JP4893013B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a technique for shortening the time required for setup for adjusting image quality in an electrophotographic image forming apparatus using a so-called rotary developing system.

  In the electrophotographic image forming apparatus, in addition to an operation for forming a toner image corresponding to an input image (hereinafter referred to as “image forming operation”), various adjustment toner patterns for adjusting image quality are formed. Some perform operations (hereinafter referred to as “setup operations”). Here, the adjustment toner pattern is, for example, a patch-like toner pattern for adjusting the density or a toner band for improving the charging ability of the toner.

  In particular, in an intermediate transfer type image forming apparatus using a rotary development system, a reference signal synchronized with the rotation cycle of an intermediate transfer member (intermediate transfer belt or the like) is generated, and each color toner is based on the reference signal. A configuration in which an image is transferred to an intermediate transfer member is common. This is because, in the intermediate transfer method, a plurality of color toner images are transferred to the intermediate transfer member in a multiple manner, and the multiple toner images are collectively transferred to a sheet. Therefore, when transferring each color toner image to the intermediate transfer member, This is because it is necessary to perform alignment so that color misregistration does not occur.

By the way, when performing a setup operation in such an image forming apparatus, it is necessary to rotate the intermediate transfer member at least once for each color in order to form an adjustment toner pattern. That is, in order to finish the setup operation, the intermediate transfer member needs to be rotated by the same number of times as the number of remaining colors or more (for example, see Patent Document 1). For this reason, such an image forming apparatus has a disadvantage that the time required for the setup operation becomes long. During the setup operation, normal image formation, that is, the image formation operation cannot be performed. Therefore, if the time required for the setup operation is long, the convenience of the user is impaired.
JP 2001-305823 A

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for shortening the time required for the setup operation in an electrophotographic image forming apparatus using a rotary development system. is there.

In order to achieve the above-described object, the present invention provides a rotating photosensitive member, an endless transfer belt having a predetermined circumferential length, and circulated by the rotation of the photosensitive member, and the photosensitive member. A charging unit for charging, an exposure unit for forming an electrostatic latent image on the photosensitive member charged by the charging unit, and each facing the photosensitive member at the same position, each corresponding to a respective N-color toner. A plurality of developing means, each of the developing means transferring a corresponding color toner to the electrostatic latent image formed on the photosensitive member by the exposing means at the opposed position; An image forming unit having a transfer unit that transfers the toner image formed by transferring the toner to the transfer belt by the multi-color developing unit; and a reference signal that is synchronized with a cycle in which the transfer belt rotates. a signal generating means, input An image forming mode for forming an image according to image data, transferring the toner image any color at a timing when the transfer belt is synchronized with the reference signal by the signal generating means generates each time one revolution As a result, the signal generating means generates an image forming mode in which toner images are transferred onto the transfer belt in multiple layers to form an image, and an adjustment toner pattern that is a set of a plurality of toner images of a plurality of color toners. and control means for operating said imaging means at a timing that is independent of the reference signal in either the setup mode for forming on the photosensitive member, wherein, in the set-up mode, the adjustment toner pattern is formed The number of rotations of the transfer belt required for the adjustment is included in the adjustment toner pattern without depending on the reference signal. Calculated in accordance with the number and sizes of the respective color toner images, the image forming apparatus for operating the image forming means such that the respective color toner images are transferred onto the transfer belt until it rotates at a rotational speed that is the calculated I will provide a. According to such an image forming apparatus, in the “setup mode” in which the setup operation is performed, the toner image is formed on the photoconductor in a manner determined by the control unit, and therefore the adjustment is performed regardless of the rotation period of the transfer belt. It is possible to form a toner pattern. The adjustment toner pattern includes, for example, a patch-like toner pattern for density adjustment and a toner band for improving toner charging ability. Since such a toner image is not necessarily transferred, it is sufficient that it is formed on the photoreceptor.

  Alternatively, the image forming apparatus may include a detection unit that detects the consumption amount of toner of each color. In this case, in the setup mode, when the consumption amount of the toner detected by the detection unit is larger than a predetermined amount, the control unit reduces the number of toner images formed by the toner or sets the size thereof. Smaller is more desirable.

Embodiments of the present invention will be described below with reference to the drawings.
[Constitution]
FIG. 1 is a block diagram schematically showing the overall configuration of an image forming apparatus 100 according to an embodiment of the present invention. As shown in the figure, the configuration of the image forming apparatus 100 is roughly divided into a control unit 10, a storage unit 20, a communication unit 30, an operation unit 40, and an image forming unit 50. The control unit 10 is an arithmetic unit including a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and executes a program stored in the ROM. Thus, the operation of each part of the image forming apparatus 100 is controlled. The control unit 10 also has a timer function for measuring an elapsed time from a certain time and a function for executing image processing for obtaining image data suitable for image formation in the image forming unit 50 by an ASIC or the like.

