JP5448084B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine.

  In general, an electrostatic latent image electrostatically formed on the surface of an image carrier is coated with a developer containing at least toner to form a toner image, and then the toner image is transferred to a transfer material such as paper. In an image forming apparatus that repeats the process, it is important that the developer always maintains a stable charge amount in order to obtain a high-quality image stably over a long period of time.

  However, the developer deteriorates due to repeated stress received from the developer regulating member provided to optimize the amount of the developer on the developer carrying member. When the developer deteriorates, the charge amount also fluctuates. In a two-component developer comprising a toner and a carrier, if the amount of charge becomes too high, the electrostatic adhesion between the toner and the carrier increases, and the toner adheres firmly to the carrier. The developing ability as a developer is lowered, and a desired image density cannot be obtained. On the other hand, if the charge amount is too low, the electrostatic adhesion between the toner and the carrier is reduced, causing background contamination and in-machine contamination due to toner scattering.

  Also in the case of a one-component developer, as in the case of a two-component developer, the developer deteriorates due to repeated stress received from the developing roller and the developer regulating member, and the additive adhering to the toner surface is buried in the toner. Or released from the toner. In addition, due to the occurrence of these events, dirt and blurring may occur due to the large difference in charge between the deteriorated toner and the newly supplied toner.

  Further, in the intermediate transfer type image forming apparatus, the charge amount becomes unstable due to the deterioration of the developer, so that the transfer of the toner image from the image carrier onto the intermediate transfer member becomes unstable, and the primary transfer There is a tendency that transfer efficiency is lowered and deterioration of a transfer image onto a transfer material such as paper becomes more remarkable.

  As described above, when the developer is deteriorated, the image quality of the transferred image onto a transfer material such as paper is deteriorated. However, these phenomena are mainly caused by the deterioration of the toner in the developer. Accordingly, by discharging the deteriorated toner, adding new toner into the developer and stirring, it is possible to obtain an output with good image quality of the transferred image onto a transfer material such as paper.

  Thus, many proposals have been made for image forming apparatuses for stably and satisfactorily forming images.

  For example, Patent Document 1 discloses a technique for performing an aging process of a developer in order to maintain the development characteristics of the developer in a stable state.

  Japanese Patent Application Laid-Open No. 2004-228561 calculates the amount of toner that will be consumed in an image from an image signal such as a write pixel, and if the amount is smaller than a predetermined steady consumption, There are disclosed a technique for preliminarily consuming outside and a technique for circulating the developer by, for example, sending it to a waste toner box when the developer is forcibly consumed.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique relating to an image forming apparatus that develops developer from a developing roller onto a photosensitive drum when the number of image dots at a predetermined number of rotations of the developing roller is smaller than a predetermined threshold. It is disclosed.

  However, in the above-described technology, it is attempted to obtain a good image quality by discharging the deteriorated toner in the developer. However, if the deteriorated toner is discharged and a new toner is replenished to refresh the developer, the toner is wasted and the cost is increased.

  In addition, in the technique disclosed in Patent Document 1, image forming conditions are determined without discharging the deteriorated toner contained in the developer. It's hard to say.

  In the techniques disclosed in Patent Document 2 and Patent Document 3, the printing rate is calculated from the number of dots corresponding to the image information and the rotation distance information of the image carrier, and the main scanning is performed when the printing rate is lower than the threshold value. A belt-like image is formed to refresh the toner. That is, the toner refresh is performed without knowing how much the toner in the two-component developer has actually deteriorated. Therefore, in some cases, there is a problem that a good image cannot be obtained due to insufficient toner refresh amount, and in other cases, the toner refresh amount is too large, so that the toner is consumed more than necessary. There is a problem. As described above, there are various problems in discharging the deteriorated toner in the developer as a means for suppressing the deterioration of the transferred image.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress the deterioration of a transferred image caused by the deterioration of the toner in the developer without discharging the toner. An image forming apparatus is provided.

