Printing apparatus, method for controlling the printing apparatus, and program

Abstract

Even in situations where single-sided and double-sided printing coexist, it provides optimal performance while enabling the output of the results that users expect. [Solution] The CPU 305 switches between and executes a plurality of printing controls, which include at least normal duplex control, which performs single-sided printing on sheets instructed to be printed on one side and double-sided printing on sheets instructed to be printed on two sides, and forced duplex control, which applies the same transport control as for sheets instructed to be printed on two sides to sheets instructed to be printed on one side that are located between a plurality of sheets instructed to be printed on two sides, so that after single-sided printing, they are transported along the transport path for double-sided printing on the sheet transport path. The CPU 305 switches between these controls based on the printing order of single-sided and double-sided printing, the number of multiple waiting positions on the sheet transport path, and the number of sheets among the sheets waiting to be fed that are either single-sided or double-sided. The CPU 305 restricts the application of forced duplex control when a predetermined sheet is included in the feed target.

Description

Technical Field

[0001] The present disclosure relates to a printing apparatus, a control method for a printing apparatus, and a program.

Background Art

[0002] Conventionally, as a method of forming an image on both the front and back sides of a large number of recording sheets, there is one that uses a circulation type sheet conveyance method. In this method, after the recording sheet is sent to the transfer unit for transferring the image, the recording sheet with the image transferred on one side is sent to the reversing unit, and the recording sheet reversed by the reversing unit is sent back to the transfer unit without being accumulated in the double-sided dedicated storage tray, and the image is transferred to the opposite side. In each of Patent Document 1 and Patent Document 2, a conveyance control method (hereinafter also referred to as mixed single- and double-sided printing control) for outputting a job in which single-sided printing and double-sided printing are mixed at high speed has been proposed. Specifically, Patent Document 1 proposes a conveyance control method (hereinafter also referred to as forced double-sided control) in which when sheets for double-sided printing and sheets for single-sided printing are mixed, the back of the sheet for single-sided printing is left blank and double-sided printing is performed to prevent interruption of double-sided circulation printing. Further, Patent Document 2 proposes a further conveyance control method (hereinafter also referred to as overtaking double-sided control) for outputting a job in which single-sided printing and double-sided printing are mixed at high speed. In overtaking double-sided control, the printing of the front surface of double-sided printing after the group of single-sided printing pages is executed before the group of single-sided printing pages, and is retreated to the double-sided conveyance path. After the printing and discharging of the group of single-sided printing pages are performed, the printing and discharging of the remaining back surface of double-sided printing are then performed. By applying such control, it becomes possible to output a mixed job of single-sided printing and double-sided printing at high speed. By applying the above control, the time during which the sheet with the image already formed on the front surface of double-sided printing is being conveyed through the double-sided conveyance path is effectively used, and single-sided printing is executed in parallel, so that the total time can be significantly reduced compared to the conventional case.

[0003] Mixed-sided double-sided printing control is changed to the optimal control depending on the condition of the paper inside the printing machine (image forming apparatus) and the mixed-sided state of the paper in the job to be printed. It tends to be difficult for the user to select the optimal mixed-sided double-sided printing control for the job to be printed, and in some cases, the performance may actually deteriorate depending on the selection of the mixed-sided double-sided printing control. In light of this situation, Patent Document 3 proposes a technology that switches between the controls disclosed in Patent Documents 1 and 2, respectively, depending on the condition of the paper inside the printing machine and the mixed-sided state of the paper in the job to be printed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 3880281 [Patent Document 2] Japanese Patent Publication No. 2012-3252 [Patent Document 3] Japanese Patent Publication No. 2021-184084 [Overview of the project] [Problems that the invention aims to solve]

[0005] In some cases, pre-printed paper, such as pre-printed paper, is placed in the paper feed tray, and printing is performed on that paper. In such cases, for example, it may be desirable that when the output is ejected, the side with the logo or other printed elements is in the expected orientation (up or down). In other words, when printing is performed on paper with such characteristics (hereinafter also referred to as paper with a specific orientation ejection), if printing and ejection from the machine are not performed in the orientation intended by the user, the output may not be what the user expected. In particular, as in the situation where the technology disclosed in Patent Document 3 is applied, if the transport control is switched according to the state of the paper inside the printing machine or the state of mixed single-sided and double-sided paper in the job to be printed, the output may not be what the user intended.

[0006] In view of the above-mentioned problems, the present invention aims to enable the output of results that meet the user's expectations while providing more favorable performance even in situations where single-sided and double-sided printing are mixed. [Means for solving the problem]

[0007] The printing apparatus according to the present invention is a printing apparatus that allows the execution of printing jobs in which single-sided printing and double-sided printing are mixed, and comprises a feeding means for feeding sheets held in a predetermined sheet holding section, a refeeding means for refeeding a target sheet from a predetermined waiting position among a plurality of waiting positions in a sheet transport path having a plurality of waiting positions for waiting for a sheet with the first side printed on it to wait in order to print an image on the second side of the target sheet with the first side printed on it, and a control means for controlling the execution of a printing job, wherein the control means performs a first printing control that performs single-sided printing on a sheet instructed to be single-sided, and performs double-sided printing on a sheet instructed to be double-sided, and The system selectively switches and executes a plurality of print controls, each including at least one print control, based on the printing order of single-sided and double-sided printing in the target print job, the number of the plurality of waiting positions, and the number of single-sided and double-sided sheets among the sheets waiting to be fed, and restricts the application of the second print control when the sheets to be fed include a predetermined sheet that is specified so that a predetermined side faces a predetermined direction when it is ejected. [Effects of the Invention]

[0008] According to the present invention, even in situations where single-sided and double-sided printing coexist, it is possible to output the results that the user expects while providing more favorable performance. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing an example of the system configuration of a printing system including an image forming apparatus. [Figure 2] This is a diagram showing an example of the configuration of an image forming apparatus. [Figure 3] This is a diagram showing an example of the configuration of the control unit of an image forming apparatus. [Figure 4] This is a diagram showing an example of the path for transporting the print media of an image forming apparatus. [Figure 5] This is a diagram showing an example of the orientation on the transport path of the paper discharged in a specific direction. [Figure 6] This is a diagram showing an example of a paper attribute setting screen and a paper setting screen. [Figure 7] This is a diagram showing an example of duplex circulation control. [Figure 8] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 9] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 10] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 11] This is a flowchart showing an example of the processing of an image forming apparatus. [Figure 12] This is a diagram showing an example of duplex circulation control. [Figure 13] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 14] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 15] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 16] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 17] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 18] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 19] This is a diagram showing an example of the transport control of an image forming apparatus. [Figure 20]It is a flowchart showing an example of the processing of an image forming apparatus.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted. In addition, the specifically - directed discharge paper (predetermined sheet) refers to paper (printing medium) specified (restricted) by settings or the like so that a predetermined surface (front surface or back surface) faces a predetermined direction (for example, upward or downward) when being discharged from the image forming apparatus. In this case, the upward direction refers to, for example, the direction in which the finished product is stacked on the paper output tray (vertically upward from the upper surface of the paper output tray). Also, the downward direction refers to the direction opposite to the upward direction, that is, the direction opposite to the direction in which the finished product is stacked on the paper output tray (the direction of the paper output tray side as seen from the finished product).

[0011] <First Embodiment> The first embodiment of the present disclosure will be described below. First, referring to FIG. 1, an example of the system configuration of a printing system including a printing apparatus (image forming apparatus) according to an embodiment of the present disclosure will be described. Reference numeral 102 indicates a host computer for transmitting print data to the image forming apparatus of the present invention. The host computer 102 has a function of transmitting a print job including print data, and also has a function of running an image processing application to perform image editing processing. Reference numeral 103 indicates a network for electronically connecting the image forming apparatus 101 and the host computer 102. The image forming apparatus 101 communicates with the host computer 102 via the network 103. In the printing system according to the present embodiment, the image forming apparatus 101 forms an image using the print data received from the host computer 102.

