Lift device, sheet supply device, image forming apparatus

Abstract

To prevent a resetting operation with a simple structure when an output pulse of a rotary encoder is used for determining the state of a lift member.SOLUTION: An encoder rotor 17 has a plurality of count targets 170 rotated in linkage with a coupling member 15 and arrayed in a peripheral direction. Each of the count targets 170 includes a plurality of detected parts 17a spaced apart from each other in the peripheral direction. A detection sensor 160 detects the detected parts 17a at detection positions, and outputs a pulse signal. A tail detected part 172 located at a rearmost part in a main rotational direction among the detected parts 17a is formed longer in the peripheral direction than the other detected parts 17a. A count unit 8e resets the count number of pulse signals when a pulse signal having a width exceeding a reset width is output during execution of a main driving operation by a driving device 14.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a lift device having a rotary encoder used to determine the lift amount of a lift member, and a sheet supplying device and an image forming apparatus equipped with the lift device. [Background technology]

[0002] In an image forming apparatus, a sheet supplying device feeds sheets stacked in a sheet cassette one by one to a conveying path. The sheet supplying device may also include a lifting device that lifts a plate-shaped lifting member on which the sheets are stacked.

[0003] In the sheet supplying device, the lift device raises the lift member until the upper surface of the sheet stacked on the lift member reaches a predetermined target position.

[0004] For example, it is known that the lift device of the sheet supplying device includes a link member that is rotationally driven, and a rotary encoder that detects the amount of rotation of the shaft of the link member (see, for example, Patent Document 1).

[0005] The link member is rotated to raise the lift member, and the number of counts of the pulse signal output by the rotary encoder represents the amount of lift of the lift member.

[0006] The number of pulse signals output by the rotary encoder from when the lift device starts operating until the top surface of the sheet reaches the target position represents the amount of the sheet stack on the lift member, i.e., the smaller the amount of lift of the lift member until the top surface reaches the target position, the greater the number of the sheets stacked. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP2000-284650 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0008] The sheet cassette is attached to a main body and can be pulled out from the main body. The link member for lifting the lift member is provided on the sheet cassette. In this case, the lift device needs to include a coupling mechanism for smoothly connecting the link member to a drive mechanism provided on the main body when the sheet cassette is attached to the main body.

[0009] Generally, in the coupling mechanism, when the coupling member provided on the main body rotates in a predetermined direction, there are cases where the coupling member engages with the link member after passing through an idling period during which the coupling member does not engage with the link member.

[0010] Therefore, when the state of the lift member is determined based on the count number of the pulse signal output by the rotary encoder, a configuration is required in which the count number of the pulse signal during the idling period is not reflected in the determination of the state of the lift member.

[0011] For example, it is conceivable that the rotary encoder is provided in the sheet cassette, In this case, the rotary encoder can detect the amount of rotation of the link member.

[0012] However, providing a configuration for electrically disconnecting or connecting the rotary encoder and the electrical components provided in the main body in response to the removal or installation of the sheet cassette is not preferable because it complicates the device configuration.

[0013] Moreover, providing a sensor for detecting whether the coupling mechanism is in an engaged state is not preferable because it increases the number of parts and complicates the device configuration.

[0014] It is also possible that the lift device performs a reset operation to check the state in which the coupling member is engaged with the link member after displacing the lift member to a predetermined initial position.

[0015] However, when the reset operation is performed, the preparation time of the lift device is increased, i.e., the downtime of the machine including the lift device is increased.

[0016] An object of the present invention is to provide a lift device that can avoid a reset operation with a simple configuration when the output pulse of a rotary encoder is used to determine the state of a lift member, and a sheet supplying device and an image forming apparatus equipped with the lift device. [Means for solving the problem]

