JPH02279344A - Ink jet print head - Google Patents

Abstract

PURPOSE: To prevent defective print easily by providing each print head with a memory element for storing a data characterizing a printhead and delivering an warm of impending exhaustion of ink. CONSTITUTION: A memory element 14 fixed to the housing of a printhead 12 comprises a magnetic medium piece, a semiconductor memory, and a laser readable optical medium and stores a data concerning to the printhead. The information characterizes the identity of printhead (date of manufacture, place of manufacture, lot number, serial number, and the like), and some operating characteristics of printhead (alignment of orifice, color of ink, liquid level of ink, operational frequency, dilution of ink, and the like). These data is read out from the printhead and used or displayed as required thus preventing defective print easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to printing technology such as an ink jet print head.

[Technical background of the invention and its problems] Over the past 50 years, inkjet printing has matured from a technical curiosity to a mainstay of office automation. Recent advances have allowed inkjet printers to produce print quality comparable to laser printers. However, even with the best current technology,
It has certain drawbacks.

One drawback is in the area of color printing. The basic technology of inkjet color printing is well developed. It essentially involves the controllable ejection of droplets of cyan, yellow, magenta, and sometimes black ink from separate printheads onto a print medium. However, in such printing methods, the relative positions of the individual print heads are adjusted so that the ink droplets generated from the printing nozzle fall onto the print medium in a desired positional relationship with the ink droplets generated from other print heads. Precise positioning is required. One approach to this need for precise relative positioning is to use a single orifice plate in which all of the necessary orifices are formed.
Some or all of the printheads have been constructed in one assembly. Since the orifice plate is formed using photolithography, the relative positioning of various print head elements can be performed with high precision. Unfortunately, configuring several print heads into one assembly
When the first ink supply of the print head runs out of ink, the overlapping assembly becomes virtually useless.

Another approach to the need for precise relative positioning is to use several separate printheads and optically sense the position of the orifice plate on the printhead after each printhead is installed in the printer. There is. Some overcasting systems detect the position of each printing hem, as shown in U.S. Pat. No. 4,709,245. If the orifice plate is fabricated using a process that allows precise definition of the edges of the orifice plate, such as photolithography, this technique horizontally characterizes the location of the printing orifice.
izing). However, this does not give any information about the vertical position of the orifice. In addition,
This technique is often ineffective if the edges of the orifice plate are not precisely defined, such as when the plate is simply cut from a master rod.

A drawback associated with color printers is that certain colors of ink can run out at inopportune times during long, complex printing jobs.

Printing complex color images can take several minutes. If one of the inks that make up the print runs out, the operation must be interrupted and the worn out print head must be replaced before the operation can be resumed. This is not just a waste of time, but what other colors of ink were used for the interrupted work? It's also food expenses.

Several attempts have been made to provide a visual indication of a dying inkjet printhead. A specific example is an inkjet printhead with a transparent ink chamber. Manufacturing considerations such as the use of durable, opaque materials are often required.

Another disadvantage of color printing systems, at least those that use separate printheads for the constituent colors, is that the print heads can be inadvertently misplaced within the printer. If the cyan ink print head were located where the magenta ink should be, the print would be defective.

[Object of the Invention 1] The present invention overcomes these and other deficiencies in conventional inkjet printing systems by providing a storage element associated with each print head capable of storing data characterizing the printing nods. The purpose is to solve the problem.

[Summary of the Invention j This data can characterize one or more of the properties of the printhead or its operating characteristics. Such operating characteristics may include the color, amount of ink within the printhead, or the location of the orifice plate on the printhead body.

This data can be read from the printhead and used or displayed as desired. Data characterizing the orifice plate position can be used to controllably advance or delay some of the orifice firing signals, for example, to compensate for misalignment. Data characterizing the color of the ink can be used to enable the printer to accept printheads of any color in any printhead receptacle. The data characterizing the amount of ink is updated to reflect ink usage during printing and can alert the user about ink that is about to be depleted.

