Coating apparatus and liquid dispensing apparatus

Abstract

When correcting the speed of the transport unit, uneven application of the liquid applied to the recording medium is reduced. [Solution] The system comprises a transport unit that applies a liquid to a recording medium by rotational motion while transporting the recording medium in a predetermined transport direction, a drive unit that rotates the transport unit, a control unit that outputs a speed command value which is a digital signal to the drive unit, a D / A converter that converts the speed command value output from the control unit into an analog voltage value, and a drive circuit that controls the rotational speed of the transport unit by the drive unit using the analog voltage value converted by the D / A converter, wherein the control unit calculates a speed command correction amount to correct the speed command value to the drive unit, and reflects the speed command correction amount in the speed command value while the transport unit is not transporting the recording medium.

Description

Technical Field

[0004]

[0001] The present invention relates to a coating device and a liquid ejection device.

Background Art

[0002] In a liquid ejection device that ejects a liquid such as ink onto a medium as a recording medium to perform image forming printing, a technique for improving image quality by applying a pretreatment agent to the medium during the image forming process is known. Generally, before the image forming process, while supporting the medium with a coating roller containing the treatment agent and a conveyance roller on the side facing the medium, the treatment agent is applied by the coating roller when the medium passes through. Such a liquid ejection device conventionally performs motor speed control based on an analog voltage value obtained by analog-converting a digital speed command value using a DA board equipped with a D / A converter.

[0003] By the way, in the motor speed control based on an analog voltage value using a conventional DA board, there is a problem that an offset of the analog voltage occurs in the DA board, causing the conveyance speed to deviate from the target speed and affecting the conveyance accuracy. Also, in the conveyance of the medium in the liquid ejection device, there is a problem that the conveyance speed changes due to torque fluctuations during medium conveyance and wear of the conveyance roller.

[0004] Therefore, Patent Document 1 discloses a technique for rotating a motor at a certain speed command value and calculating and correcting the offset amount of the speed command value from the difference between the rotation speed and the ideal rotation speed. Also, Patent Document 2 discloses a technique for calculating the actual medium conveyance speed using a conveyance sensor or the like and correcting the rotation speed of each driving means so as to reach a predetermined target speed.

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with conventional speed correction methods, when speed correction is performed while applying a pre-coating agent to the media surface with a coating roller, there are areas within the media where the coating roller moves slowly and areas where it moves quickly, resulting in uneven application of the treatment agent.

[0006] The present invention has been made in view of the above, and aims to reduce uneven application of the liquid applied to the recording medium when correcting the speed of the transport unit. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention comprises: a transport unit that applies a liquid to a recording medium by rotational motion while transporting the recording medium in a predetermined transport direction; a drive unit that rotates the transport unit; a control unit that outputs a speed command value, which is a digital signal to the drive unit; a D / A converter that converts the speed command value output from the control unit into an analog voltage value; and a drive circuit that controls the rotational speed of the transport unit by the drive unit using the analog voltage value converted by the D / A converter, wherein the control unit calculates a speed command correction amount to correct the speed command value to the drive unit, and reflects the speed command correction amount in the speed command value while the transport unit is not transporting the recording medium. [Effects of the Invention]

[0008] According to the present invention, when correcting the speed of the transport unit, it is possible to reduce unevenness in the application of the liquid applied to the recording medium. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of the overall configuration of an image forming apparatus according to the first embodiment. [Figure 2] Figure 2 shows another example of the overall configuration of an image forming apparatus. [Figure 3]Figure 3 shows an example of the configuration of a pre-coating unit in an image forming apparatus. [Figure 4] Figure 4 shows an example of the configuration of the coating section of the pre-coating unit of an image forming apparatus. [Figure 5] Figure 5 shows an example of the configuration of the coating rollers in the coating section of the pre-coating unit of an image forming apparatus. [Figure 6] Figure 6 shows another example of the configuration of the coating rollers in the coating section of the pre-coating unit of an image forming apparatus. [Figure 7] Figure 7 shows an example of the hardware configuration of an image forming apparatus. [Figure 8] Figure 8 shows an example of the relationship between the speed of the coating roller and the amount of media applied. [Figure 9] Figure 9 shows an example of the configuration of a functional block in an image forming apparatus. [Figure 10] Figure 10 is a flowchart showing the flow of the drive control process for the coating roller. [Figure 11] Figure 11 is a flowchart showing the flow of the drive control process for the coating roller according to the second embodiment. [Figure 12] Figure 12 is a flowchart showing the flow of the drive control process for the coating roller according to the third embodiment. [Figure 13] Figure 13 shows an example of a lookup table between media type and correction amount. [Modes for carrying out the invention]

[0010] Embodiments of the coating apparatus and liquid dispensing apparatus will be described in detail below with reference to the attached drawings.

[0011] (First Embodiment)

[0012] Hereinafter, embodiments of the coating device and the liquid ejection device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the following embodiments, and the constituent elements in the following embodiments include those that can be easily conceived by those skilled in the art, substantially identical ones, and those within the so-called equivalent range. Furthermore, various omissions, substitutions, changes, and combinations of the constituent elements can be made without departing from the gist of the following embodiments.

[0013] (Overall Configuration of Image Forming Apparatus) FIG. 1 is a diagram showing an example of the overall configuration of an image forming apparatus according to the first embodiment. FIG. 2 is a diagram showing another example of the overall configuration of the image forming apparatus. With reference to FIGS. 1 and 2, the overall configuration of an image forming apparatus 100, which is an example of the liquid ejection device according to the present embodiment, will be described.

