JP4826364B2 - Inkjet printer - Google Patents

Description

  In the present invention, for example, predetermined characters and images are printed by ejecting minute ink droplets of liquid ink of a plurality of colors from a plurality of nozzles to form fine particles (ink dots) on a print medium. The present invention relates to an ink jet printer.

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 such an ink jet printer, a moving body called a carriage or the like, which is integrally provided with an ink cartridge and a print head (also referred to as an ink jet head), generally reciprocates on a print medium in a direction intersecting the transport direction. While moving, liquid ink droplets are ejected (jetted) from the nozzles of the print head to form minute ink dots on the print medium, thereby printing predetermined characters and images on the print medium. Is supposed to create. 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. 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. This is not necessary, and so-called one-pass printing is possible, so that high-speed printing similar to a laser printer or the like 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”.

In such a line head type ink jet printer, it is particularly important to convey the print medium. Therefore, in Patent Document 1 below, a plurality of conveyor belts are driven at a constant speed by a single drive source, and skew of the printing medium, so-called skew, is corrected on the upstream side of the conveying belt in the printing medium conveyance direction. A shutter is provided for this purpose. In this line head type ink jet printer, the print medium of the paper feed unit is fed by the pickup roller and the transport roller. If the print medium is sent obliquely at that time, the print medium sent obliquely The leading edge of the transporting direction hits the shutter, and the leading end of the transporting direction is guided by the shutter with the deflection of the print medium and adjusted in the direction parallel to the shutter, that is, in the direction crossing the transporting direction, and then fed onto the transporting belt. The
JP 2001-113690 A

  However, in the line head type ink jet printer described in Patent Document 1, even if the orientation of the print medium in the conveyance direction is applied to the shutter and the posture is adjusted with the deflection of the print medium, When the print medium changes, the attitude of the print medium may change again. Then, if the posture of the printing medium is not appropriate on the conveying means, that is, the printing is deteriorated. A similar problem occurs even in a so-called gate roller system in which a pair of rollers is used instead of the shutter.

  Also, common to both systems, if the print medium is applied to the shutter or gate roller at a high speed, the print medium will be broken. Since posture adjustment is performed, there is a limit to shortening the posture adjustment time of the print medium. In addition, it is difficult to adjust the orientation of the print medium with the front end in the conveyance direction of the print medium being completely along the shutter or the gate roller, and a considerable orientation adjustment error occurs. In addition, the front end of the print medium in the conveyance direction hits, bends and deforms, or the front end of the print medium rubs and is damaged, and paper dust is generated from the edge of the front end in the print medium conveyance direction. So-called ear breakage may occur. In the case of a line head type ink jet printer, paper dust adheres to the nozzle surface of the ink jet head, causes ink non-ejection and so-called flight bending, leading to a decrease in mechanical reliability and a deterioration in printing. Further, the edge breakage causes a jam (paper jam) due to a collision of the print medium with the ink jet head and a printing defect due to contact with the nozzle surface, which becomes a serious defect as an ink jet printer.

  The present invention has been made paying attention to the above-described problems, and has as its object to provide an ink jet printer that does not change the posture of the print medium accompanying the transfer and can avoid various problems. Is.

[Invention 1] In order to solve the above-described problem, an inkjet printer according to Invention 1 is configured to convey a print medium in a predetermined conveyance direction at a predetermined conveyance speed, and to a print medium conveyed by the conveyance means. In an inkjet printer including an inkjet head that performs printing by discharging ink at a predetermined printing position, a printing medium attitude adjusting unit that adjusts an attitude of a printing medium conveyed by the conveying unit, and the printing medium attitude adjustment An actuator for driving the means and a control means for controlling the driving state of the actuator are provided.
According to the ink jet printer of the first aspect of the present invention, the print medium attitude adjusting means for adjusting the attitude of the print medium being conveyed by the conveying means is provided, and the drive actuator of the print medium attitude adjusting means is controlled by the control means. With this configuration, it is possible to avoid a change in posture that accompanies the transfer of a print medium whose posture has been adjusted, thereby enabling proper printing.

