JP2007217072A - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer capable of printing at an appropriate position by correctly carrying a print medium in an appropriate state. <P>SOLUTION: Feed rollers 13d, 13f, resister rollers 14d, 14f, and a resister roller 16 are arranged from a paper feed part 12 in this order. After the print medium 2 is abutted on the resister rollers 14d, 14f by the feed rollers 13d, 13f to correct the attitudes, the resister rollers 14d, 14f are driven at a speed lower than the carrying speed of the print medium to carrying the print medium 2 in the carrying direction. When the print medium is detected by a resister sensor 16, the resister rollers 14d, 14f are stopped, and the print medium 2 is on standby in the held state by the resister rollers 14d, 14f. Then, the resister rollers 14d, 14f are driven at the carrying speed of the print medium to carrying the print medium 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention, for example, an ink jet printer that prints predetermined characters and images by ejecting fine particles (ink droplets) of liquid ink of a plurality of colors from nozzles of an ink jet head and forming minute dots on a print medium. It is about.

  Such an inkjet printer is generally inexpensive and can easily obtain a high-quality color printed matter. Accordingly, along with the widespread use of personal computers and digital cameras, it has become widespread not only in offices but also in general users.

  In general, such an ink jet printer reciprocates in a direction intersecting with the conveyance direction of a print medium by a moving body called a carriage integrally provided with an ink cartridge and an ink discharge head (generally called an ink jet head). However, by discharging (jetting) and outputting fine particles of liquid ink from the nozzles of the inkjet head, minute ink dots are formed on the print medium, and predetermined characters and images are drawn to create a desired printed matter. It has become. The carriage is equipped with four color (yellow, magenta, cyan) ink cartridges including black (black) and an inkjet head for each color, so that not only monochrome printing but also full-color printing combining each color is easy. (Furthermore, 6 colors, 7 colors, or 8 colors in which light cyan, light magenta, etc. are added to these colors are also put into practical use).

  Further, in this type of ink jet printer in which printing is executed while reciprocating the ink jet head on the carriage in the direction intersecting with the conveyance direction of the print medium, the ink jet head is set to 10 in order to cleanly print the entire page. It is necessary to reciprocate several times to several tens of times. In contrast, in an inkjet printer of a type in which a long inkjet head (not necessarily integrated) having the same dimensions as the width of the print medium is disposed and the carriage is not used, the inkjet head is moved in the width direction of the print medium. There is no need, and so-called one-pass printing is possible, so that high-speed printing is possible. The former inkjet printer is generally referred to as a “multi-pass (serial) inkjet printer”, and the latter inkjet printer is generally referred to as a “line head inkjet printer”.

By the way, in this type of ink jet printer, it is necessary to correct the posture of the conveyed print medium to a predetermined posture. For example, when the print medium is transported obliquely with respect to the transport direction is called skew, if printing is performed on the print medium in such a skewed state, the original print location cannot be printed. As a method having both the print medium posture correction function and the conveyance timing adjustment function, for example, there is a method using a registration roller described in Patent Document 1 below. In this prior art, the print medium of the paper feeding unit is conveyed by a feed roller and brought into contact with a registration roller, and the feed roller is further driven therefrom to bend the print medium, and then the registration roller is driven. The bending of the printing medium is released, the posture of the printing medium is corrected by releasing the bending, and the printing medium conveyance timing is adjusted.
JP 2003-195424 A

  However, in the related art described in Patent Document 1, if the front end of the printing medium in the conveyance direction is not accurately sandwiched between the registration rollers, slippage occurs between the printing medium and the registration rollers at the start of conveyance by the registration rollers. As a result, a difference occurs between the conveyance amount (driving amount) of the registration roller and the actual movement amount of the printing medium, which causes a problem that printing cannot be performed at an appropriate position.

  The present invention has been made paying attention to the above-described problems, and provides an ink jet printer capable of printing at an appropriate position by appropriately conveying a print medium in an appropriate state. It is for the purpose.

