JP6552534B2 - Printing timing control method and industrial printing apparatus for reducing nozzle drive peak power. - Google Patents

Description

  The present invention relates to an on-demand type industrial printing apparatus, and more particularly to a print timing control method for suppressing driving peak power by simultaneously driving an electromagnetic valve type nozzle, and such a printing apparatus.

  An industrial on-demand printing apparatus draws characters or designs on a target material using a print head in which a plurality of paint discharge nozzles are arranged. In such a printing apparatus, while moving the print head and / or the target material, a dot pattern as shown in FIG. 1 is obtained by intermittently discharging the paint from each nozzle at an appropriate timing according to the character or pattern to be drawn Draw a pattern with a set of The conventional arrangement of a plurality of nozzles on the print head and its discharge control will be described below.

  The arrangement of the plurality of nozzles on the print head is as shown in FIG. 2A if the nozzles can be arranged at the dot interval (dot pitch y) in the vertical direction shown in FIG. 1, that is, if the nozzle diameter is smaller than the dot pitch y. Thus, it is easy to arrange the nozzles in a vertical row (y-axis direction). In this case, the discharge control of the nozzles is performed in synchronization with the pattern to be printed in synchronization with the movement of the dot pitch x (see FIG. 1) of the print head or the target material. FIG. 2A shows the case where, for example, the printing target material moves in the direction of the arrow. The discharge control timing is shown in FIG. 2B, where the vertical axis represents the nozzle number and the horizontal axis represents time (in units of time required for the movement of the dot pitch x), and the nozzles discharged with black circles (●) The time position at that time is shown. This is the pattern itself to be printed, as can be seen in comparison with FIG. FIG. 3 shows the discharge timing at this time. In the drawing, the black dots in each line represent the discharge timing for each nozzle of the number written at the left end. In the prior art, there is a possibility that all the nozzles can be driven simultaneously at each instant (portion enclosed by a square in the figure). In other words, one discharge timing common to all the nozzles on the head is used.

  When the nozzle diameter is larger than the dot pitch y (when the diameter of the solenoid coil for the discharge solenoid valve of the nozzle is large, etc.), the nozzles can not collide with each other as shown in FIG. 2A. In such a case, in other words, when the distance between the nozzles is larger than the dot pitch y, as shown in FIG. 4A, an arrangement method called oblique angle for spacing the nozzles by shifting the nozzles in the lateral (x) direction. It has been known. In this figure, the nozzles are indicated by dotted circles, and the nozzle discharge holes are indicated by small circles, which indicate that they are laterally shifted by 3 * x (x is a dot pitch). Even with such a nozzle arrangement, if the ejection timing is devised, a pattern can be printed by the relative movement of the print head in the horizontal direction as in the arrangement shown in FIG. 2A. FIG. 4B shows the discharge control timing in this case, and it can be seen that it is necessary to delay the discharge control by the amount the nozzle position has advanced. However, also in this case, the discharge timing of the nozzles is common to all the nozzles on the head.

Japanese Patent Application Laid-Open No. 2003-80133

  By the way, in order to discharge the paint from the nozzles, it is necessary to supply power by some method for each nozzle. For example, in the case where a paint to be pressurized is contained in the print head and this pressurized paint is discharged from the nozzles using a solenoid valve, a current for driving the solenoid valve is supplied to each nozzle. It is necessary (see Patent Document 1). When using a print head in which a plurality of nozzles are arranged as described above, there are cases where it is necessary to simultaneously drive all the nozzles depending on the character or pattern to be drawn. For example, in the case where eight nozzles are arranged in a vertical row as shown in FIG. 2A, eight nozzles must be driven simultaneously when drawing a vertical straight line as shown in FIG. 2B. Further, even in the case of the “oblique” arrangement as shown in FIG. 4A, for example, when drawing a quadrangle in FIG. 1, six nozzles are simultaneously driven at the 24th of the discharge control timing as shown in FIG. There must be. Also, considering the case where the rectangle in FIG. 1 is longer in the horizontal direction, the driving state of each nozzle in FIG. 4B also extends further to the right, so that even in the arrangement of FIG. . As described above, when all the nozzles are driven simultaneously, a large amount of power is required instantaneously, and therefore, when there is no margin in the power supply capacity, the dot diameter changes depending on the number of nozzles driven simultaneously, When all nozzles are driven simultaneously, there arises a problem that the printing quality is deteriorated due to the malfunction of the solenoid valve or the like. However, in an apparatus for printing characters, it is rare when it is necessary to drive all the nozzles at the same time in this way, and it is necessary to supply the power supply capacity necessary for the simultaneous drive for such rare conditions. The installation was also problematic in terms of economy.

