Servo valve with double spool

Abstract

This application discloses a servo valve with a double spool. The servo valve with a double spool includes a first valve seat, a second valve seat, an inner spool, a first drive assembly, and a second drive assembly, wherein the inner spool is slidably mounted to the first valve seat in a sealed state to form a small-opening servo valve, and the first drive assembly adjusts the opening by driving the inner spool to move along the first valve seat, and the first valve seat is slidably mounted to the second valve seat in a sealed state so that the first valve seat engages with the second valve seat as a spool to form a large-opening servo valve, and the second drive assembly adjusts the opening by driving the small-opening servo valve as a whole to move along the second valve seat. A beneficial effect of this application is that by integrating the two-stage spool structure, it is possible to form small-opening and large-opening servo valve structures that do not interfere with each other, thereby enabling precise control of different flow rates according to different application scenarios.

Description

Technical Field

[0001] This application relates to the technical field of valves, and particularly to a servo valve with a double spool.

Background Art

[0002] A servo valve is a control element commonly used in a hydraulic system, and can achieve flow control, pressure control, direction control, and automatic adjustment of the hydraulic system. Taking pressure control as an example, the servo valve adjusts the opening degree of the valve port by moving its own spool to achieve pressure control.

[0003] When the pressure is constant, there are mainly two spool movement control methods for the servo valve. One is the linear gain mode, that is, the valve port opening degree and the displacement of the spool are in a linear function relationship. The other is the non-linear mode, that is, the valve port opening degree and the displacement of the spool are in a power function relationship. For the above two control methods, in the case of the same flow path, the non-linear mode has higher flow regulation accuracy at small opening degrees than the linear mode, but lower flow regulation accuracy at large opening degrees than the linear mode. Therefore, conventional hydraulic systems often need to provide multiple servo valves of different modes for different opening degree requirements, which makes the connection structure of the entire hydraulic system complex and the cost relatively high.

Summary of the Invention

Problems to be Solved by the Invention

[0004] One object of this application is to provide a servo valve with a double spool that can solve at least one of the disadvantages in the above background art.

Means for Solving the Problems

[0005] To achieve at least one of the above objects, the technical solution adopted by this application is a servo valve with a double spool. The servo valve with a double spool includes a first valve seat, a second valve seat, an inner spool, a first drive assembly, and a second drive assembly. The inner spool is slidably attached to the first valve seat in a sealed state to form a small-opening servo valve. The first drive assembly adjusts the opening by driving the inner spool to move along the first valve seat. The first valve seat is slidably mounted to the second valve seat in a sealed state so as to engage with the second valve seat as a spool to form a wide-opening servo valve. The second drive assembly adjusts the opening degree by driving the small-opening servo valve to move along the second valve seat as a whole.

[0006] Preferably, the first drive assembly includes a first drive device and a first traction member. The first drive unit is fixedly mounted outside the second valve seat. The first traction member is drivably engaged with the first drive device at one end, and the other end is connected to the inner spool in the first valve seat through the second valve seat, The first traction member moves the inner spool along the first valve seat when driven by the first drive device.

[0007] Preferably, the first drive device is an electric motor, The inner spool has a non-circular cross-section or is non-rotatably engaged with the first valve seat. The first traction member includes a first transmission member and a first drive rod, The first transmission member is rotatably mounted to the first valve seat, One end of the first transmission member is engaged with the first drive device in a way that allows it to be transmitted. The other end of the first transmission member is engaged with the first drive rod by a screw or lead screw. One end of the first drive rod, away from the first transmission member, is fixed to the inner spool.

[0008] Preferably, the first transmission member includes a first rotating sleeve and a first transmission shaft. The first rotating sleeve is rotatably mounted to the first valve seat and is engaged with the first drive rod by a screw or lead screw. The first transmission shaft is fixed at one end to the first rotating sleeve and the other end is engaged with the first drive device in a manner that allows for power transmission.

