JP2010008904A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of providing an image of high quality, as well as capable of attaining cost reduction and space saving. <P>SOLUTION: The image forming apparatus is configured to detect a toner deposition amount on a toner pattern, by measuring a ratio of diffused-reflected light components at the toner-deposited part of the toner pattern formed on an intermediate transfer body 12 to regular-reflected light components at the base surface part of the intermediate transfer body 12 by an optical sensor 21. The glossiness of the base surface part is calculated, based on the intensity of the regular-reflected light at the base surface part, as measured by the optical sensor 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these.

  As an image forming apparatus using an electrophotographic image forming process such as a copying machine, a facsimile machine, or a printer, toner images of different colors carried on the surfaces of a plurality of photosensitive drums are transferred to an intermediate transfer member such as an intermediate transfer belt. 2. Description of the Related Art An indirect transfer type image forming apparatus that performs primary transfer and secondary transfer of toner images transferred to an intermediate transfer body onto a recording medium such as paper is known.

  In this type of image forming apparatus, there is a configuration in which a toner pattern for image density detection is formed on an intermediate transfer member, and the amount of toner adhesion is detected by measuring reflected light of the toner pattern with an optical sensor ( For example, see Patent Document 1). In this image forming apparatus, the developing bias, the charging potential of the photosensitive drum, the exposure amount, and the like are adjusted based on the detected toner adhesion amount to control an appropriate image density.

In general, since the surface of the intermediate transfer member is disposed in contact with a photosensitive drum, a cleaning blade, or the like, the surface of the intermediate transfer member is gradually worn and deteriorated. When the surface of the intermediate transfer member deteriorates and its surface state changes, the image quality is affected. For this reason, there is an image forming apparatus configured to grasp the surface state of the intermediate transfer member by detecting the glossiness (optical reflectance) of the intermediate transfer member using an optical sensor (see, for example, Patent Document 2). ). This image forming apparatus adjusts the transfer and fixing conditions of the image based on the detected glossiness so as to maintain the gloss of the image at a predetermined level.
JP 2001-305823 A Japanese Patent Laid-Open No. 10-10883

  The image forming apparatus disclosed in Patent Document 1 can grasp the transfer rate of toner from the photosensitive member to the intermediate transfer member by detecting the toner adhesion amount of the toner pattern formed on the intermediate transfer member. However, since the transfer rate of toner from the intermediate transfer member to the recording medium (hereinafter referred to as secondary transfer rate) cannot be grasped, it is difficult to adjust the image density transferred to the recording medium with high accuracy.

  Further, the secondary transfer rate changes with a change in glossiness (surface state) of the intermediate transfer member. For this reason, if the glossiness of the intermediate transfer member is detected by an optical sensor as in the image forming apparatus disclosed in Patent Document 2, it is possible to grasp the secondary transfer rate. However, if an optical sensor for detecting the glossiness is provided separately from the optical sensor for detecting the image density, there are problems such as high cost and an increase in the size of the apparatus accompanying an increase in installation space.

  In view of such circumstances, an object of the present invention is to provide an image forming apparatus that can provide a high-quality image and can achieve cost reduction, space saving, and the like.

  According to a first aspect of the present invention, there is provided an image carrier that carries a toner image, a charging unit that charges the image carrier, and an exposure unit that exposes a charged surface of the image carrier to form an electrostatic latent image. A developing means for supplying toner to the electrostatic latent image formed on the image carrier to form a toner image; and a toner image is primarily transferred from the image carrier and the primary transferred toner image is recorded. An optical sensor having an intermediate transfer member that is secondarily transferred to a medium, a light emitting unit that emits light, a regular reflection light receiving unit that receives specular reflection light, and a diffuse reflection light receiving unit that receives diffuse reflection light, The amount of toner adhesion of the toner pattern is detected by measuring the ratio of the diffuse reflection light component of the toner adhesion portion of the toner pattern formed on the intermediate transfer body and the regular reflection light component of the background portion of the intermediate transfer body with the optical sensor. Configured to In the image forming apparatus, which is constituted so as to calculate the glossiness of the background portion based on specular reflected light intensity of the background portion were measured by the optical sensor.