  The storage unit 20 is a storage device such as an HDD (Hard Disk Drive), and stores various data used for image formation. The storage unit 20 stores various data such as “timing to perform a setup operation”, “toner patch length”, “toner patch target density”, and “preparation time”, which will be described later. The communication unit 30 is an interface device for exchanging image data with an external device such as a personal computer or a scanner. The operation unit 40 is an input device including a touch panel, displays various types of information related to image formation, and receives instructions from the user. The image forming unit 50 forms a toner image corresponding to the image data supplied from the control unit 10 and fixes the toner image on the recording paper.

  FIG. 2 is a diagram showing the configuration of the image forming unit 50 in more detail. In the figure, the arrows indicated by broken lines indicate the conveyance path of the recording paper. Here, the recording paper is a sheet-like medium for forming an image, and is not particularly limited to paper. The image forming unit 50 includes a photosensitive drum 501, a charger 502, an exposure device 503, a developing device 504, a primary transfer roll 505, a photosensitive cleaner 506, an erase lamp 507, an intermediate transfer belt 511, A plurality of transport rolls 512, a secondary transfer roll 513, a backup roll 514, an image density sensor 515, a belt cleaner 516, a reference mark sensor 517, and a fixing device 518 are provided.

  The photosensitive drum 501 is an image carrier having a photosensitive layer on the surface, and is rotated in the direction of arrow A in the drawing by a driving unit (not shown). The diameter of the photosensitive drum 501 of this embodiment is about 40 mm. The charger 502 generates a predetermined potential difference with the photosensitive drum 501 by a high voltage power source, and uniformly charges the surface thereof. The potential generated on the photosensitive drum 501 at this time is hereinafter referred to as “charging potential”.

  The exposure device 503 exposes the photosensitive drum 501 by irradiating light beams according to the image data supplied from the control unit 10. Since the photosensitive drum 501 loses the charge corresponding to the exposure amount, the potential of the photosensitive drum 501 is changed in the portion irradiated with the beam light (hereinafter referred to as “exposure portion”). Hereinafter, the potential of the photosensitive drum 501 in the exposure unit is referred to as “exposure unit potential”. An electrostatic latent image is formed on the exposed portion due to the difference between the charged potential and the exposed portion potential.

The developing device 504 is a so-called rotary type multi-color developing device provided with developing units 504Y, 504M, 504C and 504K for respective colors of yellow (Y), magenta (M), cyan (C) and black (K). Each developing unit includes a developing roll _{DR Y, DR M, DR C} , DR K and toner cartridge _{TC Y, TC M, TC C} , the TC _K. The developing device 504 generates a predetermined potential difference between the developing roll and the photosensitive drum 501 and transfers toner to the photosensitive drum 501 by this potential difference. The potential generated at the developing roll at this time is hereinafter referred to as “developing bias potential”.

FIG. 2 shows the initial posture of the developing device 504. This state is hereinafter referred to as “home position”. The developing device 504 assumes the home position when the toner image is not formed. On the other hand, when each color developing unit performs toner transfer, the developing device 504 is rotated by a predetermined angle so that the developing roll faces the photosensitive drum 501. The position P where the photosensitive drum 501 and the developing roll face each other is hereinafter referred to as “developing position”. For example, when performing development of black toner, the developing device 504 is rotated 30 ° clockwise from the home position, moving the developing roller TC _K to the developing position (see FIG. 3). Then, cyan, when performing development of magenta and yellow toners are rotated one by 90 ° from the position shown in FIG. 3, is moved developing roller TC _C, the TC _M and TC _Y to the developing position. Note that both the photosensitive drum 501 and the developing device 504 rotate, but the positions of these opposing points are unchanged.

  The primary transfer roll 505 generates a predetermined potential difference at a position where the intermediate transfer belt 511 faces the photosensitive drum 501 (hereinafter referred to as “primary transfer position”), and the toner image is transferred to the intermediate transfer belt 511 by this potential difference. The potential generated in the primary transfer roll 505 at this time is hereinafter referred to as “primary transfer potential”. The photoconductor cleaner 506 is a blade-like member, and removes toner remaining on the surface of the photoconductor drum 501 without being transferred by the primary transfer roll 505. The erase lamp 507 discharges the surface of the photosensitive drum 501 by performing strong exposure.