[0014] The image forming apparatus 100 shown in FIG. 1 is a commercial printing machine that forms an image by an inkjet method of ejecting ink (liquid) onto a medium (recording medium) such as paper. The image forming apparatus 100 includes a paper feeding unit 101, a pre-coating unit 108 (coating device), a registration unit 102, an image forming unit 103, a drying unit 104, a cooling unit 105, a reversing unit 106, and a paper discharging unit 107.

[0015] Note that the recording medium may be other media such as plain paper, glossy paper, special paper, non-permeable substrates, ceramics, glass, or metal. Also, the recording medium may be a fabric used for clothing such as a T-shirt, textile, leather, or a building material such as wallpaper, flooring, or tiles.

[0016] The paper feeding unit 101 is a unit that separates and conveys media one by one from the paper feeding tray 120. The separated and conveyed media is fed to the pre-coating unit 108. The paper feeding unit 101 can switch the conveyance path of the media depending on whether the pre-coating of the treatment agent is performed in the pre-coating unit 108 or not. When the pre-coating of the treatment agent is not performed, the paper feeding unit 101 conveys the media along the conveyance path b shown in FIG. 1. When the pre-coating of the treatment agent is performed, the paper feeding unit 101 conveys the media along the conveyance path a shown in FIG. 1. In this embodiment, since it is premised that the pre-coating of the treatment agent is performed on the media in the pre-coating unit 108, the paper feeding unit 101 will be described as conveying the media along the conveyance path a.

[0017] The pre-coating unit 108 is a unit for applying a pre-coating treatment agent to one or both sides of the media conveyed and fed along the conveyance path a from the paper feeding unit 101. The pre-coating unit 108 conveys the media pre-coated with the treatment agent by the pre-coating unit 108 to the resist unit 102. The pre-coating treatment agent is applied as a pre-treatment for the imaging process in the imaging unit 103, and it improves the cohesiveness of the ink landing on the media.

[0018] The resist unit 102 is a unit that properly corrects the posture of the media conveyed from the pre-coating unit 108. The resist unit 102 conveys the media whose posture has been corrected by the resist unit 102 to the imaging unit 103.

[0019] The imaging unit 103 is a unit that performs imaging printing by discharging ink (liquid) onto the media conveyed from the resist unit 102. As shown in FIG. 1, the imaging unit 103 includes an imaging conveyance drum 103a and an inkjet head 103b (discharge head).

[0020] The image transfer drum 103a is a transfer drum that rotates and transfers the media transferred from the resist unit 102 to the inkjet head 103b. The inkjet head 103b is an ejection head that ejects ink onto the media transferred by the image transfer drum 103a to perform image printing.

[0021] The image-forming unit 103 transports the media that has been image-printed by the image-forming unit 103 to the drying unit 104.

[0022] The drying unit 104 is a unit that dries the media transported from the imaging unit 103. In the example of the image forming apparatus 100 shown in Figure 1, there is one drying unit 104, but this is not the only option, and multiple units may be provided depending on the drying conditions. The drying unit 104 transports the media that has been dried by the drying unit 104 to the cooling unit 105.

[0023] The cooling unit 105 is a unit that cools the dried media transported from the drying unit 104. The cooling unit 105 then transports the media cooled by the cooling unit 105 to the inversion unit 106.

[0024] The inversion unit 106 is a unit that, when printing on both sides of the media transported from the cooling unit 105, inverts the media by switching it back in path d, as shown in Figure 1, and transports it to the double-sided transport path 110. The media transported to the double-sided transport path 110 is re-feeded to the resist unit 102. The printing unit 103 prints on the second side, which is the back side of the first side that has already been printed on in the printing unit 103.

[0025] Furthermore, when printing on only one side of the media transported from the cooling unit 105, the reversing unit 106 transports the media to the paper output unit 107 via the transport path c, as shown in Figure 1.

[0026] The paper output unit 107 is a unit that outputs the media transported from the reversing unit 106 to the paper output tray.

[0027] In the image forming apparatus 100 shown in Figure 1, when the media to be printed on both sides is inverted by the inversion unit 106, an example is shown in which the media is re-feed by the resist unit 102, i.e., re-feed downstream of the pre-coating unit 108. However, as shown in the image forming apparatus 100a in Figure 2, the media may be re-feed upstream of the pre-coating unit 108.

[0028] Figure 2 shows an example of the image forming apparatus 100a where the media is re-feed in the paper feed unit 101a upstream of the pre-coating unit 108. In Figure 2, the configuration of the units downstream of the image-making unit 103 is the same as in Figure 1, so it is omitted from the illustration. The media separated and transported from the paper feed tray 120 in the paper feed unit 101a is pre-coated with a processing agent in the pre-coating unit 108, then its orientation is corrected in the resist unit 102a, and it is transported to the image-making unit 103. In the case of a double-sided printing plant, as in Figure 1, the media that has been inverted in the inversion unit 106 is re-feeded in the paper feed unit 101a upstream of the pre-coating unit 108 via the double-sided transport path 110a, and transported back to the pre-coating unit 108. In the pre-coating unit 108, the processing agent is pre-coated on the second side, which is the back side of the first side that has already been pre-coated and image-printed, and then image-printing is performed on the second side in the image-making unit 103.

