JP2014021326A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device for properly controlling toner concentration on the basis of the estimated amount of carrier in a developing unit.SOLUTION: In supplying toner, output values Vdb and Vda of a toner concentration sensor 48 before and after toner supply are acquired (S1 to S5). A current correction value of an environment correction value table 79 is added to Vda-Vdb to calculate Vdh (S6). A difference ΔV between Vdh and Vdh_std(=Vda-Vdb+0(an initial value of the environment correction value is 0)) is determined (S7). If |ΔV|<100 mV is satisfied, processing is terminated. If |ΔV|≥100 mV is satisfied, the amount of carrier is decided from ΔV by use of a control voltage correction value table 80. A control voltage for the toner concentration sensor 48 is increased with a voltage correction value based on the decided amount of carrier, thereby increasing an output of the toner concentration sensor 48.

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to an image forming apparatus that appropriately controls toner density based on an estimated carrier amount in a developing device.

  Conventionally, there is an electrophotographic image forming apparatus. In this image forming apparatus, generally, a photosensitive drum is uniformly charged and initialized, an electrostatic latent image is formed on the photosensitive drum by optical writing, and the electrostatic latent image is converted into a toner image. Is directly or indirectly transferred onto a transfer material such as paper and fixed by a fixing device.

  Such electrophotographic image forming apparatuses include those using a one-component developer composed only of toner and those using a two-component developer composed of toner and carrier. In recent years, a method using a two-component developer can cope better with the demand for high-speed printing (hereinafter also referred to as printing) processing.

  The carrier of the above two-component developer is mixed and agitated with the toner in the developing device to give the toner a predetermined charge. The charged toner temporarily adheres to the surface of the carrier and coats the surface of the carrier.

  The carrier adhering to the magnetic developing roller carries charged toner onto the photosensitive member, transfers the toner to the electrostatic latent image on the photosensitive member, and develops the toner image on the electrostatic latent image.

  The carrier from which the toner on the surface has been released remains on the developing roller, returns to the inside of the developing device, and is mixed and stirred again with new toner to be replenished to the developing device, charges the toner, and transports the toner onto the photoreceptor. , And so on.

  Toner is supplied to the developing device from a toner supply device. As a toner replenishment path from the toner supply device to the developing device, a pipe having a built-in coil screw or a replenishment path using a natural fall path due to the gravity of the toner is used.

  The developing device incorporates a toner mixing and stirring mechanism. There are two toner mixing and stirring mechanisms. One is a circulation that transports toner supplied (supplemented) from a toner supply device while mixing and stirring with a two-component developer having a lowered toner concentration (hereinafter simply referred to as developer). It is a conveying screw.

  The second is a supply conveyance screw that supplies the developer fed by the circulation conveyance screw to the magnetic developing roller while stirring and conveyance, and sends the remaining developer back to the circulation conveyance screw.

  Here, if the toner concentration in the developer of the developing device is too high, background staining or the like occurs. Conversely, if the toner density is too low, a high density image cannot be obtained. Therefore, in order to obtain a high-quality image, it is necessary to control the toner concentration of the developer in the developing device supplied to the toner image carrier within a certain range.

  Therefore, a developing device of an electrophotographic image forming apparatus that forms an image using such a developer is provided with a toner density sensor for measuring the amount of toner consumed by printing. When it is detected that the toner density is lower than a predetermined value, the developing device is replenished with toner.

  Generally, a sensor that detects magnetic permeability is used as the toner concentration sensor. There are several methods for detecting the magnetic permeability, such as a method using an inductance component of a coil, a frequency type, and a magnetic bridge type.

  In any case, the toner concentration sensor exposes a detection surface to a part of the inner wall surface of the developing device, and detects a change in magnetic permeability from the carrier in the developer around the detection surface. That is, when the toner concentration is high, the magnetic permeability decreases and the sensor output becomes weak. When the toner concentration is low, the magnetic permeability increases and the sensor output becomes strong.

  When the sensor output exceeds the replenishment reference voltage value, the toner is replenished by a shortage, and when the output falls below the reference voltage value, the replenishment is stopped. The amount of toner at this time is preferably supplied in a fixed amount per replenished time.

  If toner replenishment is insufficient, problems such as carrier pulling occur where the carrier of the developer moves to the toner image carrier together with the toner. Further, when toner is replenished excessively, problems such as toner scattering occur.

  In addition, when the carrier amount of the developer in the developing device decreases, the output of the toner concentration sensor cannot be controlled with the developer toner concentration that is initially set, and the toner concentration changes, causing problems such as carrier pulling and toner scattering. It occurs and becomes a problem.

  By the way, in order to prevent excessive toner concentration due to erroneous detection of the toner concentration sensor and to maintain a stable toner concentration, the supplied toner first passes through the toner concentration sensor without performing concentration detection simultaneously with toner replenishment. There has been proposed an image recording apparatus that detects the toner density at the time of doing so. (For example, refer to Patent Document 1.)

  This is because the toner concentration is not detected at the timing before the toner replenished from the toner replenishing port first passes through the toner concentration sensor, so that the concentration of the replenished toner can be reliably detected. is there.

  In addition, a signal processing unit that adjusts the output voltage without changing the sensitivity gradient based on the control voltage applied to the control terminal so that the toner density can be accurately detected regardless of the use state or use environment of the image forming apparatus. There has been proposed a toner concentration control device that includes an inductance detection type toner concentration sensor provided and corrects the output voltage based on the correlation of the output voltage before and after switching of the control voltage. (For example, see Patent Document 2.)

JP 2003-076130 A JP 2006-276630 A

  However, the technique described in the above-mentioned Patent Document 1 is to detect at the timing when the replenished toner comes to the position of the toner density detection sensor while being agitated, so to speak, it simply tries to properly detect the toner density itself. However, career pulling is not considered.

  Further, the technique described in the above-mentioned patent document 2 estimates the toner charge amount that has changed due to the change in the toner charge amount, and the toner density cannot be controlled as set with the initially set control voltage. The control voltage for driving and controlling is corrected, and the control voltage is not corrected in consideration of carrier pulling.

  As described above, when the carrier amount of the developer is reduced, the output of the toner density sensor cannot be properly controlled with the initially set developer toner density. If the toner density cannot be controlled properly, a problem such as further carrier pulling and toner scattering occurs due to a change in the toner density.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that appropriately controls toner density based on an estimated carrier amount in a developing device.

