Patent Publication Number: US-2009232681-A1

Title: Ultrasonic piezoelectric pump

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a piezoelectric pump, and more particularly, to an ultrasonic piezoelectric pump in which a piezoelectric pump is integrated with a fluid pipe without a check valve so that the structure can be simplified. 
     2. Description of the Related Art 
     In general, since parts for small sized electronic products and medical equipment possibly malfunction or are damaged due to heat generated therein because degree of integration of transistors is improved, cooling of the electronic parts is becoming a critical issue in electronic apparatuses using small electronic parts. 
     It is proposed a refrigerant circulation system using a piezoelectric pump, as a solution for cooling the small sized electronic components, for suctioning liquid refrigerant and for vibrating the liquid refrigerant by applying a force to the liquid refrigerant to discharge the refrigerant in a desired phase(?). 
       FIG. 13  is a conceptual view illustrating a conventional piezoelectric pump. Referring to  FIG. 13 , the conventional piezoelectric pump includes a piezoelectric actuator  100  having a suction port  110  and a discharge port  120 , and a piezoelectric device  200  installed in the piezoelectric actuator  100 . The suction port  110  and the discharge port  120  communicate with fluid pipes  300 , respectively. 
     Ends of the piezoelectric device  200  are connected to a controller  400  by lead wires  410  such that the controller  400  applies an electric field to the piezoelectric device  200  to pump a fluid while being deflected. 
     In this structure, the fluid supplied through the fluid pipe  300  is fed into the piezoelectric actuator  100  through the suction port  110 , and the fed fluid is pumped when a voltage is applied to the piezoelectric device  200  by the controller  400  and then is discharged out through the discharge port  120 . 
     The conventional piezoelectric pump includes check valves  500  respectively installed to the suction port  110  and the discharge port  120  to prevent the fluid from flowing backward when the fluid is pumped by the deflection of the piezoelectric device  200 . 
     As such, since the conventional piezoelectric pump is provided independently from the fluid pipe  300  and the check valves  500  for preventing fluid from flowing backward are provided independently from the pump, the conventional piezoelectric pump is not suitable for minimizing electronic products and medical equipment because it is difficult to make the piezoelectric pump in a small size. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has been made in view of the above problems, and it is an aspect of the present invention to provide an ultrasonic piezoelectric pump in which: a piezoelectric actuator is installed at a center of a fluid pipe; a plurality of fluid-flow holes is formed around the piezoelectric actuator; and a tapered nozzle is tapered forward and downwardly in front of the piezoelectric actuator to force a fluid to be easily discharged and to have difficulty to flow backward so that a fluid can be smoothly pumped by the piezoelectric actuator without a check valve while preventing the fluid from flowing backward. 
     It is another aspect of the present invention to provide an ultrasonic piezoelectric pump in which a voltage applied to a piezoelectric device is adjusted to quickly deform the piezoelectric device for the fluid discharge and a frequency is adjusted to have a voltage waveform to force the piezoelectric device to be restored slowly so that a fluid can be smoothly discharged. 
     It is still another aspect of the present invention to provide an ultrasonic piezoelectric pump, a piezoelectric device of which is driven by ultrasonic waves to force a fluid to flow while causing flow resonance so that efficiency of heat transfer can be improved. 
     In order to achieve the object, there is provided an ultrasonic piezoelectric pump comprising: a fluid pipe having a hollow part formed therein to permit a fluid to flow from a fluid source; a piezoelectric actuator inserted into the hollow part and including a piezoelectric device and a plurality of fluid holes; a controller connected to a lead wire to apply a driving power to the piezoelectric device; and a tapered nozzle inserted into the hollow part in front of the piezoelectric actuator and tapered forward and downwardly. 
     The piezoelectric actuator comprises: a case having a through-hole formed at the center thereof; a frame, inserted into the through-hole, to which the piezoelectric device is installed; and the fluid holes formed in the vicinity of the frame to penetrate the front side to the rear side of the case. 
     The piezoelectric device comprises a unimorph comprising: a thin plate; and a piezoelectric ceramic contacting a side of the thin plate. 
     The piezoelectric device comprises: a case having a through-hole formed at the center thereof; a pipe-shaped cylinder inserted into the through-hole; a rear plate fixed to the rear side of the cylinder to close the rear side of the cylinder; a front plate contacting an inner wall of the cylinder and used as a piston; the piezoelectric device, provided to connect the rear plate to the front plate, in which a plurality of piezoelectric ceramics are laminated; and the fluid holes formed in the vicinity of the cylinder to penetrate the front side to the rear side of the case. 
     The front plate further comprises a circular rubber ring to seal the case and to prevent the fluid from entering. 
