JP6256120B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus.

  In general, an electrophotographic image forming apparatus employs a negative / positive development method (a method for developing an exposed portion) or a positive / positive development method (a method for developing an unexposed portion). Here, in an apparatus adopting the negative / positive development system, when the photosensitive member is not charged due to a failure of the charging means or the like, the toner adheres to the entire surface of the photosensitive member, so that a so-called solid image is output. . Similarly, in the apparatus using the positive / positive development system, there is a problem that a solid image is output when the photosensitive member is not exposed due to a failure of the exposure apparatus or the like.

  When a solid image occurs, toner and recording paper are wasted. In particular, when a solid image is generated during facsimile reception, the received information is completely lost (the received data is discarded when printing is completed). For). Therefore, when a solid image is generated, it is necessary to detect this as soon as possible and immediately stop printing.

  In this regard, Japanese Patent Application Laid-Open No. 2011-28160 (Patent Document 1) determines whether or not toner is attached to an area (between sheets) where a toner image should not be transferred on the transfer belt. Disclosed is an image forming apparatus that determines whether a solid image has been detected by a sensor.

  However, in order to detect a solid image, the density sensor (light sensor) must always be driven during printing, so that there is a problem that power consumption increases accordingly.

  The present invention has been made in view of the above-described problems in the prior art, and the present invention provides a novel image forming apparatus capable of minimizing the power consumption of the density sensor when detecting a solid image. With the goal.

  As a result of intensive studies on the configuration of a novel image forming apparatus capable of minimizing the power consumption of the density sensor when detecting a solid image, the present inventor has conceived the following configuration and reached the present invention. is there.

  That is, according to the present invention, an electrophotographic image forming apparatus includes an optical density sensor for acquiring the toner adhesion amount on a transfer belt, and a predetermined pattern formed on the transfer belt. An adjustment processing execution unit that performs a predetermined adjustment process by using an abnormality detection unit that detects an abnormality in which toner adheres to a non-image area on the transfer belt based on a toner adhesion amount acquired by the density sensor; A density sensor control unit that variably controls the light emission voltage of the density sensor, wherein the density sensor control unit is a part or all of the predetermined pattern formed on the transfer belt, and the abnormality is A reference image determination unit that determines, as a solid reference image, a toner image having a toner adhesion amount equal to the toner adhesion amount at the time of occurrence, and the density sensor is driven with a default light emission voltage. A second light emission which is a light emission voltage sufficient and sufficient to detect the abnormality based on the reflected light reception voltage of the solid reference image and the default light emission voltage, which is lower than the default light emission voltage. A voltage deriving unit for deriving a voltage, wherein the abnormality detecting unit drives the density sensor with the second light emission voltage to detect the abnormality during printing.

  As described above, according to the present invention, a novel image forming apparatus capable of minimizing the power consumption of the density sensor when detecting a solid image is provided.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 3 is a configuration diagram of a control unit of the image forming apparatus of the present embodiment. 1 is a functional block diagram of an image forming apparatus according to an embodiment. FIG. 4 is a diagram illustrating a state in which an image is transferred onto an intermediate transfer belt. The flowchart which shows the setting process of the light emission voltage implemented in parallel with a high voltage electric potential adjustment process. The figure which shows the pattern for high voltage electric potential adjustment. The figure which shows the change of the reflected light received voltage of the density | concentration sensor driven with a default light emission voltage. The figure which shows the change of the reflected light received voltage of the density | concentration sensor driven with the light emission voltage for solid image detection. The flowchart which shows the setting process of the light emission voltage implemented in parallel with a color adjustment process. The figure which shows the pattern for (gamma) correction. The flowchart which shows the setting process of the light emission voltage implemented in parallel with a position shift adjustment process. The figure which shows the pattern for position shift correction tails. 6 is a flowchart illustrating a light emission voltage setting process performed in parallel with the toner discharge process. FIG. 4 is a diagram illustrating a toner discharge pattern.

  Hereinafter, although this invention is demonstrated with embodiment, this invention is not limited to embodiment mentioned later. In the drawings referred to below, the same reference numerals are used for common elements, and the description thereof is omitted as appropriate.

  FIG. 1A is a schematic configuration diagram of an electrophotographic image forming apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1A, the image forming apparatus 100 of this embodiment includes four process units (1Y, 1C, 1M, 1Bk) configured to be detachable from the main body 1. Each process unit contains toner of different colors of yellow, cyan, magenta, and black corresponding to the color separation components of the color image.

  Each process unit includes a photosensitive drum 2 as a latent image carrier, a charging roller 3 for charging the surface of the photosensitive drum 2, and development for supplying toner (developer) to the surface of the photosensitive drum 2. An apparatus 4 and a cleaning blade 5 for cleaning the surface of the photosensitive drum 2 are provided. In addition, an exposure device 6 (electrostatic latent image forming means) for exposing the surface of the photosensitive drum 2 is disposed above each process unit, and the exposure device 6, the charging roller 3, and the developing device. 4 functions as an image forming unit for forming an image on the photosensitive drum 2.

  A transfer device 7 is arranged below each process unit. Here, the transfer device 7 includes an intermediate transfer belt 8 composed of an endless belt as a transfer body, and the intermediate transfer belt 8 is stretched around a driving roller 9 and a driven roller 10 and is shown by an arrow in the figure. It is configured to be able to rotate (running around) in the direction of.

