Fluid pressure composite driving device based on screw rod self-locking precise control

Abstract

A fluid pressure composite driving device based on lead screw self-locking precise control comprises a fluid pressure execution unit, a lead screw precise control unit, a pressure source system and a control unit. The fluid pressure execution unit comprises a pressure cylinder and a piston rod, and the piston rod can move in the pressure cylinder in the axial direction. The lead screw precise control unit comprises a lead screw, a nut matched with the lead screw and a driving motor. The driving motor is used for driving one of the lead screw and the nut to rotate, and the other one of the lead screw and the nut is connected with the piston rod. That is, the screw rod can rotate and the nut is connected with the piston rod, or the nut can rotate and the screw rod is connected with the piston rod. The pressure source system is connected with the pressure cylinder through a pipeline and used for providing or releasing fluid pressure. The control unit is in signal connection with the pressure source system and used for controlling the operation state of the pressure source system so as to adjust the pressure of fluid in the pressure cylinder through execution elements (such as an electromagnetic valve and a proportional valve) in the pressure source system. The lead angle alpha of the lead screw and the equivalent friction angle phi of the lead screw nut pair meet the following condition that alpha-phi is smaller than 6 degrees. Under the condition, the lead screw pair is in a critical self-locking state, pressure maintaining self-locking can be achieved through friction force, and locking and unlocking movement can be achieved through small torque under driving of the motor.

Description

Technical Field

[0001] This invention relates to the field of fluid pressure drive technology, and more specifically to a fluid pressure composite drive device based on screw self-locking precision control. Background Technology

[0002] In fields such as industrial automation and engineering machinery, fluid pressure (hydraulic or pneumatic) driven devices are widely used due to their advantages such as high output force and compact structure. However, traditional fluid pressure driven devices have shortcomings in scenarios requiring high-precision positioning or micro-motion control. For example, they are prone to position drift due to fluid compressibility under pressure holding conditions, or crawling phenomena occur during low-speed movement. Meanwhile, although purely mechanical screw drives offer high positioning accuracy, they require high-power motors under heavy load conditions, resulting in bulky systems and high energy consumption. Therefore, how to combine the high thrust of fluid pressure with the high precision of screws, and solve the control challenges when combining the two, has become an urgent problem to be solved in this field. Summary of the Invention

[0003] 1. Purpose of the invention The purpose of this invention is to provide a fluid pressure composite drive device based on lead screw self-locking precision control, which aims to solve the problems of insufficient accuracy of fluid pressure drive, weak large load capacity of lead screw drive, and lack of coordination between the two in the existing technology. 2. Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: A fluid pressure composite drive device based on lead screw self-locking precision control includes a fluid pressure execution unit, a lead screw precision control unit, a pressure source system, and a control unit.

[0004] The fluid pressure actuator includes a pressure cylinder and a piston rod, the piston rod being able to move axially within the pressure cylinder.

[0005] The lead screw precision control unit includes a lead screw, a nut that mates with the lead screw, and a drive motor. The drive motor is used to drive one of the lead screw and the nut to rotate, while the other is connected to the piston rod. That is, the lead screw can rotate while the nut is connected to the piston rod, or the nut can rotate while the lead screw is connected to the piston rod.

[0006] The pressure source system is connected to the pressure cylinder via a pipeline and is used to provide or release fluid pressure.

[0007] The control unit is signal-connected to the pressure source system and is used to control the operating state of the pressure source system so as to adjust the fluid pressure in the pressure cylinder through the actuators (such as solenoid valves, proportional valves, etc.) in the pressure source system.

[0008] The lead angle α of the lead screw and the equivalent friction angle φ of the lead screw and nut pair satisfy the following condition: |α-φ|<6°. This condition puts the lead screw pair in a critical self-locking state, which can achieve pressure holding self-locking by using friction, and can also achieve locking and unlocking movements by small torque under motor drive.

[0009] The control unit is signal-connected to the drive motor and configured to selectively control the drive motor to enter a first operating mode or a second operating mode according to load requirements. First operating mode (fluid pressure dominant): The control unit controls the pressure source system to provide fluid pressure to the pressure cylinder and controls the drive motor to operate, so that the axial movement direction of the piston rod, driven by the lead screw precision control unit and the fluid pressure, is consistent with the direction of the fluid pressure. In this mode, the fluid pressure provides the main thrust, and the lead screw motor mainly plays a role in precise positioning, displacement control, and auxiliary drive.

