Micro valve and mass flow meter to which same is applied

Abstract

A micro valve and a mass flow meter to which same is applied. The micro valve comprises a first substrate (202), a second substrate (203), and an intermediate layer (204), wherein the intermediate layer (204) is arranged between the first substrate (202) and the second substrate (203). The intermediate layer (204) comprises: an array formed by a plurality of actuators. Each actuator comprises: a throttling orifice (401), which is provided with a throttling gas inlet and a throttling gas outlet, wherein gas flows into the throttling orifice (401) from the throttling gas inlet and flows to the second substrate (203) from the throttling gas outlet; and a cantilever (302), which moves relative to the throttling gas inlet. The opening area of the throttling gas inlet is adjusted by adjusting the distance between the cantilever (302) and the throttling gas inlet, thereby increasing the valve flow. The actuator array allows for proportional control, and can realize diffuse gas release or form a mass flow meter. In addition, a plurality of micro valves can be assembled to further increase the flow.

Description

A micro valve and mass flow meter used therein Technical Field

[0001] The present invention generally relates to the field of microvalve technology. Specifically, the present invention relates to a microvalve and a mass flowmeter used therein. Background Art

[0002] The structure of a traditional microvalve or microelectromechanical system valve (MEMS valve) is similar to that of a diaphragm valve. Figures 1A-B show schematic diagrams of existing microvalve. As shown in Figures 1A-B, an actuable diaphragm is provided at the top of the microvalve, and a valve seat is provided below the diaphragm. An actuator (or the diaphragm also serves as the actuator) pushes the diaphragm upward to open the orifice or downward to close the orifice. The flux of the microvalve is determined by the circumference of the orifice multiplied by the displacement of the diaphragm.

[0003] Traditional microvalve construction typically begins with a substrate (silicon or quartz glass) as the base. A channel for the horizontal flow of gas or liquid is etched into the substrate, and a diaphragm and / or actuator are bonded to the channel to form the complete microvalve. For more complex channels or those requiring deep etching, channels can be fabricated separately on two substrates, which are then aligned and bonded together to form the complete channel.

[0004] Due to the micron-level and even nano-level processing characteristics of the MEMS process, the thickness of the substrate used for processing is usually only 625um, the deposition thickness of lead zirconate titanate (PZT) is usually only 5um at most, the depth and aperture of deep groove etching do not exceed 1mm, and the upward movement of the diaphragm is usually at the micron level (for example, the stroke of a 25mm PZT ceramic cantilever is usually only 250um, and the micro-nano structure of MEMS can usually only achieve 10um-level movement). In other words, traditional microvalves can only achieve microliter-level flow control. Taking a 1 / 8-inch opening as an example, the diameter of the opening is 1.78mm, and a diaphragm with a stroke of 10um can only produce 1.78×0.01×3.14=0.055892mm. 2 Even if the diaphragm stroke can reach 100um, it can only produce 0.56mm 2 In the prior art, a 1 / 8-inch opening and a 100 μm stroke diaphragm still have some difficulties in achieving this, and the stroke of the diaphragm in a microvalve is usually only about 10-20 μm.

[0005] Therefore, it is necessary to propose a new type of microvalve that can achieve a larger valve flux.

[0006] Summary of the Invention

[0007] To at least partially solve the above problems in the prior art, the present invention provides a microvalve comprising:

[0008] a first substrate having a substrate gas inlet, wherein a gas flows from the substrate gas inlet to the intermediate layer;

[0009] An intermediate layer disposed between the first substrate and the second substrate, the intermediate layer comprising an array formed by a plurality of actuators, the actuators comprising:

[0010] a throttle hole having a throttle inlet and a throttle outlet, wherein gas flows from the throttle inlet into the throttle hole and flows from the throttle outlet toward the second substrate; and

[0011] a cantilever arm configured to move relative to the throttle air inlet, wherein an opening area of ​​the throttle air inlet is adjusted by adjusting a distance between the cantilever arm and the throttle air inlet; and

[0012] A second substrate has a substrate gas outlet, wherein gas flows out of the substrate gas outlet.

[0013] In one embodiment of the present invention, the microvalve further comprises:

[0014] The housing surrounds the actuator to form a gas confinement space or housing. The air inlet confinement space housing has a housing air inlet and a housing air outlet. The housing includes a metal housing, a ceramic housing, a resin housing, or a confinement space formed by an equivalent semiconductor packaging process.

[0015] In one embodiment of the present invention, the throttle hole includes:

[0016] A throttle step, which is connected to the second substrate, wherein the throttle outlet is arranged on the throttle step; and a throttle enclosure, a first end of which is connected to the first substrate, and a second end of the throttle enclosure opposite to the first end is connected to the throttle step, and the throttle inlet is arranged on the throttle enclosure.

[0017] In one embodiment of the present invention, it is provided that the first substrate further comprises:

[0018] A substrate step is connected to the first end of the throttle aperture enclosure, wherein the substrate step and / or the throttle aperture step is configured to suppress short-circuit gas flow generated by a gap between the cantilever and the second substrate and / or the first substrate.

[0019] In one embodiment of the present invention, it is provided that the cantilever has a coating of a wettable material; and\or

[0020] The cantilever includes an electrostatically driven cantilever, an electromagnetically driven cantilever, a piezoelectrically driven cantilever or an electrothermal driven cantilever.

[0021] In one embodiment of the present invention, it is provided that the cantilever is configured to move horizontally relative to the throttle air inlet; or

[0022] The cantilever arm is configured to move vertically relative to the throttle inlet.

[0023] In one embodiment of the present invention, it is provided that:

[0024] An outer frame is arranged around the middle layer to restrict airflow.

[0025] In one embodiment of the present invention, the throttle hole enclosure includes a first throttle air inlet and a second throttle air inlet opposite to the first throttle air inlet; and

[0026] The cantilever includes a first cantilever and a second cantilever, wherein the first cantilever is configured to move relative to the first throttle air inlet, and the second cantilever is configured to move relative to the second throttle air inlet.

[0027] In one embodiment of the present invention, it is provided that a grid is provided on one or more of the following items to form a laminar flow element: the substrate air inlet, the substrate air outlet, and the throttling air outlet.

[0028] In one embodiment of the present invention, it is provided that the cantilever is connected to one or more throttle holes.

[0029] In one embodiment of the present invention, a plurality of microvalves are configured to be interconnected to increase flow.

