Sheet conveying device, image forming apparatus, and determination method

Abstract

To provide a sheet conveying device, an image forming apparatus, and a determination method capable of determining whether or not a delay occurs in sheet supply by a sheet supply part without using an additional sensor.SOLUTION: The image forming apparatus 100 includes the measuring processing portion 42 configured to measure the elapsed time from the start of sheet supply by the sheet supply portion to the time of sheet detection by the sheet sensor 25, the first determination processing portion 43 configured to determine whether or not the measured time measured by the measuring processing portion 42 is shorter than the reference time, and the determination processing portion 43 configured to, when it is successively determined that the measured time is shorter than the reference time, determine whether or not a delay has occurred in the sheet supply by the sheet supply portion, based on a plurality of measured times measured after it is last determined that the measured time is not shorter than the reference time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying device, an image forming apparatus, and a determination method. [Background technology]

[0002] An image forming apparatus such as a multifunction peripheral includes a sheet transport device that transports sheets on which an image is to be formed. For example, the sheet transport device includes a lift unit, a sheet supply unit, and a detection unit. The lift unit lifts a stack of sheets. The sheet supply unit includes a transport member that rotates in contact with the upper surface of the stack of sheets lifted by the lift unit, and supplies the sheets that contact the transport member to a transport path. The detection unit detects the sheets supplied by the sheet supply unit in the transport path.

[0003] Further, there is known a sheet conveying device that uses the detection unit to measure the conveying speed of the sheet by the sheet supply unit (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-132413 Summary of the Invention [Problem to be solved by the invention]

[0005] In the sheet conveying device, a delay may occur in the supply of the sheet by the sheet supply unit, but there has been no technique for determining whether a delay has occurred in the supply of the sheet by the sheet supply unit without using an additional sensor.

[0006] An object of the present invention is to provide a sheet conveying device, an image forming apparatus, and a determination method that can determine whether a delay has occurred in the supply of sheets by a sheet supply unit without using an additional sensor. [Means for solving the problem]

[0007] According to one aspect of the present invention, a sheet transport device includes a lift unit, a sheet supply unit, a detection unit, a measurement processing unit, a first determination processing unit, and a second determination processing unit. The lift unit lifts a sheet stack. The sheet supply unit includes a transport member that rotates in contact with an upper surface of the sheet stack lifted by the lift unit, and supplies the sheet contacting the transport member to a transport path. The detection unit detects the sheet supplied by the sheet supply unit in the transport path. Each time the sheet is supplied by the sheet supply unit, the measurement processing unit measures the elapsed time from when the sheet supply unit starts supplying the sheet to when the detection unit detects the sheet. Each time the measurement processing unit measures the elapsed time, the first determination processing unit determines whether the measured time measured by the measurement processing unit is less than a predetermined reference time. When the first judgment processing unit has consecutively determined that the measured time is less than the reference time, the second judgment processing unit determines whether a delay has occurred in the supply of the sheet by the sheet supply unit based on the first measurement time that was last measured among the multiple measured times measured after the first judgment processing unit last determined that the measured time was not less than the reference time and the shortest second measurement time among the remaining times excluding the first measurement time.

[0008] An image forming apparatus according to another aspect of the present invention includes the sheet transporting device and an image forming section, the image forming section forming an image on the sheet transported by the sheet transporting device.

[0009] A determination method according to another aspect of the present invention is executed by a sheet conveying device including a lift unit that lifts a sheet stack, a sheet supply unit that includes a conveying member that rotates in contact with an upper surface of the sheet stack lifted by the lift unit and supplies the sheet contacting the conveying member to a conveying path, and a detection unit that detects the sheet supplied by the sheet supply unit in the conveying path, and the determination method includes a measurement step, a first determination step, and a second determination step. In the measurement step, each time the sheet is supplied by the sheet supply unit, an elapsed time from when the sheet supply unit starts supplying the sheet to when the detection unit detects the sheet. In the first determination step, each time the elapsed time is measured in the measurement step, it is determined whether the measured time measured in the measurement step is less than a predetermined reference time. In the second judgment step, when the first judgment step determines that the measured time is shorter than the reference time consecutively, it is determined whether a delay has occurred in the supply of the sheet by the sheet supply unit based on the first measurement time that was last measured among the multiple measured times measured after the first judgment step last determined that the measured time was not shorter than the reference time and the shortest second measurement time remaining excluding the first measurement time. [Effects of the Invention]

[0010] According to the present invention, it is possible to determine whether or not a delay has occurred in the supply of sheets by the sheet supply unit without using an additional sensor. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the appearance of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the internal configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a block diagram showing the system configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 4]FIG. 4 is a diagram showing the configuration of a sheet supply unit of the image forming apparatus according to the embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart showing an example of the reset process executed in the image forming apparatus according to the embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing an example of a paper feeding process executed by the image forming apparatus according to the embodiment of the present invention. [Figure 7] FIG. 7 is a flowchart showing an example of a delay determination process executed by the image forming apparatus according to the embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of the transition of the measurement time measured by the image forming apparatus according to the embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing the configuration of a sheet supply unit of an image forming apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0013] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Figs. 1 to 4. Fig. 1 is a perspective view showing the appearance of the image forming apparatus 100. Fig. 2 is a cross-sectional view showing the internal configuration of the image forming apparatus 100. Fig. 4 is an enlarged view of the sheet supply unit 28 shown in Fig. 2.

