JP2001301143A - Ink jet recorder and its head driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute single nozzle discrete driving and two nozzle simultaneous driving while separating more appropriately for each block of an inkjet recording head. SOLUTION: A decision is made for each recording head whether heating elements in each block are driven separately, i.e., discrete driving, or two heating elements are driven simultaneously, i.e., simultaneous driving, based on the driving frequency interval of the recording head and the resistance of the heating elements in the recording head. For that purpose, rank of each recording heads is determined by determining the resistance of ink ejecting heating elements in a plurality of recording heads mounted on a carriage (S11). For a recording head of reference rank or above (S12, YES), simultaneous driving is set (S14) and for a recording head of lower than the reference rank, discrete driving is set (S13).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for recording on a recording material by discharging ink from a recording head, and more particularly to a method of driving the head.

[0002]

2. Description of the Related Art As one type of recording device used as an output device such as a printer, a copying machine, a facsimile, or an output device such as a computer, a word processor, and a workstation, there is an ink jet recording system. The ink jet recording method is to perform recording by discharging ink from a recording unit (recording head) onto a recording material (recording paper), and it is easy to make the recording unit compact and to record a high-definition image at high speed. be able to. In addition, recording can be performed on plain paper without requiring special processing, running costs are low, and the non-impact method reduces noise and records color images using multicolor inks. Has various advantages, such as easy operation.

[0003] In particular, an ink jet type recording head which ejects ink by using thermal energy has an etching,
Through a semiconductor manufacturing process such as evaporation, sputtering, etc., an electrothermal converter, an electrode, a liquid path wall formed on a substrate,
By forming a top plate and the like, it is possible to easily manufacture a device having a high-density liquid passage arrangement (nozzle arrangement),
Further compactness can be achieved. Further, by utilizing the advantages of the IC technology and the micromachining technology, it is easy to make the recording means longer and planar (two-dimensional), and it is also easy to make the recording means full multi-layer and high-density mounting. is there.

A so-called block drive has been conventionally known as a drive system of the above-mentioned ink jet recording apparatus.
This driving method does not discharge from all the discharge ports of the print head at the same timing, but discharges one nozzle at a time for each block composed of a predetermined number of discharge ports, which is necessary for one discharge timing. Power consumption is small, and there are advantages such as prevention of generation of electrical noise.

[0005]

However, when the ejection is performed by dividing each block as described above, the time interval between the ejection from one nozzle in each block and the next ejection from the same nozzle is performed. Within (one cycle), a predetermined time is assigned to each nozzle so that ink can be ejected by all the other nozzles in the same block, and the drive voltage must be completely applied to the nozzle within that time. .

On the other hand, due to the recent high integration and high frequency driving of the printhead nozzle array, the time allocated to each nozzle is becoming shorter. In addition, if the resistance of the heating element (heater) is high, the voltage application time must be increased. In some cases, an applied voltage for ejecting ink from all the nozzles cannot be applied. Therefore, there has been a problem that the driving frequency cannot be increased.

[0007] In response, the following measures have been taken. When determining the required voltage application time for a certain product head group, the maximum value of the variation in the heater resistance is set to 3σ (σ
Is the standard deviation) (heads exceeding the maximum value of 3σ are deleted as nonstandard), and the voltage application time required to discharge a predetermined discharge amount for the nozzle of the heater resistance having the maximum resistance value is blocked. The total number of ink ejection intervals obtained by multiplying the total number of nozzles is calculated. If the total ink ejection interval does not fall within the driving cycle given by the head driving frequency, ink is ejected two nozzles at a time, instead of one nozzle at a time for each block. Since the simultaneous driving of two nozzles is inferior to the single nozzle distributed driving from the viewpoint of power consumption and noise, it is desired to perform the single nozzle distributed driving as much as possible.

Normally, a plurality of heads are simultaneously used in a color printing apparatus.
The required voltage application time at the maximum resistance value is illuminated with the driving frequency to determine whether all the heads are simultaneously driven with two nozzles or are driven one nozzle at a time. Therefore, in the case of simultaneous driving of two nozzles, simultaneous driving of two nozzles is performed even for a head which does not originally need to perform simultaneous driving of two nozzles.

The present invention has been made in view of such a conventional background, and an object of the present invention is to provide an ink jet recording apparatus capable of executing one nozzle dispersion driving and two nozzle simultaneous driving more appropriately. Is to do.

