Linear displacement actuator based on one-way shape memory alloy

Abstract

The linear displacement actuator based on the one-way shape memory alloy comprises a shell, a moving cam is arranged in the shell, an auxiliary spring and a shape memory alloy spring are arranged on the two opposite sides of the moving cam respectively, and an electrode plate I and an electrode plate II are arranged at the two ends of the shape memory alloy spring respectively. The moving cam is connected with an output rod through a roller. The problem that high-precision deformation control of an existing actuator is difficult to achieve due to the nonlinear deformation rule of the shape memory alloy is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of shape memory alloy actuators, and relates to a linear straight-line displacement actuator based on a one-way shape memory alloy. Background Art

[0002] The characteristic of shape memory alloys is that they have shape memory effect. The one-way shape memory effect means that when the material is below the end temperature of the martensitic phase transition, it is deformed by external force. If the material is heated to exceed the austenitic phase transition temperature, an austenitic phase transition will occur, accompanied by the behavior of recovering to the shape before deformation. During the phase transition, shape memory alloys can produce large recoverable deformation and recovery stress. Based on this feature, shape memory alloys are very suitable for making actuators. However, the law of deformation of shape memory alloy materials with temperature during the phase transition process is nonlinear, which increases the difficulty of accurately controlling the deformation of shape memory alloys. Summary of the invention

[0003] The purpose of the present invention is to provide a linear displacement actuator based on a one-way shape memory alloy, which solves the problem that the existing actuator is difficult to accurately control the deformation due to the nonlinear deformation law of the shape memory alloy.

[0004] The technical solution adopted by the present invention is a linear straight-line displacement actuator based on a one-way shape memory alloy, comprising a shell, a moving cam is arranged in the shell, an auxiliary spring and a shape memory alloy spring are arranged on opposite sides of the moving cam, an electrode sheet I and an electrode sheet II are arranged at both ends of the shape memory alloy spring, and the moving cam is connected to an output rod through a roller.

[0005] The present invention is also characterized in that:

[0006] Electrode sheet I is located on the inner wall of one end of the shell, electrode sheet II is located at one end of the moving cam, one end of the shape memory alloy spring is connected to the shell through electrode sheet I, and the other end of the shape memory alloy spring is connected to the moving cam through electrode sheet II.

[0007] A hole II is opened at the center of one end of the shell. The hole II and the electrode sheet I are located at the same end of the shell. The wire enters through the hole II and is connected to the electrode sheets I and II for power supply.

[0008] A hole I is provided at the top center of the shell, one end of the output rod extends out of the shell from the hole I, and the other end of the output rod is connected to the roller.

[0009] The bottom of the output rod is provided with a hole III; the roller comprises a roller wheel, a roller pin is provided at the center of the roller wheel, and the roller pin is inserted into the hole III at the bottom of the output rod to be connected with the output rod.

[0010] A rolling groove is provided on the surface of the moving cam, and the rolling groove is a wave-shaped structure.

[0011] The design method of rolling groove is:

[0012] Step 1, measuring the deformation u of the shape memory alloy spring in the austenite phase transformation stage at different temperatures T;

[0013] Step 2, assuming that the deformation u of the shape memory alloy spring obtained in step 1 is an independent variable and the temperature T is a dependent variable, and establishing a temperature function of the austenite phase transformation stage;

[0014] Step 3, the temperature function of the austenite phase transformation stage is substituted into the linear output function of the actuator to obtain the corresponding relationship between the deformation u of the shape memory alloy spring in the phase transformation stage and the output displacement of the actuator. The deformation u of the shape memory alloy spring is taken as the x-axis coordinate and the output displacement of the actuator is taken as the y-coordinate to obtain the contour equation of the rolling groove in the two-dimensional coordinate system.

[0015] The shape memory alloy spring is a nickel-titanium alloy spring with a one-way shape memory effect.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1) The driving element used in the present invention is a nickel-titanium alloy spring with a one-way shape memory effect. Compared with shape memory alloy wire, the shape memory alloy spring has the characteristics of large driving force and large deformation range, and is controlled by heating up by power on, so that the actuator has the advantages of large output displacement and convenient control.

