JP6455262B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In the image forming apparatus, the techniques described in the following Patent Documents 1 and 2 are conventionally known with respect to the transport path for transporting the developer collected by the cleaner to the developing apparatus.

  In Japanese Patent Laid-Open No. 2000-66559 as Patent Document 1 and Japanese Patent Laid-Open No. 2000-89633 as Patent Document 2, toner collected from the photosensitive drum (1) by the cleaning device (5) is used to produce an image. A configuration is described in which the toner is selectively conveyed to the waste toner container (12) or the recycled toner supply port (3B) of the developing device (3) according to the image conditions.

JP 2000-66559 A (“0015”, FIG. 1) JP 2000-89663 A (“0011”, FIG. 1)

  An object of the present invention is to suppress the deterioration of the developer with a simple configuration.

In order to solve the technical problem, an image forming apparatus according to claim 1 is provided.
An image carrier,
A developing device for developing the latent image on the surface of the image carrier into a visible image;
A transfer member for transferring an image of the image carrier to a medium;
A cleaner for cleaning the developer remaining on the surface of the image carrier after transfer;
A transport path through which the developer collected by the cleaner is transported to the developing device;
With
When printing an image only on one side of the medium, and when the density of the image formed on the image carrier is lower than a preset density, an image for consumption of a preset developer is displayed. Formed and held on the surface of the transfer member, and forms an image on the surface of the medium that passes between the transfer member and the image carrier, and the transfer member of the medium A developer held on the transfer member is attached to the side surface;
It is characterized by that.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
One side uses a used medium, and the developer held on the transfer member is attached to the surface of the medium on the transfer member side using the used surface.
It is characterized by that.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
A reversing path for reversing the medium,
With
After the developer held by the transfer member was attached to the surface of the medium on the transfer member side, the medium was turned upside down, and the developer was attached to the surface of the inverted medium on the image carrier side. It is characterized in that an image for displaying is formed.

According to the first aspect of the present invention, it is simpler than the case where an image is formed on the surface of the medium on the image holding member side and the developer held on the transfer member is not attached to the surface of the medium on the transfer member side. With the configuration, deterioration of the developer can be suppressed.
According to the second aspect of the present invention, the developer discharged from the developing device can be attached to the used surface of the medium that has been used on one side.
According to the third aspect of the present invention, the user can be notified that the developer is attached.

FIG. 1 is an overall explanatory view of an image forming apparatus according to a first embodiment. FIG. 2 is an enlarged view of a main part of the toner image forming apparatus portion of FIG. FIG. 3 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the first embodiment. FIG. 4 is a flowchart of the transfer control process of the first embodiment. FIG. 5 is a flowchart of the developer discharge process of the first embodiment, and is a flowchart of the subroutine of ST6 in FIG. FIG. 6 is a time chart according to the first exemplary embodiment, FIG. 6A is a time chart when a normal job is executed, and FIG. 6B is a time chart when a developer is discharged.

Next, specific examples of embodiments of the present invention (hereinafter referred to as examples) will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an image forming apparatus according to a first embodiment.
In FIG. 1, a printer U as an example of the image forming apparatus according to the first exemplary embodiment includes a printer main body U1 as an example of an apparatus main body. A first discharge tray TRh as an example of a first medium discharge unit is provided on the upper surface of the printer body U1. An operation unit UI is provided on the upper surface of the right part of the printer main body U1. The operation unit UI includes a display unit (not shown). The operation unit UI is configured so that a user can perform an input operation.
The printer U according to the first embodiment illustrates a host computer as an example of an image information transmission device, and specifically, a personal computer is electrically connected thereto.

The printer U has a control unit C. The control unit C can receive electrical signals such as image information and control signals transmitted from the personal computer PC. The control unit C is configured to be able to output a control signal to the operation unit UI and the electric circuit E. Further, the control unit C is electrically connected to the write circuit DL.
The writing circuit DL outputs a drive signal to an exposure device ROS as an example of a writing device in accordance with the input information. The exposure machine ROS is configured to be able to output a laser beam L as an example of writing light in accordance with an input signal.

