be described. 19 to 22 show the relationship between the magenta transfer residual toner density and the yellow retransfer toner density in the image forming unit Pb with respect to the transfer current.

(1) When ta = 0 and tb = 0 As shown in FIG. 19, the appropriate transfer current range in which both the magenta transfer residual toner density and the yellow retransfer toner density are 0.025 or less is 12 to 18 μA. Become.

  On the other hand, in the control of the second embodiment, “ta = tb = 0, k (ta) = k (tb) = 0” is substituted into the expression (2), and the target transfer current Itrb (ta, tb) is appropriate. It is set to 15 μA, which is the middle value of the range.

(2) When ta = 3000 and tb = 0 As shown in FIG. 20, the proper range of transfer current in which both the magenta transfer residual toner density and the yellow retransfer toner density are 0.025 or less is 12 to 14 μA. Become.

  On the other hand, in the control of the second embodiment, “ta = 3000, tb = 0, k (ta) = 1, k (tb) = 0” is substituted into the expression (2), and the target transfer current Itrb (ta, tb ) Is set to 13 μA, which is an intermediate value in the appropriate range.

(3) When ta = 0 and tb = 3000 As shown in FIG. 21, the appropriate transfer current range in which both the magenta transfer residual toner density and the yellow retransfer toner density are 0.025 or less is 8 to 18 μA. Become.

  On the other hand, in the control of the second embodiment, “ta = 0, tb = 3000, k (ta) = 0, k (tb) = 1” is substituted into the expression (2), and the target transfer current Itrb (ta, tb ) Is set to 13 μA, which is an intermediate value in the appropriate range.

(4) When ta = 3000 and tb = 3000 As shown in FIG. 22, the appropriate range of transfer current in which both the magenta transfer residual toner density and the yellow retransfer toner density are 0.025 or less is 8 to 14 μA. Become.

  On the other hand, in the control of the second embodiment, “ta = tb = 3000, k (ta) = k (tb) = 1” is substituted into the expression (2), and the target transfer current Itrb (ta, tb) is appropriate. It is set to 11 μA, which is the middle value of the range.

  Further, when the image formation was actually performed using the control of Example 2 for the combination of the toners (1) to (4), the density was high without causing image defects due to transfer defects. A high-quality image with stable color tone could be output.

  In addition, when the same examination was performed using toner cartridges having various production dates, a high-quality image was stabilized regardless of the combination of the elapsed time ta and tb of the yellow toner and the magenta toner. Could be output. Less transfer residual toner and retransfer toner were controlled, and no image defect due to transfer failure was observed.

  Next, setting of the target transfer current in the cyan image forming unit Pc will be described.

  When the elapsed time of yellow toner, magenta toner, and cyan toner is ta, tb, and tc days, the target transfer current Itrc (ta, tb, tc) of the image forming unit Pc is calculated by the following equation (3). .

Itrc (ta, tb, tc) = Itrc (0, 0, 0) + [{k (ta) + k (tb) + k (tc)} / 3] × α ″ (3)
Itrc (0, 0, 0) = 15 μA: target transfer current value of image forming portion Pc when new toner (yellow, magenta, cyan) is used
α ″ = − 4 μA: target transfer current offset value of the image forming portion Pc

  By substituting the aging coefficient k (tx) obtained according to the number of days elapsed from the data table of FIG. 18 into the equation (3), the target transfer current corresponding to the number of days of aging of the toner is set.

  Also in the image forming unit Pc, an appropriate target transfer current can be set by applying the control of the second embodiment regardless of the combination of the elapsed time ta, tb, and tc of yellow toner, magenta toner, and cyan toner. . This makes it possible to form a stable image without causing image defects due to residual transfer toner and retransfer toner.

  Finally, setting of the target transfer current in the image forming unit Pd will be described.

  When the elapsed time of yellow toner, magenta toner, cyan toner, and black toner is ta, tb, tc, and td days, the target transfer current Itrd (ta, tb, tc, td) of the image forming unit Pd is expressed by the following formula ( 4).

Itrc (ta, tb, tc, td) = Itrc (0, 0, 0, 0) + [{k (ta) + k (tb) + k (tc) + k (td)} / 4] × α ′ ″ · (4)
Itrc (0, 0, 0, 0) = 15 μA: target transfer current value of image forming unit Pd when new toner (yellow, magenta, cyan, black) is used
α ′ ″ = − 4 μA: target transfer current offset value of the image forming unit Pd

  A target transfer current corresponding to the elapsed time of the toner is set by substituting the elapsed time coefficient k (tx) obtained according to the elapsed time from the data table of FIG. 18 into the equation (4).