[0017] A lift device according to one aspect of the present invention includes a main body, a mounting unit, a lift member, a target state detection unit, a link member, a coupling member, a drive device, a rotary encoder, and a counting unit. The mounting unit is mounted on the main body and can be pulled out from the main body. The lift member is provided on the mounting unit so as to be displaceable up and down. The target state detection unit detects that the lift member is in a predetermined target state. The link member is provided on the mounting unit and has an engaged portion that is engaged with another member, and displaces the lift member upward when the engaged portion is rotationally driven in a main rotation direction. The coupling member is provided on the main body and has an engagement portion that engages with the engaged portion when the mounting unit is mounted on the main body, and rotates the engaged portion engaged with the engagement portion in the main rotation direction when the coupling member is rotationally driven in the main rotation direction. The drive device is capable of executing a main drive operation that rotationally drives the coupling member in the main rotation direction from the occurrence of a predetermined drive event until the target state is detected. The rotary encoder outputs a pulse signal in response to the rotation of the coupling member. The counting unit counts the pulse signal while the driving device is performing the main driving operation. The engaging unit forms a gap into which the engaged unit is inserted, and the circumferential width of the gap is greater than the width of the engaged unit. The rotary encoder includes an encoder rotor and a detection sensor. The encoder rotor rotates in conjunction with the coupling member and has a plurality of count target units arranged in a circumferential direction, and each of the count target units includes a plurality of detectable units arranged in the circumferential direction at intervals. The detection sensor detects the detectable units at a predetermined detection position and outputs the pulse signal representing the detection state of the detectable units. When the engaging unit reaches a position where it does not engage with the engaged unit as a result of the coupling member rotating in the main rotation direction, a portion of the encoder rotor between two adjacent count target units reaches the detection position.A rear detected part located at the rear end in the main rotation direction among the plurality of detectable parts in each of the count target parts is formed longer in the circumferential direction than the other detectable parts. The counting part resets the count number of the pulse signal when the pulse signal having a width exceeding a predetermined reset width corresponding to the rear detected part is output from the detection sensor while the drive device is performing the main drive operation.

[0018] A sheet feeding device according to another aspect of the present invention includes the lift device, and a sheet sending mechanism that sends out sheets stacked on the lift member of the lift device to a conveying path one by one.

[0019] An image forming apparatus according to another aspect of the present invention includes the sheet feeding device described above, and a printing device that forms an image on the sheet fed by the sheet feeding device. Effect of the Invention

[0020] According to the present invention, it is possible to provide a lift device that can avoid a reset operation with a simple configuration when the output pulse of a rotary encoder is used to determine the state of a lift member, and a sheet supplying device and an image forming apparatus equipped with the same. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a configuration diagram of an image forming apparatus including a lift device according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus. [Diagram 3] FIG. 3 is a plan view of the inside of the lift device according to the embodiment (showing a state in which a sheet cassette is attached). [Figure 4] FIG. 4 is a plan view of the inside of the lift device according to the embodiment (showing a state in which the sheet cassette is pulled out). [Diagram 5] FIG. 5 is a front view of a coupling mechanism and a rotary encoder in the lift device according to the embodiment. [Figure 6] FIG. 6 is a front view of the coupling mechanism and the rotary encoder in the first idling state in the lift device according to the embodiment. [Figure 7] FIG. 7 is a front view of the coupling mechanism and the rotary encoder in the second idling state in the lift device according to the embodiment. [Figure 8] FIG. 8 is a front view of the coupling mechanism and the rotary encoder in the third idling state in the lift device according to the embodiment. [Figure 9] FIG. 9 is a front view of the coupling mechanism and the rotary encoder in the engagement start state in the lift device according to the embodiment. [Figure 10] FIG. 10 is a front view of the coupling mechanism and the rotary encoder in the first lift-up state in the lift device according to the embodiment. [Figure 11] FIG. 11 is a front view of the coupling mechanism and the rotary encoder in the second lift-up state in the lift device according to the embodiment. [Figure 12] FIG. 12 is a front view of the coupling mechanism and the rotary encoder in the upper limit lift-up state of the lift device according to the embodiment. [Figure 13] FIG. 13 is a diagram showing an example of a pulse signal output from a rotary encoder in the lift device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 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.

[0023] A lift device 1 according to an embodiment of the present invention constitutes a part of a sheet supplying device 2. The sheet supplying device 2 constitutes a part of an image forming apparatus 10 (see FIG. 1).

[0024] [Configuration of image forming apparatus 10] As shown in FIG. 1, the image forming apparatus 10 includes a main housing 100, a sheet supplying device 2, a sheet transporting device 3, and a printing device 4.

[0025] The sheet transport device 3 and the printing device 4 are disposed in a main housing 100. As described later, a part of the sheet supply device 2 is disposed in the main housing 100, and another part of the sheet supply device 2 is attached to the main housing 100 so as to be removable.

[0026] Furthermore, the image forming apparatus 10 includes an operation device 801, a display device 802, and a control device 8. The operation device 801, the display device 802, and the control device 8 are also parts of the lift device 1.

[0027] The operation device 801 is a device that accepts operations by a person, and includes, for example, an operation button and a touch panel. The display device 802 is a device that displays information, and includes, for example, a panel display device such as a liquid crystal display unit. The control device 8 executes various data processing and controls the image forming device 10.