[0030] In one embodiment of the present invention, it is provided that the throttle outlets of multiple actuators discharge air individually or are combined into multiple groups and then discharged in groups to achieve diffused air discharge.

[0031] In one embodiment of the present invention, the microvalve further comprises:

[0032] The control circuit is connected to the plurality of actuators and is configured to control the opening degrees of the plurality of actuators respectively.

[0033] The term "opening" herein refers to the ratio of the actuator opening, which can be any value between 0-100%.

[0034] In one embodiment of the present invention, the control circuit is configured to perform the following actions:

[0035] Set the flow rate to be controlled to Q setpoint ;

[0036] Determine the maximum accurate measurement value of a single actuator max(Q actr );

[0037] Calculate i = round {Q setpoint / max(Q actr )};

[0038] Open i actuators, where the sum of the flows of i actuators is i×max(Q actr );as well as

[0039] Open the i+1th actuator and set the flow rate of the i+1th actuator to Q setpoint -i×max(Q actr ).

[0040] In one embodiment of the present invention, the control circuit is further configured to perform the following actions:

[0041] When the flow rate of the i+1th actuator is lower than the threshold, the flow rates of the j+2th actuators, i-j+1, ...i, i+1, are set to (Q setpoint -j×max(Q actr )) / (j+2).

[0042] The present invention also provides another microvalve, which comprises:

[0043] a first substrate having a substrate gas inlet, wherein a gas flows from the substrate gas inlet to the intermediate layer;

[0044] An intermediate layer disposed between the first substrate and the second substrate, the intermediate layer comprising an array formed by a plurality of actuators, the actuators comprising:

[0045] a throttle hole having a throttle inlet and a throttle outlet, wherein gas flows from the throttle inlet into the throttle hole and flows from the throttle outlet toward the second substrate; and

[0046] a diaphragm configured to control an opening of the throttle inlet; and

[0047] A second substrate has a substrate gas outlet, wherein gas flows out of the substrate gas outlet.

[0048] In one embodiment of the present invention, the first substrate is configured to constrain airflow, and the second substrate has a substrate gas inlet and a substrate gas outlet, wherein the gas flows from the substrate gas inlet to the intermediate layer, and flows back to the second substrate and then flows out from the substrate gas outlet.

[0049] The present invention further provides a mass flow meter, comprising:

[0050] microvalves; and

[0051] A sensing component is arranged on at least one of the plurality of actuators of the microvalve.

[0052] In one embodiment of the present invention, it is provided that the sensing component includes a pressure sensor and a temperature sensor, wherein the microvalve, the pressure sensor and the temperature sensor form a pressure mass flow meter; and\or

[0053] The sensing component includes a heater and a temperature sensor, wherein the microvalve, the heater and the temperature sensor form a thermal mass flow meter.

[0054] In one embodiment of the present invention, for blocked flow, the flow Q through the i-th actuator on the microvalve is adjusted according to the following formula: i :

[0055] Q i =C×P UPi ,

[0056] Among them, C represents the first correlation coefficient, P UPi represents the pressure on the first side of the i-th actuator, where the first correlation coefficient C is related to the opening area A of the i-th actuator. i Positive correlation; and\or

[0057] For non-blocking flow, the flow Q through the i-th actuator on the microvalve is regulated according to the following formula: i :

[0058] Among them, C' represents the second correlation coefficient, A i represents the opening area of ​​the i-th actuator, P DOWNi represents the pressure on the second side of the i-th actuator, R represents the universal gas constant, T represents the temperature, M represents the molecular mass, γ represents the specific heat ratio, where the second correlation coefficient C' is a constant.

[0059] The present invention has at least the following beneficial effects: It provides a microvalve comprising an array of multiple actuators. The cantilevered arms of the actuators can move relative to a throttle inlet to adjust the opening area of ​​the throttle inlet, effectively increasing valve throughput. Multiple actuators can form an actuator array, which can achieve proportional control and diffuse gas discharge or form a mass flow meter. Furthermore, multiple microvalves can be interconnected to further increase flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] To further illustrate the advantages and features of various embodiments of the present invention, a more detailed description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings depict only typical embodiments of the present invention and are not to be considered as limiting the scope of the present invention. In the drawings, for clarity, identical or corresponding components will be represented by the same or similar reference numerals.

[0061] 1A-B show schematic diagrams of existing micro valves.

[0062] FIG. 2 shows a perspective view of a microvalve and its packaging shell in one embodiment of the present invention.

[0063] FIG3 shows a schematic diagram of a microvalve according to an embodiment of the present invention.

[0064] FIG4 is a perspective view of a microvalve according to an embodiment of the present invention.

[0065] FIG5 shows a top view of a microvalve according to an embodiment of the present invention.

[0066] FIG6 shows a schematic diagram of a disassembled microvalve in an embodiment of the present invention.

[0067] FIG. 7A shows a bottom schematic diagram of a first substrate according to an embodiment of the present invention.

[0068] FIG. 7B is a schematic diagram showing a second substrate and a throttling hole according to an embodiment of the present invention.

[0069] 8A and 8B are top views of the intermediate layer when an actuator is open and closed, respectively, according to an embodiment of the present invention.

[0070] FIG9 shows a schematic diagram of a double-cantilever double-opening microvalve according to another embodiment of the present invention.

[0071] FIG10 shows a top view of a double-cantilever double-opening microvalve according to another embodiment of the present invention.

[0072] FIG11 shows a schematic diagram of a disassembled double-cantilever double-opening microvalve in another embodiment of the present invention.

[0073] FIG. 12 schematically shows the bottom portion of a first substrate according to another embodiment of the present invention.

[0074] FIG13 is a schematic diagram showing a second substrate and a throttle hole of a dual-cantilever dual-opening microvalve in another embodiment of the present invention.

[0075] FIG14 shows a schematic structural diagram of a cantilever vertically actuated microvalve according to an embodiment of the present invention.

[0076] 15A and 15B are schematic diagrams showing the middle layer of a cantilevered vertically actuated microvalve according to an embodiment of the present invention.

[0077] 16A and 16B are schematic diagrams showing the airflow direction of a microvalve with a vertically actuated cantilever according to an embodiment of the present invention.

[0078] FIG. 17 shows a schematic diagram of the arrangement of sensors on a microvalve in one embodiment of the present invention.

[0079] FIG18 shows a schematic diagram of a conventional thermal mass flowmeter.

[0080] FIG19 is a schematic diagram showing an actuator structure on a die according to an embodiment of the present invention.

