Sheet transport device, image forming apparatus, sheet transport method

Abstract

The present invention provides a sheet transport device, an image forming device, and a sheet transport method that can simplify the device configuration while suppressing the load on the motors used in the paper feed roller and lift mechanism. [Solution] The sheet conveying device comprises a drive motor, a first transmission switching unit, a second transmission switching unit, and a conveying processing unit. The first transmission switching unit switches whether or not the driving force of the drive motor is transmitted to the paper feed roller, which feeds sheets stored in the sheet storage unit toward the conveying roller. The second transmission switching unit switches whether or not the driving force of the drive motor is transmitted to the lift mechanism, which raises the sheets stored in the sheet storage unit. The conveying processing unit, in a state where the driving force of the drive motor is not transmitted to the paper feed roller by the first transmission switching unit, switches the second transmission switching unit from a non-transmission state where the driving force of the drive motor is not transmitted to the lift mechanism to a transmission state where the driving force of the drive motor is transmitted to the lift mechanism.

Description

Technical Field

[0005]

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

Background Art

[0002] In a sheet conveying device provided in an image forming device, sheets placed on a sheet placement unit are fed in order from the top, and when the number of sheets placed on the sheet placement unit decreases, the sheet placement unit may be raised using a motor (see, for example, Patent Document 1). Further, in this type of sheet conveying device, one motor may be used as a drive source for both a paper feed roller used to feed sheets from the sheet placement unit and a lift mechanism that raises the sheet placement unit, thereby simplifying the device configuration. Specifically, the presence or absence of transmission of the driving force of the motor to the paper feed roller and the lift mechanism may be switched using a drive transmission unit such as an electromagnetic clutch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a configuration where the presence or absence of transmission of the driving force of the motor to the paper feed roller and the lift mechanism is switched using a drive transmission unit, depending on the switching timing, a large load may be applied to the motor, raising concerns about failures and lifespan.

[0005] An object of the present invention is to provide a sheet conveying device, an image forming device, and a sheet conveying method capable of simplifying the device configuration while suppressing the load on the motor used for the paper feed roller and the lift mechanism.

Means for Solving the Problems

[0006] A sheet transport device according to one aspect of the present invention comprises a drive motor, a first transmission switching unit, a second transmission switching unit, and a transport processing unit. The drive motor drives a transport roller that transports a sheet fed from a sheet storage unit toward an image forming unit that forms an image on the sheet. The first transmission switching unit switches whether or not the driving force of the drive motor is transmitted to a paper feed roller that feeds the sheet stored in the sheet storage unit toward the transport roller. The second transmission switching unit switches whether or not the driving force of the drive motor is transmitted to a lift mechanism that raises the sheet stored in the sheet storage unit. The transport processing unit, in a state where the driving force of the drive motor is not transmitted to the paper feed roller by the first transmission switching unit, switches the second transmission switching unit from a non-transmission state where the driving force of the drive motor is not transmitted to the lift mechanism to a transmission state where the driving force of the drive motor is transmitted to the lift mechanism.

[0007] An image forming apparatus according to another aspect of the present invention comprises a sheet transport device and an image forming unit that forms an image on a sheet transported by the sheet transport device.

[0008] Another aspect of the present invention relates to a sheet transport method, which is performed by one or more processors that control a sheet transport device. The sheet transport device comprises a drive motor, a first transmission switching unit, and a second transmission switching unit. The drive motor drives a transport roller that transports a sheet fed from a sheet storage unit toward an image forming unit that forms an image on the sheet. The first transmission switching unit switches whether or not the driving force of the drive motor is transmitted to a paper feed roller that feeds the sheet stored in the sheet storage unit toward the transport roller. The second transmission switching unit switches whether or not the driving force of the drive motor is transmitted to a lift mechanism that raises the sheet stored in the sheet storage unit. In the sheet transport method, the processor performs the step of switching the second transmission switching unit from a non-transmission state, where the driving force of the drive motor is not transmitted to the lift mechanism, to a transmission state, where the driving force of the drive motor is transmitted to the lift mechanism, while the driving force of the drive motor is not transmitted to the paper feed roller by the first transmission switching unit. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a sheet transport device, an image forming device, and a sheet transport method that can simplify the device configuration while suppressing the load on the motors used in the paper feed roller and lift mechanism. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] Figure 2 is a block diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 3] Figure 3 is a flowchart showing an example of the procedure for transport control processing performed in an image forming apparatus according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below with reference to the attached drawings. The following embodiments are examples that embody the present invention and do not limit the technical scope of the present invention.