FIG. 2 is an enlarged view of a main part of the toner image forming apparatus portion of FIG.
1 and 2, a photoconductor PR as an example of an image carrier is disposed on the left side of the exposure machine ROS. The photoconductor PR of Example 1 is supported so as to be rotatable in the direction of the arrow about the rotation axis PRa. The photoconductor PR is irradiated with laser light L in the writing area Q1.
Around the photoconductor PR, along the rotational direction of the photoconductor PR, a charging roll CR as an example of a charging member, a developing device G, and a photoconductor cleaner CL as an example of a cleaner for an image carrier. Is arranged.
In the printer U according to the first exemplary embodiment, the photosensitive member PR, the charging roll CR, the developing device G, and the photosensitive member cleaner CL are integrated into a unit that can be attached and detached. That is, the photoconductor PR, the charging roll CR, the developing device G, and the photoconductor cleaner CL are configured to be detachable from the printer body U1 as a process unit U2.

A charging voltage is applied from the electric circuit E to the charging roll CR.
The developing device G includes a developing container V that accommodates toner as an example of a developer. Inside the developing container V, a developing roll Ga as an example of a developer holding body is rotatably supported. The developing roll Ga is disposed to face the photoreceptor PR in the developing area Q2.
Further, a developing voltage is applied from the power supply circuit E to the developing roll Ga. Further, augers Gb and Gc, which are examples of a developer conveying member, are rotatably supported in the developing container V.
The photoconductor PR, the charging roll CR, the exposure machine ROS, the developing device G, and the like constitute a toner image forming apparatus that forms a toner image on the photoconductor PR.

In FIG. 1, a plurality of paper feed trays TR <b> 1 to TR <b> 4 are provided below the printer U as an example of a medium storage unit. Each of the paper feed trays TR1 to TR4 accommodates a recording sheet S as an example of a medium.
In FIG. 1, rails RL1 as an example of container guide members are arranged on the left and right sides of each of the paper feed trays TR1 to TR4. The rail RL1 movably supports the left and right ends of the paper feed trays TR1 to TR4. Accordingly, the paper feed trays TR1 to TR4 are supported by the pair of left and right rails RL1 so as to be able to enter and exit in the front-rear direction.

In FIG. 1, a paper feeding device K is disposed at the upper left of each of the paper feeding trays TR1 to TR4. The paper feeding device K has a pickup roll Rp as an example of a medium take-out member. On the left side of the pick-up roll Rp, a separating roll Rs as an example of a separating member is disposed. The separating roll Rs includes a feed roll as an example of a medium conveying member and a retard roll as an example of a medium separating member.
On the left side of the sheet feeding device K, a sheet feeding path SH1 as an example of a medium transport path is disposed. The sheet feed path SH1 extends upward. A plurality of transport rolls Ra as an example of a medium transport member are arranged in the paper feed path SH1. A registration roll Rr, which is an example of a medium transport timing adjustment member, is disposed at the upper end, which is the downstream end of the sheet feed path SH1.

A manual feed tray TR0 as an example of a manual feed unit is mounted on the left side of the printer U. The right end of the manual feed tray TR0 is connected to the left end of a manual feed path SH2 as an example of a manual feed path. The right end of the manual feed path SH2 is connected to the paper feed path SH1.
In FIG. 1, a transfer roll Rt, which is an example of a transfer device and is an example of a transfer member, is disposed above the registration roll Rr. The transfer roll Rt faces and contacts the photoconductor PR in the transfer region Q3. Accordingly, the transfer roll Rt according to the first exemplary embodiment rotates following the rotation of the photoconductor PR. A transfer voltage is applied from the power supply circuit E to the transfer roll Rt.

The photoreceptor cleaner CL is disposed on the downstream side of the transfer roll Rt with respect to the rotation direction of the photoreceptor PR. The photoreceptor cleaner CL includes a cleaning blade 42 as an example of a cleaning member. The cleaning blade 42 is formed in a plate shape. One end of the cleaning blade 42 is in contact with the photoconductor PR.
A cleaner container 41 as an example of a cleaning container is disposed above the cleaning blade 42. The cleaning blade 42 is supported by the cleaner container 41. A space in which the developer can be stored is formed inside the cleaner container 41. Inside the cleaner container 41, a recovery auger 43 as an example of a developer conveying member is rotatably supported. A recovery path CL4 as an example of a developer transport path is supported at the front end of the cleaner container 41. The recovery path CL4 extends from the photoconductor cleaner CL to the developing device G.

