An electrostatic hydraulic actuator for robot joints

Abstract

The present invention belongs to the field of robotics and discloses an electrostatic hydraulic actuator for a robot joint, comprising a motor, a two-dimensional plunger pump, and a swing cylinder. The swing cylinder comprises a swing cylinder stator and a swing cylinder rotor. The outer wall of the swing cylinder stator is surrounded by a plurality of swing cylinder stator blades. The swing cylinder stator is also provided with a first swing cylinder stator oil-passing structure and a second swing cylinder stator oil-passing structure. The inner wall of the swing cylinder rotor is surrounded by a plurality of swing cylinder rotor blades. The cavity between the outer wall of the swing cylinder stator and the inner wall of the swing cylinder rotor is divided into a plurality of first working chambers and a second working chamber by the swing cylinder stator blades and the swing cylinder rotor blades. The two-dimensional plunger pump is provided with a first plunger pump oil-passing structure and a second plunger pump oil-passing structure. The present invention abandons the integrated valve block and removes the overflow valve required for general EHA overload protection. Overload protection is achieved through motor stall detection, thereby minimizing the size of the EHA and reducing costs.

Description

Technical Field

[0001] The present invention relates to the field of robots, and in particular to an electrostatic hydraulic actuator for robot joints. Background Art

[0002] Robots have been widely used in automated industrial production lines. Currently, robot joints typically utilize servo motors coupled with harmonic or RV reducers as actuators. However, these actuators suffer from low power density. Hydraulic systems, by contrast, offer advantages such as a high power-to-weight ratio, compact design, fast response, and stable operation at low speeds. However, due to the high energy loss, oil contamination and leakage, and high noise levels associated with traditional hydraulic systems, their application in robotics remains limited. Technological advancements have led to the development of electrostatic hydraulic actuators (EHAs). These closed-loop pump-controlled systems not only offer the high power-to-weight ratio and high output of traditional hydraulic systems, but also boast significant advantages such as high electromechanical integration, high energy efficiency, and high reliability. Current EHAs typically integrate the servo motor, hydraulic pump, relief valve, hydraulic cylinder, and other auxiliary hydraulic components and sensors through integrated valve blocks or tubing. This results in a bulky and bulky overall structure. Furthermore, the frequent forward and reverse rotation of the motor causes significant heat generation, which in turn limits the performance of hydraulic robots.

[0003] At present, there are two main forms of motion output of rotary hydraulic joints in China. One is to use a direct-acting cylinder through a gear rack, a spiral mechanism or other linear rotation conversion mechanism to achieve the output of rotational motion and torque. Due to the existence of the motion conversion mechanism, this inevitably causes the overall size of the entire mechanism to be large, power loss and low motion accuracy. The other commonly used is the vane-type swing cylinder, which can directly convert the hydraulic pressure into rotational motion and torque output. However, most of the current vane-type swing cylinders have the problems of large size and heavy mass. If the volume of the vane-type swing cylinder is reduced, it is necessary to consider the problem of excessive leakage or jamming due to deformation under the action of hydraulic pressure. Summary of the Invention

[0004] The object of the present invention is to provide an electrostatic hydraulic actuator for a robot joint to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An electrostatic hydraulic actuator for a robot joint comprises a motor and a two-dimensional plunger pump connected to the motor, and also comprises a swing cylinder arranged on the motor and sleeved on the outside of the two-dimensional plunger pump;

[0007] The oscillating cylinder includes a oscillating cylinder stator sleeved on the outside of the two-dimensional plunger pump and a oscillating cylinder rotor rotatably sleeved on the outside of the oscillating cylinder stator, the outer wall of the oscillating cylinder stator is surrounded by a plurality of oscillating cylinder stator blades, and the oscillating cylinder stator is also provided with a first oscillating cylinder stator oil-passing structure and a second oscillating cylinder stator oil-passing structure, the inner wall of the oscillating cylinder rotor is surrounded by a plurality of oscillating cylinder rotor blades, the oscillating cylinder stator blades and the oscillating cylinder rotor blades are staggered, and the cavity between the outer wall of the oscillating cylinder stator and the inner wall of the oscillating cylinder rotor is divided into a plurality of first working chambers and second working chambers by the oscillating cylinder stator blades and the oscillating cylinder rotor blades, the first working chamber and the second working chamber are also staggered, the first working chamber is communicated with the first oscillating cylinder stator oil-passing structure, and the second working chamber is communicated with the second oscillating cylinder stator oil-passing structure;

