阅读说明：本技术 图像形成系统 (Image forming system ) 是由 白崎晴一 于 2021-07-02 设计创作，主要内容包括：本发明提供图像形成系统,其包括图像形成装置、薄片体供给装置、薄片体后处理装置和控制部。图像形成装置具有薄片体存放部、第一供纸部和图像形成部。薄片体供给装置具有薄片体堆放部、第二供纸部和中继输送部。薄片体供给装置具有剩余量检测机构。中继输送部具有汇合部。当连续印刷中从汇合部至第一供纸部的记录薄片体的输送通道中滞留的记录薄片体的滞留张数多于一个薄片体摞所含的记录薄片体的构成张数,且由剩余量检测机构检测的插入薄片体的剩余量在规定量以下时,控制部对来自第一供纸部的输出薄片体的供给进行控制,以使记录薄片体的滞留张数少于记录薄片体的构成张数。(The invention provides an image forming system, which comprises an image forming device, a sheet feeding device, a sheet post-processing device and a control part. The image forming apparatus includes a sheet storage unit, a first sheet feeding unit, and an image forming unit. The sheet feeding device includes a sheet stacking unit, a second sheet feeding unit, and a relay conveying unit. The sheet feeding device includes a remaining amount detecting mechanism. The relay conveyance unit has a junction. When the number of sheets left in a conveyance path of recording sheets from the junction to the first sheet feeding unit is greater than the number of constituent recording sheets in one sheet stack and the remaining amount of inserted sheets detected by the remaining amount detecting mechanism is less than or equal to a predetermined amount during continuous printing, the control unit controls the feeding of output sheets from the first sheet feeding unit such that the number of left recording sheets is less than the number of constituent recording sheets.)

1. An image forming system characterized by comprising:

an image forming apparatus includes: a sheet storage unit for storing recording sheets; a first sheet feeding unit configured to feed the recording sheets one by one from the sheet storage unit to a downstream side in a sheet conveying direction; and an image forming unit configured to form an image on the recording sheet fed by the first sheet feeding unit;

a sheet feeding device connected to a downstream side of the image forming apparatus, the sheet feeding device including: a sheet stacking portion for stacking an inserted sheet; a second sheet feeding unit configured to feed the inserted sheets stacked in the sheet stacking unit one by one; and a relay conveying unit configured to receive the recording sheet fed by the first sheet feeding unit and the inserted sheet fed by the second sheet feeding unit and convey the recording sheet to a downstream side in the sheet conveying direction;

a sheet post-processing device connected to a downstream side of the sheet feeding device, forming a sheet stack including the inserted sheet and the recording sheet, and performing a predetermined post-processing; and

a controller for controlling the image forming apparatus, the sheet feeding device and the sheet post-processing device,

the sheet feeding device includes a remaining amount detecting mechanism for detecting a remaining amount of the inserted sheets in the sheet stacking portion,

the relay conveying unit includes a junction of a conveying path for conveying the inserted sheet and a conveying path for conveying the recording sheet,

when the number of left sheets remaining in the conveyance path of the recording sheets from the merging portion to the first sheet feeding portion in continuous printing is greater than the number of constituent recording sheets included in one sheet stack, and the remaining amount of the inserted sheets detected by the remaining amount detecting mechanism is equal to or less than a predetermined remaining amount level, the controller controls the feeding of the recording sheets from the first sheet feeding portion such that the number of left sheets is less than the number of constituent recording sheets.

2. The image forming system according to claim 1,

further comprising a measuring device for measuring the number of left recording sheets,

when the remaining amount of the inserted sheet is equal to or less than the predetermined remaining amount level and the remaining number of recording sheets measured by the measuring device is greater than the constituent number of recording sheets, the control unit controls the feeding of the recording sheets from the first sheet feeding unit such that the remaining number of recording sheets is less than the constituent number of recording sheets.

3. The image forming system according to claim 2,

a recording portion for recording the number of remaining recording sheets measured by the measuring device,

when the remaining amount of the inserted sheet is equal to or less than the predetermined remaining amount level when the number of the formed recording sheets is less than the number of the remaining recording sheets recorded in the recording portion, the control portion controls the feeding of the recording sheets from the first sheet feeding portion such that the number of the remaining recording sheets is less than the number of the formed recording sheets.

4. The image forming system according to any one of claims 1 to 3, wherein the first sheet feeding unit feeds the recording sheets at a first timing during continuous printing, and the control unit controls the first sheet feeding unit to feed only a first recording sheet of the plurality of recording sheets included in one sheet stack at a second timing longer than the first timing when the remaining amount of the inserted sheets is equal to or less than the predetermined remaining amount level.

5. The image forming system according to any one of claims 1 to 3, wherein the controller controls the first sheet feeding unit to delay feeding of a plurality of recording sheets included in one sheet stack from the sheet storage unit at equal intervals when the remaining amount of the inserted sheets is equal to or less than the predetermined remaining amount level.

6. The image forming system according to any one of claims 1 to 3, comprising an input unit configured to input a value of the predetermined remaining amount level of the inserted sheet.

7. The image forming system according to any one of claims 1 to 3,

a notification unit capable of notifying the remaining amount of the inserted sheet,

the control is configured to notify, by the notification unit, that the remaining amount of the inserted sheet is decreased when the remaining amount of the inserted sheet is equal to or less than the predetermined remaining amount level.

Technical Field

The present invention relates to a sheet feeding device in which a cover sheet, a mount sheet, and the like are inserted between a plurality of sheets of paper on which an image is formed by an image forming apparatus such as an image forming apparatus, a facsimile machine, a printer, and the like, and an image forming system using the sheet feeding device.

Background

A conventional image forming system includes an image forming apparatus, a sheet feeding device connected to a downstream side of the image forming apparatus, and a sheet post-processing device connected to a downstream side of the sheet feeding device. In the above-described image forming system, a cover sheet and an interleaving sheet are inserted from a sheet feeding device into between a plurality of recording sheets on which images are formed by an image forming apparatus, a sheet bundle including the recording sheets and the interleaving sheet is created, and the sheet bundle is post-processed by a sheet post-processing apparatus to create a booklet.

A recording sheet is loaded into a sheet feeding section of an image forming apparatus. Recording sheets are fed from a sheet feeding unit to an image forming unit of an image forming apparatus one by one at a predetermined interval. The recording sheets on which images are formed in the image forming unit are fed one by one to the sheet feeding device. On the other hand, the inserted sheet is stacked on a sheet stacking portion of the sheet feeding device. The sheet feeding device inserts an inserted sheet between a plurality of recording sheets conveyed one by one from the image forming apparatus at a predetermined timing. Then, the recording sheet and the inserted sheet are sent to a sheet post-processing apparatus.

Further, such an image forming system may include a remaining amount detection sensor for detecting a remaining amount of an inserted sheet. If the remaining amount detection sensor detects that the remaining amount of the inserted sheet is reduced, the user can be prompted to replenish the inserted sheet.

In the image forming system, a buffer portion that can convey and retain a small amount of inserted sheets may be provided in the sheet feeding device. When the image forming system starts to make a booklet, the inserted sheets are conveyed to the buffer portion and are stored in the buffer portion. When the remaining amount of the inserted sheets in the sheet stacking portion is used up, the feeding of the inserted sheets from the buffer portion is started.

Disclosure of Invention

The invention aims to provide an image forming system which restrains the production of a booklet without a cover while restraining the increase of the production cost, the enlargement of the device and the reduction of the production rate.

An image forming system according to a first aspect of the present invention includes: an image forming apparatus includes: a sheet storage unit for storing recording sheets; a first sheet feeding unit configured to feed the recording sheets one by one from the sheet storage unit to a downstream side in a sheet conveying direction; and an image forming unit configured to form an image on the recording sheet fed by the first sheet feeding unit; a sheet feeding device connected to a downstream side of the image forming apparatus, the sheet feeding device including: a sheet stacking portion for stacking an inserted sheet; a second sheet feeding unit configured to feed the inserted sheets stacked in the sheet stacking unit one by one; and a relay conveying unit configured to receive the recording sheet fed by the first sheet feeding unit and the inserted sheet fed by the second sheet feeding unit and convey the recording sheet to a downstream side in the sheet conveying direction; a sheet post-processing device connected to a downstream side of the sheet feeding device, forming a sheet stack including the inserted sheet and the recording sheet, and performing a predetermined post-processing; and a controller that controls the image forming apparatus, the sheet feeding device, and the sheet post-processing device, wherein the sheet feeding device includes a remaining amount detecting mechanism for detecting a remaining amount of the inserted sheet in the sheet stacking portion, the relay conveying portion includes a junction portion of a conveying path for conveying the inserted sheet and a conveying path for conveying the recording sheet, and the controller controls the feeding of the recording sheet from the first sheet feeding portion when a remaining number of the recording sheet remaining in the conveying path for the recording sheet from the junction portion to the first sheet feeding portion during continuous printing is greater than a number of constituent recording sheets included in one sheet stack, and the remaining amount of the inserted sheet detected by the remaining amount detecting mechanism is equal to or less than a predetermined remaining amount level, the number of accumulated recording sheets is smaller than the number of constituent recording sheets.

According to the first configuration of the present invention, when the number of output sheets included in one sheet stack is larger than the number of output sheets present between the junction portion and the first sheet feeding portion in continuous printing, if the remaining amount of inserted sheets is equal to or smaller than the predetermined amount, the number of output sheets present between the junction portion and the first sheet feeding portion in continuous printing is smaller than the number of recording sheets included in one sheet stack. Therefore, even if the remaining amount of inserted sheets runs out and the feeding of recording sheets from the sheet feeding unit is stopped, the feeding of recording sheets of the number of recording sheets or more included in the sheet stack to the sheet post-processing apparatus can be suppressed.

Drawings

Fig. 1 is a schematic diagram of internal configurations of an image forming apparatus 1, a sheet feeding device 2, and a sheet post-processing apparatus 3 constituting an image forming system 100.

Fig. 2 is a partially enlarged view showing a state where the remaining amount of the inserted sheet P2 in the sheet stacking portion 16 is equal to or larger than a certain amount.

Fig. 3 is a partially enlarged view showing a state where the remaining amount of the inserted sheet P2 in the sheet stacking portion 16 is a certain amount or less.

Fig. 4 is a block diagram showing a control path of the image forming system 100 of the present invention.

Fig. 5 is a flowchart illustrating an example of control of feeding the recording sheet P1 and the insertion sheet P2.

Fig. 6 is a flowchart illustrating an example of control of feeding the recording sheet P1 and the insertion sheet P2.

Fig. 7 is a flowchart illustrating an example of control of feeding the recording sheet P1 and the inserted sheet P2.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

First, an image forming system 100 according to the present invention including an image forming apparatus 1, a sheet feeding device 2, and a sheet post-processing device 3 (sheet post-processing device) will be described with reference to fig. 1. Although the image forming system 100 has been described in the present embodiment in the case of using an inkjet recording printer as the image forming apparatus, other image forming apparatuses (e.g., a laser printer, an image forming apparatus, and a facsimile machine) may be used. A direction in which the recording sheet P1 fed from the image forming apparatus 1 and the inserted sheet P2 inserted from the sheet feeding device 2 are conveyed toward the sheet post-processing apparatus 3 is referred to as a sheet conveying direction. The sheet post-processing apparatus 3 is disposed downstream in the sheet conveying direction, and the first sheet feeding unit 4 of the image forming apparatus 1 and the sheet stacking unit 16 of the sheet feeding device 2, in which the sheets P2 are stacked, are referred to as upstream in the sheet conveying direction.

Fig. 1 is a schematic diagram of internal configurations of an image forming apparatus 1, a sheet feeding device 2, and a sheet post-processing apparatus 3 constituting an image forming system 100. A sheet feeding device 2 is connected downstream of the image forming apparatus 1. The sheet post-processing apparatus 3 is connected to the downstream side of the sheet feeding device 2.

The image forming apparatus 1 includes a first paper feed unit 4 and a first conveying unit 5. The first sheet feeding unit 4 is provided at a lower portion of the image forming apparatus 1 and accommodates a plurality of recording sheets P1. The first conveying unit 5 feeds the recording sheets P1 one by one from the first sheet feeding unit 4 to the downstream side in the sheet conveying direction.

The first sheet feeding unit 4 includes a plurality of (here, 3) sheet cassettes 4a (sheet storage unit). The paper feed cassettes 4a are arranged in parallel in the vertical direction. By mounting recording sheets P1 of different sizes on each sheet feeding cassette 4a, booklets containing recording sheets of various sizes can be created.

The first conveying section 5 has a paper feed path 7 and a plurality of paper feed sections 6. The paper feed path 7 is connected to each paper feed cassette 4a and extends from a side of the first paper feed unit 4 toward a downstream side in a sheet conveying direction. The paper feed path 7 is provided with a plurality of conveying roller pairs 10 for conveying the recording sheet P1 therein to the downstream side in the sheet conveying direction.

The sheet feeding section 6 is provided between the sheet conveying path 7 and each sheet feeding cassette 4 a. The sheet feeding portion 6 is provided with a pair of sheet feeding rollers 11 that feed a recording sheet P1 accommodated in the first sheet feeding portion 4 to the sheet feeding path 7.

The paper feed portion 6 is provided with a paper feed detection sensor 12. The sheet feed detection sensor 12 detects that a recording sheet P1 is fed from the first sheet feeding unit 4. The detection signal of the paper feed detection sensor 12 is sent to the control section 59 of the image forming apparatus 1 (see fig. 4). The measurement device 73 for measuring the number of sheets P1 fed is constituted by the sheet feed detection sensor 12 and a sheet feed counter 13 (number-of-sheets measurement unit) described later.

An image recording unit 8 (image forming unit) is disposed above the first paper feed unit 4, and is adjacent to the paper feed path 7 in the height direction. A reverse conveyance path 9 is provided which branches off from the paper feed path 7 and extends upward of the image recording section 8.

An endless conveyor belt 14 wound around a plurality of rollers including a drive roller is provided below the image recording section 8. The conveyor belt 14 is provided with a plurality of air holes (not shown) for sucking air. The recording sheet P1 fed from the first sheet feeding unit 4 and arriving on the conveying belt 14 passes below the image recording unit 8 while being sucked and held on the conveying belt 14 by a sheet suction unit provided inside the conveying belt 14.

The image recording unit 8 includes a plurality of ink jet print heads that eject ink toward the recording sheet P1 sucked and held by the conveying belt 14 and conveyed. The inks of 4 colors (cyan, magenta, yellow, and black) stored in the respective ink cartridges (not shown) are supplied to the respective ink jet print heads in accordance with the colors of the ink jet print heads, respectively.

When image recording is performed on both sides of the recording sheet P1, the recording sheet P1 on which recording has been completed on one side is conveyed to the reversing conveyance path 9, and the conveyance direction is switched (reversed). Then, the recording sheet P1 is reversed and conveyed again to the image recording portion 8 with the non-image-recorded side facing upward, and an image is recorded. The recording sheet P1 on which a predetermined image is recorded by the image recording portion 8 is discharged one by one from a pair of discharge rollers 15 provided near an opening at a downstream end of the paper feed path 7.

The sheet feeding device 2 feeds the recording sheets P1 discharged from the image forming apparatus 1 one by one, and inserts a front cover, a back cover (cover), a mount (insert) for identification, and the like used for binding between the fed recording sheets P1 at a predetermined timing into the sheet P2. Then, the recording sheet P1 and the inserted sheet P2 are sent to the sheet post-processing apparatus 3.

The sheet feeding device 2 includes an insertion conveyance path 25, a relay conveyance unit 17, an insertion conveyance path 18, and a second sheet feeding unit 80. The second sheet feeding portion 80 is provided above the sheet feeding device 2. The relay transport unit 17 is provided below the second paper feed unit 80. The relay conveying unit 17 receives the recording sheet P1 conveyed from the image forming apparatus 1 and conveys the recording sheet P to the downstream. The insertion conveyance path 18 is provided between the second sheet feeding portion 80 and the relay conveyance portion 17. The insertion conveyance path 18 merges with the relay conveyance section 17 at a merging section 19.

The relay conveyance unit 17 includes: a feeding inlet 20 that opens to an upstream side in the sheet conveying direction and receives a recording sheet P1 output from the image forming apparatus 1; a relay conveying path 21 extending from the feed port 20 to a downstream side in a sheet conveying direction; and a relay conveying roller 22 provided at a position midway in the relay conveying path 21 and conveying the recording sheet P1 downstream in the relay conveying path 21.

The second sheet feeding unit 80 includes one or more (2 in this case) sheet feeding units 24 for feeding the inserted sheet P2.

The sheet feeding unit 24 includes a sheet stacking portion 16, a remaining amount detecting mechanism 70, and an upstream end opening 23. The sheet stacking portion 16 stacks the insertion sheets P2. The remaining amount detecting mechanism 70 is provided in the sheet stacking portion 16 and detects the remaining amount of the inserted sheet P2. The upstream end opening 23 is adjacent to the sheet stacking portion 16 in the sheet conveying direction.

The insertion conveyance path 25 extends in the sheet conveyance direction from the upstream-side end opening 23 to the junction 19 that merges with the relay conveyance path 21. The insertion conveying path 25 is a path that communicates the sheet stacking portion 16 with the relay conveying path 21.

The paper feed unit 24 is provided above the upstream-side end opening 23. The paper feed unit 24 includes a feed roller 27, and the feed roller 27 is provided adjacent to the upstream end opening 23 of the insertion conveyance path 25 in the sheet conveyance direction. The sheet feeding roller 27 is in contact with an upper surface of the sheet stacking portion 16 on which the sheet P2 is inserted. A conveying roller pair 26 is provided at a position midway in the sheet conveying direction in the conveying path 25.

The paper feed unit 24 rotates the paper feed roller 27 in a state where the paper feed roller 27 is in contact with the upper surface of the inserted sheet P2, and feeds the inserted sheet P2 to the insertion conveyance path 25. The inserted sheet P2 fed into the insertion conveyance path 25 is conveyed to the junction 19 by the conveyance roller pair 26, inserted into the relay conveyance path 21 in the junction 19, and conveyed to the sheet post-processing apparatus 3. In this way, the second sheet feeding unit 80 inserts the sheet P2 from the sheet stacking unit 16 to between the plurality of recording sheets P1 passing through the junction unit 19 at a predetermined timing.

A junction sensor 28 that can detect the recording sheet P1 that has reached the junction 19 is provided in the junction 19 of the relay conveying path 21. The detection signal of the junction sensor 28 is sent to the control unit 59 (see fig. 4).

The sheet stacking portion 16 is provided with a sheet detection sensor 75. The sheet detection sensor 75 detects whether or not a sheet P2 is inserted into the sheet stacking portion 16. When the inserted sheet P2 in the sheet stacking portion 16 runs out, the sheet detection sensor 75 transmits a detection signal to the control portion 59 of the image forming apparatus 1.

An insertion detection sensor 29 for detecting the passage of the insertion sheet P2 is provided midway along the insertion conveyance path 25 from the upstream-side end opening 23 to the junction 19. The detection signal of the insertion detection sensor 29 is transmitted to the control unit 59 of the image forming apparatus 1 (see fig. 4).

The sheet post-processing apparatus 3 performs predetermined post-processing such as a punching process and a stapling process on a sheet bundle including a plurality of recording sheets P1 fed out from the image forming apparatus 1 and an insertion sheet P2 inserted between the plurality of recording sheets P1.

The sheet post-processing apparatus 3 is provided with a sheet feeding port 31 for receiving a recording sheet P1 conveyed from the sheet feeding device 2 and an inserted sheet P2. The sheet post-processing apparatus 3 includes a punch forming device 32, an end binding unit 33, and a saddle-stitching/intermediate folding unit 36 provided therein. The punching device 32 performs a punching process on the recording sheet P1 and the inserted sheet P2 fed from the sheet feeding port 31. The end binding unit 33 forms a sheet bundle by stacking a plurality of fed recording sheets P1 and an inserted sheet P2, aligns the ends of the sheet bundle, and binds the sheet bundle with a binding staple. The saddle stitching/intermediate folding unit 36 performs a binding process on the center of the sheet bundle, and then folds the sheet bundle into a booklet shape around the binding portion. A main tray 34 that can be raised and lowered to a position suitable for discharging a sheet bundle and a sub tray 35 fixed to the upper portion of the sheet post-processing apparatus 3 are provided on a side surface of the sheet post-processing apparatus 3.

The punch forming device 32 is disposed above the sheet post-processing apparatus 3. The recording sheet P1 and the inserted sheet P2 that have passed through the relay conveying path 21 of the sheet feeding device 2 are fed from a sheet feeding port 31 provided at the upper right of the sheet post-processing apparatus 3 to pass through the punching device 32. When the binding process is not performed on the recording sheet P1 and the inserted sheet P2, the recording sheet P1 and the inserted sheet P2 are discharged to the sub tray 35 as they are. When the stapling process is performed, the sheet is conveyed to the end-binding unit 33 or the saddle stitching/intermediate folding unit 36 disposed below the punch forming device 32.

The end binding unit 33 is constituted by a stapler, a processing tray (both not shown), and the like. The fed recording sheet P1 and the inserted sheet P2 are stacked on the processing tray in a stack of sheets. The stack of sheets moves to a stapler provided at an end of the processing tray in a state where the front end of the stack is aligned, staples the end, and then is discharged to the main sheet tray 34 along the processing tray.

The saddle stitching/intermediate folding unit 36 is disposed below the end binding unit 33. The saddle stitching/intermediate folding unit 36 is constituted by a saddle stitching stapler, an intermediate folding device, a paper guide (none of which is shown), and the like. The saddle stitching stapler performs a binding process on a central portion of a sheet bundle stacked in a sheet guide. The sheet bundle stapled by the saddle stitching stapler is folded into a booklet shape by the intermediate folding device around the stapling portion, and then discharged to the booklet tray 37.

As described above, the sheet feeding device 2 includes the plurality of sheet stacking portions 16. By stacking different insertion sheets P2 in each sheet stacking portion 16, booklets using different types of insertion sheets P2 for front cover, back cover, and the like can be produced.

In this way, a predetermined number of recording sheets P1 fed from the image forming apparatus 1 and a predetermined number of inserted sheets P2 fed from the sheet feeding apparatus 2 are conveyed to the sheet post-processing apparatus 3 to form a stack of sheets, and the stack of sheets is subjected to predetermined post-processing to produce a booklet.

Next, a mode of detecting the remaining amount of the inserted sheet P2 in the sheet stacking portion 16 by the remaining amount detecting mechanism 70 will be described in detail with reference to fig. 2 and 3. Fig. 2 and 3 are partially enlarged views showing the vicinity of the paper feed unit 24 from the sheet width direction. Fig. 2 shows a state where the remaining amount of the inserted sheet P2 in the sheet stacking portion 16 is equal to or larger than a predetermined amount. Fig. 3 shows a state where the remaining amount of the inserted sheet P2 in the sheet stacking portion 16 is equal to or less than a predetermined amount.

As shown in fig. 2 and 3, the sheet stacking portion 16 includes a bottom surface 38 inclined to rise from a downstream side (right side in the drawing) to an upstream side (left side in the drawing) in the sheet conveying direction, and an upright wall portion 39 located at a downstream end of the bottom surface 38. An upstream end opening 23 inserted into the conveyance path 25 is provided in an upper portion of the standing wall portion 39.

A lift plate 40 is disposed on the bottom surface 38 of the sheet stacking portion 16. The inserted sheet P2 in the sheet stacking portion 16 is stacked on the lifting plate 40. The lift plate 40 is adjacent to the standing wall portion 39 of the sheet stacking portion 16 in the sheet conveying direction. An upstream end portion (not shown) of the lifting plate 40 is rotatably supported so that a downstream end portion of the lifting plate 40 can be raised and lowered in a height direction (vertical direction in the drawing).

A lifting mechanism 41 for lifting and lowering a downstream end of the lifting plate 40 is provided between the bottom surface 38 of the sheet stacking portion 16 and the lifting plate 40. The lift mechanism 41 includes a blade 42, a drive source 71 (see fig. 4) such as a motor that generates power, and a rotatable drive shaft 43 connected to the drive source 71.

The drive shaft 43 is located below the lift plate 40 and extends in a sheet width direction (a direction perpendicular to the drawing sheet) perpendicular to the sheet conveying direction. The work sheet 42 is a rectangular plate-like member elongated in the sheet conveying direction. The upstream end of the working piece 42 is fixed to the drive shaft 43. The blade 42 rotates about the drive shaft 43 in accordance with the rotation of the drive shaft 43. This causes the downstream end of the blade 42 to swing in the vertical direction (vertical direction in the figure).

When the drive shaft 43 is rotated counterclockwise (in the direction of the arrow in the figure) by the power of the drive source 71, the downstream end of the blade 42 is raised by the rotation. Here, as described above, the drive shaft 43 is disposed below the lift plate 40, and the working piece 42 fixed to the drive shaft 43 is also located below the lift plate 40. Therefore, the downstream-side end portion of the operating piece 42 comes into contact with the back surface of the lift plate 40 while rising, thereby lifting the downstream-side end portion of the lift plate 40. In this way, the lift mechanism 41 can raise and lower the downstream end of the lift plate 40 by the swing of the operating piece 42 using the power of the drive source 71.

A detection piece 44 is provided on the drive shaft 43 at a position different from the position of the working piece 42 in the sheet width direction. The detection piece 44 is a small piece elongated in the sheet conveying direction. A through-hole 45 penetrating in the sheet width direction is formed in the upstream end of the detection piece 44. By inserting the drive shaft 43 into the through-hole 45, the detection piece 44 is supported by the drive shaft 43 so as to be rotatable by a predetermined angle about the drive shaft 43. A light shielding portion 46 having a rectangular plate shape extending to the downstream side in the sheet conveying direction is formed at the downstream side end portion of the detection piece 44.

When the operation piece 42 is rotated by a predetermined angle or more about the drive shaft 43, the downstream end of the detection piece 44 swings upward from a position parallel to the bottom surface 38 from the bottom surface following the rotation of the operation piece 42.

The detection piece 44 and the drive shaft 43 are connected by a link mechanism 47. The link mechanism 47 has an engaging projection (first engaging portion) 48 projecting radially from the drive shaft 43, and an engaging hole (second engaging portion) 49 formed in the detection piece 44 for inserting the engaging projection 48. The engaging hole 49 is a concave hole recessed in the direction in which the engaging projection 48 projects. An engaging surface 50 facing the circumferential direction of the drive shaft 43 is formed on the upper surface of the inner peripheral surface of the engaging hole 49 with respect to the outer peripheral surface of the engaging projection 48.

As shown in fig. 2, when the downstream end of the operating piece 42 is at a relatively low position and the lift plate 40 is in a lowered state, that is, when the rotation angle of the drive shaft 43 is relatively small, a gap 51 is formed between the engaging projection 48 and the engaging surface 50. When the drive shaft 43 rotates counterclockwise in the drawing from the above state, the engaging projection 48 also rotates about the drive shaft 43, and the gap 51 between the outer peripheral surface of the engaging projection 48 and the engaging surface 50 becomes smaller. When the drive shaft 43 is further rotated from the above state, the engagement projection 48 comes into contact with the engagement surface 50. At this time, as shown in fig. 3, the rotation of the driving shaft 43 is transmitted to the detection piece 44 via the engaging surface 50, and the detection piece 44 is rotated about the driving shaft 43. Thus, the detection piece 44 rotates following the operation piece 42 with a timing different from the rotation of the operation piece 42.

When the lift plate 40 is raised from the lower limit position by the counterclockwise rotation of the operating piece 42, the detection piece 44 is connected to the operating piece 42 at the connection position and follows the rotation of the operating piece 42 at a constant angle. When the lift plate 40 is lowered from the sheet feeding position (position where the upper surface of the inserted sheet P2 contacts the sheet feeding roller 27), the detection piece 44 and the operation piece 42 are integrally rotated to the connection position, and when the lift plate 40 is further lowered and the detection piece 44 contacts the bottom surface 38 to stop rotating, only the operation piece 42 is rotated, and at the lower position, the operation piece 42 and the detection piece 44 are substantially parallel.

As shown in fig. 2 and 3, a remaining amount detection sensor 52 is provided on the bottom surface 38 of the sheet stacking portion 16 so as to be adjacent to the detection piece 44 in the sheet conveying direction. The remaining amount detection sensor 52 includes a light emitting portion 53 and a light receiving portion (not shown) facing each other in the sheet width direction. The light receiving part of the remaining amount detection sensor 52 receives the light emitted from the light emitting part 53.

As shown in fig. 2, when the engaging projection 48 and the engaging surface 50 have a gap 51, the light shielding portion 46 of the detection piece 44 is inserted between the light emitting portion 53 and the light receiving portion of the remaining amount detection sensor 52. That is, when the rotation angle of the drive shaft 43 is relatively small and the rotation of the drive shaft 43 is not transmitted to the detection piece 44, the light shielding portion 46 of the detection piece 44 is at the same height as the light emitting portion 53 of the remaining amount detection sensor 52. Therefore, the light emitted from the light emitting portion 53 is blocked by the light blocking portion 46, and the light receiving portion does not receive the light emitted from the light emitting portion 53.

From this state, as described above, when the driving shaft 43 rotates and the light-shielding portion 46 rises to a position higher than the light-emitting portion 53 as shown in fig. 3, the light-receiving portion receives the light emitted from the light-emitting portion 53. In this way, by detecting that the detection piece 44 has risen to a position higher than the light emitting unit 53 by the remaining amount detection sensor 52, it is possible to detect that the downstream end of the operation piece 42 has risen, that is, the lift plate 40 has risen to a height higher than the predetermined height. The detection result of the remaining amount detection sensor 52 is sent to the control section 59.

As shown in fig. 2 and 3, the paper feed unit 24 includes an apparatus main body 54 disposed above the lift plate 40, a paper feed roller 27 provided in the apparatus main body 54, and a light blocking sheet 55 projecting in the sheet width direction from the apparatus main body 54. The apparatus main body 54 is provided to be movable up and down in an up-and-down direction (up-and-down direction in the drawing). The sheet feed roller 27 is adjacent to the upstream end opening 23 of the insertion conveyance path 25 in the sheet conveyance direction.

A lift sensor 56 is provided at a position facing the apparatus main body 54 in the sheet width direction. The lift sensor 56 includes a light emitting portion 57 and a light receiving portion (not shown) facing each other in the sheet width direction. The light receiving portion receives light emitted from the light emitting portion 57. The elevation sensor 56 can detect that the inserted sheet P2 is in contact with the sheet feeding roller 27 and the apparatus main body 54 is at a position higher than a predetermined height. The detection result of the elevation sensor 56 is sent to the control unit 59 (see fig. 4).

When the lift plate 40 is lowered and the feed roller 27 does not contact the upper surface of the inserted sheet P2, the light-shielding sheet 55 is inserted between the light-emitting portion 57 and the light-receiving portion of the lift sensor 56. Thus, the light-shielding sheet 55 shields the light emitted from the light-emitting portion 57 of the lift sensor 56. When the lift plate 40 is raised, the upper surface of the inserted sheet P2 contacts the sheet feeding roller 27, and the lift plate 40 is further raised, the sheet feeding roller 27 is pushed upward by the inserted sheet P2. Thus, the device main body 54 is raised, and the light shielding sheet 55 is pulled out from between the light emitting portion 57 and the light receiving portion of the lift sensor 56. Therefore, the light emitted from the light emitting portion 57 is received by the light receiving portion.

As shown in fig. 2 and 3, when the lift plate 40 is raised and the upper surface of the inserted sheet P2 contacts the feed roller 27, the feed roller 27 is rotated in the sheet conveying direction (counterclockwise in the figure), and the inserted sheet P2 is fed to the upstream end opening 23 of the relay conveying path 21. In this way, the sheet feeding roller 27 can continuously feed the inserted sheets P2 positioned on the upper surfaces of the plurality of inserted sheets P2 one by one to the insertion conveyance path 25.

From the state of fig. 2, the inserted sheets P2 in the sheet stacking portion 16 are fed one by one to the insertion conveyance path 25, and when the remaining amount of the inserted sheets P2 is reduced, the position of the upper surface of the inserted sheets P2 in the sheet stacking portion 16 is lowered. At this time, the force pressing the paper feed roller 27 becomes weak, and the apparatus main body 54 descends. When the apparatus main body 54 is lowered and the light-shielding sheet 55 is inserted again between the light-emitting portion 57 and the light-receiving portion of the lift sensor 56, the light emitted from the light-emitting portion 57 is shielded by the light-shielding sheet 55.

Here, the control unit 59 is connected to the driving source 71, the remaining amount detection sensor 52, and the elevation sensor 56. The control unit 59 may control the driving of the driving source 71 based on the detection result of the elevation sensor 56 (see fig. 4).

When the light-shielding sheet 55 shields the light emitted from the light-emitting portion 57 of the lift sensor 56, the control unit 59 operates the driving source 71 to raise the lift plate 40. In this way, the upper surface of the inserted sheet P2 rises and the apparatus main body 54 rises again, so the light-shielding sheet 55 also rises. As shown in fig. 3, when the light-shielding sheet 55 is lifted up and pulled out from between the light-emitting portion 57 and the light-receiving portion of the lift sensor 56, the light-receiving portion of the lift sensor 56 receives the light emitted from the light-emitting portion 57. At this time, the control section 59 stops the elevation of the elevation plate 40. The control unit 59 controls the drive source 71 to raise and lower the lift plate 40.

As described above, the controller 59 raises the lift plate 40 until the lift sensor 56 detects the rise of the light-shielding sheet 55 by the contact between the upper surface of the inserted sheet P2 and the feed roller 27. As shown in fig. 2, when the remaining amount of the inserted sheet P2 is larger than a predetermined amount, the lift plate 40 is raised only to a position lower than a predetermined height. At this time, a slight gap 51 is formed between the outer peripheral surface of the engaging projection 48 and the engaging surface 50, and the rotation of the drive shaft 43 is not transmitted to the detection piece 44. Therefore, the downstream end portion (light-shielding portion 46) of the detection piece 44 is inserted between the light-emitting portion 53 and the light-receiving portion of the remaining amount detection sensor 52 without being raised. Thus, the remaining amount detection sensor 52 detects that the detection piece 44 is not lifted.

When the sheet feeding roller 27 rotates in the sheet conveying direction from this state to feed the inserted sheets P2 one by one, the upper surface of the inserted sheet P2 lowers as described above. Therefore, the control section 59 raises the lift plate 40. At this time, since the control unit 59 controls the drive source 71 to rotate the drive shaft 43, the gap 51 between the outer periphery of the engaging projection 48 and the engaging surface 50 is reduced. When the drive shaft 43 further rotates and the outer peripheral surface of the engaging projection 48 comes into contact with the engaging surface 50 and the gap 51 disappears, the rotation of the drive shaft 43 is transmitted to the detection piece 44. When the drive shaft 43 further rotates from this state, the detection piece 44 gradually rotates. As shown in fig. 3, when the remaining amount of the inserted sheet P2 is less than the predetermined amount, the light-shielding portion 46 of the detection piece 44 reaches a position higher than the light-emitting portion 53 of the remaining amount detection sensor 52, and the light-receiving portion of the remaining amount detection sensor 52 receives the light emitted from the light-emitting portion 53 (that is, the remaining amount detection sensor 52 detects the rise of the downstream end portion (light-shielding portion 46) of the detection piece 44.)

The remaining amount detecting mechanism 70 includes the above-described remaining amount detecting sensor 52, the lift mechanism 41, the lift plate 40, the paper feeding unit 24, and the lift sensor 56, and determines that the remaining amount of the sheet stacking portion 16 has reached the predetermined amount or less based on the detection result of the remaining amount detecting sensor 52.

Fig. 4 is a block diagram showing a control path of the image forming system of the present invention. Further, since various controls are required for each part of the apparatus when the image forming system is used, the control section 59 itself becomes complicated. Here, the parts of the control unit 59 necessary for carrying out the present invention will be described in detail.

The control unit 59 includes at least a cpu (central Processing unit)60 as a central Processing unit, a rom (read Only memory)61 (recording unit) as a storage unit dedicated to reading, a ram (random Access memory)62 as a storage unit readable and writable, a temporary storage unit 63 for temporarily storing image data and the like, the paper feed counter 13, the insertion counter 30, the copy count counter 64, and an I/F (interface) 65. The controller 59 transmits and receives control signals to and from the image forming apparatus 1, the sheet feeding device 2, and the sheet post-processing apparatus 3 via the I/F65. Although the entire image forming system is controlled by the controller 59 of the image forming apparatus 1, the controller may be provided in the sheet post-processing apparatus 3 or the sheet feeding apparatus 2.

The ROM61 stores data such as control programs for the system and numerical values necessary for control. The RAM62 stores necessary data generated during control of the system, data temporarily necessary for control, and the like.

The ROM61 stores therein a numerical value of the maximum number of recording sheets P1 that can be present between the first sheet feeding portion 4 and the merging portion 19 (hereinafter referred to as "maximum number of left sheets") set for each image forming mode. The maximum number of retained sheets varies depending on the time required for image formation. The time required for image formation differs depending on the image forming mode, such as monochrome printing, color printing, single-sided printing, double-sided printing, and sheet size, and therefore the time for the recording sheet P1 to reach the junction 19 from the first sheet feeding portion 4 also differs. The optimum maximum number of retained sheets is selected in accordance with the print contents instructed by the user.

The sheet feed counter 13 counts the number of sheets P1 fed from the first sheet feeding unit 4 based on the detection result of the sheet feed detection sensor 12. The insertion counter 30 counts the number of sheets P2 fed from the sheet stacking portion 16 based on the detection result of the insertion detection sensor 29.

The number-of-copies counter 64 counts the number of copies of the sheet bundle conveyed to the sheet post-processing apparatus 3 based on the detection result of the insertion detection sensor 29 and the count value of the insertion counter 30. For example, when a booklet including one cover and one back cover is prepared, if the count value of the insertion counter 30 is an odd number and the insertion detection sensor 29 detects the feeding of the inserted sheet P2, the fed inserted sheet P2 is determined to be the inserted sheet P2 that is the back cover of the booklet, and the number of copies is counted by the copy counter 64.

Note that the paper feed counter 13, the insertion counter 30, and the number-of-copies counter 64 may not be separately provided, and the RAM62 may store the number of times.

The controller 59 also sends control signals from the CPU60 to each unit and each device in the system including the image forming apparatus 1, the sheet post-processing apparatus 3, and the sheet feeding apparatus 2 via the I/F65. Further, signals indicating the states of the respective sections and devices and input signals are transmitted to the CPU60 via the I/F65. Examples of the parts and devices controlled by the control unit 59 include the first sheet feeding unit 4, the image recording unit 8 of the image forming apparatus 1, the second sheet feeding unit 80 of the sheet feeding device 2, the hole punching forming device 32 of the sheet post-processing apparatus 3, the end binding unit 33, and a stapler (see fig. 1).

The operation unit 66 (input unit) is provided with a liquid crystal display unit 67 (notification unit), a light emitting diode 68 indicating various states, and a numeric keypad 69, and a user inputs an instruction by operating the operation unit 66 to perform various settings of the image forming apparatus 1, the sheet post-processing apparatus 3, and the sheet feeding apparatus 2, and execute various functions such as an image forming function and a post-processing function. The liquid crystal display section 67 displays the state of the system, displays the image formation status and the number of printed copies, and is used as a touch panel for performing functions such as double-sided printing and monochrome inversion, and various settings such as magnification setting and density setting. Numeric keys 69 are used for setting the number of copies to be printed, inputting a FAX number of a destination when image forming apparatus 1 has a FAX function, and the like.

The operation unit 66 is provided with a start key for instructing the user to start image formation, a stop/clear button used when image formation is suspended, a reset button used when various system settings are set to default states, and the like.

Further, the image forming system 100 may be configured as follows: the external input device 72 is connected to an external input device such as a personal computer or a tablet terminal, and an instruction is input to perform various settings of the image forming apparatus 1, the sheet post-processing apparatus 3, and the sheet feeding apparatus 2, thereby executing various functions.

Here, when the maximum number of remaining sheets is less than the number of recording sheets P1 included in one sheet stack (hereinafter referred to as "predetermined number of sheets to be output"), there is no recording sheet P1 of which the number of sheets to be output is equal to or greater than the predetermined number of sheets to be output from the paper feed portion 6 to the merging portion 19. Therefore, when the remaining amount of the inserted sheet P2 runs out and feeding of a new recording sheet P1 from the first sheet feeding unit 4 is stopped, the number of sheets does not exceed the predetermined number of sheets to be fed even if a number of recording sheets P1 have already been fed. The fed sheets of recording sheets P1 are discharged to the sub tray 35 of the sheet post-processing apparatus 3 without being post-processed. Therefore, a booklet without a cover is not produced.

On the other hand, when the maximum number of remaining sheets is larger than the predetermined number of sheets to be fed, even if the remaining amount of the inserted sheet P2 runs short and feeding of a new recording sheet P1 from the first sheet feeding portion 4 is stopped, there is a possibility that the recording sheet P1 exceeding the predetermined number of sheets to be fed exists between the sheet feeding portion 6 and the merging portion 19 at this point. Therefore, there is a risk that the recording sheets P1, from which the predetermined number of sheets are output, are conveyed to the sheet post-processing apparatus 3, and a booklet without a cover is formed.

Here, the control portion 59 creates booklets as usual when the maximum number of left sheets is less than the predetermined number of output sheets, and when the maximum number of left sheets is greater than the predetermined number of output sheets and the remaining amount of the inserted sheet P2 is greater than a predetermined amount. When the maximum number of remaining sheets is larger than the predetermined number of sheets to be output and the remaining amount of the inserted sheet P2 is equal to or less than the predetermined amount, the feeding interval of the recording sheets P1 is delayed so that the number of recording sheets P1 existing between the paper feeding portion 6 and the merging portion 19 is not more than the predetermined number of sheets to be output. In this way, the image forming system 100 prevents the booklet without a cover from being produced, and can suppress a decrease in productivity.

The change in the feeding interval of the recording sheet P1 may be a constant standby time set so that the feeding is performed at a timing (second timing) longer than the feeding timing (first timing) of the other recording sheet P1 only when the next (i.e., first) recording sheet P1 is fed after the feeding of the inserted sheet P2, or may be an even standby time set when all the recording sheets P1 are fed.

Although the user may misunderstand that the image forming apparatus 1 is malfunctioning if the recording sheets P1 are fed at different intervals, it is possible to suppress the misunderstanding if the feeding interval of the recording sheet P1 is set to a uniform standby time when all the recording sheets P1 are fed.

Next, the paper feed control by the control section 59 will be described with reference to the flowcharts of fig. 5 to 7. Fig. 5 to 7 are flowcharts showing an example of feeding control of the recording sheet P1 and the inserted sheet P2.

As shown in fig. 5, when the user inputs a print instruction from the operation unit 66 (yes in step 1), it is determined whether or not the maximum number of remaining sheets is less than the predetermined number of output sheets based on the content of the print instruction (step 2).

When it is determined in step 2 that the maximum number of remaining sheets is less than the predetermined number of sheets to be output (yes in step 2), the recording sheet P1 is fed from the first sheet feeding unit 4, and the inserted sheet P2, which is a cover of the booklet, is fed from the sheet stacking unit 16 (step 3). If it is determined in step 2 that the maximum number of remaining sheets is equal to or greater than the predetermined number of output sheets (no in step 2), the process proceeds to step 12 shown in fig. 6.

When the recording sheet P1 and the inserted sheet P2 are fed in step 3, it is determined whether or not the remaining amount of the inserted sheet P2 is present in the sheet stacking portion 16 based on the detection result of the sheet detection sensor 75 (step 4). If it is determined in step 4 that the remaining amount of the inserted sheet P2 is present (yes in step 4), the paper feed counter 13 counts the number of sheets to be fed of the recording sheet P1 based on the detection result of the paper feed detection sensor 12 (step 5). If it is determined in step 4 that the remaining amount of the inserted sheet P2 is not present, the booklet forming operation is suspended, and the content of the empty remaining amount of the inserted sheet P2 is displayed on the liquid crystal display unit 67 (step 11).

After the number of sheets P1 fed is counted in step 5, it is determined whether or not the timing of insertion of the sheet P2 is the bottom of the booklet (step 6). For example, when a booklet including 3 recording sheets is to be prepared, the number of recording sheets P1 fed is not equal to the number of sheets required for 1 booklet (here, 3 sheets) at the time when the count value of the sheet feed counter 13 is 1 or 2, and therefore, the timing of inserting the insertion sheet P2 is not included (no in step 6). In this case, the process proceeds to step 7, and the recording sheet P1 is fed, and steps 5 to 7 are repeated until the timing of insertion.

When the count value of the sheet feed counter 13 reaches the predetermined number of output sheets of the recording sheet P1 in the determination of step 6, that is, when the timing to insert the insertion sheet P2 is reached ("yes" in step 6), the insertion sheet P2, which is the back cover of the booklet, is fed from the sheet stacking portion 16 to the junction portion 19 (step 8). Next, the insertion detection sensor 29 detects the feeding of the inserted sheet P2 that is to be the back cover, and the number-of-copies counter 64 counts the number of copies of the sheet bundle conveyed to the sheet post-processing apparatus 3 (step 9).

Then, it is determined whether or not a predetermined number of sheet stacks are fed (step 10). Here, for example, when a print instruction to create a 5-fold book is input to the image forming system 100, and the count value of the number-of-copies counter 64 is 4 or less, the number of sheet bundles conveyed to the sheet post-processing apparatus 3 does not reach the predetermined number of copies to be created (here, 5 copies). Therefore, the above-described steps 3 to 10 are repeated again until the number of copies counter 64 is equal to the number of copies made.

If the count value of the insertion counter 30 is equal to the predetermined number of sheets to be formed in step 10 (yes in step 10), the booklet forming job is ended after predetermined post-processing is performed on all the sheet bundles conveyed to the sheet post-processing device 3.

In step 3, when the sheet feeding detection sensor 12 does not detect the feeding of the recording sheet P1 within a predetermined time from the feeding when the recording sheet P1 is fed, it is determined that the remaining amount of the recording sheet P1 in the first sheet feeding unit 4 is used up, the booklet creation operation is suspended, and the liquid crystal display unit 67 displays the content of the remaining amount of the recording sheet P1 (not shown). The presence or absence of the remaining amount of the sheet feeding cassette 4a may be determined by separately providing a sensor for detecting the presence or absence of the remaining amount of the recording sheet P1 in the sheet feeding cassette 4a and determining the remaining amount based on the detection result of the sensor.

Next, the following control when it is determined in step 2 that the maximum number of remaining sheets is equal to or greater than the predetermined number of sheets to be output (no in step 2) will be described with reference to fig. 6.

When it is determined in step 2 that the maximum number of remaining sheets is equal to or greater than the predetermined number of sheets to be output ("no" in step 2), it is next determined whether or not the remaining amount of the inserted sheets P2 in the sheet stacking portion 16 is greater than the predetermined number of sheets (step 12). When it is determined that the remaining amount of the inserted sheet P2 is larger than the predetermined number of sheets (yes in step 12), the recording sheet P1 is fed from the first sheet feeding unit 4, and the inserted sheet P2 is fed from the sheet stacking unit 16 (step 13). If it is determined that the remaining amount of the inserted sheet P2 is less than the predetermined number of sheets (no in step 12), the process proceeds to step 20 in fig. 7.

When the recording sheet P1 and the inserted sheet P2 are fed in step 13, the paper feed counter 13 counts the number of sheets P1 fed (step 14). Next, it is determined whether or not the timing to insert the sheet P2 is the insertion timing (step 15). If the timing is not the insertion timing (no in step 15), the recording sheet P1 is fed (step 16), and steps 14 to 16 are repeated until the insertion timing is reached. If the timing is an insertion timing (yes in step 15), the process proceeds to step 17. Since steps 17 and 18 are the same as steps 8 and 9 described above, the description thereof will be omitted.

In step 19, it is determined whether or not the sheet bundle of a predetermined number of sheets is conveyed to the sheet post-processing apparatus 3. When the predetermined number of sheet bundles are conveyed (yes in step 19), the booklet forming job is ended after predetermined post-processing is performed on all the sheet bundles conveyed to the sheet post-processing device 3. If the predetermined number of sheets has not been conveyed (no in step 19), the process returns to step 12.

Next, the following control when it is determined in step 12 that the remaining amount of the inserted sheets P2 in the sheet stacking portion 16 is less than the predetermined number of sheets (no in step 12) will be described with reference to fig. 7.

When it is determined in step 12 that the remaining amount of the inserted sheets P2 in the sheet stacking portion 16 is less than the predetermined number, the inserted sheets P2 are fed from the sheet stacking portion 16, and the feeding of the recording sheets P1 is delayed by the feeding interval (step 20). Next, it is determined whether or not the sheet P2 is left on the sheet stacking portion 16 based on the detection result of the sheet detection sensor 75 (step 21). If it is determined in step 21 that no inserted sheet P2 remains on the sheet stacking portion 16 (no in step 21), the booklet forming operation is suspended and the content of the empty remaining amount of the inserted sheet P2 is displayed on the liquid crystal display portion 67 (step 28).

If it is determined in step 21 that the inserted sheet P2 remains in the sheet stacking portion 16 (yes in step 21), the sheet feed counter 13 counts the number of sheets to be fed of the recording sheet P1 (step 22). Next, it is determined whether or not the timing to insert the sheet P2 is the insertion timing (step 23). Here, if the timing for inserting the sheet P2 is not the insertion timing (no in step 23), the feeding interval is delayed until the recording sheet P1 is fed from the first sheet feeding unit 4 (step 24), and steps 22 to 24 are repeated until the insertion timing is reached.

The feeding interval of the recording sheets P1 in steps 20 and 24 is delayed such that the number of recording sheets P1 existing between the junction portion 19 and the first sheet feeding portion 4 during continuous printing is less than the number of recording sheets P1 included in one sheet stack.

If it is determined in step 23 that the timing is the insertion timing (yes in step 23), the insertion sheet P2 is fed (step 25), and the number-of-copies counter 64 counts the sheet bundle conveyed to the sheet post-processing apparatus 3 (step 26).

After counting the number of sheets of the sheet bundle in step 26, it is determined whether or not the number of sheets of the sheet bundle conveyed to the sheet post-processing apparatus 3 reaches a predetermined number of booklets to be made (step 27). Here, if the predetermined number of copies of booklets is reached (yes in step 27), a predetermined post-processing is performed on all the sheet bundles conveyed to the sheet post-processing apparatus 3, and then the booklet creation job is ended. If not, return to step 20.

In this way, the controller 59 controls the feeding of the recording sheet P1 so that no recording sheet P1 with the number of output sheets equal to or greater than the predetermined number is present between the paper feed portion 6 and the merging portion 19.

Here, when a recording sheet is stopped at an intermediate position in a paper feed path of the image forming apparatus, the recording sheet is generally burned by internal heat, or the position in the sheet conveying direction is shifted when the operation is restarted, thereby causing an image failure. Therefore, when the remaining amount of the inserted sheet runs out, the recording sheet present in the image forming apparatus may be conveyed to the downstream side without being stopped in the sheet conveying path, and a booklet without a cover may be produced. In order to solve such a problem, in the conventional image forming system, in order to suppress the formation of a booklet without a cover, when the remaining amount of the inserted sheet is smaller than a predetermined amount, the inserted sheet is first fed, and then the feeding of the recording sheet is made to wait until the sheet detection sensor detects that the remaining amount of the inserted sheet exists. Therefore, when the remaining amount of inserted sheets is reduced, the feeding interval of the recording sheets is delayed, and therefore, it takes time to create booklets, which reduces productivity.

In contrast, the image forming system 100 according to the present embodiment first determines whether or not the maximum remaining sheet number is smaller than the predetermined output sheet number, and if so, creates booklets as they are even if the remaining amount of the inserted sheet P2 is smaller than a predetermined amount (see fig. 5). Further, as described above, even if the maximum number of sheets left is equal to or greater than the predetermined number of sheets to be output, there is no risk that a booklet without a cover is produced while the number of sheets P2 inserted is more than a predetermined amount, and therefore, the booklet is produced as usual. Thus, the productivity can be suppressed from being lowered.

In step 3 and step 13, although feeding of the inserted sheet P2 serving as a cover and feeding of the recording sheet P1 are performed in the same step, the inserted sheet P2 and the recording sheet P1 are fed at a timing when the inserted sheet P2 is fed into the sheet post-processing apparatus 3 before the recording sheet P1. As long as the inserted sheet P2 serving as a cover is fed into the sheet post-processing apparatus 3 before the recording sheet P1, the recording sheet P1 may be fed from the first sheet feeding unit 4 at the same time as the feeding timing of the inserted sheet P2, or may be fed before the inserted sheet P2 is fed from the sheet stacking unit 16. In this way, the recording sheet P1 can be fed without causing a standby state in which the sheet P2 is inserted, and booklets can be efficiently made.

When the predetermined number of output sheets is less than the maximum remaining number of sheets and the remaining amount of the inserted sheet P2 is less than the predetermined amount (step 20), the subsequent feeding of the recording sheet P1 is delayed by the feeding interval (step 20, step 24). In this way, when the remaining amount of the inserted sheet P2 is used up, no more recording sheets P1 than the predetermined number of sheets to be output can be present between the junction unit 19 and the first sheet feeding unit 4, and therefore, the formation of a booklet without a cover can be suppressed.

As described above, the image forming system 100 of the present embodiment can suppress the production of a booklet without a cover and the reduction in productivity.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

For example, although the maximum remaining number is stored in the ROM61 in advance in the above embodiment, the maximum remaining number may be calculated each time a booklet making job is performed. At this time, a timer 74 (time measuring unit) is provided in the controller 59, and the conveyance speed of the recording sheet P1 for each image forming mode and the sheet feeding interval (time) of the recording sheet P1 for each image forming mode are recorded in the ROM61 (see fig. 4).

When the user instructs printing, the recording sheet P1 is fed. When the paper feed detection sensor 12 detects the feeding, the timer 74 starts time measurement. When the recording sheet P1 reaches the merging portion 19 and the merging sensor 28 detects the recording sheet P1, the time measurement by the timer 74 is completed. The maximum number of retained sheets is calculated from the measured time and the conveyance speed and paper feed interval selected based on the print content instructed by the user. The calculated maximum number of retained sheets is stored in the temporary storage unit 63 or the RAM 62.

The maximum number of accumulated sheets varies depending on the specification of the sheet feeding device 2 connected downstream of the image forming apparatus 1, depending on the distance from the first sheet feeding portion 4 to the merging portion 19. Further, depending on the image forming mode, the time required for forming an image varies, and the maximum number of retained sheets also varies. With the above configuration, even when the sheet feeding device 2 is replaced with another sheet feeding device or when the image forming mode is changed, the above control (step 2 in fig. 5) can be performed based on the accurate maximum number of remaining sheets, and it is possible to more effectively suppress a decrease in productivity and suppress the production of booklets without covers.

The maximum remaining number of sheets may be calculated only in the first booklet creation job after the sheet feeding device 2 is replaced with another sheet feeding device or the image forming mode is changed to a different image forming mode, and the calculated value may be stored in the RAM 62. The calculated value stored in the RAM62 may be used in the booklet creation job next or later unless the image forming mode is changed or the sheet feeding device 2 is replaced. At this time, the maximum remaining number stored in the RAM62 may be updated every time the sheet feeding device is replaced or the image forming mode is changed.

When the remaining amount of the inserted sheet P2 in the sheet stacking portion 16 is smaller than a predetermined amount, the above-described control (step 20 to step 28) may be performed to display information notifying that the remaining amount is decreased on the liquid crystal display portion 67. In this way, the user can recognize the decrease in the remaining amount of the inserted sheet P2 as soon as possible and replenish the inserted sheet P2 before the remaining amount of the inserted sheet P2 is used up and the booklet creation job is stopped. Thus, a decrease in productivity can be suppressed. As a method of notifying the reduction of the remaining amount, in addition to displaying information on the liquid crystal display unit 67, a method of transmitting sound information from a speaker, lighting of a warning lamp, a buzzer notification, and the like can be cited.

In the case of using an image forming system combining a sheet feeding device for inserting a cover sheet, a slip sheet, and the like into a sheet on which an image is formed by an image forming apparatus and a sheet post-processing device for performing post-processing such as stapling, the present invention can suppress an increase in manufacturing cost and an increase in size of the apparatus, and suppress a reduction in productivity and the production of a booklet without a cover.