JP2020142442A - Liquid discharge device, and image forming device - Google Patents

Abstract

To provide a liquid discharge device which can adequately correct a detection error of a position of a sheet material, and an image forming device.SOLUTION: A liquid discharge device includes a rotation member which holds a sheet material on a peripheral surface and conveys it, a liquid discharge part which discharges a liquid on the sheet material, a sheet material position detection part which detects a position of the sheet material, a first signal output part which outputs a first signal in response to a rotation amount of the rotation member, a second signal output part which outputs a second signal correlating with a moving amount of the sheet material on a peripheral surface of the rotation member, a correction data storage part which stores correction data obtained on the basis of the first signal and the second signal to correct the second signal, and a discharge timing generation part which generates a discharge timing of the liquid discharge part on the basis of the second signal and the correction data.SELECTED DRAWING: Figure 7

Description

The present invention relates to a liquid discharge device and an image forming device.

As a device for discharging a liquid, a device is known in which a sheet material is supported on a rotating member such as a transport drum and conveyed, and a liquid is applied to the sheet material by a liquid discharging portion to form an image.

In addition, a liquid discharge device that controls the discharge timing based on the output of a sensor such as an encoder that reads the scale attached to the peripheral surface of the rotating member corrects the detection error of the position of the sheet material due to the eccentricity of the rotating member. The technology is disclosed (see, for example, Patent Document 1).

However, a cumulative error may be included in the period (pitch) of the scale attached to the peripheral surface of the rotating member, or an attachment error may occur when the scale is attached to the peripheral surface of the rotating member. In the technique of Patent Document 1, there is a case that the detection error of the position of the sheet material cannot be appropriately corrected due to such a cumulative error and an attachment error.

The present invention has been made in view of the above points, and an object of the present invention is to appropriately correct a detection error of a position of a sheet material.

The liquid discharge device according to one aspect of the disclosed technique includes a rotating member that supports and conveys a sheet material on a peripheral surface, a liquid discharge portion that discharges liquid to the sheet material, and a sheet that detects the position of the sheet material. The material position detection unit, the first signal output unit that outputs the first signal according to the rotation amount of the rotating member, and the second signal that correlates with the movement amount of the sheet material on the peripheral surface of the rotating member are output. A second signal output unit, a correction data storage unit that stores correction data for correcting the second signal acquired based on the first signal, the second signal, the second signal, and the second signal. It has a discharge timing generation unit that generates a discharge timing of the liquid discharge unit based on the correction data, and a discharge control unit that controls the liquid discharge unit according to the discharge timing.

According to one embodiment of the present invention, the detection error of the position of the sheet material can be appropriately corrected.

It is a figure which shows an example of the structure of the image forming apparatus which concerns on embodiment. It is a top view which shows an example of the structure of the liquid discharge unit which concerns on embodiment. It is a front view explaining an example of the structure around the transport drum which concerns on embodiment. It is a top view explaining an example of the structure around the transport drum which concerns on embodiment. It is a block diagram which shows an example of the hardware composition of the image forming apparatus which concerns on embodiment. It is a block diagram which shows an example of the functional structure of the image forming apparatus which concerns on 1st Embodiment. It is a figure explaining an example of the acquisition method of the correction data which concerns on embodiment. It is a flowchart which shows an example of the processing of the correction data acquisition part which concerns on embodiment. It is a timing chart explaining an example of the generation method of the discharge timing which concerns on embodiment. It is a flowchart which shows an example of the image formation processing of the image forming apparatus which concerns on embodiment. It is a block diagram which shows an example of the functional structure of the image forming apparatus which concerns on 1st Embodiment.

Hereinafter, modes for carrying out the invention will be described with reference to the drawings. In each drawing, the same components may be designated by the same reference numerals and duplicate description may be omitted.

Image formation, recording, printing, printing, printing, and modeling in the terms of the embodiment are all synonymous.

Further, in the embodiment, the "device for discharging the liquid" is a device provided with a liquid discharge head or a liquid discharge unit and driving the liquid discharge head to discharge the liquid. The "device for discharging liquid" and the "device for discharging liquid" are synonymous.

The "device for discharging the liquid" can also include means for feeding, transporting, and discharging paper to which the liquid can adhere, and also includes a pretreatment device, a posttreatment device, and the like.

For example, as a "device for ejecting a liquid", there is an image forming apparatus which is a device for ejecting a liquid such as ink to form an image on paper.

The above-mentioned "material to which a liquid can adhere" means a material to which a liquid can adhere at least temporarily, such as one that adheres and adheres, and one that adheres and permeates.

The "liquid" may have a viscosity and surface tension that can be discharged from the head, and is not particularly limited, but has a viscosity of 30 mPa · s or less at room temperature, under normal pressure, or by heating or cooling. It is preferable to have. More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, polymerizable compounds, resins, functionalizing materials such as surfactants, biocompatible materials such as DNA, amino acids and proteins, and calcium. , Solvents, suspensions, emulsions, etc. containing edible materials such as natural dyes, etc., for example, inks for inkjets, surface treatment liquids, constituents of electronic elements and light emitting elements, and formation of electronic circuit resist patterns. It can be used for applications such as liquids for three-dimensional modeling.

Further, the "device for discharging the liquid" includes, but is not limited to, a device in which the liquid discharge head and the device to which the liquid can adhere move relatively. Specific examples include a serial type device that moves the liquid discharge head, a line type device that does not move the liquid discharge head, and the like.

