Patent Publication Number: US-9429368-B2

Title: Temperature-sensing piezoelectric dispenser

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/KR2014/007472 filed on Aug. 12, 2014, which claims priority under 35 U.S.C §119(a) to Korean Patent Application No. 10-2013-0096739 filed on Aug. 14, 2013. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     TECHNICAL FIELD 
     The inventive concept relates to a temperature-sensing piezoelectric dispenser, and more particularly, to a dispenser including a piezoelectric pump dispensing a liquid by using a piezoelectric element as an actuator. 
     BACKGROUND ART 
     A dispenser supplying a predetermined amount of liquid that is in liquid form, such as water, oil, or resin is used in various fields such as in a semiconductor process or in the medical field. 
     Particularly in a semiconductor process, a dispenser is frequently used in an underfill process to fill a package of a semiconductor device with a resin. In a process of manufacturing a light emitting diode (LED) device, a dispenser is used in a process of coating a LED chip of the LED device with a phosphorescent liquid in which a phosphorescent material and a resin are mixed. 
     The dispenser as described above includes, as a core element, a pump that receives a liquid and dispenses a fixed amount of the liquid to an exact position. 
     Various pumps structures such as a screw pump or a linear pump are available. Recently, a piezoelectric pump that uses a piezoelectric element as an actuator has been developed and used in a semiconductor process or the like to perform a dispensing operation at a high speed. 
     KR 2005-0079557 (published on Aug. 10, 2005) discloses a piezoelectric pump structure comprising a plurality of piezoelectric actuators, on which a piezoelectric element is attached, and which are sequentially operated in connection with one another at different displacement differences to pump a fluid. 
     A piezoelectric actuator used in a piezoelectric pump is usually formed of a ceramic material. Most piezoelectric actuators including such ceramic piezoelectric actuators generate heat when operating according to an applied voltage. When a temperature of the piezoelectric actuator increases due to heat generated in the piezoelectric actuator, dynamic characteristics of the piezoelectric actuator are changed, and the lifetime of the piezoelectric actuator is also reduced. 
     Thus, a piezoelectric pump or a piezoelectric dispenser having a structure capable of preventing an increase in a temperature of a piezoelectric actuator is required. 
     DETAILED DESCRIPTION OF THE INVENTIVE CONCEPT 
     Technical Problem 
     The inventive concept provides a temperature-sensing piezoelectric dispenser capable of sensing a temperature generated in a piezoelectric actuator and cooling the piezoelectric actuator based on the sensed temperature. 
     Technical Solution 
     According to an aspect of the inventive concept, there is provided a temperature-sensing piezoelectric dispenser comprising: a pump body comprising a cooling line, through which a cooling fluid flows; a lever that is rotatably installed with respect to a hinge axis installed in the pump body; a piezoelectric actuator installed in the pump body and having a tip portion that is contactable to the lever as a length of the piezoelectric actuator is increased when a voltage is applied to the piezoelectric actuator to press and rotate the lever with respect to the hinge axis; a valve rod that is liftably connected to the lever according to rotation of the lever; a valve body comprising a storing unit, into which a tip portion of the valve rod is inserted and in which a liquid is stored, an inlet, through which the liquid flows into the storing unit, and a nozzle, through which the liquid of the storing unit is discharged according to advance and retreat of the valve rod with respect to the storing unit; a temperature sensor installed in one of the piezoelectric actuator and the pump body to measure a temperature; a cooling pump for supplying a cooling fluid to the cooling line of the pump body; and a control unit for operating the piezoelectric actuator and receiving the temperature sensed by using the temperature sensor to operate the cooling pump. 
