Partial print fluid short detection
阅读说明:本技术 部分打印流体短路检测 (Partial print fluid short detection ) 是由 本·波斯尔 詹姆斯·哈斯勒 于 2017-06-23 设计创作,主要内容包括:部分打印流体短路检测系统可以检测打印头中的部分打印流体短路。部分打印流体短路检测系统包括用于检测打印头的打印间隙的时序电路,并且部分打印流体短路检测系统可以响应于对打印间隙的检测来检测部分打印流体短路。(A partial printing fluid short detection system may detect a partial printing fluid short in a printhead. The partial printing fluid short detection system includes a timing circuit for detecting a print gap of the printhead, and the partial printing fluid short detection system may detect a partial printing fluid short in response to detection of the print gap.)
1. A partial printing fluid short detection system for detecting a partial printing fluid short in a printhead, the system comprising:
a timing circuit coupled to a printhead to detect a print gap of the printhead based on print data provided by a printhead controller; and
a comparator coupled to the timing circuit, wherein, in response to the timing circuit detecting the print gap, the comparator is to compare the measured current drawn by the printhead to a threshold printhead current value, and
in response to the measured current drawn by the printhead exceeding the threshold printhead current value, the comparator is to send a printing fluid short indication to detection circuitry.
2. The system of claim 1, wherein the detection circuit is to receive the printing-fluid short indication from the comparator and to provide a printing-fluid short notification to a processor, wherein, in response to receiving the printing-fluid short notification, the processor is to send a command to the printhead controller to power down the printhead.
3. The system of claim 1, wherein the timing circuit is reset in response to a signal derived from the print data, and the signal indicates firing of nozzles on the printhead.
4. The system of claim 1, further comprising a current measurement circuit connected to the printhead to measure a current drawn by the printhead and provide the measured current drawn to the comparator.
5. The system of claim 4, wherein the current measurement circuit is an ammeter.
6. The system of claim 1, wherein the detection circuit comprises a printing fluid short checker coupled to the timing circuit and the comparator, and wherein the printing fluid short checker receives an over current signal from the comparator and outputs the printing fluid short indication to a processor.
7. The system of claim 1, wherein to detect the print gap, the timing circuitry is to measure a gap upon receiving a predetermined value in the print data.
8. The system of claim 7, wherein the predetermined value indicates firing of a print nozzle on the printhead.
9. The system of claim 8, wherein the print data is associated with a drop count of the print nozzle.
10. The system of claim 1, wherein the timing circuit comprises a watchdog timer.
11. A system as defined in claim 10, wherein the watchdog timer is reset in response to any of the drop counts increasing in a clock cycle.
12. The system of claim 1, wherein the timing circuit detects the print gap when the printhead is not printing for a predetermined amount of time.
13. A method for partial printing fluid short detection, comprising:
detecting a print gap;
measuring a current drawn by a printhead during the print gap;
comparing the measured current drawn by the printhead to a threshold printhead current value; and
generating a partial printing fluid short circuit indication in response to the measured current drawn by the printhead exceeding the threshold printhead current value.
14. The method of claim 13, further comprising isolating the printhead in response to the generation of the partial printing fluid short indication.
15. A printer, comprising:
a processor;
a printhead controller for receiving print commands from the processor;
a printhead comprising a plurality of nozzles, wherein the printhead controller is to fire the plurality of nozzles based on the print command;
a partial printing fluid short detection system comprising:
a timing circuit coupled to the printhead to detect a print gap of the printhead based on print data provided by a printhead controller; and
a comparator coupled to the timing circuit and detection circuit, wherein, in response to detection of the print gap by the timing circuit, the comparator is to compare the measured current drawn by the printhead to a threshold printhead current value, and
in response to the measured current drawn by the printhead exceeding the threshold printhead current value, the comparator is to send a partial printing fluid short indication to detection circuitry,
wherein the detection circuit is to receive the partial printing fluid short indication from the comparator and to provide a partial printing fluid short notification to a processor, wherein, in response to receiving the partial printing fluid short notification, the processor is to send a command to the printhead controller to isolate the printhead.
