Image forming apparatus, image forming method, and program

Abstract

To provide an image forming apparatus, an image forming method, and a program that can execute transfer FF control with reduced error elements.SOLUTION: The present invention comprises: an image forming part that forms a latent image on an image carrier according to a print image from an image controller; a developing current monitoring part that monitors a developing current flowing from a developing high-voltage power supply to a developing unit that develops the latent image on the image carrier; a transfer unit that transfers, to a recording sheet, a visible image obtained by the developing unit developing the latent image, and is supplied with a transfer bias; a memory that divides the print image into a plurality of division areas for every constant section in a conveyance direction of the visible image, and stores the developing current for every division area; a timer that notifies the timing at which a leading end of each division area reaches a transfer start position of the transfer unit; and a determination unit that, every time the timing is notified, determines the transfer bias according to the developing current for every division area.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, an image forming method, and a program. [Background technology]

[0002] A technology has been developed that realizes a high transfer rate by controlling the transfer bias in response to the shading of an image in an image forming apparatus (hereinafter referred to as transfer FF (feedforward) control). In transfer FF control, the print image is divided into multiple divided areas at fixed intervals in the image transport direction, the number of pixels (pixel count value) in the divided areas is counted, the image area ratio, which is the ratio between the pixel count value and the area of ​​the divided area, is calculated, and when the divided area is transferred, the transfer bias value (current or voltage) is controlled in response to the image area ratio of the divided area. This makes it possible to control the transfer bias in response to the shading of the image and obtain a high transfer rate.

[0003] Patent document 1 discloses a means for ensuring transfer efficiency by controlling the transfer current of the transfer charger in a timely manner using a CPU for engine control in accordance with the B / W ratio of the image signal, with the aim of ensuring stable transfer efficiency and obtaining good images by responding precisely to changes in the environment and printing pattern for each part of an image. Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned transfer FF control estimates the image shading based on the pixel count value (image area ratio) and sets the transfer bias. Therefore, the installation environment of the printing machine, the charge amount of the toner, the state of the charging unit and the photoconductor, the output accuracy of the high-voltage power supply applied for charging and development, etc. may become error elements. In addition, in the technology described in Patent Document 1, an error occurs between the calculated value (theoretical value) and the actual amount of toner developed due to the installation environment of the printing machine, the charge amount of the toner, the state of the charging roller and the photoconductor, the output accuracy of the high-voltage power supply applied for charging and development, etc., and the control of the bias value applied to the transfer unit according to the image area ratio based on the pixel count value includes an error element.

[0005] The present invention has been made in view of the above, and has an object to provide an image forming apparatus, an image forming method, and a program capable of implementing transfer FF control with reduced error factors. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the present invention comprises an image forming unit that forms a latent image on an image carrier in accordance with a print image from an image controller, a development current monitoring unit that monitors a development current flowing from a development high-voltage power supply to a development unit that develops the latent image on the image carrier, a transfer unit that transfers a visible image developed by the development unit onto a recording sheet and is supplied with a transfer bias, a memory that divides the print image into a plurality of divided areas at regular intervals in the transport direction of the visible image and stores the development current for each divided area, a timer that notifies the timing when the tip of each divided area reaches the transfer start position of the transfer unit, and a determination unit that determines the transfer bias in accordance with the development current for each divided area each time the timing is notified. Effect of the Invention

[0007] According to the present invention, it is possible to perform transfer FF control with fewer error factors. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a schematic configuration of transfer FF control of a conventional laser beam printer. [Diagram 2] FIG. 2 is a diagram for explaining an example of transfer FF control in the image forming apparatus according to the first embodiment. [Diagram 3] FIG. 3 is a diagram for explaining an example of the relationship between the development current and the set value of the transfer bias in accordance with the darkness and lightness of a printed image. [Figure 4] FIG. 4 is a diagram for explaining an example of transfer FF control in the image forming apparatus according to the second embodiment. [Diagram 5] FIG. 5 is a diagram for explaining an example of transfer FF control in the image forming apparatus according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an image forming apparatus, an image forming method, and a program will be described in detail with reference to the accompanying drawings.

