Constant force mechanism

Abstract

A constant force mechanism comprises a rack, a moving part, an output part, a positive stiffness structure and a negative stiffness structure, and the moving part is movably arranged on the rack; the output part is movably arranged on the rack, and the output part is movably connected with the moving part and drives the moving part to move, so that the output part and the moving part get close to each other or get away from each other; the positive stiffness structure comprises a first curved beam and a second curved beam which are connected between the rack and the moving part, and the first curved beam and the second curved beam are arranged in a crossed mode. The negative stiffness structure comprises a first permanent magnet and a second permanent magnet, the first permanent magnet is arranged on the rack, the second permanent magnet is arranged on the side, away from the positive stiffness structure, of the moving part, and the S pole of the second permanent magnet is opposite to the N pole of the first permanent magnet, or the N pole of the second permanent magnet is opposite to the S pole of the first permanent magnet. According to the constant force output device, the elastic deformation force of the positive stiffness structure and the magnetic force of the negative stiffness structure are overlapped, so that the resultant force is kept constant within a certain displacement range, and constant force output is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of constant force control, in particular to a constant force mechanism. BACKGROUND

[0002] A constant force mechanism is a mechanical device that can achieve constant force output within a certain range of motion. Unlike conventional elastic mechanisms that follow Hooke's law, the output force of a constant force mechanism does not change with the elastic displacement of the mechanism within the constant force interval. This characteristic makes it have wide application prospects in the fields of flexible operation / grippers, micro-positioning platforms, robot polishing end effectors, vibration isolation devices, etc. For example, a constant force mechanism can be used in polishing end effector design, which guarantees constant contact force through the mechanical properties of the mechanism, thereby improving the consistency of the polished surface.

[0003] Existing constant force mechanisms can generally be divided into two categories: rigid constant force mechanisms and flexible constant force mechanisms. Rigid constant force mechanisms can achieve constant force output within a large stroke by parallelly arranging cam spring mechanisms, multi-link spring mechanisms, and negative stiffness mechanisms such as permanent magnets with linear springs, but have the problems of large number of components and large size of the mechanism. Although flexible constant force mechanisms use flexible beams as elastic elements, they reduce the number of components and achieve compact structure design, but their constant force interval is small, which is difficult to meet the application requirements of large stroke. SUMMARY

[0004] The purpose of the present application is to provide a constant force mechanism to solve the problems of large size and small constant force output interval of the constant force mechanism.

[0005] To achieve the purpose of the present application, the present application provides the following technical solutions:

[0006] In a first aspect, the present application provides a constant force mechanism, comprising:

[0007] a rack;

[0008] a moving part movably arranged on the rack;

[0009] an output part movably arranged on the rack, the output part being movably connected with the moving part and driving the moving part to move, so that the output part and the moving part move closer to or farther away from each other;

[0010] a positive stiffness structure comprising a first curved beam and a second curved beam connected between the rack and the moving part, the first curved beam and the second curved beam being arranged in cross;

[0011] The negative stiffness structure comprises a first permanent magnet and a second permanent magnet, the first permanent magnet is arranged on the frame, the second permanent magnet is arranged on the moving part away from one side of the positive stiffness structure, the S pole of the second permanent magnet is opposite to the N pole of the first permanent magnet, or the N pole of the second permanent magnet is opposite to the S pole of the first permanent magnet.

[0012] In one embodiment, the first curved beam and the second curved beam are symmetrically arranged.

[0013] In one embodiment, the constant force mechanism further comprises a support seat and a lever, the support seat is arranged on the frame, the middle part of the lever is hinged to the support seat, the first end of the lever is hinged to the output part, and the second end of the lever is hinged to the moving part.

[0014] In one embodiment, the output part extends to one side close to the moving part and has a connecting frame, the connecting frame is provided with a first connecting shaft, and the first connecting shaft is hinged to the first end of the lever.

[0015] The lever is provided with a sliding groove extending from the middle part to the second end, the support seat is provided with a second connecting shaft, and the moving part is provided with a third connecting shaft, and the second connecting shaft and the third connecting shaft are arranged in the sliding groove.

[0016] In one embodiment, the second connecting shaft is sleeved with a first bearing, the third connecting shaft is sleeved with a second bearing, the outer ring of the first bearing abuts against the groove wall of the sliding groove, and the outer ring of the second bearing abuts against the groove wall of the sliding groove.

[0017] In one embodiment, the moving part is provided with a containing groove, and at least part of the lever, at least part of the support seat and at least part of the connecting frame are accommodated in the containing groove.

