JP7409164B2 - Sheet conveyance device and image forming system - Google Patents

Description

The present disclosure relates to a sheet conveying device and an image forming system.

2. Description of the Related Art Conventionally, there has been known a printing device that pulls out a sheet from a wound sheet roll in the direction of a recording head using a conveyance roller, and prints an image on the pulled out sheet (for example, see Patent Document 1).

In this printing device, the diameter of the sheet roll is determined. The determined diameter of the sheet roll is used for sheet conveyance control. The diameter of the sheet roll is measured using, for example, a distance sensor. Alternatively, the diameter of the sheet roll is estimated based on the conveyance amount of the sheet when the sheet is conveyed by the conveyance roller and the rotation amount of the sheet roll.

Japanese Patent Application Publication No. 2014-076669

2. Description of the Related Art A sheet conveyance device that pulls out and conveys a sheet from a sheet roll may be provided with a tensioner between the sheet roll and the conveyance roller to apply tension to the sheet.

The tensioner includes a movable part that contacts the seat and applies tension to the seat. The movable parts are displaced under the urging force of an elastic material such as a spring in order to apply appropriate tension to the seat.

In a device equipped with such a tensioner, the posture of the sheet pulled out from the sheet roll changes under the influence of the displacement of the tensioner. Therefore, with the above-described conventional method of estimating the diameter of the sheet roll based on the amount of conveyance of the sheet by the conveyance roller and the amount of rotation of the sheet roll, the diameter of the sheet roll cannot be estimated accurately.

Therefore, according to one aspect of the present disclosure, in a sheet conveying device equipped with a tensioner, the diameter of the sheet roll can be estimated with high accuracy from the conveyance amount of the sheet, etc., without directly measuring the diameter of the sheet roll with a sensor. It is desirable to be able to provide technology.

A sheet conveyance device according to one aspect of the present disclosure includes a holder, a rotation measuring device, a conveyance roller, a tensioner, a position detector, a motor, and a controller. The holder holds a sheet roll around which a sheet is wound. The rotation measuring device measures the amount of rotation of the sheet roll.

The conveyance roller conveys the sheet pulled out from the sheet roll held by the holder. The tensioner is a movable tensioner, is provided between the holder and the conveyance roller, and comes into contact with the sheet pulled out from the sheet roll by the conveyance roller. A position detector detects the position of the tensioner.

The motor generates driving force to rotate the conveyance roller so that the sheet is conveyed. The controller is configured to control the motor. The controller adjusts the sheet roll based on the conveyance amount of the sheet due to the rotation of the conveyance roller driven by the motor, the rotation amount of the sheet roll measured by the rotation measuring device, and the position of the tensioner detected by the position detector. Estimate the diameter.

According to this sheet conveying device, even in an environment where the posture of the drawn sheet from the sheet roll to the conveyance roller changes depending on the position of the tensioner, the amount of sheet conveyance by the conveyance roller and the amount of rotation of the sheet roll can be adjusted. Based on this, the diameter of the sheet roll can be estimated with high accuracy. Therefore, according to one aspect of the present disclosure, the diameter of the sheet roll can be estimated with high accuracy without directly measuring the diameter of the sheet roll using a sensor.

According to one aspect of the present disclosure, an image forming system including the above-described sheet conveying device and a processing head may be provided. The processing head can form an image on the sheet downstream of the conveyance roller in the sheet conveyance direction.

1 is a diagram illustrating a configuration of an image forming system according to one aspect of the present disclosure. It is a figure explaining the function of a tensioner. FIG. 1 is a block diagram illustrating the electrical configuration of an image forming system. 3 is a flowchart showing processing executed by the main controller. FIG. 2 is a block diagram showing the configuration of a speed controller. It is a block diagram showing the composition of a tension controller. It is a flow chart showing processing performed by a roll diameter estimator. It is a graph showing the relationship between tensioner position and path length. FIG. 3 is an explanatory diagram regarding a method for estimating a roll diameter. It is a graph showing a change in the estimated value of the roll diameter. It is a flowchart showing a part of initial processing. It is a flowchart showing origin setting processing performed by a main controller in a second embodiment. It is a flowchart showing the process which a roll diameter estimator performs in a third embodiment. It is a flowchart showing the switching process of state quantity noise which a roll diameter estimator performs in a third embodiment. It is a block diagram showing the composition of the tension controller in a third embodiment.

Exemplary embodiments of the present disclosure will be described below with reference to the drawings.
[First embodiment]
The image forming system 1 of this embodiment shown in FIG. 1 is configured to form an image on a sheet Q pulled out from a sheet roll Q0. This image forming system 1 functions as a sheet conveying device for conveying the sheet Q toward the lower side of the recording head 40 .

The image forming system 1 includes a holder 10, a tensioner 15, a conveyance roller 20, a nip roller 25, a belt mechanism 30, and a recording head 40. In FIG. 1, the configuration downstream of the belt mechanism 30 in the conveying direction of the sheet Q is omitted. For example, a cutter for cutting the sheet Q is provided downstream of the belt mechanism 30.

The holder 10 removably holds the sheet roll Q0. The sheet roll Q0 has a structure in which the sheet Q is wound around a hollow core material. The holder 10 includes a rotating shaft 10A that is inserted through the core material of the sheet roll Q0, and a holder body (not shown) that rotatably holds the rotating shaft 10A.

The holder main body is fixed within a casing (not shown) of the image forming system 1. The core material of the sheet roll Q0 is fixed to the rotating shaft 10A of the holder 10 so as not to slip. Thereby, the sheet roll Q0 rotates together with the rotating shaft 10A of the holder 10.

After the sheet Q0 is attached to the rotating shaft 10A, the sheet Q is manually moved from the sheet roll Q0 through the tensioner 15 to a position where it passes the nip point P2 between the conveyance roller 20 and the nip roller 25. pulled out until A point P1 in FIG. 1 indicates a point at which the sheet Q is pulled out from the sheet roll Q0.

The conveyance roller 20 rotates and conveys the sheet Q nipped between it and the nip roller 25 in the conveyance direction indicated by the thick arrow. As shown in FIG. 2, the tensioner 15 is configured as a roller that can be displaced in the front-rear direction, and is connected to a spring member 16.

When the tensioner 15 is displaced forward, it is arranged so as to receive a backward biasing force from the spring member 16. The tensioner 15 applies tension to the sheet Q using this biasing force. The front here corresponds to the conveyance direction of the sheet Q, and the rear corresponds to the direction opposite to the conveyance direction of the sheet Q.

The tensioner 15 is displaced forward in response to a pressing force from the sheet Q when the sheet Q pulled out from the sheet roll Q0 is conveyed by the conveyance roller 20. The pressing force corresponds to the tension of the sheet Q. The dotted line shown in FIG. 2 shows a state in which the tensioner 15 and the seat Q shown by the solid line are displaced to the position shown by the dotted line due to the force from the seat Q.

The position of the tensioner 15 in the longitudinal direction is stabilized at a position where the urging force of the spring member 16 and the tension of the sheet Q are balanced. The image forming system 1 is configured to estimate the tension of the sheet Q using the position of the tensioner 15 as an index and perform tension control (details will be described later).

The belt mechanism 30 is disposed downstream of the conveyance roller 20 in the conveyance direction, and conveys the sheet Q conveyed from the conveyance roller 20 further downstream. As shown in FIG. 1, the belt mechanism 30 has a structure in which a belt 33 is wound around a driving roller 31 and a driven roller 32. The drive roller 31 rotates the belt 33 by rotational movement synchronized with the conveyance roller 20 .

The belt mechanism 30 further includes a first opposing roller 35 at a position facing the drive roller 31 with the belt 33 in between, and a second opposing roller 36 at a position facing the driven roller 32 with the belt 33 in between.

As the belt 33 rotates, the sheet Q conveyed from the conveyance roller 20 passes between the first opposing roller 35 and the belt 33 and is conveyed downstream. Further, the sheet Q is conveyed downstream between the second opposing roller 36 and the belt 33. Due to the rotation of the belt 33, the sheet Q is conveyed at the same speed as the conveyance speed of the sheet Q by the conveyance roller 20.

According to one example, the belt mechanism 30 can have an air suction function. That is, the belt 33 may have a large number of minute holes through which air passes, and a suction device (not shown) for sucking air may be provided below the belt 33. The sheet Q may be conveyed while being attracted to the surface of the belt 33 by air suction by a suction device.

The recording head 40 is provided above the belt mechanism 30 and forms an image on the sheet Q passing therethrough. The recording head 40 is a line head, and simultaneously forms an image on the entire line direction of the sheet Q passing below the recording head 40 . The line direction here is a direction along the surface of the sheet Q, and is a direction perpendicular to the conveying direction of the sheet Q, in other words, the longitudinal direction of the sheet Q.

The recording head 40 may be, for example, an inkjet head that forms an image on the sheet Q using an inkjet method. The recording head 40 may be a thermal head that forms an image on the sheet Q using a thermal method or a thermal transfer method.

When the recording head 40 forms an image using an inkjet method, a fixing device 45 for drying and fixing the ink may be provided downstream of the recording head 40 in the transport direction. The fixing device 45 may be provided adjacent to the recording head 40 on the belt mechanism 30, as shown by the dotted line in FIG.

Next, the electrical configuration of the image forming system 1 will be described in detail. As shown in FIG. 3, the image forming system 1 includes a controller 50 that centrally controls the entire system. The image forming system 1 further includes a supply motor 61, a motor driver 63, a rotary encoder 65, and a measurement circuit 67 to control the rotation of the sheet roll Q0 mounted on the holder 10.

