Lead screw end position limiting and cushioning structure

Abstract

This invention belongs to the field of lead screw transmission technology and discloses a lead screw end limiting and buffering structure, including a lead screw and a limiting and buffering device. The limiting and buffering device is located at the end of the lead screw. When the nut on the lead screw moves to the end of the lead screw, the limiting and buffering device first limits the axial and rotational movement of the nut. When the limiting torque set by the limiting device is exceeded, the limiting device fails, thereby buffering. The buffer is located between the fixed part and the rotating part. The closer the distance between the fixed part and the rotating part, the greater the force exerted by the buffer on the rotating part. During normal operation, this invention achieves a reliable mechanical limiting function through the limiting pin, with high limiting accuracy. Under abnormal impact conditions, the limiting pin fails at the set torque threshold, limiting the peak instantaneous impact load below the set value, effectively protecting the lead screw, nut, and other structural components from damage, and avoiding the problem of excessive impact load generated by rigid limiting structures.

Description

Technical Field

[0001] This invention belongs to the field of lead screw transmission technology, and relates to a lead screw transmission device, specifically a lead screw end buffer structure. Background Technology

[0002] A lead screw drive is a mechanical transmission mechanism that converts rotary motion into linear motion, and it is widely used in aerospace electromechanical actuators, CNC machine tools, precision positioning platforms, and other fields. In a lead screw drive system, the nut moves along the lead screw axis to achieve linear motion. When the nut moves to the end of the lead screw, a limit mechanism is required to prevent the nut from disengaging from the lead screw, and protective measures for abnormal operating conditions must also be considered.

[0003] Currently, products using lead screw drives typically employ a rigid limiting structure at the end of the stroke. This structure uses a rigid stop at the end of the lead screw, achieving limiting through rigid contact when the nut reaches the end. However, this rigid limiting structure has significant technical drawbacks: when the nut reaches the end at high speed, the rigid stop generates a large instantaneous impact load, which can be several times the normal operating load, causing excessive stress on structural components such as the lead screw, nut, or stop, leading to failure. To avoid structural failure, the strength and stiffness of the structural components need to be increased, which inevitably leads to an increase in the size and weight of the components. Furthermore, rigid impact also increases the risk of lead screw nut jamming, affecting the reliability and service life of the system.

[0004] To address the impact problem caused by rigid limiting, another technical solution is to employ an axial elastic buffer structure. This structure uses an elastic element (such as a compression spring or rubber buffer pad) at the end of the lead screw to absorb impact energy through axial compression deformation. However, this axial elastic buffer structure also has technical shortcomings: First, the elastic element needs to directly bear the axial impact load of the nut and the inertial load during deceleration at the end of the product. To provide sufficient buffering capacity, the stiffness and size of the elastic element must be large, resulting in a long axial length and large overall size of the buffer structure. Second, because the buffer stroke is limited by the compression of the elastic element, the buffer stroke is usually short, resulting in limited energy absorption capacity. Under high-speed impact conditions, the buffering effect is poor, and a large residual impact load may still be generated.

[0005] Therefore, a new lead screw end limiting and buffering structure is needed that can achieve reliable mechanical limiting function during normal operation, effectively suppress impact load and provide sufficient buffer protection under abnormal bottom impact conditions, while maintaining the characteristics of compact structure and light weight. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a lead screw end buffer structure that achieves mechanical limiting at the lead screw end while suppressing the impact load when the nut abnormally hits the bottom, and buffers and decelerates the screw, reducing the risk of lead screw nut jamming and structural damage.

[0007] The technical solution of the present invention is as follows: A lead screw end limiting and buffering structure includes a lead screw and a limiting and buffering device. The limiting and buffering device is located at the end of the lead screw. When the nut on the lead screw moves to the end of the lead screw, the limiting and buffering device first limits the axial and rotational movement of the nut. When the limiting torque set by the limiting device is exceeded, the limiting device fails, and then buffering occurs. The limiting and buffering device includes a fixed part, a rotating part, a limiting pin, and a buffer. The fixed part is fixedly connected to the end of the lead screw. The rotating part is rotatably sleeved on the lead screw. The limiting pin connects the rotating part and the lead screw and bears the rotational torque of the rotating part. The buffer is located between the fixed part and the rotating part. The closer the distance between the fixed part and the rotating part, the greater the force exerted by the buffer on the rotating part. The direction of the force exerted by the buffer on the rotating part is opposite to the axial movement of the nut.

