An inkjet printing system, as one example of a fluid ejection system, may include a printhead, an ink supply which supplies liquid ink to the printhead, and an electronic controller which controls the printhead. The printhead, as one example of a fluid ejection device, ejects drops of ink through a plurality of nozzles or orifices and toward a print medium, such as a sheet of paper, so as to print onto the print medium. In some examples, the orifices are arranged in at least one column or array such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. It is to be understood that features of the various examples described herein may be combined, in part or whole, with each other, unless specifically noted otherwise.
To achieve optimal fluid ejection die performance, the fluid ejection die temperatures should be monitored and controlled. A single thermal sense monitor circuit may be used to monitor the temperature of each of a plurality of dies by sequentially switching between the dies to receive and process a temperature signal from each die. Switching between a plurality of dies to sequentially monitor the temperature of each die via the thermal sense monitor circuit may result in noise on the temperature signal line input to the thermal sense monitor circuit.
According, disclosed herein is a fluid ejection system including a plurality of fluid ejection dies and a thermal sense monitor circuit. Each die includes a temperature sensor. The thermal sense monitor circuit may include a shared thermal sense line coupled to a local thermal sense line of each die and a biasing circuit to bias the temperature sensor of each die via the shared thermal sense line and each local thermal sense line. The thermal sense monitor circuit may also include a clamping circuit to clip the temperature signal on the shared thermal sense line and a controller to sequentially select each die to output a temperature signal to the shared thermal sense line. The clamping circuit may include a precision gate threshold metal-oxide-semiconductor field-effect-transistor (MOSFET) to clip a voltage of the temperature signal at the threshold voltage of the MOSFET. The clamping circuit reduces or prevents noise on the shared thermal sense line when switching between the dies.
As previously described above with reference to
Operational amplifier 132 is configured as a unity gain amplifier (i.e., a buffer) to buffer the temperature signal on shared thermal sense line 102. ADC 136 receives the buffered temperature signal and converts the temperature signal to a digital value. ADC 136 outputs the digital value to controller 140. Controller 140 may use the digital value of the temperature signal from each of the plurality of fluid ejection dies to control the temperature of each of the fluid ejection dies. Controller 140 may control the temperature of each of the fluid ejection dies by controlling a heating element disposed on each of the fluid ejection dies. In other examples, controller 140 may use the digital value of the temperature signal from each of the plurality of fluid ejection dies for other suitable purposes. Controller 140 may include a microcontroller, an application-specific integrated circuit (ASIC), or other suitable logic circuitry.
Precision gate threshold MOSFET 160 clips the voltage on signal line 154 at the threshold voltage of precision gate threshold MOSFET 160. In one example, resistor 152 is 43 KΩ and resistor 156 is 3.3 MΩ. In one example, when the voltage on signal path 154 reaches 1.8 V, transistor 162 starts to turn on, and by 1.9 V is fully on. In this way, the voltage on signal line 154 is clipped at 1.9 V by conducting voltage above the threshold to common or ground node 130 through the drain to the source of transistor 162. Precision gate threshold MOSFET 160 is largely unaffected by temperature (e.g., has a temperature coefficient less than 2.5 mV/° C.), allowing for a wide operating swing while maintaining the precision voltage threshold for clipping. Precision gate threshold MOSFET 160 may also have a rapid clamping response less than 15 ns. Clamping circuit 106 prevents the voltage on signal line 154 from railing due to a temporary fluid ejection die disconnect time, such as when transitioning the shared thermal sense line from connection to one die to connection to another die.
Each fluid ejection die 2021 to 202N enables its temperature sensor 2041 to 204N in response to receiving an address signal corresponding to the fluid ejection die 2021 to 202N, respectively. Thermal sense monitor 212 sequentially selects each temperature sensor 2041 to 204N of each of the plurality of fluid ejection dies 2021 to 202N to output a temperature signal to shared thermal sense line 208 and clips the temperature signal on shared thermal sense line 208.
In response to fluid ejection die 202 receiving the address signal corresponding to fluid ejection die 202, diode stack 220 and 224 is enabled to receive a biasing current from a thermal sense monitor through local thermal sense line 206. In response to the biasing current, diode stack 220 and 224 outputs a temperature signal (i.e., voltage) on local thermal sense line 206 corresponding to the temperature of fluid ejection die 202.
With the clamping circuit, waveform 258 is clipped at a voltage as indicated at 262 just above (e.g., 0.1-0.2 VDC) the thermal sense voltage range (e.g., 0-1.7 VDC) as indicated at 264. According, at 2701 to 270N each fluid ejection die 1 to N is sequentially selected to output a temperature signal to the shared thermal sense line, respectively. The temperature signal may be converted to a digital value by an ADC after a sample delay period 2721 to 272N for each selected fluid ejection die 1 to N, respectively. Due to the clamping circuit, an additional sampling margin 2741 to 274N on the falling edge of each switched local thermal sense line and an additional sampling margin 2761 to 276N on the rising edge of each switched local thermal sense line is available for each sampling period, respectively. This allows for extra room when the position of the ADC trigger sample delay is adjusted, thus eliminating false readings and noise due to settling time after switching in a temperature sensor and rise time after a temperature sensor is turned off.