  In order to solve the above-described problems, an image recording apparatus according to the present invention includes a developer tank that circulates a developer containing toner and a carrier that develops an electrostatic latent image on an image carrier, and the developer tank described above. Based on the comparison result of the toner density sensor disposed in the developer circulation path and outputting the density information of the toner in the developer, the replenishment port disposed in the circulation path, and the comparison unit. When it is determined that replenishment is necessary, a toner replenishment unit that replenishes toner from the replenishment port to the developing tank with a constant replenishment amount, and when it is determined that replenishment is necessary The output value of the toner density sensor before the toner is replenished, and the toner at the timing when the developer portion containing the toner replenished from the replenishing port by the toner replenishing unit moves to the position where the toner density sensor is disposed. Concentration sensor output A carrier amount estimation unit that estimates a carrier amount in the developer based on a difference between output values of the toner density sensor before and after the replenishment of the toner indicated by a comparison result by the comparison unit; Control for correcting the control voltage for controlling the output value of the toner density sensor so as to increase when the carrier amount estimation unit estimates that the carrier amount in the developer is smaller than the intended carrier amount. A voltage correction unit.

  The present invention can provide an image forming apparatus that appropriately controls the toner density based on the estimated carrier amount in the developing device.

1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer, main body apparatus) according to Embodiment 1 of the present invention. 1 is a circuit block diagram including a printer control device according to Embodiment 1. FIG. (a), (b) is an expanded sectional view which shows the developing device of the printer based on Example 1 with a photosensitive drum. (a) is the figure which looked at the inside of the developing tank from the horizontal direction, in order to show clearly the arrangement relationship of each member in the developing tank of the developing device of the printer concerning Example 1. FIG. (a) is a diagram showing a pulse signal with a narrow period that appears superimposed on the output signal that should be the original output value of the toner density sensor, (b) is a cross-sectional view showing the internal configuration of the developer and the developer return path It is. (a) is a characteristic diagram showing the relationship between the toner concentration of the developer and the output of the toner concentration sensor, and (b) is a characteristic diagram showing the relationship between the variation amount of the carrier of the developer and the output of the toner concentration sensor. (a), (b), and (c) are characteristic diagrams showing a slightly extreme example of the state of change in toner density caused by a change in carrier amount. (a) is a diagram showing a table of environmental correction values, (b) is a difference calculation value obtained from the toner density before and after toner replenishment, a carrier amount estimated from the difference calculation value, and a control voltage correction value corresponding to the carrier amount It is a table. It is a flowchart of the processing operation regarding the setting of the control voltage which controls the output of the toner density sensor controlled by the control device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a two-component developer composed of a toner and a carrier is used. In the following description, the two-component developer is simply referred to as a developer.

  FIG. 1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (hereinafter simply referred to as a printer) according to Embodiment 1 of the present invention.

  An image forming apparatus 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, a transfer belt unit 3, a toner supply unit 4, a paper feeding unit 5, and a belt. It is composed of a type fixing unit 6.

  The image forming unit 2 is in contact with the lower running portion surface 8a of the transfer belt 8 of the transfer belt unit 3 and multi-stages four developing devices 9 (9y, 9m, 9c, 9k) from right to left in FIG. It consists of a side-by-side configuration. The image forming unit 2 is held by a frame of the main body of the image forming apparatus 1 so that it can be moved up and down from the printing execution position shown in FIG. 1 to a maintenance position below it.

  Of the four developing devices 9, three developing devices 9y, 9m, and 9c on the downstream side (right side in the figure) are yellow (Y), magenta (M), and cyan (C), which are subtractive three primary colors, respectively. A mono-color image is formed with the color toner, and the developing device 9k forms a monochrome image mainly with black (K) toner used for characters and dark portions of the image.

  Each of the developing devices 9 has the same configuration except for the color of the toner that develops the image. Therefore, the configuration of the developing device 9k for black (K) toner will be described below as an example.

  The developing device 9 includes a photosensitive drum 10 at the top. The photosensitive drum 10 has a peripheral surface made of, for example, an organic photoconductive material. A cleaner 11, a charging roller 12, an optical writing head 13, and a developing roller 15 of the developing device 14 are disposed around the periphery of the photosensitive drum 10.

  The developing device 14 includes a first stirring / conveying member 16 and a second stirring / conveying member 17 in two developing tanks located below the developing roller 15. Details of the first and second stirring and conveying members 16 and 17 will be described later.

  The transfer belt unit 3 has an endless transfer belt 8 that extends in the shape of a flat loop in the left-right direction in the figure at approximately the center of the main unit, and the transfer belt 8 is stretched over the transfer belt 8. A driving roller 18 and a driven roller 19 are provided to circulate and move counterclockwise as indicated by arrows a and b in the figure.

  The above-described transfer belt 8 is directly transferred to the surface of the belt that circulates below by a primary transfer roller 21 that is integrated with the unit and pressed against the photosensitive drum 10 via the transfer belt 8 (primary transfer). Then, the toner image is conveyed to the secondary transfer unit 23 to the paper for further transfer (secondary transfer) to the paper.

  In the transfer belt unit 3, the cleaning blade 25 of the belt cleaner 24 is disposed in contact with the surface of the belt 18 that is stretched around the driving roller 18. A waste toner collecting container 26 is detachably disposed below the belt cleaner 24.

  In the belt cleaner 24, the cleaning blade 25 abuts on the surface of the transfer belt 8 to scrape and remove the waste toner, and the waste toner is sent to a lower waste toner collection container 26 by a conveying member.

  The toner supply unit 4 includes four toner hoppers 27 (27y, 27m, 27c, and 27k) disposed above the upper running unit of the transfer belt 8. The four toner hoppers 27y, 27m, 27c, and 27k contain yellow (Y), magenta (M), cyan (C), and black (K) toners, respectively.

  As shown in FIG. 1, the image forming unit 2 and the toner supply unit 4 are divided into upper and lower parts with the transfer belt unit 3 interposed therebetween. The toner hopper 27 of the toner supply unit 4 and the developing device 9 of the image forming unit 2 are not particularly shown, but include a pipe, a coil screw provided inside the pipe, a vertically arranged toner natural fall pipe, and the like. Are connected by a toner supply device.

  The toner supply unit 4 includes yellow (Y), magenta (M), cyan (C), and black (Y) as indicated by Y, M, C, and K (hereinafter referred to as “YMCK”) in FIG. One of the toners K) is supplied to the developing device 14 of the developing device 9 through the toner supply path.

