A high-precision hydraulic drive robot joint module

Abstract

The application discloses a high-precision hydraulic driving robot joint module and belongs to the technical field of rotary driving execution mechanisms. The application solves the problems of loose structure, high manufacturing cost, low precision and lack of dustproof lubrication of the existing hydraulic rotary joint. The joint module comprises an output shaft, a first flange, a second flange, two connecting shafts and two groups of symmetrically arranged hydraulic oil cylinders; the connecting shafts rigidly connect the two flanges to form a rigid frame, and the output shaft is supported at both ends by bearings on the two flanges; each group of oil cylinders comprises a fixed piston rod and a movable cylinder barrel, the piston rod is fixed at both ends on the two flanges, two independent axial oil holes are arranged in the piston rod and are connected with two working cavities of the oil cylinder and hydraulic oil ports on the two flanges, respectively; a pin shaft is arranged on the cylinder barrel, a double-head spiral groove is arranged on the outer periphery of the output shaft, and the pin shaft is in sliding fit with the spiral groove; the joint module further comprises a magnetic grid encoder and a dustproof cover, the dustproof cover forms a closed inner cavity with the two flanges and is filled with lubricating grease to realize dry oil lubrication.

Description

Technical Field

[0001] This invention relates to the field of rotary drive actuator technology, specifically a high-precision hydraulic drive robot joint module. Background Technology

[0002] In heavy-duty and harsh working environments, robot joint modules using electric drives are bulky, difficult to manufacture, and costly; therefore, hydraulic drives are more commonly used. Existing conventional hydraulic rotary joints suffer from uneven driving torque, poor motion stability, and lack precise displacement detection components, making it impossible to achieve accurate matching and control of linear displacement and rotation angle, thus failing to meet high-precision transmission requirements. Traditional helical gear hydraulic oscillating joints have a loose structure, are difficult to manufacture, inconvenient to maintain, and lack effective dustproof lubrication design, resulting in poor durability under harsh conditions. Therefore, developing a compact, low-cost, durable, highly accurate, easily maintainable hydraulic rotary joint with dustproof dry-oil lubrication has become an urgent technical problem to be solved in this field. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies by providing a high-precision hydraulically driven robot joint module, achieving core advantages such as compact structure, low manufacturing cost, durability, precise output rotation, and low maintenance cost. Furthermore, by adding a dust cover and constructing a closed lubrication chamber, it achieves dry oil lubrication of the internal transmission pairs and bearings, preventing dust intrusion and improving the service life and operational reliability of the joint under harsh working conditions.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A high-precision hydraulically driven robot joint module includes an output shaft, a first flange, a second flange, two connecting shafts, and two sets of hydraulic cylinders.

[0006] The two ends of the output shaft are rotatably supported by bearings on the first flange and the second flange, respectively.

[0007] Two connecting shafts are symmetrically arranged on both radial sides of the output shaft and parallel to the output shaft. The two ends of the connecting shafts are fixedly connected to the first flange and the second flange, respectively, forming a rigid frame.

[0008] Two sets of hydraulic cylinders are symmetrically arranged between the first flange and the second flange, respectively located on both sides of the output shaft. Each set of hydraulic cylinders includes a fixed piston rod and a linearly movable cylinder barrel. The two ends of the piston rod are fixedly connected to the first flange and the second flange, respectively. The piston rod has two independent axial oil holes, which connect the two working chambers of the hydraulic cylinder to two hydraulic oil ports provided on the first flange and the second flange, respectively.

[0009] The cylinder is equipped with a pin. The outer circumferential surface of the output shaft is provided with a double-headed helical groove, and the pin is slidably fitted into the helical groove.

[0010] External hydraulic oil enters the two working chambers of the hydraulic cylinder through the hydraulic oil port on the flange and the two independent axial oil holes in the piston rod, driving the cylinder to move linearly along the piston rod. The pin on the cylinder pushes the spiral groove on the output shaft, causing the output shaft to rotate.