[0008] The two-dimensional plunger pump is provided with a first plunger pump oil-passing structure and a second plunger pump oil-passing structure, wherein the first plunger pump oil-passing structure is correspondingly connected to the first swing cylinder stator oil-passing structure, and the second plunger pump oil-passing structure is correspondingly connected to the second swing cylinder stator oil-passing structure;

[0009] The electrostatic hydraulic actuator for the robot joint is configured as follows: the motor drives the two-dimensional plunger pump to work, and the two-dimensional plunger pump sucks and discharges the oil in the first working chamber through the first plunger pump oil-passing structure and the first swing cylinder stator oil-passing structure, and sucks and discharges the oil in the second working chamber through the second plunger pump oil-passing structure and the second swing cylinder stator oil-passing structure, so that the volumes of the first working chamber and the second working chamber increase and decrease, thereby driving the swing cylinder rotor to rotate.

[0010] Furthermore, the first swing cylinder stator oil passage structure includes a first stator oil groove and a first swing cylinder stator oil hole. The first stator oil groove is arranged on the inner wall of the first swing cylinder stator and is connected to the first plunger pump oil passage structure. One end of the first swing cylinder stator oil hole is connected to the first stator oil groove, and the other end is connected to the first working chamber.

[0011] Furthermore, the second swing cylinder stator oil passage structure includes a second stator oil groove and a second swing cylinder stator oil hole, the second stator oil groove is arranged on the inner wall of the first swing cylinder stator, and one end of the second swing cylinder stator oil hole is connected to the second stator oil groove, and the other end is connected to the second working chamber.

[0012] Furthermore, concave oil storage tanks are respectively provided on both sides of the swing cylinder rotor blades.

[0013] Furthermore, the two-dimensional plunger pump includes a pump body and a plunger slidably inserted in the pump body. The inner cavity between the plunger and the pump body is divided into a first plunger cavity and a second plunger cavity by a boss on the plunger. The first plunger cavity and the second plunger cavity are sucked and discharged in turn as the plunger reciprocates, and the volumes of the first plunger cavity and the second plunger cavity increase and decrease.

[0014] The first plunger pump oil passage structure includes a first undercut groove and a first oil suction and discharge port. The first undercut groove is provided on the outer wall of the pump body and is communicated with the first swing cylinder stator oil passage structure. One end of the first oil suction and discharge port is communicated with the first plunger cavity, and the other end is communicated with the first undercut groove.

[0015] The second plunger pump oil passage structure includes a second countersunk groove and a second oil suction and discharge port. The second countersunk groove is arranged on the outer wall of the pump body and is connected to the second swing cylinder stator oil passage structure. One end of the second oil suction and discharge port is connected to the second plunger cavity, and the other end is connected to the second countersunk groove.

[0016] Furthermore, the motor is a wet brushless motor, which includes a motor pump housing and a motor shaft, an oil separator, a motor stator winding, a magnet and a motor rotor arranged in the motor pump housing. The oil separator separates the inner cavity of the motor pump housing into a first oil area and a motor stator mounting cavity. The motor shaft, magnet and motor rotor are located in the first oil area. The motor shaft and the oil separator are rotatably connected through a bearing. The motor rotor is connected to the motor shaft. The magnet ring is arranged on the motor rotor. The motor stator winding is arranged in the motor stator mounting cavity and is arranged opposite to the magnet.

[0017] Furthermore, the upper end of the motor pump housing has a mounting port, the lower end of the two-dimensional plunger pump extends into the mounting port and is connected to the motor shaft, the lower roller and lower curved guide rail of the two-dimensional plunger pump are located in the mounting port, and the first oil area is connected to the mounting port.

[0018] Furthermore, the upper end of the swing cylinder stator has a third oil area, and the upper roller and upper curved guide rail of the two-dimensional plunger pump are located in the third oil area.