[Invention 2] The inkjet printer according to Invention 2 is the inkjet printer according to Invention 1, wherein a plurality of the print medium posture adjusting means are arranged in a direction intersecting a print medium conveying direction by the conveying means. The print medium posture adjusting means is individually driven by a plurality of actuators, and the drive state of the plurality of actuators is individually controlled by the control means.
According to the ink jet printer of the second aspect of the present invention, a plurality of print medium posture adjusting means are arranged in a direction intersecting the print medium conveying direction, and the drive actuators of these print medium adjusting means are individually controlled by the control means. Therefore, for example, if the print medium adjusting means adjusts the conveyance speed of both ends of the print medium in the direction intersecting the conveyance direction, the posture can be adjusted without hitting the print medium. Thus, the posture adjustment time can be shortened, and posture adjustment errors can be prevented from being suppressed, and various problems can be avoided.

  [Invention 3] The ink jet printer of Invention 3 is the ink jet printer of Invention 2, further comprising a print medium position detecting means for detecting the position of the print medium at a position corresponding to the print medium attitude adjusting means, and the control. The means controls the drive states of the plurality of actuators based on print medium position information at a plurality of locations in a direction intersecting the print medium conveyance direction detected by the print medium position detection means. .

  According to the ink jet printer according to the third aspect of the present invention, the print medium position detection unit is disposed at a position corresponding to the print medium posture adjustment unit, and a plurality of directions intersecting the print medium conveyance direction detected by the print medium position detection unit are provided. Since the drive state of the plurality of actuators is controlled based on the print medium position information at the location, it is possible to perform more accurate print medium posture control by closed loop feedback control.

  [Invention 4] Further, in the inkjet printer of Invention 4, in the inkjet printer of Invention 3, when the print medium posture adjusting means adjusts the conveyance speed of the print medium to adjust the posture of the print medium, The control means sets the print medium conveyance speed adjustment amount of the print medium attitude adjustment means based on the print medium position information at a plurality of locations in the direction intersecting the print medium conveyance direction detected by the print medium position detection means, The drive state of the plurality of actuators is controlled so that the print medium conveyance speed adjustment amount is achieved.

  According to the ink jet printer of the fourth aspect of the present invention, the print medium conveyance speed adjustment of the print medium attitude adjustment unit is performed based on the print medium position information at a plurality of locations in the direction intersecting the print medium conveyance direction detected by the print medium position detection unit. Since the drive state of the plurality of actuators is controlled so that this print medium conveyance speed adjustment amount is achieved, more accurate print medium attitude control is possible and the print medium is conveyed. At this time, the posture can be controlled, and the required printing time including the posture adjustment time can be shortened.

[Invention 5] The inkjet printer according to Invention 5 is the inkjet printer according to Invention 4, wherein the control means is configured such that an average value of the print medium conveyance speeds of the plurality of print medium attitude adjustment means is a predetermined conveyance speed of the print medium. The print medium conveyance speed adjustment amount of the print medium attitude adjustment means is set so as to always match.
According to the ink jet printer according to the fifth aspect of the present invention, the print medium transport speed of the print medium orientation adjusting unit is such that the average value of the print medium transport speeds of the plurality of print medium posture adjusting units always matches the predetermined transport speed of the print medium. Since the adjustment amount is set, the conveyance speed of the entire printing medium during posture control can be set to a predetermined conveyance speed, so that the conveyance of the printing medium can be made smooth and the printing medium of any posture can be used. The required printing time including the posture adjustment time can be made constant.

[Invention 6] The inkjet printer according to Invention 6 is the inkjet printer according to any one of Inventions 1 to 5, wherein the print medium posture adjusting means is stretched between a drive roller and a driven roller disposed in the print medium conveyance direction. In addition, it is a conveying means composed of a plurality of conveying belts arranged in the direction intersecting with the printing medium conveying direction.
According to the ink jet printer of the sixth aspect of the invention, the conveying means is composed of a plurality of conveying belts stretched between the driving roller and the driven roller disposed in the printing medium conveying direction and provided in a direction crossing the printing medium conveying direction. The print medium orientation adjustment means eliminates the need for a separate print medium orientation adjustment means, simplifies the configuration, enables control of the print medium orientation on the conveyor belt, and transfers by printing before printing. The media attitude change factor can be avoided.

  [Invention 7] The ink jet printer according to Invention 7 is the ink jet printer according to any one of Inventions 1 to 5, wherein the conveying means is a conveying belt stretched between a driving roller and a driven roller disposed in the printing medium conveying direction. The printing medium posture adjusting means is composed of a rotating body that is disposed to face the printing medium conveying surface of the conveying means and that can be conveyed in contact with the printing medium.

