JP3862108B2 - Printing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printing apparatus that performs printing by landing ink droplets at a predetermined dot pitch on a printing paper while moving a print head of an inkjet method or the like in a certain direction.
[0002]
[Prior art]
Since the conventional printing apparatus prints dots at a predetermined printing dot interval (for example, about 0.08 mm) while moving the print head to the left and right, each position is generated based on the position signal generated from the linear encoder and the encoder sensor. Generally, the ink ejection timing of the nozzle is determined.
[0003]
The types of linear encoder and encoder sensor include an optical type and a magnetic type. Here, the optical type will be described.
[0004]
Parallel to the fixed and the moving direction of the print head tape-shaped called linear encoder. On this linear encoder, a pattern having a uniform interval between a transparent portion and an opaque portion is printed at a pitch P corresponding to the print dot interval. An optical encoder sensor in which a light emitting element is placed in one direction of this linear encoder and a light receiving element is placed on the opposite side is fixed to the print head unit. When the print head moves, the encoder sensor generates position signals at a pitch equal to the pitch P of the linear encoder pattern. By ejecting ink from each nozzle on the print head in synchronization with this position signal, it is possible to perform dot printing at a predetermined pitch.
[0005]
[Problems to be solved by the invention]
In a conventional printing apparatus, a large number of nozzles are arranged on the print head, and are arranged over a large range L (for example, L = 100 mm) in the carriage movement direction. For the nozzles arranged in this way, the printing timing of all the nozzles is determined based on the position signal obtained from one encoder sensor.
[0006]
The case of FIG. 3 will be further described.
[0007]
On the front surface of the print head 1, nozzles 5 are arranged at equal intervals (P × N) in the carriage movement direction. Here, the interval between the nozzles in row 1 and the nozzles in row 10 is Ln = 9 × P × N in the carriage movement direction. Consider that after the nozzles in row 1 are ejected, the print head moves Ls to the left and ejects the nozzles in row 10. If the encoder sensor counts exactly (9 × N) during the Ls movement, the print head has moved by Ls = 9 × N × P, and the dot position by the previously printed column 1 and the carriage It is possible to print the dots by the column 10 at the same position in the moving direction. However, when the material of the linear encoder is, for example, a resin such as a polyester film, the length of the linear encoder expands and contracts due to changes in ambient temperature and humidity. Consider a case where the linear encoder expands and contracts and the pitch P changes by ΔP longer. In this case, the distance that the encoder sensor moves while counting (9 × N) signals is longer by (9 × ΔP × N) than before expansion / contraction. Due to the difference in the movement distance, the dots printed by the columns 1 and 10 do not line up at the same position. That is, expansion and contraction of the linear encoder is a problem that not Alignment occurs print dot arrangement causes.
[0008]
The present invention, even when the print head is arranged a number of nozzles in the moving direction, relatively unaffected not Alignment greater linear encoder printing dot arrangement of thermal deformation as a minimum, It is an object to obtain a printing apparatus with good print quality.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a print head unit having means for printing dots on printing paper by ejecting ink, and a plurality of nozzles serving as the ejection ports, and the print head unit. Carriage means that moves to the left and right, a linear encoder that is mounted parallel to the carriage movement direction of the print head unit, and is fixed to the print head unit at a position corresponding to the linear encoder, and is positioned at a predetermined pitch as the print head moves. In a printing apparatus comprising an encoder sensor for generating a signal, a plurality of the encoder sensors are mounted side by side in the carriage movement direction, and the nozzles of the print head unit are divided into the same number of nozzle groups as the encoder sensors. corresponded by the output of each of the encoder sensor And controlling the One nozzle group.
[0010]
Further, the same number of encoder sensors as the nozzle rows arranged in the carriage direction on the print head unit are arranged, and the corresponding nozzle rows are controlled by the output of each encoder sensor.
[0011]