The supply motor 61 is connected to the rotating shaft 10A of the holder 10 via a gear (not shown), and is arranged to apply power to the rotating shaft 10A. The rotating shaft 10A of the holder 10 receives power from the supply motor 61 and rotates. The sheet roll Q0 rotates together with the rotating shaft 10A.

Supply motor 61 may be a DC motor. The supply motor 61 generates rotational torque according to the drive current input from the motor driver 63 to drive the rotating shaft 10A. The motor driver 63 inputs a drive current to the supply motor 61 according to the operation amount _USR input from the controller 50.

The rotary encoder 65 is provided on the rotating shaft 10A of the holder 10 or the rotating shaft of the supply motor 61, and outputs an encoder signal according to rotation. The measurement circuit 67 measures the rotational position and rotational speed (in other words, the rotational angle and angular velocity) of the sheet roll Q0 as physical quantities related to the rotational movement of the sheet roll Q0 based on the encoder signal input from the rotary encoder 65, The measured rotational position and rotational speed are input to the controller 50. The rotational position and rotational speed of the rotating shaft 10A correspond to the rotational position and rotational speed of the sheet roll Q0.

The image forming system 1 further includes a transport motor 71, a motor driver 73, a rotary encoder 75, and a measurement circuit 77 as components for controlling the rotation of the transport roller 20.

Conveyance motor 71 may be a DC motor. The conveyance motor 71 is connected to the conveyance roller 20 via a gear, and generates a rotational torque according to a drive current inputted from a motor driver 73 to rotationally drive the conveyance roller 20 . The motor driver 73 inputs a drive current corresponding to the operation amount _UPF input from the controller 50 to the transport motor 71.

The rotary encoder 75 is provided on the rotation axis of the conveyance roller 20 or the rotation axis of the conveyance motor 71, and outputs an encoder signal according to rotation. The measurement circuit 77 measures the rotational position and rotational speed (in other words, the rotational angle and angular velocity) of the conveyance roller 20 as physical quantities related to the rotational movement of the conveyance roller 20 based on the encoder signal input from the rotary encoder 75. The measured rotational position and rotational speed are input to the controller 50.

The image forming system 1 further includes a position detector 80 that detects the position of the tensioner 15. The position detector 80 detects a position X of the tensioner 15 in the longitudinal direction with respect to a predetermined origin position, and inputs the detected position X to the controller 50. Position detector 80 may be configured with a linear encoder, for example.

The image forming system 1 further includes a head driver 90, a registration sensor 91, a user interface 95, and a communication interface 97. The head driver 90 is configured to drive the recording head 40 according to a control signal from the controller 50. The registration sensor 91 is configured to detect the leading edge of the sheet Q passing therethrough upstream of the belt mechanism 30 and input the detection signal to the controller 50 .

The user interface 95 includes a display section that displays various information for the user, and an input section that accepts operations from the user. For example, the display section is a liquid crystal display, and the input section is a touch panel on the liquid crystal display.

The communication interface 97 is configured to be able to communicate with the information device by wire or wirelessly. The communication interface 97 may be a USB interface or a wired/wireless LAN interface. The information device may be a personal computer or a tablet terminal owned by the user.

The controller 50 includes a main controller 51, a print controller 53, a speed controller 55, and a tension controller 57. The main controller 51 includes a processor 51A and a memory 51B. The memory 51B includes RAM and flash memory.

Processor 51A executes various processes according to computer programs stored in memory 51B. In the following, the processing executed by the main controller 51 may be understood to be executed by the processor 51A according to a computer program.

The print controller 53, speed controller 55, and tension controller 57 are configured by, for example, ASIC. The print controller 53 inputs a control signal to the head driver 90 to cause the recording head 40 to form an image on the sheet Q based on the image data to be printed, which is input from the main controller 51. do.

The speed controller 55 determines a manipulated _{variable UPF} for the transport motor 71 so that the transport roller 20 rotates at a target rotational speed according to instructions from the main controller 51, and inputs the determined manipulated variable _UPF to the motor driver 73. It is configured as follows. According to this embodiment, the conveyance speed of the sheet Q is controlled by controlling the rotational speed of the conveyance roller 20.

The tension controller 57 determines the operation amount _USR for the supply motor 61 so that the sheet Q is conveyed with the target tension according to the instruction from the main controller 51, and applies the determined operation amount _USR to the motor driver 63. configured to input.

When the main controller 51 receives a print command from the information device through the communication interface 97, it executes the process shown in FIG. In cooperation with the print controller 53, speed controller 55, and tension controller 57, each part within the image forming system 1 is controlled.

When starting the process shown in FIG. 4, the main controller 51 executes initial processing (S110). The initial process includes a process of arranging the head of the sheet Q at a predetermined starting point. The starting point may be a position where the leading edge of the sheet Q is detected by the registration sensor 91, or may be a position where the leading edge of the sheet Q is moved a predetermined distance downstream in the conveying direction from this position.

The starting point may be defined as the position where the leading edge of the sheet Q enters the belt mechanism 30, or may be defined as the position on the sheet conveyance path where the recording head 40 forms an image on the sheet Q, which is necessary for accelerating the sheet Q. The point may be a distance upstream in the transport direction.

When the head of the sheet Q is placed at the starting point, the main controller 51 starts the conveyance process of the sheet Q (S120). In the conveyance process, the main controller 51 inputs into the speed controller 55 a speed profile indicating the target rotational speed of the conveyance roller 20 until the sheet Q stops at the target stop position, and causes the speed controller 55 to adjust the speed of the conveyance roller 20 according to the speed profile. Execute rotation speed control.

The speed profile indicates a target rotational speed in an acceleration section, a target rotational speed in a constant speed section, and a target rotational speed in a deceleration section. By controlling the rotational speed of the conveyance roller 20 according to this speed profile, the sheet Q accelerates until it reaches a predetermined speed, moves at a constant speed after reaching the predetermined speed, and then decelerates.

In the conveyance process, the main controller 51 further inputs to the tension controller 57 a tension profile indicating the target tension until the sheet Q stops at the target stop position, and causes the tension controller 57 to execute tension control of the sheet Q according to the tension profile. .

After starting the conveyance process, the main controller 51 waits until the rotational speed control shifts to the constant speed section (S130), and when the rotation speed control shifts to the constant speed section, starts the printing process (S140). In the printing process, the main controller 51 causes the print controller 53 to execute drive control of the recording head 40 to cause the recording head 40 to form an image on the sheet Q based on the image data to be printed. Through this control, the recording head 40 repeatedly performs an image forming operation in the line direction on the sheet Q in accordance with the movement in the conveyance direction.

When an image based on the image data to be printed is formed on the sheet Q by the movement of the sheet Q and the synchronized image forming operation of the recording head 40, and the printing process and the conveyance process are completed (Yes in S150), the main controller 51 ends the process. Processing is executed (S160). The termination process includes a process of notifying the user through the user interface 95 of the termination of printing. Thereafter, the main controller 51 ends the process shown in FIG. 4.

Next, the detailed configuration of the speed controller 55 will be explained using FIG. 5. The speed controller 55 adjusts the conveyance roller 20 to the target rotation speed by calculating the operation amount _UPF for the conveyance motor 71 based on the deviation between the rotation speed of the conveyance roller 20 measured by the measurement circuit 77 and the target rotation speed. is configured to provide feedback control. The actual rotational speed hereinafter means a measured value of the rotational speed.

The speed controller 55 includes a speed command device 101 , a deviation calculator 103 , a PID controller 105 , a static friction compensator 107 , and an adder 109 . The speed command device 101 outputs the target rotational speed ω _r at each point in time from the start of control according to the speed profile input from the main controller 51.

The deviation calculator 103 calculates the deviation E _V =(ω _r −ω _PF ) between the target rotation speed ω _r from the speed command device 101 and the actual rotation speed ω _PF input from the measurement circuit 77. The PID controller 105 calculates the operation amount _UV for the transport motor 71 based on the deviation _EV input from the deviation calculator 103.

The PID controller 105 includes a proportional element that amplifies the deviation E _V with a gain G _p and outputs it, an integral element that amplifies the integral value INT (E _V ) of the deviation E _V with a gain G _i and outputs it, and a and a differential element that amplifies the differential value DIF (E _V ) of _V by a gain G _d and outputs the amplified differential value DIF (E V ) of V. The PID controller 105 calculates the sum of the outputs from the proportional element, the integral element, and the differential element as the manipulated variable _UV for the transport motor 71.

Static friction compensator 107 outputs a compensation amount C for compensating for a deficiency in manipulated variable _UV caused by static friction. The compensation amount C is a constant value when the actual rotational speed ω _PF is zero, that is, in a stationary state, and is zero when the actual rotational speed ω _PF is non-zero, that is, in a non-stationary state.

The adder 109 corrects the manipulated variable U _V output from the PID controller 105 using the compensation amount C, and inputs the corrected manipulated variable U _PF =U _V +C to the motor driver 73 . The motor driver 73 inputs a drive current corresponding to the manipulated variable _UPF input from the speed controller 55 to the transport motor 71, thereby controlling the transport motor 71 so that a rotational torque corresponding to the manipulated variable _UPF is generated. drive The rotation speed of the conveyance roller 20 and the corresponding conveyance speed of the sheet Q are feedback-controlled by this speed controller 55.