[0011] To convert the linear motion of the hydraulic cylinders into the rotational motion of the output shaft while ensuring a compact structure and ease of assembly, this invention supports the output shaft at both ends to a first flange and a second flange via bearings, and the two flanges are rigidly connected by two symmetrical connecting shafts to form a rigid frame. Two sets of hydraulic cylinders are symmetrically arranged on both sides of the output shaft, with piston rods fixed to the flanges and cylinder barrels movable. The pins on the cylinder barrels slide into the double-headed helical grooves on the output shaft. This arrangement allows the cylinder barrels to move linearly after the hydraulic oil enters, while the pins slide along the helical grooves, forcing the output shaft to rotate. The symmetrical arrangement of the two cylinders ensures balanced driving torque, and the output shaft is not subjected to additional radial force. Two independent axial oil holes connect the two working chambers to the hydraulic oil ports on the two flanges, ensuring that the oil inlet and return paths do not interfere with each other and avoiding the problem of oil chambers being interconnected and unable to establish a pressure difference. This overall design requires no complex gear machining, has a compact structure, and low manufacturing cost.

[0012] To withstand both radial and bidirectional axial loads, and to ensure the coaxiality and axial positioning accuracy of the output shaft rotation, this invention uses an angular contact ball bearing, with the outer ring of the angular contact ball bearing in contact with the end face of the corresponding flange. This arrangement ensures that the axial position of the bearing's outer ring is precisely defined by the flange end face, preventing axial movement of the output shaft under heavy loads and bidirectional thrust, thus maintaining rotational accuracy over a long period.

[0013] To ensure the parallelism and spacing accuracy between the first and second flanges, and to facilitate the disassembly and maintenance of the joint, this invention features positioning stops at both ends of the connecting shaft, which precisely engage with the positioning holes on the flanges to achieve high-precision axial positioning. External threads are machined on the ends of the connecting shaft that protrude from the flanges, and the connection is secured with lock nuts. This design makes the entire frame a detachable rigid structure, ensuring rigidity during operation while allowing for the replacement of any individual component (such as the hydraulic cylinder). Maintenance can be performed without damaging the entire machine, significantly reducing maintenance costs.

[0014] To reduce transmission friction, improve motion smoothness and rotational accuracy, and avoid the gap and wear problems inherent in traditional tooth meshing, this invention uses a continuous, smooth, cylindrical, positively spaced spiral equidistant curved surface structure for the double-headed spiral groove. The pin is cylindrical, and the two are precisely fitted together to form a low-friction sliding pair. Simultaneously, a cylinder pin end cap is fixed to the end of the cylinder barrel, with the pin integrally formed on the outside of the end cap. This integral forming avoids the connection gaps and loosening that may occur with separate assembly, improving transmission reliability. The precise fit between the cylindrical pin and the continuous, smooth spiral groove ensures smooth motion without any crawling.

[0015] There is a definite proportional relationship between the linear displacement of the cylinder and the rotation angle of the output shaft, which allows the joint to calculate the rotation angle based on the cylinder stroke even without an angle sensor, and also facilitates the implementation of algorithms for closed-loop control. This invention sets each half-stroke of the cylinder's linear reciprocating movement to correspond to the output shaft rotation. The 180° ratio ensures a simple integer multiple relationship between the lead and the required rotational stroke angle. The control system requires no complex calculations and has no cumulative errors.

[0016] To address the shortcomings of existing hydraulic joints, such as the lack of precise displacement detection and the inability to achieve closed-loop angle control, this invention incorporates a magnetic encoder. The magnetic encoder is mounted on the connecting shaft, with its detection end fixedly connected to the outer wall of the cylinder. It detects the linear displacement of the cylinder in real time and feeds it back to the control system. The magnetic encoder is a non-contact measurement device, resistant to oil and dust, making it particularly suitable for harsh environments. Based on the cylinder displacement and the aforementioned proportional relationship, the control system accurately calculates the actual rotation angle of the output shaft, compares it with the target value, and adjusts the hydraulic valve to achieve high-precision closed-loop control. The positioning accuracy far exceeds that of traditional hydraulic swing joints.

[0017] To prevent impurities from entering the internal transmission pairs (pins and spiral grooves, bearings, etc.) under harsh working conditions such as dust and humidity, and to extend the service life of the joints, this invention adds a dust cover. The dust cover is fitted over the outside of the first and second flanges, with both ends sealing against the outer circumference of the flanges to form a closed inner cavity. All moving parts are located within this closed cavity. The cavity is filled with grease to achieve dry lubrication. Compared to thin oil lubrication, dry lubrication does not require a complex sealing and circulation system, is less prone to leakage, and the grease can adhere to the moving surfaces, preventing leakage even when installed at an angle or upside down, making it particularly suitable for any posture of the robot joint.

[0018] To further improve the sealing level and durability of the dust cover while maintaining a lightweight design, this invention uses wear-resistant and corrosion-resistant engineering plastics (such as polyoxymethylene and nylon) to make the dust cover, which is fixed to the flange with pins to prevent relative rotation or axial movement. A sealing ring is added to the contact surface between the dust cover and the flange to effectively prevent the intrusion of fine particles from water spray or high-concentration dust environments. This design allows the joint module to be used in extreme and harsh working conditions such as mining machinery, construction robots, and marine engineering equipment, significantly improving reliability.

[0019] To prevent hydraulic oil leakage from the connection between the piston rod and the flange, and to prevent external contaminants from entering the cylinder through this connection, this invention incorporates a seal (such as an O-ring) at the connection point. Since the piston rod remains stationary, this seal is a static seal, characterized by its simple structure, high reliability, and long service life. This ensures the sealing integrity of the hydraulic system and prevents pressure drops and environmental pollution caused by leakage.

[0020] To ensure that the two symmetrically arranged hydraulic cylinders generate equal and directional thrust under the same oil pressure, and to enable synchronous movement of the two cylinders without uneven loading, this invention designs the two rod-side chambers of the two sets of hydraulic cylinders to have the same effective cross-sectional area. If the cross-sectional areas are different, the cylinders on both sides will move at different speeds, leading to additional bending moments on the output bearing, which can cause jamming or premature bearing wear in severe cases. This design ensures the smooth movement and transmission accuracy of the joint module, and extends the life of the sliding pairs and bearings.

[0021] In summary, compared with existing helical gear hydraulic swing joints, the present invention has the advantages of compact structure, low manufacturing cost, durability, precise output rotation, and low maintenance cost, and can be adapted to harsh working conditions with high dust and humidity.

[0022] This invention provides a high-precision hydraulically driven robot joint module, which has the following advantages:

[0023] 1. Compact structure and high power density

[0024] This invention abandons the complex tooth structure and bulky housing required by traditional helical gear meshing, and adopts a modular design with a symmetrical arrangement of piston rod fixed double-acting hydraulic cylinders and the output shaft directly supported by the flanges at both ends. The two connecting shafts fasten the first and second flanges into a rigid integral frame, and the hydraulic cylinder, pin shaft, and helical groove are all accommodated between the two flanges. The overall size is small and easy to integrate into the narrow arm segment of an articulated robot.

[0025] 2. Manufacturing costs are significantly reduced.

[0026] Traditional helical gear oscillating joints require high-precision helical teeth to be machined on the inner wall of the cylinder. This tooth machining requires specialized equipment, resulting in high tool costs and low efficiency. This invention replaces tooth meshing with a sliding fit between a pin and a helical groove. The helical groove can be machined on a standard CNC lathe, and the pin is simply formed from a standard round bar, eliminating the need for high-precision tooth machining equipment. This significantly reduces the difficulty of component machining and material costs, resulting in an overall manufacturing cost far lower than that of helical gear hydraulic oscillating joints.

[0027] 3. High output rotation accuracy and good controllability

[0028] This invention integrates a magnetic encoder to detect the linear displacement of the cylinder in real time, and combines this with a fixed proportional relationship that "a cylinder moving half a lead corresponds to a 180° rotation of the output shaft," achieving backlash-free angular displacement feedback. The magnetic encoder is a non-contact measurement device with no mechanical hysteresis. The detection data can be fed back to the control system, enabling closed-loop precise control of the output shaft rotation angle, with positioning accuracy far exceeding that of traditional helical gear joints.

[0029] 4. High durability and adaptable to harsh working conditions.

[0030] This invention incorporates a dust cover and adds a sealing ring to its contact surface with the flange, forming a fully enclosed inner cavity filled with grease for dry lubrication. Key friction components such as the sliding pair between the pin and the spiral groove, and the angular contact ball bearing, are always kept in a clean and well-lubricated environment, isolating them from external dust and preventing corrosion of internal components. Compared to open structures or those relying solely on dust covers, this invention completely blocks the path for dust and water mist to enter the joint, eliminating leakage risks and significantly improving operational reliability under harsh conditions.

[0031] 5. Easy to repair and low maintenance cost

[0032] This invention employs a modular, split-type structure: the output shaft and bearing are integrated as a single unit, while the two hydraulic cylinders are separate components. The connecting shaft and flange are connected via a lock nut, and the dust cover is a detachable part. When a component wears out or fails, simply remove the dust cover, loosen the lock nut, and remove the second flange to individually extract the faulty hydraulic cylinder for repair or replacement, without needing to disassemble the output shaft, the other hydraulic cylinder, or the bearing. This simplifies maintenance and significantly reduces labor and parts costs.

[0033] 6. The driving torque is smooth and without pulsation.

[0034] Two sets of hydraulic cylinders are symmetrically arranged, and the two rod-side chambers have the same effective cross-sectional area. Under the same oil pressure, they generate equal and parallel thrusts, which jointly drive the output shaft to rotate, resulting in balanced force on the output shaft. Simultaneously, the pin engages with a continuous, smooth, cylindrical, helical, equidistant curved groove, ensuring a constant transmission ratio throughout the entire stroke. This eliminates torque fluctuations caused by tooth pitch errors or backlash during toothed meshing, resulting in smooth motion, making it particularly suitable for robot applications requiring precise force control. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0037] Figure 2 for Figure 1 A cross-sectional view of the overall structure of AA.

[0038] Figure 3 This is a schematic diagram of the external structure of the present invention.

[0039] In the diagram: 1 - Output shaft, 2 - Angular contact ball bearing, 3 - First flange, 4 - Second flange, 5 - Cylinder end cover, 6 - Cylinder pin end cover, 7 - Piston rod, 8 - Cylinder barrel, 9 - Locking nut, 10 - Connecting shaft, 11 - Magnetic encoder, 12 - Dust cover. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] See Figure 1 and Figure 3 This embodiment provides a high-precision hydraulically driven robot joint module, which is suitable for the wrist joint or base rotation joint of engineering robotic arms, requiring heavy load, high precision and working environment with high dust.

[0043] like Figure 1-2As shown, the joint module includes an output shaft 1, two sets of angular contact ball bearings 2, a first flange 3, a second flange 4, a cylinder end cover 5, a cylinder pin end cover 6, two fixed piston rods 7, two movable cylinders 8, a locking nut 9, two connecting shafts 10, a magnetic encoder 11, and a dust cover 12.

[0044] Bearings are installed at both ends of the output shaft 1. The left end of the output shaft 1 is mounted in the central shaft hole of the first flange 3 via a set of angular contact ball bearings 2, and the right end is mounted in the central shaft hole of the second flange 4 via another set of angular contact ball bearings 2. The outer ring of each set of angular contact ball bearings 2 is interference-fitted with the inner wall of the corresponding flange shaft hole, and the inner ring of the bearing is interference-fitted with the journal of the output shaft 1. The end face of the outer ring of the angular contact ball bearing 2 is tightly fitted with the end face of the flange to withstand bidirectional axial loads. In this way, the output shaft 1 can rotate freely relative to the first flange 3 and the second flange 4 without axial movement.

[0045] like Figures 1-3 As shown, two connecting shafts 10 are symmetrically arranged on both radial sides of the output shaft 1, and the axis of the connecting shafts 10 is parallel to the axis of the output shaft 1. Each connecting shaft 10 has a locating stop (i.e., a cylindrical section with a slightly smaller diameter) machined at both ends. Locating holes are provided at corresponding positions on the first flange 3 and the second flange 4. During assembly, the locating stops at both ends of the connecting shaft 10 are inserted into the locating holes of the first flange 3 and the second flange 4, respectively, to achieve high-precision coaxial positioning. The ends of the connecting shaft 10 that protrude from the flanges are machined with external threads. The locking nut 9 engages with these external threads, pressing the first flange 3 and the second flange 4 towards the center from the outside, making the entire structure a rigid integral frame. The spacing of this frame is equal to the length between the locating stops at both ends of the connecting shaft 10.

[0046] like Figure 1-2 As shown, two sets of hydraulic cylinders are symmetrically arranged on the left and right sides of the output shaft 1, located between the first flange 3 and the second flange 4. Each set of hydraulic cylinders includes a fixed piston rod 7 and a linearly movable cylinder 8.