[0014] For ease of explanation, the vertical direction in the installation state where image forming apparatus 100 is usable (the state shown in FIG. 1) is defined as the up-down direction D1. Also, the front-to-back direction D2 is defined with the face on the left front side of image forming apparatus 100 on the paper shown in FIG. 1 as the front (front face). Also, the left-to-right direction D3 is defined with the front face of image forming apparatus 100 in the installation state as the reference point.

[0015] Image forming apparatus 100 is a multifunction peripheral having multiple functions such as a scan function, a print function, a fax function, and a copy function. Note that the present invention may be applied to image forming apparatuses such as printers, fax machines, and copy machines.

[0016] As shown in FIG. 3, the image forming apparatus 100 includes an ADF (Auto Document Feeder) 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, an operation display unit 5, a storage unit 6, and a control unit .

[0017] The image forming unit 3, paper feed unit 4, storage unit 6, and control unit 7 are housed in a housing 100A of the image forming apparatus 100 (see FIGS. 1 and 2). The housing 100A is formed in a substantially rectangular parallelepiped shape. The ADF 1 and image reading unit 2 are provided on the upper side of the housing 100A (see FIGS. 1 and 2). The operation display unit 5 is provided on the front side of the housing 100A (see FIG. 1).

[0018] The ADF 1 transports a document whose image is to be read by the image reading unit 2. The ADF 1 includes a document setting unit, a plurality of transport rollers, a document presser, and a paper discharge unit.

[0019] The image reading unit 2 reads an image of a document. That is, the image reading unit 2 realizes the scanning function. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device).

[0020] The image forming unit 3 forms an image based on image data on a sheet SH1 (see FIG. 2) supplied from the paper feed unit 4. In other words, the image forming unit 3 realizes the print function. Specifically, the image forming unit 3 forms an image by electrophotography. The image forming unit 3 includes a photosensitive drum, a charging device, an optical scanning unit (LSU), a developing device, a transfer device, a cleaning device, and a fixing device.

[0021] The operation display unit 5 is a user interface of the image forming apparatus 100. The operation display unit 5 includes a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 7. For example, the display unit is a flat panel display such as a liquid crystal display. The operation unit inputs various information to the control unit 7 in response to user operations. For example, the operation unit includes operation keys and a touch panel.

[0022] The storage unit 6 is a non-volatile storage device, such as a flash memory.

[0023] The control unit 7 performs overall control of the image forming apparatus 100. As shown in FIG. 3, the control unit 7 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various types of arithmetic processing. The ROM 12 is a non-volatile storage device that pre-stores information such as control programs for causing the CPU 11 to execute various processes. The RAM 13 is a volatile or non-volatile storage device used as a temporary storage memory (work area) for the various processes executed by the CPU 11. In the control unit 7, the CPU 11 executes various control programs pre-stored in the ROM 12. In this way, the control unit 7 performs overall control of the image forming apparatus 100. The control unit 7 may be configured with an electronic circuit such as an integrated circuit (ASIC). The control unit 7 may also be a control unit provided separately from a main control unit that performs overall control of the image forming apparatus 100.

[0024] The paper feed unit 4 supplies the sheet SH1 (see FIG. 2) to the image forming unit 3.

[0025] As shown in FIGS. 2 and 3, the paper feed unit 4 includes a paper feed cassette 21, a pickup roller 22, a paper feed roller 23, a separation roller 24, a sheet sensor 25, a pull-out sensor 26, and a conveyance path 27.

[0026] A sheet stack SB1 (see FIG. 2) is placed in the paper feed cassette 21. For example, the sheet stack SB1 including sheets SH1 such as paper, coated paper, postcards, envelopes, and transparencies is placed in the paper feed cassette 21. As shown in FIGS. 1 and 2, the paper feed cassette 21 is provided at the bottom of the housing 100A. The paper feed cassette 21 is also provided so as to be removable from the housing 100A in a removal direction D4 (see FIG. 1) along the front-rear direction D2.

[0027] As shown in FIG. 2, the paper feed cassette 21 includes a lift plate 31, a lifting mechanism 32, an end cursor 33, and a pair of side cursors .

[0028] The lift plate 31 lifts the sheet stack SB1 (see FIG. 2) placed in the sheet cassette 21. The lift plate 31 is a flat member provided at the bottom of the sheet cassette 21. The sheet stack SB1 is placed on the upper surface of the lift plate 31. The lift plate 31 is provided rotatable around a rotation shaft 31A (see FIG. 2) extending in the front-rear direction D2. Specifically, the right end of the lift plate 31 is supported rotatable around the rotation shaft 31A. The lift plate 31 is an example of a lift unit of the present invention.

[0029] The lifting mechanism 32 raises and lowers the lift plate 31. As shown in FIG. 2, the lifting mechanism 32 includes a rotating shaft 32A and a push-up plate 32B. The rotating shaft 32A extends in the front-rear direction D2. The push-up plate 32B extends from the rotating shaft 32A in a direction perpendicular to the extension direction of the rotating shaft 32A. The push-up plate 32B is formed in the shape of a long flat plate in the front-rear direction D2. The rotating shaft 32A and the push-up plate 32B are provided below the lift plate 31.

