A kind of inertial piezoelectric actuator with adjustable pre-tightening force

Abstract

The application discloses a kind of inertial piezoelectric actuator of wear state real-time evaluation pre-tightening force adjustable and controlled, including upper end shell, clamping mechanism, adjusting screw, pre-tightening piezoelectric stack, rhombus ring, piezoelectric stack, lower end shell and base, each component is from top to bottom by centroid located in same straight line;The application is compact in structure, power-off locking, based on inertial actuation principle, linear displacement output is generated using asymmetric sawtooth wave driving voltage;Based on piezoelectric effect, the contact wear state between sliding components is detected using electric charge.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inertial piezoelectric actuators, and particularly relates to an inertial piezoelectric actuator with real-time wear state evaluation and adjustable pre-tightening force. BACKGROUND

[0002] An inertial piezoelectric actuator is a mechanism that uses asymmetric driving signals, asymmetric mechanical clamping structures or asymmetric friction forces as a control mode and forms driving through inertial impact motion.

[0003] Scientific and engineering progress has enabled researchers to focus on developing miniaturized devices and systems with high precision and accuracy, and the development of technology to meet the needs of small systems has paved the way for the development of micro-nano technology, which has been applied to various fields such as biomedical aerospace, microelectronics, micro-optics, etc. Compared with other types of piezoelectric drives, inertial piezoelectric actuators have the main advantages of simple structure, fast response speed, high resolution, large stroke, fast motion speed and low cost, and can achieve large stroke while having nanoscale positioning accuracy. Therefore, inertial piezoelectric actuators are suitable for occasions that require high resolution and large stroke. At present, technology workers have successfully applied inertial piezoelectric actuators to high-precision positioning mechanisms, multi-degree-of-freedom drives, micro-robot joints and micro-manipulators.

[0004] A stick-slip inertial piezoelectric actuator realizes driving through periodic friction coupling of the rotor-stator friction pair. During operation, the friction pair contact surface will inevitably wear, changing the physical and mechanical properties of the friction contact and thus changing the output characteristics of the actuator and causing the actuator to fail. The time-varying nature of the friction pair of the traditional linear inertial piezoelectric actuator affects the high smoothness and high accuracy of the inertial actuator. SUMMARY

[0005] In order to overcome the problems existing in the prior art, the purpose of the present application is to provide an inertial piezoelectric actuator with real-time wear state evaluation and adjustable pre-tightening force, which can obtain the contact state such as wear of the wear pair in real time, and adjust the pre-tightening force in real time according to the wear degree to regulate the output characteristics and maintain the high-performance output of the actuator.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] The application discloses a kind of wear state real-time evaluation pre-tightening force controllable inertial piezoelectric actuator, including upper end shell 1, clamping mechanism 2, adjusting screw 3, pre-tightening piezoelectric stack 4, diamond ring 5, piezoelectric stack 6, lower end shell 7 and base 8 arranged sequentially from top to bottom, the center of these components is located on the same vertical line;Track is processed in upper end shell 1, track is closely attached with clamping mechanism 2, the nut of adjusting screw 3 is pressed on the upper end surface of clamping mechanism 2, the screw rod of adjusting screw 3 passes through the short shaft of clamping mechanism 2, the lower end of adjusting screw 3 is fixed with pre-tightening piezoelectric stack 4 by hemispherical end cap, pre-tightening piezoelectric stack 4 is embedded in the upper end of diamond ring 5 which is integrally processed with clamping mechanism 2, piezoelectric stack 6 is installed in diamond ring 5 with interference, diamond ring 5 is embedded in the track of lower end shell 7, and the lower end surface of diamond ring 5 is connected with base 8, and base 8 is also connected with lower end shell 7.

[0008] The pre-tightening force of the actuator can be adjusted.According to the triangular displacement transmission principle, the compression deformation of the short shaft of the clamping mechanism 2 in the vertical direction can be converted into the expansion deformation of the long shaft in the horizontal direction.When the adjusting screw is screwed into the upper end surface of the diamond ring 5 by a predetermined angle, the clamping mechanism 2 is compressed in the vertical direction due to the pressing of the nut of the adjusting screw, and the compression deformation of the short shaft is converted into the expansion deformation of the long shaft of the clamping mechanism 2 in the horizontal direction, so that the pre-tightening force of the clamping mechanism 2 is changed.