  The image forming apparatus of the present invention can calculate the glossiness of the background portion by measuring the background portion of the intermediate transfer member with an optical sensor. When the glossiness of the background portion of the intermediate transfer member changes, the image density on the recording medium also changes accordingly.By controlling the image forming conditions of the image forming apparatus based on the calculated glossiness, the image density Can be maintained at an appropriate concentration. In addition, by using an optical sensor used for toner pattern detection to detect glossiness, it is not necessary to separately provide an optical sensor for glossiness detection, thereby reducing cost and space. Is possible.

  According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the regular reflection light intensity of the background portion measured by the optical sensor has a preset specified value. An image forming apparatus configured to correct a light emission amount, and corresponds to the light emission amount after correction based on information indicating a relative relationship between the light emission amount of the light emitting unit and the glossiness of the background portion. The glossiness of the background portion is calculated.

  By detecting the glossiness of the intermediate transfer member based on the information (light emission amount after correction) obtained at the time of correcting the light emission amount, the time required for detecting the glossiness and the time required for correcting the light emission amount can be reduced. A part of them can be overlapped, and the total processing time required for adjusting the image density can be shortened. Thereby, the waiting time of the user at the time of image density adjustment can be shortened.

  A third aspect of the present invention is the image forming apparatus according to the second aspect, wherein the correction of the light emission amount and the calculation of the glossiness are performed immediately before forming a toner pattern on the intermediate transfer member.

  As a result, the total processing time required for adjusting the image density can be shortened, and the waiting time of the user when adjusting the image density can be shortened.

  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 information indicates a relative relationship between the glossiness of the background portion and the secondary transfer rate of the toner image. The secondary transfer rate of the toner image corresponding to the calculated glossiness is calculated.

  When the secondary transfer rate changes, the image density on the recording medium also changes accordingly. Therefore, it is possible to maintain the image density at an appropriate density by calculating the secondary transfer rate as described above and controlling the image forming conditions of the image forming apparatus based on the calculated secondary transfer rate. Become.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the toner adhesion amount on the intermediate transfer member when the toner image is primarily transferred to the intermediate transfer member is m, and the secondary transfer rate of the toner image. Is E, and the toner adhesion amount on the recording medium when the toner image is secondarily transferred to the recording medium is M. When the relative relationship of m, E, and M is expressed by the following formula (1), the above calculation is performed. The target value of the toner adhesion amount on the intermediate transfer member is calculated by substituting the secondary transfer rate of the toner density and the preset optimum value of the toner adhesion amount on the recording medium into the following formula (1). It is comprised as follows.
m × E = M ... Formula (1)

  By adjusting the toner adhesion amount on the intermediate transfer member based on the calculated target value of toner adhesion amount, the toner adhesion amount on the recording medium can be optimized and the image density can be maintained at an appropriate density. Is possible.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the image forming condition is controlled so that the target value of the toner adhesion amount on the intermediate transfer member becomes the calculated target value. It is a thing.

  Thereby, the toner adhesion amount on the recording medium can be set to an optimum value, and the image density can be maintained at an appropriate density.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the image forming condition is controlled by controlling at least one of the charging unit, the exposure unit, and the developing unit. Is.

  Thereby, the image density can be maintained at an appropriate density.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the second aspect, the image forming apparatus further includes a warning unit that issues a warning when the corrected light emission amount is out of a preset normal range.

  When the corrected light emission amount is out of the normal range, there is a possibility that an abnormality has occurred in the optical sensor or the intermediate transfer member. If an abnormality occurs in the optical sensor or the intermediate transfer member, it is difficult to maintain an appropriate image density. Therefore, this can be notified by giving a warning.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the second or eighth aspect, the difference between the pre-correction light emission amount and the post-correction light emission amount exceeds a preset threshold value indicating occurrence of an abnormality. A warning means for issuing a warning is provided.

