Sheet feeding device and image forming device

Abstract

To provide a sheet feeding device and an image forming device, capable of detecting the stopping timing of a lift plate and determining the remaining number of sheets on the lift plate with a simple configuration.SOLUTION: A first sensor 62 detects the upper surface. A rotation member 70 is linked to the rotation of a drive shaft 12a of a lifting mechanism 12 and has a plurality of detected parts 72 and a plurality of void parts 73. The plurality of target parts, one of the plurality of detected parts 72 and the plurality of void parts 73, includes a first target part and a plurality of second target parts with short circumferential lengths. A controller 8 performs the initial lift-up control until the first sensor 62 detects the upper surface. The controller 8 determines the remaining number of sheets according to the number of specific changes in the detection signal of a second sensor 74 when the initial lift-up control is being executed. Further, the controller 8 rotates the drive shaft 12a in the reverse rotation direction until a state occurs in which the detection signal of the second sensor 74 continues in a specific state for a specific time.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a sheet supplying device and an image forming apparatus capable of determining the amount of sheets remaining on a lift plate that can be raised and lowered. [Background technology]

[0002] The image forming apparatus includes a sheet feeder that feeds sheets to a printing device. For example, the sheet feeder raises a lift plate on which sheets can be stacked to a specific height by a lifting mechanism, and feeds the sheets stacked on the lift plate one by one to a subsequent stage.

[0003] It is also known that in the sheet supplying device, an upper limit sensor detects the timing when the lift plate stops rising, and a lower limit sensor detects the timing when the lift plate stops descending (see, for example, Patent Document 1).

[0004] It is also known that the amount of rotation of the motor of the lifting mechanism during the period in which the lift plate is raised is measured, and the amount of sheets remaining on the lift plate is determined based on the measured value of the amount of rotation (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-169592 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, it is desirable that the detection of the stop timing of the lift plate and the determination of the remaining amount of sheets on the lift plate be realized with as simple a configuration as possible.

[0007] An object of the present invention is to provide a sheet supplying device and an image forming apparatus that can detect the timing for stopping the lift plate and determine the amount of sheets remaining on the lift plate with a simple configuration. [Means for solving the problem]

[0008] A sheet supplying device according to one aspect of the present invention includes a lift plate, a lifting mechanism, a feeding mechanism, a first sensor, a rotating member, a second sensor, and a control device. The lift plate is capable of stacking sheets. The lifting mechanism has a drive shaft and raises and lowers the lift plate by rotating the drive shaft. The feeding mechanism feeds the stacked sheets on the lift plate one by one to a subsequent stage. The first sensor detects the top surface of the stacked sheets on the lift plate at a supply position above the lift plate, or the upper surface of the lift plate when a sheet break occurs. The rotating member rotates in conjunction with the rotation of the drive shaft around a shaft portion, and has a plurality of detection portions and a plurality of gap portions alternately arranged along a circumferential direction around the shaft portion. The second sensor detects one of the plurality of detection portions that is present at a predetermined detection position. The control device controls the lifting mechanism and determines the remaining amount of sheets on the lift plate. When the drive shaft rotates in a forward rotation direction to raise the lift plate from the lowest position to the highest position, the plurality of detection target portions and the plurality of gaps pass through the detection position. The plurality of target portions, which are either the plurality of detection target portions or the plurality of gaps, include a first target portion that is located at the detection position when the lift plate is located at the lowest position, and a plurality of second target portions whose length in the circumferential direction is shorter than that of the first target portions. When a start event occurs, the control device executes an initial lift-up control for rotating the drive shaft in the forward rotation direction until the first sensor detects the upper surface. Furthermore, the control device determines the remaining sheet amount according to a signal change count, which is the number of specific changes in the detection signal of the second sensor when the initial lift-up control is being executed. Furthermore, when an end event occurs, the control device executes a lift-down control for rotating the drive shaft in a reverse rotation direction opposite to the forward rotation direction until a state occurs in which the detection signal of the second sensor is in a specific state and continues for a specific time corresponding to the circumferential length of the first target portions.

