Image forming apparatus

Abstract

To provide an image forming apparatus capable of shortening a printing time by switching the number of interleaf sheets when productivity is suppressed by an operation condition fluctuating during continuation of image forming processing.SOLUTION: The image forming apparatus includes an image forming part for forming an image on a conveyed sheet-like medium, a medium conveying part for successively conveying the medium to the image forming part based on the conveying order of the medium determined by the preset number of staying sheets, and a control part for controlling at least the operations of the image forming part and the medium conveying part. In the image forming apparatus, a control part includes at least a productivity suppression determination part for determining the necessity of the suppression of productivity in an image forming part on the basis of the fluctuation of an image forming operation environment during the execution of image forming processing, and a productivity maintaining setting derivation part for deriving the setting of a medium conveyance part capable of maintaining the productivity after suppression when it is determined that the suppression of productivity is necessary.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] In an image forming device that continuously forms images on both sides of multiple sheet-like media, an interleaf method is known that switches the order of image formation on both sides (front and back) of the media, thereby suppressing a decrease in productivity related to the image formation process, i.e., shortening the time required for the image formation process.

[0003] In an image forming device that changes the set fixing temperature depending on the type of media, a technology has been disclosed that shortens the image formation time when performing a specific continuous image forming operation that forms images on multiple media in a situation where two or more types of media are mixed (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed in Patent Document 1 shortens the waiting time for temperature switching by changing the transport order of media so that image formation processes on the same type of media (media with the same fixing temperature) are continuous when performing image formation processes on a mixture of media with different fixing temperatures. This conventional technology determines whether images can be formed on different types of media at similar temperatures based on the current fixing temperature, and changes the transport order using an interleaf method.

[0005] However, in the conventional technology, whether image formation on two different types of media is possible at similar temperatures and there is no waiting time for temperature adjustment is determined by judging the difference between the fixing temperature at the start of the image formation process and the set temperature of the media, and the conveying order is changed accordingly. In other words, the interleaf method does not solve the problem of productivity suppression due to fluctuating fixing conditions while image formation is being continuously performed.

[0006] The present invention aims to provide an image forming apparatus that enables shortening of printing time by switching the number of interleaf sheets when productivity is suppressed due to fluctuating operating conditions during the image forming process. [Means for solving the problem]

[0007] In order to solve the above technical problems, one aspect of the present invention comprises an image forming unit that forms an image on a sheet-like medium that is transported thereto, a medium transport unit that sequentially transports the medium to the image forming unit based on a transport order of the medium determined by a predetermined number of sheets remaining, and at least a control unit that controls the operation of the image forming unit and the medium transport unit, wherein the control unit has at least a productivity suppression determination unit that determines whether or not productivity suppression is necessary in the image forming unit based on fluctuations in the image formation operating environment during execution of the image formation process, and a productivity maintenance setting derivation unit that, when it is determined that productivity suppression is necessary, derives settings for the medium transport unit that can maintain productivity after the suppression. [Effects of the Invention]

[0008] According to the present invention, when productivity is restricted due to operating conditions that change during the continuation of image formation processing, it is possible to shorten the printing time by switching the number of interleaf sheets. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an outline of an embodiment of an image forming apparatus according to the present invention; [Figure 2] 10A to 10C are diagrams for explaining an example of operation using the interleaf method in the embodiment. [Figure 3] FIG. 2 is a hardware configuration diagram of a control block in the embodiment. [Figure 4] FIG. 2 is a functional configuration diagram of a control block in the embodiment. [Figure 5] FIG. 10 is an image diagram of transport control by an interleaf method that can be performed in the embodiment. [Figure 6]10A and 10B are conceptual diagrams illustrating transport control by an interleaf method when productivity is suppressed, which can be performed in the embodiment. [Figure 7] 10 is a flowchart showing an example of transport control involving a change in the number of inter-leaf sheets when productivity is suppressed, which can be performed in the embodiment. [Figure 8] 10 is a flowchart showing another example of transport control involving a change in the number of inter-leaf sheets when productivity is suppressed, which can be performed in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and redundant description may be omitted.

[0011] [Embodiment of Image Forming Apparatus] First, an overview of an image forming apparatus according to the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of an MFP1 as an embodiment of an image forming apparatus. As shown in Fig. 1, MFP1 is an apparatus capable of executing an image forming process using a so-called electrophotographic method. Note that the electrophotographic method is a well-known technology, so a detailed description thereof will be omitted.

[0012] The MFP 1 is composed of at least a main body 10, an image reading unit 20, an operation unit 30, and a control unit 50. The main body 10 includes at least a medium input unit 11, a transfer unit 12 and a fixing unit 13 that constitute an image forming unit, a medium output unit 14, a transport unit 15 that constitutes a medium transport unit, and the control unit 50.

[0013] The medium carry-in unit 11 includes at least a medium storage tray 111 that stores paper P, which is a sheet-like medium, as an object on which an image is formed, and a surface transport adjustment unit 112 that includes a pickup roller that separates the topmost sheet of paper P stacked on the medium storage tray 111 and transports it to the transport unit 15. The medium storage tray 111 may be configured with multiple stages according to the size of the paper P, etc.

[0014] The surface transport adjustment unit 112 operates to adjust the timing of the start of transport of the paper P so that the paper P reaches the transfer unit 12 or the fixing unit 13 in accordance with the timing of image transfer onto the paper P, based on an instruction to the MFP 1 to perform image formation processing on the surface of the paper P.