  According to the ink jet printer of the seventh aspect of the present invention, the conveying belt stretched between the driving roller and the driven roller arranged in the printing medium conveying direction is used as the conveying means, and the conveying means including the conveying belt is arranged on the printing medium conveying surface. Since the rotating medium disposed oppositely and capable of being conveyed in contact with the printing medium is used as the printing medium attitude adjusting means, the printing medium attitude on the conveying belt can be controlled, and the printing medium by transfer or the like before printing Attitude change factors can be avoided.

[Invention 8] The inkjet printer of Invention 8 is the inkjet printer of Inventions 6 and 7, characterized in that the printing medium attitude adjusting means adjusts the attitude of the printing medium on the conveying belt. is there.
According to the ink jet printer of the eighth aspect of the invention, since the posture of the print medium is adjusted on the conveyance belt, it is possible to avoid the print medium posture change factor due to the transfer or the like before printing.

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 the ink jet printer of the present embodiment, FIG. 1a is a plan view thereof, and FIG. 1b is a front view thereof. In FIG. 1, a print medium 1 is a line head type ink jet printer that is transported in the direction of the arrow in the figure from the right to the left in the figure, and is printed in a print area in the middle of the conveyance. FIG. 1 shows a state in which the print medium 1 passes through the print area.

  In the figure, reference numeral 2 denotes a head unit disposed in the print area, reference numeral 3 denotes an ink jet head provided in the head unit 2, and a transport unit for transporting the print medium 1 below the head unit 2. 4R and 4L are provided. The transport units 4R and 4L are composed of six first transport belts 5R and 5L arranged at predetermined intervals in a direction intersecting with the transport direction of the print medium 1 (hereinafter also referred to as nozzle row direction). Is done.

  Of the six conveyor belts 5R and 5L, the three conveyor belts 5R on the right side in the nozzle array direction and the three conveyor belts 5L on the left side in the nozzle array direction are divided. That is, the right drive roller 6R is disposed on the downstream side in the print medium conveyance direction of the three conveyance belts 5R on the right side in the nozzle row direction, and the right driven roller 7R is disposed on the upstream side in the print medium conveyance direction. A left driving roller 6L is disposed on the downstream side of the three conveying belts 5L in the printing medium conveyance direction, and a left driven roller 7L is disposed on the upstream side in the printing medium conveyance direction. The three conveying belts 5R on the right side in the nozzle row direction are wound and stretched around the right driving roller 6R and the right driven roller 7R, and the three conveying belts 5L on the left side in the nozzle row direction are arranged on the left driving roller 6L and the left driven roller. The right electric motor 8R is connected to the right driving roller 6R, and the left electric motor 8L is connected to the left driving roller 6L.

  Therefore, when the right drive roller 6R is rotationally driven by the right electric motor 8R, the right conveyance unit 4R composed of the three conveyance belts 5R on the right side in the nozzle row direction is synchronized with each other and moved at the same speed, and the left electric motor 8L When the left driving roller 6L is rotationally driven by the above, the left conveyance unit 4L composed of the three conveyance belts 5L on the left side in the nozzle row direction is synchronized with each other and moves at the same speed. However, if the rotation speeds of the right electric motor 8R and the left electric motor 8L are different, the conveyance speed in the nozzle row direction can be changed. Specifically, the rotation speed of the right electric motor 8R is changed to that of the left electric motor 8L. When the rotational speed is higher than the left side, the conveyance speed on the right side in the nozzle row direction can be made larger than that on the left side, and when the rotation speed of the left electric motor 8L is higher than the rotation speed of the right electric motor 8R, The speed can be made larger than that on the right side, thereby adjusting the transport posture of the print medium. Therefore, the right and left transport units 4R and 4L themselves constituted by the right and left transport belts 5R and 5L themselves constitute the print medium posture adjusting means of the present invention.

 The ink-jet head 3 is arranged so as to be shifted in the conveyance direction of the imprinting medium 1 for each of six colors, for example, yellow (Y), magenta (M), cyan (C), and black (K). Ink is supplied to each inkjet head 3 from an ink tank of each color (not shown) via an ink supply tube. Each inkjet head 3 is formed with a plurality of nozzles in a direction intersecting with the transport direction of the print medium 1 (that is, in the nozzle row direction), and a necessary amount of ink droplets are simultaneously ejected from these nozzles to a necessary location. As a result, minute ink dots are formed and output on the print medium 1. By performing this for each color, it is possible to perform so-called one-pass printing by passing the print medium 1 conveyed by the conveyance units 4R and 4L once. That is, the area where the ink jet heads 3 are 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 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.

