Electric proportional valve and control method

Abstract

The invention provides an electric proportional valve and a control method, the electric proportional valve comprises a valve body and a control unit, and the valve body is provided with a gas inlet pipeline connected with a gas source, a gas outlet pipeline connected with a gas load and a gas exhaust pipeline communicated with the external environment; the control unit adjusts the proportion of the gas amount entering the gas outlet pipeline and the gas exhaust pipeline from the gas inlet pipeline based on closed-loop feedback control; a gas release pipeline is further arranged in the valve body, and part of gas in the gas outlet pipeline can be discharged to the external environment in the mode that the gas amount participating in closed-loop feedback control in the gas outlet pipeline is reduced. According to the electric proportional valve, the air pressure oscillation phenomenon of the air outlet pipeline under the low-flow and high-frequency switching air using demand scene can be remarkably reduced, and rapid, accurate and stable tracking of the target air pressure is achieved.

Description

Technical Field

[0001] This application relates to the technical field of valves, and particularly to an electro-pneumatic proportional valve and a control method. Background Art

[0002] In an automated control system, especially in a pneumatic control system, an electro-pneumatic proportional valve is connected between a high-pressure gas source and a pneumatic load, and controls the amount of gas flowing to the pneumatic load through feedback closed-loop control. Currently, the closed-loop feedback control adopted by electro-pneumatic proportional valves generally involves a proportional controller setting a PID adjustment amount based on the difference between the measured air pressure and the target air pressure, and then converting it into a control signal such as PWM to adjust the gas volume ratio output by the gas source to the outlet pipeline (connected to the gas-using load) and the exhaust pipeline (connected to the external environment).

[0003] An electronic proportional pressure control device can immediately provide the required output pressure, maintain stability within a specified time, and continuously adjust the output according to dynamic conditions to maintain pressure stability. However, in a dynamic and continuous flow process, even within the stability tolerance range, instability peaks may occur. These fluctuations may come from unexpected backpressure, an increase in the gas volume demand of the load, a sudden change in the inlet pressure, or a significant temperature change. The proportional valve is required to respond quickly and stabilize the fluctuations.

[0004] The two main factors affecting control accuracy are stability and filling time (the time required to restore to the set air pressure value after the air pressure decreases due to reasons such as load gas consumption, inlet pressure, and pipeline restrictions). Generally, the nozzle size of the internal valve needs to be designed according to the gas consumption demand of the load, and at the same time, the proportional controller needs to set the PID value within a reasonable range to accurately and quickly achieve the target air pressure output.

[0005] However, in the actual use process, there is a situation where it is impossible to balance the valve flow determined by the load gas consumption and the PID value setting range that meets accuracy and speed: Due to the limitations of the mechanical structure and gas chamber volume in the valve body, the PID value adjustment setting is only effective within a relatively small window. If the gas volume demand is large, it will simultaneously cause unstable air flow in the measurement gas path. Once it exceeds the threshold range, the oscillation problem cannot be solved by adjusting the PID parameters; although stabilizing the measurement air flow by reducing the aperture of the measurement gas path can avoid system oscillation, it will inevitably lead to an increase in the air pressure measurement time and cannot achieve high-speed adjustment of the outlet air pressure.

[0006] Therefore, it is necessary to improve the structure and control method of the existing electro-pneumatic proportional valve to achieve high-speed, accurate, and stable control of the outlet gas volume. Summary of the Invention

[0007] This application provides an electro-pneumatic proportional valve through embodiments to solve the problems of oscillation circuits and inaccurate flow control existing in the prior art due to the too small volume of the proportional valve or the too large valve flow rate.

[0008] The electro-pneumatic proportional valve includes a valve body and a control unit. An air inlet pipeline connected to an air source, an air outlet pipeline connected to an air-consuming load, and an exhaust pipeline communicating with the external environment are provided on the valve body. The control unit adjusts the ratio of the air volume entering the air outlet pipeline and the exhaust pipeline from the air inlet pipeline based on closed-loop feedback control:

[0009] A bleed pipeline is further provided in the valve body. The bleed pipeline can discharge a part of the gas in the air outlet pipeline to the external environment in a way that reduces the air volume participating in the closed-loop feedback control in the air outlet pipeline.

[0010] Preferably, the maximum air flow rate of the bleed pipeline is much smaller than the maximum air flow rate of the air outlet pipeline and / or the exhaust pipeline.

[0011] Further, the bleed pipeline discharges a part of the gas in the air outlet pipeline to the external environment before the air pressure in the air outlet pipeline is measured, so that the air volume participating in the closed-loop feedback control in the air outlet pipeline is reduced.

[0012] Further, the control unit adjusts the ratio of the air volume entering the air outlet pipeline and the exhaust pipeline from the air inlet pipeline based on closed-loop feedback control by comparing the difference between the air pressure in the air pressure measurement pipeline and the target air pressure, wherein the air pressure measurement pipeline communicates with the air outlet pipeline;

[0013] The position where the bleed pipeline communicates with the air outlet pipeline is closer to the air inlet pipeline than the position where the air pressure measurement pipeline communicates with the air outlet pipeline.

[0014] Preferably, the number of the bleed pipelines is greater than or equal to 2.

[0015] Preferably, the electro-pneumatic proportional valve further includes an opening and closing valve for switching the communication state between at least one of the bleed pipelines and the external environment.

[0016] Preferably, the electro-pneumatic proportional valve further includes a flow regulating valve for regulating the gas flow rate discharged from at least one of the bleed pipelines to the external environment.

[0017] Preferably, one end of the bleed pipeline communicates with the air outlet pipeline, and the other end communicates with the exhaust pipeline. And the bleed pipeline can discharge a part of the gas in the air pipeline to the external environment from the exhaust pipeline when the passage between the exhaust pipeline and the air inlet pipeline is completely closed.

[0018] Preferably, the electro-hydraulic proportional valve further includes a buffer cavity, which is arranged inside the valve body and communicates with at least one of the exhaust pipelines inside or outside the valve body.

[0019] Preferably, the volume of the buffer cavity is much larger than the volume of the exhaust pipeline.

