JP2008122814A - Image forming apparatus and dew condensation determination method for same apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exactly determine the presence or absence of dew condensation in an image forming apparatus. <P>SOLUTION: In a density control operation for optimizing image forming conditions based on the result of detecting the density of a patch image, the density of the patch image is sampled (step S102). When the density is too low, a dew condensation determination operation is performed for determining the presence or absence of dew condensation in the apparatus (step S111). The dew condensation determination is made based on the temperature in the apparatus and the result of the detection of humidity. If the density of the patch image is too low and the environment in the apparatus is in condition that easily cause dew condensation, it is determined that cause of insufficient density is dew condensation. If it is determined that dew condensation has occurred, a condensation removal operation (step S113) is performed by rotating an intermediate transfer belt, and so on for a predetermined time, thereby removing dew condensation. Then, a patch image formation is carried out again (steps S101 and S102). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for determining the presence or absence of condensation that may occur in an image forming apparatus.

  In an image forming apparatus that forms an image using toner, such as a copying machine, a printer, and a facsimile machine, depending on the use conditions, condensation may occur in the apparatus, and normal operation may not be desired. As a technique for dealing with such a problem, for example, there are techniques described in Patent Document 1 and Patent Document 2. In the technique described in Patent Document 1, a heater for eliminating condensation is provided inside the apparatus, and heating by the heater is started when a time set by a user setting has elapsed after the apparatus is turned off. Therefore, condensation is eliminated before the power is turned on. Further, in the technique described in Patent Document 2, condensation on the exposure unit is removed without providing a heater. That is, when the laser light from the exposure unit is not detected by the light detection sensor provided at a predetermined position under the condition where the occurrence of condensation is predicted, the motor for rotating the rotary polygon mirror and the ventilation fan are driven for a predetermined time. To remove condensation.

JP-A-6-194902 (FIG. 3) JP 2006-91206 A (FIG. 4)

  This type of image forming apparatus is not provided with a configuration for directly detecting the presence or absence of condensation. That is, the possibility of condensation is only indirectly detected from the detection results of the temperature and humidity in or around the apparatus. Therefore, when there is a possibility of condensation, processing for uniformly removing condensation is performed regardless of whether or not condensation that actually affects the operation of the apparatus has occurred. . As a result, in the conventional technique, even when condensation is not actually generated, the process for removing condensation is executed, which may result in waste of power consumption and processing time. Further, since the dew condensation is not detected over the entire system related to the image formation, there is a problem that it is not possible to cope with the dew condensation generated locally.

  The present invention has been made in view of the above problems, and an object thereof is to provide a technique capable of accurately determining the presence or absence of condensation that may occur in an image forming apparatus.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an image carrier that can carry a toner image, an image forming unit that forms a toner image and carries the toner image on the image carrier, and the image forming unit Density detection means for detecting the density of a toner image as a patch image formed on the image carrier, environment detection means for detecting at least one of temperature and humidity in the apparatus, and density detection by the density detection means And control means for performing dew condensation determination for determining the presence or absence of dew condensation in the apparatus based on the result and the environment detection result by the environment detection means.

  According to another aspect of the present invention, there is provided a method for determining condensation in an image forming apparatus that forms a toner image as a patch image on an image carrier and detects the density thereof, and determines at least one of temperature and humidity in the image forming apparatus. It is detected as an internal environment of the apparatus, and the presence or absence of condensation in the apparatus is determined based on the density detection result of the patch image and the internal environment detection result of the apparatus.

  In the invention configured as described above, the density detection result of the actually formed patch image and the environment detection result in the apparatus are integrated to determine the presence or absence of condensation. In order for the density detection result of the patch image to be appropriate, it is necessary that the patch image itself is formed with an appropriate density and that the density is appropriately detected. Therefore, the density detection result of the actually formed patch image reflects the overall status of the apparatus including both the part related to image formation and the part related to density detection. By determining the density detection result in consideration of the environment detection result in the apparatus, it is possible to accurately determine the presence or absence of condensation that may occur in the image forming apparatus.

  Here, for example, a density control operation for controlling the image density is performed by optimizing the operating conditions of the image forming unit when forming a toner image based on the density detection result of the patch image, and the density control operation is performed. The dew condensation determination may be performed based on the density detection result of the patch image formed in step S2. By doing so, it is not necessary to individually form patch images for the density control operation and the dew condensation determination, so that wasteful toner consumption can be suppressed and processing time can be shortened.

  As a more specific aspect, for example, when the density detection result of the patch image is not within a predetermined appropriate range, the dew condensation determination can be performed based on the environment detection result. When the density detection result of the patch image is not within a predetermined appropriate range, condensation may occur in any part of the apparatus, but there may be other abnormalities. Therefore, in such a case, by making a determination together with the environment detection result, it is possible to determine the presence or absence of condensation in a manner distinct from other abnormalities.