[0009] According to another aspect of the present invention, there is provided an image forming apparatus including the sheet supplying device, a printing device, and a notification device, the printing device forming an image on a sheet supplied by the sheet supplying device, and the notification device notifying information on a remaining amount of sheets determined by the sheet supplying device. Effect of the Invention

[0010] According to the present invention, it is possible to provide a sheet supplying device and an image forming apparatus that can detect the timing for stopping the lift plate and determine the amount of sheets remaining on the lift plate with a simple configuration. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. [Diagram 3] FIG. 3 is a configuration diagram of a sheet supplying device in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a diagram showing the sheet supplying device when a sheet shortage occurs in the image forming apparatus according to the embodiment. [Diagram 5] FIG. 5 is a diagram showing a rotation detection mechanism in the first lowest state in the image forming apparatus according to the embodiment. [Figure 6] FIG. 6 is a diagram showing a rotation detection mechanism in the second lowest state in the image forming apparatus according to the embodiment. [Figure 7] FIG. 7 is a diagram showing a rotation detection mechanism in an intermediate state in the image forming apparatus according to the embodiment. [Figure 8] FIG. 8 is a diagram showing a rotation detection mechanism in the uppermost state in the image forming apparatus according to the embodiment. [Figure 9] FIG. 9 is a diagram showing a first example of a time chart of two detection signals when lift-up control is performed in the image forming apparatus according to the embodiment. [Figure 10]FIG. 10 is a diagram showing a second example of a time chart of two detection signals when the lift-up control is performed in the image forming apparatus according to the embodiment. [Figure 11] FIG. 11 is a diagram showing an example of a time chart of two detection signals when the lift-down control is performed in the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0013] [Configuration of image forming apparatus 10] An image forming apparatus 10 according to the embodiment includes a main body 1 and a sheet supplying device 2 (see FIG. 1).

[0014] Furthermore, the image forming apparatus 10 includes a conveying device 3, a printing device 4, and a control device 8, which are arranged inside the main body 1. Furthermore, the image forming apparatus 10 includes an operation device 801 and a display device 802, which are arranged on the upper surface of the main body 1 (see FIG. 1).

[0015] The sheet supplying device 2 feeds a sheet 9 to the conveying device 3 in the main body 1. The sheet 9 is a sheet-like image forming medium such as paper or a resin sheet.

[0016] The conveying device 3 includes a plurality of pairs of conveying rollers 31. The conveying device 3 conveys the sheet 9 by the rotation of the plurality of pairs of conveying rollers 31. The conveying device 3 conveys the sheet 9 along a conveying path 300 in the main body 1, and further discharges the sheet 9 from the conveying path 300 to a discharge tray 100.

[0017] The printing device 4 forms an image on the sheet 9 conveyed along the conveying path 300. That is, the printing device 4 forms an image on the sheet 9 supplied by the sheet supply device 2.

[0018] 1, the printing device 4 forms an image on a sheet 9 by an electrophotographic method. In this case, the printing device 4 includes an exposure device 40, a photoconductor 41, a charging device 42, a developing device 43, a transfer device 44, a cleaning device 45, and a fixing device 46.

[0019] The charging device 42 charges the surface of the photoconductor 41. The exposure device 40 writes an electrostatic latent image onto the charged surface of the photoconductor 41. The developing device 43 develops the electrostatic latent image into a toner image.

[0020] A transfer device 44 transfers the toner image from the photoreceptor 41 to a sheet 9. A cleaning device 45 removes waste toner from the surface of the photoreceptor 41. A fixing device 46 fixes the toner image on the sheet 9 by applying heat and pressure to the toner image on the sheet 9.

[0021] The printing device 4 may be a device that forms an image on the sheet 9 by a method other than the electrophotographic method, such as an inkjet method.

[0022] The sheet supplying device 2 has a housing 20 and a sheet cassette 21 attached to the housing 20 so as to be removable. The housing 20 is disposed below the main body 1.

[0023] The sheet cassette 21 is an example of a sheet storage unit capable of storing the sheets 9. The sheet supplying device 2 includes a lift plate 11 and a lifting mechanism 12 disposed in the sheet cassette 21.

[0024] Here, a state in which the sheet cassette 21 is installed in a predetermined position in the housing 20 is referred to as an installed state. Also, a state in which a part or the whole of the sheet cassette 21 is pulled out from the housing 20 is referred to as an uninstalled state.

[0025] The sheet supplying device 2 further includes a cassette sensor 5 that detects whether the sheet cassette 21 is in the installed state. The cassette sensor 5 is disposed inside the housing 20.

[0026] The cassette sensor 5 detects the sheet cassette 21 approaching a predetermined position. For example, the cassette sensor 5 is a reflective optical sensor or a contact type microswitch.