Tension control is realized by a tension controller 57 shown in FIG. The tension controller 57 shown in FIG. 6 supplies the sheet Q based on the deviation between the target tension and the tension of the sheet Q estimated from the position The operation amount _USR for the motor 61 is calculated. Thereby, the tension controller 57 feedback-controls the tension of the sheet Q to the target tension.

As shown in FIG. 6, the tension controller 57 includes a tension command device 110, a tension estimator 120, a deviation calculator 130, a PID controller 140, a roll diameter estimator 150, a feedforward controller 160, It includes an adder 170 and a gain setter 180.

The tension command device 110 outputs the target tension T _r at each time point from the start of control according to the tension profile input from the main controller 51 . The tension estimator 120 estimates the tension T acting on the sheet Q based on the position X of the tensioner 15 input from the position detector 80. Specifically, the tension estimator 120 can calculate, as the estimated tension T, a value k·X obtained by multiplying the position X of the tensioner 15 by a specific proportionality coefficient k.

The deviation calculator 130 calculates the deviation E _T =T _r −T between the target tension T _r and the estimated tension T. The PID controller 140 calculates a feedback operation amount U _B for the supply motor 61 based on the deviation E _T inputted from the deviation calculator 130 .

As shown in FIG. 6, the PID controller 140 includes a proportional gain amplifier 141, an integral gain amplifier 142, a differential gain amplifier 143, an integrator 145, a differentiator 146, and an adder 148. The deviation _ET from the deviation calculator 130 is input to a proportional gain amplifier 141, an integrator 145, and a differentiator 146. The proportional gain amplifier 141 amplifies the input deviation E _T by a gain K _p and outputs the amplified deviation E T .

The integrator 145 performs an integral operation on the deviation E _T and inputs an integral value INT (E _T ) of the deviation E _T to the integral gain amplifier 142 . The integral gain amplifier 142 amplifies the input integral value INT(E _T ) of the deviation E _T by a gain K _i and outputs the amplified value.

The differentiator 146 performs a differential operation on the deviation E _T and inputs the differential value DIF (E _T ) of the deviation E _T to the differential gain amplifier 143 . The differential gain amplifier 143 amplifies the input differential value DIF(E _T ) of the deviation E _T by a gain K _d and outputs the amplified value.

The adder 148 outputs the output K _p · _ET from the proportional gain amplifier 141, the output K _i ·INT ( _ET ) from the integral gain amplifier 142, and the output K _d ·DIF (ET ₎ from the differential gain amplifier 143. is added, and the added value K _p · _ET +K _i ·INT( _ET )+K _d ·DIF( _ET ) is output as the feedback operation amount U _B for the supply motor 61.

The adder 170 converts the sum value U _B +U _F of the feedback operation amount U _B inputted from the PID controller 140 and the feedforward operation amount U _F inputted from the feedforward controller 160 into an operation for the supply motor 61 . Output as quantity _USR .

Feedforward controller 160 includes a differentiator 161, an acceleration torque estimator 163, and an FF gain amplifier 165. The differentiator 161 differentiates the rotational speed ω _PF of the conveyance roller 20 inputted from the measurement circuit 77 to calculate the rotational acceleration α of the conveyance roller 20 . Rotational acceleration corresponds to angular acceleration. The rotational acceleration α calculated by the differentiator 161 is hereinafter expressed as an actual rotational acceleration α.

The acceleration torque estimator 163 estimates the acceleration torque τ of the supply motor 61 necessary to rotate the sheet roll Q0 in accordance with the acceleration of the conveyance roller 20, in other words, the acceleration of the sheet Q, based on the actual rotational acceleration α. do. Specifically, the actual rotational acceleration α, the roll diameter R which is the radius of the sheet roll Q0, the radius _Rp of the conveying roller 20, and the inertia J(R) of the sheet roll Q0 estimated from the roll diameter R, Based on this, the acceleration torque τ is calculated according to the formula τ=J(R)・(R _p /R)・α.

When the rotational acceleration of the conveyance roller 20 is α, the acceleration of the sheet Q conveyed by the rotation of the conveyance roller 20 is R _p ·α. In order to pull out the sheet Q from the sheet roll Q0 at the same acceleration, the sheet roll Q0 needs to rotate at a rotational acceleration (R _p /R)·α. Assuming that the inertia is J, the acceleration torque required to realize this rotation is J·(R _p /R)·α.

A function J(R) for calculating the inertia J(R) of the sheet roll Q0 when the roll diameter is R is prepared in advance and calculated by the acceleration torque estimator 163. The radius _Rp of the conveyance roller 20 is a fixed value determined by the machine. The roll diameter R of the sheet roll Q0 is estimated by the roll diameter estimator 150 (details will be described later).

The acceleration torque estimator 163 calculates the acceleration torque τ based on the information on the roll diameter R input from the roll diameter estimator 150 and based on the above equation. The FF gain amplifier 165 adjusts the calculated acceleration torque τ to be amplified by the gain _KFF , and outputs the adjusted acceleration torque _KFF ·τ as the feedforward manipulated variable _UF . Normally, the gain K _FF has a value of 1, but it can be finely adjusted from the value 1 depending on the mechanical characteristics of the rotating system.

The motor driver 63 inputs to the supply motor 61 a drive current corresponding to the above-mentioned manipulated variable U _SR =U _F +U _B that includes the feedforward manipulated variable U _F calculated in this way as a component, thereby increasing the manipulated variable U The supply motor 61 is driven so that a rotational torque corresponding to _SR is generated. By performing feedforward control and feedback control on the supply motor 61 in this manner, the tension of the sheet Q is controlled to the target tension.

In this embodiment, the gain setter 180 is further configured to adjust the gains K _p , K _i , and K _d in the PID controller 140 based on the roll diameter R estimated by the roll diameter estimator 150 . The gains K _p , K _i , and K _d are calculated according to the functions K _p (R), K _i (R), and K _d (R) with the roll diameter R as a variable, and when the roll diameter is R, K _p =K _p ( R), K _i =K _i (R), and K _d =K _d (R). The functions K _p (R), K _i (R), and K _d (R) are determined in advance through tests.

Next, the operation of estimating the roll diameter R by the roll diameter estimator 150 will be explained. The roll diameter estimator 150 estimates the roll diameter R every sampling period _ts by executing the process shown in FIG. 7 (S260). The process shown in FIG. 7 starts when the conveyance of the sheet Q starts, and ends when the conveyance of the sheet Q ends.

When the process shown in FIG. 7 is started, the roll diameter estimator 150 sets the current time t to the reference time t ₀ (S210). The roll diameter estimator 150 further calculates the rotational position θ PF (t) of the transport roller 20, the sheet, and the rotational position θ _PF (t) of the conveying roller 20 at every sampling period _ts , as data necessary for estimation until the estimation start condition for the roll diameter R is satisfied. The rotational position θ _SR (t) of the roll Q0 and the position X(t) of the tensioner 15 are accumulated and stored (S210).

The period until the estimation start condition is satisfied may be a period from the reference time _t0 until a predetermined time _t1 , which will be described later, has elapsed, or a period shorter than that. The rotational position θ _PF (t) indicates the rotational position θ _PF of the transport roller 20 measured by the measurement circuit 77 at time t. The rotational position θ _SR (t) indicates the rotational position θ _SR of the sheet roll Q0 measured by the measurement circuit 67 at time t. Position X(t) indicates the position X of the tensioner 15 detected by the position detector 80 at time t.

After completing the process of S210, the roll diameter estimator 150 repeatedly executes the processes of S220 to S290 every sampling period _ts . In S220, the roll diameter estimator 150 stores the rotational position θ _PF (t) of the transport roller 20, the rotational position θ _SR (t) of the sheet roll Q0, and the position X(t) of the tensioner 15 at the current time t.

Thereafter, the roll diameter estimator 150 calculates the sheet conveyance amount L(t) from the reference time _t0 to the current time t using the radius _Rp of the conveyance roller 20 and the rotational position _θPF of the conveyance roller ₂₀ at the reference time t0. (t ₀ ) and the rotational position θ _PF (t) of the transport roller 20 at the current time t (S230). Specifically, the roll diameter estimator 150 calculates the sheet conveyance amount L(t) according to the formula L(t)=R _p ·(θ _PF (t)−θ _PF (t ₀ )).

Further, the roll diameter estimator 150 calculates the amount of rotation δθ(t) of the sheet roll Q0 from the reference time _t0 to the current time t (S240). Below, the amount of rotation of the sheet roll Q0 is also expressed as the amount of roll rotation.

In S240, the roll diameter estimator 150 calculates the formula δθ based on the rotational position θ _SR (t ₀ ) of the sheet roll Q0 at the reference time t ₀ and the rotational position θ _SR (t) of the sheet roll Q0 at the current time t. The roll rotation amount δθ(t) is calculated according to (t)=θ _SR (t)−θ _SR (t ₀ ). The roll rotation amount δθ(t) is calculated in an angular dimension that does not require information about the roll diameter R.

The roll diameter estimator 150 further calculates the amount of change δD(t) in the path length D from the reference time _t0 to the current time t (S250). The path length D here means the conveyance path length of the sheet Q from point P1 to point P2 shown in FIG. In other words, the path length D matches the length of the sheet Q in the transport direction from point P1 to point P2.

Tensioner 15 is movable. Therefore, by changing the position X of the tensioner 15, the conveyance path length of the sheet Q from point P1 to point P2 changes as shown in FIG. 2. As shown in FIG. 8, the path length D becomes shorter as the position X of the tensioner 15 increases, that is, as the tensioner 15 moves forward.

