Image formation device

Abstract

To provide an image formation device that highly accurately calculates an amount of retrieval toner even in an abnormal state like jamming, or sheet-size miss-matching.SOLUTION: An amount of toner actually transferred to a sheet is calculated from a sheet width of the sheet, or position information on the sheet, and upon calculating an amount of retrieval toner, a subtraction is performed from an amount of developing toner. An image formation device comprises: transfer means of transferring a toner image formed on an image carrier to the sheet; a pixel storage unit that stores a pixel for each single line of the toner image; a sheet information detection unit that detects a position or size of the sheet ; a retrieval container that retrieves toner remaining on a conveyance belt; and a retrieval amount computation unit that calculates the amount of retrieval toner to be retrieved to the retrieval container, in which the retrieval amount computation unit is configured to calculate the amount of retrieval toner, using the pixel for each single line of the pixel storage unit, and sheet position information of the sheet information detection unit, or information of a sheet size detection unit.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus including a developing device that develops an electrostatic image formed on an image carrier.

Background Art

[0002] In a conventional image forming apparatus using an electrophotographic method, a toner image formed on a drum or a belt as an image carrier may remain on the image carrier without being transferred to a recording material. The toner remaining on the image carrier is collected from the image carrier by a cleaning mechanism and stored in a collected toner container. The collected toner container is detachable from the apparatus main body of the image forming apparatus, and when it is full of toner, it can be removed from the apparatus main body and replaced with a new collected toner container. There is an image forming apparatus provided with a near-full detection sensor that detects a state (near-full state) less than the full state in order to detect that the toner has become full. When the near-full detection sensor detects the near-full state, the amount of transfer toner transferred to the paper is calculated and subtracted from the toner supply amount supplied to the developing device based on the pixel value. This subtraction result is used as the collected toner amount, and when the collected toner amount exceeds a predetermined amount, it is determined that the container is full.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the following problems occur when a jam occurs during paper conveyance or when the user accidentally sets a paper with a width smaller than the image width in the paper feed port (paper size mismatch).

[0005] After an image is formed on the image carrier, if the recording material stops before reaching the transfer drum, all the toner used for image formation becomes recovered toner.

[0006] Also, when a sheet of paper with a width smaller than the image width is set in the paper feed port due to a user's incorrect operation, the amount of toner transferred to the paper becomes less than the amount of developed toner.

[0007] However, in the means of the prior example, since the amount of recovered toner is calculated assuming that all the developed toner is transferred to the paper, a difference occurs between the actual amount of recovered toner and the calculated amount.

[0008] An object of the present invention is to provide an image forming apparatus capable of accurately calculating the amount of recovered toner even when a jam or a paper size mismatch occurs.

Means for Solving the Problems

[0009] In order to solve the above-described problems, the present invention has the following configuration. That is, the image forming apparatus of the present invention includes transfer means (22) for transferring a toner image formed on an image carrier to a sheet of paper, a pixel storage unit (320) for storing pixels for each line of the toner image, a paper information detection unit (310) for detecting the position and size of the sheet of paper, a recovery container (24) for recovering toner remaining on the transport belt, and a recovery amount calculation unit (304) for calculating the amount of toner recovered in the recovery container. The recovery amount calculation unit (304) calculates the amount of recovered toner using the pixels for each line of the pixel storage unit and the paper position information of the paper information detection unit (310) or the information of the paper size detection unit (S1100, S1110, S1120, S1330).

Effects of the Invention

[0010] According to the present invention, even when a jam or a paper size mismatch occurs, the amount of recovered toner can be accurately calculated.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention according to the claims, and not all combinations of the features described in this embodiment are essential for the solution means of the present invention. The present invention can be implemented in various applications such as printers, various printing machines, copiers, FAX machines, and multifunction machines.

[0013] <First Embodiment> [Configuration of Image Forming Apparatus] Before explaining the characteristic parts of this embodiment, the overall configuration of the image forming apparatus will be explained.

[0014] FIG. 1 is a schematic diagram showing an example of a cross-sectional configuration of an image forming apparatus. The image forming apparatus 1 forms an image by an image forming unit using an electrophotographic process, transfers the formed image to a sheet S, which is a recording material, by a transfer unit, and fixes the image on the sheet S by heating the sheet S with an image transferred thereon by a fixing unit. The image forming apparatus described in this embodiment is a four-color full-color multifunction printer (color image forming apparatus) using an electrophotographic process. This will be described in detail below.