[0008] Furthermore, the fixing component is the inner ring of a ring spring, which is axially fixed to the end of the lead screw by a limiting bolt, which is axially installed at the end of the lead screw.

[0009] Furthermore, the buffer component is the outer ring of a ring spring, which together with the inner ring of the ring spring and the rotating component forms a ring spring structure.

[0010] Furthermore, the rotating component is a lead screw stop. The end of the lead screw stop facing the nut is provided with a first limiting boss, and the end of the nut facing the lead screw stop is provided with a second limiting boss. The shapes of the first limiting boss and the second limiting boss are matched with each other, so that the rotational torque of the nut can be transmitted to the lead screw stop.

[0011] Furthermore, the limit pin is a shear pin, which connects the lead screw stop to the lead screw and bears the rotational torque transmitted from the nut to the lead screw stop. When the torque is greater than the shear strength of the shear pin, the shear pin will shear off.

[0012] Furthermore, both the outer ring of the lead screw stop and the inner ring of the outer ring of the annular spring are made of wear-resistant material.

[0013] Furthermore, a conical surface is provided on the outer circular surface of the lead screw stop, and a conical surface is provided on the outer circular surface of the inner ring of the annular spring. The conical surface of the lead screw stop and the conical surface of the inner ring of the annular spring are arranged face to face. Two conical surfaces are provided on the inner circular surface of the outer ring of the annular spring, which respectively fit into the conical surface of the lead screw stop and the conical surface of the inner ring of the annular spring.

[0014] Furthermore, the cone angle of all cone surfaces is between 12° and 30°.

[0015] Furthermore, a torque transmission structure is provided between the inner ring of the annular spring and the lead screw.

[0016] Furthermore, to increase the buffer stroke, multiple outer rings of the annular spring can be set, and correspondingly, an inner ring of the annular spring can be added to the outer rings of the annular spring.

[0017] The advantages of this invention are as follows: 1. During normal operation, the present invention achieves a reliable mechanical limiting function through the limiting pin, with high limiting accuracy. Under abnormal impact conditions, the limiting pin fails at the set torque threshold, limiting the peak value of the instantaneous impact load to below the set value, effectively protecting the screw, nut and other structural components from damage, avoiding the problem of excessive impact load generated by the rigid limiting structure, and without increasing the size and weight of the structural components.

[0018] 2. This invention amplifies the axial force and converts it into frictional torque through a force amplification structure (such as a conical structure). The force amplification factor can reach 2.0 to 4.7 times, which makes the buffer stroke more than 3 times longer than that of the traditional axial elastic buffer structure, and the single energy absorption capacity is increased by more than 200%, resulting in a significant buffering effect. At the same time, due to the force amplification effect, the elastic buffer does not need to directly bear a large axial load, and the axial length of the structure can be reduced by 40%, achieving the goal of compact structure and light weight.

[0019] 3. In this invention, the friction torque increases with the axial displacement of the rotating part, achieving gradual deceleration. This avoids the secondary impact that may occur in traditional buffer structures, making the deceleration process smooth and controllable. It further reduces the impact on structural parts and nuts, and reduces the risk of screw nut jamming.

[0020] 4. The present invention has a simple structure, with the main components including a fixing part, a rotating part, a limiting pin, and an elastic buffer part. It is easy to process and manufacture, and the cost is low. By selecting different limiting pin parameters (such as the diameter and material of the shear pin) and the cone angle, the limiting failure torque and buffer characteristics can be flexibly adjusted to adapt to different application scenarios and load requirements, and it has good adjustability and versatility.

[0021] 5. By adopting wear-resistant materials, torsion transmission structure and other optimization measures, this invention further improves the wear resistance of the friction surface and the reliability of the system, resulting in a long service life and low maintenance costs. It is particularly suitable for fields such as aerospace electromechanical actuators where safety and reliability requirements are high. Attached Figure Description

[0022] 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. 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.

[0023] Figure 1 This is a schematic diagram of a lead screw end limiting and buffering structure.

