JP2013037218A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that prevents as much as possible wasteful toner consumption due to unnecessary refresh in replacing a toner container, and effectively prevents image defect immediately after replacing the toner container.SOLUTION: In an image forming device 100, a refresh process, in which toner is splashed from a developing roller 33 toward a photoreceptor drum 1 to perform toner forcible consumption, is executed after replacing a toner container 6, supplying unused toner to a developing device 3 and executing aging, to selectively transfer deteriorated toner to the surface of the photoreceptor drum 1. Whether to execute the refresh process and the amount of toner to be ejected in the refresh process are determined on the basis of the amount of toner consumed in the developing device 3 within a predetermined period from the latest refresh process to the replacement of the toner container 6.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic process, and more particularly to an image forming apparatus including a detachable toner container for supplying toner to a developing device.

  In general, in a developing device using a one-component developer, by repeating image formation, a toner having a small particle size adheres to the surface of a developing roller (toner carrier) due to a mirror image force due to a high charge amount, This prevents the toner particles from being frictionally charged with the toner carrier. Therefore, the toner is transported to the photosensitive drum (electrostatic latent image carrier) in a state where the toner carrier is not uniformly charged, which may cause problems such as a decrease in image density and image fog. Such a phenomenon is likely to occur particularly when the document printing rate on the image is low, that is, when toner particles are likely to remain on the developing roller due to a small amount of toner flying from the developing roller to the photosensitive drum.

  Therefore, by applying an AC bias superimposed on a DC bias to the developing roller during non-image formation, a pattern with a high printing rate such as a solid image is developed to cause a large amount of toner to fly to the photosensitive drum side, An image forming apparatus capable of executing a so-called refresh mode in which toner on a developing roller is forcibly consumed has been developed. For example, in Patent Document 1, when there are few print dots in one image (the print rate is low), a bias is applied so that the toner on the developing roller is forcibly consumed after image formation, and the toner on the developing roller is refreshed. An image forming apparatus that forms a uniform toner thin layer by charging (replacement) is disclosed.

  On the other hand, in a color image forming apparatus, a system that uses a two-component developer containing toner and a magnetic carrier and replenishes the developing device with a toner container is frequently used. In such a two-component development type image forming apparatus, toner replenishment may not be performed stably immediately before the remaining amount of toner in the toner container becomes empty (empty), and the toner concentration in the developing apparatus is low. It is easy to change. For this reason, the charge amount of the toner tends to increase, and if the toner container is replaced in this state, image fogging or toner scattering may occur after the toner is replenished.

  Further, in a development system that includes a magnetic roller (developer carrier) disposed opposite to the developing roller and supplies toner onto the developing roller using a magnetic brush formed on the surface of the magnetic roller, the toner on the developing roller There is a risk that the charge amount becomes high, the flying property to the photosensitive drum is deteriorated, and the image density is lowered.

  In order to solve such a problem, Patent Document 2 discloses that a developing sleeve of a developing device in which an average printing density (average printing rate) is lower than a predetermined value among a plurality of developing devices is used when a non-image is formed. A color image forming apparatus is disclosed in which the above toner is refreshed and toner is refreshed simultaneously on the developing sleeves of two or more developing devices.

  Further, the unused toner replenished from the toner container has a higher charging ability than the deteriorated toner in the developing device, and has a large electrostatic adhesion to the carrier. Therefore, in Patent Document 3, the number of times that the average printing rate before toner replenishment continuously falls below the threshold value, or the toner replenishment and aging operations to the developing device when the driving time of the developing device reaches a preset value. After refreshing, the number of times the average printing rate has continuously dropped below the threshold, or if the developing device drive time has not reached the preset value, before the toner supply to the developing device and the aging operation In other words, an image forming apparatus that suppresses waste of toner due to forced consumption of undegraded toner and an increase in waste toner is disclosed.

JP 2000-310909 A JP 2003-195607 A JP 2007-34051 A

  By the way, in an image forming apparatus using a two-component developer, when the toner container becomes empty and toner supply to the developing apparatus is not performed, the toner density T / C (ratio of toner to carrier) in the developing apparatus decreases. To do. Therefore, it is possible to determine the replacement timing of the toner container by detecting T / C using a toner concentration sensor such as a magnetic permeability sensor.

  Here, the charge amount of the toner in the developing device when the toner container is replaced varies depending on the printing condition immediately before the toner container is empty. For example, when the average printing rate immediately before the toner container is emptied is low, the toner consumption is reduced, and the toner stays in the developing device for a long time, so the charge amount of the toner is increased. On the other hand, when the average printing rate immediately before the toner container is emptied is high, the toner consumption is increased, and the toner stays in the developing device, so the toner charge amount is reduced.

  However, when refreshing is performed using the method of Patent Document 3 after replacement of the toner container, the refresh operation is performed uniformly before or after toner supply. For this reason, there is a problem in that refresh is executed even when the toner charge amount in the developing device is low and toner does not need to be forcibly consumed, leading to waste of toner.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an image forming apparatus capable of effectively preventing an image defect immediately after replacement of a toner container while minimizing waste of toner due to execution of an unnecessary refresh process when the toner container is replaced. The purpose is to provide.

  In order to achieve the above object, the present invention has a toner carrier that is disposed opposite to an image carrier, carries toner and supplies the image carrier, and a toner image corresponding to an electrostatic latent image on the surface of the image carrier. A developing device that forms toner, a replaceable toner container that contains toner to be replenished to the developing device, and a toner remaining amount detecting means that can detect a toner end in which the toner in the toner container becomes empty, In an image forming apparatus capable of executing a refresh process for discharging toner from the toner carrier side to the image carrier side during non-image formation, toner consumption within a predetermined period from the latest refresh process to the detection of the toner end Control means for determining whether or not to execute the refreshing process immediately after replacement of the toner container based on the amount is provided.