  The intermediate transfer belt 511 is an endless belt member having a predetermined circumferential length, and the transport roll 512 stretches the intermediate transfer belt 511. In the present embodiment, the peripheral length of the intermediate transfer belt 511 is 600 mm. At least one of the transport rolls 512 has a drive unit, and moves the intermediate transfer belt 511 in the direction of arrow B in the drawing. As the intermediate transfer belt 511 rotates, the toner image transferred by the primary transfer roll 505 is a nip region formed by the secondary transfer roll 513 and the backup roll 514 (hereinafter referred to as “secondary transfer position”). Moved to. Note that a reference mark detected by a reference mark sensor 517 is attached to the intermediate transfer belt 511. The position of the reference mark is arbitrary, but the number is one.

  The reference mark sensor 517 is an optical sensor that detects a reference mark on the intermediate transfer belt 511 at a predetermined position. The reference mark sensor 517 outputs a reference signal to the control unit 10 when detecting the reference mark.

  The image density sensor 515 is an optical sensor that detects the density of the toner image before the secondary transfer (hereinafter referred to as “image density”) upstream of the secondary transfer position. Specifically, the image density sensor 515 detects the image density based on the intensity of the reflected light (regular reflected light or diffuse reflected light) when the toner image is irradiated with light. The image density sensor 515 of the present embodiment outputs values from “0” to “1023” according to the amount of reflected light. In this embodiment, the lower the output value, the higher the image density (darker), and the higher the output value, the lower the image density (lighter).

  The secondary transfer roll 513 and the backup roll 514 generate a predetermined potential difference at a position where the intermediate transfer belt 511 faces the recording sheet, and the toner image is transferred to the recording sheet by the potential difference. The secondary transfer roll 513 is electrically grounded and has a reference potential. Hereinafter, the potential generated in the backup roll 514 is referred to as “secondary transfer potential”. The secondary transfer roll 513 is provided so as to be able to contact and separate by rotation of the cam, and is configured to be separated from the intermediate transfer belt 511 by about 2 mm when a setup operation described later is performed.

  The belt cleaner 516 is a blade-like member, and removes toner remaining on the intermediate transfer belt 511 without being transferred by the secondary transfer roll 513. The fixing device 518 includes a heating roll and a pressure roll, and the toner image transferred to the recording sheet is fixed by heating and pressing the recording sheet with these roll members.

[Operation]
With the above configuration, the image forming apparatus 100 forms a toner image corresponding to the image data input by the user, and fixes the toner image on the recording paper. Such a mode for performing a normal image forming operation is hereinafter referred to as an “image forming mode”. In addition to such normal image formation, the image forming apparatus 100 uses various toner images (hereinafter referred to as “adjustment toner patterns”) for adjusting the image quality of the image forming unit 50 at a predetermined timing. Perform setup operation to form. The timing at which the image forming apparatus 100 performs the setup operation may be, for example, every time when a predetermined time elapses or every time a predetermined number of sheets are output, or when the power is turned on or during standby, It may be during or after the exchange of goods or between jobs. Note that a mode for performing such a setup operation is hereinafter referred to as a “setup mode”.

  Various toner images are included in the adjustment toner pattern in the present embodiment. For example, a patch-like toner pattern for density adjustment, a toner band for improving toner charging capability, a toner pattern for registration correction, and a blade-like shape such as a photoreceptor cleaner 506 and a belt cleaner 516 For example, a toner band for preventing the member from turning over is applicable. In short, the adjustment toner pattern is a toner image different from the toner image corresponding to the image data input by the user, and may be any toner image for adjusting the image quality.

  Next, an example of a setup operation performed by the image forming apparatus 100 will be described. Here, the toner pattern for adjustment is a patch-like toner pattern for density adjustment (hereinafter referred to as “toner patch”) and a toner band for improving toner charging ability (hereinafter simply referred to as “toner band”). It is assumed that there are two types, and the execution timing of the setup operation is every elapse of a predetermined time. It is assumed that the time indicating the timing for executing the setup operation is stored in the storage unit 20. In the present embodiment, three toner patches are formed for each color. The three toner patches have different target densities.

  FIG. 4 is a flowchart for explaining the operation performed by the image forming apparatus 100, and will be described with reference to FIG. In performing this operation, it is assumed that the control unit 10 of the image forming apparatus 100 causes the image forming unit 50 to perform normal image formation as shown in step S1. That is, the control unit 10 causes the image forming unit 50 to perform an operation in the image forming mode. At this time, it is assumed that the control unit 10 continues to measure the time elapsed since the setup operation was performed immediately before by the timer function.

