Patent Grant
10357967
The following disclosure relates to the field of image formation, and in particular, to printheads and the use of printheads.
Image formation is a procedure whereby a digital image is recreated on a medium by propelling droplets of ink or another type of print fluid onto a medium, such as paper, plastic, a substrate for 3D printing, etc. Image formation is commonly employed in apparatuses, such as printers (e.g., inkjet printer), facsimile machines, copying machines, plotting machines, multifunction peripherals, etc. The core of a typical jetting apparatus or image forming apparatus is one or more liquid-droplet ejection heads (referred to generally herein as “printheads”) having nozzles that discharge liquid droplets, a mechanism for moving the printhead and/or the medium in relation to one another, and a controller that controls how liquid is discharged from the individual nozzles of the printhead onto the medium in the form of pixels.
A typical printhead includes a plurality of nozzles aligned in one or more rows along a discharge surface of the printhead. Each nozzle is part of a “jetting channel”, which includes the nozzle, a pressure chamber, and an actuator, such as a piezoelectric actuator. A printhead also includes a drive circuit that controls when each individual jetting channel fires based on image data. To jet from a jetting channel, the drive circuit provides a jetting pulse to the actuator, which causes the actuator to deform a wall of the pressure chamber. The deformation of the pressure chamber creates pressure waves within the pressure chamber that eject a droplet of print fluid (e.g., ink) out of the nozzle.
One problem with printheads is that a print fluid may settle and thicken in the pressure chamber at or near the nozzle where the print fluid is exposed to air. The viscosity of the print fluid may change due to exposure to air and sitting idle in a pressure chamber, which can negatively affect the jetting characteristics of the jetting channels. It is therefore desirable to design printheads that are less susceptible to these and other problems.
Embodiments described herein provide enhanced drive circuits for printheads. A drive circuit as described herein selectively applies a drive waveform to actuators for jetting channels based on image data. For example, if the image data specifies jetting for a pixel at a jetting channel, then the drive circuit may apply one or more jetting pulses from the drive waveform to an actuator of the jetting channel. If the image data specifies non-jetting for a pixel at a jetting channel, then the drive circuit converts a jetting pulse from the drive waveform to a non-jetting or tickle pulse that is applied to an actuator of the jetting channel. The non-jetting pulse causes a fluid meniscus at the nozzle of the jetting channel to move without ejecting a droplet from the jetting channel. Thus, even though a droplet is not ejected from the jetting channel, the fluid meniscus is moved so that the print fluid doesn't settle or at least does not settle as fast. One advantage to converting a jetting pulse to a non-jetting pulse is that the drive waveform may contain a train of uniform jetting pulses, and does not have to be altered to include both non-jetting pulses and jetting pulses. This allows for the frequency of the jetting pulses on the drive waveform to be increased, which may increase printing speed of the printhead.
One embodiment comprises a printhead having one or more rows of jetting channels configured to jet droplets of a print fluid. Each jetting channel comprises an actuator, a pressure chamber, and a nozzle. The printhead also has a head driver configured to receive one or more data signals, and to receive a drive waveform comprising a series of jetting pulses. Each of the jetting pulses has an amplitude configured to eject a droplet from a jetting channel. Responsive to the data signal(s) indicating jetting by a jetting channel during a jetting period, the head driver is configured to apply one or more of the jetting pulses on the drive waveform to the actuator of the jetting channel. Responsive to the data signal(s) indicating non-jetting by the jetting channel during the jetting period, the head driver is configured to clip the amplitude of a jetting pulse on the drive waveform to generate a non-jetting pulse that is applied to the actuator of the jetting channel. The non-jetting pulse is configured to activate the actuator of the jetting channel to create movement of a fluid meniscus at the nozzle of the jetting channel without ejecting a droplet.
