JP2002200802A - Printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing apparatus capable of maintaining a preferable printing quality at the top and bottom of a paper and capable of achieving high-speed printing. SOLUTION: In a printer comprising a means for detecting the top and bottom of a paper and a means for detecting a position with the paper 2 pressed insufficiently, a printing operation is executed in a designated printing mode in a range with the paper 2 pressed sufficiently, and a low speed printing and one-way printing are executed in the other range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus such as an ink-jet printer or a dot printer, and more particularly to a printing apparatus capable of maintaining good print quality even at the leading and trailing ends of paper and capable of high-speed printing.

[0002]

2. Description of the Related Art Conventionally, an ink jet printer having a full-color print head mounted on a carriage and printing on paper has been widely used.

FIG. 7 is a perspective view showing a mechanism of a main part of a conventional ink jet printer.

In the drawing, reference numeral 51 denotes a print head which is mounted on a carriage and moves in the direction of an arrow 53;
The sheet is fed in the direction and printed by the print head 51.

In such an ink jet printer, when the paper 52 floats from a platen (not shown) when the paper 52 is conveyed, the print head 51 and the paper 5
2 cannot be kept uniform, which affects print quality. To solve this problem, use paper 5
In general, a mechanism for holding two or two places by mechanical parts is employed. That is, FIG. 8 is a view for explaining the state of the paper at the time of the conventional paper feeding. As shown in FIG.
A pair of roll-shaped paper presses 54 for pressing the upper surface of the paper 52 are disposed with the paper press 54 interposed therebetween, and the paper presses 54 prevent the paper 52 from rising.

[0006]

However, as shown in FIG. 8B, the leading end or the trailing end of the paper 52 cannot hold the end point of the paper 52, and the paper holder 54
Is not sufficiently pressed, and the paper floats. In such a state, the print head 51 and the paper 5
2 cannot be maintained properly, and the print head 51 may come into contact with the paper 52. In such a case, if the high-speed print mode is selected as the print mode, the print head 51 moves at a high speed in a state where the paper 52 is in contact with the print head 51, so that the paper 52 is rubbed or damaged. . In addition, since the manner in which ink is applied varies depending on the location of the paper 52,
The print quality at the leading end and the trailing end is degraded. Further, when the print mode is set to the bidirectional print mode, the paper 52 is rubbed left and right by the print head 51, and the support of the paper 52 is weak.
The feeding of the paper 52 becomes inaccurate, and the printing quality is significantly reduced. In the bidirectional printing mode, the normal printing head 51 performs a printing operation while moving from left to right in FIG. 7 when printing, but returns when the printing head 51 returns from right in FIG. This is the mode that prints when moving to the left. In such a bidirectional printing mode, high-speed printing can be realized because printing is performed even after the print head 51 returns. However, if the print positions do not exactly match on the way to and from the return, a problem occurs in the print quality.

As a method for solving these problems, it is conceivable to reduce the overall printing speed, or to change to unidirectional printing in which printing is performed only in one direction. However, when such an operation is performed, the overall time required for printing is lengthened and the performance as a printer is affected.

Accordingly, an object of the present invention is to provide a printing apparatus capable of maintaining good print quality even at the leading and trailing ends of paper and capable of high-speed printing.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a printer provided with means for detecting the leading edge and the trailing edge of a sheet, and means for detecting a position at which the sheet is no longer held sufficiently. Is characterized in that printing is performed in a designated print mode, and in the other range, low-speed printing and one-way printing are performed.

That is, according to the present invention, in order to secure print quality at the leading and trailing ends of a page, the printing speed is set regardless of the print mode setting value when the printing portion is located at a certain portion from the leading or trailing end of the page. When the print portion is located at a certain portion from the leading or trailing edge of the page, the printing is forcibly performed in one direction even when the bidirectional printing is selected as the setting.

According to the present invention, it is possible to obtain a printing apparatus which can maintain good print quality at the leading and trailing ends of a sheet and can perform high-speed printing.

