Control device, image forming apparatus, and drive control method

Abstract

The objective is to provide a control device that can suppress contact between a recording medium experiencing a transport malfunction and a liquid discharge head. [Solution] A control device according to one aspect of the present invention includes a detection unit that detects a transport abnormality of a recording medium in a cylindrical drum that transports the recording medium while winding it, and a control unit that controls the position of a head unit equipped with a liquid discharge head that discharges liquid onto the recording medium and the movement speed of the head unit, wherein the control unit controls the movement speed of the head unit when a transport abnormality occurs in the recording medium.

Description

Technical Field

[0001] The present invention relates to a control device, an image forming apparatus, and a drive control method.

Background Art

[0002] In an image forming apparatus, when a recording medium having conveyance abnormalities such as floating contacts the nozzle surface of a liquid ejection head, it may cause adhesion of foreign substances to the nozzle surface and reduce the ink ejection performance. Patent Document 1 discloses a technique for retracting a liquid ejection head to a predetermined retracted position when detecting floating of a conveyed recording medium.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Even in a configuration where the liquid ejection head is retracted after detecting conveyance abnormalities such as floating of the recording medium as in the technique described in Patent Document 1, when the printing speed is increased, there is a risk that the recording medium will reach the nozzle surface. Therefore, there is a risk that the recording medium with conveyance abnormalities will contact the nozzle surface of the liquid ejection head and damage the head unit or the liquid ejection head.

[0004] An object of the present invention is to provide a control device capable of suppressing contact between a recording medium with conveyance abnormalities and a liquid ejection head in order to solve the above problems.

Means for Solving the Problems

[0005] A control device according to an aspect of the present invention includes a detection unit that detects conveyance abnormalities of a recording medium on a cylindrical drum that conveys the recording medium while winding it, and a control unit that controls the position and the moving speed of a head unit on which a liquid ejection head that ejects liquid onto the recording medium is mounted. When conveyance abnormalities occur in the recording medium, the control unit controls the moving speed of the head unit.

Effects of the Invention

[0006] According to the control device of the present invention, contact between the recording medium experiencing a transport abnormality and the liquid discharge head can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows a schematic configuration of an image forming apparatus according to the first embodiment of the present invention. [Figure 2] This figure shows a schematic configuration of the image forming section in the image forming apparatus shown in Figure 1. [Figure 3] This is a hardware configuration diagram of a control device according to the first embodiment of the present invention. [Figure 4] This is a block diagram showing the functional configuration of a control device according to the first embodiment of the present invention. [Figure 5] This is a flowchart illustrating the drive control method according to the first embodiment of the present invention. [Figure 6] This is a diagram illustrating the paper output position of a recording medium according to a second embodiment of the present invention. [Figure 7] This is a flowchart illustrating a drive control method according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0008] The embodiments for carrying out the invention will be described below with reference to the drawings. In each drawing, the same reference numerals are used for identical components, and redundant explanations may be omitted.

[0009] [First Embodiment] <Example of configuration of image forming apparatus 1> Figure 1 is a diagram showing the schematic configuration of an image forming apparatus 1 according to the first embodiment of the present invention. The image forming apparatus 1 comprises an image forming unit 10, a paper feeding unit 20, a resist adjustment unit 30, a drying unit 40, a recording medium inversion unit 50, and a first paper discharge unit 60, which are embodiments of the present invention.

[0010] The image forming apparatus 1 includes a control device 70. The control device 70 may be included in the image forming unit 10 as shown in the figure, or it may be included in other components. Alternatively, the control device 70 may be an external device that is communicatively connected to the image forming apparatus 1. The control device 70 controls the operation of the entire image forming apparatus 1.

[0011] In the image forming unit 10, a head unit 12, which is a liquid ejection head unit that prints ink, an example of a liquid, using an inkjet method, is arranged radially at an angle along the surface of a cylindrical drum 11, with predetermined ink colors already filled in. The drum 11 carries the recording medium W on its surface.

[0012] The head unit 12 is equipped with a liquid ejection head that ejects ink onto the recording medium W. The head unit 12 ejects ink from the outside of the circumference onto the outer surface of the recording medium W held on the surface of the drum 11, thereby forming an image on the recording medium W.