The roll diameter estimator 150 calculates the path length D(X(t)) corresponding to the position X(t) of the tensioner 15 at the current time t. Furthermore, a path length D(X(t ₀ )) corresponding to the position X(t ₀ ) of the tensioner 15 at the reference time t ₀ is calculated.

The roll diameter estimator 150 calculates the path lengths D(X(t ₀ )), D(X(t)) according to a function D(X) or a table indicating the correspondence between the position X and the path length D stored in advance. can be calculated.

The function D(X) can be theoretically derived based on the position X of the tensioner 15 and the geometric relationship between the points P1 and P2. _{Regarding the position _ _ _} (X) may be calculated.

The roll diameter estimator 150 may have a table that describes the path lengths D ₁ , D ₂ , D ₃ , . . . at each of the plurality of positions X ₁ , X ₂ , X ₃ , . The roll diameter estimator 150 refers to the table and calculates the path lengths D(X(t ₀ )) and D(X(t)) corresponding to the positions X(t ₀ ) and X(t) by linear interpolation. You may.

In S250, the roll diameter estimator 150 calculates the formula δD( _t )=D(X(t))−D(X (t ₀ )), the amount of change δD(t) in the path length D is calculated.

Thereafter, the roll diameter estimator 150 uses the formula R=( The roll diameter R of the sheet roll Q0 is calculated as an estimated value according to L(t)+δD(t))/δθ(t) (S260).

The component (L(t)+δD(t)) included in the above equation corresponds to the length of the sheet Q pulled out from the sheet roll Q0 between reference time _t0 and time t. The component δθ(t) corresponds to the amount of rotation of the sheet roll Q0 when the sheet Q is pulled out by the length (L(t)+δD(t)).

Therefore, according to the formula R=(L(t)+δD(t))/δθ(t), the radius of the sheet roll Q0 when the sheet Q is conveyed by the length (L(t)+δD(t)) R can be calculated. According to this formula, when the radius R is approximately constant in the period from time _t0 to time t, the radius R can be calculated with high accuracy.

After calculating the roll diameter R in S260, the roll diameter estimator 150 determines whether the termination condition is satisfied in the subsequent S270. If it is determined that the termination condition is satisfied (S270: Yes), the process shown in FIG. 7 is terminated. Before this end, the roll diameter estimator 150 can store the roll diameter R calculated in the previous step S260 in the memory 51B as the latest estimated value of the roll diameter R via the main controller 51 (S275).

The roll diameter estimator 150 determines that the termination condition is satisfied when the sheet conveyance ends normally and when the sheet conveyance ends abnormally (Yes in S270), and ends the process shown in FIG. I can do it.

If it is determined that the end condition is not satisfied (No in S270), the roll diameter estimator 150 determines whether a time _2t1 , which is twice the predetermined time _t1 , has elapsed from the reference time _t0 ( S280). If the roll diameter estimator 150 determines that the time has not elapsed (No in S280), the process moves to S220.

If it is determined in S280 that the time 2t ₁ has elapsed, the roll diameter estimator 150 moves to S290 and updates the reference time t ₀ to a time (t ₀ +t ₁ ) advanced by the time t ₁ . After that, the process moves to S220. In this way, the roll diameter estimator 150 executes the processes of S220 to S290 every sampling period _ts , and estimates the roll diameter R in S260.

That is _, the roll diameter estimator 150 shifts the reference time t ₀ by ₁ time t as shown by _the broken line in FIG. During the period (t ₀ +2t ₁ ), the amount of change δD in the sheet conveyance _amount L(t), the roll rotation amount δθ(t), and the path length D from the reference time t ₀ to the time t is calculated every sampling period t s. The roll diameter R is calculated based on (t). According to FIG. 9, time _t1 is 0.5 seconds. At this time, the sampling period _ts may be 1 millisecond.

In FIG. 10, the change in the roll diameter R calculated by the method described above is shown by a solid line. According to FIG. 10, the correct roll diameter R is 69 mm, and when the calculated roll diameter R is within the range of 67 mm to 71 mm, it can be evaluated that the roll diameter R is calculated with good accuracy. .

In this embodiment, the roll diameter R is calculated by taking into account not only the conveyance amount L(t) of the sheet Q by the conveyance roller 20 but also the change amount δD(t) in the path length D. Therefore, the roll diameter R can be quickly adjusted. Moreover, it can be estimated with high accuracy.

In FIG. 10, the broken line indicates the roll diameter R' estimated according to the formula R'=L(t)/δθ(t) without considering the amount of change δD(t) in the path length D. As can be understood from the comparison between the roll diameter R shown by the solid line and the roll diameter R' shown by the broken line, according to the technology of the present disclosure that takes into account the amount of change δD(t) in the path length D, the amount of change δD It is possible to estimate the roll diameter R more quickly and with higher accuracy than when (t) is not considered. The dashed line shown in FIG. 10 indicates the path length D as a difference from the specific path length _D0 .

Next, details of the initial processing (S110 shown in FIG. 4) executed by the main controller 51 will be described using FIG. 11. When the main controller 51 starts the initial processing (S110), as shown in FIG. 11, the main controller 51 determines whether or not the previous sheet conveyance was normally completed (S310).

If it is determined that the process has ended normally (Yes in S310), the main controller 51 shifts the process to S330. On the other hand, if it is determined that the process has ended abnormally (No in S310), it is determined whether the previous abnormal end was due to a jam (S320).

If the main controller 51 determines that the previous abnormal termination was due to a jam (Yes in S320), the process proceeds to S330, and if it determines that the abnormal termination was due to a cause other than a jam (No in S320), the process proceeds to S360. Transition.

Abnormal terminations other than jams include abnormal terminations due to sheet roll Q0 becoming empty. When the sheet roll Q0 becomes empty, a new sheet roll Q0 is attached to the holder 10. If the previous sheet conveyance does not exist, the main controller 51 formally makes a negative determination in S310 and S320, and proceeds to S360.

In S330, the main controller 51 sets the roll diameter R of the sheet roll Q0 to be used in tension control during the period until the roll diameter estimator 150 starts estimating the roll diameter R to the latest estimated value stored in the memory 51B. Set.

Specifically, the main controller 51 sets the latest estimated value read from the memory 51B as the current roll diameter R to the feedforward controller 160 and gain setter 180 included in the tension controller 57. When the roll diameter R is newly estimated by the roll diameter estimator 150, the roll diameter R set in the feedforward controller 160 and the gain setting device 180 is updated to the estimated value.

After setting the roll diameter R in S330, the main controller 51 enables the feedforward control of the tension controller 57 by allowing the feedforward controller 160 to operate (S340).

Furthermore, the main controller 51 sets the conveyance mode of the sheet Q to the "high speed" mode by inputting a speed profile for high-speed conveyance to the speed controller 55 as a speed profile that defines the target rotational speed of the conveyance roller 20. (S350).

Thereafter, the main controller 51 moves to S390 and causes the speed controller 55 and tension controller 57 to execute rotational speed control and tension control so as to convey the sheet Q at high speed to the starting point using the speed profile input in S350. After that, the main controller 51 ends the process shown in FIG. 11.

On the other hand, when proceeding to S360, the main controller 51 discards the latest estimated value of the roll diameter R stored in the memory 51B. After that, the main controller 51 disables the feedforward control by prohibiting the operation of the feedforward controller 160 (S370).

In subsequent S380, the main controller 51 sets the conveyance mode of the sheet Q to the "low speed" mode by inputting the speed profile for low speed conveyance to the speed controller 55. In the speed profile of the low speed mode, the target rotational speed in the constant speed section where the maximum speed is reached is lower than that of the high speed mode.

Thereafter, the main controller 51 moves to S390 and causes the speed controller 55 and tension controller 57 to execute rotation speed control and tension control so as to transport the sheet Q at a low speed to the starting point using the speed profile input in S380. After that, the main controller 51 ends the process shown in FIG. 11.

This state in which the operation of the feedforward controller 160 is prohibited during low-speed conveyance is maintained until the roll diameter estimator 150 starts estimating the roll diameter R anew. In other words, the feedforward controller 160 can calculate the feedforward operation amount U _F based on the roll diameter R from the time when information on the newly estimated roll diameter R is obtained from the roll diameter estimator 150. can.

In addition, when the latest estimated value of the roll diameter R is discarded in S360, the gain setter 180 uses the value given from the main controller 51 for a period until the roll diameter R is newly estimated by the roll diameter estimator 150. Gains K _p =K _p (R _s ), K _i =K _i (R _s ), and K _d =K _d (R _s ) according to the standard roll diameter R _s are set in the PID controller 140 .

According to the image forming system 1 of the present embodiment described above, the roll diameter estimator 150 in the controller 50 calculates the measured sheet conveyance amount L(t) and the measured rotation amount of the sheet roll Q0. Based on the rotation amount δθ(t) and the detected position X of the tensioner 15, the roll diameter R, which is the radius R of the sheet roll Q0, is estimated.

In particular, the roll diameter estimator 150 transports the sheet Q from a first point P1 where the sheet Q is pulled out from the sheet roll Q0 to a second point P2 where the sheet Q is nipped by the transport roller 20 and the nip roller 25. The amount of change δD(t) in the path length D(t) is estimated based on the position X(t) of the tensioner 15.

The roll diameter estimator 150 calculates the amount of sheet Q to be pulled out (L(t)+δD( t)) and the roll rotation amount δθ(t), the roll diameter R is estimated.