[0030] The rear end of the rotation shaft 32A is connected to a motor (not shown) provided outside the sheet cassette 21 via a joint (not shown) provided outside the sheet cassette 21. The rotation shaft 32A and the lifting plate 32B receive a rotational driving force supplied from the motor via the joint and rotate in a second rotation direction D7 shown in FIG. 4. When the rotation shaft 32A and the lifting plate 32B rotate in the second rotation direction D7, the lifting plate 31 is pushed up by the lifting plate 32B and rotates in a first rotation direction D6 (see FIG. 4) shown in FIG. 4. As a result, the sheet stack SB1 placed on the upper surface of the lifting plate 31 is lifted upward.

[0031] The joint portion is restricted from rotating in the direction opposite to the second rotation direction D7. For example, the joint portion includes a ratchet mechanism that restricts the joint portion from rotating in the direction opposite to the second rotation direction D7. By restricting the joint portion from rotating in the direction opposite to the second rotation direction D7, the rotation of the rotation shaft 32A engaged with the joint portion is also restricted in the direction opposite to the second rotation direction D7. This restricts the lift plate 31 from descending due to its own weight.

[0032] When the sheet cassette 21 is pulled out from the housing 100A in the pulling-out direction D4, the engagement between the rotation shaft 32A and the joint portion is released, thereby releasing the joint portion from restricting the rotation of the rotation shaft 32A and the lift plate 32B in the direction opposite to the second rotation direction D7, and the lift plate 31 descends under its own weight.

[0033] The end cursor 33 is provided so as to be movable along the sheet conveying direction D5 shown in Fig. 4. The end cursor 33 adjusts the position of the sheet bundle SB1 in the sheet conveying direction D5 by abutting the sheet bundle SB1 placed in the sheet feed cassette 21 against a wall surface 21A (see Fig. 4) on the downstream side of the sheet feed cassette 21 in the sheet conveying direction D5. The pair of side cursors 34 are provided so as to be interlocked so as to move toward or away from each other along the width direction of the sheets SH1, which is perpendicular to the sheet conveying direction D5. The pair of side cursors 34 adjust the position of the sheets SH1 in the width direction by sandwiching and holding the sheet bundle SB1 placed in the sheet feed cassette 21.

[0034] As shown in FIGS. 2 and 4, the pickup roller 22 is provided above the lift plate 31. The pickup roller 22 rotates while contacting the upper surface of the sheet stack SB1 lifted by the lift plate 31, thereby transporting the uppermost sheet SH1 (see FIG. 2) of the sheet stack SB1 to the separation section 28A (see FIG. 4). Here, the separation section 28A is a nip formed between the paper feed roller 23 and the separation roller 24. The pickup roller 22 transports the sheet SH1 in a sheet transport direction D5 (see FIG. 4). The sheet transport direction D5 is a direction perpendicular to the front-rear direction D2. The pickup roller 22 is an example of a transport member of the present invention.

[0035] Specifically, the pickup roller 22 is rotatable about an axis extending in the front-rear direction D2. The pickup roller 22 rotates by receiving a rotational driving force supplied from a motor (not shown) while in contact with the upper surface of the sheet SH1. As a result, the pickup roller 22 applies a conveying force in the sheet conveying direction D5 to the sheet SH1 in contact with the pickup roller 22.

[0036] The pickup roller 22, the paper feed roller 23, and the separation roller 24 constitute a sheet supply unit 28 (see FIGS. 2 and 4) that supplies the sheet SH1 that comes into contact with the pickup roller 22 to a conveying path 27 (see FIG. 2). The conveying path 27 is a passage along which the sheet SH1 moves from the sheet supply unit 28 to the image forming unit 3.

[0037] 2 and 4, the paper feed roller 23 is provided downstream in the sheet conveyance direction D5 of the pickup roller 22. The paper feed roller 23 comes into contact with the upper surface of the sheet SH1 (see FIG. 2) conveyed by the pickup roller 22, and conveys the sheet SH1 beyond the detection position of the sheet sensor 25 (see FIG. 2). The paper feed roller 23 conveys the sheet SH1 in the sheet conveyance direction D5.

[0038] Specifically, the paper feed roller 23 is rotatable about an axis extending in the front-rear direction D2. The paper feed roller 23 rotates by receiving a rotational driving force supplied from a motor (not shown) while in contact with the upper surface of the sheet SH1. As a result, the paper feed roller 23 applies a conveying force in the sheet conveying direction D5 to the sheet SH1 in contact with the paper feed roller 23.

[0039] 2 and 4, separation roller 24 is provided below paper feed roller 23 and facing paper feed roller 23. Separation roller 24 forms separation section 28A (see FIG. 4) between separation roller 24 and paper feed roller 23. Separation section 28A separates sheet SH11 (see FIG. 9) conveyed by pickup roller 22 from other sheet SH12 (see FIG. 9) accompanying sheet SH11.

[0040] Specifically, the separation roller 24 has a shaft 24A (see FIG. 4) extending in the front-rear direction D2. The separation roller 24 is fixed to the shaft 24A and rotates integrally with the shaft 24A. The shaft 24A is rotatably supported by a bearing (not shown) provided inside the housing 100A. The bearing is biased toward the paper feed roller 23 by a biasing member (not shown), such as a coil spring, provided inside the housing 100A. This biases the separation roller 24 toward the paper feed roller 23, and a nip portion that holds the sheet SH1 between the separation roller 24 and the paper feed roller 23, i.e., a separation portion 28A, is formed.

