JP2012103560A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of accurately controlling toner density by discriminating a tilt of a developing device, that is, a tilt of a main body device with a low-cost configuration.
A control voltage correction table 88 for a toner concentration sensor 62 has a detection signal of 2.5 V when the developing device 14 filled with a developer 83 having a toner concentration of 6% is in a horizontal state. When the output of the toner density sensor 62 is measured by gradually increasing the inclination of the developing device 14 whose control voltage is initially set to 5.75 V so as to be output from the horizontal state by an angle of 0.5 degrees to a maximum of 8.0 degrees. The voltage gradually decreases from 2.50V when horizontal to 1.70V by 0.05V. The correction control voltage value for maintaining this output at 2.50 V is tested in practice, and the numerical value described in the lower half of the control voltage value (V) column 92 is obtained. When the angle is tilted in the minus direction, the upper half of the control voltage value (V) column 92 is obtained. Using this, the driving voltage of the toner density sensor 62 is corrected.
[Selection] Figure 10

Description

  The present invention relates to an image forming apparatus capable of accurately controlling toner density by discriminating the inclination of a developing device, that is, the inclination of a main body device, with a low-cost configuration.

  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 unit, a pipe having a built-in coil screw or a natural fall path due to toner gravity 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 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.

  In such a toner concentration sensor, if the developer stays on the detection surface, it becomes impossible to detect the accurate toner concentration. If an accurate toner density cannot be detected, a malfunction may be caused in controlling the toner replenishment amount.

  Therefore, the elastic sheet material is fixed so as to be parallel to the shaft portion at a position facing the detection surface of the toner density sensor of the shaft portion of the circulation conveyance screw that circulates and conveys the developer in the developing device. Thus, a sensor that cleans the detection surface of the toner density sensor has been proposed. (For example, refer to Patent Document 1.)

  In such a toner concentration sensor, if the developing device is always kept horizontal, the developer amount on the detection surface is constant, so that the toner concentration can be detected accurately, and the toner replenishment amount control device malfunctions. There is no.

  However, the place where the image forming apparatus main body is actually installed is not always horizontal. When the apparatus main body is inclined, the developer amount on the detection surface of the toner density sensor changes more than the reference amount.

  As described above, when the developer amount on the detection surface of the toner concentration sensor changes more than the reference amount, the toner concentration cannot be detected accurately, and the toner replenishment amount control device malfunctions.

  In view of this, there have been proposed an apparatus for detecting the inclination with two toner density sensors and an apparatus for detecting the inclination of the apparatus main body by installing toner density sensors at different locations in the two developing units. In this way, erroneous detection of the toner density can be prevented by detecting the inclination of the apparatus main body and issuing a warning. (For example, see Patent Document 2.)

JP 05-150650 A JP 2008-040227 A

  However, it is uneconomical to use two sensors to detect the tilt of the apparatus body as in the technique of Patent Document 2 above. Further, there is a problem in detection accuracy in detecting the inclination of the apparatus main body from the inclination detection data of a plurality of developing devices.

  The present invention has been made in view of the above circumstances, and provides an image forming apparatus capable of accurately controlling toner density by discriminating the inclination of the developing unit, that is, the inclination of the main body apparatus with a low-cost configuration. Objective.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a toner density sensor control voltage reference value stored in a memory of a new developer containing a developer having a proper toner density, and the new article. Control unit for reading out the toner density sensor control voltage reference value from the memory when the developing device is mounted on the image forming apparatus main body, and the toner density sensor control voltage reference value read out by the control voltage reading unit The sensor driving means for driving the toner density sensor of the new developing device, the sensor output reading means for reading the output value of the toner density sensor driven by the sensor driving means, and the sensor output reading means The output value of the toner density sensor and the new developer containing the developer having the appropriate toner density are installed horizontally. A difference calculating means for calculating a difference from an appropriate output value to be output by the toner density sensor, a relationship between the difference calculated by the difference calculating means and the inclination of the developing unit corresponding to the difference, and the inclination And a table showing a relationship between the toner density sensor control voltage value to be corrected so that the output value of the toner density sensor at the inclination degree becomes the appropriate output value, and the sensor driving means includes the difference calculation The inclination of the new developer is acquired based on the difference calculated by the means and the table, and is corrected to the appropriate output value of the toner density sensor based on the acquired inclination and the table. The toner density sensor control voltage value to be acquired is acquired, and the toner density sensor is driven by the acquired toner density sensor control voltage value.

