Stacked precision micro-actuator based on multilayer ceramic capacitors

Abstract

The application discloses a kind of stack type precision micro-actuators based on multilayer ceramic capacitor, including n multilayer ceramic capacitor, n multilayer ceramic capacitor is divided into m capacitor group, each capacitor group contains s multilayer ceramic capacitor, s multilayer ceramic capacitor in the same capacitor group is stacked layer by layer, electrode on the same side is connected in parallel, adjacent two multilayer ceramic capacitor is bonded fixed connection, different capacitor group is stacked layer by layer and is connected in series in turn, the upper and lower surface of actuator and the alumina ceramic sheet bonded between adjacent two capacitor groups are connected.The application is in the form of multilayer ceramic capacitor stack actuator using grouping series connection, both can obtain larger output displacement, can also reduce the capacitance value of multilayer ceramic capacitor stack actuator as a whole, improve the drive voltage required for excitation, reduce drive current, can show the characteristics of high frequency actuation in precision occasion, and the power amplifier that can be adapted can also be easily obtained.

Description

Technical Field

[0001] This invention relates to the field of precision microactuator technology, and in particular to a stacked precision microactuator based on multilayer ceramic capacitors. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs) are composed of multiple layers of ceramic materials and possess advantages such as small size, low cost, wide capacitance range, low ESL and ESR, and good frequency response. Recent research has shown that MLCCs exhibit excellent micro-actuation characteristics. Specifically, when a DC-biased driving voltage is applied to a MLCC, it displays a significant inverse piezoelectric effect, resulting in a certain output displacement. Furthermore, the output displacement exhibits good linearity and extremely low hysteresis with respect to the driving voltage. These phenomena enable MLCC actuators to be used in micro-actuation and micro-manipulation fields, such as providing micro-displacement actuation in high-precision and high-resolution positioning and motion applications.

[0003] Currently, piezoelectric ceramic actuators are the most common type of actuator in the field of micro-displacement drive technology. Piezoelectric ceramic micro-displacement actuators have advantages such as high power density, large output force, small size and compact structure. However, due to the inherent characteristics of piezoelectric materials, there is a large nonlinearity and hysteresis between the input voltage and output displacement under high electric field, which greatly limits their performance in positioning systems.

[0004] Figure 1 The diagram shows a schematic of a single multilayer ceramic capacitor in the prior art. The single multilayer ceramic capacitor has a thickness d... 33 The displacement generated by the direction is limited, with a maximum output displacement of about 800nm, which obviously cannot meet the requirements in micro-actuation applications that require larger displacement. Figures 2 to 4 The figures shown are a three-dimensional structural diagram, an electrical connection diagram, and an equivalent circuit diagram of a stacked multilayer ceramic capacitor actuator in the prior art. This type of multilayer ceramic capacitor actuator uses multiple multilayer ceramic capacitors mechanically stacked layer by layer, with each layer electrically connected in parallel. The layers of multilayer ceramic capacitors are glued together to form an integral structure. Because this type of multilayer ceramic capacitor actuator typically has high capacitance, the stacking of multiple multilayer ceramic capacitors makes the overall capacitance of the actuator very large, requiring a very high drive current to achieve high-speed drive. This places high demands on the power amplifier during the drive process. Therefore, under a certain drive current, the frequency characteristics of this multilayer ceramic capacitor actuator will decrease, thus affecting the precision drive of the multilayer ceramic capacitor stack actuator in high-speed applications. Figure 4Taking the equivalent circuit of the multilayer ceramic capacitor parallel stack actuator shown as an example, assuming the capacitance of a single multilayer ceramic capacitor is C0 and the maximum driving voltage is V0, then the maximum driving current required to drive a single multilayer ceramic capacitor is I0 = 2πfC0·V0; if n multilayer ceramic capacitors are used to make a multilayer ceramic capacitor parallel stack actuator, then the equivalent capacitance is C Pn =n·C0, maximum driving voltage V Pn =V0, maximum drive current I Pn =n·I0. Summary of the Invention