     Advantageous Effects 
     According to the temperature-sensing piezoelectric dispenser according to the inventive concept, a temperature of a piezoelectric actuator is measured and the piezoelectric actuator is cooled based on the measured temperature, thereby accurately controlling a liquid discharged according to an operation of the piezoelectric actuator. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a piezoelectric pump of a temperature-sensing piezoelectric dispenser according to an embodiment of the inventive concept; 
         FIG. 2  is a perspective view of the piezoelectric pump illustrated in  FIG. 1 ; 
         FIG. 3  is a side view of the piezoelectric pump illustrated in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the piezoelectric pump illustrated in  FIG. 2  cut along a line IV-IV; 
         FIG. 5  is a cross-sectional view of the piezoelectric pump illustrated in  FIG. 2  cut along a line V-V; 
         FIG. 6  is a block diagram illustrating major elements of the temperature-sensing piezoelectric dispenser illustrated in  FIG. 1 ; 
         FIGS. 7 through 9  are schematic views for explaining an operation of the piezoelectric pump of the temperature-sensing piezoelectric dispenser illustrated in  FIG. 1 ; and 
         FIG. 10  is a schematic view for explaining an operation of the piezoelectric pump of the temperature-sensing piezoelectric dispenser according to another embodiment of the inventive concept. 
     
    
    
     BEST MODE 
     Hereinafter, a temperature-sensing piezoelectric dispenser according to the inventive concept will be described more fully with reference to the accompanying drawings. 
       FIG. 1  is a front view of a piezoelectric pump of a temperature-sensing piezoelectric dispenser according to an embodiment of the inventive concept.  FIG. 2  is a perspective view of the piezoelectric pump illustrated in  FIG. 1 .  FIG. 3  is a side view of the piezoelectric pump illustrated in  FIG. 1 . 
     Referring to  FIGS. 1 through 3 , the temperature-sensing piezoelectric dispenser according to the present embodiment includes a piezoelectric pump  100 , a control unit  200 , and a cooling pump  70 . The piezoelectric pump  100  includes a pump body  10  and a valve body  20 . 
     The pump body  10  and the valve body  20  are detachably coupled to each other by using a bolt as illustrated in  FIG. 1 . 
     A hinge axis  11  is mounted in the pump body  10 , and the lever  30  extending in a horizontal direction is rotatably installed with respect to the hinge axis  11 . The valve rod  40  extending in a vertical direction is inserted into the valve body  20 . The lever  30  and the valve rod  40  are connected to each other, and when the lever  30  rotates with respect to the hinge axis  11 , the valve rod  40  is lifted up or lowered down. 
     A first piezoelectric actuator  51  and a second piezoelectric actuator  52  are installed in the pump body  10  and rotate the lever  30  with respect to the hinge axis  11 . The first piezoelectric actuator  51  and the second piezoelectric actuator  52  are formed of piezoelectric elements. That is, the first piezoelectric actuator  51  and the second piezoelectric actuator  52  are formed of piezoelectric elements whose length increases or decreases according to a potential of a voltage applied to the piezoelectric elements. Here, an embodiment will be described, in which multi-stack piezoelectric actuators formed by stacking multiple piezoelectric elements are configured as the first piezoelectric actuator  51  and the second piezoelectric actuator  52 . 
     As illustrated in  FIG. 4 , the first piezoelectric actuator  51  and the second piezoelectric actuator  52  arranged in parallel to each other in a vertical direction are installed in the pump body  10 . The first piezoelectric actuator  51  and the second piezoelectric actuator  52  are disposed with the hinge axis  11  therebetween and such that lower end portions thereof respectively contact a top surface of the lever  30 . When a voltage is applied to the first piezoelectric actuator  51  to increase a length of the first piezoelectric actuator  51 , the lever  30  rotates counter-clockwise with respect to  FIG. 4 , and when a voltage is applied to the second piezoelectric actuator  52  to increase a length of the second piezoelectric actuator  52 , the lever  30  rotates clockwise with respect to  FIG. 4 . 
     A first adjustment unit  61  and a second adjustment unit  2  that are respectively disposed on upper ends of the first piezoelectric actuator  51  and the second piezoelectric actuator  52  are installed in the pump body  10 . In the present embodiment, the first adjustment unit  61  and the second adjustment unit  62  which are in the form of set screws are screw-coupled to the pump body  10  while respectively contacting tip portions of the first piezoelectric actuator  51  and the second piezoelectric actuator  52 . The first adjustment unit  61  adjusts a position of the first piezoelectric actuator  51  with respect to the lever  30  and the pump body  10 , and the second adjustment unit  62  adjusts a position of the second piezoelectric actuator  52  with respect to the lever  30  and the pump body  10 . When the first adjustment unit  61  is tightened to move the first piezoelectric actuator  51  forward with respect to the pump body  10 , the first piezoelectric actuator  51  may be lowered to be close to or in close contact with the lever  30 . The second adjustment unit  62  is also operated in the same manner as the first adjustment unit  61 . 