  The paper feed unit 5 includes one paper feed cassette 29. A paper take-out roller 31, a feed roller 32, a separating roller 33, and a standby conveyance roller pair 34 are disposed in the vicinity of the paper feed port (right side of the drawing) of the paper feed cassette 29.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 34, a secondary transfer roller 35 that is in pressure contact with the driven roller 19 via the transfer belt 8 is disposed, and the above-described secondary transfer onto the paper is performed. Part 23 is formed.

  A diffuse reflection type density sensor 36 is disposed in the vicinity of the lower running portion surface 8a of the transfer belt 8 at a substantially intermediate position between the secondary transfer portion 23 and the most downstream developing device 9m. A belt-type heat fixing unit 6 is disposed downstream (upward in the drawing) of the secondary transfer portion.

  Further downstream of the belt-type heat fixing unit 6, a pair of unillustrated unloading rollers for unloading the fixed sheet from the belt-type heat fixing unit 6 and a sheet discharge tray on which the unloaded paper is formed on the upper surface of the apparatus. A pair of paper discharge rollers (not shown) for discharging paper to 37 is disposed. An operation panel unit 38 is disposed at an upper end of the main body located to the right of the paper discharge tray 37 with a slight inclination.

  FIG. 2 is a circuit block diagram including the control device of the printer 1 described above. As shown in FIG. 2, the circuit block is centered on the printer controller 40. The printer controller unit 40 is connected to an I / F (interface) 43 and a head controller unit 44 of a network controller unit 42 via a plurality of buses 41.

  The operation panel unit 38 described above is connected to the I / F 43 of the network controller unit 42 via another bus 41. The I / F 43 receives a signal such as print data from a host device (not shown) such as a personal computer.

  The network controller unit 42 transmits print data input from the outside via the I / F 43 to the head controller unit 44, and transmits command data included in the print data and instruction data input from the operation panel unit 38 to the printer controller unit. 40.

  An EEPROM (electrically erasable programmable ROM) 45, a ROM (read only memory) 46, and a paper feed motor 47 are further connected to the printer controller 40 via a bus 41.

  The printer controller 40 reads out a control program stored in the ROM 46, and in accordance with the read-out control program, a diffuse reflection type sensor 36, a registration sensor 49, a DDS (developer drum set for each YMCK, in this example, the developing device 9 Each part is controlled according to the sensor output received from the new and old detection sensors 51 and the like.

  Also, the printer controller 40 monitors whether the sensor output signal received from the toner density sensor 62 (62y, 62m, 62c, 62k) for each YMCK exceeds the toner supply threshold, and exceeds the toner supply threshold. At this time, the toner replenishing devices 57, 58, 59, and 60 corresponding to YMCK are driven to replenish toner to the developing device 9.

  Further, the printer controller 40 applies a control voltage for controlling the output voltage of the toner density sensor 62 (62y, 62m, 62c, 62k) for each YMCK to the toner density sensor 62y, 62m, 62c, 62k. The unit 61 is provided.

  Although described in detail later, the sensor control voltage application unit 61 applies a sensor control voltage to be applied to the toner density sensor 62 (62y, 62m, 62c, 62k) for each YMCK based on the carrier amount estimated by the printer controller unit 40. Correct and change.

  The printer controller 40 controls optical writing of the heads (optical writing heads 13) for each YMCK via the head controller 44 based on the print data received from the network controller 42.

  On the other hand, the printer controller 40 controls the paper feed motor 47 to transport the paper to the secondary transfer unit 23 based on the print data, and controls the high-pressure unit 52 to drive the drive unit 53 for each YMCK. , 54, 55, and 56, a bias voltage is applied to the charging roller 12, the developing roller 15, the primary transfer roller 21, the secondary transfer roller 35, and the like.

  Further, the printer controller 40 estimates a carrier amount, which will be described in detail later, based on an output signal output for the toner density sensor 62 for each YMCK to detect a toner replenishment threshold and an output signal after toner replenishment. Then, a new toner density sensor control voltage value corresponding to the estimated value is acquired, and the toner density sensor is driven by the acquired new toner density sensor control voltage value.

  3A and 3B are enlarged sectional views showing the developing unit 14 together with the photosensitive drum 10. FIG. As shown in FIG. 3, the developing device 14 includes two developing tanks 65 (65 a and 65 b) partitioned by an outer wall 63 and an inner partition wall 64.

  In the upper developing tank 65a, the developing roller 15 and the first stirring and conveying member 16 described above are disposed. A doctor blade 66 is in contact with the developing roller 15. The above-described second stirring / conveying member 17 is disposed in the lower developing tank 65a. In the developing tank 65a, a toner density sensor 62 is arranged with its detection surface 67 exposed in the tank.

  The first agitating and conveying member 16 includes a rotating shaft 68 and a helical fin 69 fixed to the rotating shaft 68 in a spiral shape. The second stirring / conveying member 17 includes a rotating shaft 71 and a spiral fin 72 fixed to the rotating shaft 71 in a spiral shape.

  The first agitating / conveying member 16 rotates counterclockwise in the figure as indicated by an arrow c, and the paper surface of the figure as indicated by an arrow e while stirring the developer in the developing tank 65a by the spiral fin 69. The developer is conveyed from the near side in the depth direction to the other side, and the developer is supplied to the developing roller 15.

  The developing roller 15 supplies only the developer toner to the photosensitive drum 10 to form (develop) the electrostatic latent image on the circumferential surface of the photosensitive drum 10 as a toner image. The carrier of the developer on the developing roller 15 from which only the toner has been taken up by the photosensitive drum 10 is mixed with the developer in the developing tank 65a, and enters the developing tank 65b at an outlet (not shown) on the other side in the depth direction of the drawing. Send it back.

  The second agitating and conveying member 17 in the developing tank 65b rotates counterclockwise in the figure as indicated by an arrow d, and the developer in the developing tank 65b is indicated by an arrow f while stirring the developer in the helical fin 72. In this way, the sheet is conveyed from the other side in the depth direction of the drawing to the near side.

  If the toner density of the developer is less than the specified level, the toner density sensor 62 detects a decrease in toner density. When a decrease in toner density is detected, a predetermined amount of toner based on a correction value, which will be described in detail later, is supplied from a toner hopper 27 corresponding to the developing device 14 of the toner supply unit 4 through a supply port.

  The second agitating and conveying member 17 feeds the developer to the developing tank 65a at a supply port (not shown) on the near side in the depth direction of the drawing while stirring and conveying the developer. In this way, the reflux of the developer and the replenishment of the toner are repeated, and the development with the toner proceeds sequentially.