  Even in the image forming unit Pd, the control of the second embodiment is applied to achieve an appropriate target regardless of the combination of the elapsed time ta, tb, tc, and td of yellow toner, magenta toner, cyan toner, and black toner. Transfer current can be set. This makes it possible to form a stable image without causing image defects due to residual transfer toner and retransfer toner.

Second Embodiment
FIG. 23 is an explanatory diagram of a configuration of the developing device according to the second embodiment.

  As shown in FIG. 1, in the second embodiment, only the developing devices attached to the image forming portions Pa, Pb, Pc, Pd are replaced with the developing devices 1a (1b, 1c, 1d: not shown) shown in FIG. It is done. The developing device 1a has the same reference numerals as those in the first embodiment in order to refer to FIG. 1, but the internal structure and the toner used are different from those in the first embodiment.

  As shown in FIG. 4, also in the second embodiment, the constant voltage applied to the transfer rollers 5a, 5b, 5c, and 5d attached to the image forming portions Pa, Pb, Pc, and Pd is set by transfer voltage control (ATCV). To do. The target transfer current used in the transfer voltage control is set according to the number of days ta, tb, tc, and td of the yellow toner, the magenta toner, the cyan toner, and the black toner by the control in the first or second embodiment. .

  Therefore, in the following, the developing device 1a will be described, and a description overlapping that of the first embodiment will be omitted.

  As shown in FIG. 1, the developing devices 1a, 1b, 1c, and 1d are filled with predetermined amounts of yellow, magenta, cyan, and black magnetic toners (one-component developer), respectively.

  As shown in FIG. 23, the developing sleeve 101 of the developing device 1a is made of a non-magnetic metal element tube, rotates around a fixed magnet 102, and carries magnetic toner on the surface in a raised state.

  The regulating member 103 is in contact with the cylindrical surface of the developing sleeve 101. When the one-component developer 107 passes through this contact portion, the magnetic toner is frictionally charged to a negative polarity by friction between the developing sleeve 101 and the regulating member 103.

  Even with such a configuration, it has been found that the charge amount of the toner decreases depending on the number of days elapsed in the inventory period. For this reason, if image formation is performed without taking into account the temporal change of the magnetic toner, there is a possibility that an image defect due to the retransfer toner may occur.

  Actually, when the target transfer current value of the transfer voltage control (ATVC) is set to 15 μA which is assumed to form an image with a new toner, and an image is formed using a toner having a time elapsed of 3000 days, the retransfer toner is transferred to each image forming unit. Increased. For this reason, the image density is reduced, a defective image whose color changes is generated, and an increase in the amount of waste toner is also confirmed.

  Therefore, also in the image forming apparatus of the second embodiment, the target transfer current is set by performing the control in the above-described first and second embodiments. As a result, as in the first embodiment, regardless of the combination of the elapsed time ta, tb, tc, and td of the yellow toner, magenta toner, cyan toner, and black toner, the transfer residual toner and the retransfer toner are used. Image defects no longer occur. As a result, stable and high-quality image formation is possible.

<Third Embodiment>
The image forming apparatus 100 according to the first embodiment is a tandem direct transfer type image forming apparatus in which image forming portions Pa, Pb, Pc, and Pd of yellow, magenta, cyan, and black are arranged.

  However, the present invention can be carried out by an apparatus other than the direct transfer type image forming apparatus, as long as it is an image forming apparatus that supports a plurality of colors of toner on a conveyance body (recording material or intermediate transfer body).

  The image forming apparatus of the third embodiment is a tandem intermediate transfer type image forming apparatus in which a plurality of image forming units similar to those of the first embodiment are arranged in a linear section of a rotating intermediate transfer belt. Here, a plurality of image forming units sequentially transfer and superimpose toner images on a rotating intermediate transfer belt in sequence. Then, a plurality of color toner images carried on the intermediate transfer belt are collectively and secondary-transferred onto a recording material by a secondary transfer unit disposed downstream of the image forming unit disposed on the most downstream side.

  Even in such a tandem type intermediate transfer type image forming apparatus, the target transfer current described in the first or second embodiment can be set in the transfer voltage control in a plurality of image forming units.

  This reduces the occurrence of defective images due to toner retransfer even when toner is replenished after many years, and even if the toner after many years has been replenished, the user can obtain an image with normal density and color tone. Can be output.

<Fourth embodiment>
The image forming apparatus according to the fourth embodiment is a one-drum type image forming apparatus in which yellow, magenta, cyan, and black developing units are provided on one image carrier. Here, toner images of a plurality of colors are sequentially formed on one image carrier for each color, transferred one color at a time to a conveyance body (recording material or intermediate transfer body), and superimposed on the conveyance body.

