Sheet feeding control method, sheet feeding device, image forming apparatus

Abstract

Ensure appropriate sheet spacing even if there are delays in sheet feeding. [Solution] The sheet detection device 25 detects each sheet at a position downstream of the sheet feeding direction relative to the feeding rotating body 22. The timing device 8e measures the elapsed time from the time when the feeding process for each sheet is started until the time when each sheet is detected by the sheet detection device 25. The control device 8 derives a reference feeding time based on one or more reference measurement times measured by the timing device 8e when one or more reference feeding processes that satisfy the number condition are executed. The control device 8 adjusts the timing for the feeding mechanism 20 to start the feeding process for each sheet to be fed by the feeding process after the reference feeding process has been executed, based on the reference feeding time.

Description

Technical Field

[0001] The present invention relates to a sheet feeding control method, a sheet feeding device, and an image forming device for controlling the feeding timing of sheets.

Background Art

[0002] An image forming apparatus includes a sheet conveyance device and a printing device that forms an image on a conveyed sheet. The sheet conveyance device includes a sheet feeding device that feeds the uppermost sheet in the stacked sheets to a conveyance path, and a plurality of sets of conveyance roller pairs that convey the sheet along the conveyance path.

[0003] The sheet feeding device includes a sheet detection device that detects the sheet fed to the conveyance path. It is known that the image forming apparatus measures the feeding speed of the sheet based on the detection result of the sheet detection device (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in the sheet feeding device, a measurement process for measuring the time from when the feeding of the sheet is started until the sheet is detected by the sheet detection device is executed. The measurement time obtained by the measurement process represents the feeding state of the sheet.

[0006] For example, when the feeding of the sheet is delayed due to deterioration of components in contact with the sheet or the like, the delay time is reflected in the measurement time. The feeding delay affects the sheet interval.

[0007] The object of the present invention is to provide a sheet feeding control method, a sheet feeding device, and an image forming apparatus that can ensure appropriate sheet spacing even when there is a delay in sheet feeding. [Means for solving the problem]

[0008] A sheet feeding control method according to one aspect of the present invention is a method for controlling a sheet feeding device. The sheet feeding device comprises a feeding mechanism, a lift mechanism, a sheet detection device, and a timing device. The feeding mechanism has a feeding rotating body that contacts the upper surface of the topmost sheet in the stacked sheets, and performs a feeding process to feed each sheet from the stacked sheets to a transport path by rotating the feeding rotating body. The lift mechanism lifts the stacked sheets to a contact position where the upper surface of the topmost sheet in the stacked sheets contacts the feeding rotating body. The sheet detection device detects each sheet at a position downstream of the feeding rotating body in the sheet feeding direction. The timing device measures the elapsed time from the time the feeding process for each sheet is started until the time each sheet is detected by the sheet detection device. The sheet feeding control method includes the control device deriving a reference feeding time based on one or more reference feeding processes measured by the timing device when one or more reference feeding processes are performed that satisfy the count condition, which is one or more feeding processes performed a predetermined number of times after the lift mechanism lifts the loaded sheet to the contact position. Furthermore, the sheet feeding control method includes the control device adjusting the feeding start timing, based on the reference feeding time, to cause the feeding mechanism to start the feeding process for each of the sheets to be fed by the feeding process after the reference feeding process has been executed.

[0009] A sheet feeding device according to another aspect of the present invention comprises the feeding mechanism, the lift mechanism, the sheet detection device, the timing device, and the control device that implements the sheet feeding control method.

[0010] An image forming apparatus according to another aspect of the present invention comprises a sheet feeding device and a printing device that forms an image on each sheet fed by the sheet feeding device. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a sheet feeding control method, a sheet feeding device, and an image forming apparatus that can ensure appropriate sheet spacing even when there is a delay in sheet feeding. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a configuration diagram of an image forming apparatus according to an embodiment. [Figure 2] Figure 2 is a block diagram showing the configuration of the control device in the image forming apparatus according to the embodiment. [Figure 3] Figure 3 is a diagram showing the configuration of the sheet feeding device in the image forming apparatus according to the embodiment. [Figure 4] Figure 4 shows the sheet feeding apparatus in the image forming apparatus according to the embodiment before the feeding process is started. [Figure 5] Figure 5 is a flowchart showing an example of the sheet feeding control procedure in an image forming apparatus according to this embodiment. [Figure 6] Figure 6 is a flowchart showing an example of the procedure for the first timing adjustment process in the image forming apparatus according to the embodiment. [Figure 7] Figure 7 is a flowchart showing an example of the procedure for positional misalignment detection in an image forming apparatus according to an embodiment. [Figure 8] Figure 8 is a flowchart showing an example of the procedure for the second timing adjustment process in the image forming apparatus according to the embodiment. [Figure 9] Figure 9 shows a first example of the relationship between the reference feeding time, the target measurement time, and the positional displacement time in an image forming apparatus according to an embodiment. [Figure 10]FIG. 10 is a diagram showing a second example of the relationship among a reference feeding time, a target measurement time, and a positional deviation time in the image forming apparatus according to the embodiment. [Figure 11] FIG. 11 is a diagram showing a third example of the relationship among a reference feeding time, a target measurement time, and a positional deviation time in the image forming apparatus according to the embodiment. [Figure 12] FIG. 12 is a diagram showing a fourth example of the relationship among a reference feeding time, a target measurement time, and a positional deviation time in the image forming apparatus according to the embodiment. [Figure 13] FIG. 13 is a diagram showing a fifth example of the relationship among a reference feeding time, a target measurement time, and a positional deviation time in the image forming apparatus according to the embodiment. [Figure 14] FIG. 14 is a flowchart showing a procedure of a modified example of the first timing adjustment process.

Embodiments of the Invention

[0013] [[ID=…]] [[ID=…]] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are merely examples of embodying the present invention and do not limit the technical scope of the present invention.

[0014] [Configuration of Image Forming Apparatus 10] The image forming apparatus 10 according to the embodiment includes a sheet feeding device 2, a sheet conveying device 3, and a printing device 4. Further, the image forming apparatus 10 also includes a control device 8, an operation device 801, a display device 802, and the like.

[0015] Furthermore, the image forming apparatus 10 includes a main housing 1 that houses the sheet feeding device 2, the sheet conveying device 3, and the printing device 4. The main housing 1 includes a lower housing 1a that forms the housing of the sheet feeding device 2.

[0016] The sheet feeding device 2 includes a sheet cassette 200, a feeding mechanism 20, a lift mechanism 21, and a fed sheet detection device 25 (see FIG. 1). The feeding mechanism 20 includes a pickup roller 22, a delivery roller 23, and a retard roller 24.

[0017] The sheet cassette 200 houses the loading sheet 90 and is retractably mounted in the lower housing 1a. The sheet cassette 200 is an example of a sheet storage unit.

[0018] The pickup roller 22 and the delivery roller 23 are each rotatably supported and spaced apart. The pickup roller 22 contacts the upper surface of the top sheet on the loading sheet 90. The feeding mechanism 20 further includes a feeding motor 230 that rotates the pickup roller 22 and the delivery roller 23 (see Figure 3).

[0019] The feeding mechanism 20 performs the feeding process by rotating the pickup roller 22 and the delivery roller 23. The feeding process involves feeding each of the sheets 9 from the loading sheet 90 to the transport path 30. The transport path 30 is the passage for each of the sheets 9.

