JP2007144722A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an image from getting deteriorated by the rotational motion of a carriage. <P>SOLUTION: The inkjet recording device comprises a transfer means to transfer recording mediums, a carriage carrying a recording head which prints image information by discharging ink droplets to the recorded surfaces of the recording mediums from nozzle openings, a driving means to move the carriage back and forth along a guide shaft in a main scanning direction, bearing sections provided in the carriage to receive the guide shaft, a flexible endless belt member which drives the carriage, a fixed section provided in the carriage to attach the belt member in a stretched condition, and a control means including a constant speed area and acceleration and deceleration areas before and after the constant speed area and permitting ink discharge even in the acceleration and deceleration areas within the reciprocation movement range of the carriage in the main scanning direction. The inclination of a plane including straight lines connecting the fixed section and the center of gravity of the carriage with respect to the nozzle forming surface of the recording head is 40 to 50°. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a configuration of a carriage on which a recording head is mounted in an ink jet recording apparatus.

  In an ink jet recording apparatus, a plurality of ink ejection openings are provided on the front surface of a recording head, and ejection energy generating elements corresponding to the respective ejection openings are driven based on recording information, and the ink ejection openings are used for recording materials such as recording paper. Information is recorded (image formation) by ejecting a recording material (ink) toward the head. In this type of ink jet recording apparatus, at both ends of the movement range of the carriage in the main scanning direction, the carriage temporarily stops and then moves in the opposite direction. Speed region). Further, since ink is ejected from the recording head while the carriage is moving, the ink landing position on the recording paper is shifted forward in the movement direction from the ink ejection position. For this reason, if ink ejection is performed at the same carriage position for the same position in the main scanning direction on the image in the forward path and the backward path, the ink landing position is shifted. In order to prevent such a shift, it is necessary to correct the ink ejection position with respect to the same position on the image in at least one of the forward path and the backward path. Since the magnitude of the deviation of the ink landing position with respect to the ink discharge position varies depending on the carriage speed, correction of the ink discharge position as described above is relatively easy in the constant speed region, but difficult in the acceleration / deceleration region. For this reason, in the conventional ink jet recording apparatus, the printing area is set inside the constant speed area, and printing is performed only inside the constant speed area. In the conventional ink jet recording apparatus, as described above, only the inside of the constant speed area is the printing area. Therefore, the printing time is increased by the acceleration / deceleration area on both sides of the constant speed area, and the apparatus is large. There is a problem of becoming.

Therefore, in the conventional technique, for example, a carriage position detection unit using a linear encoder and a carriage speed detection unit that detects the output pulse cycle of the encoder are used to perform printing even in the acceleration / deceleration region of the carriage. In some cases, the position correction amount is calculated from the speed modulation at the carriage speed (see, for example, Patent Document 1). Also, a print command signal is generated before the print head's flight time (the time from when the print command is given until the ink reaches the recording material from the head to form dots) to correct the landing position. (For example, refer to Patent Document 2).
JP 2004-34650 A JP-A-6-198970

  However, even in a configuration in which printing can be performed by correcting the print command signal, excessive ink droplet landing misalignment occurs in the acceleration printing section and the deceleration printing section. This is because there is always manufacturing between the guide shaft that supports the carriage and the bearing of the carriage, and a large change in the posture of the carriage occurs in the acceleration region and the deceleration region. When the posture changes greatly in the carriage, the ink discharge port of the mounted recording head fluctuates and a large landing position deviation occurs. Therefore, when ink is ejected in the acceleration region and the deceleration region, there is a problem in that the landing position shifts due to the rotational movement of the carriage, leading to image deterioration.

Accordingly, an ink jet recording apparatus of the present invention includes a transport unit that transports a recording medium, a carriage on which a recording head that prints image information by ejecting ink droplets from nozzle openings on a recording surface of the recording medium, and the carriage Driving means for reciprocating in the main scanning direction along the guide shaft, a bearing provided in the carriage for receiving the guide shaft, a flexible endless belt member for driving the carriage, The fixed portion provided on the carriage so that the belt member is attached and the reciprocating movement range of the carriage in the main scanning direction include a constant speed region and an acceleration / deceleration region before and after the constant speed region. And an ink jet recording apparatus provided with a control means capable of performing ink ejection,
An inclination of a plane including a group of straight lines connecting the fixed portion and the center of gravity of the carriage with respect to the nozzle formation surface of the recording head is 40 to 50 °.

  According to the present invention, when printing is performed in the acceleration area and the deceleration area of the carriage, it is possible to suppress occurrence of a large landing position deviation and obtain an image without impairing the print quality.