  [Invention 1] In order to solve the above-described problems, an inkjet printer according to Invention 1 is an inkjet that conveys a print medium from a paper feed unit to a print region and ejects ink droplets from nozzles of an inkjet head to perform printing on the print medium. In the printer, a feed roller is disposed ahead of the paper feed unit in the print medium conveyance direction, a registration roller is disposed ahead of the feed roller in the print medium conveyance direction, and the print medium is detected ahead of the registration roller in the print medium conveyance direction. The registration sensor is installed, and the posture is corrected by abutting the print medium against the registration roller with the feed roller, and then the registration roller is driven at a speed lower than the print medium conveyance speed to convey the print medium in the conveyance direction. When the registration sensor detects the print medium, the registration roller is stopped and the print medium is sandwiched between the registration rollers. And machine, then, is characterized in that for conveying the printing medium by driving the registration roller in the printing medium conveyance speed.

  According to the ink jet printer according to the first aspect of the present invention, the feed roller is disposed ahead of the feed unit in the print medium conveyance direction, the registration roller is disposed ahead of the feed roller in the print medium conveyance direction, and the registration roller conveys the print medium. A registration sensor that detects the print medium is arranged at the end of the direction, and the posture is corrected by abutting the print medium against the registration roller with the feed roller, and then the registration roller is driven at a speed lower than the print medium conveyance speed. When the print medium is conveyed in the conveyance direction and the print medium is detected by the registration sensor, the registration roller is stopped and the print medium is held between the registration rollers, and then the registration roller is driven at the print medium conveyance speed. Since the print medium is transported, the print medium transport direction is securely sandwiched between the registration rollers. Since the conveyance of the print medium by conveying the printing medium and from there the positive state can be made proper, it is possible to perform printing in the correct position.

[Invention 2] The inkjet printer of Invention 2 is characterized in that, in the inkjet printer of Invention 1, when the printing medium is sandwiched and conveyed by the registration rollers, the feeding of the printing medium by the feed roller is released. is there.
In the ink jet printer according to the second aspect of the present invention, when the print medium is sandwiched between the registration rollers and conveyed, the sandwich of the print medium by the feed roller is released, so that the registration roller and the feed roller rotate in an asynchronous state. Driving can be avoided, and thereby wrinkles and poor conveyance of the print medium can be avoided.

Next, a first embodiment of the inkjet printer of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an ink jet printer according to the present embodiment, FIG. 1a is a front view of the ink jet printer according to the present embodiment, and FIG. 1b is a plan view. Reference numeral 1 in the figure denotes an endless conveying belt for conveying a printing medium 2 such as printing paper. The conveyor belt 1 is wound around a driving roller 3 disposed at the left end in the figure, a driven roller 4 disposed at the right end in the figure, and a tension roller 5 disposed below the central part thereof. It has been turned. The drive roller 3 is driven to rotate in the direction of the arrow in the figure by a conveyance motor (not shown), and the print medium 2 is attracted to the conveyance belt 1 charged by a charging roller, which will be described later. Transport to the left, that is, in the direction of the arrow. The driven roller 4 is grounded so as to apply a voltage with the conveying belt 1 being sandwiched between the driven roller 4 and a contact portion of a charging roller described later. The tension roller 5 is urged downward by a spring (not shown), thereby applying tension to the transport belt 1.

  A charging roller 7 as a charging unit is in contact with the conveying belt 1 so as to face the driven roller 4, and a DC power supply 8 is connected to the charging roller 7. The arrangement of the charging roller 7 corresponds to the position immediately before the feeding position of the print medium 2. The charging roller 7 charges the surface of the conveyance belt 1 made of a medium / high resistance by charging, charges the print medium 2 by the charge, and charges and conveys the print medium 2 by the dielectric polarization. The print medium 2 is attracted to the surface of the conveyance belt 1 by electrostatic force due to the electric charge of the dielectric portion on the surface of the belt 1. The charging roller 7 is pressed against the transport belt 1 by a spring (not shown).

  A pressure roller 9 is disposed above the driven roller 4. The pressure roller 9 is configured to be pressed downward, that is, to the driven roller 4 side by a pressure solenoid (not shown), and has a function of pressing the print medium 2 against the conveyance belt 1 on the driven roller 4. As described above, when the print medium 2 is mounted on the outer peripheral surface of the charged transport belt 1 and the print medium 2 is pressed against the transport belt 1 by the pressure roller 9, the print medium 2 is placed on the outer peripheral surface of the transport belt 1 by dielectric polarization. Adsorbed.

  Reference numeral 11 in FIG. 1 denotes an inkjet head. The ink-jet head 11 is arranged so as to be shifted in the transport direction of the printing medium 2 for each of the four colors of yellow (Y), magenta (M), cyan (C), and black (K). Ink is supplied to each inkjet head 11 from an ink tank of each color (not shown) via an ink supply tube. Each inkjet head 11 is formed with a plurality of nozzles in a direction intersecting with the conveyance direction of the print medium 2, and by ejecting a necessary amount of ink droplets from these nozzles to a necessary location at the same time, the print medium 2. A minute ink dot is formed and output on the top. By performing this for each color, it is possible to perform so-called one-pass printing by passing the print medium 2 adsorbed on the conveyor belt 1 once. That is, the area where the inkjet head 11 is disposed corresponds to the print area.

  As a method for discharging and outputting ink from each nozzle of the ink jet head, there are an electrostatic method, a piezo method, a film boiling ink jet method, and the like. In the electrostatic system, when a drive pulse is applied to the electrostatic gap, which is an actuator, the diaphragm in the cavity is displaced, causing a pressure change in the cavity, and ink drops are ejected from the nozzle by the pressure change. It is. In the piezo method, when a driving pulse is applied to a piezo element that is an actuator, the diaphragm in the cavity is displaced to cause a pressure change in the cavity, and an ink droplet is ejected and output from the nozzle by the pressure change. . In the film boiling ink jet method, there is a minute heater in the cavity, the ink is instantaneously heated to 300 ° C. or more, the ink becomes a film boiling state, bubbles are generated, and ink droplets are ejected from the nozzle by the pressure change. That's it. Any ink output method can be applied to the present invention.

  A paper discharge sensor 21 for detecting the print medium 2 discharged to the paper discharge unit is disposed downstream of the drive roller 3 in the print medium conveyance direction. A paper feed sensor 22 for detecting the print medium 2 conveyed to the print area of the inkjet head 11 is disposed upstream of the inkjet head 11 in the print medium conveyance direction. A linear scale 23 is affixed to the outer peripheral surface of the conveyor belt 1, and a belt encoder 24 that reads the linear scale 23 is disposed. Further, a belt index 25 is formed on one side of the conveyance belt 1 in the width direction so as to protrude from the side, and a belt index sensor 26 such as an optical sensor for detecting the belt index 25 is disposed. ing.

  The print medium 2 before being fed is stored in the paper feed unit 12, and feed rollers 13 d and 13 f for feeding the print medium 2 of the paper feed unit 12 are arranged at the destination of the paper feed unit 12 in the print medium conveyance direction. The registration rollers 14d and 14f are disposed ahead of the feed rollers 13d and 13f in the print medium conveyance direction. The registration rollers 14d and 14f are for correcting the posture of the printing medium 2 abutted by the feed rollers 13d and 13f and adjusting the conveyance timing of the printing medium 2. As shown in FIG. 2, for example, one of the registration rollers 14d and 14f is driven by a stepping motor (not shown), and the other registration roller 14f is driven by the driving side registration roller 14d. A rotation arm 50 is attached to the driven side registration roller 14 f, and a registration solenoid 51 is attached to the rotation arm 50. Accordingly, when the registration solenoid 51 is driven, the rotation arm 51 is rotated, and accordingly, the driven registration roller 14f moves up and down in the figure. Abutting (the print medium 2 may be interposed) and spaced apart from the driving side registration roller 14 when positioned above the figure. In this structure, the feed rollers 13d and 13f have the same structure.

  A pre-registration sensor 15 is disposed in front of the registration rollers 14d and 14f in the printing medium conveyance direction, and a registration sensor 16 is disposed in the printing medium conveyance direction ahead of the registration rollers 14d and 14f. Both the pre-registration sensor 15 and the registration sensor 16 are for detecting the print medium 2 and are turned ON when the print medium 2 is conveyed to the sensor position.

  FIG. 3 shows a control device for controlling the ink jet printer of the present embodiment. This control device is equipped with a computer system as an arithmetic processing device, and includes a CPU 32 that is a central arithmetic processing device responsible for various controls and arithmetic processing. Further, as a drive circuit for driving an actual apparatus based on the calculation processing result of the CPU 32, a DC motor drive circuit 34 for driving and controlling a conveyance motor 33 for driving the drive roller 3 and a drive side registration roller 14d are driven. A stepping motor driving circuit 37 for driving and controlling a stepping motor 35 for driving the driving side feed roller 13d and a registration solenoid driving for driving and controlling a registration solenoid 51 for moving the driven side registration roller 14f. A circuit 38, a feed solenoid drive circuit 39 for driving and controlling a feed solenoid 53 for moving the driven feed roller 13f, a pressure contact solenoid drive circuit 40 for driving and controlling the pressure contact solenoid 53 for moving the pressure contact roller 9, and an inkjet head 11 a head driver 41 for controlling drive. The outputs of the pre-registration sensor 15, the registration sensor 16, the paper feed sensor 22, the paper discharge sensor 21, the belt index sensor 26, and the belt encoder 24 are also input to the CPU 32. Also, print image data is input from the host computer 60 to the CPU 32.

  When the control device obtains print image data from the host computer 60 via an interface (not shown), the CPU 32 executes predetermined processing on the print image data, and based on the processing data and input data from various sensors. The control signal is output to each drive circuit and driver. Each drive circuit and driver outputs a drive signal for each device, and for example, actuators, solenoids, and motors corresponding to a plurality of nozzles of the inkjet head 11 are operated to execute print processing on the print medium 2. Each component in the control device is electrically connected via a bus (not shown).

Next, of the arithmetic processing performed in the CPU 32 of the control device, the arithmetic processing until the print medium 2 of the paper feeding unit 12 is sandwiched between the registration rollers 14d and 14f and is set in the transport standby state is described using the flowchart of FIG. explain. In this calculation process, first, various solenoids and motors are initially set in step S1.
In step S2, the feed roller stepping motor 36 is driven at the printing medium conveyance speed.

Next, the process proceeds to step S3, where it is determined whether the pre-registration sensor 15 has detected the print medium 2. If the pre-registration sensor 15 has detected the print medium 2, the process proceeds to step S4. Wait.
In step S4, the feed roller stepping motor 36 is driven at a printing medium conveyance speed by a predetermined pulse, the printing medium 2 is abutted against the registration rollers 14d and 14f, and the printing medium 2 is further bent.

Next, the process proceeds to step S5, where the feed roller stepping motor 36 is stopped.
In step S6, the registration roller stepping motor 35 is driven at a lower speed than the printing medium conveyance speed.
In step S7, the feed solenoid 52 is contracted to separate the driven side feed roller 13f from the drive side feed roller 13d or the print medium 2.

Next, the process proceeds to step S8, where it is determined whether or not the registration sensor 16 has detected the printing medium 2. If the registration sensor 16 has detected the printing medium 2, the process proceeds to step S9. stand by.
In step S9, the registration roller stepping motor 35 is stopped and then returned to the main program.

  Next, among the calculation processes performed in the CPU 32 of the control device, the calculation process from the standby state in which the printing medium 2 is sandwiched between the registration rollers 14d and 14f to the printing process and discharging is shown in the flowchart of FIG. It explains using. In this calculation process, first, in step S11, it is determined whether or not the belt index 25 is detected by the belt index sensor 26. If the belt index sensor 26 detects the belt index 25, the process proceeds to step S12. In case you wait.

In step S12, the print position of the print medium 2 is adjusted.
In step S13, the registration roller stepping motor 35 is driven at the printing medium conveyance speed.
In step S14, the registration solenoid 51 is contracted to separate the driven registration roller 14f from the driving registration roller 14d or the print medium 2.

Next, the process proceeds to step S15, and a printing process is performed by performing a calculation process of FIG.
In step S16, the print medium 2 is discharged by a discharge roller (not shown), and then the process returns to the main program.

Next, the calculation process of the printing process performed in step S15 of the calculation process of FIG. 5 will be described with reference to the flowchart of FIG. In this calculation process, first, in step S31, it is determined whether or not the belt index 25 is detected by the belt index sensor 26. If the belt index sensor 26 detects the belt index 25, the process proceeds to step S32. In case you wait.
In step S32, the counter that counts the signal of the belt encoder 24 is reset.

Next, the process proceeds to step S33, and the signal of the belt encoder 24 is counted.
Next, the process proceeds to step S34, where it is determined whether or not the counted signal of the belt encoder 24 has reached a predetermined value and the print start position is reached. If the print start position is reached, the process proceeds to step S35. Otherwise, the process proceeds to step S33.

In step S35, the ink jet head 11 is driven to eject ink droplets from a predetermined nozzle.
Next, the process proceeds to step S36, where it is determined whether or not all the image data has been printed. If all the image data has been printed, the process proceeds to step S16 of the arithmetic processing in FIG. Control goes to step S35.

  Among these calculation processes, the conveyance, printing, and paper discharge processes of the print medium 2 by the calculation processes of FIGS. 5 and 6 are the same as those of the conventional ones. On the other hand, a feature of the present embodiment is that the printing medium 2 of the paper feeding unit 12 is sandwiched between registration rollers 14d and 14f and placed in a transport standby state by the arithmetic processing of FIG. That is, in this embodiment, after the printing medium 2 is abutted against the registration rollers 14d and 14f by the feed rollers 13d and 13f, and further, the feed rollers 13d and 13f are driven to bend the printing medium 2, and then the registration rollers 14d and 14f. Is driven at a lower speed than the predetermined printing medium conveying speed, and the driven feed roller 13f is separated. When the registration sensor 16 detects the leading edge of the printing medium 2, the registration rollers 14d and 14f are temporarily stopped, and the registration roller 14d and 14f waits with the leading edge of the printing medium 2 sandwiched between the registration rollers 14d and 14f. 14 d and 14 f are driven at a predetermined print medium conveyance speed to supply the print medium 2 onto the conveyance belt 1.

  This print medium conveyance state is shown in FIG. 7 by the speeds of the feed rollers 13d and 13f and the registration rollers 14d and 14f. For example, when the feed rollers 13d and 13f are started to drive at time t0 and the pre-registration sensor 15 detects the print medium 2 at time t1, the feed roller stepping motor 36 is then driven for the designated pulse to print the print medium 2 Is pressed against the registration rollers 14d and 14f, and the print medium 2 is further bent. When the printing medium 2 is bent, the feed rollers 13d and 13f are stopped at time t2, and then the registration rollers 14d and 14f are driven at low speed at time t3. As a result, the deflection of the printing medium 2 is released and the posture is corrected, and the leading end of the printing medium 2 is securely sandwiched between the registration rollers 14d and 14f. Next, when the registration sensor 16 detects the print medium 2 at time t4, the registration rollers 14d and 14f are temporarily stopped, and the standby is performed with the leading end portion of the print medium 2 sandwiched between the registration rollers 14d and 14f. Thereafter, at time t5, the registration rollers 14d and 14f are driven at a predetermined printing medium conveyance speed, and the printing medium 2 is supplied onto the conveyance belt 1.

  In FIG. 8, the movement trajectory from the feeding to the discharging of one print medium 2 is represented as the movement distance of the front end portion and the rear end portion in the transport direction of the print medium 2. The time corresponded to FIG. In the figure, time t3.5 is the time when the driven-side feed roller 13f is separated from the driving-side feed roller 13d or the print medium 2, and as a result, the deflection of the print medium 2 is released and the transport direction of the print medium 2 is reached. The rear end portion is lowered rearward in the transport direction, and the posture of the print medium 2 is corrected at this time.

  As described above, according to the ink jet printer of the present embodiment, the feed rollers 13d and 13f are disposed in the print medium conveyance direction ahead of the paper feed unit 12, and the registration rollers 14d are disposed in the print medium conveyance direction ahead of the feed rollers 13d and 13f. , 14f, a registration sensor 16 for detecting the printing medium 2 is arranged in the printing medium conveyance direction ahead of the registration rollers 14d, 14f, and the printing medium 2 is transferred to the registration rollers 14d, 14f by the feed rollers 13d, 13f. After the abutting and position correction, the registration rollers 14d and 14f are driven at a speed lower than the printing medium conveyance speed to convey the printing medium 2 in the conveyance direction. When the registration sensor 16 detects the printing medium, the registration roller 14d is detected. , 14f is stopped and the print medium 2 is put on standby with the registration rollers 14d and 14f sandwiched between them. After that, the registration rollers 14d and 14f are driven at the printing medium conveyance speed to convey the printing medium 2. Therefore, the leading end of the printing medium 2 in the conveyance direction is securely sandwiched between the registration rollers 14d and 14f. By transporting the print medium 2 from the proper posture and transporting the print medium 2 therefrom, the print medium 2 can be transported appropriately, so that printing can be performed at an appropriate position.

  Further, since the printing roller 2 is not sandwiched by the feed rollers 13d and 13f when the printing medium is sandwiched and conveyed by the registration rollers 14d and 14f, the registration rollers 14d and 14f and the feed rollers 13d and 13f are asynchronous. In this state, it is possible to avoid rotational driving, thereby avoiding wrinkles and poor conveyance of the print medium 2.

  In each of the above embodiments, only an example in which the inkjet printer of the present invention is applied to a line head inkjet printer has been described in detail. However, the inkjet printer of the present invention can be of any type including a multi-pass printer. It can be applied to an inkjet printer.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows 1st Embodiment of the inkjet printer of this invention, (a) is a front view, (b) is a top view. It is explanatory drawing of the registration roller of FIG. It is a block diagram which shows the control apparatus of the inkjet printer of FIG. It is a flowchart of the arithmetic processing performed with CPU of FIG. It is a flowchart of the arithmetic processing performed with CPU of FIG. It is a flowchart of the subroutine performed by the arithmetic processing of FIG. It is explanatory drawing of the effect | action of the arithmetic processing of FIG. It is explanatory drawing of the effect | action of the arithmetic processing of FIG. 4 thru | or FIG.

Explanation of symbols

  1 is a conveying belt, 2 is a printing medium, 3 is a driving roller, 4 is a driven roller, 5 is a tension roller, 7 is a charging roller, 8 is a DC power supply, 9 is a pressure contact roller, 11 is an inkjet head, and 12 is a paper feeding unit. , 13d and 13f are feed rollers, 14d and 14f are registration rollers, 15 is a pre-registration sensor, 16 is a registration sensor, 21 is a paper discharge sensor, 22 is a paper feed sensor, 23 is a linear scale, 24 is a belt encoder, and 25 is Belt index, 26 is a belt index sensor, 32 is a CPU

Claims (2)

  In an ink jet printer that transports a print medium from a paper feed unit to a print area and ejects ink droplets from nozzles of an ink jet head to print on the print medium, a feed roller is disposed at the end of the paper feed unit in the print medium transport direction. , A registration roller is disposed ahead of the feed roller in the printing medium conveyance direction, a registration sensor that detects the printing medium is disposed ahead of the registration roller in the printing medium conveyance direction, and the feed roller abuts against the registration roller. After correcting the position, the registration roller is driven at a speed lower than the printing medium conveyance speed to convey the printing medium in the conveyance direction. When the registration sensor detects the printing medium, the registration roller is stopped and the printing medium is registered. Stand by between the rollers, and then drive the registration roller at the printing medium conveyance speed to carry the printing medium. Inkjet printer characterized by.   2. The ink jet printer according to claim 1, wherein when the printing medium is sandwiched between the registration rollers and conveyed, the printing medium is nipped by the feed roller.

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