[0018] 2) The present invention converts the nonlinear deformation law of the shape memory alloy itself into a linear straight-line displacement output, thereby improving the resolution of deformation controlled by temperature, thereby improving the control accuracy of the shape memory alloy actuator and reducing the control difficulty.

[0019] 3) The present invention clamps the slider by both the shape memory alloy spring and the auxiliary spring, which can play a self-locking function while controlling the output, ensuring the stability of the output displacement, and restores the shape of the shape memory alloy spring by the auxiliary spring, overcoming the disadvantage that the one-way memory effect cannot automatically restore the initial state, and the required displacement can be output any number of times. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the linear straight displacement actuator based on a one-way shape memory alloy of the present invention;

[0021] Figure 2 It is a structural schematic diagram of a housing of a linear straight displacement actuator based on a one-way shape memory alloy according to the present invention;

[0022] Figure 3 It is a structural schematic diagram of a moving cam of a linear straight displacement actuator based on a one-way shape memory alloy of the present invention;

[0023] Figure 4 It is a structural schematic diagram of an output rod of a linear straight displacement actuator based on a one-way shape memory alloy according to the present invention;

[0024] Figure 5 It is a structural schematic diagram of a linear straight displacement actuator roller based on a one-way shape memory alloy of the present invention;

[0025] Figure 6 It is a structural schematic diagram of a shape memory alloy spring of a linear straight displacement actuator based on a one-way shape memory alloy according to the present invention.

[0026] In the figure, 1. housing, 2. moving cam, 3. output rod, 4. roller, 5. auxiliary spring, 6. shape memory alloy spring, 11. hole I, 12. hole II, 13. electrode sheet I, 21. rolling groove, 22. electrode sheet II, 31. hole III, 41. roller pin, 42. roller wheel. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] The present invention is based on a linear displacement actuator of a one-way shape memory alloy, such as Figure 1 As shown, it includes a housing 1, and the housing 1 is a closed cavity structure. Figure 2 As shown, an electrode sheet I13 is provided on one side of the inner wall of the shell 1, a hole I11 is provided on the top of the shell 1, an output rod 3 extends out of the shell 1 through the hole I11 to output a linear displacement, a moving cam 2 is provided in the inner cavity of the shell 1, and the size of the moving cam 2 is consistent with the inner cavity of the shell 1, so that the moving cam 2 can only move back and forth in the inner cavity of the shell 1 in a direction perpendicular to the output rod 3, a roller 4 is provided at the lower end of the output rod 3, and a shape memory alloy spring 6 and an auxiliary spring 5 are provided on both sides of the moving cam 2 in the inner cavity of the shell 1.

[0030] Example 2

[0031] like Figure 3 As shown, the surface of the moving cam 2 is provided with a rolling groove 21, and the roller 4 is embedded in the rolling groove 21 on the surface of the moving cam 2. The roller 4 can move in the rolling groove 21, and an electrode sheet II22 is provided at the bottom of one end of the moving cam 2. The size and shape of the electrode sheet I13 and the electrode sheet II22 are exactly the same.

[0032] like Figure 4 As shown, the bottom of the output rod 3 is provided with a hole III31. Figure 5 As shown, the roller 4 is composed of a roller pin 41 and a roller wheel 42. The roller pin 41 is inserted into the hole III at the bottom of the output rod 3 to be connected to the output rod 3. The roller wheel 42 is embedded in the rolling groove 21 on the side of the movable cam 2 and can only move in the rolling groove 21. Since the position of the output rod 3 is constrained by the hole I11 on the housing 1, the position of the roller 4 is determined by the movable cam 2 and the output rod 3. No additional fixation is required. The roller 4 itself can only move up and down following the output rod 3.

[0033] Example 3

[0034] A hole II12 is opened at the center of one end of the shell 1. The hole II12 and the electrode sheet I13 are located at the same end of the shell 1. The wire enters through the hole II12 and is connected to the electrode sheet I13 and the electrode sheet II22 for power supply.

[0035] The auxiliary spring 5 is arranged on the right side of the moving cam 2 in the inner cavity of the shell 1, and the two ends of the auxiliary spring 5 are respectively in contact with the moving cam 2 and the shell 1. The shape memory alloy spring 6 is arranged on the left side of the moving cam 2 in the inner cavity of the shell 1, and the two ends of the shape memory alloy spring 6 are respectively in contact with the electrode sheet I13 and the electrode sheet II22 to achieve connection with the external power supply.