[0009] Preferably, the output terminal of the first drive unit is engaged with the first transmission member so as to be ductile by a spline, Alternatively, the output terminal of the first drive unit meshes with a second gear provided on the first transmission member via a first gear, and the difference in width between the first gear and the second gear is greater than or equal to the opening stroke of the large-opening servo valve.

[0010] Preferably, the second drive assembly includes a second drive unit and a second traction member. The second drive unit is fixedly mounted outside the second valve seat. The second traction member is fitted onto the first traction member, one end of which is drivably engaged with the second drive device, and the other end of which is provided within the second valve seat and connected to the first valve seat. The second traction member moves the small-opening servo valve by driving the second drive device.

[0011] Preferably, the second drive device is an electric motor, The first valve seat has a non-circular cross-section or is non-rotatably engaged with the second valve seat. The second traction member includes a second transmission member and a second drive rod, The second transmission member is rotatably mounted to the second valve seat, One end of the second transmission member is engaged with the second drive unit via a gear so as to be able to transmit power, The other end of the second transmission member is engaged with the second drive rod by a screw or lead screw. The end of the second drive rod that is not connected to the second transmission member is fixed to the first valve seat.

[0012] Preferably, the second transmission member includes a second rotating sleeve and a second transmission shaft, The second rotating sleeve is rotatably attached to the second valve seat and engaged with the second driving rod by a screw or a lead screw, One end of the second transmission shaft is fixed to the second rotating sleeve, and the other end is engaged with the second driving device through a gear so as to be transmissible.

[0013] Preferably, the inner spool is attached to the first inner chamber of the first valve seat so as to be slidable in a sealed state, The first valve seat is attached to the second inner chamber of the second valve seat so as to be slidable in a sealed state, An oil passage is provided in the inner spool to communicate the oil inlet of the first valve seat with the first inner chamber, A first oil passage port communicating with the second inner chamber is provided on a side portion of the first inner chamber of the first valve seat.

[0014] Preferably, the oil inlet of the first valve seat is engaged with the inner spool through a tapered surface, The oil inlet of the second valve seat is also engaged with the first valve seat through a tapered surface.

[0015] Compared with the prior art, the beneficial effects of the present application are as follows.

[0016] By integrating the two-stage spool structure, a small-opening servo valve and a large-opening servo valve structure that do not interfere with each other can be formed, whereby accurate control of different flow rates can be performed according to different application scenarios.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic diagram of the overall structure of the present application. [Figure 2] It is a partial structural schematic diagram when the small-opening servo valve according to the present application is opened. [Figure 3] It is a partial structural schematic diagram when the large-opening servo valve according to the present application is opened. [Modes for carrying out the invention]

[0018] The present application will be further described below in relation to specific embodiments. In this specification, any reference to terms such as “one embodiment,” “several embodiments,” “example,” “specific example,” or “several examples” means that the specific features, structures, materials, or properties described in conjunction with the embodiment or example are included in at least one embodiment or example of this application. In this specification, exemplary expressions for the above terms should not necessarily be construed as being limited to the same embodiment or example. Furthermore, the specific features, structures, materials, or properties described can be combined in an appropriate manner within any one or more embodiments or examples. Moreover, those skilled in the art can combine or link different embodiments or examples described herein.

[0019] Furthermore, in the description of this application, the directions or positional relationships indicated by directional terms such as "center," "horizontal," "vertical," "length," "width," "thickness," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," and "counterclockwise" are directions or positional relationships shown based on the drawings, and are solely for the convenience and simplification of the description of this application. They do not imply or suggest that the devices or elements shown must necessarily have a specific direction, or must be configured or operated in a specific direction, and should not be understood as limitations on the specific scope of protection of this application.

[0020] Furthermore, terms such as "First," "Second," etc., used in the specification and claims of this application are intended to distinguish similar subjects and do not necessarily indicate a specific order or sequence.