[0028] The sheet supplying device 2 includes a lifting device 1 and a sheet sending mechanism 21. The lifting device 1 includes a mounting unit 11, a lifting member 12, a linking member 13, a driving mechanism 14, a rotary encoder 16, and an upper surface detection sensor 18.

[0029] The lift member 12 is a plate-like member on which the sheets 9 are stacked. The sheet supplying device 2 sends the sheets 9 stacked on the lift member 12 one by one to the conveying path 30. The sheets 9 are sheet-like image forming media such as paper or a resin sheet. The sheets 9 are an example of an object placed on the lift member 12.

[0030] The fitting unit 11 is attached to the main housing 100 and can be pulled out from the main housing 100. In this embodiment, the fitting unit 11 is a so-called sheet cassette that can accommodate sheets 9. The main housing 100 is a main body of the image forming apparatus 10 and also a main body of the lift device 1.

[0031] The lift member 12 is provided to the mounting unit 11 so as to be vertically displaceable. In this embodiment, the lift member 12 is supported by the mounting unit 11 so as to be vertically displaceable about a rotation shaft 12a.

[0032] The link member 13 is rotatably provided on the mounting unit 11. The link member 13 displaces the lift member 12 upward by being rotationally driven in a predetermined main rotation direction R1.

[0033] The link member 13 has a shaft portion 13a and a support portion 13b. The shaft portion 13a is disposed below the lift member 12 and is rotatably supported. The support portion 13b is formed by extending from the shaft portion 13a along a direction intersecting the axial direction D1 of the shaft portion 13a (see FIGS. 1 and 3).

[0034] The support portion 13b supports the lift member 12 from below, and lifts the lift member 12 by rotating in conjunction with the shaft portion 13a in the main rotation direction R1 (see FIG. 1).

[0035] The drive mechanism 14 rotationally drives the link member 13 in the main rotation direction R1. Specifically, the drive mechanism 14 rotationally drives a coupling member 15, which will be described later, to rotate a shaft portion 13a of the link member 13 in the main rotation direction R1 via the coupling member 15. When the shaft portion 13a rotates, the support portion 13b rotates around the shaft portion 13a in the main rotation direction R1.

[0036] The upper surface detection sensor 18 detects that the upper surface of the sheet 9 placed on the lift member 12 is located at a predetermined target position. For example, the upper surface detection sensor 18 is a reflective photosensor or a contact-type limit switch.

[0037] In this embodiment, the position of the upper surface of the sheet 9 placed on the lift member 12 at the target position is an example of the lift member 12 being in a predetermined target state. The upper surface detection sensor 18 is an example of a target state detection unit that detects that the lift member 12 is in the target state.

[0038] The drive mechanism 14 raises the lift member 12 from the lowest initial position until the target state is detected, and holds the lift member 12 at the position where the target state is detected. In Fig. 1, the lift member 12 positioned at the initial position is shown by a virtual line (two-dot chain line).

[0039] The rotary encoder 16 outputs a pulse signal in response to the rotation of the coupling member 15. The count number of the pulse signal output by the rotary encoder 16 represents the amount of lift of the lift member 12.

[0040] Furthermore, the number of counts of the pulse signal output by the rotary encoder 16 from when the lift device 1 starts operating until the target state is detected represents the amount of sheets 9 loaded on the lift member 12. That is, the smaller the amount of lift of the lift member 12 until the target state is detected, the greater the number of loaded sheets 9.

[0041] When the lift member 12 is in the target state, the sheet sending mechanism 21 sends out an upper sheet, which is the uppermost sheet among the sheets 9 stacked on the lift member 12, from the lift member 12 to the conveying path 30. In this way, the sheet sending mechanism 21 sends out the sheets 9 stacked on the lift member 12 to the conveying path 30 one by one.

[0042] The sheet delivery mechanism 21 includes a delivery roller 21a and a separation unit 21b. The delivery roller 21a is urged against the upper surface of the upper sheet and delivers the upper sheet from above the lift member 12 by being driven to rotate.

[0043] When a plurality of sheets 9 have been sent out by the delivery roller 21a, the separation unit 21b sends out only the upper sheet to the conveyance path 30. The separation unit 21b retains the sheet 9 overlapping below the upper sheet.

[0044] The sheet transport device 3 includes a transport path 30, a plurality of transport roller pairs 31, and a discharge tray 32. The plurality of transport roller pairs 31 transport the sheet 9 supplied from the sheet supply device 2 along the transport path 30, and further discharge the sheet 9 from a discharge opening 30a of the transport path 30 onto the discharge tray 32.