[0020] Preferably, the valve body is provided with an air inlet, an air outlet, and an exhaust port arranged along its circumferential direction. The air inlet direction of the intake pipeline through the air inlet is parallel to the air outlet direction of the outlet pipeline flowing to the load through the air outlet. The exhaust direction of the exhaust pipeline flowing to the external environment through the exhaust port is perpendicular to the air inlet direction of the intake pipeline through the air inlet;

[0021] Another side surface located between the air inlet and the air outlet is provided with an exhaust pipeline. One end of the exhaust pipeline communicates with the external environment, and the other end communicates with the outlet pipeline.

[0022] Preferably, the exhaust pipeline communicates with the air outlet through a first partition cavity, or the exhaust pipeline is connected through and penetrates between the side walls adjacent to the air outlet and the exhaust port, or the exhaust pipeline is connected through and penetrates between the side walls adjacent to the first partition cavity and the exhaust port, and is located between the air pressure measurement pipeline of the outlet pipeline and the first partition cavity. The airflow after the air pressure is adjusted by the exhaust pipeline enters the air pressure measurement pipeline.

[0023] Preferably, a valve core driving component is accommodated inside the valve body, and the lower part of the valve core driving component is accommodated inside the first partition cavity;

[0024] The valve core driving component includes a valve rod, a diaphragm connected to the top of the valve rod, a convex ring sleeved on the valve rod, and a first valve core and a second valve core respectively located at both ends of the valve rod. The second valve core is located below the diaphragm, and the convex ring plays a limiting role on the second valve core. The bottom end of the valve rod passes through the intermediate valve body and extends to the bottom of the main valve body. The second piston of the second valve core is limited between the lower end face of the cavity of the intermediate valve body and the convex ring, and the two cooperate to form an exhaust valve port. A second spring is arranged inside the second valve core;

[0025] The first valve core is arranged as an intake valve core between the main valve body and the bottom cover. The first piston of the first valve core is limited to the lower end face of the bottom of the main valve body, and the two cooperate to form an intake valve port. A first spring for driving the first piston to close the intake valve port is arranged inside the first valve core.

[0026] This application also provides a control method through an embodiment for controlling the aforementioned electro-hydraulic proportional valve. The control method includes the following operations:

[0027] Adjust the ratio of the gas volume entering the outlet pipeline and the exhaust pipeline from the intake pipeline through closed-loop feedback control; and,

[0028] Control a part of the gas in the outlet pipeline to be discharged to the external environment through the exhaust pipeline.

[0029] An electro-pneumatic proportional valve and a control method provided by an embodiment of the present application can discharge a part of the gas in the outlet pipeline to the external environment by reducing the gas volume participating in the closed-loop feedback control in the outlet pipeline through a separate exhaust pipeline arranged between the outlet pipeline and the external environment, without changing the pipe diameter of the air pressure measurement pipeline, and without prolonging the air pressure measurement response time, can significantly reduce the impact of the airflow entering the air pressure measurement pipeline and the generation of airflow fragments at low flow rates, enabling the air pressure sensor to quickly and accurately obtain the true air pressure value in the outlet pipeline and damping the airflow, thereby significantly reducing the air pressure oscillation phenomenon in the outlet pipeline in the gas consumption demand scenario of low flow rate and high-frequency switching, and achieving fast, accurate, and stable tracking of the target air pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic structural diagram of an existing electro-pneumatic proportional valve;

[0031] Figure 2 is Figure 1 a partially enlarged schematic structural diagram of;

[0032] Figure 3 is Figure 1 a partially enlarged schematic structural diagram of the electro-pneumatic proportional valve shown when the intake pipeline is closed;

[0033] Figure 4 is Figure 1 a partially enlarged schematic structural diagram of the electro-pneumatic proportional valve shown when the intake pipeline, the outlet pipeline, and the exhaust pipeline are all opened;

[0034] Figure 5 is a schematic diagram of the air pressure oscillation in the outlet pipeline when the existing electro-pneumatic proportional valve performs low-flow output control;

[0035] Figure 6 is a schematic structural diagram of an electro-pneumatic proportional valve provided according to the first specific embodiment of the present application;

[0036] Figure 7 is a partially enlarged schematic diagram of the gas pipeline part of the electro-pneumatic proportional valve provided according to the first specific embodiment of the present application;

[0037] Figure 8 is a diagram of the air pressure change in the outlet pipeline when the electro-pneumatic proportional valve provided according to the first specific embodiment of the present application controls the gas output volume;

[0038] Figure 9 A partial enlarged schematic diagram of the gas pipeline part of the electro-hydraulic proportional valve provided according to the second specific embodiment of the present application;

[0039] Figure 10 A partial enlarged schematic diagram of the gas pipeline part of the electro-hydraulic proportional valve provided according to the third specific embodiment of the present application;

[0040] Figure 11 A partial enlarged schematic diagram of the gas pipeline part of the electro-hydraulic proportional valve provided according to the fourth specific embodiment of the present application;

[0041] Figure 12 A partial enlarged schematic diagram of the gas pipeline part of the electro-hydraulic proportional valve provided according to the fifth specific embodiment of the present application;

[0042] Figure 13 A partial enlarged schematic diagram of the gas pipeline part of the electro-hydraulic proportional valve provided according to the sixth specific embodiment of the present application;

[0043] Figure 14 An overall structural schematic diagram of an electro-hydraulic proportional valve provided according to the seventh specific embodiment of the present application;

[0044] Figure 15 An exploded structural schematic diagram of an electro-hydraulic proportional valve provided according to the seventh specific embodiment of the present application;

[0045] Figure 16 A sectional view of an electro-hydraulic proportional valve provided according to the seventh specific embodiment of the present application;

[0046] Figure 17 A sectional view of an electro-hydraulic proportional valve in another direction provided according to the seventh specific embodiment of the present application;

[0047] Figure 18 A sectional view of an electro-hydraulic proportional valve with a buffer cavity provided in another direction according to the seventh specific embodiment of the present application;

[0048] Figure 19 A flowchart of the control method of the electro-hydraulic proportional valve provided according to the eighth specific embodiment of the present application.