[0021] In this application, unless otherwise explicitly provided and limited, technical terms such as “attach,” “interconnect,” “connect,” and “fix” should be understood in a broad sense. For example, it may be a connection, a removable connection, or an integrated connection. It may be a mechanical connection or an electrical connection. It may be a direct connection or an indirect connection via an intermediate medium, or an internal communication between two elements or an interaction relationship between two elements. A person skilled in the art will be able to understand the specific meaning of the above terms in this invention, depending on the specific situation.

[0022] In this application, unless otherwise explicitly provided and limited, the phrase "above" or "below" the second feature of the first feature may include cases where the first and second features are in direct contact, or cases where they are in contact not by direct contact, but by other features interposed between them. The phrase "above," "above," or "upper side" of the second feature may include cases where the first feature is directly above or diagonally above the second feature, or simply means that the horizontal height of the first feature is greater than that of the second feature. The phrase "below," "below," or "lower side" of the second feature may include cases where the first feature is directly below or diagonally below the second feature, or simply means that the horizontal height of the first feature is less than that of the second feature.

[0023] The technical terms “including” and “having,” and all 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 apparatus comprising a series of steps or units may include other steps or units that are not explicitly described or are specific to those processes, methods, products, or apparatus, without necessarily being limited to the steps or units explicitly described.

[0024] In one preferred embodiment of the present invention, as shown in Figure 1, a servo valve with a double spool includes a first valve seat 1, a second valve seat 3, an inner spool 2, a first drive assembly 4, and a second drive assembly 5, wherein the inner spool 2 is slidably mounted to the first valve seat 1 in a sealed state to form a small-opening servo valve, thereby adjusting the opening of the first valve port 10 of the first valve seat 1 by moving the inner spool 2 along the first valve seat 1. The first drive assembly 4 may be mounted to the second valve seat 3 or to another external location, provided that stable operation and driving of the first drive assembly 4 can be ensured. The first drive assembly 4 may be drivably engaged with the inner spool 2, thereby adjusting the opening by moving the inner spool 2 along the first valve seat 1 as driven by the first drive assembly 4. The first valve seat 1 is slidably mounted to the second valve seat 3 in a sealed state so that the first valve seat 1 engages with the second valve seat 3 as a spool to form a wide-opening servo valve, thereby adjusting the opening of the second valve port 30 of the second valve seat 3 by moving the first valve seat 1 along the second valve seat 3. The second drive assembly 5 may be mounted to the second valve seat 3 or to another external location, provided that stable operation and driving of the first drive assembly 4 can be ensured. The second drive assembly 5 may be drivably engaged with the first valve seat 1 so that the first valve seat 1 adjusts its opening by moving along the second valve seat 3 when driven by the second drive assembly 5.

[0025] Compared to conventional methods, the present invention allows for the integration of a two-stage spool structure, enabling the creation of small-opening and large-opening servo valve structures that do not interfere with each other. This allows for precise control of different flow rates according to different application scenarios. Furthermore, by using the small-opening servo valve as the spool for the large-opening servo valve, the number of servo valve components can be effectively reduced. This reduces costs and minimizes the required installation space for the servo valve.

[0026] As shown in Figures 1 to 3, the oil inlets of the first valve seat 1 and the second valve seat 3 are located on the same side, the first valve port 10 of the first valve seat 1 and the second valve port 30 of the second valve seat 3 are in communication, and the opening size of the first valve port 10 is smaller than the opening size of the second valve port 30.

[0027] When nonlinear valve opening control is required in small valve opening situations, the first valve seat 1 must ensure that its end opening and the oil inlet of the second valve seat 3 are sealed. In this case, the inner spool 2, driven by the first drive assembly 4, slides in a sealed state along the first inner chamber 12 of the first valve seat 1, opening the first valve port 10. As a result, the oil flows in from the oil inlet of the first valve seat 1, passes through the opened first valve port 10, and flows out from the second valve port 30. The specific flow path is shown by the dashed line in Figure 2.