  Since the detection surface 67 of the toner density sensor 62 is disposed so as to be exposed in the tank, the developer tends to stay on the detection surface 67. If the developer stays on the detection surface 67, the detection accuracy of the toner density sensor 62 is lowered.

  In order to prevent the detection accuracy of the toner density sensor 62 from deteriorating, the rotation shaft 71 of the second agitating / conveying member 17 in the developing tank 65b is positioned so as to rotate opposite the detection surface 67 of the toner density sensor 62. Further, a cleaning blade 75 including a blade holding portion 73 and an elastic sheet (blade) 74 held by the blade holding portion 73 is fixed.

  The cleaning blade 75 rotates together with the rotating shaft 71 of the agitating and conveying member 17, and rubs the detection surface 67 of the toner concentration sensor 62 with the elastic sheet 74 as shown in FIG. The developer to be retained is removed and replaced with the developer conveyed immediately thereafter.

  This prevents erroneous detection of the toner concentration that may be caused by the developer staying on the detection surface 67 of the toner concentration sensor 62.

  FIG. 4 (a) shows the configuration of each part in the developing tank 65b in order to easily show the positional relationship between the second stirring and conveying member 17, the cleaning blade 75, and the toner concentration sensor 62 in the developing tank 65b. FIG. 4 is a diagram viewed from the lateral direction indicated by an arrow g in FIG.

  FIG. 4B is an enlarged view of a portion surrounded by a broken line h in FIG. 4 (a) and 4 (b), the inclination of the spiral fin 72 of the second agitating and conveying member 17 is reversed. This is shown in FIG. 4 (b) in FIG. 4 (a). This is because the case is seen from the opposite side of the page.

  4 (a) and 4 (b), the same components as those shown in FIGS. 3 (a) and 3 (b) are assigned the same numbers as those in FIGS. 3 (a) and 3 (b). Show. As shown in FIG. 4A, the toner concentration sensor 62 is arranged with its detection surface 67 exposed so as to protrude slightly into the tank of the developing tank 65b in order to increase detection accuracy.

  However, the inner wall of the tank is gently formed with an inclination in the front, rear, left and right directions from the protruding corner of the detection surface 67 of the toner concentration sensor 62 so that the developer flows smoothly.

  By the way, the output value of the toner density sensor 62 indicates an average of the output values. The average here is to average the values of the pulse signals having a narrow cycle appearing superimposed on the output signal that should be the original output value of the toner density sensor 62.

  FIG. 5A is a diagram showing a pulse signal 70 with a narrow period that appears superimposed on the output signal that should be the original output value of the toner density sensor 62. FIG. 5B is a cross-sectional view showing the internal structure and the developer return path by cutting the developing device 14 in the direction indicated by the arrow g in FIG.

  5 (b) shows the same components as those shown in FIGS. 1, 3 (a), 3 (b) and 4 (a), 4 (b). , (b) and FIGS. 4 (a), (b) are given the same numbers. 5B, the illustration of the cleaning blade 75 shown in FIGS. 3A and 3B and FIGS. 4A and 4B is omitted, and the toner density sensor 62 is also shown very simply. Yes.

  Here, the reason why the pulse signal 70 having the above-described narrow period is generated by being superimposed on the original output value of the toner density sensor 62 will be described. As shown in FIG. 3B, the elastic sheet 74 of the cleaning blade 75 moves the detection surface 67 of the toner concentration sensor 62 at a constant period along with the rotation of the rotation shaft 71 of the second stirring and conveying member 17. Rub.

  While the elastic sheet 74 rubs against the detection surface 67, the elastic sheet 74 presses the developer against the detection surface 67, and the density of the developer on the detection surface 67 increases, and the toner density sensor 62 The output value rises slightly.

  Immediately after the sliding of the detection surface 67 by the elastic sheet 74 is completed, the elastic sheet 74 jumps off the developer in the vicinity of the detection surface 67, so that a gap is generated in the vicinity of the detection surface 67 and development on the detection surface 67 is performed. The density of the agent decreases, and the output value of the toner concentration sensor 62 slightly decreases.

  As described above, the detection output value of the toner density sensor 62 periodically changes in accordance with the cycle in which the elastic sheet 74 rubs the detection surface 67 during the stirring operation by the second stirring / conveying member 17. This is a pulse signal 76 having a narrow period shown in FIG.

  That is, the Max value 76 a of the pulse signal 76 indicates the timing at which the elastic sheet 74 of the cleaning blade 75 rubs against the detection surface 67 of the toner concentration sensor 62. The Min value 76b of the pulse signal 76 indicates the timing at which the elastic sheet 74 is separated from the detection surface 67. The output value of the toner concentration sensor 62 described below is obtained by calculating the average value of the output values of the pulse signal 76 as described above.

  On the other hand, as shown in FIG. 3A, the developing device 14 shown in FIG. 5B includes two developing tanks 65 (65a, 65b) partitioned by the outer wall 63 and the inner partition wall 64. In the upper developing tank 65a, the developing roller 15 and the first stirring and conveying member 16 described above are disposed.

  The above-described second stirring / conveying member 17 is disposed in the lower developing tank 65a. In the developing tank 65a, a toner density sensor 62 is arranged with the detection surface 67 shown in FIG. 3A exposed in the tank.

  The first agitating / conveying member 16 rotates counterclockwise as indicated by an arrow c in FIG. 3A, and the developer in the developing tank 65a is agitated by the spiral fin 69 as shown in FIG. As shown by arrows e (e1, e2, e3) of FIG. 3A, the developer is transported from the near side to the far side in FIG. 3A and from right to left in FIG. 15 is supplied.

  The developing roller 15 supplies only the developer toner to the photosensitive drum 10 shown in FIG. 3 to form (develop) the electrostatic latent image on the circumferential surface of the photosensitive drum 10 as a toner image. The developer carrier on the developing roller 15 from which only the toner has been taken up by the photosensitive drum 10 is mixed with the developer in the developing tank 65a, and the other side in the depth direction of FIG. 3 (a), FIG. 5 (b). Then, it returns to the developing tank 65b at the outlet 77 at the left end.

  The second agitating / conveying member 17 in the developing tank 65b rotates counterclockwise in FIG. 3A as indicated by an arrow d in FIG. 3A, and the developer in the developing tank 65b is spirally formed. While stirring with the fins 72, as indicated by arrows f (f1, f2, f3) in FIG. 5 (b), from the far side in the depth direction of FIG. 3 (a), to the near side in FIG. 5 (b), from left to right. Transport.