[0012] As shown in Figures 1 and 2, the image forming apparatus 1 according to this embodiment includes an operation display unit 10, an ADF (Auto Document Feeder) 11, an image reading unit 12, an image forming unit 13, a sheet transport unit 14, a storage unit 15, a control unit 16, a paper feeding unit 22, a paper discharge unit 23, and the like. The image forming apparatus 1 may also include multiple paper feeding units 22 or paper discharge units 23.

[0013] Image forming apparatus 1 is a multifunction device having functions such as a printer, scanner, copier, and facsimile. The present invention is not limited to multifunction devices like image forming apparatus 1, but is applicable to any image forming apparatus such as a copier, printer, or facsimile machine. Furthermore, an apparatus comprising a sheet transport unit 14 and a control unit 16 is an example of a sheet transport apparatus according to the present invention.

[0014] The operation display unit 10 includes a display unit such as a liquid crystal display for displaying information, and an operation unit such as a touch panel for receiving user operations on the display unit. The ADF 11 is an automatic document transport device that transports documents to be read by the image reading unit 12, and includes a document setting unit, transport rollers, a document holder, and a paper output unit. The image reading unit 12 includes a document glass, a light source, a mirror, an optical lens, and a CCD (Charge Coupled Device). The image reading unit 12 then performs an image reading operation to read the image of a document transported by the ADF 11 or a document set on the document glass and output it as document data.

[0015] The image forming unit 13 performs an image forming operation in which it forms an image based on the original data on a sheet P transported from the paper feeding unit 22 by the sheet transport unit 14 using either an electrophotographic or inkjet method. Specifically, if the image forming unit 13 is an electrophotographic image forming unit, it includes a photoreceptor drum, a charger, an exposure device, a developing device, a transfer device, and a fixing device.

[0016] The sheet transport unit 14 includes a transport path 140, transport rollers 141, paper feed rollers 143, drive motor 151, paper feed clutch 152, lift clutch 153, lift sensor 154, sheet sensors 155-157, and the like.

[0017] The transport path 140 is used to guide the sheet P from the paper feeding unit 22 through the image forming unit 13 to the paper discharge unit 23. In the sheet transport unit 14, after the sheet P is transported from the paper feeding unit 22 to the image forming unit 13 via the transport path 140, the sheet P, after the image has been formed in the image forming unit 13, is transported to the paper discharge unit 23. Various electrical components provided in the sheet transport unit 14 are electrically connected to the control unit 16 via a drive circuit (not shown) and are controlled by the control unit 16.

[0018] The paper feeding unit 22 includes a sheet storage unit 220 for accommodating the sheet P on which the image is formed, a sheet placement unit 221, a lift member 222, and the like. In the paper feeding unit 22, the sheet storage unit 220 is provided to be removable or pull out. For example, the direction of removal or pull-out of the sheet storage unit 220 is the depth direction or left-right direction of the paper surface in Figure 2.

[0019] The sheet P, which will be housed inside the sheet storage section 220, is placed on the sheet placement section 221. The sheet placement section 221 is rotatably supported at one end opposite the transport path 140 by a pivot shaft 221A. The free end of the sheet placement section 221 on the transport path 140 side is supported by the bottom of the sheet storage section 220 before the sheet storage section 220 is mounted on the paper feeding section 22. When the sheet storage section 220 is mounted on the paper feeding section 22, the bottom of the sheet placement section 221 is supported by a lift member 222 provided on the paper feeding section 22. The lift member 222 is rotatably supported by a pivot shaft 222A.

[0020] The rotation shaft 222A is connected to the drive shaft of the drive motor 151 via the lift clutch 153 and gears (not shown). Then, when the rotation shaft 222A rotates and the lift member 222 rotates, the end on the conveyance path 140 side of the sheet placement portion 221 rises. In the present embodiment, a lift mechanism 230 for raising the sheet P accommodated in the sheet storage portion 220 is configured by the sheet placement portion 221, the lift member 222, the rotation shaft 222A, and the like. And the lift mechanism 230 is driven by the driving force transmitted from the drive motor 151 to the rotation shaft 222A.