     A first returning unit  63  and a second returning unit  64  disposed respectively below the first piezoelectric actuator  51  and the second piezoelectric actuator  52  are installed in the pump body  10 . The first returning unit  63  applies a force to the first piezoelectric actuator  51  in a direction opposite to a direction in which the first piezoelectric actuator  51  presses the lever  30 . Likewise, the second returning unit  64  applies a force to the second piezoelectric actuator  52  in a direction opposite to a direction in which the second piezoelectric actuator  52  presses the lever  30 . The first returning unit  63  and the second returning unit  64  may be springs that respectively provide an elastic force under the first piezoelectric actuator  51  and the second piezoelectric actuator  52  in a direction in which the first piezoelectric actuator  51  and the second piezoelectric actuator  52  are contracted with respect to the pump body  10 , or may be fluid ducts. According to the present embodiment, springs  63  and  64  which are plate springs are installed in the pump body  10  to transmit an elastic force to the first piezoelectric actuator  51  and the second piezoelectric actuator  52 . If a pneumatic pressure or a fluid pressure is used unlike the present embodiment, a fluid duct may be used to transmit a pneumatic pressure or a fluid pressure to the first piezoelectric actuator  51  and the second piezoelectric actuator  52  to thereby transmit a force in a direction in which the first piezoelectric actuator  51  and the second piezoelectric actuator  52  are returned to an original position. 
     Referring to  FIG. 4 , a temperature sensor  210  is installed on each of the first piezoelectric actuator  51  and the second piezoelectric actuator  52 . The temperature sensor  210  may be installed on the piezoelectric actuators  51  and  52  or in the pump body  10 . Here, an embodiment in which the temperature sensor  210  is installed on the piezoelectric actuators  51  and  52  will be described. The temperature sensor  210  measures a temperature of the piezoelectric actuators  51  and  52  and transmits the temperature to the control unit  200 . A pump PCB  200  is installed in the pump body  10 , and the pump PCB  220  receives a control signal from the control unit  200  and transmits the control signal to the piezoelectric actuators  51  and  52 . The temperature measured by using the temperature sensor  210  is transmitted to the control unit  200  via the pump PCB  200 . 
     The control unit  200  is disposed outside the piezoelectric pump  100  and is electrically connected to the piezoelectric pump  100  to control an operation of the piezoelectric pump  100 . That is, the control unit  200  is electrically connected to the first piezoelectric actuator  51  and the second piezoelectric actuator  52  of the piezoelectric pump  100  to supply power thereto to thereby control the operation of the piezoelectric actuators  51  and  52 . When the piezoelectric pump  100  is used by installing the same in a horizontal transporting unit that transports the piezoelectric pump  100  in forward and backward directions and to the left and the right, the control unit  200  controls an operation of the horizontal transporting unit. That is, according to the temperature-sensing piezoelectric dispenser according to the inventive concept, the control unit  200  may use the horizontal transporting unit to move the piezoelectric pump  100  forward or backward or to the left or the right to thereby dispense a liquid to products disposed below the piezoelectric pump  100 . The control unit  200  may also adjust a movement speed of the piezoelectric pump  100  by controlling the horizontal transporting unit. 
     Cooling lines  71 ,  72 ,  73 , and  74  through which a cooling fluid may flow are formed in the pump body  10  as illustrated in  FIG. 5 . According to the present embodiment, air is supplied to the pump body  10  through the cooling lines  71 ,  72 ,  73 , and  74 . The cooling lines  71 ,  72 ,  73 , and  74  formed in the pump body  10  are formed to discharge the air supplied to the cooling pump  70  by allowing the air to pass through space in which the piezoelectric actuators  51  and  52  are installed. 