[0049] Reference numerals in the figure

[0050] Electrical proportional valve 1, existing electrical proportional valve 1', valve body 11, air inlet 1.1, air inlet valve port 1.11, exhaust valve 1.12, air outlet 1.2, exhaust port 1.3, air bleed port 1.4, first partition chamber 110, second partition chamber 119, first valve core 17', second valve core 17", main valve body 111, bottom cover 112, intermediate valve body 113, pilot seat 114, control unit 12, first control air circuit 131, second control air circuit 132, third control air circuit 133, solenoid valve exhaust air circuit 134, control box 14, supply solenoid valve 141, exhaust solenoid valve 142, upper chamber 151, lower chamber 152, diaphragm 153, check valve 154, valve post 16, convex ring 161, first piston 171, second piston 172, spring 18, first spring 181, second spring 182, intake pipeline 2, intake pipeline branch 21, outlet pipeline 3, air pressure measurement pipeline 31, outlet pipeline branch 32, air pressure sensor 33, exhaust pipeline 4, air bleed pipeline 5, on-off valve 61, flow regulating valve 62, buffer cavity 7. Specific embodiments

[0051] Hereinafter, the present application will be further described based on preferred embodiments with reference to the accompanying drawings.

[0052] In the description of the embodiments of the present application, it should be noted that if terms such as "upper", "lower", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the products of the embodiments of the present application are habitually placed during use, it is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. For the convenience of understanding, various components in the drawings are enlarged or reduced, but this approach is not intended to limit the protection scope of the present application.

[0053] In addition, in the description of the present application, in order to distinguish different units, terms such as first and second are used in this specification, but these are not limited by the manufacturing order and should not be construed as indicating or implying relative importance. In the detailed description and claims of the present application, their names may be different.

[0054] The terms used in this specification are for the purpose of describing the embodiments of the present application, but are not intended to limit the present application. It should also be noted that unless otherwise clearly specified and defined, if terms such as "set", "connected", "connected to" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be specifically understood.

[0055] To clearly illustrate the improvements of the technical solution of this application over the prior art, first, the working principle of the existing electro-pneumatic proportional valve and the problems it has will be described.

[0056] [Prior art and existing problems]

[0057] Figure 1 Fig. shows a schematic structural diagram of an existing electro-pneumatic proportional valve 1'. Figure 2 For Figure 1 the circle A in is enlarged for display. Referring to Figure 1 and Figure 2 , the shape of the electro-pneumatic proportional valve 1' is generally defined by the valve body 11. Inside the valve body 11, it includes the following structural or functional units:

[0058] 1) Gas pipeline structure, including an intake pipeline 2 connected to a gas source (not shown in the figure), an outlet pipeline 3 connected to a load using gas, and an exhaust pipeline 4 connected to the external environment.

[0059] Generally, a high-pressure gas source is used as the gas source. The high-pressure gas output flows through the electro-pneumatic proportional valve 1'. The electro-pneumatic proportional valve 1' adjusts the gas volumes of the outlet pipeline 3 and the exhaust pipeline 4 according to the target air pressure, so that the air pressure in the outlet pipeline 3 for driving the load (such as a cylinder, a pressure vessel, or a pneumatic component that needs to receive a preset air pressure at a preset frequency, etc.) can reach the target air pressure as much as possible.

[0060] 2) Control air circuit structure, including a first control air circuit 131, a second control air circuit 132, a third control air circuit 133, a solenoid valve exhaust air circuit 134, a supply solenoid valve 141, and an exhaust solenoid valve 142.

[0061] Among them, one end of the first control air circuit is connected to a branch pipeline 21 of the intake pipeline led out from the intake pipeline 2, and the other end is connected to the intake port of the supply solenoid valve 141. Both ends of the second control air circuit 132 are respectively connected to the outlet port of the supply solenoid valve 141 and the intake port of the exhaust solenoid valve 142. The outlet port of the exhaust solenoid valve is connected to the external environment through the solenoid valve exhaust air circuit 134.

[0062] Further, a third control air circuit 133 is led out from the second control air circuit 132 to output control gas to the upper chamber described later.

[0063] 3) Gas volume distribution mechanical structure, including an upper chamber 151, a lower chamber 152, a diaphragm 153, a valve stem 16, a first piston 171, and a second piston 172.

[0064] Among them, the upper chamber 151 and the lower chamber 152 are separated by an elastic diaphragm 153 into two non-connecting spaces. The upper chamber 151 is communicated with the third control air path 133 to receive the control gas output from the air supply solenoid valve 141. One end of the valve stem 16 is formed into a relatively flat sheet structure and fixedly connected to the diaphragm 153. Its cylindrical main body passes through the second piston 172 and then abuts against or is fixedly connected to the upper end of the first piston 171. Springs 18 are elastically abutted on the sides of the first piston 171 and the second piston facing away from each other. In addition, a convex ring is provided on the cylindrical main body of the valve stem 16 on the side of the second piston 172 facing the first piston 171.

[0065] 4) The air pressure measurement air path 31 is led out from the air outlet pipe 3 and connected to the air pressure sensor 33. In addition, preferably, an air outlet pipe branch 32 connected to the lower chamber 152 is also led out from the air outlet pipe 3. The air outlet pipe branch 32 can be led out separately from the air outlet pipe 3, or as Figure 1 shown, led out from the air pressure measurement air path 31.

[0066] 5) The control unit 12 adjusts the ratio of the gas volume entering the air outlet pipe 3 and the exhaust pipe 4 from the air inlet pipe 2 based on closed-loop feedback control.

[0067] Specifically, when the electro-pneumatic proportional valve is connected to the power supply and powered on, the control unit 12 simultaneously receives the target air pressure signal Sig_t and the air pressure measurement signal Sig_m of the air outlet pipe 3 measured and fed back by the air pressure sensor 33. Through the closed-loop feedback control known to those skilled in the art, the PID adjustment amount is set according to the difference between the two. On this basis, the control command Ctr_1 for controlling the opening and closing of the air supply solenoid valve 141 and the control command Ctr_2 for controlling the opening and closing of the exhaust solenoid valve 142 are generated. Generally, both Ctr_1 and Ctr_2 can be in the form of PWM signals.

