A shape memory alloy reciprocating actuator with adjustable preload

Abstract

The present invention discloses a shape memory alloy reciprocating actuator with adjustable preload, comprising a shell, a displacement platform, a displacement platform limiting protrusion, a spring, an adjustable preload device, a shape memory alloy wire and a limiting mechanism; the shell comprises an upper base plate, a lower base plate and a cylinder, and the upper base plate and the lower base plate are both arranged horizontally; the displacement platform comprises a plate portion, which is arranged horizontally and located inside the shell; the displacement platform limiting protrusion is arranged on the inner wall of the cylinder and is also located below the plate portion; the spring is arranged vertically and located inside the shell, with the upper end in contact with the plate portion and the lower end in contact with the lower base plate; the adjustable preload device comprises a head and a rod portion that are connected to each other, the head portion is located outside the shell, the rod portion is arranged vertically and passes through the lower base plate into the shell, the length of the rod portion inserted into the shell is adjustable, and the preload force of the shape memory alloy wire can be controlled by adjusting the length of the rod portion inserted into the shell; the shape memory alloy wire is arranged vertically and located inside the shell, the upper end is fixedly connected to the displacement platform, and the lower end is fixedly connected to the rod portion.

Description

Technical Field

[0001] The invention belongs to the field of actuators and relates to a shape memory alloy reciprocating actuator with adjustable preload force. Background Art

[0002] Reciprocating actuators are widely used in various fields, including displacement control, micromechanical systems, and medical devices. Traditional mechanical reciprocating actuators often use motor structures, which have problems such as complex structure, difficult stroke adjustment, and high power loss.

[0003] Due to their unique properties, shape memory alloys can eliminate their low-temperature deformation and restore their pre-deformation shape after heating. The working principle of shape memory alloys is that they change their shape below the phase transition temperature. When the temperature of the shape memory alloy reaches the phase transition temperature, the shape memory alloy will return to its original shape.

[0004] Existing technologies primarily design shape memory alloy reciprocating actuators by pre-stretching the shape memory alloy wire below its phase transition temperature, then heating it to restore it to its original shape. Compared to traditional electromagnetic and hydraulic actuators, shape memory alloy reciprocating actuators have a simpler structure, typically consisting of one or more shape memory alloy elements. This makes them lighter in size and weight, making them suitable for applications with limited space. Furthermore, shape memory alloys offer high power density, enabling high force and rapid displacement output within a relatively small space, thus enabling more compact and lightweight mechanical actuators.

[0005] However, the stroke of the shape memory alloy reciprocating actuator will attenuate during use, which in turn affects the reciprocating actuation performance of the entire actuator. Therefore, it is necessary to adjust the preload force of the shape memory alloy reciprocating actuator. The preload force of the shape memory alloy reciprocating actuator in the prior art is difficult to adjust. For example, patent CN108252883A discloses a flexible rotary actuator based on shape memory alloy wire. The spiral spring pre-stretches the shape memory alloy wire. By changing the temperature of the shape memory alloy, the shape memory alloy is deformed, so that the memory alloy exerts a tensile force on the spiral spring, causing the spiral spring to deform and produce relative rotation, thereby generating rotational motion. This technology only considers the actuation process, and does not take into account the wire elongation phenomenon caused by wire fatigue during the use of the actuator, and cannot adjust the preload force. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art and provide a shape memory alloy reciprocating actuator with adjustable preload. The present invention designs a reciprocating actuator with simple structure and reliable performance, which can solve the problems of complex structure, high difficulty in stroke adjustment, large power loss, and mechanical fatigue phenomenon that is prevalent under high-frequency use in traditional mechanical reciprocating actuators, resulting in displacement stroke not meeting expectations; the actuator of the present invention uses shape memory alloy as the driving material. Shape memory alloy is very sensitive to temperature. When the temperature exceeds the alloy phase transition point, the shape memory alloy undergoes martensitic reverse phase transition accompanied by a change in shape. For wire materials, the reversible phase transition is often accompanied by length contraction when heating and length extension when cooling.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A shape memory alloy reciprocating actuator with adjustable preload force, comprising a housing, a displacement platform, a displacement platform limiting protrusion, a spring, an adjustable preload device, a shape memory alloy wire, and a limiting mechanism;

