JP2009163115A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which does not perform improper patch formation while securing highly accurate toner amount control in view of the printing ratios of a specific area and a specific color, consequently shortens the time required for this control and improves productivity (average printing speed). <P>SOLUTION: The image forming apparatus includes: a toner image forming means which continuously forms toner images; a calculation means which calculates the printing ratios of the plurality of specific areas of the toner image; a test image forming means which forms test images corresponding to each specific area; a detection means which detects the density of each test image; a judgment means which judges whether each specific area is a high printing ratio area whose printing ratio reaches a predetermined reference value or a low printing ratio area whose printing ratio does not reach the predetermined reference value; and a control means which controls the toner amount of the toner image forming means, based on the density of the test image corresponding to the specific area judged as the low printing ratio area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, or a multifunction peripheral.

  In many image forming apparatuses such as copying machines and printers, a photoconductor is usually scanned and exposed with a laser beam to form an electrostatic latent image on the photoconductor, and toner is attached to these electrostatic latent image portions with a developing container. The toner image is transferred to a transfer material to form an image.

  In recent years, in a color machine, an intermediate transfer belt is generally employed as a means for transferring an image on a photosensitive member to a transfer material. In this type of apparatus, the toner amount of the toner image is controlled by an optical sensor system (a system in which the toner density is determined from the amount of reflection by irradiating the toner image with light). In order to compensate for this, a test image (an image for detecting the density of the toner image developed on the photoreceptor in a non-contact manner and called a “patch”) is formed and corrected at the end of the job. Yes.

  That is, when a patch is formed in another area other than the area where the toner image is formed on the photosensitive member and transferred to the intermediate transfer belt, and the toner image is formed based on the density of the transferred patch. The amount of toner is controlled. The patch is usually formed using specific image data of about 20 mm square stored in a memory or the like.

  Further, more excellent toner amount control is adopted for continuous printing of a document having a high printing rate (ratio of the pixel area to a predetermined area of the paper) or when the developer replacement cycle is long. That is, patches are periodically formed on the photoconductor during continuous printing, not at the end of the job as described above. That is, as shown in FIG. 12, a technique for controlling the toner amount by forming a patch 1203 between two toner images 1202 on the intermediate transfer belt B1 is disclosed in, for example, Patent Document 1 below. ing.

  Here, the accuracy of toner amount control is improved as the interval between patch formations is shortened, but there is a problem in that productivity (average printing speed) is reduced due to a slower printing pace.

  By the way, if a method of periodically creating a patch on the photosensitive member (for example, every five toner images) and controlling the toner amount, the following inconvenience occurs. That is, if printing with a high printing rate continues, the toner consumption rate is fast, so both the toner concentration in the developer container (component ratio with the carrier) and the toner charge amount are likely to become unstable. Control becomes unstable. On the other hand, in the case of printing with a low printing rate, the toner consumption is slow, and the control of the toner amount in printing is likely to be stable. Therefore, even if image density control is performed periodically as described above, the accuracy of toner amount control varies depending on the printing rate.

Therefore, a technique for changing the frequency of controlling the toner amount with high or low printing rate is disclosed in Patent Document 2 below. In this prior art, the printing rate of an image being printed is always detected, the printing rates of documents at regular intervals are averaged, and patches are formed stepwise according to the printing rate.
JP 2006-79001 A JP 2002-062696 A

  However, the above prior art has the following problems.

  In the technique of Patent Document 2, since the printing rate of originals with a constant interval (exemplified as about every 80 toner images) is averaged, printing with extremely high printing rate such as a photograph is several pages. It is not possible to deal with such cases. In such a case, the toner is consumed rapidly, and the toner density and the toner charge amount in the developing container as described above tend to become unstable. Is not secured and is improper control. That is, an average print rate of about 80 pages is not a reference for toner amount control.

  Also, for example, in printing that includes a part of a photo, if the area where the patch is formed overlaps with the area where the patch is formed, the average print rate is increased even though the toner is partially consumed rapidly. Since it is calculated to be low, there is a disadvantage that patch formation is performed at normal intervals.