[0068] The air supply solenoid valve 141 and the exhaust solenoid valve 142 adjust the gas volume entering the third control air path 133 from the first control air path 131 (and the gas volume discharged to the external environment through the solenoid valve exhaust air path 134) under the control of Ctr_1 and Ctr_2. Thereby, the diaphragm 153 between the upper chamber 151 and the lower chamber 152 deforms with the change of the gas volume, driving the valve stem 16 to move up and down, and using the first piston 171 and the second piston 172 to adjust the gas volume flowing through the air outlet pipe 3 and the exhaust pipe 4.

[0069] For example, like Figure 2As shown, when the valve stem 16 moves downward to the lowest point driven by the diaphragm 153, the first piston 171 is at the lowest point, the intake pipeline 2 is communicated with the exhaust pipeline 3 and the opening diameter, and the second piston 172 closes the passage between the exhaust pipeline 4 and the intake pipeline 2 under the action of the spring 18. At this time, most of the gas (except for the part entering the control air circuit, the air pressure measurement pipeline 31 and the branch of the exhaust pipeline 32) entering the electro-pneumatic proportional valve 1' from the intake pipeline 2 will flow to the load through the exhaust pipeline 3, causing the air pressure in the exhaust pipeline 3 to rise rapidly.

[0070] Figure 3 and Figure 4 The enlarged schematic diagrams (the enlarged areas are the same as Figure 2 ) respectively show two other possible gas volume distribution states. Among them, when the electro-pneumatic proportional valve 1' is in Figure 3 the state shown, the valve stem 16 moves upward to the highest point driven by the diaphragm 153, and the first piston 171 is elastically reset by the spring 18, completely closing the passage from the intake pipeline 2 to the exhaust pipeline 3. At the same time, the second piston 172 moves upward driven by the convex ring 161, opening the passage between the exhaust pipeline 3 and the exhaust pipeline 4 to the maximum, and the gas is discharged to the external environment through the exhaust pipeline 4, causing the air pressure in the exhaust pipeline 3 to drop rapidly; when the electro-pneumatic proportional valve 1' is in Figure 4 the state shown, the passages between the intake pipeline 2 and the exhaust pipeline 3 and the exhaust pipeline 4 are all opened. A part of the gas entering the electro-pneumatic proportional valve 1' from the intake pipeline 2 enters the exhaust pipeline to drive the load, and the other part is discharged to the external environment through the exhaust pipeline 4.

[0071] Preferably, the control unit 12 can be connected to a computer, a tablet computer or a mobile phone, and display the above various signals, control instructions, etc. on the display screen of the above device in the form of signal info to monitor the working state of the electro-pneumatic proportional valve.

[0072] Obviously, through the closed-loop feedback control of the control unit 12, the electro-pneumatic proportional valve 1' will continuously switch among the Figures 2 to 4 three states shown, so as to adjust the ratio of the gas volume entering the exhaust pipeline 3 and the exhaust pipeline 4 from the intake pipeline 2, so that the air pressure in the exhaust pipeline 3 reaches the preset target air pressure.

[0073] In addition, it should also be pointed out that Figure 1The cross-sectional view shown only illustrates the working principle of an existing electro-pneumatic proportional valve 1'. Although there are differences in the structures of other existing electro-pneumatic proportional valves, for example, the control air circuit, solenoid valve, and control unit 12 can be integrated into the interior of the valve body 11 to achieve miniaturization of the device; or the first piston 171 and the second piston 172 can be designed to move synchronously with the valve stem 16; or only one solenoid valve is used to control the ratio of the gas entering the upper chamber and discharged to the external environment. The above structural changes do not affect its working principle, that is: the control unit 12 adjusts the ratio of the gas volume entering the outlet pipeline 3 and the exhaust pipeline 4 from the inlet pipeline 2 based on closed-loop feedback control.

[0074] In the pneumatic control of the electro-pneumatic proportional valve, it is a complex task to achieve a balance between the response speed and stability according to the specific application requirements of the driving load. As described in the background art, the two main factors affecting the performance of closed-loop feedback control are stability and filling time. Among them, for some application scenarios with low requirements for response speed (for example, the load state does not change frequently), the length of the filling time is not the key consideration factor. Therefore, the tolerance for PID adjustment is relatively high, that is, the stable tracking of the air pressure in the outlet pipeline 3 to the target air pressure can be achieved through a longer filling time. However, in some scenarios with high requirements for filling time, the situation will become more complex.

[0075] For example, in the field of precision dispensing, the gas flow required for each dispensing is extremely low. And after each dispensing operation, in order to avoid unnecessary dripping of the dispensing needle under the pressure of the residual air pressure in the glue bucket, it is necessary to extract the gas above the glue bucket, and then quickly restore the air pressure to the target air pressure after the start of the next dispensing operation. At the same time, in order to improve the efficiency of the dispensing process, it is generally necessary to further shorten the interval between two dispensing operations (at a frequency of 5 times per second, or higher). Thus, the air pressure in the pipeline needs to repeatedly perform operations of filling to the target air pressure at a low flow rate -> maintaining stability -> decompression -> filling to the target air pressure again within an extremely short cycle.

[0076] Obviously, in the above application scenarios, it will be extremely challenging to simultaneously meet the low flow rate, high response speed, and high stability of the outlet pipeline. This is because in the above small-flow application scenarios, the gas volume of the downstream load is usually very small. Correspondingly, the volume inside the valve that matches it will also decrease. When the requirement of quickly tracking the target air pressure needs to be met, although the ideal situation is to quickly reach the pressure through rapid inflation. However, the limitation of the volume inside the valve will cause the compressed air to violently impact the space when the inlet valve opens, resulting in the pressure exceeding the set point. Before the pressure stabilizes, the air pressure sensor will detect the reflected air debris, prompting the exhaust valve to open and discharge the excess pressure from the volume, immediately resulting in the pressure being too low. This deviation in the air pressure detection result due to volume limitation will cause the air pressure in the outlet pipeline 3 to be asFigure 5 The periodic oscillation shown

[0077] There are two ways to eliminate the terrible oscillation loop caused by excessive flow due to too small volume and too large valve. First, the oscillation can be eliminated by modifying the PID settings of the device. If the downstream volume of the device is specified correctly, but the controlled pressure is unstable or oscillates, it may be that the PID value is set too high and needs to be adjusted. Both the proportional and integral settings need to be weakened or reduced until the anomaly disappears. However, this adjustment is only effective within a relatively small window. Once exceeded, instability will occur and have an adverse impact on accuracy and resolution. Second, reducing the aperture of the air pressure detection pipeline can prevent excessive air from passing through the air pressure sensing element, thereby reducing overshoot and undershoot. However, the physical principle of fluid dynamics determines the speed of compressed gas passing through the specified path. Too small an aperture will inevitably lead to an extended time for obtaining an accurate value of air pressure measurement, and instead result in an extended filling time.