[0009] The shell includes an upper bottom plate, a lower bottom plate and a cylinder, and the upper bottom plate and the lower bottom plate are both arranged horizontally;

[0010] The translation stage includes a plate portion, which is horizontally arranged and located in the shell;

[0011] The limiting protrusions of the translation stage are set on the inner wall of the cylinder and are located below the plate. The number of the limiting protrusions of the translation stage and their height in the cavity can be adjusted appropriately according to actual application requirements;

[0012] The spring is arranged vertically and is located in the housing, with its upper end in contact with the plate portion and its lower end in contact with the lower base plate;

[0013] The adjustable preload device includes a head and a rod that are connected to each other. The head is located outside the housing, and the rod is vertically arranged and penetrates the housing through the lower base plate. The length of the rod inserted into the housing is adjustable. Adjusting the length of the rod inserted into the housing can control the preload force of the shape memory alloy wire.

[0014] The shape memory alloy wire is arranged vertically and is located in the housing, with the upper end fixedly connected to the displacement stage and the lower end fixedly connected to the rod;

[0015] The limiting mechanism is used to limit the horizontal sliding of the spring;

[0016] The matching relationship between the various components satisfies the following conditions: when the temperature of the shape memory alloy wire is not greater than its austenite transition temperature, the plate portion is in contact with the upper base plate; when the temperature of the shape memory alloy wire is greater than its austenite transition temperature, the shape memory alloy wire contracts, driving the plate portion downward until it contacts the limiting protrusion of the translation stage;

[0017] The actuator of the present invention can be driven by actively applying current or by passively changing the ambient temperature, thereby achieving cyclical self-restoring displacement motion.

[0018] The present invention primarily uses an adjustable preload device to adjust the preload force of the shape memory alloy wire. The upper end of the shape memory alloy wire is fixedly connected to the displacement stage, and the lower end is fixedly connected to the rod. When the actuator is not heated, the plate is dominated by the spring force. At this time, the plate is tightly attached to the upper base plate. Ignoring the weight of the displacement stage, there are several limit states at this time:

[0019] First, when the shape memory alloy wire is initially completely relaxed, that is, the preload force is 0, the upward elastic force of the spring on the plate is equal to the downward reaction force of the upper base plate on the plate;

[0020] The second is to shorten the length of the rod inserted into the shell. At this time, the shape memory alloy wire begins to tighten, that is, the preload force is not 0. At this time, the upward elastic force of the spring on the plate = the downward pulling force of the shape memory alloy wire on the plate + the downward reaction force of the upper base plate on the plate;

[0021] The third is to further shorten the length of the rod inserted into the shell, so that the plate and the upper base plate are in a critical state of being out of contact but still in contact. At this time, the upward elastic force of the spring on the plate is just equal to the downward pulling force of the shape memory alloy wire on the plate, and the downward reaction force of the upper base plate on the plate is 0.

[0022] In the first, second, and third cases above, the plate and upper base are in contact, meaning the spring length remains constant. According to the spring force formula (F = kx), the upward force exerted by the spring on the plate remains constant. What changes are the downward pulling force exerted by the shape memory alloy wire on the plate and the downward reaction force exerted by the upper base on the plate. This range of tension in the shape memory alloy wire is the adjustable range of the preload force referred to in this invention.

[0023] Theoretically, the greater the preload force, the greater the stroke provided by the shape memory alloy wire and the shorter the fatigue life of the actuator. Furthermore, over long-term use, the shape memory alloy wire gradually develops a two-way shape memory effect and fatigues itself, causing the wire to relax and the stroke (actuation distance) provided by the wire to decrease. Therefore, to overcome the stroke attenuation problem, the shape memory alloy wire needs to be re-preloaded to ensure a stable actuator stroke.

