JP2012194408A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent prolongation of a waiting time for a user due to detection of a pre-transfer reflected light quantity on a belt background portion while moving an intermediate transfer belt around it before a test toner image is formed.SOLUTION: An image forming apparatus includes an update storage processing circuit 519 that samples a pre-transfer regular reflection output voltage Vsg_reg and a pre-transfer diffuse reflection output voltage Vsg_dif, which are output voltages from a first reflective optical sensor 130, reflecting a reflected light quantity in an area where no toner image based on the image information is transferred, in an entire area in the circumferential direction of an intermediate transfer belt, during an image forming operation based on image information. The update storage processing circuit 519 performs processing for updating values of the Vsg_reg and the Vsg_dif stored in a flash memory 519b for the area based on the sampling result.

Description

  The present invention uses a reflective optical sensor to detect the amount of reflected light in a state where the test toner image is transferred on the surface of the belt member, before and after the test toner image is transferred. The present invention relates to an image forming apparatus that adjusts an image forming condition of an image forming unit based on the result.

  In general, in an electrophotographic image forming apparatus, if the characteristics of toner and various members in the apparatus change due to changes in the environment such as temperature and humidity, the toner adhesion amount per unit area with respect to the output toner image Changes to cause fluctuations in image density. Therefore, it is a general practice to stabilize the image density by adjusting the image forming conditions as described below each time a predetermined timing such as every predetermined number of sheets is output. That is, a gradation pattern image composed of a plurality of test toner images is formed on the surface of a belt member such as an intermediate transfer belt, and a toner adhesion amount per unit area with respect to each test toner image is detected by a reflective optical sensor. . The target image density is obtained by adjusting the image forming conditions such as the development potential and the latent image writing light intensity based on the detection results.

  On the other hand, in the tandem image forming apparatus, the result of detection of the relative position shift of the toner images of yellow (Y), magenta (M), cyan (C), and black (K) by the reflective optical sensor. On the basis of this, there is also known one that adjusts the image forming conditions to reduce misalignment. In the tandem method, toner images of different colors are formed on the surfaces of a plurality of latent image carriers (for example, photoconductors) disposed along the surface of an endless belt member, and then the toner images are formed on the belt member or belt. This is a method of superimposing and transferring on a recording sheet on a member. In such a tandem system, the position of the latent image formed between the latent image carriers of each color is because the optical path position in the optical system that performs optical writing of the latent image on the latent image carrier varies slightly due to temperature changes. As a result, the toner images of the respective colors are misaligned. Further, the positional deviation of the toner images of the respective colors also occurs when the linear velocities of the latent image carriers and the belt members of the respective colors vary due to various factors. Therefore, after each test toner image formed on the latent image carrier of each color is transferred to the surface of the belt member, each color is determined based on the timing at which the presence of the test toner image is detected by the reflective optical sensor. A relative displacement amount of the toner image is detected. Each color toner is adjusted by adjusting the image forming conditions such as the latent image writing start timing, the surface tilt angle of the reflecting mirror of the optical system, and the driving speed fluctuation pattern of the latent image carrier or belt member based on the detection result. This reduces image displacement.

  As in these image forming apparatuses, in order to calculate the toner adhesion amount with respect to the test toner image on the belt member and to grasp the position of the test toner image, the test toner image on the surface of the belt member is used. It is necessary to measure in advance the amount of reflected light in a state before being transferred as the amount of reflected light before transfer. In order to accurately determine the amount of toner adhered to the test toner image, the ratio or difference between the reflected light amount before transfer and the reflected light amount after transfer, which is the reflected light amount on the belt surface after the test toner image is transferred, is obtained. This is because it needs to be detected. In addition, in order to accurately detect the presence or absence of the toner image on the belt member, it is necessary to accurately grasp the difference between the reflected light amount before transfer and the reflected light amount after transfer with respect to the reflected light amount detected by the reflective optical sensor. Because there is.

  In the past, the amount of reflected light before transfer described above was measured in a randomly selected region among all regions in the circumferential direction of the belt member. Even if the test toner image is not formed on the area, the amount of reflected light before transfer is measured in that area. However, the light reflectivity of the surface of the belt member may cause a large error in the belt circumferential direction due to a difference in the toner fixing amount and the scratch amount. Even if there is no such error, the distance between the reflective optical sensor and the belt surface in the belt circumferential direction may vary depending on the belt thickness deviation in the belt circumferential direction or the eccentricity of the roller around the belt member. Large errors can occur. Due to these errors, the sampling result of the reflected light quantity before transfer may fluctuate greatly in the process of making the belt member go around once. Nevertheless, if only the pre-transfer reflected light amount in a randomly selected region in the entire circumferential direction of the belt member is used, a large error occurs in the calculation result of the toner adhesion amount and the detection timing of the test toner image. I will let you.

  In recent years, for example, an image forming apparatus described in Patent Document 1 has been proposed in which the amount of reflected light before transfer of a belt member is sampled over one belt. Of the sampling results for one belt revolution, the one corresponding to the belt area carrying the test toner image is used for the calculation of the toner adhesion amount, thereby improving the detection accuracy of the toner adhesion amount, The toner image can be detected more accurately.

  However, in such a configuration, before forming the test toner image or detecting the post-transfer reflected light amount in the belt area after the test toner image is transferred, the reflected light amount before transfer is transferred over one belt. It is necessary to measure in advance. As a result, there is a problem that the waiting time of the user becomes very long.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a reflected light amount before transfer while moving the belt member over one circumference before forming a test toner image. It is an object of the present invention to provide an image forming apparatus capable of avoiding a prolonged waiting time of a user due to detection of the above.

  The inventors of the present invention increase the waiting time of the user by sampling the amount of reflected light before transfer over the entire circumference of the belt, mainly when the image forming condition adjustment processing is performed during the continuous printing operation. Focused on the time when Specifically, in general, the timing for performing the image forming condition adjustment processing includes a timing for performing warm-up immediately after turning on the power, a timing for performing a predetermined number of prints, and the like. Immediately after the power is turned on, all or part of the image forming condition adjustment processing can be performed in parallel with warm-up such as raising the temperature of the fixing roller of the fixing device. For this reason, the waiting time of the user is not extended at all by sampling the amount of reflected light before transfer over the entire circumference of the belt immediately after the power is turned on, or even if it occurs. On the other hand, when the execution timing of the image forming condition adjustment processing comes during the continuous printing operation, the continuous print job being executed is temporarily interrupted and the image forming condition adjusting processing is executed. In this case, the amount of reflected light before transfer is sampled at predetermined time intervals over the entire circumference of the belt, a test toner image is formed, or the amount of reflected light after transfer in the belt region after the transfer of the test toner image is detected. Processing is performed by interrupting a continuous print job being executed. Then, the time required for sampling the amount of reflected light before transfer for one rotation of the belt appears as an extension of the waiting time of the user as it is.

In order to achieve the above object, an invention according to claim 1 includes an image carrier that carries a toner image on its moving surface, an image information acquisition unit that acquires image information, and the image information acquisition unit. Based on the acquired image information, image forming means for forming a toner image on the surface of the image carrier, and transferring the toner image on the surface of the image carrier to the surface of an endless belt member that moves endlessly A transfer means for transferring the toner image to a recording member or a transfer member for transferring the toner image to a recording member held on the surface of the belt member; and a reflective optical sensor for detecting the amount of reflected light on the surface of the belt member; The pre-transfer reflected light that is the reflected light amount in the state before the test toner image is transferred is detected on the surface of the surface where the test toner image is transferred. Updating means for updating the value already stored in the information storage means based on the detection result, and after the transfer, which is the reflected light amount in the state where the test toner image is transferred for the area An image forming condition adjusting unit that performs an image forming condition adjusting process for adjusting an image forming condition of the image forming unit based on the reflected light amount and the pre-transfer reflected light amount stored in the information storage unit. In the forming apparatus, during the image forming operation based on the image information, the amount of reflected light of the region where the toner image based on the image information is not transferred out of the entire area in the circumferential direction of the belt member is reflected. And a process of updating the pre-transfer reflected light amount value stored in the information storage unit for the area based on the detection result. To run as a updating process and is characterized by being configured the updating means.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a plurality of the reflective optical sensors that detect the reflected light amount are provided at different positions in the width direction of the belt member, and the reflective optical sensors are provided. The update means is configured to individually perform the update process and the storage process for each sensor.
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the reflective optical sensor detects at least a diffuse reflection light amount among a regular reflection light amount and a diffuse reflection light amount on the belt member surface. In addition, in the update process, the pre-transfer reflected light amount in the information storage means for an area where the detection result of the pre-transfer reflected light amount for the diffusely reflected light by the reflective optical sensor exceeds a predetermined threshold The update means is configured to perform a process of canceling the update.
According to a fourth aspect of the present invention, in the image forming apparatus of the second aspect, as the first reflective optical sensor that is one of the plurality of reflective optical sensors, the amount of specularly reflected light and diffuse reflection on the surface of the belt member. Among the light amounts, one that detects at least the diffuse reflection light amount is used, and the pre-transfer reflection light amount of the diffuse reflection light by the first reflection optical sensor in the update process for the first reflection optical sensor. For the region where the detection result exceeds a predetermined threshold, the update unit is configured to perform a process of canceling the update of the reflected light quantity before transfer in the information storage unit.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, as a second reflective optical sensor different from the first reflective optical sensor, a regular reflected light amount and a diffuse reflected light amount on the belt member surface. Among them, the one that detects only the regular reflection light quantity is used, and the toner image based on the image information is not transferred in the entire area of the belt member in the update process for the second reflective optical sensor. The region passing through the position facing the second reflective optical sensor in the state passes the position facing the first reflective optical sensor in a state where the toner image based on the image information is not transferred, and the first Lined up in the belt width direction with respect to a region where the pre-transfer reflected light amount of the diffusely reflected light by one reflection type optical sensor is larger than a predetermined threshold value. If that is, for that area, so as to implement the process of abandoning the updating of the pre-transfer amount of reflected light in the information storage means, characterized in that constitute the updating means.
According to a sixth aspect of the present invention, in the image forming apparatus according to any of the first to fifth aspects, the update process is performed when power is first turned on after factory shipment or when the belt member is replaced with a new one. Instead of starting the image forming operation, a new storage process for newly detecting the reflected light quantity before transfer and storing the detection result in the information storage means is performed over one rotation of the belt member. The update means is configured to be implemented.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, a non-volatile device is used as the information storage unit.