[0020] The feed roller 23 and retard roller 24 are located in the area between the sheet cassette 200 and the transport path 30. The retard roller 24 is located below the feed roller 23 and faces the feed roller 23. The retard roller 24 forms a nip between itself and the feed roller 23, sandwiching each sheet 9.

[0021] In the sheet feeding device 2, the sheet feeding direction D1 is the direction from the sheet cassette 200 to the transport path 30 (see Figure 1). The delivery roller 23 is positioned downstream of the pickup roller 22 in the sheet feeding direction D1 (see Figures 1 and 3).

[0022] The pickup roller 22 is an example of a feeding rotating body. The discharge roller 23 is an example of a discharge rotating body that rotates together with the feeding rotating body.

[0023] The retard roller 24 is rotatably supported. The feeding mechanism 20 further includes a torque limiter 24a connected to the rotation axis of the retard roller 24, and a spring 241 that biases the retard roller 24 toward the feed roller 23 (see Figure 3).

[0024] When the feeding process is performed, a torque DR1 in the forward rotation direction acts on the retard roller 24 from either the rotating feed roller 23 or the sheet 9 moving toward the conveying path 30.

[0025] The torque limiter 24a restricts the rotation of the retard roller 24 in the forward rotation direction DR1 when the torque acting on the retard roller 24 in the forward rotation direction DR1 is less than or equal to the rated torque (see Figure 3).

[0026] The retard roller 24 blocks the accompanying sheets by contacting the leading edge of one or more accompanying sheets that are fed out with each sheet 9 when the feeding process is performed. In this way, the retard roller 24 separates the accompanying sheets from each sheet 9. The accompanying sheets are fed out from the sheet cassette 200 so that they overlap the underside of the top sheet on the stacked sheet 90.

[0027] Furthermore, if the torque acting on the retard roller 24 from either the rotating discharge roller 23 or the sheet 9 moving toward the conveyor path 30 exceeds the rated torque of the torque limiter 24a, the retard roller 24 rotates in the forward rotation direction DR1. This prevents either the discharge roller 23 or the sheet 9 from receiving excessive frictional force from the retard roller 24.

[0028] The retard roller 24 is an example of a separating member that separates the auxiliary sheet from the uppermost sheet of the loading sheet 90. A non-rotating separating pad may be used as the separating member instead of the retard roller 24.

[0029] In the following description, the position of each sheet 9 when its leading edge is aligned with the cassette front wall surface 200a is referred to as the initial reference position P1 (see Figures 1 and 3). The cassette front wall surface 200a is the inner wall surface of the downstream end of the sheet cassette 200 in the sheet feeding direction D1. The position between the feed roller 23 and the retard roller 24 is referred to as the separation position P2 (see Figures 1 and 3). The separation position P2 can also be said to be the position of the feed roller 23 in the sheet feeding direction D1.

[0030] The lift mechanism 21 is located within the sheet cassette 200 and is supported by the sheet cassette 200. The lift mechanism 21 supports the loading sheet 90 so that it can be raised and lowered.

[0031] The lift mechanism 21 is a mechanism for lifting the loading sheet 90 from a separation position to a contact position. The separation position is the position where the upper surface of the top sheet of the loading sheet 90 is separated from the pickup roller 22. The contact position is the position where the upper surface of the top sheet of the loading sheet 90 is in contact with the pickup roller 22.

[0032] The lift mechanism 21 comprises a lift plate 211 and a push-up plate 212. The lift plate 211 is rotatably supported around a pivot axis 211a, which is positioned along the bottom plate of the sheet cassette 200. That is, the lift plate 211 is rotatable up and down around the pivot axis 211a.

[0033] The loading sheet 90 is placed on the lift plate 211. When the lift plate 211 rotates upward, the loading sheet 90 rotates upward, and when the lift plate 211 rotates downward, the loading sheet 90 rotates downward.

[0034] The push-up plate 212 is positioned below the lift plate 211 and is supported so as to be rotatable around a pivot shaft 212a that is positioned along the bottom plate of the sheet cassette 200. In other words, the push-up plate 212 is rotatable up and down around the pivot shaft 212a.

[0035] The push-up plate 212 rotates in a first rotational direction by the driving force of a motor (not shown), thereby pushing the lift plate 211 and the loaded sheet 90 on the lift plate 211 upward. That is, the lift mechanism 21 lifts the loaded sheet 90 on the lift plate 211 from the separated position to the contact position by rotating the push-up plate 212 in the first rotational direction.

[0036] Meanwhile, the push-up plate 212 rotates in the second rotational direction by the driving force of the motor, thereby lowering the lift plate 211 and the loading sheet 90 on the lift plate 211. In other words, the lift mechanism 21 lowers the loading sheet 90 on the lift plate 211 from the contact position to the separation position by rotating the push-up plate 212 in the second rotational direction.

[0037] The feed sheet detection device 25 detects each sheet 9 being fed by the feeding process at a detection position P3 downstream of the feed roller 23 in the sheet feeding direction D1. For example, the feed sheet detection device 25 includes a pivotably supported actuator and a photosensor that detects when the actuator swings. The actuator swings by coming into contact with each sheet 9 passing through the detection position P3.

[0038] The sheet feeding detection device 25 may also be a transmissive or reflective photosensor that detects each sheet 9 passing through the detection position P3.

[0039] The sheet feeding device 2 further includes a mounting detection device 26 located on the lower housing 1a (see Figure 1). The mounting detection device 26 detects whether the sheet cassette 200 is in a mounted state, mounted in the lower housing 1a, or in an unmounted state, pulled out from the lower housing 1a.

[0040] For example, the mounting detection device 26 is a reflective photosensor or microswitch that detects a portion of the sheet cassette 200 in the mounted state.

[0041] When the seat cassette 200 is in the aforementioned mounting state, the lift mechanism 21 can lift the loading sheet 90 to the aforementioned contact position.

[0042] The sheet cassette 200 further comprises an end cursor 213 and a pair of side cursors 214. The end cursor 213 is provided to be movable along the sheet feeding direction D1. The end cursor 213 is positioned along the rear end of the loaded sheet 90 placed on the lift plate 211. This prevents the loaded sheet 90 from shifting upstream of the initial reference position P1 in the sheet feeding direction D1.

[0043] A pair of side cursors 214 are arranged to be interlocked so as to move toward or away from each other along the width direction D2, which is perpendicular to the sheet feeding direction D1.

[0044] The pair of side cursors 214 are positioned along both ends of the loading sheet 90 placed on the lift plate 211 in the width direction D2. This prevents the loading sheet 90 from shifting from a specific position in the width direction D2.

[0045] The sheet conveying device 3 conveys each of the sheets 9 supplied by the sheet feeding device 2 along the conveying path 30. In this embodiment, the sheet conveying device 3 includes a plurality of pairs of conveying rollers 31 and a conveying sheet detection device 32 arranged along the conveying path 30.

[0046] Multiple sets of conveying rollers 31 convey each sheet 9 by rotating individually. Each set of conveying rollers 31 includes a resist roller set 31a and a discharge roller set 31b.

[0047] The resist roller pair 31a is positioned at resist position P4 in the transport path 30. The discharge roller pair 31b is positioned at the end of the transport path 30.

[0048] The resist roller pair 31a pauses each sheet 9 fed by the sheet feeder 2 at the resist position P4, and then sends it to the print position P5 in the transport path 30.

[0049] The transport sheet detection device 32 detects each sheet 9 as it moves towards the resist position P4 after being fed into the transport path 30 by the sheet feeding device 2. The transport sheet detection device 32 has the same configuration as the feeding sheet detection device 25.