  Furthermore, when this conventional technique is used for color printing, for example, when printing with many yellow portions is performed, yellow toner is consumed rapidly, and the toner density and toner charge amount become unstable in the yellow developing container. . However, in such a case, it is judged that the printing rate of only yellow is high, but the average printing rate is low, and there is a disadvantage that patch formation is performed at regular intervals.

  The present invention has been made in view of such a problem, and in consideration of the printing rate of a specific area, this control is achieved by ensuring high-accuracy toner amount control and not performing inappropriate patch formation. An object of the present invention is to provide an image forming apparatus that shortens the time required for improving the productivity.

  In order to achieve the above object, the present invention employs the following means.

  In the present invention, a toner image forming unit that continuously forms a toner image, a calculating unit that calculates a printing rate of a plurality of specific areas of the toner image, and a test image forming unit that forms a test image corresponding to each of the specific areas Detecting means for detecting the density of each test image, and each specific area is a high printing rate area in which the printing rate has reached a predetermined reference value or a low printing rate region in which the printing rate has not reached the predetermined reference value And a control unit for controlling the toner amount of the toner image forming unit based on the density of the test image corresponding to the specific region determined to be the low printing rate region. .

  Here, the control means controls the toner amount only when the printing rate of the toner image does not reach a predetermined reference value. As a result, when printing with a high printing rate continues, unnecessary toner amount control is not performed, and a reduction in productivity (average printing speed) can be prevented. Further, in these cases, unnecessary patch formation and toner amount control can be prevented by not forming a test image (patch) in the first place.

  As described above, according to the present invention, it is possible to realize an image forming apparatus in which productivity is improved by controlling the toner amount with high accuracy in consideration of the printing rate of a specific area.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the position and size of the members are drawn with emphasis as appropriate in the drawings. In the following embodiments, a printer will be described as an example of the image processing apparatus of the present invention, but the present invention is not limited to this. In other words, the image processing apparatus of the present invention only needs to include an image forming unit, and may be a so-called multi function peripheral (MFP) having a function as a copying machine or a facsimile machine, or an apparatus having only a copying function.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment.

  FIG. 1 shows an example of an image forming apparatus to which the present invention is applied using a printer as an example, and includes tandem image forming units FY, FM, FC, and FK for forming a color image. The image forming units FY, FM, FC, and FK are in contact with the transfer belt B1, the cleaning unit B2 for cleaning the surface of the transfer belt B1, and the transfer belt B1 along the moving direction of the transfer belt B1. The yellow, cyan, magenta, and black photosensitive drums 10Y, 10M, 10C, and 10K are provided. Further, in order to measure the density of a patch (see FIGS. 6, 8, and 9), which is a density detection image, on the downstream side of the black photosensitive drum 10K when viewed from the moving direction of the transfer belt B1. The patch density sensor (detection means 406) is arranged.

  The yellow photosensitive drum 10Y includes a developing device HY for developing the electrostatic latent image formed on the peripheral surface of the photosensitive drum 10Y with toner, and a peripheral surface for charging the peripheral surface of the photosensitive drum 10Y. A charger 11 is provided next to the charger 11. Similarly, chargers 11M and 11C for charging the peripheral surfaces of the developing devices HM, HC, and HK and the photosensitive drums 10Y to 10K with respect to the photosensitive drums 10M, 10C, and 10K for magenta, cyan, and black. , 11K. Further, in order to transfer the respective toner images carried on the peripheral surfaces of the respective photoconductive drums 10Y to 10K to the transfer belt B1, transfer rollers are provided on the peripheral surfaces of the respective photoconductive drums 10Y to 10K with the transfer belt B1 therebetween. 20Y, 20M, 20C, and 20K are arranged.

  The transfer belt B <b> 1 is stretched between the driving roller 21 and the driven roller 22, and is given a predetermined tension by the tension roller 23. The transfer belt B1 moves in the direction of the arrow, so that the four photosensitive drums 10Y to 10K rotate counterclockwise in FIG.