[0045] The printing device 4 executes a printing process for forming an image on a sheet 9 conveyed by the sheet conveying device 3 .

[0046] 1, the printing device 4 is a device that performs the printing process by electrophotography. However, the printing device 4 may be a device that performs the printing process by inkjet printing.

[0047] As shown in FIG. 2, the control device 8 includes a central processing unit (CPU) 81, a random access memory (RAM) 82, a secondary storage device 83, and peripheral devices such as a signal interface 84.

[0048] The CPU 81 is a processor that executes various types of data processing and control by executing computer programs. The RAM 82 is a computer-readable volatile storage device. The RAM 82 temporarily stores the computer programs executed by the CPU 81 and data that is output and referenced in the course of the CPU 81 executing various types of processing.

[0049] The secondary storage device 83 is a computer-readable non-volatile storage device. The secondary storage device 83 can store and update the computer programs and various data. For example, one or both of a flash memory and a hard disk drive are adopted as the secondary storage device 83.

[0050] The signal interface 84 converts signals output by various sensors into digital data, and transmits the converted digital data to the CPU 81. Furthermore, the signal interface 84 converts control commands output by the CPU 81 into control signals, and transmits the control signals to the devices to be controlled.

[0051] The CPU 81 includes a plurality of processing modules that are realized by executing the computer programs, including a main control unit 8a, a lift control unit 8b, a transport control unit 8c, a print control unit 8d, and a determination unit 8e.

[0052] The main control unit 8a executes control to start various processes in response to operations on the operation device 801, control of the display device 802, and the like.

[0053] The lift control unit 8b controls the lift device 1. Specifically, the lift control unit 8b starts the drive mechanism 14 when a predetermined drive event occurs, and stops the drive mechanism 14 when the target state is detected by the upper surface detection sensor 18. The drive mechanism 14 in operation rotates and drives the coupling member 15 in the main rotation direction R1.

[0054] In the following description, the operation of rotating the coupling member 15 in the main rotation direction R1 from the occurrence of the drive event until the detection of the target state is referred to as the main drive operation. The drive mechanism 14 and the lift control unit 8b that controls the drive mechanism 14 are an example of a drive device that executes the main drive operation. The drive mechanism 14 rotates the coupling member 15 at a constant speed.

[0055] The conveyance control unit 8c controls the conveyance of the sheet 9 by controlling the sheet conveying device 3. The conveyance control unit 8c controls the timing of conveying the sheet 9 to the printing device 4.

[0056] The transport control unit 8c generates the driving event every time a print job that requests execution of the print process is input. When the print job requests the print process to be performed on a plurality of sheets 9, the transport control unit 8c sequentially generates a plurality of driving events according to the transport status of the sheets 9.

[0057] The print control unit 8d causes the printing device 4 to execute the print process in synchronization with the conveyance of the sheet 9 by the sheet conveying device 3.

[0058] The determination unit 8e counts the pulse signals when the lift control unit 8b causes the drive mechanism 14 to perform the main driving operation. Furthermore, the determination unit 8e determines the amount of the sheets 9 on the lift member 12 according to the count number of the pulse signals during the period when the main driving operation is being performed.

[0059] The determination unit 8e can also determine the amount of lift of the lift member 12 from the initial position according to the number of counts of the pulse signal during the period in which the main driving operation is being performed. The determination unit 8e is an example of a count unit that counts the pulse signal.

[0060] In this embodiment, the lift control unit 8b and the determination unit 8e constitute a part of the lift device 1. That is, the lift device 1 includes the lift control unit 8b and the determination unit 8e in the CPU 81.

[0061] Incidentally, the mounting unit 11 is mounted to the main housing 100 and can be pulled out from the main housing 100. Also, the link member 13 that lifts the lift member 12 is provided on the mounting unit 11. In this case, the lift device 1 needs to be provided with a coupling mechanism that smoothly connects the link member 13 to a drive mechanism provided on the main body when the mounting unit 11 is mounted to the main housing 100.

[0062] Generally, in the coupling mechanism, when the coupling member 15 provided on the main housing 100 rotates in a predetermined direction, it may engage with the link member 13 after passing through an idling period during which it does not engage with the link member 13. A specific example of this structure will be described later.

[0063] Therefore, when the state of the lift member 12 is determined based on the count number of the pulse signal output by the rotary encoder 16, a configuration is required in which the count number of the pulse signal during the idling period is not reflected in the determination of the state of the lift member 12.

[0064] For example, the rotary encoder 16 may be provided in the fitting unit 11. In this case, the rotary encoder 16 can detect the amount of rotation of the link member 13.

