A piezoelectric valve

Abstract

The application discloses a piezoelectric valve, comprising: a valve body defining a cavity; a piezoelectric sheet arranged in the cavity to form a sealed cavity between the piezoelectric sheet and the inner wall of the valve body; a first fluid channel, the first end of the first fluid channel extending from outside the valve body into the sealed cavity and opposite the bottom surface of the piezoelectric sheet, a ring-shaped rubber sleeve being sleeved on the first end, the ring-shaped rubber sleeve being in interference fit with the first end, so that when the piezoelectric sheet is not driven by external force, the ring-shaped rubber sleeve abuts against the bottom surface of the piezoelectric sheet to close the first end; a second fluid channel extending from the sealed cavity to outside the valve body; a circuit board arranged in the cavity and outside the sealed cavity, the circuit board being electrically connected with the piezoelectric sheet. The ring-shaped rubber sleeve is in interference fit with the first end, and the ring-shaped rubber sleeve and the bottom surface of the piezoelectric sheet are mutually attached to form double sealing to prevent fluid leakage, and the sealed cavity is mutually sealed and isolated from the wall body to avoid fluid erosion of the circuit board and other electronic components.

Description

Technical Field

[0001] This application relates to the field of fluid control technology, and more specifically, to a piezoelectric valve. Background Technology

[0002] In precision fluid control applications such as industrial automation and medical equipment, piezoelectric valves have become core control components due to their advantages of fast response, high precision, and small size. They work by applying a driving signal to a piezoelectric element, which deforms due to the piezoelectric effect, driving the valve core to control fluid flow and control its on / off state.

[0003] However, the existing piezoelectric elements have relatively small displacement and output force, which cannot meet the demand for large flow rates; the output force is weak, making it difficult to overcome the resistance of high-pressure fluids, thus limiting their application range and allowing them to work only under low-pressure and low-load conditions. Utility Model Content

[0004] One objective of this application is to provide a piezoelectric valve to solve the problems of small displacement and low output force of piezoelectric valves.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows: a piezoelectric valve, comprising: a valve body defining a cavity; a piezoelectric element disposed within the cavity, thereby forming a sealed cavity between the piezoelectric element and the inner wall of the valve body; a first fluid channel, a first end of the first fluid channel extending from the valve body into the sealed cavity and facing the bottom surface of the piezoelectric element, an annular rubber sleeve being fitted onto the first end, the annular rubber sleeve being interference-fitted with the first end so that when the piezoelectric element is not driven by external force, the annular rubber sleeve abuts against the bottom surface of the piezoelectric element to close the first end; a second fluid channel extending from the sealed cavity into the valve body; and a circuit board disposed within the cavity and outside the sealed cavity, the circuit board being electrically connected to the piezoelectric element.

[0006] As a preferred embodiment, the bottom surface of the piezoelectric sheet is provided with a valve protrusion, which fits against the annular rubber sleeve when the piezoelectric sheet is not driven by an external force.

[0007] As another preferred embodiment, the diameter of the valve plate protrusion is larger than the outer diameter of the annular rubber sleeve.

[0008] Further preferably, the upper end of the annular rubber sleeve has an annular sealing surface, and the plane where the annular sealing surface is located is higher than the plane where the first end is located.

[0009] Further preferably, the piezoelectric valve further includes a cover plate disposed between the circuit board and the piezoelectric element. The cover plate has a cover plate support edge on the side facing the piezoelectric element, which abuts against the top surface of the piezoelectric element to apply a downward preload. The first end abuts against the bottom surface of the piezoelectric element to apply an upward first support force. The valve body has a valve body support edge that protrudes relative to the inner wall of the valve body and abuts against the bottom surface of the piezoelectric element to apply an upward second support force. When the piezoelectric element is not driven, the resultant force of the first and second support forces, along with the preload, keeps the piezoelectric element in balance.

[0010] In a further preferred embodiment, the cover plate is provided with at least one terminal block, one end of which is electrically connected to the circuit board, and the other end of which is connected to a metal spring pin, which is then electrically connected to the piezoelectric sheet. The terminal block and the metal spring pin are arranged in a one-to-one correspondence.

[0011] In a further preferred embodiment, the cover plate support edge, the top surface of the piezoelectric sheet, and the side of the cover plate facing the piezoelectric sheet together define a receiving cavity, which can accommodate the metal spring needle, and the height of the metal spring needle is less than or equal to the height of the cover plate support edge.

[0012] Further preferably, the width of the cover plate support along the horizontal direction is 1mm-3mm.