  In this image forming apparatus, for example, when the absolute value of the difference exceeds 300 mV (millivolt), the sensor driving unit acquires the inclination of the new developer based on the difference and the table, and The toner density sensor control voltage value to be corrected to the appropriate output value of the toner density sensor is acquired based on the acquired inclination degree and the table, and the toner density sensor control voltage value is used to acquire the toner density sensor control voltage value. The sensor is driven, the sensor output reading means reads the output value of the toner density sensor driven by the sensor driving means, and the difference calculating means outputs the output of the toner density sensor read by the sensor output reading means. A difference between the value and an appropriate output value to be output by the toner density sensor, and the sensor driving means And the toner density sensor control voltage to be corrected to the appropriate output value of the toner density sensor based on the acquired slope degree and the table. A value is acquired, and the toner density sensor is driven by the acquired toner density sensor control voltage value.

  In the image forming apparatus, for example, the sensor driving unit may control the toner concentration sensor control voltage value for driving the toner concentration sensor when the absolute value of the difference is 300 mV (millivolt) or less. It is configured to set the voltage reference value.

  According to the present invention, it is possible to provide an image forming apparatus capable of accurately controlling toner density by discriminating the inclination of the developing unit, that is, the inclination of the main body apparatus with a low-cost configuration.

1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer) according to Embodiment 1 of the 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. FIG. 3 (a) shows the configuration of each part of the developing tank in order to show the arrangement relationship among the second stirring / conveying member, the cleaning blade, and each part of the toner density sensor in the developing tank of the developing device of the printer according to the first embodiment. (B) is an enlarged view of a portion surrounded by a broken line h in (a). 6 is a diagram illustrating an example of an output of a toner density sensor of the developing device of the printer according to the first embodiment. FIG. FIG. 6 is a diagram illustrating a pulse signal with a narrow period that appears superimposed on an output signal that should be the original output value of the toner density sensor of the printer according to the first exemplary embodiment. FIG. 4 is a cross-sectional view illustrating an internal configuration and a developer return path by cutting the developing device of the printer according to the first embodiment in a direction indicated by an arrow g in FIG. (a) is a diagram showing the relationship between the toner concentration sensor and the developer when the developing device is in a horizontal state, and (b) is the relationship between the toner concentration sensor and the developer when the developing device is inclined in an angle plus direction from the horizontal plane. FIG. 4C is a diagram showing a relationship between the toner density sensor and the developer when the developing device is inclined in the minus direction from the horizontal plane. 6 is a graph showing a change in the output value of the toner density sensor when an inclination is generated in the developing device that is initially set so that the output value of the toner density sensor becomes 2.5 V with respect to the toner density of 6%. 7 is a correction table of control voltage for the toner density sensor when a new developing device whose control voltage is initially set so that the output value of the toner density sensor for 2.5% of the toner density is 2.5 V is installed at an inclination. . After correction based on the correction table, the sensor output when the developer is inclined minus 5 degrees with respect to the output value graph of the set output value 2.5 V when the toner density is 6% and the developer is horizontal is also inclined plus 5 degrees. The sensor output at this time also shows an output value of 2.5 V with respect to the toner density of 6%. (a) is a flowchart of a process that makes it possible to accurately control the toner density by determining the inclination of the developing device using a correction table, and (b) is based on the output of the toner density sensor corrected in the process of (a). 7 is a flowchart of processing for properly supplying toner to a developer.

