JP2005342960A - Ink feeder, recorder, ink feeding method, and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress variation of a negative pressure in a recording head to be small by positively controlling a feeding pressure of ink. <P>SOLUTION: A pump 36 and a valve 35 are set in an ink feeding passage between an ink tank 40 and the recording head 811. The feeding pressure of ink is positively controlled by activating the pump 36 and the valve 35. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink supply device and an ink supply method for supplying ink to which a negative pressure is applied to a recording head, and a recording device and a recording method for recording an image using the recording head.

  An ink jet recording apparatus that ejects ink from a recording head to a recording medium to form an image can form a high-definition image using a small recording head in which a plurality of nozzles are arranged at high density, It is known as having many advantages such as being able to realize colorization with a relatively inexpensive and small configuration by arranging a plurality of recording heads and supplying different colors of ink to each recording head. Yes. For this reason, the ink jet recording apparatus is used in various image output apparatuses such as printers, facsimiles, and copiers regardless of business use or home use.

  In such an ink jet recording apparatus, it is important to maintain the ink in the recording head at a constant negative pressure in order to stabilize the ink ejection operation of the recording head. Therefore, in general, an ink supply system that supplies ink to the recording head is provided with a negative pressure generating means, and ink to which negative pressure is applied by the negative pressure generating means is supplied to the recording head.

  Conventionally, as such a negative pressure generating means, there is a configuration in which a negative pressure is generated by utilizing the capillary action of a sponge-like ink absorber housed in an ink tank (for example, Patent Document 1). Further, in order to maintain the inside of the ink tank at a negative pressure, a configuration including a biasing means such as a spring for biasing the flexible member forming at least a part of the ink tank to the outside of the ink tank is adopted. (For example, Patent Document 2). There is also a configuration in which an ink tank is provided at a position below the recording head and a negative pressure is applied to the ink using a water head difference (for example, Patent Document 3).

  The ink to which a constant negative pressure is applied by such a negative pressure generating means is supplied so as to be drawn into the recording head due to a differential pressure from the negative pressure in the recording head that rises as the ink is ejected. The As a result, the inside of the recording head is maintained at a constant negative pressure.

Japanese Patent Application Laid-Open No. 07-068877 JP 2001-315350 A Japanese Patent Laid-Open No. 06-183018

  However, the ink supply system provided with the negative pressure generating means as described above utilizes the pressure difference caused by the negative pressure in the recording head that rises as the ink is ejected to remove ink from the ink tank to the recording head. For example, when the ink consumption per unit time in the recording head rapidly increases, the supply of ink cannot catch up, and the negative pressure in the recording head may increase. Further, when the ink consumption per unit time in the recording head is rapidly reduced, the negative pressure in the recording head may tend to decrease due to the inertia of the ink. When the negative pressure in the recording head fluctuates, the ink ejection operation of the recording head becomes unstable, and there is a possibility that the recording quality of the image is lowered. In particular, in an industrial recording apparatus that records an image on a large recording medium at high speed, the negative pressure in the recording head is likely to fluctuate due to the large range of instantaneous ink consumption change, resulting in high recording quality. In order to meet the demand, it is important to suppress the fluctuation of the negative pressure in the recording head.

  An object of the present invention is to provide an ink supply apparatus, a recording apparatus, an ink supply method, and a recording method that can suppress fluctuations in negative pressure in the recording head by actively controlling the ink supply pressure. There is.

  The ink supply device of the present invention is an ink supply device that applies a negative pressure to the ink accommodated in the ink tank and then supplies the negative pressure to the recording head. A pump provided in an ink supply path to the recording head and capable of pumping ink in the ink flow path in at least one direction; and an opening degree of the ink supply path provided in the ink supply path. And a control means for controlling the pump and the valve according to the pressure of the ink in the recording head so as to maintain the negative pressure of the ink in the recording head within a predetermined range. It is characterized by providing.

  According to another aspect of the present invention, there is provided a recording apparatus for recording an image using a recording head to which ink is supplied. The recording apparatus includes the ink supply apparatus described above for supplying ink to the recording head.

  The ink supply method of the present invention is an ink supply method for supplying a negative pressure to ink stored in an ink tank and then supplying the negative pressure to the recording head. A pump provided in an ink supply path to the recording head and capable of pumping ink in the ink flow path in at least one direction; and an opening degree of the ink supply path provided in the ink supply path. And a valve that can be adjusted according to the pressure of the ink in the recording head so that the negative pressure of the ink in the recording head is maintained in a predetermined range during a recording operation using the recording head. And controlling the pump and the valve.

  In the recording method of the present invention, when an image is recorded using the recording head, a negative pressure is applied to the ink stored in the ink tank, and then the ink applied with the negative pressure is supplied to the recording head. A recording method comprising: a pump provided in an ink supply path between the ink tank and the recording head, capable of pumping ink in the ink flow path in at least one direction; and in the ink supply path And a valve capable of adjusting the opening of the ink supply path so as to maintain the negative pressure of the ink in the recording head within a predetermined range during a recording operation using the recording head. In addition, the pump and the valve are controlled in accordance with the pressure of the ink in the recording head.

  According to the present invention, the negative pressure in the recording head is changed by actively controlling the ink supply pressure using a pump and a valve provided in the ink supply path between the ink tank and the recording head. As a result, the recording operation using the recording head can be stabilized and a high-quality image can be recorded.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment is an application example as an apparatus incorporated in an image forming system as shown in FIGS.

(Outline of image forming system)
1 and 2 are a block diagram and a schematic perspective view, respectively, showing an outline of the image forming system. The printer complex system of this example generally includes an information processing apparatus 100 and an image forming apparatus 200. The image forming apparatus 200 includes a medium conveying apparatus 117 and a printer complex system 400. The printer complex system includes a plurality of independent engines. Printer units (hereinafter also referred to as “printing apparatus” or “recording apparatus”) 116-1 to 116-5.

  Here, the information processing apparatus 100 is a supply source of image data to be formed, and divides one image into regions, and divides each image into a plurality of printer units 116-1 to 116-5 constituting the printer complex system 400. Supply image data. The medium transport device 117 transports a recording medium 206 having a size in the width direction corresponding to the recordable range by the arrangement of the printer units 116-1 to 116-5. Further, the end (paper end) of the recording medium 206 is detected, and a signal for defining the recording start position of each printer unit 116-1 to 116-5 is output.

  The printer complex system 400 includes a plurality of (in this example, five) printer units 116-1 to 116-5 arranged to divide a recording area on the recording medium 206 and perform recording. Each printer unit independently performs a printing operation (recording operation) on the recording area in charge at a timing defined by the medium transport device 117 based on the divided image data supplied from the information processing apparatus 100. To do. Each printer unit has a recording head for ejecting black (K) ink to the three primary colors of yellow (Y), magenta (M), and cyan (C) in order to perform full color recording on the recording medium 206. The ink of each color is supplied from the ink tanks 203Y, 203M, 203C, and 203K, which are ink supply sources, to each recording head.

  In FIG. 1, a CPU 101 is a central processing unit that controls system control of the information processing apparatus 100 in general. In the information processing apparatus 100, the CPU 101 includes an application program for generating and editing image data under the control of an operating system (OS), an image dividing program according to the present embodiment, and a plurality of printer units 116-. The control program (printer driver) 1-116-5 and the control program (described later with reference to FIG. 5) of the medium transport device 117 are executed.

  The system bus of the CPU 101 has a hierarchical bus configuration, and is connected to, for example, a PCI bus as a local bus via the host / PCI bridge 102 and further connected to the ISA bus via the PCI / ISA bridge 105. Connected to devices on each bus.