  On the other hand, four primary transfer rollers 11 are disposed as primary transfer means at positions facing the four photosensitive drums 2. Each primary transfer roller 11 presses the inner peripheral surface of the intermediate transfer belt 8 at each position, and a primary transfer nip is formed at a location where the pressed portion of the intermediate transfer belt 8 and each photosensitive drum 2 come into contact with each other. Has been.

  A secondary transfer roller 12 as a secondary transfer unit is disposed at a position facing the drive roller 9. The secondary transfer roller 12 presses the outer peripheral surface of the intermediate transfer belt 8, and a secondary transfer nip is formed at a location where the secondary transfer roller 12 and the intermediate transfer belt 8 are in contact with each other.

  Further, a belt cleaning device 13 for cleaning the surface of the intermediate transfer belt 8 is disposed on the outer peripheral surface of the intermediate transfer belt 8 on the right end side in the drawing. A waste toner transfer hose (not shown) extending from the belt cleaning device 13 is connected to an entrance of a waste toner container 14 disposed below the transfer device 7.

  On the other hand, a lower portion of the main body 1 is provided with a paper tray 15 that stores recording paper P as a recording medium, a paper feed roller 16 that carries the recording paper P out of the paper tray 15, and the like. On the other hand, a pair of paper discharge rollers 17 for discharging the recording paper to the outside and a paper discharge tray 18 for stocking the discharged recording medium are disposed on the upper portion of the main body 1. Further, a conveyance path R for guiding recording paper from the lower paper tray 15 to the upper paper discharge tray 18 is formed in the main body 1.

  A pair of registration rollers 19 is disposed on the conveyance path R in the middle from the paper feed roller 16 to the secondary transfer roller 12. A fixing device 20 for fixing the image on the recording paper is provided on the way from the secondary transfer roller 12 to the paper discharge roller 17. The fixing device 20 includes a fixing roller 21 as a fixing rotator that is heated by a heating source, a pressure roller 22 as a pressure rotator that pressurizes the fixing roller 21, and the like. A fixing nip is formed at a location where the pressure roller 22 is in pressure contact with each other.

  Here, in the image forming apparatus 100 of the present embodiment, a density sensor 30 (density detection means) for detecting the adhesion amount of toner on the intermediate transfer belt 8 on the outer peripheral surface of the intermediate transfer belt 8 on the left end side in the drawing. Is disposed.

  FIG. 1B shows a configuration diagram of the density sensor 30. As shown in FIG. 1B, the density sensor 30 is configured as an optical reflective density sensor including a light emitting element 32 referred to as an LED or the like and a light receiving element 34 referred to as a phototransistor or a photodiode. ing. In the density sensor 30, light is emitted from the light emitting element 32 to the intermediate transfer belt 8 that is the detection target surface, and the light receiving element 34 receives the specularly reflected light from the intermediate transfer belt 8 and generates the reflected light detection voltage. It is configured to detect. The light emission amount of the light emitting element 32 is variably configured by controlling the light emission voltage for driving the density sensor 30.

  Here, the light emitted from the light emitting element 32 to the surface of the intermediate transfer belt 8 (the surface on which the toner image is not formed) is almost regularly reflected, but the light emitted to the toner image is absorbed and diffused. The ratio of regular reflection is reduced. In this regard, the density sensor 30 uses the difference in characteristics to determine the ratio between the reflected light detection voltage Vsg on the surface of the intermediate transfer belt 8 (the surface on which the toner image is not formed) and the reflected light detection voltage Vsp of the toner image. (Vsp / Vsg) is calculated, and the toner adhesion amount is obtained from the detected voltage ratio (Vsp / Vsg) using a lookup table or function prepared in advance.

  The schematic configuration of the image forming apparatus 100 according to the present embodiment has been described above. Next, the image forming operation of the image forming apparatus 100 will be described.

  In the image forming apparatus 100, when an image forming operation is started, the photosensitive drums 2 of the process units (1Y, 1C, 1M, 1Bk) are rotationally driven in the clockwise direction in the drawing by a driving device (not shown), and each photosensitive member is driven. The surface of the drum 2 is uniformly charged to a predetermined polarity by the charging roller 3. The surface of each charged photoconductive drum 2 is irradiated with laser light from the exposure device 6 to form an electrostatic latent image on the surface of each photoconductive drum 2.

  At this time, the image information to be exposed to each photosensitive drum 2 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. Thus, by supplying toner from each developing device 4 to the electrostatic latent image formed on the photosensitive drum 2, the electrostatic latent image is visualized as a toner image (developer image). The

  Subsequently, when the drive roller 9 is rotationally driven counterclockwise in the figure, the intermediate transfer belt 8 is driven to travel in the direction indicated by the arrow in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 11. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 11 and each photosensitive drum 2.

  Subsequently, each color toner image formed on the photosensitive drum 2 of each process unit is sequentially superimposed and transferred onto the intermediate transfer belt 8 by the transfer electric field formed in the primary transfer nip. A full-color toner image is carried on the surface 8. Residual toner adhering to the surface of each photosensitive drum 2 after the toner image is transferred is removed by the cleaning blade 5, and then the surface is subjected to a neutralizing action by a neutralizing device (not shown) so that the surface voltage is reduced. Initialized to prepare for the next image formation.

