JP2007245351A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder which maintains the positioning accuracy and is prevented from taking time in positioning even when such a situation that hinders fine positioning of a carriage occurs because the friction characteristic changes caused by adhesion of mist to the carriage and a shaft. <P>SOLUTION: When a carriage position reaches the vicinity of a target position, a position grasping means which detects that the carriage position reaches the vicinity of the target position stops an integral compensation term of a control means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that records an image on a recording medium by moving a carriage mounted with a recording head.

  2. Description of the Related Art Conventionally, recording devices equipped in printers, copiers, facsimiles, and the like record images (including characters and symbols) on recording materials such as paper and plastic thin plates (for example, OHP sheets) based on image information. It is configured as follows. This recording apparatus can be classified into an ink jet type, a wire dot type, a thermal type, a thermal transfer type, a laser beam type, etc., depending on the recording method of the recording means used.

  Among them, an ink jet recording apparatus (ink jet recording apparatus) performs recording by ejecting ink from a recording means such as an ink jet recording head (hereinafter also referred to as a recording head) to a recording medium such as a recording sheet. is there. The recording means can be easily downsized and high-definition images can be recorded at high speed.

  However, if a situation occurs in which it is difficult to stably eject ink only to a specific nozzle among a plurality of nozzles provided in the ink jet recording head, it becomes a defective nozzle. Since the recording is not performed with the defective nozzle, a portion where recording is not performed is generated in a streak shape in the recorded image.

  In order to detect such non-ejection of ink, a method of detecting non-ejection using a light emitting element such as an LED and a light receiving element such as a photodiode is used. In this method, the ink jet head is stopped at a predetermined detection position, ink droplets are ejected into a light beam that exits the light emitting element and reaches the light receiving element, and non-ejection is detected from the output of the light receiving element.

The light emitting element and the light receiving element are arranged so that the optical axis connecting them is parallel to the ejection port array of the inkjet head and intersects the flight path of the ejected ink droplets. It is provided so as to be wider than the range. Thereby, all the ink droplets ejected from each ejection port of the inkjet head can pass through the detection range between the light emitting element and the light receiving element. When ink is ejected satisfactorily and the ink droplet passes through this detection range, the ink droplet blocks light from the light emitting side, reducing the amount of light to the light receiving side, and a change in the output of the light receiving element is obtained. It is configured. The ejected ink droplet is a droplet having a minute diameter, and usually does not completely block light from the light emitting side by ejection from one ejection port. Accordingly, if the output of the transmissive photosensor changes to a certain amount or more, it is detected that ink ejection is normal, and conversely, if the output change is less than a certain amount, it is detected that ink ejection is defective. The discharge failure detection technique described above is used as an effective means because it can perform detection without adding special components to the inkjet head. (See Patent Document 1)
By the way, when detecting the ejection failure as described above, it is necessary to align the photosensor optical axis and the ejection port array of the inkjet head, and eject ink from each ejection port so as to intersect the optical path. . In that case, basically, the amount of movement from the reference position of the head to the optical axis is set in advance, and the head is moved in accordance with this, whereby the photosensor optical axis and each ejection port array of the inkjet head And positioning. As the image quality is increased and the number of colors is increased, the intervals between the ejection port arrays are narrowed, and high-precision positioning accuracy is required.

Positioning control is realized by detecting the position of the carriage and feeding it back. (See Patent Document 2)
JP-A-8-309963 JP 2003-019838 A

  In addition to the ink droplets that form an image when ink is ejected, minute mist-like droplets (hereinafter referred to as mist) are generated. These mists adhere everywhere in the recording apparatus.

  FIG. 6 shows the friction between the shaft and the carriage. The horizontal axis indicates the speed of the carriage, and the horizontal axis indicates the magnitude of the carriage friction. Generally, friction when the speed is 0 is called static friction, and friction when the speed is high is called dynamic friction.

  The thin line in the figure indicates a state where mist is not attached to the shaft or carriage bearing, and the thick line indicates a state where a large amount of mist is attached. The overall friction increases due to the mist adhesion, but it can be seen that the increase in static friction is larger than the increase in dynamic friction.

  In other words, a large force is required to start moving, but a large force is not necessary when moving, that is, it is difficult to move and is difficult to stop.

  In such a case, during a minute positioning operation, continuous vibration is repeated in the vicinity of the target position, or it takes time for positioning, an undischarge failure cannot be detected, and image degradation and output may take time.

  A carriage mounted with a print head for recording on a recording material, a position detecting means for detecting the position of the carriage, a position grasping means for detecting that the position of the carriage has reached the target position, and a carriage and a belt are combined. Drive means for scanning the carriage, control means for controlling the carriage position and speed, and switching means for switching operation / stop of the integral term of the control means. When the carriage position reaches the vicinity of the target position, integration is performed. Stop the compensation term.