The "liquid discharge unit" is a liquid discharge head integrated with functional parts and a mechanism, and is an assembly of parts related to liquid discharge. For example, the "liquid discharge unit" includes a combination of at least one of a head tank, a carriage, a supply mechanism, a maintenance / recovery mechanism, and a main scanning movement mechanism with a liquid discharge head.

Here, "integration" means, for example, a liquid discharge head and a functional component, a mechanism in which the mechanism is fixed to each other by fastening, adhesion, engagement, etc., or one in which one is movably held with respect to the other. Including. Further, the liquid discharge head, the functional parts, and the mechanism may be detachably attached to each other.

For example, as a liquid discharge unit, there is a liquid discharge head and a head tank integrated. In addition, there are some that are connected to each other by a tube or the like to integrate the liquid discharge head and the head tank. Here, a unit including a filter can be added between the head tank of these liquid discharge units and the liquid discharge head.

Further, as a liquid discharge unit, there is a liquid discharge head and a carriage integrated.

Further, there is a liquid discharge unit in which the liquid discharge head and the scanning movement mechanism are integrated by holding the liquid discharge head movably by a guide member forming a part of the scanning movement mechanism. In some cases, the liquid discharge head, the carriage, and the main scanning movement mechanism are integrated.

Further, as a liquid discharge unit, there is a carriage to which a liquid discharge head is attached, in which a cap member which is a part of the maintenance / recovery mechanism is fixed, and the liquid discharge head, the carriage, and the maintenance / recovery mechanism are integrated. ..

Further, as a liquid discharge unit, there is a liquid discharge unit in which a tube is connected to a head tank or a liquid discharge head to which a flow path component is attached, and the liquid discharge head and a supply mechanism are integrated. The liquid of the liquid storage source is supplied to the liquid discharge head through this tube.

The main scanning movement mechanism shall also include a single guide member. Further, the supply mechanism includes a single tube and a single loading unit.

The "liquid discharge head" is a functional component that discharges and ejects liquid from a nozzle.

Piezoelectric actuators (laminated piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use electrothermal conversion elements such as heat-generating resistors, and electrostatic actuators that consist of a vibrating plate and counter electrodes are used as energy sources for discharging liquid. Includes what to do.

Hereinafter, an embodiment will be described by taking as an example a case where the “device to which the liquid can adhere” is used as the sheet material and the “device for discharging the liquid” is an on-demand line scanning inkjet image forming apparatus.

[First Embodiment]
<Structure of the image forming apparatus according to the first embodiment>
FIG. 1 is a diagram showing an example of the configuration of the image forming apparatus according to the present embodiment. Further, FIG. 2 is a plan view showing an example of the configuration of the liquid discharge unit 23 of FIG.

The image forming apparatus 1 includes a carry-in section 10, an image forming section 20, a drying section 30, and a carry-out section 40. In the image forming apparatus 1, the image forming unit 20 applies a liquid to the sheet material P, which is a sheet-like member carried in from the carrying-in unit 10, to form a required image, and the drying unit 30 adheres to the sheet material P. After the liquid is dried, the sheet material P is discharged to the carry-out section 40.

The carry-in unit 10 feeds the carry-in tray 11 on which a plurality of sheet materials P are loaded, the feeding device 12 that separates and sends out the sheet materials P one by one from the carry-in tray 11, and the sheet material P to the image forming unit 20. It includes a resist roller pair 13.

As the feeding device 12, any feeding device such as a device using rollers and rollers and a device using air suction can be used. The sheet material P sent out from the carry-in tray 11 by the feeding device 12 is sent out to the image forming unit 20 by driving the resist roller pair 13 at a predetermined timing after the tip of the sheet material P reaches the resist roller pair 13. ..

The image forming unit 20 discharges liquid toward the transport drum 21, which is an example of a rotating member as a transport unit that supports and transports the sheet material P on the outer peripheral surface, and the sheet material P supported on the transport drum 21. It is provided with a liquid discharge unit 22.

Further, the image forming unit 20 includes a transfer cylinder 24 that receives the sent sheet material P and delivers it to the transfer drum 21, and a transfer cylinder 25 that transfers the sheet material P conveyed by the transfer drum 21 to the drying unit 30.

The tip of the sheet material P transported from the carry-in unit 10 to the image forming unit 20 is gripped by a sheet gripper provided on the surface of the transfer cylinder 24, and is conveyed as the transfer cylinder 24 rotates. The sheet material P conveyed by the transfer drum 24 is delivered to the transfer drum 21 at a position facing the transfer drum 21.

A sheet gripper is also provided on the surface of the transport drum 21, and the tip of the sheet material P is gripped by the sheet gripper. A plurality of suction holes are dispersedly formed on the surface of the transport drum 21. The suction device 26, which is a suction unit, generates a suction airflow inward from the suction hole of the transport drum 21.

The tip of the sheet material P delivered from the transfer cylinder 24 to the transfer drum 21 is gripped by the sheet gripper, and is attracted onto the transfer drum 21 by the suction airflow of the suction device 26, so that the transfer drum 21 rotates. It is transported along with it.

