JP6390362B2 - Image forming apparatus, image forming apparatus control method, and image forming apparatus control program - Google Patents

Description

  The present invention relates to a technique for determining whether or not to perform image formation when the cumulative usage of a developing unit is high.

  Conventionally, for example, Patent Document 1 is disclosed as a technique in the case where the degree of cumulative use of the developing unit is high. Patent Document 1 discloses a configuration in which image formation is not performed until toner replacement is performed when the remaining amount of toner is equal to or less than a predetermined value, that is, when the cumulative usage of the developing unit is high. .

Japanese Patent Laid-Open No. 4-16865

  However, in the above-described prior art, when the cumulative usage of the developing unit is high, image formation is not performed, and user convenience is reduced.

  On the other hand, when image formation is performed when the cumulative usage of the developing unit is high, there is a possibility that image quality defects in which toner adheres to the outside of the electrostatic latent image on the photoconductor may occur.

  Therefore, the present specification discloses a technique for determining to perform image formation while suppressing the occurrence of image quality defects when the degree of cumulative use of the developing unit is high.

  An image forming apparatus made for the purpose of solving this problem includes an image forming unit that performs an image forming operation, a density detecting unit that detects the density of an image formed, and a control unit, and the control unit includes: A developing unit that constitutes a part of the image forming unit, wherein a cumulative usage level of the developing unit that develops an electrostatic latent image on a photoreceptor constituting a part of the image forming unit is equal to or less than a usage threshold value A first determination process for determining whether or not, a mark formation process for forming a mark with a predetermined development bias by the image forming unit, and a density of the mark detected by the density detection unit for the predetermined development bias. A correction process for correcting the development bias to a target density, a second determination process for determining whether an absolute value of the predetermined development bias after the correction process is equal to or greater than a bias threshold value, and the first determination Processing smell When the cumulative use degree is determined to be less than or equal to the use threshold value, the image forming operation is performed, and when it is determined that the cumulative use degree is higher than the use threshold value, When the absolute value of the predetermined development bias after the correction process is determined to be equal to or greater than the bias threshold value, an image forming process for performing the image forming operation is executed.

  In this way, when the cumulative usage of the developing unit is high, it is possible to determine whether or not to perform image formation based on the developing bias for producing the target density, while suppressing the occurrence of image quality defects. Image formation can be performed.

  In addition, a temperature detection unit that detects a temperature corresponding to the temperature of the developing unit may be provided, and the bias threshold may be a value that varies depending on the temperature detected by the temperature detection unit.

  In this way, when the cumulative usage of the developing unit is high, it is possible to determine whether or not to perform image formation taking into account the temperature that affects the toner charge amount. Image formation can be performed while suppressing the occurrence of poor image quality with high accuracy.

  The bias threshold value may be larger as the temperature detected by the temperature detection unit is higher.

  In this way, in particular, image formation can be performed while suppressing the occurrence of image quality defects that are more likely to occur at higher temperatures.

  Further, in the second determination process, the control unit determines whether the temperature is equal to or lower than a temperature threshold value that is larger as the absolute value of the predetermined development bias after the correction process is larger. It may be determined whether or not an absolute value of the predetermined developing bias after the correction processing is equal to or greater than the bias threshold value.

  The bias threshold value may be different depending on the type of paper on which the image is formed.

  In this way, it is possible to determine whether or not to form an image with higher accuracy than in the case where the ease of toner application, which differs depending on the paper type, is not considered in consideration of the ease of toner application, which differs depending on the paper type.

  The image forming unit includes a plurality of sets of the photosensitive member and the developing unit, and the bias threshold value in each developing unit is an arrangement order of the photosensitive member corresponding to the developing unit with respect to the other photosensitive members. It may be different depending on.

  In this way, considering the ease of occurrence of image quality failure due to paper dust, etc., which differs depending on the arrangement order of the corresponding photoconductors, the image is more accurately obtained than when the arrangement order of the corresponding photoconductors is not considered. It can be determined whether or not to form.

  Further, the image forming unit includes a plurality of sets of the photoconductors and the developing units having different corresponding toner components, and the bias threshold value in each developing unit varies depending on the corresponding toner components. There may be.

  In this way, it is possible to determine whether or not to form an image with higher accuracy than in the case where the component of the toner to be developed is not considered in consideration of the tendency of occurrence of poor image quality that varies depending on the component of the toner to be developed.

  And a receiving unit that receives an instruction to perform the image forming operation, wherein the control unit determines that the cumulative usage level is higher than the usage level threshold value in the first determination process. After the image forming instruction is received by the printing unit and before the second determination process, the correction process is performed based on the mark formed process and the mark formed by the mark forming process. The second determination process may be performed based on the corrected predetermined developing bias.

In this way, it is possible to make a determination with higher accuracy than in the case where it is determined whether or not to perform image formation based on a developing bias that is not close to the current state.
it can.