In FIG. 1, a fixing device F is supported above the transfer roll Rt. The fixing device F includes a heating roll Fh as an example of a heat fixing member and a pressure roll Fp as an example of a pressure fixing member. The heating roll Fh and the pressure roll Fp are in contact with each other in the fixing region Q4. Driving is transmitted to the heating roll Fh from a driving source (not shown) to rotate. The heating roll Fh is supplied with electric power for heating a heater (not shown) from the electric circuit E.
The process unit U2 as an example of the toner image forming apparatus, the transfer roll Rt, and the fixing device F constitute an image recording unit U2 + Rt + F that records an image on the sheet S.

Above the fixing device F, a sheet guide F1 as an example of a medium guiding portion is formed. A sheet discharge roll R1 as an example of a medium discharge member is disposed on the right side of the sheet guide F1. A medium discharge port Ha is formed on the right side of the paper discharge roll R1. A first discharge tray TRh is disposed below the medium discharge port Ha.
In FIG. 1, a connection path SH3 as an example of a medium transport path is disposed above the fixing device F and on the left side of the paper discharge roll R1. The connection path SH3 extends to the left from the medium discharge port Ha.

A reversing unit U3, which is an example of a medium reversing device, is supported on the left side surface of the printer body U1 above the manual feed tray TR0. A reversing path SH4 as an example of a medium transport path is formed inside the reversing unit U3. The upper end of the inversion path SH4 is connected to the left end of the connection path SH3. The lower end of the reversing path SH4 joins the sheet feeding path SH1 on the upstream side of the registration roll Rr.
A second discharge path SH6 as an example of a medium transport path is formed above the reversing unit U3. The second discharge path SH6 has a right end connected to the connection path SH3 and branches off from the inversion path SH4. The left end of the second discharge path SH6 extends to the left side surface of the reversing unit U3. A face-up tray TRh1 as an example of a second discharge unit is supported on the left side surface of the reversing unit U3. Accordingly, the sheet S that has passed through the second discharge path SH6 is configured to be discharged to the face-up tray TRh1.

(Function of image forming apparatus)
In the printer U of the first embodiment having the above-described configuration, the image information transmitted from the personal computer PC is input to the control unit C. The control unit C converts the input image information into information for forming a latent image at a preset time and outputs the information to the writing circuit DL. The exposure machine ROS outputs a laser beam L based on the signal received by the writing circuit DL. The control unit C controls operations of the operation unit UI, the writing circuit DL, the power supply circuit E, and the like.
1 and 2, the surface of the photoreceptor PR is charged by a charging roll CR to which a charging voltage is applied. The surface of the photoreceptor PR charged by the charging roll CR is exposed and scanned by the laser beam L of the exposure machine ROS in the writing area Q1 to form an electrostatic latent image. The surface of the photoconductor PR on which the electrostatic latent image is formed sequentially passes through the development area Q2 and the transfer area Q3.

  In the developing area Q2, the developing roll Ga faces the photoconductor PR. The developing roll Ga rotates while holding the developer inside the developing container V on the surface. Therefore, the electrostatic latent image on the surface of the photoconductor PR is developed into a toner image as an example of a visible image by the toner image held on the surface of the developing roll Ga. The developer inside the developing container V is circulated while being stirred by the augers Gb and Gc.

Each of the paper feed trays TR1 to TR4 accommodates a sheet S on which an image is recorded. The sheets S accommodated in the respective sheet feeding trays TR1 to TR4 are taken out by the pickup roll Rp of the sheet feeding device K. The sheets S taken out by the pickup roll Rp are separated one by one by the separating roll Rs. The sheet S separated by the separating roll Rs is fed to the sheet feeding path SH1. The sheet S in the sheet feeding path SH1 is conveyed toward the registration roll Rr by the conveyance roll Ra.
The sheet S fed from the manual feed tray TR0 is conveyed to the registration roll Rr through the manual feed path SH2. The sheet S conveyed to the registration roll Rr is conveyed to the transfer area Q3 by the registration roll Rr in accordance with the timing when the toner image on the surface of the photoconductor PR moves to the transfer area Q3.

In the transfer area Q3, the toner image on the surface of the photoconductor PR is transferred to the sheet S passing through the transfer area Q3 by the transfer roll Rt to which the transfer voltage is applied.
In FIG. 2, the photosensitive member PR after passing through the transfer region Q3 is cleaned by removing the toner attached to the surface by the cleaning blade. The toner removed by the cleaning blade 42 is collected in the cleaner container 41. The toner collected in the cleaner container 41 is conveyed by the collection auger 43. The toner conveyed by the collection auger 43 is returned to the inside of the developing container V through the collection path CL4. That is, the developer collected by the photoreceptor cleaner CL is reused by the developing device G.
The photoconductor PR whose surface is cleaned by the photoconductor cleaner CL is charged again by the charging roll CR.

The sheet S on which the toner image is transferred in the transfer area Q3 is conveyed to the fixing area Q4 of the fixing device F in a state where the toner image is not fixed.
In the fixing region Q4, the sheet S is sandwiched between the heating roll Fh and the pressure roll Fp, and the toner image is heated and fixed.
The sheet S on which the toner image is fixed by the fixing device F is guided by the sheet guide F1 and conveyed to the paper discharge roll R1. When the sheet S is discharged to the first discharge tray TRh, the sheet S sent to the discharge roll R1 is discharged from the medium discharge port Ha to the first discharge tray TRh.

During double-sided printing, the sheet S on which an image is recorded on the first side rotates the paper discharge roll R1 in a state where the trailing end in the transport direction has passed the sheet guide F1. Accordingly, the sheet S is conveyed to the reversing path SH4 through the connection path SH3. The sheet S conveyed on the reversing path SH4 is conveyed to the registration roll Rr in a state where the front and back sides are reversed. Therefore, the image on the second side is recorded again from the registration roll Rr to the transfer area Q3.
When the sheet S is discharged to the face-up tray TRh1, the sheet S conveyed through the connection path SH3 by the reverse rotation of the discharge roll R1 is carried into the second discharge path SH6. Then, the sheet S conveyed through the second discharge path SH6 is discharged to the face-up tray TRh1.

(Description of the control part of Example 1)
FIG. 3 is a block diagram illustrating the functions of the control unit of the image forming apparatus according to the first embodiment.
In FIG. 3, the control unit C of the printer U has an input / output interface I / O for inputting / outputting signals to / from the outside. In addition, the control unit C includes a ROM (read only memory) in which a program for performing necessary processing, information, and the like are stored. In addition, the control unit C includes a random access memory (RAM) for temporarily storing necessary data. The control unit C includes a central processing unit (CPU) that performs processing according to a program stored in a ROM or the like. Therefore, the control part C of Example 1 is comprised by the small information processing apparatus, what is called a microcomputer. Therefore, the control part C can implement | achieve various functions by running the program memorize | stored in ROM etc.

(Signal output element connected to control unit C)
The control unit C receives an output signal from the operation unit UI and other signal output elements (not shown).
The operation unit UI includes an input button UIa for inputting the number of prints and an arrow, a display unit UIb as an example of a notification member, and the like.

(Controlled element connected to control unit C)
The control unit C is connected to a drive circuit D1 as a main drive source, a power supply circuit E, and other control elements (not shown). The control unit C outputs those control signals to the circuits D1, E and the like.
D1: Main Drive Source Drive Circuit The main drive source drive circuit D1 rotationally drives the photoreceptor PR, the fixing device F, and the like via a main motor M1 as an example of the main drive source.

E: Power Supply Circuit The power supply circuit E includes a development power supply circuit Ea, a charging power supply circuit Eb, a transfer power supply circuit Ec, a fixing power supply circuit Ed, and the like.
Ea: Power Supply Circuit for Development The power supply circuit for development Ea applies a development voltage to the development roll of the development device G.
Eb: Charging power supply circuit The charging power supply circuit Eb applies a charging voltage for charging the surface of the photoreceptor PR to each of the charging rolls CR.
Ec: Power supply circuit for transfer The power supply circuit Ec for transfer applies a transfer voltage to the transfer roll Rt.
Ed: Power supply circuit for fixing The power supply circuit for fixing Ed supplies power for heating the heater to the heating roll Fh of the fixing device F.

(Function of control unit C)
The control unit C has a function of executing a process according to an input signal from the signal output element and outputting a control signal to each control element. That is, the control unit C has the following functions.
C1: Image Forming Control Unit The image forming control unit C1 controls the driving of each member of the printer U, the application timing of each voltage, and the like according to the image information transmitted from the host computer, and performs the image forming operation. Run a job.
C2: Drive Source Control Unit The drive source control unit C2 controls the drive of the main motor M1 via the main drive source drive circuit D1, and controls the drive of the photoconductor PR and the like.

