JP2007136728A - Inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording apparatus capable of improving image deterioration by changing time of an ejection timing derived from an image deterioration mechanism due to elastic deformation for image deterioration due to elastic deformation of a carriage shaft. The purpose is to do.
A representative configuration of an ink jet recording apparatus according to the present invention is such that an ink jet recording apparatus of the present invention scans a carriage mounted with a recording head in parallel with a recording surface of a recording medium. In an ink jet recording apparatus that scans the carriage by transmitting a driving force from a carriage motor to the carriage via a belt and records on a recording medium by ejecting ink. The ink ejection timing is changed according to the guide member, the carriage movement direction, and the carriage position.
[Selection] Figure 4

Description

  The present invention relates to an ink jet recording apparatus that performs recording on a recording medium by ejecting ink while scanning a carriage on which a recording head is mounted.

A conventional inkjet recording apparatus is an apparatus that performs recording by scanning a carriage mounted with a recording head that reciprocates perpendicularly to the conveyance direction of a recording medium such as paper or an OHP sheet. Is a recording method for jetting. This ink jet recording apparatus is applied to printers, copiers, facsimiles and the like because of low noise, low running cost, easy miniaturization of the apparatus, and easy colorization. In recent years, the requirements for the material of the recording medium have been diversified, and to a recording apparatus that uses cloth, leather, or metal as a recording medium in addition to paper or resin thin plate (OHP sheet or the like) that is a normal recording medium. Also comes to be used. In such an ink jet recording apparatus, the recording head has a fixed interval with respect to the recording medium, and the ink ejected from the recording head flies through the space between the recording head and the recording medium and reaches the recording medium. To record. The recording head is formed with an ejection port (usually a plurality) for ejecting ink, and the size of the ejection port is recently becoming smaller with higher image quality. The ink jet recording apparatus is an extremely excellent recording apparatus having a simple configuration, but there is also a technical problem that should be fully considered. Ink jet recording apparatuses eject ink from a recording head to cause the ink to fly through the space between the recording head and the recording medium surface. Accordingly, when the ink flying time or the ejection vector fluctuates, image deterioration occurs. Therefore, parallelism when driving the carriage on which the recording head is mounted and the flatness of the recording medium are important problems. In a conventional ink jet recording apparatus, a carriage shaft is configured so as to maintain parallelism when the carriage is driven, and the carriage shaft is supported by a chassis. Further, the conveyance path for supporting the recording medium is also configured to maintain flatness. However, in reality, there is a problem of flatness of the carriage shaft and the conveyance path, and image deterioration occurs because the flatness of the recording medium cannot be maintained. Therefore, in order to improve these, there is a configuration in which a change in the distance between the recording head and the recording medium is detected and the ink discharge timing is changed to land on the ideal position (see Patent Document 1).
JP 2005-28715 A

  By the way, an elastic deformation of the carriage shaft can be cited as a main cause of the deterioration of the planarity of the carriage shaft. This elastic deformation is mainly caused by its own weight and carriage mass. When the carriage shaft is elastically deformed, it has an arcuate shape as shown in FIG. 4, and the distance between the recording head and the recording medium surface varies depending on the position of the carriage. This variation in distance causes variations in ink flight time and causes image degradation. Further, since the carriage shaft has an arcuate shape, the recording head surface is inclined. As a result, the ink discharge vector also varies. As described above, there is a problem that the carriage shaft is elastically deformed to cause image deterioration.

An ink jet recording apparatus of the present invention includes a carriage on which a recording head is mounted, and a guide member that is mounted so as to scan the carriage in parallel with the recording surface of a recording medium. In an inkjet recording apparatus that scans the carriage by transmitting to the carriage and records on a recording medium by discharging ink,
The ink ejection timing is changed according to the guide member, the carriage movement direction, and the carriage position.

  The ink jet recording apparatus of the present invention can improve the image deterioration problem caused by the distance variation between the recording head and the recording medium surface due to elastic deformation of the carriage shaft at low cost without configuring a sensor or the like. In addition, it is possible to improve the image degradation problem caused by the variation in the ejection vector of the ink with the print head tilted, which cannot be improved by detecting the distance variation by the sensor.

  A first embodiment of an ink jet recording apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an ink jet recording apparatus according to the present embodiment. As shown in FIG. 1, the ink jet recording apparatus A includes a recording head 1, a carriage 2, a support plate 3, a flexible substrate 4, a carriage shaft 5, a guide shaft 6, a belt 7, a pulley 9, pulleys 10, 11, 12, and discharge. It has a roller 13 and a housing 14. The recording head 1 can be mounted with an ink jet recording head. The carriage 2 mounts the recording head 1 and scans along the carriage shaft 5 and the guide shaft 6. The support plate 3 has an electrical connection (not shown) for supporting the recording head 1 and transmitting a recording signal to an electrical connection (not shown) of the recording head 1. The flexible substrate 4 connects an electrical connection part (not shown) of the support plate 3 and a main body control part (not shown). An electrical command value (a signal for ejecting ink) from the main body is transmitted to the support substrate 3 through the flexible substrate 4 and image recording is performed. The carriage shaft 5 and the guide shaft 6 are guide members attached so as to scan the carriage 2 parallel to the recording surface of the recording medium. The belt 7 is stretched around pulleys 9 and 10 disposed at both ends of the apparatus. The carriage 2 is fixed to the belt 7. A driving force is transmitted from the carriage motor 11 to the pulley 9 via a mechanism such as a gear, and the belt 2 is rotated so that the carriage 2 scans the recording medium. The conveyance roller 12 is driven by a conveyance motor (not shown) and conveys the recording medium. The discharge roller 13 discharges the recording medium on which the image is recorded to the outside of the apparatus. A carriage shaft 5, a guide shaft 6, and the like are fixed to the housing 14, and the above mechanism is configured. FIG. 2 is a perspective view of a carriage on which the recording head is mounted. In FIG. 2, arrows A, B, and C are a carriage scanning direction axis (A axis), a sheet conveyance direction axis (B axis), and an axis perpendicular to the recording medium (C axis). As shown in FIG. 2, power is transmitted from the carriage motor 11 to the carriage 2 by the belt 7, and the carriage 2 is scanned. The optical element 16 attached to the carriage 2 reads the linear scale 15 provided in parallel with the carriage shaft 5 to detect the position of the carriage 2 in the scanning direction. By this position detection, the carriage 2 is scanned to a desired recording position, and an ink discharge command signal is generated. In the recording head 1, the recording head generates heat energy when a current flows through the substrate in contact with the ink, and a foaming phenomenon occurs. Due to this phenomenon, droplets are formed at the ejection port, and the ink is ejected onto a recording medium to perform desired image recording.