  When the difference between the light emission amount before correction and the light emission amount after correction exceeds a threshold indicating the occurrence of abnormality, it is difficult to maintain the image density appropriately. Therefore, this can be notified by giving a warning.

  A tenth aspect of the present invention is the image forming apparatus according to the eighth or ninth aspect, further comprising a cleaning unit that cleans the optical sensor, and the cleaning unit cleans the optical sensor when the warning unit issues a warning. It is comprised so that it may do.

  When the warning is given, there is a possibility of erroneous detection due to the optical sensor being dirty. Therefore, it is possible to eliminate the cause of erroneous detection by cleaning the optical sensor with the cleaning means.

  According to the image forming apparatus of the present invention, since the glossiness of the intermediate transfer member can be detected, the image forming conditions of the image forming apparatus can be controlled based on the detected glossiness. Thereby, the image density can be maintained at an appropriate density, and a high-quality image can be provided.

  Further, an optical sensor used for detecting a toner pattern on the intermediate transfer member can be used as an optical sensor for detecting glossiness. Thereby, it is not necessary to separately provide an optical sensor for detecting the glossiness, and it is possible to reduce costs and save space.

  FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. The image forming apparatus of the present invention shown in FIG. 1 has four process units 1Y, 1C, 1M for forming an image with developers of different colors of yellow, cyan, magenta and black corresponding to color separation components of a color image. , 1Bk.

  The process units 1Y, 1C, 1M, and 1Bk have the same configuration except that they store different color toners. Therefore, the configuration of one process unit 1Y will be described as an example.

  The process unit 1Y includes a photosensitive drum 2 as an electrostatic latent image carrier, a charging roller 3 as a charging unit for charging the surface of the photosensitive drum 2, and a development for forming a toner image on the surface of the photosensitive drum 2. A developing device 4 as a means, a cleaning blade 5 as a cleaning means for cleaning the surface of the photosensitive drum 2, and a static elimination lamp 6 as a static elimination means for neutralizing the surface of the photosensitive drum 2 are provided.

  Above each of the process units 1Y, 1C, 1M, and 1Bk, an exposure device 7 is disposed as an exposure unit that exposes the surface of the photosensitive drum 2. An intermediate transfer unit 8 is disposed below each process unit 1Y, 1C, 1M, 1Bk. The intermediate transfer unit 8 has an endless intermediate transfer belt 12 as an intermediate transfer member that carries a toner image. The intermediate transfer belt 12 is stretched around a plurality of rollers 9, 10, 11 such as a driving roller and a driven roller, and is configured to be able to run around in the direction of the arrow in the figure.

  On the inner peripheral surface of the intermediate transfer belt 12, four primary transfer rollers 13Y, 13C, 13M, and 13Bk as transfer means are disposed to face the four photosensitive drums 2. The four photosensitive drums 2 are in pressure contact with the outer peripheral surface of the intermediate transfer belt 12, and a primary transfer nip is formed at each pressure contact portion.

  A secondary transfer roller 14 is disposed at a position facing one roller 10 among the plurality of rollers over which the intermediate transfer belt 12 is stretched. The secondary transfer roller 14 is in pressure contact with the outer peripheral surface of the intermediate transfer belt 12, and a secondary transfer nip is formed at the pressure contact portion.

  A belt cleaning device 20 is disposed on the right side of the intermediate transfer belt 12 as a cleaning unit for cleaning the surface of the intermediate transfer belt 12.

  A recording medium supply unit 15 that accommodates a recording medium such as paper or an OHP sheet is disposed below the image forming apparatus. The recording medium supply unit 15 is provided with a supply roller for carrying out the recording medium (not shown).

  Between the recording medium supply unit 15 and the intermediate transfer unit 8, a pair of registration rollers 16a and 16b, a recording medium conveyance unit 17 having a conveyance belt stretched between a driving roller and a driven roller, and a fixing device 18 are disposed. Has been.

  The fixing device 18 includes, for example, a fixing roller 18a, an auxiliary roller 18b, a fixing belt 18c stretched between these rollers 18a and 18b, and a pressure roller 18d. The pressure roller 18d is in pressure contact with the fixing roller 18a via the fixing belt 18c, and forms a fixing nip at the pressure contact portion between the pressure roller 18d and the fixing belt 18c. Further, at least one of the fixing roller 18a and the auxiliary roller 18b has a heating source such as a heater.