[0024] When the actuator starts to be powered on, the length of the shape memory alloy wire will shrink, driving the plate to completely break away from the contact with the upper base plate and move downward. At this time, the downward pulling force of the shape memory alloy on the plate is greater than the upward elastic force of the spring on the plate, and the length of the spring is reduced during this process, then the elastic force F = kx. The greater the distance the shape memory alloy drives the plate to move downward, the greater the reverse elastic force provided by the spring. Due to the closed nature of the actuator structure and the length of the shape memory alloy wire will be affected by fatigue, the shape memory alloy wire will also fatigue and become longer with the increase of usage time. Therefore, by adjusting the length of the rod inserted into the shell, the shape memory alloy wire can be kept in a taut state, so that the reciprocating drive efficiency of the actuator is maximized. If the shape memory alloy wire is not tightened, the effective stroke of the shape memory alloy wire contraction will be correspondingly shortened when the actuator heats up, thereby shortening the displacement stroke of the plate.

[0025] The plate is placed between the upper base plate and the spring; in the initial state, the temperature of the shape memory alloy wire is not higher than its austenite transition temperature, and the plate is subjected to the elastic force of the spring, the tension of the shape memory alloy wire, and the reaction force of the upper base plate. At this time, the tension of the shape memory alloy wire is less than the elastic force of the spring, and the plate is limited and tightly attached to the upper base plate; in the working state, when the temperature of the shape memory alloy wire is higher than its austenite transition temperature, the shape memory alloy wire contracts, and the downward tension of the shape memory alloy wire on the plate is greater than the upward elastic force of the spring on the plate, causing the plate to move downward until it contacts the limiting protrusion of the displacement platform; when the temperature of the shape memory alloy wire drops to no more than its austenite transition temperature, the shape memory alloy wire will return to the initial state under the action of the spring; thereby, the plate can achieve cyclic reciprocating motion.

[0026] The downward tension and displacement of the plate caused by the heating and contraction of the shape memory alloy wire are related to the choice of wire material. In practical applications, it is necessary to select the appropriate length and thickness of the shape memory alloy wire to match the requirements. The selection of shape memory alloy wire needs to consider:

[0027] Select shape memory alloy wire of appropriate thickness to provide sufficient tension;

[0028] Select the appropriate length of shape memory alloy wire to provide sufficient displacement stroke;

[0029] The selection of springs needs to consider:

[0030] When the actuator is not working, the spring exerts a large upward force on the plate, causing the plate to cling tightly to the upper base plate.

[0031] When the actuator is working, the downward pulling force of the shape memory alloy wire on the plate is greater than the upward elastic force of the spring on the plate. At this time, the plate moves downward under the influence of the tension of the shape memory alloy wire;

[0032] The actuator's recovery movement mainly relies on the force of the spring. Therefore, it is necessary to ensure that the spring can provide good durability and sufficient elasticity to keep the plate tightly against the base plate when the actuator is not working. Therefore, the selection of the spring also needs to consider:

[0033] The uncompressed length of the spring before it is placed in the housing;

[0034] The wire diameter of the spring;

[0035] When the plate portion contacts the upper base plate, the upward elastic force of the spring is greater than the detwinning stress of the shape memory alloy wire.

[0036] As the preferred technical solution:

[0037] As described above, a shape memory alloy reciprocating actuator with adjustable preload, the displacement platform also includes a vertically arranged needle portion, which is located above the plate portion and fixedly connected thereto; a displacement through hole is provided in the middle of the upper base plate; the needle portion passes through the displacement through hole, and low-viscosity lubricating oil is applied between the two, and the displacement through hole can limit the displacement path of the needle portion; the total height of the needle portion and the plate portion is greater than the distance between the upper base plate and the limiting protrusion of the displacement platform, so that when the actuator is working, the needle portion is not pulled out of the displacement through hole, thereby limiting the displacement path of the needle portion; the plate portion does not contact the cylinder, so as to avoid the friction generated between the two affecting the movement of the plate portion.