[0047] The piston rod 7 is a hollow structure with two independent axial oil holes inside, extending from both ends of the piston rod 7 towards the middle but not connecting to each other. At the end of each axial oil hole (located in the working chamber), a radial oil hole is provided, extending to the outer cylindrical surface of the piston rod 7 and opening into the annular working chamber between the cylinder 8 and the piston rod 7. Both ends of the piston rod 7 are inserted into the corresponding shaft holes of the first flange 3 and the second flange 4, respectively, and are fixedly connected by threads or flange bolts. O-rings (seals) are installed at the connection between the piston rod 7 and the flanges to achieve a static seal and prevent hydraulic oil leakage.

[0048] The cylinder 8 is cylindrical and fits around the piston rod 7. Its inner bore slides into the outer cylindrical surface of the piston rod 7, and a piston sealing ring is provided on the mating surface. A cylinder end cover 5 is fixed to the left end of the cylinder 8, and a cylinder pin end cover 6 is fixed to the right end. Both are connected to the cylinder 8 by screws and sealed with sealing rings. A protruding pin is integrally formed on the outer side of the cylinder pin end cover 6 (the side facing the output shaft 1). The end of the pin is machined into a hemispherical or arc shape.

[0049] The outer circumferential surface of the middle part of the output shaft 1 (i.e., the part located between the first flange 3 and the second flange 4) is machined with a continuous, smooth cylindrical positive spiral equidistant curved surface groove. The cross-section of the spiral groove is cylindrical, forming a precision clearance fit with the pin. The lead of the spiral groove is determined according to the ratio of the required rotation angle to the cylinder stroke. In this embodiment, when the cylinder 8 moves linearly by half a lead, the output shaft 1 rotates exactly 180°. Therefore, if the output shaft needs to rotate ±180°, the cylinder stroke reciprocates by half a pitch S. In addition, by improving the fit accuracy between the pin and the cylindrical positive spiral equidistant spiral groove, optimizing the bearing support, and enhancing the rigidity of the main shaft, high-precision repeatable positioning output of the output shaft 1 can be achieved; by increasing the hardness of the contact surface between the pin and the cylindrical positive spiral equidistant curved surface groove, wear resistance and durability are improved.

[0050] like Figure 3 As shown, the magnetic encoder 11 includes a magnetic scale and a reading head. The magnetic scale is a flexible steel strip, attached to the side wall of the connecting shaft 10; the reading head is fixedly mounted on the outer wall of the cylinder 8 via an L-shaped bracket and moves synchronously with the cylinder 8. A non-contact gap is maintained between the reading head and the magnetic scale. When the cylinder 8 moves, the reading head reads the position information on the magnetic scale and outputs a linear displacement signal in real time. This signal is connected to the robot controller, which calculates the real-time angle of the output shaft 1 based on the proportional relationship of "half a lead S corresponds to 180°", compares it with the command angle, and adjusts the hydraulic oil flow and direction through a servo valve to achieve closed-loop control.

[0051] like Figures 1-3 As shown, the dust cover 12 is a cylindrical shell, injection molded from engineering plastics (such as polyoxymethylene POM). The inner diameters of both ends of the dust cover 12 are slightly larger than the outer diameters of the first flange 3 and the second flange 4. After being fitted over the flanges, sealing rings are provided between the two ends and the outer circumferential surface of the flanges. The dust cover 12 is fixed to the flanges by radial pins to prevent circumferential rotation or axial detachment. The dust cover 12, the first flange 3, and the second flange 4 together form a closed inner cavity. This inner cavity is filled with sufficient grease (dry oil lubricating medium) so that all transmission pairs (pins and spiral grooves, angular contact ball bearings 2, and sliding surfaces of piston rods and cylinders) are immersed or wetted in the grease and isolated from external dust and moisture.

[0052] High-pressure oil supplied by an external hydraulic pump station enters an independent axial oil hole in the piston rod 7 of the upper hydraulic cylinder through a control valve group and a hydraulic oil port on the first flange 3. The oil then flows into the working chamber (rod chamber) of the upper cylinder near the first flange 3 through a radial oil hole at the end of the hydraulic oil port. The hydraulic oil pressure acts on the annular force-bearing surface inside the cylinder 8, pushing the cylinder 8 towards the second flange 4.

