Shaft assembly, motor and robot

Abstract

The application provides an axle assembly, a motor and a robot, which comprises a rotating shaft, the rotating shaft comprises an output end, the output end comprises a hollow cavity, the hollow cavity is used for accommodating a connecting shaft, the output end further comprises an outer ring body and a first elastic wall surrounding the hollow cavity, a first annular cavity surrounding the hollow cavity is formed between the outer ring body and the first elastic wall, and the first elastic wall can be deformed towards the hollow cavity when the pressure in the first annular cavity is increased, so that the technical problems of high connection precision between the output shaft and the load shaft and repeatable disassembly can be solved.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, specifically relating to a shaft assembly, a motor, and a robot. Background Technology

[0002] Servo motors, as high-precision actuators, are widely used in CNC machine tools, industrial robots, semiconductor equipment, and other fields. The connection method between their output shaft and the load end (such as lead screw, reducer input shaft, load spindle) directly affects the transmission accuracy, dynamic response, and long-term stability of the system.

[0003] In existing technologies, the output shaft and the load end are typically connected by machining keyways on both the motor shaft and the load end, using a flat key to transmit torque. This method is simple in structure and low in cost. However, there is a clearance (typically 3-10μm) between the key and the keyway, which causes mechanical backlash during transmission, introducing positional errors in high-precision positioning scenarios.

[0004] To improve the connection accuracy between the output shaft and the load end, existing technologies use thermal bonding or anaerobic adhesive bonding to achieve a fixed connection. This method can achieve zero clearance, but it cannot be repeatedly disassembled and reassembled, making on-site disassembly impossible once assembled, which brings difficulties to equipment maintenance.

[0005] Improving the connection accuracy between the output shaft and the load shaft while enabling repeated disassembly of the output shaft and the load shaft is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] Therefore, the present invention provides a shaft assembly, a motor, and a robot that can solve the technical problem of high connection accuracy between the output shaft and the load shaft and can be repeatedly disassembled.

[0007] In a first aspect, the present invention provides a shaft assembly including a rotating shaft, the rotating shaft including an output end, the output end including a hollow cavity for accommodating a connecting shaft, the output end also including an outer ring body and a first elastic wall surrounding the hollow cavity, the outer ring body and the first elastic wall forming a first annular cavity surrounding the hollow cavity, and the pressure increase in the first annular cavity can cause the first elastic wall to deform toward the hollow cavity.

[0008] In some embodiments, a second elastic wall is further provided between the first elastic wall and the outer ring body, and a second annular cavity surrounding the first annular cavity is formed between the second elastic wall and the outer ring body. The pressure increase in the second annular cavity can cause the second elastic wall to deform toward the first annular cavity. The first annular cavity and the second annular cavity are independent of each other.

[0009] In some embodiments, along the axial direction of the hollow cavity, the first annular cavity includes at least a first front cavity and a first rear cavity, the first front cavity and the first rear cavity being independent of each other.

[0010] In some embodiments, the first front cavity is close to the end face of the output terminal, and the first rear cavity is far from the end face of the output terminal; the portion of the first elastic wall surrounding the first front cavity is a first front annular wall, the portion of the first elastic wall surrounding the first rear cavity is a first rear annular wall, and the thickness of the first front annular wall is less than the thickness of the first rear annular wall.

[0011] In some embodiments, when a second annular cavity, a first front cavity, and a first rear cavity are provided, at least one of the first front cavity, the first rear cavity, and the second annular cavity is provided with a thermally sensitive element that expands and contracts with temperature changes.

[0012] In some embodiments, when a second annular cavity, a first front cavity, and a first rear cavity are provided, at least one of the first front cavity, the first rear cavity, and the second annular cavity is provided with a pressure stabilizing device.

[0013] In some embodiments, the pressure stabilizing device includes a spring accumulator and / or a bellows accumulator.

[0014] In some embodiments, the length of the first elastic wall in the axial direction is L, and the radial thickness of the first elastic wall is [missing information]. ,0< < , The change along the axial direction is as follows: ,in, Let α be the wall thickness of the first elastic wall at its center in the axial direction, α be the gradient coefficient, and L be the length of the first elastic wall (1). With the axial direction of the hollow cavity (301) as the Z-axis and the center of the first elastic wall (1) in the axial direction as point O, the distance from the center of the first elastic wall (1) to both ends in the axial direction is L / 2. Z0 represents the distance from point 0 on the Z-axis. The direction along the axial direction towards both ends is positive, and Z0 ≤ L / 2.