[0028] If it is possible to ensure that the inner spool 2 and the first valve seat 1 remain relatively stationary during the subsequent valve opening adjustment process, then when linear valve opening control is required in a wide-opening scenario, the end opening of the first valve seat 1 and the oil inlet of the second valve seat 3 may be sealed or directly open. For the sake of explanation, the following explanation will use the case where the end opening of the first valve seat 1 and the oil inlet of the second valve seat 3 are sealed as an example. The first valve seat 1 slides in a sealed state along the second inner chamber 31 of the second valve seat 3 by the drive of the second drive assembly 5, opening the second valve port 30. As a result, the oil flows in from the oil inlet of the second valve seat 3 and flows out along the opened second valve port 30. The specific flow path is shown by the dashed line in Figure 3. During the movement of the first valve seat 1, the inner spool 2 must maintain synchronized movement with the first valve seat 1.

[0029] Furthermore, in order to ensure a stable seal between the inner spool 2 and the oil inlet of the first valve seat 1, and to ensure a stable seal between the first valve seat 1 and the oil inlet of the second valve seat 3, the oil inlet of the first valve seat 1 may be engaged with the end opening of the inner spool 2 via a tapered surface, and the oil inlet of the second valve seat 3 may also be engaged with the end opening of the first valve seat 1 via a tapered surface.

[0030] In this embodiment, as shown in Figure 1, the first drive assembly 4 includes a first drive unit 41 and a first traction member, the first drive unit 41 being fixedly mounted outside the second valve seat 3, one end of the first traction member being drivably engaged with the output terminal of the first drive unit 41, and the other end of the first traction member being connectable to the inner spool 2 in the first valve seat 1 through the second valve seat 3. When adjustment of the opening degree of the small-opening servo valve is required, the first drive unit 41 can be activated. As a result, the first traction member can move the inner spool 2 along the first valve seat 1 by driving the first drive unit 41.

[0031] The operating mode in which the first traction member drives the inner spool 2 is linear motion. On the other hand, there are various specific drive methods by which the first drive device 41 drives the first traction member to realize the linear motion of the inner spool 2. For example, the first drive device 41 may directly drive the first traction member to move it linearly, thereby moving the inner spool 2 synchronously. Alternatively, for example, the first drive device 41 may rotate the first traction member and further realize the linear motion of the inner spool 2 by a transmission structure such as a lead screw or a screw.

[0032] When the first drive unit 41 directly drives the first traction member to cause linear motion, the structure commonly used for the first drive unit 41 is an air cylinder or a hydraulic cylinder. Therefore, it is necessary to additionally provide an air source or an oil source to the first drive unit 41. Furthermore, both air cylinders and hydraulic cylinders are susceptible to leakage, and as a result, leakage from the air cylinder or hydraulic cylinder can reduce the accuracy of opening control of the small-opening servo valve. Therefore, in this embodiment, the movement of the inner spool 2 is achieved by the first drive unit 41 rotationally driving the first traction member. That is, the first drive unit 41 is preferably an electric motor, and the opening of the small-opening servo valve can be controlled accurately by servo control of the electric motor.

[0033] Specifically, as shown in Figures 1 and 2, the inner spool 2 has a non-circular cross-section or is non-rotatably engaged with the first valve seat 1 so that the inner spool 2 can subsequently perform stable linear motion. The first traction member includes a first transmission member and a first drive rod 44, the first transmission member being rotatably attached to the first valve seat 1, one end of the first transmission member being rotatably engaged with the first drive unit 41, and the other end of the first transmission member being engaged with the first drive rod 44 by a screw or lead screw. The end of the first drive rod 44 away from the first transmission member is fixed to the inner spool 2.

[0034] When it is necessary to control the opening degree of a small-opening servo valve, the first drive unit 41 is activated, and as a result the first transmission member rotates due to the drive of the first drive unit 41. Since the first transmission member can only rotate around the first valve seat 1 and cannot move axially, the engagement of the first transmission member with the first drive rod 44 by a screw or lead screw drives the first drive rod 44 and moves the inner spool 2 axially. The nonlinear mode of the inner spool 2 can be realized by controlling the rotational speed of the first drive unit 41 to be non-constant.