Another embodiment comprises a drive circuit for a printhead having one or more rows of jetting channels configured to jet droplets of a print fluid using actuators. The drive circuit includes a head driver comprising an electrical interface configured to receive one or more data signals representing data to be printed by the printhead. The head driver further comprises an electrical bus configured to receive a drive waveform comprising a series of jetting pulses. Each of the jetting pulses has an amplitude configured to eject a droplet from a jetting channel. The head driver further comprises a plurality of switching elements, where a switching element of the plurality of switching elements is connected between the electrical bus and an actuator of a jetting channel. The switching element is configured to close to enable a conductive path between the electrical bus and the actuator, and to open to disable the conductive path. Responsive to the data signal(s) indicating jetting by the jetting channel during a jetting period, the switching element is configured to apply at least one of the jetting pulses on the drive waveform to the actuator. Responsive to the data signal(s) indicating non-jetting by the jetting channel during the jetting period, the switching element is configured to clip the amplitude of a jetting pulse on the drive waveform to generate a non-jetting pulse that is applied to the actuator. The non-jetting pulse is configured to activate the actuator of the jetting channel to create movement of a fluid meniscus at a nozzle of the jetting channel without ejecting a droplet.
Another embodiment comprises a method for driving a printhead comprising one or more rows of jetting channels configured to jet droplets of a print fluid. The method comprises receiving one or more data signals, and receiving a drive waveform comprising a series of jetting pulses. The method further comprises selectively applying the drive waveform to actuators of the jetting channels based on the data signal(s). When the data signal(s) indicate jetting by a jetting channel during a jetting period, selectively applying the drive waveform comprises applying one or more of the jetting pulses on the drive waveform to an actuator of the jetting channel. When the data signal(s) indicate non-jetting by the jetting channel during the jetting period, selectively applying the drive waveform comprises clipping the amplitude of a jetting pulse on the drive waveform to generate a non-jetting pulse that is applied to the actuator of the jetting channel
The above summary provides a basic understanding of some aspects of the specification. This summary is not an extensive overview of the specification. It is intended to neither identify key or critical elements of the specification nor delineate any scope particular embodiments of the specification, or any scope of the claims. Its sole purpose is to present some concepts of the specification in a simplified form as a prelude to the more detailed description that is presented later.
Some embodiments of the present disclosure are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings.
The figures and the following description illustrate specific illustrative embodiments. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the embodiments and are included within the scope of the embodiments. Furthermore, any examples described herein are intended to aid in understanding the principles of the embodiments, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the inventive concept(s) is not limited to the specific embodiments or examples described below, but by the claims and their equivalents.
Jetting channel 302 as shown in
Drive circuit 400 also includes a head driver 410 coupled to piezoelectric actuators 310. Head driver 410 may be an example of electronics 226 of printhead 104 as shown in
Piezoelectric actuators 310 are the actuating devices for jetting channels 302 that act to jet a droplet out of a nozzle 314 in response to a jetting pulse. A piezoelectric actuator 310, for example, converts electrical energy directly into linear motion. To jet from a jetting channel 302, one or more jetting pulses of the drive waveform 404 are provided to a piezoelectric actuator 310. A jetting pulse causes a deformation, physical displacement, or stroke of a piezoelectric actuator 310, which in turn acts to deform a wall of pressure chamber 312 (e.g., diaphragm 316). Deformation of the chamber wall generates pressure waves inside pressure chamber 312 that force a droplet from jetting channel 302 (when specific conditions are met). A standard jetting pulse is therefore able to cause a droplet to be jetted from a jetting channel 302 with the desired properties when the jetting channel 302 is at rest.
The following provides an example of jetting a droplet from a jetting channel using jetting pulse 500, such as from jetting channel 302 in
Head driver 410 also includes a plurality of switching elements 606, which may also be referred to as transmission gates. A switching element 606 is associated with an individual jetting channel 302, which means that an individual switching element 606 is electrically coupled to a piezoelectric actuator 310 of a jetting channel 302 (which is illustrated as a capacitor). A switching element 606 is configured to selectively apply the drive waveform 404 to piezoelectric actuators 310 of jetting channels 302 based on a data signal(s). To selectively apply the drive waveform 404, a switching element 606 is configured to close to form or enable a conductive path between electrical bus 604 and a piezoelectric actuator 310, and to open to break or disable the conductive path. Switching element 606 may comprise a transistor, a logic switch, a gate or gate array, etc., that receives input and control signals, and outputs an output signal when the switch is closed.