  If the toner density of the developer is less than the specified level, the toner density sensor 62 detects a decrease in toner density. When a decrease in toner density is detected, toner Tn is supplied from the toner hopper 27 corresponding to the developing device 14 of the toner supply unit 4 through a toner supply path (not shown) as shown in FIG. The

  In FIG. 5B, the toner supply port is not particularly shown, but the toner supply port is connected to substantially the same position as the outlet 77. That is, the replenishment toner is replenished in the vicinity of the outlet 77 where the developer in the developing tank 65a whose toner density has been reduced by the development is sent back to the developing tank 65b.

  The second agitating and conveying member 17 feeds the developer to the developing tank 65a through the supply port 78 on the front side in the depth direction of the paper in FIG. 3A and the right side in FIG. 5B while agitating and conveying the developer. . In this way, the reflux of the developer and the replenishment of the toner are repeated, and the development with the toner proceeds sequentially.

  As for the sensitivity output of the toner density sensor 62 related to the determination of whether or not toner replenishment is necessary, as the toner in the developing device 14 decreases, the magnetic permeability of the developer increases and the output increases. . The control unit calculates the toner concentration (%) of the developer from the sensor output, and replenishes the toner when the toner concentration falls below the toner replenishment threshold value Dth to keep the toner concentration of the developer constant.

  The developer in the developing device 14 is configured to circulate in the developing device 14. However, since the toner supply port that is substantially the same as the outlet 77 and the toner density sensor 62 are separated from each other, even if toner is supplied. Although it takes time for the developer replenished with toner to reach the sensor position, the developer flows at a constant speed (t time).

  Therefore, the control unit obtains the output of the toner concentration sensor 62 after time t after issuing the toner replenishment command, and calculates the toner concentration of the developer as described above. In this case, the control unit determines that there is no toner in the toner hopper 27 when the decrease in toner concentration is detected and the toner concentration does not increase after time t after issuing the toner replenishment command.

  FIG. 6A is a characteristic diagram showing the relationship between the toner density of the developer and the output of the toner density sensor 62, and FIG. 6B shows the relationship between the variation amount of the developer carrier and the output of the toner density sensor 62. It is a characteristic view which shows a relationship.

  In FIG. 6A, the horizontal axis indicates the toner density of the developer, and the vertical axis indicates the output of the toner density sensor 62. In this example, the toner density is 6% as an optimum value, and the sensor control voltage is initially set so that the sensor output at that time is 2.5v. When the toner density is reduced to, for example, 5%, the sensor output greatly increases. When the toner density is increased to, for example, 7%, the sensor output greatly decreases.

  In FIG. 6B, the horizontal axis indicates the amount of change in the developer carrier, and the vertical axis indicates the output of the toner density sensor 62. In this example, the initial carrier amount is 280 g. As shown in FIG. 6B, when the carrier amount fluctuates from 280 g to 270 g (−10 g), the toner output slightly increases and the sensor output slightly decreases.

  When the carrier amount further decreases and fluctuates from the initial value of 280 g to 260 g (−20 g), the toner output is greatly increased and the sensor output is greatly decreased. Incidentally, the toner replenishing unit has a mechanism capable of replenishing a constant amount of toner.

  FIGS. 7A, 7B, and 7C are characteristic diagrams showing the state of change in toner density caused by the change in the carrier amount as described above, with a slightly extreme example. 7A, 7 </ b> B, and 7 </ b> C, the horizontal axis indicates time (s), and the vertical axis indicates the toner density and the output (V) of the toner density sensor 62.

  Here, the toner density shown on the vertical axis indicates that the lower the density, the higher the density, and the lower the density, the lower the density. That is, the values for the vertical axes of the density graphs a, b, and c shown in FIGS. 7A, 7B, and 7C are the output (V) of the toner density sensor 62 and the output (V). The toner density (%) is inversely proportional to ().

  The horizontal axis, which is the coordinate time axis, shows the time difference t from the position ps of the toner density sensor 62 in the developing device 14 to the position pt of the toner supply port. Here, the density graphs a, b, and c are circulation type graphs that move from the toner supply port position pt to the position ps of the toner density sensor 62 along the time axis and return to the origin. It is easy to understand if you think there is.

  A broken line Dth indicates a toner replenishment threshold value of the toner density sensor output (V), and broken lines D0, D1, and D2 below the toner corresponding to the toner density immediately after the replenishment of the toner of the reference replenishment amount Tn is performed. The output (V) of the density sensor 62 is shown.

  FIG. 7A shows a characteristic diagram when the carrier amount is normal (when the developing device is new). At this time, when it is detected that the sensor output indicating the toner density is lower than the toner replenishment threshold Dth as shown in the graph a ′, the toner of the reference replenishment amount Tn is replenished at time pt.

  In this case, since the carrier amount is normal, the output (V) of the toner concentration sensor 62 when the developer containing the toner just replenished at time pt and the toner immediately after replenishment is detected at time ps after time t. ) Is D0, which is a level where the density is slightly higher, and changes at a normal density that is slightly higher than the toner replenishment threshold value Dth, as shown in graph a.

  Note that the difference between the output value of the toner density sensor 48 before toner supply at this time and the output value of the toner density sensor 48 after toner supply is Vdh_std.

  FIG. 7B shows a characteristic diagram when the carrier amount is slightly insufficient (for example, −10 g) than usual. At this time, when it is detected that the sensor output indicating the toner density is lower than the toner replenishment threshold Dth as shown in the graph b ′, it is assumed that the toner of the reference replenishment amount Tn is also replenished at time pt.

  In this case, since the carrier amount is slightly insufficient, the output (V) D1 of the toner density sensor 62 corresponding to the toner density immediately after replenishment at time ps after time t is the normal time shown in FIG. The density is slightly higher than that immediately after the replenishment, and as shown in the graph b, the density changes slightly above the normal toner replenishment threshold Dth.

  At this time, the difference between the output value of the toner density sensor 48 before toner supply and the output value of the toner density sensor 48 after toner supply is set to Vdh1.

  FIG. 7C shows a characteristic diagram when the carrier amount is larger than usual and insufficient (for example, −20 g). At this time, when it is detected that the sensor output indicating the toner density is lower than the toner replenishment threshold Dth as shown in the graph c ′, the toner of the reference replenishment amount Tn is also replenished at this time pt.

  In this case, since the carrier amount is largely insufficient, the output (V) D2 of the toner concentration sensor 62 corresponding to the toner concentration immediately after replenishment at the time ps after the time t is the normal time shown in FIG. As shown in the graph c, the density is higher than that immediately after the replenishment of toner, and changes at a density that greatly exceeds the toner replenishment threshold value Dth.

  At this time, the difference between the output value of the toner density sensor 48 before toner supply and the output value of the toner density sensor 48 after toner supply is set to Vdh2.

  As described above, when the amount of carrier decreases with time due to carrier pulling, the toner concentration increases even with a certain amount of toner, and the toner concentration sensor 48 may erroneously detect the timing of toner replenishment. Arise.

  By the way, the developing device 9 including the photosensitive drum 10 which is a consumable product is mounted with a non-volatile memory. When the developing device 9 is mounted on the main device 1, the control unit of the main device reads the data in the non-volatile memory, and the developing device 9 is new. If it is determined, a value such as a voltage value for controlling the toner density sensor 62 is read, and these values are set in a predetermined storage area of the EEPROM 45.

  The voltage value for controlling the toner density sensor is such that when the developing device 9 including the photosensitive drum 10 is assembled and produced and shipped, the toner concentration of the developer filled in the developing device 14 of the developing device 9 is 6%. When set to, the output is set to 2.5V.

  However, as shown in FIGS. 7A, 7B, and 7C, when the carrier amount decreases with time, the toner density is initially set even if a predetermined amount of toner is supplied. There is a problem that it does not become a high concentration.

  Therefore, the present inventor replenishes a certain amount of toner based on the characteristic diagrams shown in FIGS. 7A, 7B, and 7C, and the developer containing the replenished toner is supplied to the toner density sensor 62. The carrier amount in the developing device 14 was estimated from the state of fluctuation of the sensor output when the position reached.

  When the variation in the sensor output is small, the control voltage to the toner density sensor 48 is left as it is, and when the variation in the sensor output is large, it is determined that the carrier amount in the developing device 14 has decreased, and the carrier amount is estimated. The control voltage to the toner density sensor 48 is corrected based on the estimated carrier amount. Also, since the variation value changes depending on the environment, it has an environmental correction value.

  FIG. 8A shows a table of environmental correction values, and FIG. 8B shows a difference calculation value acquired from the toner density before and after toner replenishment, a carrier amount estimated from the difference calculation value, and this carrier amount. Is a table of control voltage correction values corresponding to

  The environmental correction value table 79 shown in FIG. 8 (a) has the lowest temperature and the lowest humidity as “1”, the highest temperature and the highest humidity as “10”, and the whole is 1-10, etc. The environmental correction value of the environmental value “1” is set to “+10 mV”, the environmental correction value of the environmental value “10” is set to “+28 mV”, and a value that is sequentially increased from “+10 mV” to “+28 mV” by “+2 mV” It is set as a correction value.

  Further, in the control voltage correction value table 80 shown in FIG. 8B, the left end column 81 indicates the output of the toner density sensor before the toner supply Vdb, and the developer immediately after the toner supply is the density by the toner density sensor 28 after t time. When Vda is detected, Vda is the output of the toner density sensor 48, and the difference “Vda−Vdb” plus an environmental correction value is used as a reference value for correction. 0, −100, −200, −300, −400 , −500 (mV).

  Further, in the central column 82 of the control voltage correction value table 80, the difference from the initial amount of the carrier amount in the developing device 14 estimated based on the reference value in the left end column 81 is set to 0, −5, −10, It is shown in 6 stages of −15, −20, and −25 (g).

  In the right end column 83 of the control voltage correction value table 80, a control voltage for maintaining a predetermined toner density detection output with respect to the difference (variation amount) from the initial amount of the carrier amount estimated as described above. Correction values (differences from the initial setting of 2.5 V) are shown in five stages of 0, +120, +145, +170, +195, and +220 (mV).

  As shown in FIG. 6B, the relationship between the fluctuation amount of the carrier amount of the developer and the output of the toner density sensor 62 is that the total amount of toner is a normal amount when the carrier amount decreases from the reference amount. Even if it exists, the sensor output decreases. Therefore, the control device determines that the toner density is high.

  In order to prevent this erroneous determination and maintain a normal toner amount corresponding to the toner replenishment threshold value Dth, as shown in the control voltage correction value table 80 of FIG. In proportion, the control voltage to the toner density sensor 62 is corrected upward.

  Then, when the carrier amount decreases from the reference amount, the control voltage is raised upward even when a signal indicating that the toner concentration is high (decreased sensor output) is output with the reference control voltage even when the toner amount is normal. Since the correction is made, the toner density sensor 62 also outputs the sensor output corrected upward.

  As a result, even when the carrier amount is reduced from the reference amount, an appropriate timing of toner replenishment can be obtained based on the sensor output corrected above the toner density sensor 62, and thus the proper toner amount can be maintained. .

  FIG. 9 is a flowchart of processing operations related to setting of the control voltage of the toner density sensor 62 controlled by the control device shown in FIG. In this process, the environment correction value table 79 and the control voltage correction value table 80 shown in FIGS. 8A and 8B are used. This process is performed when the output value of the toner density sensor 62 exceeds the toner supply voltage threshold.

  In FIG. 9, when the toner supply process is started (step S1), the control device first sets the rotation speed of the YMCK supply motor (step S2). In this process, the rotation speed of the toner replenishing motor engaged with each YMCK toner hopper 27 is set to a preset rotation speed.

  Next, the output value Vdb of the toner concentration sensor 62 before toner supply is held (step S3). In this process, the output value Vdb of the toner density sensor 62 before toner replenishment is stored in a predetermined storage area of the EEPROM 45.

  Subsequently, the toner replenishing motor corresponding to the toner replenishment is rotationally driven based on the rotation speed set in the process of step S2, and a certain amount of toner is replenished (step S4).

  Next, the control device acquires the output value Vda of the toner density sensor 62 after time t from when the toner is replenished, and holds the acquired sensor output value Vda (step S5). In this process, the output value Vda of the toner density sensor 62 after toner replenishment is stored in a predetermined storage area of the EEPROM 45.

  Subsequently, the control device adds the current environmental correction value to the difference “Vda−Vdb” between the output value Vda of the toner density sensor 62 after toner replenishment and the output value Vdb of the toner density sensor 62 before toner replenishment. Vdh is calculated (step S6).

  In this process, 10 environmental correction values from +10 mV to +28 mV shown in the environmental correction value table 79 of FIG. 8A are applied to Vdh1 or Vdh2 of FIGS. 7B and 7C. In this process, an environmental correction value corresponding to the current environmental value is selected, and the result of adding the selected environmental correction value to “Vda−Vdb” is used as a value Vdh.

