Spring device based on cam mechanism and design method thereof

Abstract

The invention discloses a spring device based on a cam mechanism and a design method thereof, and relates to the field of springs.The spring device comprises a supporting device, two spring subsystems and a pull rope, each spring subsystem comprises a rotating disc assembly and an elastic piece, and the rotating disc assembly and the supporting device form rotating connection around a rotating axis; the elastic pieces are connected with the corresponding rotating disc assemblies and the corresponding supporting devices. A groove of which the inner bottom wall is a cam curved surface is formed in the outer side wall of the turntable assembly; the pull rope comprises two pull rope sections, the two pull rope sections are fixedly connected with the two rotating disc assemblies respectively, and the pull rope sections are wound on a cam curved surface; the pull rope sections can pull the corresponding rotating disc assemblies to rotate around the rotating axes under the action of external force and enable the corresponding elastic pieces to be stretched or compressed. The rotating disc assembly can rotate around the rotating axis under the action of restoring force of the corresponding elastic piece. And the shapes and sizes of the curved surfaces of the two cams are obtained according to the expected rigidity and the rigidity of the two elastic pieces. Springs with different rigidity characteristics can be obtained, and machining and manufacturing are easy.

Description

Technical Field

[0001] The invention relates to the technical field of springs, and in particular to a spring device based on a cam mechanism and a design method thereof. Background Art

[0002] Spring devices can be used to achieve functions such as shock absorption, resetting and energy storage, and are widely used. At present, spring devices are mostly wire springs composed of wire wound into a spiral shape. The stiffness design of the wire spring is the key to ensuring that it has a specific elongation under specific load conditions. The current stiffness design steps of the wire spring mainly include: First, determine the material, spring wire diameter, spring outer diameter, effective number of turns and other parameters of the wire spring according to the requirements, and use the formula K = Gd 4 / 8D 3 n calculates the stiffness of the wire spring, where K is the stiffness of the wire spring, G is the shear modulus of the wire spring, d is the wire diameter of the wire spring, D is the outer diameter of the wire spring, and n is the effective number of coils of the wire spring; second, comprehensively consider the nonlinear characteristics of the wire spring material, the manufacturing process and the test conditions of the wire spring, and optimize the material selection of the wire spring and the dimensional parameters such as the spring wire diameter and the spring outer diameter. In the above steps, due to the limitations of the spring material and structure, the shape of the stiffness curve of the wire spring is also subject to certain restrictions, mostly such as Figure 8 The line spring stiffness curve shown makes it difficult to design springs with different stiffness characteristics according to different stiffness characteristic requirements. Summary of the invention

[0003] The purpose of the present invention is to provide a spring device based on a cam mechanism and a design method thereof to solve the problems existing in the prior art, to obtain springs with different stiffness characteristics to meet different stiffness requirements, and to expand the application range of the spring device based on the cam mechanism; and the spring device is easy to process and manufacture.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a spring device based on a cam mechanism, comprising a supporting device, a spring subsystem and a pull rope, wherein:

[0006] There are two spring subsystems, each of which includes a turntable assembly and an elastic member. Each turntable assembly is connected to the support device in a rotational connection around a rotation axis, and each elastic member is connected to the corresponding turntable assembly and the support device. A groove is provided on the outer side wall of each turntable assembly, and the inner bottom wall of the groove is a cam surface.

[0007] The pull rope includes two pull rope segments, and the two pull rope segments are respectively fixedly connected to the two turntable assemblies, and each pull rope segment is wound around a corresponding cam surface; each pull rope segment can pull the corresponding turntable assembly to rotate around the rotation axis under the action of external force, and stretch or compress the corresponding elastic member; each turntable assembly can rotate around the rotation axis under the action of the restoring force of the corresponding elastic member.

[0008] Preferably, two pulleys are further included, and each of the pull ropes is sequentially wound around one of the cam curved surfaces and an outer side wall of a pulley.

[0009] Preferably, a displacement assembly is further included, and each of the pull ropes can be fixedly connected to the output end of the displacement assembly, and the output end of the displacement assembly can move in a direction perpendicular to the rotation axis under the action of an external force.

[0010] Preferably, the displacement assembly includes a slide rail and a slider, the slide rail is fixedly connected to the support device, the slider is slidably connected to the slide rail, and the slider is the output end of the displacement assembly.