[0015] Transfer unit 12, which serves as an image transfer section, executes a process of transferring onto paper P an image created based on image data to be formed, which is specified in image formation job information, that is, instruction information for the image formation process input to MFP 1. The image transferred by transfer unit 12 is a latent image formed on a photosensitive member based on the image data, which is visualized by applying a developer (toner, etc.). Therefore, transfer unit 12 transfers an image made of the developer onto paper P. At this time, the operation timing and transfer temperature of transfer unit 12 are adjusted by control unit 50, and controlled so that transfer onto paper P is optimal.

[0016] The fixing unit 13 as an image fixing section performs a process for fixing the image transferred onto the paper P onto the paper P. The fixing temperature in the fixing unit 13 is also adjusted by the control section 50.

[0017] The medium discharge unit 14 has a discharge section 141 and an inversion section 142. The discharge section 141 constitutes an outlet for discharging paper P that has had an image formed only on its front side. The inversion section 142 performs an inversion conveyance operation for switching back paper P that requires image formation on its back side to an inversion conveyance section 151.

[0018] Conveyance unit 15 constituting the medium conveyance section has at least a reverse conveyance section 151 and a reverse conveyance adjustment section 152. Reverse conveyance section 151 constitutes a conveyance section that returns paper P to transfer unit 12 in order to form an image on the back side of paper P that has been switched back by reverse section 142. When forming an image on the back side, reverse conveyance adjustment section 152 adjusts the timing of conveying paper P to transfer unit 12 to match the timing of image transfer in transfer unit 12 onto target paper P, based on an instruction for image formation processing to MFP 1.

[0019] The image reading unit 20 is a unit that reads an image from a medium placed on a document tray and generates image data. The configuration, functions, and operations of the image reading unit 20 are well known, so detailed description thereof will be omitted.

[0020] The operation unit 30 corresponds to an operation display unit that displays a screen for inputting operation instructions to the MFP 1 and setting information for operation. The MFP 1 is configured so that the operation conditions and settings used in the image formation process described below can be changed as appropriate on the operation unit 30. The operation unit 30 receives, for example, an input of a set number of interleaf sheets described below. When the interleaf sheet number is input on the operation unit 30, the interleaf sheet number is held in a retention and transport setting unit 502 described below, and the interleaf sheet number is made available for use in the control of the image formation process by the image formation control unit 503.

[0021] The control unit 50 controls the overall operation of the MFP 1. Details of the control unit 50 will be described later.

[0022] [MFP1 Operation Overview] Here, an overview of the image forming process executed in the MFP 1 will be described. Fig. 2 is a diagram illustrating the process of forming images on both sides (front and back) of a sheet of paper P. The MFP 1 is capable of executing interleaf type transport control. That is, when performing image formation processing on both sides of multiple sheets of paper P consecutively, the transport order is reversed from when an image is formed on the front side of one of the multiple sheets of paper P loaded in the medium storage tray 111 until when an image is formed on the back side of the same sheet of paper P.

[0023] Therefore, the MFP 1 temporarily stores multiple sheets of paper P on which images are to be formed on both sides in the transport unit 15, changes the transport order, and executes a transport control process that improves productivity defined by the number of processes per unit time of image formation processing (number of image formation processes). Also, an interleaf sheet in the case where the number of sheets to be stored (number of interleaf sheets) is assumed to be three will be referred to as a "three-sheet interleaf sheet."

[0024] 2 shows an overview of the operation of the MFP 1 when performing image formation processing using a three-sheet interleaf. For example, assume that an instruction is given to perform continuous double-sided image formation processing on multiple sheets of paper P in the MFP 1. First, as shown in FIG. 2(a), the first sheet of paper P (paper P1) is carried into the transport unit 15 from the medium storage tray 111, and image formation is performed on the front side (paper P1f) of the sheet P1 as the first side.

[0025] 2(b), in order to form an image on the back side (sheet P1b) of sheet P1 as the second side, sheet P1 is switched back and conveyed to the reverse conveying section 151. At this time, two sheets P (sheet P2) are also conveyed from the medium storage tray 111 to the conveying unit 15, and an image is formed on the front side (sheet P2f) of sheet P2.

[0026] 2(c), in order to form an image on the back side (sheet P2b) of sheet P2, sheet P2 is switched back and conveyed to reverse conveyance section 151. Then, a third sheet P (sheet P3) is carried from medium storage tray 111 into conveyance unit 15, and image formation is performed on the front side (sheet P3f) of sheet P3. At this time, sheet P1 is in a state waiting to be conveyed to transfer unit 12 in reverse conveyance adjustment section 152 until image formation on sheet P3f is completed.

[0027] Next, as illustrated in Figure 2(d), when an image is formed on paper P3f, the paper passes through the fixing unit 13, is switched back, and is transported to the reverse transport section 151, paper P1, which was waiting in the reverse transport adjustment section 152, is transported to the transfer unit 12 to form an image on paper P1b.

[0028] Thereafter, an image is formed on sheet P1b, and sheet P1 is discharged from discharge section 141. As a result, the number of sheets P remaining in transport unit 15 of MFP1 becomes two, and the next sheet P is carried in from medium storage tray 111.

[0029] 2(c), sheet P2 waits in the reverse transport adjustment unit 152 until image formation processing is completed on the front side (sheet P4f) of the fourth sheet P (sheet P4). After image formation on sheet P4f is completed, sheet P2 is transported to perform image formation on sheet P2b. By repeating this operation thereafter, when performing continuous double-sided image formation, the number of double-sided image formation processes that can be completed per unit time can be increased, thereby improving the productivity of the MFP 1. As described above, in the case of a three-sheet interleaf print, the order of image formation on both sides of each sheet P is reversed and performed while three sheets P are retained in the transport unit 15.

[0030] 2(c), if an abnormality occurs in the processing of the MFP1 and operation is stopped, the three sheets of paper P remaining there will be in a transport failure state and must be removed and discarded. Therefore, if the number of remaining sheets increases, the amount of work required when an abnormality occurs in the device will increase.