  In these inventions, in parallel with the image forming operation for forming the toner image based on the image information, the value of the reflected light quantity before transfer already stored in the information storage means is updated to the same value as the actual detection result. Perform the update process. At this time, since the image forming operation is being performed, the belt region that is the target of detection of the reflected light quantity before transfer is not necessarily in a state where the toner image is not carried. It may be a toner transfer region carrying a toner image based on image information. Therefore, the update means does not update the pre-transfer reflected light amount for the toner transfer region in the entire area of the belt member in the circumferential direction, and the pre-transfer reflected light amount in the information storage means is not updated only for the non-toner transfer region. Update the data. Even if it is an area where the amount of reflected light before transfer could not be updated because it is a toner transfer area, the toner image is not transferred in the course of the belt member moving around by the image forming operation. It becomes possible to update the reflected light amount before transfer in the background area. As described above, by performing the process of updating the reflected light amount before transfer during the image forming operation, the continuous image forming operation is temporarily interrupted when the execution timing of the image forming condition adjustment processing arrives during the continuous image forming operation. Thereafter, it is possible to immediately form a test toner image without updating the pre-transfer reflected light amount over one belt. Therefore, it is possible to avoid an increase in the waiting time of the user by moving the belt member over one turn and updating the reflected light amount before transfer before forming the test toner image.

FIG. 1 is a schematic configuration diagram illustrating a main part of a printer according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating an image forming unit for K in the printer. FIG. 3 is a perspective view showing a transfer unit in the printer. FIG. 3 is an enlarged configuration diagram illustrating a first reflective optical sensor of the printer. FIG. 2 is a block diagram showing a part of an electric circuit in the printer. 6 is a flowchart illustrating a processing flow of image forming condition adjustment processing performed by the control unit of the printer. The expanded block diagram which expands and shows the 1st reflection type optical sensor and its periphery. The enlarged block diagram which expands and shows the 2nd reflection type optical sensor of the printer, and its circumference | surroundings. 6 is a flowchart illustrating a processing flow of image forming condition adjustment processing performed by the control unit of the printer according to the embodiment. 6 is a graph showing a relationship between a pre-transfer voltage Vsg acquired by an experiment and a belt position in the circumferential direction of the intermediate transfer belt. 6 is a graph showing a relationship between a post-transfer voltage Vsp obtained by an experiment and a belt position in the circumferential direction of the intermediate transfer belt. 6 is a graph showing the relationship between “Vsp / Vsg” acquired by experiment and the belt position in the circumferential direction of the intermediate transfer belt. 3 is a flowchart showing a processing flow of temporary storage processing performed by a first arithmetic unit in an arithmetic circuit of an update storage processing circuit of the printer. The flowchart which shows the processing flow of the update process implemented by the 2nd calculating part in the calculating circuit.

  Hereinafter, an embodiment of an electrophotographic printer will be described as an image forming apparatus to which the present invention is applied. FIG. 1 is a schematic configuration diagram illustrating a main part of a printer according to an embodiment.

  In addition to the configuration shown in FIG. 1, the printer has a print controller (denoted by reference numeral 410 in FIG. 5 to be described later) that processes image data sent from a PC (personal computer) and converts it into exposure data, and a high pressure. A high pressure generating device (indicated by reference numeral 416 in FIG. 5 described later) to be generated, a control unit (indicated by reference numeral 406 in FIG. 5 described later) for controlling an image forming operation, and recording paper P as a recording member are supplied. A paper feeding device (not shown), a manual feed tray (not shown) for manually feeding the recording paper P, a paper discharge tray (not shown) for discharging the recording paper P on which an image has been formed, and the like are provided.

  In FIG. 1, what is indicated by reference numeral 200 is a transfer unit as transfer means. The transfer unit 200 includes a driving roller 201, a cleaning backup roller 202, a primary transfer nip entrance roller 203, four primary transfer rollers 204Y, C, M, and K, a secondary transfer nip entrance roller 205, an intermediate transfer belt 206, A belt cleaning device 207, a secondary transfer roller 208, a cleaning roller 209, and the like are included. Then, the endless intermediate transfer belt 206 as a belt member is moved endlessly in the counterclockwise direction in the figure by the rotational driving of the driving roller 201 while being stretched by a plurality of rollers disposed inside the belt loop. The subscripts Y, C, M, and K attached to the end of the reference numerals indicating the four primary transfer rollers indicate members for yellow, cyan, magenta, and black. The same applies to the subscripts Y, C, M, and K attached to the other symbols.

  The intermediate transfer belt 206 has a three-layer structure in which an elastic layer and a surface layer are sequentially laminated on the front surface of the belt base layer having the largest thickness. The belt base layer is made of, for example, a material obtained by combining a fluorine resin having a small elongation or a rubber material having a large elongation with a material that is difficult to stretch, such as canvas. The elastic layer is made of, for example, fluorine-based rubber or acrylonitrile-butadiene copolymer rubber, and is laminated on the front surface of the belt base layer. Further, the surface layer is formed by coating, for example, a fluorine resin on the front surface of the elastic layer.

  Below the transfer unit 200, four image forming units for Y, C, M, and K as image forming means are arranged along the lower stretched surface of the intermediate transfer belt 206. These image forming units include drum-shaped photoreceptors 101Y, 101C, M, and K, developing devices 103Y, 103C, M, and K, drum cleaning devices 120Y, 120C, 120M, and 120K. The tops of the peripheral surfaces of the photoreceptors 101Y, 101C, 101M, and 101K are brought into contact with the lower stretched surface of the intermediate transfer belt 206 to form primary transfer nips for Y, C, M, and K. .

  Above the transfer unit 200, Y, C, M, and K toner bottles 90Y, C, M, and K, which respectively store Y, C, M, and K toners (not shown), are intermediate transfer belts 206. It is arrange | positioned so that it may line up along the upper tension surface. The Y, C, M, and K toners stored in the toner bottles 90Y, 90C, 90M, and 90K are respectively developed by developing devices 103Y, 103C, and M by driving toner supply devices for Y, C, M, and K (not shown). K is replenished. The toner bottles 90Y, 90C, 90M, and 90K can be individually attached to and detached from the main body of the image forming apparatus, and are replaced with new ones when the internal toner runs out.

  An optical writing unit 290 is provided below the four image forming units arranged along the belt lower tension surface. This optical writing unit 290 emits Y, C, M, and K writing light Lb by driving a semiconductor laser (not shown) provided in the optical writing unit 290 based on the image information. . Then, the writing light Lb optically scans the photosensitive members 101Y, 101C, 101M, and 101K serving as latent image carriers, and rotates around the photosensitive members 101Y, 101C, 101M, and 101K rotated in the counterclockwise direction in the drawing. Write an electrostatic latent image on the surface. The emission of the writing light Lb is not limited to the laser, but may be, for example, an LED (light emitting diode).

  Next, the configuration of the image forming unit will be described by taking the image forming unit for K as an example. The image forming units for other colors (Y, C, M) have the same configuration except that the color of the toner to be used is different, and the description thereof will be omitted.