Embodiments of the Invention FIGS. 1-3 illustrate one or more printing assemblies 12, a storage element 14 associated with each printing assembly, a printer circuit 16, and an interface 18 connecting the printer circuit to the storage element. 1 shows a printing device 10 according to an embodiment of the present invention.

The illustrated printing assembly 12 includes an inkjet printhead with a housing 20, an ink chamber 22, an orifice plate 24 having a plurality of orifices 26 in fluid communication with the ink chamber, and a plurality of jets for ejecting ink from the orifices. A resistor 28 is provided. A plurality of alignment mechanisms 30 are provided on the housing of the print head.
are arranged and cooperate with a corresponding alignment mechanism 32 in the associated carriage 34 to ensure proper mechanical alignment of the printheads as they are carried by the carriage within the printing device lo (proper alignment). A similar alignment mechanism and related alignment techniques are shown in U.S. Pat. No. 4,755,836, the contents of which are incorporated herein by reference.

Mounted in the housing of the printhead 12 is a storage element 14 that may contain, for example, a piece of magnetic media;
It is composed of a semiconductor memo IJ-, an optical medium that can be written and read by a laser, and the like.

This memory stores data regarding the print head. Such information may include the nature of the printhead (date of manufacture, location of manufacture, lot number, serial number, etc.) or certain operating characteristics of the printhead (orifice alignment, ink color, ink level, operating frequency, ink dilution, etc.). This data can be read from the printhead and used or displayed as desired.

FIG. 3 shows details of printer circuit 16 used in one embodiment of the invention. This circuit includes a normal data memory 36 for storing data to be printed, this data (A
, 5CII format, etc.) into a series of timing impulses required for the individual firing resistors 28 of the inkjet printhead 12. These signals are adjusted by the drive circuit 40 to the voltage level required to actually drive the injection resistor. These steps are conventional and found in any inkjet printer.

Connected to the output of the signal generating circuit 38 is a monitoring circuit 42 which counts the number of ink drops that the print head is commanded to print. This number is directly related to the amount of ink consumed by the print head during a given printing job. Preferably, the printhead memory 14 contains data indicating the relative amount of ink remaining in the ink chambers (this data is first loaded during manufacturing and set to match the total ink fill value). . The numbers measured by the monitoring circuit 42 can be used to periodically update this data.

In the illustrated embodiment, this updating is accomplished by a magnetic read/write head 44 mounted near the path of the carriage 34 and reading from and writing to the printhead's magnetic strip memory 14 each time the printhead passes that location. Preferably,
Each time the printer IO is powered on, the print head 12
is preferably passed through the read/write head 44 and the ink level data on the magnetic strip memory of the print head is read. This data is loaded into volatile memory 46 associated with monitoring circuit 42. Subsequently, as the printer is used, the monitoring circuit decrements this memory 46 to reflect the ejection of ink from the print head. Each time the print head passes read/write head 44, this decremented value is stored in volatile memory 46 inside the printer.
from there to the magnetic piece 14 of the print head, which updates the previous value. In this manner, the printer's volatile memory 46 is continuously updated by monitoring the signals provided to the printhead. Print head magnetic strip memory 14 is updated periodically (ie, each time it passes the read/write head) by data transfers from memory 46. Although the data in memory 46 is erased when the printer is powered down, the data on the print head's magnetic strip memory remains and is read and used to reinitialize memory 46 the next time the printer is powered on. When a print head is removed from a printer and used in another printer, data indicating the amount of remaining ink is transferred along with the print head to the new printer.

Connected to the monitoring circuit 42 is a low power ink indicator 48, shown here as a light emitting diode. This indicator signals the operator when the level of ink in the printhead (as indicated in memory 46) falls below a threshold. This value may be set, for example, to a value that corresponds to the amount of ink required to print one solid page.

By alerting the user that the print head is about to run out of ink, problems with printing complex color graphics or running out of one color of ink before completion can be avoided.