[0065] However, providing a configuration for electrically disconnecting or connecting the rotary encoder 16 and the electrical components provided in the main housing 100 depending on whether the fitting unit 11 is pulled out or attached is not preferable because it would complicate the device configuration.

[0066] Moreover, providing a sensor for detecting whether the coupling mechanism is in an engaged state is not preferable because it increases the number of parts and complicates the device configuration.

[0067] In addition, it is conceivable that the lift device 1 performs a reset operation to check the state in which the coupling member 15 is engaged with the link member 13 after displacing the lift member 12 to the initial position.

[0068] However, when the reset operation is performed, the preparation time of the lift device 1 becomes longer. That is, the downtime of the sheet supplying device 2 including the lift device 1 becomes longer.

[0069] On the other hand, the lift device 1 realizes, with a simple configuration, a configuration in which the count number of the pulse signal during the idling period is not reflected in the determination of the state of the lift member 12. The configuration will be described below.

[0070] 3 to 5, the link member 13 has an engaged portion 130 that is engaged with another member. When the engaged portion 130 is rotationally driven in the main rotation direction R1, the link member 13 displaces the lift member 12 upward.

[0071] In this embodiment, the engaged portion 130 includes one or more protruding portions 13c extending from a portion of the shaft portion 13a toward one end along a direction intersecting the axial direction D1. For example, the protruding portions 13c are parallel pins fixed to the shaft portion 13a.

[0072] In the example shown in FIGS. 3 to 5, the engaged portion 130 includes two overhanging portions 13c formed to extend in two directions forming an angle of 180° in a first circumferential direction which is the circumferential direction of rotation of the link member 13.

[0073] Furthermore, the coupling member 15 is rotatably provided on the main housing 100, and has a base portion 15a and an engagement portion 150. The first circumferential direction is also the circumferential direction in which the coupling member 15 rotates.

[0074] The base 15a is disposed apart from the engaged portion 130 in the axial direction D1, and is rotationally driven by the drive mechanism 14. In the example shown in Figs. 4 and 5, the drive mechanism 14 includes a motor 14a, a gear mechanism 14b, and a drive body 14c. The drive body 14c is a member integral with the coupling member 15, and is rotatably supported. The gear mechanism 14b transmits the rotational force of the motor 14a to the drive body 14c.

[0075] The engaging portion 150 engages with the engaged portion 130 in the main rotation direction R1 when the fitting unit 11 is attached to the main housing 100. The coupling member 15 is rotationally driven in the main rotation direction R1, thereby rotating the engaged portion 130 engaged with the engaging portion 150 in the main rotation direction R1. This causes the link member 13 to rotate in the main rotation direction R1.

[0076] In this embodiment, the engaging portion 150 includes a plurality of protruding portions 15b formed to protrude from the base portion 15a along the axial direction D1 toward the engaged portion 130. The plurality of protruding portions 15b are formed side by side at intervals in the first circumferential direction (see FIG. 5).

[0077] 5, the engagement portion 150 includes four protrusions 15b arranged at a pitch of 90° in the first circumferential direction. Therefore, two of the four protrusions 15b arranged at a pitch of 180° engage with the two overhanging portions 13c.

[0078] 4, when the fitting unit 11 is pulled out from the main housing 100, the engagement between the engaging portion 150 and the engaged portion 130 is released. In this embodiment, the pulling-out direction D11 and the fitting direction D12 of the fitting unit 11 are directions along the axial direction D1.

[0079] When the engagement between the engaging portion 150 and the engaged portion 130 is released, the protruding portion 13c returns to the position shown in Figures 5 to 9, the link member 13 rotates in the opposite direction to the main rotation direction R1, and the lift member 12 descends to the initial position shown by the virtual line in Figure 1.

[0080] The coupling member 15 having the engaging portion 150 and the engaged portion 130 constitute a coupling mechanism that connects the drive mechanism 14 and the link member 13 together.

[0081] The rotary encoder 16 includes an encoder rotor 17 and a detection sensor 160. The encoder rotor 17 rotates in conjunction with the coupling member 15. The encoder rotor 17 has a plurality of count target portions 170 arranged in a second circumferential direction, which is the circumferential direction of rotation of the encoder rotor 17 (see FIG. 5).

[0082] In this embodiment, the driver 14c and the base 15a of the coupling member 15 are engaged in the main rotation direction R1 and the opposite direction thereof, so that the first circumferential direction and the second circumferential direction are the same.

