Low hysteresis piezoelectric pump

Abstract

The present invention provides a low-hysteresis piezoelectric pump that uses a piezoelectric element as an actuator to dispense liquid, and can maintain accurate viscous liquid discharge characteristics by adjusting the applied voltage in response to changes in the behavioral characteristics of the piezoelectric actuator due to reasons such as temperature changes.

Description

[0001] Cross-reference to related applications

[0002] This application is based on and claims the benefit of Korean Patent Application No. 10-2021-0191188 filed on December 29, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to a low hysteresis piezoelectric pump, and more particularly, to a low hysteresis piezoelectric pump that uses a piezoelectric element as an actuator to dispense liquid. Background Art

[0004] Dispensers that supply precise amounts of viscous liquids, such as water, oil, or resin, are used in various fields, such as semiconductor processing and the medical field.

[0005] Specifically, in the case of semiconductor manufacturing, dispensers are often used in the underfill process and are also widely used to fill the interior of semiconductor device packages with resin. In the process of manufacturing light-emitting diode (LED) devices, dispensers are used to apply phosphor mixed with phosphor material and resin in LED devices to LED chips.

[0006] In such dispensers, a pump that dispenses a precise amount of supplied liquid at an exact location serves as a key device.

[0007] There are various types of pump structures, such as a screw pump and a linear pump. Recently, in order to perform dispensing at high speed, a piezoelectric pump using a piezoelectric element as an actuator has been developed and used in semiconductor processes.

[0008] Korean Patent Registration No. 1301107 (registered on August 14, 2013) discloses a piezoelectric pump including a pump body and a valve body, which are detachably coupled to each other. A hinge axis is mounted on the pump body, and a lever extending in a horizontal direction is rotatably mounted relative to the hinge axis. A valve stem extending in a vertical direction is mounted on the valve body. The lever and the valve stem are connected to each other so that when the lever rotates around the hinge axis, the valve stem moves up and down. A pair of piezoelectric actuators are mounted on the pump body to rotate the lever relative to the hinge axis. Each of the pair of piezoelectric actuators is composed of a piezoelectric element whose length increases or decreases depending on the potential of an applied voltage.

[0009] The piezoelectric actuators used in these types of piezoelectric pumps are typically made from a ceramic material called lead zirconium titanate (PZT). These piezoelectric actuators generate heat during use, increasing their temperature. However, as the temperature of the piezoelectric actuator increases, the piezoelectric actuator's behavior changes. Therefore, even if the applied voltage driving the piezoelectric actuator is set according to operating conditions, the performance of the piezoelectric pump will change if the piezoelectric actuator's temperature rises during operation. Furthermore, as the temperature of the piezoelectric actuator increases, hysteresis increases, and the correspondence between the applied voltage and the amount of deformation of the piezoelectric actuator changes.

[0010] To address this issue, piezoelectric pumps equipped with a piezoelectric actuator cooling system have been developed and are being used. However, using a cooling system increases the size of the piezoelectric pump. Furthermore, depending on the type of cooling system, there are limitations in maintaining a constant temperature of the piezoelectric pump, making it difficult to maintain pump performance. Using liquid cooling, such as water, creates the risk of process failure due to cooling liquid leakage.

[0011] Therefore, there is a need for a low-hysteresis piezoelectric pump that can maintain the dispensing performance of the piezoelectric pump despite changes in the piezoelectric characteristics due to temperature variations of the piezoelectric actuator. Furthermore, there is a need for a low-hysteresis piezoelectric pump that can maintain the dispensing performance, taking into account the performance changes of the piezoelectric actuator within a predetermined temperature range, which inevitably occurs even when a cooling device is used. Summary of the Invention

[0012] An object of the present disclosure is to provide a low-hysteresis piezoelectric pump capable of maintaining discharge performance of a viscous liquid even when the characteristics of a piezoelectric actuator change.