[0010] 1 is a diagram showing an example of a schematic configuration of transfer FF control of a conventional laser beam printer. The conventional laser beam printer is an example of an image forming apparatus having a photoconductor 101, a charging unit 102, a laser driving section 103, a developing unit 104, a high-voltage developing power supply 105, a transfer unit 106, a high-voltage transferring power supply 107, a control board 108, an image processing video controller 111, a pixel counter 112, etc.

[0011] The photoconductor 101 is an example of an image carrier. The charging unit 102 charges the photoconductor 101 with a charging bias. The image processing video controller 111 sends pixel data determined by the print image to the laser driving unit 103, and the laser driving unit 103 forms an electrostatic latent image on the charged photoconductor 101 based on the pixel data.

[0012] The developing unit 104 is an example of a developing unit that develops the electrostatic latent image into a visible image. The developing high voltage power supply 105 is an example of a developing high voltage power supply that applies a developing bias to the developing unit 104. The transfer unit 106 is an example of a transfer unit that transfers the visible image to an image holding member (e.g., paper, intermediate transfer belt).

[0013] The transfer high voltage power supply 107 is an example of a transfer high voltage power supply that applies a transfer bias to the transfer unit 106. The control board 108 has a development control circuit 108a and a transfer control circuit 108b. The development control circuit 108a controls the development bias applied to the development unit 104 by the development high voltage power supply 105. The transfer control circuit 108b is an example of a transfer control circuit that controls the set value of the transfer high voltage power supply 107 depending on whether the number of pixels obtained is large or small, based on the pixel count of a pixel counter 112 that counts the pixels.

[0014] Next, the mechanism of transfer FF control in the above-mentioned conventional laser beam printer will be described. The basic image creation process for transferring a visible image to an image holding member is the same as the known electrophotographic process. For example, a laser beam printer charges a photoconductor 101 with a charging unit 102, writes an electrostatic latent image according to an input image with a laser driving unit 103, transfers toner to develop the image with a developing unit 104, and transfers the image to an image holding member such as paper or an intermediate transfer belt with a transfer unit 106.

[0015] Next, the transfer control circuit 108b divides the print image into a plurality of divided regions at fixed intervals in the image transport direction, and counts a pixel counter value, which is the number of pixels in the pixel data for each divided region. Furthermore, the transfer control circuit 108b calculates the image area ratio for each divided region based on the counted pixel counter value. Then, the transfer control circuit 108b controls the setting value of the transfer high voltage power supply 107 according to the image area ratio.

[0016] (First embodiment) Fig. 2 is a diagram for explaining an example of transfer FF control in the image forming apparatus according to the first embodiment. Specifically, Fig. 2 is a diagram for explaining an example of application of transfer FF control to primary transfer in an electrophotographic image forming apparatus.

[0017] As shown in FIG. 2, the image forming apparatus according to the present embodiment includes a photoconductor 101, a charging unit 102, a laser driving unit 103, a developing unit 104, a developing high voltage power supply 105, a transfer unit 106, a transfer high voltage power supply 107, a developing current monitor circuit 109, a control board 110, an image processing video controller 111, and the like.

[0018] The photoconductor 101 is an example of an image carrier.

[0019] The charging unit 102 applies a charging bias to the photoconductor 101 to charge the photoconductor 101 .

[0020] The laser driving unit 103 receives pixel data determined by the print image from the image processing video controller 111, and forms an electrostatic latent image on the charged photoconductor 101 based on the pixel data. In other words, the laser driving unit 103 is an example of an image forming unit that forms an electrostatic latent image (an example of a latent image) on the photoconductor 101 in accordance with the print image input from the image processing video controller 111 (an example of an image controller).

[0021] The developing unit 104 is an example of a developing unit that forms a visible image by developing the electrostatic latent image on the photoconductor 101 by attaching toner to the electrostatic latent image. The developing high-voltage power supply 105 is an example of a developing high-voltage power supply that applies a developing bias to the developing unit 104.