[0031] The number of interleaf sheets is determined by the length of the transport path in the internal configuration of MFP1 (transport unit 15), the size of the paper P on which images are formed (length in the transport direction), and the interval (paper spacing) between consecutively transported papers P.

[0032] In the correlation between the transport path length and the size of the paper P, the greater the allowable number of interleaf sheets, the shorter the paper interval, resulting in improved productivity in the number of double-sided image formation processes. Here, productivity is an index expressed by the number of sheets of paper P that can complete image formation processing per unit time, and is an example of an indicator of the processing capacity of the MFP1.

[0033] In MFP1, if the temperature of transfer unit 12, which performs the transfer process, or the temperature of fixing unit 13, which performs the fixing process, exceeds the upper temperature limit specified in the specifications, the quality of the image formation process will deteriorate, so a "productivity suppression process" is executed to suppress productivity and maintain quality.

[0034] When productivity needs to be reduced due to a change in the image formation operating environment during image formation processing using a three-sheet interleaf as illustrated in FIG. 2, it becomes necessary to lengthen the time interval between image formation processing. For example, when productivity needs to be reduced due to a rise in temperature of the fixing unit 13, the execution interval of the image formation processing is lengthened to reduce the number of image formation processing operations per unit time. To achieve this, transport control is performed to widen the gap between multiple sheets of paper P. Specifically, the time for which the reverse transport adjustment unit 152 waits for transport is lengthened. Therefore, the time for which three sheets of paper P remain stuck becomes longer. If an abnormality occurs in the MFP 1 in this state, the three sheets of paper P must be discarded.

[0035] On the other hand, if productivity is being restricted by fixing factors because image quality takes priority, it is necessary to leave a gap between sheets and wait for the fixing temperature to stabilize. In this case, it is sufficient if each sheet P is delivered in time for the restricted productivity. Therefore, by not setting the maximum number of interleaf sheets, which is determined based on the size of the sheet P and the length of the transport path, etc., that will most improve productivity, it is possible to perform image formation processing that satisfies the required productivity without becoming a rate-limiting factor, even if the number of interleaf sheets is reduced.

[0036] In this state, if an abnormality occurs in the MFP 1, the number of sheets P to be discarded can be reduced compared to when the number of inter-leaf sheets is not changed.

[0037] [Embodiment of the control configuration of MFP1] Fig. 3 is a block diagram showing an example of a control system provided in MFP 1. In Fig. 3, control unit 50, which is a control means, has a microcomputer composed of a CPU, ROM, RAM, etc., and is connected to storage unit 51, operation unit 30, and I / O board 52, which is a temperature detection interface unit.

[0038] Furthermore, the control unit 50 is also connected to a paper transport drive motor driver 1501 , a development drive motor driver 1205 , a photosensitive member drive motor driver 1203 , a transfer drive motor driver 1291 , a fixing drive motor driver 1303 , and a fixing heater driver 1301 .

[0039] The I / O board 52 operates the temperature sensor 53 in response to an instruction from the control unit 50, converts the temperature detection signal (detection voltage) of the temperature sensor 53 into a digital signal, and inputs it to the control unit 50. These constitute a temperature detection means for detecting the temperature inside the device.

[0040] For example, a temperature sensor 53 serving as a temperature detection means detects the temperatures of the transfer unit 12 and the fixing unit 13 and notifies the control unit 50. Based on the temperature information from the temperature sensor 53, the control unit 50 determines whether or not productivity can be reduced.

[0041] It is also possible to provide a plurality of temperature sensors 53, convert the temperature detection signals from the plurality of temperature sensors 53 into digital signals, input them to the control unit 50, and calculate the average of these signals on the control unit 50 side to use it as input information for the detected temperature. Also, it is possible to convert the temperature detection signals from one or more temperature sensors 53 arranged in the main body 10 of the MFP 1 into digital signals and input them to the control unit 50.

[0042] Based on instructions from the control unit 50, the development drive motor driver 1205 controls the power supply to each development drive motor 1206 that rotates the development roller in each development unit of each image forming unit, and rotates the development sleeve of each development roller at a predetermined rotational speed or stops the rotation.

[0043] A paper transport drive motor driver 1501 drives and controls a paper transport drive motor 1502 that rotates and drives rollers related to paper transport among a plurality of transport roller pairs arranged in the transport unit 15, based on instructions from the control unit 50. A photoconductor drive motor driver 1203 drives and controls a photoconductor drive motor 1204 that rotates and drives each of a plurality of photoconductors that make up the image forming unit, based on instructions from the control unit 50.

[0044] A transfer drive motor driver 1291 drives and controls a transfer drive motor 1202 that rotates a drive roller that moves an intermediate transfer belt that constitutes the image forming unit, based on instructions from the control unit 50. A fuser drive motor driver 1303 drives and controls a fuser drive motor 1304 that rotates a drive roller in the fuser unit 13, based on instructions from the control unit 50. A fuser heater driver 1301 turns on and off power to a fuser heater 1302 that corresponds to the heat source of the heating roller in the fuser unit 13 and the heat source of the pressure and heating roller, based on instructions from the control unit 50.

[0045] The storage unit 51 is, for example, a storage device that uses a storage medium such as a semiconductor memory, a magnetic disk, or an optical disk, and stores data on the detected temperature detected by the temperature sensor 53, as well as setting data for various control conditions such as a threshold temperature Tth, which will be described later. The data in the storage unit 51 can be written to and read from the control unit 50. Alternatively, a memory in the control unit 50 may be used in place of the storage unit 51.