[0012] Referring to Figure 2, an example of the configuration of the image forming apparatus 101 according to this embodiment will be described. Reference numeral 201 indicates a control unit that operates software for performing various controls on the image forming apparatus 101. Reference numeral 202 indicates an operating unit for issuing operational instructions to the image forming apparatus 101. Reference numeral 203 indicates a toner supply unit for supplying toner, which is an example of a printing agent, to the image forming section of the image forming apparatus 101. The toner supply unit 203 is equipped with an opening / closing door, allowing an operator to supply toner through the opening / closing door. Reference numeral 204 indicates the image forming unit. The image forming unit 204 uses toner supplied from the toner supply unit 203 to form the image specified in the print data and transfer it to the transfer belt. Reference numeral 205 indicates an intermediate transfer belt. The image transferred to the intermediate transfer belt 205 is then transferred to a printing medium such as a sheet or paper. Reference numeral 206 indicates a fuser. The fuser 206 fixes the toner to the printing medium by applying heat and pressure to the printing medium onto which the image has been transferred by the intermediate transfer belt 205. Reference numeral 207 indicates the excess toner collection unit. Toner that is not transferred to the printing medium by the intermediate transfer belt 205 is accumulated in the excess toner collection unit 207. Reference numeral 208 indicates a paper feed device (an example of a sheet holding unit) for feeding printing media. Reference numeral 209 indicates the paper transport unit. The printing media fed from the paper feeder 208 passes through the paper transport unit 209, where toner is transferred and fixed. Reference numeral 210 indicates a switchback section for reversing the printing medium. Reference numeral 211 indicates a print media input slot for loading print media from an external paper feeder. Reference numeral 212 indicates a print media discharge unit for discharging the fixed print media to an external output device.

[0013] Referring to Figure 3, an example of the configuration of the control unit 201 of the image forming apparatus 101 will be described. Reference numeral 301 indicates the overall configuration of the control unit 201 of the image forming apparatus 101. Reference numeral 302 indicates an operating unit for receiving user input for the image forming apparatus 101. Reference numeral 303 indicates a network cable for connecting the image forming apparatus 101 to external equipment via a network. Reference numeral 304 indicates a line cable for connecting the image forming apparatus 101 to external equipment via a telephone line. Reference numeral 305 indicates a CPU (Central Processing Unit) that runs a program for controlling the entire controller 301. Code 306 indicates RAM (Random Access Memory) managed by a program running on the CPU 305. RAM 306 is used for purposes such as a receive buffer to temporarily store data received from an external source and an image data buffer to temporarily store image data rasterized by RIP. Reference numeral 307 indicates an interface for connecting the operation unit 302 and the control unit 201. Reference numeral 308 indicates an interface for connecting the control unit 201 to a network via a network cable 303. Reference numeral 309 indicates an interface for connecting the control unit 201 to the telephone line 304. Reference numeral 310 indicates a ROM (Read Only Memory) for storing programs, data, etc., that run on the CPU 305. Reference numeral 311 indicates a hard disk, which is a non-volatile storage device capable of storing diverse data over the long term. Reference numeral 312 indicates the CPU bus. Each component indicated by reference numerals 305 to 311 is connected to each other via the CPU bus 312 so that data can be sent and received from one another.

[0014] Reference numeral 324 indicates an image bus connected to a group of hardware for image processing. Reference numeral 313 indicates an interface for connecting the CPU bus 312 and the image bus 324. Reference numeral 321 indicates a raster image processor (RIP) that has the function of converting image description data input from an external source into bitmap image data. Reference numeral 314 indicates an interface for connecting the RIP 321 and the image bus 324 via the image transfer bus 318. Reference numeral 315 indicates a data compression device for compressing data. Reference numeral 322 indicates the paper feeding and paper output device. Reference numeral 323 indicates a printer unit. For example, the configuration illustrated in Figure 2 may be applied to the printer unit 323. Reference numeral 316 indicates an interface for connecting the printer unit 323 and the paper feed and output device 322 to the image bus 324 via data buses 319 and 320. Reference numeral 317 indicates an image processing device for performing various image processing operations on bitmap image data generated by RIP321. The image processing device 317 has functions for digitally processing bitmap image data, such as a function to combine two pages of bitmap image data into one page of bitmap image data.

[0015] The CPU 305 issues printing commands to the printer and paper feed / ejector via data buses 319 and 320, in accordance with instructions received by the operation unit 302 or instructions indicated by signals transmitted from an external device via the network cable 303. As a result, the printer and paper feed / ejector perform printing.

[0016] Referring to Figure 4, an example of a path for transporting the printing media in the image forming apparatus 101 will be described. Reference numeral 401 indicates a receiving port for loading printing media from an external device into the printing media transport path. Reference numeral 402 indicates a receiving opening for loading printing media from the paper feeder 208 into the printing media transport path. Reference numeral 421 indicates an outlet for discharging the printing media from the printing media transport path to an external device. Each of the symbols 403 to 420 indicates a printing media transport roller provided on a transport path for transporting printing media. The operation of each of the printing media transport rollers 403 to 420 is controlled independently according to the transport path of the printing media.

[0017] First, we will explain the case where printing is performed on only one side of the printing media and the printed side is ejected facing upwards. In this case, the operation of the printing media transport rollers is controlled in the order of reference numerals 403, 404, 405, 406, 407, and 421 to transport the printing media. Next, we will describe the case where printing is performed on only one side of the printing media and the printed side is ejected. In this case, the operation of the printing media transport rollers is controlled in the order of reference numerals 403, 404, 405, 406, 408, 409, 410, 411, 412, 411, 413, 414, and 421 to transport the printing media. Next, we will explain the case where printing is performed on both sides of the printing media. In this case, the operation of the printing media transport rollers is controlled in the order of symbols 403, 404, 405, 406, 408, 409, and 410 to transport the printing media. Then, the operation of the printing media transport rollers is controlled in the order of symbols 411, 412, 411, 415, 416, 417, 418, 419, 420, 403, 404, 405, 406, 407, and 421 to transport the printing media. Furthermore, the transport path including the print media transport rollers 411 and 412 is the section where the print media is switched back, and control to reverse the rotation of the print media transport rollers may be applied. In addition, the print media transport rollers 406 and 411 are equipped with a mechanism for switching the sheet transport path that transports the print media.

[0018] Next, with reference to Figure 5, an example of the orientation of paper discharged in a specific direction along the transport path will be explained. Figure 5(a) shows a case where a specific-direction discharge sheet is reversed on one side, using the transport path shown in Figure 4. In the example shown in Figure 5(a), the specific-direction discharge sheet 501 (△ marks indicate the orientation of the paper), which is set downwards in the paper feed stage, is transported sequentially in the order of reference numerals 502, 503, and 504. From there, it is reversed and discharged from the machine with the paper orientation facing downwards, as indicated by reference numerals 505 and 506. Figure 5(b) shows the case where a specific-direction output sheet is printed on one side without being reversed, using the transport path shown in Figure 4. The specific-direction output sheet (△ marks indicate the orientation of the paper) 511, which is set downwards in the paper feed stage, is transported sequentially in the order of reference numerals 512 and 513, and is ejected from the machine with the paper orientation facing upwards. Figure 5(c) shows the case of double-sided printing of paper discharged in a specific direction, using the transport path shown in Figure 4. Paper discharged in a specific direction (△ marks indicate the orientation of the paper) 521, which is set downwards in the paper feed stage, is transported sequentially in the order of reference numerals 522, 523, and 524, then reversed and transported sequentially in the order of reference numerals 525, 526, and 527, and discharged from the machine with the paper orientation facing downwards. In other words, in the case of printing a specific-direction output sheet on one side without reversing, as shown in Figure 5(b), and in the case of printing a specific-direction output sheet on both sides, as shown in Figure 5(c), the orientation of the output is reversed even though the paper is loaded in the same orientation in the paper feed tray. Similarly, in the case of printing a specific-direction output sheet on one side without reversing, as shown in Figure 5(b), and in the case of printing a specific-direction output sheet on one side with reversal, as shown in Figure 5(a), the orientation of the output is reversed even though the paper is loaded in the same orientation in the paper feed tray.

[0019] Next, with reference to Figure 6, the paper attribute setting screen and the paper setting screen will be explained. Each screen shown in Figure 6 is displayed on the operation unit 302 shown in Figure 3. Specifically, Figure 6(a) shows an example of the paper attribute editing screen 601. On the paper attribute editing screen 601, a series of candidate paper IDs for editing are presented for selection, and when any candidate is selected and the edit button 603 is pressed, the paper attribute setting screen 604 shown in Figure 6(b) is displayed. Here, we assume that paper ID 1, with reference numeral 602, is selected and the edit button 603 is pressed. The paper attribute settings screen 604 allows you to change the attribute values ​​for each type of paper. The preprint paper attribute 605 indicates that, unlike regular blank paper, the orientation of the paper surface is important. The paper setting screen 606 shown in Figure 6(c) is an example of a screen for setting paper for a paper feed tray. The paper setting screen 606 displays the current settings for each paper feed tray. When the paper ID setting button 607 is pressed, the paper ID list screen 608 shown in Figure 6(d) is displayed. The paper ID list screen 608 displays a list of each paper ID edited in the paper attribute editing screen 601. When a paper ID is selected on the paper ID list screen 608, the selected paper ID is set for the target paper feed tray.