  Further, according to the present invention, in the image forming apparatus having the above-described configuration, the control unit immediately after replacement of the toner container based on a toner consumption amount within a predetermined period from the most recent refresh process until the toner end is detected. A toner discharge amount when the refresh process is executed is determined.

  Further, according to the present invention, in the image forming apparatus having the above-described configuration, the control unit increases the toner discharge amount in steps as the toner consumption amount in a predetermined period from the most recent refresh process to the detection of the toner end is small. It is characterized by increasing.

  According to the present invention, in the image forming apparatus having the above-described configuration, the toner remaining amount detecting unit can detect a near end where the toner in the toner container has become a predetermined amount or less before detecting the toner end, and the control The means determines whether or not the refresh process needs to be performed immediately after replacement of the toner container, or a toner discharge amount when the refresh process is performed, based on a toner consumption amount from the near end to the toner end. It is characterized by that.

  According to the present invention, in the image forming apparatus having the above-described configuration, the control unit calculates a toner consumption amount using an average printing rate within a predetermined period from the most recent refresh process until the toner end is detected. It is characterized by.

  According to the first configuration of the present invention, whether or not the refresh process needs to be performed immediately after the replacement of the toner container is determined based on the toner consumption within a predetermined period from the most recent refresh process until the toner end is detected. As a result, when the amount of toner consumption is large, unnecessary execution of the refreshing process can be stopped and toner waste can be suppressed.

  According to the second configuration of the present invention, in the image forming apparatus having the first configuration, when the execution of the refresh process immediately after the replacement of the toner container is determined, the toner end is detected from the latest refresh process. By determining the toner discharge amount based on the toner consumption amount within a predetermined period until the toner is discharged, waste of toner can be suppressed by setting the toner discharge amount during execution of the refresh process to an appropriate amount.

  Further, according to the third configuration of the present invention, in the image forming apparatus having the second configuration, the control unit has a small amount of toner consumption within a predetermined period from the most recent refresh process until the toner end is detected. By increasing the toner discharge amount stepwise, the deteriorated toner can be sufficiently discharged by increasing the toner discharge amount when the refresh process is executed under the condition that the ratio of the deteriorated toner in the developing device increases.

  According to the fourth configuration of the present invention, in the image forming apparatus having any one of the first to third configurations, the toner remaining amount detecting means detects the toner in the toner container before detecting the toner end. It is possible to detect the near end that has become below the fixed amount, and the control means determines whether or not the refresh process needs to be performed immediately after replacement of the toner container or the refresh process is executed based on the toner consumption from the near end to the toner end. By determining the toner discharge amount at that time, it is possible to determine whether or not the refresh process needs to be performed, which reflects the state of the toner in the developing device more accurately when the toner container is replaced, or an appropriate toner discharge amount.

  According to the fifth configuration of the present invention, in the image forming apparatus having any one of the first to fourth configurations, the control unit is within a predetermined period from the most recent refresh process until the toner end is detected. By calculating the toner consumption amount using the average printing rate, it is possible to calculate the toner consumption amount easily and with high accuracy.

1 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus 100 according to the present invention. Side surface sectional view which shows the example of 1 structure of the developing device 3 used for the image forming apparatus 100 of this invention. Plan sectional drawing which shows one structural example of the stirring part in the image development apparatus 3 of this invention. The figure which shows an example of the bias waveform applied to a developing roller and a magnetic roller Side sectional view schematically showing the toner container 6 1 is a block diagram showing a control path of an image forming apparatus 100 according to the present invention. Flowchart showing a control example of the refresh process when the toner container 6 is replaced The flowchart which shows the other example of a refresh process at the time of replacement | exchange of the toner container 6

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the image forming apparatus of the present invention. In FIG. 1, an image forming apparatus 8 (a monochrome multifunction device is shown as an example here) is provided with an image forming section 8 for forming a monochrome image by charging, exposing, developing, and transferring processes.

  Next, the image forming unit 8 will be described. Around the photosensitive drum 1 rotatably disposed, a charging device 2 for charging the photosensitive drum 1, an exposure device (laser scanning unit or the like) 4 for exposing image information to the photosensitive drum 1, and photosensitive A developing device 3 that forms a toner image on the body drum 1 and a cleaning device 5 that removes toner remaining on the photosensitive drum 1 are disposed. Further, a static eliminator (not shown) for removing residual charges on the surface of the photosensitive drum 1 is provided on the upstream side or the downstream side of the cleaning device 5 with respect to the rotation direction of the photosensitive drum 1 (the direction of arrow A in FIG. 1). It has been. An image forming process is performed on the photosensitive drum 1 while rotating the photosensitive drum 1 in the direction of arrow A.

  The paper P on which the toner image is transferred is accommodated in a paper feed cassette 10 at the lower part of the apparatus, and a nip portion between the photosensitive drum 1 and the transfer roller 9 via the paper feed roller 11 and the registration roller pair 13. It is conveyed to (transfer nip part).

  The image reading unit 20 includes a scanner lamp that illuminates the document during copying, a scanning optical system equipped with a mirror that changes the optical path of reflected light from the document, and a condensing lens that focuses the reflected light from the document to form an image. And a CCD sensor or the like (both not shown) that converts the imaged image light into an electrical signal, and reads a document image and converts it into image data.