[0081] FIG. 20A shows a schematic diagram of a grid below a cantilever according to an embodiment of the present invention.

[0082] 20B shows a side view of a grid below one cantilever in accordance with one embodiment of the present invention.

[0083] FIG21 shows a control logic diagram of an actuator array in one embodiment of the present invention.

[0084] FIG22 shows a schematic diagram of a microvalve in another embodiment of the present invention.

[0085] FIG23 is a schematic diagram showing the airflow at an actuator in an embodiment of the present invention.

[0086] FIG. 24 is a schematic diagram showing changes in pressure and flow rate of a blocked flow in one embodiment of the present invention. DETAILED DESCRIPTION

[0087] It should be noted that the components in the drawings may be shown exaggeratedly for the sake of illustration and are not necessarily correct to scale. In the drawings, identical or functionally identical components are provided with the same reference numerals.

[0088] In the present invention, unless otherwise specified, the phrases "disposed on," "disposed above," and "disposed above" do not exclude the presence of intermediate components. Furthermore, "disposed on or above" merely indicates the relative positional relationship between two components and, in certain circumstances, such as after reversing the product orientation, can be converted to "disposed below or below," and vice versa.

[0089] In the present invention, each embodiment is only intended to illustrate the aspects of the present invention and should not be construed as limiting.

[0090] In the present invention, unless otherwise specified, the quantifiers "a" and "an" do not exclude the presence of multiple elements.

[0091] It should also be noted that in the embodiments of the present invention, for the sake of clarity and simplicity, only a portion of the parts or components may be shown, but those skilled in the art will understand that, under the teachings of the present invention, the required parts or components can be added according to the needs of the specific scenario. In addition, unless otherwise stated, the features of different embodiments of the present invention can be combined with each other. For example, a feature in the second embodiment can be used to replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment also falls within the scope of disclosure or description of this application.

[0092] It should also be noted that, within the scope of the present invention, terms such as "same," "equal," and "equal to" do not imply absolute equality of values, but rather allow for a certain reasonable error. In other words, such terms also encompass "substantially the same," "substantially equal," and "substantially equal." Similarly, in the present invention, terms such as "perpendicular to" and "parallel to" indicating direction also encompass the meaning of "substantially perpendicular to" and "substantially parallel to."

[0093] In addition, the numbering of the steps of the methods of the present invention does not limit the order in which the steps are to be performed. Unless otherwise specified, the steps of the methods may be performed in different orders.

[0094] The present invention will be further described below with reference to the accompanying drawings in conjunction with specific embodiments.

[0095] FIG2 shows a perspective view of a microvalve and its packaging housing in one embodiment of the present invention. As shown in FIG2 , the microvalve is encapsulated within a housing 201, and gas can flow in or out through vents on the housing 201. The housing 201 can be encapsulated using common metal, ceramic, or resin packaging processes. The microvalve may include multiple actuators, each of which may include a first substrate 202, a second substrate 203, and an intermediate layer 204. The intermediate layer 204 is disposed between the first substrate 202 and the second substrate 203. The first substrate 202 and the second substrate 203 are provided with air inlets and / or air outlets. Gas can flow in from the first substrate 202 or the second substrate 203, flow through the intermediate layer 204, and flow out from the opposite side of the second substrate 203 or the first substrate 202. Gas can also flow in from the first substrate 202 or the second substrate 203, flow through the intermediate layer 204, and flow out from the same side of the first substrate 202 or the second substrate 203.

[0096] The intermediate layer 204 is provided with an opening (Orifice) and a horizontally arranged cantilever (Cantilever), and the cantilever is also the diaphragm in the microvalve, wherein the cantilever can be provided with a coating of a wet material to protect the cantilever. An outer frame can be provided around the intermediate layer 204 to constrain the airflow. In the intermediate layer 204, the cantilever can move relative to the opening to adjust the distance between the cantilever and the opening, thereby changing the opening / flux of the opening to achieve proportional adjustment of the microvalve. A step can be provided at the position where the opening is close to the first substrate 202 and the second substrate 203, and the step can reduce or even eliminate the short-circuit airflow generated by the gap between the cantilever and the first substrate 202 and the second substrate 203. The cantilever can be an electrostatic, electromagnetic, piezoelectric or electrothermal driven cantilever.

[0097] Furthermore, it should be understood that in FIG. 2 and other figures in the specification, the curvature of the cantilever is exaggerated to illustrate the principle, and may be disproportionate to the actual situation.

[0098] Figure 3 shows a schematic diagram of a microvalve according to one embodiment of the present invention. As shown in Figure 3, the microvalve structure is shown after the encapsulating shell is removed, and the outer frame surrounding the intermediate layer 204 is omitted. It can be seen that a plurality of air holes 301 are provided on the first substrate 202 fabricated using a MEMS process, and a cantilever 302 is provided on the intermediate layer 204.

[0099] Figure 4 shows a perspective schematic diagram of a microvalve according to one embodiment of the present invention. Figure 5 shows a top view of a microvalve according to one embodiment of the present invention. As shown in Figures 4 and 5, the intermediate layer 204 includes multiple actuators, each of which includes a cantilever 302 and a throttle hole 401. The throttle hole 401 includes a throttle hole outlet 4011 and a surrounding barrier 4012 disposed around the throttle hole outlet 4011.

[0100] In the present invention, the microvalve can be a matrix array formed by multiple small microvalves (actuators). The microvalve can include n×m outlets on the outer frame, each outlet corresponding to i (i=1 or 2) throttle holes 401. Therefore, the microvalve can be regarded as an array of m×n×i actuators. During the packaging process, if the n×m outlets on the outer frame are not merged, or if they are merged into x×f outlets (x<m, y<n), the microvalve can be made to discharge air evenly on a plane.

[0101] In the present invention, the microvalve is usually a die on a wafer packaged in a package. The packaged package can be connected to a vacuum coupling radial seal (VCR) connector, or can be arranged on a pipeline module by surface mounting. Since the size of the die is limited by the exposure area (Short Size) of the photolithography machine, in order to increase the flow rate of the microvalve, multiple dies can also be packaged in a single package, wherein each die is constructed with an array of multiple actuators. The cantilever 302 of the actuator can be fixed at a single point or two points, and each cantilever 302 corresponds to one or more throttling holes 401. A grid can be provided in the throttling hole 401 to reduce the Reynolds coefficient of the throttling hole 401, thereby making the throttling hole 401 constitute a laminar flow element.