Specifically, the roll diameter estimator 150 calculates the sheet conveyance amount L(t) during the period t 0 _{to t from the reference time t 0 to} the time t, which is the period corresponding to the estimated time t, and the roll rotation amount δθ( t) and the amount of change δD(t) in the path length D, the roll diameter R is estimated according to the relational expression R=(L(t)+δD(t))/δθ(t).

Therefore, according to the image forming system 1 of the present embodiment, even in an environment where the posture and path length D of the sheet Q change due to a change in the position X of the tensioner 15, a dedicated sensor such as an optical distance sensor can be used. The roll diameter R can be estimated with high accuracy without providing it in the image forming system 1. In other words, the roll diameter R can be estimated with high accuracy without directly measuring the roll diameter R using a dedicated sensor.

In particular, in this embodiment, as shown in FIG. 9, the roll diameter estimator 150 updates the reference time t ₀ to a time advanced by the time t ₁ every time 2t ₁ elapses from the reference time t ₀ . The roll diameter estimator 150 calculates the sheet conveyance _amount L( _t ), the roll rotation amount δθ(t), and the change amount δD( t), the roll diameter R is estimated.

In this way, in this embodiment, the roll diameter R at time t is estimated based on the observed values regarding sheet conveyance during the observation period t ₀ to t, but this observation period partially overlaps with the previous observation period. By updating to include the time period, the observation period is continuously changed when repeatedly estimating the roll diameter R. Therefore, according to this embodiment, compared to the case where the observation period is updated so as not to include overlapping time periods, it is possible to suppress the high frequency error component of the estimated roll diameter R, and stably R can be estimated.

In addition, in this embodiment, the roll diameter R estimated by the roll diameter estimator 150 is stored at the end of sheet conveyance (S275). Furthermore, during the next sheet conveyance, until the roll diameter estimator 150 starts estimating the roll diameter R, the feedforward operation amount U _F is calculated based on the previously stored roll diameter R, and this feedforward The supply motor 61 is controlled by the manipulated variable U _SR based on the manipulated variable U _F and the feedback manipulated variable U _B .

However, if the previous sheet conveyance ended abnormally, and the abnormal end was due to an abnormal end other than a jam, the roll diameter R stored last time should be changed in consideration of the possibility that the sheet roll Q0 has been replaced. Discard and disable feedforward control. That is, the tension controller 57 controls the rotation of the supply motor 61 only by feedback control, in other words, only by the feedback operation amount _UB .

However, with only feedback control, it is expected that the error in conveying the sheet Q until it is placed at the starting point will be larger than when conveying the sheet Q with both feedforward control and feedback control. Therefore, in this embodiment, when the feedforward control is disabled, a speed profile for low-speed conveyance is set in the speed controller 55, and the sheet Q is conveyed at a low speed.

That is, when the supply motor 61 is controlled by both feedforward control and feedback control, the sheet Q is conveyed at high speed by controlling the conveyance roller 20 based on the speed profile for high-speed conveyance, but only by feedback control. When the supply motor 61 is controlled, the sheet Q is conveyed at a low speed by controlling the conveyance roller 20 based on the speed profile for low-speed conveyance.

Therefore, according to the present embodiment, even when highly accurate control cannot be performed due to lack of information on the roll diameter R, deterioration in control accuracy can be suppressed by controlling the conveyance of the sheet Q at a low speed. If the sheet Q is placed at the starting point with low control accuracy, the sheet Q may be excessively conveyed due to the control error, and the sheet Q may come into contact with the recording head 40 . According to the present embodiment, the occurrence of such a problem can be suppressed by controlling the conveyance of the sheet Q at low speed.

As described above, in this embodiment, when an abnormal termination other than a jam occurs, the feedforward control that requires information on the roll diameter R is disabled. The reason for this is that due to the replacement of the sheet roll Q0, the accuracy that the roll diameter R is the previous estimated value is low.

As can be understood from this context, the processes of S310 and S320 correspond to determining the degree of accuracy of the stored roll diameter R. Therefore, the invalidation of the feedforward control may be realized by determining whether the accuracy of the stored roll diameter R is high or low using a method different from S310 and S320.

If the controller 50 determines that the accuracy is high, the controller 50 performs a feed based on the latest estimated value of the roll diameter R stored last time until the roll diameter estimator 150 starts estimating the roll diameter R. Forward control can be executed. If it is determined that the accuracy is low, feedforward control can be disabled.

Next, the image forming system 1 of the second embodiment and the third embodiment will be described. The image forming system 1 of the second embodiment and the third embodiment is a modification of the image forming system 1 of the first embodiment.

Therefore, in the following, configurations and processes of the image forming system 1 of the second embodiment and the third embodiment that are different from those of the first embodiment will be selectively explained, and configurations and processes similar to those of the first embodiment will be explained. are given the same reference numerals and step numbers as in the first embodiment, and explanations of their configuration and processing will be omitted.

[Second embodiment]
The image forming system 1 of the second embodiment is configured such that the main controller 51 executes the origin setting process shown in FIG. 12.

The origin setting process is executed immediately after the image forming system 1 is started before the conveyance process of the sheet Q is started, in order to set the position X of the tensioner 15 detected by the position detector 80 to zero at the origin position of the tensioner 15. be done. The origin setting process may be executed before or after the beginning of the sheet Q is placed at a predetermined starting point in the initial process (S110).

The origin position of the tensioner 15 is a position where the tensioner 15 is at rest when the spring material 16 is at its natural length and no elastic force is generated from the spring material 16. When the tensioner 15 is at the home position, the tension of the sheet Q acting on the tensioner 15 is zero.

When the origin setting process is started, the main controller 51 rotates the supply motor 61 by a predetermined amount in the forward rotation direction with the conveyance roller 20 stopped, and feeds the sheet Q (S410). The forward rotational direction of the supply motor 61 corresponds to the rotational direction in which the sheet Q moves downstream in the conveyance direction.

The predetermined amount is such that even when the tensioner 15 is at the limit position corresponding to the maximum tension before executing the process in S410, the sheet Q is deflected due to feeding, and the tension acting on the tensioner 15 on the sheet Q is thereby lost. , the amount of feed of the sheet Q is predetermined to be sufficient for the tensioner 15 to move to the origin position and remain stationary there.

Therefore, upon completion of the process in S410, the tensioner 15 normally moves to the original position. In subsequent S420, the main controller 51 assumes that the tensioner 15 is at the origin position and resets the detected position X of the tensioner 15 by the position detector 80 to zero. Thereby, the position detector 80 is initially set to detect the position X of the tensioner 15 as a relative position from the origin position of the tensioner 15.

Thereafter, the main controller 51 reversely rotates the supply motor 61 with the conveyance roller 20 stopped, rewinds the sheet Q, and ends the origin setting process shown in FIG. 12 (S430).

In S430, the main controller 51 completes the rewinding of the sheet Q when the tension of the sheet Q reaches a predetermined constant tension based on the position X of the tensioner 15 detected by the position detector 80. Additionally, the feed motor 61 can be controlled through the tension controller 57. The constant tension may be a target tension during subsequent conveyance of the sheet Q.

As mentioned above, examples of position detectors 80 include linear encoders. As a linear encoder, it has a fixed mechanical origin position on the encoder scale, and can detect the position based on this origin position, as well as the position relative to the position reset by software. Contains encoders.

According to the second embodiment, even in a case where the position detector 80 performs position detection as a relative position from a software-reset position, such as when the latter encoder is used as the position detector 80, the position Based on the detection position X by the detector 80, the tension of the sheet Q can be estimated with high accuracy.

[Third embodiment]
Next, an image forming system 1 according to a third embodiment will be described. The image forming system 1 of the third embodiment is configured to estimate the roll diameter r by estimating the state quantity related to the rotation system of the sheet roll Q0 using an extended Kalman filter. In the third embodiment, the roll diameter explained using the variable R in the first embodiment will be explained using the variable r.

The Kalman filter is a technology that performs highly accurate estimation of state quantities by correcting state quantities by feeding back errors between actual observed values and observed values obtained from a preset observation model. In the extended Kalman filter, for application to nonlinear systems, the state equation and observation equation are Taylor expanded and linearly approximated.

In this embodiment, the extended Kalman filter is designed as follows. When the thickness of the sheet Q is μ, when the sheet roll Q0 rotates 2π, the roll diameter r changes by the thickness μ. Therefore, the relationship between the roll diameter r and the rotation amount θ of the sheet roll Q0 is expressed by the following equation.

The rotation amount θ of the sheet roll Q0 can be observed through the rotary encoder 65 and the measurement circuit 67. The time differential dr/dt of the roll diameter r can be expressed by the following equation using the angular velocity ω of the sheet roll Q.

The state quantity x regarding the rotation system of the sheet roll Q0 is defined as follows using the roll diameter r, the rotation amount θ of the sheet roll Q0, and the rotation speed ω, that is, the angular velocity ω of the sheet roll Q0. The superscript T is a transposition symbol.

Assuming that the estimation of the roll diameter r using the extended Kalman filter is performed while the sheet Q is being conveyed at a constant speed, the time evolution model for the above state quantity x, in other words, the state equation is expressed by the following equation. Definable.

上記多変数ベクトル値関数ｆのヤコビ行列Ａは、次式で定義される。

The Jacobian matrix A of the multivariable vector-valued function f is defined by the following equation.

