JPS6377748A - Head driving unit for ink jet printer - Google Patents

Abstract

PURPOSE:To set the pulse feeding of a pulse motor at irregular intervals thereby to prevent dots from being superposed in a displaced manner by adding an offset amount varied at each line or each step in a standard driving timing. CONSTITUTION:A rotary encoder 9 generates a pulse whenever a rotary drum rotates at a predetermined angle, a counter 11 uses the pulse as a reset signal and a count input, and outputs a calculated value to a comparator 12. A memory 13 stores a standard pulse number corresponding to a rotating angle set on the drum, an adder 14 inputs the standard pulse, and adds the offset amount from an offset setter 15 having a random number generator. The comparator 12 outputs a coincidence signal at a timing that the offset amount is added when the outputs of the counter 11 and the adder 14 coincide with each other to drive a pulse motor 8. Accordingly, step feeding is set at irregular intervals, the timing of generating the displacement of dots is varied to prevent the dots from being superposed in a displaced manner.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a rotating drum scanning type inkjet printer, and relates to a head driving device equipped with a plurality of ink heads for color printing.

(b) The fifth factor in the conventional technology is the schematic structure of the inkjet color printer. Four ink heads +31. Installed. Ink head (31, +41. (51, +61
The 5-carrier v (installation on 71 The positions or ejection positions of ink droplets are different in the circumferential direction of the rotating drum (2), but are the same in the axial direction.The carriage (7) is arranged between two pulleys. It is attached to an endless belt and is intermittently moved from left to right by a pulse motor f81c connected to one of the pulleys.

(9) is a rotary encoder with one rotation drum (2
), and as shown in Figure 'IJf116, there is a pulse signal Z which produces one pulse each time the rotary drum (2) rotates by a predetermined angle, and a pulse signal Z which produces one pulse each time it rotates. emanate.

Recording is then performed using a rotating drum (2) by a servo motor (1).
) is driven for main scanning, and the pulse motor (8) is used to drive the ink head (3), (41, +51. Apply a signal to eject ink droplets.

The recording position of each color must be specified for each head. Positioning in the circumferential direction on the drum (2) with one rotation is performed by the pulses output by the rotary encoder (9).
Since each head has a different physical position, it is necessary to devise ways to correct this.

On the other hand, while the single-rotation drum (2) rotates once (; scanning is performed so that the head moves by a predetermined step, the pulse motor (8) Requires a signal to drive.

Figure 7 shows the relationship between these signals, and the pulse signal Z
After one elementary pulse appears per drum rotation, recording is started by the yellow head located upstream in the drum rotation direction.

Then magenta and cyan are delayed by time t.

Recording by the black heads is started sequentially.

This time t is determined by the rotational speed of the rotating drum (2) and the distance between the heads. The recording is then completed in the same order, but the pulse signal PM for driving the pulse motor (8) requires, for example, eight elementary pulses during one period of the pulse signal Z. The yellow shown in this Figure 6,
Magenta, cyan, and black heads (3);
(41, (5+,
)'s output A1. Regarding the head drive system of the above-mentioned inkjet printer, Japanese Patent Application Laid-Open No. 1986-
45984 Publication 1: Since it is detailed, the explanation will be omitted here.

(c) Problems to be Solved by the Invention When the resolution of an inkjet printer using a rotating drum scanning method is 12 lines per line, the main scanning direction, that is, the rotating drum (
2) in the sub-scanning direction during one rotation.

The carriage (7) is moved by the drive of the pulse motor (8) by 1/12. As described above, the pulse motor (8) for moving the carriage (7) is fed stepwise in N steps per rotation of the rotating drum.

The same feeding was performed on all lines. Therefore, dot misalignment inevitably occurs at each feeding point, and when this misalignment overlaps, there is a problem in that printing becomes uneven to the extent that it is visible to the naked eye.

2) Means for solving the problems The head driving device for inkjet printing of the present invention has the following features:
Generates a pulse according to the rotation of the rotating drum (2), drum 1
a pulse generating means that generates M pulses by rotation; a counting means that counts the number of pulses from the pulse generating means;
A storage means for storing a reference pulse number corresponding to a preset rotation angle of the rotating drum, an addition means for adding an offset amount to the reference pulse number, a setting means for setting the offset amount, and a counting means. It consists of a comparing means for comparing the output with the output of the adding means, and a driving means for driving the sub-scanning pulse motor according to the output from the comparing means.