  As shown in FIG. 2, the photosensitive drums 10Y to 10K are charged to predetermined potentials by chargers 11Y, 11M, 11C, and 11K, respectively, and originals are exposed by exposure devices 12Y, 12M, 12C, and 12K. An image corresponding to the image is written, thereby forming an electrostatic latent image. The electrostatic latent images are developed into toner images of different colors by the developing devices HY, HM, HC, and HK. The toner images of the respective colors are transferred onto the transfer belt B1 by the transfer rollers 20Y to 20K, and the toner images are superimposed on the transfer belt B1.

  The toner remaining on the surface of the photosensitive drums 10Y to 10K after the transfer as described above is wiped off by the blade 35, and is output to a predetermined container by the discharge roller 31, and then the photosensitive drums 10Y to 10K. The surface is neutralized by the static eliminator 13.

  On the other hand, the sheet P is separated from the cassette 2 that can store a plurality of sheets P by the transport unit 6 toward the image forming units FY, FM, FC, and FK at a predetermined interval. Be transported. The toner image transferred to the transfer belt B1 is transferred by the secondary transfer unit 3 to the paper P conveyed to the image forming units FY, FM, FC, and FK.

The control unit 30 includes image forming units FY and FM including the photosensitive drums 10Y to 10K, the developing devices HY, HM, HC, and HK, the chargers 11Y, 11M, 11C, and 11K, and the transfer rollers 20Y to 20K. , FC and FK control the operation control of each image forming member. Also, the operation control of the transport mechanism including the transport roller B1 is performed. Further, the detection output of the density sensor (detection means 406) is supplied to the control unit 30, whereby the control unit 30 detects the density of a patch (described later) that is an image for density detection. It can be carried out.
Next, the configuration of the developing device HY will be described. Each color developing device HY, HM, HC, HB has the same configuration.

  The developing device HY includes a developing container 40 and a developing roller 40a, and the developing container 40 stores therein a powdery developer composed of yellow toner particles and a carrier.

  The developing roller 40a is in contact with the photoconductive drums 10Y to 10K, and an image instructed to be formed by the host device by the potential difference between the electrostatic latent image on the surface of the photoconductive drums 10Y to 10K and the developing bias applied to the developing roller 40a. A toner image corresponding to the above is formed on the surface of the photosensitive drums 10Y to 10K (developing operation).

  Under such a configuration, the image forming apparatus 1 that has received an image formation instruction from a host device such as a personal computer (PC), etc., outputs toner images of each color corresponding to the received image data to the image forming units FY, FM. , FC and FB are used. The toner image formed in each image forming unit is transferred to the intermediate transfer belt B1, and is superimposed on the intermediate transfer belt B1 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 2 is taken out from the paper storage unit 2 one by one by a paper feeding device (not shown) and transported on the paper transport unit 6. Then, the sheet is sent to the secondary transfer unit 3 in synchronization with the primary transfer to the intermediate transfer belt B1, and the color toner image on the intermediate transfer belt B1 is secondarily transferred to the sheet by the secondary transfer unit 3. The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 4 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged by a paper discharge device 5 to a paper discharge tray section 7 provided on the outer periphery of the image forming apparatus 1. The toner remaining on the intermediate transfer belt B1 after the secondary transfer is removed from the intermediate transfer belt B1 by the intermediate transfer belt cleaning unit B2.

  FIG. 3 is a functional block diagram of the control unit 30 of the image forming apparatus 1 according to the present embodiment.

  The image forming apparatus 1 includes a CPU (Central Processing Unit) 201, a RAM (Random Access Memory) 202, a ROM (Read On 7 Memory) 203, a HDD (Hard Disk Drive) 204, and a driver 205 corresponding to each drive unit in the printing. They are connected via an internal bus 206. The CPU 201 uses, for example, the RAM 202 as a work area, executes a program stored in the ROM 203, the HDD 204, and the like, and exchanges data and commands with the driver 205 based on the execution result, as shown in FIG. The operation of each driving unit is controlled. Further, each means (shown in FIG. 4) to be described later other than the drive unit also operates as each means when the CPU 201 executes the program.

(Embodiment 1)
First, Embodiment 1 of the present invention will be described. In the first embodiment, the toner amount is not controlled when the printing rate of the specific area of the toner image does not satisfy the predetermined condition, and is controlled when the predetermined condition is satisfied.