  Two pairs of feed rollers 9 for feeding the printing medium 1 of the paper feeding unit 28 onto the conveying belts 5R and 5L are provided upstream of the driven rollers 7R and 7L in the printing medium conveying direction. A paper feed guide plate 10 for transferring the print medium 1 is provided between the feed roller 9 and the conveyor belts 5R and 5L. On the other hand, two discharge rollers 12 for discharging the print medium 1 on the conveyance belts 5R and 5L to the discharge unit 11 are provided in pairs on the downstream side of the drive rollers 6R and 6L in the print medium conveyance direction. Yes. A paper discharge guide plate 13 for transferring the print medium 1 is provided between the paper discharge roller 12 and the conveyor belts 5R and 5L.

  A belt charging roller 14 is disposed upstream of the driven rollers 7R and 7L in the print medium conveyance direction and below the paper feed guide plate 10 and is in contact with the conveyance belts 5R and 5L. The belt charging roller 14 is charged by a power source (not shown), and charges the conveying belts 5R and 5L that contact the belt charging roller 14 by charging them. In general, these belts are formed of a medium / high resistance body or an insulator, so that when charged by the belt charging roller 14, the charge applied to the surface thereof is also composed of a high resistance body or an insulator. The print medium 1 can be caused to generate dielectric polarization, and the print medium 1 can be adsorbed to the belt by electrostatic force generated between the charge generated by the dielectric polarization and the charge on the belt surface. The charging means may be a so-called corotron that drops the charge.

  In the present embodiment, print medium position sensors 15R and 15L made of, for example, photoelectric sensors are disposed outside the conveying belts 5R and 5L. The print medium position sensors 15R and 15L detect the front end positions in the transport direction at both ends in the direction intersecting the transport direction of the print medium 1 on the outer side of the corresponding position, that is, in the direction intersecting the print medium transport direction. Is. Incidentally, when the width in the direction intersecting the transport direction of the print medium 1 is narrow, as shown in FIG. 2, the printing medium position sensors 15R and 15L correspond to both ends in the direction intersecting the transport direction of the print medium. What is necessary is just to arrange | position in the position to perform.

  Therefore, according to this ink jet printer, the surface of the conveyor belts 5R and 5L is charged by the belt charging roller 14, and in this state, the print medium 1 is fed from the paper feeding unit 28 by the feed roller 9, and a spur and a roller (not shown) are provided. When the print medium 1 is pressed against the conveyor belts 5R and 5L by the paper pressing roller configured as follows, the print medium 1 is attracted to the surfaces of the conveyor belts 5R and 5L by the action of the dielectric polarization described above. In this state, when the driving rollers 6R and 6L are rotationally driven by the electric motors 8R and 8L, the rotational driving force is transmitted to the driven rollers 7R and 7L via the conveyor belts 5R and 5L.

  In this manner, the conveying belts 5R and 5L are moved downstream in the conveying direction while the printing medium 1 is adsorbed, the printing medium 1 is moved below the head unit 2, and the nozzles formed on the inkjet heads 3 of the respective colors. Ink droplets are ejected from the printer to print. When printing by the inkjet head 3 is completed, the print medium 1 is further moved downstream in the transport direction, and the paper discharge roller 12 is discharged to the paper discharge unit 11 while being separated from the surface of the transport belts 5R and 5L. .

  Also, as shown in FIG. 3, for example, when the print medium 1 fed from the paper feed unit 28 onto the conveyor belts 5R and 5L by the feed roller 9 is slanted, that is, when there is a skew, FIG. As shown in FIG. 1, the posture of the print medium 1 is adjusted before the print medium 1 arrives at the inkjet head 3 on the most upstream side in the print medium conveyance direction of the head unit 2, and as shown in FIG. The print is made to pass through the print area in the posture.

