JP2008276118A - Method of measuring toner concentration measurement sensitivity, toner concentration control method, toner concentration controller, developing device, image forming apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring the toner concentration measurement sensitivity by taking into consideration the attached state of the sensor to a developing device, to provide a toner concentration control method and a toner concentration controller for controlling the toner concentration, using the measuring sensitivity acquired by the method while taking into consideration variation in the output value of the sensor caused according to the environment, to provide a developing device using the methods and the controller, and to provide an image forming apparatus and an image forming method using the toner concentration controller and the developing device. <P>SOLUTION: In the toner concentration measuring sensor 56Y, the output voltage thereof can be adjusted by adjusting the input voltage thereof. A first input voltage for acquiring the output voltage corresponding to the reference toner concentration in the sensor 56Y before being installed in the developing means 50Y and a second input voltage for acquiring the output voltage corresponding to the reference toner concentration in the sensor 56Y after being installed in the developing means 50Y are used, then, the sensitivity of the sensor 56Y is measured on the basis of a difference voltage between the first input voltage and the second input voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses a toner density measurement sensitivity measurement method for measuring toner density measurement sensitivity in a developing device provided in an image forming apparatus such as a copying machine, a facsimile machine, a printer, etc., and uses the toner density measurement sensitivity obtained by this method. The present invention relates to a toner density control method and a toner density control device for controlling the toner density, such a developing device using these, and an image forming device and an image forming method using such a toner density control device or developing device.

  In a developing device that is provided in an image forming apparatus such as a copying machine, a facsimile machine, or a printer and that performs development using a two-component developer containing toner and a magnetic carrier, the toner concentration in the developer used for development is In view of the influence on the image to be formed, as described in [Patent Document 1], [Patent Document 2], etc., such toner density is detected by a sensor, and toner is replenished based on the detection result. Thus, the toner density is set to a predetermined range suitable for development, and the developing ability is maintained.

  If the toner density becomes excessively high, image density rises, toner scatters, developer leakage from the developing device, scumming, etc. occur, and if the toner density decreases excessively, the image density decreases and the image carrier is exposed. Control of toner concentration is important because carrier adhesion occurs.

  A magnetic permeability sensor is known as a sensor for detecting the toner concentration. The magnetic permeability sensor uses the fact that the magnetic permeability of the developer changes depending on the toner concentration, and its output characteristic is that the magnetic permeability increases because the carrier ratio increases when the toner concentration is low, and the toner concentration is low. When the value is high, the carrier ratio decreases, and thus the magnetic permeability decreases. The decrease in toner density and the increase in output value are in a substantially proportional relationship.

  Since such a magnetic permeability sensor has a higher sensitivity as the distance to the developer is shorter, a hole is formed in the wall of the developer accommodating portion in the developing device, the magnetic permeability sensor is inserted into the hole, and the detection portion of the magnetic permeability sensor is developed. It is common to place it in contact with the agent.

However, when the magnetic permeability sensor is arranged in this way, there are the following problems.
1. It is necessary to open a hole penetrating the bottom surface of the developer accommodating portion so as to be always in contact with the developer, and the installation place is restricted.
2. If the hole diameter does not match the outer diameter of the magnetic permeability sensor inserted into the hole, the developer leaks from the gap. In order to prevent developer leakage, a seal member is required.
3. If the top surface of the tip of the magnetic permeability sensor is not aligned with the inner wall surface of the developer container, the bottom surface of the developer container will be uneven, and this unevenness will not allow the developer to circulate properly. The developer stays in the vicinity of the installation position of the toner and the toner concentration cannot be detected accurately.
4. To eliminate such stagnation, Mylar, wings, and fins are attached to the position of the stirring member that mixes the developer at the position corresponding to the tip of the permeability sensor, and the detection part located at the tip of the permeability sensor Although the stirring performance is improved so that the developer always flows in, the accuracy of detection is improved by attaching mylar, feathers, and fins, but the flow of the developer is seen from the entire developer container. Since only that portion is delayed, the conveying ability of the toner in the original circulation path is lowered.

  Therefore, in [Patent Document 1], the magnetic permeability sensor is fixed to the outer wall of the developer accommodating portion, thereby eliminating the need to make a hole in the developer accommodating portion and inserting the magnetic permeability sensor into the hole. And a technique for detecting the toner density without causing the above-mentioned problems.

JP 2004-139038 A JP 2004-226868 A

  However, in such a technique, the thickness of the developer accommodating portion at the fixed position of the magnetic permeability sensor, the shape error of the magnetic sensor mounting structure, and the tape or adhesive used for attachment when attaching the magnetic permeability sensor. The sensitivity of the magnetic permeability sensor changes depending on the thickness. That is, the sensitivity of the magnetic permeability sensor depends on the thickness of the developer container. Such a change in sensitivity can be avoided to some extent by reducing the tolerances such as the thickness, but reducing the tolerances increases the manufacturing cost.

  Further, a change in the sensitivity of the magnetic permeability sensor can also occur in an arrangement mode in which the magnetic permeability sensor is inserted into a hole formed in the developer accommodating portion. This is because the amount of the surrounding developer can change according to the position occupied by the tip of the magnetic permeability sensor with respect to the inner wall surface of the developer accommodating portion.

  Therefore, it is necessary to measure the toner concentration in consideration of the change in sensitivity of the magnetic permeability sensor that occurs according to the state in which the magnetic permeability sensor is attached to the developing device.

  Furthermore, it has been found that the output value of the magnetic permeability sensor may change greatly depending on the change in the flow state of the developer. That is, the output value may vary depending on the developer flow state even at the same toner concentration. Therefore, when the toner density is directly determined from the output value, there is a case where a deviation occurs between the toner density based on the output value and the actual toner density, and there is a problem that the control accuracy of the toner density is lowered.

  When the control accuracy of the toner density is lowered, the toner density becomes excessively high or low, and the above-described problems occur. Therefore, the control accuracy of the toner density must be maintained.

  The change in the developer flow state may be that the developer is not flowing stably, the fluidity of the developer changes due to carrier deterioration, or the change in the bulk density of the developer due to the amount of charge of the toner. It is generated by doing.

  Changes in the developer flow state also occur due to toner degradation. When the image area ratio, that is, the number of pixels per unit area is less than about 5%, the toner is deteriorated by a long time for the toner to be transported through the circulation path in the developing device, and stress is increased. This is caused by the embedding and detachment of additives such as silica and titanium on the surface and the deterioration of fluidity.

  The change in the flow state of the developer may also be caused by a change in the toner density according to the image area ratio, although it depends on the developer used. When forming an image with a low image area ratio, the toner density increases, which may cause problems such as scumming and toner scattering, and when forming an image with a high image area ratio, the toner density decreases and the carrier adheres to the image carrier. This may cause screw pitch unevenness in the formed image.

  In particular, when the toner concentration is increased, such as when the toner concentration is 10% or more, the fluidity of the developer deteriorates rapidly. Therefore, when the image formation with a low image area ratio is continuously performed, the fluidity of the developer is very likely to occur due to the large stress on the toner.

  [Patent Document 2] proposes a technique for adjusting a transfer condition in accordance with a toner consumption amount per unit operation of a developing device, but does not mention adjustment of an output value of a magnetic permeability sensor.

  It has been found that the sensitivity of the magnetic permeability sensor varies depending on the usage environment of the developer. Since the charge amount of the developer changes according to the environment, the fluidity and the bulk density also change.

  Therefore, in order to maintain the toner concentration appropriately, it is necessary to consider the change in the output value depending on the position where the magnetic permeability sensor is installed, and further the magnetic permeability including the change in the flow state of the developer and the usage environment of the developer. It is desirable to consider changes in the sensor output value.

  The present invention uses a toner concentration measurement sensitivity measurement method for measuring the toner concentration measurement sensitivity in consideration of a state where a sensor such as a magnetic permeability sensor is attached to the developing device, and uses the toner concentration measurement sensitivity obtained by this method. Toner density control method and toner density control apparatus for controlling toner density in consideration of changes in sensor output value that occur according to the environment as needed, such developing device using these, such toner density control device or developing device An object of the present invention is to provide an image forming apparatus and an image forming method using the above.

  In order to achieve the above object, the invention according to claim 1 measures the sensitivity of the toner concentration measurement inside the developing means of a toner concentration measurement sensor for measuring the toner concentration of a developer containing toner and carrier. A toner density measurement sensitivity measuring method, wherein the toner density measurement sensor is capable of adjusting an output voltage by adjusting an input voltage, and corresponds to a toner density used as a reference in the toner density measurement sensor before installing the developing means. A first input voltage for obtaining an output voltage and a second input voltage for obtaining an output voltage corresponding to the reference toner density in the toner density measuring sensor after the developing means is installed are In the toner density measurement sensitivity measurement method, the sensitivity is measured based on a differential voltage between the input voltage and the second input voltage.

  The invention according to claim 2 is a toner concentration control method for controlling the toner concentration of the developer inside the developing means using the sensitivity measured using the toner concentration measurement sensitivity measuring method according to claim 1, Using the toner density measurement sensitivity measurement method, the output voltage to be output from the toner density measurement sensor after the development means is installed, corresponding to the limit toner density in a predetermined range of toner density including the reference toner density is used. The toner density control method determines the toner density of the developer in the developing means based on the determined output voltage and controls the toner density of the developer inside the developing means.

