Patent Publication Number: US-2007103498-A1

Title: Inkjet printhead

Description:
This application claims priority as a divisional application of U.S. application Ser. No. 10/865,655 filed on Jun. 10, 2004, entitled “Inkjet Printhead.” 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention generally relates to printing apparatus and in some embodiments, more particularly, to inkjet printers.  
      Inkjet print heads typically require a well-controlled substrate temperature to maintain a consistent ink viscosity and jetting performance. Currently, inkjet print heads include a temperature sense resistor (TSR) integrated into a chip to monitor the substrate temperature. The chip can also have dedicated power field effect transistors (FETs) to control the heating elements, as in U.S. Pat. No. 6,102,515 which is hereby incorporated by reference insofar as it relates to the use of FETs to control heating elements in print heads. In some examples, a printer control unit periodically monitors the TSR(s) to determine the substrate temperature. Then, the control unit turns heating elements on and off, accordingly, to maintain the proper substrate temperature for optimum jetting performance.  
     SUMMARY OF THE INVENTION  
      In some conventional print head designs, the positions of one or more TSRs can interfere with fluid flow to the heater nozzle of the print head (e.g., presenting detrimental topographical effects when placed over the fluid flow paths). Also, some print heads have TSRs that are located sufficiently far from the heating elements (which are typically positioned over portions of the ink flow) to generate inaccurate temperature readings in some conditions.  
      In some embodiments of the present invention, one or more temperature sense elements can be positioned with respect to the inkjet print head such that the temperature sense element(s) can provide accurate temperature readings while not interfering with ink flow or while providing reduced interference with ink flow. In some embodiments, the temperature sense elements include TSRs.  
      Some embodiments of the present invention provide an inkjet print head including a substrate, and comprising at least one actuator positioned proximate to a surface of the substrate; a control circuit coupled to the at least one actuator for controlling the actuator; and a temperature sense element positioned substantially between the at least one actuator and the control circuit.  
      In some embodiments, an inkjet print head is provided, and comprises at least one actuator positioned proximate to a surface of a substrate; and a temperature sense element embedded in the substrate and positioned such that at least a portion of the temperature sense element is in substantial overlapping relationship with at least a portion of the at least one actuator.  
      Some embodiments of the present invention provide an inkjet print head comprising a first plurality of heating elements forming a first heating array, the first heating array positioned to heat ink in at least a portion of a first plurality of ink chambers; a second plurality of heating elements forming a second heating array, the second heating array positioned to heat ink in at least a portion of a second plurality of ink chambers; a first control circuit coupled to the first heating array for controlling the first heating array; a second control circuit coupled to the second heating array for controlling the second heating array; a first temperature sense element positioned substantially between the first heating array and the first control circuit; and a second temperature sense element positioned substantially between the second heating array and the second control circuit.  
      In some embodiments, a method of controlling a temperature of an inkjet print head having a control circuit operatively coupled to a temperature sense element is provided, and comprises: heating ink in an ink chamber with a heater; and sensing a temperature of a substrate with the temperature sense element in at least one of a first location substantially between the control circuit and the heater and a second location in which the temperature sense element at least partially overlaps the heater. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of an inkjet print head.  
       FIG. 2  is a partial exploded view of the print head illustrated in  FIG. 1 .  
       FIG. 3  is a plan view of a portion of an inkjet print head according to one embodiment.  
       FIG. 4  is a plan view of a portion of an inkjet print head according to another embodiment. 
    
    
     DETAILED DESCRIPTION  
      Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof, and can include additional items. The terms “mounted,” “connected” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.  
       FIG. 1  illustrates an inkjet print head  10  having a housing  12  that defines a nosepiece  13  and an ink reservoir  14  containing ink or an insert (e.g., a foam insert or other fluid-retaining insert) saturated with ink. The inkjet print head  10  illustrated in  FIG. 1  has been inverted to illustrate a nozzle portion  15  of the print head  10 . The nozzle portion  15  is located at least partially on a bottom surface  111  of the nosepiece  13  for transferring ink from the ink reservoir  14  onto a printing medium, such as, for example, paper (including without limitation stock paper, stationary, tissue paper, homemade paper, and the like), film, tape, photo paper, a combination thereof, and any other medium used or usable in inkjet printing apparatus. The nozzle portion  15  can include a substrate (e.g., a chip  16 , not visible in  FIG. 1 ) and a nozzle plate  20  having a plurality of nozzles  22  that define a nozzle arrangement and from which ink drops are ejected onto a printing medium that is advanced through a printing apparatus (not shown).  