[0038] In the shape memory alloy reciprocating actuator with adjustable preload force as described above, the spring is a cylindrical coil spring.

[0039] As described above, the shell of the shape memory alloy reciprocating actuator with adjustable preload is a cylindrical shell. The shape of the shell does not have to be cylindrical, and can also be square or other shapes that meet the requirements of practical applications. Since the spring used in the present invention is preferably a cylindrical coil spring, from the perspective of space utilization and material saving, the shell is preferably a cylindrical shell.

[0040] In the shape memory alloy reciprocating actuator with adjustable preload as described above, the spring and the shape memory alloy wire are coaxial. The purpose of this arrangement is to make the elastic force of the spring and the tension of the shape memory alloy wire on the same straight line. If the two forces are not coaxial, the actuation efficiency will be reduced and the stroke may not meet the actual application requirements.

[0041] In the shape memory alloy reciprocating actuator with adjustable preload force as described above, the limiting mechanism is located in the housing and consists of a horizontally arranged spring limiting protrusion b and a horizontally arranged spring limiting protrusion a;

[0042] The spring limiting protrusion b is located below the plate portion and is fixedly connected thereto; the spring limiting protrusion a is located above the lower base plate and is fixedly connected thereto;

[0043] The spring is simultaneously mounted on the spring limiting protrusion b and the spring limiting protrusion a. The spring limiting protrusion b and the spring limiting protrusion a are circular plates with diameters equal to the inner diameter of the spring. The purpose of this setting is to prevent the spring from slipping horizontally. The two ends of the spring can also be fixed in the shell by welding or gluing, but these methods will make the replacement and maintenance of the actuator parts difficult. Therefore, it is preferred to fix the spring by the spring limiting protrusion a and the spring limiting protrusion b, and there is no fixed requirement for the height of the spring limiting protrusion a and the spring limiting protrusion b, as long as the limit spring can be stabilized.

[0044] In the shape memory alloy reciprocating actuator with adjustable preload force as described above, the plate portion is a circular plate; the housing, the plate portion, the spring limiting protrusion b, and the spring limiting protrusion a are coaxial.

[0045] As described above, a shape memory alloy reciprocating actuator with adjustable preload force, the adjustable preload device also includes a displacement adjustment nut, which is arranged horizontally and fixed in the spring limiting protrusion a; the rod is a threaded rod, and the displacement adjustment nut is sleeved on it and threadedly connected to it; the preload force of the shape memory alloy wire is adjusted by rotating the head, and the head can be provided with rotational force by a hexagonal wrench or a box wrench.

[0046] The shape memory alloy reciprocating actuator with adjustable preload force as described above, wherein the translation stage further includes a fixed structure, the fixed structure being a block having a through-hole in the middle thereof matching the screw rod of the screw, the fixed structure being located below the spring limiting protrusion b and fixedly connected thereto;

[0047] A fixing bolt is provided in the housing, and the fixing bolt includes a screw, a compression nut, and a gasket;

[0048] The screws are arranged horizontally, and the screw rods of the screws pass through the gasket, the fixing structure, and the compression nut in sequence, and the screw rods of the screws are threadedly connected with the compression nut; a fixing hole is provided on the screw rod of the screw, and the shape memory alloy wire passes through the fixing hole and is tightly fixed between the screw nut and the gasket.

[0049] In the shape memory alloy reciprocating actuator with adjustable preload force as described above, the connection points between the shape memory alloy wire, the fixing bolt and the rod are all insulated.

[0050] In the shape memory alloy reciprocating actuator with adjustable preload force as described above, the cylinder and the lower base are fixedly connected, and the cylinder and the upper base are threadedly connected.

[0051] Beneficial effects:

[0052] The present invention realizes the cyclical displacement movement of the actuator by combining the acting forces of the spring and the shape memory alloy wire.