[0022] The transfer unit 106 is an example of a transfer unit that receives (applies) a transfer bias (primary transfer bias) from a transfer high-voltage power supply 107 and transfers the visible image on the photoconductor 101 to an image holding member (an example of a recording sheet). The transfer high-voltage power supply 107 applies a transfer bias to the transfer unit 106. The development current monitor circuit 109 is an example of a development current monitor section that monitors the development current flowing from the development high-voltage power supply 105 to the development unit 104.

[0023] The control board 110 includes a memory 110a, a timer 110b, and a transfer control circuit 110c. The transfer control circuit 110c controls the transfer bias of the transfer high voltage power supply 107 based on the development current monitored by the development current monitor circuit 109.

[0024] Here, the developing current changes according to the image density. The developing bias is a constant voltage control, and controls the electric field generated between the charged photoconductor 101 and the photoconductor 101, thereby causing the charged toner to adhere to the photoconductor 101. The amount of charge movement is a current, and the amount of charged toner movement is the developing current, so the amount of toner adhesion and the developing current are proportional to each other.

[0025] For this reason, the control board 110 divides the print image into a plurality of divided areas at regular intervals in the transport direction of the visible image (image transport direction), and has a memory 110a (an example of a memory) that stores the development current for each divided area, and a timer 110b (an example of a timer) that notifies the timing at which the leading end of the divided area reaches the transfer position (an example of a transfer start position) of the transfer unit 106. Here, the transfer position may be a position at which the visible image developed by the development unit 104 is transferred to the image holding member. Then, the transfer control circuit 110c of the control board 110 functions as an example of a determination unit that determines the transfer bias of the transfer high voltage power supply 107 according to the development current for each divided area every time the timing is notified from the timer 110b.

[0026] In conventional transfer FF control, the shading of a printed image is estimated based on the pixel count number (image area ratio) in a divided area by counting the pixels of the printed image sent from the image processing video controller 111. The estimation of the shading of a printed image based on the pixel count number does not take into account error elements such as the installation environment of the printing machine, the charge amount of the toner, the state of the charging unit and the photoconductor, and the output accuracy of the high voltage power supply applied for charging and development.

[0027] In contrast, in this embodiment, the transfer control circuit 110c estimates the shading of the print image based on the development current for each divided area, as described above. As a result, the estimation of the shading of the print image based on the development current includes error elements such as the installation environment of the printer, the charge amount of the toner, the state of the charging unit 102 and the photoconductor 101, and the output accuracy of the high voltage power supply applied for charging and development, so that transfer FF control with fewer error elements can be implemented.

[0028] 3 is a diagram for explaining an example of the relationship between the development current and the set value of the transfer bias according to the darkness and lightness of the printed image. In the graph of FIG. 3, the vertical axis represents the development current or the transfer current (transfer bias), and the horizontal axis represents time.

[0029] As shown in Fig. 3, the darker the print image, the higher the development current, and the lighter the print image, the lower the development current. The transfer control circuit 110c divides the print image into regular intervals in the image transport direction, and controls the set value of the transfer bias of the transfer high voltage power supply 107 for each divided area. The development current monitor circuit 109 constantly monitors the development current and transmits it to the memory 110a.

[0030] The memory 110a calculates and stores the average value of the development current monitored for each divided area. The timer 110b pre-stores the image (visible image) transport speed and the length of the image (visible image) transport path during printing (transfer). This allows the timer 110b to measure the timing when each divided area of ​​the print image reaches the transfer position. When the transfer control circuit 110c is notified by the timer 110b of the timing when the leading edge of each divided area of ​​the print image reaches the transfer position, it determines the transfer bias (here, the transfer current) according to the development current of that divided area.

[0031] Furthermore, when the leading edge of the next divided area reaches the transfer position, the transfer control circuit 110c changes the transfer bias according to the development current of that divided area. By repeating this process for the number of divided areas, transfer FF control with less error can be realized.