  When the image formation shown in step S1 is completed, the control unit 10 determines whether or not to perform a setup operation (step S2). The determination at this time is made, for example, by comparing the time measured by the timer function with a value stored in advance. Here, if the time measured by the timer function is larger than a value stored in advance, the control unit 10 switches from the image forming mode to the setup mode. On the other hand, if the time measured by the timer function is equal to or less than the value stored in advance, the control unit 10 determines whether there is a print job to be processed (step S9), and there is a print job to be processed. If so, normal image formation is continued (step S1). On the other hand, if there is no print job to be processed, the image forming operation is terminated and a standby state is entered.

  When the operation is switched to the operation in the setup mode, the control unit 10 performs a process of calculating the toner band length (Lb) (step S3). This process is specifically shown in the flowchart shown in FIG. Here, the “length” is a distance in the moving direction of the photosensitive drum 501, and is not a distance in the width direction of the photosensitive drum 501.

  Referring to FIG. 5, first, the control unit 10 calculates an average value of the image density (hereinafter referred to as “average image density (D)”) based on an image formed after the previous setup operation is executed. Calculation is performed for each color (step S31). The average image density is a value indicating the ratio of the sum of the areas of the portions where the toner images are formed to the sum of the areas of the images formed after the immediately preceding setup operation is executed. For example, if all the images formed after the previous setup operation for a certain color are solid images (ie, 100% density), the average image density for that color is “100%”. If the color formed in the image formed after the previous setup operation is not included at all, the average image density for that color is “0%”.

  Next, the control unit 10 determines whether or not the average image density of each color is equal to or higher than a predetermined density (here, “5%”) (step S32). When the average image density is equal to or higher than the predetermined density, the control unit 10 determines that the toner in the developing unit is sufficiently discharged, and determines that the toner band of that color is not formed. That is, at this time, the control unit 10 sets the value of Lb to “0” (step S33). Note that the length (Lb) of the toner band is “0”, which means that the toner band of this color is not formed.

On the other hand, when the average image density is less than the predetermined density, the control unit 10 does not sufficiently discharge the toner in the developing unit, and the toner charging ability is reduced (that is, the toner is deteriorated). ) And decide to form a toner band of that color. At this time, the control unit 10 calculates the value of Lb by executing the calculation shown in the following equation (1) (step S34).
Lb = X−X × (D / 5) (unit: mm) (1)

  As is apparent from the equation (1), the length (Lb) of the toner band changes according to the average image density (D). The length of the toner band becomes longer as the average image density is smaller, and becomes the longest (X mm) when the average image density is “0%”. In other words, the smaller the amount of toner discharged after the previous setup operation is performed, the lower the toner charging ability in the development unit. Therefore, more toner is forcibly discharged to charge the toner. It means to improve.

  Although the value of X described above is arbitrary, it is necessary to determine it appropriately so that the adjustment toner pattern does not become longer than necessary. In the present embodiment, the value of X is “100 (mm)”. This length is sufficient to improve the charging ability of the toner, but of course, the value of X may be made larger.

  Returning to the description of FIG. After calculating the length of each color toner band in step S3, the control unit 10 subsequently calculates the operation timing of the image forming unit 50 for forming the adjustment toner pattern (hereinafter referred to as “setup timing”). Perform (step S4). This process is specifically shown in the flowchart shown in FIG. Describing along the drawing, the control unit 10 first calculates the time required to form the adjustment toner pattern (hereinafter referred to as “setup sequence time (Ts)”) (step S41). Here, the setup sequence time is determined by the length of the toner band of each color, the length of the toner patch, and the preparation time for image formation. Among these, the length of the toner patch and the preparation time are predetermined values determined in advance. That is, the setup sequence time changes according to the length of the toner band. The longer the toner band, the longer the setup sequence time.

Next, the control unit 10 calculates the rotation speed (Nb) of the intermediate transfer belt 511 required for forming the adjustment toner pattern (step S42). The control unit 10 calculates the rotation speed of the intermediate transfer belt 511 by executing a calculation represented by the following equation (2).
Nb = INT (Ts / Tb) +1 (2)

  In the equation (2), the value Tb indicates the time required for the intermediate transfer belt 511 to make one rotation, and is a value determined by the peripheral length of the intermediate transfer belt 511 and the rotation speed. The function INT (x) is a function that truncates the decimal part of the value x and returns an integer part. For example, the value of INT (1) is “1”, and the value of INT (2.5) is “2”. Is. That is, the value Nb calculated at this time is always an integer.

  After calculating the rotation speed of the intermediate transfer belt 511, the control unit 10 calculates the setup timing based on the rotation speed (Nb) and the length (Lb) of each color toner band (step S43). At this time, the control unit 10 can form a toner image of each color included in the adjustment toner pattern before the intermediate transfer belt 511 rotates “Nb”, so that the charging potential, the exposure amount, the development bias potential, the primary The transfer potential, the rotation timing of the developing device 504, and the detection timing of the image density sensor 515 are determined.