[0041] When only one sheet SH1 is present in the separation unit 28A, the separation roller 24 is driven to rotate in a rotation direction D8 shown in FIG. 4 by a force transmitted from the sheet SH1 conveyed by the sheet feed roller 23. Furthermore, when sheets SH11 and SH12 (see FIG. 9) are present in the separation unit 28A, the separation roller 24 is restricted from rotating in the rotation direction D8. For example, the sheet supply unit 28 includes a torque limiter that restricts the rotation of the shaft 24A in the rotation direction D8 when the torque transmitted to the shaft 24A in the rotation direction D8 is less than a predetermined first threshold. When sheets SH11 and SH12 are present in the separation unit 28A, the rotation of the separation roller 24 in the rotation direction D8 is restricted, and the movement of the sheet SH12 in contact with the separation roller 24 in the sheet conveyance direction D5 is restricted due to contact friction with the separation roller 24. As a result, as the sheet SH11 contacting the pickup roller 22 is conveyed, another sheet SH12 moving together with the sheet SH11 is separated from the sheet SH11.

[0042] As shown in FIG. 2, the sheet sensor 25 is provided downstream of the paper feed roller 23 in the sheet conveying direction D5. The sheet sensor 25 detects the sheet SH1 supplied by the sheet supply unit 28 in the conveying path 27. For example, the sheet sensor 25 includes an actuator that is moved by contact with the sheet SH1, and a reflective or transmissive optical sensor that detects the movement of the actuator. In the image forming apparatus 100, the timing of supplying the next sheet SH1 by the sheet supply unit 28 is determined based on the timing of detection of the sheet SH1 by the sheet sensor 25. The sheet sensor 25 is an example of a detection unit of the present invention.

[0043] The withdrawal sensor 26 detects the withdrawal of the sheet cassette 21 from the housing 100A. For example, the withdrawal sensor 26 includes a push switch that changes from an ON state to an OFF state in response to the withdrawal of the sheet cassette 21 from the housing 100A.

[0044] Incidentally, a sheet conveying device is known that uses the sheet sensor 25 to measure the conveying speed of the sheet SH1 by the sheet supply unit .

[0045] In the image forming apparatus 100, a delay may occur in the supply of the sheet SH1 by the sheet supply unit 28. However, conventionally, there has been no technology for determining whether a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28 without using an additional sensor.

[0046] In contrast, in the image forming apparatus 100 according to an embodiment of the present invention, it is possible to determine whether or not a delay has occurred in the supply of the sheet SH1 by the sheet supply section 28 without using any additional sensors, as will be described below.

[0047] [Configuration of control unit 7] Next, the configuration of the control unit 7 will be described with reference to FIG.

[0048] 3, the control unit 7 includes a displacement processing unit 41, a measurement processing unit 42, a first determination processing unit 43, a second determination processing unit 44, an acquisition processing unit 45, and a notification processing unit 46. An apparatus including the paper feed unit 4 and the control unit 7 is an example of a sheet conveying apparatus of the present invention.

[0049] Specifically, a paper feed control program for causing the CPU 11 of the control unit 7 to execute a reset process (see the flowchart in FIG. 5) and a paper feed process (see the flowchart in FIG. 6), which will be described later, is stored in advance in the ROM 12 of the control unit 7. The paper feed control program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and installed in a storage device such as the memory unit 6.

[0050] The control unit 7 executes the paper feed control program stored in the ROM 12 using the CPU 11, thereby functioning as each of the above-mentioned processing units.

[0051] Note that some or all of the processing units included in the control unit 7 may be configured with electronic circuits. The paper feed control program may also be a program for causing multiple processors to function as the processing units included in the control unit 7.

[0052] The displacement processing unit 41 displaces the sheet stack SB1 placed in the sheet cassette 21 to a position where the sheet stack SB1 comes into contact with the pickup roller 22 using the lift plate 31 when a predetermined specific timing arrives.

[0053] For example, the specific timing is the timing of executing the first image forming process after the paper feed cassette 21 is pulled out from the housing 100A. The image forming process is a process of forming an image on a sheet SH1 supplied by the paper feed unit 4 using the image forming unit 3.

[0054] Each time the sheet supply unit 28 supplies the sheet SH1, the measurement processing unit 42 measures the elapsed time from when the sheet supply unit 28 starts supplying the sheet SH1 to when the sheet sensor 25 detects the sheet SH1.

[0055] In the image forming apparatus 100, sheet SH3 (see FIG. 4) below sheet SH2 (see FIG. 4) to be conveyed by the pickup roller 22 may be pulled by sheet SH2 and fed out of the sheet stack SB1 (see FIG. 4). That is, sheet SH3 to be conveyed next by the pickup roller 22 may move downstream in the sheet conveyance direction D5 from the reference position P1 (see FIG. 4). The reference position P1 is the position where the leading edge of the uppermost sheet SH1 in the sheet stack SB1 is located when the sheet stack SB1 is lifted by the lift plate 31.

[0056] When sheet SH3, which is next transported by the pickup roller 22, is being fed out from the sheet bundle SB1, the measurement time measured by the measurement processing unit 42 during the transport of sheet SH3 is shorter than when sheet SH3 is not being fed out from the sheet bundle SB1. In other words, when the measurement time measured by the measurement processing unit 42 is shorter than a predetermined reference time, it can be determined that sheet SH3, which was transported at the time of measurement, was being fed out from the sheet bundle SB1. When the measurement time measured by the measurement processing unit 42 is equal to or longer than the reference time, it can be determined that sheet SH3, which was transported at the time of measurement, was not being fed out from the sheet bundle SB1.