[0020] Refer to Figure 7 to explain the double-sided circulation control. Figure 7(a) is a schematic diagram of the transport path during double-sided printing, showing the waiting position of paper awaiting refeed. Figure 7(b) shows the feeding sequence for a 9-sheet circulation, where 5 sheets of paper are awaiting refeed, as shown in Figure 7(a). Specifically, Figure 7(a) shows the case where printing media are simultaneously present on the transport path described above. Multiple waiting positions exist on the transport path, and each of the reference numerals 701 to 705 indicates a waiting position for printing media. In the example shown in Figure 7(a), the printing media shown to be located at waiting positions 701 to 705 indicate a situation where the printing media are waiting to be printed on their respective back sides after printing has been completed on the front side of each printing media. When performing double-sided printing, productivity is improved by alternately feeding paper for front-side printing and re-feeding paper for back-side printing from the receiving slot 401 or 402.

[0021] Figure 7(b) shows the output sequence of paper feeding and refeeding when printing five sheets of double-sided paper. As shown in Figure 7(a), in the transport path of this image forming apparatus, it is possible to have five sheets of paper, indicated by reference numerals 701 to 705, waiting in a standby position for refeeding. Therefore, for example, five sheets of paper are fed first, and then the waiting sheets indicated by reference numerals 701 to 705 are refeeded. This standby position for refeeding is determined by the length of the transport path and the mechanical configuration of the image forming apparatus. In the example shown in Figure 7(b), as indicated by reference numeral 751, there are nine sheets of paper that can be refeeded after being fed, and this is called a nine-sheet cycle.

[0022] Figure 8 is an explanatory diagram illustrating an example of transport control of an image forming apparatus according to this embodiment, showing the difference between normal double-sided printing and forced double-sided printing. For convenience, in the following explanation, "paper (printing media) designated for single-sided printing" may be simply referred to as "single-sided," and "paper (printing media) designated for double-sided printing" may be simply referred to as "double-sided." For example, "5 double-sided sheets" indicates that there are 5 sheets of paper designated for double-sided printing, and "1 single-sided sheet" indicates that there is 1 sheet of paper designated for single-sided printing. The example shown in Figure 8 illustrates a case where 5 double-sided sheets (1-5), 1 single-sided sheet (6), and 5 double-sided sheets (7-11) are printed.

[0023] Figure 8(a) shows an example of a control method commonly referred to as "double-sided printing." Double-sided printing is a control method in which double-sided printing transport control is performed for double-sided printing paper, and single-sided printing transport control is performed for single-sided printing paper. In other words, for double-sided printing, the printing media is transported in the order of reference numerals 403, 404, 405, 406, 408, 409, 410, 411, 412, 411, 415, 416, 417, 418, 419, and 420 as shown in Figure 4. Then, the printing media is transported in the order of 403, 404, 405, 406, 407, and 421. Furthermore, for single-sided printing, the printing media is transported in the order of reference numerals 403, 404, 405, 406, 407, 421 as shown in Figure 4, or in the order of 403, 404, 405, 406, 408, 409, 410, 411, 412, 411, 413, 414, 421. As shown in Figure 8(a), double-sided printing control is performed in print area 801, and all paper is re-fed before the next single-sided print in print area 802 is performed. After single-sided printing is performed in print area 802, double-sided printing control is performed again in print area 803 in order to perform the next double-sided print. In typical double-sided printing, when switching from double-sided to single-sided printing, the refeeding of all the paper on both sides is completed before the switch occurs. This switching operation is also referred to as the double-sided cycle being interrupted.

[0024] Figure 8(b) illustrates an example of a control method called forced duplex printing. Forced duplex printing is a transport control method that performs double-sided printing on a single-sided sheet of paper, leaving the reverse side blank. In the example shown in Figure 8(b), the sixth sheet of paper is single-sided, but double-sided printing is performed with the reverse side blank. In Figure 8(b), the sixth sheet of paper is shown with hatching. By applying this control method, it becomes possible to continue double-sided cyclical control for all sheets of paper within the printing range 811. Therefore, compared to applying normal duplex control for the number of sheets shown in range 851, it is expected that applying forced duplex control will improve performance.

[0025] Figure 9 is an explanatory diagram illustrating another example of transport control of the image forming apparatus according to this embodiment. The example shown in Figure 9 shows an example where normal double-sided and forced double-sided control are applied to 10 single-sided sheets (1-10) and 5 double-sided sheets (11-15). Since the forced double-sided control was explained with reference to Figure 8, a detailed explanation is omitted. Figure 9(a) shows an example of the case where standard double-sided control is applied. In the example shown in Figure 9(a), 10 sheets (1-10) are fed single-sided in the print area 901, and 5 sheets (11-15) are fed double-sided in the print area 902 in a 9-sheet cycle (5 sheets are fed first). Figure 9(b) shows an example of when forced duplex control is applied. In the example shown in Figure 9(b), 10 single-sided sheets (1-10) are passed through the duplex pass for printing, resulting in a 9-sheet cycle of 10 single-sided sheets (1-10) and 5 double-sided sheets (11-15) within the print range 911. The forced duplex control aims to improve performance by passing one side of a double-sided stack of paper through the duplex pass, thus continuing the duplex circulation. However, as shown in the example in Figure 9, if there are no double-sided sheets in the preceding stack, it may actually cause the paper to pass through the duplex pass excessively, potentially degrading performance. Therefore, in the example in Figure 9, it can be seen that normal duplex feeding completes the paper feed 10 sides (the period shown as range 951) faster than forced duplex feeding.

[0026] Figure 10 is an explanatory diagram illustrating another example of transport control of the image forming apparatus according to this embodiment. The example shown in Figure 10 shows an example in which normal double-sided and forced double-sided control are applied to 5 double-sided sheets (1-5), 10 single-sided sheets (6-15), and 5 double-sided sheets (16-20). Figure 10(a) shows an example of when normal double-sided control is applied. In the example shown in Figure 10(a), double-sided printing is performed in a 9-sheet cycle for 5 sheets (1-5) in the print area 1001. In addition, 10 sheets (6-15) are fed into the print area 1002, and double-sided printing is performed in a 9-sheet cycle for 5 sheets (16-20) in the print area 1003. Figure 10(b) shows an example of when forced duplex control is applied. In the example shown in Figure 10(b), 10 single-sided sheets (6-15) are passed through the duplex pass for printing, resulting in a 9-sheet cycle of duplex printing control within the print range 1011, consisting of 5 double-sided sheets (1-5), 10 single-sided sheets (6-15), and 5 double-sided sheets (16-20). As can be seen by comparing Figure 10(a) and Figure 10(b), in the example shown in Figure 10, normal double-sided control is two-sided better in performance than when forced double-sided control is applied, as indicated by the reference numeral 1051.

[0027] In the example shown in Figure 8, forced double-sided control aims to improve performance by passing one side of the paper stack through the double-sided pass to continue the double-sided circulation. On the other hand, even in cases where one side exists between double-sided paper stacks, as in the example shown in Figure 10, if the amount of one side between the double-sided paper stacks is relatively large, the disadvantages of forcing one side through the double-sided pass may outweigh the advantages.

[0028] Next, with reference to Figure 11, an example of the processing of the image forming apparatus according to this embodiment will be described, with particular attention to the processing related to switching between normal double-sided control and forced double-sided control.

[0029] In S1101, the CPU 305 determines whether the first sheet of paper on the paper queue held in RAM 306 is single-sided or not. If the CPU 305 determines in S1101 that the first sheet is single-sided, it proceeds to S1102; if it determines that it is double-sided, it proceeds to S1107. Note that if the first sheet in the paper queue is double-sided, it is difficult to control the single-sided paper to go to the double-sided pass, as this is because double-sided paper is already being transported. Therefore, in this case, the CPU 305 applies normal double-sided control in S1107.

[0030] In S1102, the CPU 305 determines whether all the paper waiting to be fed is single-sided or not. If CPU 305 determines in S1102 that all paper is single-sided, it proceeds to S1107. If it determines that not all paper is single-sided (at least one sheet is double-sided), it proceeds to S1103. Note that if all paper is single-sided, CPU 305 recognizes that there is no single-sided / double-sided mix, and therefore, controls that improve performance in single-sided / double-sided mixes, such as forced double-sided printing, become meaningless. For this reason, in S1107, CPU 305 applies normal double-sided control and prints single-sided paper as single-sided.

[0031] In S1103, the CPU 305 determines whether the paper fed immediately before was double-sided or not. If the CPU 305 determines in S1103 that the paper fed immediately before was double-sided, it proceeds to S1104. If it determines that the paper fed immediately before was not double-sided (i.e., single-sided), it proceeds to S1107. Forced duplexing, which continues double-sided circulation on a stack of already fed double-sided paper, does not work if the paper fed immediately before was single-sided. Therefore, if the paper fed immediately before was single-sided, the CPU 305 does not apply forced duplexing control, but instead applies normal duplexing control in S1107. As mentioned above, there are cases where applying forced duplexing when the paper fed immediately before was single-sided can be disadvantageous, as shown in Figure 9.