[0013] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0014] A low-hysteresis piezoelectric pump from the present disclosure comprises: a pump body; a valve operating component comprising a lever installed so as to be rotatable relative to a hinge axis installed on the pump body, and a valve stem connected to the lever to move up and down according to the rotation of the lever; a piezoelectric actuator installed on the pump body and having an end portion that can contact the lever, wherein the piezoelectric actuator stretches and presses the lever when a voltage is applied to rotate the lever around the hinge axis; a valve body comprising a reservoir into which the end portion of the valve stem is inserted and in which liquid is stored, an inlet through which liquid is introduced into the reservoir, and a nozzle through which liquid in the reservoir is discharged according to forward / backward movement of the valve stem in the reservoir; a displacement detection sensor installed in the piezoelectric actuator to detect the operating displacement of the piezoelectric actuator; and a control unit electrically connected to the piezoelectric actuator and the displacement detection sensor to apply voltage to operate the piezoelectric actuator, and receive a detection signal about the operating displacement of the piezoelectric actuator from the displacement detection sensor.

[0015] In addition, a low-hysteresis piezoelectric pump according to the present disclosure includes: a pump body; a valve operating component including a lever installed so as to be rotatable relative to a hinge axis installed on the pump body, and a valve stem connected to the lever so as to move up and down according to the rotation of the lever; a pair of piezoelectric actuators installed on the pump body in parallel with each other, wherein the hinge axis is inserted between the pair of piezoelectric actuators and each has an end portion that can contact the lever, wherein the pair of piezoelectric actuators are extended and press the lever when a voltage is applied to rotate the lever about the hinge axis; a valve body including an end portion of the valve stem inserted therein and a liquid a reservoir in which liquid is stored, an inlet through which liquid is introduced into the reservoir, and a nozzle through which the liquid in the reservoir is discharged according to the forward / backward movement of the valve stem in the reservoir; a pair of displacement detection sensors respectively installed in the pair of piezoelectric actuators to detect the operating displacement of the pair of piezoelectric actuators; and a control unit electrically connected to the pair of piezoelectric actuators and the pair of displacement detection sensors to apply a voltage to operate the pair of piezoelectric actuators, and receive a detection signal about the operating displacement of the pair of piezoelectric actuators from the pair of displacement detection sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0017] Figure 1 is a front view of a low hysteresis piezoelectric pump according to an embodiment of the present disclosure.

[0018] Figure 2 for Figure 1 A perspective view of the low hysteresis piezoelectric pump shown in FIG.

[0019] Figure 3 for Figure 1Cross-sectional view of the low hysteresis piezoelectric pump shown in .

[0020] Explanation of Figure Numbers

[0021] 100: pump body;

[0022] 200, 300: piezoelectric actuator;

[0023] 210, 310: position controller;

[0024] 400: valve operating parts;

[0025] 410: hinge axis;

[0026] 420: Leverage;

[0027] 421: Capture groove;

[0028] 430: valve stem;

[0029] 431: capture protrusion;

[0030] 500: valve body;

[0031] 510: reservoir;

[0032] 520: Entrance;

[0033] 530: nozzle;

[0034] 600, 700: displacement detection sensor;

[0035] 800: control unit;

[0036] 810: Lever displacement sensor. DETAILED DESCRIPTION

[0037] Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout the text. In this regard, the present embodiment may have different forms and should not be construed as being limited to the description set forth herein. Therefore, the embodiments are described below only by reference to the accompanying drawings to explain various aspects. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. When preceding a list of elements, expressions such as "at least one of" modify the entire list of elements rather than modifying the individual elements of the list.

[0038] Hereinafter, a low hysteresis piezoelectric pump according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0039] Figure 1 is a front view of a low hysteresis piezoelectric pump according to an embodiment of the present disclosure, Figure 2 for Figure 1A perspective view of a low hysteresis piezoelectric pump is shown in FIG. Figure 3 for Figure 1 Cross-sectional view of the low hysteresis piezoelectric pump shown in .

[0040] refer to Figures 1 to 3 The low hysteresis piezoelectric pump of this embodiment includes a pump body 100, a pair of piezoelectric actuators 200 and 300, a valve operating component 400, a valve body 500, a pair of displacement detection sensors 600 and 700, a lever displacement sensor 810 and a control unit 800.