[0024] Figure 2 This is a cross-sectional schematic diagram of a lead screw end limiting and buffering structure.

[0025] Explanation of reference numerals in the attached diagram: 1-lead screw; 2-lead screw stop; 3-outer ring of the annular spring; 4-inner ring of the annular spring; 5-limit bolt; 6-shear pin. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0027] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0028] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0030] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] First embodiment: A lead screw end limiting and buffering structure includes a lead screw and a limiting and buffering device. The limiting and buffering device is located at the end of the lead screw. When the nut on the lead screw moves to the end of the lead screw, the limiting and buffering device first limits the axial and rotational movement of the nut. When the limiting torque set by the limiting device is exceeded, the limiting device fails, and then buffering occurs. The limiting and buffering device includes a fixed part, a rotating part, a limiting pin, and a buffer. The fixed part is fixedly connected to the end of the lead screw. The rotating part is rotatably sleeved on the lead screw. The limiting pin connects the rotating part and the lead screw and bears the rotational torque of the rotating part. The buffer is located between the fixed part and the rotating part. The closer the distance between the fixed part and the rotating part, the greater the force exerted by the buffer on the rotating part. The direction of the force exerted by the buffer on the rotating part is opposite to the axial movement of the nut.

[0032] The fixing component is the inner ring of a ring spring, which is axially fixed to the end of the lead screw by a limit bolt, which is axially installed at the end of the lead screw.

[0033] The buffer component is the outer ring of a ring spring. The outer ring of the ring spring, together with the inner ring of the ring spring and the rotating component, forms a ring spring structure.

[0034] The rotating component is a lead screw stop. The end of the lead screw stop facing the nut has a first limiting boss, and the end of the nut facing the lead screw stop has a second limiting boss. The shapes of the first limiting boss and the second limiting boss are matched with each other, so that the rotational torque of the nut can be transmitted to the lead screw stop.

[0035] The limit pin is a shear pin that connects the lead screw stop to the lead screw and bears the rotational torque transmitted from the nut to the lead screw stop. When the torque exceeds the shear strength of the shear pin, the shear pin will break.

[0036] Both the outer ring of the lead screw stop and the inner ring of the outer ring of the annular spring are made of wear-resistant material.

[0037] A conical surface is provided on the outer circular surface of the lead screw stop, and a conical surface is provided on the outer circular surface of the inner ring of the annular spring. The conical surface of the lead screw stop and the conical surface of the inner ring of the annular spring are arranged face to face. Two conical surfaces are provided on the inner circular surface of the outer ring of the annular spring, which respectively fit with the conical surface of the lead screw stop and the conical surface of the inner ring of the annular spring.

[0038] The cone angle of all cone surfaces is between 12° and 30°.

[0039] A torque transmission structure is installed between the inner ring of the annular spring and the lead screw.

[0040] To increase the buffer stroke, multiple outer rings of the annular spring can be set, and correspondingly, an inner ring of the annular spring can be added to the outer rings of the annular spring.

[0041] A lead screw end limiting and buffering structure, the working process of which is as follows: When the nut is running normally to the end of the lead screw 1, the boss on the nut contacts the boss on the lead screw stop 2; The lead screw stop 2 restricts the nut from rotating further, thus achieving a mechanical limit on the nut; When the nut moves at an abnormally high speed to the end of the lead screw 1, the boss on the nut hits the boss on the lead screw stop 2. When the torque during impact exceeds the shear strength of shear pin 6, shear pin 6 is sheared off. The nut engages with the lead screw stop 2 via the boss, continuing to drive the lead screw stop 2 to rotate and move axially; When the lead screw stop 2 rotates, a frictional torque is generated between its conical surface and the conical surface of the outer ring 3 of the annular spring, and this frictional torque is transmitted to the nut. When the lead screw stop 2 moves axially, it compresses the outer ring 3 of the annular spring through the conical surface, and the outer ring 3 of the annular spring expands under the compression of the conical surface. As the lead screw stop 2 moves axially, the normal pressure between the conical surfaces gradually increases, thereby gradually increasing the frictional torque; The nut gradually decelerates under the action of frictional torque until it stops rotating, and the buffering ends. If the buffer stroke of the lead screw stop 2 is fully compressed, the lead screw stop 2 will be in rigid contact with the inner ring 4 of the annular spring and will transmit the axial force to the limit bolt 5. The limit bolt 5 will bear the impact load after the nut decelerates. After the nut stops rotating, if the external load is removed, the nut will retract under the elastic force of the ring spring.