  In particular, it is preferable to perform the condensation determination when the density detection result of the patch image does not reach the lower limit value of the appropriate range. An image density abnormality caused by condensation often appears to be less than the original density because the toner contains moisture or water droplets adhere to the image carrier. That is, the influence of dew condensation is particularly suspected when the concentration detection result is lower than the appropriate range. Thus, in such a case, the presence or absence of condensation can be accurately determined by making a determination together with the environment detection result.

  In this case, when the environment detection unit is a temperature sensor that detects the temperature in the apparatus, in the dew condensation determination, it may be determined that there is dew condensation when the temperature detected by the temperature sensor is lower than a predetermined temperature. The “predetermined temperature” here is preferably selected to a temperature at which the possibility of dew condensation is increased when the apparatus is left in an environment below that temperature, and can be, for example, about 5 degrees Celsius. . This is because when the patch image density becomes abnormal under such temperature conditions, it is very likely that the cause is due to condensation.

  Further, when the environment detection unit is a humidity sensor that detects humidity in the apparatus, in the dew condensation determination, it may be determined that dew condensation is present when the humidity detected by the humidity sensor is higher than a predetermined humidity. The “predetermined humidity” here is preferably selected to be a humidity at which the possibility of dew condensation is increased when the apparatus is left in an environment above that humidity. For example, the relative humidity may be about 90%. it can. This is because when the patch image density becomes abnormal under such a humidity condition, it is very likely that the cause is due to condensation.

  Further, when the environment detection means is configured to detect the temperature and humidity in the apparatus, in the dew condensation determination, when the detected temperature is higher than a predetermined temperature and the humidity is lower than the predetermined humidity, there is no dew condensation. You may make it determine. By determining the presence or absence of condensation based on the combination of temperature and humidity, the determination of condensation can be performed with higher accuracy. Further, even if the density of the patch image is abnormal under conditions of high temperature or low humidity, there is a high possibility that it is not due to condensation.

  Further, it is desirable that the dew condensation determination be performed at least immediately after the apparatus is turned on. This is because condensation is most likely to occur when the device is not warmed immediately after power-on. Further, the subsequent operation can be optimized by performing the dew condensation determination immediately after the power is turned on. For example, it is possible to prevent an image with inferior quality from being output as a result of forming an image with condensation.

  Further, when it is determined by the condensation determination that condensation is present, the condensation determination may be performed again after a predetermined time has elapsed. Since condensation is eliminated with the passage of time, it is possible to determine whether or not condensation has been eliminated by performing the condensation determination again after a period of time.

  Further, when it is determined by the condensation determination that condensation is present, a condensation elimination operation for eliminating condensation may be further executed. By doing so, it is possible to remove the condensation in a shorter time than when waiting for the condensation to be eliminated naturally, and to use the apparatus for image formation at an early stage. This condensation elimination operation may be performed whenever it is determined that condensation is present, and only when an image formation request is input from the outside after it is determined that condensation is present, prior to forming an image based on the request. May be performed. Even if it is determined that there is condensation, if the image is not formed immediately thereafter, it is expected that the condensation will be naturally eliminated during the standby time.

  In the following, two embodiments of an image forming apparatus to which the present invention is applied will be described. The apparatus configuration in both embodiments is the same, and only the mode of the control operation is different between the two embodiments. Therefore, the apparatus configuration common to both embodiments will be described first, and then the details of the control operation in each of the two embodiments will be described.

(Explanation of device configuration)
FIG. 1 is a diagram showing a configuration example of an image forming apparatus to which the present invention can be preferably applied. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus forms a full color image by superposing four color toners (developers) of yellow (Y), cyan (C), magenta (M), and black (K), or only black (K) toner. The image forming apparatus forms a monochrome image using In this image forming apparatus, when an image signal is given to the main controller 11 from an external device such as a host computer, the CPU 101 provided in the engine controller 10 controls each part of the engine unit EG in response to a command from the main controller 11. Then, a predetermined image forming operation is executed, and an image corresponding to the image signal is formed on the sheet S.

  In the engine unit EG, the photosensitive member 22 is provided to be rotatable in the arrow direction D1 in FIG. A charging roller 23, a rotary developing unit 4 and a cleaning unit 25 are arranged around the photosensitive member 22 along the rotation direction D1. The charging roller 23 is applied with a predetermined charging bias, and charges the outer peripheral surface of the photosensitive member 22 to a predetermined surface potential. The cleaning unit 25 removes the toner remaining on the surface of the photosensitive member 22 after the primary transfer, and collects it in a waste toner tank provided inside. The photosensitive member 22, the charging roller 23, and the cleaning unit 25 integrally constitute the photosensitive member cartridge 2, and the photosensitive member cartridge 2 is detachably attached to the apparatus main body as a whole.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 22 charged by the charging roller 23. The exposure unit 6 exposes the light beam L onto the photosensitive member 22 in accordance with an image signal given from an external device, and forms an electrostatic latent image corresponding to the image signal.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. That is, in this apparatus, the developing unit 4 is configured as a support frame 40 that is rotatably provided around a rotation axis that is orthogonal to the paper surface of FIG. A yellow developing unit 4Y, a cyan developing unit 4C, a magenta developing unit 4M, and a black developing unit 4K are provided. The developing unit 4 is rotationally driven in the arrow direction D3 by a developing unit drive motor (not shown) which is a stepping motor controlled by the engine controller 10. Further, the apparatus main body is provided with a rotary lock 45 that comes into contact with and separates from the developing unit 4. If necessary, the rotary lock 45 abuts on the outer peripheral portion of the support frame 40 of the developing unit 4 to act as a brake and lock mechanism that restrains the rotation of the developing unit 4 and stops and positions the developing unit 4 at a predetermined position. .