The liquid discharge unit 22 includes a liquid discharge unit 23 (23A to 23F). For example, the liquid discharge unit 23A is a cyan (C) liquid, the liquid discharge unit 23B is a magenta (M) liquid, the liquid discharge unit 23C is a yellow (Y) liquid, and the liquid discharge unit 23D is black (K). Discharge each of the liquids. Further, the liquid discharge units 23E and 23F are used for discharging any of YMCK or a special liquid such as white or gold (silver). Further, a discharge unit for discharging a treatment liquid such as a surface coating liquid can be provided.

As shown in FIG. 2, the liquid discharge unit 23 is a full-line type in which a plurality of liquid discharge heads (hereinafter, simply referred to as “heads”) 100 having a nozzle row 101 in which a plurality of nozzles are arranged are arranged on a base member 52. The head etc.

The discharge operation of each liquid discharge unit 23 of the liquid discharge unit 22 is controlled by a drive signal corresponding to the print information. When the sheet material P supported on the transport drum passes through the region facing the liquid discharge unit 22, liquids of each color are discharged from the liquid discharge unit 23, and an image corresponding to the image data is formed on the sheet material P. To.

The drying section 30 sucks the drying mechanism section 31 for drying the liquid adhering on the sheet material P by the image forming section 20 and the sheet material P conveyed from the image forming section 20 (suction). A suction transport mechanism unit 32 (for transport) is provided.

The sheet material P conveyed from the image forming unit 20 is received by the suction transfer mechanism unit 32, then conveyed so as to pass through the drying mechanism unit 31, and is delivered to the carry-out unit 40. When passing through the drying mechanism portion 31, the liquid on the sheet material P is subjected to a drying treatment. As a result, the liquid content such as water in the liquid evaporates, the colorant contained in the liquid is fixed on the sheet material P, and the curl of the sheet material P is suppressed.

The unloading unit 40 includes a unloading tray 41 on which a plurality of sheet materials P are loaded. The sheet material P conveyed from the drying unit 30 is sequentially stacked and held on the carry-out tray 41. The image forming apparatus 1 is provided with a pretreatment section for pretreating the sheet material P on the upstream side of the image forming section 20, or performing post-treatment on the sheet material P to which the liquid is attached. The post-treatment unit may be arranged between the drying unit 30 and the carrying-out unit 40.

Examples of the pretreatment unit include those that perform a precoating treatment in which a treatment liquid for reacting with a liquid to suppress bleeding is applied to the sheet material P. Further, as the post-processing unit, a sheet reversal transfer process for reversing the sheet printed by the image forming unit 20 and sending it to the image forming unit 20 again for printing on both sides of the sheet material P, or a plurality of sheets are used. Examples include those that perform binding processing and the like.

<Structure of 1st signal output unit and 2nd signal output unit>
Next, a portion related to detection for performing discharge timing control in the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a front view illustrating an example of the configuration around the transport drum in the present embodiment. Further, FIG. 4 is also a plan view. However, in FIG. 4, one discharge unit is shown for simplification.

An encoder wheel 202 is provided on the shaft 21a of the transport drum 21, and an encoder sensor 203 that reads the encoder wheel 202 is arranged. The encoder wheel 202 and the encoder sensor 203 constitute the first encoder 201, which is an example of the first signal output unit. The first encoder 201 is a rotary encoder and outputs a first signal (output pulse) corresponding to the rotation amount (rotation drive amount) of the transport drum 21.

Further, an encoder scale 212 is attached to the peripheral surface of the transport drum 21, and an encoder sensor 213 that reads the encoder scale 212 is arranged. The encoder scale 212 and the encoder sensor 213 constitute a second encoder 211 which is an example of the second signal output unit. The second encoder 211 is a linear encoder and outputs a second signal (output pulse) according to the amount of movement of the peripheral surface of the transport drum 21. The second signal is a signal that correlates with the amount of movement of the sheet material P on the peripheral surface of the transport drum 21.

As an example, a rotary encoder and a linear encoder are composed of a scale (scale) as a measure and a detector for detecting position information. The scale detection signal by the detector is output as an output pulse. The scale interval is hereinafter referred to as a scale period or pitch. Further, the pulse period in the output pulse corresponds to the scale period, and is hereinafter referred to as the output pulse period.

Here, the encoder sensor 213 constituting the second encoder 211 is arranged in the vicinity of each of the plurality of liquid discharge units 23. In this embodiment, it is attached to the base member 52 of the liquid discharge unit 23. Therefore, the encoder sensor 213 of each liquid discharge unit 23 and the encoder scale 212 of the transport drum 21 each constitute the second encoder 211.

Further, a sheet material position sensor 220, which is a sheet material position detecting means for detecting the tip of the sheet material P, is arranged on the upstream side in the transport direction of the liquid discharge unit 23A which is the most upstream in the transport direction.

In the present embodiment, the sheet material position sensor 220 detects the tip of the sheet material P, but it may be configured to read the mark (resist mark) attached to the sheet material P. By adopting a configuration that reads the resist, it is possible to handle not only the cut sheet material but also the case of using a continuous medium such as continuous paper.

<Hardware configuration of the image forming apparatus according to the first embodiment>
FIG. 5 is a block diagram showing an example of the hardware configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 5, the image forming apparatus 1 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, and an NVRAM (Non-Volatile Random Access). It includes a Memory) 304, an external device connection I / F (Interface) 308, a network I / F 309, an operation panel 330, and a bus line 310. Further, the image forming apparatus 1 includes a transport driver 312, a liquid discharge unit driver 322, a drying driver 332, and an encoder I / F 342. The transfer driver 312 is in the carry-in section 10, the transfer drum 21, and the carry-out section 40, the liquid discharge unit driver 322 is in the liquid discharge unit 23, the drying driver 332 is in the drying section 30, and the encoder I / F 342 is in the first encoder 201, first. The two encoders 211 and the sheet material position sensor 220 are electrically connected to each other.