  On the other hand, in the lower part of the image forming apparatus 100, the recording paper P accommodated in the paper tray 15 is sent out to the transport path R by rotating the paper feed roller 16. The recording paper P sent out to the transport path R is timed by the registration roller 19 and sent to the secondary transfer nip between the secondary transfer roller 12 and the driving roller 9 facing it. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 8 is applied to the secondary transfer roller 12, and a transfer electric field is formed in the secondary transfer nip. Then, the toner images on the intermediate transfer belt 8 are collectively transferred onto the recording paper P by the transfer electric field formed in the secondary transfer nip.

  The recording paper P to which the toner image has been transferred is conveyed to the fixing device 20, and the recording paper P is heated and pressed by the fixing roller 21 and the pressure roller 22 to fix the toner image. The recording paper P on which the toner image is fixed is discharged to a paper discharge tray 18 by a paper discharge roller 17. Further, the toner remaining on the intermediate transfer belt 8 after the transfer is removed by the belt cleaning device 13, and the removed toner is conveyed to the waste toner container 14 and collected.

  The image forming operation of the image forming apparatus 100 according to the present embodiment has been described above. Next, a control unit that controls the operation of the image forming apparatus 100 will be described.

  FIG. 2 shows the configuration of the control unit of the image forming apparatus 100. As shown in FIG. 2, the CPU 25 comprehensively controls access to various devices connected to the system bus 28 based on a control program stored in the ROM 26, and is connected via an I / O 29. Controls input / output of electrical components (including the concentration sensor 30 described above), motors, clutches, heaters and the like. The ROM 26 stores a program for realizing functional means described later. The CPU 25 performs communication processing with an external device such as a host computer via the external I / F 24. The RAM 27 functions as a main memory and work area of the CPU 25, and is used as a recording data development area, an environment data storage area, and the like. Further, the image processing IC 31 transmits image data (including a pattern image described later) to the exposure device 6.

  The control unit of the image forming apparatus 100 according to the present embodiment has been described above. Next, functional units realized by executing a predetermined computer program in the above-described control unit will be described with reference to functional blocks illustrated in FIG. This will be described with reference to the drawings. FIG. 3 shows only the configuration related to the gist of the present invention, and the illustration of other configurations included in the electrophotographic image forming apparatus is omitted.

  As shown in FIG. 3, the image forming apparatus 100 includes an adjustment processing execution unit 110, an abnormality detection unit 120, and a density sensor control unit 130. Hereinafter, the role played by each functional unit will be specifically described.

  The adjustment processing execution unit 110 is a functional unit for performing predetermined adjustment processing necessary for maintaining image quality, and forms a predetermined pattern on the intermediate transfer belt 8 and uses the pattern. Perform the adjustment process. Hereinafter, the four adjustment processes performed by the adjustment process execution unit 110 will be listed and described.

(High voltage potential adjustment processing)
When the image forming apparatus 100 is activated, a toner image having a gradation pattern is formed on the intermediate transfer belt 8. Specifically, a predetermined pattern is formed under a plurality of voltage application conditions, and a plurality of patches (toner images) having different gradations are formed on the intermediate transfer belt 8. Thereafter, the toner adhesion amount of each patch is detected by the density sensor 30, and the high voltage potential used for development and charging is corrected based on the detected toner adhesion amount.

(Color adjustment processing)
When the image forming apparatus 100 is activated, a toner image having a γ correction pattern (dither gradation pattern) is formed on the intermediate transfer belt 8. Specifically, a plurality of dither patterns (toner images) having different gradations are formed on the intermediate transfer belt 8. Thereafter, the toner adhesion amount of each dither pattern is detected by the density sensor 30, and the γ value of each color is corrected based on the detected toner adhesion amount.

(Position adjustment processing)
When the image forming apparatus 100 is activated, a toner image having a misregistration correction pattern is formed on the intermediate transfer belt 8. The formed pattern (toner image) is detected by the density sensor 30, the skew amount is calculated based on the detection timing, and the positional deviation is corrected based on the skew amount.

(Toner discharge process)
The toner staying in the developing unit for a long time deteriorates and becomes difficult to be charged. In view of this point, when a period in which printing is not performed continues for a certain time or longer, a toner image of a toner discharge pattern is formed on the intermediate transfer belt 8 so that old toner is discharged from the developing device and replaced with new toner.

  Next, the abnormality detection unit 120 will be described. The abnormality detection unit 120 is a functional unit for performing “solid image detection” based on the toner adhesion amount acquired by the density sensor 30. Hereinafter, “solid image detection” performed by the abnormality detection unit 120 will be described.

  In the image forming operation of the image forming apparatus 100, an electrostatic latent image is formed on an effective image area defined on the surface of the photosensitive drum 2 based on a frame gate signal (sub-scanning direction) and a line gate signal (main scanning direction). Is formed. Then, the toner supplied from the developing device 4 adheres to the electrostatic latent image formed on the photosensitive drum 2 to form a developer image (toner image).

  Thereafter, the toner image formed in the effective image area on the photosensitive drum 2 is transferred to the intermediate transfer belt 8. FIG. 4 shows a state in which an image for one page (indicated by symbol G) is transferred onto the intermediate transfer belt 8. Here, an area (indicated by reference numeral A) indicated by a broken line surrounding the image G corresponds to an effective image area defined on the photosensitive drum 2. Hereinafter, this area A is referred to as “image area A”. Here, an image forming operation is normally performed in a region (indicated by reference numeral B) positioned between the rear end in the sub-scanning direction of the image region A1 and the front end in the sub-scanning direction of the image region A2 subsequent thereto. As long as the toner image is transferred, the toner image is not transferred. Hereinafter, this region B is referred to as “non-image region B”.