[0018] In one embodiment, the frame comprises a bottom plate, a top plate and a guide rod, the guide rod is connected between the bottom plate and the top plate, the moving part and the output part are sleeved on the guide rod, the first end of the first curved beam and the first end of the second curved beam are connected with the top plate, the second end of the first curved beam and the second end of the second curved beam are connected with the moving part, and the first permanent magnet is arranged on the bottom plate.

[0019] In one embodiment, the constant force mechanism further comprises an adjusting screw, the frame further comprises a first side plate and a second side plate, the first side plate and the second side plate are spaced apart and connected between the bottom plate and the top plate, and the adjusting screw is rotationally connected to the first side plate and the second side plate.

[0020] The support seat is sleeved on the adjusting screw and is threadedly connected, one end of the adjusting screw is connected with a hand wheel, and the adjusting screw drives the support seat to slide relative to the bottom plate.

[0021] In one implementation, the bottom plate is provided with a first mounting groove, the moving part is provided with a second mounting groove, the first permanent magnet is arranged in the first mounting groove, and the second permanent magnet is arranged in the second mounting groove.

[0022] In one implementation, the positive stiffness structure is provided with two, and the two positive stiffness structures are symmetrically arranged on two sides of the connecting frame.

[0023] The negative stiffness structure is provided with four, and two of the negative stiffness structures are symmetrically arranged on two sides of the connecting frame with the other two negative stiffness structures.

[0024] Compared with the prior art, the application has at least the following beneficial effects:

[0025] 1. In the application, the constant force mechanism is provided with movable output parts and moving parts, the output parts are used to be connected with external actuators, the first curved beam and the second curved beam in the positive stiffness structure are connected between the frame and the moving parts, the first permanent magnet in the negative stiffness structure is arranged on the frame, the second permanent magnet is arranged on the moving part, and the magnetic pole of the first end of the second permanent magnet is opposite to that of the first end of the first permanent magnet. When the input force of the external actuator acts on the output part to displace the output part, the first permanent magnet and the second permanent magnet arranged with the same magnetic pole generate a nonlinear magnetic attraction force which decreases with the increase of displacement, having a negative stiffness characteristic; the first curved beam and the second curved beam with a special shape generate a nonlinear elastic deformation force which increases with the increase of displacement, having a positive stiffness characteristic. By connecting the positive stiffness structure and the negative stiffness structure in parallel, the elastic deformation force of the positive stiffness structure and the magnetic force of the negative stiffness structure are superimposed on each other, so that the resultant force of the two forces remains relatively constant within a certain displacement range, thereby realizing constant force output.

[0026] 2. In the application, the first curved beam and the second curved beam of the positive stiffness structure are arranged in cross to enhance the rigidity and stability of the whole structure, which can effectively resist external interference and vibration and ensure the smoothness of the moving part and the output part during movement. At the same time, the negative stiffness structure provides a non-contact force adjustment mode through magnetic force, reducing the problems of friction, wear and fatigue caused by mechanical contact and improving the service life and reliability of the mechanism.

[0027] 3. In the application, by reasonably designing the parameters of the positive stiffness structure and the negative stiffness structure, such as the stiffness of the curved beam, the magnetic strength and relative position of the permanent magnet, the constant force mechanism can realize constant force output within a larger displacement range, having higher flexibility and designability.

[0028] 4、In the present application, the positive stiffness structure is integrated between the moving part and the rack, and the cross curved beam is used to realize the guiding and elastic supporting functions, thereby reducing the number of independent components. Compared with the single elastic element structure of the flexible constant force mechanism, the synergy of the cross curved beam and the permanent magnet can expand the constant force interval, avoid the output force fluctuation caused by the limited deformation of the elastic element, and effectively solve the contradiction between the compact layout and the constant force interval. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0030] Figure 1 It is a perspective view of the constant force mechanism of one embodiment of the present application;

[0031] Figure 2 It is a front view of the constant force mechanism of one embodiment of the present application;

[0032] Figure 3 It is a sectional view of the negative stiffness structure position of the constant force mechanism of one embodiment of the present application;

[0033] Figure 4 It is a sectional view of the center position of the constant force mechanism of one embodiment of the present application;

[0034] Figure 5 It is an exploded view of the constant force mechanism of one embodiment of the present application;

[0035] Figure 6 It is a partial structure perspective view of the constant force mechanism of one embodiment of the present application;

[0036] Figure 7 It is a partial structure exploded view of the constant force mechanism of one embodiment of the present application.