  Further, a humidity detection unit that detects humidity corresponding to the humidity of the developing unit may be provided, and the bias threshold value may be different depending on the temperature and the humidity detected by the humidity detection unit.

  In this way, it is possible to determine whether or not to perform image formation with higher accuracy than in the case where it is not determined whether or not to perform image formation according to the humidity that affects the toner charge amount.

  An image forming apparatus made for the purpose of solving this problem includes an image forming unit that performs an image forming operation, a density detecting unit that detects the density of an image formed image, and a control unit, and the control unit Is a developing unit that constitutes a part of the image forming unit, and the cumulative usage of the developing unit that develops the electrostatic latent image on the photosensitive member that constitutes a part of the image forming unit is used. A first determination process for determining whether or not the threshold is equal to or less than a threshold; a mark formation process for forming a mark with a predetermined development bias by the image forming unit; and the mark formed with the predetermined development bias detected by the density detection unit In the second determination process for determining whether or not the density is equal to or higher than the density threshold value, and in the first determination process, when the cumulative use degree is determined to be equal to or lower than the use threshold value, the image forming operation is performed. Done, cumulative When it is determined that the use degree is higher than the use threshold, the image is formed when it is determined in the second determination process that the density of the mark formed with the predetermined development bias is equal to or higher than the density threshold. And an image forming process for performing a forming operation.

  In this way, when the cumulative usage of the developing unit is high, it is possible to determine whether or not to perform image formation based on the mark density at a predetermined developing bias, thereby suppressing the occurrence of image quality defects. Image formation can be performed.

  A control method for realizing the functions of the image forming apparatus, a computer program, and a computer-readable storage medium storing the computer program are also novel and useful.

  According to the present invention, when the cumulative usage of the developing unit is high, it is possible to determine to perform image formation while suppressing the occurrence of image quality defects.

1 is a cross-sectional view illustrating an internal configuration of a printer according to an embodiment. FIG. 2 is a block diagram illustrating an electrical configuration of the printer illustrated in FIG. 1. 5 is a flowchart illustrating a procedure of development bias correction processing executed by a printer. It is a figure which shows arrangement | positioning of a mark sensor. (A) is a figure showing the characteristic C1 which shows the relationship between the developing bias Vb and the temperature T. FIG. FIG. 5B is a diagram illustrating a characteristic C1 indicating the relationship between the developing bias Vb and the temperature T when the sheet type X is plain paper, and a characteristic C2 indicating the relationship between the developing bias Vb and the temperature T when the sheet is glossy paper. It is. 6 is a flowchart illustrating a procedure of image forming processing executed by a printer.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Embodiments of an image forming apparatus according to the invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a printer that forms an image by electrophotography.

  The printer 100 of this embodiment mainly includes a paper feeding unit 10, an image forming unit 20, and a paper discharge unit 30.

  The paper feed unit 10 includes a paper feed tray 11, a paper feed roller 12, and a registration roller 13.

  The paper feed tray 11 is located below the printer 100 and accommodates a sheet before image transfer. The sheets stored in the sheet feeding tray 11 are fed toward the image forming unit 20 by driving the sheet feeding roller 12 and the registration roller 13.

  The image forming unit 20 forms a toner image by an electrophotographic method, transfers the toner image to a sheet, an exposure device 22 that irradiates the process unit 21 with light, and unfixed toner on the sheet. A fixing device 23 for fixing and a conveying belt 24 for conveying the sheet to the transfer position of the process unit 21 are mainly provided.

  The process unit 21 can form a color image and is arranged in parallel corresponding to each color of cyan (C), magenta (M), yellow (Y), and black (K). Specifically, a process unit 21C that forms an image with C-color toner, a process unit 21M that forms an image with M-color toner, a process unit 21Y that forms an image with Y-color toner, and a K-color toner And a process unit 21K that forms an image with toner. In the sheet conveyance direction from the sheet feeding unit 10 toward the sheet discharge unit 30, the process units 21C, 21M, 21Y, and 21K are arranged at equal intervals in this order from the downstream side. Note that the order of the process units is not limited to this. Each color toner is a toner having different components.

  The process unit 21K includes a drum-shaped photoconductor 1, a charging device 2 that uniformly charges the surface of the photoconductor 1, and a developing device 4 that develops the electrostatic latent image on the photoconductor 1 with toner. And a transfer device 5 for transferring the toner image on the photosensitive member 1 to a sheet or a conveying belt 24. The photoreceptor 1 and the transfer device 5 are disposed in contact with the transport belt 24. The photoconductor 1 is opposed to the transfer device 5 with the conveyance belt 24 interposed therebetween. The developing device 4 includes a developing device 4A and a toner storage portion 4B, and supplies the toner in the toner storage portion 4B to the photoreceptor 1 by the developing device 4A to which the developing bias Vb is applied. The developing device 4 can be replaced through an opening when a cover (not shown) provided in the casing of the printer 100 is opened. The other process units 21C, 21M, and 21Y have the same configuration as the process unit 21K.

