JP2012254858A - Conveyance device, printing device, and conveyance method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conveyance device and the like, the device conveying a sheet-shaped object to a processing position by a two sets of rollers, and capable of always maintaining slackness of the sheet-shaped object between the two sets of rollers constantly, and capable of eliminating action of back-tension to a downstream roller without enlargement of the scale of the device.SOLUTION: The conveyance device includes: an upstream roller that supplies a sheet-shaped medium to be processed to a conveyance path; a downstream roller that conveys the supplied medium to a processing position; and a control unit that, in order to convey the medium to be processed at a constant speed, controls driving both the rollers using the constant speed as a target speed of the conveyance speed by the upstream roller and the downstream roller. The control unit changes the target speed of the upstream roller to eliminate a conveyance amount difference based on the difference between the a conveyance amount by the upstream roller and a conveyance amount by the downstream roller from the start time point of the conveyance operation, in each conveyance operation.

Description

  The present invention relates to an apparatus for conveying a sheet-like material to a processing position with two sets of rollers, and in particular, always keeps the slack of the sheet-like material between two sets of rollers without increasing the scale of the device. The present invention relates to a transport device that can eliminate the action of back tension on a downstream roller.

  Conventionally, since an apparatus such as a printer performs processing on a sheet-like medium such as paper, an apparatus for conveying the sheet-like object is required. As such a conveyance device, a commonly used one is, for example, an upstream roller that supplies a medium to a conveyance path from a portion that stores a sheet-like medium, and printing that supplies the supplied medium along the conveyance path. And a downstream roller that conveys the processing to a position where the processing is performed.

  In such a transport apparatus, it is required to accurately control the supply speed of the medium from the downstream roller in order to execute processing such as printing on the transported medium with high quality with high accuracy. However, if there is a back tension pulled from the upstream side in the downstream roller, there is a problem that it is difficult to control.

  Therefore, as a technique for overcoming this problem, a proposal as in Patent Document 1 below has been conventionally made. This document shows that the drive timing of the upstream roller is advanced and the amount of conveyance is increased.

JP 2008-56367 A

  However, in the method described in Patent Document 1, the driving timing that is advanced and the method of increasing the conveyance amount are fixedly determined regardless of the situation, so that appropriate control is always performed according to the changing conveyance state. There are issues in terms. For example, the force applied to each roller and the transport force vary depending on the wear status of each roller and the storage status of the media (or roll diameter if the media is roll paper). The medium may become loose between the side roller and the downstream roller, or on the contrary, the medium may become too slack and rub against a member in the transport path, and back tension occurs on the downstream roller. There is a fear. Further, there is a problem that the apparatus scale must be increased in order to keep a large amount of slack so that the slack does not disappear and to prevent the slack from coming into contact with members in the transport path.

  In particular, when transport is performed for a long time, the transport amount of both rollers varies further depending on the storage status of the transported media (roll paper slack, fanfold paper), etc., even during constant speed transport. And the problems described above become significant.

  Accordingly, an object of the present invention is an apparatus that conveys a sheet-like material to a processing position with two sets of rollers, and always keeps the slackness of the sheet-like material between the two sets of rollers, thereby increasing the scale of the apparatus. It is to provide a transport device that can eliminate the action of back tension on the downstream roller without any problems.

  In order to achieve the above object, one aspect of the present invention includes an upstream roller that feeds a sheet-like processed medium to a conveyance path, a downstream roller that supplies the fed medium to a processing position, and In order to transport the medium to be processed at a constant speed, a control device that controls the driving of the two rollers using the constant speed as a target speed of the transport speed by the upstream roller and the downstream roller. The control unit, in each transport operation, based on the difference between the transport amount by the upstream roller and the transport amount by the downstream roller from the start of the transport operation, so that the transport amount difference is eliminated, Changing the target speed of the upstream roller.

  Furthermore, in the above-mentioned invention, the preferable aspect is that the relationship information between the transport amount difference and the amount of change in the target speed of the upstream roller is held in advance, and the target speed is changed according to the relationship information. Features.

  Furthermore, in the above-mentioned invention, the preferable aspect further includes a driven roller installed on each of the upstream roller and the downstream roller so as to face each of the rollers with the processing medium interposed therebetween, And an encoder installed on each of the driven rollers, wherein the control unit obtains the transport amount difference based on information detected by the encoders.

  Furthermore, in the above invention, a preferred aspect is characterized in that the relation information is held for each type of the medium to be processed.