[0015] Secondly, the present invention also provides an electric motor, including a housing and the aforementioned shaft assembly, wherein the output end is located outside the housing.

[0016] Thirdly, the present invention provides a robot, including a connecting shaft and the motor, one end of the connecting shaft being fixed inside the hollow cavity.

[0017] This invention achieves high-precision alignment by setting a first annular cavity and a first elastic wall at the output end, inserting the connecting shaft into the hollow cavity, and filling the first annular cavity with high-pressure fluid, causing the first elastic wall to deform towards the hollow cavity, thereby squeezing the connecting shaft from the entire circumference. At the same time, it can be repeatedly disassembled. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a motor connected to a connecting shaft according to an embodiment of the present invention;

[0020] Figure 2 This is an embodiment of the present invention. Figure 1 Sectional view along line AA;

[0021] Figure 3 This is an embodiment of the present invention. Figure 1 Enlarged view at point B in the middle;

[0022] Figure 4 This is a schematic diagram of an embodiment of the present invention with a first annular cavity and a second annular cavity.

[0023] Figure 5 This is an embodiment of the present invention. Figure 4 Enlarged view at point C;

[0024] Figure 6 This is a schematic diagram of an embodiment of the present invention with three annular cavities;

[0025] Figure 7 This is an embodiment of the present invention. Figure 6 Enlarged view at point D;

[0026] Figure 8 This is a schematic diagram of an embodiment of the present invention with a thermistor element provided;

[0027] Figure 9 This is a schematic diagram of an embodiment of the present invention with a pressure stabilizing device.

[0028] Figure 10 This is a schematic diagram of an embodiment of the present invention with a check valve.

[0029] Figure 11 This is a schematic diagram of the sealing screw plug according to an embodiment of the present invention;

[0030] The attached figures are labeled as follows:

[0031] 1. First elastic wall; 101. First annular cavity; 1011. First front cavity; 1012. First rear cavity; 1013. First hollow cavity; 2. Second elastic wall; 201. Second annular cavity; 11. First front annular wall; 12. First rear annular wall; 3. Rotating shaft; 301. Hollow cavity; 302. Output end; 303. Outer ring body; 4. Connecting shaft; 5. Thermistor; 6. Pressure stabilizing device; 7. Sealing plug; 801. Guide section; 802. Thin-walled deformation section; 803. Positioning section; 804. Check valve. Detailed Implementation

[0032] 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. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0033] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0034] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0035] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0036] Servo motors, as high-precision actuators, are widely used in CNC machine tools, industrial robots, semiconductor equipment, and other fields. The connection method between their output shaft and the load end (such as lead screw, reducer input shaft, load spindle) directly affects the transmission accuracy, dynamic response, and long-term stability of the system.

[0037] Currently, the connection between servo motors and load terminals mainly adopts the following methods:

[0038] 1. Keyway connection

[0039] Torque is transmitted using a flat key by machining keyways on both the motor shaft and the load end. This method is simple in structure and low in cost, but it has inherent drawbacks: there is a clearance (typically 3-10 μm) between the key and the keyway, resulting in mechanical backlash during transmission, which can introduce positional errors in high-precision positioning scenarios. In addition, keyway machining can cause stress concentration, affecting the fatigue life of shaft components.

[0040] 2. Traditional expansion sleeve connection

[0041] A keyless connection is achieved by using an external expansion sleeve (such as a conical expansion sleeve or a locking disc) to generate radial pressure through axial tightening of the bolts. This method can eliminate transmission backlash, but installation requires multiple sequential tightening of the bolts, which is cumbersome and requires high torque control; disassembly requires special tools, resulting in poor maintenance convenience.

[0042] 3. Heat fitting or adhesive bonding

[0043] Fixed connections are achieved using thermal bonding or anaerobic adhesive bonding. This method can achieve zero gaps, but it cannot be repeatedly disassembled and reassembled. Once assembled, it cannot be disassembled on-site, which brings difficulties to equipment maintenance.

[0044] 4. Hydraulic chuck connection

[0045] Some high-speed spindles use external hydraulic chucks to clamp the cutting tools using external hydraulic tools. This type of structure also suffers from increased axial length, and the hydraulic system is separate from the motor body, resulting in low integration.