[0011] Preferably, the supporting device comprises a base and two fixed shafts, each of the fixed shafts can be fixedly connected to the base, and each of the turntable assemblies can generate relative rotation with one of the fixed shafts around the axis of the corresponding fixed shaft.

[0012] Preferably, each of the turntable assemblies includes a turntable and a cam plate, each of the turntables is connected to the supporting device in a rotational connection around the rotation axis, and each of the elastic members is connected to the turntable of the corresponding turntable assembly; each of the cam plates is fixedly connected to an end of the corresponding turntable away from the supporting device, and the groove is provided on the outer wall of each of the cam plates.

[0013] Preferably, the cam surfaces of the two turntable assemblies are the same or different surfaces, and the two elastic members are the same or different elastic members.

[0014] The present embodiment provides a spring device design method based on the cam mechanism-based spring device, characterized in that it includes the following steps: determining the expected stiffness of the cam mechanism-based spring device, obtaining the stiffness of the two elastic members, and obtaining the shape and size of the two cam surfaces according to the expected stiffness and the stiffness of the two elastic members.

[0015] Preferably, it also includes: determining the maximum spring displacement, maximum spring output force and dimensional parameters of the spring device based on the cam mechanism, and determining the angular range, torque range and stiffness parameters of each elastic member according to the maximum spring displacement, the maximum spring output force and the dimensional parameters; testing each selected elastic member to obtain an actual stiffness curve of each elastic member; and obtaining the shape and size of the two cam surfaces according to the expected stiffness and the actual stiffness curves of the two elastic members.

[0016] Preferably, it also includes: obtaining the stiffness of the two spring subsystems according to the expected stiffness, and selecting the stiffness of the two elastic parts according to the stiffness of the two spring subsystems respectively, and the selection method includes: making the potential energy of each elastic part when each elastic part is at the maximum deformation greater than the potential energy of the spring device based on the cam mechanism when it is at the maximum spring displacement.

[0017] Compared with the prior art, the present invention has achieved the following technical effects:

[0018] The present invention provides a spring device based on a cam mechanism and a design method thereof, comprising a supporting device, a spring subsystem and a pull rope, wherein: there are two spring subsystems, each spring subsystem comprises a turntable assembly and an elastic member, each turntable assembly is formed with a supporting device in a rotational connection around a rotation axis, and each elastic member is connected to the corresponding turntable assembly and the supporting device. It should be noted that the turntable assembly and the elastic member of each spring subsystem are in one-to-one correspondence; a groove is provided on the outer side wall of each turntable assembly, and the inner bottom wall of the groove is a cam surface; the pull rope comprises two pull rope segments, the two pull rope segments are respectively fixedly connected to the two turntable assemblies, and each pull rope segment is wound around a corresponding cam surface; each pull rope segment can pull the corresponding turntable assembly to rotate around the rotation axis under the action of an external force, and stretch or compress the corresponding elastic member; each turntable assembly can rotate around the rotation axis under the action of the restoring force of the corresponding elastic member.

[0019] By selecting the elastic part, the stiffness of the elastic part can be determined. By pulling the pull rope, the two pull rope segments respectively pull the two turntable assemblies to rotate around the rotation axis, thereby compressing or stretching the elastic part. Since the inner bottom wall of the groove is a cam surface, when the stretched free end moves the same displacement, the rotation angle of the turntable assembly is different, so that the stiffness of the spring device based on the cam mechanism is different from the stiffness of the elastic part. Therefore, after determining the elastic part, the shape and size of the cam surface are adjusted to obtain springs with different stiffness characteristics. For example, springs with various nonlinear stiffness can be obtained to meet different stiffness requirements, thereby expanding the application range of the spring device based on the cam mechanism; and it is easy to process and manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic structural diagram of a spring device based on a cam mechanism provided in Example 1;

[0022] Figure 2 A schematic diagram of a partial structure of a spring device based on a cam mechanism provided in Example 1;

[0023] Figure 3 A schematic diagram of the structure of the support device and the slide rail provided in Example 1;

[0024] Figure 4 A schematic diagram of the structure of the turntable provided in Example 1;