  FIG. 2 is an enlarged configuration diagram showing an image forming unit for K. At the end of the reference numerals indicating the various members and devices constituting the image forming unit for K, a suffix “K” should be added. However, in FIG. In the image forming unit for K, a charging device 102 for uniformly charging the photosensitive member 101, a developing device 103, a drum cleaning device 120, and the like are disposed around the drum-shaped photosensitive member 101.

  The charging device 102 is of a contact charging type in which a charging roller to which a charging bias is applied by a power source (not shown) is brought into contact with the photoconductor 101, and a discharge is generated between the charging roller and the photoconductor 101 to cause the photoconductor. The peripheral surface of 101 is uniformly charged. Instead of the contact charging method using a charging roller, a contact discharge method using a charging brush or a non-contact charging method using a scorotron charger may be used.

  The developing device 103 includes a stirring unit 104 that stirs a two-component developer containing a magnetic carrier (not shown) and a non-magnetic toner, and a developing unit 105 that houses a developing sleeve described later. . In the stirring unit 104, a two-component developer (hereinafter simply referred to as “developer”) is conveyed while being stirred. More specifically, in the stirring unit 104, a first screw member 106 and a second screw member 107 are arranged in parallel, and a partition plate is provided between the two screws. Although the space which accommodates both screws is divided individually by this partition plate, openings are formed at both ends of the partition plate in the screw axial direction. As a result, both spaces communicate with each other at both ends in the screw axis direction. Hereinafter, the space in which the first screw member 106 is accommodated is referred to as a first stirring chamber, and the space in which the second screw member 107 is accommodated is referred to as a second stirring chamber.

  The second screw member 107 is located below the developing unit 105, and the upper end side of its peripheral surface faces the lower end side of the developing sleeve 109 accommodated in the developing unit 105. Then, while being driven to rotate by a driving means (not shown), the developer in the second agitating chamber is supplied to the developing sleeve 109, which will be described later, in the course of transporting the developer from the back side to the front side in the direction orthogonal to the drawing sheet, The used developer is received from 109. The developer conveyed to the front side end in the drawing by the second screw member 107 enters the first stirring chamber through the opening of the partition plate.

  The first screw member 106 conveys the developer in the first stirring chamber from the near side to the far side in the direction orthogonal to the drawing surface while being driven to rotate by a driving means (not shown). A toner concentration sensor (hereinafter referred to as a T sensor) 108 is fixed to the bottom wall of the first stirring chamber, and detects the toner concentration of the developer conveyed by the first screw member 106. This detection result is sent to a control unit (not shown) as a toner density signal. Based on the toner density signal, the control unit appropriately drives a toner supply device for K (not shown) to supply an appropriate amount of toner into the first agitation chamber. As a result, the toner density of the developer whose toner density has been reduced accompanying development at the developing unit 105 is recovered. The developer conveyed to the far side end in the drawing by the first screw member 106 enters the second stirring chamber through the other opening provided in the partition plate. In this way, the developer in the developing device 103 is circulated and conveyed through a path of the first stirring chamber → the second stirring chamber → the developing unit → the second stirring chamber → the first stirring chamber. Then, the toner concentration is adjusted in the first stirring chamber.

  The developing unit 105 is provided with a cylindrical developing sleeve 109 that is rotationally driven by a driving unit (not shown). The developing sleeve 109 is provided on the peripheral surface of the developing unit 103 through an opening provided in the casing of the developing device 103. The part is exposed outside the casing. Then, the exposed portion is opposed to the photoconductor 101 through a predetermined gap. Further, the developing sleeve 109 includes a magnet roller (not shown) in the hollow. The magnet roller is fixed so that it cannot rotate with the developing sleeve 109 so as not to rotate.

  The developer conveyed by the second screw member 107 in the second stirring chamber described above is attracted to the surface of the developing sleeve 109 by the magnetic force generated by the magnet roller, and is pumped up to the sleeve surface. Then, as the sleeve rotates, the layer thickness on the sleeve is regulated when passing through the gap between the sleeve and the regulating blade 110, and then conveyed to the developing region facing the photoreceptor 110.

  A developing electrode (not shown) is disposed inside the developing sleeve 109 made of a nonmagnetic material, and a developing bias is applied thereto. In the developing area, a developing electric field is formed between the electrostatic latent image on the photoconductor 101 and the developing sleeve 109. The developer transported to the developing area is raised by a magnetic force generated by a developing magnetic pole (not shown) of the magnet roller to form a magnetic brush, and the tip of the brush is rubbed against the photoreceptor 101. Then, the toner in the magnetic brush is separated from the magnetic carrier by the action of the above-described developing electric field and transferred to the electrostatic latent image on the photosensitive member 101. By this transfer, the electrostatic latent image on the photoconductor 101 is developed into a toner image as a visible image.

  When the developer that has passed through the developing region with the rotation of the developing sleeve 109 comes to a position facing the second stirring chamber, the sleeve is caused by the action of a repulsive magnetic field formed by two homopolar magnetic poles (not shown) of the magnet roller. Detach from the surface and fall into the second stirring chamber.

  As a result, the toner in the developer is transferred to the electrostatic latent image portion on the photosensitive member 101, and the electrostatic latent image on the photosensitive member 101 is visualized to form a toner image. The developer that has passed through the development region is transported to a portion where the magnetic force of the magnet is weak, and is separated from the development sleeve 109 and returned to the agitation unit 104.

  Although the developing device 103 adopting the two-component developing method using the two-component developer has been described, a one-component developing method developing device using the one-component developer (toner) not including the magnetic carrier may be adopted. .

  The toner image formed on the peripheral surface of the photoconductor 101 enters the primary transfer nip due to the contact between the photoconductor 101 and the intermediate transfer belt 206 as the photoconductor 101 rotates in the clockwise direction in the drawing. Then, primary transfer is performed on the front surface of the intermediate transfer belt 206. The surface of the photoconductor 101 that has passed through the primary transfer nip enters a position facing the drum cleaning device 120.

  The drum cleaning device 120 has a cleaning blade 121 made of polyurethane rubber or the like, for example, and presses the tip of the cleaning blade 121 against the photoreceptor 101. A small amount of untransferred toner that has not been transferred to the intermediate transfer belt 206 adheres to the surface of the photoreceptor 101 that has passed through the primary transfer nip. This transfer residual toner is scraped off from the surface of the photoreceptor 101 by the cleaning blade 121 and collected in the drum cleaning device 120.

  The drum cleaning device 120 includes a conductive fur brush 122 that rotates while contacting the surface of the photoconductor 101 just before entering the contact position with the cleaning blade 121, and the transfer residual toner is also removed by the fur brush 122. Remove.

  The toner removed from the photosensitive member 101 by the cleaning blade 121 and the fur brush 122 is accommodated inside the drum cleaning device 120 and discharged outside the device by the discharge screw 123. The discharged toner is collected in a waste toner bottle (not shown).

  In FIG. 1 described above, the surface of the photoreceptor 101K is uniformly charged to, for example, −700 [V] by the charging device (102 in FIG. 2), and the electrostatic latent image irradiated with the laser beam by the optical writing unit 290 is used. The potential of the image portion is, for example, −120 [V]. On the other hand, the developing bias voltage applied to the developing sleeve (109 in FIG. 2) is, for example, −470 [V], which generates a developing potential of 350 [V]. Such image forming conditions are appropriately changed according to the result of the potential control.

  The primary transfer rollers 204Y, C, M, and K of the transfer unit 200 are in contact with the back side of the primary transfer nip for Y, C, M, and K of the intermediate transfer belt 206. In this way, a primary transfer bias is applied to the primary transfer roller 204Y in contact with the back surface of the belt by a power source (not shown). Thus, the primary transfer electric field for electrostatically moving the toner images on the photoconductors 101Y, 101C, 101M, and 101K from the surface of the photoconductor toward the belt side in the primary transfer nips for Y, C, M, and K. Is formed. In this printer, the primary transfer rollers 204Y, 204C, 204M, and 204K are used as means for forming the primary transfer electric field. However, a conductive brush shape or a non-contact corona charger may be used. Good.

  The intermediate transfer belt 206 sequentially passes through the primary transfer nips for Y, C, M, and K along with the endless movement thereof. Then, Y, C, M, and K toner images are sequentially superimposed on the front surface and primarily transferred. As a result, a superimposed toner image is formed on the front surface of the intermediate transfer belt 206 after passing through the primary transfer nip for K by superimposing the Y, C, M, and K toner images.