  According to a third aspect of the present invention, in the toner density control method according to the second aspect, the determined output voltage is corrected based on at least one of a temperature and a humidity of a use environment of the developing unit.

  According to a fourth aspect of the present invention, in the toner density control method according to the second or third aspect, the determined output voltage is corrected based on a toner consumption rate by the developing means.

  According to a fifth aspect of the present invention, in the toner density control method according to the fourth aspect, the toner consumption rate by the developing unit is obtained based on the number of pixels on the image carrier that is developed by the developing unit. And

  According to a sixth aspect of the present invention, in the toner density control method according to the fourth aspect, the toner consumption rate in the developing unit is obtained based on the operating rate of the toner replenishing unit that replenishes the developing unit with toner. And

  According to a seventh aspect of the present invention, there is provided a toner density control device for controlling a toner density by using the toner density control method according to any one of the second to sixth aspects.

  According to an eighth aspect of the present invention, there is provided a developing device for controlling a toner density by using the toner density control method according to any one of the second to sixth aspects.

  According to a ninth aspect of the present invention, in the developing device according to the eighth aspect of the present invention, the apparatus includes a developer container that houses the developer, and an attachment member that attaches the toner concentration measurement sensor to the outer surface of the developer container. And

  A tenth aspect of the present invention is an image forming apparatus having the toner density control device according to the seventh aspect or the developing device according to the eighth or ninth aspect.

  According to an eleventh aspect of the present invention, there is provided an image forming apparatus including a plurality of the developing devices according to the eighth or ninth aspects, wherein the output voltage to be output is determined for each developing device.

  A twelfth aspect of the invention is an image forming method for forming an image using the developing device according to the eighth or ninth aspect or the image forming apparatus according to the tenth or eleventh aspect.

  The present invention is a toner concentration measurement sensitivity measuring method for measuring the sensitivity of measurement of the toner concentration inside the developing means of a toner concentration measurement sensor for measuring the toner concentration of a developer containing toner and a carrier, The toner density measurement sensor can adjust an output voltage by adjusting an input voltage, and a first input voltage for obtaining an output voltage corresponding to a toner density as a reference in the toner density measurement sensor before the developing unit is installed. And a second input voltage for obtaining an output voltage corresponding to the reference toner density in the toner density measuring sensor after the developing means is installed, and the first input voltage and the second input voltage are Since there is a toner density measurement sensitivity measurement method for measuring the sensitivity based on the differential voltage, it occurs depending on the state of attachment of the toner density measurement sensor to the developing means. It is possible to provide a toner density measurement sensitivity measuring method that can accurately measure the sensitivity in consideration of the difference in the output value of the toner density measurement sensor and contribute to improving the detection accuracy of the toner density. .

  The present invention relates to a toner concentration control method for controlling the toner concentration of the developer in the developing means using the sensitivity measured using the toner concentration measurement sensitivity measuring method according to claim 1, which is the reference. The output voltage to be output from the toner concentration measurement sensor after the development means is installed, corresponding to the limit toner concentration in a predetermined range of toner concentrations including the toner concentration, was measured using the toner concentration measurement sensitivity measurement method. Since the toner density control method determines the toner density based on the determined output voltage and controls the toner density of the developer inside the developing unit based on the determined output voltage, the toner generated according to the mounting state of the toner density measuring sensor with respect to the developing unit By using the sensitivity measured accurately in consideration of the difference in the output value of the density measurement sensor, it should be output from the toner density measurement sensor. By improving the detection accuracy of the toner density to determine the output voltage, to improve the control accuracy of the toner density, it is possible to provide a good development, the toner density control method that can contribute to the image formation.

  If the determined output voltage is corrected based on at least one of the temperature and humidity of the environment in which the developing unit is used, the output value of the toner concentration measuring sensor generated according to the mounting state of the toner concentration measuring sensor with respect to the developing unit. The output voltage to be output from the toner density measurement sensor is determined by using the accurately measured sensitivity in consideration of the difference in the difference, and the determined output voltage is further based on the temperature and humidity of the usage environment of the developing unit. By correcting, the change in the output value of the toner density measurement sensor that occurs according to the temperature and humidity is alleviated or eliminated, and the toner density detection accuracy is improved, so that the toner density control accuracy is improved. It is possible to prevent or suppress toner scattering, carrier adhesion to the image carrier, screw pitch unevenness on the formed image, etc. It is possible to provide a toner density control method that can contribute to the image formation.

  If the determined output voltage is corrected based on the toner consumption rate by the developing means, the difference in the output value of the toner density measuring sensor that occurs according to the mounting state of the toner density measuring sensor to the developing means is taken into consideration. By using the accurately measured sensitivity, the output voltage to be output from the toner density measurement sensor is determined, and the determined output voltage is further corrected based on the toner consumption rate of the developing unit, so that the consumption The control of the toner density is improved by alleviating or eliminating the change in the output value of the toner density measurement sensor that occurs according to the rate and improving the toner density detection accuracy, and the toner fluidity resulting from the consumption rate Prevents or suppresses background stains, toner scattering, carrier adhesion to the image carrier, and screw pitch unevenness in the formed image. It can be, good development, it is possible to provide a toner density control method that can contribute to the image formation.

  If the toner consumption rate by the developing means is obtained based on the number of pixels on the image carrier that is developed by the developing means, the toner density measurement that occurs according to the mounting state of the toner density measuring sensor to the developing means By using the accurately measured sensitivity in consideration of the difference in sensor output value, the output voltage to be output from the toner density measurement sensor is determined, and the determined output voltage is further developed by the developing means. By correcting based on the number of pixels on the body, the change in the output value of the toner density measurement sensor caused by the number of pixels with high estimation accuracy is alleviated or eliminated, and the toner density detection accuracy is improved, Improves toner density control accuracy, and results in changes in toner fluidity caused by the change in toner fluidity, toner scattering, Yaria adhesion, prevent the occurrence of screw pitch unevenness to form the image or can be suppressed, it is possible to provide a good development, the toner density control method that can contribute to the image formation.

  If the toner consumption rate by the developing means is determined based on the operating rate of the toner replenishing means that replenishes toner in the developing means, the toner density measurement that occurs according to the state of attachment of the toner density measuring sensor to the developing means By using the accurately measured sensitivity in consideration of the difference in the output value of the sensor, the output voltage to be output from the toner density measuring sensor is determined, and the determined output voltage is further based on the operating rate of the toner replenishing means. By correcting the error, the change in the output value of the toner density measurement sensor that occurs according to the operating rate is alleviated or eliminated, and the toner density detection accuracy is improved by improving the toner density detection accuracy. Dirty stains caused by changes in toner fluidity due to high and low operating rates, toner scattering, carrier adhesion to image carrier, formation It is possible to prevent or suppress the occurrence of screw pitch unevenness on the image, good development, it is possible to provide a toner density control method that can contribute to the image formation.

  The present invention resides in a toner concentration control device that controls the toner concentration using the toner concentration control method according to any one of claims 2 to 6, so that the toner concentration measurement sensor is attached to the developing means according to the attached state. By using the sensitivity measured accurately in consideration of the difference in the output value of the generated toner density measurement sensor, the output voltage to be output from the toner density measurement sensor is determined, thereby improving the toner density detection accuracy. Therefore, it is possible to provide a toner concentration control device that improves the control accuracy of the toner concentration and can contribute to good development and image formation.

  The present invention resides in a developing device that controls the toner concentration using the toner concentration control method according to any one of claims 2 to 6, and therefore the toner generated according to the mounting state of the toner concentration measuring sensor in the developing device By using the sensitivity measured accurately in consideration of the difference in the output value of the density measurement sensor, the output voltage to be output from the toner density measurement sensor is determined and the toner density detection accuracy is improved. Concentration control accuracy is improved, good development can be performed, it can contribute to good image formation, and the conditions for attaching the toner concentration measurement sensor are relaxed, thereby reducing costs. It is possible to provide a developing device capable of

  If the developer container that contains the developer and the attachment member that attaches the toner concentration measurement sensor to the outer surface of the developer container are provided, the toner concentration measurement sensor including the attachment member in the developing device is attached. By using the sensitivity measured accurately in consideration of the difference in the output value of the toner density measurement sensor generated accordingly, the output voltage to be output from the toner density measurement sensor is determined and the toner density detection accuracy is improved. As a result, the control accuracy of the toner density is improved, it is possible to perform good development, contribute to good image formation, and the conditions related to the attachment of the toner density measurement sensor are eased. It is possible to provide a developing device that can be suppressed.

  Since the present invention resides in the toner density control device according to claim 7 or the image forming apparatus having the developing device according to claim 8 or 9, the toner density generated according to the mounting state of the toner density measuring sensor in the developing means To determine the output voltage to be output from the toner density measurement sensor and improve the toner density detection accuracy by using the sensitivity measured accurately in consideration of the difference in the output value of the measurement sensor. Control accuracy is improved, good development can be performed, good image formation can be performed, and the conditions relating to the attachment of the toner concentration measurement sensor are relaxed, so that cost can be reduced. An image forming apparatus can be provided.

  Since the present invention is provided in an image forming apparatus that includes a plurality of the developing devices according to claim 8 and 9 and determines the output voltage to be output for each developing device, the toner density measurement sensor mounted state in each developing device Toner density measurement taking into account the difference in properties and conditions of the toner and carrier used by using the accurately measured sensitivity taking into account the difference in the output value of the toner density measurement sensor that occurs according to the By determining the output voltage to be output from the sensor and improving the toner density detection accuracy, the toner density control accuracy in each developing device is improved, and each developing device performs good development. Better image formation, and the conditions for attaching the toner density measurement sensor are relaxed, which can reduce costs. It is possible to provide an image forming apparatus.

  Since the present invention is an image forming method for forming an image using the developing device according to claim 8 or 9, or the image forming device according to claim 10 or 11, the toner density measuring sensor is attached to the developing means. By using the sensitivity measured accurately in consideration of the difference in the output value of the toner density measurement sensor that occurs according to the toner density, the output voltage to be output from the toner density measurement sensor is determined and the toner density detection accuracy is improved. As a result, the toner density control accuracy is improved, good development can be performed, good image formation can be performed, and the conditions for attaching the toner density measurement sensor are relaxed, thereby reducing the cost. It is possible to provide an image forming method that can be suppressed.

  FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is a multifunction peripheral of a copying machine, a printer, and a facsimile machine, and can perform full-color image formation, but other image forming apparatuses, that is, a monochrome machine, a copying machine, and a printer. It may be a single facsimile, or another multi-function machine such as a copier / printer multi-function machine. When used as a printer, the image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside. This is the same when the image forming apparatus 100 is used as a facsimile.

  The image forming apparatus 100 can form an image on a sheet-like recording medium using not only plain paper generally used for copying, but also OHP sheets, cardboard, cardboard, cardboard, and envelopes. It is. The image forming apparatus 100 is also a double-sided image forming apparatus capable of forming images on both sides of a transfer sheet as a recording medium.

  The image forming apparatus 100 includes a main body 101 that occupies a center position in the vertical direction, a reading device 21 that is positioned above the main body 101 and that reads a document, and a document that is loaded and loaded with a document toward the reading device 21. An automatic document feeder 22 called ADF, and a paper feed table on which transfer paper is placed between the photoconductive drums 20Y, 20M, 20C, 20BK and the transfer belt 11 positioned below the main body 101. As a sheet feeding device 23.

  The image forming apparatus 100 includes a plurality of photosensitive drums 20Y, 20M, 20C, and 20BK that can form images as images corresponding to colors separated into yellow, magenta, cyan, and black, respectively. 1 is a tandem type image forming apparatus that employs a tandem structure in which the two are arranged side by side. The photosensitive drums 20Y, 20M, 20C, and 20BK have the same diameter, and are transfer belts as intermediate transfer belts that are intermediate transfer members that are endless belts disposed almost at the center inside the main body 101 of the image forming apparatus 100. 11 are arranged at equal intervals on the outer peripheral surface side, that is, on the image forming surface side.

  The transfer belt 11 is movable in the arrow A1 direction, which is the clockwise direction in the figure, while facing the respective photosensitive drums 20Y, 20M, 20C, and 20BK. The visible image, that is, the toner image formed on each of the photoconductive drums 20Y, 20M, 20C, and 20BK is superimposed and transferred onto the transfer belt 11 that moves in the direction of the arrow A1, and is then collectively transferred onto the transfer paper. It has become. As described above, the image forming apparatus 100 employs the indirect transfer method.

  In the superimposing transfer to the transfer belt 11, the toner images formed on the photosensitive drums 20Y, 20M, 20C, and 20BK are transferred to the same position on the transfer belt 11 while the transfer belt 11 moves in the A1 direction. As described above, voltage is applied by primary transfer rollers 12Y, 12M, 12C, and 12BK as transfer chargers disposed at positions facing the respective photosensitive drums 20Y, 20M, 20C, and 20BK across the transfer belt 11. , The timing is shifted from the upstream side to the downstream side in the A1 direction, and the transfer is performed at a position immediately below each photosensitive drum 20Y, 20M, 20C, 20BK, that is, a transfer position.

  The photosensitive drums 20Y, 20M, 20C, and 20BK are arranged in this order from the upstream side in the A1 direction. The photosensitive drums 20Y, 20M, 20C, and 20BK are provided in image stations 60Y, 60M, 60C, and 60BK, respectively, for forming yellow, magenta, cyan, and black images.

  The image forming apparatus 100 is arranged opposite to the image forming unit 60 as an image forming unit constituted by four image stations 60Y, 60M, 60C, and 60BK, and below the respective photosensitive drums 20Y, 20M, 20C, and 20BK. A transfer belt unit 10 as a belt unit, which is an intermediate transfer unit provided with the transfer belt 11, and is disposed so as to face the transfer belt 11 and is in contact with the transfer belt 11. A secondary transfer unit 76 as a secondary transfer device that includes a secondary transfer belt 5 as a transfer member that rotates in the same direction as the transfer belt 11 and transfers and conveys the toner image on the transfer belt 11 to transfer paper; An intermediate transfer belt cleaning device 14 disposed opposite to the belt 11 for cleaning the transfer belt 11. .

  The image forming apparatus 100 also includes an optical scanning device 8 that is an exposure unit that is a writing unit as an optical writing device that is a writing unit disposed facing the image stations 60Y, 60M, 60C, and 60BK. The transfer sheet conveyed from the feeding device 23 is transferred between the transfer belt 11 and the secondary transfer belt 5 at a predetermined timing in accordance with the toner image formation timing by the image stations 60Y, 60M, 60C, and 60BK. And a sensor (not shown) for detecting that the leading edge of the transfer paper has reached the registration roller pair 13.

  The image forming apparatus 100 also serves as a belt-fixing type fixing unit for transferring the toner image on the transfer belt 11 transferred by the secondary transfer unit 76 and fixing the toner image on the transfer paper. A fixing unit 6, a paper discharge unit that discharges the fixed transfer paper to the outside of the main body 101, and a reverse path that transports the transfer paper toward the registration roller pair 13 again. 79 and the paper discharge unit 79, when the transfer paper having an image formed on one side is conveyed to the reverse path, the transfer paper is switched back and reversed, and is again conveyed toward the registration roller pair 13. And a duplex unit 96 which is a sheet reversing device as a refeed unit.

  The image forming apparatus 100 also includes a paper discharge tray 75 that is disposed outside the main body 101 and on which image-formed transfer paper is stacked, a manual paper feeding device 33 that is disposed on the right side surface of the main body 101 in FIG. A temperature detection sensor (not shown) as temperature detection means for detecting temperature, a humidity detection sensor (not shown) as humidity detection means for detecting environmental humidity, an operation panel (not shown) for operating the image forming apparatus 100, and an image forming apparatus And control means (not shown) for controlling the operation of the whole 100.

  In addition to the transfer belt 11, the transfer belt unit 10 includes primary transfer rollers 12Y, 12M, 12C, and 12BK, a drive roller 72, a transfer inlet roller 73, and a tension roller 74 around which the transfer belt 11 is wound. ing.

  In addition to the secondary transfer belt 5, the secondary transfer unit 76 is disposed so as to face the secondary transfer belt 5 and the driving roller 15 and the driven roller 16 around which the secondary transfer belt 5 is wound. And a transfer entrance roller 73 serving as a counter roller pressed through. The secondary transfer unit 76 may be configured to employ a transfer roller or a non-contact charger, but in this case, another member for transporting the transfer paper toward the fixing device 6 is required.

  The optical scanning device 8 scans and exposes the surfaces to be scanned formed by the surfaces of the photosensitive drums 20Y, 20M, 20C, and 20BK, and forms a laser beam based on an image signal for forming an electrostatic latent image. The laser beam is scanned by a polygon mirror (not shown) that emits a laser beam (not shown), a polygon mirror (not shown) that scans the laser beam emitted by the light source, and a polygon motor (not shown) that rotates the polygon mirror. The laser beam is imaged on the photosensitive drums 20Y, 20M, 20C, and 20B, and a large number of optical elements (not shown) for scanning are provided.

  The fixing device 6 includes a heating roller 62 having a heat source therein, a fixing belt 64 wound around the heating roller 62, a fixing roller 65 wound around the fixing belt 64 together with the heating roller 62, and the fixing roller 65. And a pressure roller 63 that presses the fixing belt 64, and the transfer paper carrying the toner image is passed through a fixing portion that is a pressure contact portion between the fixing belt 64 and the pressure roller 63, so that heat and pressure can be obtained. By this action, the carried toner image is fixed on the surface of the transfer paper.

  A paper discharge unit 79 transports the fixed transfer paper transported from the fixing device 6 toward the duplex unit 96, a paper discharge roller 98 that discharges the paper to the outside of the main body 101, and a fixed transfer. There is provided a switching claw 94 for switching whether the paper is guided to the paper discharge path with the conveying roller 97 and discharged out of the main body 101 or the paper is guided to the reverse path with the paper discharge roller 98 to enter the duplex unit 96.

  The duplex unit 96 is a tray 92 on which transfer paper having an image formed on one side, which has been conveyed from the paper discharge unit 79, is temporarily stacked, a reverse roller 93 that switches back the transfer paper on the tray 92, and a reverse roller. The sheet feeding roller 95 and the like for feeding the transfer sheet switched back by 93 to the registration roller 13 are provided.

The sheet feeding device 23 includes a paper bank 26 having a paper feed cassette 25 on which a large number of transfer papers are stacked, and a paper feed that makes contact with the upper surface of the uppermost transfer paper among the transfer papers stacked on the paper feed cassette 25. A feed roller 24 serving as a roller, a separation roller 27 that separates the transfer paper fed by the feed roller 24 one by one, and a transfer paper fed by the paper feed roller 24 and the separation roller 27 to the registration roller pair 13. It has a conveyance roller 28 that conveys the paper toward and a paper feed path 29 through which the transfer paper conveyed by the conveyance roller 28 passes.
The sheet feeding path 29 is provided so as to be continuous from the sheet feeding device 23 into the main body 101, and a conveyance roller 28 is also disposed in the sheet feeding path 29 in the main body 101.

  In the sheet feeding device 23, the feeding roller 24 is rotated in the counterclockwise direction in the drawing, and the separation roller 27 acts to guide the uppermost transfer paper into the paper feeding path 29, so that the conveying roller 28 The sheet is fed toward the registration roller pair 13 by rotation, and the transferred transfer paper is abutted against the registration roller pair 13 and stopped.

  The manual paper feed device 33 includes a manual feed tray 34 on which transfer paper is stacked, a feed roller 35 as a paper feed roller that contacts the upper surface of the uppermost transfer paper among the transfer papers stacked on the manual feed tray 34, It has a separation roller 36 for separating the transfer paper fed by the feed roller 35 one by one, and a paper sensor for detecting that the transfer paper is placed on the manual feed tray 34.

  In the manual sheet feeding device 33, the feeding roller 35 is driven to rotate in the clockwise direction in the drawing, and the separation roller 36 acts to guide the uppermost transfer sheet into the sheet feeding path 29 on the main body 101 side and to register the sheet. The transfer paper fed to the roller pair 13 is transported against the registration roller pair 13 and stopped.

The reading device 21 includes a contact glass 21a on which a document is placed, a light source (not shown) that irradiates light on the document placed on the contact glass 21a, and a first light source (not shown) that reflects light reflected from the light source. A first traveling body 21b that includes a reflector and travels in the left-right direction in FIG. 1; a second traveling body 21c that includes a second reflector (not shown) that reflects light reflected by the reflector of the first traveling body 21b; An image forming lens 21d for forming an image of light from the second traveling body 21c, a reading sensor 21e for receiving the light passing through the image forming lens 21d and reading the contents of the document are provided.
The automatic document feeder 22 is rotatable, and the contact glass 21a is exposed when the automatic document feeder 22 is rotated upward.

  The temperature detection sensor and the humidity detection sensor are designed to detect at least the temperature and humidity in the usage environment of the developing means such as the developing device 50Y to be described later. When the temperature and humidity differ between the developing means, they may be provided in each developing means. The detected temperature and humidity are input to the control means.

The operation panel includes a start button for starting copying and the like, and a numeric keypad for inputting the number of copies.
The control means includes a CPU, a memory as a storage means, and the like.

  Regarding the image stations 60Y, 60C, 60M, and 60BK, the configuration will be described as a representative of the configuration of the image station 60Y including the photosensitive drum 20Y. Since the configuration of other image stations is substantially the same, in the following description, for the sake of convenience, reference numerals corresponding to the reference numerals assigned to the configuration of the image station including the photosensitive drum 20Y are used for other image stations. A detailed description will be omitted as appropriate for the station configuration, and those with Y, C, M, and K at the end of the reference numerals are used to form yellow, cyan, magenta, and black images, respectively. It is assumed that this is the configuration.

  As shown in FIG. 2, the image station 60Y including the photosensitive drum 20Y has a primary transfer roller 12Y and a cleaning member around the photosensitive drum 20Y along the rotation direction B1 that is counterclockwise in the drawing. It has a cleaning device 40Y as a means, a charging device 30Y as a charging unit as a charging means, and a developing device 50Y as a developing unit as a developing means.

  The photosensitive drum 20Y, the cleaning device 40Y, the charging device 30Y, and the developing device 50Y are integrated to form a process cartridge 95Y. The process cartridge 95Y can be pulled out of the main body 101 along a guide rail (not shown) fixed to the main body 101, can be pushed into the main body 101, and is detachably installed on the main body 101. .

  When the process cartridge 95Y is pushed into the main body 101, it is loaded and positioned at a predetermined position suitable for image formation. Making a process cartridge in this way is very preferable because it can be handled as a replacement part, so that the maintainability is remarkably improved.

  The process cartridge 95Y is configured by integrating at least the photosensitive drum 20Y and the developing device 50Y among the photosensitive drum 20Y, the cleaning device 40Y, the charging device 30Y, and the developing device 50Y. 101 is a unit that is detachably installed in the unit 101.

  The charging device 30Y includes a charging roller 31Y that rotates in contact with the surface of the photosensitive drum 20Y, and a cleaning roller 32Y that rotates in contact with the charging roller 31Y. The charging roller 31Y is connected to a voltage applying means (not shown) for applying a bias of an alternating current component to a direct current, and in the charging region facing the photosensitive drum 20Y, the surface of the photosensitive drum 20Y is neutralized at the same time as the charging roller 31Y. The polarity is charged.

The cleaning roller 32Y cleans the charging roller 31Y by rotating following the charging roller 31Y.
As described above, in this embodiment, a charging system using a contact roller is used. However, the charging system may use a proximity roller or a non-contact type such as a scorotron system. It may be.

A predetermined voltage suitable for primary transfer is applied to the primary transfer roller 12Y by a bias application unit and a bias control unit having a power source (not shown).
As shown in FIG. 2, the optical scanning device 8 shown in FIG. 1 irradiates a region between the charged region and the developing region on the photosensitive drum 20Y with a laser beam L that is light-modulated according to image information. The surface of the photosensitive drum 20Y after being charged by the charging roller 31Y is exposed to form an electrostatic latent image that is visualized as a yellow toner image by the developing device 50Y.

  The cleaning device 40Y has a cleaning case 43Y having an opening at a portion facing the photoconductor drum 20Y, and scrapes off unnecessary materials such as residual toner, carrier, and paper dust on the photoconductor drum 20Y in contact with the photoconductor drum 20Y. The brush roller 45Y as a rotating brush to be cleaned and the rotating direction B1 of the photosensitive drum 20Y contact the photosensitive drum 20Y at a position downstream of the brush roller 45Y and scrape off unnecessary matter on the photosensitive drum 20Y. And a cleaning blade 41Y as a blade for cleaning.

  The cleaning device 40Y is also rotatably supported by the cleaning case 43Y. The cleaning device 40Y is scraped by the brush roller 45Y and the cleaning blade 41Y. It has a discharge screw 42Y that constitutes a part of a waste toner path (not shown) for conveyance.

  The developing device 50Y includes a developing case 55Y having an opening at a portion facing the photoreceptor drum 20Y, and a developer carrying member disposed in close proximity to the photoreceptor drum 20Y so as to face the photoreceptor drum 20Y from the opening. A developing roller 51Y as a body, and a developing blade 52Y as a doctor as a regulating member that regulates the developer on the developing roller 51Y to a certain height.

  The developing device 50Y is also disposed below the developing case 55Y so as to face each other, and is driven to rotate in opposite directions to stir the developer and to supply the developer to the developing roller 51Y. The first conveying screw 53Y and the second agitating screw 54Y as supply members, the partition wall 57Y provided between the first conveying screw 53Y and the second conveying screw 54Y, and the first conveying screw partitioned by the partition wall 57Y. 53Y, and a second storage chamber 59Y that constitutes a developer storage section as a developer storage device that stores the second transport screw 54Y.

  The developing device 50Y also includes a toner hopper 80Y that stores yellow toner, and a T sensor as a toner concentration measuring sensor that is provided at the bottom of the second storage chamber 59Y and serves as a toner concentration detecting unit that measures the toner concentration in the developer. A toner concentration detection sensor 56Y as a toner concentration detection device and a double-sided tape 86Y as an attachment member to which the toner concentration detection sensor 56Y is attached to the second storage chamber 59Y are provided.

  The developing device 50Y also includes a bias applying unit (not shown) that applies a developing bias of a DC component, a developing driving unit (not shown) that drives the developing roller 51Y, and the first transport screw 53Y and the second transport screw 54Y in opposite directions. (Not shown) for supplying toner to the second storage chamber 59Y from the toner hopper 80Y.

  The developing roller 51Y includes a magnet roller 81Y as a magnetic field generating unit, and a nonmagnetic developing sleeve 82Y that includes the magnet roller 81Y and is driven in the C1 direction, which is the clockwise direction in the drawing, by the developing driving unit.

  Although not shown, the magnet roller 81Y has a plastic roller fixed to the developing case 55Y and a magnet block that is a plurality of magnets forming a plurality of magnetic poles embedded in the plastic roller 84Y.

  The developing sleeve 82Y is rotatably supported by the developing case 55Y and the magnet roller 81Y. A developing bias of an appropriate size is applied between the developing sleeve 82Y and the photosensitive drum 20Y by a bias applying unit. The gap between the developing sleeve 82Y and the photosensitive drum 20Y in the developing region, that is, the developing gap is set to be 0.3 ± 0.05 mm.

  The developing blade 52Y is formed of a SUS material. A gap between the developing sleeve 82Y and the developing blade 52Y, that is, a doctor gap is set to be 0.5 ± 0.04 mm.

The developer is a two-component developer containing toner and carrier.
The carrier is a magnetic carrier, and has a core material and a resin coating layer formed on the surface of the core material. The resin coating layer contains conductive particles in which a conductive coating layer comprising a tin dioxide layer and an indium oxide layer containing tin dioxide provided on the tin dioxide layer is provided on the surface of the substrate particles. .

  The toner is a non-magnetic toner and is mainly composed of a binder resin, a release agent, and a colorant. The binder resin contains a hybrid resin having a vinyl polymer and a polyester polymer. The content of the hybrid resin with respect to the content of the release agent is formed to be in the range of 0.5 to 3.

  The toner concentration in the developer is controlled to be within a predetermined range of about 4 to 11% by weight based on detection by the toner concentration detection sensor 56Y, and will be described later by the control means. Is always kept at an appropriate value, and contributes to obtaining a high-quality image. The toner density decreases with the consumption of toner by development, and when the toner density detection sensor 56Y detects that the toner density falls below the lower limit value of the predetermined range described above, the toner replenishing means from the toner hopper 80Y. Toner is supplied to the second storage chamber 59Y.

  The first transport screw 53Y and the second transport screw 54Y are disposed so as to extend in the width direction of the developing roller 51Y, in other words, in the direction perpendicular to the paper surface in FIG. 2, which is the longitudinal direction of the developing roller 51Y.

  The first transport screw 53Y is rotationally driven by the transport driving means, and supplies the developer in the first storage chamber 58Y to the developing roller 51Y while transporting the developer from the back side to the front side in FIG. The developer transported to the vicinity of the end in the first storage chamber 58Y by the first transport screw 53Y enters the second storage chamber 59Y through an opening (not shown) formed in the partition wall 57Y.

  In the second storage chamber 59Y, the second transport screw 54Y is rotationally driven by the transport drive means to transport the developer sent from the first storage chamber 58Y in the opposite direction to the first transport screw 53Y. . At this time, when the toner is replenished from the toner hopper 80Y, the replenished toner is conveyed while being agitated and mixed in the developer. The developer transported to the vicinity of the end of the second storage chamber 59Y by the second transport screw 54Y returns to the first storage chamber 58Y through another opening (not shown) provided in the partition wall 57Y.

  The toner thus supplied is agitated and mixed by the first conveying screw 53Y and the second conveying screw 54Y while being agitated and conveyed with the developer, frictionally charged, and supplied and carried on the developing roller 51Y.

  The developing roller 51Y whose developer thickness is regulated by the developing blade 52Y and whose layer thickness is regulated is developed in the developing area between the developing roller 51Y and the photosensitive drum 20Y by the rotation and the developing bias by the bias applying means. An appropriate amount of developer is carried by the developing blade 52Y, and the yellow toner in the developer is electrostatically transferred to the electrostatic latent image formed on the surface of the photosensitive drum 20Y, and the electrostatic latent image is formed. A visible image is formed as a yellow toner image.

The developer that has consumed the yellow toner by the development is returned to the developing device 50Y as the developing roller 51Y rotates.
In this embodiment, the DC component developing bias is applied by the bias applying means. However, the developing bias may be an AC component, or an AC component superimposed on the DC component.

  Thus, in the developing device 50Y, the developer stirred and transported by the first transport screw 53Y and the second transport screw 54Y is pumped up by the magnetic force of the magnet roller 81Y and carried on the developing sleeve 82Y, and the photosensitive drum 20Y. The toner is supplied to the latent image on the photosensitive drum 20Y and developed. The developer that has consumed the toner after development is released from the surface of the developing sleeve 82Y into the first storage chamber 58Y, and is stored in the first storage chamber 58Y and the second storage chamber 59Y by the first transport screw 53Y and the second transport screw 54Y. The cycle in which the developer is stirred and pumped up to the surface of the developing sleeve 82Y is repeated. The magnet block is arranged to repeat such a cycle.

  In the image forming apparatus 100 having such a configuration, when copying, a document is set on the automatic document feeder 22 or the automatic document feeder 22 is rotated upward to place a document on the contact glass 21a. Then, the automatic document feeder 22 is rotated downward to be closed, and the start button on the operation panel is pressed. When the image forming apparatus 100 is used as a printer, an image forming start operation is performed after image data to be formed is selected and input by an external input device such as a PC connected to the image forming apparatus 100.

When copying is performed and the original is set on the automatic document feeder 22, the read original is read by the reading device 21 after the set original is fed onto the contact glass 21a. Is placed on the contact glass 21a, the document is read by the reading device 21 when the start button is pressed, and image data is generated.
Based on the generated image data or the input image data, the image stations 60Y, 60M, 60C, and 60BK having the above-described configuration operate.

  In the image station 60Y, the surface of the photosensitive drum 20Y is uniformly charged by the charging roller 31Y as it rotates in the B1 direction, and corresponds to the yellow color by exposure scanning of the laser light L from the optical scanning device 8. An electrostatic latent image is formed, and the electrostatic latent image is satisfactorily developed with yellow toner by the developing device 50Y, and the yellow toner image obtained by the development is moved in the A1 direction by the primary transfer roller 12Y. Unnecessary materials including toner, which is primarily transferred to the transfer belt 11 and remains after transfer, are removed by the cleaning device 40Y and used for the next charge removal and charging by the charging roller 31Y.

  Similarly, toner images of the respective colors are formed on the other photosensitive drums 20C, 20M, and 20BK, and the formed toner images of the respective colors are transferred to the A1 direction by the primary transfer rollers 12C, 12M, and 12BK. 11 is sequentially transferred to the same position on the head. The toner image superimposed on the transfer belt 11 moves to the secondary transfer nip, which is a position facing the secondary transfer roller 5, as the transfer belt 11 rotates in the A1 direction, and is secondarily transferred onto the transfer paper. .

  The transfer paper conveyed between the transfer belt 11 and the secondary transfer roller 5 is fed out from the corresponding paper feed cassette 25 by one rotation of the sheet feeding device 23 selected by the sheet feeding device 23 and fed. Is fed from the manual feed tray 34 by the rotation of the feed roller 35 of the manual paper feed device 33, or fed from the duplex unit 96 by the paper feed roller 95. At the timing when the tip of the toner image on the transfer belt 11 faces the secondary transfer belt 5 based on the detection signal from the sensor by the registration roller pair 13. It has been sent out.

  When the toner image of all colors is transferred and carried on the transfer paper, it enters the fixing device 6 and passes through the fixing portion between the fixing belt 64 and the pressure roller 63 due to the action of heat and pressure. The carried toner image is fixed, and a color image is formed on the transfer paper. The fixed transfer paper that has passed through the fixing device 6 is stacked on the paper discharge tray 75 via the paper discharge roller 98 or on the duplex unit 96 via the conveyance roller 97 according to the position of the switching claw 94. Enter to prepare for double-sided image formation. On the other hand, the transfer belt 11 that has finished the secondary transfer is cleaned by removing residual toner and the like remaining on the intermediate transfer belt cleaning device 14 to prepare for the next image formation.

  In such an image forming process, yellow, cyan, magenta, and black toners are consumed in the developing devices 50Y, 50C, 50M, and 50BK, respectively. When a decrease in toner density is detected by the toner density detection sensor 56Y or the like provided in each of the developing devices 50Y, 50C, 50M, and 50BK, yellow, cyan, magenta, and black are transferred from the toner hopper 80Y. The toner of each color is supplied to the second storage chamber 59Y and the like by the toner replenishing means.

  Regarding the toner density control, the developing device 50Y among the developing devices 50Y, 50C, 50M, and 50BK will be described as a representative. For the other developing devices 50C, 50M, and 50BK, the toner density is controlled in the same manner as the developing device 50Y. Therefore, the description of the toner density control for the developing devices 50C, 50M, and 50BK is omitted.

  The toner concentration detection sensor 56Y measures the toner concentration based on the magnetic permeability of the developer, and its output is taken out as a voltage Vout and input to the control means, and the toner concentration is discriminated based on the magnitude of the voltage Vout. The The toner concentration is in units of% by weight.

  In a developer containing toner and a magnetic carrier, if the toner concentration is low, the carrier ratio increases and the magnetic permeability is increased.If the toner concentration is high, the carrier ratio is decreased and the magnetic permeability is decreased. As shown in FIG. 3, the decrease in the toner density TC and the increase in the voltage Vout are in a directly proportional relationship.

  The toner concentration detection sensor 56Y is attached to the outer surface of the bottom of the second storage chamber 59Y by a double-sided tape 86Y. However, as shown in FIG. 4, the sensitivity decreases as the distance from the developer increases. Proportional relationship. Therefore, the sensitivity of the toner density detection sensor 56Y depends on the thickness of the developing case 55Y constituting the second storage chamber 59Y and the thickness of the double-sided tape 86Y.

  In FIG. 4, the case thickness corresponds to the sum of the thickness of the developing case 55Y and the thickness of the double-sided tape 86Y in the second storage chamber 59Y. The actual machine T sensor sensitivity is the sensitivity of the toner concentration detection sensor 56Y in a state where the toner concentration detection sensor 56Y is attached to the bottom outer surface of the second storage chamber 59Y. As shown in the figure, the sensitivity of the toner concentration detection sensor 56Y is a value obtained by dividing the voltage Vout, which is the output voltage, by the toner concentration and inverting the sign.

  If the toner density becomes excessively high, image density rises, toner scatters, developer leakage from the developing device, scumming, etc. occur, and if the toner density decreases excessively, the image density decreases and the image carrier is exposed. Control of toner concentration is important because carrier adhesion occurs.

  Therefore, it is necessary to accurately detect the toner density, and for that purpose, it is necessary to measure the toner density in consideration of the sensitivity of the toner density detection sensor 56Y. Therefore, in the developing device 50Y, the toner density is measured in consideration of the difference in sensitivity of the toner density measurement before and after the toner density detection sensor 56Y is attached to the developing case 55Y.

  The toner concentration detection sensor 56Y can input a voltage, and the voltage Vout, which is an output voltage, can be adjusted by adjusting the voltage Vcnt, which is the input voltage.

  Therefore, if the voltage Vcnt is adjusted so as to obtain the same voltage Vout when measuring the developer having the same toner density at different distances, the change in the voltage Vcnt corresponds to the change in sensitivity. When the voltage Vcnt is increased, the voltage Vout is also increased, and when the voltage Vcnt is decreased, the voltage Vout is also decreased.

  Here, the sum of the thickness of the developing case 55Y and the thickness of the double-sided tape 86Y with the toner density detection sensor 56Y attached, that is, the design value of the case thickness, in other words, the standard case thickness is 0.8 mm. That is, the toner density when the developing device 50Y is new is 7%, and the voltage Vout at this time is 3.0V.

  In measuring the sensitivity, this state is reproduced in a pseudo manner before the toner density sensor 56Y is attached. Specifically, a magnetic test piece simulating an actual developer is prepared, and the distance between the test piece and the toner density sensor 56Y is adjusted, so that the case thickness is 0.8 mm and the toner density is 7%. Is virtually created, and the voltage Vcnt is adjusted so that the voltage Vout becomes 3.0 V in this state. The voltage Vcnt obtained by this inspection is set as a voltage Vcnttest which is the first input voltage.

  If the test piece can completely reproduce the toner concentration of 7%, the voltage Vcnt is adjusted in a state where the distance between the test piece and the toner concentration sensor 56Y is 0.8 mm.

  A test piece that reproduces 4%, 11%, or the like in addition to a toner density that reproduces 7% is used, and the voltage Vout is measured at the determined voltage Vcnttest. The voltage Vout at this time is defined as a voltage Vouttest. The voltage Vouttest is shown in FIG.

  Next, the toner concentration sensor 56Y is attached to the bottom outer surface of the second storage chamber 59Y in a state where the toner concentration is 7%, and the voltage Vcnt is adjusted so that the voltage Vout becomes 3.0V while changing the case thickness. . The voltage Vcnt obtained at this time is set as a voltage Vcntreal which is the second input voltage.

  FIG. 5 shows the difference between the reference case thickness and the case thickness used for the measurement when the case thickness and toner concentration standards are 0.8 mm and 7%. A relationship between a case thickness difference that is a thickness and a voltage ΔVcnt that is a differential voltage obtained by subtracting the voltage Vcnttest from the voltage Vcnreal is shown. From the figure, it can be seen that as the case thickness difference increases, the voltage ΔVcnt increases, that is, the voltage Vcntreal increases, and that the case thickness difference and the voltage ΔVcnt have a proportional relationship.

  FIG. 6 shows the relationship between the voltage ΔVcnt and the actual machine T sensor sensitivity obtained from the data shown in FIGS. As shown in FIG. 4, when the case thickness is 0.8 mm, which is the standard thickness, the actual machine T sensor sensitivity is 0.4 (−V / wt%). When the actual machine T sensor sensitivity is 0.4 (−V / wt%), the voltage ΔVcnt is 0 (V).

  That is, when the voltage ΔVcnt is 0 (V), it indicates that the case thickness is the target 0.8 mm. In addition, when the voltage ΔVcnt> 0 (V), it indicates that the case thickness is thicker than the target 0.8 mm, and when the voltage ΔVcnt <0 (V), the case thickness is It shows that it is thinner than the target 0.8mm.

  When the case thickness is 0.8 mm, which is the standard thickness, the sensitivity of the actual machine T sensor is 0.4 (-V / wt%). This is the result of the above inspection using a test piece. The situation is also reproduced in some cases. Therefore, in FIG. 6, this state is the inspection value T sensor sensitivity.

  Since the voltage ΔVcnt and the actual machine T sensor sensitivity are in a proportional relationship, if the voltage ΔVcnt is known, the sensitivity of the toner density sensor 56Y can be measured based on the voltage ΔVcnt. In other words, it can be seen that the actual device T sensor sensitivity can be predicted by measuring the voltage Vcnreal.

  The developing device 50Y employs a toner density control method that measures the sensitivity by such a toner density measurement sensitivity measurement method and controls the toner density as follows based on the measured sensitivity.

  FIG. 7 shows the toner density TC at the actual machine T sensor sensitivity predicted when the case thickness is 0.16 mm thicker than the target 0.8 mm and the voltage ΔVcnt is 1.2 (V). A relationship with a voltage Voutref which is an output voltage is shown. When the voltage ΔVcnt is 1.2 (V), the actual machine T sensor sensitivity predicted from FIG. 6, in other words, the sensitivity of the toner density sensor 56Y measured is about 0.3 (−V / wt%). The relationship between the toner concentration TC and the voltage Voutref in FIG. 7 is obtained by a straight line in which the sensitivity is about 0.3 (−V / wt%) and the voltage Vout is 3.0 (V) at a toner concentration of 7%. It is what was done.

  Such sensitivity is obtained by sampling the voltage Vout while changing the voltage Vcnreal when the power is first turned on after the developing device 50Y is installed in the main body of the image forming apparatus 100, and is set to the voltage Vcnreal when the voltage Vout becomes 3.0V. Based on the initial setting, the voltage ΔVcnt is calculated. The voltage Vcnreal at which the voltage Vout becomes 3.0 V may be obtained from a linear function composed of the voltage Vcnreal and the voltage Vout.

  In the figure, the voltage Vouttest is a toner whose inclination is a test value T sensor sensitivity 0.4 (−V / wt%) when the case thickness is 0.8 mm and the voltage ΔVcnt is 0 (V). This is represented by a straight line with a voltage Vout of 3.0 (V) at a concentration of 7%.

  Here, in the case where the toner density detection sensor 56Y is attached to the outer surface of the bottom of the second storage chamber 59Y and development is actually performed, assuming that the case thickness matches the target 0.8 mm, the voltage Voutref is It matches the voltage Vouttest. In this case, the voltage Voutref is a value to be taken as the voltage Vout at 11% which is the upper limit of the toner density control range of 4 to 11% which is the initial target range including 7% which is the reference of the toner density. The lower limit is 1.4V.

  However, when the case thickness is 0.16 mm thicker than the target 0.8 mm, the voltage ΔVcnt is 1.2 (V). Therefore, as shown in the figure, the voltage Voutref is the voltage Vouttest. Is different. At the upper limit of 11%, which is the upper limit of the toner density control range at this time, the voltage Voutref has a lower limit value of 1.8V. This lower limit voltage is defined as a voltage Voutrefmin.

  As described above, the voltage Voutref is corrected according to the case thickness. At 4%, which is the lower limit value below the toner density control range, the voltage Voutref has an upper limit value of 3.9 V. When the voltage Vout falls below this value, the control means According to the control, the toner replenishment from the toner hopper 80Y is started even if the toner density is lowered. This upper limit voltage is defined as voltage Voutrefmax.

  By controlling the toner concentration within the initial target range in this way, ground contamination, toner scattering, etc. due to excessive increase in toner concentration due to sensitivity reduction when the case thickness is thicker than the target thickness can be prevented. In addition, ID reduction due to excessive decrease in toner density due to an increase in sensitivity when the case thickness is thinner than the target is prevented or suppressed.

  Since the thickness of the case includes the thickness of the double-sided tape 86Y, such inconvenience caused by the upper and lower sensitivity due to the thickness of the double-sided tape 86Y is also prevented. The attachment member for attaching the toner concentration detection sensor 56Y to the developing case 55Y is not limited to the double-sided tape 86Y, but may be any adhesive, a rib formed on the developing case 55Y, a screw, or a complicated mechanism. In any case, the attachment error is included in the case thickness, and the toner density control accuracy is good.

  Further, the toner density detection sensor 56Y may be of a type in which a hole is formed in the developing case 55Y, inserted into the hole, and the detecting portion is exposed in the developing case 55Y. In this case, the sensitivity varies depending on the positioning error such as the protruding amount of the toner density detection sensor 56Y in the developing case 55Y. By including such an error in the case thickness, the control accuracy of the toner density is increased. It becomes good.

  In realizing such a toner density measurement sensitivity measurement method and toner density control method, the memory of the control means includes at least the data shown in FIG. 3 or the data shown in FIG. Necessary items are stored in advance as functions or tables when the developing case 55Y, the process cartridge 95Y, or the image forming apparatus 100 is shipped.

  The control means functions as an input voltage determining means for performing an input voltage determining step for obtaining a voltage Vcntreal and a voltage ΔVcnt when the voltage Vout becomes 3.0 V at the time of initial setting, and a differential voltage determining means for performing a differential voltage determining step.