[0035] Although an example is given in which the first transmission member is engaged with the first drive rod 44 by a screw, the first transmission member may be inserted into the first drive rod 44 and engaged by a screw, or the first drive rod 44 may be inserted into the first transmission member and engaged by a screw. There are various specific mounting methods for the first transmission member and the first drive rod 44, but below, for ease of understanding, one such structure will be given as an example and explained in detail.

[0036] Specifically, as shown in Figures 1 to 3, the first transmission member includes a first rotating sleeve 43 and a first transmission shaft 42. A pair of mounting covers 6 are provided inside the first valve seat 1, spaced apart in the longitudinal direction, and the mounting covers 6 may be fixed to the first valve seat 1 by welding or bolting so that a rotatable mounting space is formed between the two mounting covers 6. The first rotating sleeve 43 is located within the rotatable mounting space and is engaged with the two mounting covers 6 at both ends via thrust bearings. This allows the first rotating sleeve 43 to be rotatably mounted to the first valve seat 1. The first transmission shaft 42 is fixed to one end of the first rotating sleeve 43 away from the inner spool 2, and the other end of the first transmission shaft 42 extends from the second valve seat 3 and is drivably engaged with the first drive unit 41. The first drive rod 44 may be engaged with the first rotating sleeve 43 by a screw or lead screw, so that when the first drive device 41 is operated, the first transmission shaft 42 can rotate the first rotating sleeve 43 synchronously. In this way, the first rotating sleeve 43 moves the inner spool 2 by its engagement with the first drive rod 44 by a screw or lead screw.

[0037] As can be seen from the above, when the large-opening servo valve is operated, the entire small-opening servo valve moves along the second valve seat 3. Since the first transmission shaft 42 is fixed to the first rotating sleeve 43, the first transmission shaft 42 moves in sync with the small-opening servo valve. In order to stabilize the connection between the first drive unit 41 and the first transmission shaft 42, the first drive unit 41 is provided to be floating, that is, so that the first drive unit 41 can move axially in sync with the first transmission shaft 42, or a floating structure is provided between the output end of the first drive unit 41 and the first transmission shaft 42. This allows the first transmission shaft 42 to move axially relative to the first drive unit 41 while maintaining a stable and transmittable connection with the first drive unit 41. Considering actual usage scenarios, a floating setting for the first drive unit 41 may not meet the requirements in some usage scenarios. Therefore, in this embodiment, it is preferable to provide a floating structure between the output end of the first drive unit 41 and the first transmission shaft 42. Since the specific mounting positions of the first drive unit 41 and the first transmission shaft 42 are different, the specific structure of the floating structure is also different. To make it easier to understand, the following will explain in detail using two specific examples.

[0038] Example 1: Embodiment 1: The output terminal of the first drive unit 41 is coaxial with the axis of the first transmission shaft 42. In this case, the output terminal of the first drive unit 41 can be engaged with the first transmission shaft 42 by a spline to form a floating structure.

[0039] Example 2: As shown in Figure 1, in Embodiment 1, the output terminal of the first drive unit 41 is not coaxial with the axis of the first transmission shaft 42. In this case, the output terminal of the first drive unit 41 meshes with the second gear 421 provided on the first transmission shaft 42 via the first gear 411, and there is a difference in width between the first gear 411 and the second gear 421, and the difference in width is greater than or equal to the opening stroke of the large-opening servo valve. Specifically, the width of the first gear 411 may be greater than the width of the second gear 421, and the width of the second gear 421 may be greater than the width of the first gear 411, and this can be independently selected according to the actual needs of those skilled in the art.