  The secondary transfer roller 208 disposed outside the loop of the intermediate transfer belt 206 is in contact with the front surface of the belt so as to sandwich the belt with the driving roller 201 disposed inside the loop. A secondary transfer nip is formed. The drive roller 201 is grounded around the secondary transfer nip, whereas a secondary transfer bias having a polarity opposite to that of the toner is applied to the secondary transfer roller 208. As a result, a secondary transfer electric field is formed in the secondary transfer nip to electrostatically move the toner from the belt front surface side to the secondary transfer roller 208 side as the second transfer means.

  The printer includes a paper feed cassette (not shown), in which a plurality of recording papers are stored in a bundle of paper stacked in the thickness direction. The paper feed cassette sends out the uppermost recording paper in the paper bundle toward the paper feed path at a predetermined timing. The fed recording paper P is sandwiched between the rollers of the registration roller pair 250 disposed near the end of the paper feed path. The registration roller pair 250 sandwiches the leading end portion of the recording paper P between both rollers while rotating its own two rollers, but immediately after that, the rotation driving of both rollers is stopped. Then, at the timing when the recording paper P can be superimposed on the superimposed toner image on the intermediate transfer belt 206 at the secondary transfer nip, the rotational driving of both rollers is resumed. For the recording paper P sandwiched between the secondary transfer nips, the superimposed toner image on the intermediate transfer belt 206 is batch-transferred collectively by the action of the above-described secondary transfer electric field, and combined with the white color of the recording paper P, is full color. It becomes an image. In the transfer unit 200, a transfer charger may be used in place of the secondary transfer roller 208 as means for forming a secondary transfer electric field.

  A fixing device 260 is disposed above the secondary transfer nip. The fixing device 260 forms a fixing nip by bringing a fixing roller 261 containing a heat source such as a halogen lamp and a pressure roller 262 into contact with each other. Then, both rollers are rotationally driven so as to move the surfaces in the same direction at the fixing nip. The recording paper P that has passed through the secondary transfer nip enters the fixing device 260 and is then sandwiched by the fixing nip. Then, the full color image is fixed by nip pressure or heating.

  Of the entire area in the circumferential direction of the intermediate transfer belt 206, the edge of the cleaning blade 210 that is cantilevered by the belt cleaning device 207 is in contact with the portion around the cleaning backup roller 202. Transfer residual toner and a gradation pattern image, which will be described later, attached to the surface of the intermediate transfer belt 206 after passing through the secondary transfer nip are removed from the belt surface by the cleaning blade 210.

  When printing using the printer, first, image information is transmitted to the printer by a printer driver of a PC (personal computer) (not shown). The printer sends the image information to the control unit and the image processing unit.

  Upon receiving the image information, the control unit drives various drive motors (not shown) to move the intermediate transfer belt 206 endlessly. At the same time, the photoreceptors 101Y, 101C, 101M, and 101K of each image forming unit are also driven to rotate. Further, the image processing unit sends an optical writing signal generated based on the image information to the optical writing unit 290. The optical writing unit generates Y, C, M, and K writing light Lb based on the optical writing signal, and optically scans the photoreceptors 101Y, 101C, 101M, and 101K. As a result, electrostatic latent images for Y, C, M, and K are formed on the respective photoreceptors 101Y, 101C, 101M, and 101K, and are visualized by the developing devices 103Y, 103C, M, and K. In this way, Y, C, M, and K toner images are formed on the photoreceptors 101Y, 101C, 101M, and 101K. These Y, C, M, and K toner images are primarily transferred to the intermediate transfer belt 206 at the Y, C, M, and K primary transfer nips to form a superimposed toner image.

  On the other hand, in a paper feed cassette (not shown), the recording paper P is sent out by the rotational drive of the paper feed roller. The fed recording paper P is separated into one sheet by a separation roller (not shown) and enters the paper feed path, and is then sandwiched between the registration roller pair 250. When recording paper P not set in a paper feed cassette (not shown) is used, the recording paper P set in a manual feed tray (not shown) is sent out by a paper feed roller (not shown) and separated into one sheet by a separation roller (not shown). Thereafter, the sheet is fed into the registration roller pair 250.

  The registration roller pair 250 feeds the recording paper P toward the secondary transfer nip at a timing at which it can be superimposed on the superimposed toner image formed on the intermediate transfer belt 206. Note that the registration roller pair 250 is generally used while being grounded, but a bias may be applied to remove paper dust from the recording paper P.

  The superposed toner image on the intermediate transfer belt 206 is secondarily transferred collectively onto the recording paper P fed out by the registration roller pair 250 and sandwiched between the secondary transfer nips. Thereafter, the recording paper P passes through the fixing device 260 and is then discharged out of the apparatus. When an image is also formed on the other side of the recording paper P on which the toner image is fixed on one side by the fixing device 260, the recording paper P that has passed through the fixing device 260 is first used by a switchback device (not shown). The image is retransmitted to the registration roller pair 250 while being reversed.

  FIG. 3 is a perspective view showing a transfer unit as transfer means. Of the entire area of the intermediate transfer belt 206 in the circumferential direction, the first reflective optical sensor 130, the second reflective optical sensor 136, and the third reflective optical sensor 137 are respectively set at predetermined positions around the drive roller 201. Facing each other through a gap. The first reflective optical sensor 130 is disposed so as to face the central portion in the belt width direction at the hanging portion. Further, the second reflective optical sensor 136 is disposed so as to face one end portion in the belt width direction at the hanging portion. Further, the third reflective optical sensor 137 is disposed so as to face the other end portion in the belt width direction at the hanging portion.

  FIG. 4 is an enlarged configuration diagram showing the first reflective optical sensor 130. In the figure, the first reflection type optical sensor 130 includes an LED 131 as a light emitting element, a regular reflection type light receiving element 132, a diffuse reflection type light receiving element 133, a condensing lens 134, a casing 135, and the like. In addition, you may use a laser light emitting element etc. instead of LED as a light emitting element. In addition, as the regular reflection type light receiving element 111 and the diffuse reflection type light receiving element 112, phototransistors are used, but it is also possible to use a photodiode or an amplifier circuit.

  Infrared light emitted from the LED 110 passes through the condenser lens 113 and then reaches the test toner image formed on the intermediate transfer belt 206. A part of the infrared light is specularly reflected on the surface of the test toner image to become specularly reflected light, and then retransmits through the condenser lens 113 and is received by the specular reflection type light receiving element 111. The regular reflection type light receiving element 111 outputs a voltage corresponding to the amount of received light. This output value is converted into digital data by an A / D converter (not shown) and then input to a control unit described later. The other part of the infrared light is diffusely reflected on the surface of the test toner image to become diffusely reflected light, and then retransmits through the condenser lens 113 and is received by the diffuse reflection type light receiving element 112. . The diffuse reflection type light receiving element 112 outputs a voltage corresponding to the amount of received light. This output value is converted into digital data by an A / D converter (not shown) and then input to a control unit described later.

  The regular reflection type light receiving element 111 is disposed inside a dedicated cylindrical member (not shown) and is made independent of the LED 131 and the diffuse reflection type light receiving element 112. The opening of the cylindrical member has the above-described regular reflection light. The direction is to accept. Further, the diffuse reflection type light receiving element 112 is disposed inside a dedicated cylindrical member (not shown) and is made independent of the LED 131 and the regular reflection type light receiving element 111, and the opening of the cylindrical member is provided with the diffuse reflection light described above. The direction is to accept. By doing so, the light reception directivity of regular reflection light and diffuse reflection light is enhanced.

  Although the first reflective optical sensor 130 has been described, the second reflective optical sensor 136 and the third reflective optical sensor 137 have substantially the same configuration as the first reflective optical sensor 130. However, the second reflection type optical sensor 136 and the third reflection type optical sensor 137 are each provided with only a regular reflection type light receiving element among a regular reflection type light receiving element and a diffuse reflection type light receiving element. Different from the reflective optical sensor 130.

  FIG. 5 is a block diagram illustrating a part of an electric circuit in the printer according to the embodiment. In the figure, a control unit 500 that functions as an updating unit or an image forming condition adjusting unit includes a CPU (Central Processing Unit) 500a. Also, a ROM (Read Only Memory) 500b that stores a control program and various data, and a RAM (Random Access Memory) 500c that temporarily stores various data are included. The control unit 500 is connected to various peripheral devices via an I / O unit 510 that relays signal transmission / reception to / from various peripheral devices. In FIG. Only the main ones are shown. An input port 520 as an image information acquisition unit acquires image information sent from an external personal computer or the like. The optical writing control unit 505 controls driving of the optical writing unit 290 based on the image information acquired by the input port 520. The toner replenishing device 270 also develops Y, M, C, and K toners in Y, M, C, and K toner bottles (90Y, C, M, and K) into Y, M, C, and K developing devices. (103Y, C, M, K) are replenished individually. Further, the T sensor (108Y, C, M, K) for Y, C, M, K is a toner of developer in the developing device (103Y, C, M, K) for Y, C, M, K. The concentration is measured. The toner replenishment control circuit 506 controls the driving of the toner replenishing device 270 based on the detection result of the toner density by the Y, M, C, and K toner density sensors 108Y, M, C, and K. . The various power supply circuits 507 output the above-described primary transfer bias for each color, secondary transfer bias, a developing bias for applying to the developing sleeve of the developing device for each color, and the like. The first A / D converter 501 converts the output voltage value from the first reflective optical sensor 130 into digital data. The second A / D converter 502 converts an output voltage value from a second reflective optical sensor 136 described later into digital data. The third A / D converter 503 converts an output voltage value from a third reflective optical sensor 137 described later into digital data. The belt drive motor 505 is a motor that is a drive source of the drive roller (201) and the intermediate transfer belt (206). The operation display unit 506 includes a display for displaying an image, various keys for receiving input information from the operator, and the like. The input port 520 receives image information sent from an external personal computer or the like.

  The optical writing control circuit 505 controls driving of the optical writing unit 290 based on a control signal input from the control unit 500 via the I / O unit 510. The various power supply circuits 507 control bias output values from the various power supply circuits based on control signals input from the control unit 500 via the I / O unit 510.

  A driven encoder 507 connected to the I / O unit 510 is attached to the transfer unit 200 so as to detect the rotational angular velocity of the secondary transfer entrance roller 205 shown in FIG. The secondary transfer entrance roller 205 is a driven roller that rotates following the endless movement of the intermediate transfer belt 206, and its rotational angular velocity reflects the moving speed of the belt. That is, the driven encoder 507 functions as a speed detection unit that detects the moving speed of the intermediate transfer belt 206. The controller 500 can grasp the moving speed of the intermediate transfer belt 206 based on the output signal from the driven encoder 507.

  The control unit 500 is configured to perform the following image forming condition adjustment processing at a predetermined timing such as every elapse of a predetermined time or every predetermined number of sheets printed. That is, first, a gradation pattern image is formed on the intermediate transfer belt (206). As shown in FIG. 6, the gradation pattern image includes a Y gradation pattern portion Py, a C gradation pattern portion Pc, an M gradation pattern portion Pm, and a K gradation pattern portion Pk. The Y gradation pattern portion Py includes five patch-like Y test toner images having different toner adhesion amounts per unit area. Similarly, the gradation pattern portions (Pc, Pm, Pk) of the other colors each include five patch-like test toner images having different toner adhesion amounts. As shown in the figure, the gradation pattern image having these gradation pattern portions is formed at the central portion of the intermediate transfer belt 206 in the belt width direction, and the test toner images are arranged at predetermined intervals in the belt circumferential direction. These test toner images sequentially pass through a region facing the first reflective optical sensor 130 as the intermediate transfer belt 206 moves endlessly.

Taking the Y gradation pattern portion Py of the gradation pattern portions of each color as an example, this is composed of five Y test toner images in which the toner adhesion amount gradually increases step by step. The Y toner adhesion amount (image density) per unit area with respect to these Y test toner images is detected by the first reflective optical sensor 130. These detection results are stored in the RAM 500b of the control unit 500 as a post-transfer voltage VpY _i for Y (i = 1 to 5). The post-transfer voltage VpY _i represents the post-transfer reflection amount on the intermediate transfer belt 206, and the post-transfer reflection amount correlates with the toner adhesion amount to the test toner image. That is, the post-transfer voltages VpY ₁ , VpY ₂ , VpY ₃ , VpY ₄ , and VpY ₅ for Y indicate the amount of Y toner attached to the _first , _second , _third , _fourth , and _fifth Y test toner images. Based on the post-transfer voltage VpY _{i and the} like, the control unit 500 calculates the Y toner adhesion amount for each Y test toner image. Then, based on the calculation result, the image forming conditions for Y are adjusted so that the target Y toner adhesion amount can be realized. Examples of the method for adjusting the image forming conditions include a method for adjusting the uniform charging potential of the photosensitive member and the developing bias as described in JP-A-9-211191. Further, the toner concentration of the developer may be adjusted. Although only the Y toner adhesion amount has been described, the toner adhesion amounts of other colors are calculated in the same manner, and the image forming conditions for other colors are adjusted based on the calculation results to stabilize the image density of each color. Is planned.

  When the image density of each color is stabilized in this way, the controller 500 then applies a resist skew detection patch pattern as shown in FIG. 7 to both ends of the intermediate transfer belt 206 in the width direction. Form. Each of these patch patterns has eight test toner images arranged at predetermined intervals in the sub-scanning direction. They are the first Y test toner image, the first C test toner image, the first M test toner image, the first K test toner image, the second Y test toner image, the second C test toner image, and the second M test toner. An image and a second K toner image are formed in this order. The first Y test toner image formed at one end in the belt width direction and the first Y test toner image formed at the other end in the belt width direction are formed on the condition that they are aligned with each other in the belt width direction. Is done. The same applies to the other seven test toner images.

  Each test toner image in the patch pattern formed at one end in the belt width direction is detected by the second reflective optical sensor 136. Each test toner image in the patch pattern formed at the other end portion in the belt width direction is detected by the third reflective optical sensor 137. If the test toner images are arranged in a straight line along the belt width direction at the one end and the other end, they are detected by the reflective optical sensor at the same timing. However, if they are formed slightly shifted in the belt circumferential direction, the detection timing of these test toner images is shifted. The control unit 500 detects the inclination of the image based on this deviation.

  In addition, if the first Y test toner image, the first C test toner image, the first M test toner image, and the first K test toner image are formed without positional deviation in the same patch pattern, these four patterns are used. The test toner image is detected by the reflective optical sensor at equal time intervals. The same applies to the second Y test toner image, the second C test toner image, the second M test toner image, and the second K test toner image. However, if the position of the test toner image is relatively shifted between the colors, the detection time interval is not equal. Based on the time interval, the control unit 500 grasps the amount of positional deviation of the toner image between the colors.

  When the image tilt and the amount of positional deviation are grasped in this way, the control unit 500 adjusts the optical writing start timing to each color photoconductor by the optical writing unit 209 as the image forming condition, or tilts the optical mirror. To suppress the positional deviation of each color toner image and the skew of the image.

  Although the gradation pattern portions Py, Pc, Pm, and Pk of the respective colors in the gradation pattern image shown in FIG. 6 are provided with five test toner images having different toner adhesion amounts, A gradation pattern portion having six or more test toner images having different toner adhesion amounts may be formed.

A post-transfer reflected light amount (post-transfer voltage Vp _i ) obtained by reflection on each test toner image in the gradation pattern portion of each color is detected by the first reflective optical sensor 130 and is applied to each test toner image. In order to obtain the toner adhesion amount, it is necessary to measure the first pre-transfer regular reflection output voltage Vsg1_reg and the first pre-transfer diffuse reflection output voltage Vsg1_dif in advance. The first pre-transfer regular reflection output voltage Vsg1_reg is a regular reflection light reception of the first reflection optical sensor 130 that detects the amount of regular reflection light in the belt region where the test toner image is transferred before the toner image is transferred. This is the output voltage value from the element (111). The first pre-transfer diffuse reflection output voltage Vsg1_dif is an output voltage value from the diffuse reflection type light receiving element (112) of the first reflection type optical sensor 130 that detects the amount of diffuse reflection light in the same state. The first pre-transfer regular reflection output voltage Vsg1_reg is used when obtaining the K toner adhesion amount in the K test toner image. The first pre-transfer diffuse reflection output voltage Vsg1_dif is used when obtaining the Y, M, and C toner adhesion amounts in the Y, M, and C test toner images.

  FIG. 8 is a graph showing the relationship between the position in the circumferential direction of the intermediate transfer belt 206 and the first pre-transfer regular reflection output voltage Vsg_reg. The reflected light amount of the background portion of the intermediate transfer belt 206 is theoretically constant regardless of the position in the belt circumferential direction. However, in practice, the value of the first pre-transfer regular reflection output voltage Vsg_reg varies greatly depending on the position in the belt circumferential direction. This is because the intermediate transfer belt 206 has local dirt and scratches. For this reason, the post-transfer voltage VpKi for the above-described K gradation pattern portion Pk is affected by the fluctuation of the first pre-transfer regular reflection output voltage Vsg_reg. For example, when the post-transfer voltage VpKi is measured by forming a plurality of K gradation pattern portions Pk composed of five K test toner images in the belt movement direction, a graph as shown in FIG. 9 is obtained. Since the portion surrounded by the red circle in FIG. 8 is affected by the fluctuation of the portion surrounded by the red circle in FIG. 8, the value does not accurately reflect the K toner adhesion amount. Therefore, the toner adhesion amount is grasped based on, for example, the difference between the post-transfer voltage VpKi and the first pre-transfer regular reflection output voltage Vsg_reg. By doing so, for example, as shown in FIG. 10, it is possible to grasp an accurate K toner adhesion amount that is not affected by fluctuations in the first pre-transfer regular reflection output voltage Vsg_reg. Note that the K toner adhesion amount may be grasped by the ratio between the post-transfer voltage VpKi and the first pre-transfer regular reflection output voltage Vsg_reg instead of the difference. In addition, the K toner adhesion amount has been described. Similarly, the Y, M, and C toner adhesion amounts are similarly set to the difference or ratio between the post-transfer voltages VpYi, VpMi, and VpCi and the first pre-transfer diffuse reflection output voltage Vsg_reg. It is necessary to grasp based on.