[0041] The pair of piezoelectric actuators 200 and 300, the valve operating member 400, the pair of displacement detection sensors 600 and 700, and the lever displacement sensor 810 are housed inside the pump body 100. The pump body 100 is detachably coupled to the valve body 500 by a fixing member (not shown), such as a bolt. Furthermore, the pump body 100 is electrically connected to the control unit 800.

[0042] The pair of piezoelectric actuators 200 and 300 are mounted on the pump body 100. Each of the pair of piezoelectric actuators 200 and 300 is formed of a piezoelectric element. The length of the piezoelectric element increases or decreases according to the potential of the applied voltage, which is the voltage applied to the piezoelectric element, thereby rotating the lever 420 relative to the hinge axis 410. In this embodiment, the piezoelectric actuators 200 and 300 will be described as an example of a multi-stack type in which a plurality of piezoelectric elements are stacked.

[0043] In the low-hysteresis piezoelectric pump of this embodiment, the pair of piezoelectric actuators 200 and 300 includes a first piezoelectric actuator 200 and a second piezoelectric actuator 300 .

[0044] First piezoelectric actuator 200 and second piezoelectric actuator 300 are arranged side by side in a vertical direction and supported by pump body 100. First piezoelectric actuator 200 and second piezoelectric actuator 300 are arranged so that their lower ends 220 and 320 contact the upper surface of lever 420, with hinge shaft 410 interposed therebetween. Position controllers 210 and 310 are respectively installed at positions corresponding to the upper ends of first piezoelectric actuator 200 and second piezoelectric actuator 300 in pump body 100.

[0045] The first position controller 210 and the second position controller 310 are screw-coupled to the pump body 100 in a state where their end portions are in contact with the end portions of the first piezoelectric actuator 200 and the second piezoelectric actuator 300, respectively. The first position controller 210 controls the position of the first piezoelectric actuator 200 relative to the lever 420 and the pump body 100, and the second position controller 310 controls the position of the second piezoelectric actuator 300 relative to the lever 420 and the pump body 100. That is, when the first position controller 210 is tightened and presses the first piezoelectric actuator 200, the first piezoelectric actuator 200 descends to close or tightly contact with the lever 420. The second position controller 310 operates in the same manner as the first position controller 210.

[0046] The valve operating member 400 includes a hinge shaft 410, a lever 420, and a valve stem 430. The hinge shaft 410 is mounted on the pump body 100. The lever 420 extends horizontally and is rotatably mounted on the hinge shaft 410. The valve stem 430 extends vertically and is connected to one end of the lever 420. When the lever 420 rotates relative to the hinge shaft 410, the valve stem 430 moves up and down. The valve stem 430, connected to the lever 420, moves up and down relative to the reservoir 510 in accordance with the rotation of the lever 420.

[0047] The lever 420 and the valve stem 430 can be connected using various methods. In this embodiment, the valve stem is connected to the lever 420 so that it can be moved up and down by hooking onto the lever 420. A horizontally open capture groove 421 is formed in the end portion of the lever 420. In other words, the capture groove 421 of the lever 420 is formed in a "C" shape. A capture protrusion 431 is formed on the upper end of the valve stem 430. The capture protrusion 431 is inserted into the capture groove 421 of the lever 420 to enable rotational connection to the lever 420. Because the capture groove 421 is horizontally open, the capture protrusion 431 moves horizontally relative to the capture groove 421, allowing the capture groove 421 and the capture protrusion 431 to be attached and detached from each other. Furthermore, because the capture groove 421 is formed horizontally, even if the capture groove 421 moves up and down due to the rotation of the lever 420, the capture protrusion 431 will not fall out of the capture groove 421 and move up and down relative to the valve body 500. When the lever 420 and the valve stem 430 need to be separated from each other, the catching protrusion 431 may be horizontally moved so as to be easily separated from the catching groove 421 .