  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 unit 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. Consists of a parallel 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.

  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 a toner supply path (not shown).

  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, 61 corresponding to each YMCK are driven to replenish toner to the developing device 9.

  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 unit 40, based on an output signal output for the toner density sensor 62 for each YMCK to detect the toner replenishment threshold, details the inclination of the developing device 9 to be described later and a new one corresponding to the inclination. The toner density sensor control voltage 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, toner is supplied from the toner hopper 27 corresponding to the developing device 14 of the toner supply unit 4 through the 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.

  FIG. 5 is a diagram showing an example of the output of the toner density sensor 62 described above. In FIG. 5, the horizontal axis indicates time (second (s)), and the vertical axis indicates the output average (voltage (V)) of the toner density sensor 62. Solid line graphs 76 (76a, 76b, 76c) indicate changes in the output value of the toner density sensor 62.

  Here, in order to explain the output of the toner density sensor 62, the two-component developer is again considered as being divided into carrier and toner. When there is a lot of toner, the magnetic permeability of the two-component developer is lowered and the output value of the magnetic permeability sensor, that is, the toner density sensor 62 is lowered.

  Conversely, when the amount of toner is small, the magnetic permeability of the two-component developer increases and the output value of the magnetic permeability sensor, that is, the toner density sensor 62 increases. For this reason, the output value of the toner density sensor 62 corresponding to the developer density to which the toner is to be replenished is set in advance in, for example, the EEPROM 45 as a replenishment threshold 77 (value indicated by the broken line in FIG. 5).

  Then, after starting printing at time t1 in FIG. 5, the amount of toner decreased at time t2 is detected by an increase in the output value of toner density sensor 62, and YMCK corresponding to the increase in output value of toner density sensor 62 is detected. The toner supply device of any of the developing devices 9 is driven to supply toner to the developing device 9.

  If the output value of the toner density sensor 62 satisfies the replenishment threshold value 77 at time t3, the driving of the toner replenishing device is stopped and toner replenishment is stopped.

  Although not shown in the figure, if the toner concentration falls below a predetermined value (see time t2) and the toner concentration does not increase within a predetermined time (see time t3) even if the toner replenishment operation is performed, the toner It is determined that there is no toner in the hopper 27, and the printing process is stopped.

  Incidentally, the output value of the toner density sensor 62 indicated by the solid line graph 76 (76a, 76b, 76c) in FIG. 5 indicates the average of the output values. Here, the average is to average the values of the pulse signals having a narrow period appearing superimposed on the solid line graph 76 (76a, 76b, 76c) which should be the original output value of the toner density sensor 62.

  FIG. 6 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 62. Here, the reason why the pulse signal 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 78 having a narrow period shown in FIGS. 6 (a) and 6 (b).

  That is, the Max value 78 a of the pulse signal 78 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 78 b of the pulse signal 78 indicates the timing at which the elastic sheet 74 is separated from the detection surface 67.

  The output value of the toner density sensor 62 indicated by the solid line graph 76 (76a, 76b, 76c) in FIG. 5 is obtained by calculating the average value of the output values of the pulse signal 78 as described above.

  FIG. 7 is a cross-sectional view showing the internal structure and the developer reflux path by cutting the developing device 14 in the direction indicated by the arrow g in FIG. In FIG. 7, the same components as those in FIGS. 3 (a) and 3 (b) are denoted by the same reference numerals as those in FIGS. 3 (a) and 3 (b). Further, in FIG. 7, the cleaning blade 75 is not shown, and the toner density sensor 62 is shown very simply.

  In FIG. 7, the second agitating and conveying member 17 supplies the developer 81 from the developing tank 65b to the developing tank 65a, and the first agitating and conveying member 16 supplies the developer from the developing tank 65a to the developing tank 65b. The outlet 82 is shown. The arrows shown in the developing tanks 65a and 65b indicate the direction in which the developer returns.