[0025] Figure 5 A schematic diagram of the working principle of the cam mechanism provided in Example 1;

[0026] Figure 6 A force analysis diagram based on a cam mechanism provided in Example 1;

[0027] Figure 7 The desired stiffness curve in the spring device design method provided in Example 2;

[0028] Figure 8 A typical wire spring stiffness curve provided in the background art;

[0029] In the figure: 100, spring device based on cam mechanism; 1, supporting device; 101, base; 102, fixed axis; 103, slot; 2, spring subsystem; 201, elastic member; 202, turntable; 203, cam plate; 204, mounting hole; 205, claw; 206, fixed seat; 3, pull rope; 4, pulley; 5, slide rail; 6, slider; 7, rolling bearing; 8, support column. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The purpose of the present invention is to provide a spring device based on a cam mechanism and a design method thereof to solve the problems existing in the prior art, to obtain springs with different stiffness characteristics to meet different stiffness requirements, and to expand the application range of the spring device based on the cam mechanism; and the spring device is easy to process and manufacture.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] like Figures 1 to 6 As shown, the present embodiment provides a spring device 100 based on a cam mechanism, comprising a supporting device 1, a spring subsystem 2 and a pull rope 3, wherein: there are two spring subsystems 2, each spring subsystem 2 comprises a turntable assembly and an elastic member 201, each turntable assembly is formed with the supporting device 1 with a rotational connection around a rotation axis, each elastic member 201 is connected with the corresponding turntable assembly and the supporting device 1, it should be noted that the turntable assembly and the elastic member 201 of each spring subsystem 2 are in one-to-one correspondence; a groove is provided on the outer wall of each turntable assembly, and the inner bottom wall of the groove is a cam surface; the pull rope 3 comprises two pull rope segments, the two pull rope segments are respectively fixedly connected to the two turntable assemblies, and each pull rope segment is wound around a corresponding cam surface; each pull rope segment can pull the corresponding turntable assembly to rotate around the rotation axis under the action of an external force, and stretch or compress the corresponding elastic member 201; each turntable assembly can rotate around the rotation axis under the action of the restoring force of the corresponding elastic member 201.

[0035] By selecting the elastic member 201, the stiffness of the elastic member 201 can be determined; the position of the pull rope 3 on the turntable assembly is limited by the groove, so that the pull rope 3 is at the same height of the corresponding turntable assembly; the pull rope 3 is pulled, so that the two pull rope segments respectively pull the two turntable assemblies to rotate around the rotation axis, thereby compressing or stretching the elastic member 201. Since the inner bottom wall of the groove is a cam surface, when the stretched free end moves the same displacement, the rotation angle of the turntable assembly is different, so that the stiffness of the spring device 100 based on the cam mechanism is different from the stiffness of the elastic member 201. Therefore, after determining the elastic member 201, the shape and size of the cam surface are adjusted to obtain springs with different stiffness characteristics. For example, it is possible to obtain Figure 7 The spring with nonlinear stiffness shown can meet different stiffness requirements, expand the application range of the spring device 100 based on the cam mechanism, and is easy to process and manufacture.

[0036] It should be noted that the pull rope 3 can be two or one. When there are two pull ropes 3, each of the two pull ropes 3 has a pull rope segment.

[0037] Furthermore, the present embodiment further comprises two pulleys 4 , and each pull rope 3 is sequentially wound around a cam curved surface and an outer side wall of a pulley 4 .

[0038] Furthermore, the present embodiment further comprises a displacement assembly, each of the pull ropes 3 can be fixedly connected to the output end of the displacement assembly, and the output end of the displacement assembly can move in a direction perpendicular to the rotation axis under the action of an external force. The displacement assembly can limit the moving direction of the free end of the pull rope 3, and can simultaneously drive two pull ropes 3 to move along a straight line at the same time, with a simple structure and easy control.

[0039] Furthermore, the displacement assembly includes a slide rail 5 and a slider 6. The slide rail 5 is fixedly connected to the support device 1. The slider 6 is slidably connected to the slide rail 5. The slider 6 is the output end of the displacement assembly.

[0040] Furthermore, the supporting device 1 includes a base 101 and two fixed shafts 102 , each fixed shaft 102 can be fixedly connected to the base 101 , and each turntable assembly can generate relative rotation with a fixed shaft 102 around the axis of the corresponding fixed shaft 102 .