  Here, consider a case where the surface of the photosensitive drum 2 is not normally charged due to a failure of the charging roller or the like. In this case, as a result of the occurrence of an electric field opposite to the normal electric field in the unexposed portion on the photosensitive drum 2, the toner adheres to the portion of the photosensitive drum 2 that should not be developed. As a result, an unintended developer image (hereinafter referred to as a solid image) is formed, which is transferred to a recording sheet and output. When such an abnormality occurs, if the discovery is delayed, the toner and recording paper are wasted, and in the case of a facsimile, the received content may be lost. In order to avoid such a situation, it is necessary to detect an abnormality causing a solid image as soon as possible and immediately stop printing.

  With regard to this point, in the present embodiment, focusing on the fact that the toner is transferred to the non-image area B that should not be transferred when an abnormality that causes a solid image occurs, the toner in the non-image area B The occurrence of an abnormality is detected by monitoring the presence / absence of the presence or absence by the concentration sensor 30. The above is the content of “solid image detection” performed by the abnormality detection unit 120.

  Next, the density sensor control unit 130 will be described. The density sensor control unit 130 is a functional unit for variably controlling the light emission voltage of the density sensor 30 in order to minimize the power consumption of the density sensor 30, and includes a solid reference image determination unit 132 and a voltage derivation unit 134. Consists of.

  Here, since the density sensor 30 is conventionally assumed to be used in the above-described three adjustment processes (high voltage potential adjustment process, color adjustment process, and positional deviation adjustment process), the light emission voltage of the density sensor 30 is A higher default voltage was set so that all patterns used in the three adjustment processes could be detected.

  However, when performing solid image detection, it is necessary to always drive the density sensor 30 during printing. Therefore, if the density sensor 30 is driven with the conventional default voltage, its power consumption becomes excessive.

  In this regard, the density sensor control unit 130 drives and controls the density sensor 30 with a light emission voltage that is necessary and sufficient to detect a solid image in order to minimize power consumption of the density sensor for solid image detection.

  In addition, the density sensor control unit 130 is at least one selected from the four adjustment processes (the high-voltage potential adjustment process, the color adjustment process, the misalignment adjustment process, and the toner discharge process) performed by the adjustment process execution unit 110 described above. In parallel with the two processes, a process for calculating a light emission voltage necessary and sufficient for detecting a solid image is performed, and the calculated light emission voltage for solid image detection is set in the density sensor 30. Hereinafter, the setting process of the light emission voltage for image detection performed by the density sensor control unit 130 in parallel with the four adjustment processes described above will be described in order.

(First embodiment)
In the first embodiment, a light emission voltage for detecting an image is set in the density sensor 30 in parallel with the high-voltage potential adjustment process performed when the image forming apparatus 100 is activated. Hereinafter, a flow in which the process for setting the emission voltage for solid image detection is performed in parallel with the high-voltage potential adjustment process will be described based on the flowchart shown in FIG.

  In the high-voltage potential adjustment process, in step 101, a toner image of a high-voltage potential adjustment pattern (hereinafter simply referred to as a pattern) is formed on the intermediate transfer belt 8. FIG. 6 shows a pattern (2g) formed on the intermediate transfer belt 8. As shown in FIG. 6, the pattern (2g) is composed of a plurality of patches (rectangular toner images) having different gradations. In the case of a color printing machine, a pattern (2g) for four colors (Y, M, C, Bk) is formed.

  In the subsequent step 102, the toner adhesion amount of each patch constituting the pattern (2g) is acquired based on the reflected light reception voltage detected by the density sensor 30.

  In the subsequent step 103, as shown in FIG. 6, the relationship between the toner adhesion amount of each patch and the applied high voltage when each patch is imaged is plotted, and an approximate curve that interpolates all the plots is obtained as a relational expression (2c). .

  In the subsequent step 104, when the solid reference image determining unit 132 generates an abnormality (solid image) from the pattern (2g) formed on the intermediate transfer belt 8 based on the relational expression obtained in step 103. A patch having an amount of toner adhering to the amount of toner adhering to the intermediate transfer belt 8 is determined. Hereinafter, the patch determined here is referred to as a “solid reference image”.

  In the present embodiment, the “solid reference image” can be determined by the following procedure. First, as a premise, a toner adhesion amount (2b) comparable to a solid image is defined in advance. Here, the toner adhesion amount (2b) has a meaning as a threshold for detecting a solid image. In step 104, the toner adhesion amount (2b) is input to the relational expression (2c) to obtain a high voltage potential (2e). Then, a patch (2f) formed by applying a voltage lower than the acquired high voltage potential (2e) and closest to the high voltage potential (2e) is determined as a solid reference image.

  In the subsequent step 105, it is determined whether or not the solid reference image has been successfully determined. When the determination of the solid reference image is successful (step 105, Yes), in the subsequent step 106, the voltage deriving unit 134 derives the light emission voltage and the detection threshold voltage for solid image detection. Hereinafter, a procedure for deriving the light emission voltage and detection threshold voltage for solid image detection will be described in detail.