[0032] In S1104, the CPU 305 determines whether or not there is paper waiting to be re-fed. If the CPU 305 determines in S1104 that there is paper waiting to be re-fed, it proceeds to S1105; otherwise, it proceeds to S1107. Note that if the paper fed immediately before was not waiting to be re-fed for double-sided printing, it has already been ejected from the machine as double-sided paper. Forced duplex control is a control that continues the double-sided circulation for a stack of double-sided paper that has already been fed, so it cannot be performed when there is no paper waiting to be re-fed and the double-sided circulation is interrupted. Therefore, if there is no paper waiting to be re-fed, the CPU 305 does not apply forced duplex control, but instead applies normal duplex control in S1107.

[0033] In S1105, the CPU 305 determines whether the number of single-sided papers among the papers waiting to be fed is less than "the normal number of double-sided circulating sheets - 1". If CPU 305 determines in S1105 that the number of single-sided sheets is less than "normal double-sided circulation number - 1", it proceeds to S1106. If it determines that the number of single-sided sheets is "normal double-sided circulation number - 1" or greater, it proceeds to S1107. Note that when processing double-sided, single-sided, and double-sided stacks consecutively, if the number of single-sided stacks is large (greater than or equal to "normal double-sided circulation number - 1"), applying forced double-sided control is less efficient in terms of performance compared to applying normal double-sided control. Therefore, CPU 305 limits the application of forced double-sided control and applies normal double-sided control. The performance degradation associated with applying forced double-sided control in this case is as described above, refer to Figure 10.

[0034] In S1106, the CPU 305 determines whether or not there is a sheet of paper waiting to be fed in a specific direction for ejection. If the CPU 305 determines in S1106 that there is paper waiting to be fed in a specific direction, it proceeds to S1107; otherwise, it proceeds to S1108. As mentioned above with reference to Figure 5, if the control applied to paper ejected in a specific direction is changed from single-sided printing to double-sided printing, the orientation of the paper ejected in that direction will change, and the user may not be able to obtain the output they expected. Therefore, if there is paper ejected in a specific direction among the paper waiting to be fed, the CPU 305 does not apply forced double-sided control, but instead applies normal double-sided control in S1107. On the other hand, if the CPU 305 determines in S1106 that there is no paper waiting to be fed in a specific direction, it will apply forced duplex control in S1108.

[0035] By applying the above-described control, it is expected that performance will be improved when printing a mix of single-sided and double-sided pages, by selectively switching the applicable print control according to the state of the printing device and the mix of single-sided and double-sided printing to be performed. Furthermore, in situations where paper with a specific output direction may be used, it becomes possible to output the results in the manner expected by the user while achieving the above-described performance improvements.

[0036] <Second Embodiment> A second embodiment of this disclosure will be described below with reference to Figures 12 to 20. First, an example of double-sided circulation control will be explained with reference to Figure 12. Figure 12(a) shows the feeding sequence for a 9-sheet cycle, with the 5 sheets of paper shown in Figure 7 waiting to be re-fed. Unlike Figure 12(a), Figure 12(b) shows the paper feeding sequence for a 5-sheet cycle where 3 sheets of paper are re-fed. Figure 12(c) shows the paper feeding order and spacing between sheets when a 5-sheet circulation is performed on the transport path for a 9-sheet circulation shown in Figure 12(a), as shown in Figure 12(b). Figure 12(d) shows the relationship between the number of sheets that can be fed in advance in the 9-sheet cycle shown in Figure 12(a) and the 5-sheet cycle shown in Figure 12(b). The details of each of Figures 12(a) through 12(d) are explained below.

[0037] Figure 12(a) is a diagram showing the output sequence of paper feeding and refeeding when printing five sheets of double-sided paper. As explained with reference to Figure 7, in the transport path of an image forming apparatus according to one embodiment of the present disclosure, it is possible to have five sheets of paper, indicated by reference numerals 701 to 705, waiting in a standby position for refeeding. Therefore, in the example shown in Figure 12(a), for example, five sheets of paper are fed first, and then the waiting sheets indicated by reference numerals 701 to 705 are refeeded. The standby position of the paper for refeeding is determined by the length of the transport path and the mechanical configuration of the image forming apparatus. In the example shown in Figure 12(a), as indicated by reference numeral 1251, there are nine sheets of paper before the fed paper becomes ready for refeeding, and this is referred to as a nine-sheet cycle.

[0038] Furthermore, in models that can feed three sheets of paper in advance, control such as that shown in Figure 12(b) may be applied. The example shown in Figure 12(b) is a printing control method in which sheets 1 to 3 are fed in advance, and then re-feeding and feeding are performed alternately. As indicated by the reference numeral 1261, the example shown in Figure 12(b) is called a 5-sheet cycle because there are 5 sheets of paper before the fed paper becomes re-feedable.

[0039] Figure 12(c) shows an example of a 5-sheet cycle performed on a transport path with 5 waiting positions for paper to be held for refeed, as illustrated in Figure 7. In this case, even if 3 sheets are fed first, as in the 5-sheet cycle, the actual transport path is long, so, similar to the example shown in Figure 12(a), 9 sheets of paper space are required between feeding and the same paper being refeeded. Therefore, as indicated by reference numerals 1271 and 1272, there will be gaps between the sheets, and the performance may decrease by the period indicated by reference numeral 1281 compared to the 9-sheet cycle illustrated in Figure 5(b).

[0040] Figure 12(d) shows an example of the relationship between the number of sheets that can be circulated double-sided in the image forming apparatus according to this embodiment and the number of sheets that can be fed in advance. In this case, "number of sheets that can be fed in advance * 2 - 1" is the number of sheets that can be circulated double-sided. This number of sheets that can be circulated double-sided varies depending on the transport path of the image forming apparatus and the size of the paper being printed. Therefore, the values ​​shown in the example in Figure 12(d) are just examples. Also, in the overtaking double-sided control described later with reference to Figure 14, the number of sheets that can be circulated double-sided may be less than in normal double-sided control. In the example of this embodiment, the number of sheets that can be circulated double-sided in normal double-sided is 9, and the number of sheets that can be circulated double-sided in overtaking double-sided is 5.

[0041] Referring to Figure 13, an example of transport control of the image forming apparatus according to this embodiment will be explained, focusing on the difference between normal double-sided control and overtaking double-sided control. The example shown in Figure 13 shows a case where eight single-sided sheets (1-8) and one double-sided sheet (9) are printed. Figure 13(a) shows an example of the case where standard double-sided control is applied. In the example shown in Figure 13(a), single-sided printing is performed on 8 single-sided sheets in print range 1301, and double-sided printing is performed on 1 double-sided sheet in print range 1302. In order to perform double-sided printing on one sheet in print range 1302, the transport path for the double-sided pass shown in Figure 4 is required, which increases the gap between the sheets. This gap can be a factor in performance degradation.

[0042] Figure 13(b) shows an example where follow-up duplex control is applied. Follow-up duplex control is a control method proposed to improve performance, as the empty space between paper feeding and re-feeding in normal duplex printing, as exemplified by the print range 1302, can be a factor in performance degradation. Follow-up duplex control is a control method in which, in single-sided and then double-sided printing, the single-sided printing is overtaken, the feed side of the subsequent double-sided printing is printed, and single-sided printing is performed in the empty space. In the example shown in Figure 13(b), the first side of the 9th sheet of double-sided printing paper, which is behind the 1st to 8th sheets of single-sided printing paper, is fed first and printed. Then, as shown in the print range 1311, the overtaken single-sided printing of sheets 1 to 8 is performed, and then the second side of the 9th sheet of double-sided printing paper is printed. In the example shown in Figure 13(b), the overtaken single-sided sheets 1 to 8 are shown with a black background. From this point forward, for convenience, single-sided paper that has been overtaken by the overtaking double-sided control will be shown with a black background in the diagrams.