[0019] Furthermore, a swing cylinder rotor hoop is provided on the outer wall of the swing cylinder rotor, a second rotor bushing and a first rotor bushing are provided at the upper and lower ends of the swing cylinder rotor respectively, and an end cover is provided at the upper end of the swing cylinder stator.

[0020] Compared with existing technologies, this invention offers the following advantages: it eliminates the integrated valve block and the overflow valve typically required for EHA overload protection. Instead, it implements overload protection through motor stall detection, minimizing the size and cost of the EHA. The moving components of the pump and motor in the EHA are immersed in oil, providing sufficient lubrication to reduce friction and wear, slow operating temperature rise, and absorb noise. The modular design of this invention allows for component selection based on actual operating conditions, resulting in a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the main structure of the present invention;

[0022] Figure 2This is a schematic diagram of the cross-sectional structure of the main view of the present invention, in which the two-dimensional plunger pump is not cut open;

[0023] Figure 3 This is a schematic diagram of the three-dimensional cross-sectional structure of the present invention;

[0024] Figure 4 This is a schematic diagram of the top view of the structure of the present invention when the bushing and the end cover are removed;

[0025] Figure 5 It is the structural diagram of the swing cylinder rotor;

[0026] Figure 6 It is a structural diagram of the swing cylinder stator;

[0027] Figure 7 This is a schematic diagram of the cross-sectional structure of the main view of the swing cylinder stator;

[0028] Figure 8 It is a schematic diagram of the cross-sectional structure of the left side view of the swing cylinder stator;

[0029] Figure 9 Schematic diagram of the plunger structure of a two-dimensional plunger pump.

[0030] In the figure: 1 motor, 2 swing cylinder, 3 motor shaft, 4 first oil area, 5 oil separator, 6 motor stator winding, 7 magnet, 8 motor pump housing, 9 motor rotor, 10 coupling, 11 first rotor bushing, 12 swing cylinder rotor hoop, 13 second undercut groove, 14 second oil area, 15 first undercut groove, 16 swing cylinder rotor, 17 swing cylinder stator, 18 second rotor bushing, 19 end cover, 20 third oil area, 21 suction and discharge port, 22 pump sealing groove, 23 two-dimensional plunger pump, 2 4 Swinging cylinder rotor blades, 25 Swinging cylinder stator blades, 26 Oil storage tank, 27 First swing cylinder stator oil hole, 28 Second swing cylinder stator oil hole, 29 First stator oil groove, 30 Second stator oil groove, 31 First working chamber, 32 Second working chamber, 33 First plunger chamber, 34 Second plunger chamber, 35 Pump body, 36 Plunger, 37 Lower roller, 38 Lower curved guide rail, 39 Upper roller, 40 Upper curved guide rail, 41 Lower distribution groove, 42 Upper distribution groove, 43 Mounting port. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] See also Figures 1-9An electrostatic hydraulic actuator for a robot joint includes a motor 1, a two-dimensional plunger pump 23 connected to the motor 1, and a swing cylinder 2 arranged on the motor 1 and sleeved on the outside of the two-dimensional plunger pump 23. The swing cylinder 2 includes a swing cylinder stator 17 that is sleeved on the outside of the two-dimensional plunger pump 23 and a swing cylinder rotor 16 that is rotatably sleeved on the outside of the swing cylinder stator 17. A number of swing cylinder stator blades 25 are arranged around the outer wall of the swing cylinder stator 17. The swing cylinder stator 17 is also provided with a first swing cylinder stator oil-passing structure and a second swing cylinder stator oil-passing structure. A number of swing cylinder rotor blades 24 are arranged around the inner wall of the swing cylinder rotor 16. The swing cylinder stator blades 25 and the swing cylinder rotor blades 24 are arranged alternately. The cavity between the outer wall of the swing cylinder stator 17 and the inner wall of the swing cylinder rotor 16 is divided into a number of first working chambers 31 and second working chambers 32 by the swing cylinder stator blades 25 and the swing cylinder rotor blades 24. The first working chamber 31 and the second working chamber 32 are also arranged alternately. The first working chamber 31 is connected to the first swing cylinder stator oil-passing structure, and the second working chamber 32 is connected to the second swing cylinder stator oil-passing structure. The two-dimensional plunger pump 23 is provided with a first plunger pump oil-passing structure and a second plunger pump oil-passing structure. The first plunger pump oil-passing structure is correspondingly connected to the first swing cylinder stator oil-passing structure, and the second plunger pump oil-passing structure is correspondingly connected to the second swing cylinder stator oil-passing structure.