[0010]

A head driving method for an ink jet recording apparatus includes a plurality of recording heads each having a plurality of ejection ports, and the ejection ports of each recording head are formed by a plurality of blocks each including a predetermined number of ejection ports. A head driving method for an ink jet recording apparatus that forms an image by discharging ink in the discharge port by driving an ink discharge heating element provided in the discharge port for each block. Distributed driving in which the heating elements in the block are divided and driven one by one for each block of
It is characterized in that it is determined for each head whether to perform the simultaneous driving in which the recording head is divided into two parts at the same time, based on the driving frequency interval of the recording head and the resistance value of the heating element of the recording head. .

By setting the driving method of the heating element for each head as described above, it is possible to minimize the power consumption of the recording apparatus and the generation of noise.

More specifically, a predetermined recording head group is ranked on the basis of the resistance values of the heating elements for ink ejection, and based on the driving frequency, the ranking is close to the maximum rank of the maximum resistance value. A predetermined rank having a relatively small existence probability is set as a reference rank, and the rank of each of the recording heads is determined by checking the resistance values of the heating elements for ink ejection of the plurality of recording heads mounted on the carriage,
The simultaneous driving is performed for print heads having a rank equal to or higher than the reference rank, and the distributed driving is performed for print heads having a rank lower than the reference rank.

[0013] The ink jet recording apparatus according to the present invention comprises:
Providing a recording head having a plurality of ejection ports, dividing the ejection ports into a plurality of blocks composed of a predetermined number of ejection ports, and driving an ink ejection heating element provided in the ejection ports for each block, In an ink jet recording apparatus that forms an image by discharging ink in the discharge port, the recording apparatus further includes a driving unit that drives the recording head for each of the divided blocks, and the driving unit divides the heating elements in the block one by one. To determine whether to perform the distributed driving in which the recording head is driven separately or the simultaneous driving in which the driving is divided into two parts at the same time based on the driving frequency interval of the recording head and the resistance value of the heating element of the recording head. Features.

More specifically, the apparatus comprises a carriage on which a plurality of recording heads are mounted, and each of the recording heads mounted by confirming an ink discharge heating element of the plurality of recording heads mounted on the carriage. Means for determining a rank related to the resistance value of the heating element for ink ejection, a table defining an applied voltage pattern for each determined rank, and performing the simultaneous driving for print heads of ranks equal to or higher than the reference rank, A driving method setting means for performing the distributed driving is provided for a recording head having a rank smaller than the reference rank.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, referring to FIG. 1, a schematic configuration of a plotter which is an example of an ink jet type image recording apparatus of the present invention will be described. The blotter 10 is a platen 1 on which a recording paper 12 which is a recording material conveyed in the direction of arrow A is placed.
4 is provided. Above the platen 14, two scanning rails (guide rails) 16 are extended in parallel with the platen 14. A carriage 20 that reciprocates in directions of arrows B and C (a direction orthogonal to the direction of arrow A) by a motor (not shown) and a belt 18 is attached to the scanning rail 16 via a slide bearing (not shown). I have.

The carriage 20 has four print heads 22K (black), 22C (cyan), 22M (magenta), and 22Y (yellow) having ink discharge ports (nozzle outlets) for discharging ink. .

In forming an image on the recording paper 12 such as roll paper, the recording paper 12 is placed on the platen 14 and a part of the outer peripheral surface is exposed from an opening (not shown) formed in the platen 14. The recording paper 12 is conveyed by rotating the conveyance roller 24 by a motor (not shown) while nipping the recording paper 12 by the conveyance roller 24 and a pinch roller 26 for pressing both ends of the recording paper 12 from above. The carriage 20 is reciprocated in the directions of arrows B and C above the recording paper 12 so that the image signal including the image information transmitted from the head control unit 44 (see FIG. 2) to each of the print heads 22K, 22C, 22M and 22Y. Ink is ejected from the nozzle based on the image to form an image on the recording paper 12. Specifically, one scanning of the carriage 20 on the recording paper 12 forms an image portion (one band) having a width corresponding to the nozzle width of the head. By repeating this band formation while intermittently moving the recording paper 12, recording of the entire image is completed.

FIG. 2 is a schematic diagram showing the ink ejection surface of the head 22. In this example, ink is ejected from a nozzle row 33 having 144 nozzles. A heater base having a heating element is located on an aluminum base plate 34 below the nozzle row 33.

FIG. 3 shows an aluminum base plate 34.
It is a top view which shows the heating element arrange | positioned at the top. In the downstream portion in the direction in which ink is ejected (direction of arrow D),
Heating element array 36 for discharging ink from each nozzle
Are formed. The heating element rows 36 corresponding to the 144 nozzle rows 33 are divided into block units of 16 nozzles. In this example, there are nine blocks. However, the present invention is not limited to this. For example, in the case of 160 nozzles, there are 10 blocks.