  A discharge tray 19 for stocking the recording medium discharged to the outside is provided on the right side surface of the image forming apparatus.

  A reflective optical sensor 21 is disposed at a position facing the outer peripheral surface of the intermediate transfer belt 12.

  As shown in FIG. 2, the optical sensor 21 includes a light emitting unit 22 configured by an LED or the like, and two light receiving units 23 and 24 configured by a phototransistor or the like. One of the two light receiving units 23, 24 functions as a regular reflection light receiving unit that receives specular reflection light, and the other light receiving unit 24 is a diffuse reflection light receiving unit that receives diffuse reflection light. Function as.

  As shown in the block diagram of FIG. 3, the overall operation of the image forming apparatus is controlled by a control unit 25 configured by a computer or the like. The control means 25 is connected with a warning means 26 that issues a warning when an abnormality occurs in the optical sensor 21 and the like, and a cleaning means 27 that cleans the optical sensor 21.

The basic operation of the image forming apparatus will be described below with reference to FIG.
In the process unit 1Y, the photosensitive drum 2 is rotated in the direction of the arrow in the figure, and the surface of the photosensitive drum 2 is charged to a uniform high potential by the charging roller 3. Next, a laser beam is irradiated from the exposure device 7 to the surface of the photosensitive drum 2 based on the image data, and the potential of the irradiated portion is lowered to form an electrostatic latent image. The toner charged by the developing device 4 is electrostatically transferred to the portion of the electrostatic latent image formed on the surface of the photosensitive drum 2 to form a yellow toner image (visualization).

  The primary transfer roller 13Y is applied with a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner. As a result, a transfer electric field is formed in the primary transfer nip between the primary transfer roller 13Y and the photosensitive drum 2. Then, in the primary transfer nip, the toner image on the rotating photosensitive drum 2 is primarily transferred to the intermediate transfer belt 12 running in the direction of the arrow in the figure.

  In each of the other process units 1C, 1M, and 1Bk, a toner image is similarly formed on the photosensitive drum 2, and the four color toner images are primarily transferred to the intermediate transfer belt 12 so as to overlap each other.

  Further, the surface of the photosensitive drum 2 after the primary transfer process is cleaned by the cleaning blade 5 to remove residual toner. Further, the residual charge remaining on the surface of the photosensitive drum 2 is neutralized by the neutralizing lamp 6.

  On the other hand, a supply roller (not shown) disposed in the recording medium supply unit 15 is rotated to send out the recording medium P. The sent recording medium P is temporarily stopped by the registration rollers 16a and 16b.

  Further, a voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 14 to form a transfer electric field in the secondary transfer nip. Alternatively, a similar transfer electric field may be formed by applying a voltage having the same polarity as the charging polarity of the toner to the roller 10 facing the secondary transfer roller 14. Thereafter, the driving of the registration rollers 16a and 16b is resumed, and the recording medium P is sent to the secondary transfer nip in synchronism with the toner image on the intermediate transfer belt 12. Then, the toner image on the intermediate transfer belt 12 is collectively transferred onto the recording medium P by the transfer electric field formed in the secondary transfer nip. Further, after the secondary transfer, the toner remaining on the surface of the intermediate transfer belt 12 is removed by the belt cleaning device 20.

  The recording medium P to which the toner image has been transferred is conveyed to the fixing device 18. The recording medium P sent to the fixing device 18 is heated and pressurized when passing through the fixing nip between the fixing roller 18a and the pressure roller 18d, and the toner image is fixed on the recording medium P. Thereafter, the recording medium P is discharged to the discharge tray 19 and stocked.

  In addition, the image forming apparatus of the present invention is configured such that an image density can be controlled to an appropriate density by forming a toner pattern (tone pattern) for detecting the image density and detecting the toner adhesion amount of the toner pattern. Has been. The image density control method in the image forming apparatus of the present invention will be described below.

  In the same manner as the image forming operation described above, a toner pattern for image density detection is formed on the surface of each photosensitive drum 2, and the toner pattern is transferred onto the intermediate transfer belt 12. When the toner pattern on the intermediate transfer belt 12 is conveyed to a position facing the optical sensor 21 as the intermediate transfer belt 12 travels, the light emitted from the light emitting unit 22 of the optical sensor 21 is applied to the toner pattern. Is done. The light applied to the toner pattern is reflected and received by the two light receiving portions 23 and 24.

  At this time, since the background portion of the intermediate transfer belt 12 to which the toner is not attached is formed smoothly, the reflected light component at the background portion has a large regular reflection light component. On the other hand, since the toner adhesion portion of the toner pattern has a rough surface, the reflected light component at the toner adhesion portion has a larger diffuse reflection light component. By measuring the ratio of the regular reflection light component and the diffuse reflection light component in the reflected light, the toner adhesion amount of the toner pattern can be detected.

  Moreover, the ratio of the regular reflection light component in a reflected light and a diffuse reflection light component is measured on the basis of the regular reflection light component in a background part. Therefore, the output voltage value (output value) of the regular reflection light receiving unit 23 when the regular reflection light from the background is received is set to a preset specified voltage value (specified value). However, when the surface (background portion) of the intermediate transfer belt 12 is deteriorated, the output voltage value with respect to the reference background portion changes even when the same amount of light is emitted. Therefore, before the detection of the toner pattern by the optical sensor 21, the light emission amount of the light emitting unit 22 is corrected (calibrated) so that the output voltage value of the optical sensor 21 with respect to the background portion becomes a predetermined value. ing.

With reference to the flowchart of FIG. 4, the light emission amount correction method will be described.
First, the light emission amount of the light emitting unit 22 is set to a certain light emission amount L ₁ (S 11), and the background portion of the intermediate transfer belt 12 is irradiated with light with the light emission amount L ₁ . Then, the regular reflection light intensity at the background portion at this time is measured by the regular reflection light receiving unit 23 of the optical sensor 21. The intensity of the regular reflection light is measured as the output voltage value Vsg ₁ of the regular reflection light receiving unit 23 (S12). Further, the light emission amount L ₁ is changed to a different light emission amount L ₂ to irradiate the background portion with light, and similarly, the output voltage value Vsg ₂ of the regular reflection light receiving unit 23 is measured. In this way, the process of irradiating the background portion with the light emission amount L of the light emitting unit 22 and measuring the output voltage value Vsg at that time is repeated a predetermined number of times. Based on the data obtained by this measurement, a relational expression (approximate curve) indicating the relative relationship between the light emission amount L of the light emitting unit 22 and the output voltage value Vsg is calculated by the least square method (S13). Next, by using the calculated relational expression, the light emission amount Lcal is determined so that the output voltage value Vsg of the regular reflection light receiving unit 23 becomes a preset specified voltage value Vcal. Then, the light emission amount L is corrected to the light emission amount Lcal corresponding to the specified voltage value Vcal (S14).

  Further, in the present embodiment, after the light emission amount is corrected, it is confirmed whether or not the optical sensor 21 and the intermediate transfer belt 12 are normal.

  Specifically, as shown in the flowchart of FIG. 5, after performing the light emission amount correction (S21), it is determined whether or not the corrected light emission amount Lcal is within a preset normal range ( S22).

  When it is determined that the corrected light emission amount Lcal is higher than the upper limit value Lmax of the normal range (Lcal> Lmax), or it is determined that the corrected light emission amount Lcal is lower than the lower limit value Lmin of the normal range. If this is the case (Lcal <Lmin), there is a risk of contamination or failure of the optical sensor 21 or the occurrence of defective cleaning or scratches on the surface of the intermediate transfer belt 12, so a warning is issued by the warning means 26 (S24). On the other hand, when it is determined that the corrected light emission amount Lcal is between the upper limit value Lmax and the lower limit value Lmin of the normal range (Lmin ≦ Lcal ≦ Lmax), the process proceeds to the next step without issuing a warning.

  Next, the corrected light emission amount Lcal and the pre-correction light emission amount Lcal-past are compared, and the difference between the corrected light emission amount Lcal and the pre-correction light emission amount Lcal-past is a preset abnormality. It is determined whether or not a threshold value Z indicating occurrence has been exceeded (S23). In the image forming apparatus of the present invention, the light emission amount after each correction is stored by the control means 25, and the light emission amount after correction immediately before the current correction is set as the light emission amount Lcal-past before correction. deal with.

  If it is determined that the difference between the corrected light emission amount Lcal and the pre-correction light emission amount Lcal-past exceeds a preset threshold value Z, as described above, A warning is issued by the warning means 26 because there is a possibility of a failure or a cleaning failure of the surface of the intermediate transfer belt 12 or a scratch (S24). Further, after the warning is issued, the operation of the image forming apparatus is temporarily stopped so that the user can check and eliminate the abnormality. On the other hand, when it is determined that the difference between the corrected light emission amount Lcal and the pre-correction light emission amount Lcal-past does not exceed the preset threshold value Z, no warning is issued and the optical sensor 21 and the intermediate The confirmation operation is terminated because there is no abnormality in the transfer belt 12.

  Further, the flowchart of FIG. 6 shows another method for confirming whether the optical sensor 21 or the intermediate transfer belt 12 is normal. In this case, after correcting the light emission amount (S31), similarly to FIG. 5, the determination as to whether or not the corrected light emission amount is within the normal range (S32), the corrected light emission amount and the correction. It is determined whether or not the difference in the previous light emission amount exceeds the threshold value Z (S33). As a result, if it is determined that the light emission after correction is not within the normal range, or if it is determined that the difference between the light emission after correction and the light emission before correction exceeds the threshold value Z, an error occurs. It is stored in the control means 25 as there is.

  On the other hand, if it is determined that the corrected light emission amount is within the normal range, and it is determined that the difference between the corrected light emission amount and the light emission amount before correction does not exceed the threshold value Z, the optical sensor 21 The confirmation operation is terminated because there is no abnormality in the intermediate transfer belt 12.

  If there is an error, the cleaning unit 27 cleans the light emitting unit 22 and the regular reflection light receiving unit 23 of the optical sensor 21 (S35). Thereafter, the light emission amount is corrected again (S31), the determination of whether or not the light emission amount after correction is within the normal range (S32), and the difference between the light emission amount after correction and the light emission amount before correction is a threshold value. It is determined whether or not Z is exceeded (S33). As a result, if no error occurs, it is determined that the abnormality of the optical sensor 21 and the intermediate transfer belt 12 has been resolved, and the confirmation operation is terminated. If an error occurs, the optical sensor 21 is further cleaned (S35).

  As described above, the optical sensor 21 is repeatedly cleaned every time an error occurs. As a result, when it is determined that the number of errors has reached a predetermined number X set in advance (S34), the optical sensor 21 is cleaned. It is determined that the abnormality cannot be resolved even if it is performed, and a warning is issued by the warning means 26 (S36).

FIG. 7 shows a flowchart of the image density control method of the present invention.
As shown in the flowchart of FIG. 7, after the light emission amount correcting step (S41) and the optical sensor 21 and the intermediate transfer belt 12 are confirmed to be abnormal (S42), the intermediate transfer belt 12 is checked. A step of calculating the glossiness of the background portion (S43) is performed.

  Specifically, information indicating the relative relationship between the light emission amount of the light emitting portion and the glossiness of the background portion of the intermediate transfer member is stored in the control unit 25 in advance, and information indicating this relative relationship is used. Thus, the glossiness G corresponding to the light emission amount Lcal of the light emitting unit 22 after correction is calculated.

