JP7344468B2 - image forming system - Google Patents

Description

The present invention relates to an image forming system.

Conventionally, in a conveyance device that conveys a sheet, a gripper such as a gripper is provided on a conveyance rotary body such as a cylinder or a drum, and the conveyance rotary body is rotated while the sheet is gripped by the gripping portion to convey the sheet to the desired location. There are known techniques to do this.

Patent Document 1 is related to this type of technology. Patent Document 1 describes a conveyance unit that grips the leading edge of a sheet of paper using a gripper provided on a conveyance drum and conveys the paper to an image recording section, an ink drying section, or the like.

By the way, in a conveying means equipped with a conveying rotating body provided with a gripping portion as described above, when a sheet is delivered to the conveying rotating body, if there is a shift in the timing of sheet delivery, the leading edge of the sheet may not be at a predetermined gripping position. There are problems in that the sheet cannot be reached and the transfer fails, or that the sheet advances too far and the leading end hits a gripping part and becomes deformed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming system including a conveying device that can reduce the deviation in the timing of transferring sheets to a conveying rotary body.

The present invention includes a conveyance device that conveys a sheet, an image forming section that forms an image on the sheet conveyed by the conveyance device, and a preprocessing device that performs predetermined pretreatment on the sheet before image formation. An image forming system comprising: a conveyance device that conveys the sheet; a sheet detection device that detects the sheet conveyed by the conveyance device; and a sheet detection device that detects the sheet conveyed by the conveyance device. A transporting rotary body having a receiving section for receiving at a receiving position, a rotation detection means for detecting a rotational position of the transporting rotary body, and a control section for controlling a transporting speed of the transporting means, the transporting means comprising: After the conveyance of the sheet is temporarily stopped before the predetermined pre-processing is performed, the conveyance of the sheet is restarted based on the detection signal of the rotation detecting means, and the control unit is configured to control the control unit so that the conveyance of the sheet is restarted based on the detection signal of the rotation detecting means. In the image forming system, the conveying speed of the conveying means is controlled based on the timing at which the sheet is detected by the sheet detecting means, from when the sheet is detected by the sheet until the sheet reaches the receiving position.

According to the present invention, it is possible to reduce the deviation in the timing of transferring sheets to the conveying rotor.

1 is a schematic configuration diagram of an image forming system according to an embodiment of the present invention. It is a perspective view of a 1st transfer cylinder and a gripper. It is a side view of a 1st transfer cylinder and a gripper. 7 is a diagram illustrating a control flow from when sheet conveyance is restarted until the sheet is conveyed to a receiving position. FIG. FIG. 3 is a diagram for explaining a method of controlling the conveyance speed. FIG. 2 is a schematic configuration diagram of an image forming system according to another embodiment of the present invention. It is a top view of a conveyance device. It is a figure for explaining conveyance operation. It is a figure for explaining conveyance operation. It is a figure for explaining conveyance operation. It is a figure for explaining conveyance operation. It is a figure for explaining conveyance operation. It is a figure for explaining conveyance operation. FIG. 3 is a diagram for explaining a method of calculating a positional deviation amount. FIG. 3 is a diagram for explaining a method of calculating a positional deviation amount.

Hereinafter, the present invention will be explained based on the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are given the same reference numerals as much as possible so that they can be easily distinguished. Omitted.

FIG. 1 is a schematic configuration diagram of an image forming system 1 according to an embodiment of the present invention.

As shown in FIG. 1, the image forming system 1 includes a sheet feeding device 11, a preprocessing device 12, an image forming device 13, a drying device 14, a cooling device 15, a reversing device 16, and a sheet discharging device 17. , a transport device 20 , a control section 50 , and an operation section 53 .

The sheet feeding device 11 includes a sheet cassette 111 for stacking sheets, a feeding device 112 for feeding sheets from the sheet cassette 111, and a plurality of conveying roller pairs 113 as a conveying means for conveying the fed sheets. , is provided. A plurality of sheets stacked on the sheet cassette 111 are separated one by one by a feeding device 112, and then sent to the preprocessing device 12 by a pair of conveying rollers 113.

The preprocessing device 12 is a device that performs predetermined preprocessing on the sheet before image formation. Specifically, the pretreatment device 12 includes a treatment liquid application device 120 that applies a treatment liquid such as a chemical that reacts with the ink to suppress bleeding. The pre-processing device 12 also includes a first transport path 121 for transporting the sheet transported from the sheet supply device 11 to the processing liquid coating device 120, and a first transport path 121 for transporting the sheet conveyed from the sheet supply device 11 to the processing liquid coating device 120, and a first transport path 121 for reversing the sheet that has passed through the processing liquid coating device 120. a second conveyance path 122 for conveying the sheet to the treatment liquid coating device 120 again; a third conveyance path 123 for conveying the sheet to the image forming device 13 without passing through the treatment liquid coating device 120; is provided. Further, these conveyance paths 121 to 123 include a plurality of conveyance roller pairs 124 as conveyance means for conveying sheets, and a plurality of sheet sensors 125a to 125c as sheet detection means for detecting conveyed sheets. It is provided.