[0036] The auxiliary spring 5 is a common pure steel spring, such as Figure 6 As shown, the shape memory alloy spring 6 is a nickel-titanium alloy spring with a one-way shape memory effect. The auxiliary spring 5 in the initial state is in a fully extended state, the shape memory alloy spring 6 is in a fully contracted state (the shape memory alloy is in the martensite phase), and the roller 4 is at the rightmost end of the rolling groove 21 on the moving cam 2.

[0037] The motion law of the output rod 3 is determined by the motion law of the roller 4 in the rolling groove 21, and the motion law of the roller 4 is determined by the deformation law of the shape memory alloy spring 6 and the curve shape (profile) of the rolling groove 21. The actuator realizes the conversion of the nonlinear deformation law of the shape memory alloy spring 6 during the austenite phase transformation into the linear displacement of the output rod 3 by designing the curve shape of the rolling groove 21. The specific steps of the profile design of the rolling groove 21 are as follows:

[0038] Step 1, according to the constitutive relationship of the shape memory alloy spring 6, or by experimentally measuring the temperature corresponding deformation data of the shape memory alloy spring 6, a temperature-deformation curve u=f(T) is obtained, where u is the deformation of the shape memory alloy spring 6, and T is the temperature;

[0039] Step 2, in preparation for converting the deformation of the shape memory alloy spring 6 into the x-axis coordinate of the rolling groove 21 profile, swap the independent variable and the dependent variable of the temperature-deformation curve u=f(T), use the deformation u to obtain the temperature T, and obtain the deformation-temperature function T=g(u);

[0040] Step 3. Since the output mode of the actuator is linear, there is a displacement function d=k·T, where d is the displacement output by the actuator, and k is the proportional coefficient, which represents the proportional relationship between temperature and output displacement. The k value determines the actuation range of the actuator, which is determined by actual needs. The deformation of the shape memory alloy spring 6 is used as the x-axis coordinate of the profile, and the deformation-temperature function T=g(u) is substituted into the displacement function d=k·T to obtain d=k·g(u), which is the profile equation of the rolling groove, where the deformation u of the shape memory alloy spring 6 is the x-axis coordinate, and the output displacement d of the actuator is the y-axis coordinate.

[0041] The working process of the linear linear displacement actuator based on the one-way shape memory alloy of the present invention is divided into two stages: output stage and reset stage, specifically:

[0042] During the output stage, the output rod 3 is extended outward from the housing 1. The control method is that the electrode sheet I13 and the electrode sheet II22 are in contact with the two ends of the shape memory alloy spring 6, and the shape memory alloy spring 6 is energized to increase its temperature to above the starting temperature of the austenite phase transformation, so that the shape memory alloy spring 6 undergoes an austenite phase transformation and thus produces elongation deformation. When the shape memory alloy spring 6 is elongated, it pushes the moving cam 2 to move toward the side where the auxiliary spring 5 is located, squeezing the auxiliary spring 5. At this time, the roller 4 produces relative movement in the rolling groove 21 due to the movement of the moving cam 2, thereby driving the output rod 3 to extend outward.

[0043] In the reset stage, the output rod 3 is retracted from the outside of the housing 1 to the inside to the initial position. The control method is that the electrode sheet I13 and the electrode sheet II22 are in contact with the two ends of the shape memory alloy spring 6, and the external power supply is turned off to cool the shape memory alloy spring 6 to below the martensitic start temperature. After the shape memory alloy spring 6 undergoes a martensitic phase transformation, it stops generating a driving force. Therefore, the auxiliary spring 5 compressed in the output stage begins to rebound. After the auxiliary spring 5 rebounds and stretches, it pushes the moving cam 2 to move to the side where the shape memory alloy spring 6 is located, squeezes the shape memory alloy spring 6 to shrink it and produce a martensitic phase transformation. At this time, the roller 4 produces a relative movement in the rolling groove 21 due to the movement of the moving cam 2, thereby driving the output rod 3 to shrink inward.