In order to achieve the above object, the invention of claim 1 discloses an image carrier, latent image forming means for forming a latent image on the surface of the image carrier, and a latent image formed on the image carrier. A developing unit that forms an image and forms a toner image on the image carrier, an intermediate transfer member that is provided at a position in contact with the image carrier, and includes a belt member that is stretched by a plurality of stretching rollers; A lubricant application device for applying a lubricant to a surface of the intermediate transfer member facing the image carrier, a primary transfer unit for transferring a toner image of the image carrier onto the intermediate transfer member, and A secondary transfer unit that transfers the toner image on the intermediate transfer member to a recording medium, an image density control unit that performs control to adjust image forming conditions so that the image density of the formed image becomes a predetermined image density, In the image forming apparatus comprising: the intermediate transfer by the coating device Lubricant amount adjusting means for adjusting the amount of lubricant to be applied on top, toner pattern forming means for forming a toner pattern on the intermediate transfer member, and detecting the toner pattern formed on the intermediate transfer member A toner pattern detecting means; and a calculating means for quantitatively calculating the degree of deterioration of the toner using a plurality of detection results obtained from the toner pattern by the toner pattern detecting means. In response, the lubricant amount adjusting means is controlled, and the calculation formula of the calculating means is a plurality of output results output when the toner pattern formed on the intermediate transfer member is detected by the toner pattern detecting means. When the maximum value of each output result is Reg_max, Dif_max, and the minimum value is Reg_min, Dif_min, The degree D_gran of reduction toner is characterized in that the following expression.
D_Gran = α * (Reg_max−Reg_min) + β * (Dif_max−Dif_min)
α, β: Constants of transfer characteristics specific to the image forming apparatus obtained in advance.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the lubricant supply device includes a coating roller for applying a lubricant to at least a surface of the intermediate transfer member facing the image carrier, A lubricant supply unit that contacts the application roller and supplies the lubricant to the application roller, and a lubricant amount adjusting unit adjusts a pressing force of the lubricant supply unit against the application roller. It is characterized by being.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the transfer current set when transferring the toner pattern formed on the image carrier onto the intermediate transfer member is optimal. The transfer current is set 10 to 50% lower than the transfer current .
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the secondary transfer means includes a secondary transfer roller, the secondary transfer roller, and an intermediate transfer member. An opposing opposing roller, and transferring a toner image on the intermediate transfer member onto a recording medium by applying a transfer current to the secondary transfer roller or the opposing roller of the secondary transfer roller, When transferring the toner image from the intermediate transfer member to the recording medium, as a supplementary means for correcting the transfer efficiency, the transfer current of the secondary transfer means is changed based on the calculation result of the degree of toner deterioration. And a secondary transfer current control means.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the toner pattern detecting means is means for detecting optical characteristics of the toner image formed on the intermediate transfer member. It is characterized by being common.
In the present invention, the toner pattern detection means uses a plurality of detection results obtained from the toner pattern, and the calculation means quantitatively calculates the degree of toner deterioration, so that the actual state of the deteriorated toner in the developer is quantitatively determined. Can be determined. The primary transfer efficiency of the toner image on the image carrier made of deteriorated toner onto the intermediate transfer member can be changed by changing the lubricant application amount. Therefore, according to the calculated result, the lubricant amount adjusting means for adjusting the amount of lubricant applied to the intermediate transfer member is controlled to change the lubricant application amount, so that the toner image on the intermediate transfer member is changed. The primary transfer efficiency to the recording medium can be appropriately controlled. By controlling in this way, it is possible to suppress the deterioration of the transferred image due to the deterioration of the toner in the developer without discharging the deteriorated toner.

  According to the present invention, the actual state of the deteriorated toner in the developer can be quantitatively determined, and the toner in the developer is deteriorated by appropriately changing the lubricant application amount based on the result. It is possible to suppress the deterioration of the transferred image due to the occurrence without discharging the deteriorated toner.

1 is a schematic configuration diagram illustrating a main part of a printer according to an embodiment. 2 is an explanatory diagram illustrating a schematic configuration of an image forming unit of the printer. FIG. FIG. 3 is a block diagram showing a control diagram related to a toner adhesion amount detection sensor in the present embodiment. FIG. 3 is an explanatory diagram illustrating an optical sensor that detects a toner adhesion amount of black toner. FIG. 3 is an explanatory diagram illustrating an optical sensor that detects a toner adhesion amount of color toner. FIG. 6 is an explanatory diagram showing the relationship between the toner adhesion amount, regular reflection light output and diffuse reflection light output. FIG. 4 is a flowchart showing a procedure for detecting a toner pattern of an intermediate transfer belt by an optical sensor and detecting a degree of deterioration of toner in a developer. The table which shows the deterioration degree of the toner in a developing agent, and the lubricant application quantity with respect to it. The flowchart figure which shows the procedure of process control. Explanatory drawing which shows the relationship between lubricant application amount and transfer efficiency. The expanded block diagram which shows the lubricant supply unit in a lubrication agent application apparatus with the surrounding structure. The expanded block diagram which shows the lubricant supply unit of the state which weakened the pressing force of the lubricant with respect to a lubricant application roller. FIG. 3 is an explanatory diagram showing a relationship between a degree of deteriorated toner in a developer and a blurring rank. In this embodiment, an example image of a stage sample used for rough ranking.

  Hereinafter, an embodiment in which the present invention is applied to a printer which is an electrophotographic image forming apparatus will be described.

  FIG. 1 is a schematic configuration diagram illustrating a main part of the printer according to the present embodiment. As shown in FIG. 1, the printer forms image forming units 102Y (yellow), 102M (magenta), 102C (cyan), and 102K (black) along an intermediate transfer belt 101 stretched around a plurality of stretching rollers. Is provided. Also, the toner images formed by the image forming units 102Y, 102M, 102C, and 102K are sequentially transferred so as to be superimposed on the intermediate transfer belt 101 by the primary transfer devices 106Y, 106M, 106C, and 106K. Further, an image detection device 110 as a toner adhesion amount detection unit that detects a toner adhesion amount of a toner image transferred onto an intermediate transfer belt, which will be described later, is provided to face the intermediate transfer belt 101. The toner image on the intermediate transfer belt 101 is transferred to a transfer paper 112 as a recording material by a secondary transfer device 111. Further, an intermediate transfer belt cleaner 114 as a cleaning unit that cleans transfer residual toner and the like on the intermediate transfer belt, and a lubricant application device 115 that applies a lubricant onto the cleaned intermediate transfer belt are provided.

  FIG. 2 is an explanatory diagram showing a schematic configuration of the image forming units 102Y, 102M, 102C, and 102K. Here, the configurations of the image forming units 102Y, 102M, 102C, and 102K are different in toner color to be used, but are basically the same. Therefore, hereinafter, the reference numerals corresponding to the respective colors are omitted, The description will be made without distinguishing from each other.

  Around the photoconductor 202, a charging device 201 as a charging means for charging the surface of the photoconductor, a writing device 203 as an exposure means for writing an electrostatic latent image on the surface of the photoconductor with writing light L, and an electrostatic latent image A developing device 205 as a developing means for developing with toner, a photoconductor cleaner 200 as a cleaning means for cleaning transfer residual toner on the photoconductor, and an erase (static eliminating device) 207 as a static eliminating means for neutralizing the surface of the photoconductor. A potential sensor 210 is provided as potential detection means.