[0046] To address at least some of the aforementioned technical problems, the present invention provides a shaft assembly, such as... Figure 1-11As shown, the device includes a rotating shaft 3, which includes an output end 302. The output end 302 includes a hollow cavity 301 for accommodating a connecting shaft 4. The output end 302 also includes an outer ring body 303 and a first elastic wall 1 surrounding the hollow cavity 301. The outer ring body 303 and the first elastic wall 1 form a first annular cavity 101 surrounding the hollow cavity. The pressure increase in the first annular cavity 101 can cause the first elastic wall 1 to deform toward the hollow cavity 301.

[0047] The output end 302 has a hollow cavity 301 to accommodate the connecting shaft 4. Hydraulic drive of the first annular cavity 101 between the first elastic wall 1 and the outer ring body 303 causes the first elastic wall 1 to radially contract, achieving full-circumference clamping of the connecting shaft 4. This results in zero-backlash transmission (i.e., hydraulic pressure causes the first elastic wall 1 to uniformly contract radially, generating a full-circumference clamping force on the load shaft, completely eliminating clearance, resulting in high transmission rigidity and suitability for high-precision positioning scenarios). The structure is compact and easy to assemble and disassemble, while also enabling automatic centering. The centering progress depends on the machining accuracy of the first annular cavity 101 and is less affected by the operator. Hydraulic expansion causes the first elastic wall 1 to deform uniformly, automatically coaxializing the load shaft and rotor shaft, avoiding eccentricity problems caused by keyway connections or single-screw locking. This reduces the difficulty of connecting the rotating shaft 3 and the load shaft and also improves centering accuracy.

[0048] Furthermore, the first annular cavity 101 is provided with a first oil injection port and a first pressure relief port. The first oil injection port is equipped with a one-way valve 804 and a sealing plug 7 to prevent high-pressure fluid in the first annular cavity 101 from flowing out from the first oil injection port before the sealing plug 7 is covered after oil injection. After high-pressure oil is injected, the oil chamber pressure can be maintained without the need for continuous pressure supply from an external hydraulic source. The structure is simplified and highly reliable. That is, locking and releasing can be completed by pressurizing through a single oil injection port and releasing pressure through the pressure relief port, without the need for multiple bolts in sequence, thus shortening maintenance time.

[0049] Furthermore, the shaft 3 is equipped with a micro hydraulic circuit inside, which is introduced into the first annular cavity 101 from the end face of the shaft 3 or radially.

[0050] Furthermore, high-pressure oil can be injected into the first annular cavity 101.

[0051] Furthermore, the first elastic wall 1 is a thin-walled structure.

[0052] With the first pressure relief port closed, the connecting shaft 4 (the load shaft, also the load end) is inserted into the hollow cavity 301. High-pressure oil is injected through the first oil injection hole, and then the first oil injection port is sealed with the sealing plug 7. When disassembling the connecting shaft 4, the first pressure relief port can be opened. Hydraulic oil pressure causes the thin-walled section (first elastic wall 1) to undergo elastic deformation, and the inner hole of the thin wall radially contracts, applying uniform radial pressure throughout the circumference of the inserted load shaft to achieve keyless and gapless friction locking transmission. After the pressure is released, the thin wall elastically recovers, and the load shaft can be freely withdrawn.

[0053] Unlike existing heat-fitting or adhesive connections, this review supports multiple disassembly and assembly with almost no damage to the mating surfaces (the mating surfaces only experience wear when inserting or removing the connecting shaft 4), and can be reused multiple times within its service life.

[0054] The disassembly operation between connecting shaft 4 and rotating shaft 3 is more convenient, reducing the difficulty and time cost of equipment maintenance.

[0055] By establishing a mechanical model of the radial deformation of the thin-walled inner layer and the oil pressure, precise control of the clamping force can be achieved, avoiding plastic deformation caused by overpressure or slippage caused by underpressure.

[0056] Furthermore, the wall surface of the first elastic wall 1 facing the hollow cavity 301 includes, in the axial direction, a guide section 801, a thin-walled deformation section 802, and a positioning section 803. Among these,

[0057] Guide section 801: Guide section 801 forms a flared opening for guiding the load shaft during insertion.

[0058] Thin-walled deformable section 802: The wall thickness is 1-3mm (determined according to shaft diameter and torque requirements). This section forms a first annular cavity 101 with the outer ring body 303. The first elastic wall 1 has a clearance fit with the load shaft (clearance 0.01-0.03mm) in the unpressurized state, which facilitates the insertion of the load shaft.