  A control device for controlling itself is provided in the ink jet printer. FIG. 5 shows a block diagram of a print medium attitude control device built in the control device. The actuators for driving the print medium orientation adjusting means of this embodiment are electric motors 8R and 8L. The print medium attitude control device calculates the position information of the print medium 1 from the outputs of the right and left print medium position sensors 15R and 15L, and the print medium position information calculation unit 16 calculates the print medium position information. The print medium conveyance speed adjustment amount calculation unit 17 that calculates the adjustment amount of the conveyance speed of the print medium 1 from the position information of the printed medium 1 and the print medium 1 calculated by the print medium conveyance speed adjustment amount calculation unit 17 It consists of right and left drivers 18R and 18L that output drive signals to the right and left electric motors 8R and 8L based on the adjustment amount of the conveyance speed. The print medium position information calculation unit 16 and the print medium conveyance speed adjustment amount calculation unit 17 are constructed in a computer system (not shown).

  Next, the position information of the print medium 1 calculated by the print medium position information calculation unit 16 and the print medium conveyance speed adjustment amount calculated by the print medium conveyance speed adjustment amount calculation unit 17 will be described. For example, as shown in FIG. 3, among the directions intersecting the transport direction (hereinafter referred to as the width direction), the upper part of the figure (hereinafter referred to as the right side) precedes and the lower part of the figure (hereinafter referred to as the left side). Is followed, the transport speed of the right transport section 4R composed of the right transport belt 5R is decreased, and the transport speed of the left transport section 4L composed of the left transport belt 5L is increased. The difference in position between the right and left transport directions of the print medium 1 is, for example, the time when the right print medium position sensor 15R detects the leading end of the print medium 1 in the transport direction and the left print medium position sensor 15L It can be obtained by multiplying the difference from the time at which the center portion of one conveyance direction is detected by the predetermined conveyance speed of the print medium 1.

When the difference between the positions of the right side and the left side of the print medium 1 in the width direction is the distance ΔL, the time when the distance ΔL is calculated, in this case, the front end of the print medium 1 in the transport direction is the transport belt 5R. From the time t _{0 when} it reaches 5L to the time t ₂ immediately before the print medium 1 arrives at the upstreammost ink jet head 3 in the print medium conveyance direction of the head unit 2, the right conveyance of the right conveyance belt 5R. The section 4R delays the right end of the print medium 1 in the width direction by a half value (ΔL / 2), and the left transport section 4L including the left transport belt 5L sets the left end of the print medium in the width direction to a half value of the distance ( It is sufficient to advance by ΔL / 2).

For example, when the leading end portion of the print medium 1 in the transport direction has a predetermined transport speed v _{0 of the} print medium, the transport speed v _R of the right transport unit 4R including the right transport belt 5R is set to the time t ₀ as shown in FIG. 6a. and accelerating at a constant acceleration until the middle of the time t ₁ of time t _2, the while decelerating at a constant acceleration from time t ₁ to time t _2, the as shown in Figure 6b, the left transport unit 4L consisting left conveyor belt 5L Assuming that the transport speed v _L is decelerated at a constant acceleration from time t ₀ to time t ₁ and accelerated at a constant acceleration from time t ₁ to time t ₂ , the predetermined transport speed v ₀ and the actual speeds v _R , v The area of the speed difference from _{L, that} is, the area of the triangle in the figure, is the operation amount at the position of the end portion in the print medium width direction. In this way, the transport speed v of the entire print medium 1 always matches the predetermined transport speed v ₀ .

The height of the triangle is expressed as ΔL / 2 (t ₁ −t ₀ ) = ΔL / 2 (t ₂ −t ₁ ) = ΔL / (t ₂ −t ₀ ). Further, the position where the distance ΔL between the right side and the left side in the width direction of the print medium 1 is calculated, in this case, the position where the front end of the print medium 1 in the transport direction reaches the transport belts 5R and 5L, and the print medium 1 is the head unit. When the distance to the position immediately before reaching the inkjet head 3 on the most upstream side in the print medium conveying direction 2 is L, the time difference (t ₂ −t ₀ ) is expressed as L / v _0, and thus the height of the triangle Is v ₀ · ΔL / L. Therefore, the maximum arrival speed of the conveyance speed v _R of the right conveyance section 4R including the right conveyance belt 5R is v ₀ (1 + ΔL / L), and the minimum arrival speed of the conveyance speed v _L of the left conveyance section 4L including the left conveyance belt 5L. Becomes v ₀ (1−ΔL / L).