[0083] Further, the coupling member 15 is supported by the driver 14c so as to be displaceable from a reference position where the coupling member 15 can engage with the engaged portion 130 to the opposite side of the engaged portion 130. A spring 19 elastically biases the coupling member 15 toward the reference position.

[0084] The count target portions 170 are provided consecutively at a pitch of a predetermined angle in the second circumferential direction.

[0085] Each of the count target portions 170 includes a plurality of light blocking portions 17a arranged at intervals in the second circumferential direction. The detection sensor 160 detects the light blocking portion 17a at a predetermined detection position P1, and outputs a pulse signal indicating the detection state of the light blocking portion 17a.

[0086] In the example shown in FIG. 5, four count target portions 170 are provided consecutively at a pitch of 90° in the second circumferential direction.

[0087] In this embodiment, the maximum rotation angle permitted for the link member 13 is less than 90°. The count target portions 170 are arranged in the second circumferential direction at a pitch greater than the maximum rotation angle permitted for the link member 13.

[0088] Each of the count target portions 170 has three light blocking portions 17a aligned in the second circumferential direction. The light blocking portions 17a in the multiple count target portions 170 have the same configuration. Each of the count target portions 170 may have four or more light blocking portions 17a aligned in the second circumferential direction.

[0089] In this embodiment, the detection sensor 160 is a transmissive photosensor. The light-shielding portions 17a are portions that block the detection light of the photosensor. In the encoder rotor 17, the portions between the light-shielding portions 17a in the second circumferential direction are gaps 17b.

[0090] The encoder rotor 17 has a plurality of light-shielding portions 17a and a plurality of gaps 17b arranged alternately over the entire second circumferential direction. In this embodiment, the light-shielding portions 17a are an example of a portion to be detected by the detection sensor 160. When a reflective photosensor is used as the detection sensor, a reflector that reflects light is used instead of the light-shielding portions 17a.

[0091] Fig. 13 shows an example of a pulse signal output from the detection sensor 160 of the rotary encoder 16. For convenience, Fig. 13 shows an example in which an active HIGH pulse signal is output when the light-shielding portion 17a is detected by the detection sensor 160.

[0092] It is also possible that the detection sensor 160 outputs an active low pulse signal when detecting the light blocking portion 17a.

[0093] In this embodiment, the determination unit 8e counts up the pulse signal at each rising edge of the pulse signal. In Fig. 13, a time point CP1 at which the determination unit 8e counts up the pulse signal is shown.

[0094] As described above, the determination unit 8e determines the load of the sheets 9 on the lift member 12 according to the count number of the pulse signal during the period when the main driving operation is being performed. For example, the determination unit 8e determines the ratio of the load of the sheets 9 to the maximum load of the sheets 9 on the lift member 12 as the load of the sheets 9. In the following description, the period during which the main driving operation is being performed is referred to as the main driving period.

[0095] For example, the determination unit 8e determines the amount of the sheets 9 stacked on the basis of the count number of the pulse signal in the main driving period and the post-count-up time, which is the time from the final count-up time point CP1 in the main driving period to the end point of the main driving period.

[0096] The count number of the pulse signal is previously associated with a boundary value of the stack amount of sheets 9. Here, the count number of the pulse signal is denoted as i, and the boundary value corresponding to the count number is denoted as SL(i).

[0097] The determination unit 8e determines that the amount of stacked sheets 9 is less than the first boundary value SL(1) when the count number i is 0. In other cases, the determination unit 8e derives the amount of stacked sheets 9 as a value obtained by adding the boundary value SL(i) and the result of multiplying the post-count-up time by a predetermined coefficient.

[0098] 5, the engaging portion 150 forms a gap into which the engaged portion 130 is inserted along the axial direction D1, and the width of the gap in the first circumferential direction is larger than the width of the engaged portion 130. In other words, the engaged portion 130 forms a gap into which the engaging portion 150 is inserted along the axial direction D1, and the width of the gap in the first circumferential direction is larger than the width of the engaging portion 150.

[0099] Therefore, when the coupling member 15 rotates in the main rotation direction R1, the engaging portion 150 may engage with the engaged portion 130 after an idling period SC1 during which the engaging portion 150 does not engage with the engaged portion 130.

[0100] The idling period SC1 shown in Fig. 13 is the maximum period that can occur in this embodiment. In addition, in Fig. 13, the period during which the engaging portion 150 is engaged with the engaged portion 130 is shown as an engagement period SC2.

[0101] Depending on the configurations of the count target section 170 and the coupling mechanism, the idling period SC1 may reach the range indicated by the dashed line in FIG.

[0102] 6 to 8 show states of the coupling mechanism and the rotary encoder 16 during the idling period SC1. Hereinafter, these states will be referred to as idling states. The state shown in Fig. 6 will be referred to as the first idling state, the state shown in Fig. 7 as the second idling state, and the state shown in Fig. 8 as the third idling state.

[0103] In FIG. 13, a first idling time point IP1 corresponds to the first idling state in FIG. 6, a second idling time point IP2 corresponds to the second idling state in FIG. 7, and a third idling time point IP3 corresponds to the third idling state in FIG. 8.

[0104] 5 and 9 show an engagement start state in which the engaging portion 150 engages with the engaged portion 130 while the lift member 12 remains in the initial position. In this embodiment, the inclination of the engaged portion 130 generally represents the inclination of the lift member 12.

[0105] In the following description, of the multiple light-shielding portions 17a in each count target portion 170, the one located at the front in the main rotation direction R1 is referred to as a front light-shielding portion 171, and the one located at the rear end in the main rotation direction R1 is referred to as a rear light-shielding portion 172. The front light-shielding portion 171 is an example of a front detectable portion, and the rear light-shielding portion 172 is an example of a rear detectable portion.

[0106] 13, a leading detection period PD1 is a period during which a pulse signal is output when the leading light shielding portion 171 passes through the detection position P1, and a trailing detection period PD2 is a period during which a pulse signal is output when the trailing light shielding portion 172 passes through the detection position P1.

[0107] As shown in Figure 9, when the coupling member 15 rotates in the main rotation direction R1 and the engaging portion 150 moves from a non-engaged position to an engaged position with respect to the engaged portion 130, the portion between two adjacent count target portions 170 on the encoder rotating body 17 reaches the detection position P1.

[0108] In other words, when the engaging portion 150 is in the engagement start state, a portion between two adjacent count target portions 170 in the encoder rotating body 17 is located at detection position P1. In this embodiment, when the engaging portion 150 is in the engagement start state, a boundary portion between two adjacent count target portions 170 in the encoder rotating body 17 is located at detection position P1.

[0109] Further, the rear light-shielding portion 172 in each of the count target portions 170 is formed to be longer in the second circumferential direction than the other light-shielding portions 17a.

[0110] The determination unit 8e resets the count number of the pulse signal when the pulse signal having a width exceeding a predetermined reset width W1 is output from the detection sensor 160 while the drive mechanism 14 is performing the main drive operation (see FIG. 13).

[0111] The reset width W1 is larger than the pulse width corresponding to the length of all light shielding portions 17a other than the rear light shielding portion 172 in the second circumferential direction, and is smaller than the pulse width corresponding to the length of the rear light shielding portion 172 in the second circumferential direction.

[0112] Furthermore, the determination unit 8e records the count number of the pulse signal in the secondary storage device 83, and when the drive mechanism 14 executes the main drive operation after the CPU 81 is started, starts counting the pulse signal with the count number recorded in the secondary storage device 83 as an initial value. As a result, when the CPU 81 is restarted after being stopped, the drive mechanism 14 does not need to perform an operation of returning the lift member 12 to the initial position.

[0113] The first idling time point IP1 and the second idling time point IP2 in FIG. 13 are points prior to the boundary time point TP1, which is a time point preceding the end point of the idling period SC1 by the time period corresponding to the reset width W1.

[0114] Here, consider a case where the first idling state in Fig. 6 corresponding to the first idling time point IP1 or the second idling state in Fig. 7 corresponding to the second idling time point IP2 is a state in which the operation of the drive mechanism 14 starts. In this case, the engagement period SC2 starts with the count number always reset.

[0115] 8 corresponding to the third idling time point IP3 is a state in which the operation of the drive mechanism 14 starts. In this case, the engagement period SC2 starts without the count number being counted up midway.

[0116] In this embodiment, the pulse signal during the idling period is not reflected in the count number of the pulse signal at the end of the main driving operation, so there is no need to cause the driving mechanism 14 to perform the reset operation or to provide a sensor for detecting the engagement start state.

[0117] Furthermore, since the rotary encoder 16 is provided in the main housing 100, there is no need for a mechanism for electrically disconnecting or connecting the attachment unit 11 in response to the attachment or removal of the attachment unit 11.

[0118] Therefore, by adopting this embodiment, it is possible to provide a lift device 1 that can avoid the reset operation with a simple configuration.

[0119] [Application example] Application examples of the lift device 1 will now be described.

[0120] The encoder rotor 17 in this application example has a configuration in which the light blocking portion 17a and the gap portion 17b shown in Fig. 5 are interchanged. In this case, the detection sensor 160 is a sensor that detects the gap portion 17b at the detection position P1.

[0121] That is, in this application example, the gap 17b is an example of a detection target portion detected by the detection sensor 160. When this application example is adopted, the same effects as when the above-described embodiment is adopted can be obtained. [Explanation of symbols]

[0122] 1: Lifting device 2: Sheet feeder 3: Sheet transport device 4: Printing device 8: Control device 10: Image forming device 11: Mounting unit 12: Lifting parts 13: Link member 13a:Shaft part 13b: Support part 13c: Overhang 14: Driving mechanism 15: Coupling parts 16: Rotary encoder 17: Encoder rotor 17a: Light shielding part (detected part) 17b:Void part 18: Top detection sensor 21: Sheet delivery mechanism 100: Main housing (main body) 130: Engaged part 150: Engagement part 160: Detection sensor 170: Counting section 171: Leading light shielding part 172: Rear shading section

Claims

1. A main body portion, a mounting unit that is mounted on the main body and can be pulled out from the main body; A lift member provided on the mounting unit so as to be vertically displaceable; a target state detection unit that detects whether the lift member is in a predetermined target state; a link member provided on the mounting unit, the link member having an engaged portion adapted to be engaged with another member, the link member displacing the lift member upward when the engaged portion is rotationally driven in a main rotation direction; a coupling member that is provided on the main body portion, has an engaging portion that engages with the engaged portion when the mounting unit is mounted on the main body portion, and is rotationally driven in the main rotation direction to rotate the engaged portion engaged with the engaging portion in the main rotation direction; a drive device capable of executing a main drive operation for rotationally driving the coupling member in the main rotation direction from the occurrence of a predetermined drive event until the target state is detected; a rotary encoder that outputs a pulse signal in response to rotation of the coupling member; a counting unit that counts the pulse signals while the driving device is performing the main driving operation, the engaging portion forms a gap into which the engaged portion is inserted, and the circumferential width of the gap is greater than the width of the engaged portion; The rotary encoder includes: an encoder rotor that rotates in conjunction with the coupling member and has a plurality of count target portions that are arranged in a circumferential direction, each of the count target portions including a plurality of detectable portions that are arranged in a circumferential direction at intervals; a detection sensor that detects the detection target portion at a predetermined detection position and outputs the pulse signal that represents a detection state of the detection target portion, when the coupling member rotates in the main rotation direction so that the engaging portion moves from a non-engaged position to an engaged position with respect to the engaged portion, a portion of the encoder rotating body between two adjacent count target portions reaches the detection position, A rear detected portion located at the rear end in the main rotation direction among the plurality of detected portions in each of the count target portions is formed longer in the circumferential direction than the other detected portions, The counting unit resets the count number of the pulse signal when the pulse signal having a width exceeding a predetermined reset width is output from the detection sensor while the drive device is performing the main drive operation.

2. 2. The sheet supplying device according to claim 1, wherein the counting unit records a count number of the pulse signal in a non-volatile memory device, and when the drive device performs the main drive operation after the counting unit is started, starts counting the pulse signal with the count number recorded in the non-volatile memory device as an initial value.

3. 3. The sheet supplying device according to claim 1, wherein the count target portions are arranged in the circumferential direction at a pitch greater than a maximum rotation angle allowed for the link member.

4. The link member is A shaft portion disposed below the lift member and rotatably supported thereon; a support portion extending from the shaft portion in a direction intersecting an axial direction of the shaft portion, supporting the lift member from below and rotating in the main rotation direction in conjunction with the shaft portion to lift the lift member; the engaged portion including one or more protruding portions formed by extending from a portion of the shaft portion toward one end along a direction intersecting the axial direction, The coupling member is a base portion that is disposed apart from the engaged portion in the axial direction and is driven to rotate; The lift device according to any one of claims 1 to 3, further comprising: the engaging portion including a plurality of protruding portions each formed to protrude from the base portion along the axial direction toward the engaged portion and arranged at intervals in the circumferential direction of the rotation of the base portion.

5. The lift device according to claim 1 , wherein the target state is a state in which an upper surface of an object placed on the lift member is located at a predetermined target position.

6. A lift device according to any one of claims 1 to 5; a sheet delivery mechanism that delivers the sheets stacked on the lift member of the lift device one by one to a transport path.

7. The sheet supplying device according to claim 6 ; a printing device that forms an image on the sheet fed by the sheet feeding device.

Images