JP2010107668A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus using toner as a developer, wherein the concentration of the developer is judged with high accuracy by a simple method, so as to accurately perform the concentration control of the developer. <P>SOLUTION: A toner is blended with a fluorescent material in an amount of 1 to <10 wt.% smaller than the amount (10 to 40%) generally to be blended for developing fluorescence as a color material. A standard patch by the toner is formed on a transfer belt, and an ultraviolet illumination optical sensor 20 is arranged at the reading position thereof. The fluorescent material contained in the toner of the standard patch is excited by the ultraviolet illumination of the optical sensor 20 so as to illuminate fluorescence, the illumination wavelength of the fluorescence is received and is converted into a toner deposition amount by a sensor output/toner deposition amount data table, which is compared with a concentration data table beforehand stored in a memory device, a development bias is changed in accordance with the level of the toner concentration, and concentration control is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that uses a simple method to determine the concentration of a developer with high accuracy and accurately controls the concentration of the developer in an image forming apparatus that uses toner as a developer.

  Conventionally, an image forming apparatus using toner as a developer is known. In such an image forming apparatus, if the density of the developer is uneven, it is impossible to form an accurate image. Therefore, it is necessary to control the developer concentration at appropriate intervals to control the developer concentration appropriately.

  For example, in an image recording apparatus that uses a two-component developer of a non-magnetic toner and a magnetic carrier, a toner concentration sensor that detects a change in the magnetic permeability of the developer and detects the toner concentration of the developer is prepared. The toner that properly corrects the toner density of the image recording apparatus by changing the control voltage for controlling the intensity of the magnetic field generated by the toner density sensor in accordance with the change in the humidity of the developer detected in step 1 and the temperature in the image recording apparatus A density control method has been proposed. (For example, refer to Patent Document 1.)

  According to Patent Document 1, in an image recording apparatus using a two-component developer, an appropriate toner concentration can be maintained even if the humidity of the two-component developer changes or the temperature inside the device changes. Yes.

  Also, for example, in order to keep the developing ability constant over time, the toner density control reference value is changed according to the toner replacement amount within a certain period by grasping the transition of the image area ratio of the output image. In addition, there has been proposed a method for guiding the toner density in the developing device to an appropriate range by changing the image forming condition at a predetermined execution interval. (For example, see Patent Document 2.)

According to Patent Document 2, it is possible to correct the toner density control reference value according to the toner replacement amount within a certain period, and to change the image forming condition at a predetermined execution interval. It can be applied to any image output pattern.
JP 05-061353 A JP 2007-148260 A

  By the way, the technique of Patent Document 1 performs density control by measuring the mixing ratio of toner and carrier using a magnetic permeability sensor as density control of a conventional toner composed of a non-magnetic toner and a magnetic carrier. Are susceptible to the adverse effects of magnetic fields from developing devices such as magnet rollers.

  Further, in the technique of Patent Document 2, in order to measure the development γ (development capability) first, the potential of the patch writing unit is fixed, the development bias is changed, and the density of 10 gradations is measured on the photosensitive member. This reference patch is imaged, transferred to a transfer belt, the reference patch is measured, and the measurement result is used for toner density control.

  However, in this reference patch measurement, the reflected light when the reference patch is irradiated with an optical sensor is received and the density of the reference patch is measured. As shown in this example, the reflected light irradiated with light in a dark place is measured. When measuring the toner, since the reflection brightness of the toner itself is low, the sensitivity variation of the light receiving portion of the optical sensor is large, and it is necessary to create a strict relative table in advance, which is problematic because it requires a difficult technique. .

  In view of the above-described conventional situation, an object of the present invention is an image forming apparatus that accurately determines the developer concentration by a simple method in an image forming apparatus using toner as a developer, and accurately controls the developer concentration. Is to provide.

  The image forming apparatus of the present invention has a developer containing a fluorescent material and a light source that excites the fluorescent material contained in the developer, and excites the fluorescent material contained in the developer by the light source, An optical sensor that measures the luminance of the fluorescence emitted by the fluorescent material by the excitation, and a developer concentration determination unit that determines the concentration of the developer based on the luminance measured by the optical sensor. Is done.