[0029] (Configuration of the pre-coating unit) Figure 3 shows an example of the configuration of the pre-coating unit of the image forming apparatus. Figure 4 shows an example of the configuration of the coating section of the pre-coating unit of the image forming apparatus. Figure 5 shows an example of the configuration of the coating rollers in the coating section of the pre-coating unit of the image forming apparatus. Figure 6 shows another example of the configuration of the coating rollers in the coating section of the pre-coating unit of the image forming apparatus. The configuration of the pre-coating unit 108 of the image forming apparatus 100 according to this embodiment will be described with reference to Figures 3 to 6.

[0030] As shown in Figure 3, the pre-coating unit 108 includes a coating section 108a, inlet rollers 301-305, outlet rollers 306-309, purge rollers 310-313, a re-inlet roller 314, and outlet rollers 315 and 316.

[0031] The coating unit 108a is a device that enters the pre-coating unit 108 from the inlet H and applies a pre-coating agent to the media conveyed by the inlet rollers 301 to 305. Details of the configuration of the coating unit 108a will be described later.

[0032] The inlet rollers 301-305 are transport rollers that transport the media that has entered the pre-coating unit 108 from the inlet H to the coating section 108a along the transport path A.

[0033] The exit rollers 306-309 are rollers that transport the media coated with the treatment agent in the coating section 108a along the transport paths B and C shown in Figure 3.

[0034] When applying a treatment agent to both sides of a media, the media is first coated on the first surface at the coating section 108a, then passes through exit rollers 306-309, and is then transported along the transport path D by a purge roller 310 via branching claws (not shown).

[0035] On the other hand, when the treatment agent is applied to only one side of the media, the media is first coated on the first surface in the coating section 108a, then passes through the exit rollers 306-309, and is then transported to the resist unit 102 along the transport path J by exit rollers 315 and 316 via branching claws (not shown).

[0036] The purge roller 310 is a conveying roller used to transport media coated with a treatment agent on its first surface to purge rollers 311-313 for switchback.

[0037] The purge rollers 311-313 are transport rollers that transport the media conveyed by the purge roller 310 along the transport paths E and G shown in Figure 3, and then switch back. The media that has been switched back by the purge rollers 311-313 is transported again to the coating section 108a along the transport path F by the re-entry roller 314, and the treatment agent is applied to the second surface. The transport paths E and G used by the purge rollers 311-313 can also be used as purge paths.

[0038] The re-entry roller 314 is a conveying roller that transports the media, which has been switched back by the purge rollers 311-313, to the coating section 108a along the transport path F.

[0039] Exit rollers 315 and 316 are transport rollers that transport the media, which has been transported along transport paths B and C by exit rollers 307 to 309, to the resist unit 102 along transport path J.

[0040] Furthermore, as shown in the image forming apparatus 100a in Figure 2, when the media inverted by the inversion unit 106 is re-feed upstream of the pre-coating unit 108, it is possible to apply the processing agent to both sides of the media in the pre-coating unit 108 before it is transported to the resist unit 102a. Alternatively, the media may be coated only on the first side in the pre-coating unit 108 and then transported to the resist unit 102a, where an image is printed on the first side, and then, via the double-sided transport path 110a, the processing agent is applied to the second side in the pre-coating unit 108. In this case, since there is no need to switch back the media within the pre-coating unit 108, the pre-coating unit 108 may not include the purge rollers 310-313 and the re-entry roller 314.

[0041] With the above configuration, as shown in Figure 3, the media discharged from the paper feeding unit 101 is transported from the inlet H to the coating unit 108a via the transport path A. The media coated with the treatment agent by the coating unit 108a is sent to the transport path C via the transport path B. When the treatment agent is applied to only one side, the media coated with the treatment agent by the coating unit 108a is sent directly to the resist unit 102 via the horizontal transport path J.

[0042] Next, the specific configuration of the coating section 108a of the pre-coating unit 108 will be described with reference to Figures 4 to 6.

[0043] As shown in Figure 4, the coating section 108a includes a coating roller 201, a fixed roller 202, a squeeze roller 203, a pressure roller 204, a press roller 205, a pan for the processing agent liquid 211, an inlet sensor 511, and an outlet sensor 512. As shown in Figure 4, the rollers are arranged from bottom to top in the order of squeeze roller 203, fixed roller 202, coating roller 201, pressure roller 204, and press roller 205.

[0044] The coating roller 201 is a roller that applies a liquid pre-coating agent supplied from the surface of the fixed roller 202 to the underside of the media P conveyed from the upstream conveying path 212 by rotational motion. The coating roller 201 is also a conveying unit that, together with the pressure roller 204, grips the media P to which the pre-coating agent has been applied and conveys it toward the downstream conveying path 213. Details of the configuration of the coating roller 201 will be described later.

[0045] The fixed roller 202 is a roller that supplies the processing agent supplied from the squeeze roller 203 to the coating roller 201 by rotational motion.

[0046] The squeeze roller 203 is impregnated with the treatment agent contained in the treatment agent liquid pan 211 and supplies the treatment agent to the fixed roller 202 by rotational motion. The squeeze roller 203 also has the function of agitating the treatment agent contained in the treatment agent liquid pan 211.

[0047] The pressure roller 204 is a roller that applies pressure to the coating roller 201 from above. In addition, when the media P is conveyed to the coating roller 201 from the upstream conveying path 212, the pressure roller 204 applies pressure to the media P against the coating roller 201.