[0013] In a further preferred embodiment, the piezoelectric valve further includes a sealing element, which is disposed on the side of the circuit board away from the cover plate, and the sealing element is in contact with the circuit board to seal the cavity.

[0014] Further preferably, the piezoelectric sheet is rectangular or circular, and the thickness of the piezoelectric sheet is 0.1mm-2mm.

[0015] Compared with the prior art, the beneficial effects of this application are as follows: (1) The annular rubber sleeve is interference-fitted with the first end, and the annular rubber sleeve is in contact with the bottom surface of the piezoelectric sheet to form a double seal to prevent fluid leakage. The sealed cavity is sealed and isolated from the wall to prevent fluid from corroding electronic components such as circuit boards.

[0016] (2) The piezoelectric sheet directly drives the sealing action without redundant transmission components, resulting in fast response and precise fluid control. Attached Figure Description

[0017] Figure 1 An exploded view of a piezoelectric valve provided in an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the internal structure of a piezoelectric valve provided in an embodiment of this application.

[0019] Figure 3 This is a schematic diagram of the annular rubber sleeve.

[0020] In the diagram: 10. Piezoelectric valve; 11. Valve body; 111. Cavity; 112. Valve body support edge; 12. Piezoelectric element; 121. Sealing cavity; 122. Valve element protrusion; 13. First fluid channel; 131. First end; 132. Annular rubber sleeve; 1321. Annular sealing surface; 14. Second fluid channel; 15. Circuit board; 151. Metal spring pin; 16. Cover plate; 161. Cover plate support edge; 162. Receiving cavity; 17. Seal. Detailed Implementation

[0021] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0022] In the description of this application, it should be noted that the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., which indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of this application.

[0023] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0024] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0025] This application provides a piezoelectric valve 10, such as Figures 1-2 As shown, where Figure 1The first fluid channel 13 and the second fluid channel 14 are not shown from the perspective of the view. The piezoelectric valve 10 includes a valve body 11, a piezoelectric element 12, a first fluid channel 13, a second fluid channel 14, and a circuit board 15. The valve body 11 defines a cavity 111. The piezoelectric element 12 is disposed in the cavity 111, so that a sealed cavity 121 is formed between the piezoelectric element 12 and the inner wall of the valve body 11. The circuit board 15 is disposed outside the sealed cavity 121 and is electrically connected to the piezoelectric element 12. The first end 131 of the first fluid channel 13 extends from the outside of the valve body 11 into the sealed cavity 121. The second fluid channel 14 extends from the sealed cavity 121 to the outside of the valve body 11, limiting the fluid path of the first fluid channel 13 and the second fluid channel 14 within the sealed cavity 121, preventing fluid from seeping into the electrical connection area between the piezoelectric element 12 and the circuit board 15, preventing short circuits or performance degradation of the piezoelectric element 12 due to fluid erosion, and improving the moisture-proof and corrosion-proof capabilities of the piezoelectric valve 10.

[0026] In one embodiment, the bottom surface of the piezoelectric element 12 is provided with a valve protrusion 122. The diameter of the valve protrusion 122 is larger than the outer diameter of the annular sleeve 132. When the piezoelectric element 12 is not driven by an external force, the valve protrusion 122 and the annular sleeve 132 sleeved on the first end 131 fit together, thereby sealing the first end 131 and closing the piezoelectric valve 10. When the piezoelectric element 12 is driven by an external force, the piezoelectric element 12 deforms, causing a gap to be created between the valve protrusion 122 and the annular sleeve 132, thereby opening the piezoelectric valve 10. It can be understood that the annular sleeve 132 is made of rubber and has a certain elasticity. The annular sleeve 132 fits tightly against the bottom surface of the piezoelectric element 12, which can not only seal the small gap and prevent leakage, but also buffer the impact and wear caused by the vibration of the piezoelectric element 12, extending the life of the piezoelectric element 12. Furthermore, such as Figure 3 As shown, the upper end of the annular rubber sleeve 132 has an annular sealing surface 1321. The plane where the annular sealing surface 1321 is located is higher than the plane where the first end 131 is located, so that when the piezoelectric valve 10 is closed, the annular rubber sleeve 132 can fully fit with the valve plate protrusion 122 to achieve a seal. At the same time, it can also reduce the contact area between the first end 131 and the valve plate protrusion 122 to prevent wear between them.