[0010] Second operating mode (motor-driven): The control unit controls the pressure source system to provide no or a low fluid pressure, and the piston rod is primarily driven by the drive motor. In this mode, the torque of the drive motor overcomes the friction of the lead screw and nut pair to achieve precise positioning and displacement control.

[0011] 3. Core Invention Points and Beneficial Effects 3.1 Core Invention Points The core of this invention lies in the fact that, through structural design and parameter matching, the screw drive system is placed in a controllable critical self-locking state, thereby organically combining the large thrust driven by fluid pressure with the precise control of motor drive, achieving a unity of large load and precise control.

[0012] Specifically, this is achieved through the following technical means: 1. Structural innovation: It adopts a configuration that combines a fluid pressure actuator and a lead screw precision control unit for combined drive.

[0013] 2. Parameter innovation: By precisely matching the lead angle (α) of the lead screw with the equivalent friction angle (φ) of the lead screw and nut pair, the condition of |α - φ| < 6° is met, so that the system works in the critical self-locking region.

[0014] 3. Control Innovation: An adaptive control strategy based on load demand was designed, which can switch between "composite drive" and "precision control" modes.

[0015] 3.2 Beneficial Effects Based on the above-mentioned core inventions, the present invention has achieved the following significant beneficial effects: 1. Extremely high energy utilization efficiency In the critical self-locking state, when the fluid pressure and load are close to equilibrium, the drive motor only needs to apply a very small torque (less than 10% of the torque required by the traditional pure motor drive scheme) to accurately control the piston rod displacement, thus achieving precise positioning of large loads with minimal energy input.

[0016] 2. Excellent handling and safety When the fluid thrust is excessive, the lead screw's self-locking effect can effectively "isolate" the excessive thrust and prevent system impact. The load's movement is entirely controlled by the motor's programmed control, achieving "high output and precise control." At the same time, the critical self-locking characteristic gives the system an inherent fail-safe mechanism, automatically locking in the event of power failure to prevent accidental falls.

[0017] 3. Higher speed and dynamic performance Traditional methods employ small lead angles to ensure self-locking, resulting in slow movement speeds or high motor speeds. This invention eliminates the self-locking constraint, allowing for the use of larger lead angles, thereby achieving higher linear motion speeds at the same motor speed and improving the dynamic response capability of the equipment.

[0018] 4. Significant advantages in system cost and integration. An architecture of "centralized pressure source + distributed precision control actuator" can be adopted, replacing multiple high-power motors with a single hydraulic pump, which greatly reduces the total cost, complexity, energy consumption and size of multi-actuator systems. Attached Figure Description

[0019] Figure 1 This is a cross-sectional structural diagram of the fluid pressure actuator and the lead screw precision control unit according to an embodiment of the present invention.

[0020] Figure 2 A schematic diagram showing the arrangement of distributed fluid pressure actuators in a multi-pressure source system; Explanation of reference numerals in the attached figures 1-Fluid pressure actuator, 11-Pressure cylinder, 12-Piston rod, 21-Lead screw, 22-Nut, 23-Drive motor, 31-Pipeline, 32-High-pressure source, 33-Secondary high-pressure source, 34-Adjustable pressure source Detailed Implementation The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only used to explain the present invention and are not intended to limit the present invention. Example

[0021] Combination Figure 1 As shown, this embodiment provides a fluid pressure composite drive device based on lead screw self-locking precision control, including a fluid pressure execution unit 1, a lead screw precision control unit, a pressure source system, and a control unit.

[0022] The fluid pressure actuation unit 1 is a hydraulic cylinder, including a pressure cylinder 11 and a piston rod 12. The piston rod 12 can move axially within the pressure cylinder 11. The lead screw precision control unit includes a lead screw 21, a nut 22, and a drive motor 23. The piston rod 12 has a hollow structure, with one end used to connect to the load and the other end rigidly connected to the nut 22. In this embodiment, the output shaft of the drive motor 23 is rigidly connected to the lead screw 21 to drive the lead screw 21 to rotate. The nut 22 is rigidly connected to the end of the piston rod 12. When the lead screw 21 rotates, the nut 22 drives the piston rod 12 to move axially in a linear motion.

[0023] The pressure source system is a hydraulic source, including an oil tank, a hydraulic pump, a relief valve, a solenoid directional valve, and other actuators. The pressure source system is connected to the cavities on both sides of the pressure cylinder 11 via pipeline 31. The control unit (such as a PLC or embedded controller) is electrically connected to the solenoid directional valve and the drive motor 23 in the pressure source system via signal lines.