More above configuration, the nozzle arrangement the linear sensor is shared is minimized in the movement direction, it is possible to halt minimize the effects of non-integer rows of printing dots aligned due to dimensional changes in the thermal expansion of the linear encoder .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings.
[0013]
In FIG. 1, reference numeral 1 denotes a print head which performs printing by ejecting ink from nozzles 5 arranged on the front surface thereof. The print head 1 is fixed to the carriage base 2. The carriage base 2 is held on two guide rails 3 so as to be slidable left and right. A carriage motor 24 is fixed to the frame 21, and a drive pulley 23 is fixed to the shaft of the carriage motor 24. A driven pulley (not shown) is mounted on the other end of the frame. A timing belt 22 is hung between the drive pulley 23 and the driven pulley. One place on the circumference of the timing belt 22 is fixed to the carriage base 2 by a belt clamp 25. As the carriage motor 24 rotates forward and backward, power is transmitted to the carriage base 2 via the timing belt 22, and the print head 1 moves to the left and right in the axial direction of the guide rail 3.
[0014]
The linear encoder 11 is arranged in parallel with the guide rail 3 and is fixed on the frame 21. An encoder sensor 12 is attached to the carriage base 2 so as to face the linear encoder 11. Two encoder sensors 12 are provided, and are set apart by a certain distance in the carriage movement direction. Here, the left encoder sensor 12a determines the drive timing of the nozzles 5 from the left half row 1 to the row 5, and the right encoder sensor 12b drives the nozzles 5 from the right half row 6 to the row 10. The timing is determined.
[0015]
FIG. 2 is a diagram schematically showing the relationship between the nozzle arrangement and the encoder.
[0016]
The encoder sensor 12 a takes charge of the nozzles 5 from the first row to the fifth row. In this case, the maximum amount of dot deviation caused by expansion / contraction of the linear encoder 11 occurs between the rows 1 and 5. Shift amount at this time is represented by (4 × ΔP × N), come out to less than half in the case of a single encoder sensor 12 is a conventional method, therefore it is possible to improve the print quality.
[0017]
Preferably, the number of encoder sensors is increased to the same number as the number of nozzle rows, that is, 10 in this example, and only one row of nozzles 5 is controlled with respect to one encoder sensor 12. Since the distance to the nozzle 5 position can be reduced to 0, even if the linear encoder 11 expands and contracts, it is not affected. For this reason, it is possible to obtain a better print quality.
【The invention's effect】
As described above, according to the present invention, it is possible to configure a printing apparatus that minimizes the influence of misalignment of print dot alignment due to expansion and contraction of the linear encoder, and it is possible to obtain a printing apparatus with good print quality.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a printing apparatus of the present invention.
FIG. 2 is a schematic diagram showing the relationship between the nozzle arrangement of FIG. 1 and an encoder.
FIG. 3 is a schematic diagram showing a relationship between a conventional nozzle arrangement and an encoder.
[Explanation of symbols]
1 is a print head, 2 is a carriage base, 3 is a guide rail, 5 is a nozzle, 11 is a linear encoder, 12 is an encoder sensor, 21 is a frame, 22 is a timing belt, 23 is a drive pulley, 24 is a carriage motor, 25 is It is a belt clamp.

Claims (2)

A print head section having means for printing dots on a printing paper by ejecting ink, wherein a plurality of nozzles serving as the ejection openings are disposed; carriage means for moving the print head section to the left and right; and the print head Printing apparatus comprising: a linear encoder attached in parallel to the carriage movement direction of the printing section; and an encoder sensor fixed to the print head at a position corresponding to the linear encoder and generating a position signal at a predetermined pitch as the print head moves In
A plurality of the encoder sensors are mounted side by side in the carriage movement direction, and the nozzles of the print head section are divided into the same number of nozzle groups as the encoder sensors, and one nozzle corresponding to the output of each encoder sensor. A printing apparatus for controlling a group. The number of encoder sensors equal to the number of nozzle rows arranged in the carriage direction on the print head unit is provided, and each corresponding nozzle row is controlled by the output of each encoder sensor. Printing device.

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