[0059] Positioning section 803: Located at the end of the thin-walled deformation section 802 (the end closest to the housing), positioning section 803 is a positioning step used to limit the insertion depth of the load shaft.

[0060] The rotating shaft 3 has an internal oil injection channel (also referred to as the miniature hydraulic circuit above), which is radially opened from the shaft extension section of the rotating shaft 3, introduced from the outer circumference of the rotating shaft 3, and connected to the first annular cavity 101. The end of the oil injection channel (the oil injection end) has an internal thread for installing the sealing plug 7. A one-way valve 804 (such as a ball spring type) is provided in the middle of the oil injection channel or at the inlet of the annular oil cavity to prevent oil backflow.

[0061] Preferred, such as Figure 1 and Figure 2 , Figure 4 and Figure 5As shown, a second elastic wall 2 is also provided between the first elastic wall 1 and the outer ring body 303. A second annular cavity 201 surrounding the first annular cavity 101 is formed between the second elastic wall 2 and the outer ring body 303. The pressure increase in the second annular cavity 201 can cause the second elastic wall 2 to deform toward the first annular cavity 101. The first annular cavity 101 and the second annular cavity 201 are independent of each other.

[0062] By setting up independent first annular cavities 101 and second annular cavities 201, which are controlled by first elastic walls 1 and second elastic walls 2 respectively, two levels of independently adjustable clamping force distribution are achieved, further optimizing the stress distribution of the contact surface, eliminating edge stress concentration, improving fatigue life, and allowing flexible adjustment of the clamping force ratio of the inner and outer layers according to different working conditions.

[0063] In addition, safety redundancy is improved. If one of the devices used to inject oil into the first annular cavity 101 and the second annular cavity 201 fails, the other device can inject high-pressure oil into the two annular cavities in two separate injections. This achieves a mutual backup effect and effectively improves the safety and stability of the shaft assembly.

[0064] Preferred, such as Figure 6 and Figure 7 As shown, along the axial direction of the hollow cavity 301, the first annular cavity 101 includes at least a first front cavity 1011 and a first rear cavity 1012, and the first front cavity 1011 and the first rear cavity 1012 are independent of each other.

[0065] The first annular cavity 101 is divided axially into a first front cavity 1011 and a first rear cavity 1012, which allow independent control of the clamping force at different axial positions of the output end 302. This achieves an axial gradient design in the wall thickness direction, resulting in uniform pressure distribution on the contact surface, eliminating edge stress concentration, and improving fatigue life. It also facilitates the application of differentiated clamping strategies to different axial sections. By achieving differentiated clamping force distribution, stress distribution is optimized, improving fatigue life; and it can adapt to load shafts of different shapes (such as tapered shaft ends).

[0066] Furthermore, the clamping force can be independently adjusted according to the force requirements (such as torque and bending moment distribution) of different sections of the load shaft. This allows for step-by-step assembly with "positioning first, then locking," improving assembly accuracy. Even if some sections fail, the remaining sections can still maintain basic connection functionality, achieving redundancy and improving safety. When one of the first front cavity 1011 and the first rear cavity 1012 cannot be effectively pressurized, the other cavity can temporarily clamp the connecting shaft 4, preventing a sudden disconnection between the rotating shaft 3 and the connecting shaft 4 and thus avoiding a safety accident.

[0067] Furthermore, when high-pressure oil can be injected into either the first front cavity 1011 or the first rear cavity 1012 to achieve connection with the connecting shaft 4, injecting high-pressure oil into both cavities simultaneously improves safety. Even if one cavity fails to hold securely, the shaft assembly can still function normally, thus enhancing its stability. In this case, the first front cavity and the first rear cavity 1012 achieve a mutual backup effect.

[0068] Furthermore, a first intermediate cavity 1013 may be provided between the first front cavity 1011 and the first rear cavity 1012.

[0069] Preferred, such as Figure 6 and Figure 7 As shown, the first front cavity 1011 is close to the end face of the output terminal 302, and the first rear cavity 1012 is far away from the end face of the output terminal 302; the portion of the first elastic wall 1 surrounding the first front cavity 1011 is the first front ring wall 11, and the portion of the first elastic wall 1 surrounding the first rear cavity 1012 is the first rear ring wall 12, and the thickness of the first front ring wall 11 is less than the thickness of the first rear ring wall 12.