[0053] The present invention effectively overcomes the problem that the edge of the needle portion of the displacement platform slips off the edge of the shell through the limiting effect of the upper base plate and the limiting protrusion of the displacement platform.

[0054] The spring limiting protrusion of the present invention effectively prevents the lateral sliding of the spring and limits the direction of the spring force.

[0055] The present invention can accurately adjust the preload force of the shape memory alloy wire through the adjustable preload force structure, thereby controlling the displacement stroke of the actuator, and effectively overcoming the problem of attenuation of the stroke of the shape memory alloy reciprocating actuator during use.

[0056] The present invention enables the displacement stage to move within the shell by changing the combined force of the spring and the shape memory alloy wire, thereby realizing a self-circulating reciprocating movement of the structure, and has strong practicality in mechanical connectors, mechanical processing, valves, sensor feedback devices, etc.

[0057] The reciprocating actuator of the shape memory alloy with adjustable preload of the present invention has broad application prospects in the fields of micro-mechanics, sensor feedback, etc. The actuator can realize displacement change and recovery in a short time; the adjustment of the preload is closely related to the contraction stroke of the shape memory alloy wire. By adjusting the adjustable preload device on the actuator, the driving stroke can be dynamically adjusted according to actual application requirements. Appropriate preload can also increase the displacement stroke of the shape memory alloy wire. In addition, by adjusting the preload of the shape memory alloy wire, the problem of attenuation of the stroke of the shape memory alloy reciprocating actuator during use is effectively overcome, thereby improving the reciprocating actuation performance of the entire actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Schematic diagram of the structure of the shape memory alloy reciprocating actuator with adjustable preload force of the present invention;

[0059] Figure 2 Schematic diagram of the housing structure of the shape memory alloy reciprocating actuator with adjustable preload force of the present invention;

[0060] Figure 3 It is a front view of the structure of the shape memory alloy reciprocating actuator with adjustable preload force of the present invention;

[0061] Figure 4 It is a structural schematic diagram of the adjustable pre-tightening device of the present invention;

[0062] Figure 5 Schematic diagram of the connection structure between the adjustable pre-tightening device and the lower base plate of the present invention;

[0063] Figure 6 Schematic diagram of the connection structure of the two ends of the shape memory alloy wire of the present invention;

[0064] Figure 7 This is a schematic diagram of the connection structure between the shape memory alloy wire and the fixing bolt of the present invention;

[0065] Figure 8 Schematic diagram of the connection structure between the fixing bolt and the translation stage of the present invention;

[0066] Figure 9 It is a structural schematic diagram of the fixing bolt of the present invention;

[0067] Figure 10 Schematic diagram of the structure of the translation platform of the present invention;

[0068] Figure 11 Schematic diagram of a single displacement drive of the present invention; FIG a is a schematic diagram of the initial state of a single displacement drive of the present invention, and FIG b is a schematic diagram of the final state of a single displacement drive of the present invention;

[0069] Figure 12 A schematic diagram of the connection between the upper base plate and the housing of the present invention;

[0070] Among them, 1-shell, 11-displacement through hole, 12-displacement platform limiting protrusion, 13-mounting hole, 14-spring limiting protrusion a, 15-upper base plate, 16-lower base plate, 17-cylinder, 2-spring, 3-adjustable preload device, 31-rod, 32-displacement adjusting nut, 33-head, 4-shape memory alloy wire, 5-fixing bolt, 51-screw, 52-pressing nut, 53-gasket, 54-fixing hole, 6-displacement platform, 61-needle, 62-spring limiting protrusion b, 63-fixing structure, 64-plate. DETAILED DESCRIPTION

[0071] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0072] A shape memory alloy reciprocating actuator with adjustable preload, such as Figures 1 to 3 As shown, it includes a housing 1, a limiting mechanism, a displacement platform 6, a displacement platform limiting protrusion 12, a spring 2, a fixing bolt 5, an adjustable pre-tightening device 3 and a shape memory alloy wire 4;