  When performing the copying operation, the image reading unit 20 reads the image data of the document and converts it into an image signal. On the other hand, in the image forming unit 8 in the main body of the image forming apparatus 100, the photosensitive drum 1 rotating in the direction A in the drawing is uniformly charged by the charging device 2, and the original image data read by the image reading unit 20 is converted into the original image data. An electrostatic latent image is formed on the photosensitive drum 1 by the laser beam from the exposure device 4 based on this, and toner is attached to the electrostatic latent image by the developing device 3 to form a toner image. The toner is supplied to the developing device 3 from the toner container 6. On the other hand, the paper P is transported from the paper feed cassette 10 to the registration roller pair 13 via the paper feed roller 11 and the paper transport path 12.

  Then, the paper P is conveyed from the registration roller pair 13 to the nip portion between the photosensitive drum 1 and the transfer roller 9 at a predetermined timing, and the toner image formed on the surface of the photosensitive drum 1 at the nip portion is the paper P. Transcribed above. Thereafter, the toner remaining on the surface of the photosensitive drum 1 is removed by the cleaning device 5 in preparation for the subsequent formation of a new electrostatic latent image. The paper P on which the toner image is transferred is conveyed to the fixing unit 7.

  The sheet P conveyed to the fixing unit 7 is heated and pressurized when passing through the nip portion (fixing nip portion) of the pair of fixing rollers 14 to fix the toner image on the surface of the sheet P, thereby forming a predetermined image. Is done. The paper P on which the image is formed is distributed in the transport direction by the transport guide member 16 disposed in the branch portion of the paper transport path 12 through the transport roller pair 15 and is sent as it is (or sent to the reverse transport path 19 to both sides. After being copied), the sheet is discharged to the discharge tray 18 via the discharge roller pair 17.

  Specifically, the sheet conveying path 12 is bifurcated into the left and right forks on the downstream side of the conveying roller pair 15, and one path (the path branched in the right direction in FIG. 1) communicates with the discharge tray 18. ing. The other path (the path branched in the left direction in FIG. 1) is configured to communicate with the reverse conveyance path 19.

  2 is a side sectional view of the developing device 3 mounted on the image forming apparatus of the present invention, and FIG. 3 is a plan sectional view of the developing device 3 (a sectional view taken along the line XX ′ in FIG. 2). As shown in FIGS. 2 and 3, the developing device 3 includes a developing container 30 that stores a two-component developer (hereinafter also simply referred to as a developer) including toner and a magnetic carrier (hereinafter also simply referred to as a carrier). The developing container 30 is partitioned into a first stirring chamber 30b and a second stirring chamber 30c by a partition wall 30a. In the first and second agitating chambers 30b and 30c, a first agitating screw 31a and a first agitating screw 31a for charging the toner (positively charged toner) supplied from the toner container 6 (see FIG. 1) with a carrier, agitating the mixture, and charging them. Two stirring screws 31b are rotatably disposed.

  Then, the developer is agitated by the first agitating screw 31a and the second agitating screw 31b and conveyed in the axial direction (the directions of arrows B and C in FIG. 3), and the developer passages formed at both ends of the partition wall 30a. It circulates between the 1st and 2nd stirring chambers 30b and 30c via 30a and 30b. That is, a developer circulation path is formed in the developer container 30 by the first and second stirring chambers 30b and 30c and the developer passages 40a and 40b.

  The developing container 30 extends obliquely upward to the left in FIG. 2, and a magnetic roller 32 is disposed above the first stirring screw 31 a in the developing container 30, and the developing roller 33 is disposed obliquely upward to the left of the magnetic roller 32. Are arranged opposite to each other. The developing roller 33 faces the photosensitive drum 1 on the opening side (left side in FIG. 2) of the developing container 30, and the magnetic roller 32 and the developing roller 33 are clockwise in FIG. Rotate to.

  A toner concentration sensor 41 is disposed in the second stirring chamber 30c so as to face the second stirring screw 31b, and a supply port 61a (see FIG. 5) of the toner container 6 is connected to the toner supply port 30d. As shown in FIG. 3, the toner replenishing port 30d is disposed at the end of the second stirring chamber 30c as viewed in a plan view.

  As the toner concentration sensor 41, a magnetic permeability sensor that detects the magnetic permeability of the two-component developer in the developing container 30 is used. Here, the toner concentration is the ratio (T / C) of the toner to the magnetic carrier in the developer, and in this embodiment, the toner permeability is detected by the toner concentration sensor 41, and the detection result thereof. Is output to a control unit 90 (see FIG. 6) which will be described later, and the control unit 90 determines the toner density from the output value of the toner density sensor 41. The control unit 90 transmits a control signal to the toner supply motor 27 (see FIG. 5) according to the determined toner density, and supplies a predetermined amount of toner into the developing container 30 from the toner supply port 30d.

  The sensor output value changes according to the toner concentration. The higher the toner concentration, the higher the ratio of toner to the magnetic carrier, and the higher the ratio of toner that does not pass magnetism, the lower the output value. On the other hand, the lower the toner concentration, the lower the ratio of toner to magnetic carrier, and the higher the ratio of magnetic carrier that passes magnetism, the higher the output value.

  The magnetic roller 32 includes a non-magnetic rotating sleeve 32a and a fixed magnet body 32b having a plurality of magnetic poles (here, five poles) contained in the rotating sleeve. In the present embodiment, the magnetic pole of the fixed magnet body 32 b has a five-pole configuration including a main pole 45, a regulation pole (head cutting pole) 46, a transport pole 47, a separation pole 48, and a pumping pole 49.