[0070] The first front cavity 1011 is close to the end face of the output end 302, and the first rear cavity 1012 is far away from the end face. The thickness of the first front ring wall 11 is less than the thickness of the first rear ring wall 12. This axial wall thickness gradient design makes the area near the end face more deformable and provides stronger support in the area far from the end face. This makes the pressure on the contact surface more uniform along the axial direction, eliminates edge stress concentration, and improves fatigue life. At the same time, the constraint stiffness of the connecting shaft 4 is reduced near the end face, which is beneficial for compensating for thermal deformation.

[0071] Preferred, such as Figure 8 As shown, when a second annular cavity 201, a first front cavity 1011, and a first rear cavity 1012 are provided, at least one of the first front cavity 1011, the first rear cavity, and the second annular cavity 201 is provided with a thermally sensitive element 5 that expands and contracts with heat.

[0072] At least one thermally sensitive element 5 is installed in the first front cavity 1011, the first rear cavity 1012, and the second annular cavity 201. Utilizing the thermal expansion and contraction characteristics of the material, adaptive compensation of the clamping force is achieved within the operating temperature range. This ensures that the connection structure maintains a stable clamping force even with temperature changes, preventing loosening due to thermal expansion or overpressure due to thermal contraction. This improves the environmental adaptability and operational stability of the shaft assembly. It also enhances the connection stability of the structure under wide temperature range conditions, making it suitable for harsh environments such as outdoor equipment or aerospace.

[0073] Preferred, such as Figure 9As shown, when a second annular cavity 201, a first front cavity 1011, and a first rear cavity 1012 are provided, at least one of the first front cavity 1011, the first rear cavity, and the second annular cavity 201 is provided with a pressure stabilizing device 6.

[0074] At least one pressure stabilizing device 6 is provided in the first front cavity 1011, the first rear cavity 1012, and the second annular cavity 201. This device can absorb pressure fluctuations in the hydraulic system, keep the deformation of the first elastic wall 1 stable, thereby achieving precise control of the clamping force, avoiding plastic deformation caused by overpressure or slippage caused by underpressure, and improving the reliability and reusability of the connection.

[0075] By incorporating a pressure stabilizing device 6, automatic compensation is achieved when oil pressure decreases, or ultra-high pressure grease is used instead of hydraulic oil, utilizing its thixotropic properties to maintain pressure. This alternative embodiment exhibits a lower pressure decay rate during long-term use compared to the traditional structure. No periodic pressure replenishment is required, achieving a maintenance-free design.

[0076] Preferred, such as Figure 9 As shown, the pressure stabilizing device 6 includes a spring accumulator and / or a bellows accumulator.

[0077] The pressure stabilizing device 6 uses a spring accumulator and / or a bellows accumulator. The spring accumulator has a simple structure and fast response, while the bellows accumulator has a large compensation capacity and is fatigue resistant. The two can be flexibly selected or combined according to different working conditions to effectively suppress hydraulic fluctuations and ensure precise control and long-term stability of clamping force.

[0078] The rotor shaft inner hole is provided with an axial positioning step, or with the help of an axial adjusting nut, to achieve precise positioning of the load shaft insertion depth. At the same time, axial pre-tightening can be performed before hydraulic locking to further improve the connection rigidity.

[0079] Preferred, such as Figure 3 As shown, the first elastic wall 1 has a length L in the axial direction and a radial thickness of L. , The change along the axial direction is as follows: ,in, Let α be the wall thickness of the first elastic wall 1 at its center in the axial direction, α be the gradient coefficient, and L be the length of the first elastic wall 1. With the axial direction of the hollow cavity 301 as the Z-axis and the center of the first elastic wall 1 in the axial direction as the zero point, the distance from the center of the first elastic wall 1 to both ends in the axial direction is L / 2. Z0 represents the distance from point 0 on the Z-axis. The direction along the axial direction towards both ends is positive, and Z0 ≤ L / 2.

[0080] The first elastic wall 1 has an axial length of L and a radial thickness of t(z). The variation of t(z) along the axial direction is as follows: , The range is 0 < < Z0 ≤ L / 2. For example... Figure 3 As shown, t0 is the wall thickness of the first elastic wall 1 at its center in the axial direction, α is the gradient coefficient, L is the length of the first elastic wall (1), the axial direction of the hollow cavity (301) is taken as the Z-axis, the center of the first elastic wall (1) in the axial direction is taken as the 0 point, the distance from the center of the first elastic wall (1) to both ends in the axial direction is L / 2, Z0 is the distance from the 0 point on the Z-axis, and the direction along the axial direction to both ends is positive. Therefore .

