JPH0313069B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides N (N>
3) Place the inkjet head on a straight line,
The present invention relates to an inkjet recording device that performs printing on both forward and backward passes by moving the ink jet back and forth.

In a conventional serial printer, especially a serial printer using an inkjet head, in order to perform multicolor printing or simultaneous printing of multiple lines in the same color, the print head must be moved in a straight line as shown in Figure 1a or b. The configuration is such that they are arranged in a shape. In the figure, 1 is an ink jet head, 2 is a head installation stand, 3 is an ink discharge port, and 4 is a recording paper. In this configuration, when the head 1 is moved relatively in the horizontal direction , letters, numbers, figures, etc. are recorded as a collection of dots on the recording paper surface 4 in multiple colors or in a single color.

In the head arrangement shown in Figure 1a, each line is recorded one line at a time, and yellow, magenta, cyan, and
Multicolor recording can be obtained by supplying black or other ink. On the other hand, the head arrangement shown in FIG. 1b shows that it is possible to record four lines at a time in one scan.

By the way, in the head arrangement configuration shown in FIGS. 1a and 1b, due to structural constraints (size, shape, etc.) of the heads 1, it is not possible to arrange the mutual spacing of the heads 1 so that the density is the same as the printing density. If this is not possible, for example, in the case of a Stemme type head, the outer diameter is approximately 10 x 15 mm, so the spacing between the heads is necessarily 10 mm or more. Therefore, recording dots caused by application of image signals at the same timing are formed on the recording paper 4 at a distance corresponding to the head spacing.

If the head arrangement shown in Fig. 1a is arranged at an inclination angle θ in relation to the printing density with respect to the main scanning direction X as shown in Fig. 2, the head spacing will be and print density can be matched.

Therefore, for the character "B" formed by 5 x 7 dots shown in the figure, dots are formed on ₄ lines _D1 to D in the first scan, and after the paper is fed for 4 lines (Y scan), the remaining dots are formed in the second scan. Print D ₅ to D ₇ lines to complete the character.
Furthermore, if seven heads are arranged, characters can of course be printed in one scan.

However, the spacing between the heads hardly changes in the main scanning direction . The positional deviation of the dots caused by this spatial spread has conventionally been corrected by adding a temporal correction term (for example, see Japanese Patent Application Laid-Open No. 1983-6538). In other words, the spatial spread of the head is calculated by the number of pulses synchronized with the print position synchronization pulse that is emitted every time one dot is scanned by the head installation base, and the print image signal is transferred to a shift register or RAM (random access memory). Correct the delay line position using . Therefore, in printing with the head arrangement shown in FIG. 3, the head 51 is delayed by a distance l ₁ minute (actually the number of pulses corresponds to l ₁ , but will be expressed as l ₁ below) with respect to the first head 51. By operating the head 52, then operating the head 53 with a delay of l ₂ minutes, and finally operating the head 54 at a timing delayed by l ₃ minutes from the head 51, characters or figures with no misalignment can be printed. Printing on the recording paper 55 becomes possible. Here, in order to shorten the actual recording time, it is assumed that printing will be performed on the return pass (left scan) in addition to the outward pass (right scan). In the head arrangement shown in FIG.
The last head is head 54. Since this is reversed for backward printing, head 54 becomes the first head and head 51 becomes the last head. As a result, the positional reference head (first head) in printing changes, so that the amount of delay of the image signal for position correction described above also needs to be changed in accordance with the change in the first head. That is, in FIG. 3, the delay amount supplied to the head 52 during the outward trip is supplied to the head 53 on the return trip, and similarly the delay amount supplied to the head 53 during the outward trip is supplied to the head 52. Further, by similarly switching the delay amount for the heads 51 and 54, reciprocating printing is possible without dot misalignment. This premise is
The heads located in the middle (heads 52 and 53 in FIG. 3) are placed exactly at the same distance from the heads located at both ends (heads 51 and 54 in FIG. 3). In other words, it is possible only when l ₁ = l ₄ and l ₄ = l ₅ hold. However, in reality, when the Stemme type head is arranged as shown in Figure 3, the above-mentioned l ₁ = l ₄ ,
It is extremely difficult to establish l ₂ = l ₅ for the following reasons.