  The developing roller 33 includes a cylindrical developing sleeve 33a and a developing roller side magnetic pole 33b fixed in the developing sleeve 33a. The magnetic roller 32 and the developing roller 33 are predetermined at the facing position (opposing position). It is facing with a gap of. The developing roller side magnetic pole 33b is different in polarity from the opposing magnetic pole (main pole) 45 of the fixed magnet body 32b.

  Further, a spike cutting blade 35 is attached to the developing container 30 along the longitudinal direction of the magnetic roller 32 (direction perpendicular to the paper surface of FIG. 2), and the spike cutting blade 35 rotates in the rotation direction of the magnetic roller 32 (see FIG. 2 (clockwise direction) 2, it is positioned upstream of the opposing position of the developing roller 33 and the magnetic roller 32. A slight gap (gap) is formed between the tip of the ear cutting blade 35 and the surface of the magnetic roller 32.

  A DC voltage (hereinafter referred to as Vslv (DC)) and an AC voltage (hereinafter referred to as Vslv (AC)) are applied to the developing roller 33, and a DC voltage (hereinafter referred to as Vmag (DC)) is applied to the magnetic roller 32. And an alternating voltage (hereinafter referred to as Vmag (AC)) is applied. These DC voltage and AC voltage are applied to the developing roller 33 and the magnetic roller 32 from the developing bias power source 53 via the bias control circuit 51 (both see FIG. 6). The control unit 90 transmits a control signal to the bias control circuit 51 to control Vslv (DC), Vslv (AC), Vmag (DC), and Vmag (AC) applied from the developing bias power supply 53.

  As described above, the first stirring screw 31a and the second stirring screw 31b circulate in the developing container 30 while the developer is being stirred to charge the toner, and the first stirring screw 31a causes the developer to move to the magnetic roller 32. Be transported. Then, a magnetic brush (not shown) is formed on the magnetic roller 32, and the thickness of the magnetic brush on the magnetic roller 32 is regulated by the earbrushing blade 35, and then the opposite portion between the magnetic roller 32 and the developing roller 33. A thin toner layer is formed on the developing roller 33 by the potential difference ΔV between the Vmag (DC) conveyed and applied to the magnetic roller 32 and the Vslv (DC) applied to the developing roller 33 and a magnetic field.

  The first and second stirring screws 31a and 31b in the developing device 3 are connected to a developer stirring motor (not shown) via a gear train, and the first and second stirring screws 31a and 31b are connected to the first and second stirring screws 31a and 31b based on a control signal from the control unit 90. The second stirring screws 31a and 31b are driven. In addition, by connecting the developer stirring motor to the magnetic roller 32 and the developing roller 33 through a gear train, the driving source of the magnetic roller 32 and the developing roller 33 can also be used.

  The toner layer thickness on the developing roller 33 varies depending on the resistance of the developer and the difference in rotational speed between the magnetic roller 32 and the developing roller 33, but can be controlled by ΔV. When ΔV is increased, the toner layer on the developing roller 33 is thickened, and when ΔV is decreased, the toner layer is thinned. The range of ΔV at the time of development is generally about 100V to 350V.

  FIG. 4 is a diagram illustrating an example of a bias waveform applied to the developing roller 33 and the magnetic roller 32. As shown in FIG. 4A, a composite waveform Vslv (solid line) in which a rectangular wave Vslv (AC) having a peak-to-peak value of Vpp1 is superimposed on Vslv (DC) is applied to the developing roller 33. The magnetic roller 32 is applied with a composite waveform Vmag (broken line) in which Vmag (DC) has a peak-to-peak value of Vpp2 and Vmag (AC) of a rectangular wave having a phase different from Vslv (AC). The

  Therefore, the voltage applied between the magnetic roller 32 and the developing roller 33 is a composite waveform Vmag−Vslv having Vpp (max) and Vpp (min) as shown in FIG. Note that Vmag (AC) is set so that the duty ratio is larger than Vslv (AC). Actually, an AC voltage having a partially distorted shape is applied instead of a complete rectangular wave as shown in FIG.

  The toner thin layer formed on the developing roller 33 by the magnetic brush is conveyed to the opposite portion between the photosensitive drum 1 and the developing roller 33 by the rotation of the developing roller 33. Since Vslv (DC) and Vslv (AC) are applied to the developing roller 33, the toner flies from the developing roller 33 to the photosensitive drum 1 due to a potential difference with the photosensitive drum 1, and the static on the photosensitive drum 1. The electrostatic latent image is developed.

  Remaining toner that is not used for development is conveyed again to the opposing portion of the developing roller 33 and the magnetic roller 32 by the rotation of the developing roller 33 and is collected by the magnetic brush on the magnetic roller 32. Then, the magnetic brush is peeled off from the magnetic roller 32 by the same-polar part (peeling pole 48, pumping pole 49) of the fixed magnet body 32b, and then circulated between the first and second stirring chambers 30b, 30c. Returned to the drug. Then, a magnetic brush is formed on the magnetic roller 32 again as a two-component developer uniformly charged with an appropriate toner concentration, and conveyed to the earbrush blade 35.

  FIG. 5 is a side sectional view schematically showing the toner container 6. The toner container 6 includes a container container 61 that stores unused toner, a conveying screw 62, a stirring paddle 63, a toner replenishing motor 27, and a stirring motor 28.

  A supply port 61a connected to the toner supply port 30d (see FIG. 2) of the developing container 30 is formed at one end portion in the longitudinal direction (direction perpendicular to the paper surface of FIG. 5) of the bottom of the container container 61. The agitation paddle 63 has a film-like agitation blade 63a that extends from the shaft part to one side in the radial direction and is developed in the longitudinal direction of the container. The toner in the container container 61 is stirred by the rotation of the stirring blade 63a, and the stirred toner is transferred to the conveying screw 62 side.

