JP2016142856A - Image forming apparatus, control method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restore electrification performance of a photoreceptor by decreasing residual electric charges in the photoreceptor, which are produced during an image forming operation.SOLUTION: An image forming apparatus comprises: a photoreceptor (photoreceptor drum 51); an electrification part (a grid electrode 52B and a grid bias circuit 220) which electrifies the photoreceptor; an exposure part which exposes the photoreceptor; a development part (a development roller 54) which develops an electrostatic latent image formed on the photoreceptor with a developer; a transfer part (a transfer roller 74) which transfers the developer image carried by the photoreceptor to a transfer medium; and a control part 100. The control part 100 performs an image forming operation for forming the developer image on the transfer medium, and a restoring operation for imparting a larger amount of electric charges to the photoreceptor from the electrification part compared to the case where the image forming operation is performed and turning the photoreceptor by one or more rotations when the image forming operation is not performed.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus including a control unit that performs an image forming operation, a control method by the control unit, and a program for operating the control unit.

  Conventionally, an electrostatic latent image corresponding to an image pattern is formed on the photosensitive drum by an exposure device, so that the surface potential of the non-uniform photosensitive drum is made uniform before the next charging. There is known an image forming apparatus provided with a pre-charging exposure apparatus that exposes the entire surface in the axial direction (see Patent Document 1).

JP 2009-175675 A

  By the way, the photosensitive drum usually has a conductor tube and a photosensitive layer provided on the surface of the tube. When the toner is a positive toner, a positive charge is charged on the surface of the photosensitive layer when the photosensitive layer is charged for printing.

  When the photosensitive layer is exposed, positive and negative charges are generated inside the photosensitive layer, and the negative charges are transported to the surface, so that the positive charges charged on the surface are canceled by the negative charges, Thereby, an electrostatic latent image is formed. The positive charge generated inside the photosensitive layer is transported to the element tube side and flows to the ground through the element tube.

  If the charge transport capability in the photosensitive layer is not sufficient for the charge generated inside the photosensitive layer, the charge remains in the photosensitive layer when printing is continued. For this reason, there is a problem in that negative charges remaining inside are transported to a place charged for printing and the surface potential is lowered.

  Accordingly, an object of the present invention is to reduce the residual charge inside the photoconductor generated during the image forming operation and restore the charging performance of the photoconductor.

In order to solve the above problems, an image forming apparatus according to the present invention includes a photoconductor, a charging unit that charges the photoconductor, an exposure unit that exposes the photoconductor, and an electrostatic latent image formed on the photoconductor. A developing unit that develops an image with a developer, a transfer unit that transfers the developer image carried on the photosensitive member to a transfer medium, and a control unit.
The control unit is configured to form an image forming operation for forming the developer image on the transfer medium, and to charge a larger amount of charge from the charging unit to the photoconductor than in the image forming operation when the image forming operation is not performed. And a recovery operation of rotating the photoconductor more than once.

  According to this configuration, when the image forming operation is not performed, a larger amount of charge is applied from the charging unit to the photoconductor than in the image forming operation to rotate the photoconductor more than once, so the photoconductor generated during the image forming operation It is possible to restore the charging performance of the photosensitive member by reducing the residual charge inside.

  In the above-described configuration, the control unit may be configured to make the charging bias of the charging unit larger in the recovery operation than in the image forming operation.

  According to this, in the recovery operation, the charging bias of the charging unit is made larger than that in the image forming operation, so that a larger amount of charge can be applied from the charging unit to the photoconductor than in the image forming operation.

  In the above-described configuration, the control unit may be configured so that, in the recovery operation, the rotation speed of the photoconductor is slower than that during the image forming operation while the charging unit is activated. Good.

  According to this, in the recovery operation, by making the rotation speed of the photoconductor slower than in the image forming operation, a larger amount of charge can be applied from the charging unit to the photoconductor than in the image forming operation.

  In the above-described configuration, the control unit may be configured to turn off the transfer bias of the transfer unit in the recovery operation.

  In the recovery operation, if a transfer bias having a polarity opposite to that of the developer is applied to the transfer portion, the surface potential of the photoconductor decreases due to the transfer bias, thereby suppressing the residual charge removal operation inside the photoconductor. There is a risk of being. On the other hand, in the recovery operation, it is possible to suppress the residual charge removal operation inside the photosensitive member from being suppressed by turning off the transfer bias of the transfer unit.

  In the above configuration, the control unit may be configured to separate the developing unit from the photoconductor in the recovery operation.

  In the recovery operation, if the photosensitive member and the developing unit are kept in contact with each other, the surface potential of the photosensitive member may be lowered due to the influence of the developing bias of the developing unit. The removal operation may be suppressed. On the other hand, in the recovery operation, it is possible to suppress the residual charge removal operation inside the photosensitive member from being suppressed by separating the developing unit from the photosensitive member.

  In the configuration described above, the control unit may be configured to execute the recovery operation after the image forming operation.

  According to this, it is possible to shorten the waiting time from when the print command is received until the image forming operation is executed, as compared with the case where the recovery operation is executed before the image forming operation.

  In the above-described configuration, the control unit may be configured to interrupt the image forming operation and execute the recovery operation when the image forming operation is continuously performed for a predetermined time.

  Since the amount of accumulated residual charge in the photoconductor increases in proportion to the continuous printing time, the recovery operation is performed when the continuous printing continues for a predetermined time, so that the influence of the residual charge occurs in the subsequent printing. Can be suppressed.

  In the configuration described above, the control unit may be configured to increase the frequency of executing the recovery operation as the usage amount of the photoconductor increases.

  The larger the amount of the photoconductor used, the lower the charge transport capability inside the photoconductor. Therefore, by increasing the frequency of the recovery operation according to the decrease in the charge transport capability, even if the charge transport capability is reduced, Residual charges inside the body can be reduced well.

  In the above-described configuration, the control unit may be configured to increase the number of rotations of the photoconductor as the usage amount of the photoconductor increases in the recovery operation.