Printhead assembly 302 includes a thermal sense monitor 305 electrically coupled to at least one printhead or fluid ejection device 306. Fluid ejection device 306 includes at least two fluid ejection dies 308, where each fluid ejection die 308 ejects drops of fluid through a plurality of orifices or nozzles 309. In one example, the drops are directed toward a medium, such as print media 324, so as to print onto print media 324. In one example, print media 324 includes any type of suitable sheet material, such as paper, card stock, transparencies, Mylar, fabric, and the like. In another example, print media 324 includes media for three-dimensional (3D) printing, such as a powder bed, or media for bioprinting and/or drug discovery testing, such as a reservoir or container. In one example, nozzles 309 are arranged in at least one column or array such that properly sequenced ejection of ink from nozzles 309 causes characters, symbols, and/or other graphics or images to be printed upon print media 324 as printhead assembly 302 and print media 324 are moved relative to each other.
Each Fluid ejection die 308 may be a fluid ejection die 202 previously described and illustrated with reference to
Fluid supply assembly 310 supplies fluid to printhead assembly 302 and includes a reservoir 312 for storing fluid. As such, in one example, fluid flows from reservoir 312 to printhead assembly 302. In one example, printhead assembly 302 and fluid supply assembly 310 are housed together in an inkjet or fluid-jet print cartridge or pen. In another example, fluid supply assembly 310 is separate from printhead assembly 302 and supplies fluid to printhead assembly 302 through an interface connection 313, such as a supply tube and/or valve.
Carriage assembly 316 positions printhead assembly 302 relative to print media transport assembly 318, and print media transport assembly 318 positions print media 324 relative to printhead assembly 302. Thus, a print zone 326 is defined adjacent to nozzles 309 in an area between printhead assembly 302 and print media 324. In one example, printhead assembly 302 is a scanning type printhead assembly such that carriage assembly 316 moves printhead assembly 302 relative to print media transport assembly 318. In another example, printhead assembly 302 is a non-scanning type printhead assembly such that carriage assembly 316 fixes printhead assembly 302 at a prescribed position relative to print media transport assembly 318.
Electronic controller 320 communicates with printhead assembly 302 through a communication path 303, carriage assembly 316 through a communication path 317, and print media transport assembly 318 through a communication path 319. In one example, when printhead assembly 302 is mounted in carriage assembly 316, electronic controller 320 and printhead assembly 302 may communicate via carriage assembly 316 through a communication path 301. Electronic controller 320 may also communicate with fluid supply assembly 310 such that, in one implementation, a new (or used) fluid supply may be detected.
Electronic controller 320 receives data 328 from a host system, such as a computer, and may include memory for temporarily storing data 328. Data 328 may be sent to fluid ejection system 300 along an electronic, infrared, optical or other information transfer path. Data 328 represent, for example, a document and/or file to be printed. As such, data 328 form a print job for fluid ejection system 300 and includes at least one print job command and/or command parameter.
In one example, electronic controller 320 provides control of printhead assembly 302 including timing control for ejection of fluid drops from nozzles 309. As such, electronic controller 320 defines a pattern of ejected fluid drops which form characters, symbols, and/or other graphics or images on print media 324. Timing control and, therefore, the pattern of ejected fluid drops, is determined by the print job commands and/or command parameters. In one example, logic and drive circuitry forming a portion of electronic controller 320 is located on printhead assembly 302. In another example, logic and drive circuitry forming a portion of electronic controller 320 is located off printhead assembly 302.
Electronic controller 320 may also receive the sensed temperature from each of the at least two fluid ejection dies 308 via thermal sense monitor 305. Electronic controller 320 may use the sensed temperature from each of the at least two fluid ejection dies 308 for numerous purposes, such as to control the temperature of each of the at least two fluid ejection dies 308 to achieve optimal printing performance.
Fluid reservoir 404 supplies fluid to each of the at least two fluid ejection dies 408. In one example, fluid reservoir 404 supplies black ink to one fluid ejection die 408 and colored ink to another fluid ejection die 408. In other examples, multiple fluid reservoirs may be included to supply different colors of printing fluid to fluid ejection dies 408. As such, in one example, fluid flows from reservoir 404 to each fluid ejection die 408 through an interface connection 406, such as a supply tube and/or valve. In one example, fluid reservoir 404, the at least two fluid ejection dies 408, and thermal sense monitor 412 are housed together within housing 402 to form an inkjet or fluid-jet print cartridge or pen.
Although specific examples have been illustrated and described herein, a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.
Filing Document | Filing Date | Country | Kind |
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PCT/US2018/021756 | 3/9/2018 | WO | 00 |