  FIG. 4 is a functional block diagram of the image forming apparatus 1 in the present invention, and FIG. 5 is a flowchart showing the operation of the image forming apparatus 1 in the first embodiment. FIG. 6 is an explanatory diagram of patch formation in the first embodiment.

  The toner image forming unit 401 continuously forms color toner images on the intermediate transfer belt B1 with the above-described configuration based on the image data stored in the RAM 202. The counter 402 counts the number of toner images (step S501 in FIG. 5). On the other hand, the calculation means 403 starts referring to the image data in order to calculate the printing rate (the ratio of the pixel area to the predetermined area) of the specific area of each toner image (step S502).

  The specific area 605 of this embodiment is a partial area of the toner image as shown in FIG. Here, “part” is the entire area of the toner image. For example, in printing that includes a photograph, the entire area of the toner image is consumed even though the toner is consumed rapidly. This is because the average printing rate is calculated low. Therefore, in the specific area 605, an area where a photograph or the like is frequently inserted in one toner image is designated in advance (coordinates are stored in the RAM 202). Further, in order to increase the accuracy of calculating the toner image printing rate, in the present embodiment, two specific areas 605, a first specific area 605a and a second specific area 605b, are provided. First, the calculation unit 403 calculates the printing rates of the first and second specific areas 605a and 605b (step S503).

  Subsequently, when the number of the toner images reaches a predetermined value (step S504), the determination unit 408 determines whether the first and the second toner images have a specific number (for example, three) of toner images immediately before the number reaches the predetermined value. It is determined whether each of the second specific areas 605a and 605b is a high printing ratio area in which the printing ratio has reached a predetermined reference value or a low printing ratio area in which the predetermined reference value has not been reached (step). S505). Then, the test image forming means 405 is a test image corresponding to the first and second specific areas 605a and 605b (an image for detecting the density of the toner image developed on the photoconductor in a non-contact manner, (Referred to as “patches”) (steps S506, S510). This patch formation is performed in the same manner as in the background art. That is, as shown in FIG. 6, patches 607 (607a and 607b) are formed between the continuously formed toner images 601 and 602, and patches 608 (608a and 608b) are formed between the toner images 603 and 604. The

  Next, the detection means 406 such as an optical sensor detects the densities of the patches 607a and 607b corresponding to the first and second specific areas 605a and 605b, respectively (steps S507 and S511). Based on the detected density, the control unit 407 controls the toner amount of the toner image forming unit 401 (steps S508 and S512).

  Here, the activation of the control means 407 is determined depending on whether the specific area 605 is the high print ratio area or the low print ratio area. That is, for example, when the first specific area 605a is a low printing rate area (Yes in step S505), the activation unit 406 activates the control unit 407 to control the toner amount of the toner image forming unit 401 (step S508). . On the other hand, when the first specific area 605a is a high printing rate area (No at Step S505), the control unit 407 is not activated and the toner amount of the toner image forming unit 401 is not controlled (Step S512).

  The printer waits until the printing rate of the first specific area 605a becomes equal to or less than a specified value (that is, until the printing area becomes a low printing rate area) (printing of the toner image is continuously performed). For example, when the printing rate of the first specific area 605a of the toner image 613 and the two toner images preceding the toner image 613 is equal to or less than a specified value, the toner amount is determined based on the patch 616 formed immediately thereafter. Control. The toner remaining from the intermediate transfer belt B1 is removed by the cleaning unit B2, and the operation ends (step S509).

  That is, for example, when there are only a few areas with extremely high printing rates such as photographs, the toner is consumed rapidly, and both the toner density and the toner charge amount in the developing container 40 are unstable. Prone. Therefore, even if the normal toner amount control is performed, the accuracy is not ensured, and even if the density of the patch is detected in such a case, this control is not a reference. For this reason, in such a case, it can be said that not controlling the toner amount leads to an improvement in productivity (average printing speed).

  The specified values for the specific number of sheets and the printing rate are individually and specifically set in consideration of whether the image forming apparatus is mainly used for printing a document or the like, or for printing a photograph or the like. (The numerical value is stored in the RAM 202).