[0073] like Figure 2 、 12 As shown, the housing 1 is a cylindrical housing, comprising an upper base plate 15, a lower base plate 16 and a cylinder 17. The upper base plate 15 and the lower base plate 16 are arranged horizontally, the lower base plate 16 and the cylinder 17 are fixedly connected, the upper base plate 15 is threadedly connected to the cylinder 17, and a displacement through hole 11 is provided in the middle of the upper base plate 15;

[0074] The limiting mechanism is located in the housing 1 and is composed of a horizontally arranged spring limiting protrusion b 62 and a horizontally arranged spring limiting protrusion a14, both of which are circular plates; the spring limiting protrusion a14 is located above the lower base plate 16 and is fixedly connected thereto;

[0075] like Figure 10 As shown, the displacement stage 6 includes a horizontally arranged circular plate portion 64, a vertically arranged needle portion 61, and a block-shaped fixing structure 63. The needle portion 61, plate portion 64, spring-limiting protrusion b 62, and fixing structure 63 are sequentially connected from top to bottom. The plate portion 64, spring-limiting protrusion b 62, and fixing structure 63 are all located within the housing 1 and do not contact the cylinder 17. The needle portion 61 passes through the displacement through hole 11, and low-viscosity lubricating oil is applied between the needle portion 61 and the displacement through hole 11.

[0076] The housing 1, the plate portion 64, the spring limiting protrusion b 62, and the spring limiting protrusion a 14 are coaxial;

[0077] The displacement stage limiting protrusion 12 is provided on the inner wall of the cylinder 17 and is located below the plate portion 64;

[0078] The total height of the needle portion 61 and the plate portion 64 is greater than the distance between the upper base plate 15 and the limiting protrusion 12 of the displacement stage;

[0079] Spring 2 is a cylindrical coil spring, arranged vertically and located in housing 1, with its upper end sleeved on spring limiting protrusion b 62 and its lower end sleeved on spring limiting protrusion a 14. Its inner diameter is equal to the diameters of spring limiting protrusion b 62 and spring limiting protrusion a 14;

[0080] like Figure 8 As shown, the fixing bolt 5 is arranged in the housing 1 and includes a screw 51, a compression nut 52, and a washer 53;

[0081] The screw 51 is arranged horizontally, and the screw rod of the screw 51 passes through the washer 53, the fixing structure 63, and the compression nut 52 in sequence. The screw rod of the screw 51 is threadedly connected with the compression nut 52, and a fixing hole 54 is provided on the screw rod of the screw 51;

[0082] like Figure 4 As shown, the adjustable preload device 3 includes a head 33, a rod 31 and a displacement adjustment nut 32;

[0083] like Figure 5 As shown, the displacement adjustment nut 32 is arranged horizontally and fixed in the spring limiting protrusion a 14; the head 33 is located outside the housing 1; the rod 31 is a threaded rod and arranged vertically, and passes through the lower base plate 16 and the displacement adjustment nut 32 in sequence and penetrates into the housing 1, and the penetration length is adjustable; the displacement adjustment nut 32 is connected to the rod 31 by a thread;

[0084] like Figures 6-7 As shown in Figures 9 and 9, the shape memory alloy wire 4 is arranged vertically and is located in the housing 1. The spring 2 is coaxial with the spring 2. The upper end passes through the fixing hole 54 and is tightly fixed between the nut and the washer 53 of the screw 51. The lower end is fixedly connected to the rod 31. The connection points between the shape memory alloy wire 4, the fixing bolt 5 and the rod 31 are all insulated.

[0085] The matching relationship of each component satisfies the following conditions: when the temperature of the shape memory alloy wire 4 is not greater than its austenite transformation temperature, the plate portion 64 fits in contact with the upper base plate 15; when the temperature of the shape memory alloy wire 4 is greater than its austenite transformation temperature, the shape memory alloy wire 4 contracts, driving the plate portion 64 to move downward until it contacts the limiting protrusion 12 of the displacement stage.