  The transport screw 62 has a spiral blade 62a formed in a spiral shape with a constant phase (pitch) in the longitudinal direction around its shaft portion, and is disposed at the bottom of the container container 61 so as to face the supply port 61a. ing. When the transport screw 62 rotates, the toner stirred by the stirring paddle 63 is transported toward the supply port 61a by the advance of the phase of the spiral blade 62a, and is supplied to the developing container 30 through the supply port 61a.

  The toner replenishment motor 27 and the agitation motor 28 are DC motors that rotate the conveying screw 62 and the agitation paddle 63, respectively. It is done. The stirring blade 63a of the stirring paddle 63 extends from the shaft portion to the outer edge of the conveying screw 62 in the radial direction, and can contact the spiral blade 62a.

  When the toner is sufficiently stored in the container 61, the stirring paddle 63 stirs the toner and supplies it to the conveying screw 62. When the toner replenishing motor 27 is driven to rotate at a constant speed, the conveying screw 62 replenishes a constant amount of toner corresponding to the rotational speed into the developing container 30 from the supply port 61a. Thereby, the toner concentration of the developer in the developing container 30 is kept constant. If the toner concentration in the developer in the developer container 30 detected by the toner concentration sensor 41 does not increase despite the toner being supplied, the control unit 90 indicates that the toner in the toner container 6 is empty. When it is determined that the toner container 6 is present, a display indicating that the toner remaining amount in the toner container 6 is empty (hereinafter referred to as toner end) is displayed on the liquid crystal display unit 71 (see FIG. 6), and the user is prompted to replace the toner container 6.

  However, if the display of the toner end is suddenly performed, if it takes time to prepare the replacement toner container 6, the user may not be able to use the image forming apparatus 100. Therefore, the state near the toner end (hereinafter referred to as the near end) is set and displayed before the toner end is displayed, and the time for the user to prepare the replacement toner container 6 is secured by the near end display.

  The toner replenishment speed of the toner container 6 is constant when the remaining amount of toner in the toner container 6 is sufficient, but the replenishment speed decreases when the remaining amount of toner in the toner container 6 decreases. Therefore, when the toner supply amount (toner supply speed) per unit time from the toner container 6 decreases to a predetermined amount, a near end is displayed, and when the toner supply amount further decreases, a toner end is displayed. The near end may be detected based on the toner concentration in the developer in the developer container 30 detected by the toner concentration sensor 41 as in the case of the toner end, or printing calculated from the image signal of the image to be printed. It can also be predicted using rates.

  Next, the control path of the image forming apparatus of the present invention will be described. FIG. 6 is a block diagram showing an example of a control path used in the image forming apparatus of the present invention. It should be noted that since various control of each part of the apparatus is performed when the image forming apparatus 100 is used, the control path of the entire image forming apparatus 100 becomes complicated. Therefore, here, a portion of the control path that is necessary for the implementation of the present invention will be mainly described.

  The bias control circuit 51 is connected to the charging bias power source 52, the developing bias power source 53, and the transfer bias power source 54, and operates these power sources 52 to 54 according to output signals from the control unit 90. To 54 apply a predetermined bias to the charging device 2, the magnetic roller 32, the developing roller 33, and the transfer roller 9 in accordance with a control signal from the bias control circuit 51.

  The operation unit 70 is provided with a liquid crystal display unit 71, an LED 72, and a numeric keypad 73. The user operates the operation unit 70 to input instructions, thereby performing various settings of the image forming apparatus 100 and image formation. Various functions such as are executed. The liquid crystal display unit 71 displays the state of the image forming apparatus 100, displays the image forming status and the number of copies, and can be used as a touch panel to perform various settings such as functions such as double-sided printing and black-and-white reversal, magnification setting, and density setting It has become. The LED 72 indicates the state of the image forming apparatus 100 and displays the image forming status and the number of copies to be printed. The numeric keypad 73 is used for setting the number of copies to be printed and for inputting the other party's facsimile number when the image forming apparatus 100 also has a facsimile function.

  In addition, the operation unit 70 is provided with a stop / clear button used when image formation is stopped, a reset button used when various settings of the image forming apparatus 100 are set to a default state, and the like.

  The control unit 90 includes a central processing unit (CPU) 91 as a central processing unit, a read only memory (ROM) 92 that is a read-only storage unit, a random access memory (RAM) 93 that is a read / write storage unit, A plurality of (two in this case) that transmit a control signal to each device in the temporary storage unit 94, the counter 95, and the image forming apparatus 100 for storing image data and the like, and receive an input signal from the operation unit 50. I / F (interface) 96 and at least an arithmetic unit 97 for performing arithmetic processing of numerical values necessary for control. Further, the control unit 90 can be arranged at an arbitrary location inside the apparatus main body.

  In addition, the control unit 90 transmits a control signal from the CPU 91 to the respective units and apparatuses in the image forming apparatus 100 through the I / F 96. In addition, a signal indicating the state and an input signal are transmitted from each part or device to the CPU 91 through the I / F 96. Examples of the parts and devices controlled by the control unit 90 include, for example, the exposure device 4, the fixing unit 7, the image forming unit 8, the transfer roller 9, the image reading unit 20, the toner supply motor 27, the stirring motor 28, and the bias control circuit 51. And the operation unit 70 and the like.