[0027] The lift plate 11 is capable of carrying the sheets 9. The lift plate 11 is supported so as to be capable of ascending and descending. Specifically, the lift plate 11 is supported so as to be capable of ascending and descending rotation about a rotation shaft 11a.

[0028] The lifting mechanism 12 raises and lowers the lift plate 11. The lifting mechanism 12 holds the lift plate 11 at a height according to the amount of sheets remaining on the lift plate 11. The lifting mechanism 12 includes a drive shaft 12a, a rotating member 13, and a motor .

[0029] The rotating member 13 has a base shaft 13a. When the base shaft 13a rotates in a predetermined forward rotation direction R1, the rotating member 13 rotates upward about the base shaft 13a (see FIG. 3). When the base shaft 13a rotates in a reverse rotation direction R2 opposite to the forward rotation direction R1, the rotating member 13 rotates downward about the base shaft 13a (see FIG. 3).

[0030] The rotating member 13 supports the lift plate 11 from below. The rotating member 13 raises the lift plate 11 by rotating upward. The rotating member 13 lowers the lift plate 11 by rotating downward.

[0031] The motor 14 rotates the drive shaft 12a directly or via a gear mechanism (not shown). For example, the drive shaft 12a is an output shaft of the motor 14. The lifting mechanism 12 raises and lowers the lift plate 11 by rotating the drive shaft 12a with the motor 14.

[0032] When the drive shaft 12a rotates in the forward rotation direction R1, the base shaft 13a rotates in the forward rotation direction R1 following the drive shaft 12a.

[0033] That is, the motor 14 rotates the drive shaft 12a in a forward rotation direction R1 to raise the lift plate 11. The motor 14 rotates the drive shaft 12a in a reverse rotation direction R2 to lower the lift plate 11.

[0034] The sheet supplying device 2 further includes a feeding mechanism 22. The feeding mechanism 22 feeds the sheets stacked on the lift plate 11 one by one to the downstream conveying device 3. The feeding mechanism 22 includes a feeding roller 22a and a spring 22b.

[0035] The spring 22b is an elastic member that biases the feed roller 22a toward the uppermost surface of the stack of sheets on the lift plate 11. The feed roller 22a sends out the stack of sheets on the lift plate 11 to the conveying device 3 one by one by rotating.

[0036] The operation device 801 is a device that accepts operations by a person. For example, the operation device 801 includes one or both of a touch panel and operation buttons.

[0037] The display device 802 is capable of displaying various types of information. For example, the display device 802 is a panel display device such as a liquid crystal display device.

[0038] The control device 8 controls various electric devices included in the image forming apparatus 10. The control device 8 includes a central processing unit (CPU) 80, a random access memory (RAM) 81, a secondary storage device 82, a communication device 83, and a signal interface 84 (see FIG. 2).

[0039] The CPU 80 executes various control and data processing operations by executing computer programs. The RAM 81 temporarily stores the computer programs executed by the CPU 80 and various data.

[0040] The secondary storage device 82 is a computer-readable non-volatile storage device. The secondary storage device 82 stores the computer programs executed by the CPU 80 and various data. For example, one or both of a flash memory and a hard disk drive are adopted as the secondary storage device 82.

[0041] The communication device 83 executes communication with other devices such as a host device through a network. The CPU 80 executes communication with other devices through the communication device 83. The host device is an information processing device that requests the image forming apparatus 10 to perform a print process.

[0042] The signal interface 84 converts the detection signals of the various sensors into digital detection data. The detection data is transmitted to the CPU 80.

[0043] The CPU 80 includes a plurality of processing modules that are realized by executing the computer programs, including a main control unit 8a, a supply control unit 8b, and a print control unit 8c (see FIG. 2).

[0044] The main control unit 8a executes a process of receiving various requests and a control of making other modules execute processes according to the requests. For example, the main control unit 8a receives a print request through the operation device 801 or the communication device 83. Furthermore, the main control unit 8a causes the supply control unit 8b and the print control unit 8c to execute processes according to the print request.

[0045] The supply control unit 8b controls the lifting mechanism 12 of the sheet supply device 2. Furthermore, the supply control unit 8b executes a process for determining the remaining amount of sheets on the lift plate 11 in the sheet supply device 2.

[0046] The print control unit 8c controls the feeding mechanism 22 of the sheet supply device 2, the transport device 3, and the printing device 4. The print control unit 8c executes a process of feeding the sheet 9 from the lift plate 11 to the transport path 300. Furthermore, the print control unit 8c causes the printing device 4 to execute the print process while causing the transport device 3 to transport the sheet 9.