  The charging device 201 according to the present embodiment is a non-contact type charger composed of a scorotron charger, and the grit voltage (charging bias) Vg of the scorotron charger is set to a target charging potential (in this embodiment, a negative potential). The surface potential of the photosensitive member 202 is set to the target charging potential. Further, the charging device 201 is not limited to this, and other non-contact chargers or contact chargers can also be used.

  The writing device 203 of the present embodiment uses a laser diode (LD) as a light source, and irradiates intermittent writing light, that is, repetitive pulsed writing light L, so that electrostatic charge for each dot is formed on the surface of the photoreceptor. A latent image (hereinafter referred to as a 1-dot electrostatic latent image) is formed. In this embodiment, gradation control is performed by changing the exposure time (unit exposure time) when forming a 1-dot electrostatic latent image to control the amount of toner attached to the 1-dot electrostatic latent image. It is possible. In the present embodiment, the maximum unit exposure time is divided into 15 (each unit exposure time is hereinafter referred to as “exposure duty”), and gradation control of 16 gradations is possible. Therefore, in the present embodiment, the exposure duty can be adjusted in 16 steps from 0 (not exposed) to 15 (maximum unit exposure time).

  The developing device 205 according to the present embodiment includes a developing roller as a developer carrying member disposed opposite to the surface of the photosensitive member 202, and includes a toner charged with a predetermined polarity (in this embodiment, a negative polarity) and a magnetic carrier. The two-component developer thus formed is carried on the developing roller, and toner is supplied to the surface of the photoreceptor 202. A developing bias Vb whose absolute value is sufficiently larger than the exposed portion potential VL and sufficiently smaller than the charging potential Vd is applied to the developing roller. As a result, in the development area where the surface of the photoconductor 202 and the developing roller face each other, the toner is moved toward the electrostatic latent image (exposed portion) on the surface of the photoconductor, and the electrostatic latent image on the surface of the photoconductor 202 is obtained. An electric field can be formed on the non-electrostatic latent image (non-exposed portion) on the surface of the photosensitive member 202 so that the toner does not move. It can be developed.

  When image formation is performed, first, the surface of the photoconductor 202 is charged by the charging device 201 so that the surface of the photoconductor 202 is uniformly at a target charging potential (negative potential). Next, the surface portion of the charged photoconductor 202 is exposed to the photoconductor 202 from the light source (LD) of the writing device 203 with the writing light L corresponding to the image data, whereby the exposed portion on the surface of the photoconductor 202 is exposed. As a result, the electrostatic latent image is formed on the surface of the photoconductor 202. Thereafter, the electrostatic latent image (exposed portion in this embodiment) formed on the surface of the photosensitive member 202 is developed into a toner image by toner carried on a developing roller which is a developer carrying member of the developing device 205. Is done. Specifically, a developing bias Vb having an absolute value larger than the exposure portion potential VL and smaller than the charging potential Vd is applied to the developing roller, and the toner charged to a predetermined polarity (negative polarity in this embodiment) is applied. Development is performed by electrostatically attaching to the electrostatic latent image.

  The toner image formed on the photoreceptor 202 is transferred onto the intermediate transfer belt 101 by the primary transfer device 106. Untransferred toner remaining on the photoconductor 202 without being transferred to the intermediate transfer belt 101 is collected by the photoconductor cleaner 200. Further, the surface of the photosensitive member after the toner image is transferred onto the intermediate transfer belt 101 is uniformly irradiated with the neutralizing light by the eraser 207, so that the non-electrostatic latent image portion is removed and the neutralization is uniformly performed. It will be in the state.

  The toner images of the respective colors formed by the image forming units 102Y, 102M, 102C, and 102K in this way are primarily transferred onto the intermediate transfer belt 101 so as to overlap each other. Thereafter, each color toner image transferred onto the intermediate transfer belt 101 is transferred from the intermediate transfer belt 101 to the transfer paper 112 by the secondary transfer device 111. At this time, the transfer residual toner that is not transferred onto the transfer paper 112 but remains on the intermediate transfer belt 101 is collected by the intermediate transfer belt cleaner 114. After collecting the transfer residual toner on the intermediate transfer belt 101, a lubricant is applied on the intermediate transfer belt 101 by the lubricant applying device 115, and the friction coefficient on the surface of the intermediate transfer belt is kept constant. Thereafter, the toner image is fixed on the transfer paper 112 by a fixing device (not shown), and a series of printing processes is completed.

  FIG. 3 is a block diagram showing the electrical connection of each part provided in the copier of this embodiment. As shown in FIG. 3, the copying machine according to the present embodiment includes a main control unit 41 having a computer configuration, and the main control unit 41 controls driving of each unit. The main control unit 41 includes a ROM (Read Only Memory) 44 that stores in advance fixed data such as a computer program via a bus line 45 in a CPU (Central Processing Unit) 42 that executes various calculations and drive control of each unit. A RAM (Random Access Memory) 43 that functions as a work area for storing various data in a rewritable manner is connected.

  An image detection device 110 is connected to the main control unit 41, and the image detection device 110 includes a toner adhesion amount detection sensor for each color and color misregistration correction image detection sensors 311Y, 311M, 311C, and 311K. Information detected by these sensors is sent to the main control unit 41. The main control unit 41 is also connected with a charging device, a writing device, a developing device, and a potential sensor (not shown).

  Based on the toner density formed on the intermediate transfer belt detected by the image detection device 110, the main control unit 41 is based on the developing bias of the developing device, the exposure amount (laser power / exposure time) of the optical writing unit, and the charging device. It has a function as a process condition changing means for changing the charging bias and the like.

  Next, an optical sensor which is a toner adhesion amount detection unit in the present embodiment will be described. FIG. 4 is a diagram illustrating the configuration of the black toner adhesion amount detection sensor, and FIG. 5 is a diagram illustrating the configuration of the color toner adhesion amount detection sensor.

  As shown in FIG. 4, the black toner adhesion amount detection sensor 311-1 includes a light emitting element 311-1a formed of a light emitting diode (LED) and the like, and a light receiving element 311-1b that receives specularly reflected light. . The light emitting element 311-1a irradiates light onto the intermediate transfer belt 101, and this irradiation light is reflected by the intermediate transfer belt 101. The light receiving element 311-1b receives regular reflected light of the reflected light.

  On the other hand, as shown in FIG. 5, the color toner adhesion amount detection sensor 311-2 includes a light emitting element 311-2a composed of a light emitting diode (LED) or the like, a light receiving element 311-2b that receives specularly reflected light, and diffuse reflection. It comprises a second light receiving element 311-2c that receives light. The light emitting element 311-2a irradiates light on the intermediate transfer belt 101 as in the case of the black toner adhesion amount detection sensor 311-1, and this irradiation light is reflected by the surface of the intermediate transfer belt 101. The first light receiving element 311-2b receives regular reflected light of the reflected light, and the second light receiving element 311-2c receives diffuse reflected light of the reflected light.

  In the present embodiment, GaAs infrared light emitting diodes having a peak wavelength λp of emitted light of 950 nm are used as the light emitting elements 311-1a and 311-2a. As the light receiving elements 311-1b, 311-2b, 311-2c, Si phototransistors having a peak light receiving sensitivity of 800 nm are used.

  Further, a distance (detection distance) of 5 mm is provided between the black toner adhesion amount detection sensor 311-1 and the color toner adhesion amount detection sensor 311-2 and the belt surface of the intermediate transfer belt 101 which is a detection target. Arranged.

  In this embodiment, toner adhesion amount detection sensors 311-1 and 311-2 are provided in the vicinity of the intermediate transfer belt 101, and image forming conditions such as exposure amount and development bias are determined based on the toner adhesion amount on the intermediate transfer belt. To do. Further, in this embodiment, the configuration is common to the means for detecting the optical characteristics of the toner image formed on the intermediate transfer belt 101, but it may be provided separately.

  Next, an image forming condition changing method (hereinafter referred to as process control) for obtaining appropriate and good image quality will be described with reference to FIG. The main control unit 41 executes the process control mode when the usage state and the environmental change of the photosensitive drum 202 and the developing device 205 become a predetermined value or more (S1). When the process control mode is executed, the main control unit 41 first adjusts the output value of the image detection device 110 serving as a toner density detection unit (S2).

  As described above, the image detection device 110 is located at a position facing the intermediate transfer belt 101, and includes a toner adhesion amount detection sensor and a color misregistration correction image detection sensor 311 corresponding to each color. The toner adhesion amount detection sensor and the color misregistration correction image detection sensor 311 include a light emitting element 311-2a (311-1a) made of a light emitting diode (LED) and the like, and a light receiving element 311-2b (311) that receives specularly reflected light. -1b) and a second light receiving element 311-2c that receives diffusely reflected light.

  The light receiving element 311-2a (311-1a) takes the toner adhesion amount per unit area temporarily transferred from the photoreceptor 202 and formed on the intermediate transfer belt 101 on the horizontal axis, and the output voltage value on the vertical axis. As shown in FIG. 6, the regular reflected light output has a characteristic of gradually decreasing the output voltage value as the toner adhesion amount increases, and the diffuse reflected light output has a linear characteristic of gradually increasing the output voltage value. Have. Here, FIG. 6 illustrates a graph for the toner of the magenta.

  In the calibration of the image detection device 110, the output voltage value Vref of the light receiving element when the light reflected from the intermediate transfer belt 101 is detected in a state where the intermediate transfer belt 101 is regarded as a reference plate and the light emission by the LED is turned on, The light emission amount of the LED is adjusted so that the reference (base) voltage Vba is obtained. The reference voltage Vba is stored in advance in the ROM 44, and the amount of light emitted from the LED is determined by adjusting the current If flowing through the LED.

  After adjusting the output value of the image detection device 110, the main control unit 41 next executes process control for stabilizing the solid image (S3). The process control for stabilizing the solid image is to fix the exposure amount (laser power) and charging bias, change the development bias voltage output in multiple stages, and create a plurality of toner pattern images with different toner adhesion amounts. Image.

  Then, the development bias voltage is adjusted so that the toner adhesion amount detected by the image detection device 110 becomes a target value.

  After the stabilization of the solid image, the main control unit 41 next executes process control for low gradation and adjusts the exposure amount (laser power) as the image forming process condition (S4). When the adjustment for the solid image and the low gradation is finished, the main control unit 41 stores the charging condition, the developing bias condition, and the laser power condition set by the process control in the RAM 43, and the process control is finished.

  Next, as an example of a lubricant amount adjusting unit that adjusts the amount of lubricant applied to the intermediate transfer belt 101 in this embodiment, a lubricant application roller 451 and a lubricant application roller provided in the lubricant application device 115. The pressing force adjusting means for adjusting the pressing force with the lubricant supply unit that supplies the lubricant to 451 will be described with reference to FIG. FIG. 11 is an enlarged configuration diagram showing the lubricant supply unit 450 in the lubricant application device 115 together with its peripheral configuration.