The right and left transport speed control signals v _R and v _{L in consideration} of these print medium transport speed adjustment amounts are output from the print medium transport speed adjustment amount calculation unit 17 to the right and left drivers 18R and 18L, respectively, which are driven. It is converted into a signal and output to the right and left electric motors 8R, 8L. Therefore, in the present embodiment, even if the print medium 1 fed from the paper supply unit 28 to the transport belts 5R and 5L by the feed roller 9 is skewed, the head unit 2 on the most upstream side in the print medium transport direction. Immediately before arriving at the inkjet head 3, it is adjusted to a predetermined transport posture and printing is performed in that state, so the printing performance is extremely high. The position of the print medium 1 is detected at any time by the print medium position detection sensors 15R and 15L, and the above-described transport speed control signals v _R and v _L are feedback-controlled based on the detection result. Conventionally, the correction method of the conveyance speed control signals v _R and v _L by feedback control is applied.

  Incidentally, the line head type ink jet printer can easily realize about 150 to 300 prints per minute on an A4 size print medium. The required time per sheet when printing 300 sheets per minute is 0.2 seconds. However, the printing medium attitude control by the shutter method described in the above-mentioned Patent Document 1 or the above-described gate roller method requires several hundred milliseconds to several seconds, which greatly hinders high-speed printing. On the other hand, in the ink jet printer of this embodiment that controls the posture while conveying the print medium, the cycle time of the high-speed printing can be realized.

  As described above, in the ink jet printer according to the present embodiment, the right and left transport units 4R and 4L including the right and left transport belts 5R and 5L themselves adjust the posture of the print medium 1 being transported. Since the drive actuators of the medium attitude adjusting means, that is, the right and left electric motors 8R and 8L are controlled by the control device, it is possible to avoid the attitude change accompanying the transfer of the print medium 1 whose attitude is adjusted, and to be appropriate. Printing is possible.

  Further, a plurality of print medium posture adjusting means including right and left conveying belts 5R and 5L are arranged in a direction crossing the print medium conveying direction, and electric motors 8R and 8L which are actuators for driving these print medium adjusting means. Are controlled individually by the control device, so what is the print medium 1 by adjusting the transport speed of the print medium 1 in the direction intersecting the transport direction, that is, the width direction both ends? It is possible to adjust the posture without hitting it, thereby shortening the posture adjustment time, preventing the posture adjustment error from being suppressed, and further avoiding various problems.

  Further, right and left print medium position detection sensors 15R and 15L are arranged at positions corresponding to the print medium posture adjusting means including the right and left conveyance belts 5R and 5L, and the right and left print medium position detection sensors 15R and 15L. Since the drive states of the plurality of actuators including the right and left electric motors 8R and 8L are controlled based on the detected print medium position information at a plurality of locations in the direction crossing the detected print medium conveyance direction, closed loop feedback control is performed. Accurate print medium attitude control can be performed.

  Also, the print medium posture adjustment composed of the right and left transport belts 5R and 5L based on the print medium position information at a plurality of locations in the direction intersecting the print medium transport direction detected by the right and left print medium position detection sensors 15R and 15L. Since the print medium conveyance speed adjustment amount of the means is set and the drive state of the plurality of actuators composed of the right and left electric motors 8R and 8L is controlled so that this print medium conveyance speed adjustment amount is achieved, the configuration is further improved. Accurate printing medium attitude control is possible, and attitude control can be performed while the printing medium 1 is being conveyed, thereby shortening the time required for printing including attitude adjustment time.

  In addition, the print medium of the print medium attitude adjusting unit is configured so that the average value of the print medium conveyance speeds of the plurality of print medium attitude adjusting units including the right and left conveyance belts 5R and 5L always coincides with the predetermined conveyance speed of the print medium 1. Since the conveyance speed adjustment amount is set, the conveyance speed of the entire print medium 1 during the posture control can be set to a predetermined conveyance speed, so that the conveyance of the print medium 1 can be made smooth and in any posture. Even in the print medium 1, the required print time including the posture adjustment time can be made constant.