  Provided is an ink jet recording apparatus that maintains positioning accuracy and does not take time for positioning even when mist adheres to a carriage or a shaft, friction characteristics change, and it becomes difficult to perform minute positioning of the carriage.

  FIG. 1 is a diagram schematically showing a carriage configuration of an embodiment of an ink jet recording apparatus according to the present invention.

  In the figure, reference numeral 1 denotes a carriage on which a recording head (not shown) is mounted. A guide shaft 2 is slidably inserted in the carriage 1, and the carriage 1 can reciprocate along the thrust direction (main scanning direction) of the guide shaft 2.

  Reference numeral 3 denotes a motor as drive means. A drive pulley 4 is fixed to the shaft of the motor 3. Between the drive pulley 4 and the idle pulley 5, a belt 6 as a carriage drive transmission means is stretched over, and a part of the belt 6 is fixed to the carriage 1. The belt 6 is moved by forward and reverse rotations of the CR motor 1, and the carriage moves forward and backward along the main scanning direction. An optical encoder 7 detects the position of the carriage. 8 is a discharge failure detection means.

  FIG. 2 is a schematic diagram of the discharge failure detection means.

  Light emitted from the light emitting element 10 such as an LED is incident on a light receiving element 11 such as a photodiode placed facing the light emitting element 10. Each element is arranged so as to sandwich the head 9, and the optical axis and the nozzle array are arranged in parallel.

  When the ink droplet ejected from the head 9 blocks the optical axis between the light emitting element 10 and the light receiving element 11, the output signal level from the light receiving element 10 decreases. Thereby, it is determined whether or not the nozzle discharge is normal. When one nozzle row is completed, the carriage is moved, non-discharge detection is performed on the next nozzle row, and non-discharge detection is performed on all nozzle rows.

  FIG. 3 is a block diagram of the carriage controller of this embodiment.

  The control means 12 takes a difference between a predetermined carriage driving pattern and the carriage position observed by the encoder 7 and performs a compensation calculation. The output of the control means 12 is compared with the carriage speed obtained by the speed calculation means 13, and subjected to a compensation calculation by the PI compensator 14, amplified by the drive circuit 15, and drives the motor.

  The PI compensator 14 includes a proportional compensation term 16, an integral compensation term 17, a cut-off output means 19, and a switching means 18. Normally, the output of the proportional compensation term 16 is input to the integral compensation term 17. When the position of the carriage approaches the target position and falls within the allowable range of the undischarge detection means 8, the position grasping means 20 operates, and the output of the cutoff output means 19 is input to the integral compensation term 17 by the switching means 18. The output of the cutoff output means 19 is 0, the operation of the integral compensation term 17 is stopped, the output of the integral compensation term 17 becomes a constant value, and the carriage holds its position.

The operation sequence of the present invention will be described with reference to the flowchart of FIG.
Reads the current position (S1), compares the target position with the current position (S2), and if the current position has not reached the desired position, performs control calculation (S3), outputs the command value and drives the motor (S4).

  When it reaches the range determined by the allowable error of the discharge failure detection means 8 (for example, target position ± 20 μm), the switching means switches and connects to the cut-off output means 19 (S5).

  It is determined whether the nozzle check is completed (S6). If it is completed, the driving is terminated (S7).

  FIG. 5 shows the effect of the present invention. The bold line in the figure represents the behavior of the carriage according to the embodiment of the present invention. Thus, it can be seen that even if the frictional characteristics of the carriage change, the settling is continued without a continuous vibration like a thin line. The dotted line indicates the target position, and the one-point difference line indicates the set range of the discharge failure detection means 8.

Schematic diagram of a carriage configuration of an embodiment of a recording apparatus Schematic of undischarge detection means Block diagram of the carriage control unit of this embodiment The flowchart which shows the operation | movement order of this invention Graph showing the effect of the present invention Graph showing the difference in friction due to mist adhesion

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carriage 2 Guide shaft 3 Drive means 4 Drive pulley 5 Idle pulley 6 Belt 7 Encoder 8 Undischarge detection means 9 Recording head 10 Light emitting element 11 Light receiving element 12 Compensator 13 Speed detection means 14 PI compensator 15 Drive circuit 16 Proportional term 17 Integral term 18 Switching means 19 Cut-off output means 20 Position grasping means

Claims (1)

A carriage having a print head for recording on a recording material;
Position detecting means for detecting the position of the carriage;
Position grasping means for detecting that the position of the carriage has reached the vicinity of the target position;
Driving means coupled with the carriage and a belt to scan the carriage;
Control means for controlling the position speed of the carriage, cut-off output means,
Comprising switching means for switching operation / stop of the integral term of the control means;
An ink jet recording apparatus, wherein the position compensator stops the integral compensation term when the carriage position reaches the vicinity of the target position.

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