[0013] The control device 70 controls the operation of the head unit 12 by controlling the operation of a power source, such as a drive motor (not shown), that drives the head unit 12. The power source for the head unit 12 may be a stepping motor that rotates for a specified number of pulses. Furthermore, from the viewpoint of suppressing step loss and high-speed operation of the stepping motor, the power source for the head unit 12 is preferably a DC brushless motor or a DC motor.

[0014] To control the head unit 12 with high precision, position control is used. In position control, a specified number of pulses are supplied to the power source of the head unit 12 while maintaining a constant pulse speed.

[0015] In this embodiment, the control of the head unit 12 is performed by speed control in addition to position control. When the conveyance abnormality of the recording medium W is detected by the detection means 13, which will be described later with reference to FIG. 2, the speed control is such that the head unit 12 moves away from the recording medium W, that is, in a radial direction perpendicular to the outer peripheral surface of the drum 11, at high speed based on the speed calculated by the control unit 72 shown in FIG. 4. Note that the direction in which the head unit 12 moves away from the recording medium W does not have to be strictly perpendicular to the outer peripheral surface of the drum 11, and it may be substantially perpendicular.

[0016] Next, the flow of the recording medium W during the execution of the print job in the image forming apparatus 1 will be described. First, the recording medium W stacked on the paper feed stack 21 of the paper feed unit 20 is picked up one by one by the air separation unit 22 and conveyed in the direction of the image forming unit 10.

[0017] When the recording medium W conveyed from the paper feed unit 20 reaches the registration adjustment unit 30, the inclination of the recording medium W is corrected by a pair of registration rollers 31 provided inside the registration adjustment unit 30. The correction of the inclination of the recording medium W is also referred to as registration correction.

[0018] The recording medium W whose inclination has been corrected by registration is sent to the image forming unit 10, and the leading end of the recording medium W is sandwiched by the recording medium gripper 111 provided on the surface of the drum 11, and the drum 11 rotates to convey the recording medium W to a position facing the head unit 12.

[0019] When the recording medium W is sent to the lower part of the head units 12 arranged radially for each color, ink is ejected by each liquid ejection head of the head unit 12 to form an image.

[0020] When an image is formed on the recording medium W, the recording medium W is conveyed to the drying unit 40. A drying unit 41 is attached to the drying unit 40. The recording medium W passes under the drying unit 41. The drying unit 41 prevents the occurrence of curl of the recording medium W by evaporating the moisture in the ink inside the recording medium W.

[0021] Further, the drying unit 40 is provided with a recording medium reversing unit 50 including a recording medium reversing mechanism 51. During double-sided printing, the recording medium reversing unit 50 reverses the recording medium W and conveys it again in the direction of the image forming unit 10. In the recording medium reversing unit 50, when the conveyance direction of the recording medium W is changed, the reverse conveyance unit 52 conveys the recording medium W in the direction of the image forming unit 10. Before reaching the drum 11, the inclination of the recording medium W is corrected by a registration roller pair 53 provided inside the image forming unit 10.

[0022] Then, image formation is performed on the back surface of the recording medium W in the image forming unit 10. After image formation on the desired surface is performed, the recording medium W passes through the drying unit 40 again. Thereafter, the recording medium W is conveyed to the first paper discharge unit 60 and stacked in a state where the recording media W are aligned.

[0023] FIG. 2 is a diagram showing a schematic configuration of the image forming unit 10 in the image forming apparatus 1 shown in FIG. 1. FIG. 2 shows the states of the liquid ejection heads 12a to 12f when forming an image on the recording medium W. At this time, each of the liquid ejection heads 12a to 12f is arranged while maintaining a predetermined gap G1 with respect to the surface of the drum 11.

[0024] As shown in FIG. 2, each of the liquid ejection heads 12a to 12f is arranged radially and angularly with respect to the drum 11. The liquid ejection heads 12a to 12f are arranged in a state inclined with respect to the vertical direction as they are closer to the side surface of the drum 11.

[0025] For example, the liquid ejection head 12a ejects black ink, the liquid ejection head 12b ejects cyan ink, the liquid ejection head 12c ejects magenta ink, and the liquid ejection head 12d ejects yellow ink. Further, the liquid ejection heads 12e and 12f contain special inks. The special ink may be, for example, an ink of a color that cannot be expressed only by the above four colors made by ink formulation, a color containing gold or silver, a fluorescent color, etc., or may contain a transparent coating liquid or the like.