  The ROM 92 stores a control program for the image forming apparatus 100, data necessary for control, and the like that are not changed during use of the image forming apparatus 100. The RAM 93 stores necessary data generated during the control of the image forming apparatus 100, data temporarily required for controlling the image forming apparatus 100, and the like. Further, the RAM 93 (or ROM 92) determines data necessary for toner replenishment control, such as the output value of the toner density sensor 41 and the developer circulation speed in the developing container 30, and whether or not the refresh process needs to be executed. In addition to the reference print rate used when determining the number of prints and whether or not the refresh process is necessary, the outer peripheral lengths of the developing roller 33 and the magnetic roller 32 for calculating the print length of the toner discharge pattern, and the line for the photosensitive drum 1 Speed ratio data and the like are also stored. The counter 95 adds up the number of printed sheets and counts it. For example, the RAM 93 may store the number of prints without providing the counter 95 separately.

  The computing unit 97 calculates the toner concentration in the developing device 3 from the output value of the toner concentration sensor 41 and determines the amount of toner replenished to the developing device 3 (drive time of the toner replenishing motor 27). The determined toner supply amount is transmitted to the CPU 91, and the CPU 91 transmits a control signal to the toner supply motor 27 to drive the toner supply motor for a predetermined time (or a predetermined number of rotations). Further, the CPU 91 determines whether or not the toner container 6 needs to be replaced based on the output value of the toner density sensor 41 after the toner supply. That is, when the output value of the toner density sensor 41 does not decrease after toner replenishment, it is determined that the toner container 6 is empty or nearly empty, and a near-end or toner-end display is performed on the liquid crystal display unit 71.

  When the toner in the toner container 6 becomes empty, the toner container 6 is replaced, and the toner is supplied to the developing device 3 for a longer time than when toner is supplied during image formation. When the toner immediately after being replenished without being sufficiently stirred is supplied to the developing roller 33, the charge amount of the toner is not sufficient, the image density is lowered, or the toner thin layer formed on the surface of the developing roller 33 There are cases where a part of the image is broken and detached, and is developed as a lump and random black spots are generated on the image.

  Therefore, when the toner is replenished immediately after the toner container 6 is replaced, an aging operation is performed in which the replenished unused toner and the developer in the developing container 30 are agitated for a predetermined time using the first and second agitating screws 31a and 31b. Do. The execution time of the aging operation is not particularly limited, but is appropriately set based on the amount of developer contained in the developing container 30, the cumulative number of printed sheets until the toner container 6 is replaced, or an average printing rate history to be described later. . Generally, the aging operation may be executed for about 30 seconds.

  By the way, the unused toner replenished in the developing container 30 is more easily charged than the deteriorated toner existing in the developing container 30 and is strongly restrained by the carrier. Therefore, the surface of the carrier in the developing container 30 is aged. Is occupied by unused toner. As a result, the deteriorated toner having a weak binding force from the carrier exists in a semi-floating state in the developer.

  In the image forming apparatus of the present invention, when the image forming apparatus 100 is not transferred to the recording medium, for example, when the image forming apparatus 100 is started from the power-off state or the sleep (power saving) mode to the copy start state, or a predetermined number of prints are made. When performed, it is possible to execute a refresh process in which the toner is ejected from the developing roller 33 to the photosensitive drum 1 side and the toner is forcibly consumed.

  This refresh process is performed after the toner container 6 is replaced and the developing device 3 is replenished with unused toner and the aging operation is performed, so that the deteriorated toner existing in a semi-floating state in the developer is selectively selected. Can be transferred (discharged) to the surface of the photosensitive drum 1. Specifically, the amount of toner that shifts the developing bias applied to the developing roller 33 during execution of the refresh process from the developing roller 33 to the photosensitive drum 1 with respect to the potential difference between the developing roller 33 and the photosensitive drum 1. In the graph (so-called development sensitivity curve) showing the above relationship, a range in which a significant difference is generated between the transfer amount of the deteriorated toner and the transfer amount of the unused toner is set.

  Here, when the amount of toner consumed in the developing device 3 between the execution of the most recent refresh process and the replacement of the toner container 6 is small, the amount of deteriorated toner present in the developing device 3 when the toner container 6 is replaced is large. Tend to be. On the other hand, when the amount of toner consumed in the developing device 3 between the execution of the latest refresh process and the replacement of the toner container 6 is large, the amount of deteriorated toner present in the developing device 3 when the toner container 6 is replaced is small. There is a tendency.

  Therefore, in the present invention, it is determined whether or not the refresh process is to be performed when the toner container 6 is replaced based on the toner consumption amount in the developing device 3 within a predetermined period from the execution of the most recent refresh process to the replacement of the toner container 6. I am going to judge. The toner consumption amount in the developing device 3 may be calculated over the entire period from the most recent refresh process to the toner end, or may be calculated during a partial period from the most recent refresh process to the toner end. You may do it.

  The amount of toner consumed in the developing device 3 can be obtained from the average printing rate. Assuming that the number of prints from the most recent refresh process to the toner end is A, the control unit 90 reads the print rate for each image based on the image signal read by the image reading unit 20 and stored in the temporary storage unit 94. bn is calculated, and an integrated print rate Σbn obtained by adding the print rate bn is calculated. Then, the average printing rate B (%) per printing sheet A is calculated by dividing the integrated printing rate Σbn by the printing sheet number A counted by the counter 95.

  Further, the toner consumption can be obtained by directly measuring the density of the toner image formed from the most recent refresh process to the toner end. For example, it is possible to directly measure the image density of a toner image formed on the surface of the photosensitive drum 1 using a reflection type density sensor or the like, or a toner image transferred onto paper, and the measured image density and image formation are possible. A toner consumption amount cn for each image is calculated using the ratio of the image area to the area, and an integrated toner consumption amount Σcn obtained by integrating the toner consumption amount is calculated. Then, the integrated toner consumption amount Σcn is divided by the number of printed sheets A counted by the counter 95 to calculate an average toner consumption amount C per printed sheet number A.