[0037] Explanation of reference signs:

[0038] 100, frame; 110, bottom plate; 111, first mounting slot; 120, top plate; 121, through hole; 130, guide rod; 140, first side plate; 150, second side plate; 200, moving piece; 210, third connecting shaft; 220, second bearing; 230, accommodating slot; 240, second mounting slot; 300, output piece; 310, connecting frame; 320, first connecting shaft; 400, positive stiffness structure; 410, first curved beam; 420, second curved beam; 430, intersection; 500, negative stiffness structure; 510, first permanent magnet; 520, second permanent magnet; 600, support seat; 610, second connecting shaft; 620, first bearing; 700, lever; 710, sliding groove; 800, adjusting lead screw; 900, hand wheel. DETAILED DESCRIPTION

[0039] The following are specific embodiments of the present application and further describe the technical solutions of the present application in conjunction with the drawings, but the present application is not limited to these embodiments.

[0040] Reference Figure 1 , Figure 2 and Figure 3 , the present application provides a constant force mechanism, comprising a frame 100, a moving piece 200, an output piece 300, a positive stiffness structure 400 and a negative stiffness structure 500.

[0041] The frame 100 serves as the support frame of the entire constant force mechanism, providing a basis for the installation and fixation of other components, ensuring the stability of the overall structure of the mechanism and the fixation of the relative position relationship, so that the moving piece 200, the output piece 300 and other components can move within the set spatial range.

[0042] The moving piece 200 is movably arranged on the frame 100, and the moving piece 200 can move within the movement path or range defined by the frame 100. The movement of the moving piece 200 is realized by the output piece 300, and through the movable connection with the output piece 300, the mutual approach or mutual away action between the moving piece 200 and the output piece 300 is realized.

[0043] The output piece 300 is movably arranged on the frame 100, and the movement of the output piece 300 is the source of the movement input and output of the entire constant force mechanism. The output piece 300 is used to connect with the external execution mechanism, and through the displacement of the external execution mechanism drive, the moving piece 200 drives the moving piece 200 to move, thereby changing the relative position relationship between the two.

[0044] The positive stiffness structure 400 comprises a first curved beam 410 and a second curved beam 420 connected between the frame 100 and the moving part 200, and the first curved beam 410 and the second curved beam 420 are arranged in a cross manner. The first curved beam 410 and the second curved beam 420 have a certain elastic deformation capacity, and when the moving part 200 is displaced by the output part 300, the first curved beam 410 and the second curved beam 420 will generate an elastic restoring force to try to make the moving part 200 return to the original position, and the elastic restoring force provided by the positive stiffness structure 400 is proportional to the displacement of the moving part 200.

[0045] The negative stiffness structure 500 comprises a first permanent magnet 510 and a second permanent magnet 520, the first permanent magnet 510 is arranged on the frame 100, and the second permanent magnet 520 is arranged on the moving part 200 away from the positive stiffness structure 400, and the S pole of the second permanent magnet 520 is opposite to the N pole of the first permanent magnet 510, or the N pole of the second permanent magnet 520 is opposite to the S pole of the first permanent magnet 510. When the moving part 200 is displaced, the interaction force between the magnetic poles of the first curved beam 410 and the second curved beam 420 will decrease with the increase of the displacement, and this change characteristic makes the negative stiffness structure 500 generate a force opposite to the displacement direction of the moving part 200, that is, it shows a negative stiffness characteristic.

[0046] Specifically, the constant force mechanism is arranged by arranging the movable output part 300 and the moving part 200, the output part 300 is used to be connected with the external actuator, the first curved beam 410 and the second curved beam 420 in the positive stiffness structure 400 are connected between the frame 100 and the moving part 200, the first permanent magnet 510 in the negative stiffness structure 500 is arranged on the frame 100, the second permanent magnet 520 is arranged on the moving part 200, and the magnetic poles of the two ends of the second permanent magnet 520 and the first permanent magnet 510 are opposite to each other, specifically, the S pole of the second permanent magnet 520 is opposite to the N pole of the first permanent magnet 510, or the N pole of the second permanent magnet 520 is opposite to the S pole of the first permanent magnet 510. When the input force of the external actuator acts on the output part 300 to displace the output part 300, the first permanent magnet 510 and the second permanent magnet 520 arranged with opposite magnetic poles generate a nonlinear magnetic attraction force which decreases with the increase of the displacement, and has a negative stiffness characteristic; the first curved beam 410 and the second curved beam 420 with special shapes generate a nonlinear elastic deformation force which increases with the increase of the displacement, and have a positive stiffness characteristic. By connecting the positive stiffness structure 400 and the negative stiffness structure 500 in parallel, the elastic deformation force of the positive stiffness structure 400 and the magnetic force of the negative stiffness structure 500 are superimposed on each other, so that the resultant force of the two forces can remain relatively constant within a certain displacement range, thereby realizing constant force output.

[0047] In the present application, the first curved beam 410 and the second curved beam 420 of the positive stiffness structure 400 are arranged in cross to enhance the stiffness and stability of the structure as a whole, which can effectively resist external interference and vibration and ensure the smoothness of the moving part 200 and the output part 300 during movement. At the same time, the negative stiffness structure 500 provides a non-contact force adjustment mode through magnetic force, which reduces the problems of friction, wear and fatigue caused by mechanical contact, and improves the service life and reliability of the mechanism.

