Feeding device and image forming device

Abstract

To eliminate delay in starting the drive of a roller for conveying a sheet.SOLUTION: A feeding device of the present invention separates sheets one by one from the uppermost layer of a sheet bundle set in a feeding tray using rollers and feeds them downstream, in which the rollers (feed roller 8, separation roller 9) are connected to a drive shaft via a one-way clutch, and the drive shaft is pre-rotated before rotating to start feeding the sheets.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a feeding device and an image forming apparatus. [Background technology]

[0002] The image forming apparatus is equipped with a feeding device (e.g., paper feeder) that picks up sheets (e.g., paper) one by one from the top layer of a sheet stack (e.g., a paper stack) set in a feeding tray and feeds (e.g., feeds) them to an image forming section. In the FRR feeding method and RF feeding method, this feeding device has a pickup roller that contacts the top sheet of the sheet stack to pick up the sheet, and a feeding roller and a separation roller that separate the picked sheets one by one.

[0003] The sheets separated one by one at the nip between the feed roller and separation roller are transported to the downstream transport roller by the drive of the feed roller and separation roller. The pickup roller and feed roller are stopped after the sheet is sent to the transport roller, and then the sheet is transported further downstream by the drive of the transport roller.

[0004] Even if the pickup roller and the feed roller are stopped, they continue to rotate together with the sheet being conveyed by the conveyance rollers. This co-rotation is to prevent the downstream conveyance rollers from impeding the sheet conveyance, and one-way clutches that enable the co-rotation are provided on the drive shafts of the pickup roller and the feed roller. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] When the pickup roller and feed roller rotate together, the one-way clutch is disengaged. Therefore, when the pickup roller and feed roller are next driven, a delay angle (also called backlash) occurs before the one-way clutch is connected (engaged) in the locking direction. The start of the next drive of the pickup roller and feed roller is delayed by the amount of this delay angle.

[0006] The delay in starting drive is also caused by the following factors 1) to 3) other than the delay angle of the one-way clutch. 1) Backlash in the drive gear train of the pickup roller and feed roller 2) Play between the feed roller drive shaft and the coupling 3) Play between the pickup roller and the coupling that drives it

[0007] Therefore, there is a possibility that the start of driving the pickup roller and the feed roller may be delayed further, which poses a problem that the pickup roller and the feed roller cannot be driven until the drive shaft has rotated a certain amount.

[0008] SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to eliminate the delay in starting the drive of the rollers that transport the sheet. [Means for solving the problem]

[0009] To achieve the above object, the feeding device of the present invention separates sheets one by one from the top layer of a sheet stack set in a feeding tray using a roller and feeds them downstream, and is characterized in that the roller is connected to a drive shaft via a one-way clutch, and the drive shaft is pre-rotated before rotating the drive shaft to start feeding. [Effects of the Invention]