When applying a treatment liquid to a sheet, the sheet is conveyed to a treatment liquid application device 120 through a first conveyance path 121. At this time, the sheet is detected by a sheet sensor 125a provided on the first conveyance path 121 and is temporarily stopped, and then conveyed to the treatment liquid coating device 120 at a predetermined timing. After the treatment liquid is applied to one side of the sheet by the treatment liquid application device 120, the sheet is conveyed to the image forming device 13.

Further, when applying the treatment liquid to both sides, the sheet with the treatment liquid applied to one side is conveyed to the second conveyance path 122. In the second conveyance path 122, the sheet is switched back, so that the sheet is re-transmitted to the treatment liquid coating device 120 with the front and back sides reversed. At this time, the sheet is detected by the sheet sensor 125b provided on the second conveyance path 122 and is temporarily stopped, and then conveyed to the treatment liquid application device 120 at a predetermined timing. Then, a treatment liquid is applied to the back surface of the sheet by the treatment liquid application device 120, and the sheet is conveyed to the image forming device 13.

Furthermore, when the sheet is conveyed to the image forming apparatus 13 without applying the treatment liquid, the sheet is conveyed through the third conveyance path 123. In this case, the sheet is temporarily stopped by being detected by the sheet sensor 125c provided on the third transport path 123, and then transported to the image forming apparatus 13 at a predetermined timing.

The image forming apparatus 13 includes an ink ejecting section 130 as an image forming section that ejects ink onto a sheet to form an image, a first transfer cylinder 131 as a transport rotating body that transports the sheet, a transport drum 132, and a transport drum 132. A second transfer cylinder 133 and a plurality of conveying roller pairs 134 as conveying means for conveying the sheet are provided.

The ink ejection unit 130 forms an image on a sheet by ejecting ink of a plurality of colors, and includes a plurality of liquid ejection heads 135 corresponding to the plurality of colors. The liquid ejection head 135 is a functional component that ejects and jets liquid from an ejection hole (nozzle). The ink ejected by the liquid ejection head 135 includes cyan, magenta, yellow, black, and the like. In addition to this, the liquid ejection head 135 may eject special ink such as white, gold, or silver. Further, in addition to ink, a liquid ejection head 135 may be disposed that ejects a liquid that does not form an image, such as a surface coating liquid.

The ejection operation of each of the plurality of liquid ejection heads 135 is controlled by a drive signal according to image information. Note that the image formed on the sheet is not limited to one in which significant images such as characters and figures are visualized. For example, it includes patterns that have no meaning in themselves.

The sheet conveyed from the preprocessing device 12 is conveyed by a pair of conveyance rollers 134, and is delivered to the first transfer cylinder 131, the conveyance drum 132, and the second transfer cylinder 133 in this order. The first transfer drum 131, the conveyance drum 132, and the second transfer drum 133 are all configured in the shape of a cylinder that is long in the axial direction.

A gripper 30 is provided on the circumferential surface of the first transfer drum 131 to grip and receive the leading end of the sheet. The gripper 30 is a gripping portion that grips the leading end of the sheet, and also serves as a receiving portion that receives the sheet.

FIG. 2 is a perspective view of the first transfer drum 131 and gripper 30 according to this embodiment, and FIG. 3 is a side view thereof.

As shown in FIG. 2, the gripper 30 includes a rotating shaft 31, a claw base 32, and a claw portion 33. A plurality of claws 33 are arranged on the rotating shaft 31 in a comb-teeth shape, and the plurality of claws 33 rotate (swing) simultaneously as the rotating shaft 31 rotates. A plurality of claw stands 32 are arranged on the first transfer drum 131 in correspondence to the number of claw parts 33.

A cam mechanism (cam and cam follower) for mechanically opening and closing the claw portion 33 is provided at the end of the rotating shaft 31 of the gripper 30 and on the housing side. As shown in FIG. 3, as the first transfer drum 131 rotates, the gripper 30 reaches the receiving position where it grips the sheet S, and when the leading edge of the sheet S enters between the claw portion 33 and the claw base 32, The rotating shaft 31 is rotated by the cam mechanism so that the claw portion 33 approaches the claw base 32. As a result, the leading end of the sheet S is held between the claw portion 33 and the claw base 32. Note that the configuration for rotating the rotating shaft 31 is not limited to mechanical means, and may be configured to rotate the rotating shaft 31 at an appropriate timing using a motor or the like.