  Then, based on a control command from the engine controller 10, the developing unit 4 is driven to rotate, and when these developing devices 4 Y, 4 C, 4 M, and 4 K are selectively positioned at a developing position that faces the photoreceptor 22. A developing roller 44 that is provided in the developing unit and carries toner of a selected color is disposed to face the photosensitive member 22 with a predetermined gap therebetween, and the surface of the photosensitive member 22 from the developing roller 44 at the opposed position. Toner is applied. As a result, the electrostatic latent image on the photosensitive member 22 is visualized (developed) with the selected toner color.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 stretched between a plurality of rollers 72 to 75, and a drive unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction D2 by rotationally driving the roller 73. It has. When a color image is transferred to the sheet S, the color toner images formed on the photosensitive member 22 are superimposed on the intermediate transfer belt 71 to form a color image, and the color image is taken out from the cassette 8 and conveyed. The color image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2 along the FF.

  The secondary transfer region TR2 is a nip portion where the surface of the intermediate transfer belt 71 stretched over the roller 73 and the secondary transfer roller 86 that contacts and separates from the belt surface. The sheets S stacked and stored in the cassette 8 are taken out one by one by the rotation of the pickup roller 88 and placed on the transport path FF. Then, the feed rollers 84 and 85 and the gate roller 81 are rotated and conveyed to the secondary transfer region TR2 along the conveyance path FF.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet S, the timing of feeding the sheet S to the secondary transfer region TR2 is managed. Specifically, it is as follows. A gate roller 81 is provided on the front side of the secondary transfer region TR2 on the transport path FF, and a pre-gate sheet detection sensor 801 is further provided on the front side thereof. When the pre-gate sheet detection sensor 801 detects that the sheet S conveyed on the conveyance path FF has arrived, the conveyance of the sheet S is temporarily stopped and synchronized with the timing of the circumferential movement of the intermediate transfer belt 71. By restarting the rotation of the gate roller 81, the sheet S is fed into the secondary transfer region TR2 at a predetermined timing. In this way, the toner image formed on the intermediate transfer belt 71 is secondarily transferred onto the surface of the sheet S passing through the secondary transfer region TR2.

  The sheet S on which the color image is thus formed is fixed with the toner image by the fixing unit 9 and is conveyed to the discharge tray portion 89 provided on the upper surface portion of the apparatus main body via the pre-discharge roller 82 and the discharge roller 83. Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reversal position PR behind the pre-discharge roller 82. The rotation direction of the discharge roller 83 is reversed, whereby the sheet S is conveyed in the direction of the arrow D4 along the reverse conveyance path FR. Then, it is placed again on the transport path FF before the gate roller 81. At this time, the image is transferred first on the surface of the sheet S that contacts the intermediate transfer belt 71 and transfers the image in the secondary transfer region TR2. It is the opposite surface. In this way, images can be formed on both sides of the sheet S.

  In addition to the above-mentioned pre-gate sheet detection sensor 801, sheet detection sensors 802 to 804 for detecting whether or not a sheet has passed on the path are provided at positions on the sheet conveyance path FF and the reverse conveyance path FR. The sheet conveyance timing is managed based on the outputs of these sensors, and jam detection is performed at each position.

  A cleaner 76 is disposed in the vicinity of the roller 75. The cleaner 76 includes a cleaner blade 761 that can move toward and away from the roller 75 by an electromagnetic clutch (not shown), and a waste toner tank 762. Then, the cleaner blade 761 abuts on the surface of the intermediate transfer belt 71 stretched over the roller 75 in a state of moving to the roller 75 side, and the toner remaining on the outer peripheral surface of the intermediate transfer belt 71 after the secondary transfer is removed. Remove by scraping. The toner scraped off is stored in a waste toner tank 762. The waste toner tank 762 is provided with a waste toner sensor 763 for detecting that the tank is full.

  The cleaner blade 761 is controlled to be separated and abutted so as to remove the toner remaining on the intermediate transfer belt 71 in the same rotation when the image is transferred to the sheet S in the secondary transfer region TR2. The Therefore, for example, when the apparatus continuously forms monochrome images, the image transferred to the intermediate transfer belt 71 in the primary transfer region TR1 is immediately transferred to the sheet S in the secondary transfer region TR2, and thus the cleaner blade 761. Is held in contact. On the other hand, when forming a color image, it is necessary to keep the cleaner blade 761 away from the intermediate transfer belt 71 while the toner images of the respective colors are superimposed on each other. Then, the toner images of the respective colors are superimposed on each other to complete a full-color image, and the cleaner blade 761 is brought into contact with the intermediate transfer belt 71 in order to remove residual toner in the same rotation as the secondary transfer onto the sheet S. The Rukoto.