[0043] An example of the control method for double-sided printing described above will be explained using the paper feed queues 1321 to 1329. The paper feed queue is a data structure held in RAM 306 that manages information about the paper to be fed. Single-sided or double-sided printing paper is added to the paper feed queue in the order of printing, and is removed from the queue when it is fed (in the case of double-sided printing, when the first side is fed, not when the second side is re-fed). In the paper feed queue 1321, the first 1-8 sheets of single-sided printing are represented as 1S to 8S, and the 9th sheet of double-sided printing is represented as 9D. Here, S and D are suffixes representing single-sided (Simplex) and double-sided (Duplex). In overtaking duplex control, the system checks whether there are any duplex sheets within the following "duplex circulation number - 1" range, starting from the first sheet in the paper queue waiting for feed. If there are, those duplex sheets are fed first. In the case of paper feed queue 1321, the sheets of paper following 1S are "2S, 3S, 4S, 5S, 6S, 7S, 8S, 9D". Also, since the number of sheets that can be circulated double-sided is 9, it is checked whether there are any double-sided sheets within 9-1=8 sheets. In paper feed queue 1321, 9D is exactly the 8th sheet. Therefore, 9D is fed before 1S. In the diagram, the sheets of paper that are to be fed in each paper feed queue are underlined and written in italics. That is, in paper feed queue 1321, 9D is the sheet to be fed, so the symbol 9D is underlined and written in italics. In paper queues 1322-1329, the leading sheets of paper in the queue, "1S, 2S, 3S, 4S, 5S, 6S, 7S, 8S," are fed in order. As described above, in the example shown in Figure 13, when overtaking control of both sides is applied, it is possible to expect a performance improvement of eight sides, as indicated by the reference numeral 1351, compared to when normal control of both sides is applied.

[0044] Referring to Figure 14, an example of another example of transport control in the image forming apparatus according to this embodiment, in which overtaking double-sided control is applied, will be described. Figure 14 shows an example in which 10 single-sided sheets (1-10) and 5 double-sided sheets (11-15) are printed using overtaking double-sided control. In paper queues 1421 and 1422, since there are no double-sided sheets of paper within the first eight sheets following 1S and 2S, 1S and 2S are fed, respectively. In the paper queue 1423, since there are double-sided sheets of paper up to the 8th sheet following 3S, the subsequent double-sided sheet 11D is fed first. In the paper feed queue 1424, since paper 11D was fed from paper feed queue 1423, paper 11D is removed from the paper feed queue, and double-sided paper 12D is the 8th sheet following 3S. Therefore, the subsequent double-sided paper 12D is re-fed first. The paper feed queue 1425 is the same as the paper feed queue 1424, and the subsequent double-sided paper 13D is fed first.

[0045] In the paper feed queue 1426, double-sided paper 14D exists up to the 8th sheet following 3S. However, as explained with reference to Figure 7, when overtaking duplex control is applied, double-sided and single-sided paper are mixed, so the positions that can be used as waiting positions for refeeding double-sided paper are limited to the positions indicated by the reference numerals 701, 702, and 703. This is because single-sided printed paper may pass through transport paths 408, 409, 410, 411, 412, 411, 413, 414, and 421 for reversal. If paper is placed in the waiting positions 704 and 705 for refeeding double-sided paper, a collision will occur with the paper being reversed during single-sided printing, resulting in a jam. As a result, when overtaking duplex control is applied, only 3 sheets can be fed ahead of time, and the machine effectively operates in a 5-sheet cycle. The difference in the number of sheets in the double-sided cycle between normal duplex control and overtaking duplex control is explained above with reference to Figure 12(d). In paper queue 1426, three sheets of paper are already ahead in paper queues 1423, 1424, and 1425, making it difficult to feed any more double-sided paper, so 3S will be fed. In the diagram, 14D, where the application of overtaking is restricted, is shown with hatching. In paper queues 1427-1433, similar to paper queue 1426, there are double-sided 14D sheets within the next 8 sheets, but 3 sheets have already been fed ahead of time. Therefore, the first single-sided sheets 3S, 4S, 5S, 6S, 7S, 8S, 9S, and 10S in the paper queue will be fed.

[0046] In the paper feed queue 1433, after the single-sided 10S is fed, the 11D paper that was fed in the paper feed queue 1423 located at the double-sided waiting position 701 is re-fed. Originally, the 11D could be re-fed 9 sides after it was fed. In the diagram, this point is indicated by a star marker. However, because the single-sided 7S to 10S papers that have been overtaken have been fed, the actual timing of the re-fed paper is after the feeding of the 10S. In paper queue 1434, since there are now two sheets of double-sided paper that were previously fed, paper 14D is fed. After paper 14D is fed, paper 12D is fed again, and then paper 15D is fed in paper queue 1435.

[0047] Referring to Figure 15, an example of the processing of the image forming apparatus according to this embodiment will be described, focusing on the processing when overtaking double-sided control can be applied. In S1501, the CPU 305 determines whether or not there is paper in the paper queue held in the RAM 306. If CPU 305 determines in S1501 that there is no paper on the paper queue, it proceeds to S1501 and waits for paper to be registered again. If CPU 305 determines in S1501 that there is paper on the paper queue, it proceeds to S1502.

[0048] In S1502, the CPU 305 determines whether the first sheet of paper in the paper queue is double-sided or not. If CPU 305 determines in S1501 that the first sheet of paper in the paper queue is not double-sided (it is single-sided), it proceeds to S1503; otherwise, it proceeds to S1507.

[0049] In S1503, the CPU 305 determines whether there is a double-sided sheet of paper located "the number of double-sided sheets that normally cycle - 1" minutes behind the first sheet of paper in the paper queue waiting for feed. Here, the number of double-sided sheets that normally cycle is, for example, 9 sheets in the example shown in Figure 12(d). If CPU 305 determines in S1503 that there are no double-sided sheets of paper behind it by "the number of double-sided sheets that normally cycle through - 1", it proceeds to S1504, where it feeds one side of the first sheet of paper in the paper queue. On the other hand, if CPU305 determines in S1503 that there is a double-sided sheet of paper behind it by "the number of double-sided sheets that normally cycle - 1", it proceeds to S1505.

[0050] In S1505, the CPU 305 determines whether there is an available standby position for the double-sided paper feed for the follow-up double-sided feed. In the example shown in Figure 12(d), when the follow-up double-sided control is applied, up to 3 sheets of double-sided paper can be fed in advance. If CPU 305 determines in S1505 that there is an available waiting position for double-sided feeding for follow-up double-sided feeding, it proceeds to S1506. In S1506, CPU 305 feeds double-sided paper that is located "number of double-sided sheets - 1" minutes behind the beginning of the paper waiting to be fed, which was found in S1503. On the other hand, if the CPU 305 determines in S1505 that there are no available waiting positions for double-sided overtaking, it proceeds to S1504, where it feeds one side of the leading sheet of paper in the paper feed queue.

[0051] In S1507, CPU305 determines whether there are available standby positions on both sides. If CPU 305 determines in S1507 that there are available waiting positions on both sides, it proceeds to S1509; otherwise, it proceeds to S1508. In S1508, the CPU 305 determines whether or not the paper in the double-sided standby position has been re-fed. In S1508, CPU 305 proceeds to S1508 again unless the paper in the double-sided standby position is re-fed, and waits for the re-fed paper to occur. If the paper is re-fed, it proceeds to S1509. In S1509, the CPU 305 feeds both sides of the leading sheet of paper in the paper queue.

[0052] In the example shown in Figure 14, for paper queues 1421 and 1422, the processes S1501, S1502, S1503, and S1504 are executed sequentially in the order shown in Figure 15. In other words, in this case, one side of the leading paper in the paper queue is fed. In the example shown in Figure 14, for paper queues 1423, 1424, and 1425, each process is executed sequentially in the order of S1501, S1502, S1503, S1505, and S1506 as shown in Figure 15. In other words, in this case, instead of the first sheet of paper in the paper queue, the double-sided paper found in S1503 is fed. In the example shown in Figure 14, for paper queues 1426-1433, each process is executed sequentially in the order of S1501, S1502, S1503, S1505, and S1504 as shown in Figure 15. In other words, in this case, one side of the leading sheet of paper in the paper queue is fed. In the example shown in Figure 14, for paper queues 1434 and 1435, the processes are executed sequentially in the order of S1501, S1502, S1507, S1509, or S1501, S1502, S1507, S1508, S1509, as shown in Figure 15. In other words, in this case, both sides of the leading paper in the paper queue are fed.

[0053] Referring to Figure 16, another example of transport control of the image forming apparatus according to this embodiment will be described. Figure 16 shows an example of applying normal double-sided, forced double-sided, and overtaking double-sided control to 5 double-sided sheets (1-5), 10 single-sided sheets (6-15), and 5 double-sided sheets (16-20). Note that Figure 16(a) is the same as Figure 10(a) described earlier, and Figure 16(b) is the same as Figure 10(b), so a detailed explanation of these will be omitted. Figure 16(c) shows an example where the overtaking double-sided control is applied. In the case of paper queues 1621 to 1625, the processes S1501, S1502, S1507, and S1509 shown in Figure 15 are executed sequentially. In other words, in this case, the double-sided paper at the front of the paper queue is fed. In the case of paper queues 1626-1627, the processes S1501, S1502, S1503, and S1504 are executed sequentially in the order shown in Figure 15. In other words, in this case, one side of the leading sheet of paper in the paper queue is fed. In the case of paper queues 1628-1630, the processes are executed sequentially in the order of S1501, S1502, S1503, S1505, and S1506 as shown in Figure 15. In other words, in this case, the double-sided paper found in S1503 is fed, rather than the first sheet of paper in the paper queue. In the case of paper queues 1631 to 1638, the processes are executed sequentially in the order of S1501, S1502, S1503, S1505, and S1504 as shown in Figure 15. In other words, in this case, one side of the leading sheet of paper in the paper queue is fed. In the case of paper queues 1639-1640 waiting to be fed, the processes are executed sequentially in the order of S1501, S1502, S1507, S1509, or S1501, S1502, S1507, S1508, S1509 as shown in Figure 15. In other words, in this case, the first double-sided paper in the waiting paper queue is fed. Comparing the performance of normal double-sided, forced double-sided, and overtaking double-sided control, it can be seen that the normal double-sided and overtaking double-sided control are two sides more efficient than the forced double-sided control, as indicated by the descriptive numerals 1651 and 1652.