  FIG. 7 shows a change in the reflected light reception voltage when the density sensor 30 driven with the default light emission voltage Y detects the pattern (2g) in the previous step 102. Here, in the previous step 102 (see FIG. 5), it is necessary to set a high light emission voltage Y so that the patch (2h) with the smallest toner adhesion amount in the pattern (2g) can be reliably detected. However, in solid image detection, it is only necessary to detect a larger toner adhesion amount (patch (2f) = a solid reference image toner adhesion amount) than the patch (2h), so the light emission voltage of the density sensor 30 is lower than the default value Y. Can be set.

  In order to understand this, FIG. 8 shows changes in the reflected light reception voltage when the density sensor 30 is driven with the default light emission voltage Y, and reflection when the density sensor 30 is driven with the solid image detection light emission voltage Y ′. The changes in the photoreception voltage are shown side by side. As shown in FIG. 8, when the light emission voltage of the density sensor 30 is changed from Y to Y ′, the reflected light reception voltage related to the solid reference image changes from Z to Z ′. The reflected light reception voltage Z ′ of the solid reference image corresponds to a detection threshold voltage for solid image detection.

  Here, in the present embodiment, the reflected light reception voltage Z (obtained in step 102) of the solid reference image when the density sensor 30 is driven with the default light emission voltage Y and the light emission voltage Y ′ for solid image detection. The ideal relationship between the detection threshold voltage Z ′ and the detection threshold voltage Z ′ is experimentally obtained in advance, and based on the obtained ideal relationship, the default light emission voltage Y of the density sensor 30 and the reflected light reception voltage Z of the solid reference image are input to the solid image. A lookup table or function that outputs the detection light emission voltage Y ′ and the detection threshold voltage Z ′ is prepared.

  Then, in step 106, a lookup table or function in which the reflected light reception voltage Z and the default light emission voltage Y of the reference image determined in step 104 (= the patch (2f) detected in the previous step 102) are prepared in advance. The light emission voltage Y ′ for solid image detection and the detection threshold voltage Z ′ are derived as outputs thereof.

  In the case of a color printer, in step 106, four sets of parameters (Y ′, Z ′) are obtained based on the reflected light reception voltage Z of the solid reference image for four colors (Y, M, C, Bk). In this case, the highest value (Y ′, Z ′) among the four sets of parameters is derived as a representative value.

  In the subsequent step 107, the parameters (Y ′, Z ′) derived in step 106 are set in the density sensor 30. As a result, the light emission voltage and the detection threshold voltage of the density sensor 30 are changed to voltage values lower than the default values.

  In the following step 108, calculation and setting of an appropriate high voltage potential are performed. Specifically, in FIG. 6, a preset target toner adhesion amount (2a) is input to the relational expression (2c) to obtain the high voltage potential (2d), and the high voltage potential (2d) is obtained as a developing device or a charging device. Set to.

  If the determination in step 105 has failed to determine a solid reference image (No in step 105), the process proceeds to step 109. Here, as a case where a solid reference image cannot be determined, the pattern (2g) is faded due to lack of toner, and the amount of toner attached to the patches constituting the pattern (2g) is less than the amount of toner attached (2b). Can be considered. In such a case, in step 109, the parameters (light emission voltage and detection threshold voltage) of the density sensor 30 are set to 0, and then a warning of insufficient toner is given.

  Another case in which a solid reference image cannot be determined is that an abnormality such as a charging roller failure has already occurred at the time of pattern (2g) image formation, so the toner adheres to all patches that make up the pattern (2g). It is conceivable that the amount exceeds the toner adhesion amount (2b). In such a case, in step 109, after the parameters (light emission voltage and detection threshold voltage) of the density sensor 30 are set to 0, printing is immediately stopped. That is, in the present embodiment, when some abnormality has already occurred during the high-voltage potential adjustment process, power consumption is minimized by immediately stopping power supply to the concentration sensor 30.

  As described above, according to the first embodiment, since the density sensor 30 is driven with a light emission voltage lower than the newly set default light emission voltage during the print execution period, the power consumption of the density sensor 30 is minimized. . In the present embodiment, since the setting process described above is performed every time the high-voltage potential adjustment process is executed, the density of the density sensor 30 and the intermediate transfer belt 8 (such as deterioration over time) is reflected. The parameters of the sensor 30 (light emission voltage and detection threshold voltage) are optimized in a timely manner. In addition, in the present embodiment, the setting process described above is performed by using the high-voltage potential adjustment pattern in parallel with the high-voltage potential adjustment process, so that the printing down time is not affected.

(Second Embodiment)
In the second embodiment, a light emission voltage for detecting an image is set in the density sensor 30 in parallel with the color tone adjustment process performed when the image forming apparatus 100 is activated. Hereinafter, a flow in which the process for setting the emission voltage for solid image detection is performed in parallel with the color adjustment process will be described based on the flowchart shown in FIG. In the following description, only the differences from the first embodiment will be described, and description of points that are common to the first embodiment will be omitted as appropriate.

  In the color tone adjustment process, a toner image of a γ correction pattern (hereinafter simply referred to as a pattern) is formed on the intermediate transfer belt 8 in step 201. FIG. 10 shows a pattern (6c) formed on the intermediate transfer belt 8. As shown in FIG. 10, the pattern (6c) is composed of a plurality of dither patterns having different gradations. In the case of a color printer, a pattern (6c) for four colors (Y, M, C, Bk) is formed.

  In the subsequent step 202, the toner adhesion amount of each dither pattern constituting the pattern (6c) is acquired based on the reflected light reception voltage detected by the density sensor 30.