[0050] The discharge roller pair 31b discharges each sheet 9 that has passed through print position P5 from the transport path 30 to the discharge tray 101. As will be described later, an image is formed on each sheet 9 at print position P5.

[0051] The printing device 4 forms an image on each of the sheets 9 transported by the sheet transport device 3. That is, the printing device 4 forms an image on each of the sheets 9 supplied by the sheet feeding device 2. The printing device 4 forms an image on each of the sheets 9 at the printing position P5 in the transport path 30.

[0052] In the example shown in Figure 1, the printing device 4 forms an image on each of the sheets 9 using an electrophotographic method. In this case, the printing device 4 includes a light scanning unit 40, one or more image forming units 4x, a transfer device 44, and a fixing device 46.

[0053] In the example shown in Figure 1, the printing apparatus 4 includes multiple image forming units 4x corresponding to multiple development colors. Each image forming unit 4x includes a drum-shaped photoreceptor 41, a charging device 42, a developing device 43, and a drum cleaning device 45. For example, the multiple development colors are cyan, yellow, magenta, and black.

[0054] Furthermore, the transfer apparatus 44 includes an intermediate transfer belt 440, a plurality of primary transfer devices 441 corresponding to a plurality of image forming units 4x, a secondary transfer device 442, and a belt cleaning device 443.

[0055] In each of the image forming units 4x, the charging device 42 charges the surface of the photoreceptor 41. The optical scanning unit 40 forms an electrostatic latent image on the surface of the photoreceptor 41 in each of the image forming units 4x by scanning with laser light.

[0056] In each of the image forming units 4x, the developing device 43 develops the electrostatic latent image into a toner image by supplying toner to the surface of the photoreceptor 41.

[0057] The primary transfer device 441 transfers the toner images on the surface of the photoreceptor 41 of each image forming unit 4x to the surface of the intermediate transfer belt 440. As a result, the toner images of the multiple developing colors are transferred to the surface of the intermediate transfer belt 440. At the print position P5, the primary transfer device 441 transfers the toner images on the surface of the intermediate transfer belt 440 to each of the sheets 9. The fixing device 46 fixes the toner images transferred to each of the sheets 9 by heating and pressurizing them.

[0058] In each of the image forming units 4x, the drum cleaning device 45 removes waste toner remaining on the surface of the photoreceptor 41. The belt cleaning device 443 removes waste toner remaining on the surface of the intermediate transfer belt 440.

[0059] The printing device 4 may be a device that forms images on each of the sheets 9 using a method other than electrophotography. For example, the printing device 4 may be a device that forms images on each of the sheets 9 using an inkjet method.

[0060] If an inkjet printing device 4 is used, the sheet transport device 3 may include a belt transport device that transports each sheet 9 by a rotating endless belt.

[0061] The operating device 801 is a device that accepts human input. The operating device 801 includes, for example, operating buttons and a touch panel. The display device 802 is a device that displays information. The display device 802 includes, for example, a panel display device such as a liquid crystal display unit.

[0062] The control device 8 performs various data processing operations. Furthermore, the control device 8 controls equipment such as the sheet feeding device 2, the sheet transport device 3, the printing device 4, and the display device 802.

[0063] As shown in Figure 3, the control unit 8 includes a CPU (Central Processing Unit) 81, a RAM (Random Access Memory) 82, a secondary storage device 83, and peripheral devices such as a signal interface 84. Furthermore, the control unit 8 also includes a communication device 85.

[0064] The CPU 81 is a processor that performs various data processing and control by executing computer programs. The RAM 82 is a computer-readable volatile memory. The RAM 82 temporarily stores the computer programs executed by the CPU 81 and the data that the CPU 81 outputs and references during the process of performing various processes.

[0065] The secondary storage device 83 is a computer-readable, non-volatile storage device. The secondary storage device 83 is capable of storing and updating the computer program and various types of data. For example, flash memory, a hard disk drive, or both may be used as the secondary storage device 83.

[0066] The signal interface 84 converts signals output by various sensors into digital data and transmits the converted digital data to the CPU 81. Furthermore, the signal interface 84 converts control commands output by the CPU 81 into control signals and transmits the control signals to the controlled device.

[0067] The communication device 85 performs communication with other devices such as a host device via a communication network such as a LAN. The CPU 81 sends and receives data with the other devices via the communication device 85.

[0068] The CPU 81 includes a plurality of processing modules that are realized by executing the computer program. The plurality of processing modules include a feeding control unit 8a, a transport control unit 8b, and a print control unit 8c, among others.

[0069] The feed control unit 8a performs data processing and control related to the sheet feeding device 2. The feed control unit 8a of the CPU 81 constitutes a part of the sheet feeding device 2.

[0070] The transport control unit 8b performs data processing and control related to the sheet transport device 3. The transport control unit 8b of the CPU 81 constitutes a part of the sheet transport device 3.

[0071] The print control unit 8c performs data processing and control related to the printing device 4. The print control unit 8c of the CPU 81 constitutes a part of the printing device 4.

[0072] The supply control unit 8a includes a main processing unit 8d, a timing processing unit 8e, and a state determination unit 8f, among others.

[0073] The main processing unit 8d controls the start and end of the feeding process by controlling the operation and stopping of the feeding motor 230.

[0074] For example, when a print request is input through the operating device 801 or the communication device 85, the main processing unit 8d activates the feed motor 230 to start the feed mechanism 20.

[0075] The print request is either a request to execute a single print process or a request to execute a series of print processes. The single print process is the process of forming an image on one sheet 9. The series of print processes is the process of forming images sequentially on multiple sheets 9.

[0076] The timing processing unit 8e performs a first timing process that measures the elapsed time from the time when the feeding process for each sheet 9 is started until the time when each sheet 9 is detected by the feeding sheet detection device 25. In this embodiment, the time when the feeding motor 230 starts operating is the time when the feeding process is started.

[0077] The timing processing unit 8e is an example of a timing device that performs the first timing process. The timing device may be implemented by other processors such as a DSP (Digital Signal Processor) or by circuits such as an ASIC (Application Specific Integrated Circuit).

[0078] Furthermore, the timing processing unit 8e also performs a second timing process, which measures the elapsed time from the moment each sheet 9 is detected by the sheet feeding detection device 25.

[0079] If the print request is a request to execute the continuous print process, the main processing unit 8d controls the timing of the start of the second and subsequent feeding processes based on the measurement time of the second timing process. As a result, each sheet 9 is fed to the transport path 30 at appropriate intervals.

[0080] The state determination unit 8f executes a process to determine the feeding status of each sheet 9 by the sheet feeding device 2. In this embodiment, the state determination unit 8f determines the feeding status of each sheet 9 by the sheet feeding device 2 based on the measurement time T1 of the first timing process.

[0081] The print control unit 8c controls the process of forming the electrostatic latent image on the surface of the photoreceptor 41 of each of the multiple image forming units 4x by controlling the optical scanning unit 40. In this way, the print control unit 8c controls the timing at which the toner image is formed on the surface of the photoreceptor 41 of each of the multiple image forming units 4x.

[0082] The transport control unit 8b stops the rotation of the resist roller pair 31a in response to the detection of each sheet 9 by the transport sheet detection device 32, and then rotates the resist roller pair 31a in accordance with the timing at which the toner image is formed in each of the multiple image forming units 4x. As a result, the transport control unit 8b executes control to feed each of the sheets 9 from the resist position P4 to the print position P5 in synchronization with the timing at which the toner image is formed in each of the multiple image forming units 4x.