[0033] When the electrostatic hydraulic actuator for the robot joint is working, the motor 1 drives the two-dimensional plunger pump 23 to work. The two-dimensional plunger pump 23 sucks and discharges the oil in the first working chamber 31 through the first plunger pump oil-passing structure and the first swing cylinder stator oil-passing structure, and sucks and discharges the oil in the second working chamber 32 through the second plunger pump oil-passing structure and the second swing cylinder stator oil-passing structure, so that the volume of the first working chamber 31 and the second working chamber 32 increases and decreases, thereby driving the swing cylinder rotor 16 to rotate.

[0034] Continue reading Figure 6-Figure 8 The first swing cylinder stator oil passage structure includes a first stator oil passage groove 29 and a first swing cylinder stator oil passage hole 27. The first stator oil passage groove 29 is arranged on the inner wall of the first swing cylinder stator 17, and is connected to the first plunger pump oil passage structure. One end of the first swing cylinder stator oil passage hole 27 is connected to the first stator oil passage groove 29, and the other end is connected to the first working chamber 31.

[0035] Continue reading Figure 6-Figure 8 The second swing cylinder stator oil passage structure includes a second stator oil passage groove 30 and a second swing cylinder stator oil passage hole 28. The second stator oil passage groove 30 is arranged on the inner wall of the first swing cylinder stator 17. One end of the second swing cylinder stator oil passage hole 28 is connected to the second stator oil passage groove 30, and the other end is connected to the second working chamber 32.

[0036] Continue reading Figure 4 and Figure 5Concave oil storage tanks 26 are respectively provided on both sides of the swing cylinder rotor blade 24.

[0037] Continue reading Figure 2 、 Figure 3 、 Figure 9 The two-dimensional plunger pump 23 includes a pump body 35 and a plunger 36 slidably inserted into the pump body 35. The inner cavity between the plunger 36 and the pump body 35 is divided into a first plunger cavity 33 and a second plunger cavity 34 by a boss on the plunger 36. The first plunger cavity 33 and the second plunger cavity 34 suck and discharge oil one by one as the plunger reciprocates, and the volumes of the two increase and decrease. The first plunger pump oil passage structure includes a first countersunk groove 15 and a first oil suction and discharge port. The first countersunk groove 15 is provided on the outer wall of the pump body and is connected to the first swing cylinder stator oil passage structure. One end of the first oil suction and discharge port is connected to the first plunger cavity 33, and the other end is connected to the first countersunk groove 15. The second plunger pump oil passage structure includes a second countersunk groove 13 and a second oil suction and discharge port. The second countersunk groove 13 is provided on the outer wall of the pump body and is connected to the second swing cylinder stator oil passage structure. One end of the second oil suction and discharge port is connected to the second plunger cavity 34, and the other end is connected to the second countersunk groove 13. The first oil suction and discharge port and the second oil suction and discharge port are collectively referred to as the oil suction and discharge port 21 .

[0038] Continue reading Figure 2 and Figure 3 The motor 1 is preferably a wet brushless motor, which includes a motor pump housing 8 and a motor shaft 3, an oil separator 5, a motor stator winding 6, a magnet 7 and a motor rotor 9 arranged in the motor pump housing 8. The oil separator 5 divides the inner cavity of the motor pump housing 8 into a first oil area 4 and a motor stator mounting cavity. The motor shaft 3, the magnet 7 and the motor rotor 9 are located in the first oil area 4. The motor shaft 3 is rotatably connected to the oil separator 5 through a bearing. The motor rotor 9 is connected to the motor shaft 3. The motor shaft 3 is connected to the two-dimensional plunger pump 23 through a coupling 10. The magnet 7 is annularly arranged on the motor rotor 9. The motor stator mounting cavity is an annular cavity. The motor stator winding 6 is arranged in the motor stator mounting cavity and is arranged opposite to the magnet 7. The upper end of the motor pump housing 8 has a mounting opening 43. The lower end of the two-dimensional plunger pump 23 extends into the mounting opening 43 and is connected to the motor shaft 3. The lower roller 37 and lower curved guide rail 40 of the two-dimensional plunger pump 23 are located in the mounting opening 43. The first oil area 4 is connected to the mounting opening 43. The oil in the first oil area 4 can lubricate the lower roller 37 and lower curved guide rail 40. The operating principle of the brushless motor is well known and will not be described in detail.