C3: Power Supply Circuit Control Unit The power supply circuit control unit C3 controls the power supply circuits Ea to Ed to control the voltage applied to each member and the power supplied to each member.
C4: Image Density Calculation Unit The image density calculation unit C4 calculates the image density of the page to be printed.
C5: Average Image Density Calculation Unit The average image density calculation unit C5 calculates a cumulative average image density <C> based on the image density calculated by the image density calculation unit C4.
C6: Storage Unit for Discharge Density The storage unit C6 for discharge density stores a discharge concentration Ca as an example of a determination value for forced consumption of developer. In the first embodiment, Ca = 3% is stored as an example of the discharge concentration Ca.

C7: Discharge Determination Unit The discharge determination unit C7 determines whether or not the developer of the developing device G is forcibly consumed. That is, it is determined whether or not the deteriorated developer is forcibly discharged from the developing device G. The discharge determination unit C7 according to the first exemplary embodiment determines that it is time to forcibly consume the developer when the average image density <C> is equal to or lower than the discharge density Ca. In the first embodiment, it is determined whether or not the developer of the developing device G is forcibly consumed when the cumulative number of printed sheets n is equal to or greater than the number of discharged sheets na as an example of a determination value. As an example, the ejection number na is set to na = 1000 [sheets].
C8: Discriminating Unit for Printing Operation The discriminating unit for printing operation C8 discriminates a printing mode, that is, a so-called single-sided printing mode or a duplex printing mode. The printing operation determination unit C8 according to the first exemplary embodiment determines whether or not one side is in a “backing paper mode” in which printing is performed using a used medium, that is, a backing paper.

C9: Toner Band Forming Unit The toner band forming unit C9 forms a toner band as an example of an image for consuming the developer. For example, the toner band forming unit C9 according to the first exemplary embodiment forms a toner band having a density of 100% and a size of the width of the transfer roll Rt × one round of the surface. The toner band forming unit C9 according to the first exemplary embodiment forms a toner band when it is determined that it is time for the discharge determination unit C7 to forcibly consume the developer, and the back paper mode is determined. To do.
C10: Back Image Forming Unit The back image forming unit C10 forms an image indicating that the developer is attached. The back surface image forming means C10 of Example 1 forms an image “This surface is the back surface” as an image indicating that the surface has the toner band formed thereon.

C11: Transfer Control Unit The transfer control unit C11 includes a job control unit C11A as an example of an image formation control unit, a toner band holding unit C11B as an example of a consumption image holding unit, and a cleaning operation. A cleaning cycle control unit C11C as an example of a time control unit, and a job end control unit C11D as an example of a control unit at the end of image formation. The transfer control unit C11 controls the transfer voltage applied to the transfer roll Rt via the control unit C3 of the power supply circuit.
C11A: Job Control Unit C11A applies a transfer voltage to the transfer roll Rt during job execution. For example, the control unit C11A during the job in Example 1 applies a positive transfer voltage for transferring a negative developer to the sheet S to the transfer roll Rt.

C11B: Toner Band Holding Unit The toner band holding unit C11B applies a voltage to the transfer roll Rt to hold the toner band formed by the toner band forming unit C9 on the transfer roll Rt. The toner band holding unit C11B according to the first exemplary embodiment, as an example, moves the negative developer to the surface of the transfer roll Rt and holds the negative polarity developer at the time when the toner band reaches the transfer region Q3. Apply a transfer voltage.

C11C: Cleaning Cycle Control Unit The cleaning cycle control unit C11C controls a transfer voltage during a cleaning cycle as an example of a cleaning operation. The cleaning cycle control unit C11C according to the first exemplary embodiment executes a cleaning cycle in which the developer attached to the surface of the transfer roll Rt is transferred to the photoconductor PR and collected by the photoconductor cleaner CL at the end of the job. The cleaning cycle control means C11C according to the first embodiment applies a positive voltage for a preset period at the start of the cleaning cycle, and returns the abnormally charged developer, that is, the positive developer to the photoreceptor PR. . Next, a negative voltage is applied for a preset period, and the normally charged developer, that is, the negative developer is returned to the photoreceptor PR. The period for applying the positive polarity and the negative polarity is set to a period equal to or longer than the period for one rotation of the transfer roll Rt.

C11D: Control Unit at Job End The control unit C11D at job end controls the voltage applied to the transfer roll Rt at the end of the job. In the printer U according to the first exemplary embodiment, the charging voltage, the developing voltage, and the transfer voltage are stopped in this order. Then, the control unit C11D at the end of the job according to the first embodiment applies a negative voltage until the transfer voltage is stopped in order to make it difficult for the developer to adhere to the transfer roll Rt at the end of the job.