[0026] The liquid ejection heads 12a to 12f move up and down in accordance with a specified number of pulses. When the detection means 13 detects an abnormality in the transport of the recording medium W, the drum 11 stops rotating, and the liquid ejection heads 12a to 12f move to a retracted position so as to rise at a speed faster than the speed during normal operations such as pre-printing and initial operations. Although the example shown includes six liquid ejection heads 12a to 12f in the head unit 12, the number and position of the liquid ejection heads 12a to 12f are not limited to these.

[0027] On the outer circumferential surface of the drum 11, there are recording medium grippers 111, which are claw members that hold the tip of the recording medium W and are acting as recording medium tip holding means. Multiple recording medium grippers 111, which are claw parts, are provided in the axial direction (depth direction in Figure 2) of the drum 11, and the recording medium W can be held by securely gripping the tip of the recording medium.

[0028] Furthermore, numerous air suction holes 11P are formed on the surface of the drum 11, and an air suction fan 112 installed inside the drum 11 can suck the back surface of the recording medium W, making the recording medium W tightly adhere to the surface of the drum 11. The air suction holes 11P and the air suction fan 112 function as suction holding means.

[0029] A detection means 13 is positioned upstream of the head unit 12 in the direction of transport of the recording medium W, for detecting transport abnormalities of the recording medium W transported on the surface of the drum 11. Transport abnormalities of the recording medium W include, but are not limited to, wrinkles, lifting of the recording medium W, and abnormalities of the recording medium W due to stepping motor loss.

[0030] The detection means 13 may include a laser displacement meter and an optical sensor, but is not limited to these; various sensors can be used. The position of the detection means 13 is not specified as long as it is in a position that can detect abnormalities in the transport of the recording medium W in the axial direction of the drum 11. Multiple detection means 13 may be arranged across the width of the recording medium W, which is in the axial direction of the drum 11.

[0031] <Example of the configuration of the control device 70> Figure 3 is a hardware configuration diagram of a control device 70 according to the first embodiment of the present invention. A CPU (Central Processing Unit) 101, ROM (Read Only Memory) 102, RAM (Random Access Memory) 103, and hard disk drive (HDD) 104 are connected to a bus 106. An external interface 107, a control information interface 108, and an image data interface 109 are further connected to the bus 106. These components connected to the bus 106 are capable of communicating with each other via the bus 106.

[0032] ROM 102 and HDD 104 are pre-stored with programs for the CPU 101 to operate. RAM 103 is used as the CPU 101's work memory. That is, the CPU 101 uses RAM 103 as work memory according to the programs stored in ROM 102 and HDD 104 to control the operation of the entire control unit 70. External I / F 107 supports, for example, TCP / IP (Transmission Control Protocol / Internet Protocol) and controls communication with other devices. Control information I / F 108 controls the communication of control information.

[0033] Furthermore, the image data interface 109 controls the communication of print image data and has multiple channels. For example, print image data for each color, created in the control device 70 using Y (yellow), C (cyan), M (magenta), and K (black) inks, is output from each of these multiple channels.

[0034] In this configuration, print job data transmitted from other devices is received by the external I / F 107 of the control device 70 and stored in the HDD 104 via the CPU 101. The CPU 101 performs RIP processing based on the print job data read from the HDD 104, generates bitmap data for each color, and writes them to the RAM 103. For example, the CPU 101 renders the PDL (Page Description Language) through RIP processing to generate bitmap data for each color and writes it to the RAM 103. The CPU 101 compresses and encodes the bitmap data for each color written to the RAM 103 and temporarily stores it in the HDD 104.

[0035] For example, when printing is started in the image forming apparatus 1, the CPU 101 reads the compressed and encoded bitmap data for each color from the HDD 104, decodes the compressed code, and writes the decompressed bitmap data for each color to the RAM 103. Then, the CPU 101 reads these bitmap data for each color from the RAM 103 and outputs them as print image data for each color from each channel of the image data interface 109, supplying them to the image forming unit 10. The CPU 101 also sends and receives control information to and from the image forming unit 10 via the control information interface 108 in accordance with the progress of the printing operation.