The reason for this is related to the manufacturing accuracy of the head, and the second is related to the accuracy of attaching the head to the moving table. In other words, the manufacturing accuracy of the head is the center position deviation from both ends of the head body to the ink ejection port, as shown in Figure 4. (Accuracy is not guaranteed.) Furthermore, diagonal ejection of ink related to the internal structure (accuracy of hole machining between multiple nozzle plates, etc.) is also a cause. In addition, the accuracy of mounting on the moving platform is actually determined by considering the maintainability of the head, as it requires an adjustment mechanism for each head in the vertical direction (Y direction) to make it easier to attach and detach each head. It is necessary to keep the accuracy rough. As a result, it is almost impossible to mechanically adjust the ink ejection ports of the head located in the middle to be equally spaced from the ink ejection ports of the heads located at both ends. Furthermore, when printing characters with the head arrangement shown in Fig. 3, for example, a 5 x 7 dot character structure requires 7 scans to form one character.
Dot misalignment of each printed dot is 1 per scan
Significant positional accuracy is required compared to when printing characters.

As shown in Figure 1a and Figure 2, the present invention uses N mutually independent heads (N > 3, the figure shows the case where N = 4) to move back and forth, and prints multi-color or single-color ink. In a device that reciprocally prints characters or figures, etc., due to the above drawback, it is extremely difficult to position the head placed in the middle accurately and at the same distance from the heads placed at both ends. The present invention provides an inkjet recording apparatus that corrects the dot printing position deviation during reciprocating scanning using a simple correction means and performs high-quality printing.

Hereinafter, one embodiment of the present invention will be described in detail using the circuit block diagram shown in FIG. 5 and the timing chart shown in FIG. 6.

Carriage group 30 reciprocating in FIG.
The heads Y, M, C, and B mounted on the head are four mutually independent heads arranged integrally in a row, and if we pay special attention to the heads M and C, which are located in the middle, the distance between the heads Y and M is The distances between the heads B and C are not equal, and the distances between the heads Y and C and the distances between the heads B and M are also not equal.
In addition, the position of the carriage group 30 is detected by image signal lines 41, 42, 43, 44 connected to each head and sensors (not shown) installed at both ends outside the drawing area. Figure 6 a, b),
The reciprocating motion discrimination signal 11 produced as a result and signals such as main scanning print synchronization pulses 9 which are related to print density and occur in proportion to movement displacement are connected and input/output.

Now input the same image signal to heads Y, M, C, B.
An example of printing to the same location on the outbound and return passes will be described with reference to the timing diagram in FIG. 6.

The image signals input to the image signal input line 10 at the same timing are input to gates 1a and 1b, and these gates block blocks (gates 1a and 1b) that pass only on the outward path.
side) and a block (gate 1b) that only passes through on the return route
side) by the reciprocating motion discrimination signal 11.
The image signals output from the gates 1a and 1b are input to the gate 1c, and the image signals to be applied to the first head at this gate regardless of whether it is on the forward or backward path are sent to 1c- ₁ .
The image signal applied to the next second head is 1c- ₂
The image signal applied to the third head is 1c- ₃ .
In this example, the image signals applied to the last head are input to 1c- ₄ . Each image signal other than the first head output from gates 1c- ₂ , 1c- ₃ , and 1c- ₄ is input to a delay circuit (for example, composed of a shift register, RAM, counter, etc.). In the embodiment shown in FIG. 5, delay circuits 3a, 3b, and 3c using shift registers are used as delay circuits, and the delay amount (number of shift stages) of the image signal can be preset. The delay circuit also includes a carriage group 30 as a delay shift clock.
The main scanning print synchronization pulse 9 output from the main scanning print synchronizing pulse 9 is input. Since the output of the gate 1c- ₁ is the image signal 21 to be applied to the first head, it does not pass through the delay circuit.
Furthermore, means for variably setting the amount of delay, digital switches 5a, 6a, 5b, 6b having a 4-bit configuration in the embodiment, are connected to the delay circuits 3a, 3b via selectors 4a, 4b.