The control unit functions as a sensitivity calculation unit that performs a sensitivity calculation step of calculating the sensitivity of the toner concentration detection sensor 56Y based on the voltage ΔVcnt.
The memory functions as sensitivity calculation data storage means for storing sensitivity calculation data necessary for calculating sensitivity. The sensitivity calculation data includes at least data indicating a correlation between the differential voltage and sensitivity, for example.
The memory functions as a sensitivity storage unit that performs a sensitivity storage step of storing the calculated sensitivity.

  The control means calculates at least the voltage Voutrefmax and the voltage Voutrefmin out of the voltage Voutref, performs an output voltage calculation means for performing an output voltage calculation step for calculating the voltage Voutref, and performs a limit voltage calculation step for calculating the voltage Voutrefmax and the voltage Voutrefmin. It functions as a limit voltage calculation means.

  The memory stores at least the voltage Voutrefmax and the voltage Voutrefmin among the voltages Voutref, an output voltage storage means for performing an output voltage storage step for storing the voltage Voutref, a limit for performing a limit voltage storage step for storing the voltage Voutrefmax and the voltage Voutrefmin. Functions as voltage storage means.

As described above, the voltage Vout when the developing device 50Y is used may change greatly depending on the change in the flow state of the developer, and the toner density control accuracy may be reduced.
The flow state of the developer depends on the use environment of the developing device 50Y, that is, temperature, humidity, and toner usage rate.

  FIG. 8 shows changes in sensitivity of the toner concentration detection sensor 56Y due to temperature and humidity. In the figure, HH indicates a case where the temperature is 27 ° C. and the humidity is 80 Ph%, MM indicates a case where the temperature is 23 ° C. and the humidity is 50 Ph%, and LL indicates that the temperature is 10 ° C. and the humidity. Is 15Ph%. From the figure, it can be seen that the sensitivity tends to decrease in a low temperature and low humidity environment, and the sensitivity tends to increase in a high temperature and high humidity environment.

  Therefore, even if the voltage Voutrefmax and the voltage Voutrefmin are determined as described above, the toner density to be controlled changes due to changes in temperature and humidity. That is, for example, in the same figure, when the voltage Voutrefmin is 2.0 V, the upper limit value of the toner density is changed by HH, MM, and LL, and the control range is changed.

  Therefore, as shown in Table 1 below, by correcting the voltage Voutrefmax and the voltage Voutrefmin according to the humidity, variations in the toner density control range due to the humidity environment are reduced. In the table, the upper limit side means a correction amount for the voltage Voutrefmax, and the lower limit side means a correction amount for the voltage Voutrefmin.

  The result of such correction is shown in FIG. In Table 2, only the voltage Voutrefmax is shown. In Table 2, the limiter TC means the maximum value of the toner density corresponding to the voltage Voutrefmax in the toner control range.

  As can be seen from these charts, by correcting the voltage Voutrefmax according to each humidity condition, the variation in the toner density control range due to the humidity environment is greatly improved. The temperature condition can be similarly corrected.

  FIG. 10 shows the result of comparing the relationship between the toner density TC and the voltage Vout by the image area ratio. FIG. 4A shows a state before correction described below, and FIG. 4B shows a state after correction. The image area ratio is the ratio of the area where the image is formed in the image formable area of the transfer paper. In the figure, it is assumed that the target output characteristic is the relationship between the toner density TC and the voltage Vout at an image area ratio of 5%.

  The relationship between the toner density TC and the voltage Vout is ideally the same regardless of the image area ratio, but in reality, as shown in FIG. Deviation from the output characteristics. For example, in the figure, if the voltage Voutrefmin is 2.0 V, the lower the image area ratio, the more deviated from the target toner density TC.

  Therefore, as shown in the following Table 3, by correcting the voltage Voutrefmax by applying a correction coefficient α corresponding to the image area ratio, the voltage Voutrefmax is output as a target as shown in FIG. It is close to the characteristics. This prevents the toner density TC corresponding to the voltage Voutrefmax from becoming excessive in each image area ratio, and prevents or suppresses background contamination, toner scattering, and the like. Similarly, the voltage Voutrefmax may be corrected.

  In this embodiment, the image area ratio is calculated based on the number of pixels on the photosensitive drum 20Y that is developed by the developing device 50Y. The number of pixels is calculated based on the image data used for writing by the optical scanning device 8. The image area rate can be the toner consumption rate per one development operation of the developing device 50Y per image formation, but in this embodiment, the average value in the last 1000 image formations is used. This is taken as the toner consumption rate.

  This is because if the image area ratio is calculated with a small number of sheets up to about several hundred sheets, the fluctuation becomes large and the correction is too effective. This is because there is a possibility that the effect of the correction may not be sufficient because the timing for applying the correction is delayed.

  In this embodiment, the toner consumption rate is obtained based on the image area rate, but instead of the image area rate, the toner consumption rate may be obtained based on the operating rate of the toner replenishing means. This is because the toner is replenished as much as it is consumed, and the toner consumption rate can be called the toner replenishment rate. The operation rate of the toner replenishing means is obtained by multiplying the product of the toner replenishing amount per unit time by the toner replenishing means measured in advance and the driving time of the toner replenishing means by the number of image forming sheets, for example, 1000 image forming sheets as described above Or may be obtained using a predetermined time instead of the number of formed images.

  In realizing such correction of the voltage Voutrefmax and the voltage Voutrefmin, the control unit functions as a determined output voltage correction unit that performs a determined output voltage correction step for correcting the voltage Voutrefmax and the voltage Voutrefmin.

  Particularly with regard to temperature and humidity, the control unit functions as a determined output voltage temperature and humidity correction unit that performs a determined output voltage temperature and humidity correction step of correcting the voltage Voutrefmax and the voltage Voutrefmin.

  Regarding the toner consumption rate, the control unit functions as a toner consumption rate calculation unit that performs a toner consumption rate calculation step for calculating the toner consumption rate, and corrects the voltage Voutrefmax and the voltage Voutrefmin based on the calculated toner consumption rate. It functions as a determined output voltage toner consumption rate correction means for performing a determined output voltage toner consumption rate correction step.

  In addition, regarding the number of pixels on the photosensitive drum 20Y in the toner consumption rate, the control unit functions as a pixel number calculation unit that performs a pixel number calculation step for calculating the number of pixels, and based on the calculated toner consumption rate and the number of pixels. And functioning as a determined output voltage pixel number correcting unit that performs correction of the voltage Voutrefmax and the voltage Voutrefmin, a determined output voltage pixel number correcting unit that performs a determined output voltage image area rate correcting step, and a determined output voltage image area rate correcting unit.

  Regarding the operating rate of the toner replenishing means among the toner consumption rates, the control means functions as a toner replenishing operating rate calculating means for performing a toner replenishing operating rate calculating step for calculating the operating rate, and calculates the calculated toner consumption rate and toner. It functions as a determined output voltage toner replenishment correcting means for performing a determined output voltage toner replenishment correcting step for correcting the voltage Voutrefmax and the voltage Voutrefmin based on the operating rate of the replenishing means.

  The memory functions as correction data storage means for storing correction data such as correction amounts and correction coefficients shown in Tables 1 to 3, and also stores corrected voltage Voutrefmax and voltage Voutrefmin. It functions as a corrected output voltage storage means for performing steps.

  In particular, regarding temperature and humidity, the memory functions as a temperature and humidity correction output voltage storage unit that performs a temperature and humidity correction output voltage storage step of storing the corrected voltage Voutrefmax and voltage Voutrefmin.

  Further, regarding the toner consumption rate, the memory performs an operation history storage unit that performs an operation history storage step of storing an operation history of the developing device 50Y, for example, the number of pixels on the photosensitive drum 20Y, the number of formed images, the driving time of the toner supply unit, and the like. And a toner consumption rate correction output voltage storage that stores the toner supply amount storage unit that stores the toner supply amount per unit time by the toner supply unit and that stores the corrected voltage Voutrefmax and voltage Voutrefmin. It functions as a toner consumption rate correction output voltage storage means for performing steps.

  Further, regarding the number of pixels on the photosensitive drum 20Y in the toner consumption rate, the memory performs a pixel number correction output voltage storage step for storing the corrected voltage Voutrefmax and a voltage Voutrefmin, and a pixel for performing an image area ratio correction output voltage storage step. It functions as number correction output voltage storage means and image area ratio correction output voltage storage means.

  Further, regarding the operating rate of the toner replenishing means in the toner consumption rate, the memory functions as a toner replenishing correction output voltage storing means for performing a toner replenishing correction output voltage storing step for storing the corrected voltage Voutrefmax and voltage Voutrefmin.

Thus, the developing device 50Y and the control unit constitute a toner density control device.
Such toner density measurement sensitivity measurement and toner density control are performed individually in each of the developing devices 50Y, 50C, 50M, and 50BK. As a result, even if the toner and carrier used in each of the developing devices 50Y, 50C, 50M, and 50BK are different, sensitivity measurement and toner density control are performed satisfactorily. In particular, since the flowability of the developer is likely to vary depending on the toner and the carrier, setting the correction amount and the correction coefficient individually in each of the developing devices 50Y, 50C, 50M, and 50BK makes it possible to control the toner density. It is preferable to carry out.