[0010] According to the present invention, it is possible to eliminate the delay in starting the drive of the rollers that transport the sheet. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a paper feeder according to an embodiment of the present invention; [Figure 3] FIG. 2 is a perspective view showing a drive gear train for a pickup roller and a feed roller. [Figure 4]FIG. 2 is a perspective view of a pickup roller and a feeding roller. [Figure 5] FIG. 2 is a diagram illustrating a paper feeding state of the paper feeding device. [Figure 6] 1A and 1B are cross-sectional views of a one-way clutch when engaged and when idling, respectively. [Figure 7] FIG. 2 is a block diagram showing a hardware configuration of a control unit of the image forming apparatus. [Figure 8] 1A is a diagram illustrating a state of a feed roller and a pickup roller at the start of rotation in the conventional method, and FIG. 1B is a diagram illustrating the elimination of a delay in connection by pre-rotation in this embodiment. [Figure 9] 1A is a diagram illustrating a state of a feed roller and a pickup roller at the start of rotation in the conventional method, and FIG. 1B is a diagram illustrating the elimination of a delay in connection by pre-rotation in this embodiment. [Figure 10A] FIG. 10 is a flowchart showing the control of pre-rotation performed by a control unit of the image forming apparatus. [Figure 10B] FIG. 10 is a flowchart showing the control of pre-rotation performed by a control unit of the image forming apparatus. [Figure 10C] FIG. 10 is a flowchart showing the control of pre-rotation performed by a control unit of the image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0012] Image forming equipment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an image forming apparatus equipped with a feeding device (hereinafter referred to as a paper feeding device) according to this embodiment. Here, the term "image forming apparatus" refers to an apparatus that forms an image by applying toner or ink as a developer to a sheet, which is a recording medium on which an image is recorded. Furthermore, "image formation" refers not only to applying meaningful images, such as characters or figures, to a recording medium, but also to applying meaningless images, such as patterns, to a recording medium. Furthermore, the term "sheet" refers to a recording medium or original to which a developer or ink can be applied, including not only paper (paper) but also transparencies and fabrics. Furthermore, "paper" includes not only plain paper, but also cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, and the like. In the following embodiments, sheets will be described as "paper" and developers will be described as "toner." Furthermore, the materials, shapes, and relative positions of each component are merely examples and are not intended to limit the scope of the present invention unless otherwise specified.

[0013] In Figure 1, symbol 1 is an image forming apparatus (machine) such as a copier, symbol 2 is a paper feed device, symbol 3 is a feed tray (hereinafter referred to as paper feed tray) that stores multiple sheets (hereinafter referred to as paper), symbol 4 is paper to be fed and transported, symbol 5 is an FRR paper feed unit using the FRR paper feed method, symbol 6 is a vertical transport unit (transport path) between the paper feed and relay rollers, symbol 7 is a pickup roller that feeds paper, symbol 8 is a feed roller that feeds paper one sheet at a time, symbol 9 is a separation roller that rotates forward and backward and has a function to prevent double feeding, symbol 10 is a paper feed sensor that detects paper immediately after feeding, symbol 11 is a vertical transport roller in the vertical transport unit 6, symbol 12 is a vertical transport sensor that turns ON when it detects paper in the vertical transport unit 6, and symbol 21 is a height sensor that detects the height of the top surface of the paper 4. The paper feed sensor 10, the vertical transport sensor 12, and the height sensor 21 may be optical sensors such as reflective photointerrupters in which a light emitting element and a light receiving element are integrated.

[0014] 1, reference numeral 13 denotes a relay roller that transports paper to the registration roller unit 16, reference numeral 14 denotes a relay sensor that detects paper that has reached the relay roller 13, reference numeral 15 denotes a registration sensor that is disposed immediately before the registration roller unit 16 and detects the leading edge of the paper, reference numeral 16 denotes a registration roller unit that transports paper in sync with the image on the photosensitive member 18, reference numeral 17 denotes a transfer unit that transfers the image on the photosensitive member 18 to the paper and transports it, and reference numeral 18 denotes a photosensitive member that forms an electrostatic latent image. Note that FIG. 1 illustrates an image forming apparatus that forms images by an electrophotographic method, and an imaging device that forms a toner image on the photosensitive member 18 is omitted.

[0015] The toner image transferred onto the paper by the transfer unit 17 is fixed to the paper by a fixing device (pair of fixing rollers) 19. After the toner image has been fixed, the paper is discharged by a pair of paper discharge rollers 25 to a paper stacking unit such as a paper discharge tray (not shown).

[0016] In the following embodiments, an electrophotographic printer is used as the image forming apparatus, but the image forming apparatus is not limited to this and may be any of a copying machine, a facsimile machine, a printing machine, and an inkjet recording apparatus.

[0017] The FRR paper feed system, an abbreviation for Feed Reverse Roller, is a paper feed system that has a pickup roller 7, a feed roller 8, and a separation roller 9 that has a built-in torque limiter and rotates forward (paper feed direction) and reverse (return direction) to prevent double feeding. In other words, in the FRR paper feed system, the feed roller 8 and separation roller 9 normally rotate together in the paper feed direction, but if two or more sheets of paper enter the nip between the two rollers, the separation roller 9 rotates in the reverse direction to return the second and subsequent sheets. The surface of each roller is made of a rubber material with a high friction coefficient and high durability.