[0057] Each time the elapsed time is measured by the measurement processing unit 42, the first determination processing unit 43 determines whether the measured time measured by the measurement processing unit 42 is less than the reference time. In other words, the first determination processing unit 43 determines whether the conveyed sheet SH1 has been fed out from the sheet stack SB1 at the time the measurement time is measured.

[0058] Here, the reference time is set in advance based on a design value of the conveying speed of sheet SH1 by sheet supply unit 28 and a specific conveying distance from reference position P1 (see FIG. 4) to the detection position. The specific conveying distance is the distance from reference position P1 to the detection position on the conveying path of sheet SH1. The reference time is stored in advance in the storage unit 6 or ROM 12. Note that the reference time may also be set based on the specific conveying distance and an average value of the conveying speed of sheet SH1 by sheet supply unit 28 measured when conveying sheet SH1 for the first time after the specific timing arrives.

[0059] If the transported sheet SH1 has not been unwound from the sheet stack SB1 at the time of measuring the measurement time, it is possible to determine whether a delay has occurred in the supply of sheet SH1 by the sheet supply section 28 based on the measurement time and the reference time.

[0060] On the other hand, if the transported sheet SH1 is being unwound from the sheet stack SB1 at the time the measurement time is measured, it is not possible to determine whether a delay has occurred in the supply of sheet SH1 by the sheet supply section 28 based on the measurement time and the reference time.

[0061] 8 shows an example of the transition of the measurement time measured by the measurement processing unit 42. Specifically, FIG. 8 shows an example of the transition of the measurement time from the arrival of the specific timing until the number of printed sheets reaches 30.

[0062] 8, the sheet SH1 tends to be continuously fed from the sheet bundle SB1. Moreover, during the period when the sheet SH1 is continuously fed from the sheet bundle SB1, the amount of the sheet SH1 fed from the sheet bundle SB1 gradually increases as the number of printed sheets increases after the sheet SH1 is fed.

[0063] Here, if, during a period in which the sheet SH1 is continuously fed from the sheet bundle SB1, for example, the pickup roller 22 slips and a delay occurs in the supply of the sheet SH1 by the sheet supply unit 28, the measured time becomes longer than the measured time during the previous feeding when no delay occurred (see the ninth sheet in FIG. 8). In other words, it is possible to determine whether a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28 based on the measured time during a period in which the sheet SH1 is continuously fed from the sheet bundle SB1.

[0064] When the specific timing arrives, the uppermost sheet SH1 of the sheet stack SB1 stored in the sheet cassette 21 is positioned at the reference position P1 (see FIG. 4). Therefore, as shown in FIG. 8, the measured time that is measured first after the specific timing arrives will not be shorter than the reference time.

[0065] When the first judgment processing unit 43 judges that the measured time is less than the reference time consecutively, the second judgment processing unit 44 judges whether a delay has occurred in the supply of sheet SH1 by the sheet supply unit 28 based on the last measured first measurement time among the multiple measured times measured after the first judgment processing unit 43 last judged that the measured time was not less than the reference time, and the shortest second measurement time among the remaining times excluding the first measurement time.

[0066] Specifically, when the first measured time is longer than the second measured time, the second determination processor 44 determines that a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28. Furthermore, when the first measured time is equal to or shorter than the second measured time, the second determination processor 44 determines that a delay has not occurred in the supply of the sheet SH1 by the sheet supply unit 28.

[0067] When the second judgment processing unit 44 determines that a delay has occurred in the supply of sheet SH1 by the sheet supply unit 28, the acquisition processing unit 45 acquires the difference between the first measurement time and the second measurement time as the amount of delay in the supply of sheet SH1, and when the first judgment processing unit 43 determines that the measurement time is not less than the reference time, the acquisition processing unit 45 acquires the difference between the last measured measurement time and the reference time as the amount of delay.

[0068] When the delay amount acquired by the acquisition processing unit 45 exceeds a predetermined second threshold, the notification processing unit 46 issues a notification to that effect.

[0069] For example, when the delay amount acquired by the acquisition processing unit 45 exceeds the second threshold value and a predetermined notification condition is satisfied, the notification processing unit 46 notifies that the delay amount in the supply of sheet SH1 by the sheet supply unit 28 has exceeded the second threshold value.

[0070] For example, the determination condition is that the frequency of occurrence of a supply delay in which the delay amount exceeds the second threshold exceeds a predetermined value. Alternatively, the determination condition may be that a supply delay in which the delay amount exceeds the second threshold occurs a predetermined number of times in succession. Furthermore, when the delay amount acquired by the acquisition processing unit 45 exceeds the second threshold, the notification processing unit 46 may unconditionally notify that the delay amount in the supply of the sheet SH1 by the sheet supply unit 28 has exceeded the second threshold.

[0071] For example, when the delay amount acquired by the acquisition processing unit 45 exceeds the second threshold and the notification condition is satisfied, the notification processing unit 46 causes the operation display unit 5 to display a notification screen including a message indicating that the delay amount in the supply of the sheet SH1 by the sheet supply unit 28 has exceeded the second threshold. Note that the notification screen may include a message urging maintenance of the sheet supply unit 28.

[0072] [Reset process] An example of the procedure of the reset process executed by the control unit 7 in the image forming apparatus 100 will be described below with reference to Fig. 5. Here, steps S11, S12, etc. represent the numbers of the process procedures (steps) executed by the control unit 7.

[0073] <Step S11> First, in step S11, the control unit 7 determines whether or not the sheet cassette 21 has been pulled out from the housing 100A.