  In the subsequent step 203, the dither pattern (toner image) used for calculating the light emission voltage for solid image detection from the pattern (6c) formed on the intermediate transfer belt 8 is determined as the “solid reference image”. .

  The “solid reference image” can be determined by the following procedure. First, as a premise, a toner adhesion amount (6a) comparable to a solid image is defined in advance. Here, the toner adhesion amount (6a) has a meaning as a threshold for detecting a solid image. In step 203, the toner adhesion amount is smaller than the toner adhesion amount (6a) and becomes the closest adhesion amount to the toner adhesion amount (6a) among all dither patterns constituting the pattern (6c). The dither pattern (6b) is determined as a solid reference image.

  In subsequent step 204, it is determined whether or not the determination of the solid reference image has succeeded. If the determination of the solid reference image is successful (step 204, Yes), in the subsequent step 205, the emission voltage and detection threshold voltage for solid image detection are derived. That is, in step 205, a reflected light reception voltage and a default light emission voltage of the reference image determined in step 203 (= the dither pattern (6b) detected in the previous step 102) are prepared in a lookup table (or function) prepared in advance. The emission voltage for detecting a solid image and the detection threshold voltage are derived by inputting them.

  In the next step 206, the parameters derived in step 205 (solid image detection light emission voltage and detection threshold voltage) are set in the density sensor 30, and the light emission voltage and detection threshold voltage of the density sensor 30 are lower than the default values. Change to

  In the subsequent step 207, γ correction is performed by checking the toner adhesion amount of the pattern (6c) acquired in step 202 against the γ correction table.

  Note that if the determination of the solid reference image has failed in the determination of the previous step 204 (step 204, No), the process proceeds to step 208. Since the process performed in step 208 is the same as the process performed in step 109 of the first embodiment, a description thereof will be omitted.

  As described above, according to the second embodiment, since the density sensor 30 is driven with a light emission voltage lower than the newly set default light emission voltage during the print execution period, the power consumption of the density sensor 30 is minimized. . In the present embodiment, since the setting process described above is performed every time the color adjustment process is executed, the density of the density sensor 30 and the intermediate transfer belt 8 (such as deterioration over time) is reflected. The parameters of the sensor 30 (light emission voltage and detection threshold voltage) are optimized in a timely manner. In addition, in the present embodiment, since the setting process described above is performed by using the γ correction pattern in parallel with the color tone adjustment process, the printing down time is not affected.

(Third embodiment)
In the third embodiment, a light emission voltage for detecting an image is set in the density sensor 30 in parallel with the positional deviation adjustment process performed when the image forming apparatus 100 is activated. Hereinafter, a flow in which the light emission voltage setting process for solid image detection is performed in parallel with the positional deviation adjustment process will be described with reference to the flowchart shown in FIG. In the following description, only the differences from the first embodiment will be described, and description of points that are common to the first embodiment will be omitted as appropriate.

  In the misregistration adjustment process, in step 301, a toner image of a misregistration correction pattern (hereinafter simply referred to as a pattern) is formed on the intermediate transfer belt 8. FIG. 12 shows a pattern (8a) formed on the intermediate transfer belt 8. In this embodiment, the pattern (8a) itself is used as a solid reference image. Therefore, for the image data that is the basis of the pattern (8a), the toner adhesion amount of the pattern (8a) formed on the intermediate transfer belt 8 is comparable to the solid image (that is, to detect a solid image). The appropriate gradation value is set in advance so that the toner adhesion amount having the meaning as the threshold value of the threshold value), and the adjustment processing execution unit 110 performs the intermediate transfer of the pattern (8a) having the set gradation value. Form on the belt 8. In the case of a color printer, patterns (8a) for four colors (Y, M, C, and Bk) are formed.

  In the subsequent step 302, the toner adhesion amount and position information of the pattern (8a) are acquired based on the reflected light reception voltage detected by the density sensor 30 and the timing thereof.

  In the following step 303, the light emission voltage and detection threshold voltage for solid image detection are derived. That is, in step 303, solid image detection is performed by inputting the reflected light reception voltage and the default light emission voltage of the solid reference image (= pattern (8a) detected in the previous step 402) into a lookup table or function prepared in advance. A light emission voltage and a detection threshold voltage are derived.

  In the following step 304, the parameters derived in step 303 (solid image detection light emission voltage and detection threshold voltage) are set in the density sensor 30, and the light emission voltage and detection threshold voltage of the density sensor 30 are lower than the default values. Change to

  In the subsequent step 305, the skew amount is calculated based on the position information of the pattern (8a) acquired in step 302, and the positional deviation is corrected based on the skew amount.

  As described above, according to the third embodiment, since the density sensor 30 is driven with a light emission voltage lower than the newly set default light emission voltage during the print execution period, the power consumption of the density sensor 30 is minimized. . In the present embodiment, since the above-described setting process is performed every time the misregistration adjustment process is performed, the density reflects the state of the density sensor 30 and the intermediate transfer belt 8 (such as deterioration over time). The parameters of the sensor 30 (light emission voltage and detection threshold voltage) are optimized in a timely manner. In addition, in the present embodiment, the setting process described above is performed in parallel with the misregistration adjustment process by using the misregistration correction pattern, and thus does not affect the printing downtime.