      The chip  16  can be formed of a variety of materials including, without limitation, various forms of doped or non-doped silicon, doped or non-doped germanium, or any other semiconducting material. In some embodiments, the chip  16  is positioned to be in electrical communication with conductive traces  17  provided on an underside of a tape member  18 . The chip  16  is hidden from view in the assembled print head  10  illustrated in  FIG. 1 , and is attached to the nozzle plate  20  in a removed area or cutout portion  19  of the tape member  18  such that an outwardly facing surface  21  of the nozzle plate  20  is generally flush with and parallel to an outer surface  29  of the tape member  18  for directing ink onto a printing medium via the plurality of nozzles  22  in fluid communication with the ink reservoir  14 . In other embodiments, the nozzle plate  20  can have different positions and orientations with respect to the tape member  18 , or be formed from the tape member  18 , while still falling within the spirit and scope of the present invention.  
      In the illustrated embodiment of  FIG. 1 , the tape member  18  is coupled to one side  24  of the housing  12  and the bottom surface  11  of the nosepiece  13 , although in other embodiments the tape member  18  can be coupled to any other side or sides of the print head  10  enabling electrical connection between the chip  20  and the printer controller  30  (described below).  
      In some embodiments, the tape member  18  includes a plurality of conductive traces  17  that connecting the chip  16  (or various components included in the chip  16 ) to another circuit or device. For example, in some embodiments, each conductive trace  17  directly or indirectly connects at one end to an actuator, such as a heating element  32  or a piezo element (not shown), of the chip  16  and terminates at an opposite end at a contact pad  28 . The contact pads  28  can be positioned to mate with or otherwise electrically connect to corresponding contacts on a carriage (not shown) for communication between a microprocessor-based printer controller  30  and components of the print head  10  (e.g., the heating elements  32 ). To be positioned in this manner in some embodiments, the contact pads  28  extend through the tape member  18  to the outer surface  29  of the tape member  18 . In other embodiments, the contact pads  28  can be positioned on the tape member  18  in other manners enabling electrical connection to another circuit or device. In those embodiments of the present invention having a tape member  18 , the tape member  18  can be formed of a variety of polymers or other materials capable of providing or carrying conductive traces  17  to electrically couple the nozzle portion  15  of the print head  10  to the contact pads  28  and the printer controller  30 .  
      In other embodiments, the nozzle portion  15  of the print head  10  can be electrically coupled to another circuit or device without the use of a tape member  18  as described above. By way of example only, conductive traces  17  can be provided on a surface of the housing  12 , and can extend between the chip  16  and contact pads  28  on the housing  12 . As another example, any type and number of wires or other electrical leads can be coupled to the chip  16  and to one or more electrical connectors (e.g., pins, sockets, pads, and the like) on the print head  10 , wherein the electrical connectors are adapted to be electrically coupled to another circuit or device (e.g., the printer controller  30 ). Still other manners of electrically coupling the nozzle portion  15  of the print head  10  and contact pads  38  or other electrical connectors are possible, and fall within the spirit and scope of the present invention.  
       FIG. 2  illustrates an exploded view of the nozzle portion  15  of the print head  10  illustrated in  FIG. 1 . The nozzle portion  15  includes the chip  16 , which in some embodiments defines an aperture  31 . The chip  16  also includes a surface  33  and one or more heating elements  32 . The heating elements  32  can be positioned on the surface  33  in any manner, such as by being coupled to the surface  33 , printed on the surface  33 , embedded within the surface  33  and chip  16 , and the like. The nozzle portion  15  can further include the nozzle plate  20  coupled to the chip  16 . When assembled, the surface  33  of the chip  16  is positioned substantially over the nozzle plate  20  (with reference to the orientation of the print head  10  as shown in  FIG. 2 ).  
      Some embodiments of the present invention have a film  34  covering at least a portion of the chip  16 . The film  34  can be positioned to protect circuitry of the chip  16  (e.g., components on the chip  16  necessary to maintain electrical connection between the heating element  32  and the printer controller  30 ) from corrosive properties of the ink. The film  34  can include an aperture  36  that corresponds with the aperture  31  of the chip  16 , and can include one or more other apertures  37  corresponding to the heating elements  32  for purposes that will be described in greater detail below. The chip  16  and the film  34  (if used) are coupled to the housing  12  such that the apertures  31  and  36  collectively define an ink via, and fluidly communicate with the ink reservoir  14 .  
      With continued reference to  FIG. 2 , in some embodiments the nozzle plate  20  includes a recess  40  in fluid communication with the ink reservoir  14  via the apertures  31  and  36  of the chip  16  and the film  34 , respectively. The nozzle plate  20  can further include a plurality of channels  42 , each channel  42  extending to a respective chamber  44  and in fluid communication with a respective nozzle  22 . Any portion of at least one of the recess  40 , a channel  42 , a chamber  44 , and a nozzle  22  can be collectively referred to as “flow features.” In some embodiments, the nozzle plate  20  can include more or fewer channels  42  and chambers  44  than shown in the illustrated embodiments. In some embodiments, one or more channels  42  can connect (e.g., flow) to multiple chambers  44 . Also, the chambers  44  and/or channels  42  can be different in size, shape and/or uniformity in other embodiments of the present invention.  