  In this image forming apparatus, for example, the fluorescent material is blended in the same weight ratio to each of the plurality of developers having different colors, only one optical sensor is disposed, and the developer concentration determination unit includes: Regardless of the color of the developer, the developer having the same measured luminance can be determined to have the same density.

  Further, for example, the developer contains a fluorescent material having different excitation fluorescence wavelengths for different colors, and the optical sensor excites the fluorescent material contained in the developer, and the excitation causes the fluorescent material to be excited. Measuring the wavelength and brightness of the fluorescence emitted from the developer, and the developer concentration detecting means determines the color and density of the developer based on the wavelength and the brightness obtained by the measurement by the optical sensor. It can also be configured as follows.

  According to the present invention, it is possible to provide an image forming apparatus that accurately controls the density of a developer by determining the density of the developer with high accuracy by a simple method in an image forming apparatus that uses toner as a developer. Become.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view illustrating an internal configuration of a color image forming apparatus (hereinafter simply referred to as a printer) that forms an image using a developer containing a fluorescent material according to Embodiment 1 of the present invention.

  A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, an intermediate transfer belt unit 3, a paper feeding unit 4, and a duplex printing conveyance unit 5. It consists of

  The image forming unit 2 has a configuration in which four image forming units 6 (6M, 6C, 6Y, and 6K) are arranged in a multistage manner from right to left in FIG.

  Of the four image forming units 6, three image forming units 6M, 6C and 6Y on the upstream side (the right side in the figure) are magenta (M), cyan (C) and yellow (subtractive three primary colors, respectively). A mono-color image is formed with the color toner of Y), and the image forming unit 6K forms a monochrome image with black (K) toner mainly used for dark portions of characters and images.

  Each of the image forming units 6 has the same configuration except for the color of the toner stored in the toner container (toner cartridge). Accordingly, the configuration of the black (K) image forming unit 6K will be described below as an example.

  The image forming unit 6 includes a photosensitive drum 7 at the bottom. The peripheral surface of the photosensitive drum 7 is made of, for example, an organic photoconductive material. A cleaner 8, a charging roller 9, an optical writing head 11, and a developing roller 13 of the developing device 12 are arranged around the periphery of the photosensitive drum 7.

  The developing device 12 puts one of magenta (M), cyan (C), yellow (Y), and black (K) toners in the upper toner container as indicated by M, C, Y, and K in the drawing. An intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  In addition, the developing roller 13 is provided in the lower portion of the developing device 12 at the side opening, and includes a toner stirring member, a toner supply roller for supplying toner to the developing roller 13, and a toner layer on the developing roller 13 as a fixed layer. It has a doctor blade that regulates the thickness.

  The intermediate transfer belt unit 3 has an endless transfer belt 14 extending in a flat loop shape from substantially the left and right sides of the figure at the approximate center of the main unit, and the transfer belt 14 is stretched over the transfer belt 14. A driving roller 15 and a driven roller 16 are provided to circulate and move the belt 14 counterclockwise in the drawing.

  The transfer belt 14 transfers the toner image directly onto the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 3 includes a belt position control mechanism 17 in the loop of the flat loop-shaped transfer belt 14. The belt position control mechanism 17 includes a primary transfer roller 18 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 7 via the transfer belt 14.

  The belt position control mechanism 17 has three primary transfer rollers 18 corresponding to the three image forming units 6M, 6C, and 6Y of magenta (M), cyan (C), and yellow (Y) as vertical support shafts. Rotate to the center with the same period.

  Then, the belt position control mechanism 17 rotates and moves one primary transfer roller 18 corresponding to the black (K) image forming unit 6K at a rotational movement cycle different from the cycle of the three primary transfer rollers 18. The belt 14 is moved away from the photosensitive drum 7.

  That is, the belt position control mechanism 17 moves the position of the transfer belt 14 of the intermediate transfer belt unit 3 to full color mode (all four primary transfer rollers 18 are in contact with the transfer belt 14), monochrome mode (to the image forming unit 6K). Only the corresponding primary transfer roller 18 is in contact with the transfer belt 14) and all non-transfer modes (all four primary transfer rollers 18 are separated from the transfer belt 14).

  In the intermediate transfer belt unit 3, a belt cleaner unit is disposed further upstream of the uppermost image forming unit 6M on the upstream side in the belt movement direction, and is flat and thin so as to be substantially along the entire lower surface. The waste toner collection container 19 is detachably disposed.