Of these, the CPU 301 controls the operation of the entire image forming apparatus 1. The ROM 302 stores a program or the like used to drive the CPU 301 such as an IPL. The RAM 303 is used as a work area of the CPU 301. The NVRAM 304 stores various data such as a program and cumulative error correction data, and retains various data even while the power supply of the image forming apparatus 1 is cut off. The external device connection I / F306 is connected to an external device such as a PC (Personal Computer), and communicates a control signal and printed data with the external device.

The network I / F 309 is an interface for data communication using a communication network such as the Internet. The bus line 310 is an address bus, a data bus, or the like for electrically connecting each component such as the CPU 301. The operation panel 330 is composed of a touch panel, an alarm lamp, or the like that displays the current set value, selection screen, or the like and receives input from the operator.

The transport driver 312 is a driver that controls the rollers included in the carry-in section 10, the transport drum 21, the carry-out section 40, and the motor for driving the drum. The liquid discharge unit driver 322 is a driver that controls the liquid discharge by the liquid discharge unit 23, and the drying driver 332 is a driver that controls the operation of the drying unit 30.

The sensor I / F 342 is an interface for transmitting / receiving data or signals to / from various sensors such as the first encoder 201, the second encoder 211, and the sheet material position sensor.

The functions of the transfer driver 312, the liquid discharge unit driver 322, the drying driver 332, and the encoder I / F 342 may be realized by the instructions of the CPU 301 according to the programs, respectively.

<Functional configuration of the image forming apparatus according to the first embodiment>
Next, the functional configuration of the image forming apparatus 1 will be described with reference to FIG.

FIG. 6 is a block diagram illustrating an example of the functional configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 6, the image forming apparatus 1 includes a sheet material position detecting unit 110, a first signal output unit 111, a discharge start timing determining unit 112, and a second signal output unit 113. Further, the image forming apparatus 1 includes a correction data acquisition unit 114, a correction data storage unit 115, a discharge timing generation unit 116, a discharge unit control unit 117, and a liquid discharge unit 22. Of these, the correction data acquisition unit 114, the discharge start timing determination unit 112, and the discharge timing generation unit 116 are realized by the CPU 301 of FIG. 5 executing a predetermined program.

The sheet material position detection unit 110 is realized by a sheet material position sensor 220 or the like, detects the tip of the sheet material P, and outputs the detection result to the discharge start timing determination unit 112.

The first signal output unit 111 is realized by the first encoder 201 or the like, and outputs the output pulse of the first encoder 201 to the discharge start timing determination unit 112 as the first signal.

The discharge start timing determination unit 112 outputs the first signal input from the first signal output unit 111 from the time when the detection result input from the sheet material position detection unit 110 is in the state of detecting the tip position of the sheet material P. Start counting pulses. Then, the timing at which the count number reaches a predetermined predetermined number is determined as the discharge start timing, and a signal indicating the discharge start timing is output to each of the discharge timing generation unit 116 and the discharge unit control unit 117.

By determining the discharge start timing based on the output of the first signal output unit 111, it is possible to control the superposition accuracy for each color by the liquid discharge unit 23.

The second signal output unit 113 is realized by the second encoder 211 or the like, and the output pulse of the second encoder 211 can be output as a second signal to the correction data acquisition unit 114 and the discharge timing generation unit 116, respectively. ..

By generating the discharge timing after the discharge starts at the discharge start timing based on the output of the second signal output unit 113, the spacing and position accuracy of the liquid dots applied on the sheet material P in the transport direction can be determined. It can be controlled by the actual position of the sheet material P on the transport drum 21. As a result, the discharge accuracy between liquids of the same color, which is required to be highly accurate, can be defined by the actual position of the sheet material P on the transport drum 21 acquired based on the output of the second signal output unit 113. .. At this time, the second encoder 211 included in the second signal output unit 113 detects the amount of movement of the surface of the transfer drum 21, and the sheet material P is based on the rotation accuracy of the transfer drum 21 and the component accuracy of the transfer drum 21. The position detection error can be corrected.

Here, the output of the second signal output unit 113 is based on the encoder scale 212 attached to the peripheral surface of the transport drum 21, but the period of the encoder scale 212 includes a cumulative error or the encoder scale 212. An attachment error may occur when the is attached to the peripheral surface of the transport drum 21. Then, due to such cumulative error and attachment error, it may not be possible to appropriately correct the detection error of the position of the sheet material.

Therefore, in the present embodiment, the correction data acquisition unit 114 for acquiring the correction data for correcting the influence of the cumulative error and the attachment error is provided. The correction data acquisition unit 114 generates correction data for correcting the second signal based on the first signal input from the first signal output unit 111 and the second signal input from the second signal output unit 113. It has a function of outputting to the correction data storage unit 115. The correction data and the method of acquiring the correction data by the correction data acquisition unit 114 will be described in detail separately with reference to FIGS. 7 to 8.

The correction data storage unit 115 is realized by NVRAM 304 or the like, and stores the correction data input from the correction data acquisition unit 114.