  In addition, regarding the second reflective optical sensor 136 and the third reflective optical sensor 137, there is a possibility that the test toner image cannot be detected due to an increase in the amount of regular reflection light on the background due to dirt or scratches on the belt background. is there. Specifically, for example, FIG. 11 is a graph showing the relationship between the output voltage from the second reflective optical sensor 136 that detects the patch pattern on the belt and the position in the circumferential direction of the belt. In this graph, the portions surrounded by circles are the portions corresponding to the detection timing of the test toner image, respectively. For this reason, in the portion surrounded by a red circle, as shown in FIG. 11, if the output voltage has to be greatly reduced as shown in FIG. Thus, since it does not decrease sufficiently, there is a possibility that it will not be detected as a test toner image. Therefore, the detection of the test toner image needs to be grasped based on the difference between the output voltage during test pattern detection and the first pre-transfer regular reflection output voltage Vsg_reg. Note that the value of the pre-transfer regular reflection output voltage output from the regular reflection light-receiving element of the second reflective optical sensor 136 is stored as a second pre-transfer regular reflection output voltage Vsg2_reg. The value of the pre-transfer regular reflection output voltage output from the regular reflection light-receiving element of the third reflective optical sensor 137 is stored as the third pre-transfer regular reflection output voltage Vsg3_reg.

  In the conventional image forming apparatus, prior to forming the gradation pattern image or patch pattern on the intermediate transfer belt 206, the intermediate transfer belt 206 is rotated once to make a regular reflection output voltage Vsg_reg before transfer and the transfer. The pre-diffuse reflection output voltage Vsg_dif is sampled and updated to be used for calculating the toner adhesion amount or for detecting the test toner image. Then, by making the intermediate transfer belt 206 make one turn in this way, the waiting time of the user is lengthened.

Next, a characteristic configuration of the printer according to the embodiment will be described.
In FIG. 1 described above, as the intermediate transfer belt 206, a belt provided with a home position mark (mark) at a specific position in the circumferential direction on the back surface thereof is used. Inside the loop of the intermediate transfer belt 206, a mark detection sensor 138 made of a reflective photosensor is disposed so as to face the back surface of the belt with a predetermined gap. The home position mark attached to the back surface of the intermediate transfer belt 206 is detected by the mark detection sensor 138 when passing the position facing the mark detection sensor 138 as the intermediate transfer belt 206 moves endlessly. The belt endless movement position at which the sensor detects the home position mark in this way is the home position of the intermediate transfer belt 206. The mark detection signal output from the mark detection sensor 138 is input to the optical writing control circuit 505 and the update storage processing circuit 519 as shown in FIG. The update storage processing circuit 519 has an arithmetic circuit 519a and a flash memory 519b as information storage means.

  The arithmetic circuit 519a of the update storage processing circuit 519 receives the mark detection signal sent from the mark detection sensor 138 when the intermediate transfer belt 206 is in the home position, the belt moving speed, and the reception timing. Based on the elapsed time from, it is possible to sequentially grasp which region in the circumferential direction of the intermediate transfer belt 206 is approaching the position facing the reflective optical sensor. Further, for each of the first reflective optical sensor 130, the second reflective optical sensor 136, and the third reflective optical sensor 137, the pre-transfer regular reflection output voltage Vsg_reg stored in the flash memory 519b, the pre-transfer diffuse reflection, and so on. Update processing for updating the data of the output voltage Vsg_dif to a newly sampled value is performed during a normal print job. A normal print job is based on image information sent from an external personal computer or the like, starts driving each device such as the intermediate transfer belt 206 and each photoconductor, and then finishes printing an image. This is the operation until the driving of each device is stopped.

  The optical writing control circuit 505 and the update storage processing circuit 519 distinguish and recognize a plurality of sections obtained by dividing the intermediate transfer belt 206 at intervals of 100 [μm] in the circumferential direction. Specifically, when the intermediate transfer belt 206 is in the home position, a belt region having a length of 100 [μm] facing the three reflective photosensors is recognized as the final section. Further, a 100 [μm] section adjacent to the final section on the downstream side in the belt moving direction is recognized as the 0001 section. Thereafter, the 0002th section, the 0003th section,... Are sequentially recognized at a pitch of 100 [μm] toward the downstream side. The pre-transfer regular reflection output voltage Vsg_reg and the pre-transfer diffuse reflection output voltage Vsg_dif are measured separately for each section. Specifically, the arithmetic circuit 519a of the update storage processing circuit 519 includes a temporary storage circuit that temporarily stores data. During the image forming operation, various pre-transfer regular reflection output voltages and pre-transfer diffuse reflection output voltages are sampled at intervals of 0.1 [msec] and temporarily stored in the temporary storage circuit. The reason for temporary storage is that there is a possibility that the region to be sampled is not a background portion without toner adhesion but an image portion with toner adhesion. In this case, the sampling result cannot be used as the pre-transfer regular reflection output voltage or the pre-transfer diffuse reflection output voltage, so it will be removed from the update facing later, but for the time being the background part or the image part? Regardless, the sampling result is temporarily stored in the temporary storage circuit in association with the partition name.

Taking the first pre-transfer regular reflection output voltage Vsg1_reg as an example, 0.1, 0.2, 0.3, 0 from the timing at which the mark detection signal is sent from the mark detection sensor 138 (hereinafter referred to as HP timing). Each sampling result obtained after 4 [msec] corresponds to the 0001th section. there,
・ Vsg1_reg0001-1
・ Vsg1_reg0001-2
・ Vsg1_reg0001-3
・ Vsg1_reg0001-4
Are stored in the temporary storage circuit sequentially, and then the four values are deleted from the temporary storage circuit, and the average value of the four values is
・ Vsg1_reg0001
As a temporary memory.
The sampling results obtained after 0.5, 0.6, 0.7, and 0.8 [msec] from the HP timing correspond to the 0002th section, respectively. there,
・ Vsg1_reg0002-1
・ Vsg1_reg0002-2
・ Vsg1_reg0002-3
・ Vsg1_reg0002-4
Are stored in the temporary storage circuit sequentially, and then the four values are deleted from the temporary storage circuit, and the average value of the four values is
・ Vsg1_reg0002
As a temporary memory.
Similarly, the sampling result of the first pre-transfer regular reflection output voltage Vsg1_reg from the 0003th section to the final section is temporarily stored.

  Although the temporary storage of the sampling result of the first pre-transfer regular reflection output voltage Vsg1_reg has been described, the first pre-transfer diffuse reflection output voltage Vsg1_dif, the second pre-transfer regular reflection output voltage Vsg2_reg, and the third pre-transfer regular reflection output voltage Vsg3_reg. Similarly, while sampling at intervals of 0.1 [msec], the average value of the four sampling values is temporarily stored in association with the partition name.

  In the printer according to the embodiment, the standard print mode in which the process linear velocity of the photosensitive member or the intermediate transfer belt 206 is set to 250 [mm / sec] and the high process linear velocity is set to 150 [mm / sec]. The image quality print mode is switched according to a user command. The temporary storage of the sampling results described so far is executed in the standard print mode.

  In the case of the high quality print mode, the following temporary storage is performed. That is, for example, after 0.6 [msec] from the HP timing, the belt advances 90 [μm] from the home position. Therefore, the six sampling results obtained after 1, 0.2, 0.3, 0.4, 0.5, and 0.6 [msec] from the HP timing all correspond to the 0001th section. Yes. Thereafter, the seven sampling results obtained at intervals of 0.1 [msec] in the period from 0.7 [msec] to 1.3 [msec] later all correspond to the 0002th section. Six sampling results correspond to the 0001th section, whereas seven sampling results correspond to the 0002th section. Six sampling results correspond to odd-numbered sections such as the 0001th section, while seven sampling results correspond to even-numbered sections such as the 0002th section. Therefore, the update storage processing circuit 519 temporarily stores the averaged result of the six sampling results for the odd-numbered sections. For even-numbered sections, a result obtained by averaging seven sampling results is temporarily stored.

  The optical writing control circuit 505 can specify which section of the intermediate transfer belt 206 is to be transferred based on the elapsed time from the HP timing with respect to the dot being optically written. Furthermore, it is also possible to specify whether or not the image is transferred to the first test region, the second test region, or the third test region in the section based on the writing position in the main scanning direction. is there. More specifically, for example, even in the 0001th section of the intermediate transfer belt 206, there are a region to be measured for the amount of reflected light and a region not to be measured due to a difference in position in the belt width direction. Of the 0001 section, only the region facing the first reflective optical sensor 130 is the measurement target of the first pre-transfer regular reflection light amount Vsg1_reg and the first pre-transfer diffuse reflection light amount Vsg_dif. Thus, in the belt width direction, the region that is the target of measurement of the amount of light reflected by the first reflective optical sensor 130 is the first test region. Further, the region to be measured for the amount of light reflected by the second reflective optical sensor 136 is the second region to be examined. In addition, the region to be measured for the amount of light reflected by the third reflective optical sensor-137 is the third region to be examined.

  When the optical writing control circuit 505 starts optical writing for each of the colors Y, M, C, and K, the first line at the start is transferred to which section of the intermediate transfer belt 206. Is determined based on the elapsed time from the HP timing. Then, for each of the first test area, the second test area, and the third test area in the section, the dot storage information in which the dot flag information, the section number, and the test area number are combined is updated and stored. 519. For example, it is assumed that the first line when optical writing is started is transferred to the 0001th section of the intermediate transfer belt 206. Then, the optical writing control unit 505 determines whether or not there is a dot optically written in any one of Y, M, C, and K for the 0001 section first test region. If there is an optically written dot, the intra-compartment dot information “0001-1-ON” is transmitted to the update storage processing circuit 519. The first four-digit numerical value in the intra-compartment dot information indicates the division number of the intermediate transfer belt 206. Since this is intra-compartment dot information related to the 0001th section, it is a four-digit number “0001”. Further, a single-digit numerical value sandwiched between two hyphens indicates the number of the test area. Since this is intra-compartment dot information related to the first test region, it is a single digit number “1”. The alphabet at the end indicates dot flag information. If there is an optically written dot, the alphabet is “ON”. On the other hand, when there is no optically written dot, the alphabet is “OFF”. Note that the copying machine according to the embodiment forms an image with a resolution of 600 [dpi], so the diameter of one dot is 42.3 [μm]. Therefore, about 2.4 dots can be arranged in one section of the intermediate transfer belt 206 in the belt moving direction. Therefore, the optical writing control circuit 505 performs optical writing on each test region in each section based on not only the optical writing result for one line but also the optical writing results for three consecutive lines. It is determined whether or not there is a dot. If there is a dot that extends over two consecutive sections, it is determined that there is an optically written dot. Such processing is repeated until the optical writing processing is completed.

  After a while after the update storage processing circuit 519 starts temporary storage of the pre-transfer regular reflection output voltage Vsg_reg and the pre-transfer diffuse reflection output Vsg_dif, the optical writing control circuit 505 starts optical writing, and the dot information in the section is displayed. The data is transmitted to the update storage processing circuit 519. When the update storage processing circuit 519 receives the intra-compartment dot information, the update storage processing circuit 519 specifies the temporary storage data corresponding to it. For example, it is assumed that the content of the intra-compartment dot information is “0013-1-ON”. Then, since this intra-compartment dot information indicates that there is a dot optically written for the 0013th section first test area of the intermediate transfer belt 206, the 0013th section first test area is not a background portion. It will be. Therefore, the update storage processing circuit 519 deletes the data of Vsg1_reg0013 corresponding to the 0013th section from the temporary storage circuit among the plurality of first pre-transfer regular reflection output voltages Vsg1_reg temporarily stored. Further, the data of Vsg1_dif0013 corresponding to the 0013th section among the plurality of first pre-transfer diffuse reflection output voltages Vsg1_dif temporarily stored is deleted from the temporary storage circuit.

  On the other hand, for example, it is assumed that the content of the intra-compartment dot information is “0013-1-OFF”. Then, since this intra-compartment dot information indicates that there is no dot optically written in the 0013th section first test area of the intermediate transfer belt 206, the 0013th section first test area is a background portion. It will be. Therefore, the update storage processing circuit 519 deletes the data of Vsg1_reg0013 corresponding to the 0013th section from the temporary storage circuit among the plurality of first pre-transfer regular reflection output voltages Vsg1_reg temporarily stored. At the same time, the value of Vsg1_reg0013 stored in the flash memory 519b is updated to the temporarily stored value. In other words, when the dot flag information in the intra-compartment dot information is “ON”, the corresponding temporary storage data is sampled from the belt region that is not the background portion, and the temporary storage data is deleted. On the other hand, when the dot flag information is “OFF”, the corresponding temporary storage data is sampled from the belt area which is the background portion. The value of is updated. The same process is performed for the second test region and the third test region.

  Note that after the image forming operation is started, all the sections upstream of the section corresponding to the intra-section dot information generated by the optical writing control circuit 290 are background portions. Therefore, the update storage processing circuit 519 updates temporary storage data for all sections upstream of the section of intra-compartment dot information sent first. For example, assume that the content of the intra-compartment dot information sent first is “0013-1-OFF”. In this case, the values in the flash memory 519b are all updated for the data sampled prior to the data in the 0013th section (data corresponding to the 000012, 00001, 00001,...).

  FIG. 13 is a flowchart showing a processing flow of temporary storage processing performed by the first arithmetic unit in the arithmetic circuit 519a of the update storage processing circuit 519. When the image forming operation is started, the first circuit stabilizes the speed of the intermediate transfer belt 206 at 250 [mm / sec] or 150 [mm / sec] based on the output signal from the driven encoder (507). (Step 1: Hereinafter, step is denoted as S). Then, after stabilization, the system waits for the arrival of the HP timing (S2), and when it arrives, the first pre-transfer regular reflection output voltage Vsg1_reg, the first pre-transfer diffuse reflection output voltage Vsg1_dif, and the second pre-transfer regular reflection. Temporary storage processing of the output voltage Vsg2_reg and the third pre-transfer regular reflection output voltage Vsg3_reg is started (S3). Thereafter, when a belt speed fluctuation exceeding a predetermined limit value is detected (Y in S4), temporary storage is stopped at that time (S5), and when the next HP timing comes (Y in S2), temporary storage processing is performed. Resume (S3). If the image forming operation is finished (Y in S6, Y in S7), the temporary storage process is finished (S8).

  FIG. 14 is a flowchart showing a processing flow of update processing performed by the second calculation unit in the calculation circuit 519a of the update storage processing circuit 519. When temporary storage processing is started by the first calculation unit (Y in S1), the second calculation unit waits for reception of intra-compartment dot information sent from the optical writing control circuit (S2). When the intra-compartment dot information is received, the data in the flash memory is updated to the same value as the temporary storage data only when the dot flag information in the intra-compartment dot information is “OFF” (Y in S3) (S4). ). Thereafter, temporary storage data corresponding to the intra-compartment dot information is deleted (S5). Such processing is repeated until there is no temporary storage data (S6).

  In the above configuration, the update storage processing circuit 519 updates the pre-transfer regular reflection output voltage and the pre-transfer diffuse reflection voltage for the section where dots are formed in the entire area of the intermediate transfer belt 206 in the circumferential direction. First, the pre-transfer regular reflection output voltage and the pre-transfer diffuse reflection voltage are updated only for the sections where dots are not formed. Since the dots are formed, even in a section where the update is not performed, in the process in which the intermediate transfer belt 206 circulates by an image forming operation, the section eventually becomes a section where dots are not formed. It is possible to update the regular reflection output voltage before transfer and the diffuse reflection output voltage before transfer. In this way, by updating the pre-transfer regular reflection output voltage and the pre-transfer diffuse reflection output voltage during the image forming operation, when the execution timing of the image forming condition adjustment processing arrives during the continuous image forming operation, After the continuous image forming operation is temporarily interrupted, it is possible to immediately start the image forming condition adjustment process without updating the output voltage over one belt revolution. Therefore, prior to starting the image forming condition adjustment process, it is possible to avoid an increase in the waiting time of the user by moving the intermediate transfer belt 206 over one revolution and updating the data in the flash memory. it can.

  In the state immediately after shipment from the factory, the flash memory 519b does not store the pre-transfer regular reflection output voltage or the pre-transfer diffuse reflection output voltage sampling values corresponding to each section at all. When the intermediate transfer belt 206 is replaced, all the data in the flash memory 519b does not correspond to the replaced belt. This printer uses this timing when the power is turned on for the first time after shipment from the factory, or when it is detected that the intermediate transfer belt 206 has been replaced. Thus, a new storage process for storing the data in the flash memory 519b while sampling all the data by rotating the belt once is performed.