[0039] Continue reading Figure 2 and Figure 3 The upper end of the swing cylinder stator 17 has a third oil area 20 , and the upper roller 40 and the upper curved guide rail 39 of the two-dimensional plunger pump 23 are located in the third oil area 20 .

[0040] Continue reading Figure 2 and Figure 3A swing cylinder rotor hoop 12 is provided on the outer wall of the swing cylinder rotor 16 , a second rotor bushing 18 and a first rotor bushing 11 are provided at the upper and lower ends of the swing cylinder rotor 16 respectively, and an end cover 19 is provided at the upper end of the swing cylinder stator 23 .

[0041] The present invention will be further described:

[0042] like Figure 1-Figure 3 As shown, the present invention mainly consists of three parts: a brushless motor, a two-dimensional plunger pump 23, and a swing cylinder 2. The present invention makes full use of the space of the three parts to achieve a highly integrated combination, and abandons the integrated valve block part in the traditional EHA. The brushless motor is inserted into the bottom of the motor pump housing 8, and is connected to the outer cylinder body of the two-dimensional plunger pump 23 by the thread on the head of the motor pump housing 8. The two constitute a motor-pump. At the same time, the two-dimensional plunger pump 23 is inserted into the interior of the swing cylinder stator 17 and is connected by the external thread of the motor pump housing 8. Among them, the power of the brushless motor is transmitted to the two-dimensional plunger pump 23 through the coupling 10. The two-dimensional plunger pump 23 converts the mechanical energy transmitted by the brushless motor into hydraulic energy to provide power for the swing cylinder 2. One of the suction and discharge ports 21 of the two-dimensional plunger pump 23 is used as an oil discharge port to output high-pressure oil. The high-pressure oil enters the oil circuit inside the swing cylinder stator 17. Figure 4 One of the pairs of working chambers shown, such as the first working chamber 31, and another pair of working chambers, such as the second working chamber 32, are connected to the pump's oil suction port. The oil inside these working chambers is at low pressure. Due to the pressure difference between the two pairs of working chambers, the high-pressure oil can overcome the load of the swing cylinder 2 and drive the swing cylinder rotor 16 to rotate. The oil in the working chamber with lower pressure is pressed out by the rotating swing cylinder stator blades 25 and enters the oil suction port of the two-dimensional plunger pump 23, forming an oil circulation. When the rotation direction of the brushless motor changes, the working modes of the pump's oil suction and discharge ports 21 will also be swapped, ultimately causing the movement direction of the swing cylinder 2 to change.

[0043] The interior of the robot torsional joint EHA of the present invention is divided into three oil zones. The oil in the first oil zone 4 wraps the motor shaft 3, oil-isolating sleeve 5, magnet 7 and motor rotor 9 inside the brushless motor, as well as the connection part between the brushless motor and the two-dimensional plunger pump 23. The oil in the first oil zone 4 is mainly used to absorb the heat and noise generated by the brushless motor and the connection part between the brushless motor and the two-dimensional plunger pump 23 during operation, and can provide excellent lubrication. The oil-isolating sleeve 5 of the brushless motor can, on the one hand, transmit the magnetic field of the magnet 7 and the motor stator winding 6, and on the other hand, isolate the stator winding 6 from contact with the oil. The second oil area 14 is the working area. It is composed of the first undercut groove 13, the second undercut groove 15, the first stator oil groove 29, the second stator oil groove 30, the first swing cylinder stator oil hole 27, the second swing cylinder stator oil hole 28, the first working chamber 31, and the second working chamber 32. Oil circulates back and forth between the two-dimensional plunger pump 23 and the swing cylinder 2. The closed system design has strong anti-contamination capabilities. The main task of the second oil area 14 is to drive the swing cylinder to overcome the load force. The third oil area 20 mainly wraps around the upper roller 39 of the two-dimensional plunger pump 23, providing it with lubrication.