[0078] It can be seen that based on the hardware structure of the electro-pneumatic proportional valve determined for low-flow, high-frequency pneumatic applications, once it does not match the adjustable window of the PID parameters, it will greatly increase the adjustment difficulty and it is very difficult to simultaneously meet the requirements of low flow, high response speed and oscillation suppression stability.

[0079] Therefore, this application provides a new electro-pneumatic proportional valve through embodiments, and makes corresponding structural improvements for the reasons for the above problems to achieve accurate, fast and stable tracking of the target air pressure in low-flow application scenarios. [Specific Embodiment 1]

[0081] Figure 6 FIG. is a schematic structural diagram of the electro-pneumatic proportional valve 1 provided according to Specific Embodiment 1 of this application, Figure 7 and the gas pipeline part thereof is enlarged and shown.

[0082] As Figure 6 、 Figure 7 shown, compared with the existing electro-pneumatic proportional valve 1', the electro-pneumatic proportional valve 1 provided in this application further has a vent pipeline 5 opened in the valve body. One end of the vent pipeline 5 is communicated with the outlet pipeline 3, and the other end is communicated with the external environment, forming a gas passage capable of discharging a part of the gas in the outlet pipeline 3 to the external environment.

[0083] Further, referring to Figure 7 , the position where the vent pipeline 5 is communicated with the outlet pipeline 3 is closer to the inlet pipeline 2 compared with the position where the air pressure measurement pipeline 31 is communicated with the outlet pipeline 3. Observe Figure 7From the air flow directions in each pipeline, it can be seen that during the process of the air flow f_2 in the intake pipeline 2 being proportionally output to the outlet pipeline (forming the air flow f_3) and the exhaust pipeline 5 (forming the air flow f_4), before the air flow f_3 encounters the air pressure measurement pipeline 31 and a part of it branches out and enters the air flow f_31 in the air pressure measurement pipeline, a part of it is discharged to the external environment in the form of the air flow f_5 through the exhaust pipeline 5. In this way, without changing the pipe diameter of the air pressure measurement pipeline 31 to avoid prolonging the air pressure measurement response time, it is possible to significantly reduce the impact of the air flow entering the air pressure measurement pipeline 31 and the generation of air flow fragments under low flow rates, enabling the air pressure sensor 33 to quickly and accurately obtain the true air pressure value in the outlet pipeline 3.

[0084] Figure 8 It shows the air pressure change situation of the outlet pipeline 3 when the above-mentioned exhaust pipeline 5 structure is added to the electro-pneumatic proportional valve 1 for controlling the air output volume. Comparing Figure 5 and Figure 8 it can be known that this structure that discharges a part of the gas in the outlet pipeline 3 to the external environment by reducing the amount of gas participating in the closed-loop feedback control in the outlet pipeline 3 can start from the root cause of the problem and fundamentally improve the problem of tracking air pressure oscillation in the pneumatic application scenario with fast response at low flow rates.

[0085] Preferably, the pipe diameter of the exhaust pipeline 5 is set to be significantly smaller than the pipe diameter of the outlet pipeline 3 and / or the exhaust pipeline 4, for example, less than 1 / 10 of the pipe diameter of the outlet pipeline 3 and / or the exhaust pipeline 4, or even smaller, so that the maximum air flow rate of the exhaust pipeline 5 is much smaller than the maximum air flow rate of the outlet pipeline 3 and / or the exhaust pipeline 4, to avoid the problem of insufficient air output caused by too much air flow not participating in the closed-loop feedback control in the application scenario of starting at low flow rates. [Specific Embodiment 2]

[0087] Figure 9 It is an enlarged schematic diagram of the gas pipeline part of the electro-pneumatic proportional valve 1 provided according to Specific Embodiment 2 of the present application. Only the parts different from the structure of Specific Embodiment 1 ( Figure 7 ) will be described below, and the structures of other parts not involved are the same as those Figure 6 shown.

[0088] Comparing with reference Figure 9 and Figure 7It can be seen that the difference between the electro-pneumatic proportional valve 1 provided in the second specific embodiment and the electro-pneumatic proportional valve 1 provided in the first specific embodiment lies in the setting mode of the exhaust gas pipeline 5. Specifically, it connects the air outlet pipeline 3 and the exhaust pipe 4, and the position where it connects to the exhaust pipe 4 is also closer to the intake pipe 2 than the position where the air pressure measurement pipeline 31 connects to the air outlet pipeline 3, that is: through sharing the exhaust pipe 4, the exhaust gas pipeline 5 enables a part of the air flow passing through the air outlet pipeline f_3 to enter the exhaust pipe 4 through the exhaust gas pipeline 5 before entering the air pressure measurement pipeline 31, and converges with the air flow flowing into the exhaust pipe due to the opening of the second piston 172 to form an air flow f_4' and flow out to the external environment.

[0089] By adopting the structure of the exhaust gas pipeline 5 shown in the second specific embodiment, it can be seen that even if the second piston 172 is completely closed, due to the existence of the exhaust gas pipeline 5, there is still an air flow f_4' in the exhaust pipe at this time. [Third Specific Embodiment]

[0091] Figure 10 It is an enlarged schematic diagram of the gas pipeline part of the electro-pneumatic proportional valve 1 provided in the third specific embodiment of the present application. Comparing Figure 10 with Figure 7 and Figure 9 It can be seen that in the third specific embodiment, at the end of the exhaust gas pipeline 5, that is, the end connected to the external environment, an opening and closing valve 61 for switching the opening and closing state is provided. By setting the opening and closing valve 61, the applicable application scenarios of the electro-pneumatic proportional valve 1 can be effectively expanded. For example, when the electro-pneumatic proportional valve 1 is applied to a pneumatic working scenario with a large flow rate or a low response speed and the oscillation problem is not significant, the exhaust gas pipeline 5 can be closed to avoid additional air flow loss. [Fourth Specific Embodiment]