In FIG. 3, reference numeral 35 denotes a sensor for detecting the temperature in the head, and 37 denotes a heating element for adjusting the head temperature. Normally, when this print head is driven, 1 to 16 nozzles in each block are sequentially driven one by one for each block. Therefore, at one time, each nozzle in nine blocks is simultaneously driven, and only one nozzle is driven in each block. This is one-nozzle distributed driving or odd / even (ODD / EVEN) distributed driving described later.

FIG. 4 shows a schematic control hardware configuration of the plotter shown in FIG. The CPU 40 controls the entire apparatus according to a control program stored in the ROM 41. The ROM 41 has a PWM (Pulse Width Modul) described later.
ation) table is also stored. Non-volatile memory 42
Is a nonvolatile memory for holding setting data such as a PWM table in a nonvolatile manner. The RAM 43 temporarily stores data such as image data to be recorded,
This is a memory that provides a data area for work. The print control unit 46 controls the recording head 22 under the control of the CPU 40. Although only one recording head 22 is shown in FIG.
Actually, a plurality of recording heads 22 are used for color recording or the like.
It has. Although not shown in FIGS. 2 and 3, the head 22 includes the above-described heating element array 36 and individually controls the heating element array 36 by receiving data and a control signal provided from the print control unit 46. -It has a driver 48. A rank resistor 47 having the same resistance value as each of the heating element rows of the heating element row 36 of the head is provided. Since the rank resistor 47 is formed by the same integrated circuit technology process as the heating element row 36, there is a correlation between the resistance values of the two. Therefore, the rank resistance 47
Is a reference (reference) for estimating the resistance value of the heating element array 36 of the head, and this resistance value is supplied to the CPU 4 via the amplifier AMP 45 and the A / D converter 44.
0 is read.

In the recording head having the above configuration,
The time for applying a voltage for ejecting ink from each nozzle needs to be set to a time width for ejecting a desired ejection amount. Regarding the product group of the recording heads, variations in the resistance values of the heating elements occur due to manufacturing errors as shown in the rank table 50 of FIG. This variation generally follows a normal distribution (FIG. 10). Hereinafter, the variation of the resistance value is divided into a plurality of sections 51 for each predetermined resistance range. Each of these sections is referred to herein as a head rank or simply a rank. In the example of FIG. 5, there are 24 head ranks 1 to 24, and the variation in the resistance value is a variation of 11.5 ranks in 3σ with a head rank of 12.5 as the center. For this reason, the variation is dealt with by presetting an appropriate voltage application time (voltage width) 53 to be applied to the heating element in order to obtain a predetermined ejection amount for the head rank. As can be seen from the figure, the higher the resistance value, the longer the voltage application time needs to be.

For example, the driving frequency of the recording head is 9 kHz.
In the case of z, one cycle for ejecting one from all nozzles of one head is 111 μs, so the maximum ejection interval given to a pair of nozzles of ODD-EVEN is
(111/16) × 2 = 13.875 μs. However, in this case, the required maximum voltage application time of the head rank maximum is 8 μs for one nozzle, and 8 μs × 2 = 16 μs for a pair of nozzles of ODD-EVEN.
16 × 8 = 12 to eject ink from all nozzles
A time of 8 μs is required. Since this exceeds 111 μs, ink cannot be ejected one nozzle at a time for each block.

As described above, conventionally, in order to cope with such a situation, two nozzles are ejected for each block instead of ejecting one nozzle for each block. FIG. 6 is a timing chart showing the drive timing. In the figure, HEATCYCLE indicates a time period during which one ejection is performed from all nozzles at a predetermined drive frequency, ODD indicates ejection timing of odd-numbered nozzles, and EVEN indicates ejection timing of even-numbered nozzles. ODD / EVEN is alternately or simultaneously driven to eject ink from all 16 nozzles in the block. That is, in the ODD / EVEN nozzle dispersion driving (a),
A voltage is applied to the heater one nozzle per block within the drive frequency interval. On the other hand, in the ODD / EVEN nozzle simultaneous drive (b), a voltage is applied to the heater by two nozzles for each block within the drive frequency interval. ODD / EVEN in the figure
In the nozzle dispersion driving (a) and the ODD / EVEN nozzle simultaneous driving (b), it seems that there is no delay of Δt1 in one cycle. However, in the simultaneous driving (b), the interval Δt2 between adjacent ejection timings is actually obtained. Can also be shortened, so that the time can be further reduced.