[0027] In some embodiments, such as Figure 2As shown, the piezoelectric valve 10 also includes a cover plate 16, which is vertically disposed between the piezoelectric sheet 12 and the circuit board 15. A portion of the cover plate 16 and a portion of the circuit board 15 abut against each other vertically, thereby applying a downward pre-pressure to the piezoelectric sheet 12 in the vertical direction. The fluid pressure in the first fluid channel 13 acts on the bottom surface of the piezoelectric sheet 12, forming an upward first support force. The valve body support along 112 forms an upward second support force on the bottom surface of the piezoelectric sheet 12. When there is no external driving force, the resultant force of the downward pre-pressure and the first and second support forces balances the force on the piezoelectric sheet 12 in the vertical direction, thereby confining the piezoelectric sheet 12 within the cavity 111.

[0028] It is understandable that the valve body support 112 is circumferentially arranged inside the cavity 111, and the upper surface of the valve body support 112 is an annular surface. When the piezoelectric sheet 12 is placed inside the cavity 111, the outer edge of the bottom surface of the piezoelectric sheet 12 is in contact with the upper surface of the valve body support 112.

[0029] Furthermore, such as Figure 1 As shown, the circuit board 15 and the cover plate 16 are attached to each other on one side, forming a rigid support through physical contact. The cover plate 16 is mostly made of metal or high-strength plastic, and its structural strength is much higher than that of the circuit board 15. After attachment, it can directly bear the weight of the circuit board 15 itself and external stress, preventing the circuit board 15 from deforming and breaking. The circuit board 15 and the piezoelectric sheet 12 are electrically connected through metal spring pins 151. The metal spring pins 151 can elastically expand and contract, effectively offsetting the connection interference caused by the high-frequency vibration of the piezoelectric sheet 12 and assembly errors. It can be understood that the piezoelectric sheet 12 will generate high-frequency reciprocating vibration during operation. If a rigid connection is used, the vibration will be directly transmitted to the solder joints of the circuit board 15, causing the solder pads to fatigue and fall off or the wires to break. However, the metal spring pins 151, through their own elastic deformation, can compensate for the relative displacement between the piezoelectric sheet 12 and the circuit board 15 in real time, ensuring that the electrical contact is always stable.

[0030] During assembly, the metal spring pin 151 achieves an elastic electrical connection between the circuit board 15 and the piezoelectric sheet 12. During assembly, the metal spring pin 151 is installed at an angle. This is because the contact ends of the metal spring pin 151 are mostly spherical or arc-shaped structures. When tilted, they form line-to-line contact with the surface of the piezoelectric sheet 12. Compared to the point-to-point contact when the metal spring pin 151 is assembled vertically, the tilted assembly significantly increases the contact area between the metal spring pin 151 and the piezoelectric sheet 12, thus avoiding poor contact.

[0031] In some embodiments, such as Figure 1As shown, the circuit board 15 has two terminals, which are respectively connected to the positive and negative terminals of the external power supply; the cover plate 16 has two corresponding terminals, which are connected to the terminals of the circuit board 15 after assembly; the cover plate 16 has two metal spring pins 151 on the side near the piezoelectric piece 12, one end of which is connected to the terminal of the cover plate 16, and the other end is electrically connected to the piezoelectric piece 12. It can be understood that the terminal and the metal spring pin 151 are set one-to-one. The metal spring pin 151 has a built-in spring structure. The spring is set axially inside the metal spring pin 151. After assembly, the spring is in a compressed state, providing continuous axial preload for the contact between the metal spring pin 151 and the piezoelectric piece 12.

[0032] In some embodiments, the cover plate support edge 161, the top surface of the piezoelectric sheet 12, and the side of the cover plate 16 facing the piezoelectric sheet 12 together define a receiving cavity 162. The receiving cavity 162 can accommodate the metal spring needle 151. The height of the metal spring needle 151 is less than or equal to the height of the cover plate support edge 161, and the width of the cover plate support edge 161 in the horizontal direction is 1mm-3mm. It is understood that the receiving cavity 162 provides an independent space for the metal spring needle 151 to avoid accidental friction or compression between the metal spring needle 151 and the cover plate 16; the height of the metal spring needle 151 being less than or equal to the height of the cover plate support edge 161 prevents excessive pressure between the metal spring needle 151 and the piezoelectric sheet 12 when the piezoelectric valve 10 is closed, as the piezoelectric sheet 12 does not deform, thus preventing wear of the metal spring needle 151.