  FIG. 3 is a diagram illustrating a mechanism in which the carriage shaft undergoes elastic deformation due to its own weight and carriage mass, and image degradation occurs. FIG. 3 shows a case where the carriage is scanning in the direction A in the drawing at a speed Vcr. The carriage is supported by a carriage shaft 5 fixed in parallel to the recording medium 17. When the carriage shaft is not elastically deformed, when the carriage ejects ink, it flies in the combined direction of the ink ejection speed Vjet in the −C direction and the carriage speed Vcr in the A direction. The ink flying time from ejection to landing at this time is L / Vjet. Here, the direction of gravity is the -C direction, and the carriage shaft in which elastic deformation has occurred due to its own weight and the carriage mass is as shown in 5a.

  FIG. 4 illustrates ink ejection when the carriage shaft is elastically deformed when the carriage is stationary. In FIG. 4, the deformation amounts of the carriage shafts at both ends of the carriage are represented by Da and Db. This amount of deformation can be calculated from the material characteristics. The width of the carriage is W and the inclination θ. The discharge speed Vjet is also inclined by θ with respect to the C axis due to the inclination θ of the carriage. Therefore, the ink ejection vector can be decomposed into a speed of Vjet * sin θ in the −A direction and Vjet * cos θ in the −C direction.

Thus, in FIG. 3, the fluctuation of the ink flight time can be calculated by elastic deformation. Since the distance between the recording head and the recording medium surface is L− (Da + Db) / 2, the ink flight time can be calculated as (L− (Da + Db) / 2) / (Vjet * cos θ). Therefore, with respect to the conventional ink ejection timing,
(Formula 1)
L / Vjet− (L− (Da + Db) / 2) / (Vjet * cos θ)
By delaying the time calculated in (2), it is possible to improve image degradation due to a change in the distance between the recording head and the recording medium surface.

Further, when the carriage is inclined, it has a velocity component of Vjet * sin θ in the −A direction. Since the flight time at this time is given by (L− (Da + Db) / 2) / (Vjet * cos θ) calculated earlier, the ink flight distance due to the inclination is (L− (Da + Db) / 2) / (Vjet). * Cos θ) * (Vjet * sin θ). From this, the value divided by the carriage speed Vcr is the change time for correcting the ejection vector fluctuation component due to the inclination of the carriage (Equation 2)
sgn (Da−Db) * (L− (Da + Db) / 2) * tan θ / Vcr
It becomes. At this time, the timing is delayed if sgn (Da-Db) is negative, and the timing is advanced if positive. Therefore, in the change time determined by the sum of (Equation 1) and (Equation 2), the image due to the variation in the distance between the recording head and the recording medium caused by the elastic deformation of the carriage shaft and the ejection vector variation due to the inclination of the recording head. Improve deterioration. FIG. 5 is a graph showing image deterioration in a conventional inkjet recording apparatus. The horizontal axis indicates the carriage position, and the vertical axis indicates the image deterioration amount. The larger the absolute value, the larger the image deterioration. FIG. 6 is a graph showing image deterioration in the ink jet recording apparatus to which the present invention is applied. The horizontal axis is the carriage position, and the vertical axis is the image deterioration amount. Image degradation is less than that of the prior art, and image degradation due to elastic deformation of the carriage shaft can be improved by applying the present invention.

It is a perspective view of an inkjet recording device. FIG. 3 is a perspective view of a carriage on which a recording head is mounted. It is a figure explaining the cause of image degradation. It is a figure explaining ink discharge. It is a figure which shows the image degradation in the conventional inkjet recording device. It is a figure which shows image degradation in the inkjet recording device to which this invention is applied.

Explanation of symbols

A Inkjet recording apparatus 1 Recording head 2 Carriage 2a Bearing 3 Support plate 4 Flexible substrate 5 Carriage shaft 6 Guide shaft 7 Belt 9 Pulley 10 Pulley 11 Carrier motor 13 Discharge roller 14 Housing 15 Linear scale 16 Optical element 17 Recording medium

Claims (1)

A carriage having a recording head and a guide member mounted so as to scan the carriage in parallel with the recording surface of the recording medium, and transmitting a driving force from a carriage motor to the carriage via a belt In an inkjet recording apparatus that records on a recording medium by scanning the carriage and ejecting ink,
An ink jet recording apparatus, wherein an ink discharge timing is changed according to the guide member, the carriage movement direction, and the carriage position.

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