     The piezoelectric actuator comprises: a case having a through-hole formed at the center thereof; a frame inserted into the through-hole; a piezoelectric ceramic provided in the frame to generate a deflection in the radial direction; an elastic member contacting the front side of the piezoelectric ceramic, a part of the elastic member inserted into the frame and another part of the elastic member protruding from the front side of the frame, and the protruded part having a smaller diameter than that of the part inserted into the frame and vibrating due to ultrasonic waves applied to the piezoelectric device; a fixed body to fix the elastic member to the frame, and through which the elastic member penetrates; and the fluid holes formed in the vicinity of the frame to penetrate the front side to the rear side of the case. 
     The ultrasonic piezoelectric pump further comprises a distance adjusting circular ring provided in the fluid pipe to adjust a distance between the piezoelectric actuator and the tapered nozzle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a sectional view illustrating an ultrasonic piezoelectric pump according to an embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating an actuator in  FIG. 1 ; 
         FIGS. 3 to 5  are sectional views illustrating a piezoelectric device in  FIG. 1 ; 
         FIG. 6  is a sectional view illustrating an ultrasonic piezoelectric pump according to another embodiment of the present invention; 
         FIG. 7  is a sectional view illustrating an ultrasonic piezoelectric pump according to still another embodiment of the present invention; 
         FIG. 8  is a perspective view illustrating an actuator in  FIG. 7 ; 
         FIG. 9  is a perspective view illustrating another example of the actuator in  FIG. 7 ; 
         FIG. 10  is a sectional view illustrating an ultrasonic piezoelectric pump according to still embodiment of the present invention; 
         FIG. 11  is a sectional view illustrating a piezoelectric device in  FIG. 10 ; 
         FIG. 12  is a waveform chart illustrating a voltage applied to the piezoelectric device according to an embodiment of the present invention; and 
         FIG. 13  is a conceptual view illustrating a conventional piezoelectric pump. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a sectional view illustrating an ultrasonic piezoelectric pump according to a first embodiment of the present invention. The ultrasonic piezoelectric pump includes a fluid pipe  1 , a piezoelectric pump  2 , a controller  3 , and a tapered nozzle  4 . 
     The fluid pipe  1  has a hollow part  11  formed therein through which a fluid flows from a fluid source. 
     Moreover, the piezoelectric actuator  2  is inserted into the hollow part  11  and includes a piezoelectric device  23  and a plurality of fluid holes  24 . 
       FIG. 2  is a perspective view illustrating the piezoelectric actuator of  FIG. 1 . The actuator  2  includes a case  21  with through-holes  211  formed at the center thereof, a frame  22 , inserted into the through-holes  211 , in which the piezoelectric device  23  is installed to the front side of the frame  22 , and the plurality of fluid holes  24  formed in the vicinity of the frame  22  to penetrate the front side to the rear side of the case  21  and to permit the fluid supplied to the fluid pipe  1  to flow therethrough. 
     In this case, the piezoelectric device  23 , as illustrated in  FIG. 3 , is made in the form of a unimorph having a thin plate  231  and a piezoelectric ceramic  232  contacting one side of the thin plate  231 , but may be made in the form of a bimorph, as illustrated in  FIG. 4 , having a thin plate  231  and piezoelectric ceramics  232  contacting sides of the thin plate  231 . 
     The controller  3  is connected to the piezoelectric device  23  through a lead wire  31  to apply a driving power to the piezoelectric device  23 . 
     The tapered nozzle  4  has a tapered opening  41  inserted into the hollow part  11  in front of the piezoelectric actuator and tapered forward and downwardly. Since the opening  41  is tapered forward and downwardly, the fluid can be easily discharged and has difficulty to flow backward so that the backflow of the fluid can be prevented. 
       FIG. 5  is a sectional view illustrating an ultrasonic piezoelectric pump according to a second embodiment of the present invention. Hereinafter, structures and operations of the same components as those of  FIG. 1  will be omitted. 
     Referring to  FIG. 5 , a distance adjusting circular ring  5  is provided in the hollow part  11  of the fluid pipe  1  between the piezoelectric actuator  2  and the tapered nozzle  4  to adjust a distance from the piezoelectric actuator  2  and the tapered nozzle  4 . 
     In this case, the distance between the piezoelectric actuator  2  and the tapered nozzle  4  is preferably adjusted by the distance adjusting circular ring  5  to optimize the transmission of kinetic energy of the fluid. 
       FIG. 6  is a sectional view illustrating an ultrasonic piezoelectric pump according to a third embodiment of the present invention, and structures and operations of the same components as those of the first and second embodiments of the present invention will be omitted. 
     According to this embodiment, the ultrasonic piezoelectric pump includes a fluid pipe  1 , a piezoelectric actuator  2 , a controller  3 , and a tapered nozzle  4 . 