  Further, a density sensor 60 and a vertical synchronization sensor 77 are arranged in the vicinity of the roller 75. The density sensor 60 is provided to face the surface of the intermediate transfer belt 71 and measures the image density of the toner image formed on the outer peripheral surface of the intermediate transfer belt 71 as necessary. Based on the measurement results, this apparatus adjusts the operating conditions of each part of the apparatus that affects the image quality, for example, the developing bias applied to each developing device, the intensity of the light beam L, and the like. The density sensor 60 is configured to output a signal corresponding to the image density of a region of a predetermined area on the intermediate transfer belt 71 using, for example, a reflection type photosensor. The CPU 101 can detect the image density of each part of the toner image on the intermediate transfer belt 71 by periodically sampling the output signal from the density sensor 60 while rotating the intermediate transfer belt 71.

  The vertical synchronization sensor 77 is a sensor for detecting the reference position of the intermediate transfer belt 71 and is used to obtain a synchronization signal output in association with the rotational drive of the intermediate transfer belt 71, that is, a vertical synchronization signal Vsync. Functions as a sensor. In this apparatus, the operation of each part of the apparatus is controlled based on the vertical synchronization signal Vsync in order to align the operation timing of each part and accurately superimpose the toner images formed in the respective colors.

  Further, a temperature / humidity sensor 90 for detecting the temperature and humidity in the apparatus is provided in the vicinity of the engine unit EG inside the apparatus. The CPU 101 can grasp the temperature and humidity in the apparatus based on the output of the temperature / humidity sensor 90. Moreover, it can be determined from the relationship between the detected temperature and humidity whether or not the inside of the apparatus is in a condition where condensation is likely to occur.

  Further, memory tags 49Y, 49C, 49M, and 49K are respectively attached to the outer peripheral surfaces of the developing devices 4Y, 4C, 4M, and 4K that correspond to the side surfaces of the developing unit 4 that has a substantially cylindrical shape as a whole. For example, a memory tag 49Y attached to the yellow developing device 4Y is electrically connected to the memory 491Y for storing data relating to the manufacturing lot and usage history of the developing device, the remaining amount of built-in toner, and the like. Loop antenna 492Y. In addition, memory chips 491C, 491M, and 491K and loop antennas 492C, 492M, and 492K are also provided in the memory tags 49C, 49M, and 49K provided in the other developing devices, respectively.

  On the other hand, a wireless communication antenna 109 is also provided on the apparatus main body side. The wireless communication antenna 109 is driven by a transceiver 105 connected to the CPU 101, and by performing wireless communication with the wireless communication antenna on the developing device side, the CPU 101 and a memory provided in the developing device Various data such as consumables management related to the developing device are managed by transmitting and receiving data between them.

  Further, as shown in FIG. 2, this apparatus includes a display unit 12 that is controlled by the CPU 111 of the main controller 11. The display unit 12 is constituted by, for example, a liquid crystal display, and in accordance with a control command from the CPU 111, the operation guidance to the user, the progress of the image forming operation, the occurrence of an abnormality in the apparatus, the replacement timing of any unit, etc. A predetermined message for notification is displayed.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing an image given from an external device such as a host computer via the interface 112. Reference numeral 106 is a ROM for storing a calculation program executed by the CPU 101, control data for controlling the engine unit EG, and the like. Reference numeral 107 is a RAM for temporarily storing calculation results in the CPU 101 and other data. is there.

  FIG. 3 is a diagram showing the configuration of the density sensor. The density sensor 60 includes a light emitting element 601 such as an LED that irradiates light to a winding area 71 a that is wound around the roller 75 in the surface area of the intermediate transfer belt 71. Further, the density sensor 60 includes a polarization beam splitter 603, an irradiation beam for adjusting the irradiation light amount of the irradiation light in accordance with the light amount control signal Slc provided from the CPU 101 via the light amount control signal conversion unit 680 as will be described later. A light amount monitoring light receiving unit 604 and an irradiation light amount adjusting unit 605 are provided.

  As shown in FIG. 3, the polarization beam splitter 603 is disposed between the light emitting element 601 and the intermediate transfer belt 71, and the light emitted from the light emitting element 601 is incident on the intermediate transfer belt 71. It is divided into p-polarized light having a polarization direction parallel to the plane and s-polarized light having a perpendicular polarization direction. The p-polarized light enters the intermediate transfer belt 71 as it is, while the s-polarized light is extracted from the polarization beam splitter 603 and then incident on the light receiving unit 604 for monitoring the amount of irradiation light. The light receiving element 642 of the light receiving unit 604 A signal proportional to the irradiation light amount is output to the irradiation light amount adjustment unit 605.