[0046] The operation unit 30 is disposed in a part of the main body 10. The operation unit 30 is provided in a part that is easy for the user to see and operate. The operation unit 30 is composed of various switches and buttons that can be operated by the user, a touch panel type operation panel in which a touch panel is superimposed on a liquid crystal display panel, and the like. The control unit 50 can display various information on the touch panel type operation panel of the operation unit 30, and the user can view the display and perform input operations to select an operation mode, set various data, and so on, which can then be input into the control unit 50. This serves as a guide input stage that enables the selection and input of an operation mode.

[0047] In the case of an image forming system in which this MFP 1 is configured to print a print job in accordance with a job (a group of information including commands for image formation processing and setting information necessary for image formation processing) transmitted from a host device such as a personal computer, the display, keyboard, pointing device, etc. of the host device can also function as a guide input means, together with or in place of this operation unit 30. In this case, the control unit 50 of this image forming device displays the necessary information on the display of the host device via communication means, and the user can use the keyboard, pointing device, etc. of the host device to select an operation mode and set various data, and send the information to the control unit 50 of this image forming device.

[0048] The control unit 50 reads and executes a predetermined control program to control the above-mentioned components and also executes various controls and processes relating to the change of operation mode according to the embodiment of the present invention, which will be described below.

[0049] [MFP1 functional configuration] Next, a functional configuration realized in the control unit 50 provided in the MFP 1 will be described. Fig. 4 is a functional block diagram according to this embodiment. As shown in Fig. 4, the control unit 50 has an image formation information acquisition unit 501, a retention transport setting unit 502, an image formation control unit 503, a productivity suppression determination unit 504, and a productivity maintenance setting derivation determination unit 505.

[0050] An image formation information acquisition unit 501 acquires job information input from outside the MFP 1 or from the operation unit 30. The image formation information acquisition unit 501 notifies the retention transport setting unit 502, the image formation control unit 503, and the productivity maintenance setting derivation determination unit 505 of the page information included in the job information. The page information includes size information of the paper P to be subjected to image formation processing, the number of sheets to be subjected to image formation processing (number of sheets to be imaged), whether double-sided printing is performed, the number of interleaf sheets (retention transport setting number), etc.

[0051] The retention transport setting unit 502 sets the notified number of inter-leaf sheets and notifies the image formation control unit 503. Furthermore, when the retention transport setting unit 502 receives a change notification of the number of inter-leaf sheets from the productivity maintenance setting derivation determination unit 505, it sets the number of inter-leaf sheets indicated in the change notification and notifies the image formation control unit 503.

[0052] The image forming control unit 503 controls the operation of the medium input unit 11, transfer unit 12, fixing unit 13, medium output unit 14, etc. based on the set number of interleaf sheets and the notified page information, and executes the image forming process.

[0053] The productivity suppression determination unit 504 determines whether or not productivity suppression is necessary based on the number of image formation processes (cumulative number of processes) from the image formation control unit 503, the temperature of the transfer unit 12 (transfer temperature), the temperature of the fixing unit 13 (fixing temperature), and the like notified by the temperature sensor 53. Here, productivity is an index expressed as the number of processes per unit time of image formation processes. Note that the cumulative number of processes, the transfer temperature, the fixing temperature, and the like correspond to indexes indicating the operating status of the MFP 1, which fluctuates during the execution of image formation processes.

[0054] For example, when the fixing temperature exceeds a predetermined threshold, the productivity suppression determination unit 504 determines whether it is necessary to adjust the transport interval (sheet interval) of paper P or the transport speed so as to reduce the number of image formation processes per unit time in order to suppress a temperature rise. When the MFP 1 is executing copy processes, productivity suppression is treated as "CPM down," which reduces the number of copies per unit time (CPM). When the MFP 1 is executing print processes, productivity suppression is treated as "PPM down," which reduces the number of prints per unit time (PPM).

[0055] The productivity maintenance setting derivation determination unit 505, which serves as a productivity maintenance setting derivation unit, has a productivity maintenance feasibility determination unit 5051 and a retained sheet number calculation unit 5052. When the productivity suppression determination unit 504 determines that productivity suppression is necessary, the productivity maintenance feasibility determination unit 5051 determines whether productivity can be maintained after suppression even if the number of inter-leaf sheets is reduced. The retained sheet number calculation unit 5052 calculates the number of inter-leaf sheets that can maintain productivity after suppression. The calculated number of inter-leaf sheets is notified to the retention and transport setting unit 502.

[0056] [Embodiment of transport control process] The following describes an embodiment of the transport control process that can be executed by the above-described MFP 1. The transport control process according to this embodiment is a process for controlling switching of the transport order using an interleaf method.

[0057] First, the relationship between the number of interleaf sheets and reduced productivity will be described with reference to FIGS. 5 and 6. FIG. 5 is a diagram illustrating an example of the timing at which sheets P are transported to the transfer unit 12 when images are formed on both sides of four sheets P. For example, FIG. 5(a) shows an image of a case where the interleaf setting is three sheets and no productivity reduction occurs. In contrast, FIG. 5(b) shows an example of a case where productivity reduction occurs and productivity is reduced to approximately 50%. In contrast, FIG. 5(c) shows an example of a case where the interleaf setting is two sheets.

[0058] In FIG. 5, the horizontal axis represents the time flow of the image formation process on paper P. Furthermore, comparing FIG. 5(a) and FIG. 5(b), the time interval between successively transported sheets of paper P is longer in FIG. 5(b) than in FIG. 5(a). This is because FIG. 5(b) illustrates a state in which productivity has been reduced, and illustrates a situation in which productivity is reduced to 50% compared to FIG. 5(a). To reduce productivity to 50%, the transport interval between sheets of paper P must be doubled. Therefore, the transport interval between sheets of paper P (the interval on the time axis) in FIG. 5(b) is twice as long as that in FIG. 5(a).