[0032] In this embodiment, the transfer FF control is applied to the primary transfer of the intermediate transfer method, but the transfer FF control can also be implemented in the direct transfer method. In addition, the transfer bias in this embodiment is a constant current control, but it can also be implemented by a constant voltage control. The memory 110a may take and store an integral value of the development current instead of the average value of the development current monitored for each divided area. In other words, the transfer control circuit 110c may determine the transfer bias of the transfer high voltage power supply 107 according to the average value or integral value of the development current monitored in each divided area.

[0033] In addition, there is no specification for the number of divisions of the print image, and the more divisions the print image has, the finer the control of the transfer bias can be controlled. However, the more divisions there are, the more frequently the transfer bias control needs to be changed, which increases the load on the software.

[0034] In this way, according to the image forming apparatus of the first embodiment, the estimation of the shade of the printed image based on the development current includes error elements such as the installation environment of the printing machine, the charge amount of the toner, the state of the charging unit 102 and the photosensitive member 101, and the output accuracy of the high-voltage power supply applied for charging and development, so that transfer FF control can be implemented with fewer error elements.

[0035] (Second embodiment) This embodiment is an example of application of transfer FF control to secondary transfer in an electrophotographic image forming apparatus. In the following description, the same configuration as in the first embodiment will not be described.

[0036] Fig. 4 is a diagram for explaining an example of transfer FF control in the image forming apparatus according to the second embodiment. Specifically, Fig. 4 is a diagram for explaining an example of application of transfer FF control to secondary transfer in an electrophotographic image forming apparatus.

[0037] 4, the image forming apparatus according to the present embodiment includes a photoconductor 101, a charging unit 102, a laser driving section 103, a developing unit 104, a developing high voltage power supply 105, a transfer unit (primary transfer unit) 106, a transfer high voltage power supply (primary transfer high voltage power supply) 107, a developing current monitor circuit 109, an image processing video controller 111, a control board 401, an intermediate transfer belt 402, a secondary transfer unit 403, a secondary transfer high voltage power supply 404, etc. The control board 401 includes a primary transfer memory 401a, a secondary transfer memory 401b, a primary transfer timer 401c, a secondary transfer timer 401d, a primary transfer control circuit 401e, a secondary transfer control circuit 401f, etc.

[0038] In the primary transfer unit 106, the visible image on the photoconductor 101 is transferred (primary transfer) onto the outer periphery of the intermediate transfer belt 402. Here, the intermediate transfer belt 402 is an example of a belt member that contacts the photoconductor 101. The development current monitor circuit 109 transmits the development current to a primary transfer memory 401a and a secondary transfer memory 401b. The secondary transfer memory 401b stores the sum of the development current monitored for one or more mounted photoconductor units (photoconductors 101) for each divided region of the print image in which the visible image on the intermediate transfer belt 402 is secondarily transferred onto a recording sheet.

[0039] In the image forming apparatus according to the present embodiment, when the visible image on the intermediate transfer belt 402 is transported and moves to the transfer position (for example, directly below a repulsive roller) of the secondary transfer unit 403, the printing paper is also fed so that the paper and the visible image are exactly aligned in position. The secondary transfer unit 403 is an example of a transfer unit or secondary transfer unit that transfers the visible image on the intermediate transfer belt 402 onto a recording sheet such as printing paper and is supplied with a transfer bias (secondary transfer bias) by a secondary transfer high voltage power supply 404.

[0040] The secondary transfer timer 401d stores in advance the transport speed of the print image (visible image) during printing and the length of the transport path of the print image (visible image). This allows the secondary transfer timer 401d to measure the timing at which the leading edge of each divided area of ​​the print image (visible image) during secondary transfer reaches the transfer position of the secondary transfer unit 403. In other words, the secondary transfer timer 401d is an example of a timer that notifies the timing at which the leading edge of the divided area in the image transport direction reaches the secondary transfer start position by the secondary transfer unit 403.