[0053] The volume of the other working chamber of the upper cylinder (near the second flange 4) decreases when the cylinder 8 moves. The hydraulic oil inside returns to the oil tank through the radial oil hole on the piston rod 7, another independent axial oil hole, and the oil port on the second flange 4. A seal is provided at the joint between the end face of the piston rod 7 and the flange oil port to ensure that the oil circuit is unobstructed and leak-free.

[0054] Simultaneously, the lower hydraulic cylinder is supplied with oil in the same manner: oil enters the working chamber of the lower cylinder near the first flange 3, and oil returns from its other working chamber. At this time, both cylinders 8 move synchronously towards the second flange 4.

[0055] When the cylinder 8 moves, the pin on the cylinder pin end cap 6 fixed at its end moves accordingly. Since the pin is embedded in the spiral groove of the output shaft 1, and the curved surface of the spiral groove has a guiding effect, the linear motion of the pin is forcibly converted into a thrust along the tangential direction of the groove, causing the output shaft 1 to rotate around its axis.

[0056] Let the lead of the spiral groove be S. When the cylinder 8 moves a certain distance... When x, the rotation angle θ of output shaft 1 is 360° × ( x / S). In this embodiment, the output shaft 1 rotates 180° when the cylinder 8 moves linearly by half a lead (S / 2) (lead S corresponds to a 360° rotation of the output shaft 1).

[0057] If the output shaft 1 needs to rotate in the opposite direction, then reverse oil supply is used: the working chambers of the two cylinders near the second flange 4 are simultaneously supplied with oil, and the working chambers near the first flange 3 are simultaneously returned with oil, and the two cylinders 8 move synchronously towards the first flange 3.

[0058] Because the two sets of hydraulic cylinders are symmetrically arranged and have identical structural parameters (equal effective cross-sectional area of ​​the rod chamber, same piston rod diameter, and same oil supply pressure), the thrust they generate is equal in magnitude and parallel in direction, jointly driving the output shaft 1 to rotate without generating additional bending moment. If only a single-sided cylinder is used, the output shaft will be subjected to radial force, increasing bearing wear and reducing accuracy. The symmetrical arrangement ensures balanced force on the output shaft and smooth movement.

[0059] The control system sets the target rotation angle θ target The controller is based on θ target Calculate the required displacement change of the cylinder. target= (θ target / 360°)×S(lead) (because the lead S corresponds to 360°). The magnetic encoder 11 provides real-time feedback on the actual cylinder position. actual The controller calculates the change in linear displacement of the cylinder in real time. It outputs control signals to adjust the opening size and direction of the hydraulic servo valve until... target Because magnetic encoders have high resolution, they can achieve precise control over the output shaft angle.

[0060] The dust cover 12 prevents cement dust, metal shavings, water mist, and other contaminants from entering the joint. Simultaneously, the internal grease not only lubricates all moving parts but also suspends trace particles generated during wear, preventing abrasive wear. Compared to thin oil lubrication, dry grease lubrication avoids leakage due to seal aging, making it particularly suitable for robot joints that cannot be frequently maintained. The clearance fit between the pin and the helical groove, aided by the grease, results in minimal friction and no creeping.

[0061] Typical working examples

[0062] Scenario: The shoulder joint of a six-degree-of-freedom heavy-duty hydraulic robotic arm, requiring reciprocating swing with a large load torque, in an open-pit mine (dusty and rainy).

[0063] Initial state: Output shaft 1 is at 0° position, and magnetic encoder 11 is zeroed.

[0064] Command: The controller issues a rotation command of +90°.

[0065] Calculate: The linear displacement of the cylinder corresponding to +90° = (90° / 360°)×S = S / 4.

[0066] Action: The controller opens the servo valve, and high-pressure oil simultaneously enters the working chambers of the left and right cylinders near the first flange 3, pushing the two cylinders 8 to move synchronously a distance P / 4 towards the second flange 4. The pin pushes the helical groove, and the output shaft 1 rotates 90° clockwise. The magnetic encoder continuously detects the displacement, and when the set value is reached, the controller closes the valve and locks the position. The entire dynamic response is rapid, and the repeatability is high.