  The irradiation light amount adjusting unit 605 feedback-controls the light emitting element 601 based on the signal from the light receiving unit 604 and the light amount control voltage Vlc output from the CPU 101, and the irradiation light amount irradiated from the light emitting element 601 to the intermediate transfer belt 71. Is adjusted to a value corresponding to the light amount control voltage Vlc. As described above, in this embodiment, the amount of irradiation light can be appropriately changed and adjusted in a wide range by the output signal from the CPU 101.

  Further, in this embodiment, the input offset voltage 641 is applied to the output side of the light receiving element 642 provided in the light receiving unit 604 for monitoring the irradiation light quantity, and the light emitting element as long as the light quantity control voltage Vlc does not exceed a certain signal level. 601 is configured to be kept off. The input offset voltage 641 is provided to prevent the light emitting element 601 from emitting light when the light amount control voltage Vlc is zero due to the variation in characteristics of the light emitting element 601, and to reliably turn off the light. This is to turn off the light.

  On the other hand, when the light amount control voltage Vlc exceeding the predetermined signal level is applied to the irradiation light amount adjustment unit 605, the light emitting element 601 is turned on and the intermediate transfer belt 71 is irradiated with p-polarized light as irradiation light. Then, the p-polarized light is reflected by the intermediate transfer belt 71, and the reflected light amount detection unit 607 detects the p-polarized light amount and the s-polarized light amount among the light components of the reflected light, and a signal corresponding to each light amount is sent to the CPU 101. Is output.

  As shown in FIG. 3, the reflected light amount detection unit 607 receives the polarized beam splitter 671 disposed on the optical path of the reflected light and the p-polarized light passing through the polarized beam splitter 671, and corresponds to the light amount of the p-polarized light. And a light receiving unit 670s that receives the s-polarized light divided by the polarization beam splitter 671 and outputs a signal corresponding to the light quantity of the s-polarized light. In the light receiving unit 670p, the light receiving element 672p receives the p-polarized light from the polarization beam splitter 671, and the output from the light receiving element 672p is amplified by the amplifier circuit 673p, and then the amplified signal is a signal corresponding to the amount of p-polarized light. Is output from the light receiving unit 670p. Similarly to the light receiving unit 670p, the light receiving unit 670s includes a light receiving element 672s and an amplifier circuit 673s. For this reason, the light quantity of two different component light (p polarized light and s polarized light) among the light components of reflected light can be calculated | required independently.

  In this embodiment, output offset voltages 674p and 674s are applied to the output sides of the light receiving elements 672p and 672s, respectively, and the output voltages Vp and Vs of the signals given from the amplifier circuits 673p and 673s to the CPU 101 are on the plus side. It is offset. This is to eliminate the influence of the so-called dead band in which the amount of received light does not change in the output voltage from the amplifier circuits 673p and 673s in the region where the received light is weak and the output from the light receiving elements 672p and 672s is small. is there. Thus, by applying the output offset voltages 674p and 674s, the influence of the dead zone can be surely eliminated, and an output voltage corresponding to the amount of reflected light can be output.

  Next, the density control operation of the image forming apparatus configured as described above will be described. In this image forming apparatus, the following explanation is given at the timing when the apparatus is turned on, when any unit is replaced, when returning from the sleep state, and when the number of image forming sheets reaches a predetermined number. The CPU 101 executes the density control operation to optimize the operation conditions of the apparatus in the image forming operation so that an image can always be formed with good image quality.

(First embodiment)
FIG. 4 is a flowchart showing the density control operation of the first embodiment. The density control operation shown in the flowchart of FIG. 4 is an operation for controlling the image density by optimizing the developing bias and the exposure power as density control factors for each toner color. In this density control operation, one developing unit is positioned at a developing position facing the photosensitive member 22, and a predetermined high density patch image is formed with each developing bias value while changing the developing bias applied to the developing roller 44 in multiple stages. It is formed on the intermediate transfer belt 71 (step S101). The image pattern of the patch image is preferably a high-density image having a large density change with respect to a change in development bias, and can be a solid image, for example.

  The high density patch image thus formed is irradiated with light by the density sensor 60 and the reflected light is received, and the CPU 101 samples the output of the density sensor 60 at regular intervals (step S102). Then, the image density of the patch image is obtained from the sampling result, and it is determined whether or not the density detection result is too small (step S103). This determination may be performed for all patch images while changing and setting the development bias, but typically only some of the density detection results may be used. For example, the determination can be made based on whether or not a patch image formed with the development bias set to the largest value has reached a predetermined minimum reference density.

  If the patch image density is too low, the dew condensation determination (step S111) is executed. The operation will be described later. First, the operation when it is not too low will be described. In this case, the optimum value of the development bias (optimum development bias) is calculated from the density detection result of the patch image (step S104). Subsequently, with the development bias set to the optimum value thus obtained (step S105), a patch image is formed with each energy value while changing and setting the exposure energy in multiple stages (step S106). The patch image here preferably has a relatively low density. For example, a halftone image or an image composed of isolated dot lines of about 1 on 10 off can be used.