  Other corrections may be performed on the voltage Voutrefmax and the voltage Voutrefmin. For example, a predetermined pattern is created outside the transfer area of the photosensitive drum 20Y to the transfer paper between the paper, at the JOB end, etc., and is read by the P sensor, which is a reflection type photosensor, and converted into an adhesion amount. When the amount is smaller than the adhesion amount, the voltage Voutrefmax and the voltage Voutrefmin are low, and when the amount is dark, the voltage Voutrefmax and the voltage Voutrefmin are high. Such correction is performed at an appropriate time, such as during image formation, process control at the end of JOB, and toner replenishment control is performed accordingly.

  As a result, for example, when the voltage Voutrefmax becomes 4.0 V and the voltage Voutrefmin becomes 2.0 V, as shown in FIG. 11, the voltage Vout is controlled within this range, and the toner is controlled within the corresponding toner density control range. Concentration is controlled.

  FIG. 12 shows an outline of a modification of the image forming apparatus to which the present invention is applied. The image forming apparatus 100 will be described mainly with respect to differences from the image forming apparatus 100 described above. The same parts as those of the image forming apparatus 100 described above are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  The image forming apparatus 100 includes a reading unit 121 corresponding to the reading device 21 and the automatic document feeder 22 described above, an image forming unit 122 corresponding to the main body 101 and the sheet feeding device 23, and the control unit described above. Corresponding to the scanner control unit 123 provided in the reading unit 121, the system control unit 124, the plotter control unit 125 and the image processing unit 126 provided in the image forming unit 122, and the operation unit 127 corresponding to the above-described operation panel. And have.

  The reading unit 121 includes a lamp 102, a mirror 103, a CCD 104, an amplifier 105, and an A / D conversion unit 106. The lamp 102 corresponds to the above-described light source, the mirror 103 corresponds to the above-described first and second reflectors, and the CCD 104 corresponds to the above-described reading sensor 21e. Further, although the amplifier 105 and the A / D converter 106 are not mentioned in the above description, the reading device 21 is similarly provided.

  The image processing unit 122 performs pseudo correction, filter, γ correction, gradation processing, and the like. Although not mentioned in the above description, the same processing is also performed in the above-described control means.

  The image forming unit 122 includes the photosensitive drum 20 corresponding to the above-described photosensitive drum 20Y, the developing device 50 corresponding to the above-described developing device 50Y, the writing unit 8 corresponding to the above-described optical scanning device 8, and the above-described charging. The charging device 30 corresponding to the device 30Y and the like, the cleaning device 40 corresponding to the cleaning device 40Y and the like, the fixing device 6, the sheet feeding device 23 and the sheet feeding trays 1 to 4 corresponding to the manual sheet feeding device 33 are provided. A sheet feeding device 117 is provided.

  In addition, the image forming unit 122 includes a pre-transfer charge removal lamp 111, an eraser 112, a charge removal lamp 113, and a separation charger 115. Although not mentioned in the above description, these may also be provided in the image stations 60Y, 60C, 60M, 60BK, the transfer belt unit 10, and the secondary transfer unit 76.

  In the image forming apparatus 100 having such a configuration, in the reading unit 121, the light emitted from the lamp 102 is reflected by the original surface, converted into an electric signal by the CCD 104, and after amplitude adjustment by the amplifier 105, A / D The digital image data quantized by the converter 106 is obtained.

  The generated digital image data is input to the image processing unit 122, subjected to shading correction processing, filter processing, γ correction processing, gradation processing, and the like in this order and sent to the image forming unit 122.

  The digital image data input to the image forming unit 122 is converted into laser light L in accordance with the data value in the writing unit 8, and is irradiated onto the photosensitive drum 20 charged by the charging device 30, and is applied to the surface of the photosensitive drum 20. An electrostatic latent image is formed.

  The developing device 50 adheres toner to the surface of the photosensitive drum 20 in accordance with the formed electrostatic latent image. The toner adhering to the surface of the photosensitive drum 20 is transferred onto the surface of the transfer paper sent from the paper feeding device 117, passes through the fixing device 6, and is output as a copy original.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

For example, the correction of the output voltage based on temperature and humidity may be performed based on one of temperature and humidity as necessary.
The toner concentration measurement sensor is not a magnetic permeability sensor, but measures the toner concentration by other methods as long as the present invention can be applied, such as the above-described toner concentration measurement sensitivity measurement method and toner concentration control method. May be.

  The process cartridge includes at least the image carrier and the developing device and may be detachable from the main body of the image forming apparatus. Selection of the other components constituting the process cartridge is the image carrier, This is performed as appropriate in consideration of the lifetime of the component parts, the cost, the structural ease of forming a process cartridge, and the like.

  The present invention is not a so-called tandem type image forming apparatus, but a so-called one-drum type image forming apparatus that sequentially forms toner images of each color on a single photosensitive drum and sequentially superimposes the color toner images to obtain a color image. It can be similarly applied to. In any type of image forming apparatus, the toner image of each color may be directly transferred onto a transfer sheet or the like without using an intermediate transfer member. Further, the present invention can be applied not only to a color image forming apparatus but also to a monochrome image forming apparatus as shown in FIG.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

1 is a schematic front view of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic front view showing a configuration around one image carrier among a plurality of image carriers provided in the image forming apparatus shown in FIG. 1. FIG. 3 is a correlation diagram showing the relationship between the toner density and the output voltage, which is a characteristic of the toner density measuring sensor shown in FIG. 2. FIG. 3 is a correlation diagram showing the relationship between the case thickness and sensitivity, which is a characteristic of the toner concentration measurement sensor shown in FIG. 2. FIG. 4 is a correlation diagram showing measurement results obtained by measuring a case thickness difference and a differential voltage using the toner concentration measurement sensor shown in FIG. 2. FIG. 6 is a correlation diagram showing a relationship between a differential voltage and sensitivity of the toner concentration measurement sensor shown in FIG. 2 obtained from the relationship shown in FIGS. FIG. 7 is a correlation diagram showing that the relationship between the toner concentration and the output voltage of the toner concentration measurement sensor obtained from the relationship shown in FIG. 6 is corrected according to the case thickness, and is corrected according to the case thickness. FIG. 6 is a correlation diagram showing that an output voltage for controlling the toner density obtained from the figure is obtained. It is a correlation diagram showing that the toner concentration and the output voltage of the toner concentration measurement sensor change depending on the temperature and humidity of the usage environment of the developing means. FIG. 10 is a correlation diagram illustrating a result of correcting the output voltage of the toner concentration measurement sensor based on the temperature and humidity of the usage environment of the developing unit. FIG. 6 is a correlation diagram before and after correcting the output voltage of the toner density measurement sensor based on the toner consumption rate of the developing means. FIG. 6 is a correlation diagram illustrating that toner density is controlled by a determined output voltage. It is a schematic front view of another image forming apparatus to which the present invention is applied.

Explanation of symbols

20, 20Y, 20M, 20C, 20BK Image carrier 50, 50Y, 50M, 50C, 50BK Developing means 56Y Toner density measuring sensor 86Y Mounting member Voutref, Voutrefmax, Voutrefmin Determined output voltage 100 Image forming apparatus

Claims (12)

A toner concentration measurement sensitivity measuring method for measuring a toner concentration measurement sensor for measuring a toner concentration of a developer including a toner and a carrier, and measuring the sensitivity of the toner concentration in the developing unit,
The toner concentration measurement sensor can adjust the output voltage by adjusting the input voltage,
A first input voltage for obtaining an output voltage corresponding to a toner density as a reference in the toner density measuring sensor before the developing means is installed;
A second input voltage for obtaining an output voltage corresponding to the reference toner density in the toner density measuring sensor after the developing means is installed;
A toner density measurement sensitivity measuring method for measuring the sensitivity based on a differential voltage between a first input voltage and a second input voltage.   A toner concentration control method for controlling the toner concentration of a developer inside a developing unit using the sensitivity measured using the toner concentration measurement sensitivity measuring method according to claim 1, wherein the toner concentration control method includes the reference toner concentration. Based on the sensitivity measured using the toner density measurement sensitivity measurement method, the output voltage to be outputted from the toner density measurement sensor after installing the developing means, corresponding to the limit toner density in a predetermined range of toner density. A toner density control method for determining and controlling the toner density of the developer in the developing unit based on the determined output voltage.   3. The toner concentration control method according to claim 2, wherein the determined output voltage is corrected based on at least one of temperature and humidity of a use environment of the developing unit.   4. The toner density control method according to claim 2, wherein the determined output voltage is corrected based on a toner consumption rate by the developing means.   5. The toner density control method according to claim 4, wherein the toner consumption rate by the developing unit is obtained based on the number of pixels on the image carrier that is developed by the developing unit.   5. The toner concentration control method according to claim 4, wherein a toner consumption rate by the developing unit is obtained based on an operating rate of a toner replenishing unit that replenishes toner in the developing unit.   7. A toner concentration control apparatus for controlling toner concentration using the toner concentration control method according to claim 2.   A developing device that controls toner density using the toner density control method according to claim 2.   9. The developing device according to claim 8, further comprising: a developer container that contains the developer; and a mounting member that attaches the toner concentration measurement sensor to the outer surface of the developer container.   An image forming apparatus comprising the toner density control device according to claim 7 or the developing device according to claim 8 or 9.   10. An image forming apparatus comprising a plurality of developing devices according to claim 8 or 9, wherein the output voltage to be output is determined for each developing device.   An image forming method for forming an image using the developing device according to claim 8 or 9, or the image forming device according to claim 10 or 11.

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