[0048] By reasonably designing the parameters of the positive stiffness structure 400 and the negative stiffness structure 500, such as the stiffness of the first curved beam 410 and the second curved beam 420, the magnetic strength and relative position of the first permanent magnet 510 and the second permanent magnet 520, the constant force mechanism can achieve constant force output in a larger displacement range, with higher flexibility and designability.

[0049] At the same time, the positive stiffness structure 400 is integrated between the moving part 200 and the rack 100, and the first curved beam 410 and the second curved beam 420 arranged in cross realize the functions of guiding and elastic support at the same time, reducing the number of independent components. Compared with the single elastic element structure of the flexible constant force mechanism, the synergistic effect of the first curved beam 410 and the second curved beam 420 arranged in cross and the first permanent magnet 510 and the second permanent magnet 520 arranged oppositely can expand the constant force interval, avoid the output force fluctuation caused by the limited deformation of the elastic element, and effectively solve the contradiction between compact layout and constant force interval.

[0050] Among them, the first curved beam 410 and the second curved beam 420 are arranged symmetrically, when the moving part 200 is driven by the output part 300 to produce displacement, the first curved beam 410 and the second curved beam 420 realize symmetric deformation, so that the elastic deformation amount of the first curved beam 410 and the second curved beam 420 tends to be consistent, thereby maintaining the linear stiffness output of the positive stiffness structure 400 during the movement of the moving part 200, ensuring that the elastic force generated by the positive stiffness structure 400 and the magnetic force of the negative stiffness structure 500 during the movement of the moving part 200 are accurately offset, thereby expanding the effective stroke of constant force output and improving the constant force stability.

[0051] In an embodiment, the first curved beam 410 and the second curved beam 420 are arranged to intersect to form a plurality of intersection points 430, and the plurality of intersection points 430 are in the same plane. The intersection point 430 is a contact or connection position formed by the intersection of the first curved beam 410 and the second curved beam 420 in the spatial layout, and can be implemented in a symmetrical intersection, a staggered intersection, or a periodically repeated intersection. The distribution of the intersection points 430 directly affects the mechanical properties of the positive stiffness structure 400, and the stiffness distribution of the elastic element can be optimized by controlling the number and position of the intersection points 430. The same plane means that all intersection points 430 are located in a geometric plane, which can be achieved by adjusting the bending radius, intersection angle, or installation position of the curved beam. The coplanar design of the intersection points 430 can avoid the asymmetric load distribution caused by spatial staggering, thereby improving the stability of the positive stiffness structure 400.

[0052] The optimization process of the positive stiffness structure 400 and the secondary stiffness structure 500 is as follows: the control points and structure parameters of the first curved beam 410 and the second curved beam 420 are defined by a genetic algorithm to form a shape spline curve of the first curved beam 410 and the second curved beam 420, and the deformation-elastic force relationship of the first curved beam 410 and the second curved beam 420 is calculated by a chain quantity constraint model; the initial gap between the first permanent magnet 510 and the second permanent magnet 520 is defined by a genetic algorithm, and the attractive force curve between the first permanent magnet 510 and the second permanent magnet 520 is calculated to obtain a spline curve target function and an attractive force curve target function, so as to determine the parameters of the positive stiffness structure 400 and the secondary stiffness structure 500 with the minimum force fluctuation amplitude and the maximum constant force interval.

[0053] Reference Figure 3 , Figure 4 and Figure 5 The constant force mechanism further includes a support seat 600 and a lever 700. The support seat 600 is arranged on the rack 100, and the middle part of the lever 700 is hinged to the support seat 600. The first end of the lever 700 is hinged to the output 300, and the second end of the lever 700 is hinged to the moving part 200. The support seat 600 is a structure arranged on the rack 100 for providing a rotating fulcrum of the lever 700. The lever 700 is a rigid rod with three connection points, and the output 300 and the moving part 200 are connected by the lever 700 structure, so as to realize the mutual approach or mutual separation of the output 300 and the moving part 200.

[0054] Specifically, when the output member 300 is displaced by an external force, the lever 700 rotates around the support base 600, and drives the output member 300 and the moving member 200 to move in linkage through the two hinged points at the two ends of the lever 700. The hinging of the first end of the lever 700 and the output member 300 converts the linear displacement into rotary motion, and the hinging of the second end and the moving member 200 reversely converts the rotary motion into linear displacement, thereby realizing the coordinated movement of the output member 300 and the moving member 200 moving away from or moving towards each other, and further adjusting the balance state of the positive stiffness structure 400 and the negative stiffness structure 500.