[0048] The pressing roller 205 applies a downward load to the pressure roller 204 and the coating roller 201, and rotates together with the rotation of the pressure roller 204.

[0049] The media P, transported from the upstream transport path 212, is coated with processing liquid by the coating roller 201 and then transported via the downstream transport path 213 to the outlet roller 306 side shown in Figure 3. The coating roller 201, fixed roller 202, squeeze roller 203, and pressure roller 204 are all rotated by the same drive source, motor 206, which will be described later. Of these, the coating roller 201 and squeeze roller 203 rotate clockwise in the view of Figure 4, while the fixed roller 202 and pressure roller 204 rotate counterclockwise in the view of the same figure.

[0050] The treatment agent liquid pan 211 is a pan for storing liquid treatment agents.

[0051] The inlet sensor 511 is a sensor that detects the media P being transported along the upstream transport path 212. The outlet sensor 512 is a sensor that detects the media P being transported along the downstream transport path 213 after the processing agent has been applied by the coating roller 201.

[0052] With the above configuration, as shown in Figure 4, the media P transported along the upstream transport path 212 passes through the inlet sensor 511, then the processing agent is applied to the surface of the media P between the coating roller 201 and the pressure roller 204, and then it is transported along the downstream transport path 213 and passes through the outlet sensor 512.

[0053] Next, the specific configuration of the coating roller 201 will be described with reference to Figure 5.

[0054] As shown in Figure 5, the coating roller 201 includes a roller body 201a, a roller core 201b, a bearing 201c, and a reduction gear 201d.

[0055] The roller body 201a is the roller portion that forms the main body of the coating roller 201. The roller core 201b is a metal rod member that passes through the roller body 201a in the axial direction. The bearing 201c is a bearing member that supports both ends of the roller core 201b. The reduction gear 201d is a gear fixed to one end of the bearing 201c.

[0056] The coating unit 108a further includes a motor 206 (an example of a drive unit) and an encoder 207, as shown in Figure 5. The motor 206 is preferably an AC servo motor with high output and high responsiveness. The motor 206 includes a motor shaft 206b that rotates by rotational drive, and a motor gear 206a fixed to the tip of the motor shaft 206b.

[0057] As shown in Figure 5, the reduction gear 201d and the motor gear 206a are meshed together. Therefore, when the motor shaft 206b rotates due to the rotational drive of the motor 206, the coating roller 201 rotates via the motor gear 206a and the reduction gear 201d. Furthermore, the coating roller 201 has a greater degree of freedom in the vertical direction, and is configured to be displaced vertically by pressure.

[0058] The encoder 207 is attached to the motor shaft 206b of the motor 206. The encoder 207 is a sensor that detects the rotational speed of the motor 206. The encoder 207 transmits the detected rotational speed of the motor 206 to the coating section roller driver 411, which will be described later.

[0059] The coating unit 108a may have an encoder-integrated motor 208 (an example of a drive unit) as shown in Figure 6, instead of the motor 206 that rotates the coating roller 201. The motor 208 shown in Figure 6 includes a motor shaft 208b that rotates due to rotational drive, a motor gear 208a fixed to the tip of the motor shaft 208b, and an encoder 208c built into the body of the motor 208. In this case, the reduction gear 201d and the motor gear 208a mesh, so when the motor shaft 208b rotates due to the rotational drive of the motor 208, the coating roller 201 rotates via the motor gear 208a and the reduction gear 201d. In the following description, the coating unit 108a will be described as having the motor 206 shown in Figure 5.

[0060] (Hardware configuration of image forming apparatus) Figure 7 shows an example of the hardware configuration of an image forming apparatus. Referring to Figure 7, the hardware configuration of the image forming apparatus 100 according to this embodiment will be explained, focusing on the part related to the pre-coating unit 108.

[0061] As shown in Figure 7, the image forming apparatus 100 includes a CPU (Central Processing Unit) 401, a ROM (Read Only Memory) 402, a RAM (Random Access Memory) 403, an NVRAM (Non-Volatile Random Access Memory) 404, an external device connection I / F 408, a network I / F 409, a coating section roller driver 411 (drive circuit), a transport roller driver 412, a sub-scanning driver 413, a sensor I / F 414, an inkjet head driver 420, an operation panel 430, and a DA substrate 440 having a D / A converter 441.

[0062] The CPU 401 is an arithmetic unit that controls the entire image forming apparatus 100. The ROM 402 is a non-volatile memory device that stores programs such as the IPL (Initial Program Loader). The RAM 403 is a volatile memory device used as the work area for the CPU 401.

[0063] NVRAM404 is a non-volatile memory device that stores various data such as programs and retains various data even when the power supply to the image forming apparatus 100 is turned off.

[0064] The CPU 401, ROM 402, RAM 403, and NVRAM 404 constitute the control unit 450.

[0065] The External Device Connection I / F408 is an interface that connects to external devices such as PCs (Personal Computers) via USB (Universal Serial Bus) cables, etc., and communicates control signals and data to be printed between the external device and the interface.

[0066] Network I / F409 is a TCP (Transmission Control Protocol) / IP (Internet Protocol) compliant interface for data communication via the Internet or a LAN (Local Area Network), etc. Network I / F409 may also be a wired communication interface compliant with Ethernet®, etc., or a wireless communication interface compliant with Wi-Fi®, etc.