  The main memory 103 is a RAM (Random Access Memory) provided with a temporary storage area for the OS, application program, and control program, and is also used as a working memory area for executing each program. These programs are read from, for example, the hard disk drive HDD 104 and loaded. Note that the system bus has a high-speed memory using an SRAM (Static RAM) called a cache memory 120, and codes and data that the main CPU 101 always accesses are stored here.

  A ROM (Read Only Memory) 112 is a program (BIOS; Basic Input Output System) that controls input / output devices such as a keyboard 114, a mouse 115, a CDD 111, and an FDD 110 connected via an input / output circuit (not shown). Stores an initialization program when the system is powered on, a self-diagnosis program, and the like. An EEPROM (Electronic Erasable ROM) 113 is a non-volatile memory for storing various parameters used permanently.

  The video controller 106 continuously and cyclically reads RGB display data written in a VRAM (Video RAM) 107 and continuously transfers it as a screen refresh signal to a display 108 such as a CRT, LCD, PDP (Plasma Display Panel). To do.

  A communication interface 109 with the printer units 116-1 to 116-5 is connected to a PCI bus. Usable interfaces include, for example, a bidirectional Centronics interface that conforms to the IEEE1284 standard, a USB (Universal Serial Bus), and a hub. There are connections. FIG. 1 shows a configuration in which a hub 140 is connected via the communication interface 109 and the hub 140 is further connected to each of the printer units 116-1 to 116-5 and the medium transport device 117. Further, although the wired type communication interface 109 is used in this embodiment, a communication interface such as a wireless LAN may be used.

  A printing program (printer driver) for setting the number of printing apparatuses 116-1 to 116-5 connected to the information processing apparatus 100 (that is, corresponding to the number of divisions for dividing an image of one page); Means (which will be described later in FIG. 4) for setting an area (division width) in which each of the printing apparatuses 116-1 to 116-5 is responsible for printing, and which part of the image each printing apparatus shares And an association setting means (see FIG. 3) of the print responsible section. Then, the image of one page is divided based on the contents set by these various setting means, and the image data is transferred to each of the printing apparatuses 116-1 to 116-5 to perform printing.

  As described above, the print program performs print data generation and print data transfer processing for the plurality of printing apparatuses 116-1 to 116-5, so that the program itself or print data generation processing and printing in the print program are performed. Data transfer processing can be performed in parallel (multi-process, multi-thread) and processed at high speed.

  Referring to FIG. 2 again, the information processing apparatus 100, the plurality of printing apparatuses 116-1 to 116-5, and the conveying apparatus 117 are connected via the hub 140, and transfer print data, operation start and end commands, and the like. Do. Further, each of the printing apparatuses 116-1 to 116-5 (hereinafter referred to by reference numeral 116 if not specified) and the transport apparatus 117 are also signal-connected to detect the leading edge of the recording medium 206 or set the printing leading position. In addition, a signal for synchronizing the medium conveyance speed and the printing operation (ink ejection operation) in each printing apparatus is exchanged.

  For example, yellow (Y), magenta (M), cyan (C), and black (K) inks are ejected to each printing device 116 in order to perform continuous full-color recording on the recording medium 206, for example. Four recording heads 811Y, 811M, 811C and 811K (hereinafter referred to by reference numeral 811 if not specified) are mounted. The arrangement order of the recording heads for the respective color inks in the medium conveying direction is the same among the printing apparatuses, and therefore the overlapping order of the colors is the same. The ink discharge ports of each print head are arranged over 4 inches (reference value, about 100 mm) at a density of 600 dpi (dot / inch; reference value) in the width direction of the recording medium (direction perpendicular to the medium conveyance direction). As a whole, the maximum recording width of about 500 mm is satisfied.

  The recording heads 811Y, 811M, 811C, and 811K in each printing apparatus 116 are supplied with ink of each color from the ink tanks 203Y, 203M, 203C, and 203K, which are ink supply sources, via the dedicated tubes 204. .

(Printer control system)
FIG. 3 shows a configuration example of a control system in each printing apparatus 116.
In the figure, reference numeral 800 denotes a CPU that performs overall control of the printing apparatus 116 in accordance with a program corresponding to the processing procedure described later with reference to FIG. 5, 803 denotes a ROM that stores the program and fixed data, and 805 denotes a work memory area. A RAM 814 that is used is an EEPROM that stores necessary parameters used by the CPU 800 for control even when the power of the printing apparatus is shut off.

  Reference numeral 802 denotes an interface controller for connecting the printing apparatus 116 to the information processing apparatus 100 via a USB cable, and reference numeral 801 denotes a VRAM for developing each color image data. Reference numeral 804 denotes a memory controller that transfers the received image data to the interface controller 802 to the VRAM 801 and controls to read the image data according to the progress of printing. When the divided print data is received by the interface controller 802 from the information processing apparatus 100 via the USB cable, the CPU 800 analyzes the command added to the print data, and then the image data of each color component of the print data. Is instructed to develop a bitmap in the VRAM 801. In response to this instruction, the memory controller 804 writes the image data from the interface controller 802 to the VRAM 801 at high speed.

  Reference numeral 810 denotes a control circuit for controlling the color recording heads 811Y, 811M, 811C, and 811K. Reference numeral 809 denotes a capping motor that drives a capping mechanism (not shown) for capping the surface of the recording head 811 on which the ejection openings are formed, and is driven via an input / output port 806 and a drive unit 807.

  The pump motor 820 is a reversible motor that drives a pump 48 inserted between a sub tank 40 and a recording head 811 described later (see FIG. 9). The solenoid 821 is an actuator that drives the valve 35, and the valve 35 can be controlled in an analog manner according to a PWM (Pulse Width Modulation) value set by the CPU 800 in the PWM circuit 823.

  The pump motor 508 is a servo motor that controls the mechanical pump 36 by feeding back the output of the pressure sensor 49 provided in the vicinity of the flow path in the recording head to the pump motor control unit 822. The pump motors 820 and 508, the solenoid 821, and the pressure sensor 49 are provided independently for each of the recording heads 811Y, 811M, 811C, and 811K corresponding to each ink color.

  These are characteristic components of the present invention, and details will be described later.

  When the printing apparatus 116 is not used, the capping motor 809 is driven to move the recording heads 811Y, 811M, 811C, and 811K relative to the capping mechanism to perform capping. On the other hand, when the image data to be printed is expanded in the VRAM 801, the capping motor 809 is driven to move the recording heads 811Y, 811M, 811C and 811 and the capping mechanism relative to each other to release the capping state. It waits for a print start signal from a medium transport device 117 described later.

  Reference numeral 806 denotes an input / output (I / O) port, which is connected to a motor drive unit 807, other drive means, and required sensors (not shown), and exchanges signals with the CPU 800. A synchronization circuit 812 receives a cueing signal of the recording medium and a position pulse signal synchronized with the movement of the medium from the medium conveying device 117, and generates a timing signal for executing a printing operation in synchronization with them appropriately. It is. That is, the data in the VRAM 801 is read at high speed by the memory controller 804 in synchronization with the position pulse accompanying the conveyance of the recording medium, and transferred to the recording head 811 via the recording head control circuit 810, so that color recording ( Printing).

(Conveyor configuration and control system)
Referring to FIG. 2, the medium transport device 117 is suitable for transporting a recording medium having a large size in the width direction and an arbitrary size in the transport direction. In addition, a media stage 202 is provided in order to restrict the recording surface of the recording medium 206 to be flat at a portion facing the recording head 810 included in the printing apparatuses 116-1 to 116-5. Since recording media having various thicknesses are used, means for improving the adhesion of the recording medium to the media stage 202 in order to make the recording surface flat even for thick paper. May be added. The transport motor 205 is a drive source for the transport roller row 205 </ b> A for transporting the recording medium in close contact with the upper surface of the media stage 205.

  FIG. 4 shows a configuration example of a control system of the medium transport device 117.

  In the figure, reference numeral 901 denotes a CPU that performs overall control of the medium transport device according to a program corresponding to the processing procedure described later with reference to FIG. 5, 903 denotes a ROM that stores the program and fixed data, and 904 denotes a work memory area. This is the RAM used.

  Reference numeral 902 denotes an interface for connecting the medium transport apparatus 116 to the information processing apparatus 100. Reference numeral 905 denotes an operation panel having an input unit for a user to give various instructions and inputs to the image forming apparatus and a display unit for performing a required display. In this example, the operation panel 905 is provided in the medium conveying apparatus. .

  Reference numeral 908 denotes a suction motor, which is an example of a means for improving the adhesion of the recording medium to the media stage 202 through a number of fine holes opened from the bottom of the media stage 202 to the conveyance surface of the media stage 202. It serves as a drive source for a vacuum pump that sucks the recording medium by suction. When a conveyance start command is received from the information processing apparatus 100 via the interface 902, the CPU 901 first activates the suction motor 908 so that the recording medium 206 is attracted to the upper surface of the media stage 202.

  Reference numeral 907 denotes a drive unit for driving the suction motor 908 and other required operation units. Reference numeral 909 denotes a drive unit of the transport motor 205.

  Reference numeral 912 denotes a logic circuit that receives an output of a rotary (rotary) encoder 910 provided on the shaft of the conveyance motor 205 and has a servo system for performing feedback control of the conveyance motor 205 to convey the recording medium at a constant speed. Composed. Here, the conveyance speed can be arbitrarily set by a speed instruction value written from the CPU 901 to the logic circuit 912. The rotary encoder 910 may be provided coaxially with the transport roller row 205A instead of the shaft of the transport motor 205.

  The logic circuit 912 also receives an output of a medium detection sensor 911 provided on the upstream side in the transport direction from the printing position in order to detect that the leading edge of the recording medium 206 has reached the vicinity of the printing start position. The logic circuit 912 outputs an appropriate print instruction signal to each printing apparatus according to the distance in the transport direction from the position where the medium detection sensor 911 detects the leading edge of the recording medium to each printing apparatus. In the present embodiment, as shown in FIG. 2, the printing apparatuses 116-1 to 116-5 are arranged in two rows in the transport direction, that is, the printing apparatuses 116-1 and 116-3 and the upstream side in the transport direction. 116-5 is disposed, and the printing apparatuses 116-2 and 116-4 are disposed on the downstream side, so that two types of print instruction signals 914 and 915 are output. Considering that there is an error in the mounting position of the printing apparatus, depending on the physical distance from the medium detection sensor 911 to each printing apparatus, the printing start signal 914 or 915 is independent for each printing apparatus. You may make it add correction to.

  The logic circuit 912 appropriately converts the output of the encoder 910 to generate a recording medium position pulse 913, and each printing apparatus performs a printing operation in synchronization with the position pulse 913. The resolution of the position pulse may be appropriate, and may be set for a plurality of print lines (rows), for example.

  Further, the configuration of the recording medium conveyance unit in the medium conveyance device 117 is not limited to the one provided with the fixed media stage 202 as shown in FIG. For example, an endless conveyance belt is provided between a pair of drums arranged upstream and downstream in the medium conveyance direction with respect to the printing position, and the recording medium is carried on the conveyance belt while the drum rotates. The recording medium may be transported by traveling of the transport belt. These forms can be transported on any recording medium such as cut paper or continuous paper.

(Overview of image forming system operation)
FIG. 5 shows a mutual operation procedure of the information processing apparatus 100, the printing apparatus 116 of the printer complex system 400, and the medium transport apparatus 117.

  In order to execute printing, divided print data for each printing apparatus is created on the information processing apparatus 100 (step S1001) and transmitted. The printing device 116 cancels the capping state in response to the reception of the data and develops the data in the VRAM 801 (step S1041). When reception is completed in all the printing apparatuses 116-1 to 116-5, the information processing apparatus 100 transmits a conveyance start command to the medium conveyance apparatus 117 (step S1002).

  In response to this, the medium transport device 117 first drives the suction motor 908 (step S1061), and prepares to attract the recording medium 206 onto the media stage 202. Next, the conveyance motor 205 is driven to start conveyance of the recording medium 206 (step S1062), and after detecting the leading edge (step S1063), the printing start signals 914 and 915 are sent to the printing apparatuses 116-1 to 116-5. Then, a position pulse 913 is transmitted (step S1064). As described above, the print start signal is output in relation to the distance from the medium detection sensor 911 to each printing apparatus.

  When the printing operation (step S1042) is completed in the printing apparatus 116, the printing end status is transmitted to the information processing apparatus 100 (step S1043), and the process is terminated. At this time, each recording head 801 is capped by a capping mechanism to prevent the nozzles (ejection ports) from drying and clogging.

  When printing is completed and the recording medium 206 is ejected from the media stage 202 (step S1065—YES), the medium transport device 117 transmits a transport end status to the information processing device 100 (step S1066), and then the suction motor. 908 and the transport motor 205 are stopped (steps S1067 and S1068), and the operation is finished.

(Signal system to printer complex system)
FIG. 6 is an example of a signal system to the printing apparatuses 116-1 to 116-5 constituting the printer complex system. There are roughly two signal systems connected to each of the printing apparatuses 116-1 to 116-5. One is related to transmission of divided print data (including operation start and end commands) supplied from the information processing apparatus 100, and the other is a recording timing definition signal (print start signal) supplied from the medium transport apparatus 117. And position pulse).

  In the example of FIG. 6, the former includes a hub 140 that relays between the information processing apparatus 100 and the printing apparatuses 116-1 to 116-5. For the information processing apparatus 100, the hub 140 is, for example, a 100BASE-T standard. Are connected to each of the printing apparatuses 116-1 to 116-5 via, for example, a 10BASE-T standard connector / cable 144.

  In the example of FIG. 6, the transmission system of the recording timing regulation signal includes a transfer control circuit 150 and a synchronization circuit 160, which may be provided as a circuit unit constituting the logic circuit 912 in FIG. The transfer control circuit 150 supplies the output ENCODER of the rotary encoder 910 provided on the shaft of the transport motor 205 and the detection output TOF of the leading end of the recording medium by the medium detection sensor 911 to the synchronization circuit 160.

  The synchronization circuit 160 is provided with a printing operation permission circuit 166, which is a logical product of operation preparation completion signals PU1-RDY to PU5-RDY from the printing apparatuses 116-1 to 116-5 in response to the completion of reception of the divided image data. As a result, the signal PRN-START that permits the printing operation is output when the operation preparation of all the printing apparatuses is completed (capping state is released, etc.). Further, the synchronization circuit 160 is provided with a display unit 167 such as an LED for performing display related to the operation preparation completion signals PU1-RDY to PU5-RDY so that the user can visually confirm the operation preparation completion of the printing apparatus. It has become. Further, the synchronization circuit 160 includes a reset circuit unit 168 for the user or the like to manually reset the printing apparatus, and a pause circuit unit 169 for waiting for completion of recording of one recording medium, for example. Is added.

  Further, the synchronization circuit 160 outputs position pulses 913 (for example, 300 pulse signals per 1 inch of conveyance amount of the recording medium) from the encoder output ENCODER, which are synchronization signals (Hsync) for the printing apparatuses to perform a printing operation in synchronization. And a delay circuit 164 that generates a print instruction signal 914, 915, which is a delay signal corresponding to the position of each printing apparatus in the medium conveyance direction, from the recording medium leading edge detection output TOF. .

  The recording operation of the printing apparatuses 116-1, 116-3, and 116-5 on the upstream side in the recording medium conveyance direction is a delay signal that is delayed by the distance from the medium detection sensor 911 to the installation position of these printing apparatuses. The process starts when the print instruction signal (TOF-IN1) 914 is received. If the distance from the medium detection sensor 911 to the position where the printing apparatus is disposed is zero, the print instruction signal 914 is supplied almost simultaneously with the detection output TOF.

  On the other hand, the recording operation of the printing apparatuses 116-2 and 116-4 arranged on the further downstream side is a printing instruction signal which is a delay signal delayed by the distance from the medium detection sensor 911 to the position where these printing apparatuses are arranged. (TOF-IN2) Start with reception of 915. In the present embodiment, the distance from the medium detection sensor 911 to the position where these printing apparatuses are disposed is set to 450 mm. Therefore, the position pulse 913 which is a synchronization signal (Hsync) is conveyed by 1 inch (25 inches) of the recording medium. If it is 300 pulses per .4 mm), the print instruction signal 915 is supplied with a delay of 5315 pulses from the detection output TOF.

  As described above, in order to individually correct the minute recording position in the medium conveyance direction of each printing apparatus, or in consideration of the case where the printing apparatuses are not aligned in two rows, each printing apparatus is independent. Then, a print instruction signal may be supplied.

  As is clear from FIG. 6, each of the printing apparatuses 116-1 to 116-5 receives the divided print data from the information processing apparatus 100 and responds to the recording timing regulation signal supplied from the medium transport apparatus 117. The printing operation is performed independently. That is, each of the printing apparatuses 116-1 to 116-5 is a printer unit that is complete with respect to the signal system, and the supply and recording timing of print data is transmitted to other printing apparatuses via one printing apparatus. Rather than such a configuration, the data is aligned in correspondence with the recording heads 811Y to 811K used by itself and the nozzles arranged in each recording head, and an ink discharge operation is performed at a specified timing (shift register or latch). Circuit etc.). That is, the printing apparatuses 116-1 to 116-5 have the same hardware and operate with the same software, and the operation of one printing apparatus directly affects the operation of other printing apparatuses. Nonetheless, they cooperate to print one piece of image data as a whole.

(Outline of ink system)
Each of the printing apparatuses 116-1 to 116-5 in this example is an independently operable printer, and an ink supply system for each recording head 811 and a recovery system for each recording head 811 in each printing apparatus. Ink systems including the above also have an independent configuration.

  FIG. 7 is a schematic diagram for explaining the configuration of the ink supply system, in particular, of the ink system. As shown in this figure, for the recording heads 811Y, 811M, 811C and 811K in each printing apparatus 116, from ink tanks (hereinafter also referred to as main tanks) 203Y, 203M, 203C and 203K which are ink supply sources, Ink of each color is distributed and supplied through dedicated tubes 204Y, 204M, 204C and 204K. As an ink supply method, ink may be continuously supplied as long as it is in fluid communication with the ink tank, or held in an ink supply unit provided for each recording head as will be described later. Ink supply may be performed intermittently, so that fluid communication is established when the amount of ink is reduced.

  The recovery system of the present embodiment includes a cap that is bonded to the ejection port formation surface of the recording head 811 and receives ink that is forcibly discharged from the ejection port, and further circulates the received ink in a reusable manner. Configured.

  Here, the cap can be provided below the conveying surface of the recording medium 206, that is, inside the media stage 202 so as to be able to face or abut the ejection port forming surface of the recording head. However, in consideration of the use of a continuous paper-like recording medium such as roll paper, it is arranged on the upper side of the recording medium 206 conveyance surface, that is, on the same side as the recording head 811 so that the recovery operation can be performed without removing the recording medium. May be good.

  As described above, in this embodiment, the ink supply system and the recovery system for each recording head 811 in each printing apparatus also have a configuration independent from each other among the printing apparatuses. As a result, an appropriate amount of ink can be supplied or recovered in accordance with the operating state of each printing apparatus, that is, the printing amount.

(Ink system configuration example)
FIG. 8 shows an arrangement relationship of main parts of the ink system in one printing apparatus 116, and FIG. 9 shows an example of the internal configuration of the ink system for one print head. The recording head 811 is provided with two ink connection pipes, one of which is in the negative pressure chamber 30 for generating a preferable negative pressure that balances the holding force of the ink meniscus formed at the ink discharge port of the recording head. The other is connected to an ink supply unit (hereinafter referred to as a sub tank) 40 for each recording head via a pump 48.

  FIG. 10 is an explanatory diagram showing an enlarged ink flow path configuration inside the recording head 811 and a part thereof. The recording head used in this embodiment includes nozzles arranged over a width of 4 inches at a density of 600 dpi, that is, 2400 nozzles 50. One end of the nozzle 50 is an ejection port 51, and the other end is connected to an ink supply path 54. In the nozzle 50, an electrothermal conversion element (heater) 52 that generates thermal energy for heating and foaming ink in response to energization is provided as an element that generates energy for ejecting ink. Then, the ink is heated by energizing the heater 52 for about 1 to 5 μsec, and film boiling starts at a temperature of 300 ° C. or higher on the heater surface. As a result, the ink receives an inertial force and is ejected from the ejection port 51 to land on the recording medium to form an image. The nozzle 50 is provided with a nozzle valve 53 as a fluid control element. This is displaced according to the foaming of the ink so as to effectively exert an inertial force on the ink on the ejection port side and prevent the propagation of the pressure wave on the ink on the supply path side. It is a member. Reference numeral 56 denotes a filter provided on each of the supply side and the return side of the ink supply path 54.

  As shown in FIGS. 11A, 11B, and 11C, the negative pressure chamber 30 includes an ink holding portion 31 made of a flexible member and a pair of plate-like ink holding portions 33 facing each other. The ink is held in the internal space defined by A compression spring 32 is disposed between a pair of opposed plate-shaped ink holding portions 33, and negative pressure is generated by urging the plate-shaped ink holding portions 33 in a direction away from each other by the stress in the extension direction. It is supposed to be. The negative pressure chamber 30 is disposed in the vicinity of the recording head 811 and there is almost no pressure loss at the connecting portion between the two, so that the inside thereof is almost the same as the negative pressure in the recording head. Even when the amount of ink supplied to the recording head 811 changes abruptly and the supply of ink from the pump 36 is not in time, the negative pressure chamber 30 serves as a buffer to assist the supply. Specifically, the pair of plate-like ink holding portions 33 resists the extension force of the spring 32 and is displaced in the proximity direction while compressing it, thereby reducing the internal volume of the negative pressure chamber 30 and supplying ink. Do.

  As the pressure sensor 49, various detection methods can be used in addition to a detection method that directly detects the negative pressure in the negative pressure chamber 30. For example, the optical sensor 149 in FIG. 11 can be used. The sensor 149 includes a reflecting plate 149A attached to the plate-shaped ink holding portion 33, a light emitting element (such as a light emitting diode) 149B provided at a fixed position outside the negative pressure chamber 30 facing the reflecting plate 149A, and a light receiving element. (Such as a light receiving transistor) 149C. The light from the light emitting element 149B is reflected by the reflecting plate 149A and then received by the light receiving element 149C, and the amount of received light increases when the amount of ink in the negative pressure chamber 3 is large as shown in FIG. 11B and 11C, the ink volume decreases as the ink amount in the negative pressure chamber 3 decreases. Therefore, the sensor 149 detects the ink amount in the negative pressure chamber 30 and indirectly detects the negative pressure in the negative pressure chamber 30 from the relationship between the ink amount and the negative pressure in the negative pressure chamber 30. can do.

  A mechanical ink pump (hereinafter also referred to as “mechanical pump”) 36 is connected to the negative pressure chamber 30 via a pressure adjustment valve 35 (see FIG. 9), and ink supply to the negative pressure chamber 30 is controlled. doing. The ink pump 36 in this example is a gear pump.

  Here, as a valve disposed in each part of the ink supply path including the valve 35, any type of valve may be used as long as the flow path can be appropriately opened and closed or the flow rate can be appropriately controlled according to the control signal. May be. For example, as shown in FIGS. 12A and 12B, a plunger having a ball-like valve body 56 inserted on the ink flow path and a sheet body 57 that receives the valve body 56 is moved forward and backward by a solenoid. It can be set as the valve | bulb 58 of the structure which connected 55 valve bodies. In this case, the ink flow path can be opened and closed by controlling energization to the solenoid and allowing the valve body 56 to be received / removed from the sheet body 57. FIG. 12A shows an open state of the ink flow path, and FIG. 12B shows a closed state of the ink flow path. However, with respect to the valve 35, in order to enable high-performance negative pressure control with high responsiveness, an element having a light weight such as a piezo element may be used as an actuator.

  Further, as the pump disposed in each part of the ink supply path including the pump 36, any type of pump may be used as long as it can transfer ink according to the drive signal. In particular, however, the pump 36 is capable of switching the direction of ink flow and adjusting the ink flow rate in this embodiment. That is, in the example of FIG. 9, the direction of supplying ink to the negative pressure chamber 30 (hereinafter, rotation in this direction is referred to as normal rotation) and the direction of extraction (hereinafter, rotation in this direction is referred to as reverse rotation). A gear pump capable of selectively transferring ink is shown.

  Further, the pump 36 is connected to a deaeration system 38 and removes a gas component melted in the ink transferred to the pump 36. As shown in FIG. 13, the deaeration system 38 includes an ink supply path formed of a gas-liquid separation film 39 made of a material that transmits gas and does not transmit liquid, a decompression chamber 38A that covers the surrounding space, The pump 38B (see FIG. 9) for vacuum depressurizing the gas effectively removes the gas from the ink flowing through the ink flow path via the gas permeable film 39.

  The deaeration system 38 is connected to a sub-tank 40 that stores an appropriate amount of ink that can be consumed by recording (see FIG. 9). The sub-tank 40 defines a part of the ink storage space and is appropriately disposed between the buffer member 41 that can be displaced or deformed according to the amount of ink stored and the ink tube 204 connected to the main tank 203. And a joint 42 for performing ink communication. The joint 42 is connected to the joint 43 provided in the ink tube 204 as shown in FIG. 14B when the ink in the sub tank is low, so that the ink is supplied from the main tank 203 to the sub tank 40. It is configured to be replenished appropriately.

  Valve rubbers 66 </ b> A and 66 </ b> B each having a communication hole are provided at the opposing portions of the joints 42 and 43. When the joints 42 and 43 are not connected, as shown in FIG. 14A, the valve balls 63A and 64A biased by the valve springs 65A and 65B close the openings of the communication holes in the valve rubbers 66A and 66B. ing. Thereby, both the ink flow paths connected to the joints 42 and 43 are blocked from the outside air. When connecting the joints 42 and 43, as shown in FIG. 14 (b), the valve rubbers 66A and 66B are brought into close contact with each other, and the valve ball 63A is pushed by the ball lever 67 provided on the valve ball 63B. . As a result, the valve balls 63A and 64A are separated from the valve rubbers 66A and 66B, and the ink flow paths connected to the joints 42 and 43 are connected to each other.

  The joints 42 and 43 may have any structure as long as the opening can be blocked to prevent ink leakage when not connected, and the ink flow path can be connected in a state of being blocked from outside air.

  In addition to switching the fluid communication by appropriately connecting and disconnecting the joints as described above, the supply path itself is always connected, and the fluid communication is switched on and off by an open / close valve. It may be. The point is that the ink supply between the printing devices does not interfere with each other when the required amount of ink between the printing devices differs according to the content of each divided image data. In this sense, the independence of the printing apparatus according to the present embodiment is ensured.

  15A and 15B are schematic configuration diagrams of the ink tank 203 (203Y, 203M, 203C, 203K) connected to the joint 43. FIG. The ink tank 203 of this example includes a flexible ink bag 69 that contains ink, and a tank housing 68 that contains it. An air communication hole 71 is formed in the tank housing 68, and a storage element 70 is attached to the tank housing 68. Various information related to the ink tank 203 can be stored in the storage element 70. For example, it is possible to write information such as the type of ink to be stored, the remaining amount of ink, the type of ink tank, and the like, and read and use it as necessary. The ink bag 69 is deformed as shown in FIGS. 15A and 15B according to the consumption of the ink accommodated therein. Therefore, the ink in the ink bag 69 can be supplied while being blocked from the outside air.

  As shown in FIG. 9, the other connection pipe of the recording head 811 is connected to the sub tank 40 via a pump 48. By the operation of the pump 48 and the pump 36, the sub tank 40, the negative pressure chamber 30, and the recording tank 811 are connected. Ink can be circulated between the heads 811.

  In addition, the printing apparatus 116 includes a recovery system mechanism for maintaining or recovering the ink ejection performance of the recording head 811 in a healthy state, and includes a cap 44 that seals the recording head 811 as a part thereof.

  During the recovery operation, the mechanical pump 36 is rotated in the forward direction while the pump 48 is stopped (flow path: closed). Then, the inside of the recording head 811 is suddenly pressurized from the negative pressure chamber 30, and a relatively large amount of ink is forcibly discharged from each nozzle of the recording head 811 in a short time. At this moment, each nozzle is restored to a healthy state. The forcibly discharged ink is discharged to the ink reservoir in the cap 44, but is quickly collected and reused by the sub-tank 40 through the valve 47 by the action of the pump 45 operating in advance. Thereafter, a wiping operation of the nozzle row of the recording head 811 by a wiper blade (not shown) and a preliminary ejection operation for ejecting ink that does not contribute to image recording are performed, and the recovery operation of the recording head 811 is completed.

  The printing apparatus 116 or the recording head 811 according to this embodiment includes such an ink (supply) system, so that it can be separated from the image forming system and the image forming apparatus and independently of other printing apparatuses. Control under conditions is possible, and independent installation and replacement are also possible.

(Ink operation)
In the following, an ink operation according to the usage status of the printing apparatus 116 will be described.

Preparation for shipment (see Fig. 16)
After the printing device 116 or the recording head 811 is manufactured, the pumps 36, 48 and 45 are operated while injecting ink into the tank 40 through the joint 42 as shown in FIG. Fill the ink system with ink. At this time, air from the beginning into the ink system is discharged from the exhaust port of the deaeration system 38. After that, the ink is forcibly discharged from the ejection port of the recording head 811 into the cap 44, the wiping operation by the wiper blade, and the preliminary ejection operation of the ink are performed to recover the recording head, and the test printing operation and aging are performed. Etc.

  As the ink filled in the ink system at the time of such distribution of the printing apparatus 116, in addition to the ink used for normal recording, a dedicated liquid for distribution may be filled. The dedicated liquid for logistics is a liquid that has been created in consideration of environmental changes during distribution and the lengthening of the logistics period. For example, a liquid obtained by removing color materials such as dyes and pigments from normal ink components. Can be used. However, when such a dedicated logistics liquid is used, it is necessary to replace the dedicated logistics liquid in the ink system with normal ink at the start of the recording operation.

Preparation for start of use (see Fig. 17)
After the shipped printing apparatus is installed, before starting its use, first, as shown in FIG. 17A, the joint 43 on the main tank 203 side is connected to the joint 42 and the pump 36 is rotated forward. Ink is fed into the negative pressure chamber 30. Thereafter, in order to remove bubbles accumulated in the flow path, the pumps 36 and 48 are operated as shown in FIG. 17B to remove the ink in the negative pressure chamber 30 from the recording head 811, the sub tank 40, and the deaeration system. Circulate through 38. By continuing such ink circulation for an appropriate period of time, the air in the flow path is removed to a level with no problem by the deaeration system 38. Next, in order to recover the air discharged in the vicinity of the nozzles of the recording head 811 and the sound discharge performance, the mechanical pump is stopped in a state where the pump 48 is stopped (flow path: closed) as shown in FIG. 36 is rotated in the forward direction. Then, the inside of the recording head 811 is suddenly pressurized from the negative pressure chamber 30, and a relatively large amount of ink is forcibly discharged from each nozzle of the recording head 811 in a short time. At this moment, each nozzle is restored to a healthy state. The forcibly discharged ink is discharged to the ink reservoir in the cap 44, but is quickly collected and reused by the sub-tank 40 through the valve 47 by the action of the pump 45 operating in advance. Thereafter, the wiping operation of the nozzle row of the recording head 811 by a wiper blade (not shown) and the preliminary ejection operation are performed, and the recovery operation of the recording head 811 is completed.

During printing standby (see Fig. 18)
In a normal standby state such as before starting printing, a relatively large negative pressure (a negative pressure lower by about 20 to 150 mmAq than the atmospheric pressure) is applied to the ink in the recording head 811 in order to maintain stability against environmental changes. Let That is, as shown in FIG. 18A, the pump 48 is stopped to restrict the return of the ink from the recording head 811 to the sub tank 40, and the pump 36 is reversed to transfer the ink in the negative pressure chamber 30 to the sub tank 40. Return to. As a result, the negative pressure acting on the ink in the recording head 811 increases. Then, as shown in FIG. 18B, the lower negative pressure state is maintained and the start of printing is waited. The volume of the sub tank 40 increases in the downward arrow direction in FIG. 18A by the amount of ink returned from the negative pressure chamber 30.

  However, in the negative pressure state shown in FIG. 18B, the ink supply (refill) performance to the recording head 811 at the time of printing is lowered, and it becomes difficult to drive the recording head at a high frequency. Therefore, when a print signal is input (step S1041 in FIG. 5), as shown in FIG. 18C, the pump 36 is rotated forward to perform preliminary ink supply. That is, the negative pressure chamber 30 is pressurized so that the negative pressure acting on the recording head 811 is controlled in the positive direction to obtain a negative pressure suitable for printing. The negative pressure in the negative pressure chamber 30 can be detected by the negative pressure sensor 49 or the sensor 149 (see FIG. 11). Further, the volume of the sub tank 40 is reduced by the amount of ink fed into the negative pressure chamber 30 in the upward arrow direction in FIG.

Supply control during printing (see Fig. 19)
By appropriately controlling the negative pressure adjusting valve 35 and the mechanical pump 36, a more uniform negative pressure can be obtained according to various printing duties (recording densities) corresponding to the contents of image data printed by the printing device 116 or the recording head 811. Can be maintained.

  For example, when the printing duty is low, as shown in FIG. 19A, the negative pressure adjusting valve 35 is controlled to further optimize the supply while supplying the ink by rotating the pump 36 forward at a low speed. And stabilize the negative pressure with high accuracy. That is, by supplying a small amount of ink, the negative pressure of the ink in the recording head 811 is stabilized within an optimal range, and further, the opening / closing control or the opening degree adjustment control of the negative pressure adjustment valve 35 is performed. To stabilize the negative pressure.

  In such a case, the rate at which the flow path is opened is relatively small, and the opening degree is controlled in a relatively small range.

  When the print duty (recording density) is high, the pump 36 is rotated forward at a higher speed to increase the ink supply amount and the negative pressure adjustment valve 35 is controlled as shown in FIG. Stabilize negative pressure. In that case, the rate at which the flow path is opened is relatively large, and the opening degree is controlled in a relatively large range.

  Further, when the printing operation is stopped, the negative pressure adjusting valve 35 is immediately closed as shown in FIG. This is to prevent the ink supply pressure from being applied to the negative pressure chamber 30 and the recording head 811 due to the inertia of the ink when the printing operation is stopped. If the ink supply pressure is applied, the internal pressure of the recording head increases, and there is a possibility of ink leakage from the ink discharge port, which may cause a decrease in print quality during the subsequent printing operation.

  The negative pressure adjusting valve 35 can be controlled by feeding back the output signals of the sensors 49 and 149 (see FIG. 11) that detect the negative pressure in the negative pressure chamber 30. Further, as will be described later, the negative pressure adjusting valve 35 and the pump 36 can be controlled in advance based on print data (record data).

  Further, not only the forward rotation amount and the normal rotation speed of the pump 36 but also the reverse rotation amount and the reverse rotation speed can be controlled according to the ink consumption per unit time, that is, according to the printing duty. When the pump 36 is rotated forward, the negative pressure in the recording head 811 can be suppressed by positively pressurizing the ink on the recording head 811 side according to the amount of ink consumed. When the pump 36 is reversed, it is possible to suppress a decrease in the negative pressure in the recording head 811 by positively reducing the ink on the recording head 811 side. Further, by controlling the negative pressure adjusting valve 35 in connection with such control of the pump 36, the negative pressure in the recording head 811 can be controlled with higher accuracy, and the negative pressure can be further stabilized. Can do.

  In any case, according to this embodiment, by properly controlling the negative pressure of the ink supplied to the recording head, it is possible to stably record an appropriate negative pressure regardless of the printing duty (recording density). It can be applied to the head. Therefore, for example, in an industrial recording apparatus (printing apparatus) that records an image on a large format recording medium at a high speed, even when the ink consumption per unit time changes significantly, the negative pressure is controlled with high responsiveness. Thus, the fluctuation of the negative pressure in the recording head can be suppressed small. In such an industrial recording apparatus, it is important to keep the negative pressure fluctuation in the recording head small in order to meet a particularly high recording quality requirement.

Control during recovery operation (maintenance) (see Fig. 20)
FIG. 20A is an explanatory diagram of a recovery operation for forcibly discharging ink that does not contribute to image recording from the ejection openings of the recording head 811.

  In this recovery operation, the mechanical pump 36 is rotated in the forward direction while the pump 48 is stopped (flow path: closed). Then, the inside of the recording head 811 is suddenly pressurized from the negative pressure chamber 30, and a relatively large amount of ink is forcibly discharged from each nozzle of the recording head 811 in a short time. At this moment, each nozzle is restored to a healthy state. The forcibly discharged ink is discharged to the ink reservoir in the cap 44, but is quickly collected and reused by the sub-tank 40 through the valve 47 by the action of the pump 45 operating in advance. Thereafter, the wiping operation of the nozzle row of the recording head 811 by a wiper blade (not shown) and the preliminary ejection operation are performed, and the recovery operation of the recording head 811 is completed.

  FIG. 20B is an explanatory diagram of an operation for removing a gas component melted in the ink using the deaeration system 38.

  In this operation, the pump 36 is rotated forward at a low speed, and the ink in the deaeration system 38 is supplied to the negative pressure chamber 49 little by little, and the pump 48 is operated to increase the amount of ink larger than that supplied by the pump 36. Ink is returned from the recording head 811 into the tank 40. As a result, while the ink in the negative pressure chamber 49 decreases, the ink circulates in the deaeration system 38 and the gas component melted in the ink is removed.

  FIG. 20C is an explanatory diagram of a standby state that shifts after the recovery operation.

  In this standby state, after adjusting the inside of the negative pressure chamber 49 to a predetermined negative pressure, the valve 35 is closed and the pump 48 is stopped so as to maintain the negative pressure. At this time, the negative pressure in the negative pressure chamber 49 may be set to a lower negative pressure in the same manner as in the above-described standby state of FIG.

Ink supply operation (see FIG. 21)
FIG. 21 is an explanatory diagram of an operation for supplying ink from the main ink tank 203 to the sub ink tank 40.

  When the remaining amount of ink in the sub tank 40 is reduced to a predetermined amount or less as shown in FIG. 21 (a), the joints 42 and 43 are connected as shown in FIG. 21 (b) to connect the ink in the ink tank 203. In the ink tank 40. At that time, ink can be replenished by utilizing the water head difference. Due to such ink replenishment, the flexible member of the ink tank 40 that has been deformed upward as shown in FIG. 21A is deformed downward as shown in FIG. 21B according to the amount of ink replenished. To do.

(Summary of ink control)
Next, the operation of the ink system according to this embodiment will be described with reference to FIG. 22 from the viewpoint of the print duty of the print head and the negative pressure applied to the print head.

  “Print Duty” (recording density) shown in the upper part of FIG. 22 is a printing duty (recording duty) at each operation stage of the printing apparatus. It is divided into a state of waiting for printing, waiting for printing, and waiting for the next printing immediately after printing. At the time of printing, the amount of ink to be supplied varies depending on the printing duty, that is, the usage rate of ink consumed for printing. In this example, the pump flow rate (the amount of ink supplied by the pump 36) is set as shown in the middle part of FIG. It should be noted that the manner in which the printing duty shown in the figure appears is merely an example, and it goes without saying that it varies depending on the image data.

  The negative pressure applied to the recording head 811 is detected by a pressure sensor 49 (or 149) attached to the negative pressure chamber 30 that is in the immediate vicinity of the recording head 811 and is in a negative pressure state substantially equal to the negative pressure. This detected value is shown in the lower part of FIG.

  As described above, during a pause, a relatively large negative pressure (about -120 mmAq) is applied to the recording head to maintain stability against environmental changes. At the time of printing standby, immediately before starting printing, ink supply is started as shown in the middle part of FIG. By performing such control immediately before the start of printing, sufficient ink supply performance can be ensured immediately after the start of printing, and the print quality can be improved.

  Next, in “Duty 1” at the time of printing, since the negative pressure in the recording head increases at the moment when printing is started, the pump flow rate is increased according to the value of the pressure sensor 49, and the negative pressure in the recording head is reduced. Ink supply performance is improved. In consideration of the increase in the negative pressure in the recording head at the start of printing, the negative pressure in the recording head can be further stabilized by controlling the pump 36 and the valve 35 immediately before the start of the printing operation. . At that time, the control amount and control timing of the pump 36 and the valve 35 can be set in accordance with the print duty obtained based on the print data (record data).

  Furthermore, since “Duty 2” has a higher print duty, the pump flow rate is further increased to suppress an increase in negative pressure applied to the recording head. Thereby, the ink supply can be made to follow even at a high printing speed. Further, when the printing duty changes, the negative pressure in the recording head can be further stabilized by controlling the pump flow rate before the change. At that time, the print duty before or after the change can be obtained based on the print data (record data), and the control amount and control timing of the pump 36 and the valve 35 can be set according to the print duty. .

  Similarly, in the case of “Duty 3” and “Duty 4”, the negative pressure of the ink supplied to the print head is positively controlled according to the respective print duty and the detected value of the pressure sensor 49, thereby the print head. The internal negative pressure can always be stabilized at an optimum level. Accordingly, the followability and stability of the ink supply can be improved, and a high-quality image can be recorded regardless of the print duty.

  If the negative pressure in the recording head tends to decrease due to the inertia of the ink immediately after the end of printing, it is desirable to control the pump flow rate immediately before the end of printing so as to offset the decrease. Thereby, the negative pressure in the recording head can be further stabilized. Further, by closing the valve 35 immediately after the end of printing, it is possible to suppress a decrease in the negative pressure in the recording head.

  After printing, a relatively large negative pressure is applied again in the recording head to maintain stability against environmental changes. That is, by increasing the negative pressure in the recording head, it is possible to prevent ink leakage from the ejection port of the recording head and improve the reliability of the printing apparatus even if environmental changes such as atmospheric pressure and temperature occur. .

  Here, control of the pump motor 508 using the output of the pressure sensor 49 as a feedback signal will be described with reference to FIGS. 23 and 24. FIG.

  First, FIG. 23 is a block diagram of the pressure control system. The pump motor controller 822 in the block diagram of the printing apparatus already described with reference to FIG. 3, that is, the pump motor 508 which is a servo motor, feeds back the output of the pressure sensor 49. It is a block diagram which shows the inside of the pump motor control part 822 controlled by this in detail.

  When printing is started, the CPU 800 writes a digital value corresponding to a slight negative pressure (for example, about −10 mmAq) to the DA converter 830 and supplies the digital value to the (+) input of the subtractor 834 as an analog instruction value. Since the output of the pressure sensor 49 provided in the vicinity of the recording head 811 is connected to the other (−) input of the subtractor 834, an error signal (Error) corresponding to the indicated value is input to the AD converter 831 and converted into a digital signal. CPU 800 reads the obtained value. Corresponding to the error signal including the polarity, the CPU 800 outputs a signal (DIR) for determining the rotation direction to the drive AMP 833 of the pump motor 508 for rotating the mechanical pump 36, and PWM (Pulse) for determining the drive duty of the chopper AMP 833. Width Modulation) value is set in the PWM circuit 832.

FIG. 24A shows a conversion table of PWM values with respect to the reading values of the AD converter 831.
If the error (Error) is (+) polarity, the rotation direction signal (DIR) has a value (for example, “1”) indicating a normal rotation (direction in which the inside of the recording head 811 is pressurized) is output port (I / O). Set via 806. On the other hand, if the error (Error) is (−) polarity, the rotation direction signal (DIR) is set to a value (for example, “0”) that means reverse rotation (the direction in which the inside of the recording head 811 is decompressed).

  When the absolute value of the error (Error) that is the output of the subtracter 834 is large, the drive duty of the drive AMP 833 that drives the pump motor 508 is increased to quickly shift to the desired pressure, while the absolute value of the error (Error) is If it is small, the drive duty of the drive AMP 823 is also lowered to suppress pressure overshoot and undershoot.

  Although not described in this figure, when the valve 35 is used as an auxiliary control means, it is preferable to select a lightweight valve that can respond at high speed.

  During printing, the negative pressure instruction value set in the subtractor 834 is not necessarily a constant value. The CPU 800 reads the contents of the VRAM 801 in order to predict the print duty from the number of recording pixels to be printed. Exceeds a predetermined value, and a drop in the negative pressure inside the recording head 811 is expected, a high pressure indication value can be set in the DA converter 830 immediately before that point.

  By using the feedforward control in this way, the recording operation stability of the recording head 811 is significantly improved. In such a case, a negative pressure drop due to a control delay can be considered. Therefore, as shown in FIG. 24B, there is a method of separately providing a PWM value conversion table having a high gain (AMP Gain) with respect to a pressure error (Error). . The PWM value conversion tables shown in FIGS. 24A and 24B are stored in the ROM 803 in advance.

  Further, as a method different from the adjustment of the gain (AMP Gain) with respect to the pressure error (Error), there is also a method used in combination with the control of the valve 35. The operation flow of the CPU 800 using this method will be described with reference to FIG. In the normal state (solenoid: OFF), the valve 35 is opened as shown in FIG. First, for a predetermined time, the PWM value of the solenoid drive PWM circuit 823 is set to 100% and the movement of the plunger is started (step S2501), and then the servo control of the pump motor 820 is also started. From this time point, the pump motor control unit 822 continuously performs feedback control according to the pressure value set in advance in the DA converter 830. However, the control may already be in progress (step S2502).

  Next, the CPU 800 reads the output of the pressure sensor 49 and converts it to an absolute value (step S2503), and reads the driving PWM value of the solenoid 821 from the conversion table of FIG. 25B based on the converted absolute value of the pressure error. Is set in the PWM circuit 823 (step S2504). If the pressure error is large, the valve 35 approaches an open state, and if the pressure error becomes small, the valve 35 approaches close. That is, as already described with reference to FIG. 24, an effect equivalent to the gain adjustment of the drive AMP 833 can be realized by the valve 35. In other words, when the pressure error is large, it operates so as to quickly approach the set value, and when the error is small, overshoot and undershoot with respect to a predetermined pressure are suppressed.

  The above process is continuously repeated every predetermined time (step S2505), and when the printing operation is completed (step S2506), the drive PWM value of the solenoid 821 is cleared to zero (step S2507) and the process is terminated.

(Other)
The plurality of printing apparatuses employed in the present embodiment are independent of each other. That is, the plurality of printing apparatuses are independent in space (arrangement) in relation to each other, and are also independent in the signal system and the ink system. Therefore, an appropriate amount of ink can be supplied or recovered in accordance with the operating state of each printing apparatus, that is, the printing amount. In addition, the printing apparatus can be controlled under various conditions separately from the image forming system and the image forming apparatus and independently from other printing apparatuses, and the printing apparatus can be handled and handled as a single unit. Become.

  The present invention is not limited to the embodiments described above, and appropriate modifications can be made within the scope of the idea of the present invention.

  For example, the ink can be supplied to one or a plurality of recording heads used in one printing apparatus. In addition to the full line type that performs recording without moving the recording head as described above, the printing apparatus may be a serial scan type that performs recording with movement of the recording head in the main scanning direction. The recording format and form are not specified at all and are arbitrary. In the present invention, it is only necessary that the negative pressure of ink supplied to the recording head is positively controlled by using a pump and a valve to stabilize the negative pressure.

1 is a block diagram illustrating an outline of an image forming system including a printing apparatus to which the present invention is applicable. It is a typical perspective view which shows the outline | summary of the image forming system of FIG. FIG. 2 is a block configuration diagram of a control system of the printing apparatus of FIG. 1. FIG. 2 is a block configuration diagram of a control system of a medium conveyance device provided in the image forming system of FIG. 1. 2 is a flowchart illustrating an operation procedure associated with an information processing apparatus, a printing apparatus, and a medium transport apparatus included in the image forming system of FIG. 1. FIG. 2 is a block configuration diagram of a control system in the plurality of printing apparatuses in FIG. 1. It is a schematic diagram for demonstrating the structure of the ink supply system in the some printing apparatus of FIG. FIG. 2 is a schematic diagram for explaining an arrangement relationship of main parts of an ink system in one printing apparatus of FIG. 1. FIG. 2 is a schematic diagram for explaining a configuration of an ink system of one recording head in the printing apparatus of FIG. 1. FIG. 10 is an explanatory diagram of an ink flow path configuration of the recording head in FIG. 9. (A), (b), (c) is a schematic diagram for demonstrating operation | movement of the negative pressure chamber in FIG. (A), (b) is the schematic diagram for demonstrating the structural example and operation | movement of a valve | bulb in FIG. It is a schematic diagram for demonstrating the structural example of the deaeration system in FIG. (A), (b) is a schematic diagram for demonstrating operation | movement of the joint in FIG. (A), (b) is a schematic diagram for demonstrating operation | movement of the main ink tank in FIG. (A), (b), (c) is a schematic diagram for demonstrating operation | movement of the ink type | system | group of FIG. 9 at the time of shipment. (A), (b), (c) is a schematic diagram for demonstrating operation | movement of the ink type | system | group of FIG. 9 at the time of a use start. (A), (b), (c) is a schematic diagram for demonstrating operation | movement of the ink type | system | group of FIG. 9 at the time of printing standby. (A), (b), (c) is a schematic diagram for demonstrating operation | movement of the ink type | system | group of FIG. 9 at the time of printing. (A), (b), (c) is a schematic diagram for demonstrating operation | movement of the ink type | system | group of FIG. 9 at the time of a maintenance. (A), (b) is a schematic diagram for demonstrating operation | movement of the ink system of FIG. 9 at the time of ink replenishment. FIG. 10 is a timing chart for explaining the operation of the ink system of FIG. 9. FIG. It is a figure which shows the electric block of the negative pressure control using the pressure sensor output in embodiment of this invention, and the pump control by a PWM chopper. (A), (b) is a figure which shows the conversion table of the PWM value with respect to the reading value of AD converter in embodiment of this invention. (A) is a pressure control flowchart in the case of using a valve in the embodiment of the present invention, and (b) is a diagram showing a conversion table of PWM values for driving a solenoid that operates the valve.

Explanation of symbols

30 Negative pressure chamber 36, 45, 48 Pump 40 Sub tank 100 Information processing device 101, 800, 901 CPU
112, 803, 903 ROM
116, 116-1 to 116-5 Printing device (recording device)
117 Medium conveying device 206 Recording medium 811, 811K, 811C, 811M, 811Y Recording head

Claims (13)

An ink supply device that applies a negative pressure to ink stored in an ink tank and then supplies the negative pressure to the recording head.
A pump provided in an ink supply path between the ink tank and the recording head and capable of pumping ink in the ink flow path in at least one direction;
A valve provided in the ink supply path and capable of adjusting an opening of the ink supply path;
Control means for controlling the pump and the valve according to the pressure of the ink in the recording head so as to maintain the negative pressure of the ink in the recording head in a predetermined range;
An ink supply apparatus comprising:   The ink supply according to claim 1, further comprising a negative pressure chamber that applies a predetermined negative pressure to the ink in the ink supply path between the pump and the recording head in the ink supply path. apparatus.   The ink supply apparatus according to claim 2, wherein the negative pressure chamber includes at least a part of a movable member that is biased outward by a predetermined biasing force. Detecting means for detecting ink pressure in the ink supply path corresponding to the pressure in the recording head;
The ink supply apparatus according to claim 1, wherein the control unit controls the pump and the valve based on a detection result of the detection unit.   5. The control unit according to claim 1, wherein the control unit controls the pump and the valve based on an ink consumption amount per unit time of the recording head that affects a pressure in the recording head. The ink supply device according to 1.   5. The ink supply device according to claim 1, wherein the control unit controls the pump and the valve based on a recording duty of an image that affects a pressure in the recording head. 6.   The ink supply apparatus according to claim 1, wherein the control unit closes the valve immediately after the recording operation using the recording head is completed.   The control means is capable of adjusting the pressure in the recording head in a pressure range including the negative pressure in the predetermined range by controlling the pump and the valve in accordance with the usage state of the recording head. The ink supply device according to claim 1, wherein:   The ink supply apparatus according to claim 1, wherein the recording head is used in a composite printing system including a plurality of recording apparatuses.   The ink supply apparatus according to claim 1, wherein the recording head is an ink jet recording head capable of ejecting ink. In a recording apparatus for recording an image using a recording head supplied with ink,
A recording apparatus comprising the ink supply device according to claim 1, in order to supply ink to the recording head. An ink supply method for supplying a negative pressure to an ink stored in an ink tank and then supplying the negative pressure to the recording head.
A pump provided in an ink supply path between the ink tank and the recording head and capable of pumping ink in the ink flow path in at least one direction; and provided in the ink supply path. With a valve that can adjust the opening of the supply path,
Controlling the pump and the valve according to the pressure of the ink in the recording head so that the negative pressure of the ink in the recording head is maintained in a predetermined range during a recording operation using the recording head. An ink supply method. When recording an image using the recording head, a negative pressure is applied to the ink stored in an ink tank, and then the negative pressure is applied to the recording head.
A pump provided in an ink supply path between the ink tank and the recording head and capable of pumping ink in the ink flow path in at least one direction; and provided in the ink supply path. With a valve that can adjust the opening of the supply path,
Controlling the pump and the valve according to the pressure of the ink in the recording head so that the negative pressure of the ink in the recording head is maintained in a predetermined range during a recording operation using the recording head. A recording method characterized by the above.

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