  As described above, according to the first embodiment, since the inappropriate toner amount control is not performed, the productivity (average printing speed) of the image forming apparatus is improved.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the first embodiment, when the printing rate and number of toner images do not satisfy predetermined conditions, the toner amount is not controlled. In the second embodiment, when such toner amount control is not performed, patch formation is not performed in the first place. FIG. 7 is a flowchart showing the operation in the second embodiment. FIG. 8 is an explanatory diagram of patch formation in the second embodiment.

  As in the first embodiment, the counter 402 counts the number of toner images (step S701 in FIG. 7). On the other hand, the calculation unit 403 starts referencing the image data in order to calculate the printing rate of the first specific area of each toner image (step S702). Then, the calculation unit 403 calculates the printing rate of the first and second specific areas (step S703). The first and second specific areas are the same as in the first embodiment.

  When the number has reached a predetermined value (step S704), the determination unit 408 determines the first and second specific areas 805a, 805a in the specific number (for example, three) of toner images immediately before the number reaches the predetermined value. It is determined whether each of 805b is a high printing rate area or a low printing rate area (step S705).

  For example, when the first specific area 805a is a low print ratio area (step S705 Yes) and the second specific area 805b is a high print ratio area (step S705 No), the test image forming unit 405 To work. That is, the test image forming unit 405 forms a patch corresponding to the first specific area 805a that is a low printing rate area (step S706), whereas the patch corresponding to the second specific area 805b that is a high printing rate area. Does not form.

  Therefore, the detection unit 406 detects the density of only the patch 806a corresponding to the first specific area 805a (step S707). Based on the detected density, the control unit 407 controls the toner amount of the toner image forming unit 401 (step S708). Thereafter, the toner remaining from the intermediate transfer belt B1 is removed by the cleaning unit B2, and the operation ends (step S709). Note that the test image forming unit 405 is not activated for the second specific area 805b, and returns to the reference of the image data for calculating the printing rate by the calculating unit 403 without forming the patch 806b (steps S705No → S702). ).

  That is, as shown in FIG. 8, when toner images 801 and 802 having a high printing rate are continuously formed, the patch 806 is not formed, and the toner image 803 and two preceding toner images (implementation). The patch 806 is formed after waiting for the specific area in the specific area in the case of the specific number of sheets 3 to be low as in the first embodiment). Thereby, unnecessary patch formation can be suppressed, which can contribute to improvement of productivity.

(Embodiment 3)
In this embodiment, the toner amount is controlled using both the density of the patch corresponding to the first specific area and the density of the patch corresponding to the second specific area. In the present embodiment, calculation means is provided that weights and averages the density of patches corresponding to the specific areas of the first and second specific areas. That is, it is assumed that the printing rate of the first specific area is higher than the printing rate of the second specific area. In this case, the calculation means sets the weight of the patch density detection result corresponding to the second specific area having a high printing rate to be higher than the weight of the patch density detection result corresponding to the first specific area having the low printing rate. Calculate the reduced weighted average.

  That is, for example, when there is a high printing rate area such as a photograph, the toner is consumed rapidly, and both the toner density in the developing container 40 and the toner charge amount are likely to be unstable. . Therefore, even if normal toner amount control is performed, the accuracy is not ensured, and even if the density of the patch corresponding to such a high printing rate region is detected, this control cannot be used as a reference. According to the present embodiment, by reducing the weight of the patch density corresponding to the high printing rate area, the influence of the high printing rate during continuous printing can be reduced, and the accuracy of toner amount control can be improved. it can.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the determination unit 408 determines whether the specific area is a high printing rate area or a low printing rate area for each color of the toner image, and the test image forming unit 405 determines whether the specific area is a low printing rate area. Test images are formed only for the colors determined to be present.

  For the sake of simplicity, it is assumed that the specific number is one. As shown in FIG. 9, in the first specific area 903a of the toner image 901, for example, if the printing ratio of cyan (C) and magenta (M) is high, the toner image 901 and the next toner image 902 are between. Forms patches of colors other than these, that is, yellow (Y) and black (B), and controls the toner amount of yellow (Y) and black (B) based on this. Further, in the second specific area 903b of the toner image 901, for example, if the printing ratios of magenta (M) and yellow (Y) are high, patches of colors other than these, that is, yellow (Y) and black (B) are displayed. Based on this, the toner amount control of yellow (Y) and black (B) is performed.