       FIG. 7  is a perspective view illustrating the actuator in  FIG. 6 , and as illustrated in  FIGS. 6 and 7 , the actuator  7  includes a case  21 , a cylinder  25 , a rear plate  26 , a front plate  27 , and a piezoelectric device  23 . 
     The case has a through-hole  211  formed at the center and the cylinder  25  has a pipe shape and is inserted into the through-hole  211 . 
     Moreover, the case  21  has a plurality of fluid holes  24  penetrating from the front side of the case  21  to the rear side thereof in the vicinity of the cylinder  25  to permit the fluid to flow from the front side to the rear side of the case  21 . 
     The rear plate  26  is fixed to the rear side of the cylinder  25  to close the rear side of the cylinder  25  and the front plate  27  contacts the inner wall of the cylinder  25  and plays a role of a reciprocating piston. 
     The piezoelectric device  23  connects the rear plate  26  to the front plate  27  and a plurality of piezoelectric ceramics  232  are laminated on the piezoelectric device  23  such that the piezoelectric device  23  plays a role of a rod for moving the front plate  27  forward and backward due to an external applied voltage. 
     Moreover, a distance adjusting circular ring  5  is provided in the hollow part  11  of the fluid pipe  1  between the piezoelectric actuator  2  and the tapered nozzle  4  to adjust a distance between the piezoelectric actuator  2  and the tapered nozzle  4 . 
       FIG. 8  is a sectional view illustrating another example of the actuator in  FIG. 6 . Referring to  FIGS. 6 to 8 , a circular rubber ring  271  is provided to the front plate  27  to seal the case to prevent a fluid from entering. 
     By doing so, the fluid flowing from the hollow part of the fluid pipe  1  to outside the case  21  is prevented from entering the actuator. 
     The controller  3  is connected to the piezoelectric device  23  by the lead wire  31  to apply a driving power to the piezoelectric device  23 . 
     Meanwhile, the tapered nozzle  4  is inserted into the hollow part  11  in front of the piezoelectric actuator and has an opening  41  tapered downwardly and forwardly. Since the opening  41  is tapered forward and downwardly, the fluid is easily discharged and has difficulty to flow backward so that the fluid can be prevented from flowing backward. 
     The fluid is pumped using the ultrasonic piezoelectric pump according to the first to third embodiments of the present invention by adjusting the voltage applied to the piezoelectric device  23  such that the voltage, as illustrated in  FIG. 9 , has a waveform of a voltage slowly increasing during the suctioning of the fluid and quickly decreasing during the discharge of the fluid. 
     In other words, the frequency of the voltage is adjusted to have a waveform of the voltage such that the piezoelectric device is quickly deformed to discharge the fluid and slowly returns to suction the fluid, therefore the fluid can be smoothly discharged. 
     According to the embodiments of the present invention, the ultrasonic piezoelectric device (?) transmits kinetic energy to fluid particles such that the fluid particles flow due to an inertial force. 
     In other words, the movement of the fluid caused by the inertial force resonates in association with the flow frequency of the fluid so that heat transfer can be accelerated. 
       FIG. 10  is a sectional view illustrating an ultrasonic piezoelectric pump according to a fourth embodiment of the present invention. The ultrasonic piezoelectric pump includes a piezoelectric pump  1 , a piezoelectric actuator  2 , a controller  3 , and a tapered nozzle  4 . 
     The fluid pump  1  has a hollow part  11  formed therein through which a fluid flows from a fluid source. 
     Moreover, the piezoelectric actuator  2  is inserted into and fixed in the hollow part  11 , and has a piezoelectric device  23  and a plurality of fluid holes  24 . 
     Here, the actuator  2  includes a case  21  having a through-hole  211  formed at the center, a frame  22 , inserted into the through-hole  211 , to which the piezoelectric device  23  is installed, and a plurality of fluid holes  24  formed in the vicinity of the frame  22  to penetrate the front side to the rear side of the case  21  and to permit the fluid supplied to the fluid pipe  1  to flow therethrough. 
     The piezoelectric device  23  may include a multi-layer piezoelectric disc having a plurality of thin piezoelectric ceramics  232  which resonate in the thickness direction by the application of ultrasonic waves. 
     Moreover, the controller  3  is connected to the piezoelectric device  23  by a lead wire  21  to adjust a frequency applied to the piezoelectric device  23 . 
     In other words, the controller  3  applies ultrasonic waves higher than 5 MHz to the piezoelectric device  23  having several tens of piezoelectric ceramics  232  through the lead wire  31  so that vibration in the thickness direction is obtained to discharge the fluid through the tapered nozzle  4 . 