     The cooling pump  70  is connected to the cooling lines  71 ,  72 ,  73 , and  74  of the pump body  10  to supply air. The cooling pump  70  is controlled by being connected to the control unit  200 . When a temperature sensed by the temperature sensor  210  is increased, the control unit  200  may operate the cooling pump  70  to increase a flow of air supplied through the cooling lines  71 ,  72 ,  73 , and  74 , thereby cooling the piezoelectric actuators  51  and  52 . On the contrary, when a temperature of the piezoelectric actuators  51  and  52  sensed by the temperature sensor  210  is decreased, the control unit  200  controls the piezoelectric actuators  51  and  52  such that a flow of air supplied through the cooling lines  71 ,  72 ,  73 , and  74  is reduced. The air supplied through the cooling lines  71 ,  72 ,  73 , and  74  from the cooling pump  70  contacts the piezoelectric actuators  51  and  52  to absorb heat, and then is discharged to the outside through an outlet formed in the pump body  10 . 
     The valve body  20  includes a storing unit  22 , an inlet  21 , and a nozzle  23 . The storing unit  22  is in the form of a container having an opened top portion, and the valve rod  40  is inserted into the storing unit  22  so as to tightly close the top portion of the storing unit  22 . The inlet  21  is connected to the storing unit  22 . A liquid supplied from the outside is transferred to the storing unit  22  through the inlet  21 . 
     The valve rod  40  connected to the lever  30  is lifted with respect to the storing unit  22  according to rotation of the lever  30 . As the valve rod  40  is lifted and then lowered to approach the nozzle  23  disposed under the valve rod  40 , the liquid inside the storing unit  22  is pressurized and is dispensed to the outside through the nozzle  23 . 
     The lever  30  and the valve rod  40  may be connected using various methods. According to the present embodiment, the lever  30  and the valve rod  40  are connected to each other in a manner as illustrated in  FIGS. 1 and 2 . An engaging groove  31  that is opened in a horizontal direction is formed at a tip portion of the lever  30 . That is, the engaging groove  31  of the lever  30  has a C-shape. An engaging rod  41  is formed on an upper end portion of the valve rod  40 . The engaging rod  41  is inserted into the engaging groove  31  of the lever  30  to be rotatably connected to the lever  30 . That is, rotation of the lever  30  may be converted to elevation of the valve rod  40 . As the engaging groove  31  is formed to be opened in a horizontal direction, the engaging rod  41  may be moved in a horizontal direction with respect to the engaging groove  31  to thereby detach the engaging groove  31  and the engaging rod  41  from each other. As the engaging groove  31  is formed in a horizontal direction, even if the engaging groove  31  is lifted according to rotation of the lever  30 , the engaging rod  41  is lifted or lowered with respect to the valve body  20  without being detached from the engaging groove  31 . When the lever  30  and the valve rod  40  are to be separated from each other, they may be easily separated by moving the engaging rod  41  in a horizontal direction with respect to the engaging groove  31 . 
     As described above, when referring to  FIGS. 2 and 5 , the cooling lines  71 ,  72 ,  73 , and  74  are formed in the pump body  10 . That is, cooling paths through which a cooling fluid may flow via the pump body  10  are formed in the pump body  10 . By allowing a gas or liquid of a relatively low temperature to flow through the cooling paths as described above, heat generated in the first piezoelectric actuator  51  and the second piezoelectric actuator  52  is discharged to the outside. 
     Hereinafter, an operation of the temperature-sensing piezoelectric dispenser according to the present embodiment configured as described above will be described. 