Head driver 410 may also include a plurality of selectors 608 that are coupled to switching elements 606 or are integrated with switching elements 606. A selector 608 is a logic device or processing device that selects a gating signal for a switching element 606 of a jetting channel 302 based on one or more data signals. Electrical interface 602 is configured to receive a plurality of gating signals 610-613 from control signal generator 406 that control switching elements 606. A gating signal 610-613 is a digital signal that triggers passage of another signal (i.e., a drive waveform) or blocks the other signal. The timing of when a gating signal 610-613 is “on” or “off” defines time windows where drive waveform 404 is allowed to pass to a piezoelectric actuator 310. For instance, when a gating signal 610-613 is on, a switching element 606 will close and apply the drive waveform 404 (represented by Vcom) to a piezoelectric actuator 310 that is electrically coupled to that switching element 606 for the time period in which the switching element 606 is closed. When a gating signal 610-613 is off, a switching element 606 will open and the drive waveform 404 is blocked from a piezoelectric actuator 310 for the time period in which the switching element 606 is open.
In this embodiment, three of the gating signals 611-613 represent “active” gating signals for jetting by an active jetting channel during a jetting period. An active jetting channel is a jetting channel that is designated for jetting based on the data signal(s). When selector 608 selects one of the active gating signals 611-613 for a jetting channel 302, the active gating signal 611-613 will allow one or more jetting pulses on the drive waveform 404 to pass to a piezoelectric actuator 310 of the jetting channel 302 to cause a jetting of one or more droplets for a pixel.
Also in this embodiment, one of the gating signals 610 represents an “inactive” gating signal for an inactive jetting channel during a jetting period. An inactive jetting channel is a jetting channel that is not designated for jetting based on the data signal(s). When selector 608 selects the inactive gating signal 610 for a jetting channel 302, the inactive gating signal 610 will allow only a portion of a jetting pulse 500 to pass to a piezoelectric actuator 310 of a jetting channel 302 without causing a jetting of a droplet for a pixel. Inactive gating signal 610 is an enhanced gating signal in this embodiment as it allows a portion of a jetting pulse 500 on drive waveform 404 to pass to a piezoelectric actuator 310 of a jetting channel 302 without causing a jetting of a droplet for a pixel. The pattern or timing of the “on” and “off” states of inactive gating signal 610 converts a jetting pulse 500 on drive waveform 404 to a “non-jetting” or a “tickle” pulse that is applied to a piezoelectric actuator 310. For example, an inactive gating signal 610 is on for a first portion of a leading edge of a jetting pulse, and is off for a remaining portion of the leading edge of a jetting pulse. The inactive gating signal 610 is off for a first portion of a trailing edge of the jetting pulse, and is on for a remaining portion of the trailing edge of the jetting pulse.
A conventional gating signal may block a drive waveform from a piezoelectric actuator 310 to prevent jetting by a jetting channel for a pixel, or may allow a non-jetting pulse on a drive waveform (i.e., the drive waveform is altered to include both jetting pulses and non-jetting pulses) to pass to a piezoelectric actuator 310. In this embodiment, the pattern or timing of inactive gating signal 610 acts to clip the amplitude of a jetting pulse 500 on the drive waveform 404 to generate a non-jetting or tickle pulse that is applied to a piezoelectric actuator 310. A tickle pulse is defined as a pulse having a pulse width and amplitude configured to cause a fluid meniscus at a nozzle 314 of a jetting channel 302 to move without ejecting a droplet. Thus, when a tickle pulse is applied to a piezoelectric actuator 310, the jetting channel 302 will not jet in response to the tickle pulse.
Although four gating signals 610-613 are illustrated in this embodiment, more or less gating signals may be used in other embodiments as long as at least one of the gating signals comprises an inactive gating signal that acts to convert a jetting pulse on a drive waveform to a tickle pulse.
Signal diagram 700 also shows gating signals (GS) 610-613, and the corresponding output signals 710-713 (VDO) that is applied to a piezoelectric actuator 310 by a switching element 606. When a gating signal 610-613 is high or “off”, a switching element 606 is open meaning that drive waveform 404 is blocked from a piezoelectric actuator 310. When a gating signal 610-613 is low or “on”, a switching element 606 is closed meaning that drive waveform 404 is allowed to pass to a piezoelectric actuator 310.