[0009] The service life is prolonged while the friction is increased: the upper and lower ends of the clamping mechanism 2 are coated with a hard ceramic material, and a tooth-shaped structure with a gradient is formed on the surface by chemical etching, sputtering process and laser micro-nano machining method.The ceramic material has high hardness, which increases the friction between the contact surfaces.The recesses can temporarily store the debris generated by surface wear, and solid lubricant can be added to the recesses to improve the lubrication effect and reduce surface wear.

[0010] The state of the contact surface is detected by piezoelectric effect: the pre-tightening piezoelectric stack 4 generates vibration of a fixed frequency when powered on, which is continuously transmitted to the side tooth-shaped structure through the inner diamond structure of the clamping mechanism 2.Due to the displacement gradient of the tooth-shaped structure, according to the piezoelectric effect, a continuous electric charge is generated after being subjected to a strain gradient.A voltage signal can be observed in real time by connecting a charge meter between the contact surface of the clamping mechanism 2 and the upper end shell 1.The initial voltage reading is recorded, and as the contact surface wears with time, the voltage signal gradually decreases.By tightening the adjusting screw 3, the normal friction between the contact surfaces is ensured by increasing the pre-tightening force, so that the voltage signal returns to the normal level.The voltage drop value when the piezoelectric actuator fails is measured by experiment, which is used as the failure value.The relative friction times from the initial value to the failure value of the charge meter are the service life of the piezoelectric actuator.

[0011] When the piezoelectric stack 6 is not energized, the clamping force between the clamping mechanism 2 and the track is at the desired value. To make the upper end shell 1 produce axial upward displacement, first, the piezoelectric stack 6 is slowly energized from zero voltage to full stroke voltage, the piezoelectric stack 6 slowly elongates along the axial direction, driving the clamping mechanism 2 to slowly move away from the base 8. At this time, the upward static friction force provided by the clamping mechanism 2 to the upper end shell 1 can overcome the downward inertial force, and the upper end shell 1 and the clamping mechanism 2 remain relatively static, producing upward displacement. Second, the piezoelectric stack 6 is rapidly reduced from full stroke voltage to zero voltage, the piezoelectric stack 6 rapidly contracts along the axial direction, driving the clamping mechanism 2 to rapidly move towards the base 8, and the clamping mechanism 2 returns to the initial position. At this time, the upper end shell 1 is subjected to downward sliding friction, but due to the large inertia of the upper end shell 1, the downward displacement is less than the downward displacement of the clamping mechanism 2. The difference between the first step and the second step is a step of upward displacement. Repeating the first and second steps, the upper end shell 1 produces continuous upward displacement. Similarly, to make the upper end shell 1 produce axial downward displacement, first, the piezoelectric stack 6 is rapidly energized from zero voltage to full stroke voltage, the piezoelectric stack 6 rapidly elongates along the axial direction, driving the clamping mechanism 2 to rapidly move away from the base 8. At this time, the upper end shell 1 is subjected to upward sliding friction, but due to the large inertia of the upper end shell 1, the upward displacement is less than the upward displacement of the clamping mechanism 2. Second, the piezoelectric stack 6 is slowly reduced from full stroke voltage to zero voltage, the piezoelectric stack 6 slowly contracts along the axial direction, driving the clamping mechanism 2 to slowly move towards the base 8. At this time, the upward static friction force provided by the clamping mechanism 2 to the upper end shell 1 can overcome the downward inertial force, and the upper end shell 1 and the clamping mechanism 2 remain relatively static, producing downward displacement. The difference between the first step and the second step is a step of downward displacement. Repeating the first and second steps, the upper end shell 1 produces continuous downward displacement.

[0012] Compared with the prior art, the present application has the following advantages:

[0013] 1) The present application can realize the regulation of pre-tightening force by additionally adding a pre-tightening piezoelectric stack 4. The output characteristics of friction can be adjusted by controlling the voltage signal of the pre-tightening piezoelectric stack.

[0014] 2) The present application increases the friction of the contact surface by metal surface coating, and the designed tooth-shaped structure can reduce wear and increase the service life of the piezoelectric actuator.

[0015] 3) The present application is based on piezoelectric effect, so that the wear state of the contact surface can be detected, and the influence of contact surface failure caused by wear can be reduced by adjusting the pre-tightening force. The service life of the piezoelectric actuator can be predicted by observing the reading of the external charge meter.

[0016] 4) The present application has compact structure, small volume and light weight. According to the inertial driving principle, only a single piezoelectric stack is needed to drive the load to move back and forth in a straight line. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a partial sectional view of the present invention.

[0018] Figure 2a and Figure 2b is a front view and a left view sectional view of the present invention.

[0019] Figure 3 is an exploded view of the present invention.

[0020] Figure 4 is a schematic view of the contact surface of the present invention.

[0021] Figure 5 is a timing diagram of the driving voltage for upward movement of the present invention.

[0022] Figure 6 is a timing diagram of the driving voltage for downward movement of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0024] As shown in Figure 1 , Figure 2a , Figure 2b and Figure 3 , the present invention is a wear state real-time evaluation pre-tightening force controllable inertial piezoelectric actuator, which comprises, from top to bottom, an upper end shell 1, a clamping mechanism 2, an adjusting screw 3, a pre-tightening piezoelectric stack 4, a rhombic ring 5, a piezoelectric stack 6, a lower end shell 7 and a base 8, and the centers of these components are located on the same vertical line; the upper end shell 1 is processed with a square groove track, the square groove track is tightly combined with the clamping mechanism 2, the nut of the adjusting screw 3 is pressed on the upper end surface of the clamping mechanism 2, the screw rod of the adjusting screw 3 passes through the short shaft of the clamping mechanism 2, the lower end of the adjusting screw 3 is fixedly connected with the pre-tightening piezoelectric stack 4 through a hemispherical end cap, the pre-tightening piezoelectric stack 4 is embedded in the upper end of the rhombic ring 5 which is integrally processed with the clamping mechanism 2, the piezoelectric stack 6 is installed in the rhombic ring 5 with interference, the rhombic ring 5 is embedded in the square groove track of the lower end shell 7, and the base 8 is threadedly connected with the lower end surface of the rhombic ring 5 and also threadedly connected with the lower end shell 7.

[0025] The pre-tightening force of the actuator can be adjusted, according to the principle of triangular displacement transmission, the compression deformation of the short shaft of the clamping mechanism 2 in the vertical direction can be converted into the expansion deformation of the long shaft in the horizontal direction, when the adjusting screw is screwed into the upper end surface of the rhombic ring 5 by a certain angle, the clamping mechanism 2 in the vertical direction is compressed by the pressing of the nut of the adjusting screw, and the compression deformation of the short shaft is converted into the expansion deformation of the long shaft of the clamping mechanism 2 in the horizontal direction, thereby changing the pre-tightening force of the clamping mechanism 2.

[0026] Increase friction and prolong service life: as Figure 4As shown, the hard ceramic material surface coating is carried out on the left and right end faces of the clamping mechanism 2, and the tooth-shaped structure with gradient is processed by methods including chemical etching, sputtering process and laser micro-nano processing, etc. The ceramic material has large hardness, which can increase the friction between the contact surfaces. The debris generated by surface wear can be temporarily stored in the recess, and the solid lubricant can be added in the recess to improve the lubrication effect and reduce the surface wear.

[0027] The contact surface state is detected by piezoelectric effect: the pre-tightened piezoelectric stack 4 generates a small vibration of fixed frequency by power supply, which is continuously transmitted to the side tooth-shaped structure through the inner rhombus structure of the clamping mechanism 2. Since the tooth-shaped structure has displacement gradient, according to the piezoelectric effect, a continuous small electric charge can be generated after being subjected to strain gradient. The electric charge table is connected between the contact surfaces of the clamping mechanism 2 and the upper end shell 1, and the voltage signal can be observed in real time. The initial voltage reading is recorded, and as the contact surface wear increases over time, the generated voltage signal gradually decreases. The voltage signal can be restored to the normal level by tightening the adjusting screw 3 to increase the pre-tightening force, so that the normal friction between the contact surfaces is generated. The voltage drop value when the piezoelectric actuator completely fails can be measured by experiment, which is used as the failure value. The relative friction times from the initial value to the failure value of the electric charge representation number is the service life of the piezoelectric actuator.

[0028] When the piezoelectric stack 6 is not powered, the clamping force between the clamping mechanism 2 and the square groove track is at the expected value, as shown in the figure. Figure 5 In order to make the upper end shell 1 produce axial upward displacement, the first step is to slowly power the piezoelectric stack from zero voltage to full stroke voltage. The piezoelectric stack 6 slowly elongates along the axial direction, driving the clamping mechanism 2 to slowly move away from the base 8. At this time, the upward static friction provided by the clamping mechanism 2 can overcome the downward inertia force, and the upper end shell 1 and the clamping mechanism 2 remain relatively stationary, producing upward displacement. The second step is to rapidly reduce the piezoelectric stack 6 from full stroke voltage to zero voltage. The piezoelectric stack 6 rapidly contracts along the axial direction, driving the clamping mechanism 2 to rapidly move towards the base 8. The clamping mechanism 2 returns to the initial position. At this time, the upper end shell 1 is subjected to downward sliding friction. However, since the inertia of the upper end shell 1 is large, the downward displacement is smaller than the downward displacement of the clamping mechanism 2. The difference between the first step and the second step is an upward step distance. Repeating the first and second steps, the upper end shell 1 produces continuous upward displacement. Similarly, as shown in the figure, Figure 6As shown, in order to make the upper end shell 1 axial displacement downward, the first step, piezoelectric stack 6 from zero voltage to full stroke voltage, piezoelectric stack 6 along the axial rapid elongation, drive the clamping mechanism 2 do rapid movement away from the base 8, at this time the upper end shell 1 by the sliding friction force upward, but due to the inertia of the upper end shell 1 is large, thus the upward displacement is less than the clamping mechanism 2 upward displacement, the second step, piezoelectric stack 6 from full stroke voltage slowly to zero voltage, piezoelectric stack 6 along the axial slow contraction, drive the clamping mechanism 2 slowly to the base 8 movement, at this time the upper end shell 1 by the clamping mechanism 2 provide upward static friction force can overcome the downward inertia force, the upper end shell 1 and the clamping mechanism 2 keep relative static, produce downward displacement, the first step and the second step displacement difference is a downward step, repeat the first, second step, the upper end shell 1 produce continuous downward displacement.

Claims

1. A wear state real-time evaluation pre-tightening force controllable inertial piezoelectric actuator, characterized in that, The utility model relates to a kind of piezoelectric actuator, including upper end shell (1) arranged sequentially from top to bottom, clamping mechanism (2), adjusting screw (3), pre-tightening piezoelectric stack (4), diamond ring (5), piezoelectric stack (6), lower end shell (7) and pedestal (8), the center of these components is located in same vertical line;Track is processed in upper end shell (1), track is closely attached with clamping mechanism (2), the nut of adjusting screw (3) is pressed on the upper end surface of clamping structure (2), the screw rod of adjusting screw (3) passes through the short shaft of clamping mechanism (2), the lower end of adjusting screw (3) is fixed with pre-tightening piezoelectric stack (4) by hemispherical end cap, pre-tightening piezoelectric stack (4) is embedded in the upper end of diamond ring (5) integrally machined with clamping mechanism (2), piezoelectric stack (6) is installed with interference in diamond ring (5), diamond ring (5) is embedded in the track of lower end shell (7), diamond ring (5) lower end surface is connected with pedestal (8), while pedestal (8) is also connected with lower end shell (7); While increasing friction, prolong service life: hard ceramic material surface coating is carried out on the left and right end surfaces of clamping mechanism (2), through including chemical etching, sputtering process and laser micro-nano processing method, the tooth-shaped structure with gradient of upper and lower concave-convex is processed, ceramic material has greater hardness, increases the friction between contact surfaces, the debris generated by surface wear can be temporarily stored in the recess, and solid lubricant can be added in the recess to improve the lubricating effect and reduce surface wear. Detect the state of contact surface through piezoelectric effect: pre-tightening piezoelectric stack (4) generates vibration of fixed frequency when energized, which is continuously transmitted to the side tooth-shaped structure through the inner diamond structure of clamping mechanism (2), since the tooth-shaped structure has displacement gradient, according to piezoelectric effect, a continuous electric charge can be generated after being subjected to strain gradient, and a charge table is connected between the contact surfaces of clamping mechanism (2) and upper end shell (1), so that the voltage signal can be observed in real time; record the initial voltage reading, as the contact surface wear increases over time, the voltage signal gradually decreases, tighten the adjusting screw (3) to increase the pre-tightening force to ensure that the normal friction force is generated between the contact surfaces, so that the voltage signal returns to normal level; the voltage drop value when the piezoelectric actuator completely fails is measured through experiment, which is used as failure value, then the relative friction times from the initial value to the failure value of the charge representation number is the service life of the piezoelectric actuator.