[0024] In this embodiment, the lead screw 21 is a trapezoidal lead screw with a lead angle α of 6°. The nut 22 is made of a metal-based self-lubricating material, and the equivalent friction angle φ generated by its pairing with the lead screw 21 is approximately 5° during the initial break-in period, approximately 6° during the long-term stable operation period, and approximately 8° during the wear compensation limit period. Therefore, throughout the entire design operation period, the equivalent friction angle φ ranges from 5° to 8°, always satisfying the critical self-locking condition of |α-φ| < 6°. Under this condition, calculations show that the motor torque required by this invention to drive or maintain the piston rod movement is significantly reduced, requiring only about 0.1 N·m to 2 N·m. The motor torque required by the traditional solution, under the premise of the same output of 10,000N axial thrust, using the traditional pure motor drive solution (without hydraulic assistance), requires a motor drive torque as high as 50 N·m to 70 N·m.

[0025] Comparative conclusion: This invention, through critical self-locking design and hydraulic composite drive, reduces the motor torque requirement by approximately one to two orders of magnitude (only 1% to 5% of traditional solutions), thus allowing the use of micro motors and achieving system miniaturization, weight reduction, and high efficiency.

[0026] The operating logic of the control unit is as follows: First operating mode (fluid pressure dominant): This mode is entered when a large thrust demand is detected. The control unit controls the pressure source system to supply oil to the pressure cylinder 11, generating high-pressure thrust; simultaneously, it controls the drive motor 23 to ensure that the axial movement direction of the piston rod 12 driven by the lead screw precision control unit is consistent with the direction of the fluid pressure. At this time, the fluid pressure bears most of the load, and the motor only needs to provide a small torque to achieve precise control.

[0027] Second operating mode (motor-driven): This mode is entered when the load demand is very low. The control unit controls the pressure source system to stop supplying oil or only provide a low back pressure, relying mainly on the drive motor 23 as the power source to drive the piston rod 12. Due to the small load, the motor can achieve precise displacement control by overcoming the friction of the lead screw with a small torque. Example

[0028] The difference between this embodiment and Embodiment 1 is that the fluid pressure actuator 1 is a cylinder, and the pressure source system is a pneumatic source (including an air compressor, air tank, solenoid valve, etc.). Under pneumatic drive, the entire device has a faster response speed and is suitable for light-load applications with high requirements for weight and speed. Example

[0029] The difference between this embodiment and Embodiment 1 lies in the transmission method: the drive motor 23 is used to drive the nut 22 to rotate, while the lead screw 21 is rigidly connected to the piston rod 12. That is, this embodiment adopts a structure of "nut rotation and lead screw linear motion". Example

[0030] Please see Figure 2 This embodiment optimizes the pressure source system based on Embodiment 1. The pressure source system (including high-pressure source 32, secondary high-pressure source 33, and adjustable pressure source 34) is connected to the fluid pressure actuator (1) through a multi-way valve group (such as a proportional valve or a solenoid directional valve). The control unit achieves the following functions by controlling the on / off state of the multi-way valve group: Pressure switching: According to the real-time load requirements, the control unit selectively connects the high-pressure source 32, secondary high-pressure source 33, or adjustable pressure source 34 to the circuit to match different output requirements.

[0031] Pressure combination: By combining and controlling valve groups, different pressure sources can be connected in parallel or series to the circuit to achieve pressure superposition or graded regulation.

[0032] Distributed pressure supply: The multi-way valve group has multiple output ports, which are connected to multiple distributed execution units respectively, to realize the centralized pressure supply mode of "one pump and multiple cylinders". Example

[0033] This embodiment optimizes the control unit based on embodiment 1. The control unit integrates a position closed-loop control module and a pressure closed-loop control module. The position closed-loop control module adjusts the motor speed in real time by collecting feedback signals from the encoder built into the drive motor (23); the pressure closed-loop control module adjusts the output pressure of the pressure source system in real time by collecting feedback signals from the pressure sensor installed on the pressure cylinder (11). The two modules work together to achieve precise combined control of the force and position of the piston rod (12). Example

[0034] This embodiment specifically defines the material of the nut (22). The nut (22) is made of a metal-based self-lubricating composite material, which uses a high-strength copper alloy as the matrix and is filled with graphite or molybdenum disulfide as a solid lubricant. This material combination allows the friction pair formed by the nut pair and the lead screw (21) to have a stable friction coefficient between 0.05 and 0.2, and a compressive strength of not less than 50 MPa, making it particularly suitable for high-pressure and high-load conditions. Example