  8A shows a state of the developer 63 with respect to the toner density sensor 62 when the developing device 14 shown in FIG. 7 is in a horizontal state, and FIG. 8B shows the developing device 14 from the horizontal plane 84. FIG. 8C shows the state of the developer 83 with respect to the toner density sensor 62 when it is inclined in the plus direction indicated by the arrow j, and FIG. 8C shows that the developing device 14 is tilted from the horizontal plane 84 in the minus direction indicated by the arrow k. 7 is a diagram illustrating a state of the developer 83 with respect to the toner density sensor 62 when the toner is in contact. FIG.

  When the developing device 14 is inclined in the plus direction shown in FIG. 8B, the developer 83 is shifted to the left side, that is, away from the toner concentration sensor 62, so that the developer 83 in the toner concentration sensor 62 portion is horizontal. Less than Therefore, the output of the toner density sensor 62 decreases.

  On the contrary, when the developing device 14 is inclined in the minus direction shown in FIG. 8C, the developer 83 is shifted to the right side, that is, in the direction approaching the toner concentration sensor 62, and the developer 83 in the toner concentration sensor 62 portion. Is more than when it is level. Therefore, the output of the toner density sensor 62 increases.

  As described above, even if the toner concentration of the developer 83 is the same, if the developing device 14 is inclined in either the angle plus or minus direction, the amount of the developer 83 in the toner density sensor 62 portion is increased. A difference occurs, and the output of the toner density sensor 62 changes so as to decrease or increase from the reference.

  FIG. 9 shows the toner density when the developer 14 is initially set so that the output value of the toner density sensor 62 that detects the toner density becomes 2.5 V when the toner density is 6%. It is a graph which shows the change of the output value of the sensor 62. FIG.

  As shown in FIG. 9, the developing device 14 for the toner concentrations 5%, 6% and 7% of the toner concentration sensor 62 which is initially set so that the output value becomes 2.5V with respect to the toner concentration of 6% is horizontal. When the developing device 14 is inclined 5 degrees in the minus angle direction, the sensor output 86 is high, and when the developing device 14 is inclined 5 degrees in the angle plus direction, the sensor value 86 is increased. The output 87 is low.

  Incidentally, the developing device 14 including the photosensitive drum 10 shown in FIGS. 3A and 3B is a consumable item for the printer 1. The developing device 14 is mounted with a nonvolatile memory (not shown). The nonvolatile memory of the new developing device 14 stores data indicating that the developing device 14 is new and the initial value of the control voltage for driving the toner density sensor when assembled and shipped from the factory.

  The initial value of the control voltage is a control voltage value at which the toner concentration sensor 62 can output a detection signal of 2.5 V when the developing device 14 filled with the developer 83 having a toner concentration of 6% is placed in a horizontal state. is there. In this example, it is 5.75V.

  FIG. 10 shows a control voltage correction table for the toner density sensor 62 when the printer main body is installed with the developing device 14 in which the initial value of the control voltage of the toner density sensor 62 is set as described above being inclined. It is.

  The correction table 88 has a control voltage of 5.75 V so that the toner concentration sensor 62 outputs a detection signal of 2.5 V when the developing device 14 filled with the developer 83 having a toner concentration of 6% is in a horizontal state. It is a table composed of data obtained empirically by conducting a field test in which the initially set developing device 14 is tilted in the positive and negative directions.

  In this practical test, as shown in the lower half of the inclination (degree) column 90 of the correction table 88, first, the developing device 14 is moved from the horizontal state to an angle plus direction by 0.5 degrees up to a maximum of 8.0 degrees. The inclination is gradually increased, and the output of the toner density sensor 62 at that time is measured.

  When measured, as shown in the lower half of the sensor output value (V) column 91 of the correction table 88, the sensor output gradually decreases from 2.50V in the horizontal state to 1.70V in 0.05V increments. Go. Since the toner density of 6% is unchanged, the output of the toner density sensor 62 must be 2.5V.