[0083] Incidentally, in the sheet feeding device 2, deterioration of the parts that come into contact with each sheet 9 may cause delays in the feeding of each sheet 9. Specifically, deterioration of the pickup roller 22 or the delivery roller 23 may cause the pickup roller 22 or the delivery roller 23 to slip on the upper surface of each sheet 9, resulting in delays in the feeding of each sheet 9.

[0084] The delay in feeding each sheet 9 affects the spacing between sheets. Furthermore, the delay can fluctuate due to causes other than deterioration of the sheet feeding device 2.

[0085] It is desirable to be able to correctly determine the delay state in order to correctly determine the deterioration state of the sheet feeding device 2, or to properly maintain the sheet spacing.

[0086] In the sheet feeding device 2, the feeding control unit 8a performs sheet feeding control, which will be described later (see Figure 5). As a result, the sheet feeding control includes processing to correctly determine the delay state, which fluctuates due to causes other than deterioration of the components of the sheet feeding device 2.

[0087] In the following description, one sheet of the stacking sheet 90 that is subject to the paper feeding process will be referred to as the target sheet 9a (see Figures 3 and 4). The target sheet 9a is the topmost sheet of the stacking sheet 90. The target sheet 9a is also the sheet subject to the first timing process and the second timing process.

[0088] Furthermore, the sheet that is subjected to the feeding process after the target sheet 9a in the loading sheet 90 is referred to as the next sheet 9b (see Figure 3). The next sheet 9b is the second sheet from the top in the loading sheet 90.

[0089] [Sheet feeding control] The following describes an example of the sheet feeding control procedure with reference to the flowchart shown in Figure 5. The sheet feeding control is performed by the feeding control unit 8a.

[0090] The sheet feeding control procedure described above is an example of a procedure for implementing a sheet feeding control method for controlling the sheet feeding device 2. The sheet feeding control procedure includes a procedure for implementing a sheet feeding state determination method.

[0091] In this embodiment, the control device 8, which includes the feed control unit 8a, is an example of a device that implements the sheet feed control method. The main processing unit 8d starts the sheet feed control when the print request is input through the operating device 801 or the communication device 85.

[0092] In the following description, S101, S102, ... represent identification codes for multiple processes in the sheet feeding control. In the sheet feeding control, the process of process S101 is executed first.

[0093] <Process S101> In step S101, the main processing unit 8d obtains pre-registered sheet size information from the secondary storage device 83. The sheet size information represents the size of the stacked sheets 90 stored in the sheet cassette 200.

[0094] For example, the sheet size information includes standard size information selected from a plurality of standard size candidates and sheet orientation information representing the orientation of the loading sheet 90. The standard size information is information that specifies the vertical and horizontal dimensions of the loading sheet 90, and the sheet orientation information represents whether the length of the loading sheet 90 in the sheet feeding direction D1 is the vertical or horizontal dimension.

[0095] That is, the sheet size information includes sheet length information representing the length in the sheet feeding direction D1 of the loaded sheet 90 housed in the sheet cassette 200. The length represented by the sheet length information is the vertical dimension or the horizontal dimension in the standard size information.

[0096] The main processing unit 8d inputs the sheet size information in advance via the operating device 801 or the communication device 85 and registers it in the secondary storage device 83.

[0097] After executing the process in step S101, the main processing unit 8d moves the process to step S102.

[0098] <Process S102> In step S102, the main processing unit 8d determines whether the feeding timing has arrived or not.

[0099] For example, the feeding timing is either the initial feeding timing or the subsequent feeding timing. The initial feeding timing is the timing after the print request has been input and the printer 4 has finished preparing to operate.

[0100] The subsequent feeding timing is the timing at which the feeding of the second and subsequent sheets 9 begins when the print request is a request for the continuous printing process.

[0101] Specifically, the subsequent feeding timing is the timing when the second measurement time corresponding to the previous feeding process reaches the feeding waiting time. The feeding waiting time is the time required from the moment the leading edge of each sheet 9 reaches the detection position P3 until the rear end of each sheet 9 exceeds a predetermined distance from the cassette front wall surface 200a.

[0102] In step S101, the main processing unit 8d sets the initial waiting time, which is one of a plurality of pre-set candidate waiting times corresponding to the sheet length information, as the feed waiting time. Note that the feed waiting time may be adjusted in the first timing adjustment process or the second timing adjustment process described later (see Figures 6 and 8).

[0103] The main processing unit 8d waits until it is determined that the feeding timing has arrived. When it is determined that the feeding timing has arrived, the main processing unit 8d moves the process to step S103.

[0104] <Process S103> In step S103, the main processing unit 8d causes the feeding mechanism 20 to start the feeding process. As a result, the pickup roller 22 and the delivery roller 23 rotate, and the target sheet 9a on the loading sheet 90 is fed from the lift plate 211 toward the transport path 30 (see Figure 3).

[0105] Furthermore, when the feeding process is started in step S103, the timing processing unit 8e starts the first timing process.

[0106] After executing the process in step S103, the main processing unit 8d moves the process to step S104.

[0107] <Process S104> In step S104, the timing processing unit 8e moves the process to step S107 when the sheet feeding detection device 25 transitions from a non-detection state to a sheet detection state.

[0108] The timing processing unit 8e terminates the first timing process when the feed sheet detection device 25 transitions to the sheet detection state. As a result, the timing processing unit 8e determines the target measurement time T1a, which is the result of the first timing process for the target sheet 9a (see Figures 9-12).

[0109] Figures 9-12 show an example of how the target measurement time T1a changes depending on the number of feeding cycles when the feeding process is repeated.

[0110] In step S104, if the feeding sheet detection device 25 does not transition from the sheet non-detection state to the sheet detection state, the timing processing unit 8e proceeds to step S105. In this case, the timing processing unit 8e continues the first timing process.

[0111] <Process S105> In step S105, the timing processing unit 8e selects the next process depending on whether the timing time from the first timing process exceeds a preset upper limit. The upper limit is the time used to detect an empty feed state in which the feeding mechanism 20 cannot feed the target sheet 9a.

[0112] The timing processing unit 8e moves the process to step S104 if the timing time from the first timing process does not exceed the upper limit time. As a result, the timing processing unit 8e continues the first timing process until the feed sheet detection device 25 transitions from the sheet non-detection state to the sheet detection state, provided that the timing time from the first timing process does not exceed the upper limit time.

[0113] On the other hand, if the timing time from the first timing process exceeds the upper limit time while the feeding sheet detection device 25 does not transition to the sheet detection state, the timing processing unit 8e moves the process to step S106.

[0114] <Process S106> In step S106, the main processing unit 8d outputs an error notification indicating that the empty feed condition has occurred, through either or both of the display device 802 and the communication device 85.

[0115] The display device 802 and the communication device 85 are examples of information output devices.

[0116] After executing the process in step S106, the main processing unit 8d terminates the feeding control. As a result, the feeding control is stopped.

[0117] <Process S107> In step S107, the timing processing unit 8e starts the second timing process.

[0118] After executing the process in step S107, the main processing unit 8d moves the process to step S108.

[0119] Furthermore, while the processes from step S107 onward are being executed, the transport control unit 8b instructs the sheet transport device 3 to transport the target sheet 9a along the transport path 30, and the print control unit 8c instructs the print device 4 to form an image on the target sheet 9a.