  Furthermore, in the above invention, a preferred aspect is characterized in that the medium to be treated is supplied to the upstream roller from a state of being held in a roll shape.

  Furthermore, in the above-described invention, a preferable aspect thereof is that the control unit, based on driving information of the upstream roller and the downstream roller at the time of the previous transport operation, the upstream roller at the start of the transport operation and the The start timing of the downstream roller is determined.

  In order to achieve the above object, another aspect of the present invention is to provide a printing apparatus that includes any one of the above-described transport devices and that performs printing on the target medium at the processing position.

  In order to achieve the above object, still another aspect of the present invention provides an upstream roller that feeds a sheet-like processed medium to a conveyance path, a downstream roller that supplies the fed medium to a processing position, In order to transport the medium to be processed at a constant speed, a control device that controls the driving of the two rollers using the constant speed as a target speed of the transport speed by the upstream roller and the downstream roller. In each of the transport operations, the control unit determines that the transport amount difference is based on the difference between the transport amount by the upstream roller and the transport amount by the downstream roller from the start time of the transport operation. The target speed of the upstream roller is changed so as to disappear.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

It is a schematic block diagram concerning the example of an embodiment of a printing device provided with a conveyance device to which the present invention is applied. FIG. 6 is a diagram illustrating an example of behavior of a paper feed roller 29 and a transport roller 30 in a transport operation. 6 is a flowchart illustrating an example of a process executed by a conveyance control unit 22; It is a figure for demonstrating the control at the time of constant speed conveyance. It is a figure for demonstrating wait time (DELTA) T. It is the figure which showed an example of Duty value of motors 27A and 27B with time. 3 is a schematic diagram illustrating an example of a sag sensor 34. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a schematic configuration diagram according to an embodiment of a printing apparatus including a transport device to which the present invention is applied. The printer 2 shown in FIG. 1 is a printing apparatus according to the present embodiment, and the printing apparatus prints a sheet 26 of a printing medium with a feed roller 29 (upstream roller) and a conveyance roller 30 (downstream roller). The printing process is performed by transporting to the position, and during each transport operation, the target speed of the paper feed roller 29 is changed so as to eliminate the transport amount difference according to the transport amount difference from the start of driving by the two rollers. The slack of the paper 26 between the two rollers is always kept constant.

  Further, the printer 2 appropriately delays the start timing of the transport roller 30 based on the driving state during acceleration of both rollers in the previous transport operation, and further keeps the slack of the paper 26 between the both rollers constant. To.

  As shown in FIG. 1, the printer 2 is a device that executes a printing process in response to an instruction from a host device 1 such as a computer. Here, as an example, the printer 2 uses a roll paper 25 as a paper 26. 26 is a printing apparatus that continuously performs printing while transporting 26.

  In FIG. 1, the schematic configuration of the printer 2 is schematically illustrated. However, the printer 2 includes a printing system that controls printing contents and executes a printing process on the paper 26 and a transport system that transports the paper 26.

  The printing system is provided with a printing control unit 21, which receives a printing instruction from the host device 1, issues a printing command to the head unit 23 in accordance with the instruction, and conveys the conveyance control unit 22. The paper 26 is requested to be conveyed. The head unit 23 executes a printing process on the paper 26 that moves between the head unit 23 and the platen 24 at a predetermined speed in accordance with the print command.

  In the transport system, as shown in FIG. 1, the paper 26 held as the roll paper 25 in the print medium storage location is transported to the head unit 23 along the transport path 33, and then, via the paper discharge roller 32. Then, a transport operation for discharging from the printer 2 is executed.

  For paper conveyance to the head unit 23, a paper feed roller 29 (upstream roller) and a conveyance roller 30 (downstream roller) driven by corresponding motors (27A and 27B) are provided. On both the rollers, driven rollers (28A and 28B) are disposed in a state where pressure is applied to the side of the paper 26, with the paper 26 facing each other.

  The paper feed roller 29 has a function of supplying the paper 26 held as the roll paper 25 to the transport path 33, rotates by the torque of the motor 27A transmitted through the speed reducer, and presses the paper 26 together with the driven roller 28A. The paper 26 is moved by the frictional force between the two.

  The transport roller 30 has a function of transporting the paper 26 supplied by the paper feed roller 29 to the printing position, that is, to the position of the head unit 23, and is rotated by the torque of the motor 27B transmitted through the speed reducer. The paper 26 is moved by the frictional force between the paper 26 pressed together with the driven roller 28B.