[0102] Figure 6 shows a schematic diagram of a microvalve according to an embodiment of the present invention. As shown in Figure 6, the intermediate layer 204 includes multiple actuators, each including a throttle hole 401 and a cantilever 302. The first substrate 202 and the second substrate 203 are provided with air holes 301. The first substrate 202, the intermediate layer 204, and the second substrate 203 are bonded together to form a microvalve.

[0103] Figure 7A shows a schematic bottom view of a first substrate according to one embodiment of the present invention. Figure 7B shows a schematic view of a second substrate and a throttle hole according to one embodiment of the present invention. As shown in Figures 7A and 7B, a first step 701 may be provided on the first substrate 202, and a second step 702 may be provided on the second substrate 203. During the movement of the cantilever 302, gaps exist between the cantilever 302 and the first substrate 202 and the second substrate 203, resulting in a gap between the cantilever 302 and the throttle hole 401. The step can be higher than the gap between the cantilever 302, thereby sealing the gap between the cantilever 302 and the throttle hole 401. The first substrate 202 and the second substrate 203 can be quartz, silicon, SO1, or silicon carbide substrates. Because the cantilever 302 may sag, the step below the throttle hole 401 can be shallower than the step above the throttle hole 401. In addition, the step needs to have a certain height so that the airflow can flow into the throttle hole 401 along the upper edge or the lower edge of the step to increase the flux.

[0104] FIG8A and FIG8B respectively show top views of the intermediate layer when an actuator is opened and closed in one embodiment of the present invention. As shown in FIG8A and FIG8B, during the movement of the cantilever 302, by controlling the distance between the cantilever 302 and the throttle hole 401, proportional control of the flux can be achieved. Wherein, the flux (opening area) = the circumference of the throttle hole 401 × the distance between the cantilever 302 and the throttle hole 401. The gas can flow through the throttle hole 401 and then flow out through the pores 301 on the second substrate 203 in a 90-degree fold line downward. In order to maximize the flow rate of the microvalve, it is necessary to make the maximum opening area of ​​each throttle hole 401 less than or equal to the area of ​​the corresponding outlet pore 301, and the sum of the maximum opening areas of all throttle holes 401 is less than the sum of the areas of all intake pores 301.

[0105] FIG9 shows a schematic diagram of a dual-cantilever dual-opening microvalve in another embodiment of the present invention. FIG10 shows a top view of a dual-cantilever dual-opening microvalve in another embodiment of the present invention. As shown in FIG9 and FIG10, the throttle hole 401 of the actuator is provided with a bidirectional opening, and a first cantilever 901 and a second cantilever 902 are provided at the two openings, respectively. In this embodiment, the throttle hole 401 can be formed by front and rear vertical baffles and upper and lower steps, and the flux of the throttle hole 401 is the sum of the fluxes of the two openings, wherein the sum of the fluxes of the bidirectional openings is less than or equal to the sum of the fluxes of the corresponding air outlet holes 301. The dual-cantilever dual-opening microvalve has better symmetry and is more conducive to the integrated processing of the MEMS process.

[0106] Figure 11 shows a schematic diagram of a dual-cantilever dual-opening microvalve in another embodiment of the present invention. Figure 12 shows a schematic diagram of the bottom of a first substrate in another embodiment of the present invention. As shown in Figure 12, the bottom of the first substrate 202 of the dual-cantilever dual-opening microvalve can also be provided with a first step 701, which is used to block the gap between the first cantilever 901 at the throttle hole 401 and the second cantilever 902 and the first substrate 202.

[0107] Figure 13 shows a schematic diagram of the second substrate and throttle hole of a dual-cantilever dual-opening microvalve according to another embodiment of the present invention. As shown in Figure 13 , the throttle hole 401 is arranged on the second substrate 203, and a second step 702 is provided between the throttle hole 401 and the second substrate 203.

[0108] In this embodiment, the microvalve manufacturing process may include:

[0109] The second substrate 203 and the throttle hole 401 are formed on the oxide layer of the SOI wafer by an etching process.

[0110] A first cantilever 901 and a second cantilever 902 are fabricated on the oxide layer of another SO1 wafer. The PZT layer or electrostatic actuation layer on the bimorph can be processed on both sides. The actuation layer can be processed using chemical vapor deposition (CVD), reactive physical vapor deposition (RPVD), physical vapor deposition (PVD), or sol-gel methods.

[0111] A first substrate 202 may be formed on another S01 wafer.

[0112] The SOI wafer can be doped with boron and thinned to 100-200 μm. Furthermore, a low-k passivation layer (such as a nitride-oxygen organic polymer) can be applied to the surface of the through-holes and components by CVD or other methods to protect the components from corrosion and contamination of the high-purity gas.

[0113] Figure 14 shows a schematic diagram of the structure of a vertically actuated cantilever microvalve according to an embodiment of the present invention. As shown in Figure 14, the cantilever can move up and down, and gas can flow in from above or below. Figures 15A and 15B show schematic diagrams of the middle layer of a vertically actuated cantilever microvalve according to an embodiment of the present invention. As shown in Figure 15A, the cantilever can be fixed on both sides. As shown in Figure 15B, the cantilever can be fixed on one side. The cantilever fixed on one side has a greater travel range.

[0114] Figures 16A and 16B illustrate the flow of air through a vertically actuated cantilever microvalve according to one embodiment of the present invention. As shown in Figures 16A and 16B, the gas inlet can be on either the first substrate 202 or the second substrate 203. In the embodiment shown in Figure 16A, both the gas inlet and outlet are located on the second substrate 203. This second substrate 203 allows for the distribution of incoming air and the collection and consolidation of outgoing air. The inlet and outlet channels form a jigsaw or finger-like pattern.

[0115] The microvalve with vertical cantilever actuation can obtain a filling factor of about 2 / 3 in the X-axis direction and a filling factor of about 1 / 1 in the Y-axis direction, for a total filling factor of about 50%. Assuming that every 75% of the length in the Y-axis direction can be used for gas outlet, the width of each cantilever is 70um, the distance between the cantilevers is 30um, and the average stroke of the cantilever is 5um (the stroke of the highest point of the cantilever is 10um, and the flow channel cross-section below can be approximated as a triangle). Assuming that the length and width of the die on the wafer are both 10mm, an effective size of 7.5mm can be obtained in the length direction of the die, and 100 rows of cantilevers are set. The total flux area of ​​the microvalve with vertical cantilever actuation can be 7.5mm×0.005×100×2=7.5mm 2That is to say, the flux area of ​​a 2cm×1cm die is equivalent to that of a 1 / 4 inch pipe, and the flux area of ​​a 2cm×3cm die is equivalent to that of a 3 / 4 inch pipe. And the micro valve can withstand greater pressure drop and flow rate than the pipe, so the 1cm 2 or 2cm 2 The MEMS process area can meet the application requirements of proportional control valves (MFCs) in current semiconductor equipment.