[0015] The image forming apparatus 1 includes a control unit 600 that controls each component within the apparatus. The control unit 600 functions as a control unit that performs various controls, and based on the input print information signal (for example, image data, sheet information, etc.), comprehensively controls various components within the apparatus and plays a role of executing an image forming operation. That is, the image forming apparatus 1 is capable of executing an image forming job of forming a toner image on a recording material.

[0016] The sheet S used in the description is a recording material on which an image is formed on its surface. Examples of the sheet S include plain paper, thick paper, OHP paper, coated paper, label paper, perforated paper, and the like.

[0017] The image forming apparatus 1 forms a multicolor image by superimposing four colors of developers, namely yellow (Y), magenta (M), cyan (C), and black (K) (hereinafter referred to as toner). Therefore, it is provided with an image forming station 10 (image forming unit) for forming toner images of each color. Although reference numerals in the drawings are given the suffixes YMCK, the basic configurations of the image forming stations 10 of each color are the same. Therefore, in the specification, when the description applies to the full-color image forming station, this suffix is omitted. The image forming station 10 has a rotary drum type photosensitive drum 11 (rotatable image carrier) on which an image is formed. Further, the image forming station 10 has a drum cleaning member 16 as a process means acting on the photosensitive drum 11, a charging roller 12 as a charging device, and a developing unit 14 as a developing device. The charging roller 12, which is a charging member, contacts the photosensitive drum 11 with a predetermined pressure contact force and uniformly charges the surface of the photosensitive drum 11 to a predetermined potential.

[0018] Near the image forming station 10, an exposure means 13 as an exposure means for the photosensitive drum 11 is arranged. The exposure means 13 outputs laser light corresponding to the image information one line at a time, scans and exposes the surface of the photosensitive drum 11, and forms an electrostatic latent image (electrostatic image) corresponding to the image information. From this exposure information, the pixel values of one line are measured and stored in a pixel counter 320 described later.

[0019] In the toner storage container (developing container) of the developing unit 14, toners (developers) of each color to be charged are stored. The toner stored in the toner storage container is carried and conveyed by a developing roller (rotatable developer carrier) provided in the developing unit 14. Then, the toner carried by the developing roller flies toward the photosensitive drum 11 by the action of the bias applied to the developing roller, and develops the electrostatic latent image formed on the photosensitive drum 11.

[0020] A cassette 2 for storing the sheet S is disposed at the lower part, and a paper feed tray 6 where the cassette 2 and the conveyance path merge is provided near the cassette 2. Further, a transfer belt unit 20 (hereinafter referred to as a transfer unit) is provided above the image forming station 10.

[0021] The transfer unit 20 includes an intermediate transfer belt 21 (intermediate transfer member) and a driving roller 22 for driving the same. Further, four primary transfer rollers 15 which are primary transfer devices are disposed in parallel inside the intermediate transfer belt 21. Each primary transfer roller 15 is disposed to face the photosensitive drum 11 of each image forming station.

[0022] The upper surface portion of the photosensitive drum 11 of each color of the image forming station 10 is in contact with the lower surface of the intermediate transfer belt 21 at the position of each primary transfer roller 15. This contact portion is called a primary transfer portion T1.

[0023] The driving roller 22 is a roller for rotationally driving the intermediate transfer belt 21, and a secondary transfer roller 25 which is a secondary transfer device is disposed outside the portion of the intermediate transfer belt 21 backed up by the driving roller 22. The intermediate transfer belt 21 is in contact with the secondary transfer roller 25 which is a transfer means, and this contact portion is called a secondary transfer nip portion T2.

[0024] The toner image formed on the photosensitive drum 11 is transferred (primary transfer) onto the intermediate transfer belt 21 by the action of the primary transfer roller 15 at each primary transfer portion T1. For example, when forming a full-color image, the toner images of each color formed on the four photosensitive drums 12Y, 12M, 12C, and 12K are sequentially transferred so as to be superposed on the intermediate transfer belt 21, and a multi-toner image for a full-color image is formed on the intermediate transfer belt 21.