  The larger the amount of use of the photoconductor, the lower the charge transport capability inside the photoconductor. Therefore, by increasing the number of rotations of the photoconductor in the recovery operation according to the decrease in the charge transport capability, Therefore, it is possible to favorably reduce the residual charge inside the photoconductor having a reduced charge transport capability.

  In the above-described configuration, the control unit may be configured to increase the charging bias as the usage amount of the photoconductor increases in the recovery operation.

  The larger the amount of use of the photoconductor, the lower the charge transport capability inside the photoconductor. Therefore, by increasing the charging bias in the recovery operation according to the decrease in this charge transport capability, By applying a larger amount of charge, it is possible to satisfactorily reduce the residual charge inside the photoconductor having a reduced charge transport capability.

  In the above-described configuration, the control unit may be configured to slow down the rotation speed of the photoconductor as the usage amount of the photoconductor is large in the recovery operation.

  The larger the amount of use of the photoconductor, the lower the charge transport capability inside the photoconductor. Therefore, by reducing the rotation speed of the photoconductor in the recovery operation in accordance with the decrease in the charge transport capability, Therefore, it is possible to favorably reduce the residual charge inside the photoconductor having a reduced charge transport capability.

  Further, in the above configuration, when a temperature acquisition unit that acquires temperature is provided, the control unit may be configured to increase the frequency of executing the recovery operation as the temperature is lower.

  Since the charge transport capability inside the photoconductor decreases as the temperature decreases, the frequency of the recovery operation increases according to this decrease in charge transport capability, so even if the charge transport capability decreases, the inside of the photoconductor The residual charge can be reduced satisfactorily.

  Further, in the above-described configuration, when the temperature acquisition unit that acquires the temperature is provided, the control unit is configured to increase the number of rotations of the photoconductor as the temperature is lower in the recovery operation. It may be.

  Since the charge transport capability inside the photoconductor decreases as the temperature decreases, the number of rotations of the photoconductor during the recovery operation increases according to the decrease in the charge transport capability, so By applying a larger amount of charge, it is possible to satisfactorily reduce the residual charge inside the photoconductor having a reduced charge transport capability.

  Further, in the above-described configuration, when the temperature acquisition unit that acquires the temperature is provided, the control unit may be configured to increase the charging bias as the temperature is lower in the recovery operation. .

  Since the charge transport capability inside the photoconductor decreases as the temperature decreases, increasing the charging bias in the recovery operation according to the decrease in the charge transport capability increases the charge from the charging unit to the photoconductor. By applying an electric charge, it is possible to satisfactorily reduce the residual electric charge inside the photoconductor having a reduced charge transport capability.

  Further, in the above-described configuration, when the temperature acquisition unit that acquires the temperature is provided, the control unit is configured to slow down the rotation speed of the photoconductor as the temperature is lower in the recovery operation. May be.

  Since the charge transport capability inside the photoconductor decreases with a decrease in temperature, the rotation speed of the photoconductor in the recovery operation is slowed down according to the decrease in the charge transport capability, so that the charged portion can move toward the photoconductor. By applying a larger amount of charge, it is possible to satisfactorily reduce the residual charge inside the photoconductor having a reduced charge transport capability.

  Further, in the above-described configuration, in the case where a static eliminator for reducing the surface potential of the photoconductor is provided, the control unit performs the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. It may be configured to increase the frequency of execution.

  The longer the time during which the static eliminator is operated during the image forming operation, the residual charge inside the photoconductor increases. Therefore, by increasing the frequency of executing the recovery operation according to the increase in the residual charge, the photoconductor The internal residual charge can be reduced well.

  Further, in the above-described configuration, in the case where a static eliminator for reducing the surface potential of the photoconductor is provided, the control unit performs the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. The number of rotations of the photoconductor may be increased.

  The longer the time that the static eliminator is operated during image formation operation, the more the residual charge inside the photoconductor increases. Therefore, by increasing the number of rotations of the photoconductor in the recovery operation according to the increase in this residual charge, charging By applying more charge to the photoconductor from the portion, it is possible to satisfactorily reduce the residual charge inside the photoconductor.

  Further, in the above-described configuration, in the case where a static eliminator for reducing the surface potential of the photoconductor is provided, the control unit performs the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. The charging bias may be increased.

  The longer the time for which the static eliminator is operated during the image forming operation, the residual charge inside the photoconductor increases. Therefore, by increasing the charging bias in the recovery operation in accordance with the increase in the residual charge, By applying more charge to the body, the residual charge inside the photoreceptor can be reduced well.

  Further, in the above-described configuration, in the case where a static eliminator for reducing the surface potential of the photoconductor is provided, the control unit performs the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. The photosensitive member may be configured to slow down the rotation speed.

  The longer the time that the static eliminator is activated during image forming operation, the more the residual charge inside the photoconductor increases. Therefore, by reducing the rotational speed of the photoconductor in the recovery operation according to the increase in this residual charge, By applying more charge to the photoconductor from the portion, it is possible to satisfactorily reduce the residual charge inside the photoconductor.

  Further, in the above-described configuration, the photoconductor includes a base material of a conductor and a photoconductive layer provided on the base material, and the photoconductive layer includes a charge generating material, an electron transport material, and a hole in a resin. It may be formed of a positively charged organic photosensitive layer in which a transport material is dispersed.

  Further, the control method according to the present invention is a control method for controlling the operation of the photosensitive member and the operation of the charging unit for charging the photosensitive member, and when the image forming operation is not performed, from the charging unit to the photosensitive member. In this method, a larger amount of charge is applied than in the image forming operation to rotate the photoconductor more than once. According to this control method, the same effect as described above can be obtained.

  The program according to the present invention is a program that operates a control unit that controls the operation of the photosensitive member and the operation of the charging unit that charges the photosensitive member. When the control unit is not performing an image forming operation, Then, a larger amount of charge is applied from the charging unit to the photoconductor than in the image forming operation, and the photoconductor is caused to function as a recovery unit that rotates the photoconductor more than once. According to this program, the same effects as those described above can be obtained.

  According to the present invention, the residual charge inside the photoconductor generated during the image forming operation can be reduced and the charging performance of the photoconductor can be recovered.