[0120] <Process S108> In step S108, the state determination unit 8f selects the following process depending on whether the feeding process performed in step S103 corresponds to one or more standard feeding processes that satisfy predetermined standard feeding conditions.

[0121] The aforementioned standard feeding conditions are conditions that indicate a situation in which there is no positional deviation of the target sheet 9a relative to the initial reference position P1 at the time the feeding process is started, or where the positional deviation is assumed to be negligibly small.

[0122] The next sheet 9b may be sent out as the accompanying sheet from the initial reference position P1 in the sheet feeding direction D1 when the feeding process is executed (see Figure 3). In this case, the position of the next sheet 9b is shifted in the sheet feeding direction D1 relative to the initial reference position P1. The next sheet 9b, which has experienced a positional shift, is fed as a new target sheet 9a in the next feeding process.

[0123] When the target sheet 9a with the aforementioned misalignment is fed, the target measurement time T1a is smaller compared to when the target sheet 9a without the misalignment is fed. Figures 9 and 10 show an example in which, because the misalignment of the next sheet 9b occurred in the fifth feeding process, the target measurement time T1a in the sixth feeding process was smaller than the measurement time T1 in the fifth feeding process.

[0124] Furthermore, Figures 10 to 12 show examples where the positional displacement of the target sheet 9a increases as the number of feeding processes increases. As shown in Figures 9 to 12, when the number of feeding processes after the lift mechanism 21 lifts the loaded sheet 90 to the contact position is small, the positional displacement of the target sheet 9a is often not present or is small.

[0125] In this embodiment, the standard feeding conditions include a count condition that the feeding process is either a predetermined one or predetermined multiple feeding processes after the lift mechanism 21 lifts the loading sheet 90 to the contact position.

[0126] For example, the count condition is that the feeding process is performed for the first or second time after the lift mechanism 21 lifts the loading sheet 90 to the contact position. Alternatively, the count condition is that the feeding process is performed from the ith to the jth time after the lift mechanism 21 lifts the loading sheet 90 to the contact position. i and j are, for example, positive integers less than 10.

[0127] In addition, during the first feeding process when the lift mechanism 21 has lifted the loading sheet 90 to the contact position, a relatively long target measurement time T1a may be measured. Therefore, it is possible to exclude the first feeding process from the count condition.

[0128] Furthermore, the standard feeding conditions may be the logical AND of the mounting conditions for mounting the sheet cassette 200 and the number of times conditions. The mounting conditions are those that result from the lift mechanism 21 lifting the loaded sheet 90 to the contact position for the first time after the detection result of the mounting detection device 26 changes from the unmounted state to the mounted state, and that are the one or more feeding processes performed.

[0129] The lift mechanism 21 lowers the loading sheet 90 from the contact position to the separation position before the sheet cassette 200 is pulled out from the lower housing 1a. Normally, when the sheet cassette 200 is pulled out from the lower housing 1a, an operation to replenish the loading sheet 90 or to align the loading sheet 90 is performed.

[0130] Therefore, under conditions where both the mounting conditions and the number of times conditions are met, the likelihood of the positional displacement of the target sheet 9a not occurring increases.

[0131] The state determination unit 8f moves the process to process S109 if the feeding process performed in process S103 is the standard feeding process. On the other hand, the state determination unit 8f moves the process to process S111 if the feeding process performed in process S103 does not correspond to one or more standard feeding processes.

[0132] <Process S109> In step S109, the state determination unit 8f derives a standard feeding time TFS1 based on one or more target measurement times T1a measured when the standard feeding process is executed once or more times.

[0133] For example, the state determination unit 8f derives one target measurement time T1a measured when the standard feeding process is executed once as the standard feeding time TFS1.

[0134] Alternatively, the state determination unit 8f sets a representative value of the multiple target measurement times T1a measured when the standard feeding process is executed multiple times as the standard feeding time TFS1. For example, the representative value of the multiple target measurement times T1a is the average, minimum, or median of the multiple target measurement times T1a.

[0135] Furthermore, the status determination unit 8f records the information of the set reference feeding time TFS1 in the secondary storage device 83.

[0136] The standard feeding time TFS1 is the reference value of the target measurement time T1a in the feeding process under conditions where the positional misalignment of the target sheet 9a does not occur, or where the positional misalignment is assumed to be negligibly small.

[0137] The standard feeding time TFS1 is used to determine whether or not the aforementioned positional misalignment occurs in each of the sheets 9, and to derive the amount of positional misalignment.

[0138] The aforementioned positional displacement is the amount of displacement of each sheet 9 relative to the initial reference position P1 at the time the feeding process for each sheet 9 is started.

[0139] The initial value of the standard feeding time TFS1 is the default reference time. The default reference time is determined by the design feeding speed of the feeding mechanism 20 and the path length from the initial reference position P1 to the detection position P3.

[0140] In this embodiment, the design feeding speed is the design speed when a standard sheet is fed, where the length of the sheet feeding direction D1 is the standard sheet length.

[0141] One or more target measurement times T1a measured by the timing processing unit 8e when the standard feeding process is executed once or more times are examples of one or more standard measurement times. In this embodiment, one or more of the standard measurement times are used to derive the standard feeding time TFS1.

[0142] In step S112, described later, the target measurement time T1a is the time measured by the timing processing unit 8e for the target sheet 9a that is fed after one or more of the reference feeding sheets have been fed. From the time the processing of step S107 is executed until the processing of step S112 is executed, the lift mechanism 21 holds the loaded sheet 90 in the contact position.

[0143] The state determination unit 8f executes the process in step S109 and then moves the process to step S110.

[0144] <Process S110> In step S110, the main processing unit 8d executes a first timing adjustment process, which will be described later (see Figure 6). The first timing adjustment process adjusts the timing of the start of the feeding process for the next sheet 9b based on the reference feeding time TFS1.

[0145] After executing the process in step S110, the main processing unit 8d moves the process to step S113.

[0146] <Process S111> Meanwhile, in step S111, the state determination unit 8f executes a positional deviation derivation process, which will be described later (see Figure 7). The positional deviation derivation process is a process that derives the amount of positional deviation for the target sheet 9a that is fed after the reference feeding process is executed.

[0147] The state determination unit 8f executes the process in step S111 and then moves the process to step S112.

[0148] <Process S112> In step S112, a second timing adjustment process, described later, is performed (see Figure 8). The second timing adjustment process adjusts the timing of the start of the feeding process for the next sheet 9b based on the positional deviation amount.

[0149] After executing the process in step S112, the main processing unit 8d moves the process to step S113.

[0150] <Process S113> In step S113, the main processing unit 8d selects the following process depending on whether all the feeding processes corresponding to the print request have been completed.

[0151] The main processing unit 8d moves the process to step S102 if all the feeding processes corresponding to the print request have not yet been completed. In this case, in step S102, the main processing unit 8d executes a process to determine the subsequent feeding timing based on the result of the second timing process started in step S107.

[0152] On the other hand, the main processing unit 8d terminates the sheet feeding control when all the feeding processes corresponding to the print request have been completed.

[0153] [First Timing Adjustment Process] Next, an example of the procedure for the first timing adjustment process will be described with reference to the flowchart shown in Figure 6.

[0154] In the following description, S201, S202, ... represent identification codes for multiple processes in the first timing adjustment process. In the first timing adjustment process, the process of process S201 is executed first.

