Patent Application
20140267488
The present exemplary embodiment relates generally to techniques for measuring a response to actuation of an electro-mechanical transducer in a print head assembly for an inkjet printing system. It finds particular application in methods and measurement devices for measuring the response of the transducer based on monitoring signals in the ground path of the transducer. However, it is to be appreciated that the exemplary embodiments described herein are also amenable to using recordings of the response signal in conjunction with subsequent operational or diagnostic testing of the transducer, print head assembly, or other components of the inkjet printing system.
Piezo element self-sensing is a method used in an inkjet printing system to gather information on the performance of ejectors in an inkjet print head. The technique involves recording drive/response signals from the actuation piezo elements in response to fluidic pressure waves immediately after the electrical signal that drives the piezo to eject a droplet. This technique was originally patented in the United States by Océ N. V. of The Netherlands (see, e.g., U.S. Pat. Nos. 6,682,162; 6,910,751; 6,926,388; 7,357,474; 7,488,062; and 7,703,893). The Océ patents describe the technique and various ways to either implement it or determine ejector characteristics. A similar technique was patented in the United States by Samsung (see, e.g., U.S. Pat. No. 7,866,781). The Samsung patent uses a differential configuration on the drive voltage coupled to a fixed capacitor that is matched to the capacitance of the piezo actuator.
The following documents are fully incorporated herein by reference: 1) U.S. Pat. No. 6,682,162 to Simmons et al.; 2) U.S. Pat. No. 6,910,751 to Groninger et al.; 3) U.S. Pat. No. 6,926,388 to Groninger et al.; 4) U.S. Pat. No. 7,357,474 to Groninger et al.; 5) U.S. Pat. No. 7,488,062 to Boesten et al.; 6) U.S. Pat. No. 7,703,893 to Groninger et al.; and 7) U.S. Pat. No. 7,866,781 to Kim et al.
In one aspect, a method for measuring a response to actuation of an electro-mechanical transducer in a print head assembly for an inkjet printing system is provided. In one embodiment, the method includes: providing at least a portion of a return path to system ground for an electro-mechanical transducer through a sensing circuit, wherein the electro-mechanical transducer is associated with an ink chamber in a print head assembly for an inkjet printing system, wherein the electro-mechanical transducer is configured to transfer energy to contents of the ink chamber in response to an actuation of the electro-mechanical transducer in conjunction with electronics controller and waveform amplifier modules of the inkjet printing system; monitoring a ground signal at an electro-mechanical transducer-side of the sensing circuit; monitoring a reference signal at a system ground-side of the sensing circuit; and generating a difference signal indicative of a difference between the ground and reference signals.
In another aspect, an apparatus for measuring a response to actuation of an electro-mechanical transducer in a print head assembly for an inkjet printing system is provided. In one embodiment, the apparatus includes a sensing circuit and a measurement circuit. The sensing circuit is configured to provide at least a portion of a return path to system ground for an electro-mechanical transducer. The electro-mechanical transducer is associated with an ink chamber in a print head assembly for an inkjet printing system. The electro-mechanical transducer is configured to transfer energy to contents of the ink chamber in response to an actuation of the electro-mechanical transducer in conjunction with electronics controller and waveform amplifier modules of the inkjet printing system. The measurement circuit is in operative communication with the sensing circuit and configured to monitor a ground signal at an electro-mechanical transducer-side of the sensing circuit and a reference signal at a system ground-side of the sensing circuit. The measurement circuit is also configured to generate a difference signal indicative of a difference between the ground and reference signals.
In yet another aspect, an apparatus for measuring a response to actuation of an electro-mechanical transducer in a print head assembly for an inkjet printing system is provided. In one embodiment, the apparatus includes a sensing circuit and an multi-stage amplifier circuit. The sensing circuit is configured to provide at least a portion of a return path to system ground for an electro-mechanical transducer. The electro-mechanical transducer is associated with an ink chamber in a print head assembly for an inkjet printing system. The electro-mechanical transducer is configured to transfer energy to contents of the ink chamber in response to an actuation of the electro-mechanical transducer in conjunction with electronics controller and waveform amplifier modules of the inkjet printing system. The multi-stage amplifier circuit is in operative communication with the sensing circuit and includes first, second, and third stage amplifier circuits. The first stage amplifier circuit is configured to monitor a ground signal at an electro-mechanical transducer-side of the sensing circuit and a reference signal at a system ground-side of the sensing circuit. The first stage amplifier circuit is also configured to generate a difference signal indicative of a difference between the ground and reference signals. The second and third stage amplifier circuits are in operative communication with the first stage amplifier circuit and configured to condition and amplify the difference signal to generate a response signal indicative of a response of the electro-mechanical transducer to fluidic pressure waves within the ink chamber after actuation of the electro-mechanical transducer.
This disclosure describes various embodiments of methods and measurement devices for measuring a response to actuation of an electro-mechanical transducer in a print head assembly for an inkjet printing system. The resulting response signal is based on the monitoring of signals in the return ground path for the transducer. The response signal is indicative of the response of the transducer to fluidic pressure waves within an ink chamber of the print head assembly after actuation of the transducer. A record of the response signal over a select time period can be used for subsequent operational or diagnostic testing of the transducer, print head assembly, or other components of the printing system.
The transducer, for example, may be a piezoelectric transducer which may also be referred to as a piezo actuator or piezo element. Piezo self-sensing, for example, can be used to gather information on the performance of ejectors in an inkjet print head. Signals are recorded from an actuation piezo element in response to fluidic pressure waves immediately after the electrical signal that drives the piezo to eject a droplet. The piezo electrical response is sensed by detecting a signal indicative of the ground return current for the piezo.
In one embodiment, an electronic circuit is used to detect the piezo ground return signal from one or more ejectors of an inkjet print head by monitoring the ground current between the print process control electronics/waveform amplifiers and the print head electronics. The return ground current is a shared connection to the piezo actuators. For example, a sensing resistor with less than one ohm resistance may be used in the ground current path to tap a voltage signal at a select portion of the ground return path. The voltage signal is fed into multiple gain stages with frequency filters and overvoltage protection diodes to limit overdriving the amplifiers. The diodes improve performance of the gain stage by preventing the corresponding amplifier from going into saturation.
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In another embodiment of the process 600, the electro-mechanical transducer includes a piezoelectric transducer, any suitable transducer, or any suitable actuator/sensor component in any suitable combination. In yet another embodiment of the process 600, the sensing circuit includes a current shunt device. In still another embodiment of the process 600, the sensing circuit includes a sensing resistor. In still yet another embodiment of the process 600, the difference signal is generated by at least one of a differential amplifier circuit, an operational amplifier circuit, an multi-stage amplifier circuit, or any suitable amplifier circuit in any suitable combination.
With reference to
In another embodiment of the process 700, the conditioning includes at least one of high-pass filtering, band-pass filtering, low-pass filtering, or any suitable form of signal conditioning in any suitable combination. For example, high-pass and low-pass filtering can be arranged to produce band-pass filtering. In yet another embodiment of the process 700, the response signal is generated using at least one of a differential amplifier circuit, an operational amplifier circuit, an multi-stage amplifier circuit, or any suitable amplifier circuit in any suitable combination.
In still another embodiment of the process 700, the response signal is generated using an multi-stage amplifier circuit in which a first amplifier stage is used to generate the difference signal and second and third amplifier stages are used to generate the response signal. In this embodiment, the first amplifier stage may include an instrumentation amplifier. In a further embodiment, the second and third amplifier stages include overvoltage protection diodes to limit overdriving the corresponding amplifier stage. In this embodiment, the diodes improve performance of the amplifier stages by preventing the corresponding amplifier from going into saturation. In another further embodiment, the conditioning includes using a high-pass filter between the first and second amplifier stages and using a low-pass filter between the second and third amplifier stages. In an even further embodiment, the low-pass filter includes a two-stage low-pass filter.
In still yet another embodiment, the process 700 also includes recording the response signal over a select time period for subsequent testing of at least one of the print head assembly or inkjet printing system. In another embodiment, the process 700 also includes at least temporarily storing a recording of the response signal over a select time period in a storage device for the subsequent testing of at least one of the print head assembly or inkjet printing system.
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In another embodiment, the electro-mechanical transducer 808 includes a piezoelectric transducer. In yet another embodiment of the measurement circuit 800, the sensing circuit 802 includes a current shunt device. In still another embodiment of the measurement circuit 800, the sensing circuit 802 includes a sensing resistor. In still yet another embodiment, the measurement circuit 800 is configured to use at least one of a differential amplifier circuit, an operational amplifier circuit, an multi-stage amplifier circuit, or any suitable amplifier circuit in any suitable combination in conjunction with generating the difference signal.
In another embodiment, the measurement circuit 800 is also configured to condition and amplify the difference signal to generate a response signal indicative of a response of the electro-mechanical transducer 808 to fluidic pressure waves within the ink chamber 810 after actuation of the electro-mechanical transducer 808. In a further embodiment, the measurement circuit 800 is configured to use at least one of high-pass filtering, band-pass filtering, low-pass filtering, or any suitable form of signal conditioning in any suitable combination in conjunction with the conditioning. For example, high-pass and low-pass filtering can be arranged to produce band-pass filtering. In another further embodiment, the measurement circuit 800 is configured to use at least one of a differential amplifier circuit, an operational amplifier circuit, an multi-stage amplifier circuit, or any suitable amplifier circuit in any suitable combination in conjunction with generating the response signal.
In yet another further embodiment, the measurement circuit 800 includes an multi-stage amplifier circuit with first, second, and third amplifier stages. In this embodiment, the first amplifier stage is configured to generate the difference signal and the second and third amplifier stages are configured to generate the response signal. In the embodiment being described, the first amplifier stage may include an instrumentation amplifier. In an even further embodiment, the second and third amplifier stages each includes overvoltage protection diodes configured to limit overdriving the corresponding amplifier stage. In this embodiment, the diodes improve performance of the amplifier stages by preventing the corresponding amplifier from going into saturation. In another even further embodiment, the multi-stage amplifier circuit also includes a high-pass filter between the first and second amplifier stages in conjunction with conditioning the difference signal. In this embodiment, the multi-stage amplifier circuit also includes a low-pass filter between the second and third amplifier stages in conjunction with conditioning an intermediate signal associated with the response signal. In an even yet further embodiment, the low-pass filter includes a two-stage low-pass filter.
In still another further embodiment, the measurement circuit 800 is also configured to facilitate recording of the response signal over a select time period for subsequent testing of at least one of the print head assembly 812, inkjet printing system 814, or any combination of components of the inkjet printing system 814. In still yet another further embodiment, the measurement device 800 also includes a storage device in operative communication with the measurement circuit and configured to at least temporarily store a recording of the response signal over a select time period for subsequent testing of at least one of the print head assembly 812, inkjet printing system 814, or any combination of components of the inkjet printing system 814.
In other embodiments, the storage device may be an integral component of the measurement circuit 800, print head assembly 812, electronics controller module 818, or any suitable component of the inkjet printing system 814. Similarly, in other embodiments, the measurement device 800 may be an integral component of the print head assembly 812, electronics controller module 818, or any suitable component of the inkjet printing system 814.
With reference to
The multi-stage amplifier circuit 904 is in operative communication with the sensing circuit 902 and includes first, second, and third stage amplifier circuits 922, 924, 926. The first stage amplifier circuit 922 is configured to monitor a ground signal at an electro-mechanical transducer-side 928 of the sensing circuit 902 and a reference signal at a system ground-side 930 of the sensing circuit 908. The first stage amplifier circuit 922 is also configured to generate a difference signal indicative of a difference between the ground and reference signals. The first amplifier circuit 922 may include an instrumentation amplifier. The second and third stage amplifier circuits 924, 926 are in operative communication with the first stage amplifier circuit 922 and configured to condition and amplify the difference signal to generate a response signal indicative of a response of the electro-mechanical transducer 908 to fluidic pressure waves within the ink chamber 910 after actuation of the electro-mechanical transducer 908. As shown, the first, second, and third stage amplifier circuits 922, 924, 926 may be arranged in series.
In another embodiment, the electro-mechanical transducer 908 includes a piezoelectric transducer. In yet another embodiment of the measurement circuit 900, the sensing circuit 902 includes a current shunt device. In still another embodiment of the measurement circuit 900, the sensing circuit 902 includes a sensing resistor. In still yet another embodiment of the measurement circuit 900, the second and third stage amplifier circuits 924, 926 are also configured to use at least one of high-pass filtering, band-pass filtering, low-pass filtering, or any suitable form of signal conditioning in any suitable combination in conjunction with the conditioning. For example, high-pass and low-pass filtering can be arranged to produce band-pass filtering. In another embodiment of the measurement circuit 900, the second and third stage amplifier circuits 924, 926 each include overvoltage protection diodes configured to limit overdriving the corresponding amplifier circuit. In this embodiment, the diodes improve performance of the amplifier circuits by preventing the corresponding amplifier from going into saturation.
In yet another embodiment of the measurement circuit 900, the multi-stage amplifier circuit 904 also includes a high-pass filter between the first and second stage amplifier circuits 922, 924 in conjunction with conditioning the difference signal. In this embodiment, the multi-stage amplifier circuit 904 also includes a low-pass filter between the second and third stage amplifier circuits 924, 926 in conjunction with conditioning an intermediate signal associated with the response signal. In a further embodiment, the low-pass filter includes a two-stage low-pass filter.
In still another embodiment of the measurement circuit 900, the multi-stage amplifier circuit 904 is configured to facilitate recording of the response signal over a select time period for subsequent testing of at least one of the print head assembly 912, inkjet printing system 914, or any combination of components of the inkjet printing system 914. In still yet another embodiment, the measurement circuit 900 also includes a storage device in operative communication with the multi-stage amplifier circuit 904 and configured to at least temporarily store a recording of the response signal over a select time period for subsequent testing of at least one of the print head assembly 912, inkjet printing system 914, or any combination of components of the inkjet printing system 914.
In other embodiments, the storage device may be an integral component of the measurement circuit 900, print head assembly 912, electronics controller module 918, or any suitable component of the inkjet printing system 914. Similarly, in other embodiments, the measurement device 900 may be an integral component of the print head assembly 912, electronics controller module 918, or any suitable component of the inkjet printing system 914.
It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