Next, a printer according to an example in which a more characteristic configuration is added to the printer according to the embodiment will be described.
The second calculation unit of the calculation circuit 519a mounted in the update storage processing circuit 519 of the printer according to the embodiment sets the condition that the dot flag information is ON for the temporary storage data temporarily stored in the temporary storage circuit. In addition, only the data in the flash memory opposite to the one that has the condition that the pre-transfer diffuse reflection output voltage exceeds a predetermined threshold (the condition that the pre-transfer diffuse reflection light amount is below the predetermined threshold). Perform the update process. This is because, when the amount of diffuse reflection light before transfer is equal to or greater than a predetermined threshold, there is a high possibility that the cleaning process for the corresponding section is not properly performed for some reason and toner is attached to the section.

  Note that the diffuse reflection output voltage before transfer is output only from the first reflection type optical sensor among the three reflection type optical sensors, but the remaining two reflection type optical sensors are the first reflection type optical sensors. Whether or not to update the sampling value is determined with reference to the sampling result of the diffuse reflection output voltage before transfer by the sensor. For example, the second pre-transfer regular reflection output voltage Vsg2_reg0011 is the second pre-transfer regular reflection output voltage for the 0011 section, and this is the first pre-transfer diffuse reflection output voltage Vsg1_dif0011 sampled from the same section. Based on this, it is determined whether or not to update. When the first pre-transfer diffuse reflection output voltage Vsg1_dif0011 does not exceed a predetermined threshold value, the second pre-transfer regular reflection output voltage Vsg2_reg0011 is not updated regardless of the contents of the intra-compartment dot information. This is because, in the same section, when the first test region is dirty, there is a high possibility that the second test region and the third test region are also dirty.

  In such a configuration, the data in the flash memory is updated to a sampled value from the background area that has been soiled due to poor cleaning of the intermediate transfer belt 206, and the toner adhesion amount and the toner image position. Deterioration of detection accuracy can be avoided.

  As described above, in the printer according to the embodiment, as the first reflective optical sensor 130 which is one of the plurality of reflective optical sensors, at least the diffusion light amount among the regular reflection light amount and the diffuse reflection light amount on the surface of the intermediate transfer belt 206 is diffused. What detects the amount of reflected light is used. Then, for the section where the detection result of the first pre-transfer diffuse reflection light quantity exceeds a predetermined threshold, the update storage process is performed so as to perform the process of canceling the update of the first pre-transfer diffuse reflection output voltage Vsg1_dif in the flash memory A circuit 519 is configured. In this configuration, the amount of toner adhesion caused by updating the first pre-transfer diffuse reflection output voltage Vsg1_dif to a value sampled from the background area that has become dirty due to poor cleaning of the intermediate transfer belt 206. Deterioration of detection accuracy can be avoided.

  In the printer according to the embodiment, as the second reflective optical sensor 136 that is different from the first reflective optical sensor 130, only the regular reflected light amount of the regular reflected light amount and the diffuse reflected light amount on the belt surface is obtained. Use what you want to detect. Then, the second test region passing through the position facing the second reflective optical sensor 130 in a state where the toner image based on the image information has not been transferred is transferred to the entire area of the belt. In the same section as the first test region that passes through the position facing the first reflective optical sensor and makes the amount of reflected light before transfer larger than a predetermined threshold (belt width) The update storage processing circuit 519 is configured to perform the process of canceling the update of the second pre-transfer regular reflection output voltage Vsg_reg for the second test region. . In such a configuration, the test is performed by updating the second pre-transfer regular reflection output voltage Vsg2_reg to a value sampled from the second test region that has become dirty due to poor cleaning of the intermediate transfer belt 206. It is possible to avoid deterioration of the detection accuracy of the toner image.

  In the printer according to the embodiment, when the power is first turned on after factory shipment or when the intermediate transfer belt 206 is replaced with a new one, a new storage process is performed instead of the update process. It has become. In such a configuration, since the first image formation condition adjustment processing after factory shipment or the first image formation condition adjustment processing after the belt replacement is performed, the belt is rotated once without sampling the data. The image forming condition adjustment process can be started immediately.

101Y, M, C, K: photoconductor (image carrier)
103Y, M, C, K: Developing device (part of image forming means)
120Y, C, M, K: Drum cleaning device (part of image forming means)
130: First reflective optical sensor 136: Second reflective optical sensor 137: Third reflective optical sensor 200: Transfer unit (transfer means)
290: Optical writing unit (part of image forming means)
500: Control unit (imaging condition adjusting means)
502: Input port (image information acquisition means)
519: Update storage processing circuit (update means)

JP 2006-150627 A

Claims (7)

An image carrier that carries a toner image on its moving surface;
Image information acquisition means for acquiring image information;
An image forming means for forming a toner image on the surface of the image carrier based on the image information acquired by the image information acquiring means;
The toner image on the surface of the image carrier is transferred to the surface of an endless belt member that moves endlessly and then transferred to a recording member, or the toner image is transferred to a recording member held on the surface of the belt member. A transfer means for transferring;
A reflective optical sensor for detecting the amount of reflected light on the surface of the belt member;
For the area on the surface where the test toner image is transferred, the reflected light quantity before transfer, which is the reflected light quantity in a state before the test toner image is transferred, is detected, and the reflected light quantity before transfer is already stored in the information storage means. Updating means for performing an updating process for updating the stored value based on the detection result;
For the area, the image forming means creates the reflected light quantity after transfer, which is the reflected light quantity when the test toner image is transferred, and the reflected light quantity before transfer stored in the information storage means. In an image forming apparatus comprising: an image forming condition adjusting unit that performs an image forming condition adjusting process for adjusting an image condition;
While the image forming operation based on the image information is being performed, the amount of reflected light in the region where the toner image based on the image information is not transferred out of the entire area in the circumferential direction of the belt member is reflected by the reflective optical sensor. The updating unit is configured to detect and update the pre-transfer reflected light amount value stored in the information storage unit for the area based on the detection result as the update process. An image forming apparatus. The image forming apparatus according to claim 1.
A plurality of the reflective optical sensors for detecting the amount of reflected light at different positions in the width direction of the belt member;
An image forming apparatus, wherein the updating unit is configured to individually perform the update process and the storage process for each of the reflective optical sensors. The image forming apparatus according to claim 1.
As the reflection type optical sensor, a sensor that detects at least the diffuse reflection light amount among the regular reflection light amount and the diffuse reflection light amount on the belt member surface is used.
In the update process, for the area where the detection result of the reflected light quantity before transfer for the diffusely reflected light by the reflective optical sensor exceeds a predetermined threshold, the reflected light quantity before transfer in the information storage means is updated. An image forming apparatus, wherein the updating unit is configured to perform a canceling process. The image forming apparatus according to claim 2.
As the first reflective optical sensor that is one of the plurality of reflective optical sensors, a sensor that detects at least the diffuse reflected light amount among the regular reflected light amount and the diffuse reflected light amount on the belt member surface is used.
In the update process for the first reflective optical sensor, the information storage is performed for the area where the detection result of the reflected light quantity before transfer for the diffusely reflected light by the first reflective optical sensor exceeds a predetermined threshold. An image forming apparatus, wherein the updating unit is configured to perform a process of canceling the update of the reflected light quantity before transfer in the unit. The image forming apparatus according to claim 4.
As the second reflective optical sensor different from the first reflective optical sensor, a sensor that detects only the regular reflected light amount among the regular reflected light amount and the diffuse reflected light amount on the belt member surface is used.
In the update process for the second reflective optical sensor, the entire area of the belt member passes through a position facing the second reflective optical sensor without a toner image based on the image information being transferred. The region to be passed passes through a position facing the first reflective optical sensor in a state where the toner image based on the image information is not transferred, and the reflection before reflection of the diffusely reflected light by the first reflective optical sensor In the case where the light amount is arranged along the belt width direction with respect to the region where the light amount is larger than a predetermined threshold, the pre-transfer reflected light amount in the information storage unit is updated for the region. An image forming apparatus, wherein the updating unit is configured to perform a canceling process. 6. The image forming apparatus according to claim 1, wherein:
When power is first turned on after shipment from the factory or when the belt member is replaced with a new one, the reflection before transfer is started prior to starting the image forming operation instead of the update process. An image forming apparatus according to claim 1, wherein the updating means is configured so that a new storage process for detecting a new light amount and storing a detection result in the information storage means is performed over one circumference of the belt member. The image forming apparatus according to claim 1,
An image forming apparatus using a non-volatile device as the information storage means.

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