(Explanation of flowchart of Example 1)
Next, a flow of control in the printer U according to the first embodiment will be described with reference to a flowchart, a so-called flowchart.

(Transfer control process)
FIG. 4 is a flowchart of the transfer control process of the first embodiment.
4 is performed according to a program stored in the control unit C of the printer U. This process is executed in parallel with other various processes of the printer U.
The flowchart shown in FIG. 4 is started when the printer U is turned on.

In ST1 of FIG. 4, it is determined whether or not a job that is an image forming operation is started. If yes (Y), the process proceeds to ST2. If no (N), ST1 is repeated.
In ST2, the following processes (1) to (3) are executed, and the process proceeds to ST3.
(1) The image density of the printed page is calculated.
(2) The average image density <C> is calculated.
(3) Add 1 to the cumulative number n of prints. That is, n = n + 1.
In ST3, it is determined whether or not the cumulative number of printed sheets n is equal to or greater than the number of ejected sheets n1. If yes (Y), the process proceeds to ST4. If no (N), the process proceeds to ST8.
In ST4, it is determined whether or not the average image density <C> is equal to or lower than the discharge density Ca. If yes (Y), the process proceeds to ST5, and, if no (N), the process proceeds to ST8.

In ST5, it is determined whether or not the back paper mode is set. If yes (Y), the process proceeds to ST6, and if no (N), the process proceeds to ST8.
In ST6, a developer discharge process shown in FIG. 5 described later is executed, and the process proceeds to ST7.
In ST7, the following processes (1) and (2) are executed, and the process proceeds to ST9.
(1) The average density <C> is initialized.
(2) The cumulative number n of prints is initialized.
In ST8, a transfer control process during a job is executed. That is, the transfer voltage for transferring the image to the sheet S is applied in accordance with the time when the image on the surface of the photoconductor PR reaches the transfer region Q3. Then, the process proceeds to ST9.

In ST9, it is determined whether or not the job is finished. If yes (Y), the process proceeds to ST10, and if no (N), the process returns to ST2.
In ST10, a cleaning cycle is executed. That is, after applying a positive polarity voltage for a preset period, a negative polarity voltage is applied for a preset period. Then, the process proceeds to ST11.
In ST11, stop processing is executed. That is, a negative voltage is applied for a preset period. Then, the process returns to ST1.

(Developer discharge process)
FIG. 5 is a flowchart of the developer discharge process of the first embodiment, and is a flowchart of the subroutine of ST6 in FIG.
In ST21 of FIG. 5, a toner band is formed. Then, the process proceeds to ST22.
In ST22, a voltage is applied to the transfer roll Rt to transfer and hold the toner band on the transfer roll Rt. Then, the process proceeds to ST23.
In ST23, an image to be printed is formed. Then, the process proceeds to ST24.
In ST24, a transfer voltage is applied to the transfer roll Rt to form an image to be printed. At this time, the developer held on the transfer roll Rt is rubbed against the surface on the transfer roll Rt side of the sheet S, that is, the so-called back surface. Then, the process proceeds to ST25.

In ST25, a back image is formed. Before and after this, the sheet S is conveyed on the reversing path SH4 and the front and back are reversed. Then, the process proceeds to ST26.
In ST26, a transfer voltage is applied to the transfer roll Rt to transfer the back image to the sheet S with the front and back sides reversed. Then, the flowchart of FIG. 5 is terminated and the processing returns to FIG.

(Operation of transcription control in Example 1)
FIG. 6 is a time chart according to the first exemplary embodiment, FIG. 6A is a time chart when a normal job is executed, and FIG. 6B is a time chart when a developer is discharged.
In the printer U according to the first embodiment having the above-described configuration, the developer remaining on the photoconductor PR without being transferred at the time of a job is collected by the photoconductor cleaner CL. As shown in FIG. 6A, a cleaning cycle is executed at the end of the job, and the developer attached to the transfer roll Rt is returned to the photoconductor PR and collected by the photoconductor cleaner CL. The developer collected by the photoreceptor cleaner CL is returned to the developing device G and reused.