     First, while the pump body  10 , the valve body  20 , and the other elements are assembled as shown in  FIG. 1 , a voltage is applied to the first piezoelectric actuator  51  and the second piezoelectric actuator  52 . A voltage of 50% with respect to a voltage that is to be applied to the second piezoelectric actuator  52  in order to lower the valve rod  40  to dispense a liquid through the nozzle  23  is applied to each of the first piezoelectric actuator  51  and the second piezoelectric actuator  52 . As illustrated in  FIG. 7 , as the first piezoelectric actuator  51  and the second piezoelectric actuator  52  are extended by the same length, each of lower end portions thereof is in contact with the lever  30 . In this state, the first adjustment unit  61  and the second adjustment unit  62  are respectively used to adjust positions of the first piezoelectric actuator  51  and the second piezoelectric actuator  52 . The first piezoelectric actuator  51  and the second piezoelectric actuator  52  are respectively moved forward or backward by rotating bolts  61  and  62  so that the lever  30  is in a horizontal state. Here, when the bolts  61  and  62  are rotated to move the first piezoelectric actuator  51  or the second piezoelectric actuator  52  backward, the first piezoelectric actuator  51  or the second piezoelectric actuator  52  is pushed and lifted due to an operation of the first returning unit  63  and the second returning unit  64 . 
     Initial positions of the first piezoelectric actuator  51  and the second piezoelectric actuator  52  for dispensing are set in the above-described manner. 
     In this state, a liquid is supplied to the storing unit  22  through the inlet  21  at a predetermined pressure. 
     In this state, a dispensing process of the liquid is started. 
     When a voltage of 100% is applied to the first piezoelectric actuator  51 , and a voltage of 0% is applied to the second piezoelectric actuator  52 , the first piezoelectric actuator  51  is expanded, and the second piezoelectric actuator  52  is contracted. As illustrated in  FIG. 8 , as the lever  30  rotates counter-clockwise, the valve rod  40  is lifted. Here, due to an operation of the second returning unit  64 , rotation of the lever  30  is faster. For reference, an inclination angle of the lever  30  is exaggerated in  FIG. 8  for effective description. 
     In this state, when a voltage of 0% is applied to the first piezoelectric actuator  51 , and a voltage of 100% is applied to the second piezoelectric actuator  52 , the first piezoelectric actuator  51  is contracted, and the second piezoelectric actuator  52  is expanded. As illustrated in  FIG. 9 , as the lever  30  rotates clockwise, the valve rod  40  is lowered. As the valve rod  40  inserted into the storing unit  22  is lowered, the valve rod  40  pressurizes the liquid in the storing unit  22  to discharge the liquid to the outside through the nozzle  23 , thereby dispensing the liquid. Here also, the first returning unit  63  contracts the first piezoelectric actuator  51  that is adjacent thereto to help the lever  30  rotate quickly in a clockwise direction. Like  FIG. 8 , an inclination angle of the lever  30  is exaggerated in  FIG. 9  for effective description. 
     By alternately applying a voltage to the first piezoelectric actuator  51  and the second piezoelectric actuator  52  as described above, the valve rod  40  is repeatedly lifted as illustrated in  FIGS. 8 and 9 , thereby continuously dispensing the liquid through the nozzle  23 . 
     As illustrated in  FIG. 4 , a distance between a rotational axis and the valve rod  40  is far greater than a distance between the rotational axis and the first piezoelectric actuator  51  and the second piezoelectric actuator  52 , and thus, a deformation amount of the piezoelectric actuators  51  and  52  may be sufficiently extended by using the lever  30  so as to operate the valve rod  40  within a sufficient height range. 
     The control unit  200  controlling operations of the first piezoelectric actuator  51  and the second piezoelectric actuator  52  may apply a voltage having various pulse waveforms to the first piezoelectric actuator  51  and the second piezoelectric actuator  52  according to time to thereby control dynamic characteristics of the valve rod  40 . In particular, by disposing the two piezoelectric actuators  51  and  52  with the hinge axis  11  included therebetween and configuring the two piezoelectric actuators  51  and  52  to respectively operate the lever  30 , not only descending movement but also elevation of the valve rod  40  may be controlled, and accordingly, the liquid may be quickly dispensed, and an amount of the dispensed liquid may also be accurately controlled. 
     In particular, mechanical operating characteristics of the first piezoelectric actuator  51  and the second piezoelectric actuator  52  may be accurately controlled by the control unit  200  by using an electrical method based on factors such as amplitude of a voltage to be applied, an alternating frequency of a voltage, or a deformation amount of a voltage according to time. Improvement of controlling performance with respect to an operation of the valve rod  40  as above allow easy and accurate controlling of dispensing characteristics of the dispensed liquid. 
     Due to characteristics of the piezoelectric actuators  51  and  52 , a relatively large amount of heat is generated in the piezoelectric actuators  51  and  52  during use thereof. When a temperature of the piezoelectric actuators  51  and  52  is increased due to heat generated in the piezoelectric actuators  51  and  52 , operating characteristics thereof may be degraded. In the piezoelectric pump  100  according to the present embodiment, the cooling lines  71 ,  72 ,  73 , and  74  are formed in the pump body  10  as illustrated in  FIG. 5 . By cooling the pump body  10  through the cooling lines  71 ,  72 ,  73 , and  74 , an increase in a temperature of the piezoelectric actuators  51  and  52  may be prevented. When the temperature of the piezoelectric actuators  51  and  52  is increased, piezoelectric characteristics thereof are changed and an actuation displacement of the piezoelectric actuators  51  and  52  with respect to a voltage applied to the piezoelectric actuators  51  and  52  is changed, resulting in a change of an ejection amount of a liquid discharged according to an operation of a lever. As described above, when the temperature of the piezoelectric actuators  51  and  52  is increased, the piezoelectric pump  100  may not dispense an accurate amount of liquid. 
     The temperature-sensing piezoelectric dispenser according to the present embodiment measures a temperature of the piezoelectric actuators  51  and  52  by using the temperature sensor  210  as illustrated in  FIGS. 4 and 6 , and transmits the temperature to the control unit  200 . When the temperature of the piezoelectric actuators  51  and  52  is increased beyond a preset range, the control unit  200  operates the cooling pump  70  to increase a flow of air supplied to the cooling lines  71 ,  72 ,  73 , and  74 . The control unit  200  may control the cooling pump  70  such that the temperature of the piezoelectric actuators  51  and  52  is close to a preset temperature or may set a temperature range (for example, 27° C. to 30° C.) and control the cooling pump  70  such that the temperature of the piezoelectric actuators  51  and  52  is maintained with the set temperature range. 
     Also, by preventing an increase in the temperature of the piezoelectric actuators  51  and  52  as described above, dynamic characteristics of the valve rod  40  may be uniformly maintained and a dispensing quality of the liquid may be maintained. At the same time, the lifetime of the piezoelectric actuators  51  and  52  may be increased. 
     Meanwhile, the control unit  200  may control the piezoelectric pump  100  based on previously stored dynamic characteristics of the piezoelectric actuators  51  and  52  according to temperature of the piezoelectric actuators  51  and  52 . Actuation displacement of the piezoelectric actuators  51  and  52  may vary according to temperature even when an identical voltage is applied to the piezoelectric actuators  51  and  52 . The control unit  200  may control the piezoelectric pump  100  by considering a variation in the actuation displacement of the piezoelectric actuators  51  and  52  according to temperature. The actuation displacement of the piezoelectric actuators  51  and  52  may be maintained uniform even though the temperature of the piezoelectric actuators  51  and  52  is changed as the control unit  200  adjusts a voltage, a waveform or a frequency of a current or the like applied to the piezoelectric actuators  51  and  52 , based on the temperature of the piezoelectric actuators  51  and  52  sensed by using the temperature sensor  210 . Accordingly, an ejection amount of the liquid discharged through the nozzle may be uniformly maintained. 
     According to the piezoelectric pump  100  according to the present embodiment, as the pump body  10  and the valve body  20  are detachably configured and the lever  30  and the valve rod  40  are configured to be easily connected and separated to and from each other, maintenance and cleaning are easy and the piezoelectric pump  100  may be easily configured to correspond to various characteristics of a liquid. The valve body  20  and the valve rod  40  may be easily separated from the pump body  10  by loosening a screw coupling the pump body  10  and the valve body  20  and detaching the engaging rod  41  of the valve rod  40  from the engaging groove  31  of the lever  30 . 
     When the valve body  20  is separated, it is easy to clean for next use. Even when the valve body  20  or the valve rod  40  is damaged, the valve body  20  or the valve rod  40  may be separated by using the above-described method and a new valve body  20  or a new valve rod  40  may be replaced. 