  In the figure, the lubricant supply unit 450 of the lubricant application device 115 includes a lubricant application roller 451, an urging coil spring 453, a cam shaft 454, a cam 455, a holder rotating shaft 456, and a lubricant application roller 451. A holding body 452 and a lubricant 457 which are lubricant supply units, a cam motor and a cam motor drive control unit (not shown), and the like are included. The lubricant application roller 451 described above is rotatably held on a support (not shown), and is driven by a drive device (not shown) at least when applying the lubricant. Here, as the lubricant application roller 451, a well-known roller that can hold the lubricant by deforming a contact portion with the lubricant 457 such as a sponge roller or a brush roller can be used. A solid lubricant is used as the lubricant 457.

  The holding body 452 of the lubricant supply unit 450 is supported by a support body (not shown) so that the holding body 452 can be rotated around a holding body rotation shaft 456 provided on the upper portion thereof. At the side of the holding body 452, the holding body 452 is urged toward the intermediate transfer belt 101 while the urging coil spring 53 is supported by the above-described support body.

  By this urging, the lubricant 457 held by the holding body 452 is pressed against and in contact with the lubricant application roller 451. The urging direction of the holding body 452 by the urging coil spring 453 is a direction parallel to a line connecting the lubricant application roller 451 and the rotation center of the nip backside stretching roller 446 indicated by a one-dot chain line in the drawing.

  A cam 455 that rotates around a cam shaft 454 by a driving force from a cam motor (not shown) is disposed in the vicinity of the holding body 452, and its own cam surface is abutted against the lower portion of the holding body 452. . By this abutment, the movement of the holding body 452 urged toward the intermediate transfer belt 101 by the urging coil spring 453 is restricted.

  When a cam motor (not shown) is driven to rotate forward or reversely, the cam 455 rotates around the cam shaft 454 and moves its cam surface closer to or away from the holding body 452. As a result, the contact position between the cam surface and the lower portion of the holding body 452 moves in the horizontal direction in the drawing with respect to the printer unit, and the holding body 452 rotates counterclockwise in the drawing about the holding body rotation shaft 456. Rotate slightly in the direction or slightly in the clockwise direction in the figure.

  When the holding body 452 rotates in this way, the lubricant 457 moves slightly away from or slightly closer to the lubricant application roller 452, and the pressing force of the lubricant 457 against the lubricant application roller 452 becomes weaker or stronger. I'll be relaxed. That is, in this apparatus, the holding body 452, the urging coil spring 453, the cam shaft 454, the cam 455, the holding body rotating shaft 456, the cam motor (not shown) and the control unit for controlling the cam motor drive, etc., lubricate the lubricant application roller 451. It functions as a pressing force adjusting means for adjusting the pressing force of the agent 457.

  When the cam motor is driven to rotate forward for a predetermined time, as shown in FIG. 12, the cam 455 rotates counterclockwise in the drawing by a predetermined angle around the cam shaft 454, and the holding body 452 The lower part is overcome from the urging force of the urging coil spring 453 and pushed from the right side to the left side in the figure. As a result, the holding body 452 rotates around the holding body rotation shaft 456 by a predetermined angle in the clockwise direction in the drawing, and the pressing force of the lubricant 457 against the lubricant application roller 451 is slightly weakened.

  Conversely, when the cam motor is driven in reverse, the holding body 452 rotates counterclockwise in the figure around the holding body rotation shaft 456, and the pressing force of the lubricant 457 against the lubricant application roller 451 Becomes stronger.

  Thus, the pressing force of the lubricant 457 against the lubricant application roller 451 can be adjusted by the pressing force adjusting means. When the pressing force is increased, the amount of lubricant scraped from the lubricant 457 by the lubricant application roller 451 increases, and the amount of lubricant applied to the intermediate transfer belt 101 can be increased. When the pressing force is weakened, the amount of lubricant scraped off from the lubricant 457 by the lubricant application roller 451 is reduced, and the amount of lubricant applied to the intermediate transfer belt 101 can be reduced.

  Then, the pressing force adjusting means as the lubricant amount adjusting means for adjusting the application amount of the lubricant applied on the intermediate transfer belt 101 of the present embodiment adjusts the lubricant application amount determined in stages, which will be described later. Therefore, the main controller 41 controls the pressing force of the lubricant 457 against the lubricant application roller 451 in a plurality of stages.

  Further, as described above, in this embodiment, the pressing force adjusting means for adjusting the pressing force of the lubricant 457 against the lubricant application roller 451 is used as the lubricant amount adjusting means, but the present invention is not limited to this. For example, the amount of lubricant applied to the intermediate transfer belt 101 is adjusted by making the pressing force of the lubricant 457 to the lubricant applying roller 451 constant and adjusting the number of revolutions per unit time of the lubricant applying roller 451. May be adjusted.

  Next, detection of the degree of deterioration of the toner in the developer, quantification of the degree of toner deterioration from the detected value, and determination of the lubricant application amount to the intermediate transfer belt 101 based on the quantified degree of toner deterioration. The flow will be described with reference to FIG.