[0025] The image forming apparatus 1 is provided with a paper conveyance device. A paper conveyance path Q (the broken line part in the figure) for conveying the sheet S picked up from the cassette 2 or the paper feed tray 6 upward is provided. In the paper conveyance path Q, a feed roller 3, 7, a separation roller pair 4, 8, a registration roller pair 5, a registration sensor J, a paper width sensor W, a secondary transfer roller 25, a fixing unit 30, and a discharge roller pair are arranged in this order from the upstream, and the sheet S is conveyed to the discharge tray 9.

[0026] The sheet S such as a recording paper or a plastic sheet is supplied to the secondary transfer unit nip portion T2 by the paper conveyance device in accordance with the timing when the toner image formed on the photosensitive drum 11 reaches the secondary transfer unit nip portion T2.

[0027] The toner image formed on the intermediate transfer belt 21 is transferred (secondary transfer) onto the sheet S that is sandwiched between the intermediate transfer belt 21 and the secondary transfer roller 25 and conveyed by the action of the secondary transfer roller 25 at the secondary transfer unit nip portion T2.

[0028] An intermediate transfer belt cleaner 23 (cleaning member) is disposed outside the portion of the intermediate transfer belt 21 backed up by the tension roller. The intermediate transfer belt cleaner 23 is configured by pressing (contacting) a blade-shaped elastic body against the intermediate transfer belt 21.

[0029] The toner remaining on the intermediate transfer belt 21 without being transferred to the sheet S at the secondary transfer nip portion T2 is cleaned by the intermediate transfer belt cleaner 23 and recovered into the recovered toner storage container 24. The recovered toner storage container 24 calculates the estimated recovered toner amount described later, and when the value exceeds a predetermined value, notifies the user that it is in a near-full state or a full state. The toner storage container 24 is detachable, and access to the toner storage container 24 can be achieved by opening a door on the side (not shown). When notified that it is in a near-full state or a full state, the user can replace the toner storage container 24 with another toner storage container in an empty state.

[0030] The fixing unit 30, which is a fixing device, includes a pair of rollers that press the sheet S and a heater that heats the sheet S. By heating while pressing the sheet S, the unfixed transfer toner on the sheet S is melted and fixed to the sheet S. A voltage is applied to the surface of the fixing unit 30 to suppress the toner from electrically adhering to the fixing roller pair.

[0031] The image forming apparatus 1 is equipped with an image reader 40. The image reader 40 has a function of reading an image of a document with an optical sensor and converting it into an image signal.

[0032] Also, an operation panel 50 is provided to display the state of the image forming apparatus 1 and to receive input from the user.

[0033] <Configuration of the control unit> FIG. 2 is a control block diagram showing an embodiment of the present invention. The control unit 600 in FIG. 2 is composed of a CPU 301 that controls the overall operation, a ROM 302 that stores a control program, a RAM 303 that stores data, etc., a recovery amount calculation unit 304 that calculates the recovered toner amount, and a pixel counter 320 that stores pixels for each line of the toner image. The pixel counter 320 stores a value obtained by converting the laser irradiation state on the photosensitive drum 11 into presence / absence information of an image for each pixel. There are four pixel counters for each color (pixel counter 320(Y), pixel counter 320(M), pixel counter 320(C), pixel counter 320(K)) (not shown).

[0034] The CPU 301 receives an instruction to start a printing operation from the operation panel 50 connected to the panel control unit 307 or an external device I / F 330 such as a PC. When receiving the print start instruction, the CPU 301 uses the laser control unit 315 connected to the image forming unit 309 to generate an image on the photosensitive drum 11.

[0035] Here, a method for converting the laser irradiation state into image presence / absence information will be described with reference to FIG. 7. FIG. 7 is a diagram showing the ON / OFF information of the laser irradiation of the exposure means 13Y (yellow) when printing the image in the figure on the sheet S, and the information stored in the pixel counter 320 (Y). In this embodiment, yellow will be described as an example, but the same control is performed for each color of magenta, cyan, and black. The pixel counter 320 (Y) can store pixel information for one line, and stores each pixel information in 1 bit. In this embodiment, the maximum width of one line is 297 mm (11.69 inches) equivalent to A3, the printing resolution is 600 dpi, and data for 600 × 11.69 = 7064 pixels (7064 bits) is stored. The CPU 301 divides the ON / OFF time of the laser irradiation in pixel units, and stores 0 if the laser irradiation is ON (no image) and 1 if the laser irradiation is OFF (image present) in each bit.