E) Function According to the present invention, the timing of the step feed of the pulse motor changes due to the offset, so the timing at which dot misalignment occurs changes, and it is possible to prevent dot misalignment from overlapping.

(F) Example 1 An example of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows prolag meat showing one embodiment of the present invention.

(lG is a system control unit, and this system control unit αC is composed of a microcomputer or a microprocessor, and its functions include a main controller and an internal memory, and the main controller is shown in the j82 diagram below. Alternatively, the operation shown in the fifth part is executed, and the internal memory includes an f[1 area and a program memory tr: which store various operating states.

(9) is a rotary encoder as a pulse generating means, which is connected to a one-rotation drum (2) and generates one pulse each time the rotary drum (2) rotates by a predetermined angle. During one rotation (2M pulses, in this embodiment, 4000 pulses are generated).

Further, this encoder (9) generates one pulse signal every time the rotating drum (2) rotates once. aυ is a counter serving as a counting means, and is used for each rotation of the rotating drum (; one pulse signal outputted as a reset signal and the pulse signal of the encoder (9) as a counting input.
The count value is output to the comparison means σ2.

0 is a memory as a storage means, and this memory [13 stores a reference pulse number iBl corresponding to a preset rotation angle of the one-rotation drum (1) via the system control unit αI. In order to move the carriage (7) by a predetermined step during one line, this reference pulse number IB+ corresponds to the number (N) of pulse signals that drive the pulse motor (8) for one revolution of the rotating drum (2). The number of pulses (Ml) of the encoder (9) that is output during
) is the standard for determining the timing to drive. Reference numeral 2 denotes an adding circuit as an adding means, which takes in the reference pulse stored in the memory α3 and adds an offset amount (Xi) from the offset setting means u4, which will be described later, to this reference pulse.The output from this adding circuit Q4 is It is input as the single power of comparison means port 4.

The offset setting circuit t1ω, which serves as a setting means for setting the offset amount, includes a random number generation section that generates a random value, determines the offset amount (Xi) based on the output from the random number generation section, and controls the system control section fiO. Output to.

The system control unit Ql) gives this offset t(3) to the adder circuit α4, and the offset amount t(3) is determined by the reference pulse number (B
It is added to l. The amount of offset ■) is.

If the number of pulses corresponding to one revolution of the rotary drum (2) of the encoder (9) is assumed to be 1, and the feed of the sub-scanning pulse motor (8) is N Stella and one line, then the number of pulses will be generated every 1 step. The number of pulses to be used is M/N. Therefore, the offset amount (Xl is in a range that satisfies --<X<i).

A comparison circuit (13) as a comparison means outputs a coincidence signal when the output from Kawantaro υ and the output from the adder circuit f14 match. In other words, a coincidence signal is output at the timing when the offset amount γ is added to the reference pulse IB+. is output.

In response to the output of the coincidence signal from the comparison circuit α3, the system control unit α0) applies a drive pulse to the pulse motor drive circuit α. Then, the pulse motor (8) is driven by one step, and the carriage (7) is moved by one step in the sub-scanning direction.

In addition, the head drive circuit (171 includes a system control unit 0[
11 transmits the printing start time of one line of each head, and then the counter (based on the signal from 111
A head drive circuit 1l171 drives each head circle.

Next, the system control section (l
The specific operation of this embodiment will be explained focusing on the operation of Ol.

When printing starts, in step S1, the pulse motor (8
) is set to be the first drive timing III, and the process advances to step S2. Drive timing! 11 means to drive the pulse motor at the timing of the work number (1≦■≦N) during the N steps when driving one line in N steps.

For example, for N-5 steps, the drive timing (I
l is 600.1400.22[1[], 3000°58
A reference pulse number of 00 (corresponds to Bl. Step s
Take in the offset 1it (X) set in the 2+2 & offset setting circuit (11
1=memory sequence, proceed to step S3. A Fuset Co., Ltd. (X
It is determined by the random output of the random number generator of the IH setting circuit a.

In step 83, the output of the encoder (9) is converted to a counter (
After counting by ID and calculating the rotation angle of the drum in step S4, the process advances to step S5.

In step S5, in order to calculate the number of steps A IIJ according to the drive timing, the adder circuit 2 calculates AB (reference pulse number) + X (offset amount), and the process proceeds to step S6. This reference pulse number [B) is the above-mentioned step number IBI that is set in advance depending on the number of steps. In step S6, the comparison circuit 0
Then, the step number (A(Il) obtained in step 05 is compared with the output of the counter Uυ, and a coincidence signal that is output when both outputs coincide is monitored. When a coincidence signal is output, step s7 If they do not match, the process returns to step 86 and repeats the operations from step S5 to step $5.

In step S7, a match signal (in response to the drive pulse for driving the pulse motor is sent to the motor drive circuit 4,
Proceed to step 88. When the pulse motor drive circuit receives a drive pulse, it drives the pulse motor (3) one step, and the carriage (7) is driven one step in the sub-scanning direction. In step S8, the calculation (step 1; step + 1 is performed and the process proceeds to step S9. In step S9, III is the number of steps N
If the force is larger than N, the process proceeds to step S10, and if the force is smaller than N, the process returns to step 8!1. From step 85 to step S8 until the pulse motor (8) is sent N steps. Repeat the action. In step S10, the counter 011 and the like are reset in response to the end of printing one line, and the process proceeds to step S12.

If the printing operation has not been completed, the process returns to step S1 and the above-described operation is repeated, and when the printing operation is completed, the printing operation is stopped.

FIG. 6 is a flow diagram showing another embodiment of the present invention. In this embodiment, in FIG. 2, the set setting circuit r1 is set off for each line (offset circuit r1 special random number generator)! In contrast, C is configured to change the setting of the offset amount (Xi) for each step of the pulse motor.

In this way, by adding an offset amount that changes every line or step to the reference drive timing (Bl), the pulse sending by the pulse motor (8) can be adjusted to the fourth
As shown in the figure, this occurs irregularly, and the locations where dot misalignment occurs are no longer consecutive.

In the above-described embodiment, the % offset setting means sets the offset amount based on two random numbers generated by the random number generator (although the explanation was given using two numbers, it may also be configured to periodically change the offset amount). good.

(G) As described in detail of the invention (21) According to the present invention, the step feed of the pulse motor is irregular; the timing at which dot misalignment occurs changes, and overlapping of dot misalignments can be prevented;
Visually visible unevenness in printing can be eliminated.

[Brief explanation of the drawing]

9! &1 Figure is a block diagram showing one embodiment of the present invention. @2 Cause is 70-diagram showing the operation of one embodiment of the present invention. FIG. 3 is a flowchart showing another embodiment, and FIG. 4 is a flowchart showing the present invention C.
FIG. 5 is a schematic structural diagram of an inkjet printer. The sixth factor is the signal waveform diagram of the rotary encoder output. Figure wI7 is a time chart of pulse signals required for printer control. 2... Rotating drum, 7... Carriage, 8... Pulse motor, 9... Rotary encoder, 10...
System control unit, 11... Counter, 12... Comparison circuit, 13... Memory, 14... Addition circuit, 15.
...Offset setting circuit, 16...Motor drive circuit. District

Claims (4)

[Claims] (1) Head drive for an inkjet printer in which multiple ink heads are arranged at different positions in the circumferential direction facing a rotating drum, and the heads are moved in the sub-scanning direction by N steps during one rotation of the rotating drum. In the apparatus, a pulse generating means generates a pulse according to the rotation of the rotating drum, and generates M pulses per rotation of the drum, a counting means counts the number of pulses from the pulse generating means, and a preset pulse generating means is provided. A storage means for storing a reference pulse number corresponding to the rotation angle of the rotating drum, an addition means for adding an offset amount to the reference pulse number, a setting means for setting the offset amount, an output of the counting means and an output of the addition means. A head drive device for an inkjet printer, comprising a comparison means for comparing the values, and a drive means for driving a sub-scanning pulse motor according to an output from the comparison means. (2) The inkjet printer according to claim 1, wherein the offset amount is an integer satisfying -(M/N)<X<M/N, where X is the offset amount. Head drive device. (3) The head drive device for an inkjet printer according to claim 1 or 2, wherein the setting means sets the offset amount based on a random number generated by a random number means. (4) The setting means is characterized in that the offset amount is changed periodically.
The head drive device of the inkjet printer described in 2.