  Therefore, in view of the above problems, the present invention provides a printing control method in which at least all the nozzles are not simultaneously driven to discharge at the time of printing of any pattern, and hence a printing apparatus with improved printing quality and reduced power capacity. The purpose is to provide.

  In order to solve the above-described problems, the present invention intermittently discharges paint from a plurality of nozzles arranged in a print head, and a character or a pattern on a target material moving relative to the nozzles. In the printing apparatus, the plurality of nozzles are divided into a plurality of groups, and the discharge timings of the nozzles belonging to one group do not overlap with the discharge timings of the nozzles belonging to the other group. A printing timing control method is used, in which the nozzles are controlled so as to be shifted and the arrangement of the nozzles on the print head is adjusted in accordance with the timing shift.

  As a result, the solenoid valve coils of the nozzles belonging to different groups on the print head are not driven at the same time, peak power for driving the nozzles is suppressed, and the printing quality is improved. Economicalization is planned.

  In the print timing control method, the discharge timing is sequentially shifted between the groups by the time obtained by dividing the minimum time interval t of the discharge timing of the nozzle discharge control signal by the number g of the groups. It is characterized by

  Here, the minimum time interval t of the nozzle discharge control signal has a relationship of t = x / v between the dot interval x and the transport speed v. The dot interval x is usually a predetermined value given by the printing system from the printing quality and the like, and if the conveying speed v is constant, the minimum time interval t is also constant. When the transport speed v changes, the minimum time interval t may also be changed according to the change of v so as to keep the dot interval x constant from the viewpoint of maintaining the printing quality constant.

  In the print timing control method, the interval of arrangement of the nozzles on the print head is c * x + n * x / g (c is an integer, x is a dot interval in the printing direction, and g is the number of groups) in the printing direction. n is an integer).

  After inserting bit information corresponding to g-1 blanks between dots with a bit pattern in which a pattern such as a character to be printed is developed on a memory, shift bits by c * g + n for each corresponding nozzle, The clock cycle for reading the bit pattern is multiplied by g.

  The clock cycle t divided by the number of groups g has g clock signals that differ in phase by a value obtained by multiplying m (m is an integer from 0 to g-1), and c * x + n * x / g The phase shift clock using m which is congruent to n modulo g is used for reading the bit pattern corresponding to the shifted nozzle.

  A printing apparatus which intermittently discharges paint from a plurality of nozzles disposed in a print head and draws a pattern such as characters on a target material moving relative to the nozzles, the plurality of nozzles being It has a control mechanism that can be divided into multiple groups and the discharge timing time can be shifted so that the discharge timing of the paint does not overlap between different groups, and the spacing on the print head between the nozzles that discharge the paint is The printing direction is c * x + n * x / g (c is an integer, x is a dot interval in the printing direction, g is the number of groups, and n is an integer).

  The control mechanism includes a first memory for storing symbols, such as characters to be printed, as bit patterns, the nozzle pattern, the number of clocks, and the grouping information from the bit patterns stored in the first memory. Based on this, a mechanism is provided for creating a bit pattern corresponding to the ejection state of the nozzle and performing nozzle ejection control based on the associated clock and the bit pattern.