[0036] The CPU 301 conveys the sheet S in accordance with the image created by the image forming unit 309 reaching the secondary transfer nip unit T2. The paper width, the current position of conveyance, and the paper length of the sheet S are obtained from the input signal information of the paper width sensor W and the registration sensor J of the paper information detection unit 310 connected to the CPU 301.

[0037] The control unit 600 can notify various information to the operation panel 50 or the external device I / F 330, and can display the information on the display unit of the operation panel 50 or the external device I / F 330.

[0038] Subsequently, an example of a method for calculating the recovered toner amount according to the embodiment will be described using the flowchart of FIG. 3. The control of FIG. 3 is executed by the CPU 301 reading out the control program stored in the ROM 302 or the RAM 303 and controlling various devices. Also, the control of FIG. 3 starts the flow when the CPU 301 receives an instruction to start the execution of the printing mode from the external device I / F 330 or the operation panel 50.

[0039] Upon receiving the printing instruction and job data, the CPU 301 initializes the variables stored in the RAM 303 (S1001). Specifically, it sets to zero the pixel arrays P(Y) / (M) / (C) / (K) of each color that store the amount of recovered toner per line in the sheet S, the development lines n(Y) / (M) / (C) / (K) indicating the number of lines developed with toner of each color, the transfer line m indicating the number of lines where toner has been transferred to the sheet S, the paper width pixel array Wp that stores the paper width detection result for each line after pixel conversion, the paper width count Wcnt indicating the number of lines where the paper width has been detected, the in-sheet pixels Sin(Y) / (M) / (C) / (K) indicating the number of pixels of each color within the sheet, and the out-of-sheet pixels Sout(Y) / (M) / (C) / (K) indicating the number of pixels of each color outside the sheet.

[0040] Then, according to the job instruction, the conveyance of the sheet S is started from the cassette 2 or the paper feed tray 6 (S1002).

[0041] Next, the position, width, and length of the sheet S are detected from the input information of the registration sensor J and the paper width sensor W (S1100).

[0042] Here, the details of the process of S1100 will be described using the flowchart of FIG. 4.

[0043] When the CPU 301 starts the conveyance of the sheet S, it checks for a change in the input signal of the registration sensor J (S1201).

[0044] If there is no change in the input signal, the process proceeds to the confirmation of the paper width sensor W (NO in S1201).

[0045] If there is a change in the input signal of the registration sensor J (YES in S1201) and the previous input signal was OFF while the current input signal is ON (YES in S1202), it is determined that the leading edge of the sheet S has reached the registration sensor J, and the leading edge detection time is stored in the RAM 303 (S1203).

[0046] When the previous input signal is ON and the current input signal is OFF (NO in S1202), it is determined that the rear end of the sheet S has reached the registration sensor J, and the rear end detection time is stored in the RAM 303 (S1204). Here, the length of the sheet is calculated from the leading end detection time and the rear end detection time stored in the RAM 303. Note that the length of the sheet is calculated by the formula (rear end detection time [ms] - leading end detection time [ms]) × conveyance speed [mm / s].

[0047] Next, the paper width sensor W is checked to confirm whether the sheet S is detected (S1205). Here, the paper width sensor W will be described with reference to FIG. 8. In this embodiment, a line sensor (CIS) is used for paper width detection. The paper width sensor W is packaged with a light emitting part W(a) having a light emitting element and a light receiving part W(b) having a light receiving element that receives the reflected light of the light emitted from the light emitting element and reflected by the sheet. The light irradiated from the light emitting part W(a) is reflected by the sheet S and detected by the light receiving part W(b). The CPU 301 checks the detection output of the light receiving part W(b) for each light receiving element, and if there is a portion exceeding the sheet detection threshold value, it is determined that the paper width sensor W has detected the sheet (YES in S1205). If the detection output of all the light receiving elements is below the sheet detection threshold value, it is determined that there is no sheet detection (NO in S1205). The reading resolution of the paper width sensor W is set to be equal to or higher than the printing resolution of the model, and it is desirable that the light receiving element has a memory capacity of the pixel counter 320(Y)(M)(C)(K) or more pixels. The reading resolution in this embodiment is 600 dpi, and the light receiving element has 7064 pixels.

[0048] Note that in this patent, the CIS sensor is used for explanation, but the paper width detection means is not limited to this. It is only necessary to be able to detect or estimate the width of the sheet S. It is also possible to arrange a plurality of paper detection sensors at specific intervals in the direction perpendicular to the sheet conveyance direction, and detect the paper width from the ON / OFF information of each sensor.