[0018] 1 has a three-tiered paper feed tray 3 below the image forming unit. In this embodiment, an example will be described in which paper is fed from the third tier paper feed portion.

[0019] The paper 4 loaded on the third-level paper feed tray 3 passes through the third-level FRR paper feed unit 5 and transport unit 6, and reaches the registration roller unit 16, where it temporarily stops. When the registration roller unit 16 stops, the paper stops in a slightly over-fed state at its nip, and after the required registration adjustment work (alignment with the image on the photoreceptor 18, skew correction), the registration roller unit 16 restarts and the paper begins to be transported again. The toner image is then transferred onto the paper 4, and after being fixed by the action of heat and pressure, the paper is ejected from the machine.

[0020] The following describes in detail the paper transport from the paper feed unit to the transport unit. Figure 2 is an explanatory diagram showing the paper feed and transport path from the third paper feed tray 3 to the registration roller unit 16 in Figure 1, and the configuration of the first and second stages is omitted.

[0021] In Fig. 2, elements in the third row have a C suffixed to their reference numerals, elements in the first row have an A suffix, and elements in the second row have a B suffixed. In Fig. 2, reference numeral 10C is a paper feed sensor, reference numeral 20C is a stepping motor, reference numeral 21C is a solenoid for separating (depressurizing) separation roller 9 from feed roller 8, reference numeral 22C is a bottom plate lifting motor for lifting the bottom plate of paper feed tray 3, reference numeral 23C is a height sensor for detecting the position (paper surface position) of pickup roller 7, and reference numeral 24C is a solenoid for separating pickup roller 7 from the paper surface.

[0022] ●Paper feeder As shown in Figures 3 to 5, the paper feeding device 2 includes a pickup roller 7 that comes into contact with the top surface of the paper stacked on the paper feed tray 3 and is driven to rotate in the paper feed direction (counterclockwise) to pick up the topmost paper, a feed roller 8 that is located downstream of the pickup roller 7 and is driven to rotate in the paper feed direction (counterclockwise) to feed the paper further downstream, a separation roller 9 that comes into contact with the feed roller 8 on its outer surface and is driven to rotate in the return direction (clockwise) to separate double-fed paper in cooperation with the feed roller 8, and a torque limiter TL that limits the driving force in the return direction transmitted to the separation roller 9.

[0023] In this embodiment, a common motor M transmits a rotational driving force in the paper feed direction to the feed roller 8. As will be described later, there are two driving force transmission paths from the common motor M, and different driving force transmission paths are activated during paper feeding and non-feeding to drive the feed roller 8 and / or separation roller 9.

[0024] The two drive force transmission paths are comprised of a drive force transmission path on the feed roller side and a drive force transmission path on the separation roller side. The feed roller side drive force transmission path includes a common motor M, a feed roller side gear 52 that meshes with and is driven by an output gear 51 of the common motor M, a feed roller shaft 53 that is inserted through an axis 52a of the feed roller side gear 52 so as to be relatively rotatable, a feed roller 8 whose axis is fixed to the feed roller shaft 53, and a feed roller side one-way clutch 54 that is disposed between the axis 52a of the feed roller side gear 52 and the feed roller shaft 53 and that transmits only the drive force in the paper feed direction from the common motor M to the feed roller shaft 53.

[0025] The feed roller side one-way clutch 54 cancels the driving force in the direction opposite to the paper feed direction (return direction) and rotates freely, not transmitting it to the feed roller shaft 53. The separation roller side driving force transmission path includes the common motor M, a first separation roller side gear 61 meshing with the feed roller side gear 52, a first separation roller shaft 63 inserted into an axis 61a of the first separation roller side gear 61 via the separation roller side one-way clutch 62, a first transmission gear 66 whose axis is integrally supported by the first separation roller shaft 63, a second separation roller shaft 67 whose axis is integrated with the axis of the separation roller 9, and a second transmission gear 68 whose axis is fixed to the second separation roller shaft 67 and meshes with the first transmission gear 66.

[0026] The separation roller side one-way clutch 62 transmits only the driving force in the return direction from the common motor M to the first separation roller shaft 63, and cancels and does not transmit the driving force in the paper feed direction.

[0027] In the above configuration, the paper sheets loaded on the paper feed tray 3 are fed one by one by the paper feeder 2, and are sent to the transfer unit at a predetermined timing so that the registration roller unit 16 can align the paper sheets with the image on the photosensitive drum. The paper feeder 2 separates the top of the stacked paper sheets and sends them to the lower transport path.

[0028] The pickup roller 7 rotates in contact with the surface of the top layer of the stack of sheets (paper stack) until the leading edge of the fed paper reaches the nip between the feed roller 8 and the separation roller 9, and then is separated from the paper surface by the solenoid 24C or the like. If the pickup roller 7 continues to contact the top surface of the paper and apply a feeding force to the paper, the separation ability of the separation roller 9 decreases, making it more likely that double feeding will occur.

[0029] As shown in Fig. 5(a), the feed roller 8 is driven to rotate in the direction of the arrow in the figure, and the paper is separated into individual sheets by the separation roller 9 and sent to the vertical transport roller 11. Then, as shown in Fig. 5(b), after the paper reaches the vertical transport roller 11, the motor that drives the feed roller 8 is turned off, and the paper is pulled out from the feed roller 8 and separation roller 9 by the vertical transport roller 11. At this time, the feed roller 8 is not driven, and is provided so that it can rotate in the direction of the arrow in the figure by the torque limiter 54, so that it rotates along with the transport of the paper.

[0030] A driving force in the direction opposite to the paper feed direction is applied to the second separation roller shaft 67 of the separation roller 9 via the torque limiter TL. The driving force in the return direction applied to the separation roller 9 helps to prevent double feeding when two or more sheets of paper are caught in the nip between the feed roller 8 and separation roller 9 during paper feed.

[0031] As the feeding roller side one-way clutch 54 and the separation roller side one-way clutch 62, for example, one of the following two one-way clutches can be used. Needle bearing one-way clutch

[0032] Figure 6 is a schematic diagram of a small roller-type one-way clutch CL with a cam surface formed on the inner diameter surface of the outer ring. When shaft 53 attempts to rotate clockwise relative to outer ring OUT as shown in Figure 6(a), the spring action of spring SP causes roller R to move to the meshing position of the outer ring cam surface, and the wedge action between the outer ring cam surface and shaft 53 drives outer ring OUT clockwise. When outer ring OUT rotates clockwise relative to shaft 53 as shown in Figure 6(b), shaft 53 rotates counterclockwise relative to outer ring OUT, roller R moves away from the outer ring cam surface, and outer ring OUT spins freely relative to shaft 53.

[0033] ●Spring type one-way clutch A spring-type one-way clutch is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-28600. When this spring-type one-way clutch rotates in a certain direction, the rotation causes the coil spring to deform in a tightening direction, transmitting driving force to the shaft through friction between the coil spring and the shaft. When rotating in the opposite direction, the rotation causes the coil spring to deform in a loosening direction, reducing friction between the coil spring and the shaft, thereby cutting off driving force to the shaft.

[0034] Spring one-way clutches have a simple structure and are less expensive than needle bearing one-way clutches. However, spring one-way clutches require a certain amount of rotation when connecting the drive, as the coil spring needs to deform (tighten) to transmit the drive force, and this amount of rotation is generally larger than the delay angle (backlash) of needle bearing one-way clutches.

[0035] ●Control unit 7 is a block diagram showing an example of the hardware configuration of a control unit of an image forming apparatus according to an embodiment. The control unit 101 of the image forming apparatus 1 according to this embodiment has a configuration similar to that of an information processing terminal such as a general server or a PC (Personal Computer).

[0036] The control unit 101 is connected to a CPU (Central Processing Unit) 110, a RAM (Random Access Memory) 111, a ROM (Read Only Memory) 112, a storage unit 113, and an I / F (Interface) 114 via a bus 117. A display unit 115 and an operation unit 116 are connected to the I / F 114.

[0037] The CPU 110 is a computing unit that controls the overall operation of the image forming apparatus 1. The RAM 111 is a volatile storage medium that allows high-speed reading and writing of information. When the CPU 110 processes information, the RAM 111 is used as a working area for the CPU 110. The ROM 112 is a read-only non-volatile storage medium that stores programs such as firmware.

[0038] The storage unit 113 is a non-volatile storage medium that can read and write information, and stores an OS (Operating System), various control programs, application programs, etc. The storage unit 113 is, for example, an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The I / F 114 connects and controls the bus 117 with various hardware, networks, etc.

[0039] The display unit 115 is a visual user interface that allows the user to check the status of the image forming apparatus 1. The display unit 115 is, for example, an organic EL (Electro Luminescence) display or an LCD (Liquid Crystal Display). The operation unit 116 is a user interface that allows the user to input information to the image forming apparatus 1. The operation unit 116 is, for example, a keyboard, a mouse, etc.

[0040] The above describes the hardware configuration of the control unit 101 of the image forming apparatus 1. However, the hardware configuration of the control unit 101 shown in FIG. 7 is an example, and does not need to include all of the components shown in FIG. 7, or may include other components.

[0041] ●Measures to resolve delays in consolidation 8 shows (a) an example of the start of rotation of a conventional feed roller and pickup roller, and (b) a method for eliminating coupling delays by pre-rotation according to this embodiment. The pickup roller and feed roller are driven by a stepping motor, and are driven at a slow rotation speed when the motor starts up, and then the rotation speed increases over time (slow-up).

[0042] The reason for the slow-up is 1) The torque of a stepping motor is greater at low speeds than at high speeds, so this is to prevent loss of synchronism when starting up. 2) By rotating slowly at first, slippage between the feed roller and the paper, or between the feed roller and the separation roller, can be reduced. Here, "step-out" refers to a phenomenon that occurs when the actual operation of a stepping motor cannot keep up with the control signal that rotates the stepping motor.

[0043] However, as explained in the section on conventional problems, the shaft must rotate a certain amount to connect the drive due to factors such as the delay angle of the one-way clutch, backlash in the gear train, and play between the roller and coupling, which delays the start of roller rotation as shown in Figure 8(a). To prevent this, as shown in Figure 8(b), a pre-rotation is performed before rotation begins by an amount equal to or greater than the amount of connection delay, or slightly less than the amount of connection delay, so that the feed roller and pickup roller can start rotating at the desired rotation speed. Even if the amount is slightly less than the amount of connection delay, the effect of reducing connection delay can be obtained.

[0044] 9 shows (a) an example of the start of rotation of a conventional feed roller and pickup roller, and (b) a method for eliminating coupling delays by pre-rotation according to this embodiment. The pickup roller and feed roller are driven by a DC motor, and when the motor starts up, they start rotating at a roller linear velocity (initial velocity) of 0 mm / s, and then accelerate at a constant acceleration, and after acceleration ends, they are set to rotate at a constant linear velocity (constant speed rotation).

[0045] The reason why it starts rotating at a slow speed at first is 1) The torque of a DC motor is greater at low speeds than at high speeds, which allows the motor to rotate smoothly when it starts up. 2) By rotating slowly at first, slippage between the feed roller and the paper, or between the feed roller and the separation roller, can be reduced.

[0046] However, as explained in the section on conventional problems, due to the influence of factors such as the delay angle of the one-way clutch, backlash in the gear train, and play between the roller and coupling, the shaft needs to rotate a certain amount to drive and connect the one-way clutch, which causes a delay in the start of roller drive, as shown in Figure 9(a).

[0047] To prevent this, as shown in Figure 9(b), by pre-rotating the rollers by an amount equal to or greater than the amount of coupling delay, or by an amount slightly less than the amount of coupling delay, before starting drive, the feed roller and pickup roller can start rotating at the target rotation speed. Even if the amount is slightly less than the amount of coupling delay, the effect of reducing coupling delay can be obtained.

[0048] The control performed by the control unit 101 regarding the pre-rotation of the feed roller 8 and the separation roller 9 will be described below with reference to the flow charts of FIGS. 10A to 10C. Pre-rotation flow chart (part 1) Fig. 10A shows a pre-rotation flow diagram (part 1). In Fig. 10A, pre-rotation is performed between successive sheets of paper when the sheets are fed. That is, pre-rotation is performed (S2) following a print start command (S1).

[0049] Then, paper feeding begins (S3), and when the rear edge of the paper leaves the paper feed roller, the drive of the paper feed roller stops (S4). If the next paper is to be fed from the target paper feed tray, the process returns to S2. If there is no next paper to be fed, the flow ends (S6).

[0050] Pre-rotation flow chart (part 2) Figure 10B shows the pre-rotation flow diagram (part 2). Pre-rotation can be performed between consecutive sheets of paper as shown in Figure 10A, or after the paper feeding is complete (when the rear edge of the paper has passed through the nip between the feed roller and the separator).

[0051] This allows the drive connection delay to be eliminated (or reduced) before the next paper feed from the tray, so that the first print time is not affected (is not delayed) and the number of sheets fed per hour can be prevented from decreasing.

[0052] Pre-rotation flow chart (part 3) Fig. 10C shows a pre-rotation flow diagram (part 3). In Fig. 10C, pre-rotation (S7) is performed also in the following cases 1) to 5).

[0053] 1) When the paper feed tray is set in the image forming apparatus (S5). This is because there is a possibility that a delay in connection will occur again due to reconnection with the coupling or gear train when inserting or removing the paper feed tray.

[0054] 2) When no paper has been fed from the target paper feed tray for a while (several hours or more) since the last time paper was fed from the target paper feed tray (S6). This is because, as time passes, there is a possibility that a connection delay will occur again due to vibrations or the like that may occur when the image forming apparatus is in operation.

[0055] 3) When paper was previously fed from another paper feed tray and paper is now being fed from the target paper feed tray (S4). This is because, as time passes, there is a possibility that a connection delay will occur again due to vibrations or the like that may occur when the image forming apparatus is in operation.

[0056] 4) When the power of the feeding device (image forming device in this embodiment) is turned from OFF to ON (S2). This is because if the paper feed tray is inserted or removed while the power is off, there is a possibility that a delay in connection will occur again due to reconnection with the coupling or gear train.

[0057] 5) When the power supply (power consumption state) of the feeding device (image forming device in this embodiment) returns to the normal state from the sleep state (S3). This is because if the paper feed tray is inserted or removed while the device is in sleep mode, there is a possibility that a delay in connection will occur again due to reconnection with the coupling or gear train, etc. The sleep mode is a state in which the device consumes less power than normal. In the above cases 1) to 5), the coupling delay can be eliminated (or reduced) by performing pre-rotation.

[0058] As a technology for eliminating problems caused by gear backlash, for example, Patent Document 1 (Japanese Patent No. 4662551) discloses a technology that drives the document stacking table of the document feeder in a preliminary operation to eliminate backlash in order to prevent a decrease in the amount of lift caused by backlash in the drive gear train when driving the lifting plate. However, the technology in Patent Document 1 eliminates the insufficient amount of lift of the document stacking table caused by backlash in the gear train, and does not suppress delays in starting to drive the pickup roller or feed roller.

[0059] While the present invention has been specifically described above based on the embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways within the scope of the technical ideas set forth in the claims. For example, in the above embodiments, an example was described in which a "feeding device" feeds sheets to an image forming apparatus, but the feeding device can also be applied to a document feeding device (e.g., an ADF: Automatic Document Feeder) that feeds sheets to a document reading device that reads the sheets as documents.

[0060] Supplementary Note Preferred embodiments of the present invention will be described below. <First aspect> The first aspect is a feeding device that separates sheets one by one from the top layer of a stack of sheets set in a feeding tray using a roller and feeds them downstream, characterized in that the roller is connected to a drive shaft via a one-way clutch, and the drive shaft is pre-rotated before rotating to start feeding. Pre-rotation reduces delays in connection caused by the delay angle of the one-way clutch, backlash in the gear train, and play between the roller and coupling, which are caused by the feed roller and pickup roller rotating along with the sheet during the previous feeding, making it possible to start rotating the rollers at the target speed (number of rotations) when feeding starts.This reduces slippage between the sheet and pickup roller, between the sheet and feed roller, and between the feed roller and separation roller, which occurs when feeding starts at a speed faster than the target rotation start speed, and reduces misfeeds. <Second mode> A second aspect is the feeding device of the first aspect, characterized in that the delay angle of the one-way clutch is reduced by the pre-rotation. The pre-rotation can reduce not only the delay angle of the one-way clutch, but also the amount of delay in connection due to backlash in the drive gear train and play with the coupling that drives the feed roller and pickup roller. The amount of pre-rotation can be set to be the same as the delay angle of the one-way clutch or close to the delay angle (for example, about 5 to 20° on the feed roller shaft). By setting the amount of pre-rotation to be the same as or close to the amount of rotation from the start of drive to the actual drive connection, the pickup roller and feed roller do not rotate due to the pre-rotation (drive is connected only when the pre-rotation ends). Then, there is no drive delay the next time the drive is connected, or even if the drive is connected before the pre-rotation ends, the amount of rotation of the pickup roller and feed roller during the pre-rotation is very small, so they can be driven without delay the next time the drive is connected. Furthermore, if the pre-rotation ends before the one-way clutch drive is connected, the pickup roller and feed roller do not rotate during the pre-rotation, and the delay is almost eliminated the next time the drive is connected, so there is only a slight delay in drive connection. This minimizes the rotation of the pickup roller and feed roller due to pre-rotation. It also reduces delays in the next drive, minimizing the impact on the timing of sheet transport (overfeeding or underfeeding). This allows the rollers to start rotating at the target speed (number of rotations) when feeding begins, reducing misfeeds. If feeding begins at a speed faster than the target rotation start speed, slippage occurs between the sheet and pickup roller, between the sheet and feed roller, and between the feed roller and separation roller, increasing the likelihood of misfeeds. <Third aspect> The third aspect is the feeding device of the first aspect, characterized in that the pre-rotation is performed after the rear end of the previously fed sheet has separated from the roller and before the next sheet to be fed is fed from the roller. If pre-rotation were performed from the timing of the start of feeding, the timing of the start of feeding would be delayed by the time of the pre-rotation (plus the subsequent stop), resulting in a decrease in the number of sheets fed per hour. However, if pre-rotation is performed after the trailing edge of the preceding sheet fed earlier has left the nip in the separation section of the feed roller and before the start of feeding of the next sheet to be fed (= between fed sheets), there is no delay in the start of feeding. Therefore, the effect of the first aspect can be achieved by suppressing a decrease in the number of sheets fed per hour. <Fourth aspect> A fourth aspect is the feeding device according to the first aspect, characterized in that the pre-rotation is performed after the trailing edge of the sheet has separated from the roller. Pre-rotation is not limited to between paper feeds, but is performed after paper feeding is completed. Effect: By performing pre-rotation after the previous feeding, there is no need to perform pre-rotation before the next feeding from that tray, so the effect of the first aspect can be obtained without affecting (slowing down) the time for the first print and without reducing the number of sheets fed per hour. <Fifth aspect> The pre-rotation When a sheet stack is set on the sheet feed tray, When a predetermined time has elapsed since the last feeding from the feeding tray, When a plurality of the feeding trays are provided and a sheet is fed from one feeding tray and then fed from another feeding tray, When the power is switched from OFF to ON, or When the power goes from sleep to normal, The feeding device of the first aspect is characterized in that the feeding is performed when any one of the above is performed. When the feed tray is set, it is unknown what the state of the one-way clutch connection is, the backlash of the gear train, and the state of the coupling play are, which may cause a delay in connection during feeding. In addition, if no feeding has been performed from the target tray for a while (several hours or more) since the last time feeding was performed from the target tray, the state of connection of the one-way clutch, backlash in the gear train, and play in the coupling are unknown due to the passage of time and vibrations, and there is a possibility of delays in connection when feeding. If feeding was performed from another tray last time and feeding is now being performed from the target tray, the state of connection of the one-way clutch, backlash in the gear train, and play in the coupling may be unknown due to the passage of time or vibration, and there is a possibility of a delay in connection during feeding. When the power is switched from OFF to ON, or when the power returns from sleep mode to normal mode, the feed tray may have been detached during that time, and the state of the one-way clutch connection, backlash in the gear train, or play in the coupling may be unknown due to the passage of time or vibration, which may result in a delay in connection when feeding. Therefore, by performing pre-rotation before the start of feeding, the effect of the first aspect can be reliably obtained. <Sixth aspect> A sixth aspect is an image forming apparatus having the feeding device according to any one of the first to fifth aspects. [Explanation of symbols]

[0061] 1: Image forming device 2: Paper feeder 3: Paper tray 4: Paper 5: FRR paper feed section 6: Vertical transport section 7: Pickup roller 8: Feeding roller 9: Separation roller 10: Paper feed sensor 12: Vertical conveyance sensor 13: Relay roller 16: Registration roller section 17: Transfer section 18: Photoconductor 19: Fixing device 20C: Stepping motor 21: Height sensor 22C: Bottom plate lift motor 23C: Height sensor 24C: Solenoid 37: Second separation roller shaft 51: Output gear 52: Feeding roller side gear 52a: shaft center 53: feed roller shaft 54: One-way clutch on the feeding roller side 61: First separation roller side gear 61a: shaft center 62: separation roller side one-way clutch 63: First separation roller shaft 66: First transmission gear 67: Second separation roller shaft 68: Second transmission gear 101: Control unit 110: CPU 113: Storage section 115: Display section 116: Operation unit 117: Bus CL: Roller type one-way clutch M: Common motor OUT: Outer ring TL: Torque limiter [Prior art documents] [Patent documents]

[0062] [Patent Document 1] Patent No. 4662551

Claims

1. A feeding device that separates sheets one by one from the top layer of a sheet stack set in a feeding tray using a roller and feeds them downstream, characterized in that the roller is connected to a drive shaft via a one-way clutch, and the drive shaft is pre-rotated before rotating the drive shaft to start feeding.

2. 2. The feeding device according to claim 1, wherein the pre-rotation reduces a delay angle of the one-way clutch.

3. 2. The feeding device according to claim 1, wherein the pre-rotation is performed after the trailing edge of a previously fed sheet has separated from the roller and before the next sheet is fed from the roller.

4. 2. The feeding device according to claim 1, wherein the pre-rotation is performed after the trailing edge of the sheet has been separated from the roller.

5. The pre-rotation When a sheet stack is set on the sheet feed tray, When a predetermined time has elapsed since the last feeding from the feeding tray, When a plurality of the feeding trays are provided and a sheet is fed from one feeding tray and then fed from another feeding tray, When the power supply of the feeding device is turned from an OFF state to an ON state, or When the power supply of the feeding device changes from a sleep state to a normal state, 2. The feeding device according to claim 1, wherein the feeding is performed when:

6. An image forming apparatus comprising the feeding device according to any one of claims 1 to 5.

Images