Three drive three point differentialized flexible connected lift platform

Abstract

The application discloses a three-drive three-point differentiated flexible connection lifting platform and belongs to the technical field of precise lifting equipment. The lifting platform comprises three groups of lifting drive units, three lifting plates, a carrying table, three connecting assemblies, sliders and guide rails. The three groups of lifting drive units are used for driving the three lifting plates to lift respectively. The first connecting assembly comprises a joint bearing and a flexible hinge plate, the second connecting assembly is a double joint bearing, and the third connecting assembly is a single joint bearing. The three connecting assemblies are distributed in a triangular shape and have different freedom constraint modes, so that the vertical position deviation of the three lifting plates in the lifting process can be absorbed. The three lifting plates are respectively provided with the sliders, and the sliders are in sliding fit with the vertically arranged guide rails. Through the three-point differentiated flexible connection structure and the cooperation of the interferometric distance meter closed loop control, the instantaneous height difference between the three groups of independent drives can be effectively absorbed, and the sub-micron level flatness precision is realized.

Description

Technical Field

[0001] This invention relates to the field of precision lifting equipment technology, specifically to a lifting platform with three-drive, three-point differentiated flexible connection, which is particularly suitable for high-precision lifting operations in semiconductor manufacturing, precision measurement, and optical inspection equipment. Background Technology

[0002] In fields such as semiconductor manufacturing, precision optical inspection, and ultra-precision machining, the continuous miniaturization of integrated circuit feature sizes and the constant improvement in optical inspection accuracy place increasingly stringent demands on the positioning accuracy and motion stability of the stage. Especially during long-stroke lifting movements, the stage not only needs to possess sub-micron level repeatability but also must maintain extremely high flatness throughout its entire stroke. Any slight tilt or deformation can lead to wafer scrapping or invalidation of inspection data.

[0003] Currently, traditional lifting platforms mostly employ a single-motor drive system. This involves one motor distributing power to multiple ball screws via a gearbox or worm gear reducer, which then collectively drive the platform's lifting and lowering. This system is simple in structure and easy to control, making it widely used in applications with lower precision requirements. However, as precision requirements increase, the inherent limitations of this system have become increasingly apparent. First, the gearbox itself has manufacturing and assembly errors; the backlash caused by gear meshing directly translates into positioning deviations of the platform. Second, pitch errors, inconsistent thermal expansion, and differences in stiffness among the ball screws all contribute to deviations in lifting displacement between support points, causing the platform to tilt. Practice shows that the flatness error of traditional single-motor gearbox transmission systems is typically above 100μm, and the hysteresis effect caused by backlash further deteriorates repeatability, making it unsuitable for modern precision manufacturing processes.

[0004] To address the aforementioned issues, those skilled in the art have attempted to absorb height deviations by incorporating elastic elements or buffer structures between the platform and the lifting drive mechanism. However, traditional elastic elements can only provide deformation in a single direction, failing to meet the complex deformation requirements of multiple directions and degrees of freedom during lifting, and making it difficult to reconcile the contradiction between "fully absorbing deviations" and "maintaining platform stability." Furthermore, some solutions have attempted to connect the lifting plate and the platform using ball joints or universal joints. However, the degrees of freedom provided by ball joints are often coupled; a swing in one direction can affect the posture in another, making it difficult to achieve independent decoupling between the three support points, thus limiting the effectiveness in improving flatness accuracy.

[0005] Some solutions use detection elements such as grating rulers or laser rangefinders to provide feedback on the position of the stage. However, such solutions usually only add a detection step, without changing the mechanical structure itself. The rigid connection between the stage and the lifting drive mechanism means that the height deviation will still be converted into additional stress and transmitted to the stage. Closed-loop control can only reduce the magnitude of the deviation, but cannot fundamentally eliminate the adverse effects of the deviation on the stage.