In addition, a plurality of right and left conveying belts 5R and 5L are provided which are stretched between driving rollers 6R and 6L and driven rollers 7R and 7L arranged in the printing medium conveyance direction and provided in a direction crossing the printing medium conveyance direction. Since the conveyance means (right and left conveyance parts 4R, 4L) to be used are the print medium posture adjustment means, no separate print medium posture adjustment means is required, the configuration is simplified, and printing on the conveyance belts 5R, 5L is performed. It is possible to control the medium posture, and to avoid the printing medium posture change factor due to the transfer or the like before printing.
Further, since the posture of the print medium 1 is adjusted on the right and left conveyance belts 5R and 5L, it is possible to avoid a print medium posture change factor due to a transfer or the like before printing.

  Next, a second embodiment of the ink jet printer of the present invention will be described with reference to FIG. This embodiment is similar to the first embodiment described above, and the same components are denoted by the same reference numerals, and detailed description thereof is omitted. One of the specific differences between the present embodiment and the first embodiment is that there is only one transport unit 20, and the drive roller 22 and the driven roller 23 are integrated into one drive roller 22. Only one electric motor 24 is connected to. Further, the conveyance belt 21 wound around the driving roller 22 and the driven roller 23 has no discrimination on the right side and the left side. On the other hand, on the upstream side in the print medium conveyance direction of the head unit 2 above the conveyance belt 21, right and left conveyance rollers 25R and 25L are disposed at both ends in the width direction of the print medium 1, and the right conveyance roller 25R. Is connected to the right electric motor 8R, and the left conveying motor 25L is connected to the left electric motor 8L. Further, the right and left transport rollers 25R and 25L can contact the print medium 1 on the transport belt 21 and transport the print medium 1 before being completely attracted to the charged transport belt 21. That is, the right and left transport rollers 25R and 25L constitute the print medium position adjusting unit of the present embodiment.

  In this embodiment, the posture control of the print medium 1 by the print medium position adjusting means including the right and left transport rollers 25R and 25L is performed before the print medium 1 is completely attracted to the charged transport belt 21. Except for this point, the principle is the same as that of the first embodiment. In the first embodiment, the right and left transport belts 5R and 5L adjust the transport speed of the right and left sides in the width direction of the print medium 1 to control the position, whereas in the present embodiment, the right and left transport rollers 25R, The point is that the position is controlled by adjusting the conveyance speed on the right and left sides in the width direction of the print medium 1 at 25L. Further, the principle and operation for adjusting the position by adjusting the conveyance speed are the same.

  That is, among the both ends in the width direction of the print medium, the transport speed of the transport rollers 25R and 25L on the preceding side is reduced, and the transport speed of the transport rollers 25R and 25L on the trailing side is increased. At that time, the difference in position between the right side and the left side in the width direction of the print medium 1, that is, the distance ΔL is determined by the time when the right print medium position sensor 15 R detects the front end of the print medium 1 in the transport direction and the left side print medium. It can be obtained by multiplying the difference from the time when the position sensor 15L detects the center portion in the conveyance direction of the print medium 1 by the predetermined conveyance speed of the print medium 1. The transport rollers 25R and 25L on the preceding side delay the print medium 1 by half the distance (ΔL / 2) with respect to the distance ΔL in the width direction right side and left side of the print medium 1 and follow it. The conveying rollers 2R and 25L on the side being moved forward by half the distance (ΔL / 2).

When the side that advances the print medium 1 accelerates at a constant acceleration until the intermediate time and then decelerates at a constant acceleration, the side that delays the print medium 1 decelerates at a constant acceleration until the intermediate time and then accelerates at a constant acceleration. 1 for a predetermined transport speed v ₀ , the maximum speed reached on the side on which the print medium 1 is advanced is v ₀ (1 + ΔL / L), and the minimum speed on the side on which the print medium 1 is delayed is v ₀ (1−ΔL / L). ), The average value of the two can always be made to coincide with the predetermined transport speed v ₀ . The right and left transport speed control signals v _R and v _L in anticipation of these print medium transport speed adjustment amounts are output from the print medium transport speed adjustment amount calculation unit 17 in FIG. 5 to the right and left drivers 18R and 18L. These are converted into drive signals and output to the right and left electric motors 8R and 8L, respectively. Therefore, in the present embodiment, even if the print medium 1 fed from the paper supply unit 28 is skewed, the print unit 1 is predetermined until it reaches the inkjet head 3 on the most upstream side in the print medium transport direction of the head unit 2. Therefore, the printing performance is extremely high because printing is performed in this state. The position of the print medium 1 is detected at any time by the print medium position detection sensors 15R and 15L, and the above-described transport speed control signals v _R and v _L are feedback-controlled based on the detection result. Conventionally, the correction method of the conveyance speed control signals v _R and v _L by feedback control is applied.

  According to the ink jet printer of this embodiment, in addition to the effects of the ink jet printer of the first embodiment, the transport belt 21 stretched between the drive roller 22 and the driven roller 23 disposed in the print medium transport direction is provided. A rotating member (conveying unit 20) is disposed opposite to the printing medium conveying surface of the conveying means including the conveying belt 21, and is a rotating body that can be conveyed in contact with the printing medium 1, that is, right and left conveying rollers 25R. , 25L is used as the print medium posture adjusting means, so that the print medium posture can be controlled on the conveyor belt 21, and the print medium posture change factor due to the transfer or the like before printing can be avoided.

  In the above embodiment, only an example in which the head driving device of the ink jet printer of the present invention is applied to a so-called line head type ink jet printer is described in detail. However, the head driving device of the ink jet printer of the present invention is a multipass printer. It can be applied to all types of inkjet printers.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows 1st Embodiment of the line head type inkjet printer to which the inkjet printer of this invention is applied, (a) is a top view, (b) is a front view. It is a schematic block diagram which shows the modification of the inkjet printer of FIG. 1, (a) is a top view, (b) is a front view. It is explanatory drawing of an effect | action of the inkjet printer of FIG. 1, (a) is a top view, (b) is a front view. It is explanatory drawing of an effect | action of the inkjet printer of FIG. 1, (a) is a top view, (b) is a front view. 1 is a block diagram illustrating a printing medium attitude control device of an inkjet printer. It is explanatory drawing of the printing medium conveyance speed for printing medium attitude | position control. It is a schematic block diagram which shows 2nd Embodiment of the line head type inkjet printer to which the inkjet printer of this invention is applied, (a) is a top view, (b) is a front view.

Explanation of symbols

  1 is a print medium, 2 is a head unit, 3 is an inkjet head, 4R and RL are right and left conveyance units, 5R and RL are conveyance belts, 6R and RL are right and left drive rollers, and 7R and 7L are right and left driven Rollers, 8R and 8L are electric motors, 9 is a feed roller, 10 is a paper feed guide plate, 11 is a paper discharge unit, 12 is a paper discharge roller, 13 is a paper discharge guide plate, 14 is a charging roller, 15R and 15L are on the right side And left print medium position detection sensor, 16 is a print medium position information calculation unit, 17 is a print medium conveyance speed adjustment amount calculation unit, 18R and 18L are right and left drivers, 20 is a conveyance unit, 21 is a conveyance belt, and 22 is a drive. Rollers, 23 driven rollers, 24 electric motors, 25R and 25L are right and left transport rollers

Claims (2)

Conveying means for conveying a print medium at a predetermined conveying speed in a predetermined conveying direction, and an inkjet head for performing printing by discharging ink at a predetermined printing position on the printing medium conveyed by the conveying means In the ink jet printer, a plurality of print medium attitude adjusting means arranged in a direction intersecting a print medium conveying direction by the conveying means , a plurality of actuators individually driving the plurality of print medium attitude adjusting means , Control means for individually controlling the driving state of the actuator, and print medium position detection means for detecting the position of the print medium provided at a position corresponding to the print medium attitude adjustment means, the print medium attitude adjustment means comprising: A plurality of belts are stretched between a driving roller and a driven roller disposed in the printing medium conveyance direction and are arranged in a direction intersecting the printing medium conveyance direction. A conveying means comprising a conveying belt, wherein the control means is configured to control the print medium attitude adjusting means based on print medium position information at a plurality of locations in a direction intersecting the print medium conveying direction detected by the print medium position detecting means. The print medium conveyance speed adjustment amount is set, the drive state of the plurality of actuators is controlled so that the print medium conveyance speed adjustment amount is achieved, and the average value of the print medium conveyance speeds of the plurality of print medium attitude adjustment means An ink jet printer characterized in that the print medium conveyance speed adjustment amount of the print medium attitude adjusting means is set so as to always coincide with the predetermined conveyance speed of the print medium . The inkjet printer according to claim 1 , wherein the print medium posture adjusting unit adjusts the posture of the print medium on the conveyance belt.

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