[0081] t(z) refers to the radial thickness of the first elastic wall 1 when the distance from the Z-axis point 0 is Z0.

[0082] Under hydraulic pressure, the pressure distribution at the contact surface of a structure with uniform wall thickness is uneven. The two ends are constrained by the solid structure, resulting in lower pressure at both ends and higher pressure in the middle. To achieve a uniform pressure distribution at the contact surface, the thickness of the thinner inner layer gradually decreases from the middle to both ends along the axial direction according to the formula mentioned above, making the clamping force of the first elastic wall 1 on the connecting shaft 4 more uniform. The value of α is determined through finite element optimization; α < 1, and the axial wall thickness variation formula ensures that the first elastic wall 1 achieves the same deformation effect.

[0083] A mechanical model of the deformation of the first elastic wall 1 and the oil pressure in the first annular cavity 101: Establishing the mechanical relationship between the radial deformation δ of the first elastic wall 1 and the oil pressure P: .in, Let t be the average radius of the first elastic wall 1, t be the wall thickness, E be the elastic modulus of the material, and k be the value relative to the axial length L and the average radius of the first elastic wall 1. The relevant correction factor, when L≤2 hour This model allows for the design of hydraulic pressure and wall thickness parameters based on the target clamping force.

[0084] The model shows that the radial deformation is directly proportional to the oil pressure, inversely proportional to the wall thickness, and directly proportional to the square of the average radius.

[0085] Pressure distribution control of the contact surface of the hollow cavity 301 (the inner wall surface of the hollow cavity 301, the surface used to encircle the load shaft, which is also the first elastic wall): By designing the axial wall thickness gradient of the first elastic wall 1 (such as thin at both ends and thick in the middle, or linearly changing along the axial direction), the pressure distribution of the contact surface is made to approach a rectangular distribution, avoiding the non-uniform distribution of "low pressure at both ends and high pressure in the middle" common in traditional equal wall thickness structures.

[0086] Specifically, the relationship between contact surface pressure and transmitted torque:

[0087] Pressure at the contact surface between the first elastic wall and the load shaft The relationship with oil pressure P is as follows:

[0088]

[0089] in The radius of the contact surface is approximately equal to the radius of the hollow cavity 301.

[0090] The transmitted torque T satisfies:

[0091]

[0092] Where: μ is the coefficient of friction of the contact surface, A is the contact area, A = 2π ×L, where L is the clamping length (L is the axial length of the first annular cavity 101, and also the axial length of the first elastic wall 1).

[0093] To prevent plastic deformation of the thin-walled inner layer under hydraulic pressure, the following must be met:

[0094]

[0095] in Where n is the yield strength of the material, and n is the safety factor (taken as 1.5-2.0).

[0096] Optimal wall thickness based on torque requirements Determined by the following equation:

[0097]

[0098] And it must meet the requirements for transmitting torque. Requirements:

[0099]

[0100] By establishing a thermo-mechanical coupling model and optimizing material matching and wall thickness design, the connecting structure maintains a stable clamping force within the operating temperature rise range. Thermo-mechanical coupling stability design: Based on the difference in the thermal expansion coefficients of the materials, a compensation model for the pressure change of the first annular cavity 101 with temperature is established. By selecting a matching thermal expansion material or a preset temperature compensation cavity, the clamping change rate of the connecting structure (including the first annular cavity and the first elastic wall) is controlled within ±10% within the operating temperature range of -20℃ to +80℃.

[0101] Specifically, because the thin-walled inner layer tightly holds the load shaft (in this application, the load shaft is the connecting shaft 4), the radial deformation of both must be coordinated. Differences in thermal expansion coefficients will cause changes in the contact surface pressure. < The load shaft expands more, increasing the clamping force; if < The motor shaft expands more, reducing the clamping force.

[0102] Radial deformation caused by operating temperature change ΔT satisfy:

[0103]

[0104] in The coefficient of thermal expansion of the rotor shaft material is . is the coefficient of thermal expansion of the load shaft material.

[0105] To compensate for the effect of thermal deformation on the clamping force, the volume of the first annular cavity 101 is... Designed as follows:

[0106]

[0107] Where β is the compensation coefficient, which is achieved by selecting an appropriate sealing plug material or a preset elastic compensation element; V0 is the theoretical value at the preset temperature.