[0033] In some embodiments, the piezoelectric sheet 12 is circular or rectangular in shape, and the thickness of the piezoelectric sheet 12 is 0.1mm-2mm. The valve body 11, circuit board 15 and cover plate 16 are adapted to the shape of the piezoelectric sheet 12, and are set according to the actual installation situation, which is not limited here.

[0034] In some embodiments, such as Figures 1-2 As shown, the piezoelectric valve 10 also includes a seal 17, which is located on the side of the circuit board 15 away from the cover plate 16 to seal the valve body 11, thereby increasing the sealing performance of the piezoelectric valve 10. The seal 17 is a sealant that fills irregular gaps to achieve a seal. The mating surfaces of the circuit board 15 and the valve body 11 may have irregular gaps due to machining precision. The sealant can fully fill these gaps, and after curing, it forms a seal 17 that completely fits the gaps, preventing localized leakage caused by insufficient fit.

[0035] In some embodiments, the circuit board 15 is provided with a control unit, which executes the following control method, which includes the following steps: S1, obtaining the natural frequency f0 of the piezoelectric sheet 12; S2, sending a driving signal to the piezoelectric sheet 12 to drive the piezoelectric sheet 12 to undergo periodic deformation, wherein the frequency of the driving signal is f1, and f1 satisfies: 0.5f0≤f1≤1.5f0.

[0036] In some embodiments, the circuit board 15 integrates a control circuit and a detection unit. In step S1, obtaining the natural frequency f0 of the piezoelectric element 12 includes: the control circuit sending a detection drive signal to the piezoelectric element 12; the detection unit performing detection by frequency scanning; gradually changing the frequency of the detection drive signal sent to the piezoelectric element 12 within a preset frequency range; monitoring the vibration amplitude of the piezoelectric element 12 in real time during the frequency sweep; and taking the frequency corresponding to the maximum vibration amplitude as the natural frequency f0 of the piezoelectric element 12. The standard frequency f0 of the piezoelectric element 12 is determined based on its material and size. nom And the standard frequency f nom This is usually provided by the manufacturer, and the minimum preset frequency range is 0.5f. nom The maximum value is 1.5f nom .

[0037] After obtaining the inherent frequency f0 of the piezoelectric element 12 and before executing step S2, the user needs to input the frequency f1 of the drive signal. The user inputs f1 in at least one of the following ways: manually inputting the value of f1 through a human-machine interaction device, such as a button or a touch screen; or the host computer sending a digital instruction containing f1 to the control circuit through a communication interface. No restrictions are placed on the input method here. After the user inputs f1, it is verified to determine whether the user input f1 meets the specified range. If the verification fails, the user will re-enter the f1.

[0038] In some embodiments, the circuit board 15 integrates a control circuit and a storage unit. The obtained inherent frequency f0 is stored in the storage unit. The control circuit obtains the inherent frequency f0 from the storage unit and then sends a drive signal to the piezoelectric sheet 12.

[0039] In some embodiments, f1 satisfies: 0.5f0≤f1≤1.5f0, further f1 satisfies: 0.8f0≤f1≤1.2f0, and even further, f1=f0. It can be understood that when the frequency f1 of the driving signal is equal to the natural frequency f0, the piezoelectric element 12 is in a resonant state. In the resonant state, if the amplitude exceeds the fatigue threshold of the piezoelectric element 12 material, where the fatigue threshold is related to the material of the piezoelectric element 12, it may cause excessive impact on the piezoelectric element 12, shortening its service life over long periods of operation. However, when the amplitude is within the safe threshold, the advantages of the resonant state are significant: First, in the non-resonant state, the input electrical energy can only drive the piezoelectric element 12 to produce a single, limited, small deformation, resulting in relatively small displacement and output force. In the resonant state, the vibration of the piezoelectric element 12 is completely synchronized with its own natural vibration rhythm. The energy of each driving signal input is superimposed on the energy of the previous vibration, forming a resonant amplification, significantly increasing the output force and displacement, enabling the opening of larger fluid channels, thus increasing the flow rate per unit time. In industrial production environments, after each production cycle, the gas in the pipeline needs to be discharged. When the piezoelectric element 12 is in a resonant state, the gas discharge time can be shortened, greatly increasing the discharge efficiency. Secondly, in order to increase the output force and displacement of the piezoelectric valve 10, the volume of the piezoelectric valve 10 is increased. This would significantly increase the space occupied by the piezoelectric valve 10, which would restrict the installation environment of the piezoelectric valve 10. Therefore, by adjusting f1, the piezoelectric element 12 is made to resonate. The piezoelectric valve 10 achieves displacement and output force amplification through the superposition of resonant energy, without the need for additional mechanical structures. While taking into account the flow rate of the piezoelectric valve 10, the volume of the piezoelectric valve 10 can be reduced to a certain extent, thereby increasing the adaptability of the piezoelectric valve 10.