[0055] The present application realizes bidirectional displacement transmission with fewer components through the combination design of the single lever 700 and the double hinged points, simplifies the transmission structure while ensuring the constant force adjustment accuracy, and reduces the number of components and the overall volume of the constant force mechanism.

[0056] The output member 300 extends to the side close to the moving member 200 with a connecting frame 310, and the connecting frame 310 is provided with a first connecting shaft 320 hinged with the first end of the lever 700; the lever 700 is provided with a sliding groove 710 extending from the middle to the second end, the support base 600 is provided with a second connecting shaft 610, and the moving member 200 is provided with a third connecting shaft 210, both the second connecting shaft 610 and the third connecting shaft 210 are arranged in the sliding groove 710.

[0057] The connecting frame 310 is a rigid component integrally extended with the output member 300, used for transmitting the displacement of the output member 300 to the lever 700. The sliding groove 710 is a strip-shaped through hole opened along the length direction of the lever 700, used for restricting the sliding track of the second connecting shaft 610 and the third connecting shaft 210. The third connecting shaft 210 is a driving shaft arranged on the moving member 200, used for converting the swing of the lever 700 into the linear displacement of the moving member 200.

[0058] Specifically, when the output member 300 is displaced by an external force, the connecting frame 310 drives the first connecting shaft 320 to push the lever 700 to rotate around the support base 600. The sliding groove 710 on the lever 700 allows the second connecting shaft 610 and the third connecting shaft 210 to slide along the length direction, and the moving track of the third connecting shaft 210 in the sliding groove 710 is converted into the linear motion of the moving member 200, while the sliding of the second connecting shaft 610 in the sliding groove 710 offsets the lateral deviation generated by the rotation of the lever 700. This structure converts the linear motion of the output member 300 into the compound motion of the lever 700 through the cooperation of the sliding groove 710 and the connecting shaft, and finally drives the moving member 200 and the output member 300 to move reversely in synchronization.

[0059] The application sets the sliding groove 710 on the lever 700 and cooperates with the slidable second connecting shaft 610 and the third connecting shaft 210, so that the lever 700 can adaptively adjust the fulcrum position when transmitting motion and eliminate motion interference. At the same time, the cooperation of the sliding groove 710 with the second connecting shaft 610 and the third connecting shaft 210 replaces the traditional multi-link structure, simplifies the complexity of the transmission chain, and improves the compactness of the mechanism.

[0060] Further, the first bearing 620 is sleeved on the second connecting shaft 610, and the second bearing 220 is sleeved on the third connecting shaft 210. The outer ring of the first bearing 620 abuts against the groove wall of the sliding groove 710, and the outer ring of the second bearing 220 abuts against the groove wall of the sliding groove 710. The first bearing 620 and the second bearing 220 are rolling elements for reducing friction between moving parts, and can be implemented by deep groove ball bearings or needle bearings. The outer rings of the first bearing 620 and the second bearing 220 abut against the inner wall of the sliding groove 710 to form a surface contact, which can be achieved by interference fit or gap adjustment to balance the motion accuracy and friction loss.

[0061] Specifically, when the lever 700 rotates around the hinged point of the support base 600, the second connecting shaft 610 and the third connecting shaft 210 slide in the sliding groove 710 respectively. The outer rings of the first bearing 620 and the second bearing 220 contact the groove wall of the sliding groove 710 to convert sliding friction into rolling friction, thereby reducing the resistance in the motion process of the lever 700. The inner ring of the first bearing 620 is fixed with the second connecting shaft 610, and the inner ring of the second bearing 220 is fixed with the third connecting shaft 210. The outer rings of the first bearing 620 and the second bearing 220 freely roll along the extension direction of the sliding groove 710, so that the linkage between the moving part 200 and the output part 300 is smoother, and the force transmission lag phenomenon caused by friction is avoided. The first connecting shaft 320 and the lever 700 can also be connected by a needle bearing.

[0062] In the embodiment of the application, the moving part 200 is provided with a receiving groove 230, and at least part of the lever 700, at least part of the support base 600 and at least part of the connecting frame 310 are accommodated in the receiving groove 230. The receiving groove 230 is a recessed space provided on the moving part 200, which is used to accommodate the partial structure of the lever 700, the support base 600 and the connecting frame 310.

[0063] Specifically, the depth and width of the accommodating groove 230 can be designed according to the actual sizes of the lever 700, the support base 600 and the connecting frame 310, so that at least one end of the lever 700 is always located inside the accommodating groove 230 during the hinged movement. After the partial structure of the support base 600 is embedded in the accommodating groove 230, the swing limiting of the lever 700 is realized by the cooperation of the second connecting shaft 610 and the sliding groove 710. The part of the connecting frame 310 extending into the accommodating groove 230 is hinged with the first end of the lever 700, so that when the relative movement of the output member 300 and the moving member 200 is transmitted through the lever 700, each component maintains a stable movement trajectory under the space constraint in the accommodating groove 230, avoiding external interference.