[0047] The supply control unit 8b executes the initial lift-up control when a predetermined start event occurs. In this embodiment, the start event is an event that the detection state of the cassette sensor 5 changes from the non-installed state of the sheet cassette 21 to the installed state.

[0048] In the initial lift-up control, the supply control unit 8b controls the motor 14 to rotate the drive shaft 12a in the forward rotation direction R1.

[0049] In the following description, the uppermost surface of the stacked sheets on the lift plate 11 or the upper surface of the lift plate 11 when a sheet break occurs is referred to as the upper surface. The sheet break occurs when no sheet 9 exists on the lift plate 11.

[0050] The sheet supply device 2 includes an upper surface detection device 6 that detects the upper surface at a supply position above the lift plate 11 (see FIG. 1). The upper surface detection device 6 includes a swinging member 61 and a photosensor 62.

[0051] The swingable member 61 swings from the first position to the second position by contacting the upper surface at the supply position. The photosensor 62 detects a part of the swingable member 61 when the swingable member 61 is at the first position or the second position.

[0052] In this embodiment, the photosensor 62 detects a part of the oscillating member 61 when the oscillating member 61 is in the first position, and does not detect the oscillating member 61 when the oscillating member 61 is in the second position.

[0053] That is, a state in which the photosensor 62 does not detect the pivot member 61 is a state in which the upper surface is detected at the supply position. The photosensor 62 is an example of a first sensor that detects the upper surface at the supply position.

[0054] In the initial lift-up control, the supply control unit 8b rotates the drive shaft 12a in the forward rotation direction R1 until the upper surface is detected at the supply position.

[0055] That is, the supply control unit 8b rotates the drive shaft 12a in the forward rotation direction R1, and stops the drive shaft 12a when the upper surface is detected at the supply position. In the initial lift-up control, the photosensor 62 is used to detect the stop timing of the lift plate 11.

[0056] When the upper surface is located at the feed position, the feed mechanism 22 can feed the sheet 9 .

[0057] 1 shows the lift plate 11 in its lowest position, in which case the upper surface is not detected in the feed position.

[0058] Figure 3 shows the stack of sheets on the lift plate 11 and the top surface is detected at the feed position. Figure 4 shows the top surface is detected at the feed position when the sheet run out occurs.

[0059] As described later, the supply control unit 8b also executes a process of determining the remaining amount of sheets on the lift plate 11. In this embodiment, the supply control unit 8b is an example of a device that constitutes a part of the sheet supply device 2.

[0060] Incidentally, it is desirable to realize the detection of the stop timing of the lift plate 11 and the determination of the remaining amount of sheets on the lift plate 11 with as simple a configuration as possible.

[0061] In this embodiment, the sheet supplying device 2 further includes a rotation detection mechanism 7 (see FIGS. 1, 5 to 8). The rotation detection mechanism 7 is a mechanism for detecting the rotation state of the drive shaft 12a in the lifting mechanism 12.

[0062] The supply control unit 8b controls the lifting mechanism 12 based on detection signals from the upper surface detection device 6 and the rotation detection mechanism 7, and determines the remaining amount of sheets on the lift plate 11.

[0063] The main control unit 8a executes a process of notifying the information on the remaining amount of sheets determined by the supply control unit 8b. In this embodiment, the main control unit 8a notifies the information on the remaining amount of sheets through one or both of the display device 802 and the communication device 83.

[0064] The main control unit 8a and the display device 802 are an example of a notification device that notifies the information on the remaining number of sheets. The main control unit 8a and the communication device 83 are another example of the notification device.

[0065] [Configuration of rotation detection mechanism 7] The rotation detection mechanism 7 includes a rotating member 70 and a photosensor 74 (see FIGS. 5 to 8). The rotating member 70 has a shaft portion 70a, an engagement portion 71, a plurality of protrusions 72, and a plurality of gaps 73 (see FIG. 5).

[0066] The shaft portion 70a rotates in conjunction with the rotation of the drive shaft 12a. In the example shown in Fig. 5, the shaft portion 70a is fixed to the drive shaft 12a. When the drive shaft 12a rotates, the rotating member 70 rotates about the shaft portion 70a.

[0067] In this embodiment, the rotation of the drive shaft 12a in the forward rotation direction R1 causes the rotating member 70 including the shaft portion 70a to rotate in the forward rotation direction R1. The rotation of the drive shaft 12a in the reverse rotation direction R2 causes the rotating member 70 including the shaft portion 70a to rotate in the reverse rotation direction R2. A transmission mechanism such as a gear mechanism may transmit the rotation of the drive shaft 12a to the shaft portion 70a.