(Definition)
Here, “ejection timing” refers to a specific time (for example, rise time) of an ejection control signal in which a certain nozzle may eject a dot.
“Discharge control timing” represents the timing at which nozzle discharge control is performed when a specific pattern is to be drawn in a certain discharge timing and nozzle arrangement.
“Nozzle group” refers to a set of nozzles classified according to whether or not the timings of the nozzle discharge control signals are the same. Accordingly, the ejection timings of the nozzles belonging to different groups are shifted, and the ejection timings of the nozzles belonging to the same group are the same.
The “minimum time interval t” is the shortest repetition period or the shortest time interval of the nozzle discharge control signal determined by the minimum dot interval x and the conveyance speed v. It is also an ejection time interval of the nozzles when printing with the minimum dot interval x.
“Clock” represents the timing of reading a bit pattern in a memory, and is not limited to a timer that generates a pulse at a constant time interval, but also includes an encoder signal that generates a pulse at a constant distance interval.

It is explanatory drawing which shows an example of the symbol printed by the dot pattern. It is a figure which shows one arrangement example in the prior art in the case of arrange | positioning several nozzles on a printing head. It is a figure which shows the discharge control timing in the case of printing the pattern of FIG. 1 by the nozzle arrangement | positioning of FIG. 2A. The discharge state (indicated by ●) of each nozzle is shown along the timing time axis. It is a figure which shows the discharge timing in a prior art. FIG. 6 illustrates another arrangement on a multi-nozzle printhead according to the prior art (referred to as the “brick angle”). The unit of the horizontal axis is the dot pitch x. It is a figure which shows the discharge control timing in the case of printing the pattern of FIG. 1 by the nozzle arrangement | positioning of FIG. 4A. The discharge state (indicated by ●) of each nozzle is shown along the timing time axis. It is one Example of nozzle arrangement | positioning in the 1st embodiment of this invention. It is explanatory drawing which shows the discharge control state in the nozzle arrangement | positioning shown by FIG. 5A. It is a figure which shows an example of the discharge timing at the time of setting it as the number of groups 3. It is a figure which shows the memory state on the memory of the dot pattern which should be printed shown in FIG. “1” is stored in each cell of the shaded part, and “0” is stored in each cell of the non-shaded part. FIG. 6B is a diagram showing a memory storage state in the middle of “memory development” in Example 1 (1-clock method) for making the ejection control timing of FIG. 5B from the memory state of FIG. 6A. “1” is stored in each cell of the shaded part, and “0” is stored in each cell of the non-shaded part. FIG. 6C shows the memory storage state after the final “memory expansion” from FIG. 6B. “1” is stored in each box of the shaded portion, and “0” is stored in each box of the portion without the shaded box. It is a figure which shows the memory storage state after the final "memory expansion" of Example 2 (g clock method) for making the discharge control timing of FIG. 5B from the memory state of FIG. 6A. “1” is stored in each box of the shaded portion, and “0” is stored in each box of the portion without the shaded box. It is one Example of the nozzle arrangement | positioning in the 2nd embodiment of this invention. It is explanatory drawing which shows the discharge control timing in the nozzle arrangement | positioning shown by FIG. 8A. FIG. 14 shows an example of the nozzle arrangement in the third embodiment of the present invention, in which there are six groups and three clocks. It is a figure which shows the discharge timing in the nozzle arrangement | positioning of FIG. 9A. It is a figure which shows the memory storage state in the middle of "memory expansion" of Example 3 for applying the discharge timing shown to FIG. 9B to the memory state of FIG. 6A. “1” is stored in each cell of the shaded part, and “0” is stored in each cell of the non-shaded part. FIG. 9C shows the memory storage state after the final “memory expansion” from FIG. 9C. “1” is stored in each cell of the shaded part, and “0” is stored in each cell of the non-shaded part. It is a figure which shows one Example of the nozzle arrangement | positioning in another embodiment of this invention. FIG. 11 is an explanatory view showing the discharge state of each nozzle along the timing time axis in the case of printing the pattern of FIG. 1 with the nozzle arrangement shown in FIG. 10A.