[0054] Referring to Figure 17, another example of transport control of the image forming apparatus according to this embodiment will be described. Figure 17 shows an example in which normal double-sided, forced double-sided, and overtaking double-sided control are applied to 5 double-sided sheets (1-5), 10 single-sided sheets (6-15), and 3 double-sided sheets (16-18). Figure 17(a) shows an example of when normal double-sided control is applied. In the example shown in Figure 17(a), five sheets (1-5) are printed double-sided in a 9-sheet cycle in print area 1701, ten sheets (6-15) are fed single-sided in print area 1702, and three sheets (16-18) are fed double-sided in a 9-sheet cycle in print area 1703. Figure 17(b) shows an example of when forced duplex control is applied. In the example shown in Figure 17(b), 10 single-sided sheets (6-15) are passed through the duplex path and printed, and duplex printing control is performed in a 9-sheet cycle within the print range 1711, with 5 double-sided sheets (1-5), 10 single-sided sheets (6-15), and 3 double-sided sheets (16-18) in succession.

[0055] Figure 17(c) shows an example where control on both sides of the overtaking plane is applied. In the case of paper queues 1721 to 1725, the processes S1501, S1502, S1507, and S1509 are executed sequentially in the order shown in Figure 15. In other words, in this case, the front double-sided paper in the paper queue is fed. In the case of paper queues 1726-1727, the processes S1501, S1502, S1503, and S1504 shown in Figure 15 are executed sequentially. In other words, in this case, one side of the leading sheet of paper in the paper queue is fed. In the case of paper queues 1728-1730, the processes are executed sequentially in the order of S1501, S1502, S1503, S1505, and S1506 as shown in Figure 15. In other words, in this case, the double-sided paper found in S1503 is fed, rather than the first sheet of paper in the paper queue. In the case of paper queues 1731 to 1738, the processes are executed sequentially in the order of S1501, S1502, S1503, S1505, and S1504 as shown in Figure 15. In other words, in this case, one side of the leading sheet of paper in the paper queue is fed.

[0056] In the example shown in Figure 16, the performance of the control for both the normal and overtaking sides was the same. However, in the example shown in Figure 17, as indicated by the reference numeral 1751, the control for the overtaking side performed better by four planes compared to the control for both normal sides. The difference between the example shown in Figure 16 and the example shown in Figure 17 is the number of double-sided sheets after the 10 single-sided sheets (6-15). In the example shown in Figure 16, there are 5 sheets (16-20), while in the example shown in Figure 17, there are 3 sheets (16-18). With the overtaking double-sided control, the number of double-sided sheets that can cycle is 5, so there are 3 sheets that can precede the double-sided print. For double-sided prints where the number of preceding sheets is 3 or less, the overtaking double-sided control is more advantageous than the normal double-sided control. This is because for double-sided prints where the number of preceding sheets is more than 3, it is necessary to perform double-sided printing again after the overtaking double-sided print. This could apply to sheets 19 and 20 in the example shown in Figure 16.

[0057] Referring to Figure 18, another example of transport control of the image forming apparatus according to this embodiment will be described. Figure 18 shows an example in which normal double-sided, forced double-sided, and overtaking double-sided control are applied to 5 double-sided sheets (1-5), 7 single-sided sheets (6-12), and 5 double-sided sheets (13-17). Figure 18(a) shows an example of the case where standard double-sided control is applied. In the example shown in Figure 18(a), five sheets (1-5) are printed double-sided in a 9-sheet cycle in print area 1801, seven sheets (6-12) are fed single-sided in print area 1802, and five sheets (13-17) are fed double-sided in a 9-sheet cycle in print area 1803. Figure 18(b) shows an example of when forced duplex control is applied. In the example shown in Figure 18(b), seven single-sided sheets (6-12) are passed through the duplex path for printing, and duplex printing control is performed in a 9-sheet cycle within the print range 1811, consisting of five duplex sheets (1-5), seven single-sided sheets (6-12), and five duplex sheets (13-17).

[0058] Figure 18(c) shows an example where control of both overtaking sides is applied. In the case of paper queues 1821 to 1825, the processes S1501, S1502, S1507, and S1509 are executed sequentially in the order shown in Figure 15. In other words, in this case, both sides of the leading sheet of paper in the paper queue will be fed. In the case of paper queues 1826-1828, the processes are executed sequentially in the order of S1501, S1502, S1503, S1505, and S1506 as shown in Figure 15. In other words, in this case, the double-sided paper found in S1503 is fed, rather than the first sheet of paper in the paper queue. In the case of paper queues 1829 to 1835, the processes S1501, S1502, S1503, S1505, and S1504 are executed sequentially in the order shown in Figure 15. In other words, in this case, one side of the leading sheet of paper in the paper queue is fed. In the case of paper queues 1836-1837, the processes are executed sequentially in the order of S1501, S1502, S1507, S1509, or S1501, S1502, S1507, S1508, S1509, as shown in Figure 15. In other words, in this case, both sides of the leading sheet of paper in the paper queue will be fed.

[0059] The examples shown in Figures 16 and 17 illustrate how applying forced double-sided control is disadvantageous in cases where there are relatively many single-sided sheets between double-sided stacks. The example in Figure 18 shows that, with the number of single-sided sheets between two double-sided stacks set as the threshold "number of double-sided sheets in a normal double-sided stack - 1", applying forced double-sided or overtaking double-sided control is more advantageous than applying normal double-sided control. Specifically, as indicated by the notation 1851, applying forced double-sided control results in one-sided performance improvement compared to applying normal double-sided control. Furthermore, considering the case where there are three sheets in the double-sided stack after the single-sided stack, as shown in the example in Figure 17, applying overtaking double-sided control is more advantageous than applying forced double-sided control. If there are three sheets (13-15) in the double-sided stack after seven single-sided sheets (6-12), as indicated by the notation 1852, applying overtaking double-sided control results in three-sided performance improvement compared to applying forced double-sided control.

[0060] Referring to Figure 19, another example of transport control of the image forming apparatus according to this embodiment will be described. Figure 19 shows an example in which normal double-sided, forced double-sided, and overtaking double-sided controls are applied to 5 double-sided sheets (1-5), 3 single-sided sheets (6-8), and 3 double-sided sheets (9-11). Figure 19(a) shows an example of the case when standard double-sided control is applied. In the example shown in Figure 19(a), five sheets (1-5) are printed double-sided in a 9-sheet cycle within print range 1901, three sheets (6-8) are fed single-sided within print range 1902, and three sheets (9-11) are fed double-sided in a 9-sheet cycle within print range 1903. Figure 19(b) shows an example of when forced duplex control is applied. In the example shown in Figure 19(b), three single-sided sheets (6-8) are passed through the duplex path and printed, and duplex printing control is performed in a 9-sheet cycle within the print range 1911, with five duplex sheets (1-5), three single-sided sheets (6-8), and three duplex sheets (9-11) in succession.

[0061] Figure 19(c) shows an example where control on both sides of the overtaking plane is applied. In the case of paper queues 1921 to 1925, the processes S1501, S1502, S1507, and S1509 are executed sequentially in the order shown in Figure 15. In other words, in this case, both sides of the leading sheet of paper in the paper queue will be fed. In the case of paper queues 1926-1928, the processes are executed sequentially in the order of S1501, S1502, S1503, S1505, and S1506 as shown in Figure 15. In other words, in this case, the double-sided paper found in S1503 is fed, rather than the first sheet of paper in the paper queue. In the case of paper queues 1929-1931, the processes are executed sequentially in the order of S1501, S1502, S1503, S1505, and S1504 as shown in Figure 15. In other words, in this case, one side of the leading sheet of paper in the paper queue is fed.