[0074] Specifically, when the drawer sensor 26 outputs a detection signal indicating that the sheet cassette 21 has been drawn out, the control unit 7 determines that the sheet cassette 21 has been drawn out from the housing 100A.

[0075] Here, when the control unit 7 determines that the sheet feed cassette 21 has been pulled out from the housing 100A (Yes in S11), it shifts the process to step S12. On the other hand, when the sheet feed cassette 21 has not been pulled out from the housing 100A (No in S11), the control unit 7 waits in step S11 for the sheet feed cassette 21 to be pulled out from the housing 100A.

[0076] When the sheet cassette 21 is pulled out from the housing 100A, the engagement between the rotary shaft 32A and the joint portion is released, and the lift plate 31 descends under its own weight.

[0077] <Step S12> In step S12, the control unit 7 sets a predetermined flag to OFF.

[0078] Specifically, in the image forming apparatus 100, a first storage area used for setting the flag is provided in advance in the storage unit 6. A value of "0" or "1" is stored in the first storage area. The control unit 7 sets the flag to off by storing the value of "0" in the first storage area.

[0079] [Paper Feed Processing] Next, with reference to Fig. 6, an example of the procedure of the paper feed process executed by the control unit 7 in the image forming apparatus 100 and the determination method of the present invention will be described. The paper feed process is executed when the timing for executing the image forming process arrives.

[0080] <Step S21> First, in step S21, the control unit 7 determines whether or not the specific timing has arrived.

[0081] Specifically, the control unit 7 determines that the specific timing has arrived when the flag is set to OFF.

[0082] Here, when the control unit 7 determines that the specific timing has arrived (Yes in S21), it shifts the process to step S22. On the other hand, when the specific timing has not arrived (No in S21), the control unit 7 shifts the process to step S27.

[0083] <Step S22> In step S22, the control unit 7 uses the lift plate 31 to displace the sheet stack SB1 placed in the sheet cassette 21 to a position where the sheet stack SB1 comes into contact with the pickup roller 22. The process of step S22 is executed by the displacement processing unit 41 of the control unit 7.

[0084] <Step S23> In step S23, the control section 7 causes the sheet supply section 28 to start supplying the sheet SH1.

[0085] An image based on image data is formed by the image forming unit 3 on the sheet SH1 fed in the process of step S23.

[0086] <Step S24> In step S24, the control unit 7 measures the elapsed time from when the sheet supply unit 28 starts supplying the sheet SH1 to when the sheet sensor 25 detects the sheet SH1. The processing of step S24 is an example of a measurement step of the present invention, and is executed by the measurement processing unit 42 of the control unit 7.

[0087] Here, the sheet SH1 to be fed in the processing of step S23 is the sheet SH1 that is first conveyed after the sheet feed cassette 21 is pulled out from the housing 100A and the sheet stack SB1 is set in the sheet feed cassette 21. In other words, the feed start position of the sheet SH1 to be fed in the processing of step S23 is the reference position P1 (see FIG. 4).

[0088] <Step S25> In step S25, the control unit 7 executes a delay determination process, which will be described later.

[0089] <Step S26> In step S26, the control unit 7 sets the flag to ON.

[0090] Specifically, the control unit 7 sets the flag to ON by storing the value "1" in the first storage area, which omits the processes from step S22 to step S26 until the paper feed cassette 21 is pulled out from the housing 100A.

[0091] <Step S27> In step S27, the control section 7 determines whether or not the timing for feeding the sheet SH1 has arrived.

[0092] Specifically, if sheet SH1 has not been fed after the start of the sheet feeding process, the control unit 7 determines that the sheet feeding timing has arrived at the start of the process of step S27. Also, if sheet SH1 has been fed after the start of the sheet feeding process, the control unit 7 determines that the sheet feeding timing has arrived when a predetermined time has elapsed since the sheet sensor 25 detected the previous sheet SH1.

[0093] Here, when the control unit 7 determines that the paper feed timing has arrived (Yes in S27), it shifts the process to step S28. On the other hand, when the paper feed timing has not arrived (No in S27), the control unit 7 waits for the arrival of the paper feed timing in step S27.

[0094] <Step S28> In step S28, the control section 7 causes the sheet supply section 28 to start supplying the sheet SH1.

[0095] An image based on image data is formed by the image forming unit 3 on the sheet SH1 fed in the process of step S28.

[0096] <Step S29> In step S29, the control unit 7 measures the elapsed time from when the sheet supply unit 28 starts supplying the sheet SH1 to when the sheet sensor 25 detects the sheet SH1. The processing of step S29 is an example of a measurement step of the present invention, and is executed by the measurement processing unit 42 of the control unit 7.

[0097] <Step S30> In step S30, the control unit 7 executes a delay determination process, which will be described later.

[0098] <Step S31> In step S31, the control section 7 determines whether or not feeding of the sheet SH1 has been completed.

[0099] Specifically, the control unit 7 determines that feeding of the sheets SH1 is completed when all of the sheets SH1 on which images are to be formed in the image forming process have been fed.

[0100] Here, when the control unit 7 determines that the feeding of the sheet SH1 has been completed (Yes in S31), it ends the feeding process. On the other hand, when the feeding of the sheet SH1 has not been completed (No in S31), the control unit 7 shifts the process to step S27.

[0101] [Delay determination process] Next, with reference to FIG. 7, the delay determination process executed in step S25 and step S30 of the paper feed process will be described.