The discharge timing generation unit 116 stores the discharge timing after being discharged at the discharge start timing determined by the discharge start timing determination unit 112 with the output pulse of the second signal input from the second signal output unit 113 and the correction data. It is generated based on the correction data stored in the unit 115.

In other words, the discharge timing generation unit 116 corrects the influence of the above-mentioned cumulative error and attachment error included in the second signal by adding the correction data to the output pulse of the second signal, and discharges at the discharge start timing. Generates the discharge timing after it is done. The method of generating the discharge timing by the discharge timing generation unit 116 will be described in detail separately with reference to FIGS. 9 to 10.

The discharge unit control unit 117 is realized by the liquid discharge unit driver 322 or the like, and the liquid discharge unit 22 is realized by the liquid discharge unit 23 or the like. The discharge unit control unit 117 can cause the liquid discharge unit 22 to start discharging the liquid at the discharge start timing determined by the discharge start timing determination unit 112. Further, after the start of discharge, the liquid can be discharged to the liquid discharge unit 22 at the discharge timing generated by the discharge timing generation unit 116.

<Method of acquiring correction data according to the embodiment>
Next, a method of acquiring correction data by the correction data acquisition unit 114 will be described.

The correction data acquisition unit 114 detects the amount of rotation of the transport drum 21 based on the first signal output by the first signal output unit 111 before the liquid discharge unit 22 starts discharging the liquid. At the same time, the amount of movement of the surface of the transport drum 21 is detected based on the second signal output by the second signal output unit 113. Then, the correction data is acquired by comparing the difference between the two.

The detection of the rotation amount of the transfer drum 21 and the movement amount of the surface of the transfer drum 21 is started at the timing when the transfer drum 21 is rotated by a predetermined angle from the rotation origin. More specifically, the discharge start timing determination unit 112 starts counting the output pulses of the first signal output unit 111 with reference to the rotation origin signal output by the first signal output unit 111, and when the count reaches a predetermined number. , The start trigger signal is output to the correction data acquisition unit 114. The correction data acquisition unit 114 starts detecting the rotation amount of the transfer drum 21 and the movement amount of the surface of the transfer drum 21 at the timing when the start trigger signal is input.

Further, the encoder scale 212 in the second encoder 211 always has one or more joints in the circumferential direction of the transfer drum 21, and when these joints are included in the second signal, the rotation amount of the transfer drum 21 is appropriate. May not be detected. Therefore, it is preferable that the discharge start timing determination unit 112 is set to output the start trigger signal after the joint has passed through the encoder sensor 213. As a result, the correction data acquisition unit 114 can acquire the correction data without being affected by the joint. The discharge timing generation unit 116 can appropriately correct the second signal by using the correction data to generate the discharge timing.

Here, FIG. 7 is a diagram illustrating an example of a method of acquiring correction data according to the embodiment. The horizontal axis of FIG. 7 indicates the number of output pulses of the first signal output unit 111 and the second signal output unit 113, and the vertical axis indicates the number of clocks. The number of clocks can be obtained by counting the clocks of the CPU 301 shown in FIG. In other words, the number of clocks indicates the time measured based on the clock of the CPU 301. The cycle of the output pulse can be measured by the number of clocks.

In FIG. 7, the graph 71 shown by the broken line is a value obtained by multiplying the number of pulses of the output pulse (first signal) of the first signal output unit 111 by the number of clocks indicating the measurement result of the period for each output pulse. It is a plot of the integrated values. This integrated value corresponds to the detection value of the rotation amount of the transport drum 21 by the first signal output unit 111.

Further, the graph 72 shown by the alternate long and short dash line is an integration of the values obtained by multiplying the number of output pulses (second signal) of the second signal output unit 113 by the number of clocks indicating the measurement result of the period for each output pulse. It is a plot of the values. This integrated value corresponds to the detected value of the amount of movement of the surface of the transport drum 21 by the second signal output unit 113.

Since graphs 71 and 72 are plots of integrated values, the curves are rising to the right.

In the graph 73 shown by the solid line, the integrated value of the output pulse cycle of the first signal output unit 111 (graph 71) is subtracted from the integrated value of the output pulse period of the second signal output unit 113 (graph 72). It is a plot of the difference value. In this case, the cycle of the output pulse of the second signal output unit 113 and the cycle of the output pulse of the first signal output unit 111 are synchronized, and the first signal is obtained from the integrated value of the cycle of the output pulse of the second signal output unit 113. The integrated value of the cycle of the output pulse of the output unit 111 is subtracted. Note that "synchronizing" the cycle of the output pulse of the second signal output unit 113 and the cycle of the output pulse of the first signal output unit 111 does not require perfect synchronization, and in detail, the second As described in the embodiment, it suffices if both correspond to each other.

The difference value shown in the graph 73 includes the cumulative error of the period of the encoder scale 212 included in the output pulse (second signal) of the second signal output unit 113, and the encoder scale 212 is attached to the peripheral surface of the transport drum 21. It shows the effect of the attachment error of time. The correction data acquisition unit 114 acquires the difference value data shown in the graph 73 as correction data and outputs it to the correction data storage unit 115. The correction data storage unit 115 stores the correction data input from the correction data acquisition unit 114.