(For color print heads with multiple ink chambers, 1
．． The circuits may be multiplexed so that data regarding the liquid level of each ink can be processed for each color of the magnetic piece I4. ) The memory 14 of the print head also includes the print head body 20.
Contains data regarding the alignment of the upper orifice plate. As previously mentioned, orifice plates are fabricated using photolithography to create printing orifices with precise dimensions and spacing. However, the process of attaching the orifice plate to the desired location on the printhead body cannot be performed with similar precision. To minimize print degradation that can occur due to misalignment of the orifice plate on the printhead body, data characterizing the misalignment is stored on the magnetic medium 14 and used before the firing pulses applied to the printhead. Can be used to compensate. Data characterizing the misalignment of the orifice plate on the print head can be obtained by a variety of techniques, such as eddy current sensing, mechanical probes, and optical inspection using visual or automated vision equipment.

FIG. 4 is a rough magnification of the misalignment of the orifice plate on the printhead body as seen with a vision system. The orifice plate on the printhead being inspected is displayed on a video screen. Overlaid on this image is a measurement count line and a series of u + ++ indicating the desired alignment of the orifice plate. Orifice plate misalignment can be characterized in many ways. Specifically, the optical target 54 formed at the center of the orifice array is offset in X and Y with respect to reference data 56 indicating the desired orifice plate orientation. There is also an angular offset as part of the characterization data. In the figure, the X offset is 2.4 ml, the Y offset is -0.5 ml, and the angular offset is 30'. This data can also be gathered by an operator measuring misalignment from an image on a screen. Alternatively, it can be obtained automatically by a computer linked to a viewing device. In any case, the data stored on the printhead's magnetic strip 14 can be used by the printer using the printhead when the magnetic strip is read by the read/write head 44 at power-up.

Alignment data read from the print head is stored in memory 50 associated with compensation circuitry 52 of the printer. Compensation circuit 52 varies the relative timing of firing signals provided to the orifices to minimize printing errors caused by spatial misalignment of the various orifices. As an example of a compensation process, the leading-most orifice (as the print head traverses the page) may be assumed to be the reference orifice and all other orifices mechanically aligned thereto. In FIG. 4, the leading most orifice is number 0 (depending on the direction the print head is traveling). Nearby orifice 1 lags behind orifice O by a distance equal to 5 insθ times the linear separation between them. In the illustrated system, if the orifice spacing is 6,66 m i I, the angle of misalignment is 30'', and orifice 1 is
from 6.66sine30', i.e. 3,33m
i You will be delayed by 1. The drive signal applied to orifice l must thus be delayed by a sufficient interval to allow the orifice to advance this 3,33 m i l before printing. If the carriage is moving at a speed of 5000 m i l per second, the injection signal given to it will be 3.3315000 or 0.
Must be delayed by 666m5ec.

Since the injection orifices are arranged linearly and uniformly spaced on the orifice plate, the delay from one orifice to the next progresses in an orderly manner. That is, the delay required for orifice 2 is simply twice the delay required for orifice l, the delay required for orifice 3 is simply three times the delay required for orifice l, and so on. This simplifies the compensation calculations required for compensation circuit 32.

The above compensation is based on the orifice plate 2 on the print head body 20.
Only the printing deviation due to the angular misalignment of No. 4 is considered. This angular misalignment also creates vertical compression of the print. That is, the vertical component of the distance between the top and bottom orifices is co
It is shortened at a rate of sineθ. This compression cannot be relieved within the constraints of a fixed orifice spacing. Fortunately, in most cases this is a relatively minor factor.

Additionally, compensation can be easily made to correct for horizontal or X-direction offsets to properly overlap printing from two or more orifice plates.

The signals for firing as a group to each printhead are simply delayed by an additional factor that mathematically translates the printing by them to coincide with the reference Y axis (
or proceed). In the above example, the correction for the angular misalignment described above would cause printing from the orifice to be moved to the right of the Y axis, X=(2,5*6.66sineθ+2
．． 4) or to the vertical line located at 10.733 mtl. To move this vertical line to the right and match it with the Y axis and the printing by the other compensated orifice plate, the print signal is further increased to 10.733/5000
It is regularly delayed by sec or 2.146 m5 ec.