[0068] The plurality of protrusions 72 and the plurality of voids 73 are alternately arranged in the circumferential direction about the shaft portion 70a. In this embodiment, the plurality of protrusions 72 are ribs formed in the circumferential direction about the shaft portion 70a.

[0069] 5 to 8, the rotating member 70 has four sets of projection groups, each of which has four projections 72 and four gaps 73. The four sets of projection groups are formed on the rotating member 70 at intervals of 90 degrees in the circumferential direction.

[0070] For the convenience of the mounting process of the rotating member 70, the four sets of protrusions are provided on the rotating member 70. If the rotating member 70 has one of the four sets of protrusions, the rotation detection mechanism 7 functions normally.

[0071] The photosensor 74 detects one of the plurality of protrusions 72 that is present at a predetermined detection position P1. The plurality of protrusions 72 are an example of a plurality of detection targets. The photosensor 74 is an example of a second sensor.

[0072] The multiple protrusions 72 and the multiple gaps 73 pass through the detection position P1 when the lift plate 11 rises from the lowermost position to the uppermost position as a result of the drive shaft 12a rotating in the forward rotation direction R1.

[0073] The gaps 73 include a first gap 73a and a second gap 73b. The first gap 73a is located at a detection position P1 when the lift plate 11 is located at the lowest position. Figures 1, 5, and 6 each show the lift plate 11 and the rotation detection mechanism 7 when the lift plate 11 is located at the lowest position.

[0074] The first gap 73a has a longer length in the circumferential direction than each of the second gaps 73b. In other words, each of the second gaps 73b has a shorter length in the circumferential direction than the first gap 73a.

[0075] In this embodiment, the plurality of gaps 73 are an example of a plurality of target portions. The first gap 73a is an example of a first target portion, and the plurality of second gaps 73b are an example of a plurality of second target portions.

[0076] The engaging portion 71 is a portion that engages with the engaged portion 13b. The engaging portion 71 is formed integrally with the base shaft 13a. When the rotating member 70 rotates in the forward rotation direction R1, the engaging portion 71 engages with the engaged portion 13b. With the engaging portion 71 engaged with the engaged portion 13b, the base shaft 13a rotates in the forward rotation direction R1 in conjunction with the rotation of the rotating member 70 in the forward rotation direction R1.

[0077] 5 shows the rotation detection mechanism 7 in the first lowest state. In the first lowest state, the engagement between the engaging portion 71 and the engaged portion 13b is released. When the rotating member 70 rotates in the forward rotation direction R1, the rotation detection mechanism 7 transitions from the first lowest state to the second lowest state.

[0078] 6 shows the rotation detection mechanism 7 in the first lowest state. The second lowest state is a state in which engagement between the engaging portion 71 and the engaged portion 13b begins when the rotating member 70 rotates in the forward rotation direction R1.

[0079] In other words, the second lowest state is a state in which the lift plate 11 starts to rise when the rotating member 70 rotates in the positive rotation direction R1. The engaging portion 71 and the engaged portion 13b engage with each other with a play from the first lowest state to the second lowest state.

[0080] The first gap 73a is located at a detection position P1 during the process in which the rotation detection mechanism 7 transitions from the first lowest state to the second lowest state (see FIGS. 5 and 6).

[0081] When the drive shaft 12a further rotates in the positive rotation direction R1 from the second lowest state of the rotation detection mechanism 7, the base shaft 13a rotates in the positive rotation direction R1, and the lift plate 11 rises. If the sheet break occurs, the lift plate 11 rises to the uppermost position due to the rotation of the base shaft 13a in the positive rotation direction R1.

[0082] 8 shows the rotation detection mechanism 7 in the uppermost state. When the rotation detection mechanism 7 is in the uppermost state, the lift plate 11 is located at the uppermost position (see FIG. 4).

[0083] 7 shows an example of the rotation detection mechanism 7 in an intermediate state. The intermediate state is a state between the second lowest state and the uppermost state.

[0084] [Initial lift-up control] As described above, the supply control unit 8b executes the initial lift-up control when the start event occurs. In the initial lift-up control, the supply control unit 8b rotates the drive shaft 12a in the forward rotation direction R1 until the photosensor 62 detects the upper surface.