  This operation will be described in detail with reference to the flowchart of FIG. As in the first embodiment, the counter 402 counts the number of toner images (step S001 in FIG. 10). On the other hand, the calculation unit 403 starts referencing the image data in order to calculate the print ratio of the first and second specific areas 903a and 903b of each toner image for each color (step S002). Then, the calculation unit 403 calculates the printing rate for each color of the first and second specific areas 903a and 903b (step S003). The specific area 903 is the same as that in the first embodiment.

  When the number reaches the predetermined value (step S004), the activation unit 404 first determines whether cyan (C) density control has been performed between the toner images immediately before reaching the predetermined value (step S004). Step S005c). If the density control of cyan (C) has been performed, the process proceeds to a similar determination process for magenta (M) (step S005cYes → S005m).

  Here, if the cyan (C) density control is not performed, the determination unit determines the first number of toner images of a specific number (not necessarily one) just before the number reaches the predetermined value. In the second specific area, it is determined whether or not the cyan (C) printing rate is equal to or less than a specified value (that is, whether or not cyan is a low printing rate area) (step S006c). In this embodiment, as shown in FIG. 9, it is determined that cyan in the first specific area 903a has a high printing rate and cyan in the second specific area 903b has a low printing rate.

  Then, for the first specific area where the printing rate is higher than the specified value, the process proceeds to a similar printing rate determination process for magenta (M) (step S006cNo → S006m). On the other hand, for the second specific area where the cyan (C) printing rate is equal to or less than the specified value (step S006cYes), the test image forming unit 405 forms a cyan (C) patch corresponding to the second specific area. (Step S007c).

  Then, the detection means 406 detects the density of this patch (step S008c). Based on the detected density, the control unit 407 controls the amount of cyan (C) toner in the toner image forming unit 401 (step S009c). Thereafter, the toner remaining from the intermediate transfer belt B1 is removed by the cleaning unit B2 (step S010), a toner image is formed again (step S011), and the printing rate calculation operation by the calculation unit 403 is restored (step S011). → S003).

  On the other hand, if cyan (C) density control has been performed, the process proceeds to the same density control process for magenta (M) (step S005cYes → S005m).

  Here, when the density control of magenta (M) has not been performed (step S005mNo), the determination unit determines the first and second specific areas of the specific number of toner images immediately before the number reaches the predetermined value. In 903a and 903b, it is determined whether the print rate of magenta (M) is equal to or less than a specified value (step S006m). In the present embodiment, as shown in FIG. 9, it is determined that magenta has a high printing rate in both the first and second specific areas 903a and 903b. Since the printing rate for magenta is higher than the specified value, the process proceeds to the same printing rate determination process for yellow (Y) (step S006mNo → S006y).

  If the printing rate of magenta (M) is equal to or less than the specified value (step S006m Yes), the activation unit 404 activates the test image forming unit 405 to form a magenta (M) patch (step S007m). . In that case, the detection means 406 detects the density of this patch (step S008m). Then, based on the detected density, the control unit 407 controls the amount of magenta (M) toner in the toner image forming unit 401 (step S009c). Thereafter, the toner remaining from the intermediate transfer belt B1 is removed by the cleaning unit B2 (step S010), a toner image is formed again (step S011), and the printing rate calculation operation by the calculation unit 403 is restored (step S011). → S003).

  On the other hand, if the density control of magenta (M) has been performed, the process proceeds to the same density control process for yellow (Y) (step S005mYes → S005y).

  In the same manner, when the yellow (Y) density control has not been performed (step S005yNo), the yellow (Y) print rate is increased in a specific number of toner images immediately before the number reaches the predetermined value. It is determined whether the value is equal to or less than the specified value (step S006y). If the printing rate is higher than the specified value, the process proceeds to a similar printing rate determination process for black (B) (step S006yNo → S006b).

  On the other hand, when the yellow (Y) printing rate is equal to or less than the specified value (step S006yYes), the activation unit 404 activates the test image forming unit 405 to form a yellow (Y) patch (step S006yYes). S007y).