  The present invention does not use a nozzle discharge control signal having one common timing for all nozzles on the print head as in the prior art, but the discharge timing is different for each nozzle or group of nozzles (phase or delay time). One feature is that the nozzle discharge control signal is used. FIG. 5A shows the nozzle arrangement of the first embodiment of the present invention, which is an example of an apparatus using eight nozzles. It is a nozzle layout on the print head when the distance between the nozzles does not exceed the dot pitch y (corresponding to the case of FIG. 2A of the prior art). FIG. 5B shows a case where the dot pattern shown in FIG. 1 is drawn using the nozzle arrangement shown in FIG. 5A and the number of groups is 3, that is, the nozzle discharge control signal having three discharge timings (FIG. 5C). It shows the discharge control timing of the nozzle. First, the discharge state of FIG. 5B will be described. The vertical axis represents the nozzles, and the horizontal axis represents the time axis. The discharge control state of each nozzle (● indicates discharge, and ○ indicates non-discharge). The timings ST1, ST2, and ST3 are indicated by assigning numbers 1, 2 and 3 in units obtained by dividing the minimum time interval t of the conventional nozzle into three. For example, focusing on the nozzle 1, the ejection state is shown only at timing ST1, and ejection is not performed at timings ST2 and ST3. Similarly, focusing on the nozzle 2, the ejection state is shown only at timing ST2. Next, looking at this discharge state every time, that is, in the vertical direction, the nozzles 1, 4 and 7 discharge at timing ST1, and 2, 5 and 8 discharge at ST2, and 3 and 6 discharge at ST3. I understand that. Here, nozzles 1, 4, and 7 controlled by the same timing signal ST1 are the first group, nozzles 2, 5, and 8 controlled by ST2 are the second group, and nozzles 3 and 6 controlled by ST3 are the first group. It is called 3 groups. Then, although the nozzles belonging to the same group can be simultaneously discharged, the nozzles belonging to different groups do not simultaneously discharge since they have different timings ST. Note that which nozzle is in the same group is optional. For example, the nozzles 1, 2, 3 may be in the same group, and the nozzles 4, 5, 6 may be in the same group. Come. However, since it is effective in suppressing peak power to make the number of nozzles in the same group as uniform as possible, the number of nozzles belonging to the same group should not exceed [N / g] +1. Here, [] is a Gaussian symbol indicating the integer part of the quotient, N is the number of nozzles, and g is the number of groups (= number of nozzle ejection control signals different in timing). Since nozzles belonging to the same group are driven and controlled at the same timing, depending on the print pattern, there is a possibility that they may be ejected at the same time. However, since nozzles belonging to different groups have different drive timings, any print pattern may be used. It is not driven at the same time. Therefore, in the present embodiment, the number of nozzles that can be simultaneously discharged is reduced from 8 to 3 even in the case of the largest number, and depending on the figure, the number of simultaneously discharged nozzles is less than this. Decrease to 5%).

  The above description of the reduction of the peak power of the nozzle drive control applies as it is to an ideal case where the pulse waveform for driving the nozzle is rectangular and is not influenced by the adjacent pulses. However, even if on / off of the nozzle drive current is controlled by a rectangular pulse signal, the nozzle drive current itself drives a coil having an inductance, so the number of sub timings is increased and / or the dot printing speed is accelerated. And, in fact, the result may be a “tailed” waveform that has a tail, and some of the drive pulses at adjacent or adjacent sub-timing points overlap and the peak power may not be reduced as much as the ideal value. In the nozzle discharge control signals having different timings, the discharge state (ON state) is described as not overlapping, but as long as the peak power reduction effect can be obtained, partial overlap of the nozzle discharge control signals is It is acceptable.

