JP2023063656A - Medium feeder - Google Patents

Abstract

To provide a medium feeder adapted to inhibit the occurrence of duplicate feed while suppressing the lowering in feed efficiency of a medium.SOLUTION: A medium feeder comprises a draw-out unit (e.g. external paper-feed roller 22 and a vertical-feed motor 34) that draws one sheet P at a time out of a plurality of sheets P stacked (one example of mediums) into feeding, a remaining-quantity detecting sensor 42 that detects a remaining quantity of the plurality of sheets P stacked, and a control unit 16 that controls the draw-out unit. The control unit 16, if the remaining quantity of the sheets P detected by the remaining-quantity detecting sensor 42 becomes equal to or less than a specified amount (step S1: YES), controls the draw-out unit to decrease an acceleration A at a start of drawing out of the draw-out unit (acceleration A1) (step S4).SELECTED DRAWING: Figure 4

Description

The present invention relates to a medium feeding device.

Conventionally, based on the load current of the paper feed pickup roller, it is determined whether the number of sheets to be conveyed is one or multiple, and if there are multiple sheets, the paper is picked up at a slower speed than when conveying one sheet. A sheet feeding device that drives rollers has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2002-200013).

JP 2018-076155 A

The paper feeding device described above detects, based on the load current, the occurrence of double feeding (multiple feeding) in which multiple sheets of paper are stacked on top of each other, and prevents double feeding at the start of paper feeding. not something to do.

In order to suppress the occurrence of double feeding at the start of paper feeding, it is conceivable to reduce the acceleration at the start of delivery for all media. However, if the acceleration at the start of feeding is reduced, it takes time to feed the medium, resulting in a decrease in medium supply efficiency.

By the way, a large number of media (for example, 500 to 1000) are stacked in a medium feeding device that feeds media such as paper. more likely to occur. The reason why the remaining amount of media is reduced and double feeding is likely to occur is, for example, that the weight of the stacked media increases the adhesion between the lower media (the friction between them increases). ) can be considered as one of the causes.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a medium feeding device capable of suppressing the occurrence of double feeding while suppressing a decrease in medium feeding efficiency.

In one aspect, the medium supply device includes a feeding unit that feeds out and conveys media one by one from a plurality of stacked media; a remaining amount detection sensor that detects the remaining amount of the plurality of stacked media; a control unit for controlling the feeding unit, wherein the control unit adjusts the acceleration at the start of feeding of the feeding unit when the remaining amount detection sensor detects that the remaining amount of the medium has become equal to or less than a specified amount. is controlled so as to reduce the

According to the above aspect, it is possible to suppress the occurrence of double feeding while suppressing a decrease in medium supply efficiency.

1 is a front view showing an internal structure of an image forming apparatus according to one embodiment; FIG. 3 is a control block diagram of the image forming apparatus according to one embodiment; FIG. FIG. 10 is a diagram showing the relationship between transport speed and time for explaining normal acceleration and two-stage acceleration at the start of feeding in one embodiment; 4 is a flowchart for explaining a paper feeding method according to one embodiment; 9 is a flowchart for explaining a paper feeding method in a modified example of one embodiment;

A medium feeding device according to an embodiment of the present invention will be described below with reference to the drawings, taking as an example a case in which the medium feeding device is integrally provided in an image forming apparatus.

FIG. 1 is a front view showing the internal structure of an image forming apparatus 1 according to one embodiment.

FIG. 2 is a control block diagram of the image forming apparatus.

In the following description, the up, down, left, and right directions of the paper surface of FIG. 1 are defined as up, down, left, and right directions, and the direction orthogonal to the paper surface of FIG. 1 is defined as the front and rear direction. Further, upstream and downstream in the following description mean upstream and downstream in the conveying route (conveying direction).

In FIG. 1, a thick line indicates a transport path for transporting paper P, which is an example of a medium. Of the transport paths, the printing path RP is indicated by a solid line, the circulation path RC is indicated by a dashed line, the first paper discharge path RD1 and the second paper discharge path RD2 are indicated by dashed lines, the external paper feed route RS1 and the internal paper feed route. The paper path RS2 is indicated by a chain double-dashed line. Note that the paper P will be described as an example of the medium, but the medium may be a sheet-shaped medium made of a material other than paper, or a medium having a folded portion such as an envelope.

As shown in FIGS. 1 and 2, the image forming apparatus 1 includes a housing 2, a paper feeding section 3, a belt platen conveying section 4, a printing section 5, a circulation conveying section 6, and a paper discharge section 7. , an operation panel 15 and a control unit 16 . The paper feeding unit 3, the belt platen transport unit 4, the circulation transport unit 6, and the paper discharge unit 7 function as an example of a transport unit that transports the paper P (medium).

A housing 2 shown in FIG. 1 accommodates or holds each part of the image forming apparatus 1 . The housing 2 has a front door 17 indicated by a dashed line in FIG. The front door 17 opens and closes the front surface of the housing 2 . A user can access the inside of the image forming apparatus 1 by opening the front door 17 .

