JP2021147141A - Paper feeding device - Google Patents

Abstract

To provide a paper feeding device for preventing wrinkles and folding of a printing medium generated when a rear end of the printing medium passes through a conveyance roller which executes assist control.SOLUTION: The paper feeding device comprises: an intermediate conveyance roller 15 provided on an upstream side of a conveyance path of a printing medium; a registration roller 17 which forms slackness by temporarily stopping conveyance by contacting a tip end of the printing medium conveyed by the intermediate conveyance roller 15, and further, after forming the slackness, starts rotation at a preset timing to convey the printing medium to downstream; and a control unit for executing assist control for assisting conveyance of the printing medium by the intermediate conveyance roller 15 by driving the intermediate conveyance roller 15 while the printing medium is conveyed by the registration roller 17. The control unit executes the assist control so that the slackness is eliminated until a rear end of the printing medium passes through the intermediate conveyance roller 15.SELECTED DRAWING: Figure 1

Description

The present invention relates to a paper feeding device that feeds out a printing medium such as paper from a paper feeding table and conveys the printing medium toward a printing unit on the downstream side.

Conventionally, the printing medium fed from the paper feed tray is conveyed by a conveying roller and brought into contact with the resist roller, skew correction is performed by the resist roller, and then the printing medium is conveyed from the resist roller toward the printing unit. Paper devices have been proposed.

In the conventional paper feed apparatus, the print medium is conveyed while maintaining the slack of the print medium formed by the resist roller for skew correction. This is to suppress the tension noise generated when the transfer jam is generated or the slack is eliminated due to the tension of the print medium between the transfer roller and the resist roller.

For example, in Patent Document 1, while the print medium is being conveyed by the resist roller, the assist control assists the transfer of the print medium by the resist roller by controlling the transfer speed of the resist roller and the transfer roller on the upstream side thereof. Is proposed to do. Specifically, Patent Document 1 proposes assist control so as to reduce the slack of the print medium and leave the slack of the print medium until the rear end of the print medium passes through the conveying roller.

Japanese Unexamined Patent Publication No. 2014-19576

However, as in Patent Document 1, when the assist control is performed so as to leave the slack of the print medium until the rear end of the print medium comes off, when the rear end of the print medium comes out of the conveying roller, the rear end of the print medium Because the rear end of the print medium is exposed, that is, the rear end of the print medium is returned toward the transfer roller due to the tension of the print medium, the rear end of the print medium is caught in the guide of the transfer roller, and the print medium is broken or wrinkled. It turned out to be the cause.

In view of the above circumstances, an object of the present invention is to provide a paper feeding device capable of preventing wrinkles and breakage of the print medium that occur when the rear end of the print medium comes out of a transport roller that performs assist control. Is to be.

The paper feed device of the present invention loosens when the upstream roller provided on the upstream side of the transfer path of the print medium and the tip of the print medium conveyed by the upstream roller come into contact with each other to temporarily stop the transfer. And after the slack is formed, the rotation is started at a preset timing to convey the print medium toward the downstream side, and the print medium is conveyed by the downstream side roller. It is equipped with a control unit that performs assist control that assists the transfer of the print medium by the downstream roller by driving the upstream roller, and the control unit is slackened until the rear end of the print medium passes through the upstream roller. Assist control is performed so that

According to the paper feed device of the present invention, the assist control is performed so that there is no slack until the rear end of the print medium passes through the upstream roller, so that the rear end of the print medium passes through the upstream roller. It is possible to prevent wrinkles and folds of the print medium that occur at the time.

The figure which shows the schematic structure of the inkjet printing apparatus using one Embodiment of the paper feed apparatus of this invention. A block diagram showing a schematic configuration of a control system of the inkjet printing apparatus shown in FIG. The figure for demonstrating the wrinkle and the crease of the print medium which occur when the rear end of a print medium passes through an intermediate transfer roller. Timing chart showing an example of transition of transfer speed of intermediate transfer roller and resist roller The figure for demonstrating the calculation method of the transfer speed of a resist roller and the transfer speed of an intermediate transfer roller at the time of assist control. A diagram showing an example of a table associated with multiple types of print media and their lengths.