  In such a one-drum type image forming apparatus, the date of manufacture of the toner cartridge is read from the wireless IC tag attached to the toner cartridges of a plurality of colors, and the target transfer of the transfer voltage control is performed according to the number of days of the toner. The current can be set.

<Fifth Embodiment>
The image forming apparatus according to the fifth embodiment is an image forming apparatus that replenishes a two-component developer in which toner and a carrier are mixed from a toner cartridge.

<Sixth Embodiment>
The image forming apparatus according to the sixth embodiment is a process cartridge type image forming apparatus in which a photosensitive drum, a charging device, a developing device, and a cleaning device are detachably attached to a main body of the image forming device as an integrated unit. The process cartridge is configured to replenish toner in the developing device.

<Seventh embodiment>
The image forming apparatus of the seventh embodiment performs constant current control on the voltages applied to the transfer rollers 5a, 5b, 5c, and 5d by the power sources Da, Db, Dc, and Dd shown in FIG. The control unit 41 sets the target transfer current in the constant current control according to the date of manufacture of the toner cartridges 11a, 11b, 11c, and 11d.

<Eighth Embodiment>
In the image forming apparatus according to the eighth embodiment, the power sources Da, Db, Dc, and Dd shown in FIG. 1 output a constant voltage without performing transfer voltage control. The control unit 41 sets the constant voltage lower as the date of manufacture of the toner cartridges 11a, 11b, 11c, and 11d is older.

It is explanatory drawing of a structure of the image forming apparatus of 1st Embodiment. It is explanatory drawing of a structure of an image formation part. It is explanatory drawing of a structure of a developing device. 2 is a block diagram of a control system of the image forming apparatus. FIG. It is a flowchart of control of a transfer voltage. It is a flowchart of the work | work regarding utilization of a wireless IC tag. FIG. 6 is a diagram illustrating a relationship between a transfer current and a transfer residual toner density. It is a diagram showing the relationship between the transfer current and the retransfer toner density. FIG. 7 is an explanatory diagram of a target transfer current in consideration of a transfer residual toner density and a retransfer toner density. FIG. 6 is an explanatory diagram of a relationship between the number of days of toner elapsed and the charging performance of toner. FIG. 6 is a diagram showing a relationship between a transfer current and a transfer residual toner density in toners with different days. It is a diagram of the relationship between the transfer current and the retransfer toner density in toners with different days. FIG. 6 is an explanatory diagram of a target transfer current for toner having a elapsed time of 1500 days. FIG. 6 is an explanatory diagram of a target transfer current for toner having a time elapsed of 3000 days. It is explanatory drawing of the time coefficient in Example 1. FIG. 6 is an explanatory diagram of a target transfer current set by the control of Embodiment 1. FIG. It is explanatory drawing of the result of having experimented control of Example 1. FIG. It is explanatory drawing of the time coefficient in Example 2. FIG. FIG. 6 is an explanatory diagram of control when both yellow toner and magenta toner are new toners. FIG. 10 is an explanatory diagram of control when the elapsed time of yellow toner is 3000 days and the magenta toner is a new toner. FIG. 10 is an explanatory diagram of control when yellow toner is new toner and magenta toner has 3000 days elapsed time. FIG. 10 is an explanatory diagram of control when the elapsed time is 3000 days for both yellow toner and magenta toner. It is explanatory drawing of the structure of the developing device in 2nd Embodiment.

Explanation of symbols

1a, 1b, 1c, 1d Developing devices 3a, 3b, 3c, 3d Image carrier (photosensitive drum)
5a, 5b, 5c, 5d Transfer means (transfer roller)
6a, 6b, 6c, 6d Exposure device 11a Toner replenishing means (toner cartridge)
21 Conveyor (Recording Material Conveyor Belt)
30a Recording medium (wireless IC tag)
40 Reading means (communication part)
41 setting means (control unit)
100 Image forming apparatus Da, Db, Dc, Dd Power supply means (power supply)
Pa, Pb, Pc, Pd Toner image forming means (image forming unit)
Ta transfer section

Claims (6)