[0012]

According to the first aspect of the present invention, there is provided a printer having means for detecting a leading end and a trailing end of a sheet, and means for detecting a position where the sheet is not sufficiently pressed.
The printing device is characterized in that printing is performed in the specified print mode when the paper press is sufficient, and low-speed printing and unidirectional printing are performed in the other ranges. Since only the leading edge and the trailing edge of the sheet fall, it has an effect that high printing quality can be obtained without significantly lowering the printing speed.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining a difference in a printing method depending on a position of a sheet, and illustrates a difference in a printing method depending on a portion of the sheet which is a feature of the present invention. P indicates a sheet to be printed. Now, the printing direction of the paper is assumed to be the direction indicated by the printing direction X. The range indicated by B in the printing direction X is a range in which printing is performed by a printing method corresponding to a normal print mode or the like. The print mode includes, for example, bidirectional printing at a high printing speed and microweave at a high printing quality. The print mode used here is specified from outside the printer. A certain range from the leading edge of the paper P indicated by A, and C
In general, paper holding is not sufficient for a certain range from the end of the paper P indicated by the following expression, so that the printing method is forcibly changed to a printing method that does not cause a problem in print quality regardless of the set printing method. For example, in the present embodiment, the movement of the head in the main direction is reduced to a low speed, and the printing operation is changed to a printing operation in only one direction. The method of determining the ranges A and C is basically determined by whether or not two places are pressed by the paper press as described later. In the range where the paper is pressed at two places and is stable, printing is performed in the specified print mode, and in other cases, printing is forcibly performed in the mode with less damage to the paper. If the portion in the range of A and C is made as small as possible at the stage of the mechanism design, the range of B becomes large and a reduction in speed as a whole can be prevented.

FIG. 2 is a block diagram showing the configuration of the present invention. 21 is a central processing unit for controlling the entire printer, 22
Is a read-only memory (R
OM) and 23 are random access memories (RAM) used for a work area of the program. Reference numeral 24 denotes a sheet sensor for detecting the position of the sheet, which has two states, ON and OFF, and is turned ON when the sheet comes into contact with the sheet. In this embodiment, two paper sensors 24 are used. 25 is an LF motor for feeding the paper in the sub-scanning direction, 26 is an LF control unit for controlling the LF motor,
27 is a carriage motor for moving the print head, 28
Denotes a carriage motor control unit for controlling the carriage motor 27, 9 denotes a print head that discharges ink in accordance with a given signal, and 30 denotes a head drive that controls the print head.

Next, FIG. 3 is a diagram for explaining the flow of paper in the embodiment of the present invention, and FIG. 4 is a diagram for explaining the flow of paper following FIG. 3, showing a printing apparatus for realizing the present invention. FIG. 2 illustrates a mechanism and a flow during printing, centering on paper conveyance.

3 and 4, reference numeral 1 denotes a paper feed tray for stocking printing paper, 2 denotes printing paper,
3 is a transport roller for picking up the paper 2 and transporting it to the printing mechanism, 4 is a platen for guiding the paper 2 toward the print head, 5 is a guide for preventing the paper 2 from coming off the platen 4, and 6 is the paper 2 for printing. LF roller for feeding the paper, 7 is a sensor for detecting that the leading end of the paper 2 is set near the head or approaching the end of the paper 2, 8 is a floating prevention guide for holding the paper so as not to float, Reference numeral 9 denotes a print head for outputting ink, and reference numeral 10 denotes a sensor. The sensor 10 is turned on when the paper reaches a position where the paper is properly supported at two places. Reference numeral 11 denotes a paper discharge tray for discharging printed paper.

FIG. 5 is a diagram showing the relationship between the ON / OFF of the sensor of the present invention and the speed control. In a series of printing operations, the change of ON / OFF of each sensor and the head speed at that time have been described. Things. Although the present invention does not control only the head speed, the head speed is described here as a representative example of the control contents for explanation. FIG. 6 is a flowchart of the embodiment of the present invention. In FIG. 6, the range of A is a case where the sensor 7 is on and the sensor 10 is off (range A), and the head speed is reduced. This range corresponds to the range A in FIG. When the sensor 7 is on and the sensor 10 is on (range B), the head speed is increased. This range corresponds to the range B in FIG. When the sensor 7 is off and the sensor 10 is on (range C)
Reduces the head speed as in the range of A. This range corresponds to the range C in FIG.

Next, a specific operation of the present apparatus will be described with reference to FIGS.

(1) Step 1 The paper 2 is gripped by the transport rollers 3 and transported.
The transported paper 2 is guided by a platen 4 and a guide 5 and
When transported to the F roller 6, the LF roller 6 moves the paper 2 to a location where the print head 9 is located.

(2) Step 2 When the leading end of the sheet 2 reaches the sensor 7, it is determined that the sheet 2 has reached the leading end of printing by changing the sensor 7 from OFF to ON. When the leading end of the paper 2 is detected, the printer operates the print head 9 right and left, and performs printing by discharging ink at a designated position while feeding the paper 2 with the LF roller 6. At this position, the sheet 2 is not sufficiently held, so that the printing method is forcibly changed. That is, printing is performed in one-way printing with the moving speed of the print head 9 reduced.