[0064] The application integrates multiple moving components inside the moving member 200 through the accommodating groove 230, effectively reduces the space occupation of the mechanism in the movement direction, improves the compactness of the structure, and avoids interference between the lever 700, the support base 600 and the connecting frame 310 and the external environment during movement, enhancing the stability and reliability of the operation of the constant force mechanism.

[0065] Reference Figure 3 , Figure 4 , Figure 6 And Figure 7 , the rack 100 includes a bottom plate 110, a top plate 120 and a guide rod 130, the guide rod 130 is connected between the bottom plate 110 and the top plate 120, the moving member 200 and the output member 300 are sleeved on the guide rod 130, the first end of the first curved beam 410 and the first end of the second curved beam 420 are connected with the top plate 120, the second end of the first curved beam 410 and the second end of the second curved beam 420 are connected with the moving member 200, and the first permanent magnet 510 is arranged on the bottom plate 110.

[0066] Among them, the bottom plate 110 is a base component for bearing the overall structure, the top plate 120 is a top bearing component arranged parallel to the bottom plate 110, and a rigid frame structure is formed with the bottom plate 110 through the guide rod 130 to provide movement constraint for the moving member 200 and the output member 300. The guide rod 130 is a rigid rod connecting the bottom plate 110 and the top plate 120, which can be a cylindrical metal rod, used to limit the movement trajectory of the moving member 200 and the output member 300, and ensure their axial movement. The first curved beam 410 and the second curved beam 420 are elastic beams with curved shape, whose two ends are fixed to the top plate 120 and the moving member 200 respectively, and cross-arranged to generate positive stiffness through elastic deformation, used to offset the nonlinear force of the negative stiffness structure 500. The first permanent magnet 510 is a magnetic element fixed on the bottom plate 110, which forms an opposite arrangement with the second permanent magnet 520 on the moving member 200 with opposite magnetic poles, and generates a negative stiffness effect through magnetic repulsion or attraction.

[0067] Specifically, the bottom plate 110, the top plate 120 and the guide rod 130 jointly constitute a rigid frame of the rack 100, the axial arrangement of the guide rod 130 enables the movement direction of the moving part 200 and the output part 300 to be accurately constrained when the moving part 200 and the output part 300 slide along the guide rod 130, and the moving part 200 and the output part 300 can be matched with the guide rod 130 through linear bearings to avoid deflection or jamming. The cross-connection mode of the first curved beam 410 and the second curved beam 420 enables the first curved beam 410 and the second curved beam 420 to symmetrically elastically deform when the moving part 200 is displaced, to generate a linear restoring force, thereby providing stable positive stiffness. The first permanent magnet 510 and the second permanent magnet 520 on the moving part 200 form a magnetic pole opposition, and when the moving part 200 moves away from the bottom plate 110, the magnetic repulsion force decreases with the increase of the distance, and after superimposing the elastic force of the positive stiffness structure 400, a constant force output is realized. The top plate 120 serves as a fixed end of the first curved beam 410 and the second curved beam 420, ensures the stability of the force transmission path when the first curved beam 410 and the second curved beam 420 deform, and a through hole 121 is formed in the top plate 120 to enable the output part 300 to be connected with an external actuator.

[0068] The present application integrates the movement constraint and stiffness generation of the moving part 200 and the output part 300 into a single frame through the combination of the guide rod 130 and the cross-arranged first curved beam 410 and second curved beam 420, thereby significantly simplifying the structural layout. The first permanent magnet 510 is fixed to the bottom plate 110, and the second permanent magnet 520 moves with the moving part 200, so that the direction of the magnetic force is consistent with the moving direction. The second end of the first curved beam 410 and the second end of the second curved beam 420 are both connected with the moving part 200, and through the movement of the moving part 200, the positive stiffness structure 400 and the negative stiffness structure 500 can be cooperated to realize constant force output.

[0069] The constant force mechanism further comprises an adjusting lead screw 800, and the rack 100 further comprises a first side plate 140 and a second side plate 150, which are connected between the bottom plate 110 and the top plate 120 in a spaced manner, and the adjusting lead screw 800 is rotationally connected to the first side plate 140 and the second side plate 150; the support seat 600 is sleeved on the adjusting lead screw 800 and is threadedly connected, one end of the adjusting lead screw 800 is connected with a hand wheel 900, and the adjusting lead screw 800 drives the support seat 600 to slide relative to the bottom plate 110. The adjusting lead screw 800 drives the support seat 600 to slide relative to the bottom plate 110.