[0041] Furthermore, each turntable assembly includes a turntable 202 and a cam plate 203, each turntable 202 is formed with the supporting device 1 to have a rotational connection around a rotation axis, and each elastic member 201 is connected to the turntable 202 of the corresponding turntable assembly. It should be noted that the turntable 202 and the cam plate 203 of each turntable assembly correspond one to one; each cam plate 203 is fixedly connected to one end of the corresponding turntable 202 away from the supporting device 1, and a groove is provided on the outer wall of each cam plate 203.

[0042] Furthermore, each elastic member 201 is a coil spring, the inner end of each coil spring is fixedly connected to the supporting device 1 , and the outer end of each coil spring is fixedly connected to the inner side wall of the corresponding rotating disk 202 .

[0043] As a preferred embodiment, each turntable 202 is rotatably connected to a fixed shaft 102, and the two are preferably connected by a rolling bearing 7. Specifically, the outer ring of the bearing is matched with the mounting hole 204 of the turntable 202, and the inner ring of the bearing is matched with the fixed shaft 102; the inner end of each coil spring is fixedly connected to a slot 103 on a fixed shaft 102, and the outer end of each coil spring is fixedly connected to the fixed seat 206 of the turntable 202 through a claw 205. The cam plate 203 is fixed to the turntable 202 by screws. Each pulley 4 is fixedly connected to the support device 1 through a support column 8. The two spring subsystems 2 and the two pull ropes 3 are symmetrically arranged about the same symmetry plane, and the slide rail 5 is perpendicular to the symmetry plane, and the two ends of the slide rail 5 are symmetrically arranged about the symmetry plane. The initial position of the slider 6 is located in the middle of the slide rail 5. The depth of each groove is the same everywhere, so after determining the profile of the outer wall of the cam disc 203, a groove of a specific depth can be machined on the outer wall of the cam disc 203 to obtain a cam surface, and the shape of the cam surface is consistent with the outer wall of the cam disc 203. The axes of the two fixed shafts 102 are parallel to each other.

[0044] Example 2

[0045] The present embodiment provides a spring device design method of a spring device 100 based on a cam mechanism of embodiment 1, comprising the following steps: determining the expected stiffness of the spring device 100 based on the cam mechanism, obtaining the stiffness of the two elastic members 201, and obtaining the shapes and sizes of the two cam surfaces according to the expected stiffness and the stiffness of the two elastic members 201.

[0046] Furthermore, the present embodiment also includes: determining the maximum spring displacement, maximum spring output force and dimensional parameters of the spring device 100 based on the cam mechanism, and determining the rotation angle range, torque range and stiffness parameters of each elastic member 201 according to the maximum spring displacement, maximum spring output force and dimensional parameters; testing each selected elastic member 201 to obtain the actual stiffness curve of each elastic member 201; and obtaining the shape and size of two cam surfaces according to the expected stiffness and the actual stiffness curves of the two elastic members 201. The present embodiment obtains the cam surface based on the actual stiffness curve of each elastic member 201, and can compensate for the errors caused by the structural size, material properties and manufacturing of the elastic member 201 through the contour shape of the cam surface, thereby improving the design and manufacturing accuracy of the stiffness.

[0047] Furthermore, the parameters of the main components of the device are preliminarily selected according to the maximum spring displacement, the maximum spring output force and the size parameters, such as the stiffness of the coil spring, the diameter of the base 101, the contour size of the cam surface, etc.

[0048] As a preferred implementation, this embodiment also includes: according to the use requirements, determining the expected stiffness curve F(u) of the spring device 100 based on the cam mechanism, decomposing it into stiffness curves F'(u), F"(u) of the two spring subsystems 2, and obtaining the shapes and sizes of the two cam surfaces according to the stiffness curves of the two spring subsystems 2 and the actual stiffness curves of the two elastic members 201.

[0049] Furthermore, the present embodiment further includes: obtaining the stiffness of the two spring subsystems 2 according to the expected stiffness, and selecting the stiffness of the two elastic members 201 according to the stiffness of the two spring subsystems 2, respectively, wherein the selection method includes: making the potential energy of each elastic member 201 when each elastic member 201 is at the maximum deformation greater than the potential energy of the spring device 100 based on the cam mechanism when it is at the maximum spring displacement, that is, The stiffness of the elastic member 201 is roughly selected according to the law of conservation of energy.

[0050] Furthermore, within the allowable range of size, weight and cost, larger dimensional parameters can be selected, such as the distance between the cam rotation center and the center of the pulley 4. Larger structural dimensional parameters are easier to process and can also reduce the impact of cam surface manufacturing errors.

[0051] Example 3

[0052] This embodiment provides a spring device 100 based on a cam mechanism, the cam surfaces of the two turntable assemblies are the same surface, and the two elastic members 201 are the same elastic members 201, thereby reducing the complexity of the design.

[0053] The other structures and connection methods of this embodiment are the same as those of Embodiment 1.

[0054] The design principle and method of the spring device are described by taking the spring device 100 based on the cam mechanism provided in this embodiment as an example:

[0055] In order to make the slider 6 deviate from the equilibrium position and generate a displacement u along the length direction of the slide rail 5, a force F needs to be applied to the slider 6. The magnitude of the force F is determined by the coil spring stiffness, the displacement u and the cam surface profile. Therefore, the stiffness curve (load-displacement curve) of the spring device 100 based on the cam mechanism, that is, the expected stiffness curve, is obtained in advance according to the requirements, and the coil spring stiffness is determined. Then, the cam surface profile can be designed, so that the spring device 100 based on the cam mechanism can output a force F consistent with the expected stiffness curve.

[0056] The force F acting on the slider 6 is the superposition of the forces F' and F" acting on the two spring subsystems 2, that is, F(u) = F'(u) + F" (-u). By decomposing the force F acting on the slider 6, F'(u) and F" (-u) of the two spring subsystems 2 for a given deformation u can be obtained. Since the working principles, structures, dimensions and other parameters of the two spring subsystems 2 are consistent, the working principle of one spring subsystem 2 is used as an example for explanation below.

[0057] like Figure 1 As shown, the spring device 100 based on the cam mechanism is in a balanced state, and the cam plate 203 of the spring subsystem 2 is in a Figure 5 (a) shows the position where point C and point D on the pull rope 3 are tangent to the pulley 4. At this time, force F is applied to the slider 6 to make the slider 6 slide along the slide rail 5 by a distance u. Point D on the pull rope 3 will move by a distance u to D'. Figure 5 F'(u) acts on the cam plate 203 of the spring subsystem 2, causing the rotating plate 202 fixed to the cam plate 203 to rotate by an angle α, and generates a moment G(α) around the rotation axis O on the rotating plate 202. The moment G(α) is balanced with the restoring moment M(α) generated by the coil spring on the rotating plate 202, that is, G(α)=M(α).

[0058] like Figure 6 As shown in (a), a coordinate system xOy is established, and the coordinate system xOy is fixed to the cam plate 203, O is the rotation center of the cam plate 203, and the x-axis points from O to O. 1 Initially, the line connecting the rotation center of the cam plate 203 and the center of the pulley 4 is OO 1 ,OO 1 The length is a, and the angle between the x-axis and the force F on the rope 3 is γ. Point A is the fixed point of the rope 3 on the cam, points C and D are the two tangent points between the rope 3 and the pulley 4, and point B is the tangent point between the rope 3 and the cam profile. Under the action of force F, the cam disc 203 rotates clockwise by an angle α. Since the coordinate system xOy is fixed to the cam disc 203, in the xOy coordinate system, the pulley 4 and other components rotate counterclockwise by an angle α to O 1 ',like Figure 6 As shown in (b), the tangent point between the cable 3 and the cam disc 203 is B', with coordinates (x, y). The tangent points between the cable 3 and the pulley 4 are C' and D', and the point D where the cable 3 and the pulley 4 are tangent moves a displacement u in the direction of the force. The displacement u is related to the rotation angle α of the cam disc 203, denoted as u(α), and u(α) is determined by the cam surface profile.

[0059] The displacement u and the force F(u) of the slider 6 of the spring device 100 based on the cam mechanism satisfy the spring characteristics. When the slider 6 moves at any displacement u, the micro energy dU of the micro distance du is:

[0060] dU=F(u)du (1)

[0061] When the coil spring is at any angular displacement α, the energy dV of the angular displacement dα is:

[0062] dV=G(α)dα (2)

[0063] According to the law of conservation of energy, we can get:

[0064] dU=dV (3)

[0065] According to formula (1), (2) and (3), we can get:

[0066] F(u)du=G(α)dα (4)

[0067] du / dα=G(α) / F(u) (5)

[0068] In formula (5), F(u) is determined by the expected stiffness and displacement u, where the expected stiffness is a predetermined known quantity; G(α) is determined by the stiffness of the coil spring and the deformation α of the coil spring, where the coil spring is pre-selected and its stiffness is a known quantity. Its stiffness can be obtained according to the model of the coil spring, or the coil spring can be actually measured to obtain its stiffness curve more accurately. Therefore, for any displacement u of the spring subsystem 2, the differential relationship between the displacement u and the rotation angle α can be obtained according to F(u) and G(α), and then the profile of the cam surface can be obtained. Specifically, it can be obtained by Figure 6 The geometric relationship between the variables shown and equation (5) yield the cam profile.

[0069] Depend on Figure 6 We can get:

[0070] u=s+l+r[γ-(α-β)]-s 0 -l 0 -r[γ-(α 0 -β 0 )]

[0071] =s+lr(α-β)-s 0 -l 0 +r(α 0 -β 0 ) (6)

[0072] Where, s is the arc length of AB', l is the length of B'C', r is the radius of pulley 4, γ is the angle between the x-axis and the force F on the pull rope 3, the angle between B'C' and the horizontal axis is β, r[γ-(α-β)] is the length of the arc of the pull rope 3 around the pulley 4CD; α 0 、s 0 , l 0 , β 0is the initial value of the variable when the cam plate 203 rotation angle is 0, that is, α 0 =0,s 0 is the arc length of AB, l 0 is the length of BC, β 0 is the angle between BC and the horizontal axis, β 0 The angle range is -180° to 180° (the angle when the horizontal axis rotates counterclockwise to BC is positive).

[0073] When the cam disc 203 is tangent to the pull rope 3, the coordinates (x, y) of the tangent point between the pull rope 3 and the cam surface satisfy the following relationship:

[0074]

[0075] According to the vector calculation method, we can get:

[0076]

[0077] According to the operational relationship between vectors and complex numbers, we can get from formula (8):

[0078] x+iy+(l-ir)e iβ =ae iα (9)

[0079] Differentiating equation (6) and equation (9) yields:

[0080] du=ds+dl-r(dα-dβ)=ds+dl+rdβ-rdα (10)

[0081] dx+idy+dle iβ +(l-ir)e iβ idβ=ae iα idα (11)

[0082] Substituting formula (7) into (11), we can obtain:

[0083] ds cos(β)+ids sin(β)+dle iβ +(l-ir)e iβ idβ=ae iα idα (12)

[0084] From formula (12), we get:

[0085] ds e iβ +dle iβ +(l-ir)e iβ idβ=ae iα idα (13)

[0086] Multiply both sides of formula (13) by e -iβ, we can get:

[0087] ds+dl+(l-ir)idβ=ae i(α-β) idα, that is:

[0088] ds+dl+rdβ+l dβ i=ae i(α-β) idα (14)

[0089] Since the imaginary part and the real part of formula (14) are equal, we can get:

[0090]

[0091] From formula (10) and formula (15), we can get:

[0092]

[0093] In formula (17), Determined by formula (5), we can get: In formula (17),

[0094]

[0095] Then, l is obtained by formula (15):

[0096]

[0097] From formula (9), we can get:

[0098]

[0099] From formula (20), the contour points of the cam surface can be obtained as:

[0100]

[0101] In formula (21), a is the distance between the cam rotation center and the center of pulley 4, r is the radius of pulley 4, and β and l are calculated and determined by formula (18) and formula (19) respectively.

[0102] Formula (21) shows that by determining the stiffness curve of the spring device 100 based on the cam mechanism and the stiffness curve of the coil spring, the contour point data of the cam surface can be obtained according to the corresponding values ​​on the curve. According to the contour point data of the cam surface, the cam surface is fitted and the corresponding cam surface that meets the design requirements is designed.