Here, depending on the rotation accuracy and component accuracy of the transfer drum 21, the rotation amount of the transfer drum 21 and the movement amount of the surface of the transfer drum 21 do not always match, and the detection of the first signal output unit 111 and the second signal output unit 113. The value may contain an error. Therefore, the correction data acquisition unit 114 may use the average value of the results of acquiring the difference value data shown in the graph 73 a plurality of times as the correction data. Thereby, the influence of the error of the detection value of the first signal output unit 111 and the second signal output unit 113 can be reduced.

Further, the scale period of the first encoder 201 and the second encoder 211 may vary depending on the component accuracy. Therefore, the correction data acquisition unit 114 measures the cycles of the first encoder 201 and the second encoder 211 a plurality of times, and executes the respective moving average processing. Then, the correction data may be acquired from the difference value of each moving average processing result. Thereby, the influence of the variation in the scale period of the first encoder 201 and the second encoder 211 can be reduced.

<Processing by the correction data acquisition unit according to the embodiment>
The correction data acquisition unit 114 executes the correction data acquisition process shown below as an example at the time of shipment from the factory of the image forming apparatus 1, and stores the correction data in the correction data storage unit 115. Alternatively, the correction data stored in the correction data storage unit 115 may be updated by executing the periodic calibration every predetermined cycle (one year or the like). However, the time when the correction data acquisition unit 114 executes the correction data acquisition process is not limited to these, and can be any time as long as it is before the liquid discharge unit 22 starts discharging the liquid. Is also good.

FIG. 8 is a flowchart showing an example of processing by the correction data acquisition unit 114.

First, in step S81, the correction data acquisition unit 114 inputs an output pulse (first signal) from the first signal output unit 111, and simultaneously inputs an output pulse (second signal) from the second signal output unit 113. To do.

Subsequently, in step S82, the correction data acquisition unit 114 acquires the integrated value of the period of the first signal.

Subsequently, in step S83, the correction data acquisition unit 114 acquires the integrated value of the period of the second signal.

The processes of steps S82 to S83 can be changed as appropriate, and both processes may be executed in parallel.

Subsequently, in step S84, the correction data acquisition unit 114 acquires the correction data by subtracting the integrated value of the cycle of the first signal from the integrated value of the period of the second signal.

Subsequently, in step S85, the correction data acquisition unit 114 outputs the acquired correction data to the correction data storage unit 115, and stores the correction data in the correction data storage unit 115.

In this way, the correction data acquisition unit 114 can acquire the correction data for correcting the second signal.

In step S81 of FIG. 8, an example in which the correction data acquisition unit 114 inputs the first signal and the second signal at the same time is shown, but the present invention is not limited to this. As described with reference to FIG. 7, if the period of the output pulse of the second signal output unit 113 and the period of the output pulse of the first signal output unit 111 can be synchronized and the integrated value of both can be subtracted. It is not always necessary to enter them at the same time. The correction data acquisition unit 114 inputs the first signal and the second signal in parallel, inputs the second signal after inputting the first signal, or inputs the second signal after inputting the second signal. You may enter.

<Method of generating discharge timing according to the embodiment>
Next, a method of generating the discharge timing by the discharge timing generation unit 116 will be described.

FIG. 9 is a timing chart illustrating an example of a discharge timing generation method according to the embodiment.

The discharge timing generation unit 116 inputs the start trigger signal (FIG. 9A) output by the discharge start timing determination unit 112 to start the discharge timing generation process. The discharge timing generation unit 116 corresponds to the output pulse of the second signal with reference to the correction data storage unit 115 based on the output pulse of the second signal (FIG. 9B) output by the second signal output unit 113. Acquire the corrected correction data.

The discharge timing generation unit 116 generates the discharge timing based on the discharge start timing (FIG. 9E) output by the discharge start timing determination unit 112. At this time, the timing at which the count number of the clock (FIG. 9D) becomes the count value obtained by subtracting the correction data value from the reference count value is defined as the discharge timing.

More specifically, in the example shown in FIG. 9, the rising edge of the pulse of the second signal is set as the reference timing, and the clock count is started from the rising edge of the pulse of the second signal.

First, at the start of discharge, a discharge timing signal f1 that matches the discharge start timing output by the discharge start timing determination unit 112 is generated. In the subsequent discharge, the difference value "4" count of the correction data value "+1" from the count at the time of inputting the discharge start timing is used as a reference.

That is, at the next discharge timing, the correction data value "-1" is added to the above-mentioned 4 counts from the rising edge of the output pulse of the next second signal after the first discharge timing signal f1 is generated. The discharge timing signal f2, which is the timing of the third count, is generated.

Similarly, in the next discharge timing, the discharge timing is the second count timing obtained by adding the correction data value "-2" to the above-mentioned 4 counts from the rising edge of the output pulse of the next second signal. Generate signal f3.

Since the correction data can be generated in association with each output pulse of the second signal, the correction data corresponding to the pulse is added from the output pulse of the second signal to generate the discharge timing. As a result, the second signal can be corrected, and the influence of the cumulative error of the period of the encoder scale 212 and the attachment error when the encoder scale 212 is attached to the peripheral surface of the transport drum 21 can be removed.

In this embodiment, an example based on 4 counts is shown, but the correction accuracy can be further improved by increasing the clock frequency and increasing the number of counts.

Further, in the present embodiment, the clock is counted with the rising edge of the output pulse of the second signal as the reference timing, but the falling edge or both rising and rising edges may be used as the reference timing. In this case, the correction data is also generated according to the reference timing.

