JP2011046110A - Inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise a recording medium due to cockling, depending on the image to be formed and the type of recording medium to be used, and even when an image with a small driving amount is printed, extra suction is driven and noise is increased. there were.
The driving of a negative pressure generator is controlled in accordance with the ejection amount of the ink droplets ejected from a recording head. Media suction conditions can be controlled in accordance with conditions such as the amount of ink applied to the media, transport position, print quality, and humidity, thereby preventing paper floating due to cockling. Further, there is provided an ink jet recording apparatus in which settings such as increasing the suction pressure are suppressed by fine control to suppress excessive settings and reduce noise while maintaining a high quality image.
[Selection] Figure 10

Description

  The present invention relates to an ink jet recording apparatus that records an image on a recording medium by ejecting ink from a recording head, and more particularly to an ink jet recording apparatus that includes suction force generating means for adsorbing a recording medium to a platen.

  In printers, copiers, facsimile machines, scanners, or composite devices and systems thereof, a recording apparatus that forms an image on a recording medium such as recording paper based on image information is used. As one form of such a recording apparatus, an ink jet recording apparatus that records an image by discharging ink from a discharge port of a recording head, which is a recording unit, to a recording medium is widely used. In an ink jet recording apparatus, in order to perform stable recording, it is necessary to eliminate as much as possible the effects of wrinkles and wavy deformation (also referred to as cockling) that occur due to the elongation of the paper when the ink adheres to the recording paper. For this purpose, various methods have been proposed for maintaining a constant distance between the surface of the recording paper and the recording head. In consideration of the case of using a recording medium in which curl is originally generated due to moisture or the like, a means for preventing paper floating from the platen to the recording head in the image forming unit has been proposed. This is because, when the recording medium is lifted, the floating portion is rubbed in contact with the recording head, the carriage, or a guide mechanism in the vicinity thereof, and the recording surface is damaged or fouled, causing deterioration in image quality. It is. Further, the contact between the floating portion and the discharge port surface (surface on which the discharge ports are arranged) of the recording head may affect the discharge performance.

  In view of this, a configuration has been proposed in which the platen disposed opposite to the recording head is provided with suction means for adsorbing the recording medium to the platen, thereby suppressing curling and cockling of the recording medium. As such a suction platen, for example, a suction groove having a concave shape from the support surface is provided on the recording medium support surface of the platen formed of a hollow casing, and a plurality of suction holes are formed in the suction groove, such as a fan. Patent Document 1 and Patent Document 2 disclose a configuration in which a suction force generating means generates a negative pressure inside a housing and sucks the housing.

JP-A-61-95966 JP-A-3-29359

  However, the ink jet recording apparatus provided with the conventional suction platen has the following problems. The lift of the recording medium due to cockling varies depending on the image to be formed, and also varies greatly depending on the type of recording medium used. For example, when the amount of ink droplet ejection is large, the floating due to cockling increases, and when the amount of ink droplet ejection is small or characters, the floating is small. Further, cockling is likely to occur in recording media such as plain paper and coated paper, and cockling is unlikely to occur in glossy paper and film-based recording media. In an ink jet recording apparatus provided with a conventional suction platen, suction control is performed in accordance with the maximum driving amount so as to suppress paper floating when the driving amount is large even when the driving amount is small. Therefore, even when an image with a small driving amount is printed, there is a problem that extra suction driving is performed, resulting in an increase in energy consumption and noise.

  The present invention has been made in view of such technical problems. An object of the present invention is to provide an ink jet recording apparatus that reduces noise while maintaining a necessary suction pressure by controlling suction driving in accordance with an ink droplet ejection amount.

In order to achieve the above object, the present invention provides a recording head for ejecting ink droplets from nozzles to form an image on a recording medium, a recording medium conveying apparatus for conveying the recording medium, and an image forming range of the recording head. In an ink jet recording apparatus comprising a platen for holding the recording medium and a negative pressure generating device for adsorbing the recording medium to the platen with a negative pressure, according to the ejection amount of the ink droplets ejected from the recording head And controlling the driving of the negative pressure generator.