The paper feeding unit 3 feeds the unprinted paper P to the belt platen conveying unit 4 (printing unit 5). Further, the paper feeding unit 3 re-feeds the paper P after single-sided printing to the belt platen conveying unit 4 during double-sided printing. The paper feed unit 3 includes an external paper feed tray 21, an external paper feed roller 22, first and second internal paper feed trays 23 and 24, first and second internal paper feed rollers 25 and 26, and a first and second internal paper feed motors 27 and 28, first to third internal paper feed transport roller pairs 29 to 31, internal paper feed transport motor 32, vertical transport roller pair 33, vertical transport motor 34, registration It has a roller pair 35 , a registration motor 36 , paper sensors 37 to 41 and a remaining amount detection sensor 42 .

Sheets P used for printing are stacked on the external paper feed table 21 . The external paper feed table 21 is installed so that a part thereof is exposed to the outside of the housing 2 .

The external paper feed rollers 22 feed out the paper sheets P stacked on the external paper feed table 21 one by one, and convey them toward the registration roller pair 35 along the external paper feed path RS1. The external paper feed rollers 22 are arranged at two locations, one on the upstream side and the other on the downstream side in the direction in which the paper P is transported. The downstream external paper feed roller 22 may separate the paper P even if double feeding occurs, for example, by sandwiching the paper P between a rubber separating plate (not shown) and conveying the paper P. It should be noted that the external paper feed roller 22 functions as an example of a delivery unit together with a vertical conveying motor 34 that drives the external paper feed roller 22 and will be described later. The feeding unit may be controlled by the control unit 16 so as to feed and convey media one by one from a plurality of stacked media. Therefore, instead of the external paper feed rollers 22 arranged separately on the upstream side and the downstream side in the conveying direction, a conveying member such as a single roller may be arranged. Further, instead of the external paper feed roller 22 and the vertical transport motor 34, a first internal paper feed roller 25 and a first internal paper feed motor 27, which will be described later, or a second internal paper feed roller 26 and a second internal paper feed motor, which will be described later. The motor 28 may function as the feeding section of the present embodiment.

Sheets P used for printing are stacked on the first and second internal paper feed trays 23 and 24 . A second internal paper feed tray 24 is arranged below the first internal paper feed tray 23 . The first and second internal paper trays 23 and 24 are arranged inside the housing 2 .

The first internal paper feed roller 25 feeds out the sheets P stacked on the first internal paper feed table 23 one by one, and conveys them to the first internal paper feed conveying roller pair 29 . The second internal paper feed roller 26 feeds out the sheets P stacked on the second internal paper feed table 24 one by one, and conveys them to the second internal paper feed conveying roller pair 30 .

A first internal paper feed motor 27 shown in FIG. 2 drives a first internal paper feed roller 25 and a second internal paper feed motor 28 drives a second internal paper feed roller 26 .

The first internal sheet feed roller pair 29 and the second internal sheet feed transport roller pair 30 shown in FIG. The paper P drawn out from the second internal paper feed table 24 is transported to the third internal paper feed transport roller pair 31 . The third internal paper feed transport roller pair 31 transports the paper P transported by the first internal paper feed transport roller pair 29 or the second internal paper feed transport roller pair 30 to the vertical transport roller pair 33 . The third internal paper feed transport roller pair 31 is arranged near the downstream side of the confluence of the portion extending from the first internal paper feed roller 25 and the portion extending from the second internal paper feed roller 26 of the internal paper feed path RS2. there is The first internal paper feeding/conveying roller pair 29, the second internal paper feeding/conveying roller pair 30, and the third internal paper feeding/conveying roller pair 31 convey the paper P while nipping it.

The internal paper feed transport motor 32 shown in FIG. 2 drives the first to third internal paper feed transport roller pairs 29-31.

The vertical transport roller pair 33 shown in FIG. 1 transports the paper P transported by the first to third internal paper feed transport roller pairs 29 to 31 along the internal paper feed route RS2 to the registration roller pair 35 . Further, the vertical transport roller pair 33 transports the single-sided printed paper P transported along the circulation route RC during double-sided printing to the registration roller pair 35 . The vertical transport roller pair 33 is arranged along the internal paper feed route RS2 downstream of the point where the circulation route RC joins the internal paper feed route RS2. The vertical transport roller pair 33 transports the paper P while nipping it.

A vertical transport motor 34 shown in FIG. 2 drives the vertical transport roller pair 33 . The vertical transport motor 34 also drives the external paper feed rollers 22 . The vertical transport motor 34 is connected to the vertical transport roller pair 33 and the external paper feed rollers 22 via one-way clutches (not shown). As a result, the rotation of the vertical transport motor 34 in one direction drives the vertical transport roller pair 33, and the rotation of the vertical transport motor 34 in the other direction drives the external paper feed rollers 22. FIG. Note that instead of the vertical transport motor 34, a drive section (actuator) such as a motor that drives only the external paper feed roller 22 may be arranged.

The registration roller pair 35 shown in FIG. 1 temporarily stops the sheet P conveyed by the external paper feed roller 22 or the vertical conveying roller pair 33 to correct the skew, and then conveys the sheet to the belt platen conveying section 4 . The registration roller pair 35 is arranged on the printing route RP in the vicinity of the downstream side of the confluence point of the external paper feed route RS1 and the internal paper feed route RS2. The registration roller pair 35 conveys the paper P while nipping it.

A registration motor 36 shown in FIG. 2 drives the registration roller pair 35 .

As shown in FIG. 1, the paper sensor 37 detects the paper P fed from the first internal paper feed table 23 and transported to the third internal paper feed transport roller pair 31 . The paper sensor 37 is arranged in the vicinity of the downstream side of the first internal paper feeding/conveying roller pair 29 . The paper sensor 38 detects the paper P fed from the second internal paper feed table 24 and transported to the third internal paper feed transport roller pair 31 . The paper sensor 38 is arranged in the vicinity of the downstream side of the second internal paper feeding/conveying roller pair 30 . The paper sensor 39 detects the paper P transported from the third internal paper feed transport roller pair 31 to the vertical transport roller pair 33 . The paper sensor 39 is arranged in the vicinity of the downstream side of the third internal paper feeding/conveying roller pair 31 . The paper sensor 40 detects the paper P conveyed from the vertical conveying roller pair 33 to the registration roller pair 35 . The paper sensor 40 is arranged near the downstream side of the vertical transport roller pair 33 . The paper sensor 41 detects the paper P transported by the external paper feed roller 22 or the vertical transport roller pair 33 and entering the registration roller pair 35 . The paper sensor 41 is arranged near the upstream side of the registration roller pair 35 .

The remaining amount detection sensor 42 detects the height of the external paper feed tray 21 by having one or more detection units whose detection light is shielded according to the height position of the external paper feed tray 21, for example. As a result, using the remaining amount detection sensor 42, it is detected that the remaining amount is small when the height of the external paper feed tray 21 is high, and that the remaining amount is large when the height of the external paper feed tray 21 is low. can do. That is, the remaining amount detection sensor 42 detects the remaining amount of paper P. FIG. The remaining amount detection sensor 42 may detect the remaining amount of a plurality of stacked media.

The belt platen conveying section 4 conveys the paper P conveyed from the paper feeding section 3 to the circulation conveying section 6 or the paper discharge section 7 . The belt-platen conveying section 4 is arranged downstream of the sheet feeding section 3 . The belt platen transport section 4 has a belt platen 46 , a belt platen motor 47 and a paper sensor 48 .

The belt platen 46 conveys the sheet P conveyed by the pair of registration rollers 35 while holding the sheet P by suction on the belt. The belt platen 46 can be raised and lowered by an elevation driving unit 52, which will be described later. A belt platen motor 47 drives the belt of the belt platen 46 . The paper sensor 48 detects the paper P conveyed from the registration roller pair 35 to the belt platen 46 . The paper sensor 48 is arranged between the registration roller pair 35 and the upstream end of the belt platen 46 .

The printing unit 5 prints on the paper P. FIG. In the present embodiment, an example in which the printing method by the printing unit 5 is the inkjet method will be described, but the printing method is not particularly limited.

The printing unit 5 is arranged above the belt platen 46 . The printing section 5 has a head unit 51 and an elevation driving section 52 .

The head unit 51 prints an image by ejecting ink onto the paper P conveyed by the belt platen 46 . The head unit 51 has a plurality of inkjet heads 53 and a head holder 54 .

The inkjet head 53 has a plurality of nozzles arranged along the front-rear direction (main scanning direction), and ejects ink from the nozzles. The plurality of inkjet heads 53 are arranged in parallel along the transport direction of the paper P (left-right direction).

The head holder 54 holds the inkjet head 53 . The head holder 54 is fixed at a predetermined position inside the housing 2 .

The elevation drive unit 52 raises and lowers the belt platen 46 . The elevation drive unit 52 is arranged inside the head holder 54 . The elevation drive unit 52 has wires, pulleys, motors, etc., and suspends and supports the belt platen 46 with the wires. The up-and-down drive unit 52 raises and lowers the belt platen 46 by rotating a pulley with a motor to wind and unwind the wire.

1 and 2 transports the paper P after single-sided printing from the downstream end of the belt platen 46 to the vertical transport roller pair 33 along the circulation path RC during double-sided printing. The circulation conveying section 6 includes first and second intermediate conveying roller pairs 56 and 57, an intermediate conveying motor 58, a switchback roller pair 59, a reversing motor 60, and first to third horizontal conveying roller pairs 61-63. , a horizontal conveying motor 64, an ascending conveying roller pair 65, an ascending conveying motor 66, and paper sensors 67-70.

The first and second intermediate conveying roller pairs 56 and 57 shown in FIG. 1 convey the paper P after surface printing to the switchback roller pair 59 during double-sided printing. The first and second intermediate conveying roller pairs 56 and 57 are arranged along the circulation route RC between the belt platen 46 and the switchback roller pair 59 . The first intermediate conveying roller pair 56 and the second intermediate conveying roller pair 57 convey the paper P while nipping it. The second intermediate conveying roller pair 57 is arranged downstream of the first intermediate conveying roller pair 56 .

An intermediate conveying motor 58 shown in FIG. 2 drives the first and second intermediate conveying roller pairs 56 and 57 . The intermediate transport motor 58 also drives a first post-processing paper discharge roller pair 75 and first and second paper discharge tray paper discharge roller pairs 78 and 79, which will be described later.

The switchback roller pair 59 shown in FIG. 1 is arranged downstream of the second intermediate conveying roller pair 57 in the conveying direction along the circulation path RC. The switchback roller pair 59 is arranged to face each other in the switchback route RCa of the circulation route RC, and conveys the paper while nipping it. The switchback roller pair 59 switches back the paper P conveyed by the second intermediate conveying roller pair 57 and conveys it to the first horizontal conveying roller pair 61 .

A reversing motor 60 shown in FIG. 2 drives the switchback roller pair 59 .

The first to third horizontal conveying roller pairs 61 to 63 shown in FIG. The first to third horizontal conveying roller pairs 61 to 63 are arranged along the upstream portion of the circulation route RC between the switchback roller pair 59 and the confluence point of the circulation route RC with the internal paper feed route RS2. .

The first horizontal transport roller pair 61, the second horizontal transport roller pair 62, and the third horizontal transport roller pair 63 transport the paper P while nipping it. The second horizontal conveying roller pair 62 is arranged downstream of the first horizontal conveying roller pair 61 . The third horizontal conveying roller pair 63 is arranged downstream of the second horizontal conveying roller pair 62 .

A horizontal transport motor 64 shown in FIG. 2 drives the first and second horizontal transport roller pairs 61 and 62 . The third horizontal conveying roller pair 63 is driven by a lift conveying motor 66 .

The ascending conveying roller pair 65 shown in FIG. 1 conveys the paper P conveyed by the first to third horizontal conveying roller pairs 61 to 63 to the vertical conveying roller pair 33 . The ascending conveying roller pair 65 is arranged along the downstream portion of the circulation route RC between the switchback roller pair 59 and the confluence point of the circulation route RC with the internal sheet feeding route RS2. The ascending conveying roller pair 65 conveys the paper P while nipping it.

The ascending conveying motor 66 shown in FIG. 2 drives the ascending conveying roller pair 65 and the third horizontal conveying roller pair 63 .

As shown in FIG. 1, paper sensors 67 and 68 detect paper P conveyed to switchback roller pair 59 by first and second intermediate conveying roller pairs 56 and 57 . The paper sensors 67 and 68 are arranged near the downstream side of the first intermediate conveying roller pair 56 and the second intermediate conveying roller pair 57, respectively. The paper sensors 68 and 69 detect the paper P transported to the vertical transport roller pair 33 along the circulation route RC after switchback by the switchback roller pair 59 . The paper sensors 68 and 69 are arranged near the downstream side of the first horizontal conveying roller pair 61 and the upward conveying roller pair 65, respectively.

The paper discharge unit 7 shown in FIGS. 1 and 2 discharges the printed paper P. As shown in FIG. The paper discharge unit 7 includes switching units 71 and 72, solenoids 73 and 74, first and second post-processing paper discharge roller pairs 75 and 76, a post-processing paper discharge motor 77, and first to third paper discharge rollers. It has a sheet discharge roller pair 78-80, a sheet discharge board discharge motor 81, paper sensors 82-85, and a sheet discharge board 86. FIG.

The switching unit 71 shown in FIG. 1 switches the transport path of the paper P between the first paper ejection path RD1 and the circulation path RC. The first paper discharge path RD1 is a path extending from the downstream end of the printing path RP toward a post-processing device (not shown) arranged on the right side of the image forming apparatus 1 . The switching unit 71 is arranged at a branch point between the first paper discharge route RD1 and the circulation route RC.

The switching unit 72 switches the transport path of the paper P between the first paper ejection path RD1 and the second paper ejection path RD2. The second paper discharge route RD2 is a route that branches off from the first paper discharge route RD1 and heads for the paper discharge table 86 on the downstream side of the branch point between the first paper discharge route RD1 and the circulation route RC. The switching unit 72 is arranged at a branch point where the second paper discharge route RD2 branches from the first paper discharge route RD1.

Solenoids 73 and 74 shown in FIG. 2 drive switching units 71 and 72, respectively.

The first and second post-processing paper discharge roller pairs 75 and 76 shown in FIG. 1 discharge the paper P conveyed from the belt platen 46 to the post-processing device. The first and second post-processing paper discharge roller pairs 75 and 76 are arranged along the first paper discharge path RD1.

The first post-processing paper discharge roller pair 75 and the second post-processing paper discharge roller pair 76 transport the paper P while nipping it. The second post-processing paper discharge roller pair 76 is arranged downstream of the first post-processing paper discharge roller pair 75 .

The post-processing paper discharge motor 77 shown in FIG. 2 drives the second post-processing paper discharge roller pair 76 . The first post-processing paper discharge roller pair 75 is driven by the intermediate conveying motor 58 .

The first to third paper discharge tray paper discharge roller pairs 78 to 80 shown in FIG. The first to third paper discharge tray paper discharge roller pairs 78 to 80 are arranged along the second paper discharge path RD2. The first sheet ejection tray roller pair 78, the second sheet ejection tray sheet ejection roller pair 79, and the third sheet ejection tray sheet ejection roller pair 80 convey the sheet P while nipping it. The second paper discharge tray paper discharge roller pair 79 is arranged downstream of the first paper discharge tray paper discharge roller pair 78 . The third paper discharge tray paper discharge roller pair 80 is arranged downstream of the second paper discharge tray paper discharge roller pair 79 .

A paper discharge tray motor 81 shown in FIG. 2 drives a third paper discharge tray paper discharge roller pair 80 . Note that the first and second paper discharge tray paper discharge roller pairs 78 and 79 are driven by the intermediate conveying motor 58 .

As shown in FIG. 1, the paper sensor 82 detects the paper P conveyed along the first paper discharge path RD1. The paper sensor 82 is arranged near the downstream side of the first post-processing paper discharge roller pair 75 . The paper sensors 83-85 detect the paper P conveyed along the second paper discharge route RD2. The paper sensor 83 is arranged between the branch point of the second paper discharge route RD2 from the first paper discharge route RD1 and the first paper discharge tray paper discharge roller pair 78 . The paper sensor 84 is arranged in the vicinity of the downstream side of the second paper discharge tray paper discharge roller pair 79 . The paper sensor 85 is arranged near the upstream side of the third paper discharge tray paper discharge roller pair 80 .

Sheets P discharged by the first to third paper discharge tray paper discharge roller pairs 78 to 80 are stacked on the paper discharge tray 86 . The paper discharge table 86 is arranged at the downstream end of the second paper discharge path RD2.

The operation panel 15 displays various input screens and the like, and accepts input operations by the user. The operation panel 15 has a display section 91 and an input section 92 . The display unit 91 has, for example, a liquid crystal display panel, and displays various input screens and the like. The input unit 92 receives an input operation by the user and outputs an operation signal according to the operation. The input unit 92 has various operation keys, a touch panel, and the like.

The control unit 16 has a processor (for example, a CPU: Central Processing Unit) that functions as an arithmetic processing unit, and a memory (storage unit) such as a ROM (Read Only Memory) and a RAM (Random Access Memory). Controls overall behavior. Although details will be described later, when the remaining amount of paper P is detected by the remaining amount detection sensor 42 to be equal to or less than a specified amount, the control unit 16 causes the feeding unit (the external paper feed roller 22 and the vertical transport motor 34) to The feeding unit is controlled so as to reduce the acceleration at the start of feeding.

The control unit 16 functions as a part of a medium feeding device that feeds (supplies) paper (medium) together with the feeding unit (the external paper feed roller 22 and the vertical transport motor 34) and the remaining amount detection sensor 42. FIG. That is, the image forming apparatus 1 is integrally provided with a medium feeding device. However, the medium feeding device may be arranged separately from the image forming apparatus 1 . Further, the medium supply device may supply the medium (paper P) to the image forming apparatus 1 in which the printing method of the printing unit 5 is a printing method other than the inkjet method (for example, a stencil printing method). The media may be supplied to devices other than the

A normal printing operation in the image forming apparatus 1 will be described below.

When a print job is input, the control unit 16 shown in FIGS. 1 and 2 controls the paper feed unit 3, the belt platen transport unit 4, the circulation transport unit 6, and the paper feed unit 3 to feed, transport, and eject the paper P. and controls the paper discharge unit 7 . Further, the control unit 16 performs predetermined image processing on the image data included in the print job, and then controls the inkjet head of the head unit 51 to eject ink onto the paper P conveyed by the belt platen 46 to print an image. 53.

Here, in the case of single-sided printing, as shown in FIG. 1, in the paper feeding unit 3, unprinted paper P is sequentially fed from one of the external paper feeding tray 21 and the first and second internal paper feeding trays 23 and 24. The sheets P are fed out and sequentially fed at the belt platen 46 at a timing such that each sheet P is conveyed at a predetermined sheet interval. The fed paper P is printed with ink ejected from the inkjet head 53 while being transported on the belt platen 46 at a predetermined printing transport speed. The printed paper P is discharged by the paper discharge unit 7 .

When the paper discharge destination is the post-processing device, the printed paper P is guided to the first paper discharge path RD1 by the switching units 71 and 72 . Then, the paper P is discharged to the post-processing device by the first and second post-processing paper discharge roller pairs 75 and 76 . When the paper ejection destination is the paper ejection tray 86, the printed paper P is guided to the second paper ejection path RD2 by the switching units 71 and 72. FIG. Then, the paper P is discharged to a paper discharge tray 86 by the first to third paper discharge tray paper discharge roller pairs 78-80.

In the case of double-sided printing, unprinted sheets of paper P are sequentially fed by the paper feeding unit 3 at timings in which the time between feeding timings of the respective sheets of paper P is double the feeding timing for single-sided printing. . The fed paper P is printed while being transported by the belt platen 46 in the same manner as in single-sided printing.

After single-sided printing, the paper P is guided to a circulation path RC for double-sided printing by the switching unit 71 and conveyed to the switchback roller pair 59 by the first and second intermediate conveying roller pairs 56 and 57 . Upon reaching the switchback roller pair 59 , the paper P is switched back by the switchback roller pair 59 .

Next, the paper P is conveyed to the vertical conveying roller pair 33 by the first to third horizontal conveying roller pairs 61 to 63 and the ascending conveying roller pair 65 . Then, the paper P is re-fed to the belt platen 46 by the vertical transport roller pair 33 and the registration roller pair 35 .

Here, the sheet P after single-sided printing is re-fed at a timing such that it is alternately fed to the belt platen 46 with the unprinted sheet P that is sequentially fed. As described above, in double-sided printing, the time between sheet feeding timings for each sheet P is double the sheet feeding timing for single-sided printing. For this reason, it is possible to insert the sheet P after single-sided printing between unprinted sheets P, and re-feed the sheet P after single-sided printing alternately with the feeding of the unprinted sheet P. .

After being printed on one side, the paper P is switched back by the switchback roller pair 59, and then sent to the belt platen 46 with the unprinted side facing upward. After single-sided printing, the paper P is conveyed by the belt platen 46 and printed on the non-printed side. Then, the double-sided printed paper P is discharged to the post-processing device or the paper discharge table 86 by the paper discharge unit 7 .

As described above, in double-sided printing, unprinted paper P is alternately fed and paper P after single-sided printing is re-fed. Printing on one side and printing on the unprinted side of the paper P after single-sided printing are alternately performed. As a result, double-sided printing can be performed with the same productivity per side as single-sided printing.

By the way, as the printing progresses and the remaining amount of paper P stacked on the external paper feed table 21 decreases, the remaining amount detection sensor 42 detects that the remaining amount has become less than a specified amount (for example, 10% of the full tank). is detected. In this case, the sheets P are likely to be multi-fed, so the control unit 16 controls the vertical transport motor 34 so as to reduce the acceleration when the external paper feed roller 22 starts to be fed out.

The paper feed control for reducing the acceleration at the start of feeding will be described below with reference to FIGS. 3 and 4. FIG.

FIG. 3 is a diagram showing the relationship between the conveying speed and time for explaining normal acceleration and two-stage acceleration at the start of feeding in this embodiment.

FIG. 4 is a flow chart for explaining the paper feeding method according to the present embodiment.

Note that the processing shown in FIG. 4 is performed by the control unit 16, for example, when a print job is input and paper feeding is started.

First, the control unit 16 determines whether or not the remaining amount of paper P has been detected by the remaining amount detection sensor 42 to be equal to or less than a specified amount (step S1).

When it is detected that the remaining amount of paper P has become equal to or less than the specified amount (step S1: YES), the control unit 16 determines that the preceding paper P is to be double-sided printed. After being resupplied to the printing section 5 through the circulation route RC, the preceding sheet P is waited for circulation so that the succeeding sheet P is supplied to the printing section 5 (step S2). It should be noted that if double-sided printing is not performed on the preceding sheet P, the standby process in step S2 can be omitted. Therefore, in FIG. 4, step S2 is indicated by a dashed line.

In the later-described two-stage acceleration paper feeding process (step S4), the control unit 16 sets the acceleration of the feeding unit (the external paper feeding roller 22 and the vertical conveying motor 34) at the start of feeding to normal acceleration as shown in FIG. In order to change the acceleration A (thin solid line) to a two-step acceleration (thick solid line) smaller than the acceleration A (thin solid line), the feed timing of the paper P after this change is recalculated (step S3). In addition to the paper feed speed (conveyance speed) of the feeding unit, the paper feed timing depends on, for example, the print speed (conveyance speed) of the printing unit 5, the predetermined interval between sheets P, the length of the paper P in the conveying direction, and the like. calculated based on

Next, the control unit 16 starts feeding the paper P with two-stage acceleration (step S4). In this two-step acceleration paper feeding, the control section 16 controls the feeding section so that the acceleration A1, which is lower than the acceleration A at the start of normal feeding, is continued for a period AP, and then the acceleration is increased to A2. That is, the control section 16 controls the feeding section so that the reduced acceleration A1 is increased to the acceleration A2 after a predetermined time (for example, period AP) has elapsed since the feeding section started to be fed. This acceleration A2 may be the same as the normal acceleration A. In addition, after the acceleration A1 is increased to the acceleration A2, the control of the two-step acceleration, after reaching the specified maximum speed, is similar to the control of the normal acceleration, and the specified speed at the time of contact with the registration roller pair 35 is controlled. It is preferable to decelerate to the conveying speed once and stop the conveying after the sheet P is hit. As a result, paper feeding by two-step acceleration takes longer than paper feeding by normal acceleration. In the control, if the conveying speed at the time of contact with the registration roller pair 35 is increased, the skew correction accuracy will deteriorate and noise will occur. Note that instead of paper feeding by two-step acceleration, paper feeding may be performed without increasing the acceleration that was reduced at the start of feeding, or paper feeding may be performed with three or more steps of acceleration that increases the acceleration to three or more steps. may be broken.

Next, the control unit 16 determines whether or not all sheets P of the print job have been fed (step S5). If the paper feeding is not completed (step S5: NO), the control unit 16 continues the paper feeding process with two-stage acceleration (step S4). Also, if the paper feeding is completed (step S5: YES), the process shown in FIG. 4 ends.

Returning to the remaining amount determination process of step S1 described above, if it is not detected that the remaining amount of paper P has become equal to or less than the specified amount (step S1: NO), the control unit 16 performs the normal acceleration of the feeding of the paper P. Paper is started (step S6).

Next, the control unit 16 determines whether or not the feeding of all sheets P of the print job has been completed (step S7). If the paper feeding is not completed (step S7: NO), the control unit 16 performs the remaining amount determination process of step S1 described above. Also, if the paper feeding is completed (step S7: YES), the process shown in FIG. 4 ends.

Next, a modification of this embodiment will be described with reference to FIG.

FIG. 5 is a flow chart for explaining a paper feeding method in a modified example of the present embodiment. The flowchart shown in FIG. 5 is the same as the flowchart shown in FIG. 4 except that steps S11 and S12 are performed in addition to the processing of the flowchart shown in FIG. Therefore, only matters related to the processing of steps S11 and S12 will be described.

When the remaining amount detection sensor 42 detects that the remaining amount of the paper P has become equal to or less than the specified amount (step S1: YES), the control unit 16 detects the paper information (an example of the medium information) of the paper P and the transport information. (step S11).

The prescribed conditions defined in the paper information are, for example, at least one of thickness, material (frictional force), length in the transport direction, etc. The prescribed conditions defined in the transport information are, for example, the acceleration A of the normal acceleration It is at least one of size, required print speed level of paper P, and the like.

As an example of a case where the specified condition is satisfied, if the paper P is thin paper, if the paper P is made of a specified material (frictional force) that easily causes double feeding, the length of the paper P in the transport direction is the specified length. In the above cases, the acceleration A is equal to or larger than a prescribed magnitude, and the paper P is not required to be printed at high speed.

If the specified condition is satisfied (step S11: YES), the control unit 16 performs the above-described standby process of step S2 when double-sided printing is performed on the preceding sheet P. FIG.

After that, based on at least one of the paper information (medium information) and the transport information of the paper P, the control unit 16 reduces the acceleration A1 when the feeding unit (the external paper feed roller 22 and the vertical transport motor 34) starts to be fed out. At least one of the continuous period AP and the magnitude of the acceleration A1 to be reduced at the start of the extension of the extension unit is determined (step S12). After that, the control unit 16 recalculates the feed timing of the subsequent sheets P as described above (step S3).

Here, the control unit 16 controls paper P based on at least one paper information such as the thickness, material (frictional force), length in the transport direction, and transport information such as the required level of printing speed of the paper P. , the period AP during which the acceleration A1 continues, and the magnitude of the acceleration A1 may be determined.

For example, if the paper P is thin, if the paper P is made of a material (frictional force) that easily causes double feeding, or if the length of the paper P in the transport direction is equal to or greater than a specified length, high-speed printing is performed on the paper P. If it is not required, it is preferable to lengthen the period AP or decrease the acceleration A1. The period AP may be lengthened or the acceleration A1 may be decreased as the remaining amount of paper P decreases.

Note that only one of the processing of step S11 and the processing of step S12 in FIG. 5 in the above modification may be performed. If the process of step S12 is omitted, the acceleration A1 that is reduced by the two-step acceleration and the duration AP of this acceleration A1 are set to the prescribed acceleration A1 and period AP.

In the present embodiment described above, the medium feeding device includes a feeding unit (for example, the external paper feeding roller 22 and the vertical feeding unit) that feeds and conveys the sheets P one by one from a plurality of stacked sheets P (an example of media). a motor 34), a remaining amount detection sensor 42 for detecting the remaining amount of a plurality of stacked sheets of paper P, and a control section 16 for controlling the feeding section. When the remaining amount of paper P is detected by the remaining amount detection sensor 42 to be equal to or less than the specified amount (step S1: YES), the control unit 16 reduces the acceleration A at the start of feeding of the feeding unit (acceleration A1) The feeding unit is controlled (step S4).

By the way, when a large number of sheets P (for example, 500 to 1000 sheets) are stacked on the external paper feed table 21, the weight of the stacked sheets P increases the adhesion between the sheets P at the bottom. When the degree of close contact between sheets P increases in this way, double feeding is likely to occur. By reducing the acceleration A (acceleration A1) at the start of feeding out the set, it is possible to suppress the occurrence of double feeding. Furthermore, by reducing the acceleration A at the start of feeding (acceleration A1) when the remaining amount of paper P is equal to or less than a specified amount, As compared with a mode in which the acceleration of is reduced, it is possible to suppress a decrease in paper feeding efficiency of paper P (medium feeding efficiency).

Further, in the present embodiment, the control unit 16 controls the feeding unit to increase the reduced acceleration A1 (for example, acceleration A2) after a predetermined time (for example, period AP) has elapsed from the start of feeding of the feeding unit.

As a result, the paper feed efficiency of the paper P (medium supply efficiency) can be improved compared to the case where the reduced acceleration A1 is maintained.

Further, in the modified example of the present embodiment, the control unit 16 detects that the remaining amount of the paper P is equal to or less than the specified amount by the remaining amount detection sensor 42 (step S1: YES), and When at least one of the paper information (an example of the medium information) and the transport information of the paper P is satisfied (step S11: YES), the acceleration A at the start of feeding of the feeding unit is decreased (acceleration A1 ) (step S4).

For this reason, for example, under conditions where double feeding is unlikely to occur or where high-speed printing is required, the decrease in paper feed efficiency (medium supply efficiency) of the paper P can be further suppressed by not reducing the acceleration A at the start of feeding. can be done.

Further, in the modified example of the present embodiment, the control unit 16 continues the acceleration A1 that is reduced at the start of feeding of the feeding unit based on at least one of the paper information (an example of the medium information) of the paper P and the transport information. At least one of the period AP to be held and the magnitude of acceleration (acceleration A1) to be reduced when the feeding portion starts to be fed out is determined (step S12).

Therefore, for example, when double feeding is likely to occur, the occurrence of double feeding can be further suppressed by lengthening the period AP during which the acceleration A1 is continued or decreasing the acceleration A1. In addition, for example, when double feeding is unlikely to occur, the period AP during which the acceleration A1 is continued is shortened, or the acceleration A1 is increased (smaller than the normal acceleration A) to improve the paper feed efficiency of the paper P (medium supply efficiency) can be further suppressed.

Further, in the present embodiment, the medium feeding device feeds the paper P to the printing section 5 of the image forming apparatus 1 having the circulation route RC for double-sided printing. When the remaining amount of paper P is detected by the remaining amount detection sensor 42 to be equal to or less than the specified amount (step S1: YES), the control unit 16 determines whether double-sided printing is to be performed on the preceding paper P. After the preceding paper P is resupplied to the printing unit 5 through the circulation path RC, the subsequent paper P is fed to the printing unit 5 by reducing the acceleration of the feeding unit. Delay (step S2).

Therefore, after the printing of one side of the preceding sheet P for double-sided printing is completed and before the printing of the remaining one side is completed, the acceleration of the feeding section is reduced so that the sheet P whose feeding is delayed is transferred to the printing section. 5 can be avoided. As a result, it is possible to avoid the control of adjusting the timing of re-supplying the preceding paper P for which single-sided printing has been completed to the printing unit 5 in accordance with the time at which the paper P whose feeding is delayed is discharged from the printing unit 5. can. Therefore, control by the control unit 16 can be simplified.

It should be noted that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements without departing from the scope of the present invention at the implementation stage. Also, various inventions can be formed by appropriate combinations of the plurality of constituent elements disclosed in the above-described embodiments. For example, all the components shown in the embodiments may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention. The invention described in the scope of claims at the time of filing of the present application will be additionally described below.

[Appendix 1]
a feeding unit that feeds and conveys media one by one from a plurality of stacked media;
a remaining amount detection sensor that detects the remaining amount of the plurality of stacked media;
A control unit that controls the feeding unit,
When the remaining amount detection sensor detects that the remaining amount of the medium has become equal to or less than a specified amount, the control section controls the feeding section so as to decrease the acceleration at the start of feeding of the feeding section. A medium supply device characterized by:

[Appendix 2]
The medium feeding device according to claim 1, wherein the control section controls the feeding section so as to increase the reduced acceleration after a predetermined time has elapsed since the feeding section started feeding.

[Appendix 3]
When the remaining amount detection sensor detects that the remaining amount of the medium has become equal to or less than a specified amount, the control unit detects a specified amount in at least one of medium information and transport information of the medium. 3. The medium feeding device according to appendix 1 or 2, wherein the feeding unit is controlled so as to decrease an acceleration of the feeding unit at the start of feeding when a condition is satisfied.

[Appendix 4]
Based on at least one of medium information and transport information of the medium, the control unit controls a period during which the acceleration that is reduced when the feeding unit starts to be delivered and the magnitude of the acceleration that is reduced when the feeding unit starts to be delivered. 4. The medium feeding device according to any one of appendices 1 to 3, wherein at least one of

[Appendix 5]
The medium supply device supplies the medium to a printing unit of an image forming apparatus having a circulation path for double-sided printing,
When the remaining medium amount detection sensor detects that the remaining amount of the medium has become equal to or less than a specified amount, the control unit causes the preceding medium to be subjected to the circulating medium when duplex printing is performed on the preceding medium. After being resupplied to the printing unit through a path, delaying the start of feeding the subsequent medium by reducing the acceleration of the feeding unit so that the subsequent medium is supplied to the printing unit. 5. The medium feeding device according to any one of Appendices 1 to 4.

1 Image Forming Apparatus 3 Paper Feed Unit 16 Control Unit 21 External Paper Feed Table 22 External Paper Feed Roller 34 Vertical Conveyance Motor 42 Remaining Amount Detection Sensor P Paper RC Circulation Route RS1 External Paper Feed Route

Claims (5)

a feeding unit that feeds and conveys media one by one from a plurality of stacked media;
a remaining amount detection sensor that detects the remaining amount of the plurality of stacked media;
A control unit that controls the feeding unit,
When the remaining amount detection sensor detects that the remaining amount of the medium has become equal to or less than a specified amount, the control section controls the feeding section so as to decrease the acceleration at the start of feeding of the feeding section. A medium supply device characterized by: 2. The medium feeding device according to claim 1, wherein the control section controls the feeding section so as to increase the reduced acceleration after a predetermined time has passed since the feeding section started feeding. When the remaining amount detection sensor detects that the remaining amount of the medium has become equal to or less than a specified amount, the control unit detects a specified amount in at least one of medium information and transport information of the medium. 3. The medium supply device according to claim 1, wherein, when the condition is satisfied, the feeding section is controlled so as to decrease the acceleration of the feeding section at the start of feeding. Based on at least one of medium information and transport information of the medium, the control unit controls a period during which the acceleration that is reduced when the feeding unit starts to be delivered and the magnitude of the acceleration that is reduced when the feeding unit starts to be delivered. 4. The medium feeding device according to any one of claims 1 to 3, wherein at least one of The medium supply device supplies the medium to a printing unit of an image forming apparatus having a circulation path for double-sided printing,
When the remaining medium amount detection sensor detects that the remaining amount of the medium has become equal to or less than a specified amount, the control unit causes the preceding medium to be subjected to the circulating medium when duplex printing is performed on the preceding medium. After being resupplied to the printing unit through a path, delaying the start of feeding the subsequent medium by reducing the acceleration of the feeding unit so that the subsequent medium is supplied to the printing unit. The medium feeding device according to any one of claims 1 to 4.

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