[0108] Dynamic stiffness and modal optimization: The combination of the first annular cavity 101 and the first elastic wall 1 is regarded as an elastic-friction coupling interface, and its stiffness model is established. By optimizing the clamping length to diameter ratio (L / D≥1.2, where L is the length of the first annular cavity 101 in the axial length direction of the hollow cavity 301, and D is the diameter of the hollow cavity 301), the connection stiffness reaches more than 80% of the motor shaft body, thus avoiding it becoming a weak link in the dynamic response of the system.

[0109] The above parameter design process:

[0110] 1. Determine the target transmitted torque ;

[0111] 2. Select shaft diameter Clamping length L, coefficient of friction μ;

[0112] 3. By Calculate the required oil pressure P;

[0113] 4. By Choose the wall thickness t (to ensure that δ is sufficient to generate interference);

[0114] 5. By Verify the safety of plastic deformation;

[0115] 6. If necessary, optimize pressure distribution using gradient wall thickness t(z);

[0116] 7. By Assess the thermal effects and add compensation if necessary.

[0117] The present invention also provides an electric motor, including a housing and a shaft assembly, wherein the output end 302 is located outside the housing.

[0118] The aforementioned shaft assembly is integrated inside the motor housing, with the output end 302 located outside the housing. This allows the hydraulic expansion sleeve structure to be built into the motor rotor shaft extension section (output end 302 of the rotating shaft 3). A portion of the connecting shaft 4 is inserted into the hollow cavity 301, effectively reducing the axial length of the motor (traditional couplings prevent the connecting shaft 4 and the rotating shaft 3 from aligning in the axial direction, resulting in a longer length). This improves the compactness of the motor without altering the external interface dimensions, allowing it to directly replace traditional servo motors. Simultaneously, it achieves zero-backlash transmission and high alignment accuracy, enhancing the dynamic response bandwidth of the servo system.

[0119] Furthermore, the motor is a servo motor. The servo motor is a keyless motor with integrated hydraulic expansion sleeve connection.

[0120] Because transmission backlash is eliminated and connection stiffness is high, the system's natural frequency is increased, and the dynamic response bandwidth of the servo system is improved.

[0121] The servo motor includes: a housing, a stator assembly, a rotor assembly, a front bearing, a rear bearing, a brake, an encoder, etc. The rotor assembly includes: a rotor core and a rotating shaft 3. The rotor core is fixed to the outer circumference of the rotating shaft 3. The rotor shaft has a hollow shaft structure, and its output end 302 extends out of the housing for connecting to external equipment. It is equipped with a hydraulic expansion sleeve structure (including a first annular cavity 101, a hollow cavity 301, and a first elastic wall 1).

[0122] The present invention also provides a robot, including a connecting shaft 4 and a motor, one end of the connecting shaft 4 being fixed inside the hollow cavity 301.

[0123] One end of the robot's load shaft is fixed inside the hollow cavity 301. The connection with zero backlash, high rigidity, and high alignment accuracy is achieved through hydraulic expansion sleeve, eliminating transmission gaps, increasing the system's natural frequency, and improving the dynamic response bandwidth of the servo system. At the same time, it supports multiple disassembly and assembly without damaging the mating surfaces, meeting the needs of high-frequency maintenance and modular assembly of the robot. Furthermore, the hydraulic expansion automatically makes the load shaft and rotor shaft coaxial, avoiding the eccentricity problem caused by keyway connection or single screw tightening.

[0124] In addition, the friction area caused by repeated disassembly and assembly between the load shaft and the first elastic wall 1 of the hollow cavity 301 is relatively uniform, and the coaxiality between the load shaft and the rotating shaft 3 is high. Due to the elastic properties of the first elastic wall 1 and the fact that the friction area surrounds the hollow cavity 301, it still maintains a high clamping force and coaxiality after repeated disassembly and assembly friction.

[0125] The steps for assembling the load shaft and the motor are as follows:

[0126] Step 1 is the insertion of the load shaft: Insert the load shaft (such as the input shaft of the reducer or the end of the lead screw) along the guide section 801 of the hollow cavity 301 until it abuts against the positioning step.

[0127] Step 2 is oil injection and pressurization: Connect the oil injection channel inlet using a hydraulic oil injection tool (such as a manual hydraulic pump) and inject high-pressure hydraulic oil (pressure range of 50-200MPa, determined according to shaft diameter, torque requirements, and mechanical calculation model). The hydraulic oil enters the annular oil chamber, applying uniform radial pressure to the thin-walled section, causing the thin-walled section to elastically deform and contract inward (deform towards the hollow cavity 301), thus gripping the load shaft.