[0048] The valve body 500 includes a reservoir 510, an inlet 520, and a nozzle 530. The reservoir 510 is formed in the form of a container that opens upward. The inlet 520 is connected to the reservoir 510 and delivers liquid supplied from the outside to the reservoir 510. The valve stem 430 is inserted into the reservoir 510. When the valve stem 430 is moved up and down by the valve operating member 400 as described above, the liquid in the reservoir 510 is discharged through the nozzle 530 due to the pressure generated by the valve stem 430.

[0049] First and second displacement detection sensors 600 and 700 are installed in first and second piezoelectric actuators 200 and 300, respectively. These sensors are arranged along the extension direction of first and second piezoelectric actuators 200 and 300 to detect the operational displacement of each of them. In this embodiment, each of first and second displacement detection sensors 600 and 700 is formed from a strain gauge. A strain gauge measures the strain of an object to which it is attached. The strain measured by these sensors is transmitted to a control unit 800, which calculates the deformation of each of them, taking into account the lengths of the first and second piezoelectric actuators 200 and 300.

[0050] The lever displacement sensor 810 measures the operational displacement of the valve operating member 400. To this end, the lever displacement sensor 810 is mounted on the pump body 100 and connected to the lever 420 of the valve operating member 400. The value measured by the lever displacement sensor 810 is transmitted to the control unit 800. In this embodiment, the lever displacement sensor 810 is formed by a linear variable displacement transformer (LVDT). A linear variable displacement transformer is a mechanical motion sensor that converts mechanical motion or vibration (specifically, linear motion) into a variable current, voltage, or electrical signal, and vice versa.

[0051] The control unit 800 applies a voltage to actuate the piezoelectric actuators 200 and 300. To this end, the control unit 800 includes a power supply. Simultaneously, the control unit 800 receives detection signals regarding the strain of the first and second piezoelectric actuators 200 and 300 from the first and second displacement detection sensors 600 and 700. Based on the provided strain of the piezoelectric actuators 200 and 300, the control unit 800 converts and calculates the operational displacements of the first and second piezoelectric actuators 200 and 300. The control unit 800 compares the calculated operational displacements of the first and second piezoelectric actuators 200 and 300 with a preset reference set value and checks whether the operational displacements of the first and second piezoelectric actuators 200 and 300 are equal to the preset reference set value. When the operating displacement of the first piezoelectric actuator 200 and the second piezoelectric actuator 300 is different from the reference setting value, the control unit 800 adjusts the voltage applied to the first piezoelectric actuator 200 and the second piezoelectric actuator 300 so as to adjust the operating displacement of the first piezoelectric actuator 200 and the second piezoelectric actuator 300 to be the same as the preset reference setting value.

[0052] In addition, the control unit 800 receives a detection signal regarding the operational displacement of the valve operating member 400 from the lever displacement sensor 810. The control unit 800 compares the provided operational displacement of the valve operating member 400 with a preset reference set value and determines whether the operational displacement of the valve operating member 400 is equal to or different from the preset reference set value. When the operational displacement of the valve operating member 400 is different from the reference set value, the control unit 800 adjusts and changes the voltage applied to the first piezoelectric actuator 200 and the second piezoelectric actuator 300 so as to adjust the operational displacement of the valve operating member 400 to be the same as the preset reference set value.

[0053] On the other hand, when the operational displacements of the two piezoelectric actuators 200 and 300 calculated from the pair of displacement detection sensors 600 and 700 and the operational displacement of the valve operating member 400 detected from the lever displacement sensor 810 differ from each other, the control unit 800 prioritizes the operational displacement of the valve operating member 400 and adjusts the voltages applied to the two piezoelectric actuators 200 and 300. As described above, by adjusting the voltages applied to the two piezoelectric actuators 200 and 300 according to the operational displacement of the output stage during the valve operation process, continuous quantitative discharge of the low-hysteresis piezoelectric pump can be achieved.