[0042] Second embodiment: This embodiment provides a lead screw end limiting and buffering structure. For example... Figure 1 and Figure 2 As shown, the structure includes a lead screw 1 and a limiting and buffering device disposed at the end of the lead screw 1. The limiting and buffering device includes a fixing component, a rotating component, a limiting pin, and an elastic buffer component.

[0043] The fixing component is an inner ring of a ring spring 4. The inner ring of the ring spring 4 includes an inner bore body and an outer cylindrical body. The inner diameter of the inner bore body is 30mm, which mates with the outer cylindrical surface of the lead screw 1. The outer cylindrical body of the inner ring spring 4 has a second conical surface with a cone angle of 20° and a length of 15mm. The inner ring of the ring spring 4 is axially fixed to the end of the lead screw 1 by a limiting bolt 5. The limiting bolt 5 includes a threaded section and a bolt head. The threaded section has an M8 thread and is screwed into a pre-machined M8 threaded hole at the end of the lead screw 1 to a depth of 12mm. The bolt head has a diameter of 13mm and a thickness of 5mm. The bolt head presses against the end face of the inner ring of the ring spring 4 to achieve axial fixation. The axial length of the inner ring of the ring spring 4 is 20mm, and the wall thickness is 8mm.

[0044] The rotating component is a lead screw stop 2. The lead screw stop 2 is an annular component, comprising an inner hole, an outer circular surface, and a torque transmission structure. The inner hole diameter of the lead screw stop 2 is 32mm, and it has a clearance fit with the outer circular surface of the lead screw 1, with a clearance of 2mm, allowing the lead screw stop 2 to rotate relative to the lead screw 1. The outer circular surface of the lead screw stop 2 has a first conical surface with a cone angle of 20° and a length of 15mm. This first conical surface is arranged face-to-face with the second conical surface of the inner ring of the annular spring 4, and the initial axial distance between the two conical surfaces is 15mm. The torque transmission structure is located on the end face of the lead screw stop 2 facing the nut, and includes a first limiting boss. The first limiting boss is an annular protrusion with a height of 5mm, a width of 10mm, and an outer diameter of 40mm. A second limiting boss is provided on the end face of the nut facing the lead screw stop 2. The shape of the second limiting boss matches that of the first limiting boss. When the nut moves to the end along the axial direction of the lead screw 1, the second limiting boss contacts the first limiting boss, and the rotational torque of the nut is transmitted to the lead screw stop 2 through the contact surface of the two bosses. The axial length of the lead screw stop 2 is 25mm, the outer diameter is 50mm, and the wall thickness is 9mm.

[0045] The limiting pin is a shear pin 6. Shear pin 6 is a cylindrical pin with a diameter of 5mm and a length of 40mm, made of 45# steel, and has a shear strength of 350MPa. The first end of shear pin 6 penetrates the radial hole of the lead screw stop 2 and is fixedly connected to the lead screw stop 2 with a penetration depth of 9mm, fixed by an interference fit with an interference amount of 0.02mm. The second end of shear pin 6 penetrates the radial hole of the lead screw 1 and is fixedly connected to the lead screw 1 with a penetration depth of 15mm, fixed by an interference fit with an interference amount of 0.02mm. Shear pin 6 bears the rotational torque of the lead screw stop 2. According to the shear strength calculation formula T=τ·π·d³ / 16, the shearing threshold torque of shear pin 6 is approximately 34N·m. When the rotational torque exceeds 34N·m, shear pin 6 undergoes shear fracture.

[0046] The elastic buffer is an outer ring 3 of a ring spring. The outer ring 3 is a ring-shaped elastic element with a third and fourth conical surface on its inner surface. The third conical surface is in contact with the first conical surface of the lead screw stop 2, and the fourth conical surface is in contact with the second conical surface of the inner ring 4 of the ring spring. The cone angle of both the third and fourth conical surfaces is 20°. The outer diameter of the outer ring 3 is 60 mm, the initial inner diameter is 48 mm, the wall thickness is 3 mm, and the axial length is 30 mm. The outer ring 3 is made of spring steel with an elastic modulus of 200 GPa and a Poisson's ratio of 0.3. The outer ring 3 is positioned between the inner ring 4 of the ring spring and the lead screw stop 2. In the initial state, the third conical surface of the outer ring 3 is in contact with the first conical surface but without pressure, and the fourth conical surface is in contact with the second conical surface but without pressure.