  The paper feed roller 29 and the transport roller 30 are provided with encoders 31A and 31B, respectively, and the rotational speeds of both rollers detected by them are notified to the transport control unit 22. Note that these encoders may be installed on the driven rollers 28 </ b> A and 28 </ b> B of the paper feed roller 29 and the transport roller 30, respectively. In general, in the case of the driving roller, slippage between the paper 26 and the change in roller diameter over time due to wear is more severe. Therefore, it is better to install the encoder on the driven rollers 28A and 28B. Accurate measurement can be performed.

  The conveyance control unit 22 illustrated in FIG. 1 is a part that controls the conveyance system, and controls the conveyance operation of the paper 26 based on an instruction from the print control unit 21. In particular, the drive and stop of the paper feed roller 29 and the transport roller 30 are controlled so that the paper 26 is favorably transported to the printing position. The drive / stop control of the paper feed roller 29 and the transport roller 30 has a feature of the printer 2, and the specific contents thereof will be described later.

  Although not shown, the transport control unit 22 is configured by a CPU, a ROM, a RAM, an NVRAM (nonvolatile memory), and the like, and the processing executed by the transport control unit 22 is mainly a program stored in the ROM. It is executed by the CPU operating according to the above.

  Each data necessary for the processing is temporarily stored in the RAM, and each drive data during the transport operation necessary for driving / stopping control of the paper feed roller 29 and the transport roller 30 and a wait time ΔT described later are here. Is remembered. Each stored drive data includes the drive start time, the transport speed, and the corresponding duty value of the motor 27 (here, the amount of current supplied to the motor 27) of the paper feed roller 29 and the transport roller 30.

  Further, the NVRAM previously stores relation information for determining the wait time ΔT, relation information for determining the target speed of the paper feed roller 29, and the like. Such relation information will be described later.

  In addition, the said conveyance system containing the paper feed roller 29, the conveyance roller 30, and the conveyance control part 22 corresponds to the conveyance apparatus of this invention.

  The printer 2 having the above-described configuration is characterized by the conveyance control of the paper 26, and the specific contents thereof will be described below.

  As described above, since the printer 2 executes the printing process on the paper 26 that is conveyed at a predetermined (constant) speed, basically, the conveyance control unit 22 starts the printing process. The feeding speed of the paper feeding roller 29 and the feeding roller 30 is controlled so as to quickly reach the predetermined speed, and the feeding speed is maintained until the printing process is completed, and both rollers are stopped when the printing process is completed. The transport operation and the transport process are repeatedly executed every time the print process is executed.

  Further, when the paper 26 is set for the first time, the transport control unit 22 can perform a certain slack (for example, a slack as shown in FIG. 1) on the paper 26 between the paper feed roller 29 and the transport roller 30. Both rollers are controlled to convey the paper 26 to a predetermined position. As described above, this is to prevent back tension from acting on the transport roller 30, so that the paper 26 can always be supplied from the transport roller 30 to the printing position at a constant speed. Become.

  Here, the paper feed roller 29 receives a force for pulling out the paper 26 from the roll paper 25 positioned on the upstream side as a back tension. You will receive tension.

  Accordingly, at the start of each of the transport operations, the paper feed roller 29 tends to take more time to reach the predetermined speed. FIG. 2 is a diagram illustrating an example of the behavior of the paper feed roller 29 and the transport roller 30 in the transport operation. In the figure, the horizontal axis represents the elapsed time (T) from the start of driving, and the vertical axis represents the conveyance speed (V) of each roller. A curve A in the graph shows the behavior of the paper feed roller 29, and a curve B shows the behavior of the transport roller 30.

  As described above, since a larger back tension acts on the paper feed roller 29 than on the transport roller 30, the rising of the transport speed until the target predetermined speed (Vt) is reached as shown in FIG. The paper roller 29 (curve A) becomes gentler. Therefore, there is a difference in the amount of paper transported by both rollers until the both rollers reach the predetermined speed. In the example illustrated in FIG. 2, a conveyance amount difference (ΔL) corresponding to the area formed between the curve B and the curve A is generated.

  Therefore, if both rollers are activated simultaneously at the start of the transport operation, the transport roller 30 transports more by the transport amount difference (ΔL) until both rollers reach the predetermined speed Vt and are controlled with the same transport amount. It will be. This is to reduce the slack of the paper 26 described above, and there is a possibility that the slack may be eliminated depending on the difference in the transport amount. Therefore, one object of the transport control unit 22 of the printer 2 is to eliminate the transport amount difference (during acceleration) at the start of activation.