[0049] When the CPU 301 determines that the sheet S has been detected from the information of the paper width sensor W, it stores the information of the light receiving elements of the light receiving part W(b) in the paper width pixel array Wp[Wcnt] of the RAM 303 (S1206).

[0050] Here, with reference to FIG. 8, the paper width pixel array Wp[Wcnt] will be described. The paper width pixel array Wp is a variable on the RAM 303 that stores the result of converting the paper width detection result for each line into pixel units, and stores the sheet detection information in pixel units after converting it into bits. Wcnt indicates the number of lines for which the paper width detection has been completed. When the CPU 301 detects the narrow-width sheet S in FIG. 8(Sa) with the paper width sensor W, the CPU 301 writes the sheet presence / absence information for each light-receiving element into the paper width pixel array Wp[Wcnt]. For example, if the detection result of the light-receiving portion W(b) of the rightmost light-receiving element is "no sheet", 0 is written to bit 0 of the paper width pixel array Wp[Wcnt], and if it is "sheet present", 1 is written. Similarly, when detecting the medium-width sheet S in (Sb) and the wide-width sheet S in (Sc), 0 is written to the bit position where "no sheet" is detected, and 1 is written to the bit position where "sheet present" is detected. Next, the CPU 301 adds 1 to the paper width count Wcnt (S1207). In this way, since the CPU 301 stores the position of the sheet S for each line in pixel units, it is also possible to detect that the sheet S is being conveyed in a skewed state on one side or being conveyed obliquely.

[0051] Next, it is determined whether a jam has occurred (S1220). Whether a jam has occurred is determined based on the registration sensor J and other conveyance sensor information (not shown). If the rear end cannot be detected even after the jam determination time has elapsed in addition to the sheet length conveyance time specified in the job after each sensor has detected the sheet leading edge, or if the leading edge cannot be detected even though a predetermined timing has passed, it is determined that a jam has occurred (YES in S1220).

[0052] Then, the jam information is stored in the RAM 303 (S1221), and the process proceeds to the one-line development process (S1200). Even if it is not a jam (NO in S1220), the process proceeds to the one-line development process (S1110).

[0053] Next, the one-line development process will be described using the flowchart of FIG. 5. The one-line development process is performed for each color. In this embodiment, it is performed in the order of yellow, magenta, cyan, and black. Since the processing for all colors is the same, in this embodiment, the yellow development process will be described.

[0054] The CPU 301 determines whether it is the development timing based on whether the timing at which the yellow image created on the intermediate transfer belt 21 reaches the secondary transfer nip portion T2 coincides with the sheet S (S1110).

[0055] The timing at which the sheet S reaches T2 is calculated using the distance from the sheet leading edge detection time of the registration sensor J stored in the RAM 303 and the conveyance speed between the registration sensor J and T2.

[0056] If it is determined that the timings at which the sheet S and the yellow image created on the intermediate transfer belt 21 reach the secondary transfer nip portion T2 coincide (YES in S1110), the charging roller 12Y is charged (S1111). The charged charging roller 12Y contacts the photosensitive drum 11Y with a predetermined pressure contact force, and uniformly charges the surface of the photosensitive drum 11Y to a predetermined potential. In this embodiment, the surface of the photosensitive drum 11Y is charged to a negative polarity by the charging roller 12Y.

[0057] Next, a laser beam corresponding to the image information input from an external device I / F 330 such as a PC is output from the laser control unit 315, and the surface of the photosensitive drum 11Y is scanned and exposed for one line (S1112). By this exposure, an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the surface of the photosensitive drum 11Y. At this time, the CPU 301 stores the pixel value calculated from the scanning exposure state of the laser in the pixel counter 320 (Y).

[0058] Next, obtain the pixel value from the pixel counter 320(Y) and store it in the pixel array P(Y)[n(Y)] (S1113). Next, refer to the image information and determine whether it is a high-density mode with a high toner density (S1114). If it is not the high-density mode (NO in S1114), development is performed. If it is the high-density mode (YES in S1114), the toner amount per pixel is larger than in the normal mode. Therefore, multiply the pixel array P(Y)[n(Y)] by the high-density coefficient C (S1115).

