Patent Publication Number: US-2007120893-A1

Title: Microinjectors and temperature inspection methods thereof

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates in general to microinjectors and in particular to microinjectors capable of temperature detection.  
      2. Description of the Related Art  
      Microinjection technology has been widely applied to inkjet printers, with two methodologies being thermal bubble and piezoelectric actuations. In thermal actuated inkjet printers, temperature measurement and control are important to facilitate high printing quality and longevity of use.  
      U.S. Pat. No. 6,357,863 discloses an inkjet print head chip comprising a column of ink heating resistors corresponding to a nozzle array, although precise temperature measurement of each nozzle can be difficult owing to crowding on the chip. U.S. Pat. No. 6,382,773 discloses an inkjet print head comprising a temperature-sensing layer below a heating element. However, the temperature-sensing layer can reduce flatness of the heating area and adversely influence efficiency thereof.  
     BRIEF SUMMARY OF THE INVENTION  
      Microinjectors are provided. A microinjector includes a substrate, a manifold formed by the substrate, and a plurality of jet units. Each jet unit comprises a nozzle plate disposed on the substrate, a chamber formed between the substrate and the nozzle plate, a channel connecting the chamber and the manifold, a nozzle formed on the nozzle plate, a heater disposed on an outer surface of the nozzle plate and adjacent to the nozzle, and a temperature sensor disposed on the outer surface of the nozzle plate. The heater heats the chamber to eject liquid through the nozzle. The sensor is located substantially at the center of the channel for temperature detection. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
       FIG. 1  is a sectional view of an embodiment of a microinjector;  
       FIG. 2  is a perspective diagram of two adjacent jet units of a microinjector;  
       FIG. 3  is a perspective diagram of a plurality of sensors S 1 ˜S 19  disposed in a region Ni;  
       FIG. 4  is a perspective diagram of a plurality of sensors S 1 ˜S 19  distributed in N regions N 1 ˜N 16 ;  
       FIG. 5  is a perspective diagram of another embodiment of a plurality of sensors S 1 ˜S 19  distributed in N regions N 1 ˜N 16 ; and  
       FIG. 6  is a perspective diagram of a temperature inspection method of a microinjector. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIG. 1 , an embodiment of a microinjector, such as a monolithic inkjet chip, primarily comprises a substrate  10 , a manifold  16  formed by the substrate  10 , and a plurality of jet units E. Each jet unit E comprises a nozzle plate  12 , a nozzle  18  formed on the nozzle plate  12 , a chamber  14  formed between the substrate  10  and the nozzle plate  12 , a channel  15  communicating the chamber  14  and the manifold  16 , and two heaters  20  disposed on an outer surface of the nozzle plate  12 , adjacent to the nozzle  18 . As shown in  FIG. 1 , fluid F is ejected through the nozzle  18  by thermal bubbles generated by the heaters  20 . Specifically, some jet units E further comprise a temperature sensor S on the outer surface of the nozzle plate  12 , such as a thermal resistor. The sensor S is located above the channel  15 , providing temperature measurement without interfering with fluid F and heaters  20 .  
      When the fluid F is ejected from the chamber  14  without timely replenishment, the heaters  20  can rapidly transfer heat through the nozzle layer  12  and cause empty burning of the chamber  14 . In this embodiment, the sensor S monitors and detects abnormal high temperature of the jet unit E, preventing empty burning of the chamber  14 .  
      Referring to  FIG. 2 , the manifold  16  and the chambers  14  of any two adjacent jet units E are connected via the channels  15  in different lengths. Here, the sensors S are respectively disposed in the middle of the channels  15 , to detect temperature of the jet units E. When the two chambers  14  are heated by the heaters  20  for a predetermined period, the temperature variation ΔTa and ΔTb are measured by the sensors S on the longer and shorter channels  15  respectively, wherein ΔTa&lt;ΔTb. In this embodiment, the microinjector includes M jet units E provided with M channels  15  in m different lengths, wherein M&gt;m. Specifically, the m sensors S are disposed on m of the M channels  15  for temperature detection, corresponding to the m different lengths.  