  Returning to FIG. 5A, the nozzle arrangement on the print head will be described. The nozzles are characterized in that they are arranged at equal intervals in the vertical direction and shifted to the left by 1⁄3 of one dot pitch x in the horizontal direction. If the nozzle arrangement remains in a single vertical row as in FIG. 2A of the prior art, for example, the nozzle 2 is driven at timing ST2, but this is shifted by 1/3 minimum time interval from ST1 (delay Therefore, printing is performed with a deviation of 1/3 of the minimum dot interval from the printing dot position of the nozzle 1. Similarly, the nozzle 3 is shifted by 2/3. For this reason, in order to compensate for this timing delay, they are arranged at positions shifted backward (left side) by 1/3 of the dot interval. By configuring and controlling such offset of the spatial position of the nozzles and the temporal shift of the discharge timing, the number of simultaneous discharges of the nozzles is reduced while printing as in the prior art, and peak power can be reduced. It is reducing. Such a nozzle arrangement is generally expressed by the following equation: c * x + n * x / g (where c is an integer, the number of nozzles is N, n is an integer from 0 to N-1, x is a dot interval in the printing direction, g Is represented by the number of groups).

  Next, two embodiments for obtaining the discharge control timing of each nozzle as shown in FIG. 5B will be shown. The first embodiment is a method of producing a nozzle discharge control signal having three different timings (group number g = 3) using one clock. First, it is assumed that a bit pattern corresponding to a dot to be printed as shown in FIG. 1 is stored in the memory (FIG. 6A). A bit pattern is created on the memory in which group number g-1 = 2 blank information is inserted between bits of each nozzle (each row of the bit pattern) in this bit pattern (FIG. 6B). Next, according to the corresponding nozzle arrangement, corresponding to the deviation of the nozzle arrangement for each row (in this case, the number measured in units of 1/3 of the minimum dot interval x is n), The corresponding memory row is shifted by n (FIG. 6C). We call this operation “memory expansion”. On the other hand, by setting the cycle of the clock for reading the bit pattern to g times (g is the number of groups) of the conventional method and reading the memory at this clock frequency, the ejection control signal of each nozzle can be generated from this memory information.

  Next, creation of nozzle discharge control timing according to the second embodiment will be described. In the second embodiment, as in the first embodiment, it is assumed that the bit pattern to be printed as shown in FIG. 6A is stored in the memory. The memory row corresponding to the nozzle is shifted by m in accordance with the displacement of the position of the nozzle (measured in units of the minimum dot interval x, and the decimal point is a truncated integer m). FIG. 7 shows the bit pattern on the memory thus created by "memory expansion". The same ejection control timing as in FIG. 5B can be obtained from this “memory development” as follows. For this purpose, three clock signals CL1, CL2 and CL3 are prepared in which the cycle of reading the bit pattern is the same as that of the conventional system and the phase is 120 ° or the delay time is shifted by t / 3. These three clock signals correspond to the nozzles as shown in FIG. 7, and when read from this memory, the control signals shown in FIG. 5B are obtained. For example, when looking at nozzles 1 to 3, the timing is shifted by 1⁄3 of the minimum time interval t because the signals CL1, CL2 and CL3 are read at the first timing (left end) respectively, and the same ejection control timing as in FIG. 5B Is obtained.

  Next, a second embodiment in which the nozzles are arranged as shown in FIG. 8A will be described. That is, since the nozzles 4 and 7 belong to the same group as the nozzle 1, they are arranged so that their lateral positions are in the same position as the nozzle 1, unlike FIG. 5A. The nozzles 5 and 8 are similarly arranged at the same lateral position as the nozzle 2. This arrangement is generally expressed by a formula (n mod (g)) * x / g (where the number of nozzles is N, n is an integer from 0 to N-1, x is the dot interval in the printing direction, and g is the number of groups) Can be represented by). The discharge control timing when such a nozzle arrangement is made is shown in FIG. 8B. Although detailed description is omitted, for example, the nozzle 4 is shifted to the right by 1 dot pitch x as compared to FIG. 5A, so the time of discharge control timing is advanced by one minimum time interval as compared to FIG. 5B. Furthermore, although not shown, nozzles belonging to the same group may be summarized by serial numbers 1 to 3, 4 to 6, and 7 to 8.