  According to the present invention, paper floating can be prevented by controlling suction conditions in printing conditions in which cockling is likely to occur, such as an ink driving amount of media, a transport position, print quality, and environmental conditions such as humidity. In addition, it is possible to suppress excessive control by finely controlling settings such as increasing the suction pressure under necessary conditions, and an ink jet recording apparatus that reduces noise while maintaining a high-quality image is provided.

1 is a perspective view showing an internal configuration of an ink jet recording apparatus according to an embodiment of the present invention. It is the left view which looked at the inkjet recording device of FIG. 1 from the arrow 2-2 in the figure. FIG. 2 is a longitudinal sectional view of a central portion of the ink jet recording apparatus of FIG. 1. It is a top view which shows the suction platen seen from the main body upper surface of FIG. It is a control system block diagram of one Embodiment of this invention. It is the figure which showed the relationship between PWM control (Duty) and suction pressure (kPa) of the inkjet recording device to which this invention is applied. It is a figure of the suction state when there is little ink printing amount explaining this invention. It is a figure of the suction state when there is much ink hit amount explaining the present invention. FIG. 4 is a diagram illustrating a suction state in which the leading edge of a medium in a state where the ink hit amount is large and reaches the position of a leading edge holding roller, illustrating the present invention. It is a flowchart which shows control of the negative pressure generator which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be specifically described below with reference to the drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. FIG. 1 is a perspective view showing an internal configuration of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a left side view of the ink jet recording apparatus of FIG. 1 as viewed from an arrow 2-2 in the same drawing. FIG. 3 is a longitudinal sectional view of the central portion of the ink jet recording apparatus of FIG. FIG. 4 is a top view showing the suction platen as seen from the top surface of the main body of FIG. 1 to 3, in the inkjet recording apparatus 100 according to the present embodiment, a long roll paper Pr wound in a roll shape is used as a recording medium, and the roll paper Pr is wound on a rotatable spool 11. It is installed so that it can be removed. The recording medium Pr to be unwound is sandwiched between the transport roller 23 and the pinch roller 24, and is fed along the paper feed guide and transported through the inside of the apparatus main body by the rotation of the transport roller. Inside the apparatus main body, a transport mechanism 20 for performing operations of feeding, transporting and discharging the recording medium is provided. An image recording unit 40 that records an image on the recording medium supported by the platen 28 by the recording head 41 is provided on the downstream side of the conveying roller 23 in the conveying direction. The recorded recording medium is cut into a predetermined length by an automatic cutter disposed adjacent to the downstream side of the platen 28 in the conveying direction while being conveyed along the upper surfaces of the paper discharge guide 29 and the roll paper cover 33. The cut recording medium (cut sheet) is discharged out of the apparatus main body.