Hereinafter, an inkjet printing device using an embodiment of the paper feeding device of the present invention will be described in detail with reference to the drawings. The inkjet printing apparatus of the present embodiment is characterized in the transfer control of the printing medium. First, the mechanical configuration of the entire inkjet printing apparatus will be described. FIG. 1 is a schematic configuration diagram of the inkjet printing apparatus 1 of the present embodiment. The vertical and horizontal directions indicated by the arrows in FIG. 1 are the vertical and horizontal directions in the inkjet printing apparatus 1 of the present embodiment, and the vertical direction on the paper surface is the front-rear direction.

As shown in FIG. 1, the inkjet printing device 1 of the present embodiment includes a paper feeding unit 2 (corresponding to the paper feeding device of the present invention) and a printing unit 3.

The paper feed unit 2 feeds the print medium P such as paper or film to the print unit 3 provided downstream. The paper feed unit 2 includes a plurality of paper feed stands 11, a plurality of paper feed rollers 12, a plurality of vertical transport rollers 13, a paper feed motor 14 (see FIG. 2), an intermediate transport roller 15, and an intermediate transport motor. A 16 (see FIG. 2), a resist roller 17, a resist motor 18 (see FIG. 2), and a paper sensor 19 are provided. In the present embodiment, the intermediate transfer roller 15 corresponds to the upstream roller of the present invention, and the resist roller 17 corresponds to the downstream roller of the present invention.

The paper feed tray 11 is loaded with the print medium P used for printing. The paper feed rollers 12 are provided for each paper feed tray 11, and the print media P loaded on each paper feed tray 11 is fed out one by one from the upper part and sent out to the transport path R.

The vertical transfer rollers 13 are provided for each of the paper feed pedestals 11, and the print media P fed out from each paper feed pedestal 11 by each paper feed roller 12 is conveyed to the intermediate transfer rollers 15. The vertical transfer roller 13 is arranged along the transfer path R.

The paper feed motor 14 drives the paper feed roller 12 and the vertical transport roller 13. The paper feed motor 14 can be connected to and disconnected from each paper feed roller 12 and each vertical transport roller 13 by a clutch (not shown). The clutch switches between the paper feed roller 12 and the vertical transport roller 13 to be driven.

The intermediate transfer roller 15 receives the print medium P taken out from any of the plurality of paper feed stands 11 and conveyed along the transfer path R, and conveys the print medium P to the resist roller 17. Further, the intermediate transfer roller 15 performs an assist operation while driving the resist roller 17. The assist operation is an operation of assisting the transfer of the print medium P by the resist roller 17, and is performed by the assist control of the control unit 4 described later.

The intermediate transfer roller 15 is arranged on the downstream side of the vertical transfer roller 13. The intermediate transfer motor 16 drives the intermediate transfer roller 15.

The resist roller 17 is composed of a pair of transport rollers that sandwich (nip) the print medium P. The resist roller 17 is driven by the resist motor 18. The resist roller 17 comes into contact with the tip of the print medium P conveyed by the intermediate transfer roller 15 to temporarily stop the transfer, and corrects the skew of the print medium P. As a result, a slack is formed in the print medium P, and after the slack is formed, rotation is started at a preset timing to convey the print medium P toward the printing unit 3 described later.

The paper sensor 19 is provided near the downstream side of the intermediate transfer roller 15, detects the print medium P conveyed from the intermediate transfer roller 15 toward the resist roller 17, and outputs the detection signal to the control unit 4. The control unit 4 controls the transfer of the print medium P by the intermediate transfer roller 15 and the resist roller 17 based on the detection signal detected by the paper sensor 19.

The printing unit 3 prints on the printing medium P while carrying the fed printing medium P. The printing unit 3 is arranged on the downstream side of the paper feeding unit 2. The printing unit 3 includes a belt transport unit 21 and an inkjet head unit 22.

The belt transport unit 21 sucks and holds the print medium P conveyed by the resist roller 17 on the belt 21a and conveys it. When the roller on which the belt 21a of the belt transport unit 21 is hung is driven by a motor (not shown), the belt 21a rotates and the print medium P on the belt 21a is conveyed.

The inkjet head unit 22 has a plurality of line-type inkjet heads in which a plurality of nozzles are arranged in a direction (front-back direction) substantially orthogonal to the transport direction of the print medium P. The inkjet head portion 22 is arranged above the belt transport portion 21. The inkjet head unit 22 prints an image by ejecting ink from the inkjet head onto the printing medium P conveyed by the belt conveying unit 21.

FIG. 2 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus 1 of the present embodiment. As shown in FIG. 2, the inkjet printing device 1 of the present embodiment includes a control unit 4 that controls the operation of each part of the inkjet printing device 1.

The control unit 4 includes a CPU (Central Processing Unit), a semiconductor memory, a hard disk, and the like. The control unit 4 executes a program stored in advance in a storage medium such as a semiconductor memory or a hard disk, and operates an electric circuit to operate a paper feed motor 14, an intermediate transfer motor 16, a resist motor 18, and a belt transfer unit 21. And the inkjet head unit 22 is controlled, whereby the print medium P is conveyed, and ink is ejected from the inkjet head unit 22 to the print medium P to perform printing.

Here, after the print medium P is loosened in the resist roller 17 as described above, the print medium P is conveyed by the resist roller 17 while the assist operation is performed by the intermediate transfer roller 15.

Conventionally, in order to suppress the generation of transfer jam due to the tension of the print medium P between the intermediate transfer roller 15 and the resist roller 17 and the tension noise generated when the slack is eliminated, the intermediate transfer roller maintains the above-mentioned slack. The print medium P was conveyed by the 15 and the resist roller 17.

However, if the slack formed between the resist roller 17 and the intermediate transfer roller 15 remains at the time when the rear end of the print medium P is removed from the intermediate transfer roller 15, the rear end of the print medium P is the intermediate transfer roller 15. Since the rear end of the print medium P returns toward the intermediate transfer roller 15 due to the tension of the print medium P, the rear end of the print medium P is caught in the guide of the intermediate transfer roller 15 and the print medium It was found to cause P creases and wrinkles.

FIG. 3 is a diagram showing an example of the intermediate transfer roller 15 and the guide plate G provided around the intermediate transfer roller 15. The guide plate G is provided along the transport path R, and has an opening A in which the intermediate transport roller 15 is installed. FIG. 3 shows how the rear end of the print medium P is caught in the opening A. In FIG. 1, the guide plate G is not shown.

Therefore, the control unit 4 of the present embodiment controls the transport speed of the intermediate transport roller 15 to be slower than the transport speed of the resist roller 17, thereby transporting the print medium P while gradually reducing the slack of the print medium P. do. Then, the control unit 4 performs assist control so that the above-mentioned slack is eliminated until the rear end of the print medium P passes through the intermediate transfer roller 15. In the present embodiment, the assist control is performed so that the above-mentioned slack is eliminated when the rear end of the print medium P passes through the intermediate transfer roller 15. The assist control will be described in detail later.

Next, the transport control of the print medium P in the inkjet printing apparatus 1 of the present embodiment will be described with reference to the timing chart shown in FIG. FIG. 4 is a timing chart showing changes in the transfer speeds of the intermediate transfer roller 15 and the resist roller 17. The solid line in FIG. 4 indicates the transfer speed of the resist roller 17, and the broken line indicates the transfer speed of the intermediate transfer roller 15.

First, the control unit 4 connects the paper feed roller 12 and the vertical transport roller 13 corresponding to the paper feed table 11 on which the print medium P used for printing is loaded to the paper feed motor 14 by a clutch (not shown). Then, the control unit 4 starts driving the paper feed motor 14. As a result, the paper feed roller 12 picks up the print medium P from the paper feed table 11, and the paper feed roller 12 and the vertical transport roller 13 transport the print medium P toward the intermediate transport roller 15.

Further, the control unit 4 orbitally drives the transport belt of the belt transport unit 21. The control unit 4 drives the belt transfer unit 21 so that the print medium P can be conveyed at the print transfer speed Vg.

Then, at time t1 in FIG. 4, before the print medium P conveyed by the paper feed roller 12 and the vertical transfer roller 13 reaches the intermediate transfer roller 15, the control unit 4 is subjected to the intermediate transfer roller 15 by the intermediate transfer motor 16. To start driving. When the transfer speed by the intermediate transfer roller 15 reaches a predetermined transfer speed V0, the control unit 4 maintains the transfer speed V0 for a predetermined time and then stops the intermediate transfer motor 16. As a result, the intermediate transfer roller 15 is stopped. The intermediate transfer roller 15 receives the print medium P and conveys it to the resist roller 17 during the driving period at times t1 to t2, brings the print medium P into contact with the resist roller 17, and causes a preset amount of slack. To form.

After the intermediate transfer roller 15 is stopped, at time t3, the control unit 4 starts driving the intermediate transfer roller 15 again by the intermediate transfer motor 16 and at the same time starts driving the resist roller 17 by the resist motor 18.

The control unit 4 drives the intermediate transfer roller 15 and the resist roller 17 at the same acceleration α1. Then, when the transfer speed by the intermediate transfer roller 15 reaches the preset transfer speed V3 (time t4), the control unit 4 maintains the transfer speed V3 for a preset time for transfer. On the other hand, when the transport speed by the resist roller 17 reaches the preset transport speed V1 (time t5), the control unit 4 maintains the transport speed V3 for a preset time for transport. As shown in FIG. 3, the relationship between the transfer speed V3 of the intermediate transfer roller 15 and the transfer speed V1 of the resist roller 17 is V1> V3.

Then, at time t6, the control unit 4 simultaneously starts deceleration of the intermediate transfer roller 15 and the resist roller 17 at the same deceleration α2.

When the transfer speed of the resist roller 17 reaches the preset transfer speed V2 (time t7), the control unit 4 maintains the transfer speed V2 for transfer. The transport speed V2 is substantially the same as the print transport speed Vg described above. The control unit 4 reduces the transfer speed of the resist roller 17 to V2 by the time the tip of the print medium P reaches the belt transfer unit 21.

Further, when the transport speed of the intermediate transport roller 15 reaches the preset transport speed V4 (time t7), the control unit 4 maintains the transport speed V4 for transport.

After that, the print medium P is conveyed by the resist roller 17 while the intermediate transfer roller 15 performs the assist operation, and the rear end of the print medium P passes through the intermediate transfer roller 15 at time t8.

In the present embodiment, since the transfer speed of the intermediate transfer roller 15 is slower than the transfer speed of the resist roller 17 from the time t4 to the time t8, the slack formed in the print medium P gradually increases during this period. It will decrease. Then, in the present embodiment, the transfer speed V1 to the transfer speed V4, the acceleration α1 and the reduction are performed so that the time when the rear end of the print medium P passes through the intermediate transfer roller 15 and the time when the slack of the print medium P disappears are simultaneously. The speed α2 is set. The transport speed V1 to the transport speed V4, the acceleration α1 and the deceleration α2 will be described in detail later.

When the rear end of the print medium P passes through the intermediate transfer roller 15, the control unit 4 starts the stop control of the intermediate transfer motor 16 and stops the intermediate transfer motor 16. As a result, the intermediate transfer roller 15 is stopped. Here, when the paper sensor 19 detects the rear end of the print medium P, the control unit 4 determines that the rear end of the print medium P has passed through the intermediate transfer roller 15.

After that, at the timing when the rear end of the print medium P passes through the resist roller 17, the stop control of the resist motor 18 is started to stop the resist roller 17.

Then, when the print medium P is sent from the resist roller 17 to the belt transport unit 21, the control unit 4 ejects ink from the inkjet head unit 22 to the print medium P conveyed by the belt transport unit 21. As a result, the image is printed on the print medium P.

According to the inkjet printing apparatus 1 of the above embodiment, the printing medium P is controlled so as to have no slack between the start of the assist operation and the rear end of the printing medium P passing through the intermediate transfer roller 15. Therefore, printing is performed. It is possible to prevent wrinkles and breakage of the print medium P that occurs when the rear end of the medium P passes through the intermediate transfer roller 15.

Further, as described above, the transfer speed of the intermediate transfer roller 15 during the assist control is made slower than the transfer speed of the resist roller 17 to reduce the slack of the print medium P. Therefore, the print medium can be printed by simple control. Since the slack of P can be gradually reduced, it is possible to prevent the printing medium P from being loaded due to the rapid reduction of the slack. Thereby, for example, when the print medium P is a thin paper, it is possible to prevent the print medium P from breaking.

Further, in the inkjet printing apparatus 1 of the above embodiment, when the rear end of the printing medium P passes through the intermediate conveying roller 15, the printing medium P is made to have no slack, so that the intermediate conveying roller 15 and the resist roller 17 are eliminated. It is possible to prevent the print medium P from being pulled together with the print medium P, thereby preventing jamming, tensioning noise, and breakage of the printing medium P.

Next, a method of calculating the transfer speed V3 and the transfer speed V4 of the intermediate transfer roller 15 in the assist control of the inkjet printing apparatus 1 of the above embodiment will be described. In the present embodiment, the resist roller 17 and the intermediate transfer roller 15 are conveyed with a speed difference to give a difference in the transfer amount per unit time, thereby eliminating the slack in the print medium P. .. At this time, if the difference between the transfer amounts of the resist roller 17 and the intermediate transfer roller 15 is the amount of slack in the time from the start of the assist operation to the removal of the print medium P from the intermediate transfer roller 15, the slack in the print medium P can be eliminated. become.

That is, the relationship may be as shown in the following equation.
[Transport distance of resist roller 17]-[Transport distance of intermediate transport roller 15] = [Loose amount]

When the slack disappears when the rear end of the print medium P passes through the intermediate transfer roller 15, the transfer distance of the resist roller 17 until the rear end of the print medium P passes through the intermediate transfer roller 15 is the transfer distance of the print medium P. Since the value is obtained by subtracting the distance between the resist roller 17 and the intermediate transfer roller 15 from the length, it is calculated from the following equation.
[Transport distance of resist roller 17] = [Length of print medium P]-[Intermediate transfer between resist roller 17 and
Distance of feed roller 15]

Therefore, the distance that the intermediate transfer roller 15 conveys the print medium P is given by the following equation.
[Transport distance of intermediate transfer roller] = [Length of print medium P]-[Regist roller 17 and intermediate transfer b
-Distance of La 15]-[Amount of slack]

The time until the print medium P passes through the intermediate transfer roller 15 at this time can be calculated from the transfer time of the resist roller 17, and after starting the start of the resist roller 17, the above-mentioned [Transfer distance of the resist roller 17] ] Is the time required for the resist roller 17 to convey.

Based on the above relationship, a method for obtaining a specific calculation formula for the transfer speed V3 and the transfer speed V4 of the intermediate transfer roller 15 will be described with reference to FIG. Note that FIG. 5 is a diagram showing transfer speed control of the intermediate transfer roller 15 and the resist roller 17 during assist control. _{T r1, T r2, T r3} , T r4, T v1, T v2, T v3, T v4 and _{T all} in FIG. 5 represent the time in each period shown in FIG. _5, L _{r1, L r2,} L _r3 , L _r4 , L _v1 , L _v2 , L _v3 and L _v4 represent the transport distance in each period shown in FIG. In the subscripts T and L, r means the resist roller 17, and v means the intermediate transfer roller 15. In addition, All means the entire period from time t3 to time t8.

ｓｌａｃｋ：たるみ量
Ｌ_ｖｒ：中間搬送ローラ１５とレジストローラ１７間の距離
Ｌｒ_Ａｌｌ：印刷媒体Ｐの後端が中間搬送ローラ１５を抜けるまでのレジストローラ１７の搬送距離
Ｌｖ_Ａｌｌ：印刷媒体Ｐの後端が中間搬送ローラ１５を抜けるまでの中間搬送ローラ１５の搬送距離 First, from the above relationship, the _{L Rall} is [conveyance distance of the registration rollers 17], _{L vall} is [conveyance distance of the intermediate conveyance rollers 15], the following equation (1) can be expressed by (2) ..

slack: Slack amount L _v : Distance between the intermediate transfer roller 15 and the resist roller 17 Lr _All : The transfer distance of the resist roller 17 until the rear end of the print medium P passes through the intermediate transfer roller 15 Lv _All : After the print medium P The transport distance of the intermediate transport roller 15 until the end passes through the intermediate transport roller 15.

なお、Ｌ_ｒｂは、レジストローラ１５とベルト搬送部２１（上流側のベルトプラテンローラ）間の距離 Next, the operation of the resist roller 17 can be expressed by the following equation (3).

The L _rb is the distance between the resist roller 15 and the belt transport unit 21 (upstream belt platen roller).

Further, the operation of the intermediate transfer roller 15 can be expressed by the following equation (4).

Next, each parameter in the above equation with respect to the above formula (2) (3) and the above equation (4), by organizing by substituting V3 = VrV4, the two-dimensional equations of _{V 4} as follows Can be derived.

By solving the above two-dimensional equation of V4, the calculation formula of V4 of the following equation (5) can be obtained. Ar is a resist top velocity coefficient and is a constant of 2.04. V3 can be obtained from V3 = VrV4.

As can be seen from the above equation (5), the transport speeds V3 and V4 of the intermediate transport rollers 15 change according to _{L rAll} = the length of the print medium P −L _vr. That is, the transfer speeds V3 and V4 correspond to the length of the print medium P conveyed by the intermediate transfer roller 15 (length of the print medium P −L _vr ) from the time when the drive of the intermediate transfer roller 15 is started (time t3). Change.

Therefore, the control unit 4 acquires the information on the length of the print medium P, obtains (the length of the print medium P −L _vr ), and determines the transfer speeds V3 and V4 of the intermediate transfer rollers 15 according to the values. You may try to do it. Thereby, various lengths are determined by determining the transfer speeds V3 and V4 based on the length of the print medium conveyed by the intermediate transfer roller 15, that is, the length from the intermediate transfer roller 15 to the rear end of the print medium P. Appropriate assist control can be performed on the print medium P of the above, and wrinkles and folds of the print medium P that occur during the assist control can be more reliably prevented.

Regarding the information on the length of the print medium P, for example, the control unit 4 is set with a table associated with the types of the plurality of print media P as shown in FIG. 6 and their lengths, and the control unit 4 sets the information. , It may be obtained by referring to the table based on the type of the print medium P. The information on the type of the print medium P may be acquired from the print job, or the user may set and input the information on the operation panel (not shown) of the inkjet printing apparatus 1.

Further, in the above embodiment, the transfer speed of the intermediate transfer roller 15 is controlled so that the time when the rear end of the print medium P passes through the intermediate transfer roller 15 and the time when the slack of the print medium P disappears coincide with each other. However, the time when the rear end of the print medium P passes through the intermediate transfer roller 15 and the time when the slack of the print medium P disappears do not necessarily coincide with each other, and the rear end of the print medium P is the intermediate transfer roller 15 at the latest. It suffices if the slack of the print medium P is eliminated by the time when the print medium P is removed. However, if the rear end of the print medium P remains on the intermediate transfer roller 15 when the slack of the print medium P disappears, tension occurs between the intermediate transfer roller 15 and the resist roller 17, so that the print medium P The remaining length, including the trailing edge, is preferably short enough to prevent problems due to pulling.

Further, in the above embodiment, the transfer speeds V3 and V4 of the intermediate transfer rollers 15 are made slower than the transfer speeds V1 and V2 of the resist rollers 17 so that the slack of the print medium P is gradually reduced, but it is not always necessary. Not limited to such control, for example, the transfer speed V3 and the transfer speed V1 are made the same, the transfer speed V4 and the transfer speed V2 are made the same, and the acceleration of the intermediate transfer roller 15 is made smaller than the acceleration of the resist roller 17. By making the deceleration of the intermediate transfer roller 15 larger than the deceleration of the resist roller 17, the slack of the print medium P is gradually reduced, and until the rear end of the print medium P passes through the intermediate transfer roller 15. The slack of the print medium P may be eliminated.

Further, in the present invention, not only between the resist roller 17 and the intermediate transfer roller 15 as in the above embodiment, but also between the intermediate transfer roller 15 and the vertical transfer roller 13, the printing medium P is provided by two rollers, upstream and downstream. It can also be applied to a mechanism for transporting.

Further, the above embodiment is an example in which the paper feeding device of the present invention is applied to an inkjet printing device, but the paper feeding device of the present invention is not limited to this, and other methods such as a laser method and a stencil printing method are used. It can also be applied to the printing equipment of.

The following additional notes are further disclosed with respect to the paper feeding device of the present invention.
(Additional note)

In the paper feeding device of the present invention, the control unit can perform assist control so that there is no slack by slowing the transport speed of the upstream roller to the transport speed of the downstream roller.

Further, in the paper feeding device of the present invention, the control unit can determine the transfer speed of the upstream roller according to the length of the print medium conveyed by the upstream roller from the time when the drive of the upstream roller is started. ..

Further, in the paper feeding device of the present invention, the control unit can perform assist control so that the time when the rear end of the print medium passes through the upstream roller and the time when the slack is eliminated are simultaneous.

1 Inkjet printing device 2 Paper feed unit 3 Printing unit 4 Control unit 11 Paper feed table 12 Paper feed roller 13 Vertical transport roller 14 Paper feed motor 15 Intermediate transport roller 16 Intermediate transport motor 17 Resist roller 18 Resist motor 19 Paper sensor 20 Printing section 21 Belt transport section 21a Belt 22 Inkjet head section A Opening G Guide plate P Printing medium R Transport path

Claims (4)

An upstream roller provided on the upstream side of the print medium transport path,
A slack is formed by abutting the tips of the printing media conveyed by the upstream roller and temporarily stopping the transfer, and after the slack is formed, rotation is started at a preset timing to print. A downstream roller that transports the medium downstream,
A control unit that performs assist control for assisting the transfer of the print medium by the downstream roller by driving the upstream roller while the print medium is being conveyed by the downstream roller is provided.
A paper feeding device in which the control unit performs the assist control so that the slack is eliminated until the rear end of the print medium passes through the upstream roller. The paper feeding device according to claim 1, wherein the control unit performs assist control so that the slack is eliminated by making the transport speed of the upstream roller slower than the transport speed of the downstream roller. The supply according to claim 1 or 2, wherein the control unit determines the transfer speed of the upstream roller according to the length of the print medium conveyed by the upstream roller from the time when the control unit starts driving the upstream roller. Paper device. The paper feeding device according to any one of claims 1 to 3, wherein the control unit performs the assist control so that the time when the rear end of the print medium passes through the upstream roller and the time when the slack disappears are simultaneous. ..

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