[0040] Furthermore, if the piezoelectric element 12 operates in a resonant state for an extended period, its lifespan will be reduced. By limiting the time the piezoelectric valve 10 remains in a resonant state, the lifespan of the piezoelectric element 12 can be ensured. The specific limiting method is as follows: the duration T1 of a single continuous resonant state of the piezoelectric element 12 is controlled to satisfy: 0.5S ≤ T1 ≤ 3S, to prevent the piezoelectric element 12 from breaking due to excessive vibration. After the duration T1 of a single continuous resonant state of the piezoelectric element 12 satisfies 3S, f1 is adjusted to bring the piezoelectric element 12 into a non-resonant state. The non-resonant frequency range satisfies: 0.2f0 ≤ f1 ≤ 0.8f0, and the duration T2 of the piezoelectric element 12 at the non-resonant frequency satisfies: T1 ≤ T2 ≤ 1.5T1.

[0041] Furthermore, the piezoelectric element 12 is only in a resonant state to meet specific operational requirements; otherwise, it maintains low-loss, non-resonant operation. For example, if the vibration amplitude of the piezoelectric element 12 in resonant state is 0.3 mm, and the piezoelectric valve 10 requires a displacement of 0.2 mm to open, then f1 is less than the natural frequency f0 to ensure the service life of the piezoelectric element 12. If the vibration amplitude of the piezoelectric element 12 in resonant state is 0.2 mm, and the piezoelectric valve 10 also requires a displacement of 0.2 mm to open, then f1 is equal to the natural frequency f0 to meet the displacement required for the piezoelectric valve 10 to open.

[0042] It is understandable that the piezoelectric element 12 has a pre-resonance transition region. Within the range of 0.8f0 to 1.2f0, its output force and displacement exhibit a non-linear surge characteristic with f1, making it suitable for scenarios that are not sensitive to flow rate changes but require short-term high flow rate output. Within the range of 0.2f0≤f1≤0.8f0, the piezoelectric element 12 experiences low vibration stress and stable operation, making it suitable for long-term low-loss conditions. When f1=f0, it is in a resonant state, suitable for scenarios requiring maximum opening. Therefore, f1 can be selected according to the operating conditions: 0.2f0≤f1≤0.8f0, 0.8f0≤f1≤1.2f0, or f1=f0.

[0043] Furthermore, when f1 satisfies: 0.2f0≤f1≤0.8f0, the larger f1 is, the larger the amplitude of the piezoelectric element 12 is, and the greater the opening degree of the piezoelectric valve 10 is; when f1=f0, the vibration amplitude of the piezoelectric element 12 reaches the maximum, and the opening degree of the piezoelectric valve 10 reaches the maximum.

[0044] It is understandable that when the piezoelectric element 12 operates within the range of 0.2f0≤f1≤0.8f0, its vibration stress is low and its energy conversion efficiency is stable, which reduces mechanical fatigue and thermal aging, thereby ensuring the service life of the piezoelectric element 12. When the maximum opening is required, f1 is adjusted to be equal to the natural frequency f0, thus adjusting the opening of the piezoelectric valve 10 to the maximum. After satisfying any of the following conditions, f1 is reduced, such as when the flow rate reaches the expected value or the holding time of the piezoelectric valve 10 reaches the limit value, so that f1 satisfies the limit range of 0.2f0≤f1≤0.8f0, avoiding the long-term continuation of the resonance state, which would reduce the service life of the piezoelectric element 12.

[0045] In some embodiments, the driving signal is a square wave or a sine wave.

[0046] In some embodiments, the ratio of the opening time to the closing time of the piezoelectric valve 10 is adjusted by regulating the duty cycle q of the drive signal, thereby achieving flow regulation. The duty cycle q satisfies: 10% ≤ q ≤ 90%. It can be understood that duty cycle regulation and frequency regulation are used in conjunction: when frequency regulation has reached the minimum opening degree but still cannot meet the micro-flow requirement, further adjustment of the duty cycle q achieves fine-grained flow compensation; frequency regulation controls the maximum opening degree of the piezoelectric valve, while duty cycle regulation controls the opening percentage per unit time. That is, when the piezoelectric valve 10 needs to output a very small flow rate, adjusting the opening degree solely by f1 may result in a situation where the flow rate corresponding to the minimum opening degree still exceeds the requirement. Therefore, by adjusting the opening and closing time ratio of the piezoelectric valve 10 by the duty cycle q, micro-flow control is achieved.