Example 1
Hereinafter, embodiments of the present invention will be described. FIG. 2 is a schematic perspective view showing an embodiment of an ink jet recording apparatus embodying the present invention. In FIG. 2, 1 is a head cartridge having an ink jet recording head, and 2 is a carriage for mounting the head cartridge and scanning along a carriage guide shaft. Reference numeral 3 denotes a support plate for supporting the head cartridge as well as having an electrical connection for transmitting a recording signal from the head cartridge 1 to the electrical connection. Reference numeral 4 denotes a flexible substrate for connecting the electrical connection portion of the support plate and the main body control portion, and an electric command value from the main body transmits a signal for ejecting ink to the support substrate 3 through the flexible substrate to perform print recording. . Reference numeral 5 denotes a carriage shaft for guiding the carriage 2 and is in contact with the carriage bearing 18. Reference numeral 6 denotes a guide shaft different from the carriage shaft 5 for guiding the carriage 2 in the same direction as the carriage shaft 5. Reference numeral 7 denotes a belt to which the carriage 2 is fixed and transmits power for moving the carriage, and is further stretched around pulleys 9 and 10 disposed at both ends of the apparatus. The pulley 9 is configured such that a driving force is transmitted from the motor 11 by using a mechanism such as a gear, and the carriage 2 scans the recording medium. Reference numeral 12 denotes a transport roller for transporting a recording medium such as paper during recording, and is driven by a transport motor. Reference numeral 13 denotes a paper discharge roller for discharging the recording medium. Reference numeral 14 denotes a housing for configuring these mechanisms.

  FIG. 3 shows a detailed perspective view of the carriage. The carriage 2 performs printing and recording when power is transmitted from the motor to the belt. A linear scale 15 gives position information of the carriage 2 in order to form an image at a desired position by ejecting ink. The linear scale 15 is read by 16 optical elements to detect the position. When the carriage 2 scans to the desired print position by the motor 11 by this position detection, a print command signal is generated, and in the head cartridge, the print head generates heat energy due to current flowing through the substrate in contact with the ink. A foaming phenomenon occurs. Due to this phenomenon, droplets are formed at the ejection port, and the ink is ejected to the recording medium, thereby performing desired printing and recording. Reference numeral 17 denotes a fixing portion for fixing the belt 7.

  When the carriage 2 transmits the driving force of the motor via the belt 7, the carriage rotates by acceleration and deceleration. This rotational motion exists between the carriage bearing and the guide shaft, so that it rotates about the carriage scanning direction axis (hereinafter referred to as A axis), the paper conveyance direction axis (hereinafter referred to as B axis), and the recording paper. Rotational movement around an axis perpendicular to the axis (hereinafter referred to as the C axis). FIG. 5 shows the A axis, the B axis, and the C axis. Due to the rotational movement of the carriage, the ink discharge port is displaced, so that the ink droplet cannot be landed at a desired position, resulting in image deterioration. In particular, the cause of image deterioration in the carriage scanning direction is due to the sum of the displacement of the discharge port due to the rotational movement of the carriage about the B axis and the displacement of the discharge port due to the rotational movement of the carriage about the C axis. However, when the fixing portion that fastens the belt and the carriage is in a negative position with respect to the center of gravity of the carriage and the B axis and the C axis are both in the negative position, if the driving force is transmitted to the carriage via the belt, the B axis The polarity of the displacement of the discharge port due to the rotational motion around and the polarity of the displacement of the discharge port due to the rotational motion around the C axis are reversed. The reason for this is that when the driving force is transmitted through the belt and a rotational moment is generated, the center of gravity of the fixed portion of the belt and the carriage is shown above, and the discharge port is caused by the rotational moment about the B axis. This is because the polarity having a displacement in the carriage scanning direction and the polarity having a displacement in the carriage scanning direction by the rotation moment about the C axis are reversed. These mechanisms are shown in FIGS. 7 and 8 are conceptual diagrams illustrating the same carriage 2 from different viewing angles. In FIG. 7, the rotational movement about the C axis is illustrated, and the carriage 2 obtains the driving force in the F direction from the belt fixing portion 17. The carriage rotates in the Θc direction depending on the positional relationship between the center of gravity and the belt fixing portion 17, and the discharge port 19 has a displacement in the P direction. FIG. 8 shows the rotational movement about the B axis, and the discharge port 19 is the same as that shown in FIG. The carriage 2 obtains driving force in the F direction from the belt fixing portion 17. The carriage rotates in the Θb direction due to the relationship between the position of the center of gravity and the belt fixing portion, and the discharge port 19 has a displacement in the Q direction. Therefore, with respect to the position of the discharge port 19 in a state where there is no rotational movement of the carriage, the P direction displaces the discharge port in the negative direction, the Q direction displaces the discharge port in the positive direction, and the sum total is the actual value. It becomes the position of the discharge port. As described above, the amount of ink landing position deviation in the scanning direction of the carriage has a mechanism that the displacement of the ejection port due to the mutual rotational movement cancels out. When this mechanism works most effectively, the displacement of the discharge port due to the rotational motion around the B axis, the positional displacement of the discharge port due to the rotational motion around the C axis, and the displacement of the discharge port as a whole are roughly summarized. This is shown in FIG. However, when a large difference occurs between the rotational movements about the B axis and the C axis, the effect of the mechanism is reduced. Therefore, the overall displacement of the discharge port determined by the sum of the displacement of the discharge port due to the rotational movement of the carriage about the B axis and the displacement of the discharge port due to the rotational movement of the carriage about the C axis increases, resulting in image degradation.