  2 and 3, reference numeral 21 denotes a transport motor for driving the transport roller 23, and reference numeral 22 denotes a transport pulley fixed to the transport roller shaft to transmit the drive of the transport motor 21 to the transport roller 23. is there. Reference numeral 25 denotes a pinch roller arm for rotatably supporting the pinch roller 24. Reference numeral 26 denotes a pinch roller holder for elastically supporting the pinch roller arm 25 so that the pinch roller 24 can be pressed against the conveying roller 23. is there. In FIG. 1, in the ink jet recording apparatus according to the present embodiment, a preliminary ejection receiving platen for receiving ink ejected from the recording head 41 by preliminary ejection at a position outside the recording area of the platen 28 (position on both sides). 34 is provided. Here, the preliminary discharge is performed for the following reason. If there is a portion that is hardly ejected in the ejection port of the recording head due to image data, the ink in the ejection port dries and thickens, and the ejection performance changes with other ejection ports. Then, density unevenness may occur in the image. In order to prevent this, ink is ejected outside the recording area, and the ejection performance is always maintained constant. The recording head 41 is mounted on a carriage 42 that can reciprocate in the main scanning direction (the width direction of the recording medium) along the recording medium. The carriage 42 is guided and supported so as to be slidable along the guide shaft 12 and the guide rail 13 installed in the apparatus main body. The recording head 41 is an ink jet recording head that records an image on a recording medium by ejecting ink based on image information. A discharge port array (nozzle column) configured by arranging a plurality of discharge ports in a predetermined arrangement is formed on the discharge port surface facing the recording medium of the recording head. A desired image is formed by selectively driving each ejection port constituting the ejection port array based on image information to eject ink. Here, in image formation of an ink jet recording apparatus, a multi-pass recording method is generally employed in order to eliminate image deterioration such as image unevenness and image streaks. In multi-pass printing, an image area that can be printed by the printing head in one printing scan is completed in stages by alternately repeating a plurality of printing scans and sub-scans. Increasing the number of passes improves image quality, but it also has the disadvantage of increasing printing time. Accordingly, a high-speed mode with a low number of passes, a high-quality mode with a large number of passes, and a standard mode in between are used properly according to the required image quality and printing time. Furthermore, there are different printing methods, reciprocating printing and unidirectional printing. One-way printing is to perform printing only during scanning in either the forward or backward direction during the reciprocating movement of the carriage. Compared to the case of discharging from both forward and backward directions, ejection from the same direction is performed. This improves the positional accuracy when the ink lands on the paper surface. Accordingly, the image quality can be further improved in one direction, but the printing time is doubled as a disadvantage. Therefore, this mode generally has a configuration that can be selected by the user.

  The platen 28 guides and supports the recording medium so as to form a predetermined gap between the recording head 41 and the recording medium Pr in the image forming unit. The platen 28 in the present embodiment is constituted by a suction platen that can adsorb the recording medium to the guide support surface of the platen. The suction platen 28 is supported on the upper surface of the hollow housing 30. A plurality of suction grooves 38 (see FIG. 4) connected to suction force generation means (negative pressure generation means) through the inside of the housing 30 are provided on the recording medium support surface of the suction platen 28. The housing 30 extends over a range corresponding to the platen 28 in the width direction of the apparatus main body, and the suction force generating means in the present embodiment is attached to one end of the housing 30 (the right end in FIG. 1). The suction fan unit 36 includes a suction fan 37. A dust cover 31 is detachably mounted above the downstream end of the paper discharge guide 29 in the transport direction. The recording medium is guided toward the paper discharge port 14 on the inner surface of the dust cover 31. A guide roller 32 is attached. The guide roller 32 is for suppressing the floating of the recording medium conveyed from the suction area of the platen 28. By suppressing this lifting, the recording medium can be prevented from coming into contact with the recording head 41 or the carriage 42 and being rubbed. Especially for recording media (tracing paper, thick coated paper, etc.) where curling (called printing curl) occurs when a large amount of ink is ejected to form a high-density image, or for cockling such as when the humidity is low It is effective for lifting when recording is performed under severe environmental conditions. When the printing operation is not being performed, a recovery system 166 that caps the nozzle array of the head is provided outside the 40 range of the image recording unit in order to maintain the performance of the head.

  Next, a control system of the ink jet printing apparatus will be described with reference to FIG. FIG. 5 is a block diagram showing an outline of the control system 161. The inkjet printing apparatus includes a CPU 151 that controls the entire apparatus, a ROM 152 that stores control programs and various data in a nonvolatile manner, a RAM 153 that is used as a work area used for processing in the CPU 151, a temporary storage area for data, and the like. Built in. The image data 160 input from the outside is variously converted into image signals for printing by the CPU 151, and the image signals are sent to the recording head 41 via the head driver 165. Then, ink is ejected from each nozzle and printing is performed. In the CPU 151, the amount of ink ejected in accordance with the image data is measured (dot count), and based on this, operation control in the apparatus as described later is performed. Note that the ink jet printing apparatus is also provided with an operation unit 155 for setting various items such as operations and types of recording media set in the apparatus. Here, the display unit 156 is mounted on the ink jet printing apparatus, but a computer may be connected to the ink jet printing apparatus and displayed on the computer.

In the paper conveyance control for conveying the recording medium, the CPU 151 transmits a control signal to the motor driver 163 in accordance with the image information to drive the conveyance motor 21. The driving state is detected by the encoder 171, and the CPU 151 performs control based on this information. At this time, the suction fan unit 36 connected to the suction groove 38 and the suction port 39 under the head has a suction fan 37, which is driven by the fan driver 173 at the fan rotational speed commanded by the CPU 151, and thereby transported by the recording medium To adsorb. The carriage 42 is driven by a command from the CPU 151 to the motor driver 164 based on the control conditions. Carriage position detection is performed by the encoder 172, and information such as speed and position is fed back. Further, discharge timing is generated based on the encoder 172. Further, when the nozzle in the head is recovered, the carriage 42 is driven by the carriage motor 50 to move the recording head 41 to a position opposite to the head recovery device 166. Thereafter, the CPU 151 instructs the recovery system drive driver 162 to drive the recovery system drive unit and perform a suction recovery operation to the recording head 169. (Since this recovery mechanism is based on a known technique, detailed description is omitted.)
FIG. 6 is a diagram showing the relationship between the PWM control (Duty) by the negative pressure generating means and the suction pressure (kPa) generated on the platen 28 of the ink jet recording apparatus to which the present invention is applied. According to this, the suction pressure on the main body generated when the negative pressure generating means is driven at the maximum (100%) is about 0.68 kPa, and a recording medium having a large cock ring, such as plain paper or coated paper, is used. When recording is performed with the maximum driving amount using art paper or the like, the suction pressure is necessary to prevent contact with the recording head. In addition, when the amount of driving is small with coated paper or art paper, for example, characters and lines, and the suction pressure required for recording on a recording medium with small cockling such as glossy paper or film is 0.30 to As shown in FIG. 6, the negative pressure generating means can be suppressed to about 60 to 80%.

  With reference to FIG. 7 to FIG. 9, the state and suction state of the amount of ink applied to the recording medium or the conveyance position and suction state of the recording medium will be described.

  FIG. 7 is a cross-sectional view of a conveyance state under a printing condition with a small ink deposit amount. A recording medium 201 with a small ink deposit amount is conveyed in the direction of an arrow by a conveyance roller 23 and a pinch roller 24. At this time, since the suction mechanism 200 of the recording medium 201 generates a small amount of cockling, the control duty of the suction fan 37 is set to a small condition (for example, 60%). Similarly, in FIG. 8, cockling is likely to occur at a position where the ink hit amount of the recording medium during printing is large, so the suction mechanism 200 sets the control duty of the suction fan 37 to a large condition. However, the setting varies depending on the paper type, the paper type that is likely to cause cockling is larger (90 to 100%), and the paper type that is difficult to cock is not set too large (80%). FIG. 9 shows a case where a printing medium 202 that easily causes printing curl is used and the amount of ink hit is large. In order to prevent printing curl until the leading end of the recording medium reaches the position of the tip holding roller 32, the suction mechanism 200 is a suction fan. The control duty of 37 is set to a large condition (90 to 100%). However, after the leading edge of the recording medium passes through the leading edge holding roller, the curling is suppressed, so that the suction fan duty can be reduced (80%).

  As described above, there are suction pressures necessary to prevent contact with the recording head due to paper floating (cockling, printing curl, etc.) depending on the amount of ink applied, the type of recording medium, the conveyance position of the recording medium, etc. Is stored in the table as a parameter. These parameters have different parameters depending on the printing quality, temperature and humidity environment, and the like. For example, if the print quality is high image quality mode (multi-pass or unidirectional printing), it takes a long time to print and the cockling tends to grow. Therefore, the duty is set high, and the high-speed mode (low pass or reciprocating printing) Since the paper is discharged before the growth, the duty is set low. Furthermore, the temperature and humidity environment is set to a high duty because cockling is likely to grow in a low humidity environment. For this, a temperature / humidity sensor 180 (FIG. 5) is provided in the apparatus, and the CPU 151 may set the duty based on the detection signal.

  By combining all of the above and setting the respective suction duties, it is possible to realize optimum transport conditions under any conditions.