[0054] Furthermore, the control unit 800 compares the operational displacements of the two piezoelectric actuators 200 and 300, calculated from the pair of displacement detection sensors 600 and 700, with the operational displacement of the valve operating member 400 detected by the lever displacement sensor 810 to determine a change in the performance of the two piezoelectric actuators 200 and 300, or a change in the performance of an element connected and arranged between the two piezoelectric actuators 200 and 300 and the valve operating member 400. Specifically, if there is no performance change in the two piezoelectric actuators 200 and 300, the control unit 800 determines that the performance of the element has been reduced. At this time, the operational displacements calculated from the displacement detection sensors 600 and 700 are converted and calculated into the magnitude of the stroke amplified by the lever 420 so as to correspond to the operational displacement detected by the lever displacement sensor 810. Furthermore, the operational displacements of the displacement detection sensors 600 and 700, calculated as described above, are consistent with or proportional to the operational displacement of the lever displacement sensor 810.

[0055] When the performance of the two piezoelectric actuators 200 and 300 deteriorates and it becomes difficult to adjust the operating displacement of the valve operating member 400 simply by adjusting the applied voltage, the user can replace the two piezoelectric actuators 200 and 300 with a continuous quantitative discharge method to make this possible. If the performance of the two piezoelectric actuators 200 and 300 has not degraded or has fallen below the allowable value, continuous quantitative discharge can be achieved by inspecting and replacing the associated components. For example, the liquid discharge volume of the valve operating member 400 can be adjusted to a reference set value by, for example, adjusting the tightening amount of the coupling components (position controllers 210 and 310) between the pump body 100 and the valve body 500; reassembling after separating the pump body 100 and the valve body 500; or reassembling after separating the lever 420 and the valve stem 430.

[0056] Hereinafter, the operation of the low hysteresis piezoelectric pump according to the embodiment configured as described above will be described.

[0057] First, in a state where the pump body 100, the valve body 500 and other components are assembled, the control unit 800 applies a set voltage to the first piezoelectric actuator 200 and the second piezoelectric actuator 300. Figure 3 As shown in FIG, the first piezoelectric actuator 200 and the second piezoelectric actuator 300 are alternately stretched to the same length as each other, and the lower end of each is in contact with the lever 420 .

[0058] In this state, the positions of the first piezoelectric actuator 200 and the second piezoelectric actuator 300 can be adjusted by the first position controller 210 and the second position controller 310. That is, the first position controller 210 or the second position controller 310 is rotated to move the first piezoelectric actuator 200 and the second piezoelectric actuator 300 forward and backward, respectively, so that the lever 420 can be in a horizontal state.

[0059] After initial positions of first and second piezoelectric actuators 200 and 300 for dispensing are set through the above process, liquid is supplied to reservoir 510 through inlet 520 at a constant pressure. Subsequently, a process of dispensing the liquid supplied to reservoir 510 is started.

[0060] When a voltage is applied to the first piezoelectric actuator 200, the first piezoelectric actuator 200 is stretched. When a voltage of opposite polarity is applied to the second piezoelectric actuator 300, the second piezoelectric actuator 300 is contracted. Figure 3 , the lever 420 rotates clockwise, and the valve stem 430 rises.

[0061] Similarly, when opposite voltages are applied to first piezoelectric actuator 200 and second piezoelectric actuator 300, first piezoelectric actuator 200 contracts and second piezoelectric actuator 300 extends. At this time, lever 420 rotates counterclockwise, and valve stem 430 descends. Valve stem 430, descending from reservoir 510, presses the liquid inside reservoir 510 and discharges the liquid to the outside through nozzle 530, thereby dispensing the liquid.

[0062] Thus, when voltage is alternately applied to first piezoelectric actuator 200 and second piezoelectric actuator 300, valve stem 430 repeatedly rises and falls, and liquid is continuously dispensed through nozzle 530. Since the distance between hinge axis 410 and valve stem 430 is much larger than the distance between hinge axis 410 and first piezoelectric actuator 200 and the distance between hinge axis 410 and second piezoelectric actuator 300, the deformation amount of piezoelectric actuators 200 and 300 is sufficiently amplified by lever 420, allowing valve stem 430 to operate within a sufficient height.