1 is a cross-sectional view illustrating a color printer according to an embodiment of the present invention. FIG. 6 is a diagram illustrating the separation between a photosensitive drum and a developing roller. It is a figure which shows structures, such as a control part. It is a flowchart which shows operation | movement of a control part. It is a flowchart which shows recovery operation | movement. 10 is a flowchart illustrating an operation of a control unit according to Modification 1. 10 is a flowchart showing a setting operation for a predetermined time of a control unit according to Modification 1. 10 is a flowchart showing a setting operation for a predetermined time of a control unit according to Modification 2. 10 is a flowchart showing a recovery operation of a control unit according to Modification 3. 10 is a flowchart illustrating a recovery operation of a control unit according to Modification 4. 10 is a flowchart showing a recovery operation of a control unit according to Modification 5. 14 is a flowchart showing a recovery operation of a control unit according to Modification 6.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the overall configuration of a color printer as an example of an image forming apparatus will be described, and then the features of the present invention will be described in detail.

  In the following description, the direction of the color printer is defined as “front side” on the left side toward the paper surface of FIG. 1, “rear side” on the right side toward the paper surface, “left side” on the back side toward the paper surface, and toward the paper surface. Let the near side be the “right side”. In addition, the vertical direction toward the page is defined as the “vertical direction”.

  As shown in FIG. 1, the color printer 1 includes a paper feeding unit 20 that supplies a sheet P as an example of a transfer medium in an apparatus main body 10 and an image forming unit 30 that forms an image on the fed paper P. And a paper discharge unit 90 for discharging the paper P on which the image is formed.

  The paper feed unit 20 mainly includes a paper feed tray 21 that stores the paper P and a paper transport device 22 that transports the paper P in the paper feed tray 21 to the image forming unit 30.

  The image forming unit 30 mainly includes an optical scanner 40 as an example of an exposure unit, four process units 50, a transfer unit 70, a cleaning device 60, and a fixing unit 80.

  The optical scanner 40 is disposed above the plurality of process units 50, and includes a laser light emitting unit (not shown), a polygon mirror, a lens, a reflecting mirror, and the like that are not shown. In the optical scanner 40, the laser beam is reflected by a polygon mirror or a reflecting mirror or passes through a lens and emitted, and is irradiated on the surface of a photosensitive drum 51 as an example of a photosensitive member by high-speed scanning. The

  The plurality of process units 50 are arranged side by side in the front-rear direction. The process unit 50 includes a photosensitive drum 51, a charger 52, a developing roller 54 as an example of a developing unit, a supply roller 55, and a toner storage chamber 56 for storing toner as an example of a developer. I have. Further, the process unit 50 includes a cleaning roller 57 that temporarily collects toner on the photosensitive drum 51 and a static eliminator 58 that lowers the potential of the surface of the photosensitive drum 51.

  In the process unit 50, those indicated by reference numerals 50K, 50Y, 50M, and 50C containing toners of black, yellow, magenta, and cyan are arranged in this order from the upstream side in the conveyance direction of the paper P. In the present specification and drawings, when the photosensitive drum 51 and the developing roller 54 corresponding to the color of the toner are specified, K, Y, M are associated with black, yellow, magenta, and cyan, respectively. , C is attached.

  As shown in FIG. 3, the photosensitive drum 51 includes a conductive element tube 51 </ b> A as an example of a base material and a photosensitive layer 51 </ b> B provided on the surface of the element tube 51 </ b> A. The photosensitive layer 51B is formed of a positively chargeable organic photosensitive layer in which a charge generation material, an electron transport material, and a hole transport material are dispersed in a resin. The elementary tube 51 </ b> A is connected to the ground potential of the color printer 1.

  The charger 52 includes a charging wire 52A and a grid electrode 52B provided between the charging wire 52A and the photosensitive drum 51 and having a plurality of slits.

  The developing roller 54 contacts the photosensitive drum 51 and supplies toner to the electrostatic latent image on the photosensitive drum 51 to develop the electrostatic latent image with toner. In this embodiment, when the toner is supplied from the developing roller 54 to the photosensitive drum 51, the toner is positively charged by the sliding contact between the developing roller 54 and the supply roller 55. It has come to be.

  As shown in FIG. 2, the developing roller 54 can be moved toward and away from the photosensitive drum 51 by controlling a known contact / separation mechanism TM by the control unit 100. Specifically, in the color mode, all the developing rollers 54K, 54Y, 54M, and 54C come into contact with the corresponding photosensitive drums 51K, 51Y, 51M, and 51C, and the respective photosensitive drums 51K, 51Y, 51M, and 51C are in contact with each other. Toner is supplied to the printer. In the monochrome mode, only the black developing roller 54K contacts the photosensitive drum 51K, and the other three color developing rollers 54Y, 54M, and 54C are separated from the corresponding photosensitive drums 51Y, 51M, and 51C. It is like that. Further, in the cleaning mode described later, all the developing rollers 54K, 54Y, 54M, and 54C are separated from the corresponding photosensitive drums 51K, 51Y, 51M, and 51C, respectively.

  As shown in FIG. 1, a plurality of cleaning rollers 57 are provided adjacent to each photosensitive drum 51 so as to correspond to each photosensitive drum 51. A holding bias having a polarity opposite to that of the toner is applied to the cleaning roller 57, so that the toner adhering to the photosensitive drum 51 can be temporarily held by the cleaning roller 57. It has become. Further, an ejection bias having the same polarity as that of the toner is applied to the cleaning roller 57, so that the toner held by the cleaning roller 57 can be discharged to the photosensitive drum 51, that is, moved. It has become.

  The static eliminator 58 uniformly lowers the surface potential of the photosensitive drum 51 over the entire axial direction of the photosensitive drum 51, and irradiates the entire axial direction of the photosensitive drum 51 with light. It is configured. The static eliminator 58 is provided between the transfer roller 74 and the cleaning roller 57 along the rotation direction of the photosensitive drum 51.

  The transfer unit 70 is provided between the paper feeding unit 20 and each process unit 50, and includes a driving roller 71, a driven roller 72, a conveyance belt 73, and a transfer roller 74 as an example of a transfer unit. .

  The driving roller 71 and the driven roller 72 are arranged in parallel in a spaced manner in the front-rear direction, and a conveyance belt 73 formed of an endless belt is stretched between them. The outer surface of the conveyance belt 73 is in contact with each photosensitive drum 51. In addition, four transfer rollers 74 that sandwich the conveyor belt 73 with the respective photosensitive drums 51 are arranged inside the conveyor belt 73 so as to face the respective photosensitive drums 51. A transfer bias is applied to the transfer roller 74 during transfer.

  The charger 52, the developing roller 54, the transfer roller 74, the static eliminator 58, and the cleaning roller 57 provided around the photosensitive drum 51 are arranged in this order in the rotation direction of the photosensitive drum 51. .

  The cleaning device 60 is a device that slidably contacts the conveyance belt 73 and collects toner or the like adhering to the conveyance belt 73, and is disposed facing the lower side of the conveyance belt 73.

  The fixing unit 80 is disposed on the rear side of each process unit 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82 that is disposed to face the heating roller 81 and presses the heating roller 81.

  In the image forming unit 30 configured as described above, first, the surface of each photosensitive drum 51 is uniformly charged positively by the charger 52 and then exposed by the optical scanner 40. As a result, positive and negative charges are generated inside the photosensitive layer 51B (see FIG. 3), and the negative charges are transported to the surface, so that the positive charges charged on the surface are canceled by the negative charges. An electrostatic latent image is formed. Thereafter, the toner in the developing cartridge 53 is supplied to the electrostatic latent image on the photosensitive drum 51 by the developing roller 54, so that the toner image is carried on the photosensitive drum 51.

  Next, the paper P supplied on the conveyor belt 73 passes between each photosensitive drum 51 and each transfer roller 74, so that the toner image carried on each photosensitive drum 51 is on the paper P. Transcribed. Then, as the paper P passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the paper P is thermally fixed.

  The paper discharge unit 90 mainly includes a plurality of transport rollers 91 that transport the paper P. The sheet P on which the toner image has been transferred and heat-fixed is transported by the transport roller 91 and discharged outside the apparatus main body 10.

  As shown in FIG. 3, the color printer 1 includes a control unit 100, a temperature sensor 200 as an example of a temperature acquisition unit, a wire bias circuit 210, a grid bias circuit 220 that forms a charging unit together with the grid electrode 52B, A drum driving mechanism 230, a developing bias circuit 240, a transfer bias circuit 250, a static eliminator driving circuit 260, and a cleaning bias circuit 270 are provided.

  The wire bias circuit 210 is a circuit that applies a wire current to the charging wire 52A of each charger 52, and the grid bias circuit 220 applies a grid voltage as an example of a charging bias to the grid electrode 52B of each charger 52. Circuit. The drum driving mechanism 230 is a mechanism for rotating the photosensitive drum 51 and includes a motor, a gear, a clutch, and the like. The developing bias circuit 240 is a circuit that applies a developing bias to each developing roller 54.

  The transfer bias circuit 250 is a circuit that applies a transfer bias to each transfer roller 74, and the static eliminator drive circuit 260 is a circuit that drives each static eliminator 58. The cleaning bias circuit 270 is a circuit that applies a cleaning voltage to each cleaning roller 57. Each bias described above may be a voltage or a current.

  The control unit 100 includes a CPU, a ROM, a RAM, and the like. In accordance with a program prepared in advance or a signal input from the temperature sensor 200, the control unit 100 receives a print command, the above-described paper feeding unit 20, and the image forming unit 30 ( The circuits 210 to 270) and the paper discharge unit 90 are controlled. The control unit 100 mainly performs an image forming operation for forming a toner image on the paper P, and a recovery operation for reducing the residual charge remaining in the photosensitive layer 51B of the photosensitive drum 51 and restoring the charging performance of the photosensitive drum 51. And can be executed.

  Specifically, the control unit 100 includes a wire bias control unit 110, a grid bias control unit 120, a drum drive unit 130, a count unit 131, a print count unit 132, a development bias control unit 140, and a transfer bias control. Unit 150, static eliminator control unit 160, and cleaning bias control unit 170. In other words, the control unit 100 operates based on a program stored in a storage unit (not shown), so that the wire bias control unit 110, the grid bias control unit 120, the drum driving unit 130, the count unit 131, the print count. Functions as a unit 132, a developing bias control unit 140, a transfer bias control unit 150, a static eliminator control unit 160, and a cleaning bias control unit 170. In the present embodiment, the grid bias control unit 120 and the drum driving unit 130 function as recovery means.

  The wire bias control unit 110 has a function of controlling the wire current applied to each charging wire 52 </ b> A by controlling the wire bias circuit 210. Specifically, the wire bias control unit 110 controls the wire bias circuit 210 so as to apply a constant wire current to each charging wire 52A during print control.

  The grid bias control unit 120 has a function of controlling a positive grid voltage applied to each grid electrode 52B by controlling the grid bias circuit 220. Specifically, the grid bias control unit 120 sets the grid voltage Vg applied to each grid electrode 52B to the first grid voltage Vg1 during the image forming operation, and the grid bias control unit 120 performs the grid operation during the recovery operation performed after the image forming operation. The voltage Vg is set to a second grid voltage Vg2 that is larger than the first grid voltage Vg1. In the recovery operation, the grid bias control unit 120 sets the grid voltage Vg to either the second grid voltage Vg2 or the third grid voltage Vg3 that is larger than the second grid voltage Vg2 according to the conditions. It is also configured as follows.

  The drum driving unit 130 has a function of controlling the operation of the photosensitive drum 51 by controlling the drum driving mechanism 230. In the present embodiment, when the photosensitive drum 51 is rotated, the drum driving unit 130 controls the drum driving mechanism 230 so that the photosensitive drum 51 always rotates at a constant rotational speed. In the recovery operation, the drum driving unit 130 continues the rotation of the photosensitive drum 51 from the time when the grid voltage Vg is made larger than that at the time of image formation until the photosensitive drum 51 rotates once. The drum driving mechanism 230 is controlled so that the rotation of the photosensitive drum 51 is stopped after the drum 51 is rotated once.

  The counting unit 131 counts the total time of image forming operations from the past by accumulating the time during which the image forming operation is performed from the time when the photosensitive drum 51 is in a new state to the present. It has a function of measuring the usage amount of the body drum 51. The time counted by the counting unit 131, that is, the count value is reset by replacing the photosensitive drum 51. Further, the counting method of the counting unit 131 may be a subtraction method or an addition method.

  The developing bias controller 140 has a function of controlling the developing bias applied to the developing roller 54 by controlling the developing bias circuit 240. Specifically, the development bias controller 140 performs development so that a constant positive development bias larger than the surface potential of the exposed portion of the photosensitive drum 51 is applied to the development roller 54 during the image forming operation. The bias circuit 240 is controlled.

  The transfer bias control unit 150 has a function of controlling a negative transfer bias applied to each transfer roller 74 by controlling the transfer bias circuit 250. The transfer bias controller 150 is configured to turn off the transfer bias during the recovery operation.

  The static eliminator control unit 160 has a function of controlling the static eliminator 58 on and off by controlling the static eliminator driving circuit 260 according to the temperature acquired by the temperature sensor 200 and the like. Specifically, the static eliminator control unit 160 determines whether or not the temperature is equal to or higher than a predetermined temperature. If the temperature is lower than the predetermined temperature, the static eliminator 58 is turned on in the image forming operation and is equal to or higher than the predetermined temperature. In the image forming operation, the static eliminator driving circuit 260 is controlled so that the static eliminator 58 is turned off. The predetermined temperature can be set as appropriate through experiments, simulations, and the like. Further, the static eliminator control unit 160 controls the static eliminator driving circuit 260 so that the static eliminator 58 is turned OFF in the recovery operation.

  The cleaning bias controller 170 has a function of controlling the cleaning voltage Vc applied to each cleaning roller 57 by controlling the cleaning bias circuit 270. Specifically, the cleaning bias controller 170 sets the cleaning voltage Vc to a negative first cleaning voltage Vc1 in the image forming operation, and sets the cleaning voltage Vc to a positive second cleaning voltage Vc2 in the cleaning mode. In the recovery operation, the cleaning voltage Vc is set to the third cleaning voltage Vc3 that is higher than the second cleaning voltage Vc2. In this embodiment, Vc2 <Vc3 is set, but the present invention is not limited to this, and Vc2 = Vc3 or Vc2> Vc3 may be set.

  Next, the operation of the control unit 100 will be described in detail. In the following description, description of known control such as control of the optical scanner 40 is omitted.

  As shown in FIG. 4, the control unit 100 first determines whether or not there is a print command (S1). In step S1, if the control unit 100 determines that there is no print command (No), the control unit 100 ends this control.

  In step S2, the control unit 100 determines whether or not the temperature is lower than a predetermined temperature. If the control unit 100 determines that the temperature is lower than the predetermined temperature (Yes), the static eliminator 58 is turned on (S3), and the process proceeds to step S4. If it is determined in step S2 that the temperature is equal to or higher than the predetermined temperature (No), the control unit 100 proceeds to step S4 while keeping the static eliminator 58 in the OFF state.

  In step S <b> 4, the control unit 100 executes an image forming operation for forming a toner image on one sheet of paper P. At this time, the control unit 100 sets the grid voltage Vg to the first grid voltage Vg1, and sets the cleaning voltage Vc to the negative first cleaning voltage Vc1. As a result, the surface potential of the photosensitive drum 51 becomes a potential suitable for exposure and development, and positive toner remaining on the photosensitive drum 51 without being transferred to the paper P is collected by the cleaning roller 57.

  After step S4, the control unit 100 determines whether or not the continuous printing time T is shorter than the predetermined time Tth (S5). Here, the continuous printing time T is a time during which the image forming operation is continuously performed, and is counted by the print counting unit 132. The continuous printing time T counted by the printing counting unit 132 is reset every time this control is finished.

  If it is determined in step S5 that the continuous printing time T is shorter than the predetermined time Tth (Yes), the control unit 100 determines whether or not printing for all the number of sheets instructed by the printing command has been completed. (S8). If it is determined in step S8 that printing has not ended (No), the control unit 100 returns to the process of step S4.

  When it is determined in step S5 that the continuous printing time T is equal to or longer than the predetermined time Tth (No), the control unit 100 interrupts the image forming operation (S6), and indicates a flag indicating that the image forming operation is interrupted. F is set to 1 (S7). If it is determined in step S8 that printing has ended (Yes), or after step S7, the control unit 100 executes the cleaning mode (S9). That is, the control unit 100 executes the cleaning mode (S9) and the recovery operation (S100) after the printing is completed, and forms an image when the continuous printing time T becomes equal to or longer than the predetermined time Tth during printing. The operation is temporarily interrupted to execute the cleaning mode or the recovery operation.

  In the cleaning mode, the control unit 100 separates all the developing rollers 54 from the photosensitive drum 51, and sets the cleaning voltage Vc to the positive second cleaning voltage Vc2. As a result, the toner held on the cleaning roller 57 is discharged to the photosensitive drum 51 and then transferred from the photosensitive drum 51 to the conveying belt 73 without being collected by the developing roller 54, and the cleaning device 60. To be recovered. Further, by separating the developing roller 54 from the photosensitive drum 51 in the cleaning mode, the developing roller 54 is separated from the photosensitive drum 51 in the recovery operation performed after the cleaning mode.

  After completion of the cleaning mode, the control unit 100 performs a recovery operation (S100). The recovery operation will be described later in detail.

  After step S100, the control unit 100 determines whether or not the flag F is 0, that is, whether or not the image forming operation is not interrupted (S10). If it is determined in step S10 that the flag F is 1, that is, the image forming operation is interrupted (No), the control unit 100 returns the flag F to 0 (S11), and the continuous printing time T Is reset to 0 (S12), and the process returns to step S4. If it is determined in step S10 that the flag F is 0, that is, the image forming operation is not interrupted (Yes), the control unit 100 ends this control.

Next, the recovery operation will be described in detail.
As shown in FIG. 5, in the recovery operation, the control unit 100 first has a count value counted by the count unit 131, that is, a total time that is an integrated value of the time when the image forming operation was performed in the past is less than a predetermined value. By determining whether or not there is, it is determined whether or not the usage amount of the photosensitive drum 51 is less than a predetermined value (S101). When the count value is less than the predetermined value in step S101, that is, when the usage amount of the photosensitive drum 51 is less than the predetermined value (Yes), the control unit 100 detects that the temperature detected by the temperature sensor 200 is higher than the predetermined temperature. It is determined whether or not is larger (S102).

  When the temperature is higher than the predetermined temperature in step S102 (Yes), the control unit 100 sets the grid voltage Vg to the second grid voltage Vg2 that is higher than the first grid voltage Vg1 during the image forming operation (S103). ). If it is determined in step S101 that the count value, that is, the usage amount of the photosensitive drum 51 is equal to or greater than the predetermined value (No), or if it is determined in step S102 that the temperature is equal to or lower than the predetermined temperature (No), the control is performed. The unit 100 sets the grid voltage Vg to the third grid voltage Vg3 that is larger than the second grid voltage Vg2 (S104). That is, in the recovery operation, the controller 100 increases the grid voltage Vg as the usage amount of the photosensitive drum 51 increases, and increases the grid voltage Vg as the temperature decreases.

  After step S103 or step S104, the controller 100 turns off the static eliminator 58 (S105), turns off the transfer bias (S106), sets the cleaning voltage Vc to the third cleaning voltage Vc3, and then moves the photosensitive drum 51. By making one rotation (S108), the recovery operation is completed.

According to the above, the following effects can be obtained in the present embodiment.
In the recovery operation, by making the grid voltage Vg larger than in the image forming operation and rotating the photosensitive drum 51 once, a larger amount of charge is transferred from the charger 52 to the photosensitive drum 51 than in the image forming operation. It is given over the entire circumference of the body drum 51. Therefore, the residual charge inside the photosensitive drum 51 generated during the image forming operation can be reduced by a large amount of charges, and the charging performance of the photosensitive drum 51 can be recovered.

  In the recovery operation, when the transfer bias is turned off, the surface potential of the photosensitive drum 51 is suppressed from being lowered due to the influence of the transfer bias, for example, compared to the case where a negative transfer bias is applied. It is possible to suppress the residual charge removal operation inside the photosensitive drum 51 from being suppressed.

  In the recovery operation, by separating the developing roller 54 from the photosensitive drum 51, the surface potential of the photosensitive drum 51 does not decrease due to the influence of the developing bias of the developing roller 54. It is possible to suppress the residual charge removal operation inside the drum 51 from being suppressed. In the recovery operation, when the developing roller 54 is brought into contact with the photosensitive drum 51, for example, when the developing bias is turned off or negative, the surface potential of the photosensitive drum 51 is lowered, and the above-described problem occurs.

  Since the recovery operation is performed after the image forming operation, for example, the waiting time from when the print command is received until the image forming operation is performed can be shortened as compared with the case where the recovery operation is performed before the image forming operation. .

  When the continuous printing time T becomes equal to or longer than the predetermined time Tth, that is, when the image forming operation is continuously executed for the predetermined time Tth, the image forming operation is interrupted and the recovery operation is executed. It is possible to satisfactorily reduce the residual charge before the amount of accumulated residual charge inside the photosensitive drum 51 that increases proportionally becomes too large. As a result, it is possible to suppress the influence of residual charges in subsequent printing.

  When the usage amount of the photoconductive drum 51 is large, the charge transport capability inside the photoconductive drum 51 is lowered. In this case, the grid voltage Vg is increased to the third grid voltage Vg3, and the recovery operation is performed. (S101: No), more charge can be given from the charger 52 to the photosensitive drum 51, and the residual charge inside the photosensitive drum 51 with reduced charge transport capability can be reduced well.

  When the temperature is low, the charge transport capability inside the photosensitive drum 51 is lowered. In this case, the recovery operation is performed by increasing the grid voltage Vg to the third grid voltage Vg3 (S102: No). It is possible to give a larger amount of charge to the photosensitive drum 51 from the charger 52, and to satisfactorily reduce the residual charge inside the photosensitive drum 51 whose charge transport capability is reduced.

  In the recovery operation, by turning off the charge eliminator 58, the surface potential of the photosensitive drum 51 is suppressed from being lowered by light from the charge eliminator 58, for example, compared to turning on the charge eliminator 58. It is possible to prevent the residual charge removal operation inside the photosensitive drum 51 from being suppressed due to the decrease in the above.

  In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below. In the following description, members and steps having substantially the same structure as those of the above embodiment are denoted by the same reference numerals, and description thereof is omitted.

  For example, as shown in FIGS. 6 and 7, the frequency of executing the recovery operation may be increased according to the conditions. Specifically, the flowchart of FIG. 6 includes a new process (S200) for setting a predetermined time Tth, which is a threshold of the continuous printing time T, between steps S4 and S5 of the flowchart of FIG. It has become.

  As shown in FIG. 7, when starting the step S200, the control unit 100 first determines whether or not the usage value of the photosensitive drum 51 is less than the predetermined value by determining whether or not the count value is less than the predetermined value. Whether or not (S201). When it is determined in step S201 that the count value is less than the predetermined value (Yes), the control unit 100 determines whether or not the temperature is higher than the predetermined temperature (S202).

  When the temperature is higher than the predetermined temperature in Step S202 (Yes), the control unit 100 sets the predetermined time Tth to the first time T1 (S203). When the count value is greater than or equal to the predetermined value in step S201 (No), or when the temperature is less than or equal to the predetermined temperature in step S202 (No), the control unit 100 sets the predetermined time Tth to be greater than the first time T1. A short second time T2 is set (S204).

  As described above, in step S204, by setting the predetermined time Tth to the second time T2 shorter than the first time T1, it becomes easier to determine No in step S5 of FIG. 6, so the frequency of the recovery operation is increased. be able to. In other words, in this embodiment, the control unit 100 increases the frequency of executing the recovery operation as the usage amount of the photosensitive drum 51 is larger, and increases the frequency of executing the recovery operation as the temperature is lower. Therefore, according to this embodiment, when the amount of use of the photoconductive drum 51 increases or the temperature decreases, the charge transport capability inside the photoconductive drum 51 decreases, so that the frequency of the recovery operation is increased. By increasing the value, it is possible to satisfactorily reduce the residual charge inside the photosensitive drum 51 whose charge transport capability has been lowered.

  As shown in FIG. 8, a condition for increasing the frequency of the recovery operation may be further added. Specifically, in the flowchart of FIG. 8, a new step S205 is provided between steps S202 and S203 of the flowchart of FIG.

  Step S205 is a process of determining whether or not the static elimination time, which is the time during which the static eliminator 58 is turned on during the image forming operation, is less than the specified time. The measurement of the static elimination time may be performed using a counter that starts counting when the static eliminator 58 is turned on and ends counting when the static eliminator 58 is turned off. The static elimination time measured by this counter is reset, for example, after performing the recovery operation (S100).

  If it is determined in step S205 that the static elimination time is less than the specified time (Yes), the control unit 100 sets the predetermined time Tth to the first time T1 (S203). When it is determined in step S205 that the static elimination time is equal to or longer than the specified time (No), the control unit 100 sets the predetermined time Tth to the second time T2 shorter than the first time T1 (S204).

  That is, in this embodiment, the control unit 100 increases the frequency of executing the recovery operation as the static elimination time is longer. According to this, even if the residual charge inside the photosensitive drum 51 increases due to the long charge removal time, the frequency of the recovery operation is increased according to the increase in the residual charge. The residual charge inside 51 can be reduced satisfactorily.

  As shown in FIG. 9, in the recovery operation, the number of rotations of the photosensitive drum 51 may be changed according to conditions. Specifically, in the flowchart of FIG. 9, a new step S109 is provided after step S103 of the flowchart of FIG. 5, a new step S110 is provided after step S104, and a new step S108 is provided instead of the step S108 of FIG. Step S111 is provided.

  Step S109 is a process of setting the number of rotations N of the photosensitive drum 51 to the first number of rotations N1. Here, the first number of rotations N1 can be set to a natural number such as 1, 2, for example.

  Step S110 is a process of setting the number of rotations N of the photosensitive drum 51 to a second number of rotations N2 that is greater than the first number of rotations N1. Here, the second number of rotations N2 can be set to a natural number greater than the first number of rotations N1, for example, 2 or 3.

  Step S111 is a process of rotating the photosensitive drum 51 by the number of rotations N set in step S109 or step S110. By providing such a new process, in this embodiment, the control unit 100 increases the number of rotations of the photosensitive drum 51 and increases the temperature as the usage amount of the photosensitive drum 51 increases (S101: No). Is lower (S102: No), the number of rotations of the photosensitive drum 51 is increased. Therefore, according to this embodiment, when the charge transport capability inside the photosensitive drum 51 is reduced due to an increase in the usage amount of the photosensitive drum 51 or a decrease in temperature, the photosensitive drum 51 has a By increasing the number of rotations, the amount of charge applied to the photoconductive drum 51 can be increased, and the residual charge inside the photoconductive drum 51 whose charge transport capability has been reduced can be satisfactorily reduced.

  Further, as shown in FIG. 10, in the recovery operation, the rotation speed of the photosensitive drum 51 may be changed according to conditions. Specifically, in the flowchart of FIG. 10, a new step S121 is provided instead of step S103 of the flowchart of FIG. 5, and a new step S122 is provided instead of step S104.

  Step S121 is a process of setting the rotational speed v of the photosensitive drum 51 to a second rotational speed v2 that is lower than the first rotational speed v1 that is the rotational speed of the photosensitive drum 51 in the image forming operation. Step S122 is a process of setting the rotation speed v of the photosensitive drum 51 to a third rotation speed v3 that is slower than the second rotation speed v2.

  By providing such a new process, in this embodiment, the control unit 100 causes the rotation speed v of the photosensitive drum 51 to be higher than that during the image forming operation in a state where the charger 52 is operated in the recovery operation. Slow down. As a result, in the recovery operation, the charge given from the charger 52 to the photoconductive drum 51 before the photoconductive drum 51 makes one rotation is larger than that during the image forming operation. The effect of can be obtained.

  Further, in this embodiment, the larger the usage amount of the photosensitive drum 51 (S101: No), the slower the rotation speed v of the photosensitive drum 51 and the lower the temperature (S102: No), the lower the temperature of the photosensitive drum 51. The rotational speed v is slowed down. Therefore, according to this embodiment, when the charge transport capability inside the photosensitive drum 51 is reduced due to an increase in the usage amount of the photosensitive drum 51 or a decrease in temperature, the photosensitive drum 51 has a By slowing down the rotation speed v, the amount of charge applied to the photosensitive drum 51 can be increased, and the residual charge inside the photosensitive drum 51 with reduced charge transport capability can be reduced well.

  As shown in FIG. 11, a condition for changing the grid voltage Vg or the like in the recovery operation may be further added. Specifically, in the flowchart of FIG. 11, a new step S131 is provided between steps S102 and S103 of the flowchart of FIG.

  Step S131 is the same process as step S205 described above, and is a process of determining whether or not the static elimination time, which is the time during which the static eliminator 58 is turned on, is less than the specified time. If it is determined in step S131 that the static elimination time is less than the specified time (Yes), the control unit 100 sets the grid voltage Vg to the second grid voltage Vg2 (S103), and the number of rotations N of the photosensitive drum 51 is reached. Is set to the first rotation number N1 (S109).

  When it is determined in step S131 that the static elimination time is equal to or longer than the specified time (No), the control unit 100 sets the grid voltage Vg to the third grid voltage Vg3 that is larger than the second grid voltage Vg2 (S104). The rotation number N is set to a second rotation number N2 that is larger than the first rotation number N1 (S110). That is, in this mode, in the recovery operation, the controller 100 increases the grid voltage Vg as the static elimination time increases, and increases the number of rotations of the photosensitive drum 51 as the static elimination time increases.

  According to this, even when the residual charge inside the photosensitive drum 51 increases due to the long charge removal time, the grid voltage Vg is increased or the number of rotations N is increased in accordance with the increase in the residual charge. By increasing the number, the residual charge inside the photosensitive drum 51 can be reduced well.