[0047] The working process of this structure is as follows: During normal operation, the nut moves axially along the lead screw 1 to its end, where the second limiting boss contacts the first limiting boss. The rotational torque of the nut is transmitted to the lead screw stop 2 through the boss, and the shear pin 6 bears this rotational torque. When the rotational torque is less than 34 N·m, the shear pin 6 remains intact, the lead screw stop 2 is restricted from rotating, and the nut is restricted from continuing to move axially, thus achieving the mechanical limiting function with a limiting accuracy of ±0.1 mm.

[0048] When the nut travels at high speed to the end of the lead screw 1 under abnormal operating conditions, the second limiting boss impacts the first limiting boss at high speed, generating a large instantaneous torque. When this instantaneous torque exceeds the shearing threshold of the shear pin 6 (34 N·m), the shear pin 6 breaks within 0.01 seconds, the lead screw stop 2 separates from the lead screw 1, the limiting function fails, and the system switches to buffer mode. The shearing of the shear pin 6 limits the peak instantaneous impact load to below the load corresponding to the shearing threshold, preventing the impact load from being transmitted to the lead screw 1, nut, and other structural components, thus protecting the structural components from damage.

[0049] After the shear pin 6 is cut, the nut continues to drive the screw stop 2 to rotate and move axially through the engagement of the first and second limiting bosses. When the screw stop 2 moves axially, the first conical surface presses against the third conical surface of the outer ring 3 of the annular spring, while the second conical surface supports the fourth conical surface of the outer ring 3. Under the wedge-shaped action of the conical surfaces, the axial force F is converted into a radial force, which causes the outer ring 3 of the annular spring to expand radially. According to mechanical relationships, the normal force between the conical surfaces N = F / sin(20°) ≈ 2.92F, achieving a force amplification effect with a force amplification factor of approximately 2.92 times.

[0050] When the lead screw stop 2 rotates, friction is generated between the first and third conical surfaces, producing a frictional torque at the radius of rotation. The frictional torque M = μ·N·r, where μ is the coefficient of friction (taken as 0.15) and r is the friction radius (taken as 15mm). As the lead screw stop 2 moves axially, the radial expansion of the outer ring 3 of the annular spring gradually increases, the normal force N gradually increases, and the frictional torque M gradually increases. The rate of increase of the frictional torque is approximately 1.2 N·m / mm, meaning that for every 1mm axial movement of the lead screw stop 2, the frictional torque increases by approximately 1.2 N·m. The frictional torque acts on the lead screw stop 2 and the nut, causing the nut to gradually decelerate.

[0051] The axial travel of the lead screw stop 2 is 0 to 15 mm. Within this travel, the frictional torque gradually increases from its initial value to a maximum of approximately 18 N·m. Under the action of the frictional torque, the nut gradually decelerates, and when the axial displacement is approximately 12 mm, the nut completely stops rotating, and the buffering process ends. This buffering travel of 12 mm is three times longer than the 4 mm buffering travel of the traditional axial spring buffer structure. During the buffering process, the axial impact energy is converted into frictional heat energy and continuously dissipated, with a single energy absorption capacity of approximately 120 J.

[0052] If the buffer stroke of the lead screw stop 2 is fully compressed, that is, if the nut has not completely stopped when the axial displacement reaches 15mm, then the lead screw stop 2 is in rigid contact with the inner ring 4 of the annular spring, and the axial force is transmitted to the limit bolt 5. The limit bolt 5 bears the residual impact load after the nut decelerates. Due to the buffer deceleration, the residual impact load is much smaller than the initial impact load.

[0053] After the nut stops rotating, if the external load is removed, the outer ring 3 of the annular spring reduces the radial expansion due to its own elastic restoring force, and the normal pressure between the conical surfaces decreases. Under the action of the elastic restoring force of the outer ring 3 of the annular spring, the nut retracts axially, and the screw stop 2 returns to its initial position.