  Returning again to the description of FIG. When the setup timing is calculated as described above, the control unit 10 forms an adjustment toner pattern according to the setup timing (step S5). At this time, the control unit 10 controls the image forming unit 50 so that the toner patch is formed at a predetermined target density. Then, the control unit 10 causes the image density sensor 515 to detect the primarily transferred toner patch and calculates the image density (step S6). Although the toner patch is primarily transferred, the toner band does not need to be transferred to the intermediate transfer belt 511 and is therefore scraped off by the photoconductor cleaner 506 without being primarily transferred. The toner patch detected by the image density sensor 515 is scraped off by the belt cleaner 516 without being subjected to secondary transfer.

  Subsequently, the control unit 10 corrects the image forming conditions based on the image density calculated in step S6 (step S7). The image forming conditions here are parameters that can control the image density, such as a charging potential, an exposure amount, a developing bias potential, a primary transfer potential, and a secondary transfer potential. The correction procedure performed by the control unit 10 at this time is as follows. That is, the control unit 10 compares the image density obtained by detecting the toner patch with a predetermined target density, and if there is a difference, the charging potential and the exposure amount are set so that the difference is eliminated. Then, at least one of the development bias potential, the primary transfer potential, and the secondary transfer potential is changed.

  When the image forming conditions are corrected, the setup operation is finished. At this time, the image forming apparatus 100 is switched from the operation in the setup mode to the operation in the image forming mode. Therefore, the control unit 10 starts measuring time using a timer function in preparation for the next setup operation (step S8). This measurement time is referred to in the determination in step S2.

  Thereafter, the control unit 10 determines whether there is a print job to be processed (step S9). Here, when an unprocessed print job has been input or when the above-described setup operation has been executed in a manner that interrupts the previous print job, the control unit 10 should end the subsequent print job. While causing the image forming unit 50 to perform the image forming operation (step S1), if there is no unprocessed print job, the image forming operation is terminated and a standby state is entered.

  Next, the operation of the image forming apparatus 100 performed in this way will be described with reference to a timing chart. Here, in order to easily understand the effects of the present embodiment, a timing chart in the image forming operation and a timing chart in the setup operation are shown. In addition, the timing chart in the setup operation is applied when the present invention is applied. Each case is shown below.

  First, FIG. 7 is a timing chart showing the operation of the image forming apparatus 100 in a normal image forming operation. As shown in the figure, the image forming apparatus 100 periodically transmits reference signals Tr_K, Tr_Y, Tr_M, and Tr_C. The reference signals Tr_K, Tr_Y, Tr_M, and Tr_C indicate timings for forming black (K), yellow (Y), magenta (M), and cyan (C) toner images, respectively. In this embodiment, the interval (that is, the period) at which the reference signal is transmitted is about 8 seconds.

  Based on the reference signal, the control unit 10 of the image forming apparatus 100 switches the rotation timing of the developing device 504 and the on / off of the exposure light and the developing bias potential. Specifically, the control unit 10 turns off the developing bias potential when rotating the developing device 504, and turns off the exposure light before and after rotating the developing device 504. Then, the control unit 10 turns on the primary transfer potential and transfers the toner images of each color to the intermediate transfer belt 511 in a multiple manner. When the toner images for four colors are transferred, the secondary transfer potential is turned on and transferred to the recording paper. Let

  Next, FIG. 8 is a timing chart showing the operation of the image forming apparatus 100 in the setup operation when the present invention is not applied. FIG. 9 is a diagram conceptually showing an adjustment toner pattern formed on the intermediate transfer belt 511 at this time. In FIG. 8, the primary transfer potential is on only while the toner patch is transferred, and the image density sensor 515 is on only while the toner patch passes. Further, the secondary transfer potential is always off. This is because the toner patch is not subjected to secondary transfer, and the toner band is not subjected to primary transfer or secondary transfer. In FIG. 9, the interval between adjacent broken lines corresponds to the circumferential length of the intermediate transfer belt 511.

  As shown in FIG. 8, in the conventional setup operation, each color toner patch and toner band are formed when a reference signal for each color is transmitted. Therefore, as shown in FIG. 9, even if the length of the toner band is shortened, the time required to form the entire adjustment toner pattern is hardly changed. That is, in this case, the setup operation requires time for the intermediate transfer belt 511 to rotate four times.