However, in a recording apparatus having a plurality of recording heads, when ink is ejected by two nozzles for each block as described above, the power used at one time becomes extremely large, and problems such as noise are caused. Also occurs. In the present invention, in order to minimize this problem, one nozzle is ejected per block depending on the rank of the print head.
Decide whether to eject two nozzles at a time. The determination method is as follows. Normally, as the variation of the head rank,
Average rank resistance value is 12.5 and its variation is 1 at 3σ
Since the resistance value is set to 1.5, the existence probability of the recording head deviating from this resistance value to the maximum value side is 0.18%. In such a variation, when a plurality of recording heads are used, the two recording heads may
The probability of being a head belonging to is very small at 0.0324%. Therefore, as the number of recording heads increases, the probability that all the heads belong to the head rank in such a range becomes very small.

In the case where a plurality of recording heads are used, conventionally, it is determined whether one nozzle is dispersedly driven or two nozzles are simultaneously driven in accordance with the maximum head rank. For a recording head that does not have any problem even if the ejection is performed, two nozzles are simultaneously driven.

In the present invention, when a plurality of recording heads are used, the following method is used instead of the conventional method of determining whether one nozzle is dispersedly driven or two nozzles are simultaneously driven for all heads based on the maximum value of the head rank. Adopt a method. That is, as shown in FIG. 9, after the head is replaced, the rank resistance of the head is measured (S11), and it is checked whether or not it is equal to or higher than a predetermined reference head rank (S12). If not, one-nozzle dispersion drive is set for the head (S13). If the head rank is equal to or higher than the reference head rank, simultaneous driving of two nozzles is set for the head (S1).
4). These settings are stored in a non-volatile memory. Thereby, the driving method is set for all the mounted heads.

As the "reference head rank", a head rank (for example, head rank 20) is set such that the probability that a head exceeding the rank is simultaneously used as a plurality of recording heads is extremely low. Based on this reference head rank, the magnitude of the head rank of the recording head actually mounted is determined. If the head rank is large, “two-nozzle simultaneous driving” is used, and if not, “one-nozzle distributed driving” is used. This method is effective when the actual head drive frequency is too high for the maximum head rank (rank 24), but one-nozzle distributed driving is allowed for the reference head rank. .

In this way, even in the prior art where all the heads are driven simultaneously by two nozzles, only some of the heads are driven simultaneously by two nozzles and the other heads are driven by one nozzle in a distributed manner. It can be. Moreover, the probability that a plurality of mounted recording heads are driven simultaneously by two nozzles is extremely small. As a result, the power supply capacity can be reduced, and the problems of noise generation and voltage drop due to load can be minimized.

In the case where the power supply capacity is set corresponding to the simultaneous driving of two nozzles with a maximum of two heads, it is not rare that, although extremely rare, three or more heads are simultaneously driven by two nozzles. . However, in that case, such a third head or later is regarded as a defective head and replacement is urged.
The applied voltage pattern can be determined assuming that the head rank is smaller than the actual one (in that case, the ink ejection amount is slightly reduced).

FIGS. 7A and 7B show ODD /
EVEN dispersion driving (single nozzle dispersion driving) and ODD /
An example of an applied voltage pattern for one ejection in the case of EVEN simultaneous driving (simultaneous driving of two nozzles) is shown. In each case, the applied voltage pattern to the pair of nozzles of ODD and EVEN is the minimum repetition pattern.
Here, a case where two pulses of a pre-pulse and a main pulse are used for discharging one ink droplet will be described as an example. In the figure, the horizontal axis represents time, and the vertical axis represents voltage level. Here, G indicates a global offset, P1 indicates a pre-pulse, P2 indicates an interval time, and P3 indicates each time width of a main pulse.
L indicates the time width of the local offset indicating the relative delay amount of the EVEN pulse with respect to the ODD. By setting such time widths, the timing of voltage application to the heating element for discharging ink from each nozzle is determined. In general, the discharge amount increases when the width of P1 is reduced and the width of P3 is increased so that P1 + P3 is kept constant. Conversely, the discharge amount decreases when the width of P1 is increased and the width of P3 is reduced. By utilizing such characteristics of the print head, the amount of ink ejected from the print head can be kept constant irrespective of a temperature change in the print head.

Specifically, the values of G, P1, P2, P3, and L for obtaining a predetermined discharge amount are set for each resistance value of the heating element. At this time, whether the driving is the distributed driving or the simultaneous driving is determined depending on whether the value of L is set to a value equal to or more than P1 + P2 + P3 or set to 0. The PWM table is a predetermined one of the applied voltage patterns determined for each rank resistance value. Actually, the viscosity of the ink changes in accordance with the temperature change in the recording head, so that P1 and P3 corresponding to the temperature change.
You need to select a combination. Such P1 +
Since the value of P3 varies depending on the resistance value of the heating element, a variable table of P1 and P3 is prepared for each head rank (for each rank resistance value).