  Subsequently, the control device compares the value Vdh obtained by the above calculation with the difference Vdh_std (see FIG. 7A) of the output of the toner density sensor 62 before and after the initial toner supply (step S7). In this process, it is determined whether or not “| ΔV | ≧ 100 mV”, where ΔV is the difference between the comparison results.

  If “| ΔV | ≧ 100 mV”, the carrier amount in the developer of the developing device 14 is determined from the value of ΔV, and the control voltage to the toner density sensor 62 is reset (step S8). In this processing, the control voltage correction value table 80 in FIG.

  “| ΔV | ≧ 100 mV” means that ΔV is −100 mV or less, −200 mV, −200 mV or less, −300 mV, −300 mV or less, −400 mV or less, −400 mV or less in the left end column 81 of the control voltage correction value table 80. Any of 5 types of less than −500 mV and −500 mV or less.

  Correspondingly, the difference from the initial amount of the carrier amount determined by estimation is one of −5 g, −10 g, −15 g, −20 g, and −25 g shown in the center column 82 of the control voltage correction value table 80. It is.

  As a correction value for the initial control voltage corresponding to the initial sensor output 2.5V of the toner density sensor 62 corresponding to any of the determined carrier amounts, +120 mV, shown in the right end column 83 of the control voltage correction value table 80, Any of +145 mV, +170 mV, +195 mV, and +220 mV is used as a correction value, the control voltage to the toner density sensor 62 is reset, and the process ends.

  If the sensor output fluctuation is small as in the case of “| ΔV | <100 mV” in the determination of step S7, the control voltage to the toner density sensor 62 is left as it is, and the process is terminated.

  As described above, according to this embodiment, the toner is replenished with a constant amount, the carrier amount in the developing device is estimated from the state of the fluctuation of the sensor output before and after the toner replenishment, and when the fluctuation of the sensor output is large It is determined that the amount of carrier in the developing device has decreased.

  And according to the decreased carrier amount, the setting of the control voltage for controlling the output voltage of the toner concentration sensor 62 is corrected so that the output of the toner concentration sensor 62 increases. An appropriate toner supply timing can be detected based on the sensor output of the toner density sensor 62, and an appropriate toner amount can be maintained at all times.

  In the above embodiment, in the left end column 81 of the control voltage correction value table 80, the difference between Vdh and Vdh_std including the environmental correction value is seen in increments of −100 mV. For example, you may make it see in more detail like -50mV.

  In the above embodiment, the toner supply operation is described based on the output of the toner density sensor. However, a method of determining the toner supply amount from the dot count value to be printed may be used. Further, Vdh_std when the developing device 9 is new may be held in the nonvolatile memory.

Although several embodiments of the present invention have been described, the present invention is included in the invention described in the claims and the equivalents thereof. Hereinafter, the invention described in the scope of claims of the present application will be appended.
[Appendix 1]

A developer tank that circulates a developer containing toner and a carrier for developing the electrostatic latent image on the image carrier;
A toner density sensor disposed in a circulation path of the developer in the developer tank and outputting density information of the toner in the developer;
A replenishment port disposed in the circulation path;
A toner replenishing unit that determines whether or not toner replenishment is necessary based on an output value of the toner density sensor, and replenishes toner from the replenishing port to the developing tank with a constant replenishment amount when it is determined that replenishment is necessary; ,
The output value of the toner density sensor before replenishment when it is determined that replenishment is necessary and the developer portion containing the toner replenished from the replenishment port by the toner replenishment section are arranged in the toner density sensor. A comparison unit for comparing the output value of the toner density sensor at the timing of moving to the installation position;
A carrier amount estimation unit that estimates a carrier amount in the developer based on a difference between output values of the toner density sensor before and after replenishment of the toner indicated by a comparison result by the comparison unit;
When the carrier amount estimation unit estimates that the carrier amount in the developer is smaller than the intended carrier amount, a control voltage for controlling the output value of the toner concentration sensor is output from the toner concentration sensor. A control voltage correction unit for correcting the value to increase;
An image forming apparatus comprising:
[Appendix 2]

2. The image forming apparatus according to claim 1, wherein the control voltage correction unit corrects the control voltage with a control voltage correction value including an environmental correction value.
[Appendix 3]

A developer tank that circulates a developer containing toner and a carrier for developing the electrostatic latent image on the image carrier;
A toner concentration sensor disposed in a circulation path of the developer in the developer tank and outputting density information of toner in the developer;
A replenishment port disposed in the circulation path;
A toner replenishing method for an image recording apparatus comprising:
A toner replenishing step of determining whether or not toner replenishment is necessary based on an output value of the toner density sensor, and replenishing toner from the replenishing port to the developing tank with a constant replenishment amount when it is determined that replenishment is necessary; ,
The output value of the toner density sensor before replenishment when it is determined that replenishment is necessary and the developer portion containing the toner replenished from the replenishment port by the toner replenishment section are arranged in the toner density sensor. A comparison step of comparing the output value of the toner density sensor at the timing of moving to the installation position;
A carrier amount estimating step of estimating a carrier amount in the developer based on a difference between output values of the toner density sensor before and after replenishment of the toner indicated by a comparison result in the comparison step;
When the carrier amount estimation step estimates that the carrier amount in the developer is less than the intended carrier amount, a control voltage for controlling the output value of the toner concentration sensor is output as the output of the toner concentration sensor. A control voltage correction step for correcting with a control voltage correction value in consideration of the environmental correction value so that the value increases;
A toner replenishing method comprising:
[Appendix 4]

A developer tank that circulates a developer containing toner and a carrier for developing the electrostatic latent image on the image carrier;
A toner concentration sensor disposed in a circulation path of the developer in the developer tank and outputting density information of toner in the developer;
A replenishment port disposed in the circulation path;
A toner replenishment program which is read and executed by a control unit of an image recording apparatus having
A toner replenishment procedure for determining whether or not toner replenishment is necessary based on an output value of the toner density sensor, and replenishing toner from the replenishment port to the developing tank with a constant replenishment amount when it is determined that replenishment is necessary; ,
The output value of the toner density sensor before replenishment when it is determined that replenishment is necessary and the developer portion containing the toner replenished from the replenishment port by the toner replenishment section are arranged in the toner density sensor. A comparison procedure for comparing the output value of the toner density sensor at the timing of moving to the installation position;
A carrier amount estimation procedure for estimating a carrier amount in the developer based on a difference between output values of the toner density sensor before and after the toner replenishment indicated by a comparison result of the comparison procedure;
When it is estimated that the carrier amount in the developer is less than the intended carrier amount by the carrier amount estimation procedure, a control voltage for controlling the output value of the toner concentration sensor is output as the output of the toner concentration sensor. A control voltage correction procedure for correcting with a control voltage correction value taking into account the environmental correction value so that the value increases,
A toner replenishment program comprising:

  The present invention can be used for an image forming apparatus that appropriately controls toner density based on an estimated carrier amount in a developing device.