[0041] The secondary transfer control circuit 401f changes the set value of the secondary transfer bias of the secondary transfer high voltage power supply 404 for each divided area according to the calculation result of the sum of the development current stored in the secondary transfer memory 401b. Here, the sum of the development current may be the sum of the weighted values ​​of the development current of each photoconductor unit. Since the shading and development current of the printed image (visible image) differ depending on the color and type of toner, the secondary transfer control circuit 401f may adjust the weight of the development current of each photoconductor unit. Here, the photoconductor unit is a unit including the photoconductor 101, the charging unit 102, the laser driving unit 103, the development unit 104, and the primary transfer unit 106. That is, the secondary transfer control circuit 401f is an example of a determination unit that determines the secondary transfer bias according to the development current for each divided area stored in the secondary transfer memory 401b every time the timing is notified from the secondary transfer timer 401d.

[0042] The secondary transfer high voltage power supply 404 applies a high voltage via a repulsive roller to perform secondary transfer of a visible image from the intermediate transfer belt 402 to a paper surface (recording sheet). By repeating this process for the number of divided areas, transfer FF control with less error can be realized. The time width of the divided areas can be set independently for the primary transfer and the secondary transfer.

[0043] In this way, according to the image forming apparatus of the second embodiment, in an example of application of transfer FF control to secondary transfer in an electrophotographic image forming apparatus, it is possible to obtain the same effects as those of the first embodiment.

[0044] (Third embodiment) This embodiment is an example of a combination of a transfer FF control of a primary transfer bias according to an image area ratio of each divided region and a transfer FF control of a secondary transfer bias according to a development current of each divided region in an electrophotographic image forming apparatus. In the following description, the same configuration as the second embodiment will not be described.

[0045] Fig. 5 is a diagram for explaining an example of transfer FF control in an image forming apparatus according to a third embodiment. Specifically, Fig. 5 is a diagram for explaining an example in which a conventional transfer FF control and the transfer FF control of the present invention are combined in an electrophotographic image forming apparatus.

[0046] As shown in FIG. 5, the image forming apparatus of this embodiment includes a photoconductor 101, a charging unit 102, a laser driving unit 103, a developing unit 104, a developing high voltage power supply 105, a transfer unit (primary transfer unit) 106, a transfer high voltage power supply (primary transfer high voltage power supply) 107, a developing current monitor circuit 109, an image processing video controller 111, a pixel counter 112, a control board 401, an intermediate transfer belt 402, a secondary transfer unit 403, a secondary transfer high voltage power supply 404, a pixel counter 501, and the like.

[0047] In this embodiment, pixel counter 501 counts the number of pixels (pixel count value) in a divided region and stores the pixel count value in primary transfer memory 401a. Primary transfer control circuit 401e performs transfer FF control in primary transfer using the pixel counter value stored in primary transfer memory 401a. Secondary transfer control circuit 401f performs transfer FF control in secondary transfer according to the development current.

[0048] Specifically, the primary transfer control circuit 401e counts pixel data from the image processing video controller 111 using the pixel counter 112, and controls the setting value of the primary transfer bias of the primary transfer high voltage power supply 107 for each divided area according to the image area ratio of the print image based on the pixel count value. That is, the primary transfer control circuit 401e is an example of a determination unit that calculates the image area ratio for each divided area based on the pixel count value, and determines the primary transfer bias to be supplied to the primary transfer unit 106 according to the image area ratio.

[0049] The secondary transfer control circuit 401f calculates the sum of the development currents of the respective development units 104, and controls the setting value of the secondary transfer bias of the secondary transfer high voltage power supply 404 for each divided area according to the sum. By repeating this process for the number of divided areas, transfer FF control with less error can be realized.

[0050] In this way, since the image forming apparatus according to the third embodiment has a short distance from the developing unit 104 to the primary transfer unit 106, it can be used in cases where the printing speed or software processing speed is not fast enough to reflect the development current in the primary transfer control.

[0051] In the image forming apparatus according to the second and third embodiments, as shown in Figures 4 and 5, only one photosensitive unit including a photosensitive member 101, a charging unit 102, a laser driving unit 103, a developing unit 104, and a primary transfer unit 106 is depicted, but multiple photosensitive units may be installed depending on the number of colors of toner used by the image forming apparatus.

[0052] The program executed by the image forming apparatus of this embodiment is provided in a state where it is pre-installed in a ROM (Read Only Memory) etc. The program executed by the image forming apparatus of this embodiment may be provided by being recorded in a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk) in the form of an installable or executable file.

[0053] Furthermore, the program executed by the image forming apparatus of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Also, the program executed by the image forming apparatus of the present embodiment may be provided or distributed via a network such as the Internet.

[0054] The program executed by the image forming apparatus of this embodiment has a modular configuration including each of the above-mentioned parts (developing current monitor circuit 109, transfer control circuit 110c, pixel counter 112, primary transfer timer 401c, secondary transfer timer 401d, primary transfer control circuit 401e, and secondary transfer control circuit 401f), and in terms of actual hardware, a processor such as a CPU (Central Processing Unit) reads out the program from the ROM and executes it, thereby loading each of the above-mentioned parts onto a main memory device, and the developing current monitor circuit 109, transfer control circuit 110c, pixel counter 112, primary transfer timer 401c, secondary transfer timer 401d, primary transfer control circuit 401e, and secondary transfer control circuit 401f are generated on the main memory device.

[0055] In the above embodiment, the image forming apparatus of the present invention is described as being applied to a multifunction peripheral having at least two of the functions of a copy function, a printer function, a scanner function, and a facsimile function. However, the image forming apparatus can be applied to any image forming apparatus such as a copier, a printer, a scanner device, or a facsimile device.

[0056] For example, aspects of the present invention are as follows. <1> an image forming unit that forms a latent image on an image carrier in accordance with a print image from an image controller; a developing current monitor that monitors a developing current flowing from a developing high voltage power supply to a developing unit that develops the latent image on the image carrier; a transfer unit for transferring the visible image developed by the developing unit onto a recording sheet and for receiving a transfer bias; a memory for dividing a print image into a plurality of divided regions at each fixed section in a transport direction of the visible image and storing the developing current for each of the divided regions; a timer that notifies a timing when the leading end of each divided region reaches a transcription start position of the transcription unit; a determination unit that determines the transfer bias in accordance with the development current for each of the divided regions each time the timing is notified; An image forming apparatus comprising: <2> a belt member that contacts the image carrier; a primary transfer unit that transfers the visible image onto the belt member, the transfer unit is a secondary transfer unit to which the transfer bias is supplied, the secondary transfer unit transferring the visible image on the belt member onto the recording sheet; the timer notifies a timing when a leading end of the divided area in a transport direction of the visible image reaches a secondary transfer start position by the secondary transfer unit; the determination unit determines the transfer bias in accordance with the development current for each of the divided areas stored in the memory each time the timing is notified. <1> 2. The image forming apparatus according to claim 1 . <3> the determination unit determines the transfer bias in accordance with an average value or an integral value of the development current monitored in each of the divided regions. <1> or <2> 2. The image forming apparatus according to claim 1 . <4> the determination unit calculates an image area ratio for each of the divided regions based on a pixel count value obtained by counting the number of pixels of pixel data of the print image, and determines a primary bias to be supplied to the primary transfer unit in accordance with the image area ratio. <2> or <3> 2. The image forming apparatus according to claim 1 . <5> An image forming method carried out in an image forming apparatus, comprising: forming a latent image on an image carrier in response to a print image from an image controller; monitoring a developing current flowing from a developing high voltage power supply to a developing unit which develops the latent image on the image carrier; a step of transferring the visible image developed by the developing unit onto a recording sheet and supplying a transfer bias; dividing the print image into a plurality of divided regions for each fixed section in a transport direction of a visible image obtained by developing the latent image, and storing the development current for each of the divided regions; notifying a timing when a leading end of each of the divided regions reaches a transfer start position of the transfer unit; determining the transfer bias in accordance with the developing current for each of the divided regions each time the timing is notified; An image forming method comprising the steps of: <6> Computer, a developing current monitor for monitoring a developing current flowing from a developing high voltage power supply to a developing unit which develops a latent image formed on an image carrier in accordance with a print image from an image controller; a timer for notifying a timing when a leading end of each divided area obtained by dividing the print image into a certain section in a conveying direction of the visible image reaches a transfer start position of a transfer unit to which a transfer bias is supplied and which transfers the visible image developed by the developing unit onto a recording sheet; a determination unit that determines the transfer bias in accordance with the development current for each of the divided regions each time the timing is notified; A program to make it function as such. [Explanation of symbols]