[0054] Through the above structure, this embodiment achieves reliable mechanical limiting function during normal operation. In the event of an abnormal impact, the shear pin 6 suppresses the peak instantaneous impact load, and then the force amplification effect of the conical structure and the increasing characteristics of frictional torque achieve progressive buffering and deceleration. The buffer stroke of this structure is 12mm, which is 3 times longer than that of the traditional axial spring buffer structure, and the single energy absorption capacity is approximately 120J, which is about 150% higher than that of the traditional structure. The axial length of this structure is 45mm, which is 40% smaller than the 75mm axial length of the traditional axial spring buffer structure, achieving the goal of compact structure and light weight.

[0055] Third embodiment: The difference between this embodiment and the previous embodiment is that the part where the outer circular surface of the lead screw stop 2 contacts the inner circular surface of the outer ring 3 of the annular spring is made of wear-resistant material.

[0056] The outer cylindrical surface of the lead screw stop 2, i.e., the first conical surface, is treated with carburizing and quenching. The process is as follows: the lead screw stop 2 is placed in a carburizing furnace and carburized at 920℃ for 8 hours to a carburizing depth of 0.8mm. Then, it is quenched in oil at 850℃ for 30 minutes. After quenching, the surface hardness reaches HRC58 to HRC62. The first conical surface after carburizing and quenching has high hardness and high wear resistance.

[0057] The inner circular surface of the outer ring 3 of the annular spring, specifically the third and fourth conical surfaces, is coated with a ceramic coating. The coating material is alumina ceramic, with a thickness of 0.1 mm and a hardness of HV1200. The ceramic coating is applied to the inner circular surface of the outer ring 3 of the annular spring using a plasma spraying process, and the bonding strength between the coating and the substrate is greater than 50 MPa. The ceramic coating exhibits high hardness, a low coefficient of friction, and high wear resistance.

[0058] By employing wear-resistant materials, the wear resistance of the friction surface between the first conical surface of the lead screw stop 2 and the third conical surface of the outer ring 3 of the annular spring is significantly improved. During the buffering process, relative sliding occurs between the two conical surfaces, with a sliding distance of approximately 12 mm, and the sliding speed decreases as the nut decelerates. The wear-resistant material reduces the wear depth of the friction surface from 0.5 mm per 1000 cycles for conventional materials to 0.08 mm per 1000 cycles, a reduction of approximately 84%. The coefficient of friction remains stable within the range of 0.12 to 0.15, without significantly decreasing with increasing cycle count. The service life is extended from 5000 cycles for conventional materials to 25000 cycles, a five-fold increase.

[0059] The use of wear-resistant materials enables the structure to maintain stable cushioning performance during long-term use, reducing maintenance frequency and replacement costs, and improving system reliability.

[0060] Fourth embodiment: The difference between this embodiment and the second embodiment is that a torque transmission structure is provided between the inner surface of the inner hole of the inner ring of the annular spring 4 and the outer circular surface of the lead screw 1.

[0061] The inner surface of the inner ring of the annular spring 4 is machined with splines. The splines are involute splines with a module of 1mm, 12 teeth, a tooth width of 5mm, a tooth tip circle diameter of 31mm, and a tooth root circle diameter of 29mm. The splines are evenly distributed circumferentially along the inner surface of the inner ring of the annular spring 4, with an axial length of 20mm, which is consistent with the axial length of the inner ring of the annular spring 4.

[0062] The outer circular surface of the lead screw 1 is machined with splines that mate with the splines. The module, number of teeth, and tooth width of the splines are the same as those of the inner ring 4 of the annular spring. The addendum circle diameter is 30.9 mm, the dedendum circle diameter is 29.1 mm, the spline fit accuracy is H7 / h6, and the fit method is a clearance fit with a clearance of 0.05 to 0.15 mm. The axial length of the splines is 20 mm, which is the same as the spline length of the inner ring 4 of the annular spring.