Further, the scale period of the second encoder 211 may vary depending on the component accuracy. Therefore, the difference can be canceled by measuring the period of the second encoder 211 a plurality of times and taking the moving average thereof. At this time, the difference between the cycle acquired from the moving average result and the cycle of the second encoder 211 immediately before is subtracted from the count number described above.

Further, in the present embodiment, in the liquid discharge unit 23, as described with reference to FIGS. 2 and 4, a plurality of heads 100 having a nozzle row 101 in which a plurality of nozzles are arranged are arranged on the base member 52. .. Further, the plurality of heads 100 are staggered in the transport direction. In FIG. 4, the "staggered arrangement in the transport direction" means that, of the six heads 100, the head row consisting of the three heads 100 on the left side and the head row consisting of the three heads 100 on the right side are the transport directions. It means that the position is shifted in the orthogonal direction. Further, since the plurality of heads 100 are staggered in the transport direction, the nozzle rows 101 included in the head 100 are also staggered in the transport direction according to the head 100. In such an arrangement, the discharge timing generation unit 116 generates the discharge timing for each of the nozzle rows 101.

Further, in this case, for example, one second encoder 211 may be arranged for each liquid discharge unit 23. By using the correction data in common for all the nozzle rows 101 in the liquid discharge unit 23, the number of encoder sensors 213 can be reduced.

<Image formation process by the image forming apparatus according to the embodiment>
Next, the image forming process by the image forming apparatus 1 will be described.

FIG. 10 is a flowchart showing an example of an image forming process by the image forming apparatus according to the embodiment.

When the sheet material P is passed to the transfer drum 21 by the transfer cylinder 24, the suction device 26 starts sucking the sheet material P, and the sheet material P is conveyed by the rotation of the transfer drum 21.

Then, in step S101, the sheet material position detection unit 110 detects the tip of the sheet material P and outputs the detection result to the discharge start timing determination unit 112.

Subsequently, in step S102, the discharge start timing determination unit 112 starts counting the output pulse of the first signal output unit 111 from the timing at which the detection result from the sheet material position detection unit 110 is input, and reaches a predetermined count value. At the timing, the discharge start timing of each color from each liquid discharge unit 23 is determined (determined). As a result, discharge from each liquid discharge unit 23 is started.

Subsequently, after the start of discharge, in step 103, the discharge timing generation unit 116 adds correction data to the output pulse of the second signal output unit 113, generates the discharge timing while correcting the second signal, and discharges. The timing signal is output to the discharge unit control unit 117.

Subsequently, in step S104, the discharge unit control unit 117 controls the liquid discharge unit 23 in response to the input discharge timing signal, discharges the liquid to the liquid discharge unit 23, and forms an image on the sheet material P.

<Effect>
As described above, in the present embodiment, the correction data acquisition unit 114 acquires the correction data for correcting the second signal output by the second signal output unit 113. Further, the discharge timing generation unit 116 generates the discharge timing of the liquid discharge unit 23 based on the second signal and the correction data. As a result, even if the period of the encoder scale 212 includes a cumulative error or an attachment error occurs when the encoder scale 212 is attached to the peripheral surface of the transport drum 21, the influence of the cumulative error and the attachment error is eliminated. Therefore, the detection error of the position of the sheet material can be appropriately corrected.

Further, by determining the discharge start timing based on the first signal, the accuracy of superimposition for each color can be ensured. Further, by generating the discharge timing after the discharge at the discharge start timing based on the second signal, the discharge can be performed according to the actual position of the sheet material P on the transfer drum 21. As a result, it is possible to secure the ejection accuracy between the same colors, which is required to be highly accurate, and to secure the spacing and position accuracy of the dots of the same color in the transport direction.

Further, even if a high-precision encoder is not used for the first encoder 201 of the first signal output unit 111, high-precision landing position accuracy can be obtained, and the quality of image formation can be improved.

[Second Embodiment]
Next, the image forming apparatus according to the second embodiment will be described. The description of the same components as those in the above-described embodiment will be omitted.

FIG. 11 is a block diagram showing an example of the functional configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 11, the image forming apparatus 1a includes a correction data acquisition unit 114a, and the correction data acquisition unit 114a includes a cycle adjustment unit 118.

Here, the cycle of the scale for detecting the rotation amount of the transport drum 21 of the encoder wheel 202 and the cycle of the scale for detecting the movement amount of the surface of the transport drum 21 of the encoder scale 212 may not match. Due to such a difference in period, when the correction data is acquired, the integrated value of the output pulse period of the second signal output unit 113 (graph 72) to the integrated value of the output pulse period of the first signal output unit 111 (graph 72). Graph 71) may not be synchronized and subtracted, and accurate correction data may not be obtained.

Therefore, the cycle adjustment unit 118 executes an adjustment process for making the cycle of the output pulse (first signal) of the first signal output unit 111 correspond to the cycle of the output pulse (second signal) of the second signal output unit 113. ..

As an example of such an adjustment process, the cycle adjustment unit 118 may execute a process of multiplying and dividing the output pulse of the first encoder 201 to make it the same as or an integral multiple of the cycle of the second encoder 211. it can.

Alternatively, as another example, the period adjustment unit 118 obtains an approximate expression for interpolating the discrete acquisition data (see graph 72 of FIG. 7) of the integrated value of the period of the first encoder 201. Then, each cycle of the second encoder 211 is substituted into the approximate expression to calculate the integrated value of the cycle of the first encoder 201 corresponding to each cycle of the second encoder 211. In this way, the cycle of the output pulse (first signal) of the first signal output unit 111 may be matched with the cycle of the output pulse (second signal) of the second signal output unit 113.