[0085] When the remaining amount of sheets on the lift plate 11 is relatively large, after the initial lift-up control is performed, the rotation detection mechanism 7 is held in a state between the second lowermost state and the uppermost state (see FIGS. 3 and 7).

[0086] When the remaining amount of sheets on the lift plate 11 is very small or when the sheet runs out, the rotation detection mechanism 7 is held in the uppermost state after the initial lift-up control is performed (see FIGS. 4 and 8).

[0087] 9 and 10 show examples of time charts of the first detection signal SD1 and the second detection signal SD2 when the lift-up control is performed. The first detection signal SD1 is a detection signal of the photosensor 62 of the upper surface detection device 6. The second detection signal SD2 is a detection signal of the photosensor 74 of the rotation detection mechanism 7.

[0088] The first detection signal SD1 is in an ON state when the upper surface is detected at the supply position, and the second detection signal SD2 is in an ON state when any of the multiple protrusions 72 is at the detection position P1.

[0089] 9 and 10, the ascent start point T10 is the time when the rotation member 70 starts to rotate in the forward rotation direction R1 when the rotation detection mechanism 7 is in the first lowest state. Also, the engagement time point T11 is the time when the rotation detection mechanism 7 reaches the second lowest state.

[0090] In the initial lift-up control, the supply control unit 8b executes a process of detecting the falling edge E11 of the first detection signal SD1. In this embodiment, the detection of the falling edge E11 of the first detection signal SD1 indicates that the photosensor 62 has detected the upper surface.

[0091] 9 and 10, the upper surface detection time point T12 is the time point when the falling edge E11 of the first detection signal SD1 is detected. That is, the upper surface detection time point T12 is the time point when the upper surface is detected at the supply position.

[0092] In the initial lift-up control, the supply control unit 8b stops the rotation of the drive shaft 12a when it detects the falling edge E11 of the first detection signal SD1.

[0093] The supply control unit 8b executes an initial remaining amount determination process based on the second detection signal SD2 when the initial lift-up control is being executed.

[0094] The initial remaining amount determination process includes a process of counting the number of signal changes, which is the number of specific changes in the second detection signal SD2 when the initial lift-up control is being executed, and a process of determining the sheet remaining amount based on the number of signal changes.

[0095] In this embodiment, the specific change of the second detection signal SD2 is the falling edge E12 of the second detection signal SD2 from an ON state to an OFF state (see FIGS. 9 and 10).

[0096] Fig. 9 shows an example in which the falling edge E12 of the second detection signal SD2 is detected once during the period in which the initial lift-up control is being performed, while Fig. 10 shows an example in which the falling edge E12 of the second detection signal SD2 is detected four times during the period in which the initial lift-up control is being performed.

[0097] In the example shown in FIGS. 5 to 8, the rotating member 70 has four protrusions 72 formed at equal intervals and the same length in the circumferential direction. In this case, the supply control unit 8b determines that the remaining sheet amount is 76 to 100% when the number of signal changes is 0. Furthermore, the supply control unit 8b determines that the remaining sheet amount is 51 to 75% when the number of signal changes is 1. Furthermore, the supply control unit 8b determines that the remaining sheet amount is 26 to 50% when the number of signal changes is 3. Furthermore, the supply control unit 8b determines that the remaining sheet amount is 1 to 25% when the number of signal changes is 4. Furthermore, the supply control unit 8b determines that the sheet is out of stock when the number of signal changes is 4.

[0098] [Height maintenance control] The supply control unit 8b executes height maintenance control after the initial lift-up control is executed.

[0099] The height maintenance control is a process in which, when the photosensor 62 no longer detects the upper surface, the drive shaft 12a is rotated in the forward rotation direction until the photosensor 62 detects the upper surface.

[0100] By executing the height maintenance control, the upper surface is maintained in a state where it is positioned approximately at the supply position.

[0101] In the feeding mechanism 22, the feeding roller 22a is supported so as to be movable in a direction to come into contact with and separate from the upper surface. Even if the upper surface is slightly lowered from the supply position, the spring 22b of the feeding mechanism 22 maintains the state in which the feeding roller 22a is in contact with the upper surface.

[0102] Furthermore, the supply control unit 8b executes a remaining amount update process based on the second detection signal SD2 when the height position control is being executed. The remaining amount update process includes a process of counting the number of additions, which is the number of times the specific change occurs in the second detection signal SD2 when the height position control is being executed, and updating the number of signal changes by adding the number of additions.