[0070] The adjusting screw 800 is a cylindrical transmission component with a threaded structure, and its rotary motion can be converted into linear displacement of the support seat 600. The first side plate 140 and the second side plate 150 are parallel plate structures used to fix the adjusting screw 800 and maintain the position of the rotary axis of the adjusting screw 800. The threaded connection between the support seat 600 and the adjusting screw 800 is achieved by matching the internal threaded hole of the support seat 600 with the external thread of the adjusting screw 800, which is used to convert the rotary motion of the adjusting screw 800 into the movement of the support seat 600 along the extension direction of the adjusting screw 800. The hand wheel 900 can be a rotary driving component with a gripping structure, which is used to provide a force point for manually operating the adjusting screw 800.

[0071] Specifically, when the hand wheel 900 is rotated, the adjusting screw 800 rotates, and the support seat 600 is displaced in the direction of the bottom plate 110 under the threaded cooperation. Since the position of the hinge point of the support seat 600 and the lever 700 changes, the force arm ratio between the fulcrum of the lever 700 and the output member 300 and the moving member 200 is dynamically adjusted, thereby changing the constant force value borne by the output member 300. This adjustment process does not require disassembly of the mechanism components, and continuous control of the constant force output can be achieved by simply rotating the hand wheel 900.

[0072] It should be noted that the output force F1 acting on the output member 300 and the constant force unit force F2 acting on the moving member 200 act on the lever 700 through the first connecting shaft 320 and the third connecting shaft 210, respectively. By adjusting the position of the support seat 600, the ratio of the distance L1 between the first connecting shaft 320 and the second connecting shaft 610 and the distance L2 between the second connecting shaft 610 and the third connecting shaft 210 can be changed, thereby changing the ratio of F1 to F2, and ultimately adjusting the output force F1 of the constant force mechanism through the lever 700 ratio, achieving continuous and large-range adjustment of the constant force output amplitude. At the same time, since the direction of the output force is nearly perpendicular to the extension direction of the adjusting screw 800, high constant force adjustment energy efficiency can be achieved.

[0073] The present application can achieve stepless adjustment of the constant force output value through the transmission and linkage design of the adjusting screw 800 and the support seat 600 without changing the original structure, solving the problem of limited application range caused by fixed parameter design of existing constant force mechanisms. The operator can quickly adjust the output force according to the actual working conditions by operating the hand wheel 900, improving the adaptability of the constant force mechanism to different working scenarios.

[0074] The bottom plate 110 is provided with a first mounting groove 111, the moving part 200 is provided with a second mounting groove 240, the first permanent magnet 510 is arranged in the first mounting groove 111, and the second permanent magnet 520 is arranged in the second mounting groove 240. The first mounting groove 111 is a groove on the bottom plate 110 for accommodating the first permanent magnet 510, the shape of which matches that of the first permanent magnet 510, and is used to limit the position of the first permanent magnet 510 on the bottom plate 110. The second mounting groove 240 is a groove on the moving part 200 for accommodating the second permanent magnet 520, and its structure is similar to that of the first mounting groove 111, and the relative position between the second permanent magnet 520 and the first permanent magnet 510 is ensured to be stable by fixing the second permanent magnet 520.

[0075] Specifically, the first permanent magnet 510 is embedded in the first mounting groove 111 of the bottom plate 110, and the second permanent magnet 520 is embedded in the second mounting groove 240 of the moving part 200. The sizes of the first mounting groove 111 and the second mounting groove 240 can be adjusted according to the shapes of the first permanent magnet 510 and the second permanent magnet 520 respectively, for example, rectangular grooves or circular grooves are adopted, and the first permanent magnet 510 and the second permanent magnet 520 are fixed by adhesives or press-fitting, so as to ensure that the relative position of the magnetic poles between the first permanent magnet 510 and the second permanent magnet 520 is always consistent, avoid the change of negative stiffness characteristics caused by the deviation of the first permanent magnet 510 and the second permanent magnet 520, and thus improve the stability of constant force output.

[0076] In an embodiment, two positive stiffness structures 400 are arranged symmetrically on both sides of the connecting frame 310, and four negative stiffness structures 500 are arranged symmetrically on both sides of the connecting frame 310. The two symmetrically arranged positive stiffness structures 400 can balance the stress distribution on both sides of the connecting frame 310, and avoid deflection caused by unilateral stress. The four symmetrically arranged negative stiffness structures 500 can offset the lateral deviation force generated during the movement of the moving part 200, and maintain the straight line movement track of the moving part 200.