[0059] Comparing the case where productivity is reduced to 50% of that in FIG. 5(a) as shown in FIG. 5(b) with the case where two-sheet interleaf printing is used as shown in FIG. 5(c), the timing at which image formation processing on both sides of four sheets of paper P is completed is almost the same. In this case, while satisfying the condition of reducing productivity, it is possible to reduce the number of sheets of paper P remaining in MFP 1 and the number of sheets of paper P to be discarded when an abnormality occurs.

[0060] In reality, in order to reverse and transport the paper P to perform interleaf control as in MFP1, it is necessary to perform a switchback transport after forming an image on the front side, so the transport interval for the paper P is set taking into account the time required for this switchback.

[0061] 6 shows the timing of paper P entry in transport control that requires switchback transport to switch the front and back sides in double-sided image formation processing. In each diagram in FIG. 6, the rectangular columns in the top row illustrate the timing for image formation on the front side. The rectangular columns in the top row also illustrate the timing for image formation on the back side.

[0062] The horizontal axis is the time axis, and each rectangle arranged along the time axis illustrates a time interval equal to the transport interval of paper P. If the transport interval based on the size of a certain paper P is one rectangle, then, assuming double-sided printing, after an image is formed on a certain paper P, the next paper P is transported with a transport interval of one sheet of paper P, as shown in FIG.

[0063] According to the transport control described in Figure 6, when productivity is reduced, the number of interleaf sheets is updated to the optimal setting, thereby making it possible to reduce the time required for image formation processing while satisfying the conditions for reduced productivity.

[0064] 6, the numbers written in certain rectangles indicate the order of the sheets P that are the target of the image formation process. For example, "1" indicates the timing at which image formation is performed on sheet P1.

[0065] For example, as shown in Figure 6(a), after image formation on sheet P1f is performed, by the time image formation on sheet P2f is performed next, sheet P1 is being switched back and sheet P3 has not yet been carried in. There is no image formation target on the back side (indicated by "X" in the figure).

[0066] Subsequently, after image formation on sheet P2f is performed, no image is formed on the back side until image formation on sheet P3f is performed.

[0067] After that, after image formation on sheet P3f is performed, image formation on sheet P1b is performed until image formation on sheet P4f is performed. After this, sheet P1 is discharged, so at the next timing, sheet P4 is carried in and image formation on sheet P4f is performed.

[0068] Thereafter, image formation is carried out on the sheets P2b, P3b, and P4b in this order, and double-sided image formation on the four sheets P using the three-sheet interleaf method is completed.

[0069] Figure 6(b) shows an example of a case where productivity is reduced to 67% in the image formation process shown in Figure 6(a). Figure 6(b) shows a schematic diagram of the situation where the sheet spacing is widened to accommodate the reduced productivity and to control transport using a three-sheet interleaf.

[0070] As shown in Fig. 6(b), compared to Fig. 6(a), after image formation on sheet P1f is performed, sheet P1 is being conveyed in a switchback manner until image formation on sheet P2f is next performed, and the time interval until sheet P2 is conveyed in increases. In the subsequent conveyance, the intervals between sheets P similarly increase.

[0071] Figure 6(c) shows a schematic diagram of the image formation process in Figure 6(a) when productivity is reduced to 67% and transport control is performed using two-sheet interleaf. In Figure 6(c), the sheet spacing is also increased compared to Figure 6(a) to accommodate the reduced productivity.

[0072] As shown in Fig. 6(c), in the case of two interleaf sheets, after image formation on sheet P2f, sheet P2 moves to reverse conveyance section 151, and then image formation is performed on sheet P1f. Next, image formation is performed on sheet P3f, and then image formation is performed on sheet P2b. If the number of sheets P to be image-formed is more than four, image formation on the front and back sides is performed alternately and sequentially while maintaining the number of interleaf sheets.

[0073] Comparing the example in Figure 6(c) with the example in Figure 6(b), it is clear that switching the number of interleaf sheets when productivity is being suppressed, as in Figure 6(c), can shorten the time required for image formation on the final sheet. Therefore, when productivity is suppressed to maintain image quality (suppressing an increase in transfer temperature, suppressing an increase in fixing temperature, etc.), changing the interleaf setting in the image formation process can maintain or improve the declining productivity.

[0074] As mentioned above, when productivity is reduced, whether or not changing the number of interleaf sheets can shorten the time required to position the final sheet is determined by conditions related to the image formation process, such as the length of the transport path, the time required for the sheet interval (switchback), and the linear speed.

[0075] [Transport control processing flow] Next, using Figure 7, we will explain an embodiment of a transport control process that includes processing to set the minimum number of interleaf sheets that can achieve productivity after productivity reduction occurs after double-sided image formation processing has started.

[0076] In the MFP1, the control unit 50 that sets the number of interleaf sheets acquires page information from job information including double-sided image formation processing, and determines the maximum number of interleaf sheets based on this page information, and sets it to be used in the transport control processing (S701). The maximum number of interleaf sheets determined at this time is uniquely determined from the transport path length, paper transport linear speed, productivity (number of printed sheets per unit time) information of the MFP1 that are determined in advance, and the paper size determined by the page information, etc.

[0077] Next, the control unit 50 determines whether or not productivity needs to be reduced (S702). If the image forming process is a copy process, the determination in step S702 is whether or not CPM reduction is required. If the image forming process is a print process (printer function), the determination in step S702 is whether or not PPM reduction is required.

