JPH0452145A - Ink jet printer - Google Patents

Abstract

PURPOSE:To prevent positional shift of a recording dot due to a transfer red position of a carriage in a sub scan direction in one line from occur ring and simultaneously to prevent the carriage from transferring wavily by a method wherein a d.c. mortor is used as a transfer means in the sub scan direction of the carriage, and a frame buffer is used as a means storing temporarily one screen content of a recording data. CONSTITUTION:A rotary drum 2 is rotated. One screen content of a recording data is transmitted to a frame buffer 10a from a host computer 9. Then, after the frame buffer 10a has received all one screen content of the recording data, one screen content of the recording data is transmitted to recording heads 4A-4D. Recording of one screen content is performed while a carriage 5 is being transferred at a constant speed in a sub scan direction. Then, since the carriage 5 is made to transfer smoothly at a specific speed instead of traditional stepwise transfer of the carriage 5 which was performed in recording one line, all positional shift of the recording head can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an ink jet printer of a rotating drum scanning type, which is equipped with a plurality of ink heads.

(B) Prior Art FIG. 4 shows a schematic structural diagram of an inkjet printer disclosed in Japanese Patent Application Laid-Open No. 63-77748 as a conventional head drive device.

In the figure, a rotating drum (2) is provided on which recording paper (1) is tightly wound, and this is rotationally driven by a DC motor (3). On the other hand, recording heads (4A) to (4D) eject yellow, magenta, cyan, and black ink droplets.
An arcuate carriage (5) is provided along the circumferential direction of the rotating drum (2), and a stepping motor (
6) moves this carriage (5) in the axial direction of the rotating drum (2). Then, the moving direction is the sub-scanning direction,
The rotation direction of the rotating drum (2) is called the main scanning direction.

Furthermore, the recording heads (4A) to (4D) are connected to a line buffer (10), and the line buffer (10) is connected to a host computer (9), so that information is sent from the host computer (9). The print data is stored in the line buffer (10), and once all the data for one line in the main scanning direction is collected, the print head (
4A) to (4D), and immediately thereafter, the next line of recording data is continuously transmitted from the host computer (9) to the line buffer (10) in the same manner as described above.

In the above configuration, in order to record one line in the main scanning direction, the rotating drum (2) is rotated, and during one rotation, the stepping motor (6) moves the carriage (5) to N. It is moved stepwise in the sub-scanning direction over a number of steps (N is a natural number, usually 5 or 10). That is, after the print heads (4A) to (4D) receive the print data stored in the line buffer (10), the print heads move according to the print data while moving the carriage (5) step by step. From (4A) to (4D), apply ink droplets to recording paper (1
) to form circular dots and record one line.

Furthermore, when the recording for the above-mentioned 1 line is completed ht'L, the recording heads (4A) to (4D) receive the recording data for the next 1 line from the line buffer (10), and then the stepping motor ( In step 6), the carriage (5) is further moved stepwise in the sub-scanning direction to record the next line, and by performing this continuously, one screen can be recorded.

During these recordings, the rotating drum (2) must rotate at a constant speed, and for this reason, the rotating drum (2) A rotation controller (8) detects the speed of the DC motor (3) and controls the rotation of the DC motor (3) based on the detected value, forming a so-called closed-loop servo system.

By the way, the recording heads (4A) to (4D) receive and receive one line of recording data from the line buffer (10), and send this data to the recording heads (4A) to (4D) to perform recording. However, the time until the next line of data is sent to the line buffer (10) is not constant because the host computer (9) may have to perform other calculation processing.

Therefore, when the carriage (5) finishes recording one line, it must wait until all of the recording data for the next line is available in the line buffer (10).

In the above configuration, a series of recording operations will be explained based on the flowchart shown in FIG.

In step S1, the rotating drum (2) is rotated. In step S2, one line of recording data is sent from the host computer (9) to the line buffer (10). In step S3, line buffer (1
0), if all the recorded data for one line has been received, the process advances to step S4, and if all the recorded data has not been received, the process proceeds to step S2 again.

In step S4, the recording heads (4A) to (4D)
Send the recorded data to. In step S5.

One line is recorded while moving the carriage (5) in the sub-scanning direction five times. In step S6, when recording for one line is completed, the carriage (
5) Stop moving and wait in that location. In step S7, if the next line is to be recorded, the process returns to step S2 and the above operation is repeated; if not, the process proceeds to step S8. In step S8, the rotation of the rotary drum (2) is stopped to complete the series of recording operations.

Figure 6 is a plan view of the movement timing diagram of the carriage (5) when the carriage (5) is moved in the sub-scanning direction five times to record one line. It is. Note that A1 to A7 correspond to the 1st line to the 7th line, respectively.