[0067] The control unit 450 outputs a speed command value for the motor 206. The speed command value for the motor 206 from the control unit 450 is output as a 12-bit digital value. The D / A converter 441 on the DA board 440 converts the speed command value from the control unit 450 into an analog voltage value of -10V to +10V proportional to the speed command value and outputs it to the coating roller driver 411.

[0068] The coating section roller driver 411 is a drive circuit for driving the motor 206 that rotates the coating roller 201 of the pre-coating unit 108. The coating section roller driver 411 rotates the motor 206 by outputting a drive current to the motor 206 that rotates the coating roller 201. The coating section roller driver 411 controls the speed of the motor 206 using the analog voltage value converted by the D / A converter 441 of the DA board 440 as a speed command value.

[0069] The transport roller driver 412 is a drive circuit for independently rotating the inlet rollers 301-305, outlet rollers 306-309, purge rollers 310-313, re-inlet roller 314, and outlet rollers 315 and 316 of the pre-coating unit 108.

[0070] The sub-scanning driver 413 is a drive circuit for rotating the image transport drum 103a of the image unit 103 in order to transport the media in the transport direction, i.e., the sub-scanning direction.

[0071] Sensor I / F414 is an interface for receiving signals detected by sensors such as the inlet sensor 511, the outlet sensor 512, and the encoder 207.

[0072] The inkjet head driver 420 is a drive circuit for controlling the ejection operation of the inkjet head 103b.

[0073] The control panel 430 is a device that displays setting information and various screens for the image forming apparatus 100, and includes a touch panel and alarm lamps for receiving user input.

[0074] The CPU 401, ROM 402, RAM 403, NVRAM 404, external device connection I / F 408, network I / F 409, coating roller driver 411, transport roller driver 412, sub-scanning driver 413, sensor I / F 414, inkjet head driver 420, operation panel 430, and DA board 440 (D / A converter 441) are all capable of data communication with each other via bus 410, which includes an address bus and a data bus.

[0075] Furthermore, the hardware configuration of the image forming apparatus 100 shown in Figure 7 is an example, and it is not necessary to include all of the components shown in Figure 7, or other components may be included.

[0076] (Previous problems) Here, I will briefly explain the conventional problems.

[0077] Firstly, in controlling the speed of the motor 206 using analog voltage values ​​obtained by converting digital signals to analog using the D / A converter 441 of the DA board 440, there is a problem that an offset in the analog voltage occurs in the DA board 440, causing the transport speed to deviate from the target speed and affecting transport accuracy.

[0078] Secondly, in media transport, the transport speed can change due to torque fluctuations during media transport and wear of the transport rollers, and if the speed of the coating roller 201 fluctuates during media transport, uneven coating can occur.

[0079] To solve the problems described above, techniques are known that involve rotating a motor at a certain command value, calculating and correcting the offset amount of the command value from the difference between that rotation speed and the ideal rotation speed, and calculating the actual media transport speed using transport sensors, etc., and correcting the rotation speed of each drive means so that it reaches the target predetermined speed.

[0080] However, with conventional speed correction methods, when speed correction is performed while the coating roller is applying a pre-coating agent to the media surface, areas with slower and faster speeds on the coating roller occur within the media, resulting in uneven application of the processing agent. Figure 8 shows an example of the relationship between the speed of the coating roller 201 and the amount of processing agent applied to the media. As shown in Figure 8, when the speed of the coating roller 201 is high, the amount of processing agent applied from the coating roller 201 to the media decreases. On the other hand, when the speed of the coating roller 201 is low, the amount of processing agent applied from the coating roller 201 to the media increases. Therefore, if the speed of the coating roller 201 fluctuates during media transport, uneven application will occur.

[0081] Therefore, in this embodiment, the reflection of the analog speed command to the motor 206 that drives the coating roller 201 is performed when no media is passing over the coating roller 201, that is, between the time the exit sensor 512 is not detected (the trailing end of the preceding media in the transport direction passes the position of the exit sensor 512) and the time the inlet sensor 511 is detected (the leading end of the subsequent media in the transport direction passes the position of the inlet sensor 511), thereby performing speed correction without causing uneven coating. This point will be described in detail below.

[0082] (Configuration and operation of the functional blocks of the image forming apparatus) Figure 9 shows an example of the configuration of a functional block in an image forming apparatus according to this embodiment. The configuration and operation of the functional block of the image forming apparatus 100 according to this embodiment will be described with reference to Figure 9.

[0083] As shown in Figure 9, the control unit 450 of the image forming apparatus 100 includes a sensor detection unit 501, a roller control unit 502, a transport control unit 503, and a storage unit 504.

[0084] The sensor detection unit 501 is a functional unit that acquires detection signals from the inlet sensor 511 and the outlet sensor 512, which detect the media, via the sensor I / F 414.

[0085] The roller control unit 502 is a functional unit that controls the rotation of the coating roller 201 via the coating roller driver 411. The roller control unit 502 outputs a speed command value for the motor 206 as a 12-bit digital value.

[0086] The transport control unit 503 is a functional unit that independently controls the rotation of the inlet rollers 301-305, outlet rollers 306-309, purge rollers 310-313, re-inlet roller 314, and outlet rollers 315 and 316 of the pre-coating unit 108 via the transport roller driver 412.