[0155] <Process S201> In process S201, the main processing unit 8d selects the next process depending on whether the process of deriving the standard feeding time TFS1 performed in process S109 is the first process.

[0156] The main processing unit 8d moves the process to process S202 if the process of deriving the standard feeding time TFS1 performed in process S109 is the first process. In other words, the main processing unit 8d moves the process to process S202 if the standard feeding time TFS1 obtained in process S109 is the first standard feeding time TFS1 obtained.

[0157] On the other hand, the main processing unit 8d moves the process to process S203 if the process of deriving the standard feeding time TFS1 performed in process S109 is the second or subsequent process.

[0158] <Process S202> In step S202, the main processing unit 8d sets the initially obtained reference feed time TFS1 as the reference feed time and records the latest information of the reference feed time in the secondary storage device 83. The reference feed time is used in step S203 to derive the amount of change of the reference feed time TFS1.

[0159] After executing the process in step S202, the main processing unit 8d moves the process to step S203.

[0160] <Process S203> In step S203, the main processing unit 8d selects the following process depending on whether the amount of change in the reference feeding time TFS1 exceeds a predetermined change threshold.

[0161] In process S203, the main processing unit 8d derives the difference between the standard feeding time TFS1 and the reference feeding time as the change amount. Specifically, the change amount is derived by subtracting the reference feeding time from the standard feeding time TFS1.

[0162] The main processing unit 8d proceeds to process S204 if the amount of change in the reference feeding time TFS1 exceeds the change threshold. On the other hand, the main processing unit 8d terminates the first timing adjustment process if the amount of change in the reference feeding time TFS1 does not exceed the change threshold.

[0163] <Process S204> In step S204, the main processing unit 8d changes the reference waiting time to be shorter. The initial value of the reference waiting time is the initial waiting time (see step S102).

[0164] In this embodiment, the main processing unit 8d sets the time obtained by subtracting the first correction time from the reference waiting time as the new reference waiting time. The first correction time is a predetermined time.

[0165] As will be described later, the reference waiting time is the reference time for the feed waiting time. In the second timing adjustment process, the reference waiting time or the reference waiting time adjusted is set as the feed waiting time (see Figure 8).

[0166] After executing the process in step S204, the main processing unit 8d moves the process to step S205.

[0167] <Process S205> In step S205, the main processing unit 8d adjusts the reference waiting time so that it does not fall below a predetermined lower limit time.

[0168] In other words, the main processing unit 8d sets the lower limit time as the reference waiting time if the reference waiting time corrected in step S204 is less than the lower limit time.

[0169] After executing the process in step S205, the main processing unit 8d moves the process to step S206.

[0170] <Process S206> In step S206, the main processing unit 8d sets the most recently obtained reference feed time TFS1 as the reference feed time. As a result, in the subsequent first timing adjustment process, the amount of change in the reference feed time TFS1 is derived using the reference feed time that was last set in step S206 (see step S203).

[0171] After executing the process in step S206, the main processing unit 8d terminates the first timing adjustment process.

[0172] [Position deviation derivation process] Next, an example of the procedure for the positional displacement derivation process will be described with reference to the flowchart shown in Figure 7.

[0173] In the following description, S301, S302, ... represent identification codes for multiple steps in the positional deviation derivation process. In the positional deviation derivation process, the process of step S301 is executed first.

[0174] <Process S301> In process S301, the state determination unit 8f selects the following process by comparing the target measurement time T1a with the reference feeding time TFS1.

[0175] The state determination unit 8f proceeds to process S302 if the target measurement time T1a is less than the standard feeding time TFS1. On the other hand, the state determination unit 8f proceeds to process S306 if the target measurement time T1a is not less than the standard feeding time TFS1.

[0176] A state in which the target measurement time T1a is less than the standard feeding time TFS1 is a positional misalignment state in which the target sheet 9a is located downstream of the initial reference position P1 in the sheet feeding direction D1 at the time the feeding process of the target sheet 9a is started. A state in which the target measurement time T1a is not less than the standard feeding time TFS1 is a non-positional misalignment state in which the positional misalignment state does not occur.

[0177] <Process S302> In step S302, the state determination unit 8f selects the following process depending on whether or not a continuous positional misalignment state has occurred. Figures 11 to 13 show an example of the continuous positional misalignment state.

[0178] The aforementioned continuous positional misalignment state is a condition in which one or more recent measurement times T1x and the target measurement time T1a are less than the reference feed time TFS1.

[0179] One or more recent measurement times T1x are the times measured by the first timing process of the timing processing unit 8e for one or more consecutive recent feed sheets 9x that are fed immediately before the feeding of the target sheet 9a.

[0180] Figure 11 shows an example where the target measurement time T1a is the measurement time T1 obtained in the 7th feeding process, and the most recent measurement time T1x obtained in the previous feeding process and the target measurement time T1a are both lower than the reference feeding time TFS1.

[0181] Figure 12 shows an example where the target measurement time T1a is the measurement time T1 obtained in the 9th feeding process, and the three most recent measurement times T1x obtained in the feeding process from three processes ago to the previous process, as well as the target measurement time T1a, are all below the reference feeding time TFS1.

[0182] Figure 13 shows an example where the target measurement time T1a is the measurement time T1 obtained in the 10th feeding process, and the four most recent measurement times T1x obtained in the feeding process four processes prior to the previous one, and the target measurement time T1a are all below the reference feeding time TFS1.

[0183] The state determination unit 8f proceeds to process S303 if the continuous positional misalignment state does not occur. On the other hand, the state determination unit 8f proceeds to process S304 if the continuous positional misalignment state occurs.

[0184] <Process S303> In step S303, the state determination unit 8f executes a first position deviation derivation process. The first position deviation derivation process is a process that derives the amount of position deviation according to the difference between the target measurement time T1a and the reference feeding time TFS1.

[0185] The first positional deviation derivation process includes a process of deriving the difference between the target measurement time T1a and the reference feeding time TFS1 as the positional deviation time TG1 (see Figures 10 and 11). The positional deviation time TG1 is the time required to feed the target sheet 9a by a distance corresponding to the amount of positional deviation.

[0186] Furthermore, the first positional misalignment derivation process includes a process of deriving the positional misalignment amount by multiplying the positional misalignment time TG1 by the reference feeding speed. The positional misalignment time TG1 may also be derived as the positional misalignment amount.

[0187] The aforementioned standard feeding speed is derived by dividing the path length from the initial reference position P1 to the detection position P3 by the standard feeding time TFS1. The state determination unit 8f may also derive the standard feeding speed in advance in step S109.

[0188] The state determination unit 8f terminates the position deviation derivation process after executing the process in step S303.

[0189] <Process S304> On the other hand, in step S304, the state determination unit 8f identifies the shortest measurement time TMN1, which is the shortest time among one or more recent measurement times T1x and target measurement time T1a (see Figures 11-13).

[0190] The state determination unit 8f executes the process in step S304 and then moves the process to step S305.

[0191] <Process S305> In step S305, the state determination unit 8f executes a second positional deviation derivation process. The second positional deviation derivation process is a process that derives the amount of positional deviation according to the difference between the target measurement time T1a and the shortest measurement time TMN1.

[0192] The second positional deviation derivation process includes a process of deriving the difference between the target measurement time T1a and the shortest measurement time TMN1 as the positional deviation time TG1 (see Figure 12). Furthermore, the second positional deviation derivation process includes a process of deriving the amount of positional deviation by multiplying the positional deviation time TG1 by the reference feeding speed.