[0036] Furthermore, the NVRAM105 stores various printer-related information used by programs stored in the ROM102 and HDD104.

[0037] Figure 4 is a block diagram showing the functional configuration of a control device 70 according to the first embodiment of the present invention. The control device 70 includes a detection unit 71 and a control unit 72.

[0038] The detection unit 71 detects any abnormalities in the transport of the recording medium W in the cylindrical drum 11 that transports the recording medium W while winding it around it. The detection unit 71 detects abnormalities in the transport of the recording medium W based on signals output from detection means 13 located upstream of the head unit 12 in the transport direction of the recording medium W. More specifically, the detection unit 71 detects the presence or absence of transport abnormalities such as floating based on thresholds set according to the thickness of each recording medium W, and notifies the control unit 72. If there is a transport abnormality, the control unit 72 instructs the drum 11 included in the image forming apparatus 1 to stop, and instructs the head unit 12 to retract and stop. In addition, the control unit 72 instructs components other than the drum 11 and head unit 12 to stop, etc., in accordance with the instructions given to the drum 11 and head unit 12.

[0039] The control unit 72 controls the position and movement speed of the head unit 12, which is equipped with liquid discharge heads 12a to 12f that discharge liquid onto the recording medium W. The control unit 72 also controls the operation of the drum 11.

[0040] The control unit 72 controls the movement speed of the head unit 12 when a transport abnormality occurs in the recording medium W. More specifically, the control unit 72 controls the head unit 12 in either a position control mode that controls the position of the head unit 12 or a speed control mode that controls the movement speed of the head unit 12. The control unit 72 controls the head unit 12 in speed control mode at least when a transport abnormality occurs in the recording medium W.

[0041] In speed control mode, the control unit 72 calculates the movement speed of the head unit 12 based on print information for controlling the operation of the head unit 12 and the operating speed of the power source of the head unit 12. The calculated movement speed can be a value corresponding to the transport speed of the recording medium W. The print information is, for example, information based on a print job received from a terminal device operated by the user, and is the information that forms the basis of the movement speed of the head unit 12 during printing.

[0042] Furthermore, if a transport error occurs in the recording medium W, it is preferable for the control unit 72 to control the operation of the drum 11 and the head unit 12 to perform a recovery operation after processing the recording medium W with the transport error, from the viewpoint of reducing jam processing time. When a transport error occurs in the recording medium W, paper dust from the recording medium W often adheres to the drum 11, etc., so a recovery operation such as removing the paper dust is performed during the recovery operation. Note that the recovery operation is not limited to removing paper dust, but includes various recovery operations.

[0043] <Drive control method> Figure 5 is a flowchart illustrating the drive control method according to the first embodiment of the present invention. When the control unit 72 of the control device 70 acquires print information, it calculates the movement speed of the head unit 12 and notifies the head unit 12 (S101). Then, the control unit 72 switches the control of the head unit 12 from position control mode to speed control mode (S102). The above process constitutes the process in the print preparation stage.

[0044] When printing starts, the detection unit 71 detects a transport abnormality of the recording medium W based on the signal from the detection means 13 (S103). If no transport abnormality of the recording medium W is detected (NO in S103), the detection unit 71 continues the process of detecting a transport abnormality of the recording medium W.

[0045] When an abnormality in the transport of the recording medium W is detected (YES in S103), the detection unit 71 notifies the control unit 72 of the error (S104). At this time, the control unit 72 stops the operation of the drum 11 (S105) and controls the head unit 12 in speed control mode (S106). At this time, the head unit 12 moves at high speed away from the recording medium W based on the speed calculated by the control unit 72.

[0046] When the operation of the head unit 12 stops, the control of the head unit 12 in speed control mode is completed (S107). The control unit 72 switches the control of the head unit 12 from speed control mode to position control mode (S108).

[0047] By switching to position control mode, the control unit 72 moves the head unit 12 to the stowed position (S109). Then, when the operation of the head unit 12 stops, the control of the head unit 12 in position control mode is completed (S110).

[0048] These steps carry out a drive control method according to one aspect of the present invention. However, the drive control method according to one aspect of the present invention may include other steps as appropriate, depending on the measurement conditions, measurement environment, etc.