[0040] In this embodiment, as shown in Figure 1, the second drive assembly 5 includes a second drive unit 51 and a second traction member. The second drive unit 51 is fixedly mounted outside the second valve seat 3, and the second traction member is fitted onto the first traction member, meaning that the first traction member and the second traction member are either in smooth contact or non-contact. One end of the second traction member is drivably engaged with the second drive unit 51, and the other end of the second traction member is provided within the second valve seat 3 and connected to the first valve seat 1. When adjustment of the opening degree of the wide-opening servo valve is required, the second drive unit 51 can be activated. As a result, the second traction member can move the entire narrow-opening servo valve along the second valve seat 3 by the drive of the second drive unit 51.

[0041] The operating mode in which the second traction member drives the small-opening servo valve is linear motion. On the other hand, there are various specific drive methods by which the second drive device 51 drives the second traction member to realize the linear motion of the small-opening servo valve. For example, the second drive device 51 may directly drive the second traction member to move it linearly, thereby moving the small-opening servo valve synchronously. Alternatively, for example, the second drive device 51 may rotate the second traction member and further realize the linear motion of the small-opening servo valve by a transmission structure such as a lead screw or a screw.

[0042] When the second drive unit 51 directly drives the second traction member to cause linear motion, the second drive unit 51 is typically an air cylinder or a hydraulic cylinder. Therefore, the second drive unit 51 requires the additional provision of an air source or an oil source. Furthermore, both air cylinders and hydraulic cylinders are susceptible to leakage, which can reduce the accuracy of opening control of the large-opening servo valve. In this embodiment, the second drive unit 51 rotates the second traction member to achieve movement of the small-opening servo valve. Specifically, the second drive unit 51 is preferably an electric motor, and the opening of the small-opening servo valve can be precisely controlled by servo control of the electric motor.

[0043] Specifically, as shown in Figures 1 to 3, the first valve seat 1 has a non-circular cross-section or is non-rotatably engaged with the second valve seat 3 so that the first valve seat 1 can subsequently perform stable linear motion. The second traction member includes a second transmission member and a second drive rod 54, the second transmission member being rotatably attached to the second valve seat 3, one end of the second transmission member being kinetically engaged with the second drive unit 51 via a gear, the other end of the second transmission member being engaged with the second drive rod 54 by a screw or lead screw, and the end of the second drive rod 54 away from the second transmission member being fixed to the first valve seat 1.

[0044] When it is necessary to control the opening degree of a large-opening servo valve, the second drive unit 51 is activated, and as a result the second transmission member rotates due to the drive of the second drive unit 51. Since the second transmission member can only rotate around the second valve seat 3 and cannot move in the axial direction, the engagement of the second transmission member with the second drive rod 54 by a screw or lead screw drives the second drive rod 54, which moves the first valve seat 1 in the axial direction. The linear operation mode of the small-opening servo valve can be achieved by controlling the rotational speed of the second drive unit 51 to a constant value.

[0045] Although an example is given in which the second transmission member is engaged with the second drive rod 54 by a screw, the second transmission member may also be inserted into the second drive rod 54 and engaged by a screw, or the second drive rod 54 may be inserted into the second transmission member and engaged by a screw. There are various specific mounting methods for the second transmission member and the second drive rod 54, but below, for ease of understanding, one such structure will be given as an example and explained in detail.

[0046] Specifically, as shown in Figures 1 to 3, the second transmission member includes a second rotating sleeve 53 and a second transmission shaft 52. The rotatable mounting position of the second rotating sleeve 53 is within the second valve seat 3, and the specific mounting method is generally the same as that of the first rotating sleeve 43, so a detailed explanation is omitted here. The second transmission shaft 52 is fixed to one end of the second rotating sleeve 53 away from the small-opening servo valve, and the other end of the second transmission shaft 52 extends from the second valve seat 3 and meshes with the third gear 511 at the output end of the second drive unit 51 via a fixedly mounted fourth gear 521. The second drive rod 54 may be engaged with the second rotating sleeve 53 by a screw or lead screw, and as a result, when the second drive unit 51 is operated, the second transmission shaft 52 can rotate the second rotating sleeve 53 synchronously. In this way, the second rotating sleeve 53 moves the small-opening servo valve by engaging with the second drive rod 54 via a screw or lead screw.

[0047] Furthermore, to prevent interference between the large-opening servo valve and the small-opening servo valve, through holes are formed in the centers of both the second transmission shaft 52 and the second drive rod 54. As a result, the first transmission shaft 42 can be inserted into the first valve seat 1 along the through holes in the centers of the second transmission shaft 52 and the second drive rod 54 and connected to the inner spool 2. The diameter of the first transmission shaft 42 is smaller than the inner diameter of the through holes in the centers of the second transmission shaft 52 and the second drive rod 54.

[0048] In this embodiment, as shown in Figures 1 to 3, the inner spool 2 is slidably mounted in a sealed state to the first inner chamber 12 of the first valve seat 1, and the first valve seat 1 is slidably mounted in a sealed state to the second inner chamber 31 of the second valve seat 3. An oil passage is provided inside the inner spool 2 that connects the oil inlet of the first valve seat 1 to the first inner chamber. A first oil passage 11 is provided on the side of the first inner chamber 12 of the first valve seat 1, communicating with the second inner chamber 31. By providing the oil passage and the first oil passage 11, the pressure balance at both ends of the spool can be maintained during the operation of the small-opening servo valve and the large-opening servo valve, and as a result, the motion resistance when reducing the spool opening can be reduced.

[0049] Specifically, as shown in Figures 1 to 3, the inner spool 2 is provided with a second oil passage 20 and a third oil passage 21. The second oil passage 20 is located at the center of the inner spool 2 and one end communicates with the oil inlet of the first valve seat 1. Multiple third oil passages 21 are provided and may be uniformly arranged in the circumferential direction of the inner spool 2. One end of each third oil passage 21 communicates with the first inner chamber 12 of the first valve seat 1, and the other end communicates with the second oil passage 20.

[0050] For example, in the case of a small-opening servo valve, when it is necessary to move the inner spool 2 in the direction of increasing the opening, the inner spool 2 can move away from the oil inlet of the first valve seat 1 due to the pressure of the oil. If an oil passage is not provided, when it is necessary to move the inner spool 2 in the direction of decreasing the opening, the oil supply force at the oil inlet is constant, so the tendency of the inner spool 2 to move compresses the oil at the oil inlet, increasing the pressure at the oil inlet position, and as a result, the resistance to the movement of the inner spool 2 increases. On the other hand, if an oil passage is provided in the inner spool 2, before the inner spool 2 moves, the oil at the oil inlet position of the first valve seat 1 flows along the oil passage into the first inner chamber 12 and the second inner chamber 31 so that the pressure at both ends of the inner spool 2 becomes approximately equal. Therefore, when the inner spool 2 needs to move to a smaller opening, the oil storage space of the first inner chamber 12 increases with the movement of the inner spool 2, allowing some of the oil from the oil inlet of the first valve seat 1 to flow into the first inner chamber 12 along the oil passage. This significantly reduces the resistance of the inner spool 2's movement, ensuring smooth operation of the inner spool 2's opening and further improving the accuracy of the opening control. Specifically, the direction of oil flow that maintains the pressure balance at both ends of the spool is shown by the dotted lines in Figures 2 and 3.

[0051] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art will understand that this application is not limited to the above embodiments, that the above embodiments and descriptions in the specification only represent the principles of this application, and that various modifications and improvements to this application are possible without departing from the gist and scope of this application, and that all such modifications and improvements fall within the scope for which protection is sought. The scope for which protection is sought is defined by the attached claims and equivalents. [Explanation of symbols]

[0052] 1. First valve seat 10. First valve port 11 1st oil passage port 12 1st interior room 2. Inner spool 20 2nd oil passage port 21 3rd oil passage port 3. Second valve seat 30 Second valve port 31 Second interior room 4. First drive assembly 41 First drive unit 411 First gear 42 First transmission shaft 421 Second gear 43 First Rotation Sleeve 44 First drive rod 5. Second drive assembly 51 Second drive unit 511 Third gear 52 Second transmission shaft 521 Fourth gear 53 Second Rotation Sleeve 54 Second drive rod 6. Mounting cover

Claims

1. The first valve seat and, An inner spool is slidably attached to the first valve seat in a sealed state to form a small-opening servo valve, A first drive assembly that adjusts the opening degree by driving the inner spool to move along the first valve seat, A second valve seat is slidably mounted in a sealed state to the first valve seat so as to engage with the first valve seat as a spool to form a wide-opening servo valve, A second drive assembly that adjusts the opening degree by driving the small opening servo valve to move along the second valve seat as a whole, including, A servo valve with a double spool.

2. The first drive assembly is A first drive unit fixedly attached to the outside of the second valve seat, A first traction member having one end drivably engaged with the first drive device and the other end connected to the inner spool in the first valve seat through the second valve seat, the first traction member moving the inner spool along the first valve seat by the drive of the first drive device, including, A servo valve with a double spool as described in claim 1.

3. The first drive device is an electric motor, The inner spool has a non-circular cross-section or is non-rotatably engaged with the first valve seat. The first traction member is, A first transmission member rotatably attached to the first valve seat and one end of which is ductilely engaged with the first drive device, A first drive rod, the other end of which is engaged with the first transmission member by a screw or lead screw, wherein one end of the first drive rod, away from the first transmission member, is fixed to the inner spool, including, A servo valve with a double spool as described in claim 2.

4. The first transmission member is, A first rotating sleeve is rotatably attached to the first valve seat and engaged with the first drive rod by a screw or lead screw, A first transmission shaft, one end of which is fixed to the first rotating sleeve and the other end of which is movably engaged with the first drive device, including, A servo valve with a double spool as described in claim 3.

5. The output terminal of the first drive unit is engaged with the first transmission member so as to be ductile by a spline, Alternatively, the output terminal of the first drive device meshes with a second gear provided on the first transmission member via a first gear, and the difference in width between the first gear and the second gear is greater than or equal to the opening stroke of the large-opening servo valve. A servo valve with a double spool as described in claim 3.

6. The second drive assembly is A second drive unit fixedly attached to the outside of the second valve seat, A second traction member is fitted onto the first traction member, one end of which is drivably engaged with the second drive device, and the other end of which is provided within the second valve seat and connected to the first valve seat, the second traction member moves the small-opening servo valve by being driven by the second drive device, including, A servo valve with a double spool as described in claim 2.

7. The second drive device is an electric motor, The first valve seat has a non-circular cross-section or is non-rotatably engaged with the second valve seat. The second traction member is, A second transmission member rotatably mounted to the second valve seat and one end of which is engaged with the second drive device via a gear, A second drive rod, the other end of which is engaged with the second transmission member by a screw or lead screw, wherein one end of the second drive rod, away from the second transmission member, is fixed to the first valve seat, including, A servo valve with a double spool as described in claim 6.

8. The second transmission member is, A second rotating sleeve is rotatably attached to the second valve seat and engaged with the second drive rod by a screw or lead screw, A second transmission shaft, one end of which is fixed to the second rotating sleeve and the other end of which is engaged with the second drive device so as to be movable via a gear, including, A servo valve with a double spool as described in claim 7.

9. The inner spool is slidably mounted in a sealed state to the first inner chamber of the first valve seat, The first valve seat is slidably mounted in a sealed state to the second chamber of the second valve seat. An oil passage is provided within the inner spool that connects the oil inlet of the first valve seat to the first inner chamber. A first oil passage opening is provided on the side of the first inner chamber of the first valve seat, which communicates with the second inner chamber. A servo valve with a double spool according to any one of claims 1 to 8.

10. The oil inlet of the first valve seat engages with the inner spool via a tapered surface, The oil inlet of the second valve seat is also engaged with the first valve seat via a tapered surface. A servo valve with a double spool as described in claim 1.

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