[0067] Protection verification: After continuous operation in a water mist and dust environment, disassembly and inspection revealed no visible dust inside the dust cover, the grease did not change color, and there were no scratches on the pin and spiral groove surfaces.

[0068] It should be noted that the two sets of hydraulic cylinders must maintain a symmetrical, double-acting structure with the same effective cross-sectional area of ​​the rod chamber. They cannot be simplified to single-sided spring return or single-acting cylinders; otherwise, bidirectional equal torque output and precise rotational positioning cannot be achieved.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-precision hydraulically driven robot joint module, characterized in that, include: Output shaft (1); The first flange (3) and the second flange (4) are respectively supported by bearings at both ends of the output shaft (1) on the first flange (3) and the second flange (4). Two connecting shafts (10) are symmetrically arranged on both sides of the output shaft (1) and parallel to the output shaft (1). The two ends of the connecting shafts (10) are fixedly connected to the first flange (3) and the second flange (4) respectively, forming a rigid frame. Two sets of hydraulic cylinders are symmetrically arranged between the first flange (3) and the second flange (4) and located on both sides of the output shaft (1). Each set of hydraulic cylinders includes a fixed piston rod (7) and a linearly movable cylinder (8). The two ends of the piston rod (7) are fixedly connected to the first flange (3) and the second flange (4) respectively. The piston rod (7) is provided with two independent axial oil holes, which are respectively connected to the two working chambers of the hydraulic cylinder and the two hydraulic oil ports provided on the first flange (3) and the second flange (4); The cylinder (8) is provided with a pin; The outer circumferential surface of the output shaft (1) is provided with a double-headed spiral groove, and the pin is slidably fitted in the spiral groove.

2. The high-precision hydraulically driven robot joint module according to claim 1, characterized in that, The bearing is an angular contact ball bearing (2), and the outer ring of the angular contact ball bearing (2) is in contact with the end face of the corresponding flange.

3. A high-precision hydraulically driven robot joint module according to claim 1, characterized in that, The connecting shaft (10) has positioning stops at both ends, and the ends of the connecting shaft (10) that pass through the first flange (3) and the second flange (4) are respectively provided with external threads. The first flange (3) and the second flange (4) are fastened together by locking nuts (9).

4. A high-precision hydraulically driven robot joint module according to claim 1, characterized in that, The double-headed spiral groove is a continuous and smooth cylindrical positive spiral equidistant curved surface structure. The pin is cylindrical and is precisely clearance-fitted with the inner wall of the spiral groove. The end of the cylinder (8) is fixed with a cylinder pin end cap (6), and the pin is integrally formed on the outside of the cylinder pin end cap (6).

5. A high-precision hydraulically driven robot joint module according to claim 1, characterized in that, The linear reciprocating movement of the cylinder (8) by half a lead S corresponds to the rotation of the output shaft (1). 180°.

6. A high-precision hydraulically driven robot joint module according to claim 1, characterized in that, It also includes a magnetic encoder (11), which is mounted on the connecting shaft (10). Its detection end is fixedly connected to the outer wall of the cylinder (8) for real-time detection of the linear displacement position of the cylinder (8) and feedback to the control system to realize closed-loop control of the rotation angle of the output shaft (1).

7. A high-precision hydraulically driven robot joint module according to claim 1, characterized in that, It also includes a dust cover (12), which is fitted on the outside of the first flange (3) and the second flange (4). Both ends are sealed with the outer periphery of the flange to form a closed inner cavity. The hydraulic cylinder, pin, spiral groove and bearing are all located in the closed inner cavity. The closed inner cavity is filled with grease to achieve dry oil lubrication.

8. A high-precision hydraulically driven robot joint module according to claim 7, characterized in that, The dust cover (12) is made of wear-resistant and corrosion-resistant engineering plastic and is fixed to the flange by pins; the contact surface between the dust cover (12) and the flange is provided with a sealing ring.

9. A high-precision hydraulically driven robot joint module according to claim 1, characterized in that, The connection between the piston rod (7) and the flange is provided with a seal.

10. A high-precision hydraulically driven robot joint module according to claim 1, characterized in that, The effective cross-sectional areas of the two rod-side chambers of the two sets of hydraulic cylinders are the same.

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