  Then, the amount of reflected light is sampled for each patch image and its density is detected (step S107). From the density detection result thus obtained, an optimum value of exposure energy (optimum exposure energy) for forming a low density patch image with a predetermined low density side target density is calculated (step S108). As a result, the development bias and exposure energy are optimized, and an image can be formed with a desired image density. There are many known techniques for detecting the density of a patch image and controlling the image density based on the detection result, and such known techniques can also be applied to the density control operation of this embodiment. Since it is possible, detailed explanation is omitted here.

  FIG. 5 is a flowchart showing the dew condensation determination operation. This operation is executed when the density of the patch image formed in the density control operation is too low. First, in order to determine whether or not the environment in the apparatus is a condition that tends to cause condensation, the output of the temperature and humidity sensor 90 provided in the vicinity of the engine unit EG is detected, and information on the temperature and humidity in the apparatus is obtained. Obtain (step S201). Here, when the temperature in the apparatus is a predetermined temperature, for example, 5 degrees Celsius or less (step S202), it is considered that the apparatus is in a condition where condensation is likely to occur. From this fact and the fact that the density detection result of the formed patch image is too small, it can be determined that there is condensation in the apparatus (step S205).

  Note that the reason why the density detection result of the patch image becomes abnormal due to dew condensation is that the image forming operation is hindered due to dew condensation and the density of the patch image itself is insufficient, and the density due to adhesion of water droplets or the like to the density sensor 60. Both cases where the detection cannot be performed correctly are considered. According to the experiments by the inventors of the present application, it has been found that in any case, the concentration detection result has a very strong tendency to shift to a lower direction. Therefore, when the density detection result of the patch image is too small and the inside of the apparatus is in a low temperature environment, the occurrence of condensation is suspected.

  Even if the temperature in the apparatus is equal to or higher than a predetermined temperature, it can be said that if the humidity is high, condensation is likely to occur. Therefore, the humidity in the apparatus detected by the temperature / humidity sensor 90 is determined (step S203). When the humidity in the apparatus is a predetermined humidity or higher, for example, a relative humidity of 90% or higher, there is a high possibility that the cause of insufficient concentration is dew condensation. In this case, therefore, it is determined that there is condensation (step S205). On the other hand, when the temperature in the apparatus is higher than the predetermined temperature and the humidity is lower than the predetermined humidity, the possibility of condensation is low. Therefore, in such a case, it is determined that there is no condensation (step S204).

  Returning to FIG. 4, the concentration control operation after the dew condensation determination operation will be described. The operation after the condensation determination is different depending on the result of the condensation determination (step S112). That is, when it is determined in the dew condensation determination that dew condensation is present, a predetermined dew condensation eliminating operation (step S113) for eliminating dew condensation in the apparatus is subsequently performed, and then a patch image is formed again. As the dew condensation eliminating operation, for example, it is conceivable that the rotating operation of the charging roller 23, the photosensitive member 22, and the intermediate transfer belt 71 is continuously performed for a predetermined time. By doing so, heat generation and air flow are generated inside the apparatus, and moisture removal due to condensation is promoted. In this case, it is desirable to keep the cleaner blade 761 in contact with the intermediate transfer belt 71. This is because the moisture removal effect from the intermediate transfer belt 71 by the cleaner blade 761 can be expected. Further, as another aspect of the condensation elimination operation, exhaust heat from the fixing unit may be introduced into the engine unit EG as in a known technique.

  Therefore, in the density control operation of this embodiment, it is determined whether or not the density is too low every time a patch image is formed while changing the developing bias. When the density is too low, the dew condensation determination is performed to determine the presence or absence of dew condensation, and then the dew condensation eliminating operation is performed as necessary to form a patch image again. For this reason, since the density control factor is optimized after the condensation is eliminated and the patch image density converges to an appropriate range, the influence of the condensation does not affect the result of the density control operation.

  On the other hand, if the density of the patch image is too low, but it is determined in the dew condensation determination that there is no dew condensation, it is appropriate to think that the insufficient density of the patch image is due to a cause other than the dew condensation. For example, the engine unit EG or the concentration sensor 60 may be out of order. Therefore, in this case, the operation is stopped, and a message is displayed on the display unit 12 to urge the user to ask the service person to check. Here, displaying such a message on the display unit 12 is referred to as a “service call”. By doing so, it is possible to prevent an abnormal image from being formed by using the apparatus while it is abnormal and further serious damage to the apparatus being avoided.

  As described above, in this embodiment, the presence or absence of condensation in the apparatus is determined based on the density detection result of the patch image and the output of the temperature / humidity sensor 90. More specifically, when it is detected that the density of the formed patch image is too low, a dew condensation determination is made based on the detection result of the temperature / humidity sensor 90, and the apparatus is in a low temperature or high humidity environment. It is determined that there is condensation. Thus, by using both the result of detecting the density of the patch image and the result of detecting the environment in the apparatus, in this embodiment, it is possible to accurately determine the presence or absence of condensation in the apparatus.