  In addition, an optical sensor 20 is disposed in close proximity to and facing an appropriate portion of the lower surface of the intermediate transfer belt 14 that carries and conveys four-color superimposed transfer images. The optical sensor 20 is an optical sensor having a light emitting element in a light emitting part and a light receiving element in a light receiving part, and the light emitting element is an ultraviolet light emitting optical sensor configured to emit ultraviolet light having a wavelength of 350 to 390 nm as a peak. is there.

  The paper feed unit 4 includes two paper feed cassettes 21 arranged in two upper and lower stages, and in the vicinity of the paper feed opening (right side in the figure) of the two paper feed cassettes 21, respectively, A feeding roller 23, a separating roller 24, and a standby conveying roller pair 25 are disposed.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 25, a secondary transfer roller 26 that is in pressure contact with the driven roller 16 via the transfer belt 14 is disposed, and the secondary transfer portion to the paper is arranged. Forming.

  A belt-type heat fixing device 27 is disposed downstream (upward in the drawing) of the secondary transfer portion, and the sheet after fixing is fixed to the belt-type heat fixing device 27 further downstream of the belt-type heat fixing device 27. A pair of carry-out rollers 28 for carrying out the paper and a pair of paper discharge rollers 31 for discharging the carried paper to a paper discharge tray 29 formed on the upper surface of the apparatus are disposed.

  The duplex printing conveyance unit 5 includes a start return path 32a that branches from the intermediate conveyance path between the carry-out roller pair 28 and the discharge roller pair 31 to the right lateral direction in the drawing, and then an intermediate return path 32b that bends downward. A terminal return path 32c that bends in the left lateral direction opposite to the above and eventually reverses the return sheet, and four return roller pairs 33a, 33b, 33c, and 33d arranged in the middle of these return paths are provided. ing.

  The exit of the end return path 32 c communicates with a conveyance path to the pair of standby conveyance rollers 25 corresponding to the sheet feeding cassette 21 below the sheet feeding unit 4.

  In this example, a cleaning unit 35 and a take-in roller 36 are disposed on the upper surface of the intermediate transfer belt unit 3.

  The cleaning unit 35 comes into contact with the upper surface of the transfer belt 14 and scrapes and removes the waste toner. The take-in roller 36 takes over the waste toner removed by the cleaning unit 35 and is not shown in the drawing, and is temporarily stored in the belt cleaner unit. The accumulated waste toner is conveyed to the upper part in the dropping cylinder by a conveying screw and sent to the waste toner collecting container 19 through the dropping cylinder. The waste toner collecting container 19 has the same configuration as that shown in FIGS. 3 and 4 of the prior art.

  Further, in order to bring the cleaning unit 35 into pressure contact with the transfer belt 14 with an appropriate pressure, a pressure roller 37 is provided on the intermediate transfer belt unit 3 side to press the transfer belt 14 toward the cleaning unit 35 from below. ing.

  As shown in FIG. 1, the image forming apparatus 1 does not directly transfer a toner image onto a conventional sheet, but an intermediate transfer belt on a sheet that is vertically conveyed to a secondary transfer unit by a standby conveyance roller pair 25. 14 is a method of transferring a toner image through the image forming apparatus 14.

  Therefore, it is possible to cope with a maintenance process for recovering from a problem such as a paper jam occurring in the paper transport path by simply opening the right side of FIG.

  In addition, since troubles such as paper jam do not occur in the arrangement section of the kits, the operation for attaching and detaching consumables such as the kits concentrated on the left side of FIG. 1 may be a small space that can be replaced in the longitudinal direction. It is configured as follows.

  Thereby, the dimension between kits is reduced as much as possible, and size reduction of the whole apparatus main body is achieved. Further, the optical writing head itself is also miniaturized and is configured closer to the photosensitive drum.

  FIG. 2 is a diagram illustrating an internal circuit configuration in the printer 1 having the above-described configuration. As shown in the figure, the circuit includes an interface (I / F) 40, a printer controller 41, an EEPROM (electrically erasable programmable ROM) 42, a ROM (read only memory) 43, an operation panel 44, and a head controller 45. ing.