[0062] As shown in Figure 18, the number of sheets in the single-sided stack between two double-sided stacks is set at a threshold of "normal double-sided rotation count - 1," illustrating that applying forced double-sided or overtaking double-sided control is more advantageous than applying normal double-sided control. Furthermore, the example shown in Figure 19 demonstrates that when the number of sheets in the single-sided stack between two double-sided stacks is smaller, applying forced double-sided control is more advantageous than applying overtaking double-sided control. In this case, the threshold is "(normal double-sided rotation count + 1) / 2." In this case, as indicated by the symbol 1951, it can be seen that applying forced double-sided control is two sides more advantageous in performance than applying overtaking double-sided control.

[0063] Referring to Figure 20, an example of the processing of the image forming apparatus according to this embodiment will be explained, with particular attention to the processing related to switching between normal double-sided, overtaking double-sided, and forced double-sided control. In S2001, the CPU 305 determines whether the first sheet of paper in the paper queue held in RAM 306 is single-sided or not. If CPU 305 determines in S2001 that the first sheet is single-sided, it proceeds to S2002; if it determines that it is double-sided, it proceeds to S2010. Note that if the first sheet in the paper queue is double-sided, it is difficult to control the process to move single-sided paper to the double-sided pass, as in forced double-sided processing. Therefore, in this case, CPU 305 applies normal double-sided control in S2010.

[0064] In S2002, CPU305 determines whether all the paper waiting to be fed is single-sided or not. If CPU305 determines in S2002 that all paper is single-sided, it proceeds to S2010. If it determines that not all paper is single-sided (at least one sheet is double-sided), it proceeds to S2003. Note that if all paper is single-sided, CPU305 does not have a mixed single-sided and double-sided state, so the control that improves performance when single-sided and double-sided are mixed, such as forced double-sided printing, becomes meaningless. Therefore, in this case, CPU305 applies normal double-sided control in S2010, and single-sided paper is printed as single-sided.

[0065] In S2003, CPU305 determines whether the paper fed immediately before was double-sided or not. If CPU 305 determines in S2003 that the paper fed immediately before was double-sided, it proceeds to S2004; otherwise, it proceeds to S2006. S2006 is the process executed when forced double-sided control is excluded from application. Forced double-sided control, which continues double-sided circulation for already fed double-sided paper stacks, does not work if the paper fed immediately before was single-sided. Therefore, if the paper fed immediately before was single-sided, forced double-sided control is excluded from application. As explained in Figure 9, forced double-sided control is disadvantageous when the paper fed immediately before was single-sided.

[0066] In S2004, CPU305 determines whether or not there is paper waiting to be re-fed. If CPU 305 determines in S2004 that there is paper waiting to be re-fed, it proceeds to S2005; otherwise, it proceeds to S2006. Note that if the paper fed immediately before was not waiting to be re-fed for double-sided printing, it has already been ejected from the machine as double-sided paper. Forced double-sided control is a control that continues double-sided circulation for already fed double-sided paper stacks, so it cannot function when there is no paper waiting to be re-fed and the double-sided circulation is interrupted. Therefore, CPU 305 excludes forced double-sided control from application when there is no paper waiting to be re-fed.

[0067] In S2005, CPU305 determines whether the number of single-sided papers among the papers waiting to be fed is less than "the normal number of double-sided recycled sheets minus 1". If CPU305 determines in S2005 that the number of single-sided sheets is less than "normal double-sided circulation number - 1", it proceeds to S2007. If it determines that the number of single-sided sheets is "normal double-sided circulation number - 1" or more, it proceeds to S2006. Note that when processing double-sided, single-sided, and double-sided stacks consecutively, if the number of single-sided stacks is large (greater than or equal to "normal double-sided circulation number - 1"), applying forced double-sided control is less efficient in terms of performance compared to applying normal double-sided control. Therefore, CPU305 limits the application of forced double-sided control. The performance degradation associated with applying forced double-sided control in this case is as described above, refer to Figure 16.

[0068] In S2006, CPU305 determines whether the number of double-sided papers among the papers waiting to be fed is less than or equal to "(number of double-sided circulating sheets for follow-up double-sided paper + 1) / 2". If CPU305 determines in S2006 that the number of double-sided sheets is less than or equal to "(number of double-sided sheets for follow-up double-sided processing + 1) / 2", it proceeds to S2011, where it applies the control for follow-up double-sided processing. On the other hand, if CPU 305 determines in S2006 that the number of double-sided sheets is greater than "(number of double-sided sheets in the overtaking double-sided pack + 1) / 2", it proceeds to S201 and applies normal double-sided control in S2010ni. This is because if the number of double-sided sheets among the paper waiting to be fed is greater than "(number of double-sided sheets in the overtaking double-sided pack + 1) / 2", double-sided circulation cannot be continued, and some double-sided sheets will be wasted. This case is explained above with reference to Figure 17. The example shown in Figure 16 is 5 double-sided sheets (1-5), 10 single-sided sheets (6-15), and 5 double-sided sheets (16-20). In contrast, Figure 17 shows 5 double-sided sheets (1-5), 10 single-sided sheets (6-15), and 3 double-sided sheets (16-18), where the number of double-sided sheets in the double-sided pack following the single-sided pack is less than in the example shown in Figure 16. Therefore, unlike the 19th and 20th sheets in the example shown in Figure 16(c), there are no sheets that require double-sided printing later because the double-sided cycle cannot be continued. In the example shown in Figure 17(c), the performance is better when the overtake double-sided control is applied compared to when the normal double-sided control is applied.

[0069] In S2007, CPU305 determines whether the number of double-sided papers waiting to be fed is less than or equal to "(number of double-sided circulating sheets for follow-up double-sided paper + 1) / 2". If CPU305 determines in S2007 that the number of double-sided sheets is less than or equal to "(number of double-sided sheets circulating in the overtaking double-sided section + 1) / 2", it proceeds to S2008. If it determines that the number is greater than "(number of double-sided sheets circulating in the overtaking double-sided section + 1) / 2", it proceeds to S2009. The case in which processing S2007 is executed corresponds to the case in which the conditional judgments in S2003, S2004, and S2005 determine that the number of sheets on one side of the double-sided stack is sufficiently small. In other words, it can be determined that applying overtaking double-sided control or forced double-sided control is more advantageous than applying normal double-sided control. This case is as described above with reference to Figure 18. Furthermore, in the S2007 process, similar to the S2006 process, during overtaking double-sided control, it is checked whether there are any double-sided planes that will be wasted due to the inability to continue the double-sided cycle. In cases where there are 16th and 17th planes that will be wasted due to the inability to continue the double-sided cycle, as shown in the example in Figure 18(c), applying forced double-sided control, as shown in the example in Figure 18(b), results in better performance than applying overtaking double-sided control. On the other hand, in cases up to the 15th plane where there are no 16th and 17th planes, applying overtaking double-sided control, as shown in the example in Figure 18(c), results in better performance than applying forced double-sided control.

[0070] In S2008, CPU305 determines whether the number of single-sided papers waiting to be fed is equal to or greater than "(normal double-sided circulation number + 1) / 2 - 1". If CPU305 determines in S2008 that the number of single-sided sheets is "(normal double-sided cycle count + 1) / 2 - 1" or greater, it proceeds to S2011, where it applies the overtaking double-sided control. On the other hand, if the CPU 305 has fewer single-sided sheets in S2008 than "(normal double-sided circulation number + 1) / 2 - 1", it proceeds to S2009. This case is as described above with reference to Figure 19. Specifically, even in cases where the application of overtaking double-sided control is advantageous because double-sided circulation cannot be continued and there are no wasted double-sided sheets, it is more advantageous to apply forced double-sided control when the number of single-sided sheets between the double-sided stacks is smaller.

[0071] In S2009, the CPU 305 determines whether or not there is paper waiting to be fed in a specific direction for ejection. If CPU305 determines in S2009 that there is paper waiting to be fed in a specific direction, it proceeds to S2010, where it applies normal duplex control. On the other hand, if CPU 305 determines in S2009 that there is no paper waiting to be fed in a specific direction, it proceeds to S2012, where it applies forced duplex control. The reason for applying the above control is, as mentioned above with reference to Figure 5, that when the orientation of the paper being ejected in a specific direction changes from single-sided to double-sided printing, the orientation of the paper being ejected in that direction changes, and the user may not be able to obtain the output they expected.

[0072] As described above, the image forming apparatus according to this embodiment does not apply forced duplex control to paper ejected in a specific direction, but allows the application of overtaking duplex control. By applying such control, it becomes possible to output the results that the user expects when paper ejected in a specific direction is used, while providing performance in a more favorable manner compared to the first embodiment. While preprinted paper was given as an example of paper with a specific output orientation, there are other types of paper where the orientation of the output is important. For example, single-sided coated paper, pre-punched paper, envelopes, postcards, etc., may fall under the category of paper where the orientation of the output is important. Therefore, in this disclosure, not only preprinted paper, but also single-sided coated paper, pre-punched paper, envelopes, postcards, etc., where the orientation of the output is important may be considered as paper with a specific output orientation.