  In each of the process units 21C, 21M, 21Y, and 21K, the surface of the photoreceptor 1 is uniformly charged by the charging device 2 to which a bias is applied. Thereafter, exposure is performed by light emission from the exposure device 22, and an electrostatic latent image of an image to be formed is formed on the photoreceptor 1. Next, the toner is supplied to the photoreceptor 1 through the developing device 4A to which the developing bias Vb is applied. As a result, the electrostatic latent image on the photoreceptor 1 is visualized as a toner image. The visualized toner image is transferred onto the conveyance belt 24 or a sheet conveyed by the conveyance belt 24 by passing through a contact position between the photoreceptor 1 and the transfer device 5 to which a bias is applied. . In particular, the visible toner image on the sheet is thermally fixed by the sheet passing through the fixing device 23. This operation from charging to development is an example of an image forming operation, the image forming unit 20 is an example of an image forming unit, the photosensitive member 1 is an example of a photosensitive member, and the developing device 4 is a developing unit. It is an example. In the present embodiment, it is assumed that the bias applied to the charging device 2 and the development bias Vb are positive biases. The bias applied to the charging device 2 and the development bias Vb may be negative biases.

  The paper discharge unit 30 includes a paper discharge roller 31 and a paper discharge tray 32. The sheet discharge roller 31 conveys the sheet conveyed from the image forming unit 20 toward the sheet discharge tray 32. The sheet discharge tray 32 is provided on the upper portion of the printer 100, and the sheet conveyed by the sheet discharge roller 31 is held on the sheet discharge tray 32.

  From the above, the sheet stored in the paper feed tray 11 positioned at the lower part of the printer 100 passes through the paper feed roller 12, the registration roller 13, the process unit 21, and the fixing device 23, and is discharged from the upper part via the paper discharge roller 31. It is guided to the paper tray 32 (one-dot chain line in FIG. 1). More specifically, the paper feed unit 10 takes out the sheets stored in the paper feed tray 11 one by one, and conveys the sheets onto the conveyance belt 24. Then, the image forming unit 20 transfers the toner image formed by the process unit 21 to the sheet. Thereafter, the sheet on which the toner image is transferred is conveyed to the fixing device 23, and the toner image is thermally fixed to the sheet. Then, the paper discharge unit 30 discharges the fixed sheet to the paper discharge tray 32.

  As shown in FIG. 2, the printer 100 according to this embodiment includes a controller 40 having a CPU 41, a ROM 42, a RAM 43, an NVRAM (Non Volatile RAM) 44, and an ASIC 45. The printer 100 includes a paper feeding unit 10, an image forming unit 20 that forms an image by an electrophotographic method, a paper discharge unit 30, an operation unit 50 that receives an input operation from a user, a temperature sensor 61, and humidity. A sensor 62, a mark sensor 63, and a communication interface 71 for connecting to an external device are provided, and these are controlled by the CPU 41. Note that the controller 40 in FIG. 2 is a collective term for hardware used for controlling the printer 100, such as the CPU 41, and does not necessarily represent a single piece of hardware that actually exists in the printer 100.

  The ROM 42 stores firmware that is a control program for controlling the printer 100, various settings, initial values, and the like. The RAM 43 is used as a work area from which various control programs are read or as a storage area for temporarily storing image data.

  The CPU 41 controls each component of the printer 100 while storing the processing result in the RAM 43 or the NVRAM 44 according to a control program read from the ROM 42 and signals sent from various sensors. For example, drive transmission to the paper feeding unit 10 and the paper discharge unit 30, drive transmission to each element of the image forming unit 20, bias application, and the like. The CPU 41 is an example of a control unit. The controller 40 may be a control unit, and the ASIC 45 may be a control unit.

  The operation unit 50 is provided on the exterior of the printer 100 and has various buttons for receiving input operations from the user, and a touch panel for displaying messages and setting contents. Examples of the various buttons include an instruction button that instructs the image forming unit 20 to form an image. The operation unit 50 also accepts various inputs when the user touches the touch panel with a finger. The operation unit 50 is an example of a reception unit.

  The temperature sensor 61 and the humidity sensor 62 are provided in the vicinity of the toner container 4B, and transmit humidity and a signal corresponding to the humidity to the CPU 41 and the like, respectively. If the temperature sensor 61 and the humidity sensor 62 correspond to the temperature and humidity of the toner in the toner container 4B, that is, the tendency and value of the temperature and humidity of the toner in the toner container 4B can be estimated and predicted. If so, it may not be provided near the toner storage portion 4B. The temperature sensor 61 is an example of a temperature detection unit, and the humidity sensor 62 is an example of a humidity detection unit.

  The communication interface 71 is hardware that enables communication with other devices. The printer 100 can receive an image forming instruction of a job for forming an image in the image forming unit 20 and data of the job for forming an image from an external device (not shown) via the communication interface 71.

  The mark sensor 63 is an optical sensor and transmits a signal corresponding to the amount of received light to the CPU 41. The mark sensor 63 is disposed at a position downstream of the process units 21Y, 21M, 21C, and 21K and upstream of the fixing device 23 in the sheet conveyance direction. Hereinafter, the developing bias correction process performed using the mark sensor 63 will be described with reference to FIGS.

  The development bias correction process is a process for obtaining a deviation between the ideal density defined by the printer 100 and the density of the mark actually formed, and determining the development bias Vb having the ideal density defined by the printer 100. As a procedure for developing bias correction processing, the CPU 41 first forms marks 66 having a predetermined density (for example, 100%) in each of the process units 21C, 21M, 21Y, and 21K, and transfers the marks 66 onto the conveyance belt 24. (S201). Then, the CPU 41 detects the transferred marks 66 with the mark sensor 63 (S203). Specifically, as shown in FIG. 4, the mark sensor 63 is a reflective optical sensor in which a light emitting element 64 such as an LED and a light receiving element 65 such as a phototransistor are paired. The mark sensor 63 is configured to irradiate light from an oblique direction with respect to the dotted line frame E in FIG. . The correction mark and its density can be detected based on the difference between the amount of light received when the correction mark 66 passes and the amount of light received directly from the conveyor belt 24. The mark sensor 63 is an example of a density detection unit. After S203, the CPU 41 obtains a deviation between the received light amount, that is, the density of the mark 66, and the ideal density defined by the printer 100, and sets the developing bias Vb that fills this deviation amount to each of the process units 21C, 21M, 21Y, 21K. Is determined (S205).

  When the image forming job is executed, the printer 100 determines whether a forming condition for forming the development bias correction mark 66 is satisfied. The formation conditions include, for example, user instruction input, new article detection, image formation of a predetermined number or more, continuous operation time or more of a threshold, environmental changes such as humidity and temperature exceeding a specified amount, or a combination thereof. If the forming conditions are satisfied, for example, prior to execution of the image forming job, the mark 66 is formed and development bias correction processing is performed. Then, image formation is performed with the developing bias Vb for obtaining the ideal density defined by the printer 100 corrected by the developing bias correction processing.

  FIG. 5A is a graph showing the characteristic (hereinafter referred to as characteristic C) of the absolute value of the developing bias Vb for obtaining the ideal density specified by the printer 100 with respect to the temperature T detected by the temperature sensor 61. is there. In the present embodiment, since the developing bias Vb is a positive bias, in FIG. 5A, the absolute value of the developing bias Vb is expressed as the developing bias Vb. This characteristic C is determined when either the temperature T or the developing bias Vb is determined. The characteristic C separates the region A and the region B. The area A is an area where image quality is unlikely to occur when image formation is performed. That is, when image formation is performed under the conditions of the development bias Vb and temperature T in the region A, the possibility of image quality failure is low. On the other hand, the area B is an area where image quality is highly likely to occur when an image is formed. That is, when image formation is performed under the conditions of the development bias Vb and temperature T in the region B, there is a high possibility that image quality will be poor. The characteristic C that separates these areas A and B is determined by experiments. For example, according to the characteristic C shown in FIG. 5A, the lower the absolute value of the developing bias Vb and the higher the temperature T, the higher the possibility of image quality failure. This is because, assuming that the toner charged with the opposite polarity is supplied to a portion other than the electrostatic latent image, the toner becomes easier to be charged with the opposite polarity as the developing bias Vb is lower. It is. This is also because the higher the temperature T, the higher the possibility that the humidity is higher, so the charge amount of the toner is likely to decrease, that is, the toner is likely to be charged to a reverse polarity. Further, according to the development bias correction process described above, the development bias Vb is determined to have a smaller absolute value as the toner in the toner storage unit 4B deteriorates. This is because, as the toner deteriorates, the toner becomes difficult to be charged, that is, the density is difficult to be obtained. Therefore, the developing bias Vb is set to an ideal density specified by the printer 100, that is, a value that makes it easy to obtain the density. This is because the value needs to be determined to be small. As shown in FIG. 5B, the characteristic C1 is obtained when the sheet type is plain paper, and the characteristic C2 is obtained when the sheet type is glossy paper. That is, the characteristic C differs depending on the sheet type X. This is because, depending on the thickness of the sheet, surface processing, and the like, even if the absolute value of the developing bias Vb and the temperature T are the same, the ease of transfer of toner charged to the opposite polarity to the sheet differs. Here, as an example, the case where the sheet type X is plain paper and the case of glossy paper are cited.