[0005] The technical problem this invention aims to solve is the stringent operating conditions of multilayer ceramic capacitor stack actuators in micro-actuation applications with large displacements. A novel multilayer ceramic capacitor stack actuator is proposed. By using a grouped series connection of the multilayer ceramic capacitor stack, a larger output displacement can be achieved while reducing the overall capacitance of the actuator, increasing the required excitation drive voltage, and reducing the drive current. This allows it to exhibit high-frequency actuation characteristics in precision applications, and compatible power amplifiers are readily available. Through appropriate grouped series connection, the maximum drive voltage of the multilayer ceramic capacitor stack can be matched with that of currently commercially available piezoelectric stack actuators, allowing it to replace piezoelectric stack actuators in relevant applications and reducing costs.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A stacked precision micro-actuator based on multilayer ceramic capacitors includes n multilayer ceramic capacitors, where n is a positive integer. The n multilayer ceramic capacitors are divided into m capacitor groups, and each capacitor group contains s multilayer ceramic capacitors, where m and s are both positive integers and s = n / m. The s multilayer ceramic capacitors in the same capacitor group are stacked layer by layer, and the electrodes on the same side are connected in parallel. Adjacent multilayer ceramic capacitors are bonded and fixedly connected. Different capacitor groups are stacked layer by layer and connected in series. Alumina ceramic sheets are bonded and fixedly connected to the top of the top capacitor group, the bottom of the bottom capacitor group, and between adjacent capacitor groups.

[0008] Furthermore, at least one resistor R0 is connected in parallel to the two electrodes of the s multilayer ceramic capacitors in the same capacitor bank, and the resistance value of the resistor R0 connected in parallel in different capacitor banks is the same.

[0009] Furthermore, the resistor R0 is a surface mount resistor.

[0010] Furthermore, the resistance value of the resistor R0 is much smaller than the DC leakage resistance value of the multilayer ceramic capacitor.

[0011] Furthermore, the resistance value of the resistor R0 is from 10kΩ to 500kΩ.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1. The multilayer ceramic capacitor stack actuator of the present invention exhibits good linearity and extremely low hysteresis in output displacement. In micro-actuation applications, it can still exhibit good linear characteristics without the need for compensation technology.

[0014] 2. The multilayer ceramic capacitor stack actuator of the present invention adopts a series connection form, which can reduce the overall capacitance value of the actuator, increase the required excitation driving voltage, reduce the driving current, and exhibit high-frequency actuation characteristics in precision applications.

[0015] 3. The multilayer ceramic capacitor stack of the present invention is connected in series in appropriate groups so that its maximum driving voltage can be consistent with the maximum driving voltage of currently commercial piezoelectric stack actuators. It can directly replace the existing piezoelectric stack actuators in corresponding applications, thereby reducing the cost of configuring the drive power amplifier. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the internal structure of a multilayer ceramic capacitor in the prior art.

[0017] Figure 2 This is a three-dimensional structural diagram of a multilayer ceramic capacitor parallel stack actuator in the prior art.

[0018] Figure 3 This is a schematic diagram of the electrical connections of a multilayer ceramic capacitor parallel stack actuator in the prior art.

[0019] Figure 4 This is an equivalent circuit diagram of a multilayer ceramic capacitor parallel stack actuator in the prior art.

[0020] Figure 5 This is a three-dimensional structural schematic diagram of the multilayer ceramic capacitor series stack actuator in Embodiment 1 of the present invention;

[0021] Figure 6 This is a schematic diagram of the electrical connections of the multilayer ceramic capacitor series stack actuator in Embodiment 1 of the present invention;

[0022] Figure 7 This is an equivalent circuit diagram of the multilayer ceramic capacitor series stacked actuator in Embodiment 1 of the present invention;

[0023] Figure 8 This is a three-dimensional structural schematic diagram of the multilayer ceramic capacitor series stack actuator in Embodiment 2 of the present invention;

[0024] Figure 9This is a schematic diagram of the electrical connections of the multilayer ceramic capacitor series stack actuator in Embodiment 2 of the present invention;

[0025] Figure 10 This is the equivalent circuit diagram of the multilayer ceramic capacitor series stacked actuator in Embodiment 2 of the present invention;

[0026] Figure 11 A schematic diagram of the structure of the multilayer ceramic capacitor series stack actuator of the present invention in combination with the rhombic displacement amplification mechanism.