If the Y between the orifice plates is greater than the distance between the orifices that misses in the vertical direction, a print signal directed to one orifice may lead to any orifice closer to the desired vertical position. For example, if orifice plate 24 is 13.33 ml above the intended location and the orifice spacing is 6.66 ml, the print signal originally directed to orifice O will instead be directed to orifice 3.
etc. In such a case, a signal directed to the distal orifices (orifices 4 and 5 in this example) will need to be printed by orifice 0 or orifice 1 the next time the print head passes the page. . This buffers all the signals directed to orifice 4 and orifice 5 into a shift register with stages of the pixel bones of the page, and drives orifice O and orifice l from the output of these shift registers to generate the required print signals. This is achieved by performing a delay of .

In other embodiments, instead of buffering print signals to orifices at the ends and printing with those signals during another scan of the print head, the print head and orifice plate have additional orifices at the ends of the orifice array. You can also make These additional orifices can be driven by print signals shifted from neighboring orifices if vertical misalignment needs to be corrected. This approach is easier to implement than buffer delay techniques under certain circumstances.

If the magnitude of the vertical misalignment is less than the spacing of adjacent orifices, no compensation is possible due to the constraints of fixed orifice spacing.

For convenience of explanation, the foregoing discussion has described a print head with a single linear orifice array. However, the principle explained is
It is equally applicable to more complex printheads with other orifice configurations, such as the two-row configuration used in esk Jet printheads.

Today, significant investments in equipment and labor are made to ensure ultra-accurate positioning of the orifice plate to the printhead body, but these investments are discarded when the ink runs out. Just look at the result. The technique of the present invention is much more preferred as it provides comparable print quality with much simpler positioning conditions.

With reference to examples and some variations thereof,
Although our invention has been described and illustrated in detail, it will be obvious that the invention may vary in operation and detail without departing from such principles, e.g.
Although the present invention has been described with reference to an inkjet printer, it can be effectively applied to a variety of other printing devices, such as block printers. Similarly, although the present invention has been described with reference to magnetic strip memory on the printhead, other storage elements could easily be employed. If the data in memory does not need to be updated by the printer, a variety of read-only memories may be employed, including optical bar codes encoding operational characteristics of the printhead. Also, data communication between the print head and the printer need not be done by a read/write head. Alternatively, other transmission techniques can be used, such as optical or wireless coupling. Finally, although the present invention has been described with reference to specific electrical circuitry (such as a supervisory circuit) provided within the printer, such circuitry may in alternative embodiments be part of the printhead assembly itself. It can also be used as a part.

Similarly, correction of orifice plate misalignment
It may also be done as part of the printhead electronics. The required compensation delay can be determined by, for example, the custom EEPRO of the print head.
M and can control the associated delay circuit.

In view of the above and various other embodiments to which the principles of our invention may be applied, the illustrated embodiments should be considered as exemplary only.

[Effects of the Invention] As described above, by using the present invention, misalignment of the orifice plate can be easily compensated for, and a warning regarding ink shortage can be easily given to the user. Furthermore, the conventional mounting of the print head can easily prevent printing defects due to incorrect positioning.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a print head equipped with a memory element according to an embodiment of the present invention. FIG. 2 is a diagram showing an inkjet printer using the print head. FIG. 3 is a schematic block diagram of the inkjet printer. FIG. 4 is a diagram illustrating the relative misalignment of orifice plates on the print head.

Claims (5)

[Claims] (1) An inkjet printhead comprising a housing having an ink chamber, a plurality of orifices in fluid communication with the ink chamber, and means for ejecting ink from the ink chamber through the orifices, the housing including a mechanism for operating the printhead. An inkjet printhead, characterized in that it is provided with storage means for storing data relating to characteristics. (2) Claim (1) characterized in that the storage means stores data regarding the ink color within the ink chamber.
Inkjet print head as described. (3) Claim (1) characterized in that the storage means stores data regarding the amount of ink in the ink chamber.
) described inkjet print head. 4. An ink jet printhead according to claim 1, wherein said storage means stores data relating to the relative alignment of said printhead orifice and housing. (5) Claim (1) characterized in that the storage means stores data regarding the operating frequency of the print head.
) described inkjet print head.