  The printer controller unit 41 includes a temperature / humidity sensor 46 disposed at an appropriate position inside the main body device 1 and waste toner disposed in a mounting portion formed on the main body device 1 side of the waste toner collection container 19. The sensor 47 and the optical sensor 20 are connected.

  The waste toner sensor 47 is composed of a light reflection type or light transmission type optical sensor, and detects the rotation of an encoder that engages with a rotation shaft of a waste toner carry-in screw built in the waste toner collection container 19 in the mounting portion. The detection pulse signal is output to the printer controller 41.

  The waste toner carry-in screw, that is, the encoder, does not rotate when the waste toner collection container 19 is not attached to the attachment part, and rotates normally when an empty new waste toner collection container 19 is attached to the attachment part. As the waste toner in the waste toner collection container 19 is almost full, the rotation is decelerated due to the load of the waste toner, and the rotation stops when the waste toner in the waste toner collection container 19 is full.

  The optical sensor 20 has a light source that excites a fluorescent material contained in the developer, and the light source excites the fluorescent material contained in the developer, and measures the luminance of the fluorescence emitted by the fluorescent material by this excitation. The measurement result is output to the printer controller unit 41.

  Although not shown in FIG. 1, a high voltage unit 48 including a high voltage power source is connected. The high-voltage unit 48 includes a plus or minus high-voltage power source that supplies a predetermined bias voltage to the charging roller 9, the developing roller 13, the primary transfer roller 18, the secondary transfer roller 26, and the like.

  Further, the four optical writing heads 11 shown in FIG. 1 are connected to the other head controller unit 45.

  The interface (I / F) 40 inputs print data sent from a host device (not shown), outputs image data in the print data to the head controller unit 45, and sends commands in the print data to the printer controller unit. 41 is output.

  The EEPROM 42 stores the temperature and humidity in the apparatus, an encoder rotation pulse (to be described later), a warning flag, a waste toner recovery amount after warning, and the like. The ROM 43 stores a print program and a control program.

  Although not particularly shown, the head controller unit 45 includes a frame memory composed of four areas corresponding to yellow (Y), magenta (M), cyan (C), and black (K). The head controller unit 45 creates bitmap data of yellow (Y), magenta (M), cyan (C), and black (K) based on image data input from the interface (I / F) 40.

  The yellow (Y) bitmap data is stored in the yellow (Y) storage area of the frame memory, and the magenta (M) bitmap data is stored in the magenta (M) storage area of the frame memory. The bitmap data C) is stored in the cyan (C) storage area of the frame memory, and the black (K) bitmap data is stored in the black (K) storage area of the frame memory.

  The printer controller unit 41 is a central control unit including a CPU that performs print control and system control of the printer 1 of the present embodiment. Although not particularly illustrated, numerical values such as a time counter, a print number counter, and an actual print dot number counter are provided. A counter, a register, and the like are incorporated, and each part is controlled according to a program stored in the ROM 43.

  The printer controller 41 inputs an operation signal from a key operation unit (not shown) provided on the operation panel 44, and also outputs a display signal to a display unit (not shown).

  The printer controller 41 sends a print command to the head for each of yellow (Y), magenta (M), cyan (C), and black (K) based on a command supplied from the interface (I / F) 40. Output to the controller unit 45.

  Based on the print command, the head controller unit 45 supplies yellow (Y) print data to the optical writing head 11 of the image forming unit 6K, and sends magenta (M) print data to the light of the image forming unit 6M. Supply to the writing head 11, supply cyan (C) print data to the optical writing head 11 of the image forming unit 6C, and supply black (K) print data to the optical writing head 11 of the image forming unit 6K. To do. Each color is printed by each image forming unit 6.

  The head controller unit 45 supplies the print data to each optical writing head 11 and notifies the printer controller unit 41 of the actual number of print dots. The amount of waste toner generated on the transfer belt 14 is estimated from the actual number of print dots.

  Here, a fluorescent material-containing developer that is housed in the developing device 12 of the image forming apparatus 1 and used for image formation in the present embodiment will be described.

  Conventionally, color toners of Y (yellow), M (magenta), C (cyan), and K (black) contain a pigment as a color material. Some colorants also contain a fluorescent material to develop fluorescence.