  Further, the amount of toner discharged during the execution of the refresh process may be determined according to the average printing rate B or the average toner consumption C. For example, when the calculated average printing rate B or average toner consumption C is smaller than the threshold, the larger the difference from the threshold, the smaller the toner consumption from the latest refresh process to the toner end, and the deterioration in the developing device 3 Since the ratio of toner is considered to be large, the toner discharge amount is increased.

  As a result, in the refresh process executed when the toner container 6 is replaced, it is possible to appropriately set the amount of toner to be discharged and to minimize waste of toner. The toner discharge amount can be adjusted by the developing bias applied to the developing roller 33, the charging bias applied to the photosensitive drum 1, and the refresh process execution time.

  As a specific method of increasing the toner discharge amount, a method for extending the execution time of the refresh process (drive time of the photosensitive drum 1 and the developing device 3) or a peak-to-peak of Vslv (AC) applied to the developing roller 33 is used. A method of increasing the value and / or the Duty value may be mentioned. Further, when increasing the duty value of Vslv (AC), it is preferable to increase Vslv (DC) as well.

  During the refresh process, in order to prevent the deteriorated toner discharged onto the photosensitive drum 1 from adhering to the transfer roller 9, a bias (transfer) having the same polarity as the toner charging polarity is applied to the transfer roller 9. Reverse bias) is applied.

  FIG. 7 is a flowchart showing a control example of the refresh process executed in the image forming apparatus of the present invention. The execution procedure of the refresh process will be described along the steps in FIG. 7 with reference to FIGS. First, when an image is formed by the user, an image output condition including an image signal is stored in the temporary storage unit 94 (step S1), and the cumulative number of printed sheets is counted by the counter 95 (step S2). Then, the control unit 90 determines whether or not the cumulative number of printed sheets has reached a predetermined number (step S3).

  When the cumulative number of printed sheets reaches a predetermined number, the control unit 90 executes a refresh process for discharging the toner on the developing roller 33 to the photosensitive drum 1 (step S4), and resets the cumulative count value of the counter 95. If the cumulative number of printed sheets has not reached the predetermined number in step S3, the process proceeds to the next step without executing the refresh process.

  Next, the control unit 90 detects the toner density in the developing device 3 from the output value of the toner density sensor 41, and determines whether or not the remaining amount of toner in the toner container 6 has reached the toner end (step S5). ). If the toner end has not been reached, the process returns to step S1 and the same procedure is repeated.

  On the other hand, when the toner end has been reached in step S5, the image signal stored in the temporary storage unit 94 and the cumulative number of printed sheets A from the time of the latest refresh process counted by the counter 95 to the toner end are counted. Based on this, the average printing rate B from the most recent refresh process to the toner end is calculated (step S6). In addition, the toner container 6 is replaced (step S7), and toner supply from a new toner container 6 (step S8) and an aging operation (step S9) are performed.

  Then, it is determined whether or not the average printing rate B from the most recent refresh process to the toner end is below a predetermined printing rate B0 (step S10). If B <B0, the average printing rate B is set. Based on this, the execution conditions for the refresh process are determined (step S11), and the refresh process is executed under the determined conditions (step S12).

  Specifically, a predetermined region is defined using the exposure device 4 in a state where a charging bias is applied from the charging bias power source 52 to the charging device 2 by the control signal from the bias control circuit 51 to charge the surface of the photosensitive drum 1. The surface potential of the photosensitive drum 1 is set to 0 by performing exposure or turning off the charging bias. In this state, a developing bias is applied from the developing bias power source 53 to the developing roller 33. Further, a transfer reverse bias having the same polarity as the toner is applied from the transfer bias power source 54 so that the toner does not adhere to the transfer roller 9.

  Then, the toner flies on the photosensitive drum 1 as a solid (solid) image, and the toner on the developing roller 33 is forcibly consumed. Thereafter, the cleaning is continued until the toner on the photosensitive drum 1 is completely removed by the cleaning device 5. When the cleaning is completed, a positive transfer bias is applied to the transfer roller 9 to remove the reverse polarity toner on the transfer roller 9. Returning to the photosensitive drum 1 side, this is cleaned by the cleaning device 5, and the refresh process is completed. Then, it returns to step S1 and repeats the same procedure hereafter.

  According to such control, the necessity of execution of the refresh process according to the average printing rate from the time of execution of the most recent refresh process to the replacement of the toner container 6, that is, the amount of toner consumption from the most recent refresh process, and Execution conditions are determined. As a result, it is possible to suppress unnecessary execution of the refresh process when the toner consumption is large, and when the toner consumption is small, the refresh process is performed and the toner discharge amount at the time of execution is set to an appropriate amount. can do.

  FIG. 8 is a flowchart showing another control example of the refresh process executed in the image forming apparatus of the present invention. In the control of FIG. 8, when an image is formed by the user, the image output condition including the image signal is stored in the temporary storage unit 94 (step S1), and is calculated from the image signal and the cumulative number of prints counted by the counter 95. The near-end of the toner container 6 is predicted according to the printing rate (step S2). Then, the control unit 90 determines whether the toner container 6 has reached the near end based on the calculated printing rate (step S3). When the near end has not been reached, the process returns to step S1 and the same procedure as above is repeated.

  When near end is detected in step S3, the counter 95 is reset (step S4), and the cumulative number of printed sheets A from the near end is counted (step S5). Next, the control unit 90 detects the toner density in the developing device 3 from the output value of the toner density sensor 41, and determines whether or not the remaining amount of toner in the toner container 6 has reached the toner end (step S6). .