[0059] Next, develop toner from the developing roller 12Y and develop an image for one line on the photosensitive drum Y (S1116). The toner carried on the developing roller 12Y moves from the developing roller 12Y to the photosensitive drum 11Y according to the electrostatic image in the developing unit.

[0060] Next, add 1 to the development line n(Y) (S1117). Then, transfer the image on the photosensitive drum to the intermediate transfer belt 21 (S1118). Next, check whether the processing of all colors has been completed (S1119). If the processing of all colors has not been completed (NO in S1119), perform the one-line development process for the next color. If the processing of all colors has been completed, end the one-line development process and perform the one-line transfer process.

[0061] Here, the one-line transfer process will be described with reference to FIG. 6.

[0062] The CPU 301 determines whether the sheet S is in contact with the secondary transfer nip portion T2 based on the sheet leading edge detection time information and the sheet trailing edge detection time information stored in the RAM 303. If it is not in contact, end the one-line transfer process (NO in S1120).

[0063] When the sheet S is in contact with the secondary transfer nip portion T2 (YES in S1120), an image of the full-color pixel array P(Y)(M)(C)(K)[m] is transferred to the sheet S (S1130). Next, the CPU 301 calculates the logical product (AND) of the paper width pixel array Wp[m(Y)] stored in the RAM 303 and the pixel arrays P(Y)(M)(C)(K)[m] of each color. This calculation calculates the toner transferred to the sheet S among the toner transferred to the intermediate transfer belt 21. The CPU 301 stores the calculation result of each color in the corresponding color in-sheet pixels Sin(Y)(M)(C)(K) on the RAM 303 (S1131).

[0064] Next, it is checked whether there is toner outside the range of the sheet S (S1132). Specifically, the in-sheet pixels Sin(Y)(M)(C)(K) of each color are compared with the pixel arrays P(Y)(M)(C)(K)[m], and if the values match, it is determined that all the developed toner has been transferred to the sheet S (NO in S1132). Then, as a result of transferring the developed pixel arrays P(Y)(M)(C)(K)[m] of each color to the sheet S, the amount of recovered toner generated for each color is calculated and stored in the pixel arrays P(Y)(M)(C)(K)[m]. (S1139). In this embodiment, the pixel arrays P(Y)(M)(C)(K)[m] of each color are multiplied by the recovered toner coefficient K. This is because the developed toner is not transferred to the sheet S at 100%, and about 0.01% becomes recovered toner. The recovered toner coefficient K is assumed to vary depending on the toner raw material, development, and transfer ability, and may be set to 0 when the developed toner is transferred to the sheet S at 100%. Also, in this embodiment, the recovered toner coefficients K for each of the YMCK colors are the same, but if the recovery rates differ depending on the color, each color may have a recovered toner coefficient.

[0065] When the CPU 301 determines that there is toner outside the range of the sheet S (YES in S1132), it inverts the bits of the paper width pixel array Wp[m] and calculates the logical product with the pixel arrays P(Y)(M)(C)(K)[m] of each color. The calculation result is stored in the out-of-sheet pixels Sout(Y)(M)(C)(K) of each color (S1133).

[0066] Next, the amounts of recovered toner inside and outside each color sheet are added and stored in the pixel array P(Y)(M)(C)(K)[m] (S1134).

[0067] The amount of recovered toner inside each color sheet is calculated by multiplying the in-sheet pixels Sin(Y)(M)(C)(K) of each color by the recovered toner coefficient K. (1) The amount of recovered toner outside each color sheet uses the out-of-sheet pixels Sout(Y)(M)(C)(K) as they are. (2) The in-sheet recovered toner amount (1) of each color and the out-of-sheet recovered toner amount (2) of each color are added and stored in the pixel array P(Y)(M)(C)(K)[m] of each color.

[0068] Next, 1 is added to the transfer line count m (S1140), and the 1-line transfer process ends.

[0069] When the 1-line transfer process in FIG. 6 ends, the CPU 301 refers to the jam information stored in the RAM 303 and determines whether an emergency stop is necessary (S1300). If an emergency stop is necessary (YES in S1300), all of the laser, charging, and drive motors are stopped (S1301), and the recovered toner E is calculated.

[0070] If an emergency stop is not necessary (NO in S1300), the CPU 301 refers to the rear-end information of the sheet stored in the RAM 303 and determines whether the rear end of the sheet has passed through the secondary transfer nip portion T2. This condition is met when the sheet length is shorter than the image length. If the rear end of the sheet has passed through the secondary transfer nip portion T2 (YES in S1310), the recovered toner E is calculated.