  Further, even after reaching the predetermined speed Vt (a period indicated by C in FIG. 2), as described above, particularly when the period is long, a difference occurs in the transport amount between the paper feed roller 29 and the transport roller 30. There is a case. During this period, basically, the control is executed with the target value of the transport speed by both rollers set to the predetermined speed Vt. However, if the transport speed deviates from the predetermined speed Vt due to the load fluctuation applied to the rollers, this is the case. The difference in the transport amount due to the above is not considered, and control is performed to return the transport speed to the predetermined speed Vt. Therefore, the transport amount difference may occur.

  The difference in the transport amount is not preferable because it changes the above-described constant slack. Therefore, eliminating the transport amount difference at the constant speed is one purpose of the control by the transport control unit 22.

  The transport control unit 22 performs control so as to achieve the above object and keep the slack generated in the initial state substantially constant during the transport operations. The specific control contents will be described below.

  FIG. 3 is a flowchart illustrating a procedure of processing executed by the transport control unit 22. Hereinafter, the control content of the above-described transport operation will be described with reference to FIG. One feature of the control is that the above-described difference in the conveyance amount at the start of driving is eliminated by delaying the activation timing of the conveyance roller 30, and the activation timing is determined at that time, such as the remaining amount of the roll paper 25. This is to be determined on the basis of drive data at the time of the previous transport operation, which well represents the apparatus status of the above. Here, as the drive data, the rising time difference between the paper feed roller 29 and the transport roller 30 (time difference until reaching the predetermined speed Vt), the transport amount difference (ΔL) until the paper feed roller 29 and the transport roller 30 rise up. And a method using the duty value difference (ΔD) of the motors 27 of the paper feed roller 29 and the transport roller 30 after reaching the predetermined speed, respectively.

  A further feature of the control is that from the start of the transport operation, which is detected at that time, in order to eliminate the transport amount difference that could not be completely eliminated by the start timing control and the transport amount difference that occurs during the constant speed transport described above. The target speed of the paper feed roller 29 during constant speed conveyance is changed according to the difference in conveyance amount between the two rollers.

  In each transport operation, first, when the transport control unit 22 receives a paper transport start instruction from the print control unit 21 (step S1), the transport control unit 22 acquires the value of the wait time ΔT stored in the RAM (step S2). ). This wait time ΔT is a waiting time for delaying the start timing of the transport roller 30 described above, and is information that is determined after the end of each transport operation and is held for the next transport operation. That is, the value determined during the previous transport operation. A specific determination method will be described later. Note that in the case of the first transport operation after the printer 2 is activated, a predetermined default value held in the NVRAM is acquired. Further, the value of the wait time ΔT determined during each transport operation may be stored in the NVRAM and obtained from there.

  Further, after the above instruction, the transport control unit 22 starts driving the paper feed roller 29 (step S3). That is, the motor 27A is activated, and then the control is continued so that the conveyance speed of the paper feed roller 29 becomes the target predetermined speed Vt. The conveyance control unit 22 performs drive control of the paper feed roller 29 and the conveyance roller 30 by PID control based on the detection results of the encoders 31A and 31B.

  Next, after the driving of the paper feed roller 29 is started, the transport control unit 22 waits for the acquired wait time ΔT to elapse (step S4), and starts driving of the transport roller 30 (step S5). That is, the motor 27B is activated, and then the control is continued so that the transport speed of the transport roller 30 becomes the target predetermined speed.

  In this way, by delaying the start timing of the transport roller 30 by the wait time ΔT, the above-described transport amount difference at the start of the start is substantially eliminated. The specific contents will be described later.

  Thereafter, when the paper feed roller 29 and the transport roller 30 reach the predetermined speed Vt, the constant speed drive control is executed for both rollers (step S6). In the control, since the transport roller 30 is always required to supply the paper 26 to the printing position at a constant speed, PID control is performed with the predetermined speed Vt as a target speed.

  On the other hand, for the paper feed roller 29, basically, PID control is executed with the predetermined speed Vt as a target speed in the same manner as the transport roller 30, but the difference between the transport amounts of both rollers from the start of the transport operation ( If there is [Delta] L), control is performed in which the target speed is shifted from the predetermined speed Vt by a predetermined amount in the PID control so that the transport amount difference becomes zero. That is, when the transport amount by the paper feed roller 29 is larger, the target speed is set to a value smaller than the predetermined speed Vt, and in the opposite case, the target speed is set to a value larger than the predetermined speed Vt. PID control is performed.