[0093] Figure 11 It is an enlarged schematic diagram of the gas pipeline part of the electro-pneumatic proportional valve 1 provided in the fourth specific embodiment of the present application. The difference between the fourth specific embodiment and the third specific embodiment is that the valve at the end of the exhaust gas pipeline 5 is replaced by a flow regulating valve 62. The flow regulating valve 62 can be realized in various ways known to those skilled in the art, such as a knob type or an electric control regulating type. Through the flow regulating valve 62, the flow rate of the air flow f_5 flowing out from the exhaust gas pipeline 5 to the external environment can be dynamically regulated between 0 and its maximum flow rate according to the working state of the electro-pneumatic proportional valve 1, so as to achieve a better oscillation suppression effect. [Fifth Specific Embodiment]

[0095] Figure 12FIG. 0 is an enlarged schematic view of the gas pipeline portion of the electro-pneumatic proportional valve 1 provided in the fifth specific embodiment of the present application. In this embodiment, the number of the exhaust gas pipelines 5 is increased to two. In addition, in some other embodiments, the number of the exhaust gas pipelines can also be increased to three, four or even more.

[0096] In addition, as shown in Figure 10 or Figure 11 , different flow regulating valves 62 or opening / closing valves 61 can be provided for different exhaust gas pipelines 5. The multiple exhaust gas pipelines 5 cooperating with different flow regulating or opening / closing valves can flexibly regulate the exhaust gas volume within a larger range, so as to meet the requirements of suppressing air pressure oscillation in more application scenarios. [Specific Embodiment Six]

[0098] Figure 13 FIG. 13 is an enlarged schematic view of the gas pipeline portion of the electro-pneumatic proportional valve 1 provided in the sixth specific embodiment of the present application. By comparing this embodiment with the foregoing various embodiments, it can be seen that in the sixth specific embodiment, a buffer cavity 7 is added to the exhaust gas pipeline 5. Preferably, the volume of the buffer cavity 7 is much larger than the volume of the exhaust gas pipeline 5 (i.e., the product of the cross-sectional area and the length of the exhaust gas pipeline 5). Adding the buffer cavity 7 can serve as an energy storage unit to reduce the flow velocity fluctuation during sudden flow changes and maintain the air pressure stability, and can also reduce the impact of the pressure fluctuation on the valve. [Specific Embodiment Seven]

[0100] Figure 14 FIG. 19 is an overall structural schematic view of an electro-pneumatic proportional valve provided in the seventh specific embodiment of the present application. Figure 15 FIG. 20 is an exploded structural schematic view of an electro-pneumatic proportional valve provided in the seventh specific embodiment of the present application. As shown in Figure 14 , Figure 15 , an electro-pneumatic proportional valve includes a valve body 11 and a control box 14 covering the valve body 11. A control unit 12 is arranged in the control box 14. An air inlet 1.1, an air outlet 1.2, and an exhaust port 1.3 are arranged on the valve body 11 along its circumferential direction. Among them, the air inlet 1.1 is the port where the intake pipe 2 is connected to the gas source, the air outlet 1.2 is the port where the outlet pipe 3 is connected to the load, the exhaust port 1.3 is the port where the exhaust pipe 4 communicates with the external environment. The air inlet 1.1 and the air outlet 1.2 are arranged oppositely, and the exhaust port 1.3 is arranged on one side surface between the air inlet 1.1 and the air outlet 1.2, so that the air intake direction of the gas source at the intake pipe 2 is parallel to the air outlet direction flowing to the load at the outlet pipe 3, and the air inlet 1.1 and the air outlet 1.2 are communicated through an intake valve port 1.11. The air intake direction of the gas source at the intake pipe 2 is perpendicular to the exhaust direction of the exhaust pipe 4 flowing to the external environment.

[0101] Furthermore, a drain pipe 5 is provided on another side surface between the air inlet 1.1 and the air outlet 1.2. One end of the drain pipe 5 communicates with the external environment, and the other end communicates with the air outlet pipe 3. Among them, the port of the drain pipe 5 communicating with the external environment is a pressure relief hole 1.4. The maximum air flow rate discharged outward through the pressure relief hole 1.4 of the drain pipe 5 is much smaller than the maximum air flow rate of the air outlet pipe and / or the exhaust pipe, so as to avoid the problem of insufficient air outlet caused by excessive air flow not participating in the closed-loop feedback control in the small-flow startup application scenario.

[0102] In some preferred embodiments, the drain pipe 5 discharges a part of the gas in the air outlet pipe 3 to the external environment before the air pressure in the air outlet pipe 3 is measured, so as to enable the drain pipe 5 to discharge a part of the gas in the air outlet pipe 3 to the external environment in a way that reduces the gas volume participating in the closed-loop feedback control in the air outlet pipe 3, and is used to reduce the impact and generation of air flow debris when the air flow enters the air pressure measurement pipeline at low flow rates, so that the pressure sensor can quickly and accurately obtain the true air pressure value in the air outlet pipe, thereby significantly reducing the air pressure oscillation phenomenon in the air outlet pipe in the gas consumption demand scenario with low flow rate and high-frequency switching.

[0103] Specifically, Figure 16 FIG. is a sectional view of an electro-pneumatic proportional valve provided according to Embodiment VII of the present application. Figure 17 FIG. is a sectional view of an electro-pneumatic proportional valve in another direction provided according to Embodiment VII of the present application. The valve body 11 includes a main valve body 111, a bottom cover 112 provided at the bottom end of the main valve body 1, an intermediate valve body 113 provided at the top end of the main valve body 111, and a pilot seat 114 provided on the intermediate valve body 113. The control box 14 covers the pilot seat 114. A diaphragm 153 is pressed between the pilot seat 114 and the intermediate valve body 113. The diaphragm 153 is connected to the upper end of the valve stem 16 and divides the chamber between the pilot seat 114 and the intermediate valve body 113 into two non-communicating spaces, namely an upper chamber 151 and a lower chamber 152.