  Next, a secondary transfer rate for transferring the toner image from the intermediate transfer belt 12 to the recording medium is calculated (S44). Here, the secondary transfer rate is a rate at which the toner on the intermediate transfer belt is transferred onto the recording medium when the toner image is secondarily transferred from the intermediate transfer belt 12 to the recording medium. In this embodiment, information indicating the relative relationship between the glossiness of the background portion of the intermediate transfer belt 12 and the secondary transfer rate is acquired in advance, and the information is stored in the control means 25. Then, a secondary transfer rate E corresponding to the calculated glossiness G is calculated based on the stored information indicating the relative relationship between the glossiness and the secondary transfer rate.

  In addition to the glossiness of the intermediate transfer belt 12, the secondary transfer rate varies depending on the use environment of the image forming apparatus such as temperature and humidity, the durability of the toner, and the like. Accordingly, the secondary transfer rate may be calculated in consideration of the use environment of the image forming apparatus, the durability state of the toner, and the like. For example, a category is set for each temperature / humidity state, and the relative value of the index T (developing device drive time, number of printed sheets, etc.) indicating the toner durability state and the secondary transfer rate correction rate α for each category. Stores a function indicating the relationship. The correction rate α may be calculated based on the function, and the secondary transfer rate may be corrected by multiplying the calculated secondary transfer rate E by the correction rate α.

Based on the calculated secondary transfer rate, a target value of the toner adhesion amount on the intermediate transfer belt 12 is calculated (S45). Here, the toner adhesion amount on the intermediate transfer belt 12 is the toner adhesion amount on the intermediate transfer belt 12 when the toner image is primarily transferred from the photosensitive drum 2 to the intermediate transfer belt 12. The amount of toner adhesion on the intermediate transfer belt 12 when the toner image is primarily transferred to the intermediate transfer belt 12 is m, the secondary transfer rate of the toner image is E, and the recording when the toner image is secondarily transferred to the recording medium When the toner adhesion amount on the medium is M, the relative relationship among m, E, and M is expressed by the following mathematical formula (1).
m × E = M ... Formula (1)

  The optimum value of the toner adhesion amount M on the recording medium is set in advance. Then, by substituting the optimum value of the toner adhesion amount M on the recording medium and the calculated secondary transfer rate E into the mathematical formula (1), the target value of the toner adhesion amount m on the intermediate transfer belt 12 is obtained. Can be calculated.

  Thereafter, as described above, a toner pattern is formed on the intermediate transfer belt 12 (S46), and the toner adhesion amount on the intermediate transfer belt 12 is detected by measuring the toner pattern with an optical sensor. The image forming conditions are corrected so that the toner adhesion amount detected at this time becomes the calculated target value (S48). The image forming conditions are corrected by controlling at least one of the charging bias of the charging roller 3, the developing bias of the developing device 4, and the exposure amount of the exposure device 7. By controlling the developing bias, the thickness of the toner layer of the toner image can be adjusted. Further, by controlling the charging bias or the exposure amount, it is possible to adjust the dot size (gradation reproducibility) of the toner image. As a result, the density of the toner image transferred to the recording medium can be maintained at an appropriate density, and a high-quality image can be provided.

  It should be noted that the glossiness of the intermediate transfer belt 12 (S43) can be detected independently at another timing without being continuously performed when the light emission amount is corrected (S41). However, as in the above embodiment, the time required to detect the glossiness is detected by detecting the glossiness of the intermediate transfer belt 12 based on the information (corrected light emission amount) obtained at the time of correcting the light emission amount. In addition, the time required for correcting the light emission amount can be partially overlapped, and the total processing time required for adjusting the image density can be shortened. Thereby, the waiting time of the user at the time of image density adjustment can be shortened.

  In addition, the image forming apparatus of the present invention is configured to perform both toner pattern detection and glossiness detection by one optical sensor 21. For this reason, it is not necessary to dispose the optical sensor for detecting the toner pattern and the optical sensor for detecting the glossiness independently, thereby realizing cost reduction and space saving.

  Although one example of the image forming apparatus of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. It is. For example, the configuration of the present invention is not limited to the so-called quadruple tandem type image forming apparatus in which a plurality of photosensitive drums shown in FIG. 1 are arranged, and images of different colors are sequentially transferred by one photosensitive drum. The present invention can also be applied to a so-called four-pass image forming apparatus. Further, the developer used in the image forming apparatus of the present invention may be a one-component developer or a two-component developer.

1 is an overall configuration diagram of an image forming apparatus of the present invention. 1 is a schematic view of an optical sensor provided in an image forming apparatus of the present invention. 1 is a block diagram of an image forming apparatus of the present invention. It is a flowchart figure which shows the correction method of light emission amount. It is a flowchart figure which shows the method of abnormality confirmation. It is a flowchart figure which shows another method of abnormality confirmation. It is a flowchart figure which shows the control method of image density.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Photosensitive drum 3 Charging roller 4 Developing apparatus 7 Exposure apparatus 12 Intermediate transfer belt 21 Optical sensor 22 Light emission part 23 Regular reflection light light reception part 24 Diffuse reflection light reception part 26 Warning means 27 Cleaning means

Claims (10)

An image carrier that carries a toner image, a charging unit that charges the image carrier, an exposure unit that exposes a charged surface of the image carrier to form an electrostatic latent image, and an image carrier formed on the image carrier A developing means for supplying toner to the formed electrostatic latent image to form a toner image, and an intermediate for primary transfer of the toner image from the image carrier and secondary transfer of the primary transferred toner image to a recording medium An optical sensor having a transfer body, a light emitting section for irradiating light, a regular reflection light receiving section for receiving specular reflection light, and a diffuse reflection light receiving section for receiving diffuse reflection light, is formed on the intermediate transfer body. Image formation configured to detect the toner adhesion amount of the toner pattern by measuring the ratio between the diffuse reflection light component of the toner adhesion portion of the toner pattern and the regular reflection light component of the background portion of the intermediate transfer body by the optical sensor. Device smell ,
An image forming apparatus configured to calculate a glossiness of a background portion based on a regular reflection light intensity of the background portion measured by the optical sensor. An image forming apparatus configured to correct a light emission amount of a light emitting unit of the optical sensor so that a regular reflection light intensity of the background portion measured by the optical sensor becomes a preset specified value,
The glossiness of the background portion corresponding to the corrected light emission amount is calculated based on information indicating a relative relationship between the light emission amount of the light emitting portion and the glossiness of the background portion. The image forming apparatus described.   The image forming apparatus according to claim 2, wherein the correction of the light emission amount and the calculation of the glossiness are performed immediately before forming a toner pattern on the intermediate transfer member.   The secondary transfer rate of the toner image corresponding to the calculated glossiness is calculated based on information indicating a relative relationship between the glossiness of the background portion and the secondary transfer rate of the toner image. The image forming apparatus according to any one of 1 to 3. The amount of toner adhesion on the intermediate transfer body when the toner image is primarily transferred to the intermediate transfer body is m, the secondary transfer rate of the toner image is E, and the recording medium when the toner image is secondarily transferred to the recording medium When the upper toner adhesion amount is M and the relative relationship among m, E, and M is expressed by the following formula (1), the calculated secondary transfer rate of toner density and the toner adhesion on the preset recording medium The image forming apparatus according to claim 4, wherein the target value of the toner adhesion amount on the intermediate transfer member is calculated by substituting the optimum value of the amount into the following formula (1).
m × E = M ... Formula (1)   The image forming apparatus according to claim 5, wherein the image forming condition is controlled so that a target value of the toner adhesion amount on the intermediate transfer member becomes the calculated target value.   The image forming apparatus according to claim 6, wherein the image forming condition is controlled by controlling at least one of the charging unit, the exposure unit, and the developing unit.   The image forming apparatus according to claim 2, further comprising a warning unit that issues a warning when the corrected light emission amount is out of a preset normal range.   9. The image forming apparatus according to claim 2, further comprising a warning unit that issues a warning when a difference between the light emission amount before correction and the light emission amount after correction exceeds a preset threshold value indicating occurrence of abnormality.   The image forming apparatus according to claim 8, further comprising a cleaning unit that cleans the optical sensor, wherein the optical sensor is cleaned by the cleaning unit when the warning unit issues a warning.

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