Background
The printing mechanism typically includes an inkjet printhead capable of forming images on many different types of media. As the media advances through the print zone, the inkjet printhead ejects drops of printing fluid in color through a plurality of orifices and onto a given media. The print zone may include the plane formed by the print head orifice and any scanning or reciprocating motion, and the print head may move back and forth and perpendicular to the media, or may include the motion of the media under a stationary print head with nozzles moving perpendicular to the media. Methods for discharging printing fluid from printhead orifices or nozzles may include piezoelectric and thermal techniques.
In thermal inkjet systems, a barrier layer containing printing fluid channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. The substrate layer typically contains a columnar array of heater elements, such as resistors, that are individually addressable and energized to heat the printing fluid within the vaporization chamber. Upon heating, a droplet of printing fluid is ejected from a nozzle associated with the firing resistor. Inkjet printhead nozzles are typically arranged in one or more columnar arrays that move substantially parallel to the print medium as the medium travels through the print zone. Typically, the print media is advanced under the inkjet printhead and held stationary while the printhead is transported along the width of the media, with the controller determining to fire its nozzles in accordance with the determination to form the desired image or pass over the individual swaths. The print media is typically advanced between passes of the reciprocating inkjet print heads to avoid uncertainty in the location of the ejected drops of printing fluid.
The printing mechanism may have one or more inkjet print heads corresponding to one or more colors, or "three primary colors" as is known in the art. For example, a typical inkjet printing system may have a single printhead with only black printing fluid; or the system may have four printheads, each with black, cyan, magenta, and yellow printing fluids; or the system may have three printheads, each with cyan, magenta, and yellow printing fluids. Of course, in an inkjet printing system, there are many more combinations and numbers of possible printheads, including seven and eight ink/printhead systems.
Advanced printhead designs now allow for an increased number of nozzles to be implemented on a single printhead. Thus, in a given printing mechanism, whether there is a single reciprocating printhead, multiple reciprocating printheads, or a full page printhead array, the number of drops of printing fluid that can be ejected per second increases. While such increases in firing rate and density allow for faster printing speeds or throughput, the amount of firing data that can be communicated from the print mechanism controller to one or more printheads can be correspondingly increased. The increased firing rate and density can increase the likelihood of printing fluid shorts, which can be caused by highly conductive printing fluid residue and aerosols in the inkjet printing mechanism. Increased firing rates may also result in an increased amount of power being consumed by the printhead.
Printing fluid residue can accumulate on the printhead nozzle surfaces and migrate to the printhead connector pads through normal printer operation or by removing and installing the printhead itself, creating a potential short circuit condition of the transmission lines. Similarly, airborne aerosols may deposit onto the printhead contacts, creating a potential short circuit condition of the transmission line. In addition, if the printhead die is cracked or damaged due to media impacts, printing fluid may also migrate inside the printhead and cause a partial printing fluid short circuit. A partial printing fluid short circuit may be the result of physical damage to the printhead due to the printhead being dropped. Impact of the media against the printhead may damage the printhead. In addition, thermal inkjet resistance (TIJ) can wear and cause the barrier between the printhead electronics and the printing fluid to rupture, thus the printing fluid seeps into and shorts the electronics.
Drawings
Features of the present disclosure are illustrated by way of example and not limitation in the figures(s) below, in which like numerals indicate like elements, and in which:
FIG. 1 shows a block diagram of an example of a partial printing fluid short detection system;
FIG. 2 shows a flow diagram of an example of partial print fluid short detection for a printhead;
FIG. 3 shows a flow diagram of an example method for partial printing fluid short detection; and
FIG. 4 shows a detailed diagram of an example printer with a partial printing fluid short detection system.
Detailed Description
For simplicity and illustrative purposes, the present disclosure is described primarily by reference to examples thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent, however, that the present disclosure may be practiced without limitation to these specific details. In other instances, methods and structures that would be readily apparent to one of ordinary skill in the art have not been described in detail so as not to unnecessarily obscure the present disclosure. As used herein, the terms "a" and "an" are intended to mean at least one of a particular element, the term "including" is intended to include, but is not limited to, and the term "based on" is intended to be based, at least in part, on.