[0006] Therefore, how to effectively eliminate the adverse effects of the instantaneous height difference of multiple lead screws on the stage while achieving precision control of multiple independent drives is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a lifting platform with three-drive, three-point differentiated flexible connection, which aims to solve the problem that the instantaneous height difference of the three independently driven lifting units during dynamic operation causes additional stress on the platform and affects the flatness accuracy.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following solution: The lifting platform with three-drive, three-point differentiated flexible connection includes: three sets of lifting drive units for driving the lifting of three lifting plates respectively; a first connecting component, a second connecting component, and a third connecting component, which are respectively set between the three lifting plates and the platform, and their projections on the horizontal plane are triangularly distributed. The platform is connected to the three lifting plates one-to-one through the three connecting components; wherein, the first connecting component, the second connecting component, and the third connecting component have different degrees of freedom constraint methods to absorb the vertical positional deviation of the three lifting plates during the lifting process; each of the three lifting plates is provided with a slider, and each slider slides in cooperation with a vertically set guide rail. Furthermore, the first connecting assembly includes a first joint bearing and a flexible hinge plate; the second connecting assembly includes a second joint bearing, which is a double joint bearing; the third connecting assembly includes a third joint bearing, which is a single joint bearing; the first joint bearing and the flexible hinge plate are arranged in series in the vertical direction.

[0009] Furthermore, each lifting drive unit includes a drive motor, a ball screw connected to the output end of the drive motor, and a lifting nut threaded with the ball screw. The lifting plate is fixedly connected to the lifting nut. The drive motor is a stepper motor, and the output end of the stepper motor is connected to the ball screw through a worm gear reducer.

[0010] Furthermore, there are four sliders, two of which are located on the lifting plate corresponding to the third connecting component, and the other two are located on the lifting plates corresponding to the first connecting component and the second connecting component, respectively; the two sliders located on the lifting plate corresponding to the third connecting component are located on both sides of the horizontal direction of the lifting plate.

[0011] Furthermore, it also includes an interferometric rangefinder, with a pyramidal prism mounting plate for cooperation with the interferometric rangefinder on each of the three lifting plates; it also includes a controller, which is connected to the interferometric rangefinder and each drive motor signal respectively, and is used to control the operation of each drive motor according to the detection signal of the interferometric rangefinder.

[0012] Furthermore, each ball screw is provided with an upper bearing seat and a lower bearing seat at both ends to support the rotation of the ball screw.

[0013] Furthermore, there are four guide rails. Two guide rails are located on the same side of the lifting plate corresponding to the third connecting component, and the other two guide rails are located on the same side of the lifting plate corresponding to the first connecting component and the second connecting component, respectively.

[0014] Furthermore, the projections of the three sets of lifting drive units on the horizontal plane are arranged in a triangular pattern.

[0015] The beneficial effects of this invention are as follows: 1. In this invention, three independent lifting drive units are used to drive three lifting plates respectively. With the help of the interferometric rangefinder closed-loop control, the independent and precise control of the three ball screws can be achieved, which fundamentally overcomes the problem of poor synchronization in the traditional gearbox transmission method, and enables the positioning accuracy of the lifting platform to reach the sub-micron level.

[0016] 2. In this invention, the three lifting plates and the platform are connected by three different structural connection components arranged in a triangle to form a statically determinate support structure. Through a differentiated combination of degrees of freedom constraints—a flexible hinge plate providing minute elastic deformation, a double-joint bearing providing two orthogonal swing degrees of freedom, and a single-joint bearing providing a single-direction swing degree of freedom—the vertical positional deviation between the three lifting plates is passively absorbed. When a momentary height difference occurs in the three lead screws during dynamic operation, the three connection components work synergistically: the flexible hinge plate absorbs high-frequency fretting impacts, the double-joint bearing accommodates large-angle deflections, and the single-joint bearing constrains the rotation of the platform around the vertical axis and serves as the main positioning point. This effectively avoids additional stress on the platform and ensures its flatness during dynamic lifting. Furthermore, unlike traditional elastic elements that only provide deformation in one direction, the differentiated degree of freedom combination of the three connection components can adapt to complex deformation requirements in multiple directions and multiple degrees of freedom during lifting, achieving independent decoupling between each degree of freedom and maintaining the platform's attitude stability while fully absorbing deviations.

[0017] 3. In this invention, each lifting plate achieves precise vertical guidance through the cooperation of the slider and the guide rail, limiting horizontal sway and further improving the straightness and repeatability of the lifting motion. The four guide rails adopt an asymmetrical "2+1+1" layout, with one guide rail on each side of the lifting plate corresponding to the single joint bearing to provide torsional stiffness, and one guide rail on each of the other two lifting plates to avoid over-constraint, thus balancing guiding stiffness and smooth movement. Attached Figure Description

[0018] Figure 1 This is an isometric view of the lifting platform with three-drive, three-point differentiated flexible connection according to the present invention. Figure 2 This is a front view of the lifting platform with three-drive, three-point differentiated flexible connection according to the present invention; Figure 3 This is a structural diagram of the first connecting component; Figure 4 This is a structural diagram of the second and third connecting components.