[0103] Furthermore, the remaining amount update process includes a process of updating the remaining amount of sheets according to the number of times the signal changes after the update. By executing the remaining amount update process, when the feeding mechanism 22 operates, the remaining amount of sheets is updated to the latest state.

[0104] In addition, the supply control unit 8b executes a count limiting process for limiting the number of times the signal changes are added in a specific period of time. The specific period of time is a period from when the drive shaft 12a stops due to the execution of the initial lift-up control or the height maintenance control to when the rotation time of the drive shaft 12a due to the next execution of the height maintenance control reaches a reference time.

[0105] The count limiting process is a process for limiting the number of times the signal change is added to one when the specific change occurs in the detection signal of the second sensor.

[0106] Specifically, the supply control unit 8b counts up the number of signal changes in response to the specific change in the second detection signal SD2 while the drive shaft 12a is rotating due to the initial lift-up control or the height maintenance control.

[0107] Furthermore, the supply control unit 8b monitors the occurrence of the specific change in the second detection signal SD2 even during a period in which the drive shaft 12a is stopped due to the initial lift-up control or the height maintenance control. The period in which the drive shaft 12a is stopped due to the initial lift-up control or the height maintenance control is part of the specific period.

[0108] The supply control unit 8b maintains the number of signal changes when the specific change in the detection signal of the second sensor does not occur during the specific period. Also, the supply control unit 8b counts up the number of signal changes by one when the specific change in the detection signal of the second sensor occurs once during the specific period.

[0109] On the other hand, even if the specific change in the detection signal of the second sensor occurs multiple times during the specific period, the supply control unit 8b only counts up the number of signal changes once.

[0110] After the specific period has elapsed, the supply control unit 8b counts up the number of times the specific change occurs in the second detection signal SD2 as the number of signal changes.

[0111] In the initial lift-up control or the height maintenance control, a portion near a boundary between any one of the plurality of protrusions 72 and any one of the plurality of gaps 73 may stop at detection position P1. In this case, the rotating member 70 or the photosensor 74 may vibrate, and the state of the second detection signal SD2 may change even if the rotating member 70 is stopped.

[0112] If the state of the second detection signal SD2 changes while the rotating member 70 is stopped, the remaining amount of sheets may be erroneously determined.

[0113] On the other hand, in the image forming apparatus 10, the second and subsequent specific changes in the second detection signal SD2 during the specific period are ignored. The reference time is set according to the circumferential length and moving speed of the protrusion 72 or the gap 73. This prevents erroneous determination of the remaining amount of sheets caused by vibration of the rotating member 70 or the like.

[0114] [Lift down control] The supply control unit 8b executes the lift-down control when an end event occurs. In this embodiment, the end event is an event that the detection state of the cassette sensor 5 changes from the installed state of the sheet cassette 21 to the non-installed state.

[0115] FIG. 11 is an example of a time chart of the first detection signal SD1 and the second detection signal SD2 when the lift-down control is executed.

[0116] 11, a descent starting point T20 is the time when the lift-down control is started, and a disengagement time point T21 is the time when the rotation detection mechanism 7 reaches the second lowest state.

[0117] In the lift-down control, the supply control unit 8b rotates the drive shaft 12a in the reverse rotation direction R2 until a state occurs in which the second detection signal SD2 remains in a predetermined specific state for a specific time TS1 (see FIG. 11).

[0118] The specific state is the state of the second detection signal SD2 when any of the plurality of voids 73 is present at the detection position P1. In this embodiment, the specific state is the OFF state of the second detection signal SD2.

[0119] The specific time TS1 corresponds to the circumferential length and the moving speed of the first gap 73a. The specific time TS1 is longer than the time required for each of the second gaps 73b to pass through the detection position P1 and is shorter than the time required for the first gap 73a to pass through the detection position P1.

[0120] 11, the specific state is a state from when the falling edge E22 of the second detection signal SD2 is detected to when the rising edge E23 of the second detection signal SD2 is detected. The rising edge E23 is a change of the second detection signal SD2 from the OFF state to the ON state.

[0121] In FIG. 11, the return time point T22 is the time point when a specific time TS1 has elapsed from the time point when the falling edge E22 of the second detection signal SD2 is detected without the rising edge E23 being detected.

[0122] In the lift-down control, the supply control unit 8b stops the rotation of the drive shaft 12a when the return time T22 arrives while the drive shaft 12a is being rotated in the reverse rotation direction R2.