[0044] The brushless motor of the present invention is a wet-type motor. Except for the stator windings 6, all other major components of the motor are immersed in oil. The changing magnetic field output by the stator windings 6 interacts with the brushless motor's magnets 7 to propel the motor rotor 9. The rotor 9 drives the motor shaft 3 through a coupling 10 to power a two-dimensional plunger pump 23. Due to the small size of brushless motors, heat generation is a concern. Using a wet-type motor effectively absorbs heat generated by movement, reduces noise, and significantly increases the brushless motor's service life.

[0045] The hydraulic pump of the present invention uses a two-dimensional plunger pump 23, which has a small overall size, high volumetric efficiency, fast response speed, and high operating pressure. The plunger 36 of the two-dimensional plunger pump divides the space within the pump body 35 into a first plunger chamber 33 and a second plunger chamber 34. The lower end of the plunger 36 is connected to the lower roller 37 and the coupling 10, and the upper end of the plunger 36 is connected to the upper roller 39. The plunger 36 rotates under the drive of the motor 1. At the same time, under the two-way action of the lower roller 37 and the lower curved guide rail 38, and the upper roller 39 and the upper curved guide rail 40, the plunger 36 performs a back-and-forth linear motion to control the volume of the first plunger chamber 33 and the second plunger chamber 34, thereby achieving oil suction and discharge. A distribution groove is opened on the plunger 36 every 90 degrees. A pair of upper distribution grooves 42 separated by 180 degrees connect the first plunger chamber 33, and another pair of lower distribution grooves 41 separated by 180 degrees connect the second plunger chamber 34. When the plunger chamber is in an increased volume state (oil suction), its connected flow channel is connected to the oil suction port of the pump body 35. Conversely, when the plunger chamber is in a decreased volume state (oil discharge), its connected flow channel is connected to the oil discharge port of the pump body 35. The structure and operating principle of the two-dimensional plunger pump 23 of the present invention are well known in the art and will not be described in detail.

[0046] The swing cylinder 2 used in the present invention is a double-blade swing cylinder. The swing cylinder 2 adopts an outer rotor structure. The two swing cylinder rotor blades 24 and the two swing cylinder stator blades 25 divide the inside of the swing cylinder into four oil chambers, of which a pair of oil chambers symmetrical with respect to the central axis have the same working properties, namely the first working chamber 31 and the second working chamber 32. The rotor adopts a double-blade structure to effectively increase the output torque. The swing cylinder rotor 16 can be adapted to the connection and installation of other mechanisms of the robot. Moreover, since the swing cylinder rotor 16 will be deformed under the action of hydraulic pressure, the high pressure will cause the inner side of the swing cylinder rotor 16 to be in contact with the high-pressure oil chamber and The gaps between the swing cylinder rotor blades 24 and the swing cylinder stator blades 25 and the swing cylinder stator 17 and the swing cylinder rotor 16 change, ultimately increasing internal leakage. At this time, the low-pressure chamber of the swing cylinder rotor 16 undergoes negative radial deformation under the expansion and stretching of the high-pressure chamber of the swing cylinder rotor 16, resulting in a deterioration in the cylindricity of the swing cylinder rotor 16. Excessive deformation can cause the swing cylinder rotor 16 to become stuck. Therefore, the addition of the swing cylinder rotor hoop 12 can reduce the deformation of the outer rotor of the blade-type swing cylinder due to hydraulic pressure and the stress caused by deformation while minimizing the increase in weight and volume. Oil storage tanks 26 are provided on both sides of the long sides of the swing cylinder rotor blades 24. On the one hand, a certain amount of oil can be stored when the swing cylinder rotor 16 reaches the extreme position, so that the swing cylinder will not be suffocated. On the other hand, the arc transition can reduce stress concentration.