  Here, an expression to be described later for quantifying the degree of deterioration of the toner from the detected value is formed on the intermediate transfer body by the inventor of the present invention so that transfer to the intermediate transfer body becomes difficult as the toner deteriorates. The inventors have repeatedly found experiments by paying attention to the fact that when the amount of adhesion is detected for the detected toner pattern, the variation in the value increases. The reason why the variation in the adhesion amount value for the detection toner pattern formed on the intermediate transfer member increases as the toner deterioration progresses is caused by the repeated stress that the developer receives from the developer regulating member. This is probably because the charge amount of the developer also fluctuates. It is considered that as the degree of toner deterioration progresses, the amount of toner whose charge amount contained in the developer fluctuates increases, and the variation in the value of the adhesion amount for the detection toner pattern increases.

(Step 1)
First, when the execution instruction for detecting the degree of deterioration of the toner in the developer is issued from the main control unit 41, the transfer current is changed from the currently set value to the transfer current value for detecting the deteriorated toner. The transfer current value for detecting the deteriorated toner differs depending on the toner, developer, and developing device to be used, but is a value that is 10 to 50% lower than the transfer current value that is optimized during normal operation. To do. Further, image forming conditions other than the transfer conditions are determined by the process control described above.

  There are two reasons why the transfer current value for detecting deteriorated toner is changed. First, when the transfer current is lowered, the transfer efficiency of the toner on the photoconductor 202 onto the intermediate transfer belt 101 is lowered. Since the transfer margin also decreases, the deteriorated toner whose charge amount is unstable is not easily transferred onto the intermediate transfer belt 101, and the toner pattern is likely to be in a non-uniform state. For this reason, when the transfer current is lowered, the value obtained when the toner pattern is detected by the image detection unit 110 is likely to vary, and the sensitivity for detecting the degree of toner deterioration can be increased.

The second point is that when the transfer current is lowered, the amount of toner transferred onto the intermediate transfer belt is reduced, so that the toner adhesion amount is small on the intermediate transfer belt 101. As shown in FIG. 6, looking at the toner adhesion amount 0.2 mg / cm ² near the 0.5 mg / cm ² characteristic of the specular reflection light output and the diffuse reflection light output near transferred to the intermediate transfer belt, the toner It can be seen that the variation in specular reflection light output is larger in the vicinity of 0.2 mg / cm ^{2 where the} adhesion amount is smaller (r1> r2). On the other hand, it can be seen that the diffuse reflected light output has almost the same variation for both toner adhesion amounts (d1≈d2). Therefore, if the transfer current is lowered and the amount of toner attached on the intermediate transfer belt 101 is reduced to obtain the specular reflection light output and the diffuse reflection light output, the variation in the specular reflection light output can be increased, and the degree of toner deterioration can be increased. This is because the detection sensitivity can be increased.

(Step 2)
Next, a toner pattern is created on the photoreceptor 202. Here, the size of the reference toner pattern to be created is 15 mm in the main scanning direction and 39 mm in the sub scanning direction. In the present embodiment, a solid solid writing pattern is used as the toner pattern. The toner pattern formed on the photosensitive member 202 is transferred onto the intermediate transfer belt 101 with the transfer current value for detecting the deteriorated toner set in Step 1. The toner pattern transferred onto the intermediate transfer belt 101 is detected by the image detection unit 110. When detecting this toner pattern, the sampling time interval is set to 4 msec, and at least 100 points are sampled so as not to be affected by the uneven reflection of the intermediate transfer belt 101, and a five-point moving average value is obtained.

Since the image detecting unit 110 includes the regular reflection light receiving element 311-2b and the diffuse reflection light receiving element 311-2c, outputs from the respective light receiving elements can be obtained. Here, the output from the regular reflection light receiving element is Reg (n) and the output from the diffuse reflection light receiving element is Dif (n). If 100 points are sampled and a 5-point moving average value is obtained, two data sets as shown below are obtained.
Regular reflection light output data: Reg (1), Reg (2), ..., Reg (20)
Diffuse reflected light output data: Dif (1), Dif (2), ..., Dif (20)

(Step 3)
Therefore, the maximum value and the minimum value are selected from the regular reflection light output data and the diffuse reflection light output data, and each is recorded in the RAM. The maximum value and the minimum value are referred to as Reg_max, Dif_max, Dif_min, and Dif_min, respectively.

(Step 4)
When Reg_max, Dif_max, Dif_min, and Dif_min are obtained, the degree of deteriorated toner D_Gran in the developer is calculated from these values. As described above, the higher the degree of toner deterioration, the greater the variation between the regular reflection light output data Reg (n) and the diffuse reflection light output data Dif (n) from which the toner pattern is detected. It can be quantified by the following formula.
D_Gran = α * (Reg_max−Reg_min) + β * (Dif_max−Dif_min)
Here, α and β are values obtained experimentally.
Basically, α≈1, and β is the slope slope (dif) of the first-order approximation relation between the adhesion amount and the diffuse reflected light output, the calculation formula is β = 1 / slope (dif).
In addition, a first-order approximation expression of the relationship between the adhesion amount of the graph and the diffuse reflected light output for the toner of the magenta in FIG. 6 is as follows, and the value of β is 2.4718.
y = 2.4718x + 0.1104

(Step 5)
The lubricant application amount (four types) for each color on the intermediate transfer belt 101 in accordance with the deterioration of the toner in the developer is stepped from the value of the deteriorated toner degree D_Gran under the conditions shown in the table of FIG. Judgment. FIG. 8 is a table showing the lubricant application amount according to the value of D_Gran. Here, A, B, and C in FIG. 8 are previously determined deterioration toner determination constants specific to the image forming apparatus, and C>B> A. STD1 indicates the optimum amount of lubricant applied when the toner is not loaded.