As shown in FIG. 8, such an applied voltage pattern is prepared in advance in a ROM as a PWM table 80 which defines an applied voltage pattern for distributed driving and simultaneous driving for each head rank.

While the preferred embodiment of the present invention has been described above, various modifications and changes are possible. For example,
Specific numerical values such as the number of ranks, the resistance value range, and the voltage application time are merely examples.

[0036]

According to the present invention, the driving frequency of the recording head and the resistance value of the heating element determine whether the heating element is driven one nozzle at a time for each block or two nozzles are driven at a time for each block. , The power consumption can be reduced more appropriately, and the occurrence of noise and an excessive voltage drop due to the load can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a plotter which is an example of an image recording apparatus of an ink jet system of the present invention.

FIG. 2 is a schematic diagram showing an ink ejection surface of a head 22 in the plotter of FIG.

3 is a plan view showing a heating element and the like arranged on an aluminum base plate 34 of the head of FIG. 2;

FIG. 4 is a block diagram illustrating a schematic control hardware configuration of the plotter of FIG. 1;

FIG. 5 is a diagram illustrating a rank table for describing a head rank according to the embodiment of the present invention.

FIG. 6 is a timing chart showing drive timings of ODD / EVEN distributed driving (single nozzle distributed driving) and ODD / EVEN simultaneous driving (two nozzle simultaneous driving).

FIG. 7 is a waveform diagram showing an example of an applied voltage pattern for one ejection in the case of ODD / EVEN dispersion driving (single nozzle dispersion driving) and ODD / EVEN simultaneous driving (two nozzles simultaneous driving).

FIG. 8 is a diagram showing a PWM table in which applied voltage patterns for distributed driving and simultaneous driving for each head rank are determined.

FIG. 9 is a flowchart illustrating an example of post-head replacement processing according to the embodiment of the present invention.

FIG. 10 is a diagram showing a distribution waveform relating to a variation in a heater resistance for ink ejection of a head.

[Explanation of symbols]

 33 ink ejection nozzle array 34 aluminum base plate 35 sensor for detecting temperature in head 36 heating element array for ink ejection 37 heating element for head temperature adjustment

Claims (4)

[Claims] A plurality of recording heads each having a plurality of ejection ports, wherein the ejection ports of each recording head are divided into a plurality of blocks each having a predetermined number of ejection ports, and each block is provided in the ejection ports. A head driving method of an ink jet recording apparatus for forming an image by discharging ink in the discharge port by driving the heating element for ink discharge, wherein one heating element in each block is provided for each block of each recording head. Whether to perform divided driving to drive dividedly and simultaneous driving to drive dividedly two at a time,
A head driving method for an ink jet recording apparatus, wherein a head frequency is determined for each head based on a driving frequency interval of the recording head and a resistance value of a heating element of the recording head. 2. A method according to claim 1, further comprising: ranking a predetermined group of print heads based on the resistance values of the heating elements for ejecting ink, and comparing the existence probabilities based on the driving frequency. A predetermined rank is set as a reference rank, and the resistance of the ink ejection heating elements of a plurality of print heads mounted on the carriage is determined to determine the rank of each of the print heads. 2. The head driving method for an ink jet recording apparatus according to claim 1, wherein the simultaneous driving is performed for the recording heads having the same rank, and the distributed driving is performed for the recording heads having a rank smaller than the reference rank. 3. A print head having a plurality of discharge ports,
The discharge ports are divided into a plurality of blocks each including a predetermined number of discharge ports, and an ink discharge heating element provided in each of the discharge ports is driven for each block to discharge ink in the discharge ports to form an image. A driving unit for driving the recording head for each of the divided blocks, wherein the driving unit divides and drives the heating elements in the block one by one, and simultaneously drives two by two. An ink jet printing apparatus characterized in that it is determined which of the simultaneous driving and the divided driving is performed based on the drive frequency interval of the print head and the resistance value of the heating element of the print head. 4. A carriage on which a plurality of said recording heads are mounted, and a resistance of an ink-discharging heating element of each of the mounted recording heads by checking the ink-discharging heating elements of the plurality of recording heads mounted on the carriage. Means for determining a rank related to a value; a table in which an applied voltage pattern is determined for each determined rank; and a recording head having a rank equal to or higher than the reference rank performs the simultaneous driving and prints a rank smaller than the reference rank. 4. The ink jet recording apparatus according to claim 3, further comprising: a driving method setting unit that performs the distributed driving for the head.