[0087] The memory unit 504 is a functional unit that stores various types of information. The memory unit 504 is implemented by the ROM 402 or NVRAM 404 shown in Figure 7.

[0088] The sensor detection unit 501, roller control unit 502, and transport control unit 503 described above are implemented by the execution of a program by the CPU 401 shown in Figure 7. At least a portion of the sensor detection unit 501, roller control unit 502, and transport control unit 503 may be implemented by hardware circuits such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits).

[0089] It should be noted that the functional units of the image forming apparatus 100 shown in Figure 9 are conceptual representations of their functions and are not limited to this configuration. In other words, each functional unit of the image forming apparatus 100 does not need to be configured as a distinct software module as a block as shown in Figure 9; the functions of each functional unit can be realized as a whole when a program is executed in the image forming apparatus 100. For example, multiple functional units shown as independent functional units in the image forming apparatus 100 in Figure 9 may be configured as a single functional unit. Alternatively, the functions of one functional unit in the image forming apparatus 100 shown in Figure 9 may be divided into multiple functions and configured as multiple functional units.

[0090] (Control of the motor 206 that drives the coating roller 201 in the pre-coating unit 108)

[0091] Here, Figure 10 is a flowchart showing the flow of the drive control process for the coating roller 201. As a premise for the process shown in Figure 10, the printing interval between media (the distance between the preceding media and the succeeding media) is assumed to be longer than the distance from the inlet sensor 511 to the outlet sensor 512. The control unit 450 of the image forming apparatus 100 determines the paper interval as the time from when the media passes the outlet sensor 512 until the next media detects the inlet sensor 511. In other words, the control unit 450 sets the printing interval between media to be longer than the distance from the inlet sensor 511 to the outlet sensor 512.

[0092] First, the sensor detection unit 501 determines whether the inlet sensor 511 has detected that the media has passed through (step S1).

[0093] When the sensor detection unit 501 determines that the media has passed through the entrance sensor 511 (Yes in step S1), the roller control unit 502 determines whether the media is the final sheet or not (step S2). For example, the roller control unit 502 determines that the media is the final sheet when a predetermined number of sheets of media have passed through the entrance sensor 511.

[0094] The roller control unit 502 terminates the process if it determines that the media is the final sheet (Yes in step S2).

[0095] On the other hand, if the roller control unit 502 determines that the media is not the final sheet (No. in step S2), it calculates the actual coating roller speed Vr, which is the roller rotation speed of the coating roller 201, using the encoder 207 attached to the motor shaft 206b of the motor 206, or an encoder inside the motor 208 with a built-in encoder (step S3).

[0096] The roller control unit 502 may also calculate the actual coating roller speed Vr based on the media transport speed calculated from the detection timings of the inlet sensor 511 and outlet sensor 512 obtained from the sensor detection unit 501.

[0097] Next, the roller control unit 502 calculates the speed command correction amount x for the motor 206 from the difference between the ideal transport speed Vi and the actual application roller speed Vr, where Vi is the ideal transport speed of the media (step S4).

[0098] Next, the sensor detection unit 501 determines whether the exit sensor 512 has detected that the media has passed through (step S5).

[0099] When the sensor detection unit 501 determines that the exit sensor 512 has detected that the media has passed through (Yes in step S5), the roller control unit 502 reflects the motor 206 speed command correction amount x calculated in step S4 into the analog speed command for the motor 206 that drives the coating roller 201 (step S6), thereby bringing the actual coating roller speed Vr closer to the ideal media transport speed Vi.

[0100] As described above, the reflection of the analog speed command to the motor 206 that drives the coating roller 201 is performed when no media is passing over the coating roller 201, that is, between the time the exit sensor 512 is not detected (the trailing end of the preceding media in the transport direction passes the position of the exit sensor 512) and the time the inlet sensor 511 is detected (the leading end of the following media in the transport direction passes the position of the inlet sensor 511).

[0101] By using this method, the actual speed Vr of the coating roller can be kept constant while the media is passing through the coating roller 201, thereby reducing unevenness in the amount of coating applied within the media.

[0102] As described above, according to this embodiment, a speed command correction amount is calculated to correct the speed command value for the drive unit, and the reflection of this speed command correction amount in the speed command value is carried out while the transport unit is not transporting the recording medium. This eliminates the occurrence of areas within the recording medium where the transport unit is moving at a slower speed and areas where it is moving at a faster speed. As a result, uneven application of liquids applied to the recording medium, such as uneven application of pre-coating agents, can be reduced.

[0103] (Second Embodiment) Next, a second embodiment will be described.

[0104] The second embodiment differs from the first embodiment in that it performs speed correction on the first media. In the following description of the second embodiment, the parts that are the same as those in the first embodiment will be omitted, and the parts that differ from the first embodiment will be described.

[0105] Here, Figure 11 is a flowchart showing the flow of the drive control process for the coating roller 201 according to the second embodiment.

[0106] As shown in Figure 11, first, the roller control unit 502 starts rotating the coating roller 201 either before printing (coating) begins or after printing (coating) has begun but before the media reaches the coating roller 201 (step S11).

[0107] Next, the roller control unit 502 calculates the actual coating roller speed Vr, which is the roller rotation speed of the coating roller 201, using the encoder 207 attached to the motor shaft 206b of the motor 206, or an encoder inside the motor 208 with a built-in encoder (step S12).