  However, since the fluorescent material to be blended in the developer in this example is not used as a color material but for sensor detection, the amount to be blended in order to generally develop fluorescence as a color material (10 to 40%) Less than. That is, the fluorescent material of this example blended as a sensor reading additive is less than 1 to 10% by weight of the developer.

  In general, when the wavelength and intensity of the light source to be irradiated are kept constant, the amount of the fluorescent substance contained is directly proportional to the luminance of the fluorescence emitted by the irradiation light. Therefore, if the wavelength and intensity of the light source used for the light emitting part of the optical sensor are set to predetermined constant values, the amount of fluorescent substance contained in the developer, that is, depending on the luminance of the fluorescence detected by the light receiving part, that is, The concentration of the developer can be known.

  Here, the fluorescent material to be contained in the four color toners of Y, M, C, and K may be one kind, and four kinds of fluorescent materials having different absorption wavelengths are associated with each of the four colors. May be included. Further, the fluorescent material may be a fluorescent pigment, a fluorescent dye, an organic substance, or an inorganic substance, and is not particularly limited.

  An example of a method for producing a fluorescent material-containing developer (hereinafter simply referred to as toner) in this example is as follows. First, the following five types of materials are prepared.

1. 88% by mass of toner polyester resin having a softening point of 134 ° C.
2. 5% by mass of fluorescent material (particles doped with europium in Y2 O2 S, the average particle diameter is 1.22 μm in number average, measured with FPIA-2100 manufactured by Sysmex).

3. 3% by mass of Carmine 6B as a magenta pigment
4). 3% by mass of polyethylene-based WAX (“NP056” manufactured by Mitsui Chemicals, Inc.).
5). 1% by mass of a charge imparting material (Organic boron compound “LR-147” manufactured by Nippon Carlit Co., Ltd.).

  After mixing the above five kinds of materials with a mixer, the mixture was kneaded while applying temperature (maximum temperature 160 ° C.) with a twin screw kneader. The obtained kneaded material was pulverized to about 2 mm with a mechanical pulverizer, then further pulverized to a small particle size with an airflow pulverizer, and classified to a target particle size.

  Thereafter, silica particles surface-treated with silicon oil or alkyldisilazane (2% by mass with respect to the kneaded pulverized product) were externally added to the kneaded pulverized product, and passed through a sieve to obtain a toner. The average particle diameter of this toner is 9.4 μm in volume average (D50).

  Next, in the arrangement of the optical sensor, as shown in FIG. 1, the toner is fixed on the intermediate transfer belt 14 at a position where the toner can be scanned and fixed to the frame of the main body.

  In detecting the toner density, first, the toner whose density is to be detected is transferred onto the intermediate transfer belt 14. Here, the toner to be transferred generally forms a reference patch composed of a plurality of image patterns having different densities.

  As the image form of the reference patch, the accuracy of density detection is higher when a plurality of images having different densities consisting of solid printing and halftone dot printing are formed and formed rather than a single solid printing image. Also, the above-mentioned reference patch density data table is prepared in advance on a nonvolatile memory as control data of the printer main body.

  Subsequently, a toner reference patch whose density is to be detected is transferred onto the intermediate transfer belt 14, and the reference patch transferred onto the intermediate transfer belt 14 is read by the optical sensor 20. In this reading, excitation light having a predetermined wavelength is emitted from the light emitting unit of the optical sensor 20 toward the reference patch.

  By this excitation light irradiation, the fluorescent material contained in the toner emits fluorescence having a wavelength characteristic of the fluorescent material. The light receiving unit of the optical sensor 20 detects the emission of the fluorescence and outputs a signal having a strength corresponding to the detected luminance of the emitted light to the printer controller unit 41 as a luminance signal. The printer controller unit 41 uses the luminance signal detected by the optical sensor 20 to calculate the toner adhesion amount whose luminance is detected.

  FIG. 3 is a characteristic diagram (data table) showing the relationship between the intensity of the luminance signal output from the optical sensor 20 and the toner adhesion amount. In the figure, the horizontal axis indicates the toner adhesion amount, and the vertical axis indicates the sensor output. Based on the characteristic diagram, the printer controller 41 calculates the toner adhesion amount from the detected luminance signal, and calculates the image density of the reference patch from the calculated toner adhesion amount.