  Next, a third embodiment as shown in FIG. 9A will be described. Here, it is an example when the number of groups is six. In this example, the nozzle arrangement is made narrower than the dot interval as shown in FIG. 9A. Consider the case where the pattern of FIG. 1 is discharged using the discharge timing of FIG. 9B for this nozzle arrangement. Here, in the case where the number of clocks is 3, the phases of the clocks are shifted by 0, t / 3, and 2t / 3 as in the normal case. Further, one blank information is inserted between the bits for each nozzle in the bit pattern of FIG. 6A (FIG. 9C). In accordance with this, the clock cycle is doubled. Finally, by shifting as shown in FIG. 9D according to the corresponding nozzle and clock signal for each bit, it is possible to discharge dots at the timing when the discharge timing diagram 9B and the nozzle layout diagram 9A are applied to FIG. Become.

  Next, another embodiment applicable to the case where the distance between the nozzles is larger than the dot pitch y will be described below. FIG. 10A is a layout of nozzles according to another embodiment of the present invention. In the prior art oblique angle method, the arrangement for compensating for the printing position deviation resulting from the use of the time-shifted timing signal which is a feature of the present invention is provided. In consideration of the displacement c * x due to the oblique arrangement, the nozzles are sequentially displaced by c * x + x / g (c is an integer, x is a dot interval, and g is the number of groups) between the nozzles.

  FIG. 10B is an explanatory diagram showing a discharge control state of the another embodiment. For example, since the relationship between the displacement of the nozzle arrangement and the memory development (or the ejection control signal) is also described in the description of FIGS. 6A to 6C, it is similar to FIG. 5B except that the ejection control timing is delayed due to the nozzle arrangement by the oblique angle. So I will omit the details.

  The arrangement of FIG. 10A is also an example, and each nozzle can be displaced in the x direction in a timely manner so that the nozzles do not collide with each other although not shown. However, in order to achieve the purpose of the nozzle drive peak power reduction that is the feature of the present invention, it is necessary to belong to the group of nozzles as equally as possible. Therefore, when the nozzle positional deviation is measured in dot interval x units on the basis of the nozzle at the right end, the remainder is as possible as g types of 0, x / g, 2x / g,... (G-1) x / g It involves the restriction that the nozzle positions need to be determined to be evenly distributed.

  So far, the embodiment has mainly described the case where the number of nozzles is 8 and the number of timing signals (= number of nozzle groups) g is 3 for convenience of explanation. These numbers, the numbers of nozzles, the correspondence with timing signals, and the like are merely examples for convenience of explanation, and are not intended to be limited to these.

Claims (2)

A printing timing control method in a printing apparatus that intermittently discharges paint from a plurality of nozzles arranged in a print head and draws characters or designs on a target material moving relative to the nozzles, The plurality of nozzles are divided into a plurality of groups, and the discharge timings of the nozzles belonging to one group are shifted from each other so that the discharge timings of the nozzles belonging to one group do not overlap with the discharge timings of the nozzles belonging to other groups, and The arrangement of the nozzles on the print head is adjusted in accordance with the deviation of the discharge timing , and the position of the arrangement of the nozzles on the print head is c * x + n * x with respect to the print direction with respect to a certain nozzle. / G (c is an integer, x is a dot interval, g is the number of groups, and n is an integer), and a bit pattern in which the character or design to be printed is developed on a memory In this case, bit information corresponding to g-1 blanks is inserted between dots, bits are shifted by c * g + n for each corresponding nozzle, and a clock cycle for reading a bit pattern is multiplied by g. And a printing timing control method. A printing apparatus that intermittently discharges paint from a plurality of nozzles arranged in a print head and draws characters or designs on a target material that moves relative to the nozzles. It has a control mechanism that can shift the discharge timing time so that the discharge timing of the paint does not overlap between different groups, and the interval on the print head between the nozzles that discharge the paint is printed c * x + n * x / g with respect to the direction (the c-integer, x is the dot spacing of the print direction, g is the number of groups, n represents an integer) der is, and the character or symbol to be the print was expanded on the memory In the bit pattern, bit information corresponding to g-1 blanks is inserted between dots, the bit is shifted by c * g + n for each corresponding nozzle, and the bit pattern is read. Characterized by a period g doubled printer.

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