[0049] <Effects and Effects> In the control device 70 according to this embodiment, the detection unit 71 detects a transport abnormality of the recording medium W while the operation of the head unit 12 is switched to speed control mode. Therefore, when a transport abnormality of the recording medium W occurs, the operating speed of the head unit 12 can be increased, and contact between the recording medium W experiencing the transport abnormality and the liquid ejection heads 12a to 12f can be suppressed. Furthermore, by setting the calculated movement speed to a value corresponding to the transport speed of the recording medium W, contact between the recording medium W experiencing the transport abnormality and the liquid ejection heads 12a to 12f can be suppressed even when the printing speed is increased further.

[0050] Furthermore, the control unit 72 can switch between a position control mode for controlling the position of the head unit 12 and a speed control mode for controlling the movement speed of the head unit 12. Therefore, even if a transport abnormality occurs in the recording medium W, the position control mode and speed control mode can be used interchangeably, and the head unit 12 can be moved to the desired position.

[0051] Furthermore, in speed control mode, the control unit 72 calculates the movement speed of the head unit 12 based on the printing information for controlling the operation of the head unit 12 and the operating speed of the power source of the head unit 12. Therefore, the head unit 12 can be positioned with high precision using only speed control.

[0052] [Second Embodiment] Unlike the control device 70 according to the first embodiment, the control device 70 according to this embodiment detects the amount by which the recording medium W is lifted from the surface of the drum 11 when it detects an abnormality in the transport of the recording medium W. The control unit 72 moves the head unit 12 according to the amount of movement of the head unit 12 based on the amount of lift of the recording medium W from the surface of the drum 11 detected by the detection unit 71. In the following, the same reference numerals are used for components that have already been described, and redundant explanations are omitted.

[0053] The amount of lift of the drum 11 of the recording medium W from the surface is based on the result measured by the detection means 13 shown in Figure 2, for example. The control unit 72 then controls the movement of the head unit 12 so that the greater the amount of lift, the greater the movement of the head unit 12.

[0054] Furthermore, the control unit 72 performs print stop control, which stops printing if the amount of lifting exceeds a threshold, and control to continue printing if the amount of lifting is less than the threshold. Print stop control is, for example, a control that forcibly terminates printing when an amount of lifting exceeding the threshold is detected. If the amount of lifting is less than the threshold, the control unit 72 moves the head unit 12 to a position where the recording medium W can move, returns it to its original position after the recording medium W has passed, and resumes printing. The determination of whether or not the amount of lifting exceeds the threshold is made by the detection unit 71, but may also be made by the control unit 72.

[0055] Figure 6 is a diagram illustrating the paper discharge position of the recording medium W according to the second embodiment of the present invention. The illustrated image forming apparatus 1 includes the image forming unit 10, paper feeding unit 20, resist adjustment unit 30, drying unit 40, recording medium inversion unit 50, and first paper discharge unit 60, which are components shown in Figure 1, as well as a second paper discharge unit 61. The image forming unit 10, paper feeding unit 20, resist adjustment unit 30, drying unit 40, and recording medium inversion unit 50 are the same as those already described, so their description is omitted.

[0056] The control unit 72 in this embodiment controls the recording medium W whose printing was not completed by the print stop control and the recording medium W whose printing was completed by normal printing to be discharged to different paper output positions.

[0057] Recording media W that have been printed by normal printing are discharged to, for example, the first paper discharge unit 60, and recording media W that have not been printed due to print stop control are discharged to the second paper discharge unit 61. However, the first paper discharge unit 60 and the second paper discharge unit 61, which are the paper discharge positions, are not limited to the positions shown in the figure. Completion of printing by normal printing is not limited to completion of printing due to completion of the print job, but also includes completion of printing due to, for example, stopping printing midway at the instruction of the user. Furthermore, "printing not completed due to print stop control" means that printing was not completed due to print stop control, which stops printing when the amount of lift exceeds a threshold.

[0058] In this way, by separating the output positions of recording media W that have completed printing through normal printing and recording media W that have not completed printing due to print stop control, the effort of separating recording media W that have completed printing normally from recording media W whose printing has been forcibly terminated by print stop control is eliminated.

[0059] Figure 7 is a flowchart illustrating the drive control method according to the second embodiment of the present invention. Note that the processing in steps S201 to S203 is the same as in steps S101 to S103 shown in Figure 5, so the explanation is omitted.

[0060] The detection unit 71 of the control device 70 notifies the control unit 72 of an error (S205) if the amount of lift of the drum 11 of the recording medium W from the surface is greater than or equal to a threshold (Yes in S204). At this time, the control unit 72 stops the operation of the drum 11 (S206) and forcibly terminates printing (S207). Simultaneously, the control unit 72 starts the retraction movement of the head unit 12 (S208), and completes the retraction movement of the head unit 12 when it reaches a predetermined position (S209). Then, the control unit 72 forcibly terminates printing (S207).

[0061] If the amount of lift of the drum 11 of the recording medium W from the surface is less than a threshold (No. in S204), the control unit 72 notifies the power source, such as the drive motor that drives the head unit 12, of the amount of movement of the head unit 12 based on the amount of lift (S210). The control unit 72 also calculates the movement speed of the head unit 12 based on the amount of movement (S211).

[0062] The control unit 72 initiates the retraction movement of the head unit 12 (S212). At this time, the power source, such as the drive motor, moves the head unit 12 by the notified amount at the calculated movement speed based on the instruction from the control unit 72 (S213), and completes the retraction movement of the head unit 12 when it reaches the predetermined position (S214).

[0063] If the recording medium W has not passed (No in S215), the drum 11 continues to operate until the recording medium W passes, and the head unit 12 waits in a position where the recording medium W can move. If the recording medium W has passed (Yes in S215), the control unit 72 returns the head unit 12 to its original position (S216) and resumes printing (S217), thereby continuing the printing.

[0064] These steps carry out the drive control method according to the second embodiment of the present invention. However, the drive control method according to this embodiment may include other steps as appropriate, depending on the measurement conditions, measurement environment, etc.

[0065] <Effects and Effects> In the control device 70 according to this embodiment, when a transport abnormality is detected, the control device 70 moves the head unit 12 according to the amount of movement of the head unit 12 based on the amount of lift of the recording medium W detected. Therefore, when the amount of lift is small, the control device 70 can reduce the amount of movement of the head unit 12, and since the time it takes to return the head unit 12 to its original position can be shortened, the time required to resume printing can be shortened.

[0066] Furthermore, the control device 70 performs print stop control, which stops printing if the amount of lift is above a threshold, and controls printing to continue if the amount of lift is below the threshold. Therefore, when the amount of lift is small, the control device 70 retracts the head unit 12 without stopping the transport of the recording medium W, thereby shortening the time required to restart the printing operation.

[0067] Although embodiments have been described above, the present invention is not limited to the embodiments described above, and various modifications and improvements are possible within the scope of the present invention.

[0068] Each of the functions of the embodiments described above can be realized by one or more processing circuits. Hereinafter, "processing circuit" as used herein includes processors programmed to execute each function by software, such as processors implemented by electronic circuits, as well as devices such as ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and conventional circuit modules designed to execute each of the functions described above.

[0069] Examples of the present invention are as follows: <1> A control device comprising: a detection unit for detecting abnormalities in the transport of a recording medium in a cylindrical drum that transports the recording medium while winding it; and a control unit for controlling the position of a head unit equipped with a liquid discharge head that discharges liquid onto the recording medium and the movement speed of the head unit, wherein the control unit controls the movement speed of the head unit when an abnormality in the transport of the recording medium occurs. <2> The control unit controls the head unit in either a position control mode for controlling the position of the head unit or a speed control mode for controlling the movement speed of the head unit, and controls the head unit in the speed control mode when at least one transport abnormality occurs in the recording medium. <1> The control device described above. <3> The control unit calculates the movement speed of the head unit based on the print information for controlling the operation of the head unit and the operating speed of the power source of the head unit in the speed control mode. <2> The control device described above. <4> The control unit, in the speed control mode, causes the retraction movement of the head unit to be at a speed faster than the movement speed of the head unit during normal operation. <3> The control device described above. <5> The power source of the head unit is a DC brushless motor or a DC motor. <3> or the above <4> The control device described above. <6> The control unit controls the operation of the drum and the head unit to perform a recovery operation after processing the recording medium in the event of a transport error in the recording medium. <1> from the above <5> A control device as described in any one of the following. <7> When the detection unit detects the transport abnormality, it detects the amount by which the recording medium is lifted from the surface of the drum, and the control unit moves the head unit according to the amount of movement of the head unit based on the amount of lift. <1> The control device described above. <8> The control unit performs print stop control to stop printing when the amount of lifting is greater than or equal to a threshold, and performs control to continue printing when the amount of lifting is less than a threshold. <7> The control device described above. <9> The control unit controls the recording medium, which has not been printed due to the print stop control, and the recording medium, which has been printed by normal printing, to be ejected to different paper output positions. <8> The control device described above. <10> An image forming apparatus comprising: a cylindrical drum for transporting a recording medium while winding it; a head unit equipped with a liquid discharge head for discharging liquid onto the recording medium; a control unit for controlling the position and movement speed of the head unit; and a detection unit for detecting abnormalities in the transport of the recording medium on the drum, wherein the control unit controls the movement speed of the head unit when an abnormality occurs in the transport of the recording medium. <11> A drive control method executed by a control device, comprising: detecting a transport abnormality of a recording medium in a cylindrical drum that transports the recording medium while winding it; controlling the position of a head unit equipped with a liquid discharge head that discharges liquid onto the recording medium and the movement speed of the head unit; and, if a transport abnormality occurs with respect to the recording medium, controlling the movement speed of the head unit. [Explanation of Symbols]

[0070] 1. Image forming apparatus 10 Image forming unit 11 Drums 12 Head Units 12a~12f Liquid Dispensing Head 13 Detection means 20 Paper feed section 30 Resist adjustment section 40 Drying section 50 Recording medium inversion section 60 First paper output section 61 Second paper output section 70 Control device 71 Detection unit 72 Control Unit W recording medium [Prior art documents] [Patent Documents]

[0071] [Patent Document 1] International Publication No. 2018 / 061939

Claims

1. A detection unit for detecting abnormalities in the transport of a recording medium in a cylindrical drum that transports the recording medium while winding it, A control unit that controls the position of a head unit equipped with a liquid discharge head that discharges liquid onto the recording medium and the movement speed of the head unit, Equipped with, The control unit controls the movement speed of the head unit when a transport abnormality occurs in the recording medium. Control device.

2. The control unit controls the head unit in either a position control mode for controlling the position of the head unit or a speed control mode for controlling the movement speed of the head unit, and controls the head unit in the speed control mode when at least one transport abnormality occurs in the recording medium. The control device according to claim 1.

3. In the speed control mode, the control unit calculates the movement speed of the head unit based on the print information for controlling the operation of the head unit and the operating speed of the power source of the head unit. The control device according to claim 2.

4. In the speed control mode, the control unit causes the retraction movement of the head unit to be performed at a speed faster than the movement speed of the head unit during normal operation. The control device according to claim 3.

5. The power source for the head unit is a DC brushless motor or a DC motor. The control device according to claim 3.

6. The control unit controls the operation of the drum and the head unit to perform a recovery operation after processing the recording medium in the event of a transport error. The control device according to claim 1.

7. When the detection unit detects the transport abnormality, it detects the amount by which the recording medium is lifted from the surface of the drum. The control unit moves the head unit according to the amount of movement of the head unit based on the amount of lift. The control device according to claim 1.

8. The control unit performs print stop control to stop printing when the amount of lifting is greater than or equal to a threshold, and performs print continue control when the amount of lifting is less than a threshold. The control device according to claim 7.

9. The control unit controls the output of the recording medium that was not printed due to the print stop control and the recording medium that was printed by normal printing to different output positions. The control device according to claim 8.

10. A cylindrical drum that transports the recording medium while winding it around it, A head unit equipped with a liquid dispensing head that dispenses liquid onto the recording medium, A control unit that controls the position of the head unit and the movement speed of the head unit, A detection unit for detecting abnormalities in the transport of the recording medium in the drum, Equipped with, The control unit controls the movement speed of the head unit when a transport abnormality occurs in the recording medium. Image forming apparatus.

11. A drive control method performed by a control device, A step of detecting an abnormality in the transport of the recording medium in a cylindrical drum that transports the recording medium while winding it around it, The steps include controlling the position of a head unit equipped with a liquid discharge head that discharges liquid onto the recording medium and the movement speed of the head unit, If a transport abnormality occurs in the recording medium, the step of controlling the movement speed of the head unit, A drive control method including

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