The sheet conveyed to the image forming apparatus 13 is wrapped around the circumferential surface of the first transfer drum 131 with its leading end gripped by the gripper 30, and is conveyed to a transfer position with the conveyance drum 132.

As shown in FIG. 1, a gripper 136 similar to that of the first transfer drum 131 is arranged on the circumferential surface of the conveyance drum 132, and a similar gripper 137 is arranged on the circumferential surface of the second transfer drum 133. . The gripper 136 of the conveyance drum 132 is configured in a staggered comb shape with respect to the gripper 30 of the first transfer drum 131, and sheets are transferred at positions facing each other. Furthermore, the gripper 137 of the second transfer drum 133 and the gripper 136 of the conveyance drum 132 are also configured in an alternating comb-like shape, and sheets are transferred at positions facing each other.

A suction device 138 is arranged inside the conveyance drum 132. A plurality of suction holes are formed in a distributed manner on the surface of the conveyance drum 132, and when the suction device 138 is activated, a suction flow that sucks the sheet is generated. The sheet transferred from the first transfer drum 131 to the conveyance drum 132 is gripped at the leading end by the gripper 136, and is attracted to the surface of the conveyance drum 132 by the suction airflow as the conveyance drum 132 rotates. transported.

When the sheet carried by the transport drum 132 passes through an area facing the ink ejection section 130, ink of each color is ejected from the liquid ejection head 135, forming an image according to image information. The sheet on which the image has been formed is sent from the transport drum 132 to the second transfer cylinder 133. The sheets sent to the second transfer drum 133 are sent to a belt conveyor 140 leading to the drying device 14. A suction device is disposed on the belt conveyor 140, and the sheet is conveyed through the drying device 14 while being suctioned.

The drying device 14 is provided with a heating device 141 that heats and dries the sheet conveyed by the belt conveyor 140. The heating by the heating device 141 evaporates liquid components such as water in the ink, and the ink is fixed on the sheet. As the heating device 141, a known heating device such as a hot air blower that blows hot air onto the sheet or a heat roller that heats the sheet by contacting the sheet can be used. The sheet dried by heating device 141 is conveyed to cooling device 15 by belt conveyor 140.

The cooling device 15 is provided with a cooling fan 151 that cools the sheet dried by the drying device 14, and a plurality of conveying roller pairs 152 as a conveying means for conveying the sheet. The sheet cooled by the cooling fan 151 is sent to the reversing device 16 by a pair of transport rollers 152.

The reversing device 16 is provided with a path switching device 161 that switches the path between single-sided printing and double-sided printing, and a plurality of conveying roller pairs 163 as a conveying means that conveys the sheet. In the case of single-sided printing, the sheet is sent to the sheet discharge device 17 without reversing the sheet. On the other hand, in the case of double-sided printing, the path switching device 161 switches the path and sends the sheet to the reversing path 162. The reversing path 162 is provided from the reversing device 16 to the cooling device 15, the drying device 14, and the image forming device 13, and the sheet sent to the reversing path 162 is delivered to the first transfer cylinder 131 in an overturned state. Sent. After the sheet is sent to the first transfer cylinder 131, the same image forming process as that for the front side is performed on the back side of the sheet.

The sheet discharging device 17 includes a discharging cassette 171 that stores the sheets that have passed through the reversing device 16, a discharging tray 172 that stacks the sheets that have been discharged to the outside, and a plurality of pairs of conveying rollers 173 that serve as conveying means for conveying the sheets. and are provided. The sheet conveyed to the sheet discharge device 17 is sent to a discharge cassette 171 or a discharge tray 172.

The conveying device 20 includes various conveying means for conveying sheets in each device constituting the image forming system 1. Specifically, a plurality of conveyance roller pairs 113 provided in each conveyance path of the sheet supply device 11 , the preprocessing device 12 , the image forming device 13 , the drying device 14 , the cooling device 15 , the reversing device 16 , and the sheet discharge device 17 , 124, 134, 152, 163, 173, and the belt conveyor 140.

The control unit 50 is a computer that performs various controls on the conveyance device 20 and the image forming system 1. Note that the physical location of the control unit 50 is not particularly limited. The control unit 50 may be placed at a predetermined location in the image forming system 1, or may be configured to control the image forming system 1 from a remote location via communication.

The operation unit 53 is composed of a touch panel display, buttons, and the like. The operation unit 53 may be provided in the image forming apparatus 13 or may be an external computer. The operation unit 53 is electrically connected to the control unit 50, and allows instructions to start printing and the type of sheet on which an image is to be formed to be set.

Although the overall configuration of the image forming system 1 has been described above, the configuration of the image forming system 1 can be changed as appropriate. The sheet feeding device 11, preprocessing device 12, image forming device 13, drying device 14, cooling device 15, reversing device 16, and sheet discharging device 17 that constitute the image forming system 1 are configured to be able to be separated and connected to each other. For example, some of the pretreatment device 12, drying device 14, cooling device 15, and reversing device 16 may be omitted. Further, other functional units may be added as appropriate, such as disposing a post-processing device for binding a plurality of sheets in the sheet discharging device 17.

As described above, in the image forming system 1 according to the present embodiment, the sheet supplied from the sheet supply device 11 is temporarily stopped at a predetermined position of the preprocessing device 12, and then conveyance is resumed at a predetermined timing. By doing so, the sheet is conveyed in synchronization with the gripper 30 of the first transfer cylinder 131. Specifically, the first transfer drum 131 is provided with rotation detection means 139 (see FIG. 1) for detecting its rotational position, and based on the detection signal of the rotation detection means 139, the control section 50 The rotational position of the transfer drum 131, that is, the position of the gripper 30 can be grasped. In addition to the detection signal of the rotation detection means 139, the conveyance distance from the sheet stopping position in the preprocessing device 12 to the predetermined receiving position A (see FIG. 1) where the gripper 30 receives the sheet, and the conveyance speed during that time are determined. Based on this, the control unit 50 controls the timing for resuming conveyance of the sheet, so that the sheet is conveyed to the receiving position A in synchronization with the timing at which the gripper 30 reaches the receiving position A.

However, in this embodiment, since the distance from the sheet stop position to the receiving position A of the gripper 30 is long, the timing at which the sheet reaches the receiving position A may be deviated due to variations in conveyance speed or the like. If such a shift occurs, there is a risk that the sheet may not be accurately gripped by the gripper 30, or that the leading edge of the sheet may abut against the gripper 30 and be deformed.

To solve this problem, for example, if the sheet is stopped just before the receiving position A and then the sheet is restarted in synchronization with the gripper 30, the deviation in the conveyance timing can be resolved. However, stopping the sheet just before the receiving position A is not preferable because the time required to convey the sheet increases and productivity (printing speed) decreases.

Therefore, in this embodiment, the following measures are taken so that the deviation in sheet conveyance timing can be reduced without stopping the sheet immediately before the receiving position A.

First, in this embodiment, in order to ascertain whether there is a delay or advance in sheet conveyance after the sheet conveyance is restarted until the sheet reaches the receiving position A, as shown in FIG. A sheet sensor 21 is provided in the image forming apparatus 13 as a sheet detection means for detecting a sheet. The sheet sensor 21 only needs to be able to detect the sheet from the time when the conveyance of the sheet is restarted until the sheet reaches the receiving position A, so it is not necessarily necessary to be provided in the image forming apparatus 13, and it is not necessary to provide the sheet sensor 21 in the preprocessing device 12. may be provided. That is, the position of the sheet sensor 21 may be determined as appropriate as long as it is downstream in the sheet conveyance direction from each of the sheet sensors 125a to 125c provided in the preprocessing device 12 and upstream in the sheet conveyance direction from the receiving position A. Can be changed. Hereinafter, the sheet sensor 21 will be referred to as a "timing deviation detection sensor", and control of the sheet conveyance operation will be described.

FIG. 4 is a diagram showing a control flow from when sheet conveyance is resumed until the sheet is conveyed to receiving position A.

As shown in FIG. 4, in this embodiment, when sheet conveyance is resumed from a predetermined position in the preprocessing device 12, the sheet is conveyed to the image forming device 13, and then the sheet reaches the timing deviation detection sensor 21. At this time, the leading edge of the sheet being conveyed is detected by the timing deviation detection sensor 21 (Step 1). Then, a detection signal from the timing deviation detection sensor 21 is sent to the control section 50, and the control section 50 calculates the deviation in the transport timing (Step 2). The "deviation in conveyance timing" herein refers to the deviation (delay or advance) in the timing at which the sheet reaches the receiving position relative to the timing at which the gripper 30 reaches the receiving position when the sheet is conveyed based on preset basic control. It is about. The conveyance timing shift is calculated based on the sheet detection timing by the timing shift detection sensor 21, the conveyance distance from the position of the timing shift detection sensor 21 to the receiving position A, and the speed information in the basic control during that time.

As a result, if there is no shift in the conveyance timing (“YES” in Step 3), the sheet is conveyed to the receiving position A based on the basic control described above (Step 4). On the other hand, if there is a shift in the transport timing ("NO" in Step 3), the transport speed is controlled so that the shift is eliminated or reduced, and the speed control is corrected (Step 5).

A specific method of controlling the conveyance speed will be described using FIG. 5 as an example.

FIG. 5 shows an example in which when a sheet is conveyed to the first transfer cylinder 131, the conveyance speed is reduced from V1 to the same conveyance speed V2 as that of the first transfer cylinder 131 (V1>V2). That is, the conveyance roller pair 134 located upstream of the first transfer cylinder 131 in the sheet conveyance direction initially conveys the sheet at a conveyance speed V1 faster than the conveyance speed V2 of the first transfer cylinder 131, and midway through the first transfer cylinder The sheet is conveyed at the same conveyance speed V2 as that of the transfer cylinder 131. On the other hand, the first transfer drum 131 is rotating at a constant speed V2. Note that in FIG. 5, each conveyance speed indicated by a solid line, a dotted line, or a two-dot chain line indicates the conveyance speed at the time (time) when the leading edge of the sheet passes the corresponding position in the figure.

As a result of the sheet detection by the timing deviation detection sensor 21, if there is no deviation in the transport timing, the transport speed of the transport roller pair 134 is changed at the timing Ti of the basic control, as shown by the solid line in FIG. (Change from V1 to V2) is started. This time Ti is an ideal speed change time determined from the distance L from the position of the timing shift detection sensor 21 to the receiving position A and the conveyance speeds V1 and V2. Therefore, in this case, by starting to change the conveyance speed at time Ti, the sheet can be conveyed to the receiving position A without being out of timing with the gripper 30 of the first transfer cylinder 131.

However, if there is a delay in the conveyance timing and the conveyance speed is started to be changed at time Ti in the basic control, there is a possibility that the sheet will not arrive in time for the gripper 30 to reach the receiving position A. Therefore, if there is a delay in the transport timing, as shown by the dotted line in FIG. 5, the change in transport speed is started at a time Td later than the time Ti when there is no deviation. That is, by delaying the timing of changing the conveyance speed, the time for conveying the sheet at the fast conveyance speed V1 is ensured for a long time, and the delay in the conveyance timing is reduced.

Specifically, the timing of changing the conveyance speed when there is a delay can be calculated using the following formula (1). In Equation (1), Td is the time when the change in conveyance speed starts when there is a delay, Ti is the time when the change in conveyance speed starts when there is no deviation (delay or advance), and t is the delay time of the calculated conveyance timing. , V1 is the conveyance speed before the change, and V2 is the conveyance speed after the change. Note that the time Td and the time Ti can be expressed by the time from an arbitrarily determined reference time (for example, the time from the time Ts when the sheet was detected by the timing deviation detection sensor 21 to the respective times Td and Ti).

Td=Ti+V2×t/(V1-V2)...(1)

Furthermore, if there is an advance in the conveyance timing as a result of the sheet detection by the timing deviation detection sensor 21, the conveyance speed is changed from the time Ti when there is no deviation, as shown by the two-dot chain line in FIG. It also starts at an earlier time Ta. That is, by advancing the change timing of the conveyance speed, the time for conveying the sheet at the fast conveyance speed V1 is shortened, and the advance of the conveyance timing is reduced.

The change timing (time Ta) of the conveyance speed when there is an advance can be calculated using the following formula (2). In the formula (2), Ta is the start time of changing the conveyance speed when there is an advance, t is the calculated advance time of the conveyance timing, and the other Ti, V1, and V2 are the times in the above formula (1). It is the same as the thing. Note that the time Ta and the time Ti in equation (2) are also the time from an arbitrarily determined reference time (for example, the time from the time Ts when the sheet was detected by the timing deviation detection sensor 21 to the respective times Ta and Ti). It can be expressed as

Ta=Ti-V2×t/(V1-V2)...(2)

In this way, if there is a shift in the conveyance timing as a result of sheet detection by the timing shift detection sensor 21, the conveyance speed is controlled by adjusting the change timing of the conveyance speed so that the shift is eliminated or reduced. That is, if there is a delay in the conveyance timing, by delaying the timing of changing the conveyance speed, it is possible to secure a long time for conveying the sheet at the fast conveyance speed V1, and eliminate or reduce the delay in the conveyance timing. In addition, if there is an advance in the conveyance timing, conversely, by advancing the change timing of the conveyance speed, the time for conveying the sheet at the fast conveyance speed V1 can be shortened, and the advance in the conveyance timing can be eliminated or reduced. .

Further, unlike the above example, when the sheet is conveyed to the receiving position A with the conveyance speed increased from V1 to V2 (V1<V2), control that is opposite to the above example may be performed. That is, if there is a delay in the conveyance timing, the delay in the conveyance timing can be eliminated or reduced by advancing the timing of changing the conveyance speed and shortening the time during which the sheet is conveyed at the slow conveyance speed V1. On the other hand, if there is an advance in the conveyance timing, the advance in the conveyance timing can be eliminated or reduced by delaying the timing of changing the conveyance speed and ensuring a long time for conveying the sheet at the slow conveyance speed V1. .

In addition, if the basic control is set so that the sheet is transported at a constant speed (with no deviation in the transport timing) (V1 = V2), the sheet will be transported at an appropriate timing according to the deviation in the transport timing. All you have to do is increase or decrease the speed. In that case, depending on the degree of deviation (delay or advance) in the transport timing, the magnitude of the speed increase or deceleration (amount of speed change), or the increase or decrease in speed before returning to the original transport speed after speeding up or decelerating. By adjusting the length of the speed time or deceleration time, it is possible to eliminate or reduce the shift in conveyance timing.

As described above, in the present invention, the conveyance speed is adjusted based on the timing at which the sheet is detected by the timing deviation detection sensor 21, from when the sheet is detected by the timing deviation detection sensor 21 until it reaches the receiving position A. By controlling it, it becomes possible to reduce the shift in the transport timing. This makes it possible to improve the accuracy of the conveyance timing and to convey the sheet satisfactorily.

Furthermore, in the embodiment described above, after the sheet is detected by the timing deviation detection sensor 21, the sheet is conveyed to the receiving position A without stopping conveyance, so that productivity (printing speed) can be increased. In other words, according to the present invention, it is not necessary to stop the sheet immediately before the receiving position A in order to eliminate the shift in conveyance timing, so it is possible to prevent a decrease in productivity (printing speed) caused by temporarily stopping the sheet. can be avoided. Furthermore, by setting the area where sheets are continuously conveyed without stopping the conveyance from the sheet stop position before pre-processing to receiving position A (before pre-processing is performed, sheet conveyance is stopped once). After the processing liquid is applied to the sheet, the transport roller is moved against the processing liquid applied surface of the sheet. It can prevent chafing. This makes it possible to prevent uneven coating of the processing liquid due to friction of the conveyance roller, and to avoid deterioration in image quality.

FIG. 6 is a schematic configuration diagram of an image forming system according to another embodiment of the present invention. Hereinafter, other embodiments of the present invention will be described mainly with respect to portions that differ from the above-described embodiments. The other parts are basically the same as those in the above-described embodiment, so the explanation will be omitted.

As shown in FIG. 6, the conveyance device 20 according to the present embodiment includes three CISs 101 to 103 as position detection means for detecting the position of the sheet being conveyed, and a correction system that corrects the position of the sheet while conveying the sheet. A pair of correction rollers 40 as means are provided. CIS is a contact image sensor that uses a small LED (Light Emitting Diode) as a light source and directly reads an image with a linear sensor through a lens.

The correction roller pair 40 and each CIS 101 to 103 are arranged at a position downstream of the timing deviation detection sensor 21 in the sheet conveyance direction and upstream of the first transfer cylinder 131 in the sheet conveyance direction. Further, among the three CIS 101 to 103, the first CIS 101 at the most upstream side in the sheet conveyance direction and the second CIS 102 one position downstream from this CIS 101 are located upstream of the correction roller pair 40, and the correction roller pair The transport roller pair 134 is located downstream of the transport roller pair 134 that is one upstream of the transport roller pair 134 . On the other hand, the third CIS 103 which is the most downstream in the sheet conveyance direction is arranged at a position downstream of the correction roller pair 40 and upstream of the first transfer cylinder 131.

FIG. 7 is a plan view of the transport device 20 according to this embodiment.

Each of the CIS 101 to 103 detects one end of the sheet S in the width direction shown in FIG. The side edge portion Sa is detected. Then, based on the positional information of the side edge Sa of the sheet S detected by each CIS 101 to 103, the control unit 50 calculates the widthwise positional deviation α and the skew positional deviation β of the sheet S. . Note that a specific method for calculating the width direction positional deviation α and the skew positional deviation β will be described later.

The correction roller pair 40 is composed of a driving roller and a driven roller that can come into contact with and separate from each other, and moves in the width direction of the sheet S (in the direction of the arrow X in FIG. 7) while nipping the sheet S being conveyed. The position of the sheet S is changed by rotating around the support shaft 41 within the sheet conveyance plane (in the direction of arrow Y in FIG. 7). As a result, the widthwise positional deviation α and the skew positional deviation β of the sheet S are corrected. In this embodiment, the support shaft 41 is provided at one end in the axial direction of the correction roller pair 40, but the support shaft 41 may be provided at the center position of the correction roller pair 40 in the axial direction.

Next, the transport operation in this embodiment will be explained based on FIGS. 8 to 13.

First, as in the above-described embodiment, when a sheet is conveyed from the preprocessing device 12 to the image forming apparatus 13, the sheet is conveyed by the pair of conveying rollers 134 of the image forming apparatus 13. Then, when the sheet is detected by the timing deviation detection sensor 21 and there is a deviation in the conveyance timing, the conveyance speed is controlled according to the deviation, as described above.

Thereafter, the sheet is conveyed toward the correction roller pair 40 and each of the CISs 101 to 103, as shown in FIGS. 8(a) and 8(b). At this time, the correction roller pair 40 is placed at the home position shown in FIG. 8(a), and is spaced apart from each other, waiting in a stationary state.

As shown in FIGS. 9(a) and 9(b), when the leading edge of the sheet S passes through the first CIS 101 and further reaches the second CIS 102, the first CIS 101 and the second CIS 102 close the sheet S. The position of the end portion Sa is detected (“first position detection”). Then, based on the positional information detected by these CISs 101 and 102, the widthwise positional deviation α and the skew positional deviation β are calculated.

Specifically, as shown in FIG. 14, the positional deviation α (positional deviation amount) in the width direction is calculated based on the position of the side edge Sa of the sheet S detected by the second CIS 102 and the conveyance standard set in advance. This can be obtained by comparing the distance with the position K and calculating the distance K1 between them in the width direction. Further, the skew positional deviation β (positional deviation amount) is calculated from the difference in the position of the side edge Sa of the sheet S detected by the first CIS 101 and the second CIS 102. That is, as shown in FIG. 14, when the leading edge of the sheet S reaches the second CIS 102, the first CIS 101 and the second CIS 102 detect the position of the side edge Sa of the sheet S, and By comparing the position of the side edge Sa and the transport reference position K, distances K1 and K2 in the width direction thereof are calculated. Then, using the formula tanβ=(K1-K2)/M1 from these width direction distances K1 and K2 and the preset distance M1 between the first CIS 101 and the second CIS 102, The skew positional deviation β is calculated.

Once the positional deviations α and β are calculated, the operation of the correction roller pair 40 is controlled by the control unit 50 based on the calculated positional deviations α and β. Specifically, based on the calculated positional deviations α and β, the correction roller pair 40 is moved in the width direction (for example, the arrow X1 direction in FIG. 9) and in the rotational direction within the sheet conveyance plane (for example, in the (arrow Y1 direction). As a result, a "pick-up operation" is performed in which the correction roller pair 40 directly faces the leading edge of the sheet.

Thereafter, when the pair of correction rollers 40 come into contact with each other at a predetermined timing and begin to rotate, the sheet S is received by the pair of correction rollers 40 directly facing each other, as shown in FIGS. 10(a) and 10(b). The sheet S is conveyed while being held by the conveyor belt 40 . Moreover, at this time, the upstream conveyance roller pair 134 is in a state separated from each other.

Subsequently, as shown in FIGS. 11(a) and 11(b), while the sheet S is conveyed by the correction roller pair 40, the correction roller pair 40 is moved in the direction opposite to the pick-up operation (for example, in the direction of arrow X2 in FIG. A "return operation" is performed to drive the camera in the Y2 direction). As a result, the widthwise positional deviation α and the skew positional deviation β of the sheet S are corrected. Hereinafter, this correction will be referred to as "first correction."

As a result of the skew positional deviation correction, when the sheet moves from the position shown by S to the position shown by S' in FIG. 15, the positional deviation amount in the width direction changes from α to α'. Therefore, by calculating this positional deviation amount α' in the width direction in advance, it is possible to perform positional deviation correction with higher accuracy. However, the positional deviation amount α' in the width direction changes depending on which position is used as a reference for correcting the skew positional deviation.

Thereafter, as shown in FIGS. 12(a) and 12(b), when the leading edge of the sheet S reaches the third CIS 103, the position of the side edge Sa of the sheet S is detected by the second CIS 102 and the third CIS 103. (“second position detection”). Then, based on the position information detected by these CISs 102 and 103, the width direction positional deviation α and the skew positional deviation β are calculated again using a method similar to the calculation method described above. Then, based on the calculated positional deviations α and β, the correction roller pair 40 is adjusted in the width direction (arrow X3 direction or arrow X4 direction in FIG. 12) and the rotational direction within the sheet conveyance plane (in the (arrow Y3 direction or arrow Y4 direction). As a result, the positional deviation of the sheet S is corrected. Thereafter, the sheet S is conveyed to the receiving position A without being stopped by the correction roller pair 40.

As described above, in this embodiment, after controlling the conveyance speed according to the shift in conveyance timing, the "first correction" for correcting the sheet position is performed, and furthermore, after the "first correction", the sheet position is adjusted. By performing the "second correction" that corrects the position, it is possible to highly eliminate positional deviations that occur while the sheet is being conveyed. Thereby, the sheet can be conveyed to the receiving position A of the gripper 30 with high precision, and the sheet can be gripped by the gripper 30 more reliably. Note that such "second correction" can be performed multiple times at predetermined intervals as long as the sheet is passing through the second CIS 102 and the third CIS 103.

Further, the correction roller pair 40 may be configured so that its conveyance speed can be changed. In that case, by controlling the conveyance speed of the correction roller pair 40 based on the detection result (detection timing) of a sheet detection means such as a sheet sensor, it is possible to convey the sheet to the receiving position A with higher timing accuracy. be.

Although each embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiments. In the embodiment described above, the receiving section provided on the first transfer drum 131 or the like is the gripper 30 that grips the sheet by swinging, but the receiving section may have a structure other than that for gripping the sheet. It's okay.

Further, the image forming apparatus to which the present invention is applied is not limited to an inkjet type as shown in FIG. 1, but may be an electrophotographic type using toner as a developer. By applying the present invention to an electrophotographic image forming apparatus, it becomes possible to transport the sheet in a timely manner to the transfer section where the image on the photoreceptor or the image on the intermediate transfer belt is transferred to the sheet, thereby improving the image quality. It is possible to improve.

Further, the present invention is not limited to application to an image forming apparatus, but can also be applied to, for example, a sheet folding device that performs folding processing on a sheet, a sheet inspection device that performs inspection processing on a sheet, and the like. Further, the material of the sheet is not limited, and may be made of paper, plastic film, cloth, etc.

1 Image forming system 12 Pre-processing device 13 Image forming device 20 Conveying device 21 Sheet sensor (sheet detection means)
30 Gripper (receiving part)
40 Correction roller pair (correction means)
50 Control unit 113 Conveying roller pair (conveying means)
124 Conveyance roller pair (conveyance means)
131 First transfer cylinder (conveyance rotating body)
132 Conveyance drum (conveyance rotating body)
133 Second transfer cylinder (conveyance rotating body)
134 Conveyance roller pair (conveyance means)
139 Rotation detection means 140 Belt conveyor (conveyance means)
152 Conveyance roller pair (conveyance means)
163 Conveyance roller pair (conveyance means)
173 Conveyance roller pair (conveyance means)
A Receiving position S Seat

Japanese Patent Application Publication No. 2012-157984

Claims (7)

a conveyance device that conveys the sheet;
an image forming unit that forms an image on the sheet conveyed by the conveyance device;
An image forming system comprising: a preprocessing device that performs predetermined preprocessing on the sheet before image formation,
The transport device is
a conveying means for conveying the sheet;
sheet detection means for detecting the sheet conveyed by the conveyance means;
a conveying rotating body having a receiving section that receives the sheet conveyed by the conveying means at a predetermined receiving position;
Rotation detection means for detecting the rotational position of the conveying rotor;
A control unit that controls the conveyance speed of the conveyance means,
The conveyance means temporarily stops conveyance of the sheet before the predetermined pre-processing is performed, and then resumes conveyance of the sheet based on a detection signal from the rotation detection means,
The control unit controls the conveying speed of the conveying means based on the timing at which the sheet is detected by the sheet detecting means, from when the sheet is detected by the sheet detecting means until the sheet reaches the receiving position. image forming system . a conveyance device that conveys the sheet;
an image forming unit that forms an image on the sheet conveyed by the conveyance device;
An image forming system comprising: a preprocessing device that performs predetermined preprocessing on the sheet before image formation,
The transport device is
a conveying means for conveying the sheet;
sheet detection means for detecting the sheet conveyed by the conveyance means;
a conveying rotating body having a receiving section that receives the sheet conveyed by the conveying means at a predetermined receiving position;
A control unit that controls the conveyance speed of the conveyance means,
The conveyance means temporarily stops conveyance of the sheet before the predetermined pre-processing is performed, and after restarting conveyance of the sheet, conveys the sheet to the receiving position without stopping conveyance,
The control unit controls the conveying speed of the conveying means based on the timing at which the sheet is detected by the sheet detecting means, from when the sheet is detected by the sheet detecting means until the sheet reaches the receiving position. image forming system . The control unit controls the timing at which the conveying speed of the conveying means is changed from a conveying speed different from a conveying speed of the conveying rotor to the same speed based on the timing of detecting the sheet by the sheet detecting means. 2. The image forming system according to 1 or 2 . The control unit controls an amount of speed change when accelerating or decelerating the conveyance speed of the conveyance means, or a length of the speed increase time or deceleration time, based on the detection timing of the sheet by the sheet detection means. The image forming system according to claim 1 or 2 . 5. The image forming system according to claim 1, wherein the sheet is conveyed to the receiving position without stopping conveyance after the sheet is detected by the sheet detection means. 6. Any one of claims 1 to 5, further comprising a correction means for correcting the position of the sheet in at least one of a rotational direction and a sheet width direction within a sheet transport plane after the control unit controls the transport speed. The imaging system described . 7. The image forming system according to claim 1, wherein the receiving section is a gripper that is swingably provided on the circumferential surface of the conveying rotary body and grips the sheet.