[0071] When the rear end of the sheet has not passed through the secondary transfer nip portion T2 (NO in S1310), it is determined whether the transfer of the developed toner to the sheet S has been completed for all colors. Specifically, it is determined whether the value of the development line n(Y) and the transfer line m match, and whether the development line n(Y) is 0 or more. Here, the reason for comparing the yellow development line n(Y) and the transfer line m is that the yellow development unit 14Y is the farthest from the secondary transfer nip portion T2 among the other colors. If the transfer of the yellow developed toner to the sheet S has been completed, it can be determined that the transfer of the other colors to the sheet S has also been completed.

[0072] When the full-color transfer has not been completed (NO in S1320), in order to continue the transfer to the sheet S, the process returns to the sheet position / width / length detection (S1100). When the condition is satisfied (YES in S1320), the recovery amount calculation unit 304 adds all the values in the pixel arrays P(Y)(M)(C)(K) and stores them in the single-sheet recovered toner amount E (S1330).

[0073] Next, the recovery amount calculation unit 304 adds the single-sheet recovered toner amount E to the total recovered toner amount Tsum (S1331).

[0074] Next, it is determined whether the total recovered toner amount Tsum is equal to or greater than the near-full detection threshold (S1332). If it exceeds the near-full detection threshold, the operation panel 50 displays that it is near full (S1333), prompts the user to replace the recovered toner storage container 24, and ends the printing.

[0075] Thus, when all the developing toner is transferred to the sheet S, the amount of recovered toner is calculated by multiplying the developing toner by the recovered toner coefficient. When the width of the sheet S is smaller than the image width, or when the length of the sheet S is shorter than the image length, or when the sheet S stops due to factors such as a jam and not all the developing toner is transferred to the sheet S, the amount of developing toner not transferred to the sheet S is taken as the recovered toner. Then, the amount of recovered toner is calculated by multiplying the developing toner transferred to the sheet S by the recovered toner coefficient. By these control methods, the estimation accuracy of the amount of recovered toner stored in the recovered toner storage container 24 can be kept high in any case.

Explanation of Signs

[0076] 1 Image forming apparatus 10 Image forming station 11 Photosensitive drum 13 Exposure means 14 Developing unit 21 Intermediate transfer belt 23 Intermediate transfer belt cleaner 24 Recovered toner storage container 100 Controller W Paper width sensor

Claims

1. Transfer means for transferring a toner image formed on an image carrier to a sheet, A pixel storage unit that stores pixels for each line of the toner image, A sheet information detection unit that detects the position and size of the sheet, A recovery container that recovers toner remaining on the transport belt, Comprising a recovery amount calculation unit that calculates the amount of toner recovered into the recovery container, The recovery amount calculation unit calculates the amount of recovered toner using the pixels for each line of the pixel storage unit and the sheet position information of the sheet information detection unit or the information of the sheet size detection unit. An image forming apparatus characterized by that.

2. The sheet information detection unit according to claim 1 includes a paper length detection unit that detects the paper length of the sheet, The recovery amount calculation unit obtains the recovery toner amount by calculating, from the paper length information of the paper length detection unit, how many lines out of the pixels for each line stored in the pixel storage unit are transferred to the medium. An image forming apparatus characterized by that.

3. The sheet size detection unit according to claim 1 or claim 2 includes a paper width detection unit that detects the paper width of the sheet, The recovery amount calculation unit uses the logical product of the paper width information of the paper width detection unit and the pixel information for each line stored in the pixel storage unit to calculate the amount of toner transferred to the medium and the amount of toner not transferred to the medium, and calculates the recovery toner amount. An image forming apparatus characterized by that.

4. The recovery amount calculation unit according to claim 1, claim 2 or claim 3, when the sheet conveyance is stopped, The recovery amount calculation unit obtains the recovery toner amount by calculating, from the sheet position detection unit, how many lines out of the pixels for each line stored in the pixel storage unit are transferred to the medium. An image forming apparatus characterized by that.

5. The pixel storage unit according to claim 1 or claim 2, claim 3 or claim 4 stores by increasing the addition amount per pixel in a high density mode where the toner density is high. An image forming apparatus characterized by that.

Images