[0193] In most cases, after the misalignment of each sheet 9 occurs, the amount of misalignment increases with each subsequent feeding process until the leading edge of each sheet 9 reaches the retard roller 24. Typically, the misalignment of each sheet 9 is not resolved by the feeding process.

[0194] On the other hand, even if the amount of positional displacement does not change, the target measurement time T1a may be lengthened due to the pickup roller 22 and the delivery roller 23 sliding on the upper surface of the target sheet 9a.

[0195] The second positional misalignment derivation process is a process that derives the positional misalignment amount under the assumption that the shortest measurement time TMN1 represents the reduction in feeding time caused by the positional misalignment amount of the target sheet 9a when the continuous positional misalignment state occurs.

[0196] The state determination unit 8f terminates the position deviation derivation process after executing the process in step S305.

[0197] <Process S306> On the other hand, in step S306, the state determination unit 8f sets the positional displacement amount to 0 and the positional displacement time TG1 to 0.

[0198] The state determination unit 8f terminates the position deviation derivation process after executing the process in step S306.

[0199] [Second timing adjustment process] Next, an example of the procedure for the second timing adjustment process will be described with reference to the flowchart shown in Figure 8.

[0200] In the following description, S401 to S403 represent identification codes for the three steps in the second timing adjustment process. In the second timing adjustment process, the process of step S401 is executed first.

[0201] <Process S401> In step S401, the main processing unit 8d selects the following process depending on whether the amount of positional deviation derived by the positional deviation derivation process exceeds a preset positional deviation threshold.

[0202] For example, a value less than the separation path length, which is the path length from the initial reference position P1 to the separation position P2, is set as the position deviation threshold. Alternatively, a value equal to or greater than the separation path length may be set as the position deviation threshold.

[0203] For example, if the positional displacement amount represents the length of the positional displacement, the positional displacement threshold is the separation path length or the separation path length corrected by the correction coefficient. If the positional displacement amount is the positional displacement time TG1, the positional displacement threshold is the required time obtained by dividing the separation path length by the standard feeding speed or the required time corrected by the correction coefficient.

[0204] The main processing unit 8d proceeds to process S402 if the amount of positional displacement does not exceed the positional displacement threshold. On the other hand, the main processing unit 8d proceeds to process S403 if the amount of positional displacement exceeds the positional displacement threshold.

[0205] <Process S402> In step S402, the main processing unit 8d sets the reference waiting time as the feed waiting time. After executing the process in step S402, the main processing unit 8d terminates the second timing adjustment process.

[0206] <Process S403> On the other hand, in step S403, the main processing unit 8d sets the time obtained by correcting the reference waiting time as the feeding waiting time.

[0207] In this embodiment, the main processing unit 8d sets the feed-feeding wait time to be the time obtained by adding the second correction time to the reference wait time. For example, the second correction time is the deviation time obtained by dividing the position deviation amount by the reference feed-feeding speed, or the time obtained by correcting the deviation time with a correction coefficient. Alternatively, the second correction time may be a predetermined time.

[0208] After executing the process in step S403, the main processing unit 8d terminates the second timing adjustment process.

[0209] As shown above, the main processing unit 8d adjusts the feeding start timing for initiating the feeding process for each sheet 9 to be fed by the feeding process after the standard feeding process has been executed, based on the standard feeding time TFS1 (see steps S110, S201-S206, S401-S403 and S102).

[0210] In this embodiment, the main processing unit 8d changes the feeding start timing when the amount of change in the reference feeding time TFS1 exceeds the change threshold (see step S204). Note that the process in step S204, which changes the feeding waiting time by changing the reference waiting time, is an example of a process that changes the feeding start timing.

[0211] Furthermore, the main processing unit 8d adjusts the feeding start timing for initiating the feeding process for the next sheet 9b following the target sheet 9a in accordance with the amount of positional displacement of the target sheet 9a (see steps S111-S112, S401-S403 and S102). Note that the processes in steps S402 and S403, which change the feeding waiting time, are examples of processes that change the feeding start timing.

[0212] In this embodiment, the main processing unit 8d causes the feeding mechanism 20 to start the feeding process for the next sheet 9b by processing steps S402 and S102 if the amount of misalignment of the target sheet 9a does not exceed the misalignment threshold.

[0213] In steps S402 and S102, the main processing unit 8d causes the feeding mechanism 20 to start the feeding process for the next sheet 9b when the measurement time of the second timing process for the target sheet 9a has elapsed, as set in step S402.

[0214] On the other hand, if the amount of misalignment of the target sheet 9a exceeds the misalignment threshold, the main processing unit 8d causes the feeding mechanism 20 to start the feeding process for the next sheet 9b by processing steps S403 and S102.

[0215] In steps S403 and S102, the main processing unit 8d causes the feeding mechanism 20 to start the feeding process for the next sheet 9b when the measurement time of the second timing process for the target sheet 9a has elapsed, as set in step S403.

[0216] The feeding waiting time set in process S402 is an example of a first waiting time, and the feeding waiting time set in process S403 is an example of a second waiting time that is longer than the first waiting time.

[0217] The execution of the first timing adjustment process ensures that an appropriate sheet spacing is maintained even if there is a delay in the feeding of each sheet 9. As a result, the performance degradation of the continuous printing process caused by excessively wide sheet spacing is avoided.

[0218] Furthermore, the execution of the second timing adjustment process ensures that an appropriate sheet spacing is maintained even if the initial positions of each sheet 9 are misaligned. As a result, sheet jamming and double feeding caused by excessively narrow sheet spacing are avoided.

[0219] [Variation of the first timing adjustment process] Next, the procedure for a modified example of the first timing adjustment process will be described with reference to the flowchart shown in Figure 14.

[0220] In the following description, S501, S502, ... represent identification codes for multiple steps in a modified version of the first timing adjustment process. In the modified version of the first timing adjustment process, the process of step S501 is executed first.

[0221] <Process S501> In step S501, the main processing unit 8d counts the number of delays, which is the number of times the reference feeding time TFS1 exceeds a preset delay threshold, and records the information of the number of delays in the secondary storage device 83.

[0222] In other words, the main processing unit 8d counts up the delay count when the reference feeding time TFS1 exceeds the delay threshold.

[0223] After executing the process in step S501, the main processing unit 8d moves the process to step S502.

[0224] <Process S502> In step S502, the main processing unit 8d selects the following process depending on whether the number of delays exceeds a preset threshold.

[0225] The main processing unit 8d proceeds to process S503 if the number of delays exceeds the threshold number. On the other hand, the main processing unit 8d terminates the first timing adjustment process if the number of delays does not exceed the threshold number.

[0226] In step S502, the main processing unit 8d may derive a delay frequency based on the number of delays and select the following processing depending on whether the delay frequency exceeds a preset frequency threshold.

[0227] For example, the delay frequency is the ratio of the number of delays during a period in which the feeding process is executed for a predetermined number of unit feeding cycles. The number of delays is an example of the frequency at which the reference feeding time TFS1 exceeds the delay threshold.

[0228] If the delay frequency is derived, the main processing unit 8d proceeds to process S503 if the delay frequency exceeds the frequency threshold. On the other hand, the main processing unit 8d terminates the first timing adjustment process if the delay frequency does not exceed the frequency threshold.

[0229] <Process S503> In step S503, the main processing unit 8d changes the reference waiting time to be shorter. The initial value of the reference waiting time is the initial waiting time (see step S102).