  The threshold value of the ink placement amount (dot count value) for changing the suction duty varies depending on the conditions of the printing apparatus (ink components, printing speed, platen shape, etc.), the type of printing medium, environmental conditions, and the like. Therefore, values suitable for the recording system to which the present invention is applied may be set.

  Here, although a method of determining the threshold value according to the image density is also conceivable, two reasons for setting the dot count value in the present invention will be described. First, recent ink jet printers use the same color but high density and low density (thin) ink to improve image quality. Then, it is conceivable that the density and the shot amount are not necessarily proportional, and the intermediate color has the largest shot amount. Another reason is that cockling and print curl grow as the amount of ink driven on the recording medium increases, but if the amount exceeds a certain amount, the degree of subsequent growth decreases and the amount increases. In some cases, it may be alleviated. This is due to the fact that as the moisture content increases, the fiber of the paper becomes saturated and becomes saturated, and the rigidity of the paper decreases, and the cockling changes from a large low frequency to a small high frequency. Similarly, the print curl is liable to be crushed due to a decrease in rigidity. In other words, there is a maximum value depending on the amount of ink applied. This is because it is difficult to determine the phenomenon of paper floating with the index of image density.

  FIG. 10 is a flowchart showing the control of the negative pressure generator according to one embodiment of the present invention. In the ink jet recording apparatus to which the present invention is applied, the ink droplet ejection amount is calculated (dot count) by the CPU 151 based on the image data. Then, the number of dots with respect to the threshold value is determined from the calculated ink droplet discharge amount. For example, when the number of dots is less than or equal to the threshold value 1, the drive control (PWM control) of the negative pressure generating means is set to Duty 60%. If it is less than that, the paper floating amount becomes maximum, so the duty is set to 100%. When the threshold value 2 is exceeded, the paper floating is improved as described above, so that the driving duty is set to 90% and printing is started. Of course, at the same time as the dot count, it is also possible to determine the drive condition based on a combination of the paper type, the set print mode, and the environmental condition detected from the sensor.

  As described above, by controlling the driving of the negative pressure generating means according to the ejection amount (dot count) of the ink droplets ejected from the recording head, it is possible to prevent the recording head from contacting the recording medium. In addition, it is possible to reduce energy consumption and noise.

DESCRIPTION OF SYMBOLS 14 Paper discharge port 20 Conveyance mechanism 21 Conveyance motor 23 Conveyance roller 24 Pinch roller 27 Paper feed guide 28 Platen (suction platen)
29 Paper discharge guide 30 Housing 31 Dust cover 32 Guide roller 33 Roll paper cover 36 Suction fan unit (suction force generating means)
37 Suction fan 38 Suction groove 39 Suction hole 40 Image recording unit 41 Recording head (recording means)
42 Carriage 48 Ink receiving 49 Opening 58 Communication groove 100 Inkjet recording apparatus Pr Recording medium (roll paper)
A Arrow indicating the transport direction (sub-scanning direction)

Claims (5)

A recording head that ejects ink droplets from a nozzle and forms an image on a recording medium, a recording medium conveying device that conveys the recording medium, a platen that holds the recording medium, and the recording medium that is negatively applied to the platen In an inkjet recording apparatus provided with a negative pressure generator for adsorbing,
An ink jet recording apparatus, wherein driving of the negative pressure generating device is controlled in accordance with an ejection amount of the ink droplets ejected from the recording head.   The inkjet recording apparatus according to claim 1, wherein the driving of the negative pressure generator is controlled according to the type of the recording medium.   The ink jet recording apparatus according to claim 1, wherein the driving of the negative pressure generating device is controlled according to a transport position of the recording medium by the recording medium transport apparatus.   The inkjet recording apparatus according to claim 1, wherein the driving of the negative pressure generator is controlled in accordance with image quality recorded by the recording head. According to the environmental conditions measured by the environment (temperature and humidity) sensor installed inside the recording device,
The inkjet recording apparatus according to claim 1, wherein driving of the negative pressure generator is controlled.

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