[0047] In some embodiments, when the duty cycle q is 10%, the piezoelectric valve 10 is open for only 10% of the time in each cycle and closed for 90% of the time, with the output flow rate being 10% of the continuously open state; when the duty cycle q is 90%, the piezoelectric valve 10 is closed for only 10% of the time in each cycle and open for 90% of the time, with the output flow rate being 90% of the continuously open state. By adjusting the duty cycle q, linear and fine control of the flow rate can be achieved under a fixed f1, which is especially suitable for micro-flow scenarios, such as micro-volume delivery of medical liquids, to compensate for the small flow rate requirements that cannot be covered by a single frequency adjustment, thereby increasing the applicability of the piezoelectric valve 10.

[0048] For example, when f1 has been adjusted to 0.2f0 and the piezoelectric valve 10 still needs to further reduce the output flow, keep f1 unchanged and adjust the duty cycle q of the drive signal to control the ratio of the opening time to the closing time of the piezoelectric valve 10 in each control cycle, so as to achieve the adjustment of the small flow of the piezoelectric valve 10.

[0049] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A piezoelectric valve, characterized in that, include: Valve body, the valve body defining a cavity; A piezoelectric element is disposed in the cavity, thereby forming a sealed cavity between the piezoelectric element and the inner wall of the valve body; A first fluid channel has a first end extending from the valve body into the sealing cavity and facing the bottom surface of the piezoelectric element. An annular rubber sleeve is fitted on the first end, and the annular rubber sleeve is interference-fitted with the first end so that when the piezoelectric element is not driven by external force, the annular rubber sleeve abuts against the bottom surface of the piezoelectric element to close the first end. A second fluid passage extends from inside the sealed cavity to outside the valve body; A circuit board is disposed inside the cavity and outside the sealed cavity, and the circuit board is electrically connected to the piezoelectric sheet.

2. The piezoelectric valve as described in claim 1, characterized in that, The bottom surface of the piezoelectric sheet is provided with valve protrusions. When the piezoelectric sheet is not driven by external force, the valve protrusions are in contact with the annular rubber sleeve.

3. The piezoelectric valve as described in claim 2, characterized in that, The diameter of the valve plate protrusion is larger than the outer diameter of the annular rubber sleeve.

4. The piezoelectric valve as described in claim 1, characterized in that, The upper end of the annular rubber sleeve has an annular sealing surface, and the plane where the annular sealing surface is located is higher than the plane where the first end is located.

5. The piezoelectric valve as described in claim 1, characterized in that, The piezoelectric valve further includes a cover plate disposed between the circuit board and the piezoelectric element. The cover plate has a cover plate support edge on the side facing the piezoelectric element, which abuts against the top surface of the piezoelectric element to apply a downward preload. The first end abuts against the bottom surface of the piezoelectric element to apply an upward first support force. The valve body has a valve body support edge that protrudes relative to the inner wall of the valve body and abuts against the bottom surface of the piezoelectric element to apply an upward second support force. When the piezoelectric element is not driven, the resultant force of the first and second support forces, along with the preload, keeps the piezoelectric element in balance.

6. The piezoelectric valve as described in claim 5, characterized in that, The cover plate is provided with at least one terminal block. One end of the terminal block is electrically connected to the circuit board, and the other end of the terminal block is connected to a metal spring pin, which is then electrically connected to the piezoelectric sheet. The terminal block and the metal spring pin are arranged in a one-to-one correspondence.

7. The piezoelectric valve as described in claim 6, characterized in that, The cover plate support edge, the top surface of the piezoelectric sheet, and the side of the cover plate facing the piezoelectric sheet together define a receiving cavity, which can accommodate the metal spring needle, the height of which is less than or equal to the height of the cover plate support edge.

8. The piezoelectric valve as described in claim 7, characterized in that, The width of the cover plate support along the horizontal direction is 1mm-3mm.

9. The piezoelectric valve as described in claim 5, characterized in that, The piezoelectric valve also includes a seal, which is located on the side of the circuit board away from the cover plate, and the seal is in contact with the circuit board to seal the cavity.

10. The piezoelectric valve according to any one of claims 1-9, characterized in that, The piezoelectric sheet is rectangular or circular, and the thickness of the piezoelectric sheet is 0.1mm-2mm.

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