  Of the lubricant application amounts for each color determined as described above, the largest lubricant application amount value is determined as the lubricant application amount to the intermediate transfer belt 101. Then, the lubricant application amount determined as described above is adjusted by using the lubricant application amount variable mechanism described above, and the actual image forming operation causes the toner in the developer to deteriorate. Thus, it is possible to appropriately correct a decrease in toner image transfer efficiency. In this way, it is possible to suppress the deterioration of the transferred image due to the deterioration of the toner in the developer without discharging the deteriorated toner.

  Next, the structure used for the experiment for obtaining A, B, and C performed in this embodiment is shown below. The experimental machine was Imagio ProC900, and the paper type used was Type 6200 made by NBS Ricoh. Using these experimental machines and evaluation paper, the environmental conditions of the experimental machine (temperature / humidity: 10 ° C / 15%, 23 ° C / 50%, 27 ° C / 80%) and the deterioration of the developer (new condition, 10 minutes) The stirring state and the stirring state for 60 minutes were changed, and the D_Gran and 2by2 images at that time were roughly ranked. The rough ranking is a visual evaluation using a stage sample. FIG. 13 shows the result. At this time, the value of D_Gran when the rough rank is rank 4 is A, the value of D_Gran when it is rank 3 is B, and the value of D_Gran when it is rank 2 is C.

  Here, the rough ranking of the 2-by2 image performed this time will be briefly described. A 2-by2 image is an image in which a dot pattern having a size of 2 dots in length and width is printed in a tile shape. In this image, the blur can be evaluated from the halftone uniformity. The evaluation method is compared with the stage sample and visually determines which level it is. FIG. 14 shows an example image of the stage sample used for the rough ranking. In this sample, rank 4 or higher is regarded as no problem, and rank 3 or lower is determined as problematic. In addition, the image example of the stage sample in FIG. 14 illustrates a graph of black toner in order to easily show the difference between the ranks.

  The reason for changing the lubricant application amount in accordance with the deterioration state will be described with reference to FIG. FIG. 10 is a diagram showing the relationship between the lubricant application amount and the transfer efficiency for the toner of the magenta. Here, the graph (A) in the figure shows the toner in an undegraded state, the graph (A) is the toner that has been subjected to a load by stirring for 10 minutes in the developing device, and the graph (C) is in the developing device. It shows toner loaded by 60 minutes of agitation. The transfer efficiency increases as the lubricant application amount increases, and shows a transfer efficiency peak at a certain value. However, even if the lubricant application amount is increased from that value, the transfer efficiency becomes almost constant. Further, when the toner is subjected to a load, the maximum value of the transfer efficiency is lowered depending on the degree of the load, and the amount of lubricant applied to maximize the transfer efficiency is increased.

  If a large amount of lubricant is applied in advance, the amount of lubricant consumed increases and the replacement cycle is shortened, which is disadvantageous in terms of cost. Better.

  FIG. 10 shows the lubricant application amount with respect to the unit travel distance of the photoconductor 202. Here, the travel distance of the photoconductor 202 is calculated from a value obtained by multiplying the rotation speed by the time from the start of rotation of the photoconductor 202 to the stop. Since the time during which the photosensitive member 202 is rotating is equal to the time during which the lubricant application roller 452 is driven, the unit is g / m.

  In this embodiment, the adjustment of the lubricant application amount is made in four stages including the reference application amount as shown in FIG. 8, but the present invention is not limited to this, and the adjustment of the image forming apparatus to which the present invention is applied. More stages or fewer stages may be used depending on the purpose of use.

  Further, in addition to the stepwise adjustment of the lubricant application amount, a secondary transfer roller provided in the secondary transfer means as an auxiliary means when the toner image is transferred from the intermediate transfer belt 101 to the transfer paper 112. Alternatively, the transfer current applied to the counter roller of the secondary transfer roller may be changed. With this configuration, the secondary transfer efficiency of the toner image on the intermediate transfer belt 101 can be controlled, and the transfer efficiency including finer primary transfer and secondary transfer can be controlled.

In this embodiment, the image detection unit 110 uses a plurality of detection results obtained from the toner pattern and the calculation unit quantitatively calculates the degree of toner deterioration, so that the actual state of deteriorated toner in the developer is calculated. Can be determined quantitatively. The primary transfer efficiency of the toner image made of deteriorated toner on the photosensitive member 202 to the intermediate transfer belt 101 can be controlled by changing the lubricant application amount. Therefore, according to the calculated result, the lubricant amount adjusting means for adjusting the amount of lubricant applied to the intermediate transfer body 101 is controlled to change the lubricant application amount, and the toner image on the photoreceptor 202 is changed. The primary transfer efficiency to the intermediate transfer belt 101 can be appropriately controlled. Therefore, it is possible to suppress deterioration of the transfer image transferred to the transfer paper 112 due to deterioration of the toner in the developer without discharging the deteriorated toner.
Among the plurality of output results output when the image detection unit 110 detects the toner pattern formed on the intermediate transfer belt 101, the maximum value of each output result is Reg_max, Dif_max, the minimum value is Reg_min, By using Dif_min and the degree of deteriorated toner D_gran in the developer, the following expression can be used to quantitatively calculate the degree of toner deterioration.
D_Gran = α * (Reg_max−Reg_min) + β * (Dif_max−Dif_min)
α, β: Constants of transfer characteristics specific to the image forming apparatus obtained in advance.
Further, in the present embodiment, as the lubricant amount adjusting means, the pressing force adjusting means for adjusting the pressing force of the lubricant 457 against the lubricant applying roller 451 is used, so that according to the calculated result, the lubricant applying roller By controlling the pressing force of the lubricant 457 with respect to 451 by controlling the pressing force adjusting means, the amount of lubricant applied is changed, and the primary transfer efficiency of the toner image on the photosensitive member 202 to the intermediate transfer belt 101 is appropriately controlled. Can do. Therefore, it is possible to suppress deterioration of the transfer image transferred to the transfer paper 112 due to deterioration of the toner in the developer without discharging the deteriorated toner.
In this embodiment, the transfer current set when the toner pattern formed on the photoconductor 202 is transferred onto the intermediate transfer belt 101 is set 10 to 50% lower than the optimum transfer current. As a result, the sensitivity for detecting the degree of toner deterioration can be increased, and the state of the deteriorated toner can be determined more appropriately .
In this embodiment, when the toner image is transferred from the intermediate transfer belt 101 to the transfer paper 112, the transfer efficiency is corrected when the toner image is transferred from the intermediate transfer belt 101 to the transfer paper 112. As such means, there is provided secondary transfer current control means for changing the transfer current applied to the secondary transfer roller or the opposite roller of the secondary transfer roller based on the calculation result of the degree of toner deterioration. With such a configuration, the secondary transfer efficiency of the toner image on the intermediate transfer belt 101 can be controlled, and the transfer efficiency including finer primary transfer and secondary transfer can be controlled. .
In the present embodiment, the image detection unit 110 is common with a unit that detects the optical characteristics of the toner image formed on the intermediate transfer belt 101. Therefore, it is not necessary to provide a separate detection unit, and the present invention can be performed at low cost. The effect of this can be obtained.