  When the calculated image density of the reference patch is lower than the density indicated by the density data table set in advance in the nonvolatile memory, the printer controller unit 41, for example, develops a bias so as to increase the toner density. The density is controlled so as to change.

  Taking the case where the image forming apparatus 1 is Casio N3500 as an example, the transfer bias of the photoreceptor 7 is −510V. The developing bias of the developing roller 13 is −210V. The doctor bias and the supply bias are -510V on the same wiring.

  FIG. 4 is a characteristic diagram (data table) showing the relationship between image density and development bias. In the figure, the horizontal axis indicates the developing bias, and the vertical axis indicates the image density. The printer controller unit 41 uses the characteristic diagram of FIG. 4 to perform density control by changing the developing bias of the image forming unit 6 according to the detected excess or deficiency of the image density of the reference patch. For example, when the image density is increased, the absolute value of the developing bias may be increased.

  As described above, the image forming apparatus of this example uses a fluorescent-containing developer, uses a reflective optical sensor having a light source that generates a fluorescence spectrum using the characteristics of the fluorescent substance contained in the developer, and uses a fluorescent optical sensor. The reference patch of the developer containing the material is held on the intermediate transfer belt and read by the optical sensor, and image density control is performed based on the luminance data read by the optical sensor.

  According to the present embodiment, since the light emission of the fluorescent material of the developer containing the fluorescent material is detected by the optical sensor, the brightness of the excited fluorescence is higher than the reflected light received from the normal toner. By detecting the fluorescence spectrum, highly accurate concentration detection is possible.

  Needless to say, the density detection method of this example is also applicable to density control of fluorescent toner used as a color material. Further, although the reference patch is held on the intermediate transfer belt, the density of the reference patch developed on the photosensitive drum may be read by changing the arrangement position of the optical sensor. Further, an optical sensor may be installed at a location where the toner on the paper after the paper transfer and before the fixing can be measured.

  Further, the arrangement position of the optical sensor may be changed to detect the toner density on the developing roller. However, in this case, unlike the case of the intermediate transfer belt and the photosensitive drum, a halftone image formed of halftone dots as in the reference patch cannot be formed due to the principle of the developing roller.

  However, the toner layer (toner density) on the developing roller can be changed when any one or each of the development bias, supply bias, and doctor bias is changed according to the density detection result.

  Further, although an ultraviolet light emitting optical sensor is used as the optical sensor, any optical source may be used as long as it uses a light source capable of exciting the fluorescent material in the light emitting portion to emit fluorescence. In addition, a CCD may be used as the scanner as long as it can respond to the wavelength of the fluorescence.

  In general, as a device configuration of the sensor unit, for example, irradiation light is applied to a reference patch from an irradiation light source device through a condensing device such as a lens, and the reflected wavelength is amplified through a condensing device such as a lens or a fluorescent filter. The wavelength detected by the detection device is digitized and converted into analysis data.

  In this case, the irradiation wavelength may be changed using a filter. Further, a fluorescent filter may be used to remove excitation light and scattered light for the purpose of efficiently sensing the fluorescence spectrum.

  When the irradiation wavelength is changed using a filter, four types of fluorescent materials that match the excitation wavelength of the optical sensor light source to be used and the fluorescent filter and have four different wavelengths are used, Y, M, C, And four kinds of fluorescent materials having different wavelengths corresponding to the four color developers of K and K, respectively.

  In this case, the light receiving part of the optical sensor measures the wavelength and brightness of the fluorescence emitted by exciting the fluorescent material of the developer, and the printer controller 41 based on the wavelength and brightness obtained by the measurement by the optical sensor. The developer color and its density are determined.

  In such a case, for example, when the reference patch is held on the intermediate transfer belt, the image density for each color is measured because the wavelength of the fluorescent material used is different even if the four reference patches are overlapped simultaneously. Is possible.

  However, when four colors are overlaid in this way, the influence of the transfer becomes large and it is necessary to correct the measurement value. Therefore, it is more effective to use two to three color overlayers. This is also an effective method because the time required for detection is shorter than when detecting one color at a time.

  Moreover, you may use together optical sensors other than ultraviolet irradiation. The optical sensor used in combination may be one that uses reflected light from an infrared (940 nm) light emitting diode as a light source. Further, normal visible light such as blue (470 nm), green (520 nm), and red (630 nm) may be used.