1 Full-color image forming device (printer)
DESCRIPTION OF SYMBOLS 2 Image forming part 3 Transfer belt unit 4 Toner supply part 5 Paper feed part 6 Belt type fixing unit 8 Transfer belt 8a Lower running part surface 9 (9m, 9c, 9y, 9k) Developing device 10 Photosensitive drum 11 Cleaner 12 Charging roller DESCRIPTION OF SYMBOLS 13 Optical writing head 14 Developing device 15 Developing roller 16 1st stirring conveyance member 17 2nd stirring conveyance member 18 Drive roller 19 Driven roller 21 Primary transfer roller 23 Secondary transfer part 24 Belt cleaner 25 Cleaning blade 26 Waste toner collection | recovery Container 27 (27m, 27c, 27y, 27k) Toner hopper 29 Paper feed cassette 31 Paper take-out roller 32 Feed roller 33 Rolling roller 34 Standby transport roller pair 35 Secondary transfer roller 36 Diffuse reflection type density sensor 37 Paper discharge tray 38 Operation Panel unit 40 Printer controller 1 bus 42 network controller 43 I / F (interface)
44 Head Controller 45 EEPROM (electrically erasable programmable ROM)
46 ROM (read only memory)
47 Feeding motor 49 Registration sensor 51 DDS (developer drum set: development device) new and old detection sensor 52 High pressure unit 53 Y-drive device 54 M-drive device 55 C-drive device 56 K-drive device 57 Y toner replenishing device 58 M Toner replenishing device 59 C toner replenishing device 60 K toner replenishing device 61 sensor control voltage applying unit 62 toner density sensor 62y Y toner density sensor 62m M toner density sensor 62c C toner density sensor 62k K toner density sensor 63 outer wall 64 inner partition wall 65 ( 65a, 65b) Developing tank 66 Doctor blade 67 Detection surface 68, 71 Rotating shaft 69, 72 Spiral fin 73 Blade holding part 74 Elastic sheet (blade)
75 Cleaning blade 76 Pulse signal 77 Outlet 78 Supply port 79 Environmental correction value table 80 Control voltage correction value table 81 Left end column 82 Center column 83 Right end column

Claims (4)

A developer tank that circulates a developer containing toner and a carrier for developing the electrostatic latent image on the image carrier;
A toner density sensor disposed in a circulation path of the developer in the developer tank and outputting density information of the toner in the developer;
A replenishment port disposed in the circulation path;
A toner replenishing unit that determines whether or not toner replenishment is necessary based on an output value of the toner density sensor, and replenishes toner from the replenishing port to the developing tank with a constant replenishment amount when it is determined that replenishment is necessary; ,
The output value of the toner density sensor before replenishment when it is determined that replenishment is necessary and the developer portion containing the toner replenished from the replenishment port by the toner replenishment section are arranged in the toner density sensor. A comparison unit for comparing the output value of the toner density sensor at the timing of moving to the installation position;
A carrier amount estimation unit that estimates a carrier amount in the developer based on a difference between output values of the toner density sensor before and after replenishment of the toner indicated by a comparison result by the comparison unit;
When the carrier amount estimation unit estimates that the carrier amount in the developer is smaller than the intended carrier amount, a control voltage for controlling the output value of the toner concentration sensor is output from the toner concentration sensor. A control voltage correction unit for correcting the value to increase;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the control voltage correction unit corrects the control voltage with a control voltage correction value in consideration of an environmental correction value. A developer tank that circulates a developer containing toner and a carrier for developing the electrostatic latent image on the image carrier;
A toner concentration sensor disposed in a circulation path of the developer in the developer tank and outputting density information of toner in the developer;
A replenishment port disposed in the circulation path;
A toner replenishing method for an image recording apparatus comprising:
A toner replenishing step of determining whether or not toner replenishment is necessary based on an output value of the toner density sensor, and replenishing toner from the replenishing port to the developing tank with a constant replenishment amount when it is determined that replenishment is necessary; ,
The output value of the toner density sensor before replenishment when it is determined that replenishment is necessary and the developer portion containing the toner replenished from the replenishment port by the toner replenishment section are arranged in the toner density sensor. A comparison step of comparing the output value of the toner density sensor at the timing of moving to the installation position;
A carrier amount estimating step of estimating a carrier amount in the developer based on a difference between output values of the toner density sensor before and after replenishment of the toner indicated by a comparison result in the comparison step;
When the carrier amount estimation step estimates that the carrier amount in the developer is less than the intended carrier amount, a control voltage for controlling the output value of the toner concentration sensor is output as the output of the toner concentration sensor. A control voltage correction step for correcting with a control voltage correction value in consideration of the environmental correction value so that the value increases;
And a toner replenishing method. A developer tank that circulates a developer containing toner and a carrier for developing the electrostatic latent image on the image carrier;
A toner concentration sensor disposed in a circulation path of the developer in the developer tank and outputting density information of toner in the developer;
A replenishment port disposed in the circulation path;
A toner replenishment program which is read and executed by a control unit of an image recording apparatus having
A toner replenishment procedure for determining whether or not toner replenishment is necessary based on an output value of the toner density sensor, and replenishing toner from the replenishment port to the developing tank with a constant replenishment amount when it is determined that replenishment is necessary; ,
The output value of the toner density sensor before replenishment when it is determined that replenishment is necessary and the developer portion containing the toner replenished from the replenishment port by the toner replenishment section are arranged in the toner density sensor. A comparison procedure for comparing the output value of the toner density sensor at the timing of moving to the installation position;
A carrier amount estimation procedure for estimating a carrier amount in the developer based on a difference between output values of the toner density sensor before and after the toner replenishment indicated by a comparison result of the comparison procedure;
When it is estimated that the carrier amount in the developer is less than the intended carrier amount by the carrier amount estimation procedure, a control voltage for controlling the output value of the toner concentration sensor is output as the output of the toner concentration sensor. A control voltage correction procedure for correcting with a control voltage correction value taking into account the environmental correction value so that the value increases,
A toner replenishment program comprising: