JP2007076872A - Ink jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet printer capable of detecting a position of at least either of a conveyance belt and a printing medium accurately by a simple structure. <P>SOLUTION: In this ink jet printer, for example, an end part of the conveyance belt 1 for loading and conveying the printing medium 2 is cut at a predetermined angle θ, its oblique side part 19 is obliquely moved for the direction of printing medium conveyance, for example, amount of travel of the conveyance belt 1 in the direction crossing the direction of printing medium conveyance of the oblique side part 19 accompanying with travel of the conveyance belt 1 is detected by an optical sensor 16, and amount of travel of the conveyance belt 1 in the direction of printing medium conveyance is calculated from the amount of travel to detect a position of the conveyance belt 1 or the printing medium 2. By loading printing medium 2 itself on the conveyance belt 1 by tilting it by only the predetermined angle θ for the direction of printing medium conveyance instead of the oblique side part 19 of the conveyance belt 1, an end side 22 of the printing medium 2 may be obliquely moved to detect its travel condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, for example, minute characters of liquid inks of a plurality of colors are ejected from a plurality of nozzles to form fine particles (ink dots) on a print medium, thereby drawing a predetermined character or image. The present invention relates to an ink jet printer.

Such inkjet printers are generally inexpensive and can easily obtain high-quality color prints, and therefore have become widespread not only in offices but also in general users with the spread of personal computers and digital cameras.
In general, such an ink jet printer has a moving body called a carriage in which an ink cartridge and a print head are integrally provided, reciprocating on a print medium in a direction intersecting the transport direction. By ejecting (jetting) liquid ink droplets from the nozzles to form minute ink dots on the printing medium, a desired printed matter is created by drawing predetermined characters or images on the printing medium. Yes. The carriage is equipped with four color (yellow, magenta, cyan) ink cartridges including black (black) and a print 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 a direction intersecting with the conveyance direction of the print medium, the ink jet head is set to 10 to cleanly print the entire page. Since it is necessary to reciprocate from several times to several tens of times, there is a disadvantage that it takes much printing time compared with other types of printing apparatuses such as laser printers and copying machines using electrophotographic technology.

  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. This is not necessary, and so-called one-pass printing is possible, so that high-speed printing similar to the laser printer 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 order to perform high-quality printing with this type of ink jet printer, it is necessary to accurately eject ink droplets to a target position of a print medium. In a conventional inkjet printer, an encoder pattern such as a linear scale is attached to a conveyance belt for conveying a print medium, and the encoder pattern is read by an optical sensor to detect the amount of movement of the conveyance belt or to drive the conveyance belt The ink droplet ejection timing is set by detecting the position of the print medium, for example, by detecting the amount of movement of the conveying belt with a rotary encoder attached to the driving roller. Further, in the ink jet printer described in Patent Document 1 below, for example, a comb-shaped electrode provided on a conveyance belt to adsorb a print medium is detected by an optical sensor, and the position of the print medium is detected from the amount of movement. Ink droplet ejection timing is set.
JP 2003-89446 A

However, the conventional ink jet printer has a problem that the structure is complicated because it is necessary to attach an encoder or provide a comb electrode.
The present invention has been made paying attention to the above-described problems, and provides an ink jet printer capable of accurately detecting the position of at least one of a conveyor belt and a print medium with a simple structure. It is intended to do.

  [Invention 1] In order to solve the above-mentioned problems, an inkjet printer according to Invention 1 is an inkjet printer in which a printing medium is placed on a conveying belt and conveyed, and ink droplets are ejected onto the printing medium to perform printing. While maintaining a predetermined angle with respect to the conveyance direction of the print medium, at least one of a skew portion that skews with the conveyance of the print medium and a change state of the skew portion from the conveyance belt and the print medium And a position detecting means for detecting the position of the head.

  According to the ink jet printer of the first aspect of the present invention, the state of change in the skew portion that is skewed with the conveyance of the print medium is detected while maintaining a predetermined angle with respect to the conveyance direction of the print medium. Since the configuration is such that the position of at least one of the conveyance belt and the print medium is detected from the state of change in the row portion, a simple structure can be achieved if the skew portion is configured by a part of the conveyance belt or the edge of the print medium. It is possible to accurately detect the position of at least one of the conveyor belt and the print medium.

[Invention 2] The ink jet printer of Invention 2 is the ink jet printer of Invention 1, wherein the position detecting means is an optical device for detecting a light blocking state by the skew feeding portion in order to detect a change state of the skew feeding portion. A sensor is provided.
According to the ink jet printer according to the second aspect of the present invention, if the light shielding state by the skew feeding portion is detected by the optical sensor and the state of the change is detected, at least the conveying belt and the print medium can be formed with a very simple structure. Either one of the positions can be accurately detected.

  [Invention 3] The ink jet printer of Invention 3 is the ink jet printer of Invention 2, wherein the optical sensor moves from the light shielding state by the skew feeding portion in a direction intersecting the print medium conveyance direction. The position detection means detects the amount of movement of the skew portion detected by the optical sensor in the direction intersecting the print medium conveyance direction, and conveys at least one of the conveyance belt and the print medium. The movement amount in the direction is calculated, and the position of at least one of the conveyance belt and the print medium is detected from the movement amount.

  According to the ink jet printer of the third aspect, the optical sensor detects the amount of movement of the skew portion in the direction intersecting the print medium conveyance direction from the light shielding state by the skew portion, and prints the skew portion. The movement amount in the print medium conveyance direction of at least one of the conveyance belt and the print medium is calculated from the movement amount in the direction intersecting the medium conveyance direction, and at least one of the conveyance belt and the print medium is calculated from the movement amount. The position detection configuration simplifies the configuration of the optical sensor and simplifies the method for calculating the amount of movement of at least one of the transport belt and print medium in the print medium transport direction, reducing the computational load. can do.

[Invention 4] The inkjet printer according to Invention 4 is the inkjet printer according to Invention 3, wherein the skew portion is formed at an end portion of the conveyance belt and is inclined at the predetermined angle with respect to the conveyance direction of the print medium. It is composed of a moving hypotenuse.
According to the ink jet printer according to the fourth aspect of the present invention, the oblique portion is formed by the oblique side portion formed at the end portion of the conveyance belt and moving obliquely at a predetermined angle with respect to the conveyance direction of the print medium. If the hypotenuse part is formed integrally with the part, the structure becomes even simpler and the position of the conveyor belt can be accurately detected.

 [Invention 5] The inkjet printer of Invention 5 is the inkjet printer of Invention 4, wherein the length of the oblique side portion in the print medium conveyance direction is L, and the length of the oblique side portion in the direction intersecting the print medium conveyance direction. Is Y, and A is the printing resolution per unit length in the print medium conveyance direction, the resolution B per unit length of the optical sensor is L × A / Y.

Here, the resolution B of the optical sensor is L × A / Y when it is expressed in the dpi unit system, and when expressed in the metric unit system, the resolution B is Y × A / L. Hereinafter, the resolution of the optical sensor will be described in the dpi unit system in the present invention.
According to the ink jet printer of the fifth aspect of the present invention, the length of the oblique side in the print medium conveyance direction is L, the length of the oblique side in the direction intersecting the print medium conveyance direction is Y, and the unit in the print medium conveyance direction When the print resolution per length is A, the resolution B per unit length of the optical sensor is set to L × A / Y, so that the print resolution in the print medium conveyance direction can be ensured.

[Invention 6] The inkjet printer according to Invention 6 is the inkjet printer according to Invention 3, in which the skew feeding portion is placed on the conveyance belt at an angle with respect to the conveyance direction of the print medium. It is characterized by comprising the edge of the medium itself.
According to the ink jet printer of the sixth aspect of the present invention, the print medium is obliquely placed on the conveyance belt at a predetermined angle, and the skew portion is formed on the edge of the print medium itself, so that the structure is further simplified. The position of the print medium can be accurately detected.

 [Invention 7] The inkjet printer according to Invention 7 is the inkjet printer according to Invention 6, wherein the optical sensor extends from a gap formed in the conveyance belt in a direction intersecting a print medium conveyance direction of the edge of the print medium itself. A plurality of optical sensors are arranged at an interval x = z / tan θ with respect to the print medium conveyance direction, where θ is the predetermined angle and z is the gap width. It is what.

  According to the ink jet printer of the seventh aspect of the present invention, the amount of movement of the edge of the print medium itself in the direction intersecting the print medium conveyance direction is detected by the optical sensor from the gap formed on the conveyance belt, and the predetermined angle Is θ and the width of the gap is z, a plurality of optical sensors are arranged at intervals x = z / tan θ in the print medium conveyance direction, so that the position of the print medium can be detected continuously. It becomes possible.

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. Reference numeral 1 in the figure denotes an endless conveying belt for conveying a printing medium 2 such as recording paper. The print medium 2 is a medium / high resistance sheet-like member such as recording paper or an OHP sheet. The conveyor belt 1 is made of a medium / high resistance dielectric. 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 an electric motor, 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 and charges the surface of the conveyance belt 1 made of a dielectric material, and generates dielectric polarization in the print medium 2 by the charge. The charge of the print medium 2 due to the dielectric polarization and the conveyance belt 1 The print medium 2 is attracted to the surface of the transport belt 1 by electrostatic force due to the charge of the dielectric portion on the surface. Reference numeral 10 in the drawing denotes a spring that presses the charging roller 7 against the transport belt 1.

  A paper pressing roller 9 is disposed above the driven roller 4. The paper pressing roller 9 is urged downward by a spring (not shown) and has a function of pressing the print medium 2 against the conveying 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 paper pressing roller 9, the print medium 2 becomes the outer peripheral surface of the transport belt 1 by dielectric polarization. To be adsorbed. A pair of upper and lower gate rollers 13 is disposed upstream of the paper pressing roller 9 in the conveyance direction of the printing medium 2. The gate roller 13 adjusts the timing at which the printing medium 2 fed from the paper feeding unit 14 by the pickup roller 6 is fed onto the conveying belt 1 and also bends the printing medium 2 in the conveying direction and corrects so-called skew. . Reference numeral 15 in the drawing denotes a paper discharge unit that discharges the print medium 2.

  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 (hereinafter also referred to as a nozzle row direction), and a necessary amount of ink droplets are simultaneously applied to necessary portions from these nozzles. Are ejected to form and output minute ink dots on the print medium 2. 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.

  FIG. 2 shows a detailed bottom view of the inkjet head 11. It is difficult to produce a so-called in-line type ink jet head that covers the entire width of the print medium 2, which is disadvantageous in terms of cost. Therefore, in practice, relatively small inkjet heads called inkjet blocks 11b are arranged in a staggered manner, and for example, the gap between the print widths of adjacent inkjet blocks 11b in the same nozzle row is set to the print width of the inkjet block 11b in the adjacent nozzle row. Are interpolated to constitute the inkjet head 11 having the entire width of the print medium 2 as a whole.

  As a method for ejecting 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 signal is given 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 drive signal is given to a piezo element that is an actuator, the diaphragm in the cavity is displaced to cause a pressure change in the cavity, and ink droplets are ejected 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 control device for controlling itself is provided in the ink jet printer. For example, as shown in FIG. 3, the control device prints on a print medium by controlling a printing device, a paper feeding device, and the like based on print data input from a host computer 60 such as a personal computer or a digital camera. The processing is performed. An input interface unit 61 that receives print data input from the host computer 60, and a control unit 62 configured by, for example, a microcomputer that executes print processing based on the check data input from the input interface unit 61; A drive signal generating circuit 70 for generating a drive signal COM, an oscillation circuit 71 for outputting a clock signal SCK, a control signal from the control unit 62, a drive signal COM from the drive signal generating circuit 70, and a clock from the oscillation circuit 71. An output interface unit 63 that converts the signal SCK into a drive signal for the inkjet head 11 and the electric motor 20, and outputs a light projection signal to the light projector 17 of the optical sensor 16 to be described later, or from the light receiver 18 of the optical sensor 16. Input / output interface for reading output pulses Constituted by a 4.

  The control unit 62 temporarily stores a CPU (Central Processing Unit) 62a that executes various processes such as a print process, and print data input through the input interface 61 or various data when the print data print process is executed. A ROM (Read-Only ROM) comprising a RAM (Random Access Memory) 62c that temporarily stores an application program such as print processing or the like, and a non-volatile semiconductor memory that stores a control program executed by the CPU 62a Memory) 62d. When the control unit 62 obtains print data (image data) from the host computer 60 via the input interface unit 61, the CPU 62 a executes a predetermined process on the print data, and the process data and the optical sensor 16. Based on the output pulse from the light receiver 18, a control signal is output to the output interface unit 63 and the input / output interface unit 64. As a result, from the output interface unit 63, the motor drive signal DM is directed toward the electric motor 20, the pixel data SI, the waveform pattern data SP, the latch signal LAT, the channel signal CH, the drive signal COM, and the clock signal are directed toward the inkjet head 11. SCK is output respectively.

  The inkjet head 11 includes first to third shift registers 81 to 83 and first to third shifts that sequentially store the pixel data SI and the waveform pattern data SP output from the output interface unit 63 based on the clock signal SCK. First and second latch circuits 84 and 85 that latch the stored contents of the registers 81 to 83 based on the latch signal LAT, and a control logic circuit that sets the decoding timing of the latched contents based on the latch signal LAT and the channel signal CH 86, a decoder 87 for decoding the contents latched by the first and second latch circuits 84 and 85 at the decoding timing set by the control logic circuit 86, a level shifter 88 for increasing the voltage of the signal decoded by the decoder 87, and a level shifter 88 Switch circuit 89 that is opened and closed by the output of, and switch circuit 8 It is driven by the drive signal COM output from, and includes a piezoelectric vibrator 90 as an actuator for ejecting ink droplets pressurizing the ink in the cavity.

  Returning to FIG. 1, a projector 17 of the optical sensor 16 is disposed above the driven belt 4 in the upper portion of the conveyor belt 1 so as to sandwich the front end of the conveyor belt 1 in the figure. A light receiver 18 of the optical sensor 16 is disposed below. A longitudinal sectional view of the optical sensor 16 viewed from the left side is shown in FIG. 4, and a plan view is shown in FIG. FIG. 6 is a development view of the conveyor belt 1. First, the conveyor belt 1 has one end, in this case, the lower end in FIG. 6 sandwiched between the optical sensors 16, which is slanted from the left and right sides of the figure, and the portions other than the constant width Z are isosceles triangles. Eggplant. That is, in FIG. 6, the center part of the figure is the widest and gradually narrows toward both ends. The portion where the end side is formed obliquely is defined as the oblique side portion 19.

  Each of the left and right oblique sides 19 in FIG. 6 has a predetermined angle θ constant with respect to the print medium conveyance direction. That is, when the conveyance belt 1 is moved in the print medium conveyance direction by joining the left and right ends of the conveyance belt 1 shown in FIG. The moving state is repeated in which it spreads at an angle θ, then narrows at a predetermined angle θ, and spreads again at a predetermined angle θ. Accordingly, the oblique side portion 19 constitutes the oblique portion of the ink jet printer of the present invention.

  As shown in FIG. 5, the optical sensor 16 is arranged in a direction intersecting the print medium conveyance direction, that is, in the nozzle row direction. The projector 17 of the optical sensor 16 includes, for example, an LED that is a light emitter and a collimator lens that condenses the light into parallel light. On the other hand, the light receiver 18 of the optical sensor 16 includes a plurality (a large number) of photodiodes PD arranged in the nozzle row direction as light receiving elements, and a logic circuit XOR connected to the output terminals of the photodiodes PD. Is done. FIG. 7 representatively shows a part of the light receiver 18. The logic circuit XOR is a circuit that calculates a so-called exclusive OR, and its output becomes a low level when the two inputs are the same and a high level when the two inputs are different.

  For example, eight photodiodes PD1 to PD8 shown in FIG. 7 are evenly arranged over the entire width Y in the nozzle row direction of the oblique side portion 19, and among them, the first photodiode PD1 is the width direction of the transport belt 1 ( (= Nozzle row direction) is disposed on the outermost side, and the eighth photodiode PD8 is disposed on the innermost side in the width direction (= nozzle row direction) of the transport belt 1. Assuming a situation where the width of is gradually widened and then narrowed. In the state where the width of the conveyor belt 1 is narrow and all the photodiodes PD1 to PD8 receive light, the outputs of all the photodiodes PD1 to PD8 are at the Hi level, and therefore the output of the first photodiode PD1 and the second photodiode The output of the first logic circuit XOR1 to which the output of PD2 is input is the Low level, the output of the second logic circuit XOR2 to which the output of the first logic circuit XOR1 and the output of the third photodiode PD3 are input are the Hi level, and the second The output of the third logic circuit XOR3 to which the output of the logic circuit XOR2 and the output of the fourth photodiode PD4 are input is the Low level, and the output of the third logic circuit XOR3 and the output of the fifth photodiode PD5 are input to the fourth logic. The output of the circuit XOR4 is Hi level, the output of the fourth logic circuit XOR4 and the output of the sixth photodiode PD6. The output of the fifth logic circuit XOR5 input is at the Low level, the output of the fifth logic circuit XOR5 and the output of the seventh photodiode PD7 are input at the Hi level, and the output of the sixth logic circuit XOR6. The output of the seventh logic circuit XOR7 to which the output and the output of the eighth photodiode PD8 are input is at a low level, and the final output is at a low level.

  When the conveyance belt 1 moves from this state and the first photodiode PD1 is shielded from light by the oblique side portion 19, the output becomes the low level, and therefore the output of the first logic circuit XOR1 becomes the high level. The output of the second logic circuit XOR2 is Low level, the output of the third logic circuit XOR3 is Hi level, the output of the fourth logic circuit XOR4 is Low level, the output of the fifth logic circuit XOR5 is Hi level, and the output of the sixth logic circuit XOR6 Becomes Low level, the output of the seventh logic circuit XOR7 becomes Hi level, and the final output becomes Hi level.

  When the conveyor belt 1 further moves and the second photodiode PD2 is shielded from light by the oblique side portion 19, the outputs of the first photodiode PD1 and the second photodiode PD3 become low level, so the output of the first logic circuit XOR1. The output of the second logic circuit XOR2 is Hi level, the output of the third logic circuit XOR3 is Low level, the output of the fourth logic circuit XOR4 is Hi level, and the output of the fifth logic circuit XOR5 is Low. The output of the sixth logic circuit XOR6 becomes Hi level, the output of the seventh logic circuit XOR7 becomes Low level, and the final output becomes Low level.

  Further, when the conveyance belt 1 moves and the third photodiode PD3 is shielded from light by the oblique side portion 19, the outputs of the first photodiode PD1 to the third photodiode PD3 become low level, so the output of the first logic circuit XOR1. Remains at the Low level, the output of the second logic circuit XOR2 becomes the Low level, and the output of the third logic circuit XOR3 is at the Hi level, the output of the fourth logic circuit XOR4 is at the Low level, and the output of the fifth logic circuit XOR5. Becomes Hi level, the output of the sixth logic circuit XOR6 becomes Low level, the output of the seventh logic circuit XOR7 becomes Hi level, and the final output becomes Hi level.

  When the conveyor belt 1 further moves and the fourth photodiode PD4 is shielded from light by the oblique side portion 19, the outputs of the first photodiode PD1 to the fourth photodiode PD4 are set to the low level. The output of the third logic circuit XOR3 becomes the Low level while the output of the second logic circuit XOR2 remains at the Low level. Hereinafter, the output of the fourth logic circuit XOR4 becomes the Hi level, the output of the fifth logic circuit XOR5 becomes the Low level, The output of the sixth logic circuit XOR6 becomes Hi level, the output of the seventh logic circuit XOR7 becomes Low level, and the final output becomes Low level.

  Further, when the conveyor belt 1 moves and the fifth photodiode PD5 is shielded from light by the oblique side portion 19, the outputs of the first photodiode PD1 to the fifth photodiode PD5 go to the low level, so the first logic circuits XOR1 to XOR1. The output of the fourth logic circuit XOR4 becomes the Low level while the output of the third logic circuit XOR3 remains at the Low level. Hereinafter, the output of the fifth logic circuit XOR5 becomes the Hi level, the output of the sixth logic circuit XOR6 becomes the Low level, 7 The output of the logic circuit XOR7 becomes Hi level, and the final output becomes Hi level.

  When the conveyor belt 1 further moves and the sixth photodiode PD6 is shielded from light by the oblique side portion 19, the outputs of the first photodiode PD1 to the sixth photodiode PD6 go to the low level, so that the first logic circuits XOR1 to XOR1. The output of the fifth logic circuit XOR5 becomes the Low level while the output of the fourth logic circuit XOR4 remains at the Low level. Hereinafter, the output of the sixth logic circuit XOR6 becomes the Hi level, and the output of the seventh logic circuit XOR7 becomes the Low level. The final output is at a low level.

  When the conveyor belt 1 further moves and the seventh photodiode PD7 is shielded from light by the oblique side portion 19, the outputs of the first photodiode PD1 to the seventh photodiode PD7 are set to the low level, and therefore the first logic circuits XOR1 to XOR1. While the output of the fifth logic circuit XOR5 remains at the Low level, the output of the sixth logic circuit XOR6 becomes the Low level, the output of the seventh logic circuit XOR7 becomes the Hi level, and the final output becomes the Hi level.

  When the conveyor belt 1 is further moved and the eighth photodiode PD8 is shielded from light by the oblique side portion 19, all outputs of the first photodiode PD1 to the eighth photodiode PD8 are set to the low level, and therefore the first logic circuit XOR1. The output of the seventh logic circuit XOR7 becomes the Low level while the output of the sixth logic circuit XOR6 remains at the Low level, and the final output becomes the Low level.

From this state, when the conveyor belt 1 is further moved and the eighth photodiode PD8 receives light by the opposite oblique side portion 19, only the output of the eighth photodiode becomes Hi level, so the first logic circuits XOR1 to XOR6. The output of the seventh logic circuit XOR7 becomes Hi level while the output of the logic circuit XOR6 remains Low level, and the final output becomes Hi level.
Further, when the conveyor belt 1 is moved and the seventh photodiode PD7 is also received by the opposite oblique side portion 19, the seventh photodiode PD7 and the eighth photodiode PD8 are set to the Hi level. Therefore, the first logic circuits XOR1 to XOR5 are used. The output of the sixth logic circuit XOR6 becomes Hi level, the output of the seventh logic circuit XOR7 becomes Low level, and the final output becomes Low level while the output of the logic circuit XOR5 remains Low level.

  Further, when the conveyor belt 1 moves and the sixth photodiode PD6 receives light by the opposite oblique side portion 19, the outputs of the sixth photodiode PD6 to the eighth photodiode PD8 become Hi level, so that the first logic circuits XOR1 to While the output of the fourth logic circuit XOR4 remains at the Low level, the output of the fifth logic circuit XOR5 becomes the Hi level. Hereinafter, the output of the sixth logic circuit XOR6 becomes the Low level, and the output of the seventh logic circuit XOR7 becomes the Hi level. Thus, the final output becomes Hi level.

  Further, when the conveyor belt 1 moves and the fifth photodiode PD5 is also received by the oblique side 19 on the opposite side, the outputs of the fifth photodiode PD5 to the eighth photodiode PD8 become Hi level, so the first logic circuits XOR1 to The output of the fourth logic circuit XOR4 becomes Hi level while the output of the third logic circuit XOR3 remains at Low level. Hereinafter, the output of the fifth logic circuit XOR5 becomes Low level, the output of the sixth logic circuit XOR6 becomes Hi level, The output of the seventh logic circuit XOR7 becomes the Low level, and the final output becomes the Low level.

  Further, when the conveyor belt 1 moves and the fourth photodiode PD4 is also received by the oblique side 19 on the opposite side, the outputs of the fourth photodiode PD4 to the eighth photodiode PD8 become Hi level, so that the first logic circuit XOR1 and While the output of the second logic circuit XOR2 remains at the Low level, the output of the third logic circuit XOR3 becomes the Hi level. Hereinafter, the output of the fourth logic circuit XOR4 is at the Low level, the output of the fifth logic circuit XOR5 is at the Hi level, The output of the sixth logic circuit XOR6 becomes Low level, the output of the seventh logic circuit XOR7 becomes Hi level, and the final output becomes Hi level.

  Further, when the conveying belt 1 moves and the third photodiode PD4 is also received by the oblique side 19 on the opposite side, the outputs of the third photodiode PD3 to the eighth photodiode PD8 become Hi level, so that the first logic circuit XOR1 The output of the second logic circuit XOR2 becomes Hi level while the output remains at the Low level. Hereinafter, the output of the third logic circuit XOR3 is Low level, the output of the fourth logic circuit XOR4 is Hi level, and the output of the fifth logic circuit XOR5 The output is Low level, the output of the sixth logic circuit XOR6 is Hi level, the output of the seventh logic circuit XOR7 is Low level, and the final output is Low level.

  Further, when the conveyor belt 1 moves and the second photodiode PD2 is also received by the opposite oblique side portion 19, the outputs of the second photodiode PD2 to the eighth photodiode PD8 become Hi level, so that the first logic circuit XOR1 The output becomes Hi level, and hereinafter, the output of the second logic circuit XOR2 is Low level, the output of the third logic circuit XOR3 is Hi level, the output of the fourth logic circuit XOR4 is Low level, and the output of the fifth logic circuit XOR5 is The Hi level, the output of the sixth logic circuit XOR6 becomes the Low level, the output of the seventh logic circuit XOR7 becomes the Hi level, and the final output becomes the Hi level.

  When the conveyor belt 1 further moves and receives light from the first photodiode PD1 by the oblique side 19 on the opposite side, all the outputs from the first photodiode PD1 to the eighth photodiode PD8 are at the Hi level. The output of the logic circuit XOR1 becomes the Low level. Hereinafter, the output of the second logic circuit XOR2 is the Hi level, the output of the third logic circuit XOR3 is the Low level, the output of the fourth logic circuit XOR4 is the Hi level, and the fifth logic circuit. The output of XOR5 becomes Low level, the output of the sixth logic circuit XOR6 becomes Hi level, the output of the seventh logic circuit XOR7 becomes Low level, and the final output becomes Low level.

  FIG. 8 shows this in time series. Since such a pulse is output from the light receiver 18 of the optical sensor 16, if the rising edge and falling edge of this pulse are counted by, for example, a pulse counter built in the CPU 62a of the control unit 62, the hypotenuse The amount of movement of the portion 19 in the direction intersecting the print medium conveyance direction, that is, the nozzle row direction can be detected, and the direction of the oblique side portion 19 intersecting the print medium conveyance direction, ie, the amount of movement in the nozzle row direction can be detected. Using the ratio of the length of the oblique side portion 19 in the print medium conveyance direction to the direction intersecting the print medium conveyance direction, that is, the length in the nozzle row direction (or the tangent value tan θ of the predetermined angle θ), the amount of movement of the conveyance belt 1 From which the position of the transport belt 1 or the print medium 2 adsorbed and mounted thereon can be detected.

  Here, the resolution required for the optical sensor 16 will be considered. For example, as shown in FIG. 9, the length of the oblique side 19 in the print medium conveyance direction is L (= 2), and the direction intersecting the print medium conveyance direction, that is, the nozzle row direction length is Y (= 1). Assuming that the printing resolution in the medium transport direction is A, for example, when the printing resolution A per unit length is 360 dpi, the resolution B per unit length of the optical sensor 16 needs to be 720 dpi, which is twice that. That is, the required resolution B per unit length of the optical sensor 16 is the print medium transport direction length L of the oblique side 19 × the print resolution A per unit length in the print medium transport direction / the direction intersecting the print medium transport direction. That is, the nozzle row direction length Y is obtained.

  As described above, according to the ink jet printer of the present embodiment, the skew portion (slope side portion 19) that skews with the conveyance of the print medium 2 while maintaining the predetermined angle θ with respect to the conveyance direction of the print medium 2. ) Change state is detected, and the position of at least one of the conveyance belt 1 and the print medium 2 is detected from the change state of the skew portion (slope side portion 19). By configuring the skew portion (slope side portion 19), it is possible to accurately detect the position of at least one of the conveyor belt 1 and the print medium 2 with a simple structure.

Further, since the optical sensor 16 detects the light shielding state by the oblique portion (the oblique side portion 19) and detects the change state thereof, at least the transport belt 1 and the print medium 2 can be formed with a very simple structure. Either one of the positions can be accurately detected.
Further, the optical sensor 16 detects the amount of movement of the skew portion (slope side portion 19) in the direction intersecting the print medium conveyance direction, that is, the nozzle row direction, from the light shielding state by the skew portion (slope side portion 19). The amount of movement of the conveyor belt 1 in the print medium conveyance direction is calculated from the amount of movement of the skew portion (the oblique side portion 19) in the direction intersecting the print medium conveyance direction, that is, the nozzle row direction, and the conveyance amount is calculated from the amount of movement. Since the configuration is such that the position of at least one of the belt 1 and the print medium 2 is detected, the configuration of the optical sensor 16 can be simplified, and the method for calculating the amount of movement of the transport belt 1 in the print medium transport direction can be simplified. The calculation load can be reduced.

In addition, since the oblique portion 19 is formed by the oblique side portion 19 formed at the end portion of the conveyance belt 1 and moving obliquely at a predetermined angle θ with respect to the conveyance direction of the print medium 2, the oblique side portion is formed at the end portion of the conveyance belt 1. By integrally molding 19, the structure can be further simplified and the position of the conveyor belt can be accurately detected.
Further, the length of the oblique side portion 19 in the print medium conveyance direction is L, the length of the oblique side portion 19 intersecting the print medium conveyance direction, that is, the length in the nozzle row direction is Y, and the unit length in the print medium conveyance direction When the print resolution per unit is A, the resolution B per unit length of the optical sensor 16 is L × A / Y, so that the print resolution in the print medium conveyance direction can be ensured.

  FIG. 10 shows another embodiment in which the oblique side portion 19 is formed at the end portion of the conveyor belt 1 and this is the oblique portion. In this embodiment, the ratio between the length L of the oblique side portion 19 in the print medium conveyance direction and the length Y of the oblique side portion 19 intersecting the print medium conveyance direction, that is, the length Y in the nozzle row direction is as shown in FIG. , But their dimensions are smaller than those of FIG. In the present embodiment, a plurality of oblique portions including the small oblique sides 19 are continuously formed on one end portion of the conveyance belt 1.

  The principle of detecting the position of the conveyance belt 1 and the print medium 2 in this embodiment is the same as that of the above-described embodiment, but in this embodiment, the direction intersecting the print medium conveyance direction of the oblique side portion 19, that is, the nozzle row direction. Since the length Y of the optical sensor 16 is small, the size of the optical sensor 16 can be small. For example, when a photodiode is used as the light receiving element, the number of photodiodes used is the same even if the printing resolution in the print medium conveyance direction is the same. Less. Therefore, in addition to the effects described above, the ink jet printer according to the present embodiment can be reduced in size and cost.

  Next, a second embodiment of the ink jet printer of the present invention will be described with reference to FIGS. The overall configuration of the ink jet printer of this embodiment is the same as that shown in FIGS. 1 to 3 of the first embodiment. FIG. 11 is a plan view of the conveyance belt 1 of the present embodiment. In this embodiment, the conveyance belt 1 is divided in the width direction, a gap 21 is formed between them, and the optical sensor 16 is disposed below the gap 21 and on the back side of the conveyance belt 1. In addition, the code | symbol 111K in a figure is the printing area | region of the inkjet head 11 which prints black (K), the code | symbol 111C is the printing area | region of the inkjet head 11 which prints cyan (C), the code | symbol 111M is magenta (M). A print area of the inkjet head 11 for printing, the reference numeral 111Y, indicates a print area of the inkjet head 11 for printing yellow (Y).

  In this embodiment, as shown in FIG. 12, the print medium 2 is sucked and placed on the transport belt 1 at an angle of θ with respect to the print medium transport direction. Then, the edge 22 of the print medium 2 moves obliquely with a predetermined angle θ with respect to the print medium conveyance direction, and this constitutes a skew portion of the ink jet printer of the present invention. The edge 22 of the print medium 2 that moves obliquely by a predetermined angle θ with respect to the print medium conveyance direction is detected by the optical sensor 16 from between the gaps 21 in the same manner as in the first embodiment.

  The movement amount of the edge 22 in the direction intersecting the print medium conveyance direction, that is, in the nozzle row direction is the maximum, and only the width z of the gap 21 can be obtained. Then, only the value obtained by dividing the width z of the gap 21 by the tangent value tanθ of the predetermined angle θ can be obtained as the amount of movement of the edge 2 in the print medium conveyance direction. Therefore, a plurality of optical sensors 16 need to be arranged at intervals x = z / tan θ along the print medium conveyance direction. Further, in order to perform printing up to the last nozzle line in the conveyance direction of the print medium 2 while detecting the position of the print medium 2, printing is performed while being inclined at a predetermined angle θ. From the length h in the print medium conveyance direction of the medium 2 to the position where the end 22 can be detected in the print medium conveyance direction in the print medium conveyance direction, that is, the position obtained by subtracting the interval x. It is necessary to dispose the optical sensor 16 at a position away from the last nozzle line in the print medium conveyance direction. Incidentally, the length h in the print medium conveyance direction of the print medium 2 conveyed while being inclined by the predetermined angle θ is a value obtained by multiplying the length of the print medium 2 by the cosine value cos θ of the predetermined angle θ, and the width of the print medium 2. Is obtained by multiplying by a sine value sin θ of a predetermined angle θ. The switching of the optical sensor 16 for detecting the position of the print medium 2 is controlled when the light shielding by the edge 22 has already started, that is, when all the photodiodes PD of the active optical sensor 16 are shielded from light. The CPU 62a in the unit 62 switches a switch (not shown) to activate the optical sensor 16 at the next stage in the print medium conveyance direction.

  FIG. 13 shows an example of the paper supply unit 14 that places and sucks the print medium 2 by a predetermined angle θ with respect to the print medium conveyance direction. In the drawing, the gap of the conveyor belt 1 and the optical sensor are omitted. Further, the length of the conveyor belt 1 is also shown in a shortened manner. As shown in FIG. 13 a, the paper feed unit 14 extends a fixed guide 23 that is inclined by a predetermined angle θ with respect to the print medium conveyance direction, and a movable guide 24 that is perpendicular to the fixed guide 23 is disposed at the end. Set up. As a result, as shown in FIG. 13 b, the print medium 2 is moved in the direction of the arrow by the pickup roller 6 so that the leading end of the print medium 2 abuts against the movable guide 24. When the movable guide 24 is moved upward from this state, as shown in FIG. 13C, the print medium 2 is placed and sucked on the transport belt 1, and the print medium 2 is moved at a predetermined angle θ with respect to the print medium transport direction. Just leaning.

  As described above, according to the ink jet printer of the present embodiment, the skew portion (end side 22) that skews with the conveyance of the print medium 2 while maintaining the predetermined angle θ with respect to the conveyance direction of the print medium 2. ) Change state is detected, and the position of at least one of the conveyor belt 1 and the print medium 2 is detected from the change state of the skewed portion (edge 22). By constituting the skew feeding portion 22, it is possible to accurately detect the position of at least one of the conveyor belt 1 and the print medium 2 with a simple structure.

Further, since the optical sensor 16 detects the light shielding state by the skew portion (the edge 22) and detects the change state thereof, at least the transport belt 1 and the print medium 2 can be configured with a very simple structure. Either one of the positions can be accurately detected.
Further, the optical sensor 16 detects the amount of movement of the skew portion (end side 22) in the direction intersecting the print medium conveyance direction, that is, the nozzle row direction, from the light shielding state by the skew portion (end side 22). The amount of movement of the print medium 2 in the print medium conveyance direction is calculated from the amount of movement of the skew portion (edge 22) in the direction intersecting the print medium conveyance direction, that is, the nozzle row direction, and the conveyance amount is calculated from the movement amount. Since the configuration is such that the position of at least one of the belt 1 and the print medium 2 is detected, the configuration of the optical sensor 16 can be simplified, and the method for calculating the amount of movement of the transport belt 1 in the print medium transport direction can be simplified. The calculation load can be reduced.

In addition, since the print medium 2 is obliquely placed on the conveyance belt 1 at a predetermined angle θ and the skewed portion is formed by the end side 22 of the print medium 2 itself, the structure becomes even simpler and the print medium The position of 2 can be accurately detected.
Further, the amount of movement of the edge 22 of the print medium 2 itself in the direction intersecting the print medium conveyance direction is detected by the optical sensor 16 from the gap 21 formed in the conveyance belt 1, and a predetermined angle is θ, When the gap width is z, a plurality of optical sensors 16 are arranged at intervals x = z / tan θ in the print medium conveyance direction, so that the position of the print medium 2 can be detected continuously. It becomes.

In the above embodiment, only the example of applying the light shielding sensor in which the light receiving sensor and the light projecting sensor are arranged to face each other has been described in detail. However, the reflection type in which the light projecting sensor and the light receiving sensor are disposed adjacent to each other. Sensors can also be used.
In the above embodiment, only an example in which the inkjet printer of the present invention is applied to a so-called line head type 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.

1 is a front view of a schematic configuration showing a first embodiment of an inkjet printer of the present invention. FIG. 2 is a bottom view of the ink jet head of FIG. 1. It is a block block diagram of the inkjet printer of FIG. FIG. 2 is a left side sectional view showing a mounting state of the optical sensor of FIG. 1. It is a top view of the conveyance belt of FIG. FIG. 6 is a development view of the conveyor belt in FIG. 5. It is a block diagram of the light receiver of the optical sensor of FIG. It is explanatory drawing of the output of the light receiver of FIG. It is explanatory drawing of the hypotenuse part of the conveyance belt of FIG. FIG. 6 is a development view of a conveyance belt showing another embodiment of the ink jet printer of FIG. 1. It is a top view of the conveyance belt which shows 2nd Embodiment of the inkjet printer of this invention. It is explanatory drawing which conveys a printing medium with the conveyance belt of FIG. It is explanatory drawing of the paper feed part which mounts a printing medium on the conveyance belt of 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, 6 is a pickup roller, 7 is a charging roller, 8 is a DC power supply, 9 is a paper pressing roller, 10 is a spring, 11 is an inkjet head, 13 is a gate roller, 14 is a paper feed unit, 15 is a paper discharge unit, 16 is an optical sensor, 17 is a projector, 18 is a light receiver, 19 is a hypotenuse, 20 is an electric motor, 21 is a gap, 22 is an edge, 23 is a fixed guide, and 24 is a movable guide.

Claims (7)

  In an inkjet printer that performs printing by placing a print medium on a conveyance belt and ejecting ink droplets onto the print medium, the print medium is maintained while maintaining a predetermined angle with respect to the conveyance direction of the print medium. An inkjet printer comprising: a skew portion that skews with conveyance; and a position detection unit that detects a position of at least one of a conveyance belt and a print medium from a change state of the skew portion. .  2. The ink jet printer according to claim 1, wherein the position detection unit includes an optical sensor that detects a light shielding state by the skew feeding portion in order to detect a change state of the skew feeding portion.   The optical sensor detects an amount of movement of the skew feeding portion in a direction intersecting with the print medium conveyance direction from a light shielding state by the skew feeding portion, and the position detecting means detects the skew detected by the optical sensor. The amount of movement in the print medium conveyance direction of at least one of the conveyance belt and the print medium is calculated from the amount of movement of the row portion in the direction intersecting the print medium conveyance direction, and the conveyance belt and the print medium are calculated from the movement amount. The inkjet printer according to claim 2, wherein at least one of the positions is detected.   The said skew part is comprised in the edge part of the said conveyance belt, and is comprised by the oblique side part which moves diagonally at the said predetermined angle with respect to the conveyance direction of a printing medium, It is characterized by the above-mentioned. Inkjet printer.   The length of the oblique side in the printing medium conveyance direction is L, the length of the oblique side in the direction intersecting the printing medium conveyance direction is Y, and the printing resolution per unit length in the printing medium conveyance direction is A. The inkjet printer according to claim 4, wherein the resolution B per unit length of the optical sensor is L × A / Y.   The said skew part is comprised by the edge side of the printing medium itself mounted in the said conveyance belt diagonally with the said predetermined angle with respect to the conveyance direction of the said printing medium. Inkjet printer.   The optical sensor detects the amount of movement of the edge of the printing medium itself from the gap formed in the conveyance belt in a direction intersecting the printing medium conveyance direction, and the predetermined angle is θ and the gap width is The inkjet printer according to claim 6, wherein a plurality of optical sensors are arranged at an interval x = z / tan θ with respect to the print medium conveyance direction, where z is z.

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