[0078] An example of a factor that determines in step S702 that productivity reduction is necessary is related to the status of the fixing unit 13. Whether productivity reduction is necessary based on the status of the fixing unit 13 is determined by determining the temperature of the fixing unit (temperature acquired by a sensor such as a thermistor or thermopile) and the heat storage state. For example, when determining whether productivity reduction is necessary based on the temperature of the fixing unit, the simplest method is to acquire the temperature via the temperature sensor 53 of the fixing unit 13 at the timing when the fixing process in the image forming process is executed. The temperature at this time is assumed to be "acquired temperature T1." Furthermore, the temperature used as a threshold when productivity reduction is executed is assumed to be "threshold temperature Tth."

[0079] In this case, if the "obtained temperature T1≧threshold temperature Tth" is not true (S702: NO), the control unit 50 loops the process until the image formation process specified in the job is completed using the maximum number of interleaf sheets determined in step S701 (S705: NO).

[0080] Alternatively, the conditions for productivity suppression may be set by predicting future temperatures based on the heat accumulation state, etc. The heat accumulation state can be determined, for example, by determining whether excessive heat has accumulated internally in the fixing unit 13 during a long-term image formation process immediately prior, making it more likely that excessive temperature rise will occur during subsequent printing. Therefore, it is possible to determine whether productivity suppression is necessary based on the usage status of the fixing unit 13, the operating environment of the MFP 1, etc.

[0081] Another factor that can reduce productivity is an increase in temperature inside the machine during image creation. As with the fixing unit 13, the temperature of the transfer unit 12 is acquired, and if it exceeds a threshold, it is determined that productivity needs to be reduced. In this case, the temperature can be reduced by setting the paper gap between pages long enough to allow the transfer unit 12 to stop.

[0082] If the acquired temperature T1 falls below the threshold temperature Tth, the control unit 50 cancels the productivity suppression and executes an operation based on a predetermined productivity.

[0083] In step S702, if "obtained temperature T1≧threshold temperature Tth" (S702: YES), the control unit 50 determines the productivity suppression rate based on the temperature conditions of the MFP 1. Here, methods for determining the productivity suppression rate include reducing the CPM based on the fixing temperature and changing the setting of the paper interval based on the transfer temperature.

[0084] Next, the control unit 50 determines whether productivity can be maintained even if the number of inter-leaf sheets is reduced (S703). The determination process in step S703 is performed, for example, as follows.

[0085] First, let's consider the conditions under which N sheets of interleaf printing can occur. Assuming a set productivity condition k [ppm] (number of sheets of image formation processed per 60 seconds), when performing image formation on both sides of a single sheet of paper P, the time required from the start of transfer on the first side to the start of transfer on the second side is defined as "T_duplex" (seconds). In this case, whether interleaf printing can occur can be determined by whether "T_duplex≦T_paper × (2 × N-1)" is satisfied, using "T_paper" (seconds), which is the time it takes for a sheet of paper P to be transported from its front edge to the front edge of the next sheet of paper P (total travel time of the paper length and the distance between the sheets) under the same productivity condition k [ppm].

[0086] Transforming "T_duplex≦T_paper×(2×N-1)" into an equation for the number of interleaf sheets, "N", gives "N≧{(T_duplex / T_paper)+1} / 2". Using this equation, the number of interleaf sheets can be calculated as the smallest natural number that satisfies N.

[0087] Let's say the percentage of productivity after suppression relative to the original productivity is x [%]. If no productivity suppression occurs, x = 100 [%]. For example, if normal productivity is 60 ppm, and productivity suppression reduces it to 30 ppm, then x = 50 [%].

[0088] Productivity is expressed as the number of sheets of image formation processing per 60 seconds, and can be expressed as "T_paper [seconds] = (60 [seconds] / k [ppm]) / (x [%] / 100)".

[0089] Based on the above conditions, it is possible to determine whether printing productivity can be maintained even if the number of interleaf sheets is reduced, based on the relationship between productivity and productivity suppression rate.

[0090] In step S703, if it is not possible to maintain productivity even if the number of interleaf sheets is reduced (S705: NO), the process loops until the image formation process specified in the job is completed, using the maximum number of interleaf sheets set in step S701 (S705: NO).

[0091] In step S703, when it is determined that productivity can be maintained even if the number of interleaf sheets is reduced (S703: YES), the number of interleaf sheets is changed to the minimum number that allows productivity reduction to be achieved in accordance with the formula "N≧{(T_duplex / T_paper)+1} / 2" (S704). Then, while carrying out transport control using the changed number of interleaf sheets, the process loops until the image formation process specified in the job is completed (S705: NO), and when the specified image formation process is completed (S705: YES), the process ends.

[0092] As described above, even when productivity needs to be reduced during printing while image formation processing is in progress, the number of interleaf sheets during execution of the image formation processing can be changed by temporarily stopping the feeding from the medium storage tray 111, first ejecting the paper P remaining in the reverse conveyance section 151 to create space between the sheets, changing the number of interleaf sheets to the target number, and restarting the image formation processing. Alternatively, this can be achieved by placing all of the currently interleaf sheets in the MFP 1 and then starting the image formation processing with a reduced number of interleaf sheets. Also, when productivity reduction is no longer necessary, the original target productivity can be restored.

[0093] [Modification of transport control process] Next, a modified example of the embodiment of the transport control process related to the MFP 1 will be described. The transport control process already described using Fig. 7 is applicable, for example, to the case where the fixing temperature becomes high after the end of a long period of continuous image formation processing, and the next image formation is started in a state where the conditions for suppressing productivity are met, such that the fixing temperature becomes high. The embodiment illustrated in Fig. 7 can shorten the overall time for image formation processing by changing the number of interleaf sheets from the first sheet to the minimum number that can achieve the required productivity.

[0094] On the other hand, if productivity needs to be reduced during the execution of continuous image formation processing and the number of interleaf sheets is changed to the minimum number that can achieve the required productivity determined by the productivity reduction function, it becomes difficult to achieve the above-mentioned effect. That is, it is assumed that in order to reduce the number of sheets of paper remaining inside the MFP 1, the supply of sheets P from the medium carry-in unit 11 is temporarily stopped, the transport interval (sheet interval) of the sheets P is widened, and the sheets P remaining in the transport unit 15 are ejected first. In this case, the supply of sheets P must be resumed after ejection to switch to the target number of interleaf sheets, which increases the printing time.

[0095] When control for switching the number of interleaf sheets is executed while continuous image formation processing is being performed, the time until printing is completed (first completion time Ta) that is shortened when switching to the minimum number of interleaf sheets that can achieve the required productivity is compared with the time required to switch the number of interleaf sheets, i.e., the time required until the image formation processing is completed when only productivity suppression is applied (second completion time Tb), and it may be selected to apply only when the effect of shortening the time required until the image formation processing is completed can be obtained.

[0096] The first completion time Ta and the second completion time Tb are determined from the printing conditions (linear speed, paper size, etc.) required for the image forming process, the number of interleaf sheets, and the productivity suppression rate.

[0097] Based on the above, a modified example of this embodiment will be described using the flowchart in Fig. 8. The flowchart shown in Fig. 8 partially overlaps with the flowchart shown in Fig. 7, which has already been described. However, in order to distinguish between the two, the overlapping explanations will also be provided.

[0098] First, in the MFP 1, the control unit 50 determines and sets the maximum number of inter-leaf sheets from the page information (S801). The maximum number of inter-leaf sheets determined at this time is uniquely determined from the transport path length, paper transport linear speed, productivity (number of printed sheets per unit time) information of the MFP 1 that are determined in advance, and the paper size determined by the page information, etc.

[0099] Next, the control unit 50 determines whether or not it is necessary to suppress productivity (S802). If the image forming process is a copy process, the determination in S802 is related to CPM reduction. If the image forming process is a print process (printer function), the determination in S802 is related to PPM reduction.

[0100] An example of a factor that determines in step S802 that productivity reduction is necessary is the state of the fixing unit 13. The details of determining whether productivity reduction is necessary are the same as those of step S702, which has already been described, and therefore detailed description will be omitted. If it is not determined in step S802 that productivity reduction is necessary (S802: NO), the control unit 50 sets the maximum number of interleaf sheets determined in step S801 and loops the process until the image forming process specified in the job is completed (S806: NO).

[0101] When the situation that caused the productivity suppression is resolved as a result of the productivity suppression and the productivity suppression condition is no longer met, the control unit 50 cancels the productivity suppression and executes operations based on the predefined productivity.

[0102] In step S802, when the conditions for productivity suppression are met (S802: YES), the control unit 50 determines the productivity suppression rate based on the temperature conditions, etc. of the MFP 1. Here, methods for determining the productivity suppression rate include reducing the CPM based on the fixing temperature, or changing the setting of the paper interval based on the transfer temperature.

[0103] Next, the control unit 50 determines whether productivity can be maintained even if the number of inter-leaf sheets is reduced (S803). The details of the determination process in step S803 are the same as the determination process in step S703 already described, and therefore detailed description thereof will be omitted.

[0104] In step S803, if it is not possible to maintain productivity even if the number of interleaf sheets is reduced (S803: NO), the process loops until the image formation process specified in the job is completed using the maximum number of interleaf sheets set in step S801 (S806: NO).

[0105] In step S803, if productivity can be maintained even if the number of interleaf sheets is reduced (S803: YES), the control unit 50 compares the time required to switch the number of interleaf sheets (switching time Tc) with the time saved by switching the interleaf sheets (saving time Ts). If it is determined that the saving time Ts is shorter than the switching time Tc (S804: YES), as in step S704, the control unit 50 changes the number of interleaf sheets to the minimum number that can achieve productivity reduction in accordance with the formula "N≧{(T_duplex / T_paper)+1} / 2" (S805). Then, the process loops until the image formation process specified in the job is completed (S806: NO), and ends when the specified image formation process is completed (S806: YES).

[0106] If it is not determined that the reduction time Ts is shorter than the switching time Tc (S804: NO), it is determined whether or not the user has set a priority to reduce the number of sheets P remaining in the MFP1 and to be removed due to productivity reduction when the interleaf setting has been made in advance for double-sided image formation processing (S807).If a priority setting has not been made in step S807 (S807: NO), the process loops until the image formation processing specified in the job is completed, using the setting of the maximum interleaf number determined in step S801 (S806: NO).

[0107] If priority setting is made in step S807 (S807: YES), similarly to step S704, the number of interleaf sheets is changed to the minimum number that can achieve productivity reduction in accordance with the formula "N≧{(T_duplex / T_paper)+1} / 2" (S805). Then, the process loops until the image formation process specified in the job is completed (S806: NO), and when the specified image formation process is completed (S806: YES), the process ends.

[0108] The priority setting in step S807 is assumed to have been set in advance by the user before the start of the image forming process.

[0109] In step S807, if it is determined that a priority setting has been made (S807: YES), when switching the number of interleaf sheets, if the purpose is to reduce the number of sheets P remaining inside MFP1 and reduce the effort required when a jam occurs, all remaining sheets P may be removed from MFP1 and then image formation processing may be started again with the reduced number of interleaf sheets.

[0110] As explained above, in the MFP1 according to this embodiment, when productivity suppression occurs due to fixing temperature conditions or the like while image formation processing is being performed on both sides of paper P, the MFP1 can select the minimum number of interleaf sheets that satisfies the productivity (post-suppression productivity) determined by the occurrence of productivity suppression and perform image formation.