  Therefore, an experiment is conducted to determine how much a correction control voltage value is necessary to maintain the output of the toner density sensor 62 that gradually decreases from 2.50 V to 1.70 V in steps of 0.05 V. .

  The control voltage value for correction with respect to each inclination in the angle plus direction obtained empirically in this experiment is a numerical value described in the lower half of the control voltage value (V) column 92 of the correction table 88.

  Next, in this practical test, as shown in the upper half of the inclination (degree) column 90 of the correction table 88, the developing device 14 is moved from the horizontal state to the angle minus direction by 0.5 degrees at a minimum “−8. The inclination is gradually increased to “0 degree”, and the output of the toner density sensor 62 at that time is measured.

  As a result of measurement, as shown in the upper half of the sensor output value (V) column 91 of the correction table 88, the sensor output gradually increases from 2.50V in the horizontal state to 3.30V in 0.05V increments. Go. In this case as well, since the toner density 6% is unchanged, the output of the toner density sensor 62 should be 2.5V.

  In this case as well, an experiment was conducted to determine how much control voltage value for correction is necessary to maintain the output of the toner density sensor 62, which gradually increases from 2.50V to 3.30V in increments of 0.05V. Try.

  The control voltage value for correction for each inclination in the minus direction of the angle obtained empirically in this experiment is a numerical value described in the upper half of the control voltage value (V) column 92 of the correction table 88. In the “ΔV value” column 89 of the correction table 88, the difference between the output value before correction of the toner density sensor 62 and 2.50V is described.

  Therefore, if the new developing device 14 is inclined and a difference is generated between the output of the toner density sensor 62 and 2.50 V, the inclination of the developing device 14 is calculated from the difference “ΔV value” and the correction table 88. And the correction control voltage value for correcting the output of the toner density sensor 62 can be known.

  The correction table 88 is written in a non-volatile memory built in the developing device 14 when the developing device 14 is assembled and manufactured and shipped from the factory. In the nonvolatile memory, the toner density of the developer 83 filled in the developing device 14 is 6%, and the toner density sensor 62 should output a detection signal of 2.5 V at that time, and a control voltage for that purpose. Is 5.75V, is recorded as initial setting data.

  FIG. 11 shows an output value after correcting the output of the toner density sensor 62 of the new developing device 14 having the inclination of “−5 degrees” shown in FIG. Is a graph showing the output value after correcting the output of the toner density sensor 62 of the new developing device 14 having a slope of "."

  As shown in FIG. 11, when the toner density is 6%, the horizontal output value graph 85 of the toner density sensor 62 which is set to the output value 2.5 V when the developing device 14 is horizontal, Both the sensor output 86 when the developing unit 14 is tilted by minus 5 degrees and the sensor output 87 when the developing unit 14 is tilted by plus 5 degrees both show an output value of 2.5 V with respect to the toner density of 6%.

  FIG. 12A is a flowchart of a process for determining the inclination of the developing device (that is, the inclination of the printer main body) using the correction table 88 performed by the printer controller unit 40 so that accurate toner density control can be performed. is there.

  FIG. 12B is a flowchart of a process for appropriately supplying toner to the developer whose density has been reduced based on the output of the toner density sensor 62 corrected by the process of FIG. is there.

  In FIG. 12A, when a new developing device 14 including the photosensitive drum 10 is mounted on the main body of the printer 1, the printer controller unit 40 (hereinafter simply referred to as the control unit 40) stores the memory of the developing device 14. The control voltage value (Vcont: 5.75 V shown in FIG. 10 in this example) of the toner density sensor 62 is read from the data contents of the above. Then, the read control voltage value (Vcont) is set in the toner density sensor 62 for each CMYK.