  Specifically, using the relationship information G for determining the target speed stored in advance in the above-described NVRAM, a change amount ΔV from the predetermined speed Vt is obtained by an equation: ΔV = G × ΔL, Using the change amount ΔV, the target speed (= Vt + ΔV), which is the target of the PID control at that time, is determined.

  FIG. 4 is a diagram for explaining the control during the constant speed conveyance. In FIG. 4, the conveyance speed V ((A) of FIG. 4) by the paper feed roller 29 (line A in the figure) and the conveyance roller 30 (B in the figure) during constant speed conveyance, and the above of both rollers The conveyance amount difference ΔL (FIG. 4B, line AA) is illustrated over time. Here, it is assumed that the load applied to the paper feed roller 29 suddenly pulsates in the vicinity of the period from time T01 to time T03, thereby changing the speed of the paper feed roller 29 by PID control. The transport roller 30 is controlled to be substantially constant at the predetermined speed Vt.

  In this case, after time T02, the transport amount by the paper feed roller 29 becomes larger than the transport amount of the transport roller 30, so that the paper feed roller 29 is appropriately set according to the target speed setting of the paper feed roller 29 described above. A target speed slower than the predetermined speed Vt is set and PID control is performed. Then, the speed gradually decreases from the speed that reached the maximum at time T03 due to the pulsation, and after time T04, the actual speed becomes slower than the predetermined speed Vt. Therefore, as shown by line AA, the conveyance amount When the difference ΔL starts to decrease and becomes zero (time T05), the target speed of the paper feed roller 29 is controlled to return to the predetermined speed Vt.

  In the control for simply setting the target speed to the predetermined speed Vt, if there is no load fluctuation, the speed of the paper feed roller 29 gradually decreases and approaches Vt after time T03, and the carry amount Control is continued without the difference ΔL becoming zero.

  With such control during constant speed conveyance, the conveyance amount difference that occurs during acceleration and the conveyance amount difference that occurs during constant speed conveyance that could not be completely eliminated by the control based on the wait time ΔT and real time control are eliminated. be able to. In addition, the said conveyance amount difference is calculated | required from the value detected by each encoder 31A and 31B.

  It should be noted that the above-described relation information G (here, a constant) is determined and stored in advance by an appropriate experiment. Further, since the relationship information G differs depending on the paper type such as the material and thickness of the paper 26, it is preferable to determine an appropriate value for each paper type and store it in the NVRAM so that it can be identified. In this case, when receiving an instruction to start conveyance from the print control unit 21 (S1) or the like, information on the paper type is received, and control is performed using the corresponding relationship information based on the information.

  The relationship information G is preferably changed according to the magnitude of the back tension acting on the paper feed roller 29, and the relationship information G may be corrected by the diameter of the roll paper 25 that affects the back tension. That is, the relationship information G may be expressed by a function having the roll paper diameter as a variable. In this case, the diameter of the roll paper at the time of control is directly measured by a touch sensor or a reflective sensor provided in the printer 2, the number of rotations after the roll paper 25 is attached, and the encoder (31A, 31B) can be obtained by a method of estimating based on the detection information (cumulative transport amount).

  Although the relationship between the information for determining the target speed (conveyance amount difference ΔL) and the amount of change (ΔV) from the target speed is linear, the relationship is expressed as a non-linear function f such that ΔV = f (ΔL). Also good. In order to control the amount of slack more accurately, the change amount ΔV is not limited to the above-described proportional control (deviation × gain G), but also integrated control (deviation integral × gain Gi) or differential control (deviation differentiation). X Gain Gd) may be taken into consideration. Also in these cases, the function f and the PID control method (G, Gi, Gd, ΔV calculation formulas) are determined in advance and recorded as relation information.

  When the conveyance stop instruction is received from the print control unit 21 after the constant speed conveyance described above (step S7), the conveyance control unit 22 performs control to stop driving of the paper feed roller 29 and the conveyance roller 30 (step S7). S8). In this control, each roller may be simply controlled so as to make the speed zero, but preferably, the rollers are stopped so that the transport amount of both rollers in the current transport operation is the same. Execute. As a result, the slack of the paper 26 between the paper feed roller 29 and the transport roller 30 at the start of the transport operation is more reliably held.

  In this way, when both rollers are stopped and the current transport operation is completed, the transport control unit 22 determines the weight in the next transport operation from the driving status of the paper feed roller 29 and the transport roller 30 in the current transport operation. The time ΔT is determined, and the value stored in the RAM is deleted and stored (step S9).

  The wait time ΔT is for overcoming the difference in transport amount due to the difference in behavior of the paper feed roller 29 and the transport roller 30 at the start of driving. Therefore, the wait time ΔT is determined from the behavior at the start of driving of both rollers. Can take a way to determine. Specifically, as described above, as one method, it is obtained from the rise time difference between the paper feed roller 29 and the transport roller 30.

  FIG. 5 is a diagram for explaining the wait time ΔT. FIG. 5A shows the change in speed over time when the paper feed roller 29 and the transport roller 30 start driving at the same time as in the graph shown in FIG. It corresponds to ΔT1. That is, it is a difference in required time from the start of driving of each roller until reaching the target predetermined speed Vt.

  FIG. 5B shows a change in conveyance speed over time of the paper feed roller 29 and the conveyance roller 30 when the control in the printer 2 described with reference to FIG. 3 is executed. As described above, the driving start of the transport roller 30 indicated by the curve B is delayed by the wait time ΔT from the driving start of the paper feed roller 29 indicated by the curve A. As a result, by the time when both of the two rollers reach the target predetermined speed Vt (T3 in the figure), the amounts conveyed by both rollers are substantially the same (the areas of ΔL1 and ΔL2 in the figure are substantially the same). The slack of the paper 26 is kept substantially constant during the transport operation.

  Since it can be said that the rise time difference ΔT1 and the wait time ΔT are substantially proportional to each other, a proportional coefficient k1 of ΔT = k1 × ΔT1 is determined in advance by experiment, and the information is stored in the NVRAM as the relation information described above. Keep it. Therefore, in this method, for the paper feed roller 29 and the transport roller 30, the time from the start of driving to the arrival of the predetermined speed is obtained, and in the example shown in FIG. 5B, TA and TB are obtained. ΔT1 is calculated from the difference, and the wait time ΔT is determined from the relationship ΔT = k1 × ΔT1 using the proportionality coefficient k1 which is the relationship information.

  The drive data stored in the above-described RAM is used for the above-described control during the constant-speed transfer and the determination of the wait time ΔT. The transfer control unit 22 appropriately acquires and stores these data. Further, the transport speed of the paper feed roller 29 and the transport roller 30 and the corresponding duty value of the motor 27 (here, the amount of current supplied to the motor 27) are stored at predetermined time intervals.

  The second method is a method of determining from the conveyance amount difference ΔL until the paper feed roller 29 and the conveyance roller 30 rise. Also in this case, since it can be said that the conveyance amount difference ΔL and the wait time ΔT have a substantially proportional relationship, a proportional coefficient k2 of ΔT = k2 × ΔL is determined in advance by experiment, and the information is related to the relationship described above. Information is stored in NVRAM as information. Therefore, in this method, the paper feed roller 29 and the transport roller 30 are each in the time from the start of driving until the predetermined speed is reached after the start of driving of the paper feed roller 29 (TA shown in FIG. 5B). 26 is obtained, ΔL is calculated from the difference between them, and the wait time ΔT is determined from the relationship of ΔT = k2 × ΔL using the proportionality coefficient k2 which is the relationship information.

  In the example shown in FIG. 5B, the conveyance amount during acceleration of the paper feed roller 29 is the conveyance amount from time T1 to T3, and the conveyance amount during acceleration of the conveyance roller 30 is from T2 to T4. ΔL is calculated from the difference between these carry amounts.

  Next, the third method will be described. In this method, the difference in behavior between the paper feed roller 29 and the transport roller 30 at the start of driving is measured by the duty value difference ΔD of each motor 27 of the paper feed roller 29 and the transport roller 30 after reaching the predetermined speed Vt. It is something to try. That is, the wait time ΔT is determined from the duty value difference ΔD.

  FIG. 6 is a diagram showing an example of the duty values of the motors 27A and 27B over time. The duty value indicates the amount of current supplied to each motor 27 as a relative value, and the larger this value, the greater the force to be applied to the roller.

  In FIG. 6, the duty values of the motors 27A (curve A) and 27B (curve B) from the start of driving the paper feed roller 29 and the transport roller 30 are shown. Usually, since a large force is required at the time of start-up, the Duty value has a mountain shape shown in FIG. 6 and becomes a substantially constant Duty value after reaching the target speed.

  For two rollers to be controlled to the same target speed, a larger duty value means that the driving load (the power required for driving) is larger, that is, it acts on the feeding roller 29. This indicates that the back tension is greater. Therefore, it is possible to measure the above-described rise delay at the start of driving based on the duty value difference. Therefore, in this method, the wait time ΔT is determined from the duty value difference. Further, the duty value difference to be used is not stable because the duty value fluctuates greatly in the control at the start of driving. The duty value difference ΔD in the band) is used.