[0102] <Step S41> First, in step S41, the control unit 7 determines whether the last measured time is less than the reference time. The process of step S41 is an example of a first determination step of the present invention, and is executed by the first determination processing unit 43 of the control unit 7.

[0103] Here, if the control unit 7 determines that the last measured time is less than the reference time (Yes in S41), it shifts the process to step S45. On the other hand, if the last measured time is not less than the reference time (No in S41), it shifts the process to step S42.

[0104] <Step S42> In step S42, the control unit 7 resets the specific time to the reference time, which is an initial value. The specific time is used for the determination by the second determination processing unit 44.

[0105] <Step S43> In step S43, the control unit 7 acquires the difference between the last measured time and the reference time as the delay amount. The process of step S43 is executed by the acquisition processing unit 45 of the control unit 7.

[0106] <Step S44> In step S44, the control unit 7 records the determination result as to whether or not a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28.

[0107] Specifically, in the image forming apparatus 100, a second storage area used for recording the determination result as to whether or not a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28 is provided in advance in the storage unit 6. The control unit 7 records the determination result by storing, in the second storage area, information indicating that a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28 and the amount of delay acquired by the processing of step S43 in association with the supply time of the sheet SH1.

[0108] <Step S45> In step S45, the control unit 7 determines whether the last measured time is less than the specific time. The process of step S45 is an example of a second determination step of the present invention, and is executed by the second determination processing unit 44 of the control unit 7.

[0109] Here, if the control unit 7 determines that the last measured time is less than the specific time (Yes in S45), it shifts the process to step S46. On the other hand, if the last measured time is not less than the specific time (No in S45), it shifts the process to step S48.

[0110] <Step S46> In step S46, the control unit 7 updates the specific time so that the specific time becomes the last measured time. As a result, when the first determination processing unit 43 continuously determines that the measured time is less than the reference time, the shortest time among the multiple measured times measured after the last time that the first determination processing unit 43 determined that the measured time was not less than the reference time is set as the specific time. Therefore, when the process of step S45 is next executed, the specific time can be treated as the second measured time.

[0111] <Step S47> In step S47, the control unit 7 records the determination result as to whether or not a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28.

[0112] Specifically, the control unit 7 records the determination result by storing information indicating that there was no delay in the supply of sheet SH1 by the sheet supply unit 28 in the second memory area in association with the supply time of sheet SH1.

[0113] <Step S48> In step S48, the control unit 7 acquires the difference between the last measured time and the specific time as the delay amount. The process of step S48 is executed by the acquisition processing unit 45 of the control unit 7.

[0114] <Step S49> In step S49, the control unit 7 records the determination result as to whether or not a delay has occurred in the supply of the sheet SH1 by the sheet supply unit 28.

[0115] Specifically, the control unit 7 records the judgment result by storing information indicating that a delay has occurred in the supply of sheet SH1 by the sheet supply unit 28 and the amount of delay obtained by the processing of step S48 in the second memory area in association with the supply time of sheet SH1.

[0116] <Step S50> In step S50, the control unit 7 determines whether the notification condition is met.

[0117] For example, the control unit 7 determines that the notification condition is met when the number of times that the delay amount exceeds the second threshold value exceeds a predetermined number of times among the most recent 100 paper feeds.

[0118] Here, if the control unit 7 determines that the notification condition is satisfied (Yes in S50), the control unit 7 shifts the process to step S51. On the other hand, if the notification condition is not satisfied (No in S50), the control unit 7 ends the delay determination process.

[0119] <Step S51> In step S51, the control unit 7 causes the notification screen to be displayed on the operation display unit 5. The processing of step S51 is executed by the notification processing unit 46 of the control unit 7.

[0120] This makes it possible to make the user of the image forming apparatus 100 aware of the degradation in the performance of the sheet supply unit 28. Note that the control unit 7 may stop the conveyance of the sheet SH1 until an operation from the user is received on the operation display unit 5.

[0121] In this way, in the image forming device 100, when the first judgment processing unit 43 continuously judges that the measured time is less than the reference time, it is possible to determine whether or not a delay has occurred in the supply of sheet SH1 by the sheet supply unit 28 based on the first measurement time and the second measurement time among the multiple measured times measured after the first judgment processing unit 43 last judged that the measured time was not less than the reference time.

[0122] The lift plate 31 may be configured to descend each time the image forming process is completed. In this case, if the sheet SH1 fed from the sheet stack SB1 when the lift plate 31 descends returns to the reference position P1 by its own weight or by the reverse rotation of the pickup roller 22 and the paper feed roller 23, the specific timing may be the timing of execution of the image forming process.

[0123] Furthermore, the lifting portion of the present invention is not limited to a flat plate-shaped member, but may be any member having a support surface that supports the bottom surface of the sheet stack SB1. Furthermore, the conveying member of the present invention is not limited to a roller-shaped member, but may be a belt-shaped member.

[0124] The present invention may also be applied to an inkjet image forming apparatus.

[0125] The present invention may also be applied to the ADF1.

[0126] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0127] <Appendix 1> a detection unit that detects the sheet supplied by the sheet supply unit in the transport path; a measurement processing unit that measures an elapsed time from when the sheet supply unit starts supplying the sheet to when the detection unit detects the sheet each time the sheet is supplied by the sheet supply unit; a first determination processing unit that determines whether the measured time measured by the measurement processing unit is less than a predetermined reference time each time the measurement processing unit determines; and a second determination processing unit that, when the first determination processing unit determines that the measured time is less than the reference time consecutively, determines whether a delay has occurred in the supply of the sheet by the sheet supply unit based on a first measurement time that is last measured among multiple measurement times measured after the first determination processing unit last determined that the measured time was not less than the reference time and a second measurement time that is the shortest of the remaining times excluding the first measurement time.