[0108] Next, the roller control unit 502 calculates the speed command correction amount x for the motor 206 from the difference between the ideal transport speed Vi and the actual application roller speed Vr, assuming that the ideal transport speed of the media is Vi (step S13).

[0109] Next, the roller control unit 502 reflects the speed command correction amount x of the motor 206 calculated in step S13 as an analog speed command to the motor 206 that drives the coating roller 201 (step S14), thereby bringing the actual speed Vr of the coating roller closer to the ideal conveying speed Vi of the media.

[0110] For example, the roller control unit 502 corrects the actual speed Vr of the coating roller so that it becomes the actual rotational speed of the media at the ideal transport speed Vi = 3000 rpm.

[0111] This allows speed fluctuations caused by inherent offset voltages due to the DA substrate 440 and the machine environment to be corrected before the media reaches the coating roller 201.

[0112] Thus, according to this embodiment, for example, after a predetermined time has elapsed since the application roller 201 was driven until the rotational speed stabilized, and before the inlet sensor 511 detects the first media (when the leading edge of the media in the transport direction passes the position of the inlet sensor 511), a speed command correction amount can be calculated to correct the speed command value for the drive unit, and this speed command correction amount can be reflected in the speed command value.

[0113] (Third embodiment) Next, a third embodiment will be described.

[0114] The third embodiment differs from the second embodiment in that it stores optimal roller rotation speed information for each media type in advance. In the following description of the third embodiment, the description of parts that are the same as those of the first or second embodiment will be omitted, and the parts that differ from the first and second embodiments will be described.

[0115] Here, Figure 12 is a flowchart showing the flow of the drive control process for the coating roller 201 according to the third embodiment. In this embodiment, in addition to the processing flow described in the second embodiment, the optimal roller rotation speed information (correction amount) for each media is stored in advance in the storage unit 504 of the control unit 450, thereby correcting the speed reduction for each media more precisely.

[0116] The storage unit 504 of the image forming apparatus 100 stores the media type and the correction amount y in association. Figure 13 shows an example of a lookup table for media type and correction amount y. The lookup table shown in Figure 13 associates the media type with the correction amount y. In this embodiment, a lookup table like the one shown in Figure 13 is pre-stored in the storage unit 504.

[0117] As shown in Figure 12, first, the roller control unit 502 starts rotating the coating roller 201 either before or after printing has started and before the media reaches the coating roller 201 (step S11).

[0118] Next, the roller control unit 502 calculates the actual coating roller speed Vr, which is the roller rotation speed of the coating roller 201, using the encoder 207 attached to the motor shaft 206b of the motor 206, or an encoder inside the motor 208 with a built-in encoder (step S12).

[0119] Next, the roller control unit 502 calculates the speed command correction amount x for the motor 206 from the difference between the ideal transport speed Vi and the actual application roller speed Vr, assuming that the ideal transport speed of the media is Vi (step S13).

[0120] Next, the roller control unit 502 reflects the speed command correction amount x of the motor 206 calculated in step S13 as an analog speed command to the motor 206 that drives the coating roller 201 (step S14), thereby bringing the actual speed Vr of the coating roller closer to the ideal conveying speed Vi of the media.

[0121] Next, the roller control unit 502 determines the media type from the print job information and calculates a correction amount y specific to the media type based on the lookup table shown in Figure 13, which is pre-stored in the storage unit 504 (step S21).

[0122] For example, assuming an ideal media transport speed Vi = 3000 rpm and an actual rotational speed of 3000 rpm, the required torque is generally higher for thicker paper and lower for thinner paper. Therefore, the optimal speed command correction amount x for motor 206 is assumed to be ±0% for standard paper, +0.1% for thicker paper, and -0.1% for thinner paper.

[0123] Therefore, in this embodiment, the roller control unit 502 corrects the rotation speed to 3000 rpm in step S14, and in the subsequent step S21, it determines the type of media to be used (print media information) from the print JOB information and calculates a correction amount y specific to the media type from the print media information.

[0124] Furthermore, the roller control unit 502 can acquire print job information from external devices connected via the external device connection I / F 408 or the network I / F 409.

[0125] Next, the roller control unit 502 reflects the correction amount y calculated in step S21 in the ideal transport speed Vi of the media, and sets the corrected ideal transport speed Vi2 (step S22).

[0126] For example, if the correction amount y for the next job being cardboard is 0.1%, the roller control unit 502 will: Corrected ideal transport speed Vi2 = 3000 rpm + 3000 rpm × 0.1% =3003rpm It outputs an analog voltage.

[0127] This allows the coating roller 201 to be transported at an optimal speed for each type of media. This process, as in the second embodiment, is completed before printing starts or after printing starts but before the media reaches the inlet sensor 511.

[0128] Thus, according to this embodiment, for example, after a predetermined time has elapsed since the application roller 201 was driven until the rotational speed stabilized, and before the inlet sensor 511 detects the first media (when the leading edge of the media in the transport direction passes the position of the inlet sensor 511), a speed command correction amount can be calculated to correct the speed command value for the drive unit, and this speed command correction amount can be reflected in the speed command value. Furthermore, the application roller 201 can be set to an optimal transport speed for each type of media.

[0129] Note that in the flowchart shown in Figure 12, corrections are made for each media type after the processing in step S14 shown in Figure 11. However, this is not the only option; the actual speed correction in steps S11 to S14 may be performed after reflecting the correction amount for each media type.

[0130] In the above-described embodiment, if at least one of the functional units of the image forming apparatus 100 is implemented by program execution, the program is provided pre-installed in ROM or the like. Furthermore, in the above-described embodiment, the program executed by the image forming apparatus 100 may be provided as an installable or executable file recorded on a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), flexible disk (FD), CD-R (Compact Disk-Recordable), or DVD (Digital Versatile Disc). Also, in the above-described embodiment, the program executed by the image forming apparatus 100 may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. Finally, in the above-described embodiment, the program executed by the image forming apparatus 100 may be provided or distributed via a network such as the Internet. Furthermore, in the above-described embodiment, the program executed by the image forming apparatus 100 is a module configuration that includes at least one of the above-described functional units, and in actual hardware, the CPU 401 reads the program from the above-described storage device (e.g., ROM 402, NVRAM 404, etc.) and executes it, thereby loading and generating the above-described functional units onto the main memory (RAM 403).

[0131] Examples of the present invention are as follows: <1> A conveying unit that applies a liquid to a recording medium by rotational motion while conveying the recording medium in a predetermined conveying direction, A drive unit that rotates the transport unit, A control unit that outputs a speed command value, which is a digital signal to the drive unit, A D / A converter that converts the speed command value output from the control unit into an analog voltage value, A drive circuit that controls the rotational speed of the transport unit by the drive unit based on the analog voltage value converted by the D / A converter, Equipped with, The control unit calculates a speed command correction amount to correct the speed command value for the drive unit, and reflects the speed command correction amount in the speed command value while the transport unit is not transporting the recording medium. A coating apparatus characterized by the following features. <2> An inlet sensor is provided on the upstream side in the transport direction relative to the transport section, An outlet sensor is provided on the downstream side in the transport direction relative to the transport section, Equipped with, The control unit reflects the speed command correction amount in the speed command value between the time the exit sensor becomes undetectable and the time the inlet sensor detects again. Characterized by <1> The coating apparatus described above. <3> The control unit calculates the speed command correction amount for the drive unit from the difference between the ideal transport speed of the recording medium and the actual speed of the transport unit. Characterized by <1> or <2> The coating apparatus described above. <4> The control unit calculates a speed command correction amount to correct the speed command value for the drive unit before coating or after coating has started but before the recording medium reaches the transport unit, and reflects the speed command correction amount in the speed command value. Characterized by <1> or <3> A coating apparatus as described in any one of the following. <5> The control unit, A table is stored in which the correction amount is associated with each type of recording medium. In addition to the speed command correction amount, the correction amount corresponding to the type of recording medium is reflected in the speed command value. Characterized by <4> The coating apparatus described above. <6> The aforementioned drive unit is an AC servo motor. Characterized by <1> or <5> A coating apparatus as described in any one of the following. <7> <1> or <6> A coating apparatus as described in any one of the following, A dispensing head for dispensing liquid onto a recording medium coated with liquid by the aforementioned coating device, A liquid dispensing device characterized by comprising the following features. [Explanation of Symbols]

[0132] 100 Liquid dispensing device 103b Discharge head 108 Coating device 201 Conveyor Unit 206, 208 Drive unit 411 Drive Circuit 441 D / A Converter 450 Control Unit 511 Entrance Sensor 512 Exit Sensor P recording medium [Prior art documents] [Patent Documents]

[0133] [Patent Document 1] Japanese Patent Publication No. 2000-222039 [Patent Document 2] Japanese Patent Publication No. 2005-320123

Claims

1. A conveying unit that applies a liquid to a recording medium by rotational motion while conveying the recording medium in a predetermined conveying direction, A drive unit that rotates the transport unit, A control unit that outputs a speed command value, which is a digital signal to the drive unit, A D / A converter that converts the speed command value output from the control unit into an analog voltage value, A drive circuit that controls the rotational speed of the transport unit by the drive unit based on the analog voltage value converted by the D / A converter, Equipped with, The control unit calculates a speed command correction amount to correct the speed command value for the drive unit, and reflects the speed command correction amount in the speed command value while the transport unit is not transporting the recording medium. A coating apparatus characterized by the following features.

2. An inlet sensor is provided on the upstream side in the transport direction relative to the transport section, An outlet sensor is provided on the downstream side in the transport direction relative to the transport section, Equipped with, The control unit reflects the speed command correction amount in the speed command value between the time the exit sensor becomes undetectable and the time the inlet sensor detects again. The coating apparatus according to feature 1.

3. The control unit calculates the speed command correction amount for the drive unit from the difference between the ideal transport speed of the recording medium and the actual speed of the transport unit. The coating apparatus according to feature 1.

4. The control unit calculates a speed command correction amount to correct the speed command value for the drive unit before coating or after coating has started but before the recording medium reaches the transport unit, and reflects the speed command correction amount in the speed command value. The coating apparatus according to feature 1.

5. The control unit, A table is stored in which the correction amount is associated with each type of recording medium. In addition to the speed command correction amount, the correction amount corresponding to the type of recording medium is reflected in the speed command value. The coating apparatus according to feature 4.

6. The aforementioned drive unit is an AC servo motor. The coating apparatus according to feature 1.

7. A coating apparatus according to any one of claims 1 to 6, A dispensing head for dispensing liquid onto a recording medium coated with liquid by the aforementioned coating device, A liquid dispensing device characterized by comprising the following features.

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