A first image carrier disposed along the intermediate transfer member;
First toner image forming means for forming a toner image on the first image carrier using toner supplied from a first toner replenishing means provided with a first recording medium;
A first transfer member that presses the intermediate transfer member against the first image carrier to form a first transfer portion of a toner image;
First power supply means for applying a voltage to the first transfer unit and transferring a toner image from the first image carrier to the intermediate transfer member passing through the first transfer unit;
A second image carrier disposed downstream of the first image carrier in the rotational direction of the intermediate transfer member;
Second toner image forming means for forming a toner image on the second image carrier using toner supplied from a second toner replenishing means provided with a second recording medium;
A second transfer member that presses the intermediate transfer member against the second image carrier to form a second transfer portion of the toner image;
A second power supply means for applying a voltage to the second transfer section and transferring a toner image from the second image carrier to the intermediate transfer body passing through the second transfer section;
Input means for reading first manufacturing time data from the first recording medium and reading second manufacturing time data from the second recording medium;
Setting means for setting an output voltage of the second power supply means based on the read first manufacturing time data and second manufacturing time data;
The setting means sets the output voltage of the second power supply means to be lower as the toner production time of the first toner replenishing means is older, based on the read first production time data. Image forming apparatus. A third image carrier disposed upstream of the second image carrier in the rotational direction of the intermediate transfer member;
A third toner image forming means for forming a toner image on the third image carrier using toner supplied from a third toner replenishing means provided with a third recording medium;
A third transfer member that presses the intermediate transfer member against the third image carrier to form a third transfer portion of a toner image;
And a third power supply unit that applies a voltage to the third transfer unit and transfers a toner image from the third image carrier to the intermediate transfer member that passes through the third transfer unit. ,
The input means reads third production time data from the third recording medium;
The setting means sets an output voltage of the second power supply means based on the read first manufacturing time data, second manufacturing time data, and third manufacturing time data,
The setting means sets the output voltage of the second power supply means to be lower as the toner production time of the third toner replenishing means is older based on the read third production time data. The image forming apparatus according to claim 1. An image carrier disposed along the intermediate transfer member;
A toner image forming means for forming a toner image on the image carrier using toner supplied from a toner replenishing means provided with a recording medium;
A transfer member that presses the intermediate transfer member against the image carrier to form a toner image transfer portion; and
Power supply means for applying a voltage to the transfer unit and transferring a toner image from the image carrier to the intermediate transfer member passing through the transfer unit ;
Input means for reading manufacturing time data from the recording medium;
An image forming apparatus comprising: a setting unit configured to set an output voltage of the power supply unit based on the read manufacturing time data, and to set a lower output voltage of the power supply unit for toner having an older manufacturing time .
A plurality of toner replenishing means provided with the recording medium;
The setting means outputs the output voltage of the power supply means based on the voltage value based on the manufacturing time data read from the recording medium attached to the toner replenishing means of the already transferred toner and the toner to be transferred from now on. An image forming apparatus, wherein the image forming apparatus is set in the middle of a voltage value based on the manufacturing time data read from the recording medium attached to the toner replenishing means . A plurality of the image bearing members provided with the transfer member, the toner image forming unit, and the toner replenishing unit are arranged along the rotation direction of the intermediate transfer member,
The setting means applies the output voltage applied to a transfer portion of the second and subsequent image carriers from the upstream side in the rotation direction of the intermediate transfer member to the toner replenishing unit attached to the image carrier. The voltage value based on the manufacturing time data read from the attached recording medium and the recording medium attached to the toner replenishing means attached to the image carrier upstream of the image carrier are read. 4. The image forming apparatus according to claim 3 , wherein the image forming apparatus is set in the middle of the voltage value based on the manufacturing time data. An image carrier disposed along the recording material conveyance body;
A toner image forming means for forming a toner image on the image carrier using toner supplied from a toner replenishing means provided with a recording medium;
A transfer member that presses the recording material transport member against the image carrier to form a transfer portion of a toner image;
Power supply means for applying a voltage to the transfer unit and transferring a toner image from the image carrier to a recording material carried on the recording material transport member passing through the transfer unit ;
Input means for reading manufacturing time data from the recording medium;
An image forming apparatus comprising: a setting unit configured to set an output voltage of the power supply unit based on the read manufacturing time data, and to set a lower output voltage of the power supply unit for toner having an older manufacturing time .
A plurality of toner replenishing means provided with the recording medium;
The setting means outputs the output voltage of the power supply means based on the voltage value based on the manufacturing time data read from the recording medium attached to the toner replenishing means of the already transferred toner and the toner to be transferred from now on. An image forming apparatus, wherein the image forming apparatus is set in the middle of a voltage value based on the manufacturing time data read from the recording medium attached to the toner replenishing means . A plurality of the image bearing members provided with the transfer member, the toner image forming unit, and the toner replenishing unit are arranged along the rotation direction of the recording material conveyance body,
The setting means supplies the output voltage applied to a transfer portion of the second and subsequent image carriers from the upstream side in the rotation direction of the recording material conveyance body to the toner replenishing means attached to the image carrier. A voltage value based on the manufacturing time data read from the recording medium attached to the recording medium, and the recording medium attached to the toner replenishing means attached to the image carrier upstream of the image carrier. 6. The image forming apparatus according to claim 5 , wherein the image forming apparatus is set in the middle of the voltage value based on the read manufacturing time data.

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