  From the above, the absolute value of the developing bias Vb on the characteristics C1 or C2 determined by determining the temperature T and the sheet type X is Th (T, X). According to this characteristic C1 or C2, if the absolute value of the developing bias Vb is larger than Th (T, X), (Vb, T) becomes a point in the area A, and image quality failure as a result of job image formation may occur. This is considered to be low. On the other hand, if the absolute value of the developing bias Vb is smaller than Th (T, X), (Vb, T) becomes a point in the area B, and it is considered that there is a high possibility of image quality failure as a result of job image formation.

  Subsequently, an image forming process of the printer 100 including the above-described developing bias correction process will be described. FIG. 6 shows the procedure of image forming processing executed by the printer 100. The image forming process is executed by the CPU 41 after the printer 100 is turned on.

  In the image forming process, the CPU 41 first determines whether or not a job image forming instruction has been received via the communication interface 71 or from the operation unit 50 (S101). The determination in S101 is continued until it is determined that a job image formation instruction has been received (S101: NO).

  When the CPU 41 determines that the image formation instruction for the job has been received (S101: YES), in the at least one developing device 4 used in the job, the developing device 4A from when the developing device 4 is replaced with a new one is used. It is determined whether or not the rotational speed r is equal to or greater than R (S103). That is, in at least one developing device 4, it is determined whether or not the cumulative rotational speed r of the developing device 4A is large.

  When the CPU 41 determines that the rotation speed r of the developing device 4A from the time when the developing device 4 is replaced with a new one in the at least one developing device 4 used in the job is R or more (S103: YES). Assuming that the accumulated rotational speed r of the developing device 4A is large, that is, the toner in the toner storage unit 4B may be deteriorated, it is determined whether or not to execute the job that accepted the image formation instruction in S101. In order to do this, information on the type X of the sheet used in the job for which the image formation instruction has been accepted in S101 is acquired through reception via the communication interface 71 or operation from the operation unit 50 (S105). In this embodiment, the sheet type X is, for example, plain paper or glossy paper, but this need not be the case. For example, plain paper and cardboard may be used. That is, any information regarding thickness, surface processing, and the like may be used. In step S105, the CPU 41 acquires information on the type X of the sheet to be used, and then performs the above-described development bias correction process (S107) to correct the development bias Vb.

  After the development bias correction process in S107, the CPU 41 acquires the temperature T by a signal transmitted from the temperature sensor 61 (S109).

  After S109, the CPU 41 determines whether or not the absolute value of the developing bias Vb corrected by the developing bias correcting process in S107 is equal to or greater than Th (T, X) (S111). That is, after determining in S103 that at least one developing device 4 used in the job has a large accumulated rotational speed r of the developing device 4A, the acquired sheet type X and temperature T and the absolute value of the corrected developing bias Vb are obtained. Accordingly, it is determined in step S101 whether or not to execute the job that has received the image formation instruction.

  If the CPU 41 determines that the absolute value of the development bias Vb corrected in the development bias correction process in S107 is equal to or greater than Th (T, X) (S111: YES), the CPU 41 obtains the data of the job that received the image formation instruction in S101. Then, the sheet feeding unit 10, the image forming unit 20, the paper discharge unit 30 and the like are controlled to form an image on the sheet (S113). This is because, in the case of S111: YES, it is considered that even if the job for which the instruction is accepted in S101 is executed, there is a low possibility of image quality failure in the image formation result of the job as described above. After S113, the image forming process is terminated.

  If the CPU 41 determines that the absolute value of the development bias Vb corrected by the development bias correction processing in S107 is not equal to or greater than Th (T, X) (S111: NO), the CPU 41 receives the data of the job that received the image formation instruction in S101. In other words, the job that has received the image formation instruction in S101 is not formed, and, for example, the fact that the job cannot be formed is transmitted to the external device via the communication interface 71, or the display of the operation unit 50 is displayed. It is displayed that image formation is not possible (S115). This is because, in the case of S111: NO, if image formation of a job that has received an image formation instruction in S101 is executed, there is a high possibility that a poor image quality will occur in the image formation result of the job. After S115, the image forming process is terminated.

  On the other hand, the CPU 41 assumes that the rotational speed r of the developing device 4A from when the at least one developing device 4 used in the job is replaced with a new one is not R or more, and sets the rotational speed for all the developing devices 4A used in the job. If it is determined that r is small (S103: NO), it is determined that there is a low possibility that the toner in the toner container 4B has deteriorated, and the process proceeds to S113, and an image formation instruction is accepted in S101 as described above. After accepting the job data and forming an image on the sheet, the image forming process is terminated.

  In the development bias correction process in S107, the process in S201 for forming the mark 66 with the development bias Vb for producing the ideal density specified by the printer 100 is an example of the mark formation process. The developing bias Vb for producing an ideal density defined by the printer 100 when forming the mark 66 is an example of a predetermined developing bias.

  In the development bias correction process of S107, the process of S205 for correcting the development bias at the time of forming the mark 66 to the development bias Vb for producing the ideal density specified by the printer 100 is an example of the correction process. The ideal density is an example of a target density.