[0128] <Appendix 2> An acquisition processing unit that, when the second determination processing unit determines that a delay has occurred in the supply of the sheet by the sheet supply unit, acquires the difference between the first measurement time and the second measurement time as the amount of delay in the supply of the sheet, and, when the first determination processing unit determines that the measured time is not less than the reference time, acquires the difference between the last measured measurement time and the reference time as the amount of delay; and an alarm processing unit that, when the amount of delay acquired by the acquisition processing unit exceeds a predetermined threshold, notifies that fact.

[0129] <Appendix 3> 3. An image forming apparatus comprising: the sheet conveying device according to claim 1; and an image forming unit that forms an image on the sheet conveyed by the sheet conveying device.

[0130] <Appendix 4> a sheet supply unit that includes a lift unit that lifts a sheet stack, a conveying member that rotates in contact with the upper surface of the sheet stack lifted by the lift unit, and supplies the sheet that contacts the conveying member to a conveying path; and a detection unit that detects the sheet supplied by the sheet supply unit in the conveying path, the determination method including: a measurement step that measures an elapsed time from when the sheet supply unit starts supplying the sheet to when the detection unit detects the sheet each time the sheet is supplied by the sheet supply unit; a first determination step that determines, each time the elapsed time is measured by the measurement step, whether the measured time measured by the measurement step is less than a predetermined reference time; and a second determination step that, when the measured time is consecutively determined to be less than the reference time by the first determination step, determines whether a delay has occurred in the supply of the sheet by the sheet supply unit based on a first measurement time that is last measured among multiple measurement times measured after the last time when the measured time was determined to be not less than the reference time by the first determination step, and the shortest second measurement time remaining after excluding the first measurement time. [Explanation of symbols]

[0131] 1 ADF 2 Image reading unit 3 Image forming unit 4 Paper feed section 5 Operation display section 6 Memory section 7 Control Unit 21 Paper cassette 22 Pickup roller 23 Paper feed roller 24 Separation roller 25 Sheet Sensor 26 Drawer Sensor 27 Transport path 28 Sheet supply unit 28A Separation section 31 Lift Board 41 Displacement processing section 42 Measurement processing section 43 First determination processing unit 44 Second determination processing unit 45 Acquisition processing section 46 Notification processing section 100 Image forming device

Claims

1. a lift unit that lifts the sheet stack; a sheet supply unit including a conveying member that rotates while contacting an upper surface of the sheet stack lifted by the lift unit, and that supplies the sheet that contacts the conveying member to a conveyance path; a detection unit that detects the sheet fed by the sheet feeding unit in the conveying path; a measurement processing unit that measures an elapsed time from when the sheet supply unit starts supplying the sheet to when the detection unit detects the sheet, every time the sheet is supplied by the sheet supply unit; a first determination processing unit that determines whether the measured time measured by the measurement processing unit is shorter than a predetermined reference time each time the elapsed time is measured by the measurement processing unit; a second determination processing unit that, when it is determined by the first determination processing unit that the measured time is shorter than the reference time consecutively, determines whether or not a delay has occurred in the supply of the sheet by the sheet supply unit, based on a first measurement time that is last measured among a plurality of measured times measured after the first determination processing unit last determined that the measured time is not shorter than the reference time, and a second measurement time that is the shortest among the remaining times excluding the first measurement time; A sheet conveying device comprising:

2. an acquisition processing unit that, when it is determined by the second determination processing unit that a delay has occurred in the supply of the sheet by the sheet supply unit, acquires a difference between the first measurement time and the second measurement time as an amount of delay in the supply of the sheet, and, when it is determined by the first determination processing unit that the measured time is not shorter than the reference time, acquires a difference between the last measured measurement time and the reference time as the amount of delay; a notification processing unit that notifies the user when the delay amount acquired by the acquisition processing unit exceeds a predetermined threshold; The sheet transport device according to claim 1 , comprising:

3. The sheet conveying device according to claim 1 or 2; an image forming unit that forms an image on the sheet conveyed by the sheet conveying device; An image forming apparatus comprising:

4. A determination method executed by a sheet conveying device including: a lift unit that lifts a sheet stack; a sheet supply unit that includes a conveying member that rotates in contact with an upper surface of the sheet stack lifted by the lift unit and supplies a sheet that contacts the conveying member to a conveying path; and a detection unit that detects the sheet that is supplied by the sheet supply unit in the conveying path, a measuring step of measuring an elapsed time from when the sheet supply unit starts supplying the sheet to when the detection unit detects the sheet, every time the sheet is supplied by the sheet supply unit; a first determination step of determining whether or not the measured time measured by the measuring step is shorter than a predetermined reference time each time the elapsed time is measured by the measuring step; a second determination step of determining, when it is determined in the first determination step that the measured time is continuously less than the reference time, whether or not a delay has occurred in the supply of the sheet by the sheet supply unit, based on a first measurement time that is last measured among a plurality of measured times measured after the last time it was determined in the first determination step that the measured time is not less than the reference time and a second measurement time that is the shortest among the remaining times excluding the first measurement time; A determination method including:

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