[0063] After the inner spline of the inner ring of the annular spring 4 mates with the outer spline of the lead screw 1, the inner ring of the annular spring 4 and the lead screw 1 are locked in the circumferential direction and cannot rotate relative to each other, but can move relative to each other in the axial direction. The torsional transmission capacity of the spline is calculated according to the spline strength formula T=z·h·l·b·[τ], where z is the number of teeth (12), h is the tooth height (1mm), l is the tooth width (5mm), b is the working length (20mm), and [τ] is the allowable shear stress (taken as 30MPa). The calculated torsional transmission capacity is approximately 36N·m.

[0064] During the buffering process, the lead screw stop 2 rotates and generates frictional torque, which is transmitted to the inner ring 4 of the annular spring through the outer ring 3. Because a spline torque transmission structure is provided between the inner ring 4 of the annular spring and the lead screw 1, the inner ring 4 of the annular spring will not rotate relative to the lead screw 1, ensuring reliable transmission of frictional torque to the lead screw 1 and the entire system. The spline's torque transmission capacity of 36 N·m is greater than the maximum frictional torque of 18 N·m generated during the buffering process, ensuring reliable torque transmission.

[0065] By setting up a torque transmission structure, the fixation between the inner ring of the annular spring 4 and the lead screw 1 is more reliable, and the friction torque transmission efficiency reaches more than 98%, avoiding fixation failure and buffer function failure caused by the relative rotation of the inner ring of the annular spring 4, thus improving the reliability of the system.

[0066] Fifth embodiment: The difference between this embodiment and the second embodiment is that the elastic buffer includes multiple annular spring outer rings to increase the buffer stroke.

[0067] In this embodiment, two outer rings 3 of annular springs are provided, denoted as the first outer ring and the second outer ring. The two outer rings are arranged in series along the axial direction of the lead screw 1. Correspondingly, one inner ring of annular springs is added, denoted as the middle inner ring, located between the two outer rings.

[0068] The structure of the outer ring of the first annular spring is the same as that of the outer ring 3 of the annular spring in Embodiment 1. The outer diameter is 60 mm, the initial inner diameter is 48 mm, the wall thickness is 3 mm, and the axial length is 30 mm. The inner surface of the outer ring of the first annular spring is provided with a third conical surface and a fifth conical surface. The third conical surface is in contact with the first conical surface of the lead screw stop 2, and the fifth conical surface is in contact with the outer conical surface of the inner ring of the middle annular spring.

[0069] The inner ring of the intermediate annular spring is an annular component with two conical surfaces on its outer surface. One conical surface mates with the fifth conical surface of the outer ring of the first annular spring, and the other conical surface mates with the sixth conical surface of the outer ring of the second annular spring. The inner diameter of the inner ring of the intermediate annular spring is 30 mm, which mates with the outer surface of the lead screw 1. The outer diameter is 48 mm, the axial length is 20 mm, and the wall thickness is 8 mm. The cone angle of both conical surfaces of the inner ring of the intermediate annular spring is 20°. The inner ring of the intermediate annular spring is fixed to the lead screw 1 by a limiting bolt, in the same way as the inner ring 4 of the annular spring in Embodiment 1.

[0070] The structure of the outer ring of the second annular spring is the same as that of the outer ring of the first annular spring. The outer diameter is 60 mm, the initial inner diameter is 48 mm, the wall thickness is 3 mm, and the axial length is 30 mm. The inner surface of the outer ring of the second annular spring has a sixth conical surface and a fourth conical surface. The sixth conical surface fits with the conical surface of the inner ring of the middle annular spring, and the fourth conical surface fits with the second conical surface of the inner ring 4 of the annular spring.

[0071] The working process of this structure is as follows: After the shear pin 6 is cut, the screw stop 2 moves axially. The first conical surface first presses against the third conical surface of the outer ring of the first annular spring, causing the outer ring of the first annular spring to expand radially and generate frictional torque. When the screw stop 2 continues to move axially to 15mm, the outer ring of the first annular spring is fully compressed, and the screw stop 2 contacts the inner ring of the middle annular spring.

[0072] The lead screw stop 2 continues to move axially, pushing the inner ring of the middle annular spring axially through the outer ring of the first annular spring. The conical surface of the inner ring of the middle annular spring presses against the sixth conical surface of the outer ring of the second annular spring, causing the outer ring of the second annular spring to expand radially and generate frictional torque. When the inner ring of the middle annular spring continues to move axially to 13mm, the outer ring of the second annular spring is fully compressed, and the inner ring of the middle annular spring contacts the inner ring 4 of the annular spring.