[0057] 101 Photoreceptor 102 Charging unit 103 Laser driver 104 Development unit 105 Development high voltage power supply 106 Transcription Unit 107 Transfer high voltage power supply 109 Development current monitor circuit 110,401 Control board 110a Memory 110b Timer 110c Transcriptional control circuit 111 Image processing video controller 112 Pixel Counter 401a Primary transfer memory 401b Secondary transfer memory 401c Primary Transfer Timer 401d Secondary transfer timer 401e Primary transcription control circuit 401f Secondary transfer control circuit 402 Intermediate transfer belt 403 Secondary transfer unit 404 Secondary transfer high voltage power supply [Prior art documents] [Patent documents]

[0058] [Patent Document 1] Japanese Patent Application Publication No. 10-268674

Claims

1. an image forming unit that forms a latent image on an image carrier in accordance with a print image from an image controller; a developing current monitor that monitors a developing current flowing from a developing high voltage power supply to a developing unit that develops the latent image on the image carrier; a transfer unit for transferring the visible image developed by the developing unit onto a recording sheet and for receiving a transfer bias; a memory for dividing the print image into a plurality of divided regions at regular intervals in a transport direction of the visible image and storing the development current for each of the divided regions; a timer that notifies a timing when the leading end of each divided region reaches a transcription start position of the transcription unit; a determination unit that determines the transfer bias in accordance with the development current for each of the divided regions each time the timing is notified; An image forming apparatus comprising:

2. a belt member that contacts the image carrier; a primary transfer unit that transfers the visible image onto the belt member, the transfer unit is a secondary transfer unit to which the transfer bias is supplied, the secondary transfer unit transferring the visible image on the belt member onto the recording sheet; the timer notifies a timing when a leading end of the divided area in a transport direction of the visible image reaches a secondary transfer start position by the secondary transfer unit; The image forming apparatus according to claim 1 , wherein the determination unit determines the transfer bias in accordance with the development current for each of the divided areas stored in the memory every time the timing is notified.

3. 3. The image forming apparatus according to claim 1, wherein the determination section determines the transfer bias in accordance with an average value or an integral value of the development current monitored in each of the divided regions.

4. 3. The image forming apparatus according to claim 2, wherein the determination unit calculates an image area ratio for each of the divided regions based on a pixel count value obtained by counting the number of pixels of the pixel data of the print image, and determines a primary bias to be supplied to the primary transfer unit in accordance with the image area ratio.

5. An image forming method carried out in an image forming apparatus, comprising: forming a latent image on an image carrier in response to a print image from an image controller; monitoring a developing current flowing from a developing high voltage power supply to a developing unit which develops the latent image on the image carrier; a step of transferring the visible image developed by the developing unit onto a recording sheet and supplying a transfer bias; Dividing the print image into a plurality of divided regions at fixed intervals in a transport direction of the visible image, and storing the development current for each of the divided regions; notifying the timing when the leading end of each divided region reaches a transcription start position; determining the transfer bias in accordance with the developing current for each of the divided regions each time the timing is notified; An image forming method comprising the steps of:

6. Computer, a developing current monitor for monitoring a developing current flowing from a developing high voltage power supply to a developing unit which develops a latent image formed on an image carrier in accordance with a print image from an image controller; a timer for notifying a timing when a leading edge of each divided area obtained by dividing the print image for each fixed section in a transport direction of a visible image obtained by developing the latent image reaches a transfer start position of a transfer unit to which a transfer bias is supplied and which transfers the visible image developed by the developing unit onto a recording sheet; a determination unit that determines the transfer bias in accordance with the development current for each of the divided regions each time the timing is notified; A program to make it function as such.

Images