(Fourth embodiment)
In the fourth embodiment, in the image forming apparatus 100, the light emission voltage for image detection that is solid when the period in which printing is not performed continues for a certain time or longer is set in the density sensor 30 in parallel with the toner discharge process. Hereinafter, a flow in which the light emission voltage setting process for solid image detection is performed in parallel with the toner discharge process will be described with reference to the flowchart shown in FIG. In the following description, only the differences from the first embodiment will be described, and description of points that are common to the first embodiment will be omitted as appropriate.

  In the toner discharge process, a toner image of a toner discharge pattern (hereinafter simply referred to as a pattern) is formed on the intermediate transfer belt 8 in step 401. FIG. 14 shows a pattern (10a) formed on the intermediate transfer belt 8. As shown in FIG. 14, the pattern (10a) is a fill pattern that uniformly fills the entire image area A (see FIG. 4) on the intermediate transfer belt 8. In this embodiment, the pattern (10a) itself Is used as a solid reference image. Therefore, for the image data that is the basis of the pattern (10a), the toner adhesion amount of the pattern (10a) formed on the intermediate transfer belt 8 is comparable to the solid image (that is, to detect a solid image). In this case, an appropriate gradation value is set in advance so that the toner adhesion amount having the meaning as a threshold value of the threshold value is obtained, and the adjustment processing execution unit 110 performs intermediate transfer of the pattern (10a) having the set gradation value. Form on the belt 8. In the case of a color printer, patterns (10a) for four colors (Y, M, C, and Bk) are formed.

  In the subsequent step 402, the toner adhesion amount and position information of the pattern (8a) are acquired based on the reflected light reception voltage detected by the density sensor 30 and its timing.

  In the subsequent step 403, a light emission voltage and a detection threshold voltage for solid image detection are derived. That is, in step 403, the reflected light reception voltage and the default light emission voltage of the solid reference image (= the pattern (8a) detected in the previous step 402) are input to a lookup table or function prepared in advance, thereby obtaining a solid image. The light emission voltage for detection and the detection threshold voltage are derived.

  In the following step 404, the parameters derived in step 403 (solid image detection light emission voltage and detection threshold voltage) are set in the density sensor 30, and the light emission voltage and detection threshold voltage of the density sensor 30 are lower than the default values. Change to

  As described above, according to the fourth embodiment, since the density sensor 30 is driven with a light emission voltage lower than the newly set default light emission voltage during the print execution period, the power consumption of the density sensor 30 is minimized. . In the present embodiment, since the setting process described above is performed every time the toner discharge process is executed, the density sensor reflects the state of the density sensor 30 and the intermediate transfer belt 8 (such as deterioration over time). Thirty parameters (light emission voltage and detection threshold voltage) are optimized in a timely manner. In addition, in the present embodiment, since the setting process described above is performed in parallel with the toner discharge process by using the toner discharge process pattern, the print down time is not affected.

  As described above, according to the present embodiment, when performing solid image detection, the density sensor can be driven with the minimum required light emission voltage, so that the power consumption of the density sensor can be minimized. become.

  As described above, the present invention has been described with the embodiment. However, the present invention is not limited to the above-described embodiment, and as long as the operations and effects of the present invention are exhibited within the scope of embodiments that can be considered by those skilled in the art. It is included in the scope of the present invention.

  Note that each function of the above-described embodiment can be realized by a device-executable program described in C, C ++, C #, Java (registered trademark), and the like. The program of this embodiment includes a hard disk device, a CD-ROM. , MO, DVD, flexible disk, EEPROM, EPROM and the like can be stored and distributed in a device-readable recording medium, and can be transmitted via a network in a format that other devices can.

DESCRIPTION OF SYMBOLS 1 ... Main-body part 2 ... Photoconductor drum 3 ... Charging roller 4 ... Developing device 5 ... Cleaning blade 6 ... Exposure device 7 ... Transfer device 8 ... Intermediate transfer belt 9 ... Drive roller 10 ... Follower roller 11 ... Primary transfer roller 12 ... Two Next transfer roller 13 ... Belt cleaning device 14 ... Waste toner container 15 ... Paper tray 16 ... Paper feed roller 17 ... Paper discharge roller 18 ... Paper discharge tray 19 ... Registration roller 20 ... Fixing device 21 ... Fixing roller 22 ... Pressure roller 24 ... External I / F
25 ... CPU
26 ... ROM
27 ... RAM
28 ... System bus 29 ... I / O
30 ... Density sensor 31 ... Image processing IC
32 ... Light emitting element 34 ... Light receiving element 100 ... Image forming apparatus 110 ... Adjustment processing execution unit 120 ... Abnormality detection unit 130 ... Density sensor control unit 132 ... Solid reference image determination unit 134 ... Voltage deriving unit 140 ... Storage unit

JP 2011-28160 A

Claims (14)