      Ink can travel (e.g., by gravity and/or capillary action) from the ink reservoir  14  in the housing  12  through the apertures  31  and  36 , into the recess  40 , into the plurality of channels  42 , and into the plurality of chambers  44 .  
      In some embodiments of the present invention, the heating elements  32  are positioned on the chip  16  adjacent the chambers  44 . In some embodiments, the heating elements  32  can include any element capable of converting electrical energy into heat, such as a transducer or resistor. For example, in some embodiments (including the embodiment illustrated in  FIGS. 1 and 2 ), the heating elements  32  can be thin-film resistors. Electrical signals sent from the printer controller  30  to the heating elements  32  (e.g., via the conductive traces  17  of the tape member  18 ) can heat the heating elements  32  and vaporize ink in the chambers  44 .  
      In the illustrated embodiment of  FIGS. 1 and 2 , the heating elements  32  are exposed to the chambers  44  through the apertures  37  in the film  34  (if used). As a result, when one or more electrical signals are sent from the printer controller  30  to actuate (e.g., heat) a heating element  32 , the heating element  32  heats a thin layer of ink in the adjacent chamber  44 , thereby vaporizing a volatile component of the ink and ejecting a portion of the ink occupying the chamber  44  out of the adjacent nozzle  22  in the form of an ink droplet (or drop), which can strike a desired location of a printing medium. The chamber  44  can subsequently refill with ink (e.g., by capillary action) in order to prime the chamber  44  for subsequent printing.  
      A portion of the inkjet print head  10 , particularly the substrate (e.g., chip)  16 , is illustrated in  FIGS. 3 and 4 . In the illustrated embodiments, the heating elements  32  are arranged into a first heating array  50  and a second heating array  52 . In other embodiments (not shown), the heating elements  32  can be arranged in more or fewer arrays than shown in the illustrated embodiment. The arrays  50  illustrated in  FIGS. 3 and 4  are each a row of heating elements  32 . However, in other embodiments, the heating elements  32  can be located in other manners, such as in blocks, in staggered arrangements, or in any other regular or irregular manner.  
      The chip  16  illustrated in both embodiments of  FIGS. 3 and 4  further includes control circuits  56  for controlling and activating the heating elements  32 . Any number of control circuits  56  can be used for this purpose, each of which can control and activate any number of heating elements  32 . In the illustrated embodiments of  FIGS. 3 and 4 , for example, two control circuits  56  are used, each of which controls an array  50  of heating elements  32 . In other embodiments, a single control circuit  56  controls and activates all of the heating elements  32 . In still other embodiments, multiple control circuits  56  perform this function, each controlling and activating one or more heating elements  32 .  
      In some embodiments, the control circuit  56  can include one or more field effect transistors (FETs) activating one or more heating elements  32 . For example, the control circuit  56  can include a power FET for each heating element  32 . In other embodiments, the chip  16  can include a control circuit  56  for each heating array  50  or  52 , and each control circuit  56  can include a bank of power FETs (not shown), one FET for each heating element  32  of the array  50  or  52 . In the illustrated embodiments of  FIGS. 3 and 4 , the chip  16  includes a first control circuit  58  for activating the first heating array  50  and a second control circuit  60  for activating the second heating array  52 .  
      The chip  16  further includes at least one temperature sense element positioned to sense a temperature of a location on the print head  10 . In some embodiments, the temperature sense element is or comprises a temperature sense resistor (TSR)  64 . The TSR  64  can include a polysilicon material or another material responsive to temperature. For example, the TSR  64  can include a N-type source drain (NSD) material, a N-well layer material, a P-type source drain (PSD) material, a lightly doped drain (LDD) material or another suitable material. In some embodiments, the TSR  64  can be approximately 0.05 .mu.m to approximately 5000 .mu.m wide, by approximately 0.01 .mu.m to approximately 400,000 .mu.m long, by approximately 0.05 .mu.m to approximately 4 .mu.m thick.  
      In some embodiments, the TSR  64  senses the temperature of the chip  16 , one or more of the heating elements  32 , the ink chamber  44 , or other location of the print head  10  and provides this information to the printer controller  30  or another circuit. The printer controller  30  or other circuit can use the temperature information provided by the TSR  64  when configuring activation of the heating elements  32 . In some embodiments, the TSR  64  is positioned such that the TSR  64  is in close proximity to one or more of the heating elements  32  without disrupting ink flow. In other words, the TSR  64  is not located in a position that would compromise ink flow from the ink via  68  through the channels  42  to the ink chamber  44 . The via  68 , one of the channels  42 , and one of the ink chambers  44  is shown in dashed lines in  FIGS. 3 and 4 .  