  FIG. 4 shows a conceptual diagram of the carriage 2 according to the present invention. A case where the inclination angle θ between the portion connecting the belt 7 and the carriage 2 and the straight line connecting the center of gravity of the carriage 2 and the B axis is 45 ° is shown. When the tilt angle increases or decreases from 45 ° shown in FIG. 4, one of the rotational motions about the B axis and the C axis becomes excessively large and the other is excessively small, resulting in a difference in the process of generating the rotational motion. Due to the difference in the process in which this rotational motion occurs, the mechanism of offsetting the displacement of the discharge port due to the mutual rotational motion is not effectively established. However, if the inclination angle θ between the center of gravity of the belt 7 and the carriage 2 and the straight line connecting the center of gravity of the carriage 2 and the B axis is 45 °, the driving force of the motor is transmitted to the carriage via the belt. As a result, the amount of rotation about the B axis and the amount of rotation about the C axis when the carriage accelerates or decelerates are the same. Therefore, the process of generating the rotational motion about the B axis and the rotational motion about the C axis are the same, and the rotational motion can be made equal. Therefore, the displacement of the discharge port due to the rotational motion around the B-axis and the C-axis having different polarities becomes equal, so that the overall displacement of the discharge port can be reduced. FIG. 1 shows the effect of the inclination angle between the B-axis and the straight line connecting the carriage fastening portion and the center of gravity of the carriage on the landing error amount. The horizontal axis represents the inclination angle between the B-axis and the straight line connecting the belt-carriage portion and the center of gravity of the carriage, and the vertical axis represents the landing error amount. The solid line indicates the maximum landing error amount during acceleration, and the dotted line indicates the maximum landing error amount generated during deceleration. According to FIG. 1, the maximum amount of landing error during acceleration and deceleration is the lowest when the position of the center of gravity of the carriage is between 40 ° and 50 °. The reason for this is that the mechanism effectively cancels the landing error amount by setting the inclination between the B-axis and the straight line connecting the belt and the center of the carriage described above and the center of gravity of the carriage to be around 45 °. Image degradation can be reduced.

The effect by the Example of this invention is made into a graph. 1 is a perspective view of an ink jet recording apparatus according to an embodiment of the present invention. 1 is a perspective view of a carriage on which a recording head is mounted, to which the present invention is applied. The conceptual diagram of the carriage to which this invention was applied is shown. It is a perspective view which shows the coordinate system in a subject. It is the graph which showed the phenomenon used as the principle of this invention. The conceptual diagram of the displacement of the discharge outlet by the rotational motion around the C axis is shown. The conceptual diagram of the displacement of the discharge outlet by the rotational motion around the B axis is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Head cartridge 2 Carriage 3 Support board 4 Flexible board 5 Carriage shaft 6 Guide shaft 7 Belt 11 Carriage motor 15 Linear scale 16 Optical element 17 Belt fixing part 18 Carriage bearing 19 Discharge port

Claims (1)

Conveying means for conveying a recording medium, a carriage having a recording head for printing image information by ejecting ink droplets from nozzle openings on the recording surface of the recording medium, and the carriage along the guide axis in the main scanning direction A driving means for reciprocating the guide shaft, a bearing portion provided on the carriage for receiving the guide shaft, a flexible endless belt member for driving the carriage, and the belt member so as to be attached. The fixed portion provided in the carriage and the reciprocating movement range of the carriage in the main scanning direction include a constant speed area and acceleration / deceleration areas before and after the area, and ink can be ejected in the acceleration / deceleration area. An ink jet recording apparatus comprising a control means,
An inkjet recording apparatus, wherein an inclination of a plane including a group of straight lines connecting the fixed portion and the center of gravity of the carriage with respect to a nozzle forming surface of the recording head is 40 ° or more and 50 ° or less.

Images