  As shown in FIG. 12, in the recovery operation, the rotation speed v of the photosensitive drum 51 may be decreased as the static elimination time is longer. Specifically, in the flowchart of FIG. 12, step S131 described above is provided between step S102 and step S105 of the flowchart of FIG. According to this, even if the residual charge inside the photoconductive drum 51 increases due to the long charge removal time, the rotational speed v of the photoconductive drum 51 is decreased according to the increase in the residual charge. As a result, a large amount of charge can be applied from the charger 52 to the photosensitive drum 51, so that the residual charge inside the photosensitive drum 51 can be reduced well.

  In the above-described embodiment, the grid voltage Vg is exemplified as the charging bias. However, the present invention is not limited to this, and the charging bias may be, for example, a wire current applied to the charging wire 52A. In a structure including a charging roller that charges the surface of the photosensitive drum while contacting the photosensitive drum, a bias (current or voltage) applied to the charging roller may be used.

  In the above-described embodiment, the photosensitive drum 51 is exemplified as the photosensitive member. However, the present invention is not limited to this, and may be, for example, a belt-shaped photosensitive member.

  In the embodiment, the optical scanner 40 is exemplified as the exposure unit, but the present invention is not limited to this, and may be, for example, an LED head.

  In the embodiment, the paper P such as a thick paper, a postcard, and a thin paper is exemplified as an example of the transfer medium. However, the present invention is not limited thereto, and may be an intermediate transfer belt, for example.

  In the above embodiment, the present invention is applied to the color printer 1. However, the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.

DESCRIPTION OF SYMBOLS 1 Color printer 51 Photosensitive drum 52 Charging device 54 Developing roller 74 Transfer roller 100 Control part P Paper

Claims (22)

A photoreceptor,
A charging unit for charging the photoreceptor;
An exposure unit for exposing the photoreceptor;
A developing unit for developing the electrostatic latent image formed on the photoreceptor with a developer;
A transfer portion for transferring the developer image carried on the photoreceptor to a transfer medium;
A control unit,
The controller is
An image forming operation for forming the developer image on the transfer medium;
When the image forming operation is not performed, a recovery operation is performed in which a larger amount of charge is applied from the charging unit to the photoconductor than during the image forming operation to rotate the photoconductor one or more times. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the control unit makes the charging bias of the charging unit larger in the recovery operation than in the image forming operation.   3. The control unit according to claim 1, wherein, in the recovery operation, the rotation speed of the photoconductor is made slower than that during the image forming operation in a state where the charging unit is operated. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the control unit turns off a transfer bias of the transfer unit in the recovery operation.   5. The image forming apparatus according to claim 1, wherein the control unit separates the developing unit from the photoconductor in the recovery operation. 6.   The image forming apparatus according to claim 1, wherein the control unit executes the recovery operation after the image forming operation.   The image forming apparatus according to claim 6, wherein the control unit interrupts the image forming operation and executes the recovery operation when the image forming operation is continuously executed for a predetermined time.   The image forming apparatus according to claim 1, wherein the control unit increases the frequency of executing the recovery operation as the usage amount of the photoconductor increases.   The said control part increases the frequency | count of rotating the said photoreceptor, so that the usage-amount of the said photoreceptor is large in the said recovery operation | movement. Image forming apparatus.   8. The image forming apparatus according to claim 1, wherein the controller increases the charging bias as the usage amount of the photosensitive member increases in the recovery operation. 9.   8. The image according to claim 1, wherein, in the recovery operation, the rotation speed of the photoconductor is reduced as the usage amount of the photoconductor increases. 9. Forming equipment. A temperature acquisition unit for acquiring the temperature,
The image forming apparatus according to claim 1, wherein the controller increases the frequency of executing the recovery operation as the temperature is lower. A temperature acquisition unit for acquiring the temperature,
The image forming apparatus according to claim 1, wherein the controller increases the number of rotations of the photoconductor as the temperature is lower in the recovery operation. A temperature acquisition unit for acquiring the temperature,
The image forming apparatus according to claim 1, wherein the control unit increases the charging bias as the temperature is lower in the recovery operation. A temperature acquisition unit for acquiring the temperature,
12. The image forming apparatus according to claim 1, wherein the controller slows down the rotation speed of the photoconductor as the temperature is lower in the recovery operation. Comprising a static eliminator for lowering the surface potential of the photoreceptor,
12. The control unit according to claim 1, wherein the control unit increases the frequency of executing the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. 13. The image forming apparatus described. Comprising a static eliminator for lowering the surface potential of the photoreceptor,
12. The control unit according to claim 1, wherein the controller increases the number of rotations of the photoconductor in the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. The image forming apparatus according to claim 1. Comprising a static eliminator for lowering the surface potential of the photoreceptor,
12. The control unit according to claim 1, wherein the control unit increases the charging bias in the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. 13. The image forming apparatus described. Comprising a static eliminator for lowering the surface potential of the photoreceptor,
12. The control unit according to claim 1, wherein the controller slows down the rotational speed of the photoconductor in the recovery operation as the time during which the static eliminator is operated during the image forming operation is longer. 2. The image forming apparatus according to item 1. The photoreceptor has a conductive substrate and a photosensitive layer provided on the substrate,
19. The photosensitive layer is formed of a positively charged organic photosensitive layer in which a charge generation material, an electron transport material, and a hole transport material are dispersed in a resin. 2. The image forming apparatus according to item 1. A control method for controlling the operation of a photoconductor and the operation of a charging unit for charging the photoconductor,
A control method, wherein when the image forming operation is not performed, a larger amount of charge is applied from the charging unit to the photoconductor than during the image forming operation, and the photoconductor is rotated one or more times. A program for operating a control unit for controlling the operation of the photoconductor and the operation of the charging unit for charging the photoconductor,
The control unit
A program characterized in that when the image forming operation is not performed, a larger amount of charge is applied from the charging unit to the photoconductor than at the time of the image forming operation to cause the photoconductor to function as a recovery unit that rotates one or more times. .

Images