     Here, a distance adjusting circular ring  5  may be provided in the hollow part  11  of the fluid pipe  1  between the piezoelectric actuator  2  and the tapered nozzle  4  to adjust a distance from the piezoelectric actuator  2  and the tapered nozzle  4 . 
       FIG. 11  is a sectional view illustrating an ultrasonic piezoelectric pump according to a fifth embodiment of the present invention and  FIG. 12  is an enlarged view illustrating the piezoelectric device  23  in  FIG. 23 . Referring to  FIG. 11 , the ultrasonic piezoelectric pump includes a fluid pipe  1 , a piezoelectric actuator  2 , a controller  3 , and a tapered nozzle  4 . 
     Here, the piezoelectric actuator  2  includes a case  21  with through-holes  211  formed at the center thereof, a frame  22  inserted into the through-holes  211 , the piezoelectric device  23  installed in the frame  22 , and a plurality of fluid holes  24  formed in the vicinity of the frame  22  to penetrate the front side to the rear side of the case  21 . 
     The piezoelectric device  23  includes a piezoelectric ceramic  232   a,  an elastic member  232   b,  and a fixed body  234 . 
     Here, the piezoelectric ceramic  23   a  is provided in the frame  22  and generates deflection in the radial direction. 
     The elastic member  232   b  contacts the front side of the piezoelectric ceramic  232   a,  is partially inserted into the frame  22 , and is partially protruded outwardly from the front side of the frame  22 . 
     The part of the elastic member  232   b  protruded from the frame  22  has a diameter smaller than that of the part of the elastic member  232   b  inserted into the frame  22 , and due to the small diameter, generates a large deflection. 
     The elastic member  232   b  vibrates at ultrasonic waves with a preset frequency applied to the piezoelectric ceramic  232   a  in the longitudinal direction. 
     In other words, the elastic member  232   b  does not vibrate when the frequency applied to the piezoelectric ceramic  232   a  is low, but vibrates in the longitudinal direction by which ultrasonic vibration is transmitted thereto when the frequency applied to the piezoelectric ceramic  232   a  is in the form of ultrasonic waves with several hundreds of kHz or higher. 
     Meanwhile, the elastic member  232   b  is inserted into the fixed body  234  to penetrate the same, and the fixed body  234  fixes the elastic member  232   b  to the frame  22 . 
     The controller  3  is connected to the piezoelectric device  23  by the lead wire  31  to adjust the frequency applied to the piezoelectric device  23 . 
     In the fifth embodiment of the present invention, the intensity of the frequency applied to the piezoelectric device by the controller  3  is set by modes to vibrate only the piezoelectric ceramic  232   a  generating a radial directional deflection or to apply a higher frequency to vibrate the piezoelectric ceramic  232   a  and all the piezoelectric ceramics  232   a  generating the longitudinal deflection. 
     As such, according to the embodiments of the present invention, the fluid is pumped using the piezoelectric actuator installed at the center of the fluid pipe and the tapered nozzle tapered forward and downwardly without a check valve so that the fluid is smoothly pumped. Moreover, since the ultrasonic piezoelectric pump does not include the fluid pipe separated from the fluid pump and a check valve, the ultrasonic piezoelectric pump can be made in a simple structure and is easily made in a small size. 
     Meanwhile, although the ultrasonic piezoelectric pump is described for use with a fluid, the ultrasonic piezoelectric pump can be used for gas such as air and its description will be omitted since the structure and operation thereof is identical to the case of for use with the fluid. 
     As described above, according to the ultrasonic piezoelectric pump, the piezoelectric actuator is installed at the center of the fluid pipe, a plurality of fluid-flow holes is formed around the piezoelectric actuator, and the tapered nozzle is tapered forward and downwardly in front of the piezoelectric actuator to force the fluid to be easily discharged and to have difficulty flowing backward so that the fluid can be smoothly pumped by the piezoelectric actuator without a check valve while preventing the fluid from flowing backward and the pumping efficiency can be improved. 
     Moreover, a voltage applied to the piezoelectric device is adjusted to quickly deform the piezoelectric device for the fluid discharge and a frequency is adjusted to have a voltage waveform to force the piezoelectric device to be restored slowly so that a fluid can be smoothly discharged. 
     According to the ultrasonic piezoelectric pump, the piezoelectric device is driven by ultrasonic waves to force the fluid to flow while causing flow resonance so that efficiency of heat transfer can be improved. 
     According to the ultrasonic piezoelectric pump, the flow of a fluid is controlled by the piezoelectric ceramic vibrating in the longitudinal direction or in the radial direction by the application of ultrasonic waves and the elastic member vibrating in the longitudinal direction by ultrasonic waves applied to the piezoelectric device, so that the fluid can be smoothly pumped without the backflow by the piezoelectric actuator without a check valve and the ultrasonic piezoelectric pump can be applied to small sized products. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.