[0044] The output and reset stages are both based on the initial state as the reference origin, and only the output stage is a linear motion. In the heating stage (austenite phase transformation stage), the temperature of the shape memory alloy spring 6 can be controlled by controlling the current of the external power supply. Therefore, the value of the actuator output displacement can be precisely customized by controlling the temperature of the shape memory alloy spring 6. After one output, the actuator state is reset to prepare for the next output. One point that needs to be explained is that in the elongation stage, the shape memory alloy spring 6 squeezes the auxiliary spring 5 when it is extended. Therefore, in the reset stage, the auxiliary spring 5 generates a driving force to shrink the shape memory alloy spring 6 to the initial state, thereby allowing the shape memory alloy spring 6 to have the prerequisite for the occurrence of a one-way shape memory effect. Therefore, this actuator can complete any number of displacement outputs.

[0045] The linear straight-line displacement actuator based on a one-way shape memory alloy of the present invention can convert the nonlinear deformation law of the shape memory alloy into a linear displacement output mode, thereby greatly increasing the control resolution and control accuracy of the actuation mode based on the shape memory alloy and reducing the control difficulty. At the same time, it also has the characteristics of large driving force, large deformation range and reusability.

Claims

1. A linear displacement actuator based on a one-way shape memory alloy, characterized in that: The invention comprises a housing (1), wherein a movable cam (2) is arranged in the housing (1), an auxiliary spring (5) and a shape memory alloy spring (6) are arranged on opposite sides of the movable cam (2), an electrode sheet I (13) and an electrode sheet II (22) are arranged on two ends of the shape memory alloy spring (6), and the movable cam (2) is connected to an output rod (3) via a roller (4).

2. The linear displacement actuator based on a one-way shape memory alloy according to claim 1, characterized in that: The electrode sheet I (13) is located on the inner wall of one end of the shell (1), the electrode sheet II (22) is located at one end of the movable cam (2), one end of the shape memory alloy spring (6) is connected to the shell (1) through the electrode sheet I (13), and the other end of the shape memory alloy spring (6) is connected to the movable cam (2) through the electrode sheet II (22).

3. The linear displacement actuator based on a one-way shape memory alloy according to claim 2, characterized in that: A hole II (12) is provided at the center of one end of the shell (1), and the hole II (12) and the electrode sheet I (13) are located at the same end of the shell (1). A wire enters through the hole II (12) and is connected to the electrode sheet I (13) and the electrode sheet II (22) for electricity.

4. The linear displacement actuator based on a one-way shape memory alloy according to claim 3, characterized in that: A hole I (11) is provided at the center of the top of the housing (1), one end of the output rod (3) extends out of the housing (1) from the hole I (11), and the other end of the output rod (3) is connected to the roller (4).

5. The linear displacement actuator based on a one-way shape memory alloy according to claim 4, characterized in that: The bottom of the output rod (3) is provided with a hole III (31); the roller (4) comprises a roller wheel (42), a roller pin (41) is provided at the center of the roller wheel (42), and the roller pin (41) is inserted into the hole III (31) at the bottom of the output rod (3) to be connected with the output rod (3).

6. The linear displacement actuator based on a one-way shape memory alloy according to claim 5, characterized in that: A rolling groove (21) is provided on the surface of the movable cam (2), and the rolling groove (21) is a wave-shaped structure.

7. The linear displacement actuator based on a one-way shape memory alloy according to claim 6, characterized in that: The design method of the rolling groove (21) is: Step 1, measuring the deformation u of the shape memory alloy spring (6) in the austenite phase transformation stage at different temperatures T; Step 2, assuming that the deformation u of the shape memory alloy spring (6) obtained in step 1 is an independent variable and the temperature T is a dependent variable, and establishing a temperature function of the austenite phase transformation stage; Step 3, the temperature function of the austenite phase transformation stage is substituted into the linear output function of the actuator to obtain the corresponding relationship between the deformation u of the shape memory alloy spring (6) and the output displacement of the actuator in the phase transformation stage, and the deformation u of the shape memory alloy spring (6) is taken as the x-axis coordinate and the output displacement of the actuator is taken as the y-coordinate to obtain the contour equation of the rolling groove (21) in the two-dimensional coordinate system.

8. The linear displacement actuator based on a one-way shape memory alloy according to claim 7, characterized in that: The shape memory alloy spring (6) is a nickel-titanium alloy spring having a one-way shape memory effect.

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