[0123] In the sheet supply device 2, the photosensor 74 of the rotation detection mechanism 7 is used for both determining the remaining amount of sheets and for the lift down control. By employing the sheet supply device 2, the detection of the stop timing of the lift plate 11 and the determination of the remaining amount of sheets can be realized with a simple configuration.

[0124] [Application example] Next, application examples of the sheet supplying device 2 will be described.

[0125] In this application example, the rotating member 70 has a configuration in which the multiple protrusions 72 and the multiple gaps 73 shown in Figures 5 to 8 are interchangeable. In this application example, the multiple protrusions 72 are an example of the multiple target portions.

[0126] In this application example, the specific change of the second detection signal SD2 in the initial lift-up control and the height maintenance control is the rising edge E23 of the second detection signal SD2.

[0127] In this application example, the specific state in the lift-down control is a state from when the rising edge E23 of the second detection signal SD2 is detected until when the falling edge E22 is detected.

[0128] When this application example is adopted, the same effects as when the sheet supplying device 2 is adopted can be obtained. [Explanation of symbols]

[0129] 2: Sheet feeder 4: Printing device 5: Cassette sensor 6: Upper surface detection device 7: Rotation detection mechanism 8: Control device 10: Image forming device 11: Lift plate 12: Lifting mechanism 12a: Drive shaft 13: Rotating member 13a: Base 13b: Engaged part 14: Motor 21: Sheet cassette 22: Feeding mechanism 62: Photosensor (second sensor) 70: Rotating member 70a:Shaft part 72:Protrusion (detected part) 73:Void part 73a: First gap portion (first target portion) 73b: second gap portion (second target portion) 74: Photosensor (second sensor) 83: Communication equipment 84: Signal interface P1: Detection position SD1: First detection signal SD2: Second detection signal

Claims

1. A lift plate capable of carrying sheets; a lifting mechanism that has a drive shaft and lifts and lowers the lift plate by rotating the drive shaft; a feeding mechanism for feeding the stacked sheets on the lift plate one by one to a subsequent stage; a first sensor for detecting a top surface of the lift plate at a feed position above the lift plate, the top surface being a top surface of the stack of sheets on the lift plate or a top surface of the lift plate when a sheet break occurs; a rotating member that rotates about a shaft portion in conjunction with the rotation of the drive shaft, and has a plurality of detection target portions and a plurality of gap portions that are alternately arranged in a circumferential direction about the shaft portion; a second sensor that detects one of the plurality of detection targets that is present at a predetermined detection position; and a control device for controlling the lift mechanism and determining a remaining amount of sheets on the lift plate, When the drive shaft rotates in a forward rotation direction to raise the lift plate from the lowest position to the highest position, the plurality of detection portions and the plurality of gaps pass through the detection position, the plurality of target portions, which are either the plurality of detection portions or the plurality of gap portions, include a first target portion that is located at the detection position when the lift plate is located at the lowest position, and a plurality of second target portions that are shorter in length in the circumferential direction than the first target portions, the control device executes an initial lift-up control to rotate the drive shaft in the forward rotation direction until the first sensor detects the upper surface when a start event occurs; Furthermore, the control device determines the remaining amount of the sheet according to a signal change frequency, which is a number of specific changes in the detection signal of the second sensor when the initial lift-up control is being executed, Furthermore, when an end event occurs, the control device executes lift-down control to rotate the drive shaft in a reverse rotation direction opposite to the forward rotation direction until a state occurs in which the detection signal of the second sensor is in a specific state and continues for a specific period of time corresponding to the circumferential length of the first target portion.

2. when the first sensor does not detect the upper surface after the initial lift-up control is executed, the control device executes a height maintenance control to rotate the drive shaft in the forward rotation direction until the first sensor detects the upper surface; The sheet supplying device of claim 1, further comprising: a control unit that updates the number of signal changes by adding the number of times the specific changes occur in the detection signal of the second sensor when the height maintenance control is being executed; and updates the remaining amount of sheets according to the updated number of signal changes.

3. The sheet supplying device of claim 2, wherein the control device limits the number of times the signal changes to one when the specific change occurs in the detection signal of the second sensor during a specific period from the time when the drive shaft stops due to execution of the initial lift-up control or the height maintenance control to the time when the rotation time of the drive shaft due to the next execution of the height maintenance control reaches a reference time.

4. The sheet supplying device according to any one of claims 1 to 3, a printing device for forming an image on the sheet fed by the sheet feeding device; a notification device that notifies information on a remaining amount of sheets determined by the sheet supply device.

Images