An electrophotographic image forming apparatus,
An optical density sensor for acquiring the toner adhesion amount on the transfer belt;
An adjustment processing execution unit that performs a predetermined adjustment process using a predetermined pattern formed on the transfer belt;
An abnormality detection unit that detects an abnormality in which toner adheres to a non-image area on the transfer belt based on a toner adhesion amount acquired by the density sensor;
A density sensor control unit that variably controls the light emission voltage of the density sensor;
Including
The concentration sensor control unit
A toner image that is a part or all of the predetermined pattern formed on the transfer belt and has an amount of toner equivalent to the amount of toner attached when the abnormality occurs is determined as a solid reference image. A reference image determination unit;
Based on the reflected light reception voltage of the solid reference image and the default light emission voltage when the density sensor is driven with a default light emission voltage, the light emission voltage is sufficient and sufficient to detect the abnormality, A voltage deriving unit for deriving a second light emission voltage lower than the light emission voltage of
And deriving the second light emission voltage in parallel with the predetermined adjustment process,
The abnormality detection unit
Detecting the abnormality by driving the density sensor with the second emission voltage when printing is performed;
Image forming apparatus. The concentration sensor control unit
A lookup table or function having the default emission voltage and the reflected light reception voltage of the solid reference image as input, and the second emission voltage and a threshold voltage for detecting the abnormality as an output;
The voltage deriving unit includes:
Inputting the default emission voltage and the reflected light reception voltage of the solid reference image into the lookup table or function to derive the second emission voltage and the threshold voltage;
The image forming apparatus according to claim 1 . The adjustment processing execution unit
A high voltage potential adjustment pattern is formed on the transfer belt, and a high voltage potential adjustment process is performed using the high voltage potential adjustment pattern.
The solid reference image determination unit
Determining the solid reference image from the high-voltage potential adjustment pattern;
The image forming apparatus according to claim 1 or 2. The adjustment processing execution unit
A γ correction pattern is formed on the transfer belt, and a color adjustment process is performed using the γ correction pattern.
The solid reference image determination unit
Determining the solid reference image from the γ correction pattern;
The image forming apparatus according to claim 1 or 2. The adjustment processing execution unit
A misregistration correction pattern is formed on the transfer belt so that an amount of toner equal to the amount of toner adhering when the abnormality occurs, and misregistration adjustment processing is performed using the misregistration correction pattern. Carried out,
The solid reference image determination unit
Determining the misregistration correction pattern as the solid reference image;
The image forming apparatus according to claim 1 or 2. The adjustment processing execution unit
A toner discharge pattern is formed on the transfer belt so that an amount of toner equal to the amount of toner attached when the abnormality occurs, and a toner discharge process is performed using the toner discharge pattern.
The solid reference image determination unit
Determining the toner discharge pattern as the solid reference image;
The image forming apparatus according to claim 1 or 2. The voltage deriving unit includes:
When the solid reference image determination unit fails to determine the solid reference image, zero is derived as a value of the second light emission voltage and the threshold voltage.
The image forming apparatus according to claim 2 . A computer for controlling an electrophotographic image forming apparatus;
An optical density sensor for acquiring the toner adhesion amount on the transfer belt;
Adjustment processing execution means for performing a predetermined adjustment process using a predetermined pattern formed on the transfer belt;
An abnormality detection means for detecting an abnormality in which toner adheres to a non-image area on the transfer belt based on a toner adhesion amount acquired by the density sensor;
Density sensor control means for variably controlling the light emission voltage of the density sensor;
A computer-executable program for functioning as
The concentration sensor control means includes
A toner image that is a part or all of the predetermined pattern formed on the transfer belt and has an amount of toner equivalent to the amount of toner attached when the abnormality occurs is determined as a solid reference image. Reference image determining means,
Based on the reflected light reception voltage of the solid reference image and the default light emission voltage when the density sensor is driven with a default light emission voltage, the light emission voltage is sufficient and sufficient to detect the abnormality, Voltage deriving means for deriving a second light emission voltage lower than the light emission voltage of
And deriving the second light emission voltage in parallel with the predetermined adjustment process,
The abnormality detection means is
Detecting the abnormality by driving the density sensor with the second emission voltage when printing is performed;
program. The concentration sensor control means includes
A lookup table or function having the default emission voltage and the reflected light reception voltage of the solid reference image as input, and the second emission voltage and a threshold voltage for detecting the abnormality as an output;
The voltage deriving means includes
Inputting the default emission voltage and the reflected light reception voltage of the solid reference image into the lookup table or function to derive the second emission voltage and the threshold voltage;
The program according to claim 8 . The adjustment processing execution means includes:
A high voltage potential adjustment pattern is formed on the transfer belt, and a high voltage potential adjustment process is performed using the high voltage potential adjustment pattern.
The solid reference image determining means includes
Determining the solid reference image from the high-voltage potential adjustment pattern;
The program according to claim 8 or 9 . The adjustment processing execution means includes:
A γ correction pattern is formed on the transfer belt, and a color adjustment process is performed using the γ correction pattern.
The solid reference image determining means includes
Determining the solid reference image from the γ correction pattern;
The program according to claim 8 or 9 . The adjustment processing execution means includes:
A misregistration correction pattern is formed on the transfer belt so that an amount of toner equal to the amount of toner adhering when the abnormality occurs, and misregistration adjustment processing is performed using the misregistration correction pattern. Carried out,
The solid reference image determining means includes
Determining the misregistration correction pattern as the solid reference image;
The program according to claim 8 or 9 . The adjustment processing execution means includes:
A toner discharge pattern is formed on the transfer belt so that an amount of toner equal to the amount of toner attached when the abnormality occurs, and a toner discharge process is performed using the toner discharge pattern.
The solid reference image determining means includes
Determining the toner discharge pattern as the solid reference image;
The program according to claim 8 or 9 . The voltage deriving means includes
If the solid reference image determining means fails to determine the solid reference image, deriving zero as the value of the second emission voltage and the threshold voltage;
The program according to claim 9 .