2. The inertial piezoelectric actuator with real-time wear state evaluation and adjustable pre-tightening force according to claim 1, characterized in that: The pre-tightening force of the actuator is adjustable, according to the triangular displacement transmission principle, the compression deformation of the short shaft of clamping mechanism (2) in vertical direction can be converted into expansion deformation of the long shaft in horizontal direction, when the adjusting screw is screwed into the upper end surface of diamond ring (5) by a preset angle, the clamping mechanism (2) is compressed in vertical direction due to the pressing of the nut of adjusting screw, and the compression deformation of the short shaft is converted into expansion deformation of the long shaft of clamping mechanism (2) in horizontal direction, so as to change the pre-tightening force of clamping mechanism (2).

3. The inertial piezoelectric actuator with real-time wear state evaluation and adjustable pre-tightening force according to claim 1, when the piezoelectric stack (6) is not powered, the clamping force between the clamping mechanism (2) and the track is at the desired value, in order to make the upper end shell (1) produce axial upward displacement, first, the piezoelectric stack (6) is slowly powered from zero voltage to full stroke voltage, the piezoelectric stack (6) slowly elongates along the axial direction, driving the clamping mechanism (2) to slowly move away from the base (8), at this time the upper end shell (1) is subjected to the upward static friction force provided by the clamping mechanism (2) and can overcome the downward inertial force, the upper end shell (1) and the clamping mechanism (2) remain relatively static, producing upward displacement, second, the piezoelectric stack (6) is rapidly reduced from full stroke voltage to zero voltage, the piezoelectric stack (6) rapidly contracts along the axial direction, driving the clamping mechanism (2) to rapidly move towards the base (8), the clamping mechanism (2) returns to the initial position, at this time the upper end shell (1) is subjected to the downward sliding friction force, but due to the large inertia of the upper end shell (1), the downward displacement is less than the downward displacement of the clamping mechanism (2), the difference between the displacements of the first and second steps is a step upward, repeating the first and second steps, the upper end shell (1) produces continuous upward displacement; similarly, in order to make the upper end shell (1) produce axial downward displacement, first, the piezoelectric stack (6) is rapidly powered from zero voltage to full stroke voltage, the piezoelectric stack (6) rapidly elongates along the axial direction, driving the clamping mechanism (2) to rapidly move away from the base (8), at this time the upper end shell (1) is subjected to the upward sliding friction force, but due to the large inertia of the upper end shell (1), the upward displacement is less than the upward displacement of the clamping mechanism (2), second, the piezoelectric stack (6) is slowly reduced from full stroke voltage to zero voltage, the piezoelectric stack (6) slowly contracts along the axial direction, driving the clamping mechanism (2) to slowly move towards the base (8), at this time the upper end shell (1) is subjected to the upward static friction force provided by the clamping mechanism (2) and can overcome the downward inertial force, the upper end shell (1) and the clamping mechanism (2) remain relatively static, producing downward displacement, the difference between the displacements of the first and second steps is a step downward, repeating the first and second steps, the upper end shell (1) produces continuous downward displacement.

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