  Next, the control unit 40 idles the new developing device 14 (development of the photosensitive drum 10 is not performed, and simply drives each unit to circulate the developer 83 to the two developing tanks 65 (65a, 65b). Drive) to read the output value (Vnew) of the toner density sensor 62 (step S2).

  Then, the difference ΔV between the read output value (Vnew) of the toner density sensor 62 and the set value 2.5 V of the data content (correction table 88 in FIG. 10) stored in the memory of the new developing device 14 is obtained. It is determined whether or not | ΔV | ≦ 300 mV (step S3).

  If the difference threshold value of 300 mV is | ΔV | ≦ 300 mV during the above-described field test, it is found that a large error does not occur in the subsequent output value of the toner density sensor 62 in detecting the toner replenishment timing. It depends on what you did.

  If | ΔV | ≦ 300 mV in the determination in step S3 (Yes in S3), the control unit 40 uses the control voltage value (Vcont) of the toner concentration sensor 62 read from the memory as the toner concentration thereafter. The control voltage value for driving the sensor 62 is set (step S4), and the process ends.

  On the other hand, if | ΔV |> 300 mV is determined in step S3 (No in S3), the inclination of the developing device 14 is determined from the difference ΔV and the correction table 88, and corresponds to the inclination. The control voltage value setting value (Vcont) is acquired from the control voltage value (V) column 92 of the correction table 88, and the acquired control voltage value setting value (Vcont) is used as a new control voltage value (Vcont). The sensor 62 is reset (step S).

  And the control part 40 returns to the process of step S2, and repeats step S2, S3. Therefore, if the determination in step S3 is No, steps S5, S2, and S3 are repeated until the determination in step S3 becomes Yes.

  Thereby, even when a new developing device 14 is installed with an inclination, a properly corrected control voltage value for driving the toner density sensor 62 is set.

  Following the above, in FIG. 12B, the control unit 40 starts printing (step S10). Subsequently, the control unit 40 first reads the output value T / D (V) of the toner density sensor 62 for each CMYK individually (step S11).

  Next, the control unit 40 determines whether or not the output value T / D (V) of the toner density sensor 62 for each CMYK individually read in the process of step S11 is equal to or less than the toner replenishment threshold (step S12).

  If the output value T / D (V) of the toner density sensor 62 is equal to or less than the toner replenishment threshold value (Yes in S12), the control unit 40 finishes printing (there is no print data from an external host device, or It is determined whether or not it is a stop instruction from the operation panel unit (step S13).

  If the printing is not finished (No in S13), the process returns to step S11 and the processes in steps S11 to S13 are repeated.

  If the output value T / D (V) of the toner density sensor 62 exceeds the toner replenishment threshold value in the discrimination in step S12 (No in S12), the control unit 40 has a low toner density. Toner supply is executed from one of the toner hoppers 27 (27y, 27m, 27c, 27k) corresponding to the toner color (step S14), the process returns to step S11, and steps S11, S12, and S14 are repeated.

  When the toner density is restored to an appropriate value (Yes in S12), the control unit 40 proceeds again to Step S13. If the determination in S13 is No, Step S11, S12, S13, or S11, The processes of S12, S14, and S11 are repeated.

  Eventually, when it is determined in step S13 that printing has ended (YES in S13), the control unit 40 stops driving each unit shown in FIG. 2 and ends the printing process.

  As a result, even when a new developing device 14 is installed with an inclination, an appropriate timing for supplying the toner is recognized by the output of the toner density sensor 62 driven by the corrected control voltage value, and the toner Replenishment is performed and a high-quality image can always be printed.

  The present invention can be used in electrophotographic copying machines, word processors, facsimile machines, laser beam printers, LED printers, and the like.