On the other hand, the relationship between the conveyance amount L of the sheet Q and the rotation amount θ of the sheet roll Q0, and the relationship between the conveyance speed V of the sheet Q and the rotation speed ω of the sheet roll Q0 are expressed as follows.

The above relational expression regarding the transport amount L of the sheet Q is an approximate expression because the roll diameter r changes over time. The parameter M corresponds to the amount of change δD in the conveyance path length D of the sheet Q from point P1 to point P2 shown in FIG. This corresponds to the difference between the conveying speed V of the sheet Q and the circumferential speed r·ω of the sheet roll Q0 due to . Therefore, the parameter M and the parameter ζ can be specified from the position X of the tensioner 15 detected by the position detector 80, as described in the first embodiment.

Here, the following observed quantity y is defined using the transport amount L of the sheet Q, the transport speed V of the sheet Q, and the rotation amount θ of the sheet roll Q0.

The observation model regarding this observation quantity y, in other words, the observation equation, can be defined by the following equation. In the formula below, the superscript hat means an estimated value.

上記多変数ベクトル値関数ｈのヤコビ行列Ｃは、次式で定義される。

The Jacobian matrix C of the multivariable vector-valued function h is defined by the following equation.

In this embodiment, the roll diameter r is estimated by estimating the state quantity x using an extended Kalman filter based on the state equation and observation equation described above. In estimation based on this extended Kalman filter, the state quantity x is estimated by repeating a prediction step and a filtering step.

In the prediction step, the state quantity x is calculated by the following equation based on the a posteriori estimated value x (superscript hat) one time ago, the error covariance matrix P one time ago, and the state quantity noise Q given in advance. The prior estimate x _t (superscript) and the prior error covariance matrix P _t are calculated. The following equation includes a Jacobian matrix A.

In the filtering step, the a priori estimated value x _t (superscript hat) of the state quantity x calculated in the prediction step and the prior error covariance matrix P _t , the observable quantity noise R given in advance, and the actual observable quantity y are used. , the estimated value x _t+1 (superscript) of the state quantity x and the error covariance matrix P _t+1 are calculated based on the a priori estimated value y (superscript) of the observed quantity y. The following equation includes a Jacobian matrix C.

The prior estimated value y (superscript hat) of the observed quantity y is calculated from the above-mentioned observation equation and the prior estimated value x _t (superscript hat) of the state quantity x. The parameters M and ζ are calculated based on the observed amount of change in the position X of the tensioner 15.

In this embodiment, the roll diameter r estimated by the roll diameter estimator 150 is an estimated value of the roll diameter r included in the estimated value of the state quantity x calculated here. The conveyance speed V _of the sheet Q included in the observed quantity y is the measured conveyance speed R p·ω based on the rotational speed ω _PF of the conveyance roller 20 measured by the measurement circuit 77 and the radius R _p of the conveyance roller 20 It may be _PF , or it may be the target conveyance speed R _p ·ω _r of the sheet Q based on the target rotation speed ω _r from the speed command device 101. The conveyance amount L of the sheet Q may be a measured value, or a value calculated as a time differential of the conveyance speed V=R _p ·ω _r based on the target rotational speed ω _r .

Alternatively, the observation equation h(x) may be defined without considering the parameter ζ, that is, the parameter ζ=0, and the state quantity x may be estimated. The observation equation h(x) may be defined as parameter M=0 and parameter ζ=0, and the state quantity x may be estimated.

Specifically, by executing the process shown in FIG. 13, the roll diameter estimator 150 executes the above prediction step and filtering step every sampling period _ts , updates the state quantity x, and calculates the roll diameter r. can be estimated.

The equation L=rθ−M regarding the conveyance amount L of the sheet Q described above only holds true approximately because the roll diameter r varies. In FIG. 13, the roll diameter r is estimated by applying an extended Kalman filter piecewise to such approximate establishment.

When the process shown in FIG. 13 is started, the roll diameter estimator 150 initializes the state quantity x and the error covariance matrix P (S510). Thereafter, the roll diameter estimator 150 sets the rotation amount θ of the sheet roll Q0, which is an element of the state quantity x, to zero, and further sets the rotation speed ω of the sheet roll Q0, which is an element of the state quantity x, to the transport roller Based on the estimated values of the radius _Rp and the roll diameter r of 20, the rotational speed ω=( _Rp /r)· _ωr corresponding to the target rotational speed _ωr of the conveying roller 20 is set. Furthermore, the transport amount L of the sheet Q and the rotation amount θ of the sheet roll Q0, which are elements of the observed amount y, are set to the current observed values (S520).

After completing the process of S520, the roll diameter estimator 150 executes a prediction step and a filtering step based on an extended Kalman filter to calculate an estimated value of the state quantity x (S530). In the filtering step, the measured current observation amount y is obtained. After that, the roll diameter estimator 150 outputs the estimated value of the roll diameter r based on the state quantity x (S540).

The roll diameter estimator 150 performs the calculation at every sampling period ts until the reset timing of the state quantity x arrives (Yes in S550) or until the termination condition of the process shown in FIG. 13 is satisfied (Yes in S560 ₎ . , S530-S540 are executed to update the state quantity x and output the estimated value of the roll diameter r.

When the reset timing arrives (Yes in S550), the roll diameter estimator 150 once resets the calculation result based on the extended Kalman filter before the reset timing by executing the process in S520, and then proceeds to S530. In S530, a prediction step and a filtering step are performed based on the values newly updated in S520, and an estimated value of the state quantity x is calculated.

The roll diameter estimator 150 performs piecewise estimation of the state quantity x based on the extended Kalman filter by repeatedly performing the above processing. If it is determined that the termination condition is satisfied (S560: Yes), the process shown in FIG. 13 is terminated.

Specifically, the reset timing may be when the conveyance length L of the sheet Q, which corresponds to the amount of rotation of the conveyance roller 20, exceeds the initial value by a predetermined amount. Thereby, the roll diameter estimator 150 calculates an estimated value of the state quantity x including the roll diameter r every time the sheet Q is conveyed by a predetermined amount using the segmented extended Kalman filter.

Furthermore, the roll diameter estimator 150 can estimate the state quantity x based on the extended Kalman filter by switching the set value of the state quantity noise Q as shown in FIG. 14 in S530.

According to the example shown in FIG. 14, the roll diameter estimator 150 sets the state quantity noise Q to the first state quantity noise Q 1 (S620) at the initial stage of estimating the roll diameter r (Yes in S610), and sets the state quantity noise Q to the first state quantity noise _Q1 (S620). In other periods (No in S610), the state quantity noise Q is set to the second state quantity noise _Q2 (S630).

The state quantity noise Q includes an element representing variation (specifically, variance) in the state quantity x. At the initial stage of estimation of the roll diameter r, the certainty of the roll diameter r is low, so the first state quantity noise Q ₁ is predetermined to exhibit a larger variance than the second state quantity noise Q ₂ .

In this way, the roll diameter estimator 150 sets the set value of the state quantity noise Q to the first state quantity noise Q ₁ and the second state quantity noise Q ₂ according to the certainty of the estimated roll diameter r. By switching between the two, the roll diameter r is appropriately estimated. The initial period of estimation of the roll diameter r, in other words, the first period from the start of estimation of the roll diameter r, is the period from when the sheet roll Q0 is attached to the holder 10 until the estimated value of the roll diameter r becomes stable. obtain.

In addition, the roll diameter estimator 150 may configure an extended Kalman filter by taking into account the rotational torque τ acting on the sheet roll Q0 from the supply motor 61 and the tension T of the sheet Q. For example, the equation of state may be defined as:

ロール径推定器１５０は、この状態方程式及び上記観測方程式に基づく拡張カルマンフィルタから状態量ｘを推定し、それによりロール半径ｒを推定してもよい。

The roll diameter estimator 150 may estimate the state quantity x from this state equation and an extended Kalman filter based on the observation equation, and thereby estimate the roll radius r.

Estimating the roll diameter r of the sheet Q based on the above-described extended Kalman filter is particularly meaningful when the image forming system 1 includes the tension controller 200 having the configuration shown in FIG. 15 instead of the tension controller 57.

The tension controller 200 shown in FIG. 15, which replaces the tension controller 57, includes a tension command device 110, a tension estimator 120, a deviation calculator 130, a PID controller 140, a roll diameter estimator 150, and a gain setter 180. , a first-order lag filter 210, a target speed generator 220, a deviation calculator 230, an adder 240, a supply speed controller 250, a feedforward controller 260, and an adder 270.

The deviation calculator 130 calculates the deviation E _T =T _r −T between the target tension T _r from the tension command device 110 and the estimated tension T from the tension estimator 120, as in the first embodiment. The PID controller 140 calculates the tension operation amount U _T =K _p・_ET +K _i・INT(ET)+K _d・DIF( _{ET )} based on the deviation E _T inputted from the deviation calculator 130. .

The tension operation amount U _T corresponds to the feedback operation amount U _B of the first embodiment. The gain setter 180 is configured to adjust the gains K _p , K _i , and K _d in the PID controller 140 based on the roll diameter r estimated by the roll diameter estimator 150 .

The target speed generator 220 generates a target rotational speed ω _r of the conveying roller 20 inputted from the speed command unit 101 of the speed controller 55 via the first-order lag filter 210 and a roll diameter r estimated by the roll diameter estimator 150. Based on this, the target rotational speed ω _sr of the sheet roll Q0 is calculated.