  If the effect of condensation is suspected, patch images are formed again, and density control factors such as development bias and exposure power are optimized after confirming that the density has reached an appropriate value. Condensation does not affect the result of the concentration control operation. As a result, in this embodiment, it is needless to say that there is no condensation, and the operating conditions of the apparatus can be optimized to maintain good image quality even under conditions where condensation is possible. Furthermore, when it is determined that condensation is present, the condensation elimination operation is performed prior to forming the patch image again, so that condensation can be eliminated early.

  When the density control operation is performed for a plurality of toner colors, the above-described operation may be performed for each toner color. However, the condensation determination and the condensation elimination operation are performed only for the first toner color. These may be omitted from the second color. This is because if it is confirmed by the dew condensation determination in the first color that there is no dew condensation, there is no need to deliberately perform the dew condensation determination thereafter. Also, the concentration control operation that is particularly susceptible to the condensation is performed immediately after the power of the apparatus placed at a low temperature is turned on. On the other hand, after the device is turned on and condensation is eliminated, there is a low possibility that condensation will occur again. Therefore, the dew condensation determination may be performed only in the concentration control operation immediately after the power is turned on, and the dew condensation determination may be omitted in the concentration control operation executed at other timings.

(Second Embodiment)
FIG. 6 is a flowchart showing the density control operation of the second embodiment. In contrast to the flowchart of FIG. 4 showing the density control operation of the first embodiment, only the point where step S121 is added in FIG. 6 is a change. Therefore, steps having the same processing contents are denoted by the same step numbers and description thereof is omitted. In the density control operation of this embodiment, if it is determined that condensation is present in the condensation determination (step S111), then the apparatus is placed on standby until an image formation command is input from the outside (step S121). When an image formation command is input, a dew condensation eliminating operation and an unprocessed density control operation are executed. After the density control operation is completed in this way, an image corresponding to the image formation command is formed.

  Even if condensation has occurred, if the device is kept powered on, it will eventually condense due to the heat and air flow generated inside the device, even without performing any action to remove condensation. Will be resolved. Therefore, when the image is not formed immediately after the power is turned on, the dew condensation eliminating operation is not necessarily required. Therefore, in the density control operation of this embodiment, when it is determined that there is condensation, the apparatus is set in a standby state, and the condensation elimination operation is performed only when an image formation command is given from the outside. Thereby, the aspect of the condensation elimination operation is not limited as long as it can cope with mild condensation. This is because by waiting for an image formation command to be given, it is expected that condensation has been eliminated compared to the initial stage of power-on. In addition, since the condensation elimination operation is repeated until it is determined that there is no condensation, even if it is a relief action corresponding to such mild condensation, it can be performed more frequently as necessary to reduce the degree of condensation. Can also be supported.

  Also, the operation for forming the patch image promotes the elimination of condensation, that is, the patch image forming operation itself plays a role as the condensation elimination operation, so that the operation for eliminating the condensation is not particularly performed. May be. That is, the process of step S113 may be omitted in the operations of FIGS.

(Third embodiment)
FIG. 7 is a flowchart showing the density control operation of the third embodiment. In contrast to the flowchart of FIG. 4 showing the density control operation of the first embodiment, only the point that step S110 is added in FIG. Therefore, steps having the same processing contents are denoted by the same step numbers and description thereof is omitted. In the density control operation of this embodiment, when the density of the patch image is too low, it is determined whether or not the density control operation is performed immediately after the power is turned on (step S110). In the concentration control operation executed immediately after the power is turned on, the condensation determination (step S111) is performed as in the first embodiment. In other cases, a service call is performed without performing the condensation determination.

  This is because condensation is most likely to occur in the device when the device placed in a room with a low room temperature is turned on, or when a warmed device is moved to a room with a low room temperature. This is because, if a certain amount of time elapses after the power is turned on, condensation is often eliminated. After the concentration control operation immediately after power-on is properly executed, there is a very low possibility that condensation will still occur at the time of the concentration control operation performed for the second and subsequent times. Therefore, the insufficient density of the patch image in the density control operation performed after the second power-on is very unlikely to be caused by condensation, and is highly likely to be caused by other device abnormality. . Therefore, when it is determined that the patch image density is excessive in the density control operation executed at a timing other than immediately after the power is turned on, a service call is made without performing the condensation determination.

(Other)
As described above, in each of the above embodiments, the intermediate transfer belt 71 functions as the “image carrier” of the present invention. In addition, the photosensitive member 22, the charging roller 23, the exposure unit 6, and the developing unit 4 function as an “image forming unit” of the invention, and the CPU 101 that controls these functions as the “control unit” of the invention. ing. Further, the concentration sensor 60 and the temperature / humidity sensor 90 function as the “concentration detection means” and the “environment detection means” of the present invention, respectively.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the density sensor 60 is disposed opposite to the intermediate transfer belt 71, and the intermediate transfer belt 71 functions as the “image carrier” of the present invention. By disposing 60, the photosensitive member 22 may function as the “image carrier” of the present invention.

  Further, in the first embodiment, when it is determined in the condensation determination that condensation is present, the condensation elimination operation and the subsequent patch image formation are performed one after another. However, the condensation is eliminated after a certain period of time. Therefore, the dew condensation determination may be performed again after a predetermined time.