  Further, the rotation speed r of the developing device 4A from the time of replacement of the developing device 4 is an example of a cumulative usage level of the developing unit, and R is an example of a usage threshold. Further, the process of S103 for determining whether the rotation speed r of the developing device 4A since the replacement of the developing device 4 is equal to or greater than R is an example of a first determination process.

  In S111, the process of determining whether or not the absolute value of the development bias Vb corrected in the development bias correction process of S107 is equal to or greater than Th (T, X) is an example of a second determination process. In particular, Th (T, X) is an example of a bias threshold value.

  If it is determined in step S103 that the rotation speed r of the developing device 4A since the replacement of the developing device 4 is not equal to or greater than R (S103: NO), image formation is performed in S113, and the developing device 4 is replaced. If it is determined that the rotational speed r of the developing device 4A is equal to or greater than R (S103: YES), if the absolute value of the developing bias Vb corrected in the developing bias correcting process in S107 is equal to or less than Th (T, X) (S111: YES), a series of processes for forming an image in S113 is an example of an image forming process.

  As the cumulative number of rotations r of the developing device 4A increases, the toner deteriorates and there is a possibility that the toner adheres to the electrostatic latent image on the photoreceptor 1, that is, the image quality is deteriorated. When the absolute value of the corrected developing bias Vb is high, toner adhesion hardly occurs. Therefore, even when the cumulative number of rotations r of the developing device 4A is large, if the absolute value of the developing bias Vb detected and corrected by detecting the density of the mark 66 is large, the image quality is suppressed while suppressing the occurrence of image quality. Formation can be performed.

  Further, since the absolute value of the developing bias Vb corrected by the developing bias correcting process in S107, which causes image quality defects, varies depending on the temperature T that affects the toner charge amount, it is determined whether or not image forming is performed in S111. Considering the temperature T in the determination, the determination in S111 can be performed with higher accuracy.

  In particular, the higher the temperature that affects the toner charge amount, the more likely the toner adheres even if the degree of deterioration is low, that is, the toner adheres even if the absolute value of the developing bias Vb corrected in the developing bias correcting process in S107 is large. Since it is likely to occur, when it is determined whether or not to perform image formation in S111, the image formation can be performed by setting the condition under which the image can be formed as the condition that the absolute value of the developing bias Vb increases as the temperature T increases. Can be determined with higher accuracy.

  By determining whether or not to perform image formation with Th (T, X) that differs depending on the sheet type X acquired in S105 (S111), toner paste that varies depending on the sheet type X such as thickness and surface processing, etc. It is possible to determine whether or not to perform image formation with higher accuracy in consideration of safety.

  After accepting the image formation instruction in S101 and before the determination processing of whether or not to perform image formation in S111, that is, whether or not to perform image formation in S111 by the developing bias Vb corrected immediately before. This makes it possible to make a more accurate determination with the developing bias Vb that is closer to the current state.

  In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below.

  (1) The image forming apparatus is not limited to a printer, and can be applied to any apparatus having a printing function such as a copier, a FAX apparatus, and a multifunction machine. The printer 100 according to the embodiment is a color printer and includes the process units 21C, 21M, 21Y, and 21K corresponding to the respective colors. However, the printer 100 may be a monochrome printer including one process unit.

  (2) In the above embodiment, whether or not to form an image is determined according to the characteristic C that differs depending on the sheet type X, that is, Th (T, X), but this need not be the case. For example, whether the process unit 21 performs image formation according to a different characteristic C, that is, Th (T, X) depending on the arrangement order of whether the process unit 21 is upstream or downstream in the sheet conveyance direction with respect to another process unit. It may be determined whether or not. In this way, it is possible to determine whether or not to perform image formation more accurately in consideration of the influence of paper dust and the like that differ depending on the position of the photosensitive member 1 relative to another photosensitive member 1 in the sheet conveyance direction. Alternatively, it may be determined whether or not to perform image formation according to different characteristics C, that is, Th according to the difference in the toner component of the process unit 21. In this way, it is possible to determine whether or not to form an image with higher accuracy in consideration of charging characteristics that vary depending on the toner component. According to this, for example, it may be determined whether or not to perform image formation according to the characteristic C that is different depending on the color of the toner in the toner storage unit 4A of the process unit 21, that is, Th. At that time, the difference in the sheet type X may be taken into consideration.

  (3) In the above embodiment, it is determined whether or not to perform image formation according to the characteristic C that differs depending on the absolute value of the temperature T and the developing bias Vb. In addition, it may be configured to determine whether or not to perform image formation according to a different characteristic C even in accordance with the humidity H detected by the humidity sensor 62. For example, it may be determined whether or not to perform image formation according to the characteristic C that differs depending on the absolute water content determined by the temperature T and the humidity H and the absolute value of the developing bias Vb. In this way, the charge amount of the toner can be determined with higher accuracy than in the case where it is not determined whether or not to perform image formation according to the humidity H, that is, whether image formation is performed with higher accuracy. Can be determined.