[0035] This embodiment adds a preload adjustment mechanism to the existing embodiment 1. The preload adjustment mechanism is integrated at the connection between the nut (22) and the piston rod (12), and can be a structure with double nuts and adjusting shims, or a threaded sleeve and locking nut. Through this mechanism, the axial transmission gap between the lead screw (21) and the nut (22) can be eliminated, and a constant preload force can be applied, thereby compensating for wear during long-term operation, maintaining the stability of the equivalent friction angle φ, and ensuring the long-term reliability of the self-locking performance. Example

[0036] This embodiment optimizes the key parameters of the device. The lead screw (21) is a trapezoidal lead screw, and its lead angle α is preferably in the range of 3° to 10°. The drive motor (23) is preferably a stepper motor or servo motor with an encoder. The friction pair between the lead screw (21) and the nut (22) is preferably lubricated with grease containing solid lubricating filler, and a grease replenishment device can be provided to add grease according to actual consumption in order to maintain a long-term stable coefficient of friction. Example

[0037] This embodiment specifies the lubrication method for the nut (22). The friction pair between the lead screw and the nut is lubricated with grease containing solid lubricating filler, and the consumed grease is added according to actual needs. Application areas The device described in this invention can be widely used in applications requiring high output force, positioning accuracy, and energy efficiency, such as, but not limited to: solar photovoltaic panel tracking systems, robot joint drive and control, various linear actuators, and high-precision hydraulic / pneumatic CNC equipment. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fluid pressure composite drive device based on lead screw self-locking precision control, comprising a fluid pressure execution unit (1), a lead screw precision control unit, a pressure source system, and a control unit, characterized in that: The fluid pressure actuator (1) includes a pressure cylinder (11) and a piston rod (12), wherein the piston rod (12) can move axially within the pressure cylinder (11); The lead screw precision control unit includes a lead screw (21), a nut (22) that cooperates with the lead screw (21), and a drive motor (23). The drive motor (23) is used to drive one of the lead screw (21) and the nut (22) to rotate, and the other is connected to the piston rod (12). The pressure source system is connected to the pressure cylinder (11) via a pipeline (31); The control unit is signal-connected to the pressure source system and is used to control the operating state of the pressure source system so as to adjust the fluid pressure in the pressure cylinder (11) through the actuator in the pressure source system; The lead angle α of the lead screw (21) and the equivalent friction angle φ of the lead screw nut (22) satisfy the following condition: |α-φ|<6°; The control unit is signal connected to the drive motor (23) and is configured to selectively control the drive motor (23) to enter a first working mode or a second working mode according to the load requirements. In the first working mode, the control unit controls the pressure source system to provide fluid pressure to the pressure cylinder (11) and controls the drive motor (23) to run, so that the axial movement direction of the piston rod (12) driven by the lead screw precision control unit and the fluid pressure is consistent with the action direction of the fluid pressure; In the second operating mode, the control unit controls the pressure source system to not provide or provide a low fluid pressure, and mainly relies on the drive motor (23) to drive the piston rod (12) to move.

2. The apparatus according to claim 1, characterized in that, The fluid pressure actuator (1) is a hydraulic cylinder or a pneumatic cylinder, and the pressure source system is a hydraulic source or a pneumatic source.

3. The apparatus according to claim 1, characterized in that, The pressure source system includes at least one of a high-pressure pressure source (32), a sub-high-pressure pressure source (33), and an adjustable pressure source (34).

4. The apparatus according to claim 1, characterized in that, The pressure source system is centrally located and connected to multiple fluid pressure actuators (1) via flexible pipelines (31).

5. The apparatus according to claim 1, characterized in that, The lead screw (21) is a trapezoidal lead screw with a lead angle α in the range of 3°-10°.

6. The apparatus according to claim 1, characterized in that, The drive motor (23) is a stepper motor or a servo motor with an encoder.

7. The apparatus according to claim 1, characterized in that, The nut (22) is made of a metal-based self-lubricating composite material, which is based on a copper alloy and filled with graphite or molybdenum disulfide as a solid lubricant.

8. The apparatus according to claim 1, characterized in that, The nut (22) is made of a metal-based self-lubricating composite material with self-healing properties and is filled with a continuously released solid lubricant to compensate for surface wear during long-term use.

9. The apparatus according to claim 1, characterized in that, The friction pair between the lead screw (21) and the nut (22) is lubricated with grease containing solid lubricating filler.

10. The apparatus according to any one of claims 7 to 9, characterized in that, The lead screw (21) and nut (22) adopt a double nut structure and are provided with a preload adjustment mechanism. The preload adjustment mechanism is used to eliminate axial clearance and apply preload force to compensate for wear and maintain a stable equivalent friction angle.

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