[0073] With a two-stage series arrangement, the total buffer stroke is 28 mm, consisting of 15 mm for the first stage and 13 mm for the second stage, which is approximately 2.3 times longer than the 12 mm single-stage buffer stroke in Example 1. The outer rings of the two-stage annular springs each generate frictional torque, with the total frictional torque being the sum of the two stage frictional torques. The single-cycle energy absorption capacity is approximately 280 J, an increase of approximately 133% compared to the 120 J in Example 1.

[0074] This structure is adapted to higher-speed impact conditions. Even when the nut speed reaches 1.0 m / s, it can still effectively buffer and decelerate, avoiding secondary impacts. By increasing the number of outer rings of the annular spring, the buffer stroke and energy absorption capacity can be further increased to meet the needs of different application scenarios.

[0075] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A lead screw end position limiting and cushioning structure, characterized by, It includes a lead screw (1) and a limiting and buffering device. The limiting and buffering device is located at the end of the lead screw (1). When the nut on the lead screw (1) moves to the end of the lead screw (1), the limiting and buffering device first limits the axial movement and rotational movement of the nut. When the limiting torque set by the limiting device is exceeded, the limiting device fails and then buffers the movement. The limiting and buffering device includes a fixing part, a rotating part, a limiting pin and a buffer part. The fixed part is fixedly connected to the end of the lead screw (1); the rotating part is rotatably sleeved on the outside of the lead screw (1); the limiting pin connects the rotating part and the lead screw (1) and bears the rotational torque of the rotating part; the buffer is located between the fixed part and the rotating part. The closer the distance between the fixed part and the rotating part, the greater the force exerted by the buffer on the rotating part. The direction of the force exerted by the buffer on the rotating part is the opposite direction of the axial movement of the nut.

2. The lead screw end limiting and buffering structure according to claim 1, characterized in that, The fixing component is the inner ring of the annular spring (4), which is axially fixed to the end of the lead screw (1) by the limiting bolt (5). The limiting bolt (5) is axially installed at the end of the lead screw (1).

3. The lead screw end limiting and buffering structure according to claim 2, characterized in that, The buffer is the outer ring (3) of the annular spring. The outer ring (3), the inner ring (4) of the annular spring, and the rotating part together form the annular spring structure.

4. The lead screw end limiting and buffering structure according to claim 3, characterized in that, The rotating component is a lead screw stop (2). The lead screw stop (2) has a first limiting boss at one end facing the nut, and a second limiting boss at the other end facing the lead screw stop (2). The shapes of the first limiting boss and the second limiting boss are matched to each other, so that the rotational torque of the nut can be transmitted to the lead screw stop (2).

5. The lead screw end limiting and buffering structure according to claim 4, characterized in that, The limit pin is a shear pin (6), which connects the screw stop (2) and the screw (1) and bears the rotational torque transmitted from the nut to the screw stop (2). When the torque is greater than the shear strength of the shear pin (6), the shear pin (6) will break.

6. The lead screw end limiting and buffering structure according to claim 4, characterized in that, The outer ring of the lead screw stop (2) and the inner ring of the outer ring of the annular spring (3) are both made of wear-resistant material.

7. The lead screw end limiting and buffering structure according to claim 5, characterized in that, A conical surface is provided on the outer circular surface of the screw stop (2), and a conical surface is provided on the outer circular surface of the inner ring (4) of the annular spring. The conical surface of the screw stop (2) and the conical surface of the inner ring (4) of the annular spring are arranged face to face. Two conical surfaces are provided on the inner circular surface of the outer ring (3) of the annular spring, which respectively fit with the conical surface of the screw stop (2) and the conical surface of the inner ring (4) of the annular spring.

8. The lead screw end limiting and buffering structure according to claim 7, characterized in that, The cone angle of all cone surfaces is between 12° and 30°.

9. The lead screw end limiting and buffering structure according to claim 2, characterized in that, A torque transmission structure is provided between the inner ring (4) of the annular spring and the lead screw (1).

10. The lead screw end limiting and buffering structure according to claim 3, characterized in that, Multiple annular spring outer rings (3) are set to increase the buffer stroke.

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