[0063] Control unit 800, which controls the operation of first and second piezoelectric actuators 200 and 300, applies voltages having different types of pulse waveforms to first and second piezoelectric actuators 200 and 300 over time, thereby controlling the dynamic characteristics of valve stem 430. Specifically, since two piezoelectric actuators 200 and 300 are configured to operate lever 420 with hinge shaft 410 interposed between them, not only the downward movement of valve stem 430 but also its upward movement can be controlled. Furthermore, liquid can be dispensed more quickly, and the amount of dispensed liquid can be precisely controlled.

[0064] Specifically, the control unit 800 can electrically and accurately control the mechanical operating characteristics of the first and second piezoelectric actuators 200 and 300 by using control parameters such as the magnitude of the applied voltage, the alternating frequency of the voltage, and the amount of change in the voltage over time. As a result, the control performance of the operation of the valve stem 430 is improved, making it possible to easily and accurately control the dispensing characteristics of the dispensed liquid.

[0065] Piezoelectric actuators 200 and 300 generate relatively much heat during use due to their characteristics. If the temperature of piezoelectric actuators 200 and 300 increases due to the heat generated by piezoelectric actuators 200 and 300, operational characteristics may deteriorate.

[0066] Although the characteristics of piezoelectric actuators 200 and 300 change in response to temperature increases, the low-hysteresis piezoelectric pump according to the present disclosure can maintain a constant operating displacement of valve operating member 400. The control unit 800 detects the deformation of piezoelectric actuators 200 and 300 using displacement detection sensors 600 and 700 (e.g., strain gauges mounted on piezoelectric actuators 200 and 300) and adjusts the applied voltage to correct the deformation of piezoelectric actuators 200 and 300. The control unit 800 can adjust the voltage applied to the piezoelectric actuators 200 and 300 by receiving the measured values ​​of the displacement detection sensors 600 and 700 as feedback in real time. Furthermore, the control unit 800 can control the voltage applied to the piezoelectric actuators 200 and 300 while also monitoring the measured value of the lever displacement sensor 810, comparing and matching the measured values ​​of the displacement detection sensors 600 and 700 with the measured value of the lever displacement sensor 810. Through this method, in the case of the present disclosure, regardless of characteristic changes due to, for example, temperature changes of piezoelectric actuators 200 and 300, the dispensing performance of viscous liquid can be constantly maintained. Specifically, even in the case of the present disclosure, the corresponding relationship between the operating displacement of piezoelectric actuators 200 and 300 and the applied voltage is not linear, or the change in the amount of deformation of piezoelectric actuators 200 and 300 according to the applied voltage exhibits a hysteresis curve, the lifting displacement of valve stem 430 can be kept constant. This is a more direct method than cooling piezoelectric actuators 200 and 300, and at the same time, it is a method that can more immediately and quickly compensate for the operating displacement of valve stem 430, and is therefore more effective in maintaining the quality of the viscous liquid dispensing process.

[0067] Therefore, instead of measuring the deformation of each pair of piezoelectric actuators 200 and 300 and adjusting the operating displacement individually, control unit 800 can adjust the voltage applied to the pair of piezoelectric actuators 200 and 300 so that the sum of the displacement measurement values ​​detected by each pair of displacement detection sensors 600 and 700 is maintained at a reference set value. For example, the sum of the distance valve stem 430 moves upward due to the extension of first piezoelectric actuator 200 and the distance valve stem 430 moves downward due to the extension of second piezoelectric actuator 300 becomes the lift displacement of valve stem 430 as a whole. Since the lift displacement of valve stem 430 is a direct factor in the viscous liquid discharge capacity, control unit 800 can operate piezoelectric actuators 200 and 300 to constantly maintain this value. In other words, control unit 800 uses the sum of the lengths of the first and second piezoelectric actuators 300 to adjust the applied voltage. In some cases, it is possible to operate control unit 800 by using the sum of the increased length of first piezoelectric actuator 200 and the contracted length of second piezoelectric actuator 300 .

[0068] Although preferred examples have been described above with respect to the present disclosure, the scope of the present disclosure is not limited to the forms described and illustrated above.