(3) Step 3 When the leading edge of the sheet 2 reaches the sensor 10 and the sensor 10 is turned on, the printing in the forced print mode performed in step 2 is terminated, and the printing is performed in the normal set print mode. I do.
After passing through the sensor 10, the paper 2 is pressed at two places by the floating prevention guide 8, so that it is possible to perform high-quality printing, such as bidirectional printing or microweave, which places a burden on the paper 2. is there.

(4) Step 4 When the printing progresses and the end of the paper 2 passes the sensor 7, the sensor 7 is turned off. In this state, only one of the floating prevention guides 8 functions, and the printing is again performed at a low speed. Transition. Further, when the sensor 10 is turned off, a series of printing is completed.

Next, the flow of printing will be described with reference to the flowchart shown in FIG.

(1) Step 1 First, the sheet 2 is drawn into the printer by turning the transport roller 3 until the sensor 7 is turned on. Turning on the sensor 7 indicates that the paper 2 has moved to the printing position (Step 1 in FIG. 3).

(2) Step 2 Printing is started. However, printing here is the original high speed,
By performing the one-way printing at a reduced head speed instead of the high-quality printing mode, it is possible to cope with a low holding force of the paper P. This printing method is continued until the sensor 10 is turned on (Step 2 in FIG. 3).

(3) Step 3 When the sheet 2 comes to the position where the sensor 10 is turned on, the printing method is changed to the original one and printing is performed. The printing performed here is a printing method with a relatively large load on the paper 2, such as bidirectional printing and microwave. However, in this state, no problem occurs because the sheet 2 is firmly fixed by the mechanism of the printer. Therefore, it is possible to select a high-speed, high-quality print mode. This print mode is executed until the sensor 7 is turned off (Step 3 in FIG. 4).

(4) Step 4 When the sheet 2 moves to a position where the sensor 7 is turned off, the sheet 2 cannot be fixed sufficiently again. During this period, printing is performed in the same printing mode as the method used in step 2. When the sensor 10 is turned off, the paper 2 completely deviates from the print head 9 and printing is completed (step 4 in FIG. 4).

In the present invention, the case where a sensor is desired to be used as a method of determining the range in which the low-speed printing process is performed at the leading end of the sheet has been described. However, the following method can be adopted.

(1) After the leading edge of the paper is detected by the sensor 7, the low-speed printing process is started from the time when the LF roller is rotated by a predetermined rotation angle.

(2) After the leading edge of the paper is detected by the sensor 7, printing is performed for a predetermined time, and then low-speed printing processing is started.

[0032]

According to the present invention, it is possible to employ an optimum printing method at both ends of a sheet, and to improve the printing quality without lowering the printing quality as a whole and without lowering the printing speed. Print results are obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a difference in a printing method depending on a position of a sheet.

FIG. 2 is a block diagram showing a configuration of the present invention.

FIG. 3 is a diagram illustrating the flow of a sheet in the embodiment of the present invention.

FIG. 4 is a view for explaining the flow of paper following FIG. 3;

FIG. 5 is a diagram showing a relationship between ON / OFF of a sensor of the present invention and speed control.

FIG. 6 is a flowchart of an embodiment of the present invention.

FIG. 7 is a perspective view showing a mechanism of a main part of a conventional ink jet printer.

FIG. 8 is a view for explaining a state of a sheet when a conventional sheet is fed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper feed tray 2 Paper 3 Conveyance roller 4 Platen 5 Guide 6 LF roller 7 Adjacent sensor for leading and trailing end of paper 8 Lifting prevention guide 9 Print head 10 Leading edge limit sensor 11 Discharge tray 21 Central processing unit 22 Read-only memory 23 Random Access memory 24 Paper sensor 25 LF motor 26 LF control unit 27 Carriage motor 28 Carriage motor control unit 30 Head drive

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C058 AB08 AB17 AC07 AE02 AE09 AF04 GA09 GB03 GB14 GB31 GB32 GB47 GB48 2C059 AA05 AA16 AA22 AA26 AA49 AA55

Claims (1)

[Claims] In a printer comprising means for detecting the leading end and the trailing end of a sheet and means for detecting a position where the sheet is no longer sufficiently pressed, a print mode designated in a range within which the sheet press is sufficient is specified. The printing apparatus according to claim 1, wherein the printing is performed in a low speed printing and a unidirectional printing in other ranges.