  Also in this case, it can be said that the duty value difference ΔD and the wait time ΔT are in a substantially proportional relationship. Therefore, a proportional coefficient k3 of ΔT = k3 × ΔD is determined in advance by experiment, and the information is related to the relationship described above. Information is stored in NVRAM as information. Therefore, in this method, the representative duty value of each roller after the paper feed roller 29 and the transport roller 30 reach the predetermined speed is obtained, ΔD is calculated from the difference therebetween, and the proportionality coefficient that is the relation information is obtained. Using k3, the wait time ΔT is determined from the relationship ΔT = k3 × ΔD.

  The representative duty value can be an average value of a plurality of duty values detected within a preset time.

  In these three methods, the relationship between the information for determining the wait time (ΔT1, ΔL, ΔD, collectively referred to as ΔX) and the wait time ΔT is linear. It may be a non-linear function f = f (ΔX). Also in this case, the function f is determined in advance and recorded as related information.

  In this way, the wait time ΔT is determined, stored in the RAM, and when this value is updated (step S9), a series of control processing for the transport operation is completed, and thereafter the same processing is repeated. Execute.

  It should be noted that the relationship between the information for determining the wait time (ΔT1, ΔL, ΔD) and the wait time differs depending on the type of the paper 26 and the like. You may make it prepare.

  In the above embodiment, in order to keep the slack of the paper 26 constant, both the control by the wait time ΔT and the control to change the target speed of the paper feed roller 29 are executed, but only the latter is executed. You may do it.

  Moreover, it is good also as a structure which adds the control for danger avoidance which used the slack sensor further to the control of the said embodiment. FIG. 7 is a schematic view showing an example of the sag sensor 34 in the configuration. This configuration is obtained by adding a sag sensor 34 as shown in FIG. 7 to the configuration shown in FIG. 1, and the sag sensor 34 allows slack of the paper 26 between the paper feed roller 29 and the transport roller 30. It is controlled so as not to exceed the range. Accordingly, the sag sensor 34 has a function of detecting the upper limit value (UL) and the lower limit value (LL) of the slackness.

  The upper limit value of the slackness is a limit value that may cause a trouble in conveyance such as contact with a member of the conveyance path 33 when the amount of slackness is further increased. In FIG. Represents. Further, the lower limit value of the slack is a limit value at which the back tension to the transport roller 30 may occur when the amount of slack is reduced below that. In FIG. Represents.

  The slack sensor 34 in FIG. 7 always touches the paper 26 lightly and moves up and down according to the slack of the paper 26, a rod-like member that rotates around a fulcrum according to its vertical movement, It is composed of a detection unit that detects the amount of movement of the end opposite to the tip, and when the detection unit detects that the upper limit (UL) or the lower limit (LL) has been reached, This is notified to the conveyance control unit 22.

  Note that the sag sensor 34 shown in FIG. 7 is an example, and a sensor having a different configuration such as an optical sensor or a touch sensor can be used as the sag sensor as long as it can detect the upper and lower limits of the slack.

  In the control of the above-described embodiment, control based on the driving state at the previous transport operation (control by wait time) and real-time control based on the transport amount difference at that time are performed, and the amount of slack at the start of the transport operation However, there is a possibility that the measurement errors of the encoders 31A and 31B accumulate and the above-mentioned slack that should be kept constant gradually increases or decreases. In addition, there is a possibility that a situation in which the control is not normally performed suddenly due to some failure and the amount of slackness changes abruptly.

  The configuration in which the sag sensor is added is for the purpose of avoiding danger against such a situation. In addition to the control in the above-described embodiment, the sag sensor 34 has the upper limit (UL). Alternatively, when it is detected that the lower limit value (LL) has been reached, the transport operation is stopped, or the transport amount in real-time control (control to change the target speed of the paper feed roller 29) based on the transport amount difference. The control of resetting the difference ΔL is executed.

  In the former case, since the transport operation is immediately stopped, the slack increases too much, causing a paper jam, or the slack decreases too much, and the back tension acts on the transport roller 30 to perform poor printing. This can be avoided.

  In the latter case, when it is detected that the upper limit value or the lower limit value has been reached, the transport amount difference ΔL at that time is reset in advance with respect to the upper limit value or the lower limit value. Thereafter, the control is performed with the reset value updated with the subsequent transport amount difference. That is, the control for changing the target speed of the paper feed roller 29 described above is executed according to the transport amount difference ΔL thus reset. The reset value includes the length of the sheet 26 existing between the two rollers (the feed roller 29 and the transport roller 30) in the case of the slack to be kept constant generated in the initial state, the upper limit value, or the lower limit value. Is a difference from the length of the paper 26 existing between the two rollers when the value reaches the predetermined value, and a predetermined value is stored in the NVRAM.

  Thus, by adding control using the sag sensor 34, accumulated measurement errors can be eliminated, and more accurate control becomes possible.

  As described above, in the transport system of the printer 2 according to the present embodiment, the transport amount is based on the difference in transport amount between the two rollers (the feed roller 29 and the transport roller 30) detected at that time. Since the control is performed in real time in the direction to eliminate the difference, the slack between the two rollers at the start of the transport operation is always kept substantially constant, and the sheet 26 can touch the member even if the space of the transport path 33 is small. And can be transported well. Therefore, it is possible to always avoid the action of the back tension on the transport roller 30 without increasing the apparatus scale. Thereby, paper supply at a constant speed to the printing position is realized, and high-quality printing is possible.

  Further, more accurate control can be realized by providing each of the driven rollers 28A and 28B with the encoders 31A and 31B that detect the rotational speeds of both rollers used in the control.

  Further, by changing (correcting) the above-described relation information G according to the paper type and the roll paper diameter, more accurate control can be executed.

  Further, since the start timing of the transport roller 30 is appropriately delayed based on the immediately preceding situation, the transport amount difference between the two rollers that occurs during the acceleration of the roller can be eliminated at an early stage, and more accurate control is performed. Is possible.

  Further, the transport method works more effectively in an apparatus using the roll paper 25 in which the back tension to the paper feed roller 29 is easily changed.

  Furthermore, by adding the above-described control using the sag sensor 34, a safer transport operation can be performed and the accuracy of the control can be improved.

  In this embodiment, the print medium is paper, but the present invention is not limited to this as long as it is a sheet-like medium.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 Host apparatus, 2 Printer, 21 Print control part, 22 Conveyance control part, 23 Head part, 24 Platen, 25 Roll paper, 26 Paper, 27A, B motor, 28A, B Drive roller, 29 Feed roller, 30 Conveyance roller , 31A, B Encoder, 32 Paper discharge roller, 33 Transport path, 34 Slack sensor

Claims (8)

An upstream roller that feeds the sheet-like processed medium to the conveyance path, a downstream roller that supplies the fed medium to the processing position, and the constant speed is used to convey the processed medium at a constant speed. As a target speed of the conveyance speed by the upstream roller and the downstream roller, a control unit that controls the driving of both rollers, and a conveyance device comprising:
The control unit, in each transport operation, based on the difference between the transport amount by the upstream roller and the transport amount by the downstream roller from the start time of the transport operation, so that the transport amount difference is eliminated The conveying apparatus characterized by changing the target speed of the upstream roller. In claim 1,
Relationship information between the conveyance amount difference and the amount of change in the target speed of the upstream roller is stored in advance, and the target speed is changed according to the relationship information. In claim 1 or 2,
Furthermore, each of the upstream roller and the downstream roller has a driven roller installed to face each of the rollers with the medium to be processed interposed therebetween, and an encoder installed on each of the driven rollers. And
The said control part calculates | requires the said conveyance amount difference based on the information detected by each said encoder. The conveying apparatus characterized by the above-mentioned. In claim 2,
The conveyance apparatus that holds the relation information for each type of the medium to be processed. In any one of Claims 1 thru | or 4,
The conveying apparatus, wherein the medium to be processed is supplied to the upstream roller from a state in which the medium to be processed is held in a roll shape. In any one of Claims 1 thru | or 5,
The control unit determines activation timings of the upstream roller and the downstream roller at the start of the transport operation based on drive information of the upstream roller and the downstream roller at the time of the previous transport operation. A transport device.   A printing apparatus comprising the transport apparatus according to claim 1, wherein the printing apparatus executes printing on the medium to be processed at the processing position. An upstream roller that feeds the sheet-like processed medium to the conveyance path, a downstream roller that supplies the fed medium to the processing position, and the constant speed is used to convey the processed medium at a constant speed. As a target speed of the transport speed by the upstream roller and the downstream roller, a control method for controlling the driving of both rollers, and a transport method in a transport device comprising:
The control unit, in each transport operation, based on the difference between the transport amount by the upstream roller and the transport amount by the downstream roller from the start time of the transport operation, so that the transport amount difference is eliminated Changing the target speed of the upstream roller.

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