DESCRIPTION OF SYMBOLS 1 Full color image forming apparatus 2 Image forming part 3 Transfer belt unit 4 Toner supply part 5 Paper feeding part 6 Belt type fixing unit 8 Transfer belt 8a Lower running part surface 9 (9m, 9c, 9y, 9k) Developing device 10 Photosensitive drum DESCRIPTION OF SYMBOLS 11 Cleaner 12 Charging roller 13 Optical writing head 14 Developing device 15 Developing roller 16 1st stirring conveyance member 17 2nd stirring conveyance member 18 Drive roller 19 Followed roller 21 Primary transfer roller 23 Secondary transfer part 24 Belt cleaner 25 Cleaning Blade 26 Waste toner collection container 27 (27m, 27c, 27y, 27k) Toner hopper 29 Paper feed cassette 31 Paper take-out roller 32 Feeding roller 33 Rolling roller 34 Standby conveyance roller pair 35 Secondary transfer roller 36 Diffuse reflection type density sensor 37 Output tray 38 Operation panel 0 printer controller 41 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 61 K toner replenishing device 62 Toner concentration sensor 62y Y toner concentration sensor 62m M toner concentration sensor 62c C toner concentration sensor 62k K toner concentration sensor 63 Outer wall 64 Internal partition wall 65 (65a, 65b) Developer 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 (76a, 76b, 76c) Average output of toner density sensor (V)
77 Supply threshold 78 Pulse signal 78a Pulse signal Max value 78b Pulse signal Min value 81 Supply port 82 Exit 83 Developer 84 Horizontal surface 85, 86, 87 Toner density sensor output value 88 Correction table 89 ΔV value column 90 Inclination (degree) column 91 Sensor output value (V) field 92 Control voltage value (V) field

Claims (3)

A toner concentration sensor control voltage reference value stored in a memory of a new developer containing a developer having an appropriate toner concentration; and
Control voltage reading means for reading the toner density sensor control voltage reference value from the memory when the new developer is mounted on the image forming apparatus main body;
Sensor driving means for driving the toner density sensor of the new developer at the toner density sensor control voltage reference value read by the control voltage reading means;
Sensor output reading means for reading an output value of the toner density sensor driven by the sensor driving means;
The toner density sensor outputs the output value of the toner density sensor read by the sensor output reading means and the new developer containing the developer having the proper toner density is installed horizontally. Difference calculating means for calculating a difference from the appropriate output value,
The relationship between the difference calculated by the difference calculating means and the inclination of the developing unit corresponding to the difference, and the output value of the toner density sensor at the inclination and the inclination are the appropriate output values. A table showing the relationship with the toner density sensor control voltage value to be corrected,
With
The sensor driving unit acquires the inclination degree of the new developer based on the difference calculated by the difference calculation unit and the table, and the toner based on the acquired inclination degree and the table. Acquiring the toner density sensor control voltage value to be corrected to the appropriate output value of the density sensor, and driving the toner density sensor by the acquired toner density sensor control voltage value;
An image forming apparatus. When the absolute value of the difference exceeds 300 mV (millivolt), the sensor driving unit acquires the inclination of the new developer based on the difference and the table, and the acquired inclination and the table And acquiring the toner density sensor control voltage value to be corrected to the appropriate output value of the toner density sensor, and driving the toner density sensor with the acquired toner density sensor control voltage value,
The sensor output reading unit reads an output value of the toner density sensor driven by the sensor driving unit,
The difference calculating means calculates a difference between an output value of the toner density sensor read by the sensor output reading means and an appropriate output value to be output by the toner density sensor;
The sensor driving means acquires the inclination of the new developing device based on the difference and the table, and sets the appropriate output value of the toner density sensor based on the acquired inclination and the table. Repeatedly acquiring the toner density sensor control voltage value to be corrected and driving the toner density sensor with the acquired toner density sensor control voltage value;
The image forming apparatus according to claim 1.   The sensor driving means sets the toner density sensor control voltage value that has driven the toner density sensor to the toner density sensor control voltage reference value when the absolute value of the difference is 300 mV (millivolt) or less. The image forming apparatus according to claim 1 or 2.