[0086] The above actuator can be actively driven by heating with electricity or passively driven according to changes in ambient temperature. Taking active driving with heating with electricity as an example, the use process of the above actuator is briefly described: wires are connected to both ends of the shape memory alloy wire, and the wires are externally connected to an independent power supply. Since the connection points between the shape memory alloy wire and the fixing bolt and the rod are all insulated, when the actuator is actively driven by current, the current only passes through the shape memory alloy wire. When the shape memory alloy wire is not powered, the initial state of the actuator is as follows: Figure 11 As shown in (a), the displacement stage is mainly affected by the force of the spring and fits with the upper base plate of the shell. When the shape memory alloy wire is energized, it is rapidly heated due to the Joule heating effect. When the shape memory alloy wire is heated above the critical temperature, its lattice structure undergoes a phase change, causing the shape memory alloy wire to transform from the martensite phase to the austenite phase. At the same time, the shape memory alloy wire is accompanied by a rapid contraction phenomenon. Due to the force of the shape memory alloy wire, the displacement stage drives the needle to slide in the displacement through hole until the displacement stage is limited by the displacement stage limit protrusion. This is the end state of the single displacement drive, as shown in FIG. Figure 11 As shown in (b), when the shape memory alloy wire is powered off, the spring force takes the leading role again and the actuator returns to its initial state. Figure 11 As shown in (a); for the alloy fatigue phenomenon that may occur after a long period of reciprocating displacement during use, the adjustable preload device 3 can be actively adjusted to make the actuator displacement stroke conform to the required stroke of the actual application again. Specifically, the head 33 is appropriately adjusted to make the shape memory alloy wire 4 reach a suitable preload force, so that the displacement distance of the displacement stage 6 conforms to the stroke required for the actual application.

[0087] When the above-mentioned actuator is of the actively driven type, in actual engineering applications, it can be used to control the movement of valves, pistons, etc., and by utilizing the shape memory effect of shape memory alloys, it can realize cyclic reciprocating displacement, effectively controlling the flow, pressure and direction of liquids or gases, etc. It can also be used for displacement parts in mechanical automation, etc.

[0088] When the above-mentioned actuator is of passive drive type, in engineering examples, the actuator has important applications in the industrial field. For example, it can be used as a temperature compensation device. The shape memory alloy reciprocating actuator with adjustable preload can automatically adjust its length according to changes in ambient temperature to compensate for changes in mechanical structure caused by temperature. It can also be used to manufacture valve control systems. When the actuator is affected by changes in ambient temperature, its real-time displacement changes passively. This application scenario is widely used in applications such as heating, cooling valve control systems and air-conditioning systems.

[0089] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Any portions not described in detail herein are common knowledge within the skill of a person skilled in the art. It will be apparent to those skilled in the art that various modifications and variations are possible within the spirit and principles of the present application. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A shape memory alloy reciprocating actuator with adjustable preload, characterized in that: It comprises a housing (1), a displacement platform (6), a displacement platform limiting protrusion (12), a spring (2), an adjustable pre-tightening device (3), a shape memory alloy wire (4) and a limiting mechanism; The housing (1) comprises an upper base plate (15), a lower base plate (16) and a cylinder (17), wherein the upper base plate (15) and the lower base plate (16) are both arranged horizontally; The displacement stage (6) includes a plate portion (64), which is arranged horizontally and located inside the housing (1); The displacement platform limiting protrusion (12) is arranged on the inner wall of the cylinder (17) and is located below the plate portion (64); The spring (2) is arranged vertically and is located in the housing (1), with its upper end in contact with the plate portion (64) and its lower end in contact with the lower base plate (16); The adjustable preload device (3) comprises a head portion (33) and a rod portion (31) connected to each other, wherein the head portion (33) is located outside the housing (1), and the rod portion (31) is arranged vertically and penetrates through the lower base plate (16) into the housing (1), and the length of the rod portion (31) penetrated into the housing (1) is adjustable; The shape memory alloy wire (4) is arranged vertically and is located in the housing (1), with its upper end fixedly connected to the displacement platform (6) and its lower end fixedly connected to the rod (31); The limiting mechanism is used to limit the horizontal sliding of the spring (2); The matching relationship of each component satisfies the following conditions: when the temperature of the shape memory alloy wire (4) is not greater than its austenite transformation temperature, the plate portion (64) fits the upper base plate (15); when the temperature of the shape memory alloy wire (4) is greater than its austenite transformation temperature, the shape memory alloy wire (4) contracts, driving the plate portion (64) to move downward until it contacts the limiting protrusion (12) of the displacement platform.