  (4) In the above embodiment, when it is determined in S103 that the rotation speed r of the developing device 4A is large, the process S105 for determining whether or not to immediately perform image formation is performed. When it is determined in S103 that the rotation speed r of the developing device 4A is large, the operation unit 50 may notify that the rotation speed r of the developing device 4A is large. The fact that the rotation speed r of the developing device 4A is large means that, for example, the developing device 4 needs to be replaced if it has been used sufficiently since the replacement. In this way, it is possible to promote replacement with the developing device 4 that is not sufficiently used, and it is possible to increase the possibility of image formation in S113 without determining that image formation is impossible in S111.

  (5) In the above embodiment, even if the image forming instruction is received again without replacement of the developing device 4 after performing the processing for disabling image formation in S115 (S101, S103: YES), S111 When it is determined that the absolute value of the developing bias Vb is equal to or greater than Th (S111: YES), image formation is performed, but this need not be the case. For example, after the processing that disables image formation in S115, image formation may be disabled even if the absolute value of the developing bias Vb is equal to or greater than Th until the developing device 4 is replaced. In this way, it can be suppressed that the result of whether image formation is possible or not is more complicated than the case where image formation is possible even after image formation is disabled.

  (6) In the above embodiment, the development bias correction processing in S107 is performed for all the process units 21, but this need not be the case. For example, only the process unit 21 that forms an image with a job that has received an image formation instruction in S101, and the rotation number r of the developing device 4A is determined to be R or more in S103 (S103: YES), The developing bias Vb may be corrected. In this way, it is possible to suppress toner consumption of the process unit 21 regardless of whether or not to perform image formation.

  (7) In the above embodiment, it was determined in S111 whether or not the absolute value of the developing bias Vb is equal to or greater than Th that differs depending on the temperature T and the sheet type X. However, the temperature T is equal to the developing bias Vb. It may be determined whether or not the threshold value Th is different depending on the absolute value and the sheet type X. This process is also an example of the second determination process.

  (8) In the above embodiment, it is determined in S103 whether or not the rotation speed r of the developing device 4A is large, but this need not be the case. For example, a remaining amount sensor or the like may be used to determine whether or not the remaining amount of toner in the toner storage unit 4B is less than a predetermined amount. In this case, the remaining amount of toner in the toner storage unit 4B is an example of a cumulative usage level of the developing unit, and a value obtained by subtracting the predetermined amount from the total amount when the developing device 4 is replaced is an example of a usage level threshold value. . In this case, when the remaining amount of toner is less than a predetermined amount, it is determined that the usage degree threshold is high.

  (9) In the above embodiment, in S111, it is determined whether or not the region A includes the set of the absolute value of the developing bias Vb and the temperature T corrected to determine whether or not to perform image formation. However, this need not be the case. For example, it may be determined whether or not to perform image formation by determining whether or not the density of the mark 66 formed with the fixed developing bias Vb is equal to or higher than the density threshold. This is because the density of the mark 66 formed with the fixed developing bias Vb decreases as the toner deteriorates. This is basically the same as the absolute value of the development bias Vb after the correction in the development bias correction process decreases as the toner deteriorates. The fixed development bias Vb is an example of a predetermined development bias.

  (10) The processing disclosed in the embodiments may be executed by a single CPU, a plurality of CPUs, hardware such as an ASIC, or a combination thereof. Further, the process disclosed in the embodiment can be realized in various modes such as a recording medium or a method in which a program for executing the process is recorded.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging apparatus 4 Developing apparatus 20 Image forming part 63 Mark sensor 41 CPU
100 printer

Claims (12)

An image forming unit that performs an image forming operation;
A density detector for detecting the density of the image formed;
A control unit,
The control unit is a developing unit that constitutes a part of the image forming unit, and a cumulative usage of the developing unit that develops an electrostatic latent image on a photosensitive member that constitutes a part of the image forming unit Is a first determination process for determining whether or not is less than or equal to a use threshold;
A mark forming process for forming a mark with a predetermined developing bias by the image forming unit;
Correction processing for correcting the predetermined development bias to a development bias having a density of the mark detected by the density detection unit as a target density;
A second determination process for determining whether an absolute value of the predetermined development bias after the correction process is equal to or greater than a bias threshold;
In the first determination process, when it is determined that the cumulative use degree is equal to or less than the use threshold, the image forming operation is performed.
When it is determined that the cumulative use degree is higher than the use threshold, the absolute value of the predetermined development bias after the correction process is determined to be greater than or equal to the bias threshold in the second determination process. And an image forming process for performing the image forming operation. The image forming apparatus according to claim 1,
A temperature detection unit that detects a temperature corresponding to the temperature of the developing unit;
The image forming apparatus, wherein the bias threshold value is different depending on the temperature detected by the temperature detection unit. The image forming apparatus according to claim 2,
The image forming apparatus, wherein the bias threshold value is larger as the temperature detected by the temperature detection unit is higher. The image forming apparatus according to claim 3, wherein
In the second determination process, the control unit determines whether the temperature is equal to or lower than a temperature threshold value that is greater as the absolute value of the predetermined development bias after the correction process is larger. An image forming apparatus comprising: determining whether an absolute value of the subsequent predetermined developing bias is equal to or greater than the bias threshold value. An image forming apparatus according to any one of claims 1 to 4,
The image forming apparatus according to claim 1, wherein the bias threshold value is different depending on a paper type on which the image is formed. An image forming apparatus according to any one of claims 1 to 5,
The image forming unit includes a plurality of sets of the photoconductor and the developing unit,
The image forming apparatus according to claim 1, wherein the bias threshold value in each developing unit differs according to an arrangement order of the photosensitive member corresponding to the developing unit with respect to another photosensitive member. The image forming apparatus according to any one of claims 1 to 6,
The image forming unit includes a plurality of sets of the photosensitive member and the developing unit having different toner components,
The image forming apparatus according to claim 1, wherein the bias threshold value in each developing unit differs according to a corresponding toner component. The image forming apparatus according to claim 7,
A reception unit that receives an instruction to perform the image forming operation;
The controller is
After determining that the cumulative use degree is higher than the use degree threshold in the first determination process, after receiving the image formation instruction in the reception unit, and before the second determination process The correction processing is performed based on the mark formation processing and the mark formed by the mark formation processing, and the second determination processing is performed based on the predetermined development bias corrected by the correction processing. An image forming apparatus. The image forming apparatus according to any one of claims 2 to 4 , wherein:
A humidity detector that detects humidity corresponding to the humidity of the developing unit;
The image forming apparatus, wherein the bias threshold value is different depending on the temperature and the humidity detected by the humidity detector.
An image forming unit that performs an image forming operation;
A density detector for detecting the density of the image formed;
A control unit,
The control unit is a developing unit that constitutes a part of the image forming unit, and a cumulative usage of the developing unit that develops an electrostatic latent image on a photosensitive member that constitutes a part of the image forming unit Is a first determination process for determining whether or not is less than or equal to a use threshold;
A mark forming process for forming a mark with a predetermined developing bias by the image forming unit;
A second determination process for determining whether a density of the mark formed by the predetermined developing bias detected by the density detection unit is equal to or higher than a density threshold;
In the first determination process, when it is determined that the cumulative use degree is equal to or less than the use threshold, the image forming operation is performed.
When it is determined that the cumulative use degree is higher than the use threshold, the density of the mark formed with the predetermined development bias in the second determination process is determined to be equal to or higher than the density threshold. And an image forming process for performing the image forming operation. Is the developing unit constituting a part of the image forming unit, and whether the cumulative usage of the developing unit that develops the electrostatic latent image on the photosensitive member constituting the part of the image forming unit is equal to or less than a use threshold value? A first determination step of determining whether or not,
A mark forming step of forming a mark with a predetermined developing bias by the image forming unit;
A correction step of correcting the predetermined development bias to a development bias having a density of the mark detected by a density detection unit as a target density;
A second determination step of determining whether an absolute value of the predetermined development bias after the correction step is equal to or greater than a bias threshold;
In the first determination step, when it is determined that the cumulative use degree is equal to or less than the use threshold, an image forming operation is performed, and when it is determined that the cumulative use degree is higher than the use threshold, An image forming step of performing the image forming operation when it is determined in the second determination step that the absolute value of the predetermined developing bias after the correction step is equal to or greater than the bias threshold value. A method for controlling an image forming apparatus. An image forming unit that performs an image forming operation;
A density detector for detecting the density of the image formed;
An image forming apparatus including a control unit,
A developing unit that constitutes a part of the image forming unit, wherein a cumulative usage level of the developing unit that develops an electrostatic latent image on a photoreceptor constituting a part of the image forming unit is equal to or less than a usage threshold value A first determination process for determining whether or not
A mark forming process for forming a mark with a predetermined developing bias by the image forming unit;
Correction processing for correcting the predetermined development bias to a development bias having a density of the mark detected by the density detection unit as a target density;
A second determination process for determining whether an absolute value of the predetermined development bias after the correction process is equal to or greater than a bias threshold;
In the first determination process, when it is determined that the cumulative use degree is equal to or less than the use degree threshold, the image forming operation is performed, and when it is determined that the cumulative use degree is higher than the use degree threshold. Performing an image forming process for performing the image forming operation when it is determined in the second determination process that the absolute value of the predetermined developing bias after the correction process is equal to or greater than the bias threshold value. A control program for an image forming apparatus.