[0103] Example 4

[0104] This embodiment provides a spring device 100 based on a cam mechanism, the cam surfaces of the two turntable assemblies are different surfaces, and the two elastic members 201 are different elastic members 201. Taking into account special design requirements, if the two spring subsystems 2 are required to have different structural dimensions due to the influence of the installation space, the dimensions and stiffness curves of the two spring subsystems 2 should be as close as possible on the basis of meeting the design requirements, so as to avoid the cam surfaces and coil spring parameters of the two spring subsystems 2 being particularly different.

[0105] The other structures and connection methods of this embodiment are the same as those of Embodiment 1.

[0106] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A spring device based on a cam mechanism, characterized in that: It includes a support device, a spring subsystem and a pull rope, wherein: There are two spring subsystems, each of which includes a turntable assembly and an elastic member. Each turntable assembly is connected to the support device in a rotational connection around a rotation axis, and each elastic member is connected to the corresponding turntable assembly and the support device. A groove is provided on the outer side wall of each turntable assembly, and the inner bottom wall of the groove is a cam surface. The pull rope includes two pull rope segments, and the two pull rope segments are respectively fixedly connected to the two turntable assemblies, and each pull rope segment is wound around a corresponding cam surface; each pull rope segment can pull the corresponding turntable assembly to rotate around the rotation axis under the action of external force, and stretch or compress the corresponding elastic member; each turntable assembly can rotate around the rotation axis under the action of the restoring force of the corresponding elastic member.

2. The spring device based on the cam mechanism according to claim 1, characterized in that: It also includes two pulleys, and each of the pull ropes is sequentially wound around one of the cam curved surfaces and an outer side wall of a pulley.

3. The spring device based on the cam mechanism according to claim 1, characterized in that: It also includes a displacement component, each of the pull ropes can be fixedly connected to the output end of the displacement component, and the output end of the displacement component can move in a direction perpendicular to the rotation axis under the action of an external force.

4. The cam mechanism-based spring device according to claim 3, characterized in that: The displacement assembly includes a slide rail and a slider. The slide rail is fixedly connected to the support device, and the slider is slidably connected to the slide rail. The slider is the output end of the displacement assembly.

5. The cam mechanism-based spring device according to claim 1, characterized in that: The supporting device comprises a base and two fixed shafts, each of the fixed shafts can be fixedly connected to the base, and each of the turntable assemblies can generate relative rotation with one of the fixed shafts around the axis of the corresponding fixed shaft.

6. The cam mechanism-based spring device according to claim 1, characterized in that: Each of the turntable assemblies includes a turntable and a cam plate. Each of the turntables is connected to the supporting device in a rotational connection around the rotation axis. Each of the elastic members is connected to the turntable of the corresponding turntable assembly. Each of the cam plates is fixedly connected to an end of the corresponding turntable away from the supporting device, and the groove is provided on the outer wall of each of the cam plates.

7. The cam mechanism-based spring device according to claim 6, characterized in that: The cam surfaces of the two rotating disk assemblies are the same or different surfaces, and the two elastic members are the same or different elastic members.

8. A method for designing a spring device based on a cam mechanism according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: determining the expected stiffness of a spring device based on a cam mechanism, obtaining the stiffness of two elastic members, and obtaining the shapes and sizes of two cam curved surfaces according to the expected stiffness and the stiffness of the two elastic members.

9. The spring device design method according to claim 8, characterized in that: Also includes: Determine the maximum spring displacement, maximum spring output force and size parameters of the spring device based on the cam mechanism, and determine the rotation angle range, torque range and stiffness parameters of each elastic member according to the maximum spring displacement, the maximum spring output force and the size parameters; test each selected elastic member to obtain an actual stiffness curve of each elastic member; The shapes and sizes of the two cam surfaces are obtained according to the desired stiffness and the actual stiffness curves of the two elastic members.

10. The spring device design method according to claim 9, characterized in that: Also includes: The stiffness of the two spring subsystems is obtained according to the expected stiffness, and the stiffness of the two elastic members is selected according to the stiffness of the two spring subsystems respectively. The selection method includes: making the potential energy of each elastic member when each elastic member is at a maximum deformation greater than the potential energy of the spring device based on the cam mechanism when it is at a maximum spring displacement.

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