2. The shape memory alloy reciprocating actuator with adjustable preload according to claim 1, characterized in that: The displacement platform (6) further comprises a vertically arranged needle portion (61), which is located above the plate portion (64) and fixedly connected thereto; a displacement through hole (11) is provided in the middle of the upper base plate (15); the needle portion (61) passes through the displacement through hole (11), and lubricating oil is applied between the needle portion (61) and the plate portion (64); the total height of the needle portion (61) and the plate portion (64) is greater than the distance between the upper base plate (15) and the displacement platform limiting protrusion (12); and the plate portion (64) does not contact the cylinder (17).

3. The shape memory alloy reciprocating actuator with adjustable preload according to claim 1, characterized in that: The spring (2) is a cylindrical helical spring.

4. The shape memory alloy reciprocating actuator with adjustable preload according to claim 3, characterized in that: The housing (1) is a cylindrical housing.

5. The shape memory alloy reciprocating actuator with adjustable preload according to claim 3, characterized in that: The spring (2) is coaxial with the shape memory alloy wire (4).

6. The shape memory alloy reciprocating actuator with adjustable preload according to claim 5, characterized in that: The limiting mechanism is located in the housing (1) and is composed of a horizontally arranged spring limiting protrusion b (62) and a horizontally arranged spring limiting protrusion a (14); The spring limiting protrusion b (62) is located below the plate portion (64) and is fixedly connected thereto; the spring limiting protrusion a (14) is located above the lower base plate (16) and is fixedly connected thereto; The spring (2) is simultaneously sleeved on the spring limiting protrusion b (62) and the spring limiting protrusion a (14); the spring limiting protrusion b (62) and the spring limiting protrusion a (14) are circular plates, and the diameters thereof are both equal to the inner diameter of the spring (2).

7. The shape memory alloy reciprocating actuator with adjustable preload according to claim 6, characterized in that: The plate portion (64) is a circular plate; the housing (1), the plate portion (64), the spring limiting protrusion b (62), and the spring limiting protrusion a (14) are coaxial.

8. The shape memory alloy reciprocating actuator with adjustable preload force according to claim 6, characterized in that: The adjustable preload device (3) further comprises a displacement adjustment nut (32), which is arranged horizontally and fixed in the spring limiting protrusion a (14); the rod (31) is a threaded rod, and the displacement adjustment nut (32) is sleeved on the rod and threadedly connected to the rod.

9. The shape memory alloy reciprocating actuator with adjustable preload according to claim 6, characterized in that: The displacement platform (6) further includes a fixed structure (63), which is a block. The fixed structure (63) is located below the spring limiting protrusion b (62) and is fixedly connected thereto. A fixing bolt (5) is provided in the housing (1), and the fixing bolt (5) includes a screw (51), a compression nut (52), and a gasket (53); The screw (51) is arranged horizontally, and the screw rod of the screw (51) passes through the gasket (53), the fixing structure (63), and the compression nut (52) in sequence, and the screw rod of the screw (51) is threadedly connected with the compression nut (52); a fixing hole (54) is provided on the screw rod of the screw (51), and the shape memory alloy wire (4) passes through the fixing hole (54) and is tightly fixed between the nut of the screw (51) and the gasket (53).

10. The shape memory alloy reciprocating actuator with adjustable preload force according to claim 9, characterized in that: The connection points between the shape memory alloy wire (4), the fixing bolt (5) and the rod (31) are all insulated.

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