The target speed generator 220 calculates the target rotational speed ω _sr according to the formula ω _sr = (R _p /r)·ω _r so that the conveyance roller 20 and the sheet roll Q0 rotate at the same circumferential speed. I can do it. R _p is the radius of the conveyance roller 20 as described above. The target rotational speed ω _sr of the sheet roll Q0 corresponds to the target rotational speed ω _sr of the rotating shaft 10A.

The deviation calculator 230 calculates the deviation E _W =(ω _sr −ω) between the target rotation speed ω _sr from the target speed generator 220 and the rotation speed ω of the sheet roll Q0 measured by the measurement circuit 67.

The adder 240 adds the deviation E _W to the tension operation amount U _T from the PID controller 140 to calculate the operation amount U _C =( _UT + E _w ). The supply speed controller 250 is configured as a PID controller, and calculates a feedback manipulated variable U _B ^* by adding a speed control component to the manipulated variable U _C from the adder 240 . The feedback operation amount U _B ^* is input to the adder 270 as a substitute for the feedback operation amount U _B in the first embodiment.

Specifically, the supply speed controller 250 outputs the value U _B ^* = K _wp · U _C + K _{w i} ·INT (U _C ) + K _wd · DIF (U _C ) as the feedback manipulated variable U _B ^* . DIF (U _C ) is the differential value of the manipulated variable U _C , the value INT (U _C ) is the integral value of the manipulated variable U _C , K _wp is the proportional gain, and K _wi is the integral gain , and K _wd is the differential gain.

The feedforward controller 260 uses the target rotational speed ω _r of the conveyance roller 20 that is input from the speed command unit 101 of the speed controller 55 via the first-order lag filter 210 instead of the actual rotational speed ω _PF of the conveyance roller 20 . Then, similarly to the first embodiment, the acceleration torque τ is calculated.

The feedforward controller 260 inputs the feedforward operation amount _UF corresponding to the calculated acceleration torque τ to the adder 270, as in the first embodiment. Alternatively, the feedforward controller 260 inputs into the adder 270 a feedforward manipulated variable U _F ^* , which is the feedforward manipulated variable U _F and a compensation amount for the viscous friction torque and the dynamic friction torque.

The adder 270 calculates an added value U of the feedback manipulated variable U _B ^* inputted from the supply speed controller 250 and the feedforward manipulated variable U _F or feedforward manipulated variable U _F ^* inputted from the feedforward controller 260. _B ^* +U _F or the additional value U _B ^* +U _F ^* is output as the manipulated variable U _SR for the supply motor 61.

The reason why the tension controller 200 uses the target rotational speed ω _r of the conveyance roller 20 instead of the actual rotational speed ω is as follows. A power transmission system such as gears is present between the supply motor 61 and the rotating shaft 10A of the holder 10. Therefore, there is a time lag before the drive of the supply motor 61 is reflected in the rotational movement of the sheet roll Q0. This time lag may cause a control error when the feedforward operation amount U _F is calculated based on the actual rotational speed ω _PF of the conveyance roller 20 and the supply motor 61 is controlled.

On the other hand, when calculating the feedforward operation amount U _F or the feedforward operation amount U _F ^* based on the target rotational speed ω _r of the conveyance roller 20 as in the third embodiment, the influence of the time lag is ignored. The supply motor 61 can be controlled to control the rotational movement of the sheet roll Q0.

However, when using the target rotational speed ω _r , in order to adjust the tension of the sheet Q to the target tension T _r before starting the conveyance process of the sheet Q, the conveyance roller 20 is stopped as in the process of S430. In this state, the supply motor 61 may be reversely rotated to adjust the tension of the sheet Q to the target tension _Tr , thereby performing a tensioning process.

According to the third embodiment described above, since the roll diameter r is estimated using an extended Kalman filter, it is possible to realize accurate roll diameter estimation that suppresses the effects of observation errors, signal noise, and the like. As shown in FIG. 15, when speed control is performed based on the estimated value of the roll diameter r, the estimation error of the roll diameter r affects the speed control. Therefore, accurate estimation of the roll diameter r is useful for better conveyance control of the sheet Q.

[others]
It goes without saying that the present disclosure is not limited to the exemplary embodiments described above, and can take various forms. In the first embodiment as well, similarly to the third embodiment, the acceleration torque τ may be estimated based on the target rotational speed ω _r of the conveyance roller 20, and the feedforward operation amount _UF may be calculated. The conveyance amount L of the sheet Q may be calculated based on the integral value of the target rotational speed ω _r .

The holding structure of the sheet roll Q0 by the holder 10 and the driving method of the sheet roll Q0 are not limited to the above embodiment. The image forming system 1 in which the sheet roll Q0 is rotatably supported by the rotation shaft 10A of the holder 10 by inserting the core material of the sheet roll Q0 into the rotation shaft 10A of the holder 10 has been described above.

However, the holder may also be constructed from a hollow cylindrical material having a space inside to accommodate the sheet roll Q0. The holder may be configured such that the inner surface defining the accommodation space for the sheet roll Q0 rotates. The sheet roll Q0 may be rotated in a state accommodated in the holder according to rotation of the inner surface of the holder. In addition, a roller may be provided that contacts the outer peripheral surface of the sheet roll Q0. The sheet roll Q0 may be rotated by the rotation of this roller.

The holder 10 may be configured without a shaft. In this case, a roller may be provided between the tensioner 15 and the sheet roll Q0, and the amount of rotation of the sheet roll Q0 may be measured from the amount of rotation of this roller.

The technology of the present disclosure may be applied to an image forming system that does not include the belt mechanism 30. In this case, the image forming system may be provided with a platen for supporting the sheet Q instead of the belt mechanism 30. The technology of the present disclosure may be applied to an image forming system including a serial drive type recording head instead of a line head as the recording head 40. In this case, the recording head reciprocates in the line direction to form an image on the sheet Q. The technology of the present disclosure may be applied to an electrophotographic image forming system.

The technology of the present disclosure may be applied to a system that forms an image on the front surface of the sheet Q facing outward in the radial direction of the sheet roll Q0, or on the back surface of the sheet Q facing inward in the radial direction of the sheet roll Q0. It may also be applied to a system that forms an image using The technology of the present disclosure may be applied to a system that forms images on both sides of the sheet Q. The positions of the conveyance roller 20 and the nip roller 25 may be reversed.

The technology of the present disclosure can be applied not only to a system that forms an image on a sheet Q using a coloring material, but also to various systems. For example, the technology of the present disclosure may be applied to a system that makes holes in the sheet Q to mark it, or may be applied to a system that sterilizes the surface of the sheet Q by irradiating the surface with light. The technology of the present disclosure may be applied to a system that forms a wiring pattern on a sheet-like substrate. The sheet roll Q0 and the sheet Q may be made of paper, vinyl, or a flexible printed circuit board (FPC).

The configuration of the tensioner 15 is not limited to the above embodiment. The tensioner may be constructed of an arm that is pivoted at one end and has a roller at the other end, such as a pendulum arm. In addition, the technology of the present disclosure does not limit the configuration of the rotary encoders 65, 75. The rotary encoders 65 and 75 may be magnetic rotary encoders instead of optical rotary encoders.

The print controller 53, speed controller 55, and tension controller 57 may be configured by a combination of a CPU and an ASIC. The number and presence or absence of CPUs and ASICs in each of the controller 50, main controller 51, print controller 53, speed controller 55, and tension controller 57 are not limited to the specific examples described above.

The function that one component in the above exemplary embodiment has may be distributed and provided to a plurality of components. Functions possessed by multiple components may be integrated into one component. Some of the configurations of the exemplary embodiments described above may be omitted. All aspects included in the technical idea specified from the words described in the claims are embodiments of the present disclosure.

Finally, we will explain the correspondence between terms. The process of S240 executed by the rotary encoder 65, the measurement circuit 67, and the roll diameter estimator 150 corresponds to an example of the process realized by the rotation measuring device. The process of S230 executed by the rotary encoder 75, the measurement circuit 77, and the roll diameter estimator 150 corresponds to an example of the process realized by the conveyance measuring device. The transport motor 71 corresponds to an example of a first motor, and the supply motor 61 corresponds to an example of a second motor.

The deviation calculator 103 and PID controller 105 of the speed controller 55 correspond to an example of a first feedback control element, and the deviation calculator 130 and PID controller 140 of the tension controller 57 correspond to an example of a second feedback control element. However, the feedforward controller 160 corresponds to an example of a feedforward control element.

DESCRIPTION OF SYMBOLS 1... Image forming system, 10... Holder, 10A... Rotating shaft, 15... Tensioner, 20... Conveyance roller, 25... Nip roller, 30... Belt mechanism, 40... Recording head, 50... Controller, 51... Main controller, 51A... Processor , 51B...memory, 53...print controller, 55...speed controller, 57...tension controller, 61...supply motor, 63...motor driver, 65...rotary encoder, 67...measuring circuit, 71...transport motor, 73...motor driver, 75... Rotary encoder, 77... Measurement circuit, 80... Position detector, 101... Speed command unit, 103... Deviation calculator, 105... PID controller, 110... Tension command unit, 120... Tension estimator, 130... Deviation calculation 140... PID controller, 141... Proportional gain amplifier, 142... Integral gain amplifier, 143... Differential gain amplifier, 150... Roll diameter estimator, 160... Feed forward controller, 161... Differentiator, 163... Acceleration torque estimation 180... Gain setting device, 200... Tension controller, 210... First order lag filter, 220... Target speed generator, 230... Deviation calculator, 240... Adder, 250... Supply speed controller, 260... Feedforward controller , 270...Adder.