      In the embodiment illustrated in  FIG. 3 , a first TSR  70  is located between the first control circuit  58  and the first heating array  50 , and is in a position away from the fluid flow paths (e.g., the paths from ink via  68  through channel  42  to ink chamber  44  as described above), and a second TSR  72  is placed between the second control circuit  60  and the second heating array  52 , and is also in a position away from the fluid flow paths. The positions of the first TSR  70  and the second TSR  72  enable the TSRs  70 ,  72  to be located in relatively close proximity to the heating elements  32  without detrimental topography effects to fluid flow compared to other positions (e.g., on the opposite side of the heating elements  32 , where the TSRs  70 , 72  would otherwise overlap the fluid flow paths).  
      As is seen, the TSR&#39;s  70 ,  72  have a longitudinal extent that is substantially parallel along and to an entire length of arrays  50 ,  52 , respectively, such as between individual heating elements  32 - 1  and  32 - n . In turn, the array of actuators substantially parallel the longitudinal extent of the ink via  68  on either sides  71 ,  73  thereof, so that each of the ink chambers  44  and ink channels  42  can be respectively of nearly uniform size and shape and have commonality all along a length of the via. Also, the TSR&#39;s have a fairly straight length along the length of the arrays that extends beyond terminal ends  67 ,  69  of the ink via and beyond a length of the arrays. In this manner, each TSR is able to sense local heating per an entire array and not just a portion thereof. Also, the ink via itself acts as a thermal insulator between each array  50 ,  52  so that temperature readings of TSR&#39;s  70 ,  72  are not unduly influenced by heating elements  32  on an opposite side of the ink via. Beyond the array, TSR&#39;s  70 ,  72  bend orthogonally to its longitudinal extent at positions  75 ,  77  so that it can be directed at positions  79 ,  81  around the control circuitry  56  and away from the arrays. In no instance, however, do the TSR&#39;s overlap the fluid flow paths or flow features, as before. Appreciating the chip  16  is formed as many layers, the lack of overlap between the TSR&#39;s and the fluid flow paths or features occurs in either of the vertical directions of the chip such as into or away from the paper of the figure according to traditional arrow symbols ⊙ (into) or {circle around (x)} (away). There is vertical overlap, however, between the TSR&#39;s  70 ,  72  and one or more electrical traces  85 ,  87 , as is seen, that electrically connect the control circuits  56  to either of the arrays  50 ,  52 .  
      In the embodiment illustrated in  FIG. 4 , the first TSR  70  is positioned beneath the first heating array  50 , and the second TSR  72  is positioned beneath the second heating array  52 . In other words, the first TSR  70  and the second TSR  72  can be embedded into the chip  16 . In some embodiments, the TSR  64  is embedded into the chip  16  such that the TSR  64  is still adjacent the surface  33  of the chip  16 , and may or may not be positioned over one or more ink chambers  44  or one or more ink channels  42 . In some embodiments, a thin layer (not shown) of the substrate  16  can separate the TSR  64  and any overlapping ink channels  42  or ink chambers  44 , which can eliminate topography issues presented from placing a TSR  64  directly over an ink channel  42  or chamber  44 . In the embodiment of  FIG. 4 , the TSR  70  includes an implanted material in the chip  16 , such as, for example, a NSD material, a PSD material or a N-well material. Implanted TSRs  64  can be used without presenting any topography issues that can effect fluid flow as described above.  
      In other embodiments (not shown), the chip  16  can include more or fewer TSRs  64  than the embodiments illustrated in  FIGS. 3 and 4 . For example, the chip  16  can include a dedicated TSR  64  located as described above for each heating element  32 , or can include one TSR  64  located as described above for multiple heating elements  32 . In some embodiments, the chip  16  can also include various combinations of different positions of TSRs  64 . For example, a chip  16  can include a TSR  64  positioned between the control circuit  56  and the heating elements  32 , away from the fluid flow paths (as shown in  FIG. 3 ) as well as one or more implanted TSRs  64  positioned beneath one or more heating elements  32  (as shown in  FIG. 4 ).  
      In some embodiments, (not shown), the chip  16  can include additional heating elements  32  dedicated to heating the substrate (e.g., chip  16 ) as opposed to the ink in the ink chambers  44 . The chip  16  can further include one or more TSRs  64  for providing temperature readings for these additional substrate heating elements. In still further embodiments (not shown), the heating arrays  50  and  52  can further include one or more substrate heating elements (e.g., heating elements dedicated to heating the substrate as opposed to an ink chamber) in addition to the heating elements  32  heating the ink chambers  44 .  
      The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims. For example, the present invention can be used in conjunction with inkjet print heads  10  having shapes that are different than that shown in  FIG. 1  (e.g., print heads  10  not having a nozzle portion  13  shaped as shown, print heads  10  having other dimensions and features, and the like).