[0021] Each of the conveyance rollers 14A is provided along the conveyance path 140 and is a pair of rollers that rotate by the driving force transmitted from the drive motor 151. For example, each of the conveyance rollers 141 includes a conveyance roller that conveys the sheet P from the paper feed portion 22 along the conveyance path 140 toward the image forming portion 13, and a conveyance roller that conveys the sheet P from the image forming portion 13 along the conveyance path 140 toward the paper discharge portion 23. Further, the conveyance roller 141 includes a registration roller 141A connected to the drive motor 151 via a drive transmission portion such as a clutch (not shown). And the image processing unit 161 described later controls the drive transmission portion to switch the presence or absence of the transmission of the driving force from the drive motor 151 to the registration roller 141A, and controls the timing of conveying the sheet P conveyed on the conveyance path 140 to the image forming portion 13.

[0022] The paper feed roller 143 is rotatably supported on the housing of the image forming apparatus 1 above the sheet storage portion 220. Further, the paper feed roller is biased downward by an elastic member (not shown), and is pressed against the sheet P when the uppermost sheet P placed on the sheet placement por tion 221 of the sheet storage portion 220 is at a predetermined position. And the paper feed roller 143 is connected to the drive shaft of the drive motor 151 via the paper feed clutch 152 and gears (not shown). Then, the paper feed roller 143 rotates by the driving force transmitted from the drive motor 151, and feeds the sheets P accommodated in the sheet storage portion 220 one by one in order toward the conveyance roller 141 on the conveyance path 140.

[0023] The drive motor 151 is a drive source used for driving the conveyance roller 141, the paper feed roller 143, and the lift mechanism 230. In this embodiment, the conveyance roller 141, the paper feed roller 143, and the lift mechanism 230 are driven by a single drive motor. However, in other embodiments, at least the paper feed roller 143 and the lift mechanism 230 may be driven by a single drive motor. That is, the conveyance roller 141 may be driven by a drive motor different from the paper feed roller 143 and the lift mechanism 230.

[0024] The paper feed clutch 152 is a first transmission switching unit that switches the presence or absence of the transmission of the driving force of the drive motor 151 to the paper feed roller 143 by being controlled by the control unit 16. Specifically, the paper feed clutch 152 is an electromagnetic clutch that can be switched between a transmission state in which the driving force of the drive motor 151 is transmitted to the paper feed roller 143 and a non-transmission state in which the driving force of the drive motor 151 is not transmitted to the paper feed roller 143.

[0025] The lift clutch 153 is a second transmission switching unit that switches the presence or absence of the transmission of the driving force of the drive motor 151 to the lift mechanism 230 by being controlled by the control unit 16. Specifically, the lift clutch 153 is an electromagnetic clutch that can be switched between a non-transmission state in which the driving force of the drive motor 151 is not transmitted to the lift mechanism 230 and a transmission state in which the driving force of the drive motor 151 is transmitted to the lift mechanism 230. More specifically, in this embodiment, the paper feed clutch 152 is a mechanical clutch in which the presence or absence of the transmission of the driving force is switched by switching the presence or absence of the engagement of gears depending on the presence or absence of energization.

[0026] The lift clutch 153 includes a ratchet mechanism that restricts rotation of the pivot shaft 222A in the opposite direction to the rotation direction driven by the drive motor 151. By restricting the rotation of the lift clutch 153 in the opposite direction, the rotation of the pivot shaft 222A engaged with the lift clutch 153 is also restricted in the opposite direction, thereby restricting the descent of the sheet mounting section 221 by its own weight. When the sheet storage section 220 is pulled out from the paper feeding section 22, the connection between the pivot shaft 222A and the lift clutch 153 is released. As a result, the restriction of the rotation of the pivot shaft 222A in the opposite direction by the lift clutch 153 is released, the sheet mounting section 221 descends by its own weight, and the lift member 222 also descends to a predetermined initial position.

[0027] Then, when the control unit 16 drives the drive motor 151 and the lift clutch 153 switches from a non-transmission state to a transmission state, the driving force of the drive motor 151 is transmitted to the pivot shaft 222A, causing the lift member 222 to rotate in a predetermined direction. As a result, the tilt angle of the seat mounting section 221 is changed by the lift member 222. Specifically, in Figure 1, when the lift member 222 rotates clockwise, the seat mounting section 221 rotates counterclockwise around the pivot shaft 221A and rises.

[0028] The lift sensor 154 detects when the sheet P in the sheet storage section 220 rises and the paper feed roller 143 is pressed upward. The lift sensor 154 is used to determine the timing for switching the lift clutch 153 from a transmission state to a non-transmission state (stopping the rise of the sheet placement section 221).

[0029] Specifically, when the sheet storage unit 220 is mounted on the paper feeding unit 22, the control unit 16 drives the drive motor 151 and switches the lift clutch 153 from a non-transmission state to a transmission state. As a result, the driving force of the drive motor 151 is transmitted to the pivot shaft 222A, and the sheet mounting unit 221 rises. Subsequently, when the lift sensor 154 detects that the paper feeding roller 143 has been pressed, the control unit 16 switches the lift clutch 153 from a transmission state to a non-transmission state. As a result, the transmission of the driving force of the drive motor 151 to the pivot shaft 222A is interrupted, and the rising of the sheet mounting unit 221 stops. When the uppermost sheet P of the sheet mounting unit 221 is pressed against the paper feeding roller 143 in this way, the sheet P becomes ready to be fed towards the transport path 140 by the drive of the paper feeding roller 143.

[0030] Furthermore, when the image forming unit 13 performs an image forming operation, the control unit 16 controls the sheet transport unit 14 and the paper feed unit 22 to transport the sheet P from the sheet storage unit 220 of the paper feed unit 22 to the image forming unit 13. When the image forming operation for one sheet P by the image forming unit 13 is completed, the control unit 16 also drives the drive motor 151 and switches the lift clutch 153 from a non-transmission state to a transmission state to raise the sheet feed unit 221 if the preset conditions for raising the sheet feed unit 221 are met. Subsequently, when the lift sensor 154 detects that the paper feed roller 143 has been pressed, the control unit 16 switches the lift clutch 153 from a transmission state to a non-transmission state. This cuts off the transmission of the driving force of the drive motor 151 to the rotating shaft 222A, and the raising of the sheet feed unit 221 stops.

[0031] The sheet sensors 155 to 157 are sheet detection units that detect the presence or absence of an object such as sheet P at their respective placement locations. For example, sheet sensors 155 to 157 are optical sensors equipped with a light-emitting unit and a light-receiving unit. Alternatively, sheet sensors 155 to 157 may use contact-type switches. The detection results of the presence or absence of sheet P by each of the sheet sensors 155 to 157 are input to the control unit 16 and used for detecting the position of sheet P or for JAM detection.

[0032] Specifically, the sheet sensor 155 is located between the paper feed roller 143 and the transport roller 141, and is positioned to detect the sheet P being fed from the paper feed roller 143. The sheet sensor 156 is located at one or more positions in the transport path 140, and is positioned to detect the sheet P passing through the transport path 140. The sheet sensor 157 is located between the image forming unit 13 and the paper discharge unit 23, and is positioned to detect the sheet P being discharged into the paper discharge unit 23.

[0033] The memory unit 15 is a non-volatile memory unit, such as a hard disk. For example, the memory unit 15 stores an image forming program that causes the control unit 16 to perform various processes, such as the image forming process described later.

[0034] The control unit 16 is a computer system equipped with a CPU, ROM, and RAM, and controls the operation of the image forming apparatus 1. The CPU is a processor that performs various arithmetic operations. The ROM is a non-volatile storage unit in which information such as control programs for causing the CPU to perform various operations is stored in advance. The RAM is a volatile or non-volatile storage unit used as a temporary storage memory (work area) for various operations performed by the CPU.

[0035] However, in a configuration where the transmission of motor power to the paper feed roller and lift mechanism is switched using a drive transmission unit, depending on the timing of the switch, a large load may be placed on the motor, raising concerns about malfunction or impact on its lifespan. In contrast, as explained below, the image forming apparatus 1 makes it possible to simplify the apparatus configuration while suppressing the load on the motors used in the paper feed roller and lift mechanism.

[0036] Specifically, in the image forming apparatus 1 according to this embodiment, as shown in Figure 2, the control unit 16 includes various processing units such as an image processing unit 161 and a transport processing unit 162. The control unit 16 functions as the various processing units by executing various processes according to the image forming program stored in the storage unit 15. The control unit 16 may also include one or more electronic circuits that realize some or all of the functions of the various processing units. Furthermore, the control unit 16 may include multiple processors, and each of these processors may execute various processes, thereby functioning as the various processing units.

[0037] The image processing unit 161 controls the image forming unit 13 and can perform image forming processing to print images corresponding to original data input from an external device such as a personal computer or original data stored in the storage unit 15 onto a sheet. The image processing unit 161 also controls the image reading unit 12 and can perform image reading processing to read images from originals set on the document glass or ADF 11, etc.

[0038] The transport processing unit 162 controls the transport of the sheet P on which an image is formed in the image forming process by controlling the drive motor 151, the paper feed clutch 152, the lift clutch 153, and the like. In particular, the transport processing unit 162 switches the lift clutch 153 from a non-transmission state to a transmission state when the driving force of the drive motor 151 is not transmitted to the paper feed roller 143 by the paper feed clutch 152. In other words, the transport processing unit 162 restricts the switching of the lift clutch 153 from a non-transmission state to a transmission state when the driving force of the drive motor 151 is transmitted to the paper feed roller 143 by the paper feed clutch 152. That is, the transport processing unit 162 does not create a state in which the driving force of the drive motor 151 is transmitted to both the paper feed roller 143 and the lift mechanism 230.

[0039] [Transport control processing] The following describes an example of the procedure for transport control processing executed by the control unit 16 in accordance with the image forming program, with reference to Figure 3. Here, steps S11, S12, ... represent the numbers of the processing procedures (steps) executed by the control unit 16. Note that each processing procedure in the transport control processing may be executed in parallel to the extent that similar processing results can be obtained.

[0040] The transport control process is performed by the transport processing unit 162 when a print job execution request based on original data is generated in the image forming apparatus 1 and the image forming process is executed by the image processing unit 161. The present invention may also be considered as a sheet transport method in which a processor such as the control unit 16 transports the sheet P by executing one or more steps in the transport control process.

[0041] <Step S11> In step S11, the transport processing unit 162 starts the drive of the drive motor 151, thereby starting the rotation of each of the transport rollers 141. At this time, the transport processing unit 162 does not drive the paper feed clutch 152 and the lift clutch 153. The paper feed clutch 152 is in a non-transmission state where the paper feed rollers 143 are not driven, and the lift clutch 153 is in a non-transmission state where the lift mechanism 230 is not driven. The timing for starting the drive of the drive motor 151 may be as described in step S13 below.

[0042] <Step S12> In step S12, the transport processing unit 162 determines whether or not the paper feeding timing to start the paper feeding operation has arrived. Specifically, the transport processing unit 162 determines that the paper feeding timing has arrived when the preset sheet transport start timing in the image forming process executed by the image processing unit 161 has arrived. If it is determined that the paper feeding timing has arrived (S12:Yes), the process moves to step S13, and if it is determined that the paper feeding timing has arrived (S12:No), the process waits in step S12.

[0043] <Step S13> In step S13, the transport processing unit 162 switches the paper feed clutch 152 from a non-transmission state to a transmission state. As a result, the driving force of the drive motor 151 is transmitted to the paper feed roller 143 via the paper feed clutch 152, and the feeding of sheets P into the sheet storage unit 220 by the paper feed roller 143 begins.

[0044] <Step S14> In step S14, the transport processing unit 162 determines whether it is time to terminate the paper feeding operation. Specifically, the transport processing unit 162 determines that it is time to terminate the paper feeding operation when the sheet P is detected by the sheet sensor 155 and then the sheet P is no longer detected by the sheet P. Alternatively, the transport processing unit 162 may determine that it is time to terminate the paper feeding operation when a paper feeding time, which is set in advance according to the size of the sheet P, has elapsed since the start of feeding the sheet P in step S13.

[0045] <Step S15> In step S15, the transport processing unit 162 switches the paper feed clutch 152 from a transmission state to a non-transmission state. As a result, the driving force of the drive motor 151 is no longer transmitted to the paper feed roller 143 via the paper feed clutch 152, and the paper feed roller 143 stops.

[0046] However, even when the paper feed clutch 152 is switched to a non-transmission state, the transmission of the driving force of the drive motor 151 to the paper feed roller 143 is not immediately interrupted, and there may be a period of time during which the transmission of the driving force of the drive motor 151 to the paper feed roller 143 continues. The time lag from when the paper feed clutch 152 is switched to a non-transmission state until the driving force of the drive motor 151 is no longer transmitted to the paper feed roller 143 can be known or estimated in advance depending on the specifications or type of the paper feed clutch 152. In the image forming apparatus 1, a time corresponding to the aforementioned time lag is set as a specific time and is used as the waiting time for processing in step S17 described later. For example, the aforementioned time lag includes the response time from when the power supply to the paper feed clutch 152 is stopped by the transport processing unit 162 until the paper feed clutch 152 is switched from a transmission state to a non-transmission state. Furthermore, in the case where the paper feed clutch 152 is a mechanical clutch that switches between transmitting driving force depending on whether or not the gears are engaged, as in this embodiment, the time lag includes the time it takes for the gears of the paper feed clutch 152 to separate and disengage.

[0047] <Step S16> In step S16, the transport processing unit 162 determines whether or not it is necessary to drive the lift mechanism 230. Specifically, the transport processing unit 162 determines that it is not necessary to drive the lift mechanism 230 if the lift sensor 154 detects that the paper feed roller 143 is being pressed upward. Conversely, the transport processing unit 162 determines that it is necessary to drive the lift mechanism 230 if the lift sensor 154 does not detect that the paper feed roller 143 is being pressed upward. If it is determined that it is necessary to drive the lift mechanism 230 (S16: Yes), the process proceeds to step S17, and if it is determined that it is not necessary to drive the lift mechanism 230 (S16: No), the process proceeds to step S21. The transport processing unit 162 may also determine that it is necessary to drive the lift mechanism 230 when a preset number of sheets P have been fed from the sheet storage unit 220.

[0048] <Step S17> In step S17, the transport processing unit 162 starts timing the predetermined specific time, and after the elapsed time, proceeds to step S18. As a result, the switching of the lift clutch 153 in step S18, described later, is performed at least after the specified time has elapsed since the paper feed clutch 152 was switched to the non-transmission state in step S15. In other embodiments, instead of waiting for the specified time, the process may proceed to step S18 if the driving force of the drive motor 151 is no longer transmitted to the paper feed roller 143, based on the detection result from the detection unit that detects whether or not the paper feed roller 143 is rotating, and the paper feed roller 143 is stopped.

[0049] <Step S18> In step S18, the transport processing unit 162 starts driving the lift mechanism 230 by switching the lift clutch 153 from a non-transmission state to a transmission state. That is, the driving force of the drive motor 151 is transmitted to the pivot shaft 222A of the lift mechanism 230 via the lift clutch 153, and the lift mechanism 230 is driven and the sheet P begins to rise. In other embodiments, in steps S17 to S18, the transport processing unit 162 may start driving the lift mechanism 230 by switching the lift clutch 153 from a non-transmission state to a transmission state at a timing after a predetermined time has elapsed for a specific time or longer from the timing of the start of driving of the register roller 141A.

[0050] <Step S19> In step S19, the transport processing unit 162 determines whether or not to terminate the drive of the lift mechanism 230. Specifically, the transport processing unit 162 determines not to terminate the drive of the lift mechanism 230 until the lift sensor 154 detects that the paper feed roller 143 has been pressed upward. The transport processing unit 162 also determines to terminate the drive of the lift mechanism 230 when the lift sensor 154 detects that the paper feed roller 143 has been pressed upward. If it is determined that the drive of the lift mechanism 230 should be terminated (S19: Yes), the process moves to step S20, and if it is determined that the drive of the lift mechanism 230 should be terminated (S19: No), the process waits in step S19.

[0051] Furthermore, in step S19, the transport processing unit 162 may decide to terminate the drive of the lift mechanism 230 after a preset lifting time has elapsed since the drive of the lift mechanism 230 was started in step S18 (S19: Yes). This makes it possible to omit the lift sensor 154 in the image forming apparatus 1. In this case, the transport processing unit 162 may set the lifting time based on either the rotational speed of the drive motor 151 or the thickness of the sheet P housed in the sheet housing section 220, or both.

[0052] Specifically, the conveying unit 162 may change the rotation speed of the drive motor 151 according to the thickness of the sheet P being conveyed by the conveying roller 141. When the rotation speed of the drive motor 151 changes in this way, the rotation speed of the pivot shaft 222A in the lift mechanism 230 also changes. Therefore, the conveying unit 162 may set the lifting time shorter when the rotation speed of the drive motor 151 is faster, and longer when the rotation speed of the drive motor 151 is slower. This makes it possible to keep the amount of lifting of the sheet P by the lift mechanism 230 during the lifting time the same, even when the rotation speed of the drive motor 151 changes.

[0053] Furthermore, the time it takes for the sheet P placed on the top of the sheet placement section 221 to press against the paper feed roller 143 due to the drive of the lift mechanism 230 varies depending on the thickness of the sheet P stored in the sheet storage section 220. For this reason, the transport processing unit 162 can set the lifting time shorter when the thickness of the sheet P stored in the sheet storage section 220 is thin, and longer when the thickness of the sheet P stored in the sheet storage section 220 is thick. This makes it possible to make the amount of lifting of the sheet P by the lift mechanism 230 during the lifting time the same, even if the thickness of the sheet P stored in the sheet storage section 220 is different. The thickness of the sheet P stored in the sheet storage section 220 is set according to the sheet type (plain paper, cardboard, etc.) selected in the initial settings of the image forming apparatus 1, for example.

[0054] Here, we have described a case in which the lifting time is appropriately set as the time during which the lift mechanism 230 is driven. On the other hand, in other embodiments, in the image forming apparatus 1, the start timing of the image forming process for each sheet P performed by the image processing unit 161, or the start timing of the transport of each sheet P, may be determined based on either the rotational speed of the drive motor 151 or the thickness of the sheet P housed in the sheet housing unit 220, or both. Specifically, the image processing unit 161 may determine the timing for starting the image forming process for the next sheet P after the image forming process for one sheet P has been completed, based on either the rotational speed of the drive motor 151 or the thickness of the sheet P housed in the sheet housing unit 220, or both. For example, if the image forming unit 13 is an electrophotographic image forming unit, the timing for starting the image forming process for the next sheet P is the timing for starting the process of forming an electrostatic latent image on the photoreceptor drum corresponding to the image to be formed on that sheet P.

[0055] <Step S20> In step S20, the transport processing unit 162 stops the drive of the lift mechanism 230 by switching the lift clutch 153 from a transmission state to a non-transmission state. That is, the driving force of the drive motor 151 is no longer transmitted to the pivot shaft 222A via the lift clutch 153, the drive of the lift mechanism 230 stops, and the upward movement of the seat P stops.

[0056] <Step S21> In step S21, the transport processing unit 162 determines whether the sheet P, which is the target of the image forming process, has been ejected to the paper ejection unit 23. Specifically, the transport processing unit 162 determines that the sheet P has been ejected when a preset time has elapsed from the time the sheet P is detected by the sheet sensor 157 until the sheet sensor 157 stops detecting it. Alternatively, the transport processing unit 162 may determine that the sheet P has been ejected when a preset time has elapsed from the time the feeding of the sheet P from the sheet storage unit 220 begins. If it is determined that the sheet P has been ejected (S21:Yes), the process moves to step S22, and if it is determined that the sheet P has been ejected (S21:No), the process waits in step S21.

[0057] <Step S22> In step S22, the transport processing unit 162 determines whether the print job has finished. Specifically, if the print job includes image forming operations on multiple sheets P, the print job is determined to be finished when the image forming operations on all sheets P have finished. If it is determined that the print job has finished (S22:Yes), the process moves to step S23; if it is determined that the print job has not finished (S22:No), the process returns to step S12.

[0058] <Step S23> In step S23, the transport processing unit 162 stops the drive of the drive motor 151, thereby stopping the rotation of each of the transport rollers 141.

[0059] As explained above, in the image forming apparatus 1, the drive motor 151 drives the lift mechanism 230 while the transmission of driving force from the same drive motor 151 to the paper feed roller 143 is interrupted. Therefore, compared to the case where the paper feed roller 143 and the lift mechanism 230 are driven simultaneously, a sudden increase in load on the drive motor 151 is suppressed, thereby suppressing damage or failure of the drive motor 151 and extending its lifespan.

[0060] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0061] <Note 1> A drive motor drives a transport roller that transports a sheet fed from a sheet storage unit toward an image forming unit that forms an image on the sheet, A first transmission switching unit that switches whether or not the driving force of the drive motor is transmitted to the paper feed roller that feeds the sheets stored in the sheet storage unit toward the transport roller, A second transmission switching unit that switches whether or not the driving force of the drive motor is transmitted to the lift mechanism that raises the seat housed in the seat housing section, A transport processing unit that, in a state where the driving force of the drive motor is not transmitted to the paper feed roller by the first transmission switching unit, switches the second transmission switching unit from a non-transmission state where the driving force of the drive motor is not transmitted to the lift mechanism to a transmission state where the driving force of the drive motor is transmitted to the lift mechanism, A sheet conveying device equipped with the following features.

[0062] <Note 2> The transport processing unit switches the first transmission switching unit from a transmission state in which the driving force of the drive motor is transmitted to the paper feed roller to a non-transmission state in which the driving force of the drive motor is not transmitted to the paper feed roller, to a transmission state in which a specific time predetermined as the time until the driving force of the drive motor is no longer transmitted to the paper feed roller, and then switches the second transmission switching unit to a transmission state. The sheet transport device described in Appendix 1.

[0063] <Note 3> The transport processing unit switches the second transmission switching unit to the transmission state, and then switches the second transmission switching unit to the non-transmission state after a preset rising time has elapsed. A sheet conveying device as described in Appendix 1 or 2.

[0064] <Note 4> The transport processing unit sets the lifting time based on either the rotational speed of the drive motor or the thickness of the sheet stored in the sheet storage section, or both. The sheet transport device described in Appendix 3.

[0065] <Note 5> The transport processing unit sets the lifting time to be shorter as the rotation speed of the drive motor increases. The sheet transport device described in Appendix 4.

[0066] <Note 6> The transport processing unit sets the lifting time to be shorter the thinner the sheet stored in the sheet storage section. The sheet transport device described in Appendix 4.

[0067] <Note 7> A sheet transport device as described in any of Appendix 1 to 6, An image forming unit that forms an image on a sheet conveyed by the sheet conveying device, An image forming apparatus comprising:

[0068] <Note 8> A sheet transport device comprising: a drive motor that drives a transport roller that transports a sheet fed from a sheet storage section toward an image forming section that forms an image on the sheet; a first transmission switching unit that switches whether or not the driving force of the drive motor is transmitted to a paper feed roller that feeds the sheet stored in the sheet storage section toward the transport roller; and a second transmission switching unit that switches whether or not the driving force of the drive motor is transmitted to a lift mechanism that raises the sheet stored in the sheet storage section, is controlled by one or more processors, A sheet transport method comprising the step of switching the second transmission switching unit to a state in which the driving force of the drive motor is transmitted to the lift mechanism, while the driving force of the drive motor is not transmitted to the paper feed roller by the first transmission switching unit. [Explanation of Symbols]

[0069] 1. Image forming apparatus 13 Image forming unit 14 Sheet transport section 15 Storage section 151 Drive motor 152 Paper feed clutch 153 Lift Clutch 154 Lift Sensor 155 Seat Sensor 156 Seat Sensor 157 Seat Sensor 16 Control Unit 161 Image Processing Unit 162 Conveying Processing Unit 230 Lift mechanism

Claims

1. A drive motor drives a transport roller that transports a sheet fed from a sheet storage unit toward an image forming unit that forms an image on the sheet, A first transmission switching unit switches whether or not the driving force of the drive motor is transmitted to the paper feed roller that feeds the sheets stored in the sheet storage unit toward the transport roller, A second transmission switching unit that switches whether or not the driving force of the drive motor is transmitted to the lift mechanism that raises the seat housed in the seat housing section, A transport processing unit that, in a state where the driving force of the drive motor is not transmitted to the paper feed roller by the first transmission switching unit, switches the second transmission switching unit from a non-transmission state where the driving force of the drive motor is not transmitted to the lift mechanism to a transmission state where the driving force of the drive motor is transmitted to the lift mechanism, A sheet conveying device equipped with the following features.

2. The transport processing unit switches the second transmission switching unit to the transmission state after a specific time has elapsed, which is the time from when the driving force of the drive motor is transmitted to the paper feed roller until the driving force of the drive motor is no longer transmitted to the paper feed roller, after the first transmission switching unit has been switched from a transmission state where the driving force of the drive motor is transmitted to the paper feed roller to a non-transmission state where the driving force of the drive motor is not transmitted to the paper feed roller. The sheet conveying device according to claim 1.

3. The transport processing unit switches the second transmission switching unit to the transmission state, and then switches the second transmission switching unit to the non-transmission state after a preset rising time has elapsed. The sheet conveying device according to claim 1.

4. The transport processing unit sets the lifting time based on either the rotational speed of the drive motor or the thickness of the sheet stored in the sheet storage section, or both. The sheet conveying device according to claim 3.

5. The transport processing unit sets the lifting time to be shorter as the rotation speed of the drive motor increases. The sheet conveying device according to claim 4.

6. The transport processing unit sets the lifting time to be shorter the thinner the sheet stored in the sheet storage section. The sheet conveying device according to claim 4.

7. A sheet conveying device according to any one of claims 1 to 6, An image forming unit that forms an image on a sheet conveyed by the sheet conveying device, An image forming apparatus comprising:

8. A sheet transport device comprising: a drive motor that drives a transport roller that transports a sheet fed from a sheet storage section toward an image forming section that forms an image on the sheet; a first transmission switching unit that switches whether or not the driving force of the drive motor is transmitted to a paper feed roller that feeds the sheet stored in the sheet storage section toward the transport roller; and a second transmission switching unit that switches whether or not the driving force of the drive motor is transmitted to a lift mechanism that raises the sheet stored in the sheet storage section, is controlled by one or more processors, A sheet transport method comprising the step of switching the second transmission switching unit to a state in which the driving force of the drive motor is transmitted to the lift mechanism, while the driving force of the drive motor is not transmitted to the paper feed roller by the first transmission switching unit.

Images