[0077] Specifically, the two symmetric positive stiffness structures 400 are respectively located on both sides of the connecting frame 310, and when the output part 300 drives the moving part 200 to move, the positive stiffness structures 400 on both sides synchronously generate elastic deformation in the same direction, thereby balancing the stress on both sides of the connecting frame 310. The four negative stiffness structures 500 are symmetrically arranged in two groups, and when the moving part 200 approaches or moves away from the rack 100, the two negative stiffness structures 500 in each group interact through magnetic repulsion to form a mechanical response opposite to that of the positive stiffness structure 400, and the symmetric arrangement of the two groups of negative stiffness structures 500 further eliminates the lateral moment during the movement of the moving part 200, thereby improving the stability of the overall movement of the constant force mechanism.

[0078] It should be noted that all directional indications, such as upper, lower, left, right, front, back, and the like, are used to describe the relative positions between the components shown in the accompanying drawings, the movement conditions and the like in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directional indications will also change accordingly.

[0079] In addition, the descriptions such as "first", "second", "one" and the like in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the technical features or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0080] In the present application, unless otherwise explicitly specified and limited, the terms "connection", "fixing" and the like should be understood in a broad sense, for example, "fixing" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be direct connection, or indirect connection through intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0081] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the realization of the ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the scope of protection claimed by the present application.

Claims

1. A constant force mechanism, characterized in that, include: frame; A movable component is movably mounted on the frame; An output component is movably mounted on the frame. The output component is movably connected to the movable component and drives the movable component to move, so that the output component and the movable component move closer to each other or further apart. A positive stiffness structure includes a first curved beam and a second curved beam connected between the frame and the moving part, wherein the first curved beam and the second curved beam are arranged intersectingly; The negative stiffness structure includes a first permanent magnet and a second permanent magnet. The first permanent magnet is disposed on the frame, and the second permanent magnet is disposed on the side of the moving part away from the positive stiffness structure. The S pole of the second permanent magnet is opposite to the N pole of the first permanent magnet, or the N pole of the second permanent magnet is opposite to the S pole of the first permanent magnet.

2. The constant force mechanism according to claim 1, characterized in that, The first curved beam and the second curved beam are arranged symmetrically.

3. The constant force mechanism according to claim 1, characterized in that, The constant force mechanism further includes a support base and a lever. The support base is mounted on the frame. The middle part of the lever is hinged to the support base. The first end of the lever is hinged to the output component. The second end of the lever is hinged to the moving component.

4. The constant force mechanism according to claim 3, characterized in that, The output component extends a connecting frame towards the side of the moving component, and the connecting frame is provided with a first connecting shaft, which is hinged to the first end of the lever. The lever is provided with a groove that extends from the middle of the lever to the second end. The support base is provided with a second connecting shaft, and the moving part is provided with a third connecting shaft. Both the second connecting shaft and the third connecting shaft pass through the groove.

5. The constant force mechanism according to claim 4, characterized in that, A first bearing is fitted on the second connecting shaft, and a second bearing is fitted on the third connecting shaft. The outer ring of the first bearing abuts against the groove wall of the slide, and the outer ring of the second bearing abuts against the groove wall of the slide.

6. The constant force mechanism according to claim 4, characterized in that, The movable component is provided with a receiving groove, in which at least a portion of the lever, at least a portion of the support base, and at least a portion of the connecting frame are received.

7. The constant force mechanism according to claim 4, characterized in that, The frame includes a base plate, a top plate, and a guide rod. The guide rod is connected between the base plate and the top plate. The moving part and the output part are both sleeved on the guide rod. The first end of the first curved beam and the first end of the second curved beam are both connected to the top plate. The second end of the first curved beam and the second end of the second curved beam are both connected to the moving part. The first permanent magnet is disposed on the base plate.

8. The constant force mechanism according to claim 7, characterized in that, The constant force mechanism further includes an adjusting screw, and the frame further includes a first side plate and a second side plate. The first side plate and the second side plate are connected between the bottom plate and the top plate at intervals, and the adjusting screw is rotatably connected to the first side plate and the second side plate. The support seat is sleeved on the adjusting screw and threadedly connected. One end of the adjusting screw is connected to a handwheel, and the adjusting screw drives the support seat to slide relative to the base plate.

9. The constant force mechanism according to claim 7, characterized in that, The base plate is provided with a first mounting groove, the movable component is provided with a second mounting groove, the first permanent magnet is disposed in the first mounting groove, and the second permanent magnet is disposed in the second mounting groove.

10. The constant force mechanism according to claim 7, characterized in that, Two positive stiffness structures are provided, and the two positive stiffness structures are symmetrically arranged on both sides of the connecting frame; Four negative stiffness structures are provided, with two of them arranged symmetrically on both sides of the connecting frame along with the other two negative stiffness structures.

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