[0116] Figure 17 shows a schematic diagram of the sensor arrangement on a microvalve in one embodiment of the present invention. Pressure sensors and temperature sensors can be placed at the air inlet and outlet to form a pressure-type mass flowmeter. A heater and a thermometer can be placed on the throttle orifice 401 to form a thermal mass flowmeter. In this case, the throttle orifice 401 can be equivalent to the thermal flow measurement channel in the thermal mass flowmeter. Figure 18 shows a schematic diagram of a conventional thermal mass flowmeter. As shown in Figure 18, the measurement is performed in a bypass channel. In the embodiment of the present invention shown in Figure 17, the heater and temperature sensor can be placed upstream of or within the throttle orifice 401, which is equivalent to the measurement bypass in Figure 18. Grids can be etched at the throttle orifice 401, the air inlet, and the air outlet to form a laminar flow element. In fact, in this embodiment of the present invention, because the size of the throttle orifice 401 is sufficiently small, the throttle orifice 401 and the flow channel between the first substrate 202 and the second substrate 203 can form a natural laminar flow element. Figure 20A shows a schematic diagram of a grille under a cantilever according to one embodiment of the present invention. Figure 20B shows a side view of a grille under a cantilever according to one embodiment of the present invention. As shown in Figures 20A-B, the grille under the cantilever can reduce the characteristic dimensions of the pipeline, lower the Reynolds coefficient, and form a laminar flow element (LFE). As mentioned above, laminar flow elements can also be formed by adding grilles in other intake circuits.

[0117] In an embodiment of the present invention, multiple die can be packaged together to achieve flow expansion and diffuse exhaust. Figure 19 shows a schematic diagram of the actuator structure on a die in one embodiment of the present invention. As shown in Figure 19, a 4×2 actuator structure can be provided on a die, each with four throttle holes 401, each with a bidirectional opening, and cantilevers at each opening. Assuming the cantilever length is 2 mm and the spacing between cantilevers is 100 μm, a 10×100 actuator array can be constructed on a 20×10 mm die. If each actuator is controlled, very precise flow control can be achieved. In Figure 19, four 2×2 die can be packaged together to form a larger mass flowmeter, which means the flow rate is multiplied by 4. The outlets of each throttle hole can be separated (or combined into several groups). Each outlet (or each group of outlets) can independently discharge air, achieving independent and uniform diffuse exhaust from the mass flowmeter.

[0118] The area flux of the actuator depends on min(A inlet , A orifice , A outlet ), where A inlet Indicates the area of ​​the actuator's air inlet, A outlet Indicates the area of ​​the actuator's air outlet, A orifice represents the area of ​​the orifice. The total flux of the actuator array is determined by the area flux of multiple actuators. inlet 、A orifice 、A outlet are proportional to each other, so we can determine A inlet 、A orifice 、A outlet Total MEMS process area A total The ratio between the fill factor (i.e. fill-in factor) is used to determine the fill factor. That is to say, when the die A used in the MEMS process is total When the ratio of the characteristic dimensions to each other is determined, the actuator's A can be determined. inlet 、A orifice and A outlet , and then the flux area of ​​the actuator array can be determined. When the flow rate, temperature, and pressure are determined, the flow rate of the actuator array can be determined.

[0119] The following calculation assumes that the actuator's air inlet and outlet are rectangular. Considering the rounded corners on the air inlet and outlet, the factor can be set to 3.14 / 4.

[0120] A inlet =W inlet ×L inlet , A outlet=W outlet ×L outlet , A total =W×L, where L inlet 、W inlet Indicates the length and width of the actuator's air inlet, L outlet 、W outlet Indicates the length and width of the actuator's outlet, and L and W indicate the length and width of the die.

[0121] For actuators with single cantilever and single opening, A orifice =2×(L open +H open )×Δ open , for the double-cantilever double-opening actuator, A orifice =4×(L open +H open )×Δ open , where L open 、H open Indicates the length and height of the throttle opening, Δ open Indicates the distance the cantilever moves. L open 、L inlet and L outlet Approximately. And A orifice Need to be with A inlet and A outlet Approximately, assuming H open Can be ignored, A orifice =2×L open ×Δ open .Will L outlet =L open After substitution, we can get Or for double cantilever double opening actuator

[0122] Generally speaking, the distance of cantilever movement Δ open will not be very large, so we can make W outlet 、W inlet Approximately equal to 2 or 4 times Δ open To improve the fill factor, a more accurate method is to further calculate H open (It is slightly smaller than the height of the cantilever motion.) And through the above calculation, it can be seen that when the size of the throttle hole, the air inlet and the air outlet are matched, the flux of the micro valve is traditionally limited by Δ open It has little effect on the flux of the present invention.

[0123] In one embodiment of the present invention, the height of the cantilever is close to the thickness of the SOI wafer, which is about 80-100um, the length is about 200um-3mm, and the width is about 20-50um.open 1.5-22um.Δ open A larger diameter is more conducive to the processing of throttle holes and can improve the filling factor.

[0124] As mentioned above, the optimized A inlet 、A orifice 、A outlet The size is close, so we calculate A inlet 、A outlet The filling factor can determine A total In the length direction of the die, the orthographic projections of the air inlet and outlet cannot be superimposed. After removing the enclosure of the throttle hole, the optimized filling factor in the length direction of the die is about 1 / 3. In the width direction of the outlet and the die, the width of the cantilever, the enclosure of the throttle hole, and Δ open The sum of the widths of the two cantilevers and twice the Δ open The sum of the fill factor can reach 2 / 5. Adding another fill factor of 2 / 3 (such as chamfer), the total fill factor can be 1 / 3×2 / 3×2 / 5=8.9%. 2 The size of the flux area on the die can be larger than that of the 1 / 8 inch pipe, at 250mm 2 The flux area on the die can be larger than that of a 1 / 4 inch pipe. In addition, a larger flux can be achieved by splicing the die. Compared with traditional pipes, the micro valve proposed in this invention can withstand higher flow rates. Usually, the flow rate of gas in the pipe is 12-15m / s. If the flow rate is tripled, that is, the flow rate of the gas is increased to 30-45m / s, 250mm 2 The on-die flux area can be greater than or equal to 3 / 8 inch pipe.