Inactive gating signal 610 (GS0) has a pattern or timing configured to clip the amplitude of a jetting pulse 500 on the drive waveform 404 to generate a non-jetting pulse or tickle pulse on output signal 710, which is described in further detail below. Active gating signal 611 (GS1) is on (e.g., low) for a time window to allow one jetting pulse 500 on drive waveform 404 to pass on output signal 711 to a piezoelectric actuator 310. The single jetting pulse 500 will actuate a piezoelectric actuator 310 of a jetting channel 302 once, resulting in jetting of one droplet from the jetting channel 302. Active gating signal 612 (GS2) is on for a time window to allow two jetting pulses 500 to pass on output signal 712 to a piezoelectric actuator 310. The two jetting pulses 500 will actuate a piezoelectric actuator 310 of a jetting channel 302 twice, resulting in jetting of two droplets from the jetting channel 302. Active gating signal 613 (GS3) is on for a time window to allow three jetting pulses 500 to pass on output signal 713 to a piezoelectric actuator 310. The three jetting pulses 500 will actuate a piezoelectric actuator 310 of a jetting channel 302 three times, resulting in jetting of three droplets from the jetting channel 302. As is evident in
The pattern or timing of inactive gating signal 610 acts to clip the amplitude of jetting pulse 500 to generate a non-jetting pulse 830. To clip the amplitude of a jetting pulse means to limit a pulse being applied to a piezoelectric actuator 310 to a predetermined voltage level, which is a non-jetting voltage 808. At or before time TS, inactive gating signal 610 transitions from off to on at time T1. With inactive gating signal 610 on, a switching element 606 will allow a portion of the jetting pulse 500 (i.e., a portion of the leading edge 504) to pass to a piezoelectric actuator 310 on output signal 710 during time window 801. The portion of the jetting pulse 500 that is allowed to pass during time window 801 generates a leading edge 822 of non-jetting pulse 830. Inactive gating signal 610 transitions from on to off at time T2 when the leading edge 504 of jetting pulse 500 reaches the non-jetting voltage 808 but before reaching the jetting voltage 502. With inactive gating signal 610 off, switching element 606 will block a portion of the jetting pulse 500 from piezoelectric actuator 310 on output signal 710 during time window 802. Because jetting pulse 500 is blocked during time window 802, no signal will be output on output signal 710 from switching element 606. Thus, this portion of non-jetting pulse 830 is illustrated as a dotted line, and represents a peak amplitude 823. Inactive gating signal 610 transitions from off to on at time T3 when the trailing edge 505 of jetting pulse 500 reaches the non-jetting voltage 808 but before reaching the baseline voltage 501. With inactive gating signal 610 on, switching element 606 will allow a portion of the jetting pulse 500 (i.e., a portion of the trailing edge 505) to pass to a piezoelectric actuator 310 on output signal 710 during time window 803. The portion of the jetting pulse 500 that is allowed to pass during time window 803 generates a trailing edge 824 of non-jetting pulse 830. Inactive gating signal 610 then transitions from on to off at time T4 after or when the trailing edge 505 of jetting pulse 500 reaches the baseline voltage 501.
The pattern or timing of inactive gating signal 610 therefore converts jetting pulse 500 into a non-jetting pulse 830. Non-jetting pulse 830 may be a trapezoidal pulse like jetting pulse 500, but the amplitude of non-jetting pulse 830 is limited to a threshold amplitude that will not cause jetting at a jetting channel 302. The timing of T2 and T3 may be selected so that the maximum voltage of non-jetting pulse 830 is equal to or less than the non-jetting voltage 808. Peak amplitude 823 of non-jetting pulse 830 is shown as a flat line between leading edge 822 and trailing edge 824. A piezoelectric actuator 310 may store potential energy, like a capacitor, so a voltage is retained in a piezoelectric actuator 310 after firing. This stored voltage of a piezoelectric actuator 310 is illustrated as the flat line between leading edge 822 and trailing edge 824 of non-jetting pulse 830.