      An exemplary embodiment of the microinjector, such as an inkjet chip P shown in  FIG. 3 , includes 300 jet units E having 300 channels in 19 different lengths (i.e. M=300, m=19). Here, the 300 jet units E are distributed in N regions N 1 ˜N 16  (i.e. N=16), wherein each of the regions N 1 ˜N 16  has 18 or 19 channels in different lengths (four of the regions N 1 ˜N 16  contain only 18 jet units E). The numbers of M, m, and N can be adjusted by demand, wherein M&gt;m≧N. As the channels of the same length have similar temperature behavior, temperature of these channels can be represented by one sensor applied to one thereof, such that data processing and mechanism are simplified.  
      As shown in  FIG. 3 , the sensors S 1 ˜S 19  are disposed in a region Ni among the regions N 1 ˜N 16 . Due to approximate detection circuit lengths of the sensors S 1 ˜S 19  collected in the region Ni, noise and parasitic resistance are prevented, improving measurement accuracy thereof. Referring to  FIG. 4 , another embodiment provides sensors S 1 ˜S 19  averagely distributed among the regions N 1 ˜N 16 , corresponding to 19 channels of different lengths. Here, since the number of the sensors (m=19) exceeds that of the regions (N=16), each of the regions N 1 ˜N 16  has at least one sensor, wherein the three regions N 1 ˜N 3  have two sensors, as shown in  FIG. 4 . In this embodiment, the sensors S 1 ˜S 19  not only reflect temperature of the channels in 19 different lengths, but also represent temperature of the different regions N 1 ˜N 16 .  
      Referring to  FIG. 5 , another embodiment of the first sensor S 1  is disposed in a corner region N 1  (or the corner region N 2 , N 15 , or N 16 ) farthest from the center of the microinjector, and the last sensor S 19  is disposed in a central region N 7  (or the central regions N 8 , N 9 , or N 10 ) nearest to the center of the microinjector. Here, the sensors S 1 ˜S 19  are disposed on the channels corresponding to the 19 different lengths, wherein the sensors S 1  and S 19  are respectively disposed on the longest and shortest channels thereof.  
      Referring to  FIG. 6 , the invention further provides a temperature inspection method of the microinjector. The method primarily comprises ejecting ink droplets from the jet units including the sensors S 1 ˜S 19  (step  100 ), obtaining temperature variations ΔT 1 ˜ΔT 19  by the sensors S 1 ˜S 19  (step  200 ), and determining whether the temperature variations ΔT 1 ˜ΔT 19  are between a minimum temperature Tmin and a maximum temperature Tmax (step  300 ).  
      As shown in  FIG. 6 , the micronjector is in a normal state if Tmin≦ΔT 1 ˜ΔT 19 ≦Tmax. However, if any of the temperature variations ΔT 1 ˜ΔT 19  exceeds the predetermined range between Tmin and Tmax, and ΔT 1 ≦ΔT 19  (step  400 ), the step  100  is repeated for the second time detection. Alternatively, if any of ΔT 1 ˜ΔT 19  exceeds the range between Tmin and Tmax, and ΔT 1 &gt;ΔT 19  (i.e. temperature variation of the longest channel abnormally exceeds the shortest channel), a detection circuit coupled with the sensors transmits an alarm signal to a processor (not shown), indicating the microinjector is in an abnormal state without timely replenishment. When in the abnormal state, the microinjector (such as the inkjet chip P) is to be replaced immediately. Such phenomenon described above is usually happened when ink volume of cartridge is lesser, and it causes incomplete ink replenishment for chamber with longer channel.  
      Microinjectors and temperature inspection method thereof are provided according to the embodiments. A number of sensors are disposed in some of the jet units, corresponding to different lengths of the channels, such that data processing and mechanism are simplified. The sensors can monitor and detect temperature variations due to abnormal fluid replenishment, without interference to fluid and the heaters, improving efficiency and life of the microinjector. The invention can be widely applied to inkjet printers, multi-function printers, fuel injection systems, or drug delivery systems.  
      While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements.