An electro-hydraulic servo valve based on piezoelectric actuator

Abstract

The present invention discloses an electro-hydraulic servo valve based on a piezoelectric driver, comprising a valve body, a valve core positioned within the valve body, a rotary piezoelectric driver, a gear transmission, a movable baffle, and a nozzle. The rotary piezoelectric driver receives a servo valve input signal, generates a rotary driving force, and controls the movement of the movable baffle via the gear transmission. The movable baffle and the nozzle form a variable orifice, and the movement of the movable baffle generates a force that drives the valve core. The rotary piezoelectric driver controls the valve core's drive load, enabling precise control of the electro-hydraulic servo valve's output and improving the servo valve's dynamic response. The electro-hydraulic servo valve has a simple structure, is immune to electromagnetic interference, has high precision, and offers a fast valve core response speed.

Description

Technical Field

[0001] The present invention relates to an electro-hydraulic servo control system, in particular to an electro-hydraulic servo valve based on a piezoelectric driver. Background Art

[0002] The electro-hydraulic servo valve can convert a weak electrical control signal of a few milliamperes into a huge hydraulic power output of more than tens of horsepower, drive various loads, and perform position control, speed control or force control, etc. It is an important component in the electro-hydraulic servo control system.

[0003] The driver is very important in the electro-hydraulic servo valve. Its function is to convert electrical signals into mechanical motion. It is the core of the entire servo valve, and its performance directly affects the performance of the entire servo valve.

[0004] Traditional electro-hydraulic servo valves are often driven by torque motors. Prior art, such as Chinese patent application number 2015102616525, discloses an electro-hydraulic servo valve structure in which a torque motor drives the deflection of a baffle to move the main spool. Torque motors operate on electromagnetic principles and consist of a permanent magnet, coil, magnetic conductor, and non-magnetic material. These motors have numerous intermediate links, resulting in a complex structure and slow response speed.

[0005] With the increasing demand for electro-hydraulic servo valves with fast response speed and high control accuracy, piezoelectric actuators have the characteristics of fast response, easy control and high control accuracy, providing support for the pre-stage drivers of high-speed and precision electro-hydraulic servo valves.

[0006] Piezoelectric drivers are mainly divided into rigid displacement drivers and resonant displacement drivers according to the form of displacement output. Currently, rigid displacement drivers are used as pre-stage drivers for electro-hydraulic servo valves. They come in two forms: piezoelectric stack drivers (also known as stacked piezoelectric drivers) and piezoelectric dual-chip drivers (also known as piezoelectric bending elements). In the prior art, for example, Chinese patent application No. 2020114683343 discloses a piezoelectric electro-hydraulic servo valve and a control method thereof, in which a movable nozzle is directly driven by a piezoelectric actuator. Although the performance of the electro-hydraulic servo valve using a rigid displacement piezoelectric driver has been improved to varying degrees compared to traditional servo valves, the dynamic response frequency of the servo valve is low and there is a hysteresis problem. Summary of the Invention

[0007] Purpose of the invention: In view of the above shortcomings, the present invention provides an electro-hydraulic servo valve based on a piezoelectric drive with fast response and precise control.

[0008] Technical solution: In order to solve the above problems, the present invention adopts an electro-hydraulic servo valve based on a piezoelectric driver, including a valve body, a valve core located in the valve body, a rotary piezoelectric driver, a gear transmission device, a movable baffle and a nozzle. The rotary piezoelectric driver receives the servo valve input signal, generates a rotational driving force, and controls the movement of the movable baffle through the gear transmission device. The movable baffle and the nozzle form a variable throttling hole, and the movement of the movable baffle generates a force to drive the valve core.

[0009] Furthermore, it includes two nozzles, which are located on both sides of the movable baffle. The movable baffle moves to change the distance between it and the two nozzles, changing the pressure at the ends of the two nozzles, thereby changing the working oil port pressure.

[0010] Furthermore, the gear transmission device includes an output gear arranged at the output end of the rotary piezoelectric driver and a rack meshing with the output gear. The movable baffle is fixedly connected to the rack. The rotary piezoelectric driver drives the output gear to rotate, and the rotation of the output gear drives the rack to move, thereby driving the movable baffle to move.

[0011] Furthermore, the valve body includes an upper valve body accommodating a gear transmission device and a lower valve body accommodating a valve core, the nozzle is arranged in the lower valve body, the movable baffle extends from the upper valve body to the lower valve body, a slide rail is arranged in the upper valve body, and the rack slides on the slide rail.

[0012] Furthermore, the lower valve body includes two working oil ports respectively connected to the nozzles. Changing the pressure of the working oil ports drives the valve core to move. The working oil ports are provided with pressure sensors.

[0013] Furthermore, the aperture of the nozzle end gradually decreases in the direction approaching the movable baffle.

[0014] Furthermore, the rotary piezoelectric driver includes a housing, a rotor and a stator. The stator and the rotor are in close contact through pre-pressure. A piezoelectric ceramic ring is attached to the bottom surface of the stator. The piezoelectric ceramic ring excites the stator to generate mechanical vibration. Under the action of the mechanical vibration and friction force of the stator, the rotor converts the micro-vibration on the stator surface into the macroscopic rotational motion of the rotor, and the rotor outputs the rotational motion through the rotating shaft.

[0015] Furthermore, it also includes a controller, which issues control instructions and controls the piezoelectric driver through the piezoelectric driver driving module. The controller controls the phase difference, frequency, amplitude or duty cycle of the output voltage signal of the piezoelectric driver driving module, and controls the rotation speed, rotation direction and output force of the piezoelectric driver.

[0016] Beneficial Effects: Compared with the prior art, the present invention has the significant advantage of utilizing the inverse piezoelectric effect of piezoelectric materials to apply a voltage signal with a frequency of more than 20,000 Hz to a stator elastic body to which a piezoelectric ceramic sheet is attached, causing microscopic mechanical vibrations to be generated on the surface of the stator elastic body. Through the friction between the stator and the rotor (or mover), the microscopic vibrations of the stator are converted into macroscopic rotations of the rotor (or mover), driving the movable baffle to move, thereby achieving precise control of the output of the electro-hydraulic servo valve and improving the dynamic response of the servo valve. The piezoelectric driver has the advantages of low speed, high torque, fast response speed, no electromagnetic interference, flexible structure, easy miniaturization, and self-locking when power is off. The electro-hydraulic servo valve has a simple structure, is not subject to electromagnetic interference, and has a fast valve core response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a schematic structural diagram of the electro-hydraulic servo valve of the present invention;

[0018] Figure 2 Shown is a schematic structural diagram of the gear transmission device of the present invention;

[0019] Figure 3 Shown is a diagram showing the working principle of the rotary piezoelectric actuator in the present invention. DETAILED DESCRIPTION

[0020] like Figure 1 As shown, an electro-hydraulic servo valve based on a piezoelectric driver in this embodiment includes an upper valve body 1, an output gear 2, a rack 3, a slide rail 4, a movable baffle 5, a nozzle 6, a valve core 7, a lower valve body 8, and a piezoelectric driver. The piezoelectric driver is installed in the seat body and includes a piezoelectric driver stator 9, a piezoelectric driver output shaft 10, a piezoelectric driver rotor 11, a piezoelectric driver housing 12, an electro-hydraulic servo valve controller and a piezoelectric driver drive module (drive power supply, controller); the piezoelectric driver stator and the rotor are in close contact through pre-pressure, and a piezoelectric ceramic ring is attached to the bottom surface of the piezoelectric driver stator. When the pre-drive stage receives the control signal, the piezoelectric driver is connected to the drive voltage, and the resonant working mode of the piezoelectric driver stator is excited, as shown in FIG. Figure 3 As shown, due to the inverse piezoelectric effect of piezoelectric ceramics, applying an alternating voltage with a specific phase difference between two phases can excite traveling waves in the stator, causing particles on the stator surface to produce elliptical motion. Through mechanical friction between the stator and rotor of the piezoelectric driver, the micro-vibration on the surface of stator 9 is converted into rotational motion of rotor 11, which is output through the rotating shaft. By varying the phase difference, frequency, amplitude, or duty cycle of the piezoelectric driver's driving voltage signal, the rotational speed, direction, and output force of the piezoelectric driver can be controlled.

[0021] like Figure 2As shown, the rotational motion of the piezoelectric driver is transmitted to the output gear 2 via the output shaft 10 connected to the rotor 11. The output gear 2 meshes with the rack 3. A movable baffle 5 is fixedly connected to the lower end of the rack 3. The movable baffle 5 and the rack 3 are integrally structured. The rack 3 is embedded in the slide rail 4. Driven by the output gear 2, the rack 3 can reciprocate along the slide rail 4. The reciprocating motion of the rack 3 causes the position of the movable baffle 5 to change, creating a pressure difference across the valve core 7, thereby causing the valve core 7 to move under the action of the pressure difference. The slide rail 4 is fixed in the upper valve body 1. Based on the position of the nozzle 6, the extreme position of the movable baffle 5's displacement is known, and therefore the range of engagement between the output gear and the rack is also known. By calculation, the appropriate rack length can be obtained to ensure that the output gear and the rack are always in meshing state.

[0022] The controller is connected to the piezoelectric actuator module. The controller issues commands to control the phase difference, frequency, amplitude, or duty cycle of the piezoelectric actuator module's output voltage signal, thereby controlling the piezoelectric actuator's rotational speed, direction, and output force. Pressure sensors are installed at the two working oil ports of the electro-hydraulic servo valve to detect the pressure at these ports. This pressure is processed and input into the controller as a feedback signal. The detected pressure is compared with the set value, and the difference between the two is processed and used as a control signal for the pre-drive stage, controlling the movement of the piezoelectric actuator and achieving pressure feedback compensation.

[0023] The working principle of the above electro-hydraulic servo valve is as follows:

[0024] After the electro-hydraulic servo system is supplied with oil from the oil inlet, the piezoelectric driver is not connected to the driving voltage when there is no control signal input to the pre-drive stage. At this time, the piezoelectric driver does not rotate, the movable baffle 5 is located in the middle of the two nozzles 6, the distance between the movable baffle 5 and the two nozzles 6 is equal, and the two ends of the two nozzles have equal pressure, so that the pressure of the two working oil ports is equal.

[0025] The pre-driver stage receives the control signal, applying drive voltage to the piezoelectric driver, which stimulates the resonant operating mode of the piezoelectric driver's stator. Mechanical friction between the stator and rotor converts the micro-vibration of the stator surface into rotational motion of the rotor. By varying the phase difference, frequency, amplitude, or duty cycle of the piezoelectric driver's drive voltage signal, the speed, direction, and output force of the piezoelectric driver can be controlled.

[0026] The rotational motion of the piezoelectric driver is transmitted to the output gear through the output shaft connected to the rotor. The output gear is engaged with the rack, which is embedded in the slide rail. The nozzle baffle and the rack are an integrated structure. Therefore, the rotation of the output gear drives the rack to move along the slide rail, and also drives the nozzle baffle to move along the slide rail.

[0027] When the piezoelectric driver rotates the output gear 2, causing the rack 3 to move to the left, the movable baffle 5 also moves to the left, creating a pressure differential between the two nozzles 6. This causes the working oil port pressure P1 to exceed P2, causing the valve core 7 to move rightward, driving the load. Simultaneously, the pressure sensors installed at the two working oil ports compare the measured port pressure with the set value. The difference between the two is amplified and corrected and used as the control signal for the pre-drive stage. When the measured value and the set value cancel each other out, the piezoelectric driver's driving voltage signal reaches zero, the piezoelectric driver stops rotating, the valve core 7 stops moving rightward, and the servo valve achieves a stable output.

[0028] When the piezoelectric driver rotates the output gear 2, causing the rack 3 to move to the right, the movable baffle 5 also moves to the right, creating a pressure differential between the two nozzles 6. This causes the working oil port pressure P1 to be less than P2, causing the valve core 7 to move leftward, driving the load. Simultaneously, pressure sensors installed at the two working oil ports compare the measured port pressure with the set value. The difference between the two is amplified and corrected, and then used as the control signal for the pre-drive stage. When the measured value and the set value cancel each other out, the piezoelectric driver's driving voltage signal reaches zero, the piezoelectric driver stops rotating, the valve core 7 stops moving leftward, and the servo valve achieves a stable output.

[0029] A piezoelectric actuator drives the nozzle baffle to move, creating a pressure differential between the two nozzles. This leads to unequal pressures at the two working oil ports, which in turn drives the valve core to the left or right, driving the load. This enables precise control of the dual-nozzle electro-hydraulic servo valve's output and improves the servo valve's dynamic response.

Claims

1. An electro-hydraulic servo valve based on a piezoelectric driver, characterized in that: The invention comprises a valve body, a valve core (7) located in the valve body, a rotary piezoelectric driver, a gear transmission device, a movable baffle (5) and a nozzle (6), wherein the rotary piezoelectric driver receives a servo valve input signal, generates a rotary driving force, controls the movement of the movable baffle through the gear transmission device, and the movable baffle and the nozzle form a variable throttle hole, and the movement of the movable baffle generates a force to drive the valve core; the rotary piezoelectric driver comprises a housing, a rotor and a stator, wherein the stator and the rotor are in close contact through pre-pressure, a piezoelectric ceramic ring is attached to the bottom surface of the stator, and the stator is excited to generate mechanical vibration through the piezoelectric ceramic ring, and the rotor converts the micro-vibration of the stator surface into macroscopic rotational motion of the rotor under the action of the mechanical vibration and friction force of the stator, and the rotor outputs the rotational motion through the rotating shaft; The gear transmission device comprises an output gear (2) provided at the output end of the rotary piezoelectric driver, a rack (3) meshing with the output gear (2), and the movable baffle (5) is fixedly connected to the rack (3). The rotary piezoelectric driver drives the output gear to rotate, and the output gear rotates to drive the rack to move, thereby driving the movable baffle (5) to move. The valve body comprises an upper valve body (1) accommodating a gear transmission device and a lower valve body (8) accommodating a valve core (7); the nozzle (6) is arranged in the lower valve body (8); the movable baffle (5) extends from the upper valve body (1) to the lower valve body (8); a slide rail (4) is arranged in the upper valve body (1), and the rack (3) slides on the slide rail (4).

2. The electro-hydraulic servo valve according to claim 1, characterized in that: The utility model comprises two nozzles (6), the two nozzles (6) are located on both sides of the movable baffle (5), and the movable baffle (5) moves to change the distance between the two nozzles (6), thereby changing the pressure at the ends of the two nozzles (6), thereby changing the working oil port pressure.

3. The electro-hydraulic servo valve according to claim 1, characterized in that: The lower valve body (8) includes two working oil ports respectively connected to the nozzles. Changing the pressure of the working oil ports drives the valve core (7) to move. The working oil ports are provided with pressure sensors.

4. The electro-hydraulic servo valve according to any one of claims 1 to 3, characterized in that: The aperture at the end of the nozzle (6) gradually decreases in the direction approaching the movable baffle.

5. The electro-hydraulic servo valve according to claim 1, characterized in that: It also includes a controller, which issues control instructions. The controller controls the piezoelectric driver through the piezoelectric driver driving module. The controller controls the phase difference, frequency, amplitude or duty cycle of the output voltage signal of the piezoelectric driver driving module, and controls the rotation speed, rotation direction and output force of the piezoelectric driver.

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