[0019] Reference numerals: 1. Lifting plate, 2. Platform, 3. Slider, 4. Guide rail, 5. Drive motor, 6. Ball screw, 7. Lifting nut, 8. Worm gear reducer, 9. Conical prism mounting plate, 10. Upper bearing seat, 11. Lower bearing seat, 12. First joint bearing, 13. Flexible hinge plate, 14. Double joint bearing, 15. Third joint bearing. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0022] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0023] Furthermore, for clarity and brevity, descriptions of well-known structures, functions, and configurations may have been omitted. Those skilled in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of this disclosure.

[0024] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0025] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0026] Example 1 like Figure 1 , Figure 2 As shown, the present invention provides a lifting platform with three-drive, three-point differentiated flexible connection, including three lifting plates 1, a loading platform 2, four sliders 3, four guide rails 4, three drive motors 5, three ball screws 6, three lifting nuts 7, three worm gear reducers 8, a corner cone prism mounting plate 9, three upper bearing seats 10, three lower bearing seats 11, a first joint bearing 12, a flexible hinge plate 13, a double joint bearing 14, and a third joint bearing 15.

[0027] Three lifting plates 1 are horizontally arranged on the same height plane to jointly support the stage 2. The stage 2 is located above the three lifting plates 1 and is used to support the workpiece to be processed or inspected. A corner prism mounting plate 9 is fixedly installed on the side of the stage 2 for mounting a corner prism that works in conjunction with an interferometric rangefinder.

[0028] Each lifting drive unit includes a drive motor 5, a worm gear reducer 8, a ball screw 6, and a lifting nut 7. The drive motor 5 is a stepper motor, and its output is connected to the ball screw 6 via the worm gear reducer 8. The worm gear reducer 8 reduces speed and increases torque, and its self-locking characteristic ensures the lifting platform maintains its position even when power is off. The lifting nut 7 is threaded onto the ball screw 6; when the ball screw 6 rotates, it drives the lifting nut 7 to move vertically. The upper end of each ball screw 6 is rotatably supported by an upper bearing seat 10, and the lower end is rotatably supported by a lower bearing seat 11, ensuring that the ball screw 6 rotates only around its own axis under the drive of the drive motor 5, maintaining rotational accuracy.

[0029] Three lifting plates 1 are fixedly connected to three lifting nuts 7, and rise and fall synchronously with the lifting nuts 7. The specific connection relationship of each lifting plate 1 is as follows: the first lifting plate is fixedly connected to the lifting nut of the first lifting drive unit, the second lifting plate is fixedly connected to the lifting nut of the second lifting drive unit, and the third lifting plate is fixedly connected to the lifting nut of the third lifting drive unit. A slider 3 is fixedly installed on each of the three lifting plates 1, and each slider 3 slides in engagement with a vertically arranged guide rail 4 to constrain the lifting plate 1 to move only in the vertical direction. Through the cooperation of the slider 3 and the guide rail 4, the horizontal degree of freedom of the lifting plate 1 is completely constrained, ensuring the straightness of the lifting motion.

[0030] A first connecting component, a second connecting component, and a third connecting component are respectively provided between the three lifting platforms 1 and the platform 2. For example... Figure 3 As shown, the first connecting assembly is disposed between the first lifting plate and the platform 2, including a first joint bearing 12 and a flexible hinge plate 13, which are arranged in series in the vertical direction. The flexible hinge plate 13 is made of metal material (such as beryllium bronze, stainless steel, etc.) and is formed by wire cutting or electrical discharge machining. It has the characteristics of frictionless, gapless, and high rigidity, and can provide small elastic deformation to absorb high-frequency fretting impacts and eliminate the effects of gaps. The first joint bearing 12 provides swing freedom to adapt to the angular deviation between the lifting plate and the platform.

[0031] like Figure 4 As shown, the second connecting assembly is located between the second lifting plate and the platform 2, and includes a double-joint bearing 14. The double-joint bearing 14 provides two orthogonal swing degrees of freedom. When there is a height difference between the second lifting plate and other lifting plates, the double-joint bearing 14 can deflect at a large angle, effectively preventing bending moment from being transmitted to the platform 2. The third connecting assembly is located between the third lifting plate and the platform 2, and includes a third joint bearing 15, which is a single-joint bearing. The single-joint bearing provides a swing degree of freedom in a single direction, serving as the main positioning point of the platform 2 and constraining the rotational degree of freedom of the platform 2 about the vertical axis. The other two connecting assemblies are responsible for following and compensating for this.

[0032] The three connecting components described above have different degrees of freedom constraint methods: the flexible hinge plate 13 in the first connecting component provides a micro-motion degree of freedom in the vertical direction through slight elastic deformation, and its first joint bearing 12 provides a swinging degree of freedom about the horizontal axis; the double joint bearing 14 in the second connecting component provides a swinging degree of freedom about two orthogonal horizontal axes; the single joint bearing in the third connecting component only provides a swinging degree of freedom about a single horizontal axis and constrains the rotational degree of freedom of the platform 2 about the vertical axis. The three components work together to absorb and eliminate the vertical positional deviation between the three lifting plates 1 before it is transmitted to the platform 2, thus avoiding additional stress on the platform 2.

[0033] The four sliders 3 are distributed as follows: two sliders 3 are fixedly installed on the third lifting plate corresponding to the third connecting component (single joint bearing). The two sliders 3 are located on both sides of the horizontal direction of the third lifting plate (i.e. the lifting plate is clamped by two guide rails) to provide higher lateral stiffness and torsional resistance, and to ensure the horizontal stability of the single joint bearing positioning point; one slider 3 is fixedly installed on the first lifting plate corresponding to the first connecting component, and one slider 3 is fixedly installed on the second lifting plate corresponding to the second connecting component.

[0034] The four guide rails 4 are arranged as follows: two guide rails 4 are located on both sides of the third lifting plate corresponding to the third connecting component in the horizontal direction, that is, the two guide rails 4 are located on the same side of the third lifting plate (the third lifting plate is clamped by the two guide rails); one guide rail 4 is located on the same side of the first lifting plate corresponding to the first connecting component; and one guide rail 4 is located on the same side of the second lifting plate corresponding to the second connecting component. Each guide rail 4 is vertically arranged and slides in cooperation with the corresponding slider 3.

[0035] The projections of the first, second, and third connecting components on the horizontal plane form a triangular distribution, and the projections of the three sets of lifting drive units on the horizontal plane also form a triangular distribution, with the two triangles corresponding to each other, thus balancing the forces on the structure.

[0036] Example 2 This embodiment, based on embodiment 1, further includes a closed-loop control system.

[0037] like Figure 1 As shown, a cornerstone prism mounting plate 9 is fixedly installed on the stage 2 for mounting the cornerstone prism. An interferometric rangefinder (not shown in the figure) is installed on the base or external support. The laser emitted by the interferometric rangefinder is reflected back by the cornerstone prism, and the absolute position of the stage 2 is accurately measured by the principle of interference. Since the laser wavelength is not affected by temperature and humidity, the interferometric rangefinder can directly measure the absolute position of the stage and is not affected by factors such as thermal deformation of the lead screw.

[0038] The lifting platform also includes a controller (not shown in the figure), which is connected to the interferometric rangefinder and each drive motor 5. During operation, the interferometric rangefinder detects the position signal of the stage 2 in real time and feeds it back to the controller. The controller calculates the height deviation at the three lifting plates 1 based on the detection signal and sends control commands to each drive motor 5 to drive the corresponding ball screw 6 to rotate independently to compensate for the height deviation and ensure that the stage 2 always maintains sub-micron level flatness accuracy.

[0039] As an alternative, a grating ruler can be installed on the lifting plate 1 or the guide rail 4. The displacement of each lifting plate 1 can be detected by the grating ruler and fed back to the controller to achieve closed-loop control accuracy at the micrometer level (2~5μm). Working principle The working principle of the lifting platform with three-drive, three-point differentiated flexible connection of the present invention is as follows: The drive motor 5 drives the ball screw 6 to rotate via the worm gear reducer 8. The rotation of the ball screw 6 causes the lifting nut 7 to move up and down in the vertical direction. The lifting nut 7 drives the lifting plate 1, which is fixed to it, to move up and down synchronously. The lifting plate 1 drives the slider 3 fixed on it to slide along the guide rail 4.

[0040] The three lifting drive units operate independently, and the rotation angles of each ball screw 6 inevitably have slight differences, resulting in inconsistent vertical displacements of the three lifting plates 1. This leads to a vertical positional deviation (i.e., asynchronous lifting) between the lifting plates 1. When this positional deviation is transmitted to the platform 2 through the three connecting components, the flexible hinge plate 13 in the first connecting component undergoes slight elastic deformation, the double-joint bearing 14 in the second connecting component generates bidirectional oscillation, and the single-joint bearing in the third connecting component generates unidirectional oscillation. The synergistic effect of these three deformations / oscillations with different degrees of freedom absorbs and dissipates the positional deviation, preventing additional stress on the platform 2.

[0041] Meanwhile, the interferometer uses the cornerstone prism on the cornerstone prism mounting plate 9 to detect the absolute position of the platform 2 in real time. The controller controls the rotation of each drive motor 5 according to the detection signal, realizing closed-loop feedback control to ensure that the platform 2 maintains sub-micron level flatness accuracy throughout the entire lifting stroke. Through the dual effects of the passive absorption of the mechanical structure and the active compensation of the control system, the high-precision and stable operation of the lifting platform is achieved.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A lifting platform with three-drive, three-point differentiated flexible connection, characterized in that, include: Three sets of lifting drive units are used to drive the three lifting plates (1) to rise and fall respectively; the first connecting component, the second connecting component and the third connecting component are respectively set between the three lifting plates (1) and the platform (2) and their projections on the horizontal plane are triangularly distributed. The platform (2) is connected to the three lifting plates (1) one by one through the three connecting components; among them, the first connecting component, the second connecting component and the third connecting component have different degrees of freedom constraint methods to absorb the vertical position deviation generated by the three lifting plates (1) during the lifting process; the three lifting plates (1) are respectively provided with sliders (3), and each slider (3) slides in cooperation with the vertically set guide rail (4).

2. The lifting platform with three-drive, three-point differentiated flexible connection according to claim 1, characterized in that, The first connecting assembly includes a first joint bearing (12) and a flexible hinge plate (13); the second connecting assembly includes a second joint bearing, which is a double joint bearing (14); the third connecting assembly includes a third joint bearing (15), which is a single joint bearing; the first joint bearing (12) and the flexible hinge plate (13) are arranged in series in the vertical direction.

3. The lifting platform with three-drive, three-point differentiated flexible connection according to claim 1, characterized in that, Each lifting drive unit includes a drive motor (5), a ball screw (6) connected to the output end of the drive motor (5), and a lifting nut (7) threaded with the ball screw (6). The lifting plate (1) is fixedly connected to the lifting nut (7). The drive motor (5) is a stepper motor, and the output end of the stepper motor is connected to the ball screw (6) through a worm gear reducer (8).

4. The lifting platform with three-drive, three-point differentiated flexible connection according to claim 1, characterized in that, There are four sliders (3), two of which are set on the lifting plate (1) corresponding to the third connecting component, and the other two sliders (3) are set on the lifting plate (1) corresponding to the first connecting component and the second connecting component respectively; the two sliders (3) set on the lifting plate (1) corresponding to the third connecting component are located on both sides of the horizontal direction of the lifting plate (1).

5. The lifting platform with three-drive, three-point differentiated flexible connection according to claim 3, characterized in that, It also includes an interferometric rangefinder, with three lifting plates (1) each equipped with a corner prism mounting plate (9) that works with the interferometric rangefinder; it also includes a controller, which is connected to the interferometric rangefinder and each drive motor (5) respectively, and is used to control the operation of each drive motor (5) according to the detection signal of the interferometric rangefinder.

6. The lifting platform with three-drive, three-point differentiated flexible connection according to claim 1, characterized in that, Each ball screw (6) has an upper bearing seat (10) and a lower bearing seat (11) at both ends to support the rotation of the ball screw (6).

7. The lifting platform with three-drive, three-point differentiated flexible connection according to claim 1, characterized in that, There are four guide rails (4). Two guide rails (4) are located on the same side of the lifting plate (1) corresponding to the third connecting component, and the other two guide rails (4) are located on the same side of the lifting plate (1) corresponding to the first connecting component and the second connecting component, respectively.

8. The lifting platform with three-drive, three-point differentiated flexible connection according to claim 1, characterized in that, The projections of the three sets of lifting drive units on the horizontal plane form a triangular distribution.

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