  When the toner end is reached, the average print rate B from the near end to the toner end is calculated based on the image signal stored in the temporary storage unit 94 and the cumulative number of printed sheets A counted by the counter 95 (step S7). ). Further, the toner container 6 is replaced (step S8), and toner supply from a new toner container 6 (step S9) and an aging operation (step S10) are performed.

  Then, it is determined whether or not the average printing rate B from the near end to the toner end is below a predetermined printing rate B0 (step S11). If B <B0, the refresh process is executed based on the average printing rate B. Conditions are determined (step S12), and a refresh process is executed under the determined conditions (step S13).

  In the control example of FIG. 8, the necessity of executing the refresh process when the toner container 6 is replaced and the amount of toner discharged in the refresh process are such that the remaining amount of toner in the toner container 6 before the replacement is changed from the near end to the toner end. It is determined based on the toner consumption up to. In other words, if the toner consumption from the near end to the toner end does not exceed the predetermined threshold, it is considered that the toner in the developing device 3 has deteriorated, so refreshing is performed following the replenishment of unused toner and the aging operation. Execute the process. If the toner consumption from the near end to the toner end is equal to or greater than a predetermined threshold value, it is considered that the toner in the developing device 3 has not deteriorated, so only the replenishment of unused toner and the aging operation are performed.

  When the near end is detected, the remaining amount of toner in the developing device 3 decreases until the toner container is replaced. For this reason, in order to efficiently use a small amount of toner, the refresh process is not executed from the near-end detection to the toner-end detection. In this case, it is considered that the state of the toner remaining in the developing device 3 when the toner container 6 is replaced is deteriorated as compared with normal image formation. In this control example, the toner discharge amount in the refresh process is determined based on the average printing rate from the near-end detection to the toner-end detection, so that the state of the toner in the developing device 3 when the toner container 6 is replaced is more accurate. Thus, it is possible to determine an appropriate toner discharge amount reflected in the above.

  The toner consumption from the near end to the toner end may be obtained from the average printing rate B as shown in FIG. 8, or may be obtained by calculating the average toner consumption C by directly measuring the density of the toner image. good. Here, the near-end prediction of the toner container 6 is performed based on the print rate. However, instead of the print rate, the toner concentration in the developer in the developer container 30 detected by the toner concentration sensor 41 is used. The near end of the container 6 can also be detected.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the above embodiment are not intended to limit the scope of the present invention only unless otherwise specified, and are merely illustrative examples. Only.

  In addition, the present invention is not limited to the monochrome multifunction device shown in FIG. 1, and various types of toner containers including a monochrome printer, a rotary or tandem color copying machine, a color printer, a facsimile, and the like that include toner containers for supplying toner to the developing device. Of course, it can be applied to an image forming apparatus.

  The present invention can be used for an image forming apparatus including a toner container for supplying toner to a developing device. By using the present invention, the necessity of the refresh process at the time of toner container replacement and the toner discharge amount when the refresh process is executed are set to a toner consumption amount within a predetermined range from the execution of the latest refresh process to the toner end. Therefore, unnecessary execution of the refresh process can be suppressed, and the toner discharge amount when the refresh process is performed can be set to an appropriate amount. Therefore, the image forming apparatus can suppress wasteful toner consumption other than image formation as much as possible.

1 Photosensitive drum (image carrier)
2 Charging device 3 Developing device 4 Exposure device 5 Cleaning device 6 Toner container 7 Fixing unit 8 Image forming unit 32 Magnetic roller 33 Developing roller (toner carrier)
41 Toner density sensor (toner remaining amount detection means)
51 Bias Control Circuit 52 Charging Bias Power Supply 53 Development Bias Power Supply 54 Transfer Bias Power Supply 90 Control Unit (Control Unit)
91 CPU
92 ROM
93 RAM
94 Temporary storage unit 95 Counter 100 Image forming apparatus

Claims (5)

A developing device that has a toner carrier that is disposed opposite to the image carrier and carries toner and supplies the toner to the image carrier, and forms a toner image corresponding to the electrostatic latent image on the surface of the image carrier;
A replaceable toner container for containing toner to be replenished to the developing device;
Toner remaining amount detecting means capable of detecting a toner end where the toner in the toner container is empty,
In an image forming apparatus capable of executing a refresh process for discharging toner from the toner carrier side to the image carrier side during non-image formation,
Control means for determining whether or not the refresh process needs to be performed immediately after replacement of the toner container based on a toner consumption amount within a predetermined period from the most recent refresh process until the toner end is detected. An image forming apparatus.   The control means determines a toner discharge amount when the refresh step is executed immediately after replacement of the toner container based on a toner consumption amount within a predetermined period from the most recent refresh step until the toner end is detected. The image forming apparatus according to claim 1, wherein the image forming apparatus is determined.   3. The control unit according to claim 2, wherein the control unit increases the toner discharge amount stepwise as the toner consumption amount in a predetermined period from the latest refresh step to the detection of the toner end is small. Image forming apparatus.   The toner remaining amount detecting means can detect a near end where the toner in the toner container has become a predetermined amount or less before detecting the toner end, and the control means can consume toner from the near end to the toner end. 4. The necessity of execution of the refreshing process immediately after replacement of the toner container or a toner discharge amount when the refreshing process is executed is determined based on the amount. The image forming apparatus according to any one of the above.   5. The toner consumption amount according to claim 1, wherein the control unit calculates a toner consumption amount using an average printing rate within a predetermined period from the latest refresh step to the detection of the toner end. An image forming apparatus according to claim 1.

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