[0069] For example, while the low-hysteresis piezoelectric pump equipped with the pair of piezoelectric actuators 200 and 300 and the pair of displacement detection sensors 600 and 700 has been described above as an example, the number of piezoelectric actuators 200 and 300 and the number of displacement detection sensors can vary greatly. For example, a low-hysteresis piezoelectric pump including one piezoelectric actuator and one displacement detection sensor can be implemented. In this case, the lever and valve stem operate in conjunction with the extension and contraction of the one piezoelectric actuator.

[0070] In addition, although the low-hysteresis piezoelectric pump with the lever displacement sensor 810 has been described above as an example, in some cases a low-hysteresis piezoelectric pump may be implemented without the lever displacement sensor 810. In this case, the control unit operates the piezoelectric actuator by referring only to the measurement value of the displacement detection sensor.

[0071] In addition, the structures of the pump body 100 and the valve operating member 400 may be changed to various structures other than those described and illustrated above.

[0072] The low-hysteresis piezoelectric pump of the present disclosure can maintain accurate viscous liquid discharge characteristics by adjusting an applied voltage in response to changes in the behavioral characteristics of the piezoelectric actuator depending on causes such as temperature changes.

[0073] It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should generally be considered applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and details may be made therein without departing from the spirit and scope of the appended claims.

Claims

1. A low-hysteresis piezoelectric pump, comprising: Pump body; a valve operating member comprising: a lever mounted so as to be rotatable relative to a hinge shaft mounted on the pump body; and a valve stem connected to the lever so as to move up and down according to the rotation of the lever; a pair of piezoelectric actuators mounted on the pump body in parallel with each other, wherein the hinge axis is inserted between the pair of piezoelectric actuators and each has a tip portion capable of contacting the lever, wherein the pair of piezoelectric actuators extend and press the lever when a voltage is applied to rotate the lever about the hinge axis; a valve body comprising: a reservoir into which a distal end portion of the valve stem is inserted and into which liquid is stored; an inlet through which the liquid is introduced into the reservoir; and a nozzle through which the liquid in the reservoir is discharged according to forward / backward movement of the valve stem in the reservoir; a pair of displacement detection sensors respectively installed in the pair of piezoelectric actuators to detect operational displacements of the pair of piezoelectric actuators; and a control unit electrically connected to the pair of piezoelectric actuators and the pair of displacement detection sensors to apply the voltage to operate the pair of piezoelectric actuators and receive detection signals regarding the operation displacements of the pair of piezoelectric actuators from the pair of displacement detection sensors, When the operating displacements of the pair of piezoelectric actuators calculated from the pair of displacement detection sensors and the operating displacements of the valve operating component detected from the lever displacement sensor are different from each other, the control unit gives priority to the operating displacements of the valve operating component and adjusts the voltage applied to the pair of piezoelectric actuators.

2. The low-hysteresis piezoelectric pump according to claim 1 , wherein when the operating displacements of the pair of piezoelectric actuators received from the pair of displacement detection sensors are different from a preset reference set value, the control unit adjusts the operating displacements of the pair of piezoelectric actuators to the preset reference set value by changing the voltage applied to the pair of piezoelectric actuators. 3 . The low-hysteresis piezoelectric pump according to claim 2 , wherein the control unit receives measurement values ​​of the pair of displacement detection sensors and controls the voltage applied to the pair of piezoelectric actuators in real time. 4 . The low-hysteresis piezoelectric pump according to claim 1 , wherein the control unit applies the voltage to each of the pair of piezoelectric actuators so that the pair of piezoelectric actuators alternately expand and contract. 5 . The low hysteresis piezoelectric pump according to claim 4 , wherein the lever displacement sensor is mounted on the pump body. 6 . The low hysteresis piezoelectric pump according to claim 4 , wherein the control unit changes the voltage applied to the pair of piezoelectric actuators so that a sum of the displacement measurement values ​​respectively detected by the pair of displacement detection sensors is maintained at a reference set value.

7. The low hysteresis piezoelectric pump of claim 4, wherein the pair of displacement detection sensors comprises strain gauges.

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