  On the other hand, FIG. 10 is a timing chart showing the operation of the image forming apparatus 100 in the setup operation when the present invention is applied. FIG. 11 is a diagram conceptually showing the adjustment toner pattern formed on the intermediate transfer belt 511 at this time. In these drawings, the number and size of toner patches and toner bands to be formed are the same as those in FIGS. 8 and 9 described above.

  When the present invention is applied, the control unit 10 calculates the setup sequence time, and calculates the setup timing based on the setup sequence time. Therefore, according to the image forming apparatus 100 of the present embodiment, it is possible to form each color toner patch and toner band without using the reference signal. That is, in other words, it is possible to sequentially start the formation of toner images of each color without waiting for the intermediate transfer belt 511 to make one rotation. This is of course applicable to executing the setup operation so that the toner images for a plurality of colors are well separated on the intermediate transfer body while the intermediate transfer body such as the intermediate transfer belt 511 rotates exactly once. In other words, even when toner images for a plurality of colors cannot be well separated on the intermediate transfer body during one rotation of the intermediate transfer body, the present invention can be applied to perform setup without using the reference signal. As a result, the length (Lp in FIG. 11) required to form the entire adjustment toner pattern is reduced, and the setup mode can be switched to the image formation mode at an earlier timing. As described above, since the intermediate transfer belt 511 makes one rotation in about 8 seconds, the setup operation can be completed about 8 to 24 seconds faster when the present invention is applied than when the intermediate transfer belt 511 is not applied. .

  In the image forming apparatus according to the present invention, it is possible to sequentially create toner images of respective colors in the setup mode without depending on the rotation cycle of the intermediate transfer member. Therefore, the present invention is not only applicable to the case where the toner images of the respective colors are sequentially formed without waiting for the intermediate transfer member to make one rotation, but also the time required to form the toner image of one color is made one rotation of the intermediate transfer member. Even if it is larger, it can be applied. In particular, if the time required to form a one-color toner image is not an integral multiple of the intermediate transfer member, the setup sequence time can be shortened.

[Modification]
In the above, the present invention has been described by exemplifying one preferred embodiment, but the present invention is not limited to the above-described embodiment, and can be implemented in various other modes. . In the present invention, for example, the following modifications can be applied to the above-described embodiment. These modifications can be combined as appropriate.

  In the above-described embodiment, the developing device 504 has a configuration in which developing units for each color are provided at equal intervals. However, since black toner generally tends to be used more than other toners, in recent years, a developing device 504a in which only a black toner cartridge is enlarged as shown in FIG. 12 is often used. The invention can also be applied in such a configuration. In this configuration, since the rotation angles at the time of development are not the same, the operation timing is slightly different, but there is no significant difference in essential operation.

  In the above-described embodiment, it has been described that the length of the toner band is determined based on the average image density. However, the factor that changes the length of the toner band is not limited to this. In addition, the length of the toner patch may be determined instead of the length of the toner band, and the length of each color toner patch may be determined based on, for example, the amount of use of the photoreceptor (film thickness change, etc.) Alternatively, the length of the toner patch may be determined based on the selection result of the image quality mode (high image quality mode, standard image quality mode, etc.) or the density unevenness detection result obtained by the previous toner patch density detection.

  In the above-described embodiment, the adjustment toner pattern is described as including a toner patch and a toner band. However, the present invention is not limited to this. For example, it is also possible to use an adjustment toner pattern composed only of toner patches. In this case, as shown in FIG. 13, the number of toner patches of each color may be varied. The number of toner patches for each color is determined by, for example, the amount of use and remaining amount of consumables such as toner and photoconductors, or the density unevenness caused by the density adjustment performed in the past or the previous toner patch density detection. It may be determined based on the detection result. In this case, for example, a large number of toner patches may be created for a color that has been largely corrected in the past density adjustment or a color for which the density unevenness detection result is not satisfactory. Alternatively, the number of toner patches of each color may be varied based on the selection result of the image quality mode (high image quality mode / standard image quality mode). In this case, for example, when the high image quality mode is selected, more toner patches may be created than when the standard image quality mode is selected. The image quality mode is selected by the user via the operation unit 40 or by an instruction included in the print job.

  In the above-described embodiment, it has been described that the rotational speed (Nb) of the intermediate transfer belt 511 is calculated based on the setup sequence time (Ts), and the setup timing is calculated based on the rotational speed. It is also possible to calculate the setup timing directly from In addition, as for the setup timing, setup timings for a plurality of patterns may be set in advance, and an optimum one may be selected from a plurality of patterns according to the length of the toner band for each color.