[0128] Step 3 is pressure holding and locking: After reaching the set pressure, maintain the pressure and tighten the sealing plug 7. The one-way valve 804 prevents oil backflow, the pressure in the oil chamber is maintained, and the thin-walled section remains in a clamped state. At this point, the zero-clearance fixed connection between the load shaft and the motor rotor is completed.

[0129] Step 4 is disassembly: When disassembly is required, loosen the sealing plug 7 at the pressure relief port to release the oil chamber pressure. The thin-walled section will regain its elasticity, and the load shaft and the inner hole of the rotor shaft will restore the clearance fit, allowing the load shaft to be easily pulled out.

[0130] In summary, the existing technology lacks a connection structure that can be integrated into the motor shaft extension section, reduce axial length, achieve zero backlash transmission, and support repeated disassembly and assembly.

[0131] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0132] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A shaft assembly comprising a rotating shaft (3), the rotating shaft (3) including an output end (302), characterized in that, The output end (302) includes a hollow cavity (301) for accommodating the connecting shaft (4). The output end (302) also includes an outer ring body (303) and a first elastic wall (1) surrounding the hollow cavity (301). A first annular cavity (101) surrounding the hollow cavity (301) is formed between the outer ring body (303) and the first elastic wall (1). The pressure increase in the first annular cavity (101) can cause the first elastic wall (1) to deform toward the hollow cavity (301).

2. The shaft assembly according to claim 1, characterized in that, A second elastic wall (2) is also provided between the first elastic wall (1) and the outer ring body (303). A second annular cavity (201) surrounding the first annular cavity (101) is formed between the second elastic wall (2) and the outer ring body (303). The pressure increase in the second annular cavity (201) can cause the second elastic wall (2) to deform toward the first annular cavity (101). The first annular cavity (101) and the second annular cavity (201) are independent of each other.

3. The shaft assembly according to claim 1, characterized in that, Along the axial direction of the hollow cavity (301), the first annular cavity (101) includes at least a first front cavity (1011) and a first rear cavity (1012), which are independent of each other.

4. The shaft assembly according to claim 3, characterized in that, The first front cavity (1011) is close to the end face of the output end (302), and the first rear cavity (1012) is far away from the end face of the output end (302); the portion of the first elastic wall (1) surrounding the first front cavity (1011) is the first front ring wall (11), and the portion of the first elastic wall (1) surrounding the first rear cavity (1012) is the first rear ring wall (12), and the thickness of the first front ring wall (11) is less than the thickness of the first rear ring wall (12).

5. The shaft assembly according to any one of claims 1-3, characterized in that, When a second annular cavity (201), a first front cavity (1011), and a first rear cavity (1012) are provided, at least one of the first front cavity (1011), the first rear cavity, and the second annular cavity (201) is provided with a thermally sensitive element (5) that expands and contracts with heat.

6. The shaft assembly according to any one of claims 1-3, characterized in that, When a second annular cavity (201), a first front cavity (1011), and a first rear cavity (1012) are provided, at least one of the first front cavity (1011), the first rear cavity, and the second annular cavity (201) is provided with a pressure stabilizing device (6).

7. The shaft assembly according to claim 6, characterized in that, The pressure stabilizing device (6) includes a spring accumulator and / or a bellows accumulator.

8. The shaft assembly according to claim 1, characterized in that, The first elastic wall (1) has an axial length of L and a radial thickness of L. , The change along the axial direction is as follows: ,in, Let α be the wall thickness of the first elastic wall (1) at its center in the axial direction, α be the gradient coefficient, and L be the length of the first elastic wall (1). With the axial direction of the hollow cavity (301) as the Z-axis and the center of the first elastic wall (1) in the axial direction as point O, the distance from the center of the first elastic wall (1) to both ends in the axial direction is L / 2. Z0 represents the distance from point 0 on the Z-axis. The direction along the axial direction towards both ends is positive, and Z0 ≤ L / 2.

9. An electric motor, characterized in that, Includes a housing and a shaft assembly as described in any one of claims 1-8, wherein the output end (302) is located outside the housing.

10. A robot comprising a connecting shaft (4) and a motor as claimed in claim 9, one end of the connecting shaft (4) being fixed inside the hollow cavity (301).

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