[0027] In the diagram: 1. Multilayer ceramic capacitor; 2. Alumina ceramic sheet; 3. Resistor; 4. DC drive power supply; 5. Rhomboid displacement amplification mechanism. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0029] Various connection methods can be used to construct multilayer ceramic capacitor stack actuators, including parallel and series configurations. The common feature of all these types of multilayer ceramic capacitor stack actuators is that each multilayer ceramic capacitor is mechanically stacked in series, allowing the output displacements of multiple multilayer ceramic capacitors to be superimposed in the same direction, resulting in a large output displacement. The difference lies in the electrical connection: in a parallel multilayer ceramic capacitor stack actuator, all multilayer ceramic capacitors are electrically connected in parallel, while in a series multilayer ceramic capacitor stack actuator, the multilayer ceramic capacitors must be divided into several groups. Capacitors within the same group are electrically connected in parallel, while capacitors in different groups are electrically connected in series. This difference in electrical connection manifests as different requirements for the excitation voltage and current during use.

[0030] In this embodiment, a multilayer ceramic capacitor series stack actuator is constructed using a C5750X7R1H106 model multilayer ceramic capacitor. The capacitance of this model is C0 = 10μF, and the maximum driving voltage is V0 = 50V. Therefore, the maximum driving current required to drive a single multilayer ceramic capacitor is I0 = 2πfC0·V0 = π·f mA. If n multilayer ceramic capacitors are used to construct a multilayer ceramic capacitor parallel stack actuator, the equivalent capacitance is C0. Pn =n·C0, maximum driving voltage V Pn =V0, maximum drive current I Pn=n·I0=n·π·f mA; If a multilayer ceramic capacitor series stack actuator is made using n multilayer ceramic capacitors, and the multilayer ceramic capacitors are divided into m groups (m≤n, and n and m are both positive integers; the number of multilayer ceramic capacitors in each group is the same, so that the voltage division on each group of multilayer ceramic capacitors is the same), then the equivalent capacitance is C. Sn-m =(n / m 2 )·C0=(n / m 2 10μF, maximum driving voltage V Sn-m =m·V0 =m·50V, maximum drive current I Sn-m = (n / m)·I0 = (n / m)·π·f mA. The maximum drive voltage V from the multilayer ceramic capacitor series stack actuator. Sn-m =m·V0=m·50V It can be seen that when the number of multilayer ceramic capacitors connected in series is m=2, V Sn-2 =100V, when the number of multilayer ceramic capacitors connected in series m=3, V Sn-3 =150V, this maximum drive voltage can be matched with the maximum drive voltage of currently commercial piezoelectric stack actuators.

[0031] The following section uses parallel and series stacked actuators composed of six multilayer ceramic capacitors of the above-mentioned models as examples to introduce the structural composition, electrical connection method, equivalent circuit, calculation of maximum driving voltage and current of different types of multilayer ceramic capacitor stacked actuators in this design scheme, as well as the differences in performance parameters between them and the parallel stacked actuators of multilayer ceramic capacitors used in the prior art.