     When a type of a liquid to be dispensed is changed, the piezoelectric pump  100  may be configured by replacing with another valve body  20  and another valve rod that are designed in consideration of a viscosity or other characteristics of the changed liquid. 
     The piezoelectric actuators  51  and  52  are typically formed of a ceramic material. When the piezoelectric actuators  51  and  52  are used for a long period of time, expansion displacement thereof according to an applied voltage may be changed from the initial expansion displacement due to the characteristics of the ceramic material. Also in this case, the piezoelectric pump  100  according to the present embodiment may maintain dynamic characteristics of the lever  30  and the valve rod  40  by adjusting positions of the first piezoelectric actuator  51  and the second piezoelectric actuator  52  by using the first adjustment unit  61  and the second adjustment unit  62 . 
     MODE OF THE INVENTIVE CONCEPT 
     While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, the scope of the inventive concept is not limited to the forms described and illustrated above. 
     For example, while the first returning unit  63  and the second returning unit  64  that are formed of springs or implemented using a pneumatic pressure are described above, according to circumstances, a liquid pressure may be used to implement a first returning unit and a second returning unit. Also, a pump that does not include the first returning unit and the second returning unit may be included. 
     Also, while air is described above as a cooling fluid flowing through the cooling lines  71 ,  72 ,  73 , and  74  of the pump body  10 , liquid such as cooling water or cooling oil may also be used. In this case, unlike the above-described embodiment, a temperature-sensing piezoelectric dispenser is configured such that a cooling fluid supplied through the cooling lines  71 ,  72 ,  73 , and  74  is not discharged to the outside but returns to the cooling pump to circulate. 
     Also, while the temperature sensor  210  is described above as being installed in the piezoelectric actuators  51  and  52 , according to circumstances, the temperature sensor  210  may also be installed in a portion of the pump body that is close to the piezoelectric actuators. In this case, heat generated in the piezoelectric actuators may be conducted to the pump body so that the pump body senses the increased temperature, thereby indirectly measuring a temperature of the piezoelectric actuators. 
     Also, while the lever  30  and the valve rod  40  are described as being connected via the engaging groove  31  of the lever  30  and the engaging rod  41  of the valve rod  40 , a lever and a valve rod may also be connected by using other methods. A pump body and a valve body may not be detachably coupled to each other but may be formed as a single unit. 
     Hereinafter, a piezoelectric pump used in a temperature-sensing piezoelectric dispenser according to another embodiment of the inventive concept will be described with reference to  FIG. 10 . 
     Unlike the piezoelectric pump of the temperature-sensing piezoelectric dispenser described above with reference to  FIGS. 1 through 9 , according to the piezoelectric pump of the temperature-sensing piezoelectric dispenser of the present embodiment, a first piezoelectric actuator  81  and a second piezoelectric actuator  82  are disposed to face each other in a straight line, with the lever  30  therebetween. When a voltage is applied to the first piezoelectric actuator  81 , and no voltage is applied to the second piezoelectric actuator  82 , the lever  30  rotates counter-clockwise to lift the valve rod  40 . When no voltage is applied to the first piezoelectric actuator  81 , and a voltage is applied to the second piezoelectric actuator  82 , the lever  30  rotates clockwise to lower the valve rod  40 , and a liquid is dispensed through the nozzle  23 . A first returning unit  67  and a second returning unit  68  are also disposed to face each other in a straight line, with the lever  30  therebetween. The first returning unit  67  provides an elastic force in a direction in which the first piezoelectric actuator  81  is contracted, and the second returning unit  68  provides an elastic force in a direction in which the second piezoelectric actuator  82  is contracted. 
     In regard to other elements except for arrangement of the first piezoelectric actuator  81  and the second piezoelectric actuator  82 , a temperature-sensing piezoelectric dispenser may be configured by appropriately modifying the other elements of the embodiments described with reference to  FIGS. 1 through 9  above. However, in the piezoelectric pump according to the present embodiment, the first returning unit  67  and the second returning unit  68  may be unnecessary.