[0125] In the present invention, multiple actuators can form an actuator array. Figure 21 shows a schematic diagram of the control logic of an actuator array in one embodiment of the present invention. As shown in Figure 21, multiple actuators are connected to a digital control circuit via metal vias or bonded to a substrate equipped with a control circuit. The control circuit can control the opening degree of any actuator. In one embodiment of the present invention, the number of actuators to be opened can be selected using bonded bit lines, thereby achieving more precise control of the flow rate.

[0126] For example, in an array of 100 actuators, the actuators can be configured so that the flow rate of each actuator when fully open is approximately the same. This means that a single actuator fully opening can achieve a 1% flow rate increase. Assuming the proportional opening accuracy of each actuator is 5%, the actuator array can achieve a control accuracy of 0.05%.

[0127] Furthermore, the actuators in the actuator array can be redundantly configured, thereby extending their service life. In one embodiment of the present invention, 120 actuators are configured, each with several orifices and outlets. Each outlet has an independent bit line to select its operating state. If the total flux of the actuator array is calibrated to 100 actuators, the flux of the actuator array is 120% of the nameplate value. If an actuator fails, a new backup actuator can be connected through the circuit to ensure that the valve array continues to receive sufficient flux, effectively extending the life of the device. Furthermore, the firmware can record the total number of switching cycles and total stroke of each actuator. The life of an actuator is related to the number of switching cycles, and recording the number of valve switching cycles is one method for determining its life loss. Alternatively, the stroke (distance) can be recorded. In the present invention, the excitation voltage (voltage excitation) or excitation current (current excitation) can be integrated over time. For thermal MEMS actuators, the temperature reading of the electrothermal actuator can be integrated. In working conditions, the actuator with the lowest integral value can be turned on first to make the loss of each actuator equal, thereby preventing excessive consumption of individual actuators and reaching the design life ahead of time.

[0128] A proportional control valve is one in which the controlled factor, such as pressure or flow, is proportional to the input signal, or exhibits a highly linear relationship. For example, valves driven by piezoelectric actuators often exhibit creep, hysteresis, and other phenomena, resulting in poor linearity. A common approach is to attach a piezoelectric sensor to the side of the actuator to measure its deformation, creating a closed-loop control loop to ensure linearity and achieve proportional control. Most actuators experience some degree of linearity issues.

[0129] For cantilever beam and diaphragm actuators, it is traditionally difficult to measure the actuation distance. This results in poor linearity in valve opening control and makes it difficult to improve the accuracy of flow control. In an embodiment of the present invention, the number of actuators to be opened can be selected by bonding bit lines, thereby achieving more precise control of the flow rate. Taking an actuator array with 100 actuators as an example, the actuators can be configured so that the flow rate of each actuator when fully opened is close to the same, that is, a single actuator can achieve a 1% flow rate increment when fully opened. Assuming that the accuracy of the proportional opening of a single actuator itself is 5%, the actuator array can achieve a control accuracy of 0.05%.

[0130] In the embodiment of the present invention, the process of flow control may include: assuming that the flow to be controlled is Q setpoint The maximum precise measurement value that a single actuator can drive is max(Q actr ), let i = integer {Q setpoint / max(Qactr )}, open i actuators, the sum of the flow of i actuators is i×max(Q actr ). Open the i+1th valve and set the flow of the i+1th actuator to Q setpoint -i×max(Q actr ).

[0131] When the flow rate of the i+1th actuator is low, the flow rates of the i-2th, i-1th, i, and 1+1th actuators can be set to (Q setpoint -i×max(Q actr )+3×max(Q actr )) / 4, or further set the flow rate of the ijth, i-j+1, ...i, i+1, a total of j+2 actuators to (Q setpoint -j×max(Q actr )) / (j+2).

[0132] In one embodiment of the present invention, multi-zone pressure control can be added by mounting more pressure sensors on the actuator (for thermal MFC, heaters and corresponding temperature sensors need to be added accordingly). Each set of sensors independently detects the pressure (and temperature) of each zone to further accurately control the flow rate.

[0133] In one embodiment of the present invention, three cantilevers with a length of 1 mm and a width of 100 μm have a total area of ​​0.3 mm. 2 The arch opening of the cantilever is simplified to the cantilever being lifted horizontally by 10um. It can be calculated that when the inlet and outlet pressure difference is 1bar, the amount of air that can pass through is 1.0516903e-5kg / s, which is approximately equal to 524ml / min of air (different gas types and densities will have different gas flow rates at the same operating pressure). 2 The valve corresponds to a flow rate of 500sccm, 10mm 2 The valve area can correspond to a flow rate of 16slm (100 actuators), 100mm 2 The valve area can correspond to a flow rate of 160slm (1000 actuators).

[0134] In another embodiment of the present invention, three cantilevers with a length of 1 mm and a width of 100 μm have a total area of ​​0.3 mm. 2 The arch opening of the cantilever is 15um. It can be calculated that when the inlet and outlet pressure difference is 1 bar, the volume flow rate of air that can pass through is 4.41×10 -6 m 3 / s is equal to 264.6sccm, or 0.3mm 2 The valve corresponds to a flow rate of 264 sccm, 10mm2 The valve area can correspond to a flow rate of 8.7slm (100 actuators), 100mm 2 The valve area can correspond to a flow rate of 87slm (1000 actuators).

[0135] FIG22 shows a schematic diagram of a microvalve in another embodiment of the present invention. As shown in FIG22 , the microvalve has an actuator array formed by 2×2 actuators, and the actuator array includes a circular diaphragm 2201 and corresponding throttling holes. Each diaphragm 2201 can be driven by piezoelectricity or other means. Each diaphragm 2201 can correspond to one or more throttling holes ( FIG22 takes one diaphragm 2201 corresponding to one throttling hole as an example), wherein each diaphragm 2201 corresponding to multiple throttling holes can increase the flux of a single diaphragm. The diaphragm 2201 is connected to the upstream and downstream of the throttling hole respectively, and the total flow rate Q of the microvalve is total =ΣQ i , Q i represents the flow rate of the i-th actuator.