[0032] like Figures 2 to 4 The figures shown correspond to a three-dimensional structural diagram, an electrical connection diagram, and an equivalent circuit diagram of a multilayer ceramic capacitor parallel stack actuator in the prior art. This type of multilayer ceramic capacitor stack actuator uses multiple multilayer ceramic capacitors 1 mechanically stacked layer by layer, with each layer electrically connected in parallel. The multilayer ceramic capacitors 1 are glued together to form an integral structure. Alumina ceramic sheets 2 are bonded to the upper and lower surfaces of the actuator to ensure insulation during use. Six multilayer ceramic capacitors 1 are connected in parallel. The driving voltage V0 of the DC drive power supply 4 is simultaneously applied to the two terminals of all the multilayer ceramic capacitors through two leads. Therefore, the equivalent capacitance of this six-layer ceramic capacitor parallel stack actuator is C. P6 =6C0=60μF, maximum driving voltage V P6 =V0=50V, maximum drive current is I P6 =6I0=12πfC0·V0=6π·fmA.

[0033] Example 1:

[0034] like Figures 5 to 7The diagrams shown correspond to the three-dimensional structural schematic, electrical connection schematic, and equivalent circuit diagram of the two series-connected stacked actuators composed of six multilayer ceramic capacitors 1 in this embodiment. The six multilayer ceramic capacitors 1 are divided into two capacitor groups. Within each capacitor group, three multilayer ceramic capacitors 1 are stacked layer by layer and bonded together sequentially. Alumina ceramic sheets 2 are bonded between the multilayer ceramic capacitors 1 in different capacitor groups for insulation. Alumina ceramic sheets 2 are also bonded to the upper and lower surfaces of the actuator to ensure insulation during use. The three multilayer ceramic capacitors 1 within the same capacitor group are connected in parallel, and adjacent capacitor groups are connected in series sequentially. The driving voltage V0 of the DC drive power supply 4 is applied to the two terminals of the two series-connected capacitor groups through two leads. Therefore, the equivalent capacitance of the two series-connected stacked actuators composed of the six multilayer ceramic capacitors is C. S6-2 =3C0 / 2=15μF, maximum driving voltage V S6-2 =2V0=100V, maximum drive current is I S6-2 =3I0=6πfC0·V0=3π·f mA.

[0035] When the driving voltage frequency is extremely low or DC voltage excitation is used, the voltage division ratio on each capacitor bank is determined by the ratio of the leakage resistances of each capacitor bank. However, the leakage resistance of each multilayer ceramic capacitor varies greatly (the DC leakage resistance of a single multilayer ceramic capacitor varies between several MΩ and tens of MΩ), resulting in an uncertain voltage division ratio between capacitor banks. Therefore, this invention connects a resistor 3 with a resistance of R0 in parallel to the two electrodes of each capacitor bank in the multilayer ceramic capacitor series stack actuator. When the resistance R0 of resistor 3 is much smaller than the DC leakage resistance of the multilayer ceramic capacitor 1, the voltage division between each capacitor bank can still be guaranteed to be the same under DC and extremely low frequency driving conditions. Furthermore, the resistance R0 of resistor 3 must be large enough to make the static power consumption negligible. In this embodiment, the resistance R0 of resistor 3 ranges from 10kΩ to 500kΩ. A resistance value of 100kΩ was selected for performance testing; at this resistance value, the static power consumption is negligible. Preferably, resistor 3 is a chip resistor and is bonded and fixed to the side of any one of the multilayer ceramic capacitors 1 in the corresponding capacitor group, making the actuator structure more compact and reliable.

[0036] Example 2:

[0037] like Figures 8 to 10The diagrams shown correspond to the three-dimensional structural schematic, electrical connection schematic, and equivalent circuit diagram of the three-group series-stacked actuator composed of six multilayer ceramic capacitors 1 in this embodiment. The six multilayer ceramic capacitors 1 are divided into three capacitor groups. Two multilayer ceramic capacitors 1 within each capacitor group are stacked layer by layer and bonded together sequentially. Alumina ceramic sheets 2 are bonded between the multilayer ceramic capacitors 1 in different capacitor groups for insulation. Alumina ceramic sheets 2 are also bonded to the upper and lower surfaces of the actuator to ensure insulation during use. Two multilayer ceramic capacitors 1 within the same capacitor group are connected in parallel, and the three capacitor groups are connected in series sequentially. The driving voltage V0 of the DC drive power supply 4 is applied to the two terminals of the three-group series-stacked actuator through two leads. Therefore, the equivalent capacitance of the three-group series-stacked actuator composed of six multilayer ceramic capacitors is C. S6-3 =2C0 / 3=6.67μF, maximum driving voltage V S6-3 =3V0=150V, maximum drive current is I S6-3 =2I0=4πfC0·V0=2π·f mA.

[0038] Similar to Example 1, a resistor 3 with the same resistance value is connected in parallel to the two electrodes of each capacitor bank in the multilayer ceramic capacitor series stack actuator, so that the voltage division between each capacitor bank can still be the same during DC and very low frequency driving, and the static power consumption can be ignored.

[0039] Table 1. Test results of performance parameters for three types of multilayer ceramic capacitor stack actuators.

[0040]

[0041] Comparing the series-connected actuators in the two embodiments above with the existing multilayer ceramic capacitor parallel-connected stacked actuators, it is evident that using a grouped series connection (parallel connection within a group, series connection between groups) for the multilayer ceramic capacitor stack can achieve a larger output displacement while reducing the overall capacitance of the multilayer ceramic capacitor stack actuator. This increases the required excitation drive voltage and reduces the drive current, exhibiting high-frequency actuation characteristics in precision applications. Furthermore, compatible power amplifiers are readily available. By appropriately grouping and connecting the multilayer ceramic capacitor stack in series, its maximum drive voltage can match that of currently commercially available piezoelectric stack actuators, allowing it to replace piezoelectric stack actuators in relevant applications and reducing the cost of configuring the drive power amplifier.

[0042] like Figure 11As shown, in practical use, the series stacked actuator of this application has a limited overall output displacement but high output stiffness due to the limited overall output displacement of the multilayer ceramic capacitor stacked actuator. If used in large displacement actuation applications, it can be mounted on a rhomboid displacement amplification mechanism 5 (existing technology, the specific structure and working principle of which are not detailed here) to amplify the lateral output displacement of the actuator (e.g., ...). Figure 11 The direction indicated by the solid arrow in the middle is transformed into the longitudinal output displacement of the rhomboid displacement amplification mechanism 5 (as shown by the arrow in the middle). Figure 11 (In the direction indicated by the dashed arrow in the middle), through the structural characteristics of the rhomboid displacement amplification mechanism 5, the amplitude of the longitudinal output displacement is greater than the amplitude of the lateral output displacement, thus realizing the function of displacement amplification.

[0043] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A stacked precision micro-actuator based on multilayer ceramic capacitors, comprising n multilayer ceramic capacitors, where n is a positive integer, characterized in that: n multilayer ceramic capacitors are divided into m capacitor groups. Each capacitor group contains s multilayer ceramic capacitors, where m and s are positive integers and s = n / m. The s multilayer ceramic capacitors in the same capacitor group are stacked layer by layer, and the electrodes on the same side are connected in parallel. Adjacent multilayer ceramic capacitors are bonded and fixedly connected. Different capacitor groups are stacked layer by layer and connected in series. Alumina ceramic sheets are bonded and fixedly connected to the top of the top capacitor group, the bottom of the bottom capacitor group, and between adjacent capacitor groups. In the same capacitor bank, at least one resistor R0 is connected in parallel to the two electrodes of s multilayer ceramic capacitors. The resistance values ​​of the resistors connected in parallel in different capacitor banks are the same. The resistance value R0 is much smaller than the DC leakage resistance of the multilayer ceramic capacitor, which can still ensure that the voltage division between each capacitor bank is the same under DC and extremely low frequency driving conditions; and the resistance value R0 should be large enough so that the static power consumption can be ignored.

2. The stacked precision micro-actuator based on multilayer ceramic capacitors according to claim 1, characterized in that: The resistor R0 is a surface mount resistor.

3. A stacked precision micro-actuator based on a multilayer ceramic capacitor according to claim 1 or 2, characterized in that: The resistance of the resistor R0 is between 10kΩ and 500kΩ.

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