[0073] <Other Embodiments> The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0074] Furthermore, the disclosure of this embodiment includes the following configurations, methods, and programs. (Configuration 1) A printing apparatus that allows the execution of print jobs in which single-sided and double-sided printing are mixed, comprising: a feeding means for feeding sheets held in a predetermined sheet holding section; a refeeding means for refeeding the target sheet from the downstream of a plurality of waiting positions in a sheet transport path, which has a plurality of waiting positions for holding the sheet with the first side printed, in order to print an image on the second side of the target sheet with the first side printed, in the case of double-sided printing; and a control means for controlling the execution of a print job, wherein the control means performs single-sided printing on sheets instructed to be single-sided, and performs double-sided printing on sheets instructed to be double-sided, and a plurality of A printing apparatus characterized by selectively switching and executing a plurality of print controls, each including at least one print control, based on the printing order of single-sided and double-sided printing in the target print job, the number of the plurality of waiting positions, and the number of single-sided and double-sided sheets among the sheets waiting to be fed, and restricting the application of the second print control when the sheets to be fed include a predetermined sheet that is specified so that a predetermined side faces a predetermined direction when ejected. (Configuration 2) The printing apparatus according to Configuration 1, wherein the plurality of print controls include a third print control in which the first side of a subsequent sheet instructed to be printed on both sides is printed before a sheet instructed to be printed on one side, and the single-sided printing of the sheet instructed to be printed on one side is performed before the second side of the double-sided printing of the said sheet, and the control means allows the application of the third print control even when the sheets to be fed include the paper to be discharged in a specific direction. (Configuration 3) The printing apparatus according to Configuration 1 or 2, characterized in that the paper discharged in a specific direction includes at least one of preprinted paper, single-sided coated paper, pre-punched paper, envelopes, and postcards. (Method 1) A control method for a printing apparatus that allows the execution of a print job in which single-sided and double-sided printing are mixed, comprising: a feeding step of feeding a sheet held in a predetermined sheet holding section; a refeeding step of refeeding the target sheet from the downstream of a plurality of waiting positions in a sheet transport path having a plurality of waiting positions for waiting the sheet in which the first side has been printed, in order to print an image on the second side of the target sheet in double-sided printing; and a control step of controlling the execution of a print job, wherein the control step includes a first print control that performs single-sided printing on a sheet instructed to be single-sided, and performs double-sided printing on a sheet instructed to be double-sided, and A method for controlling a printing apparatus, comprising: a second print control that applies the same transport control as for a sheet instructed to be printed on double-sided printing to a sheet instructed to be printed on double-sided printing, which is located among a plurality of sheets, so that after single-sided printing, the sheet transport path for double-sided printing is transported on the sheet transport path, and a plurality of print controls are selectively switched and executed based on the printing order of single-sided and double-sided printing in the target print job, the number of the plurality of waiting positions, and the number of sheets among the sheets waiting to be fed that are either single-sided or double-sided, and the application of the second print control is restricted when the sheets to be fed include a predetermined sheet that is specified so that a predetermined side faces a predetermined direction when it is ejected. (Program 1) A computer is a printing apparatus that allows the execution of print jobs in which single-sided and double-sided printing are mixed, comprising: a feeding means for feeding sheets held in a predetermined sheet holding section; a refeeding means for refeeding a target sheet from the downstream of a plurality of waiting positions in a sheet transport path, which has a plurality of waiting positions for holding a sheet with the first side printed on it, in order to print an image on the second side of the target sheet with the first side printed on it, in double-sided printing; and a control means for controlling the execution of a print job, wherein the control means performs single-sided printing on sheets instructed to be single-sided, and performs double-sided printing on sheets instructed to be double-sided, and performs double-sided printing on a plurality of sheets instructed to be double-sided A program for operating a printing device characterized by selectively switching and executing a plurality of print controls, including at least a second print control that applies the same transport control as for a sheet instructed to be printed on double-sided printing to a sheet instructed to be printed on double-sided printing, such that after single-sided printing, the sheet transport path of the sheet transport path is transported, based on the printing order of single-sided and double-sided printing in the target print job, the number of the plurality of waiting positions, and the number of at least one of single-sided and double-sided sheets among the sheets waiting to be fed, and restricting the application of the second print control when the sheets to be fed include a predetermined sheet that is specified so that a predetermined side faces a predetermined direction when ejected. [Explanation of Symbols]

[0075] 101 Image forming apparatus 201 Control Unit 305 CPU

Claims

1. A printing apparatus that allows the execution of print jobs containing both single-sided and double-sided printing, A feeding means for feeding sheets held in a predetermined sheet holding section, In double-sided printing, in order to print an image on the second side of a target sheet on which the first side has been printed, a refeeding means is provided to refeed the target sheet from a predetermined waiting position among the multiple waiting positions of a sheet transport path that has multiple waiting positions for the sheet on which the first side has been printed. Control means for controlling the execution of a print job, It has, The control means is A first print control that performs single-sided printing on sheets instructed to be printed on one side, and double-sided printing on sheets instructed to be printed on both sides, A second printing control applies the same transport control as for sheets instructed to be printed on both sides to a sheet instructed to be printed on both sides, so that after single-sided printing, the sheet transport path is transported along the transport path for double-sided printing. Multiple print controls, including at least the above, are selectively switched and executed based on the print order of single-sided and double-sided printing in the target print job, the number of the multiple waiting positions, and the number of at least one of the single-sided and double-sided sheets among the sheets waiting to be fed. The application of the second print control is restricted when the sheets to be fed include a predetermined sheet that is specified to have a predetermined side facing a predetermined direction when ejected. A printing apparatus characterized by the following features.

2. The aforementioned plurality of print controls include a third print control in which the first side of a subsequent sheet instructed to be printed on both sides is printed before the sheet instructed to be printed on one side, and the single-sided printing of the sheet instructed to be printed on one side is performed before the second side of the double-sided printing of the said sheet. The control means allows the application of the third print control even when the sheets to be fed include the predetermined sheets. The printing apparatus according to claim 1, characterized in that

3. The printing apparatus according to claim 1, characterized in that the predetermined sheet includes at least one of pre-printed paper, single-sided coated paper, pre-punched paper, envelopes, and postcards.

4. A method for controlling a printing apparatus that allows the execution of print jobs containing both single-sided and double-sided printing, A feeding step of feeding a sheet held in a predetermined sheet holding section, In double-sided printing, in order to print an image on the second side of a target sheet on which the first side has been printed, a refeeding step is performed in which the target sheet is refeeded from a predetermined waiting position among the multiple waiting positions of a sheet transport path that has multiple waiting positions for the sheet on which the first side has been printed, A control step that controls the execution of a print job, Includes, The control step is, A first print control that performs single-sided printing on sheets instructed to be printed on one side, and double-sided printing on sheets instructed to be printed on both sides, A second printing control applies the same transport control as for sheets instructed to be printed on both sides to a sheet instructed to be printed on both sides, so that after single-sided printing, the sheet transport path is transported along the transport path for double-sided printing. Multiple print controls, including at least the above, are selectively switched and executed based on the print order of single-sided and double-sided printing in the target print job, the number of the multiple waiting positions, and the number of at least one of single-sided and double-sided sheets among the sheets waiting to be fed. The application of the second print control is restricted when the sheets to be fed include a predetermined sheet that is specified to have a predetermined side facing a predetermined direction when ejected. A method for controlling a printing apparatus, characterized by the features described above.

5. Computers, A printing apparatus that allows the execution of print jobs containing both single-sided and double-sided printing, A feeding means for feeding sheets held in a predetermined sheet holding section, In double-sided printing, in order to print an image on the second side of a target sheet on which the first side has been printed, a refeeding means is provided to refeed the target sheet from a predetermined waiting position among the multiple waiting positions of a sheet transport path which has multiple waiting positions for holding the sheet on which the first side has been printed. Control means for controlling the execution of a print job, It has, The control means is A first print control that performs single-sided printing on sheets instructed to be printed on one side, and double-sided printing on sheets instructed to be printed on both sides, A second printing control applies the same transport control as for sheets instructed to be printed on both sides to a sheet instructed to be printed on both sides, so that after single-sided printing, the sheet transport path is transported along the transport path for double-sided printing. Multiple print controls, including at least the above, are selectively switched and executed based on the print order of single-sided and double-sided printing in the target print job, the number of the multiple waiting positions, and the number of at least one of the single-sided and double-sided sheets among the sheets waiting to be fed. The application of the second print control is restricted when the sheets to be fed include a predetermined sheet that is specified to have a predetermined side facing a predetermined direction when ejected. A program for causing a printing device to function in a particular way.

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