Here, when an image having a low density is continuously printed at the time of image formation, stirring is continued in a state where the consumption of the developer is small in the developing device G. That is, when the average image density <C> is low, the developer is likely to deteriorate. In particular, the developer collected by the photoconductor cleaner CL is subjected to a load when passing through the transfer region Q3 and when it is scraped off by the photoconductor cleaner CL, and is easily deteriorated.
In the techniques described in Patent Documents 1 and 2, when the developer is deteriorated, the developer collected by the cleaner can be discharged into a waste toner container without returning it to the developing device. However, in this configuration, there are problems that two transport routes are required, the configuration becomes complicated, and the manufacturing cost increases. On the other hand, in a configuration that does not have a means for discarding the deteriorated developer, a mode for forcibly consuming the developer by transferring the toner band to the sheet is prepared separately from the job and executed by the user. There was a problem that bothered users.

On the other hand, in Example 1, as shown in FIG. 6B, a toner band is formed on the used back surface while forming an image on the front surface in the back paper mode. In Example 1, the developer held on the transfer roll Rt is rubbed against the back surface of the sheet S. That is, it adheres with a mechanical force.
Therefore, in Example 1, a toner band is formed on the back surface without taking care of the user, and the deteriorated developer is discharged. Therefore, the deterioration of the developer accommodated in the developing device G is suppressed, and the image quality deterioration is reduced. In addition, there is no need to provide two systems, a path for returning the developer collected by the photoconductor cleaner CL to the developing device G and a path for transporting the developer to a waste container. Manufacturing costs can be reduced.

  In particular, in Example 1, when a toner band is formed, the sheet S is reversed, and a back image is formed on the surface to which the toner band is transferred. Therefore, it is possible to notify the user that the surface to which the toner band has been transferred is the back surface.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is made in the range of the summary of this invention described in the claim. Is possible. Modification examples (H01) to (H06) of the present invention are exemplified below.
(H01) In the above embodiment, the printer U as an example of the image forming apparatus is illustrated, but the present invention is not limited to this. For example, the present invention can be applied to an image forming apparatus such as a copying machine or a FAX.

(H02) In the above-described embodiment, the configuration in which the developer is discharged in the backing paper mode is exemplified, but the present invention is not limited thereto. For example, it can be executed in the single-sided printing mode using a new sheet S that is not a backing paper. At this time, it is also possible to reduce the density of the toner band and reduce the concentration of the developer that is rubbed against the back surface so that the stain on the back surface is less noticeable from the user's perspective.
(H03) In the above-described embodiment, the exemplified specific numerical values can be arbitrarily changed according to the design, specifications, and the like.

(H04) In the above embodiment, the configuration for printing the back image is illustrated, but the present invention is not limited to this. For example, the sheet S may be discharged as it is after the toner image is rubbed without printing the back image. In this case, it is not necessary to reverse the sheet S, and the time and process required for the developer discharge process can be shortened.
(H05) In the above-described embodiment, the configuration in which the back side image is notified by characters is exemplified, but the present invention is not limited to this. For example, it is possible to make an arbitrary image such as printing a large x mark.

(H06) In the above embodiment, when the sheet S is discharged as it is after the back side image is printed, the front and back sides of the bundle of printed sheets S are reversed. Therefore, after printing the back image, it is also possible to invert the image again and match the front and back.

CL ... cleaner
CL4 ... conveying path,
G: Developing device,
PR: Image carrier,
Rt: transfer member,
S ... medium
SH4 ... reverse path,
U: Image forming apparatus.

Claims (3)

An image carrier,
A developing device for developing the latent image on the surface of the image carrier into a visible image;
A transfer member for transferring an image of the image carrier to a medium;
A cleaner for cleaning the developer remaining on the surface of the image carrier after transfer;
A transport path through which the developer collected by the cleaner is transported to the developing device;
With
When printing an image only on one side of the medium, and when the density of the image formed on the image carrier is lower than a preset density, an image for consumption of a preset developer is displayed. Formed and held on the surface of the transfer member, and forms an image on the surface of the medium that passes between the transfer member and the image carrier, and the transfer member of the medium A developer held on the transfer member is attached to the side surface;
An image forming apparatus. One side uses a used medium, and the developer held on the transfer member is attached to the surface of the medium on the transfer member side using the used surface.
The image forming apparatus according to claim 1. A reversing path for reversing the medium,
With
After the developer held by the transfer member was attached to the surface of the medium on the transfer member side, the medium was turned upside down, and the developer was attached to the surface of the inverted medium on the image carrier side. The image forming apparatus according to claim 1, wherein an image for displaying is formed.

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