[0104] In some preferred embodiments, a valve element driving assembly is accommodated inside the valve body 1. The valve element driving assembly includes a valve stem 16, a diaphragm 153 connected to the top of the valve stem 16, a convex ring 161 sleeved on the valve stem 16, and a first valve element 17' and a second valve element 17" located at both ends of the valve stem 16 respectively. The second valve element 17" is located below the diaphragm 153. The bottom end of the valve stem 16 passes through the intermediate valve body 113 and extends to the bottom of the main valve body 111. The second piston 172 of the second valve element 17" is limited between the lower end face of the chamber of the intermediate valve body 113 and the convex ring 161, and the two cooperate to form an exhaust valve port 1.12. A second spring 182 is arranged inside the second valve element 17". The first valve element 17' is arranged as an intake valve element between the main valve body 111 and the bottom cover 112. The first piston 171 of the first valve element 17' is limited by the lower end face of the bottom of the main valve body 111, and the two cooperate to form an intake valve port 1.11. A first spring 181 is arranged inside the first valve element 17' to drive the first piston 171 to close the intake valve port 1.11.

[0105] Further, the intake port 1.1 and the outlet port 1.2 are oppositely opened on the side surface of the main valve body 111. When the intake valve port 1.11 is opened, the intake port 1.1 and the outlet port 1.2 are communicated through a first partition chamber 110. It should be noted that if the exhaust valve port 1.12 is in a closed state, the first partition chamber 110 is not communicated with the exhaust port 1.3. Only when the exhaust valve port 1.12 is in an open state, the gas in the first partition chamber 110 will continue to flow upward to the second partition chamber 119 and be discharged through the exhaust port 1.3.

[0106] In some preferred embodiments, the exhaust port 1.3 is arranged on the side surface of the main valve body 111 and is located between the intake port 1.1 and the outlet port 1.2. The intake direction of the gas source at the intake pipeline 2 is perpendicular to the exhaust direction of the exhaust pipeline 4 flowing to the external environment. The exhaust port 1.3 is communicated with the exhaust valve port 1.12. By adjusting the gas volume in the upper chamber 151, the up and down movement of the valve stem 16 can be controlled. By moving the position of the valve stem 16, the opening and closing and the opening degree of the first valve element 17' at the intake valve port 1.11 can be adjusted, and further the air flow pressure flowing to the outlet port 1.2 can be adjusted.

[0107] The following is an explanation in combination with the specific intake and exhaust adjustment process:

[0108] Above the intake port 1.1, there is a branch leading to the supply solenoid valve 141. When the supply solenoid valve 141 is opened and the exhaust solenoid valve 142 is closed, the compressed gas passes through the intake branch above the intake port 1.1 to the supply solenoid valve 141, and enters the upper chamber 151 through the outlet pipeline of the supply solenoid valve 141, pressing down the diaphragm 153, and then driving the second valve core 17” to press down to open the first valve core 17’, and the intake valve port 1.11 is opened to connect the intake port 1.1 and the outlet port 1.2. At this time, the pressure sensor connected above the outlet port 1.2 detects the pressure signal and outputs the secondary pressure.

[0109] When the gas pressure detected by the pressure sensor connected above the outlet port 1.2 overshoots, the control unit 12 closes the supply solenoid valve 141 and opens the exhaust solenoid valve 142. The gas in the upper chamber 151 is discharged to the external environment through the exhaust solenoid valve 142 and the exhaust small hole opened on the pilot seat 114. At this time, the second valve core 17” moves upward, the exhaust valve port 1.12 is opened, and the excess gas is discharged from the exhaust valve port 1.12. At the same time, the first valve core 17’ rebounds and reduces the channel cross-section between the intake port 1.1 and the outlet port 1.2 until the deviation is zero. The supply solenoid valve 141 and the exhaust solenoid valve 142 are both closed, and the valve core drive assembly reaches a balance at the new position, so as to obtain an output pressure proportional to the input signal.

[0110] In the above process, the drain pipeline 5 is involved throughout the whole process, and always discharges a part of the gas in the outlet pipeline 3 to the external environment in a way that reduces the gas volume participating in the closed-loop feedback control in the outlet pipeline, so as to reduce the impact of the airflow entering the pressure measurement pipeline at low flow rates and the generation of airflow fragments, and reduce the pressure oscillation phenomenon of the outlet pipeline in the gas consumption demand scenario of low flow rate and high-frequency switching.

[0111] Therefore, the applicant optimizes the installation position of the drain pipeline 5. The drain pipeline 5 is arranged on the side of the main valve body 111. One end of the drain pipeline 5 is communicated with the external environment, and the other end is communicated with the outlet port 1.2 through the first partition chamber 110, or the drain pipeline 5 is connected through the side wall adjacent to the outlet port 1.2 and the exhaust port 1.3 and is located between the pressure measurement pipeline 31 and the first partition chamber 110, so that the compressed gas first discharges part of the gas through the drain pipeline 5 and then passes through the pressure measurement pipeline 31 to the pressure sensor 33.

[0112] In some preferred embodiments, if the vent pipeline 5 is connected through the side walls adjacent to the air outlet 1.2 and the exhaust port 1.3, a check valve 154 needs to be provided on the channel from the air outlet to the exhaust port. The valve port of the check valve 154 is arranged towards the exhaust port 1.3 to prevent gas backflow and ensure that the gas flows unidirectionally from the air outlet to the exhaust port.

[0113] In some preferred embodiments, when the vent pipeline 5 is arranged on the side of the main valve body 111 and communicated with the air outlet 1.2 through the first partition cavity 110, the vent pipeline 5 is further connected with a buffer cavity 7. As Figure 18 shown, the buffer cavity 7 is arranged inside the valve body 11. The volume of the buffer cavity 7 is much larger than that of the vent pipeline 5, and it can be used as an energy storage unit to reduce the flow velocity fluctuation during sudden flow changes, maintain stable air pressure, and also reduce the impact of pressure fluctuations on the valve.

[0114] In some preferred embodiments, the number of the vent pipelines 5 is multiple, and the buffer cavity 7 is communicated with at least one of the vent pipelines 5 inside or outside the valve body 11.