As a result, the integrated value of the output pulse period of the first signal output unit 111 (graph 71) can be synchronously subtracted from the integrated value of the output pulse period of the second signal output unit 113 (graph 72). , Accurate correction data can be obtained.

The effects other than those described above are the same as those described in the first embodiment.

Although the embodiments have been described above, the present invention is not limited to the above-described embodiments specifically disclosed, and various modifications and changes can be made without departing from the scope of claims. ..

Further, each function of the embodiment described above can be realized by one or a plurality of processing circuits. Here, the "processing circuit" in the present specification is a processor programmed to execute each function by software such as a processor implemented by an electronic circuit, or a processor designed to execute each function described above. It shall include devices such as ASIC (Application Specific Integrated Circuit), DSP (digital signal processor), FPGA (field programmable gate array) and conventional circuit modules.

1 Image forming device (example of liquid discharge device)
10 Carry-in part 20 Image forming part 21 Transport drum (an example of rotating member)
201 1st encoder 202 Encoder wheel 203 Encoder sensor 211 2nd encoder 212 Encoder scale 213 Encoder sensor 22 Liquid discharge part 220 Sheet material position sensor 23 Liquid discharge unit 30 Dry part 40 Delivery part 100 Liquid discharge head 101 Nozzle row 110 Sheet material position Detection unit 111 1st signal output unit 112 Discharge start timing determination unit 113 2nd signal output unit 114 Correction data acquisition unit 115 Correction data storage unit 116 Discharge timing generation unit 117 Discharge unit control unit 118 Period adjustment unit 71 Period of 1st signal Graph of the integrated value of 72 72 Graph of the integrated value of the period of the second signal 73 Graph of the result of subtracting the integrated value of the period of the first signal from the integrated value of the period of the second signal P Sheet material

Japanese Unexamined Patent Publication No. 2016-074101

Claims (11)

A rotating member that supports and conveys the sheet material on the peripheral surface,
A liquid discharge unit that discharges liquid to the sheet material,
A sheet material position detecting unit that detects the position of the sheet material, and
A first signal output unit that outputs a first signal according to the amount of rotation of the rotating member, and
A second signal output unit that outputs a second signal that correlates with the amount of movement of the sheet material on the peripheral surface of the rotating member, and
A correction data storage unit that stores correction data for correcting the second signal acquired based on the first signal and the second signal.
A liquid discharge device having a discharge timing generation unit that generates a discharge timing of the liquid discharge unit based on the second signal and the correction data. The second signal output unit
An encoder scale provided on the peripheral surface of the rotating member and
The liquid discharge device according to claim 1, further comprising an encoder sensor that is arranged in the vicinity of the liquid discharge unit and reads the encoder scale. The amount of movement of the sheet material obtained from the integrated value of the period of the second signal and
The amount of rotation of the rotating member obtained from the integrated value of the period of the first signal, and
The liquid discharge device according to claim 1 or 2, further comprising a correction data acquisition unit that acquires the correction data based on the above. The correction data acquisition unit
The liquid discharge device according to claim 3, wherein the correction data acquisition process is executed a plurality of times, and the correction data is acquired by averaging the acquisition results of the plurality of times. The correction data acquisition unit
The moving average processing result of the moving amount of the sheet material acquired from the integrated value of the period of the second signal, the moving average processing result of the rotating amount of the rotating member acquired from the integrated value of the period of the first signal, and The liquid discharge device according to claim 3 or 4, wherein the correction data is acquired based on the above. The liquid discharge part is
It has a plurality of nozzle rows that are staggered in the transport direction of the sheet material to discharge the liquid.
The discharge timing generator
The liquid discharge device according to any one of claims 1 to 5, wherein the discharge timing is generated for each nozzle row. The liquid discharge part is
A plurality of liquid discharge units are included for each color of the liquid in the transport direction.
The second signal output unit
The liquid discharge device according to any one of claims 1 to 6, which is arranged in the vicinity of each of the plurality of liquid discharge units. The liquid discharge device according to any one of claims 3 to 7, further comprising a cycle adjusting unit for executing an adjusting process for making the cycle of the first signal correspond to the cycle of the second signal. The cycle adjusting unit
The liquid discharge device according to claim 8, wherein the first signal is multiplied and divided to be the same as the period of the second signal, or to be adjusted to an integral multiple of the period of the second signal. The cycle adjusting unit
The eighth aspect of the present invention, wherein an approximate expression obtained by interpolating the integrated value of the period of the first signal is calculated, and the period of the second signal is substituted into the approximate expression to calculate the integrated value of the period of the first signal. Liquid discharge device. A rotating member that supports and conveys the sheet material on the peripheral surface,
A liquid discharge unit that discharges liquid to the sheet material,
A sheet material position detecting unit that detects the position of the sheet material, and
A first signal output unit that outputs a first signal according to the amount of rotation of the rotating member, and
A second signal output unit that outputs a second signal that correlates with the amount of movement of the sheet material on the peripheral surface of the rotating member, and
A correction data storage unit that stores correction data for correcting the second signal acquired based on the first signal and the second signal.
An image forming apparatus having a discharge timing generation unit that generates a discharge timing of the liquid discharge unit based on the second signal and the correction data.

Images