Another technical benefit is that drive waveform 404 does not have to be altered to create a non-jetting pulse, and may consist solely of jetting pulses 500. A conventional drive waveform may be altered to include both non-jetting pulses and jetting pulses. But there is a time penalty for having non-jetting pulses and jetting pulses on the same drive waveform. Because inactive gating signal 610 acts to convert a jetting pulse 500 to a non-jetting pulse 830, drive waveform 404 may consist of a train of jetting pulses 500, which allows for higher frequency printing.
The pattern or timing of inactive gating signal 610 acts to clip the amplitude of jetting pulse 1000 to generate a non-jetting pulse 830. At or before time TS, inactive gating signal 610 transitions from off to on at time T1. With inactive gating signal 610 on, a switching element 606 will allow a portion of the jetting pulse 1000 (i.e., a portion of the leading edge 1004) to pass to a piezoelectric actuator 310 on output signal 710 during time window 801. The portion of the jetting pulse 1000 that is allowed to pass during time window 801 generates leading edge 822 of non-jetting pulse 830. Inactive gating signal 610 transitions from on to off at time T2 during step 1010 on leading edge 1004 of jetting pulse 1000. With inactive gating signal 610 off, switching element 606 will block a portion of the jetting pulse 1000 from piezoelectric actuator 310 on output signal 710 during time window 802. Because jetting pulse 1000 is blocked during time window 802, no signal will be output on output signal 710 from switching element 606. Thus, this portion of non-jetting pulse 830 is illustrated as a dotted line, and represents a peak amplitude 823. Inactive gating signal 610 transitions from off to on at time T3 during step 1012 on trailing edge 1005 of jetting pulse 1000. With inactive gating signal 610 on, switching element 606 will allow a portion of the jetting pulse 1000 (i.e., a portion of the trailing edge 1005) to pass to a piezoelectric actuator 310 on output signal 710 during time window 803. The portion of the jetting pulse 1000 that is allowed to pass during time window 803 generates trailing edge 824 of non-jetting pulse 830. Inactive gating signal 610 then transitions from on to off at time T4 after or when the trailing edge 1005 of jetting pulse 1000 reaches the baseline voltage 501.
One assumption for method 1200 is that the printhead includes one or more rows of jetting channels, such as jetting channels 302 in printhead 104. Head driver 410 receives one or more data signals representing data to be printed by the printhead (step 1202). Head driver 410 also receives a drive waveform comprising a series of jetting pulses (step 1204). Each of the jetting pulses has an amplitude configured to eject a droplet from a jetting channel. Head driver 410, as illustrated in
When using gating signals such as this, step 1208 of method 1200 may include selecting an active gating signal for a jetting channel in response to the data signal(s) indicating jetting by the jetting channel (step 1406), and controlling the switching element 606 to close when the active gating signal is on to apply one or more jetting pulses to the actuator (step 1408). Step 1210 of method 1200 may include selecting an inactive gating signal for a jetting channel in response to the data signal(s) indicating non-jetting by the jetting channel (step 1410), and controlling the switching element 606 to close for a first time window while the inactive gating signal is on, to open for a second time window when the inactive gating signal transitions from on to off, and to close for a third time window when the inactive gating signal transitions from off to on to generate the non-jetting pulse that is applied to the actuator (step 1412). Additional method steps may be employed in addition to those described above, and such method steps may be gleaned from the description provided above.
Any of the various elements or modules shown in the figures or described herein may be implemented as hardware, software, firmware, or some combination of these. For example, an element may be implemented as dedicated hardware. Dedicated hardware elements may be referred to as “processors”, “controllers”, or some similar terminology. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, a network processor, application specific integrated circuit (ASIC) or other circuitry, field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), non-volatile storage, logic, or some other physical hardware component or module.
Also, an element may be implemented as instructions executable by a processor or a computer to perform the functions of the element. Some examples of instructions are software, program code, and firmware. The instructions are operational when executed by the processor to direct the processor to perform the functions of the element. The instructions may be stored on storage devices that are readable by the processor. Some examples of the storage devices are digital or solid-state memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media.
Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. The scope of the invention is defined by the following claims and any equivalents thereof.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6331052 | Murai | Dec 2001 | B1 |
| 20120262512 | Oshima | Oct 2012 | A1 |