[0115] In some preferred embodiments, a flow regulating valve 62 is connected to the port where the vent pipeline 5 communicates with the external environment. A pressure relief hole 1.4 is provided at the flow regulating valve 62. The flow regulating valve 62 can be implemented in various ways known to those skilled in the art, such as a knob type or an electric control regulation type. By means of the flow regulating valve 62, the flow rate of the air flow f_5 flowing out from the vent pipeline 5 through the pressure relief hole 1.4 to the external environment can be dynamically adjusted between 0 and its maximum flow rate according to the working state of the electro-hydraulic proportional valve 1, so as to achieve a better oscillation suppression effect. [Specific Embodiment VIII]

[0117] Specific Embodiment VIII provides a control method for controlling the aforementioned electro-hydraulic proportional valve 1. As Figure 19 shown, this control method includes the following operations:

[0118] Step 100, adjusting the ratio of the gas volume entering the air outlet pipeline and the exhaust pipeline from the intake pipeline through closed-loop feedback control.

[0119] Step 200, controlling a part of the gas in the air outlet pipeline to be discharged from the vent pipeline to the external environment.

[0120] The specific implementation manners of the present application have been introduced in detail above. For those skilled in the art of the present technology, without departing from the principle of the present application, several improvements and modifications can still be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. An electric proportional valve, comprising a valve body and a control unit, wherein the valve body is provided with an inlet pipeline connected to an air source, an outlet pipeline connected to an air load, and an exhaust pipeline connected to an external environment, wherein the control unit adjusts the ratio of the amount of air entering the outlet pipeline and the exhaust pipeline from the inlet pipeline based on closed-loop feedback control, and is characterized in that: The valve body is also provided with an air release pipeline, which can discharge a part of the gas in the air outlet pipeline to the external environment in a manner of reducing the amount of gas in the air outlet pipeline that participates in the closed-loop feedback control.

2. The electric proportional valve according to claim 1, characterized in that: The maximum air flow rate of the air leakage pipeline is much smaller than the maximum air flow rate of the air outlet pipeline and / or the exhaust pipeline.

3. The electric proportional valve according to claim 1, characterized in that: The air release pipeline discharges part of the gas in the gas outlet pipeline to the outside before the gas pressure of the gas outlet pipeline is measured, so that the amount of gas in the gas outlet pipeline participating in the closed-loop feedback control is reduced.

4. The electric proportional valve according to claim 3, characterized in that: The control unit adjusts the ratio of the amount of air entering the air outlet pipeline and the exhaust pipeline from the air inlet pipeline based on closed-loop feedback control by comparing the difference between the air pressure in the air pressure measuring pipeline and the target air pressure, wherein the air pressure measuring pipeline is connected to the air outlet pipeline; The position where the air leakage pipeline is connected to the air outlet pipeline is closer to the air inlet pipeline than the position where the air pressure measurement pipeline is connected to the air outlet pipeline.

5. The electric proportional valve according to claim 1, characterized in that: The number of the air leakage pipelines is greater than or equal to 2.

6. The electric proportional valve according to claim 1, characterized in that: It also includes an on-off valve for switching the connection state between at least one of the air leakage pipelines and the external environment.

7. The electric proportional valve according to claim 1, characterized in that: It also includes a flow regulating valve for regulating the flow of gas discharged from at least one of the gas leakage pipelines to the external environment.

8. The electric proportional valve according to claim 1, characterized in that: One end of the bleed pipe is connected to the air outlet pipe, and the other end is connected to the exhaust pipe, and the bleed pipe can discharge a part of the gas in the air pipe from the exhaust pipe to the external environment when the passage between the exhaust pipe and the air inlet pipe is completely closed by the valve.

9. The electric proportional valve according to any one of claims 1 to 8, characterized in that: It also includes a buffer cavity, which is arranged inside the valve body and is connected with at least one of the air leakage pipelines inside the valve body or outside the valve body.

10. The electric proportional valve according to claim 9, characterized in that: The volume of the buffer cavity is much larger than the volume of the air leakage pipeline.

11. The electric proportional valve according to claim 4, characterized in that: The valve body is provided with an air inlet, an air outlet, and an exhaust port arranged along its circumference, the air inlet direction of the air inlet pipeline through the air inlet is parallel to the air outlet direction of the air outlet pipeline through the air outlet to the load, and the exhaust direction of the exhaust pipeline through the exhaust port to the external environment is perpendicular to the air inlet direction of the air inlet pipeline through the air inlet; An air release pipeline is provided on the other side surface between the air inlet and the air outlet. One end of the air release pipeline is communicated with the external environment, and the other end is communicated with the air outlet pipeline.

12. The electric proportional valve according to claim 11, characterized in that: The air leak pipeline is connected to the air outlet through the first compartment, or the air leak pipeline is connected to the adjacent side wall between the air outlet and the exhaust port, or the air leak pipeline is connected to the adjacent side wall between the first compartment and the exhaust port, and is located between the air pressure measuring pipeline of the air outlet pipeline and the first compartment, and the air flow after the air pressure is adjusted by the air leak pipeline enters the air pressure measuring pipeline.

13. The electric proportional valve according to claim 1, characterized in that: The valve body contains a valve core drive assembly, and the lower part of the valve core drive assembly is contained in the first compartment; The valve core drive assembly includes a valve column, a diaphragm connected to the top of the valve column, a convex ring sleeved on the valve column, and a first valve core and a second valve core respectively located at both ends of the valve column, and the second valve core is located below the diaphragm, and the convex ring has a limiting effect on the second valve core. The bottom end of the valve column passes through the intermediate valve body and extends to the bottom of the main valve body. The second piston of the second valve core is limited between the lower end surface of the chamber of the intermediate valve body and the convex ring, and the two cooperate to form an exhaust valve port. A second spring is arranged in the second valve core; The first valve core is arranged between the main valve body and the bottom cover as an intake valve core. The first piston of the first valve core is limited to the lower end surface of the bottom of the main valve body. The two cooperate to form an intake valve port. The first valve core is provided with a first spring that drives the first piston to close the intake valve port.

14. A control method for controlling the electric proportional valve according to claim 1, characterized in that: The following operations are included: adjusting the ratio of the amount of gas entering the air outlet pipeline and the exhaust pipeline from the air inlet pipeline through closed-loop feedback control; and, A portion of the gas in the gas outlet pipeline is controlled to be discharged from the gas leakage pipeline to the external environment.

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