  Then, the detection means 406 detects the density of this patch (step S008y). Based on the detected density, the control unit 407 controls the amount of yellow (Y) toner in the toner image forming unit 401 (step S009c). Thereafter, the toner remaining from the intermediate transfer belt B1 is removed by the cleaning unit B2 (step S010), a toner image is formed again (step S011), and the printing rate calculation operation by the calculation unit 403 is restored (step S011). → S003).

  On the other hand, when the density control of yellow (M) has been performed, the process proceeds to the same density control process for black (B) (step S005yYes → S005b), but the description is omitted because it is exactly the same process. (Step S005b → S010). If density control has already been performed for black (B), the operation ends (step S005b Yes).

  As described above, patch formation can be suppressed for colors that do not require density control, which can contribute to improvement in productivity.

  As described above, according to the present invention, inappropriate toner amount control and patch formation can be suppressed, and the productivity (average printing speed) of the image forming apparatus can be improved.

  In the above description, the toner image is formed on the intermediate transfer belt. However, this is only an example, and the present invention can be applied to all types of image forming apparatuses that form patches between toner images. .

  The image forming apparatus according to the present invention does not perform inappropriate patch formation while ensuring high-accuracy toner amount control in consideration of the printing ratio of a specific area and a specific color. For this reason, it is possible to shorten the time required for controlling the toner amount, and the productivity is improved. Therefore, it is useful as a printer, a copying machine, a multifunction machine, or the like.

1 is a schematic configuration diagram of an image forming apparatus of the present invention. 1 is a configuration diagram of an image forming mechanism in an image forming apparatus of the present invention. 1 is a hardware configuration diagram of an image forming apparatus of the present invention. 1 is a functional block diagram of an image forming apparatus of the present invention. 5 is a flowchart showing an operation in the first embodiment. FIG. 3 is an explanatory diagram of patch formation in the first embodiment. 9 is a flowchart showing an operation in the second embodiment. Explanatory drawing of the patch formation in Embodiment 2. FIG. Explanatory drawing of the patch formation in Embodiment 3. FIG. 10 is a flowchart showing an operation according to the third embodiment.

Explanation of symbols

1 Image forming device
B1 Intermediate transfer belt
FY, FM, FC, FB Image forming unit
HY, HM, HC, HB developing device 401 toner image forming means 402 counter 403 calculating means 404 starting means 405 test image forming means 406 detecting means 407 control means 408 determining means

Claims (5)

Toner image forming means for continuously forming a toner image;
Calculating means for calculating a printing rate of a plurality of specific areas of the toner image;
Test image forming means for forming a test image corresponding to each of the specific areas;
Detection means for detecting the density of each test image;
Determining means for determining whether each specific area is a high printing rate area in which the printing rate has reached a predetermined reference value or a low printing rate region in which the printing rate has not reached the predetermined reference value;
Control means for controlling the toner amount of the toner image forming means based on the density of the test image corresponding to the specific area determined to be the low printing rate area;
An image forming apparatus comprising: The image forming apparatus according to claim 1, wherein the control unit does not control a toner amount of the toner image forming unit based on a density of a test image corresponding to a specific region determined to be a high printing rate region. The test image forming means forms only a test image corresponding to the specific area determined to be a low printing rate area by the determining means,
The image forming apparatus according to claim 1, wherein the control unit controls a toner amount of the toner image forming unit based on a density of a test image formed by the test image forming unit. Further, the weight of the detection result of the density of the test image corresponding to the specific area determined to be the high printing rate area is set to the detection result of the density of the test image corresponding to the specific area determined to be the low printing rate area. Computation means for computing a weighted average smaller than the weight of
The image forming apparatus according to claim 1, wherein the control unit controls a toner amount of the toner image forming unit based on a calculation result of the calculation unit. The toner image forming means sequentially forms toner images of different colors sequentially,
The calculation means calculates the printing rate of the specific area for each color of the toner image,
The determination means determines whether each specific area is the high print ratio area or the low print ratio area for each color of the toner image;
The image forming apparatus according to claim 1, wherein the test image forming unit forms a test image corresponding to a specific region of a color determined to be the low printing rate region by the determining unit.

Images