[0136] As described above, in an embodiment of the present invention, a pressure sensor, a temperature sensor, a heater, and a temperature sensor are arranged on a microvalve to form a mass flow meter. In the mass flow meter, the flow through different actuators can be calculated using different methods depending on whether the airflow is blocked.

[0137] Blockage occurs when the flow velocity at a certain section of a pipe reaches the speed of sound. Regardless of how much the pressure outside the pipe outlet decreases, the velocity and pressure of the airflow before the sonic section remain unchanged, and the flow rate remains constant. Blockage is prone to occur in a variety of situations, including starting blockage in supersonic wind tunnels (see wind tunnel), aircraft inlet blockage, friction tube blockage, and heating tube blockage.

[0138] Taking the blockage in the aircraft inlet as an example, when the airflow Mach number is far ahead of the inlet, 00 When the Mach number at the throat is less than 1, the airflow velocity in front of the inlet increases, the velocity at the throat increases, and the flow rate increases. 00 = 1, even if the airflow velocity in front of the inlet increases, the flow rate will no longer increase, only supersonic flow and shock wave will appear after the throat; when the Mach number of the airflow far ahead is Ma 00When the ratio is greater than 1, the supersonic airflow flows directly into the inlet without any disturbance before the inlet. When the throat area is large enough to allow all incoming gas to pass through, the inlet is unobstructed. When the throat area is too small, and the flow rate that can pass is less than the flow rate that would enter directly, the throat becomes blocked, gas accumulates before the throat, and the pressure rises, forming a shock wave before the inlet. Some excess airflow overflows the outlet, resulting in a supersonic region and shock wave after the throat. Blockage in an aircraft's inlet significantly increases the aircraft's drag and significantly reduces the engine's thrust.

[0139] FIG23 shows a schematic diagram of the airflow at an actuator in one embodiment of the present invention. It should be understood that FIG23 is merely an illustration of the airflow direction and pressure at the actuator, and does not represent the actual structure of the actuator. As shown in FIG23 , for a compressible fluid, if the pressure P1 at the air inlet of the actuator remains constant, and the pressure P2 at the air outlet gradually decreases, the mass flow rate through the actuator will gradually increase to a maximum value, at which point further reduction of P2 will no longer increase the flow rate. This situation is called a choked flow. The formation of a choked flow usually requires that P1 ≥ 2P2 (the specific ratio is related to the specific heat capacity of the gas). At this time, the flow rate through the actuator is only related to P1 and is proportional to the absolute value of P1.

[0140] FIG24 shows a schematic diagram of the change of pressure and flow rate of a blocked flow in one embodiment of the present invention. The blocking point of the fluid is determined by the pressure recovery factor F of the liquid. L And the critical pressure difference ratio coefficient X of the gas without an attached tube T The liquid forms vapor and the gas reaches the speed of sound at the contraction neck. The critical pressure value can be calculated by the following formula: F F =0.96-0.28(P V / P C ) 1 / 2

[0141] Among them, F F Indicates the liquid critical pressure ratio factor, P V represents the fluid vapor pressure, P C represents the thermodynamic critical pressure.

[0142] Blockage critical pressure P at the actuator choked The ratio between P1 and P2 can be expressed as follows:

[0143] Where n represents the exponent of isentropic expansion / compression. For ideal gases in a thermal system, n is the ratio of specific heats: n = C p / C v , where C p Indicates specific heat at constant pressure, C vIt represents the specific heat at constant volume. For most process steams operating in the wet zone, n = 1.135, for superheated steam n = 1.30, for air n = 1.4, for methane n = 1.31, and for helium n = 1.667.

[0144] For air, the calculation of the critical pressure ratio can be expressed as:

[0145] The corresponding relationships between n and the critical pressure ratio of other gases may be 1.1135, 0.577; 1.300, 0.546; 1.400, 0.528; 1.667, 0.487.

[0146] The mass flow rate of the choked flow through the actuator, that is, the sonic flow with the minimum pressure equal to the critical pressure, can be expressed as follows:

[0147] Among them, m c Indicates the mass flow rate of sonic flow (kg / s), A c Indicates the nozzle area (m 2 ), ρ1 represents the density of the actuator's air inlet (kg / m 3 ).

[0148] For the case of non-blocked flow, the pressure function upstream and downstream of the actuator is The secondary flow rate can be determined by the following formula: Q = k × Function (P UP , P DOWN ).

[0149] At the actuator of non-blocking flow, the flow Specifically, it can be expressed as the following formula:

[0150] According to the above formula, in P UP 、P DOWN Under the same conditions, the flow rate Q at the actuator of non-blocking flow i The opening area A is proportional to the non-blocked flow. In the present invention, the opening area A can be adjusted by an electrical control circuit and controlled by a control unit.

[0151] In non-choked flow, the flow rate is limited by the speed of sound at the actuator outlet. UP After determination, the flow Q i It is proportional to the opening area A of the non-blocked flow. By configuring multiple actuators 402i, the upstream pressure P of the actuator 402i can be UPiThe upstream of multiple actuators 402i are connected to each other. When the flow rate (flow velocity) is large and the pipe diameter is small, a pressure difference Δ (P UPi , P UPi+1 )=v 2 fLρ / 2D. According to the present invention, the actuator is adjusted to maintain P UPi Basically unchanged, and accept the pressure difference between the upstream of multiple actuators 402i, the opening area A i Fine adjustment can achieve precise proportional control without setting pressure control valve for control. In the pressure flow control equipment, the opening area at MFC is fixed. When the downstream pressure is fixed, it is necessary to increase the P UPi To control the flow. When the flow ratio changes, P UPi Increase the corresponding Q i It will also increase.

[0152] For a blocking flow, when Q i When doubled, P UPi It will also double, and usually the flow rate Q at other actuators at this time j Will reduce, P UPj will also decrease, due to P UPi With P UPj When interconnected, backpressure can interfere with or even conflict with each other, leading to overconstraint. When flow differences are too large, precise control becomes difficult. The same applies to non-blocking flows.

[0153] When the airflow through the actuator 402i is choked, the flow rate Q at the actuator 402i is i =C×P UPi , where C represents the first correlation coefficient, which is related to the opening area A of the i actuator i Positive correlation.

[0154] Although various embodiments of the present invention have been described above, it should be understood that they are presented by way of example only and not limitation. It will be apparent to those skilled in the relevant art that various combinations, modifications, and variations may be made thereto without departing from the spirit and scope of the present invention. Therefore, the breadth and scope of the present invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined solely in accordance with the appended claims and their equivalents.