  In each of the above embodiments, the temperature / humidity sensor 90 that detects the temperature and humidity in the apparatus is provided to determine the possibility of condensation. However, the condensation condition is indirectly determined from the detection result of only one of the temperature and humidity. May be determined. That is, when the patch image density is too low, it may be determined that condensation occurs when the temperature in the apparatus is lower than a predetermined temperature or the humidity in the apparatus is higher than the predetermined humidity. In order to detect the environment in the apparatus related to the presence or absence of condensation, the output of another sensor that can indicate the possibility of condensation, such as a moisture sensor or a dew point sensor, may be used.

  In the density sensor 60 of each of the above embodiments, the reflected light from the intermediate transfer belt 71 is divided into two components, that is, a p-polarized component and an s-polarized component, and is received based on the respective received light amounts. Although the density is obtained, the present invention can be applied to an image forming apparatus that detects the patch image density by a method other than this.

  Further, although the above embodiment is an image forming apparatus capable of forming a color image on an intermediate transfer belt using four color toners, the number of colors and types of toner are not limited to the above. Further, instead of the intermediate transfer belt, another intermediate transfer member such as an intermediate transfer drum may be provided. The present invention can also be applied to an apparatus that does not include an intermediate transfer member and is configured to superimpose toner images on a photosensitive member or a recording material.

1 is a diagram illustrating a configuration example of an image forming apparatus to which the present invention can be preferably applied. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. The figure which shows the structure of a density sensor. The flowchart which shows the density | concentration control operation | movement of 1st Embodiment. The flowchart which shows a condensation determination operation | movement. The flowchart which shows the density | concentration control operation | movement of 2nd Embodiment. The flowchart which shows the density | concentration control operation | movement of 3rd Embodiment.

Explanation of symbols

  4 ... development unit (image forming means), 6 ... exposure unit (image forming means), 22 ... photosensitive member (image forming means), 23 ... charging roller (image forming means), 60 ... density sensor (density detecting means), 71 ... Intermediate transfer belt (image carrier), 90 ... Temperature / humidity sensor (environment detection means), 101 ... CPU (control means)

Claims (12)

An image carrier capable of carrying a toner image;
Image forming means for forming a toner image and carrying the toner image on the image carrier;
Density detecting means for detecting the density of a toner image as a patch image formed on the image carrier by the image forming means;
Environment detection means for detecting at least one of temperature and humidity in the device;
An image forming apparatus comprising: a control unit configured to perform dew condensation determination for determining presence or absence of dew condensation in the apparatus based on a density detection result by the concentration detection unit and an environment detection result by the environment detection unit.   The control unit executes a density control operation for controlling the image density by optimizing the operation condition of the image forming unit when forming a toner image based on the density detection result of the patch image, and the density control operation The image forming apparatus according to claim 1, wherein the dew condensation determination is performed based on a density detection result of a patch image formed in step 1.   The image forming apparatus according to claim 1, wherein the control unit performs the dew condensation determination based on the detection result of the environment detection unit when the density detection result of the patch image is not within a predetermined appropriate range.   The image forming apparatus according to claim 3, wherein the control unit performs the dew condensation determination when a density detection result of the patch image does not satisfy a lower limit value of the appropriate range.   The said environment detection means is a temperature sensor which detects the temperature in an apparatus, and the said control means determines that there is condensation when the temperature detected by the said temperature sensor is lower than predetermined temperature in the said condensation determination. Or the image forming apparatus according to 4.   The said environment detection means is a humidity sensor which detects the humidity in an apparatus, and the said control means determines with condensation when the humidity detected by the said humidity sensor is higher than predetermined humidity in the said condensation determination. Or the image forming apparatus according to 4.   The environment detection means is configured to detect the temperature and humidity in the apparatus, and the control means is configured such that, in the dew condensation determination, the temperature detected by the environment detection means is higher than a predetermined temperature, and the environment detection means 5. The image forming apparatus according to claim 3, wherein when the detected humidity is lower than a predetermined humidity, it is determined that there is no condensation.   The image forming apparatus according to claim 1, wherein the control unit performs the dew condensation determination immediately after the apparatus is turned on.   The image forming apparatus according to claim 1, wherein the control unit performs the dew condensation determination again after a predetermined time has elapsed when the dew condensation determination determines that there is dew condensation.   10. The image forming apparatus according to claim 1, wherein when the dew condensation determination determines that there is dew condensation, the control unit executes a dew condensation eliminating operation for eliminating dew condensation.   10. When an image formation request is input from the outside after determining that there is condensation by the condensation determination, a condensation eliminating operation for eliminating condensation is executed prior to forming an image based on the request. The image forming apparatus according to any one of the above. Forming a toner image as a patch image on the image carrier and detecting its density;
At least one of temperature and humidity in the image forming apparatus is detected as the internal environment,
A dew condensation determination method in an image forming apparatus, wherein the presence or absence of dew condensation in the apparatus is determined based on the density detection result of the patch image and the environment detection result in the apparatus.

Images