[0111] For example, under printing conditions before productivity reduction occurs, printing is performed using three interleaf sheets, but after productivity reduction occurs, if the required productivity is met even with two interleaf sheets, image formation can be performed using two interleaf sheets.

[0112] That is, according to this embodiment, if productivity is restricted during double-sided printing due to factors such as fixing temperature conditions, it is possible to switch to printing with the minimum number of interleaf sheets that still achieves the restricted productivity. As a result, it is possible to obtain the effects of reducing the number of sheets remaining in the machine when an abnormality occurs, shortening the time it takes to complete printing, and shortening the printing time when productivity is restricted.

[0113] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist thereof. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims.

[0114] The contents of the present invention are as follows, for example. <1> an image forming unit that forms an image on a conveyed sheet-like medium; a medium transport unit that sequentially transports the medium to the image forming unit based on a transport order of the medium determined by a preset number of remaining sheets; a control unit that controls at least the operations of the image forming unit and the medium transport unit; Equipped with The control unit includes at least a productivity suppression determination unit that determines whether or not productivity suppression is required in the image forming unit based on a change in an image forming operating environment during execution of an image forming process; a productivity maintenance setting deriving unit that, when it is determined that the productivity needs to be reduced, derives a setting for the medium conveying unit that can maintain the productivity after the reduction; The image forming apparatus is characterized by having: <2> The productivity maintenance setting derivation unit a productivity maintainability determination unit that determines whether the productivity can be maintained based on the productivity after the suppression and the number of retained sheets; a retained sheet number calculation unit that calculates the retained sheet number that allows productivity to be maintained after the suppression; have <1> 2. The image forming apparatus according to claim 1, wherein: <3> The control unit When the productivity suppression determination unit determines that the suppression of productivity is necessary based on the fluctuation of the image forming operation environment, and when the productivity maintainability determination unit determines that the productivity after the suppression can be maintained by changing the number of retained sheets, the remaining sheet number calculation unit calculates a remaining sheet number that allows the productivity to be maintained; and controlling the image forming unit and the medium transport unit based on the calculated number of remaining sheets. <2> 2. The image forming apparatus according to claim 1, wherein: <4> the image forming unit has at least an image fixing unit that fixes an image on the medium, the fluctuation in the image forming operation environment is a temperature condition of the fixing; the productivity maintenance setting deriving unit determines whether or not the productivity needs to be suppressed based on the fixing temperature. <1> ~ <3> 10. The image forming apparatus according to claim 9, wherein the first and second electrodes are arranged parallel to each other. <5> the image forming unit has at least an image transfer unit that transfers an image onto the medium, the fluctuation in the image forming operation environment is a temperature condition of the transfer; the productivity maintenance setting deriving unit determines whether or not the productivity needs to be suppressed based on the transfer temperature. <1> ~ <4> 10. The image forming apparatus according to claim 9, wherein the first and second electrodes are arranged parallel to each other. [Explanation of symbols]

[0115] 1: MFP 10: Main body 11: Media loading unit 12: Transcription unit 13: Fuser unit 14: Media ejection unit 15: Transport unit 30: Operation section 50: Control unit 53: Temperature sensor 111: Media storage tray 112: Surface transport adjustment unit 141: Unloading section 142: Inverted part 151: Reversing conveying section 152: Reverse transport adjustment unit 501: Image formation information acquisition unit 502: Retention transport setting unit 503: Image formation control unit 504: Productivity suppression determination unit 505: Productivity maintenance setting derivation determination unit 5051: Productivity Maintenance Determination Unit 5052: Retention number calculation unit [Prior art documents] [Patent documents]

[0116] [Patent Document 1] Japanese Patent Publication No. 2023-113403

Claims

1. an image forming unit that forms an image on a conveyed sheet-like medium; a medium transport unit that sequentially transports the medium to the image forming unit based on a transport order of the medium determined by a preset number of remaining sheets; a control unit that controls at least the operations of the image forming unit and the medium transport unit; Equipped with The control unit includes at least a productivity suppression determination unit that determines whether or not productivity suppression is required in the image forming unit based on a change in an image forming operating environment during execution of an image forming process; a productivity maintenance setting deriving unit that, when it is determined that the productivity needs to be reduced, derives a setting for the medium conveying unit that can maintain the productivity after the reduction; An image forming apparatus comprising:

2. The productivity maintenance setting derivation unit a productivity maintainability determination unit that determines whether the productivity can be maintained based on the productivity after the suppression and the number of retained sheets; a retained sheet number calculation unit that calculates the retained sheet number that allows productivity to be maintained after the suppression; The image forming apparatus according to claim 1 , further comprising:

3. The control unit When the productivity suppression determination unit determines that the suppression of productivity is necessary based on the fluctuation of the image forming operation environment, and when the productivity maintainability determination unit determines that the productivity after the suppression can be maintained by changing the number of retained sheets, the remaining sheet number calculation unit calculates a remaining sheet number that allows the productivity to be maintained; and controlling the image forming unit and the medium transport unit based on the calculated number of remaining sheets. The image forming apparatus according to claim 2 .

4. the image forming unit has at least an image fixing unit that fixes an image on the medium, the fluctuation in the image forming operation environment is a temperature condition of the fixing; the productivity maintenance setting derivation unit determines whether or not the productivity needs to be suppressed based on the fixing temperature. The image forming apparatus according to claim 1 .

5. the image forming unit has at least an image transfer unit that transfers an image onto the medium, the fluctuation in the image forming operation environment is a temperature condition of the transfer; the productivity maintenance setting deriving unit determines whether or not the productivity needs to be suppressed based on the transfer temperature. The image forming apparatus according to claim 1 .

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