[0047] The lower end of the swing cylinder stator 17 is connected to the motor pump housing 8 through a threaded connection. A sealing ring is provided at the bottom of the thread of the motor pump housing 8, and the entire two-dimensional plunger pump 23 is inserted into the stator; a first stator oil groove 29 and a second stator oil groove 30 are provided in the middle of the inner wall of the stator of the swing cylinder, and the two are not connected to each other. The first stator oil groove 29 and the second stator oil groove 30 are respectively provided with a first swing cylinder stator oil hole 27 and a second swing cylinder stator oil hole 28, which are respectively connected to the first working chamber 31 and the second working chamber 32. The outlets of the first swing cylinder stator oil hole 27 and the second swing cylinder stator oil hole 28 are located on the side of the long side of the two swing cylinder stator blades 17. The first and second stator oil grooves 29, 30 on the oscillating cylinder stator 17 correspond precisely to the first and second undercut grooves 13, 15 on the pump body 35, respectively. The first and second undercut grooves 13, 15 are provided with first sealing grooves 22 in the middle and on both sides to prevent internal and external leakage. These first sealing grooves 22 are fitted with O-rings and retaining rings. The upper end of the oscillating cylinder stator 17 is provided with an end cap 19, which is screwed to the stator 17. A second sealing groove, fitted with an O-ring, is provided where the inner bore of the stator 17 and the end cap 19 meet. The oil chamber enclosed by the stator 17 and rotor 16 is fitted with first and second rotor bushings 11, 18, respectively. O-rings seal the first and second rotor bushings 11, 18 against the shaft bores of the stator 17 and rotor 16.

[0048] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An electrostatic hydraulic actuator for a robot joint, comprising a motor (1) and a two-dimensional plunger pump (23) connected to the motor (1), characterized in that: It also includes a swing cylinder (2) arranged on the motor (1) and sleeved on the outside of the two-dimensional plunger pump (23); The swing cylinder (2) comprises a swing cylinder stator (17) sleeved on the outside of the two-dimensional plunger pump (23) and a swing cylinder rotor (16) rotatably sleeved on the outside of the swing cylinder stator (17). The outer wall of the swing cylinder stator (17) is surrounded by a plurality of swing cylinder stator blades (25). The swing cylinder stator (17) is also provided with a first swing cylinder stator oil-passing structure and a second swing cylinder stator oil-passing structure. The inner wall of the swing cylinder rotor (16) is surrounded by a plurality of swing cylinder rotor blades (24). The swing cylinder stator blades (25) are connected to the swing cylinder stator. The swing cylinder rotor blades (24) are staggered, and the cavity between the outer wall of the swing cylinder stator (17) and the inner wall of the swing cylinder rotor (16) is divided into a plurality of first working chambers (31) and second working chambers (32) by the swing cylinder stator blades (25) and the swing cylinder rotor blades (24). The first working chambers (31) and the second working chambers (32) are also staggered. The first working chambers (31) are in communication with the first swing cylinder stator oil passage structure, and the second working chambers (32) are in communication with the second swing cylinder stator oil passage structure. The two-dimensional plunger pump (23) is provided with a first plunger pump oil-passing structure and a second plunger pump oil-passing structure, wherein the first plunger pump oil-passing structure is correspondingly connected to the first swing cylinder stator oil-passing structure, and the second plunger pump oil-passing structure is correspondingly connected to the second swing cylinder stator oil-passing structure; The electrostatic actuator for the robot joint is configured as follows: a motor (1) drives a two-dimensional plunger pump (23) to work, and the two-dimensional plunger pump (23) sucks and discharges oil from a first working chamber (31) through a first plunger pump oil-passing structure and a first swing cylinder stator oil-passing structure, and sucks and discharges oil from a second working chamber (32) through a second plunger pump oil-passing structure and a second swing cylinder stator oil-passing structure, so that the volumes of the first working chamber (31) and the second working chamber (32) increase and decrease, thereby driving the swing cylinder rotor (16) to rotate.