The digital switches 5a and 6a are used to determine the amount of delay for the second head located next to the head, and one of the digital switches 6a is used to determine the delay amount for the head M relative to the head Y, that is, the head Y on the outward path. Set the amount of delay. Another digital switch 5a sets the amount of delay of head C with respect to the first head, that is, head B, during the return trip. Also,
Digital switches 5b and 6b are used to set the delay amount for the third head located third from the beginning, and one of the digital switches 6b is used to set the delay amount of head C with respect to the first head, that is, head Y on the outward path. Set the amount. Another digital switch 5b sets the amount of delay of head M with respect to the first head, that is, head B, during the return trip. Digital switches 5a, 5b, 6a, and 6b are input to selectors 4a and 4b, respectively, and 6a and 6b are set as delay amount preset values of delay circuits 3a and 3b during the forward movement according to the "L" level of the reciprocating motion determination signal 11 mentioned above. When the reciprocating motion discrimination signal 11 is at "H" level, 5a and 5b act as delay amount preset values. The presetting timing of the delay amount data may be performed before the start of printing of the first head, and therefore, in this embodiment, it is performed at the time of changing the scanning direction (FIG. 6d).

When an image signal is input to the delay circuits 3a and 3b, its output is delayed in relation to the preset value as shown at 22 and 23 in FIG. That is, since the image signal 21 (image signal without delay) applied to the first head and the image signal 22 applied to the second head are delayed between heads Y and M on the outward path, the delay amount preset value of the digital switch 6a is set. Since the return path is a delay between heads B and C, it is delayed by the delay amount preset value of the digital switch 5a. Similarly, the image signal 23 applied to the third head
In the forward path, the delay is between heads Y and C, so there is a delay equal to the preset value of the delay amount of the digital switch 6b, and in the return path, the delay is between heads B and M, so the delay amount is the preset value of the digital switch 5b. minutes will be delayed. Therefore, to align the print position during the forward pass, the print position of the second head is determined by adjusting the value of the digital switch 6a relative to the print position of the first head, and then the value of the digital switch 6b is adjusted. The printing position of the third head is adjusted by.

On the other hand, during the return trip, the printing positions of the second and third heads are aligned with the printing position of the first head using digital switches 5a and 5b.

On the other hand, since the delay amount of the last head with respect to the first head is constant regardless of whether it is on the forward or backward path, there is no need for a circuit corresponding to the selectors 4a and 4b shown in FIG. Therefore, only the digital switch 7 for correcting the delay amount is inputted to the delay circuit 3c, and the signal 24 in FIG.
As shown in FIG. 3, image signals with the same amount of delay are formed in the forward and backward passes.

The image signals 22, 23, 24 output from the delay circuits 3a, 3b, 3c and the image signal 21 for the first head output from the gate 1c- ₁ are input to the selector 8. Then, in order to share the delay circuit in the forward and backward passes, the image signals for each head are sent to the gates 1a and 1b, and those selected for the forward and return passes by the reciprocating motion discrimination signal 11 are sent to the head again in the selector 8 for each printing order in the scanning direction. Reassemble into the respective image signal format. That is, the image signal 41 for head Y is formed by the image signal 21 on the forward path since it is the first head, and the image signal 24 on the backward path since it is the last head.
Similarly, the image signal 42 for the other head M is formed by the image signal 22 on the outward path since it is the second head, and the image signal 23 on the return path since it is the third head. The image signal 43 for head C is the third head on the outgoing path, contrary to head M, so it is the image signal 23, and the image signal 43 on the backward path is the second head.
Since it will be the head, it is formed using the image signal 22. Finally, the image signal 44 for head B is opposite to head Y, and is formed by the image signal 24 on the forward path since it is the last head, and the image signal 21 on the backward path since it is the first head. In this way, the signals are selectively reassembled on the outbound and return trips and applied to each head. As a result, while the delay circuit is shared, it is possible to set the print positioning (delay amount adjustment) for the forward and return passes separately and independently. Even if the leading reference head for determining the print position is changed in the forward and return passes without worrying about the interval (mount) accuracy, it is possible to record without printing position deviation.

Therefore, according to the present invention, it is extremely difficult to arrange a plurality of mutually independent first to Nth (N>3) heads along a travel path and to make the spacing between the plurality of heads equal to the printing density. In a group of printer heads of a certain type (for example, Stemme type inkjet heads), a delay circuit (N-1 set) for correcting print position is shared in the forward and return paths, and,
In the reciprocating movement, it is possible to delay the information applied to heads other than the heads located at both ends as independent print timings in the forward and backward movements with a simple circuit configuration. As a result, it becomes possible to ignore the cause of print dot position deviation in the above-mentioned usage pattern, which is caused by the manufacturing precision of the head alone. It is also possible to significantly improve the cause of misalignment of printed dots caused by poor ink ejection (oblique ejection operation). Furthermore, maintenance efficiency can be improved by eliminating the need for placement accuracy when attaching the head to the moving table.

[Brief explanation of the drawing]

Figures 1a and b are layout diagrams showing an example of the basic print head layout of the present invention, Figure 2 is a layout diagram showing the layout of the same print heads and the printing relationship of the letter "B" by the same layout, and Figure 3 is a layout diagram showing an example of the layout of the basic print head of the present invention. The figure is a schematic diagram showing the deviation of the succeeding print head from the first head in the forward and backward passes in the scanning direction when the same print head is arranged linearly in the main scanning direction. Figure 4 shows the recording of the print head alone. FIG. 5 is a block diagram showing an embodiment of the dot printing position control section of the inkjet recording apparatus according to the present invention, and FIG. FIG. 1... Ink jet head, 2... Head setting table, 3... Ink ejection opening, 4... Recording paper, 1a, 1
b, 1c- ₁ , 1c- ₂ , 1c- ₃ , 1c- ₄ ...gate, 3a, 3b, 3c...delay circuit, 4a, 4b,
8... Selector, 5a, 5b, 6a, 6b, 7... Digital switch, 9... Main scanning print synchronization pulse, 1
0... Image signal input line, 11... Reciprocating motion determination signal, 21
...First head image signal, 22...Second head image signal,
23... Third head image signal, 24... Last head image signal, 30... Carriage group, 41, 42, 43,
44...Picture signal for each head, Y, M, C, B...Inkjet head.

Claims (1)

[Claims] 1. An inkjet in which mutually independent first to Nth (N>3) inkjet heads are arranged integrally in a row, and it is difficult to align the mutual spacing between the plurality of heads to the same printing density. a head group, means for reciprocating the ink jet head group relative to the recording medium in the arrangement direction, and N-1 delay circuits for delaying recording signals applied to the second to Nth ink jet heads. means for variably setting the first and second delay amounts in each of the delay circuit means corresponding to the second to (N-1)th ink jet heads; and one of the first and second delay amounts. and means for selecting and supplying the first inkjet head to the delay circuit according to the moving direction of the inkjet head group, and setting the first delay amount to a delay amount corresponding to a head spacing with respect to the leading inkjet head in the outward moving direction; The second delay amount is independently set to a delay amount corresponding to the head spacing with respect to the leading ink jet head in the direction of return movement, and the delay amount is selectively applied to the delay circuit depending on the direction of movement of the ink jet head group. What is claimed is: 1. An inkjet recording apparatus characterized in that a recording signal is delayed while supplying a recording signal and using a delay circuit means in common for reciprocating recording.