  In addition, as shown in the timing chart of FIG. 7 and the like, a standby time of about 0.2 to 0.3 seconds is generally provided from when the developing device 504 is rotated to when exposure is started. The purpose of this is to prevent image quality degradation due to vibrations caused by braking when rotation of the developing device 504 is stopped. When the developing device 504 vibrates, this vibration is transmitted and the photosensitive drum 501 also vibrates. If exposure is started before the vibration is sufficiently attenuated, streaky unevenness (banding) due to the vibration occurs in the formed electrostatic latent image, which causes a reduction in image quality. Therefore, in order to sufficiently attenuate the vibration of the photosensitive drum 501, a standby time (Tw) is provided before the exposure light is irradiated as shown in FIG.

  However, when forming the adjustment toner pattern, banding is not a big problem as compared with the normal image formation. Therefore, when performing the setup operation, for example, as shown in FIG. 14B, the waiting time (Tw) may be shortened. In this way, the setup operation can be finished earlier. In such a case, instead of a toner image used for some detection like a toner patch, a toner image that is sufficient if it is formed like a toner band is exposed first. More desirable. This is because such a toner image has no problem even if banding occurs.

  Further, as described above, in the setup operation, the secondary transfer roll 513 is separated from the intermediate transfer belt 511 by the cam. At this time, the secondary transfer potential is turned off. Simultaneously with turning off the secondary transfer potential, the control unit 10 transmits a signal indicating this (hereinafter referred to as “retract signal”), and the secondary transfer roll 513 is separated when the retract signal is transmitted. Since the secondary transfer roll 513 is separated according to the rotation of the cam, the secondary transfer roll 513 is gradually separated from the intermediate transfer belt 511 after transmission of the retract signal, and is separated by about 2 mm and stopped after about 0.6 seconds.

  Here, in the normal setup operation, as shown in the timing chart of FIG. 15A, the toner patch passes through the secondary transfer position after the secondary transfer roll 513 is completely stopped. Is formed. However, if it is desired to perform the setup operation at a higher speed, the timing at which the toner patch is formed before the secondary transfer roll 513 completely stops as shown in the timing chart shown in FIG. You may make it pass a secondary transfer position. This is because the toner does not adhere to the secondary transfer roll 513 even if the toner patch passes after the secondary transfer roll 513 has been separated from the intermediate transfer belt 511 to some extent. Specifically, since it is only necessary that the secondary transfer roll 513 is separated from the intermediate transfer belt 511 by about 1 mm, it is possible to advance the toner patch formation timing of each color by about 0.3 seconds.

  In the image forming apparatus having the configuration as in the above-described embodiment, the electrical resistance is detected by applying a predetermined voltage at the primary transfer position or the secondary transfer position, and the primary resistance is set so that the resistance becomes constant. Control to adjust the transfer potential, the secondary transfer potential, and the like may be performed. If such adjustment is performed in advance at the start of the setup operation, it is possible to perform density adjustment with higher accuracy. When the resistance is detected, it is necessary to prevent the toner image from passing through the position.

  When the resistance is detected at the start of the setup operation, the timing may be adjusted so that the resistance detection at the primary transfer position and the resistance detection at the secondary transfer position are performed at substantially the same position on the intermediate transfer belt 511. . This is shown in the timing chart shown in FIG. If detection is performed in this manner, for example, as shown in FIG. 16A, the timing for forming the toner patch can be advanced as compared with the case where both resistances are detected simultaneously. Will be able to finish.

  Further, in the above-described embodiment, the developing device 504 that forms yellow, magenta, cyan, and black toner images is shown, but the present invention can also be applied to a developing device that uses toner of five or more colors. On the other hand, in the case of a monochromatic developing device, the present invention naturally has no effect. In other words, the present invention is a technique applicable to a configuration using two or more colors of toner.

1 is a block diagram schematically showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of an image forming unit of the image forming apparatus. FIG. 6 is a diagram illustrating a state when the developing device of the image forming apparatus develops a black toner image. 5 is a flowchart illustrating an operation performed by the image forming apparatus. 6 is a flowchart illustrating processing for calculating the length of a toner band. It is the flowchart which showed the process which calculates a setup timing. 6 is a timing chart showing the operation of the image forming apparatus in a normal image forming operation. 6 is a timing chart illustrating an operation of the image forming apparatus in a setup operation when the present invention is not applied. FIG. 5 is a diagram conceptually showing an adjustment toner pattern formed on an intermediate transfer belt when the present invention is not applied. 6 is a timing chart illustrating an operation of the image forming apparatus in a setup operation when the present invention is applied. FIG. 3 is a diagram conceptually showing an adjustment toner pattern formed on an intermediate transfer belt when the present invention is applied. It is the figure which showed the modification of the image development apparatus. FIG. 6 is a diagram illustrating a modified example of an adjustment toner pattern. It is a timing chart for explaining standby time before exposure. 6 is a timing chart for explaining the separation timing of the secondary transfer roll. It is a timing chart for demonstrating the resistance detection performed in a primary transfer position and a secondary transfer position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 10 ... Control part, 20 ... Memory | storage part, 30 ... Communication part, 40 ... Operation part, 50 ... Image forming part, 501 ... Photosensitive drum, 502 ... Charger, 503 ... Exposure apparatus, 504 ... Developing device, 505... Primary transfer roll, 506... Photoreceptor cleaner, 507... Erase lamp, 511... Intermediate transfer belt, 512 .. conveyance roll, 513 .. secondary transfer roll, 514. ... Belt cleaner, 517 ... Reference mark sensor, 518 ... Fixing device

Claims (6)

An image forming apparatus for forming a multicolor image with a plurality of color toners,
A rotating photoreceptor,
An endless transfer belt having a predetermined circumference and being moved in rotation following the rotation of the photoreceptor;
Charging means for charging the photoreceptor;
An exposure unit that forms an electrostatic latent image on the photoreceptor charged by the charging unit;
Each has a plurality of developing units corresponding to the N-color toners, each facing the photoconductor at the same position, and each of the developing units is formed on the photoconductor by the exposure unit. Multi-color developing means for transferring toner of a corresponding color at the opposite position to the electrostatic latent image;
An image forming means comprising: a transfer means for transferring a toner image formed by transferring toner by the multicolor developing means to the transfer belt;
A signal generating means for generating a reference signal synchronized with a cycle in which the transfer belt makes a circular movement;
In an image forming mode for forming an image according to input image data, a toner image of any color is formed at a timing synchronized with a reference signal generated by the signal generating means each time the transfer belt makes one revolution. By the transfer, the signal generating unit generates an image forming mode in which the toner image is transferred onto the transfer belt in multiple layers to form an image, and an adjustment toner pattern that is a set of a plurality of toner images of a plurality of color toners. and control means for operating said imaging means at a timing that is independent of the reference signal in any of the setup mode of forming on said photosensitive member,
In the setup mode, the control means does not depend on the reference signal for the number of rotations of the transfer belt required to form the adjustment toner pattern, and the toner image of each color included in the adjustment toner pattern. The image forming means is operated so that the toner images of the respective colors are transferred onto the transfer belt before rotating at the calculated number of rotations. apparatus. As image quality in images formed, further comprising a standard definition mode, a selection means for selecting one of high quality high-quality mode than the standard definition mode,
The control means includes
In the setup mode, when the high image quality mode is selected by the selection unit , the number of toner images to be formed on the photoconductor is larger than when the standard image quality mode is selected, or The image forming apparatus according to claim 1, wherein the size is increased . It further comprises a detecting means for detecting the consumption amount of each color toner,
The control means includes
In the setup mode, when the consumption amount of toner detected by the detection unit is larger than a predetermined amount , the toner is formed on the photoconductor than when the consumption amount of toner detected by the detection unit is smaller than a predetermined amount. The image forming apparatus according to claim 1, wherein the number of toner images to be reduced is reduced or the size thereof is reduced . Before Symbol control means,
Calculating means for calculating a length of each color toner image included in the adjustment toner pattern in a moving direction of the photoconductor;
In a first setup mode in which the adjustment toner pattern is formed on the photoconductor during a period in which the transfer belt rotates a predetermined number of times when the total length calculated by the calculation unit exceeds a predetermined threshold. When the image forming unit is operated, and the total length calculated by the calculating unit is equal to or less than a predetermined threshold, the adjustment toner pattern during the period when the transfer belt rotates less than the predetermined number of times. The image forming apparatus according to claim 1, wherein the image forming unit is operated in a second setup mode for forming the image on the photosensitive member . Before Symbol control means,
A calculating means for calculating a time required for each color toner image included in the adjustment toner pattern to be formed on the photoconductor;
When the total time calculated by the calculating unit exceeds a predetermined threshold, the adjustment toner pattern is formed on the photoconductor during a period in which the transfer belt rotates a predetermined number of times. When the image forming unit is operated and the total time calculated by the calculating unit is equal to or less than a predetermined threshold, the adjustment toner pattern is applied to the adjustment toner pattern during the period in which the transfer belt rotates less than the predetermined number of times. The image forming apparatus according to claim 1, wherein the image forming unit is operated in a second setup mode to be formed on the photosensitive member . Before Symbol control means,
In response to the reference signal originally generated after the adjusting toner pattern is formed in the set-up mode, according to claim 1, characterized in that to perform the operation by the image forming mode to the image forming means Image forming apparatus.

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