  In terms of cost, there are two sensors, which is disadvantageous. However, it is possible to determine the toner image formed by changing the irradiation light and using two types of reflected light, so that more information can be received and the accuracy can be improved.

  Further, the optical sensor may be a sensor using visible light or infrared light emitting diodes, and a device capable of irradiating with ultraviolet rays (for example, a black light) may be installed outside. When the ultraviolet ray is irradiated, the reflected light is changed by the fluorescent material contained in the toner, so that reading is possible.

  If density control is performed in combination with a temperature / humidity sensor, the precision of density control will be higher. Of course, it can also be applied to resist correction.

  It can also be used to detect the amount of toner remaining in the developing device. In this case, the optical sensor may be installed on the main body side on the way of conveying the toner from the toner supply container into the developing device, or the toner remaining in the toner supply device of the toner supply device is observed with the sensor. An observation window may be provided at a position where it can be arranged, and the observation window may be arranged.

  When the toner in the developing device holding the toner remains, a fluorescent substance specific to the toner can be detected. When the amount of toner decreases, the detection amount by the optical sensor decreases, and when the toner is almost exhausted, the detection by the optical sensor disappears. Regardless of the color of the toner, good light sensitivity can be exhibited even in a dark place.

FIG. 2 is a cross-sectional view illustrating an internal configuration of a color image forming apparatus (printer) that forms an image using a developer containing a fluorescent material according to the first exemplary embodiment. 2 is a diagram illustrating an internal circuit configuration of the printer according to Embodiment 1. FIG. FIG. 6 is a characteristic diagram (data table) showing a relationship between intensity of a luminance signal output from the optical sensor of the printer and toner adhesion amount in the first embodiment. FIG. 6 is a characteristic diagram (data table) showing a relationship between the image density of the printer and the developing bias in the first embodiment.

Explanation of symbols

1 Image forming device (printer)
2 Image forming unit 3 Intermediate transfer belt unit 4 Paper feeding unit 5 Double-sided printing transport unit 6 (6M, 6C, 6Y, 6K) Image forming unit 7 (7m, 7c, 7y, 7k) Photosensitive drum 8 Cleaner 9 Charging roller DESCRIPTION OF SYMBOLS 11 Optical writing head 12 Developing device 13 Developing roller 14 Transfer belt 15 Drive roller 16 Drive roller 17 Belt position control mechanism 18 Primary transfer roller 19 Waste toner collection container 20 Optical sensor 21 Paper feed cassette 22 Paper take-out roller 23 Feed roller 24 Separation roller 25 Standby conveyance roller pair 26 Secondary transfer roller 27 Belt type heat fixing device 28 Unloading roller pair 29 Paper discharge tray 31 Paper discharge roller pair 32a Start return path 32b Intermediate return path 32c End return path 33a, 33b, 33c, 33d Return roller pair 35 Cleaning unit 36 Capture roller 37 Pressing roller 40 Interface (I / F)
41 Printer controller 42 EEPROM (electrically erasable programable ROM)
43 ROM (read only memory)
44 Operation Panel 45 Head Controller 46 Temperature / Humidity Sensor 47 Waste Toner Sensor

Claims (3)

A developer containing a fluorescent material;
An optical sensor that has a light source that excites the fluorescent material contained in the developer, excites the fluorescent material contained in the developer by the light source, and measures the luminance of the fluorescence emitted by the fluorescent material by the excitation. When,
Developer concentration determination means for determining the concentration of the developer based on the luminance measured by the optical sensor;
An image forming apparatus comprising: The fluorescent material is blended in the same weight ratio to each of the plurality of developers having different colors,
Only one optical sensor is arranged,
The developer concentration determination means determines that the concentration is the same for the developer having the same measured brightness regardless of the color of the developer.
The image forming apparatus according to claim 1. The developer contains fluorescent materials having different excitation fluorescence wavelengths for different colors,
The optical sensor excites the fluorescent material contained in the developer, and measures the wavelength and luminance of the fluorescence emitted by the fluorescent material by the excitation,
The developer concentration detection means determines the color of the developer and its concentration based on the wavelength and the brightness obtained by the measurement by the optical sensor.
The image forming apparatus according to claim 1.