41 Main Control Unit 101 Intermediate Transfer Belt 102Y, 102M, 102C, 102K Image Forming Unit 110 Image Detection Device 112 Transfer Paper as Recording Material 113 Density Patch 114 Intermediate Transfer Belt Cleaner 115 Lubricant Application Device 201 Charging Device 202 Photoconductor 203 Document Loading device 205 Developing device 311 Optical sensor 311-1 Adhesion amount detection sensor for black toner 311-2 Adhesion amount detection sensor for color toner 450 Lubricant supply unit 451 Lubricant application roller 452 Holder for lubricant supply unit 455 Cam 457 provided in lubricant supply unit

Japanese Patent Laid-Open No. 10-083115 JP 2006-171788 A Japanese Patent Laid-Open No. 2004-125829

Claims (5)

An image carrier;
Latent image forming means for forming a latent image on the surface of the image carrier;
Developing means for visualizing the latent image formed on the image carrier and forming a toner image on the image carrier;
An intermediate transfer member comprising a belt member provided at a position in contact with the image carrier and stretched by a plurality of stretching rollers;
A lubricant application device for applying a lubricant to the surface of the intermediate transfer member facing the image carrier;
Primary transfer means for transferring the toner image of the image carrier onto the intermediate transfer member;
Secondary transfer means for transferring the toner image on the intermediate transfer member to a recording medium;
Image density control means for performing control to adjust image forming conditions so that the image density of the formed image becomes a predetermined image density;
In an image forming apparatus comprising:
Lubricant amount adjusting means for adjusting the amount of lubricant applied to the intermediate transfer member by the coating device;
Toner pattern forming means for forming a toner pattern on the intermediate transfer member;
Toner pattern detecting means for detecting a toner pattern formed on the intermediate transfer member;
Calculation means for quantitatively calculating the degree of deterioration of the toner using a plurality of detection results obtained from the toner pattern by the toner pattern detection means;
According to the calculation result by the calculating means, the lubricant amount adjusting means is controlled ,
The calculation formula of the calculation means is that the maximum value of each output result among the plurality of output results output when the toner pattern formed on the intermediate transfer body is detected by the toner pattern detection means is Reg_max, Dif_max, If the minimum value is Reg_min, Dif_min,
An image forming apparatus, wherein the degree D_gran of the deteriorated toner in the developer is expressed by the following formula .
D_Gran = α * (Reg_max−Reg_min) + β * (Dif_max−Dif_min)
α, β: Constants of transfer characteristics specific to the image forming apparatus obtained in advance. The image forming apparatus according to claim 1.
The lubricant supply device includes an application roller that applies the lubricant to at least a surface of the intermediate transfer member facing the image carrier, and a lubricant supply unit that contacts the application roller and supplies the lubricant to the application roller. And
The image forming apparatus according to claim 1, wherein the lubricant amount adjusting means is a pressing force adjusting means for adjusting a pressing force of the lubricant supply unit with respect to the application roller. The image forming apparatus according to claim 1, wherein
The transfer current set when transferring the toner pattern formed on the image carrier onto the intermediate transfer member is set to be 10 to 50% lower than the optimum transfer current. Equipment . The image forming apparatus according to any one of claims 1 to 3 ,
The secondary transfer means includes a secondary transfer roller and a counter roller facing the secondary transfer roller via an intermediate transfer member, and transfers a transfer current to the secondary transfer roller or the counter roller of the secondary transfer roller. Transferring the toner image on the intermediate transfer member onto a recording medium,
When transferring the toner image from the intermediate transfer member to the recording medium, as an auxiliary means for correcting the transfer efficiency, the transfer current of the secondary transfer means is calculated based on the calculation result of the degree of toner deterioration. An image forming apparatus comprising a secondary transfer current control unit to be changed. The image forming apparatus according to any one of claims 1 to 4 ,
An image forming apparatus characterized in that the toner pattern detecting means is common with the means for detecting the optical characteristics of the toner image formed on the intermediate transfer member.