Claims

1. A micro valve, characterized in that: include: a first substrate having a substrate gas inlet, wherein a gas flows from the substrate gas inlet toward the intermediate layer; An intermediate layer is arranged between the first substrate and the second substrate, the intermediate layer comprising an array formed by a plurality of actuators, the actuator comprising: A throttle hole having a throttle inlet and a throttle outlet, wherein the gas flows from the throttle inlet into the throttle hole and flows from the throttle outlet toward the second substrate; and a cantilever arm configured to move relative to the throttle inlet port, wherein the opening area of ​​the throttle inlet port is adjusted by adjusting the distance between the cantilever arm and the throttle inlet port; and A second substrate has a substrate gas outlet, wherein the gas flows out of the substrate gas outlet.

2. The microvalve according to claim 1, characterized in that: Also includes: A shell surrounds the first substrate, the intermediate layer and the second substrate, the shell has a shell air inlet and a shell air outlet, and the shell includes a metal shell, a ceramic shell or a resin shell.

3. The microvalve according to claim 1, characterized in that: The throttle hole comprises: a throttle hole step connected to the second substrate, wherein the throttle outlet is arranged on the throttle hole step; and A throttle enclosure has a first end connected to the first substrate, and a second end of the throttle enclosure opposite to the first end is connected to the throttle step, and the throttling air inlet is arranged on the throttle enclosure.

4. The microvalve according to claim 3, characterized in that: The first substrate further comprises: A substrate step is connected to the first end of the throttle hole enclosure, wherein the substrate step and / or the throttle hole step is configured to suppress short-circuit gas flow generated by the gap between the cantilever and the second substrate and / or the first substrate.

5. The microvalve according to claim 1, characterized in that: The cantilever has a coating of a wettable material thereon; and\or The cantilever includes an electrostatically driven cantilever, an electromagnetically driven cantilever, a piezoelectrically driven cantilever or an electrothermal driven cantilever.

6. The microvalve according to claim 1, characterized in that: The cantilever is configured to move horizontally relative to the throttle inlet; or The cantilever arm is configured to move vertically relative to the throttle inlet.

7. The microvalve according to claim 1, characterized in that: Also includes: An outer frame is arranged around the middle layer to restrict airflow.

8. The microvalve according to claim 3, characterized in that: The throttle hole enclosure includes a first throttle air inlet and a second throttle air inlet opposite to the first throttle air inlet; and The cantilever includes a first cantilever and a second cantilever, wherein the first cantilever is configured to move relative to a first throttle air inlet, and the second cantilever is configured to move relative to a second throttle air inlet.

9. The microvalve according to claim 1, characterized in that: A grid is provided on one or more of the following to form a laminar flow element: a substrate air inlet, a substrate air outlet, and a throttle air outlet.

10. The microvalve according to claim 1, characterized in that: The cantilever is connected to one or more throttle holes.

11. The microvalve according to claim 1, characterized in that: Multiple microvalves are configured to be spliced ​​with each other to increase the flow rate.

12. The microvalve according to claim 1, characterized in that: The throttling air outlets of multiple actuators can be individually discharged or combined into multiple groups and then discharged in groups to achieve diffuse air outlet.

13. The microvalve according to claim 1, characterized in that: Also includes: The control circuit is connected to the plurality of actuators, and is configured to control the opening degrees of the plurality of actuators respectively.

14. The microvalve according to claim 13, characterized in that: The control circuit is configured to perform the following actions: Set the flow rate to be controlled to Q setpoint ; Determine the maximum accurate metering value of a single actuator max(Q actr ); Calculate i = round {Q setpoint / max(Q actr )}; Open i actuators, where the sum of the flows of i actuators is i×max(Q actr ); as well as Open the i+1th actuator and set the flow rate of the i+1th actuator to Q setpoint -i×max(Q actr ).

15. The microvalve according to claim 14, characterized in that: The control circuit is also configured to perform the following actions: When the flow rate of the i+1th actuator is lower than the threshold, the flow rates of the ijth, i-j+1th, …i, i+1th, a total of j+2 actuators are set to (Q setpoint -j×max(Q actr )) / (j+2).

16. A micro valve, characterized in that: include: a first substrate having a substrate gas inlet, wherein a gas flows from the substrate gas inlet toward the intermediate layer; The intermediate layer is arranged between the first substrate and the second substrate, and the intermediate layer includes an array formed by a plurality of actuators. The actuator comprises: A throttle hole having a throttle inlet and a throttle outlet, wherein the gas flows from the throttle inlet into the throttle hole and flows from the throttle outlet toward the second substrate; and a diaphragm configured to control the opening of the throttle inlet port; and A second substrate has a substrate gas outlet, wherein the gas flows out of the substrate gas outlet.

17. The microvalve according to any one of claims 1 and 16, characterized in that: The first substrate is configured to restrict gas flow, and the second substrate has a substrate gas inlet and a substrate gas outlet, wherein gas flows from the substrate gas inlet to the intermediate layer, flows back to the second substrate, and then flows out from the substrate gas outlet.

18. A mass flow meter, characterized in that: include: A microvalve, which is the microvalve according to any one of claims 1 to 17; and A sensing component is arranged on at least one of the plurality of actuators of the microvalve.

19. The mass flow meter according to claim 18, characterized in that The sensing component comprises a pressure sensor and a temperature sensor, wherein the microvalve, the pressure sensor and the temperature sensor form a pressure mass flow meter; and\or The sensing component includes a heater and a temperature sensor, wherein the microvalve, the heater and the temperature sensor form a thermal mass flow meter.

20. The mass flow meter according to claim 19, characterized in that For choked flow, the flow Q through the i-th actuator on the microvalve is adjusted according to the following formula: i : Q i =C×P UPi , Among them, C represents the first correlation coefficient, P UPi represents the pressure on the first side of the i-th actuator, where the first correlation coefficient C is related to the opening area A of the i-th actuator i Positive correlation; and\or For non-blocking flow, the flow Q through the i-th actuator on the microvalve is adjusted according to the following formula: i : Among them, C' represents the second correlation coefficient, A i represents the opening area of ​​the i-th actuator, P DOWNi represents the pressure on the second side of the i-th actuator, R represents the universal gas constant, T represents the temperature, M represents the molecular mass, γ represents the specific heat ratio, and the second correlation coefficient C' is a constant.

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