According to examples of the present disclosure, a partial printing fluid short detection system may detect a partial printing fluid short in a printhead. The partial printing-fluid short detection system includes a timing circuit for detecting a print gap of the printhead, and the partial printing-fluid short detection system can detect a partial printing-fluid short in response to detection of the print gap. In an example, the timing circuit detects a print gap based on print data. For example, the system may reset the timing circuit when print data is sent to the printhead. When the print data is not sent to the print head, the timing circuit counts down until tripped, which indicates that the printing performed by the print head has just occurred with a time gap. When this print gap is detected, the measured current drawn by the printhead is compared to a threshold value that represents the normal current drawn by the printhead when not printing (e.g., when the printhead is idle). A partial printing fluid short is detected when the current measured during the printing gap is above a threshold value.
The print data may include data associated with or causing printing by the print head. For example, the print data may comprise a sequence of signals generated by the printhead controller in response to receiving a print instruction from the processor. In an example, a printing fluid drop signal indicates firing of a nozzle of a printhead, such as in response to the printhead receiving print data. The timing circuit may detect a print gap using a print fluid drop signal. The print gap is the period of time when the printhead is powered on but not printing, such as when the nozzles of the printhead are not ejecting drops of printing fluid. The Printing Fluid (PF) may be a fluid applied on the printing medium. For example, the PF may be a mixture of toner or ink with various types of polymers, such as, for example, styrenated acrylics, polyolefins, polyesters, and the like. The PF may be highly conductive. The print gap may have a predetermined length. In an example, the print gap may be a predetermined number of clock cycles. The print gap may be based on hysteresis of circuitry in the system to measure the current draw and compare the current draw to a threshold. A partial printing-fluid short is an electrical short. Partial printing fluid shorts may occur in the printhead. For example, a partial print fluid short of a printhead may result in a current draw that is lower than the maximum current that the printhead can draw, but higher than the current that the printhead should draw for its current operating state, such as when the printhead is not printing. If a partial printing fluid short does not occur, the partial printing fluid short may cause the current drawn by the printhead to exceed the current that would normally be drawn. Common causes of partial printing fluid shorts in printheads are normal wear, electrical stress, or printing fluid leaks on electrical circuits or transmission lines.
In an example, the printhead is isolated by powering down once a partial printing-fluid short is detected in the printhead by the partial printing-fluid short detection system. A partial printing fluid short circuit may present a safety hazard. For example, in high power printheads, a partial printing fluid short circuit may present a fire hazard because the heat generated in the printhead may be sufficient to ignite the print media in direct contact with the printhead. In low power printheads, a partial print fluid short circuit may not present a fire hazard, but may result in significant print quality degradation due to nozzle failure. Isolation of the print head can minimize safety hazards or print quality degradation and can protect the rest of the system from further damage. Isolation of the printheads may be achieved by powering down the printheads or by terminating the connection between the printheads and the respective printhead controllers so that the printheads do not receive print data. The present disclosure uses the term "coupled" to mean electrically coupled to allow for the exchange or transmission of electrical signals between circuits.
It may be difficult to detect a partial print fluid short without a complex and comprehensive analysis of the operation of the printhead and the current draw during its operation. The partial printing fluid short detection system may detect times when no printing data is flowing to the printhead and check for partial printing fluid shorts at these times. Thus, detection of partial printing fluid shorts is simplified and may not use overly complex analysis that actively compares the actual power consumed by the printhead to the power estimated to be consumed based on print density and energy used by each printing fluid drop.
Referring initially to fig. 1, a block diagram of an example partial print fluid
The
Referring to fig. 2, a block diagram of another embodiment of a partial printing fluid
Turning to FIG. 3, a flow diagram of an
Referring to fig. 4, a block diagram of an
The DC voltage may be passed to the printhead 114 through a flexible cable along with the output print data signal generated by the
While specific description is made throughout this disclosure, representative examples of the disclosure have utility in a wide range of applications, and the above discussion is not intended and should not be construed as limiting, but is provided as an illustrative discussion of various aspects of the invention.
What has been described and illustrated herein are examples of the present disclosure and some variations thereof. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. There are numerous variations within the spirit and scope of the disclosure which are intended to be defined by the following claims and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated.
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