[0230] In this embodiment, the main processing unit 8d sets the time obtained by subtracting the first correction time from the reference waiting time as the new reference waiting time.

[0231] As mentioned above, the reference waiting time is used to set the feed waiting time in the second timing adjustment process (see Figure 8).

[0232] After executing the process in step S503, the main processing unit 8d moves the process to step S504.

[0233] <Process S504> In step S504, the main processing unit 8d adjusts the reference waiting time so as not to fall below the lower limit time, similar to step S205.

[0234] After executing the process in step S504, the main processing unit 8d terminates the first timing adjustment process.

[0235] In this modified example, the main processing unit 8d changes the feeding start timing when the number of times or frequency in which the reference feeding time TFS1 exceeds the delay threshold exceeds the number threshold or the frequency threshold (see step S503). Note that the process in step S503, which changes the feeding waiting time by changing the reference waiting time, is an example of a process that changes the feeding start timing.

[0236] When this modified example is adopted, the same effect as when the first timing adjustment process shown in Figure 6 is adopted can be obtained.

[0237] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0238] <Note 1> A feeding mechanism having a feeding rotating body that contacts the upper surface of the topmost sheet in the loading sheet, and performing a feeding process in which each sheet is fed from the loading sheet to the transport path by rotating the feeding rotating body, A lift mechanism that raises the loading sheet to a contact position where the uppermost surface of the top sheet in the loading sheet contacts the feeding rotating body, A sheet detection device that detects each of the sheets at a position downstream of the sheet feeding direction relative to the feeding rotating body, A sheet feeding control method for controlling a sheet feeding device, comprising a timing device that measures the elapsed time from the time the feeding process for each sheet is started until the time each sheet is detected by the sheet detection device, The control device derives a standard feeding time based on one or more standard feeding processes measured by the timing device when one or more standard feeding processes are performed that satisfy the count condition, which is that one or more feeding processes are performed for a predetermined number of times after the lift mechanism lifts the loaded sheet to the contact position. A sheet feeding control method comprising the control device adjusting, based on the reference feeding time, the feeding start timing for causing the feeding mechanism to start the feeding process for each of the sheets to be fed by the feeding process after the reference feeding process has been executed.

[0239] <Note 2> The sheet feeding control method according to Appendix 1, wherein the control device changes the feeding start timing when the amount of change in the reference feeding time exceeds a threshold.

[0240] <Note 3> The sheet feeding control method according to Appendix 1, wherein the control device changes the feeding start timing when the number of times or frequency in which the reference feeding time exceeds the delay threshold exceeds the number threshold or frequency threshold.

[0241] <Note 4> The aforementioned sheet feeding device, A sheet storage unit that supports the lift mechanism, houses the loaded sheet, and is retractably mounted in the housing of the sheet feeding device, When the seat storage unit is provided with an installation detection device that detects whether it is in an installed state, mounted in the housing, or in an uninstalled state, pulled out from the housing, A sheet feeding control method according to any one of the appendices 1 to 3, which satisfies the mounting condition and the number of times condition, wherein the one or more reference feeding processes are performed when the lift mechanism first lifts the loaded sheet to the contact position after the detection result of the mounting detection device changes from the non-mounted state to the mounted state.

[0242] <Note 5> A feeding mechanism having a feeding rotating body that contacts the upper surface of the topmost sheet in the loading sheet, and performing a feeding process in which each sheet is fed from the loading sheet to the transport path by rotating the feeding rotating body, A lift mechanism that raises the loading sheet to a contact position where the uppermost surface of the top sheet in the loading sheet contacts the feeding rotating body, A sheet detection device that detects each of the sheets at a position downstream of the sheet feeding direction relative to the feeding rotating body, A timing device that measures the elapsed time from the time when the feeding process for each of the sheets is started until the time when each of the sheets is detected by the sheet detection device, A sheet feeding device comprising a control device that implements the sheet feeding control method described in any one of the above appendices 1 to 4.

[0243] <Note 6> The sheet feeding device described in Appendix 5 above, An image forming apparatus comprising: a printing device that forms an image on each sheet fed by the aforementioned sheet feeding device. [Explanation of Symbols]

[0244] 1a: Lower enclosure 2: Sheet feeding device 4: Printing device 8: Control device 10: Image forming apparatus 20: Feeding mechanism 21: Lift mechanism 22: Pickup Roller 23: Feed Roller 24: Retard Roller 24a: Torque limiter 25: Feeding sheet detection device 26: Wearing detection device 30: Conveyor path 200: Sheet Cassette 200a: Cassette tip wall 211: Lift plate 212: Push-up board

Claims

1. A feeding mechanism having a feeding rotating body that contacts the upper surface of the topmost sheet in the loading sheet, and performing a feeding process in which each sheet is fed from the loading sheet to the transport path by rotating the feeding rotating body, A lift mechanism that raises the loading sheet to a contact position where the uppermost surface of the top sheet in the loading sheet contacts the feeding rotating body, A sheet detection device that detects each of the sheets at a position downstream of the sheet feeding direction relative to the feeding rotating body, A sheet feeding control method for controlling a sheet feeding device, comprising a timing device that measures the elapsed time from the time the feeding process for each sheet is started until the time each sheet is detected by the sheet detection device, The control device derives a standard feeding time based on one or more standard feeding processes measured by the timing device when one or more standard feeding processes are performed that satisfy the count condition, which is one or more feeding processes performed a predetermined number of times after the lift mechanism lifts the loaded sheet to the contact position. A sheet feeding control method comprising the control device adjusting, based on the reference feeding time, the feeding start timing for causing the feeding mechanism to start the feeding process for each of the sheets to be fed by the feeding process after the reference feeding process has been executed.

2. The sheet feeding control method according to claim 1, wherein the control device changes the feeding start timing when the amount of change in the reference feeding time exceeds a threshold.

3. The sheet feeding control method according to claim 1, wherein the control device changes the feeding start timing when the number of times or frequency in which the reference feeding time exceeds a delay threshold exceeds a number threshold or frequency threshold.

4. The aforementioned sheet feeding device, A sheet storage unit that supports the lift mechanism, houses the loaded sheet, and is retractably mounted in the housing of the sheet feeding device, When the seat storage unit is provided with an installation detection device that detects whether it is in an installed state, mounted in the housing, or in an uninstalled state, pulled out from the housing, A sheet feeding control method according to any one of claims 1 to 3, wherein the one or more reference feeding processes are performed when the lift mechanism first lifts the loaded sheet to the contact position after the detection result of the mounting detection device changes from the non-mounted state to the mounted state, satisfying the mounting condition and the number of times condition.

5. A feeding mechanism having a feeding rotating body that contacts the upper surface of the topmost sheet in the loading sheet, and performing a feeding process in which each sheet is fed from the loading sheet to the transport path by rotating the feeding rotating body, A lift mechanism that raises the loading sheet to a contact position where the uppermost surface of the top sheet in the loading sheet contacts the feeding rotating body, A sheet detection device that detects each of the sheets at a position downstream of the sheet feeding direction relative to the feeding rotating body, A timing device that measures the elapsed time from the time when the feeding process for each of the sheets is started until the time when each of the sheets is detected by the sheet detection device, A sheet feeding device comprising a control device that implements the sheet feeding control method described in any one of claims 1 to 3.

6. The sheet feeding device according to claim 5, An image forming apparatus comprising: a printing device that forms an image on each sheet fed by the aforementioned sheet feeding device.

Images