Claims (18)

a holder that holds a sheet roll around which the sheet is wound;
a rotation measuring device that measures the amount of rotation of the sheet roll;
a conveyance roller that conveys the sheet pulled out from the sheet roll held by the holder;
a movable tensioner provided between the holder and the conveyance roller and in contact with the sheet pulled out from the sheet roll to the conveyance roller;
a position detector that detects the position of the tensioner;
a motor that generates a driving force for rotating the conveyance roller so that the sheet is conveyed;
a controller configured to control the motor;
Equipped with
The controller is configured to control the amount of conveyance of the sheet caused by the rotation of the conveyance roller driven by the motor, the amount of rotation of the sheet roll measured by the rotation measuring device, and the amount of rotation of the tensioner detected by the position detector. A sheet conveying device that estimates a diameter of the sheet roll based on the position of the sheet roll. a conveyance measuring device that measures the conveyance amount of the sheet due to rotation of the conveyance roller;
The controller is configured based on the conveyance amount of the sheet measured by the conveyance measuring device, the rotation amount of the sheet roll measured by the rotation measuring device, and the position of the tensioner detected by the position detector. 2. The sheet conveyance device according to claim 1, wherein the diameter of the sheet roll is estimated. The controller includes:
controlling the motor so that the sheet is transported at a preset target transport speed;
of the sheet roll based on the conveyance amount of the sheet corresponding to the target conveyance speed, the rotation amount of the sheet roll measured by the rotation measuring device, and the position of the tensioner detected by the position detector. The sheet conveying device according to claim 1, wherein a diameter is estimated. further comprising a nip roller that nips the sheet together with the conveyance roller,
The controller determines the amount of change in the conveyance path length of the sheet from a first point where the sheet is pulled out from the sheet roll to a second point where the sheet is nipped by the conveyance roller and the nip roller. Based on the amount of withdrawal of the sheet from the sheet roll, estimated based on the position of the tensioner, and determined from the amount of conveyance of the sheet due to rotation of the conveyance roller and the amount of change, and the amount of rotation of the sheet roll. 4. The sheet conveying device according to claim 1, wherein the sheet conveying device estimates the diameter of the sheet roll. The controller calculates the diameter R of the sheet roll by the transport amount L of the sheet due to the rotation of the transport roller in a period corresponding to the estimated time, the rotation amount δθ of the sheet roll in the period, and the 5. The sheet conveyance apparatus according to claim 4, wherein the estimation is made according to the relational expression R=(L+δD)/δθ based on the amount of change δD in the conveyance path length. The controller determines the amount of change in the conveyance path length during the period according to a formula or table representing the relationship between the position X of the tensioner and the conveyance path length D of the sheet from the first point to the second point. δD is the transport path length D(X(t ₀ )) determined from the position X(t ₀ ) of the tensioner at the start time t ₀ of the period, and the position X( 6. The sheet conveying apparatus according to claim 5, wherein the difference between the conveying path length D(X(t)) and the conveying path length D(X(t)) determined from t) is calculated as D(X(t))−D(X(t ₀ )). The controller repeatedly estimates a diameter R of the sheet roll,
The start time and end time of the period are updated according to changes in the estimated time so as to include a time zone that overlaps with the period corresponding to the previous estimated time,
Thereby, the controller determines the diameter R of the sheet roll based on the transport amount L, the rotation amount δθ, and the change amount δD in a period including a time zone that overlaps with the period corresponding to the previous estimated time. The sheet conveyance device according to claim 5 or claim 6, wherein the sheet conveyance device estimates . The sheet conveying device includes:
a first motor as the motor configured to rotationally drive the conveyance roller;
a second motor configured to rotationally drive the sheet roll held by the holder;
Equipped with
The controller controls the first motor and the second motor so as to control the second motor based on the estimated diameter of the sheet roll. sheet conveyance device. The controller includes:
Repeatedly estimating the diameter of the sheet roll and storing the estimated diameter of the sheet roll as an estimated value,
If the predetermined condition is satisfied, the first motor and the second motor are controlled by a first control, and if the predetermined condition is not satisfied, the first motor is controlled by a second control. and controlling the second motor;
In the first control, the second motor is controlled to control the tension of the sheet based on the estimated value, and the first motor is controlled so that the sheet is conveyed at a first speed. ,
In the second control, the second motor is controlled to control the tension of the sheet not based on the estimated value, and the sheet is conveyed at a second speed lower than the first speed. The sheet conveyance device according to claim 8, wherein the first motor is controlled so as to control the first motor. The controller includes:
Repeatedly estimating the diameter of the sheet roll and storing the estimated diameter of the sheet roll as an estimated value,
Furthermore, determining whether the accuracy of the stored estimated value is high or low,
When it is determined that the accuracy is high, the first motor and the second motor are controlled by a first control, and when it is determined that the accuracy is low, the first motor and the second motor are controlled by a second control. controlling the second motor;
In the first control, the second motor is controlled to control the tension of the sheet based on the estimated value, and the first motor is controlled so that the sheet is conveyed at a first speed. ,
In the second control, the second motor is controlled to control the tension of the sheet not based on the estimated value, and the sheet is conveyed at a second speed lower than the first speed. The sheet conveyance device according to claim 8, wherein the first motor is controlled so as to control the first motor. The controller includes:
In the first control,
a first feedback control element that calculates a first operation amount for the first motor based on an observed value and a target value of the rotational movement of the conveying roller;
a second feedback control element that calculates a second operation amount for the second motor based on the observed position of the tensioner and the target tension;
and a feedforward control element that calculates a correction amount for the second manipulated variable based on the estimated value. controlling the second motor;
In the second control,
By determining the operation amount for the first motor and the second motor using the first feedback control element and the second feedback control element without using the feedforward control element, the operation amount can be determined based on the estimated value. The sheet conveyance device according to claim 9 or 10, wherein the first motor and the second motor are controlled so that the second motor is controlled without any movement. further comprising a nip roller that nips the sheet together with the conveyance roller,
A processing head that performs predetermined processing on the sheet is provided downstream of the transport roller in the transport direction of the sheet,
In the second control, the controller may control the speed of the sheet to be lower than the first speed in the process in which the sheet nipped by the transport roller and the nip roller is transported to a position facing the processing head. The sheet conveying device according to any one of claims 9 to 11, wherein the first motor is controlled so that the sheet is conveyed at a second speed. The controller includes:
Before conveying the sheet by rotation of the conveyance roller,
The second motor is controlled so that the sheet is sent out by a predetermined amount from the sheet roll, and the position of the tensioner when the control ends is regarded as the origin position, and the position detector detects the relative position from the origin position. setting the position detector to detect the position of the tensioner as
Furthermore, the second motor is configured to rewind the sheet onto the sheet roll until the position of the tensioner detected by the position detector moves from the original position due to the application of tension to the sheet. configured to control
The predetermined amount is a predetermined amount that is sufficient for the sheet to be fed out from the sheet roll until the tensioner comes to rest at the origin position due to the deflection of the sheet. The sheet conveying device according to any one of the items. The controller estimates, using a Kalman filter, a state quantity related to the rotation system of the sheet roll, including a diameter of the sheet roll, based on the conveyance amount of the sheet, the rotation amount of the sheet roll, and the position of the tensioner. 14. The sheet conveying device according to claim 1, wherein the diameter of the sheet roll is estimated by: The Kalman filter is
A time evolution model of the state quantities including, as the state quantities, the diameter R of the sheet roll, the amount of rotation θ of the sheet roll, and the angular velocity ω of the sheet roll, and the time including the thickness μ of the sheet. development model

and an observation model including a transport amount L of the sheet, a transport speed V of the sheet, and a rotation amount θ of the sheet roll, and further including a parameter M related to the position of the tensioner.

is an extended Kalman filter based on
The parameter M is the amount of change in the conveyance path length of the sheet from a first point where the sheet is pulled out from the sheet roll to a second point where the sheet receives a conveyance force from the conveyance roller; The sheet conveying device according to claim 14, wherein the calculation is based on the amount of change in the position of the tensioner. The Kalman filter is
A time evolution model of the state quantities including, as the state quantities, the diameter R of the sheet roll, the amount of rotation θ of the sheet roll, and the angular velocity ω of the sheet roll, and the time including the thickness μ of the sheet. development model

and an observation model including a transport amount L of the sheet, a transport speed V of the sheet, and a rotation amount θ of the sheet roll, and further including a parameter M and a parameter ζ related to the position of the tensioner. model

is an extended Kalman filter based on
The parameter M is the amount of change in the conveying path length of the sheet from a first point where the sheet is pulled out from the sheet roll to a second point where the sheet receives a conveying force from the conveying roller; The parameter ζ is the difference between the conveyance speed V of the sheet and the circumferential speed R・ω of the sheet roll due to the change in the conveyance path length, and the parameter M and the parameter ζ are the difference in the position of the tensioner. The sheet conveyance device according to claim 14, wherein the sheet conveyance device is calculated based on the amount. The controller sets a state quantity noise that defines a variation in the state quantity to be larger in a first period from the start of estimating the diameter of the sheet roll than in a second period after the first period. The sheet conveying apparatus according to any one of claims 14 to 16, wherein the state quantity is estimated using the Kalman filter while changing the set value of the state quantity noise. A sheet conveying device according to any one of claims 1 to 17,
a processing head that forms an image on the sheet downstream of the conveyance roller in the conveyance direction of the sheet;
An image forming system comprising:

Images