2. The electrostatic hydraulic actuator for robot joints according to claim 1, characterized in that: The first swing cylinder stator oil passage structure comprises a first stator oil passage groove (29) and a first swing cylinder stator oil passage hole (27); the first stator oil passage groove (29) is arranged on the inner wall of the first swing cylinder stator and is in communication with the first plunger pump oil passage structure; one end of the first swing cylinder stator oil passage hole (27) is in communication with the first stator oil passage groove (29), and the other end is in communication with the first working chamber (31).

3. The electrostatic hydraulic actuator for robot joints according to claim 1, characterized in that: The second swing cylinder stator oil passage structure comprises a second stator oil passage groove (30) and a second swing cylinder stator oil passage hole (28). The second stator oil passage groove (30) is arranged on the inner wall of the first swing cylinder stator. One end of the second swing cylinder stator oil passage hole (28) is communicated with the second stator oil passage groove (30), and the other end is communicated with the second working chamber (32).

4. The electrostatic hydraulic actuator for robot joints according to claim 1, characterized in that: Concave oil storage tanks (26) are respectively provided on both sides of the swing cylinder rotor blade (24).

5. The electrostatic hydraulic actuator for robot joints according to claim 1, characterized in that: The two-dimensional plunger pump (23) comprises a pump body (35) and a plunger (36) slidably inserted into the pump body (35); an inner cavity between the plunger (36) and the pump body (35) is divided into a first plunger cavity (33) and a second plunger cavity (34) by a boss on the plunger (36); the first plunger cavity (33) and the second plunger cavity (34) suck and discharge as the plunger (36) reciprocates, and the volumes of the first plunger cavity (33) and the second plunger cavity (34) increase and decrease; The first plunger pump oil passage structure comprises a first undercut groove (15) and a first oil suction and discharge port, wherein the first undercut groove (15) is provided on the outer wall of the pump body and is in communication with the first swing cylinder stator oil passage structure, and one end of the first oil suction and discharge port is in communication with the first plunger cavity (33), and the other end is in communication with the first undercut groove (15); The second plunger pump oil passage structure comprises a second recessed groove (13) and a second oil suction and discharge port. The second recessed groove (13) is provided on the outer wall of the pump body and is communicated with the second swing cylinder stator oil passage structure. One end of the second oil suction and discharge port is communicated with the second plunger cavity (34), and the other end is communicated with the second recessed groove (13).

6. The electrostatic hydraulic actuator for robot joints according to claim 1, characterized in that: The motor (1) is a wet brushless motor, comprising a motor pump housing (8) and a motor shaft (3), an oil separator (5), a motor stator winding (6), a magnet (7) and a motor rotor (9) arranged in the motor pump housing (8). The oil separator (5) separates the inner cavity of the motor pump housing (8) into a first oil area (4) and a motor stator mounting cavity. The motor shaft (3), the magnet (7) and the motor rotor (9) are located in the first oil area (4). The motor shaft (3) and the oil separator (5) are rotatably connected via a bearing. The motor rotor (9) is connected to the motor shaft (3). The magnet (7) is annularly arranged on the motor rotor (9). The motor stator winding (6) is arranged in the motor stator mounting cavity and is arranged opposite to the magnet (7).

7. The electrostatic hydraulic actuator for robot joints according to claim 6, characterized in that: The upper end of the motor pump housing (8) has a mounting opening (43), the lower end of the two-dimensional plunger pump (23) extends into the mounting opening (43) and is connected to the motor shaft (3), the lower roller (37) and the lower curved guide rail (38) of the two-dimensional plunger pump (23) are located in the mounting opening (43), and the first oil area (4) is connected to the mounting opening (43).

8. The electrostatic hydraulic actuator for robot joints according to claim 1, characterized in that: The upper end of the swing cylinder stator (17) has a third oil area (20), and the upper roller (39) and the upper curved guide rail (40) of the two-dimensional plunger pump (23) are located in the third oil area (20).

9. The electrostatic hydraulic actuator for robot joints according to claim 1, characterized in that: A swing cylinder rotor hoop (12) is provided on the outer wall of the swing cylinder rotor (16), a second rotor bushing (18) and a first rotor bushing (11) are provided at the upper and lower ends of the swing cylinder rotor (16), and an end cover (19) is provided at the upper end of the swing cylinder stator (17).

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