Conventionally, the timing at which the carriage (5) is moved five times, that is, at which timing in one line the carriage (5) is moved in the sub-scanning direction is randomly changed for each line. This is a position randomly shifted by X from B1-B5 on line B in FIG.

Therefore, when recording each line, the carriage (5)
Since the movement positions of the dots are not the same between adjacent lines, the positional deviation of the recording dots at that position no longer exists continuously in the sub-scanning direction. However, this does not solve the essential problem of eliminating the positional deviation of recorded dots in each line, and therefore, the quality of the printed image is not good.

Furthermore, since the movement of the carriage (5) is performed intermittently for each line, undulations such as overshoots, undershoots, etc. are likely to occur when the carriage (5) moves, which may cause the recording position to shift. Likely to happen.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned problems. The purpose is to prevent hitting and moving at the same time.

(d) Means for Solving the Problems The present invention provides a means for solving the problems,
In an inkjet printer, a plurality of recording heads arranged along the circumferential direction are held by a carriage, and recording is performed by moving the carriage in the axial direction of the rotary drum while rotating the rotary drum. It is characterized by comprising a DC motor for movement and a frame buffer for temporarily storing one screen worth of recording data immediately before being transmitted to the recording head.

(E) Function The recording data from the host computer is temporarily stored in a frame buffer, and once the recording data for one screen has been received, this recording data is sent to the recording head, and the carriage is moved by the DC motor. The screen is recorded while moving at a constant speed in the sub-scanning direction.

(f) Example An example of the present invention will be explained based on FIGS. 1 to 3,
Components that are the same as those of the conventional example are given the same numbers and their explanations will be omitted.

In FIG. 1, (6a) is a DC motor that moves the carriage (5) at a constant speed in the sub-scanning direction; (10a)
is a frame buffer that temporarily stores recording data for one screen from the host computer (9).

In the above configuration, a series of recording operations will be explained based on the flowchart shown in FIG.

In step S1, the rotating drum (2) is rotated. In step S2, one screen worth of recording data is transferred from the host computer (9) to the frame buffer (10a).
Send to. In step S3, if the frame buffer (10a) receives the recording data for the screen,
The process proceeds to step S4, and if all data has not been received, the process proceeds to step S2 again. In step S4,
One screen worth of print data is sent to the print heads (4A) to (4D). In step S5, the carriage (5)
One screen is recorded while moving at a constant speed in the sub-scanning direction. In step S6, the rotating drum (2)
The series of recording operations is completed by stopping the rotation of the .

Here, as shown in FIG. 3, the movement of the carriage (5) in step S5 in the flowchart is at a constant speed until the recording for one screen is completed, and as soon as the recording for one screen is completed, It is supposed to stop.

Therefore, instead of the conventional stepwise movement of the carriage (5) during recording of one line, the carriage (5) moves smoothly at a constant speed, eliminating any positional deviation of the recording dots. be able to.

With the above configuration, all the recorded data for one screen from the host computer (9) is stored in the frame buffer (10a), and the carriage (5) is moved at a constant speed by the DC motor (6a). By moving in the scanning direction, it is necessary to move the carriage (5) step by step while recording one line, as in the conventional example, or to make the carriage (5) wait after recording one line. disappears.

(G) Effects of the Invention The present invention uses a DC motor as a means for moving the carriage in the sub-scanning direction, and a frame buffer as a means for temporarily storing one screen's worth of recorded data.
It is possible to prevent the recording dots from being displaced due to the movement position of the carriage in the sub-scanning direction within one line, and to prevent the carriage from moving in a wavy manner.

Furthermore, since recording for one screen can be performed continuously, there is no need to wait for the carriage after recording one line, and the time required to record one screen is not unnecessarily increased. .

[Brief explanation of drawings]

FIG. 1 is a schematic structural diagram of an inkjet printer of the present invention, FIG. 2 is a flowchart of a recording operation in the present invention, FIG. 3 is a movement timing diagram of a carriage of the present invention, and FIG. 4 is a schematic diagram of a conventional inkjet printer. structural diagram,
FIG. 5 is a flowchart of the recording operation in the conventional example, and FIG. 6 is a movement timing chart of the carriage in the conventional example. (1) Recording paper, (2) Rotating drum, (3)
...DC motor, (5)...Carriage, (6a)
...DC motor, (9)...host computer,
(10)...Line buffer, (10a)...Frame buffer. Figure 2 Figure 3 Secondary leg direction Figure 5

Claims (1)

[Claims] (1) A carriage holds a plurality of recording heads arranged circumferentially facing a rotating drum around which a recording medium is wound, and while rotating the rotating drum, the carriage is moved around the rotating drum. An inkjet printer that performs recording by moving the carriage in an axial direction, comprising: a DC motor that moves the carriage; and a frame buffer that temporarily stores one screen worth of recording data immediately before being sent to the recording head. inkjet printer.