High-rigidity low-friction precision electric linear mechanism

Abstract

The invention provides a high-rigidity low-friction precise electric linear mechanism. The high-rigidity low-friction precise electric linear mechanism comprises a base, a cylinder body, a motor, a lead screw, a nut, a push rod, a moving pair dense ball bearing assembly, a cylindrical pair dense ball bearing assembly and a piston (7). The cylinder body is fixed to the base through screws, the motor is fixedly connected to the lower end of the base and is in transmission connection with the lead screw through a flat key, the lead screw and the nut are matched to form a ball screw assembly, the nut is fixedly connected with the push rod, and the upper end and the lower end of the push rod are supported by the two dense ball bearings, so that the stress mode of the push rod is improved. Traditional sliding friction is changed into rolling friction, the friction coefficient of the push rod is reduced, and the service life is prolonged; the jerk value of the push rod in the diameter direction is restrained through the dense ball bearing assembly, and the push rod positioning precision is improved; the piston is installed at the upper end of the lead screw and plays an auxiliary supporting role in the push rod, the dense ball bearing plays a main role in supporting the push rod, and the radial supporting rigidity of the push rod is improved through combination of the piston and the dense ball bearing.

Description

Technical Field

[0001] This invention relates to the field of electric linear transmission technology, specifically to a high-rigidity, low-friction precision electric linear mechanism. Background Technology

[0002] In fields such as industrial automation, precision experimental equipment, and military equipment, linear transmission mechanisms are core actuators. Currently, the mainstream linear transmission elements include electric cylinders, hydraulic cylinders, and pneumatic cylinders. Compared with hydraulic cylinders and pneumatic cylinders, electric cylinders have significant advantages: they are energy-efficient, clean, and highly adaptable to various environments; they have high transmission efficiency; their positioning accuracy is superior to traditional hydraulic and pneumatic mechanisms; they have a simple structure, occupy less space, and are easy to maintain. They also possess high reliability, high safety, stable operation, long service life, fast response, wide speed adjustment range, precise control, and good synchronization. Therefore, they are gradually being promoted and used in various industrial applications and special fields. The core working principle of an electric cylinder is that a computer sends instructions to a servo driver, which drives a servo motor to rotate. This motor, through a reducer and reversing gear transmission mechanism, drives a ball screw pair to rotate. After the screw nut is radially limited, it reciprocates linearly with the push rod under the drive of the screw's rotational torque. A multi-turn absolute encoder is usually installed at the end of the screw as a position feedback device to provide real-time feedback on the push rod's position. Some products also integrate manual functions, emergency devices, locking functions, limit switches, and alarm functions. However, the existing electric cylinders still have significant structural design flaws, making it difficult to meet the micron-level positioning accuracy requirements of precision mechanical equipment. Specific problems are as follows: 1. During the extension and retraction of the push rod, a sliding bearing is used to support the outer cylindrical surface of the push rod. The sliding friction results in a large friction force, which not only affects the smoothness of the movement, but also aggravates the wear of the components. 2. Existing designs only improve the positioning accuracy of the push rod end by increasing the machining accuracy of the ball screw, ignoring the significant impact of the radial oscillation error of the push rod on the positioning accuracy, resulting in a large straightness error; 3. The rotation limit between the push rod and the cylinder body adopts the method of sliding groove and pin engagement. During the movement, sliding friction is generated. After long-term use, the engagement clearance will gradually increase, further reducing the positioning accuracy and stability of the electric cylinder.

[0003] To address the shortcomings of the existing technologies, this invention proposes a structurally optimized high-rigidity, low-friction precision electric linear mechanism. Through innovative support structures and limiting methods, it solves the core problems of high friction, low precision, and insufficient rigidity. Summary of the Invention

[0004] This invention provides a high-rigidity, low-friction precision electric linear mechanism, aiming to solve the problems mentioned in the background art.

[0005] This invention is implemented as follows: a high-rigidity, low-friction precision electric linear mechanism includes a base, a cylinder, a motor, a lead screw, a nut, a push rod, a movable ball bearing assembly, a cylindrical ball bearing assembly, and a piston. The cylinder is fixed to the base with screws. The motor is fixed to the lower end of the base and connected to the lead screw via a key. The lead screw and nut cooperate to form a ball screw assembly, and the nut is fixed to the push rod. The movable ball bearing assembly consists of a cylinder, a push rod, a ball guide sleeve, and steel balls B. The cylindrical ball bearing assembly consists of a bearing seat, a push rod, a ball retainer, and steel balls A. The two sets of assemblies are respectively arranged at the lower and upper ends of the push rod. The piston is fixed to the upper end of the lead screw and inserted into the blind hole of the push rod, with a clearance fit to the push rod to provide auxiliary support.

[0006] Preferably, in the high-rigidity, low-friction precision electric linear mechanism, the inner wall of the cylinder is provided with 8 cylinder V-grooves evenly distributed along the circumference, and the outer surface of the lower end of the push rod is provided with 8 push rod V-grooves corresponding to and adapted to the cylinder V-grooves; the steel balls B are positioned by the dense ball guide sleeve, arranged in 3 layers along the axial direction, with 8 balls evenly distributed along the circumference in each layer, and the steel balls B form a four-point contact fit with the cylinder V-grooves and the push rod V-grooves, constraining the push rod to move only along the axis.

[0007] Preferably, in the high-rigidity, low-friction precision electric linear mechanism, the bearing housing is fixed to the upper end of the cylinder body by screws, the ball retainer is disposed in the gap between the bearing housing and the push rod, and the upper end is limited by the bearing cover B; the ball retainer is provided with 3 sets of ball holes A distributed along the axis, each set of ball holes A is evenly distributed along the circumference, and the 3 sets of ball holes A are staggered in pairs, the steel ball A is housed in the ball hole A, constraining the push rod to have two degrees of freedom: movement along the axis and rotation around the axis.

[0008] Preferably, in the high-rigidity, low-friction precision electric linear mechanism, a pair of tapered roller bearings configured "back-to-back" are installed in the center hole of the base. An inner spacer and an outer spacer are provided between the two sets of tapered roller bearings along the axis. The lead screw is engaged with the inner ring of the tapered roller bearing and is fixed by two locking nuts. A bearing cover A is provided at the upper end of the base to limit the axial displacement of the tapered roller bearing.

[0009] Preferably, in the high-rigidity, low-friction precision electric linear mechanism, the outer surface of the piston is provided with piston V-grooves distributed along the axial direction, and the piston V-grooves are used to realize the exhaust function.

[0010] Preferably, in the high-rigidity, low-friction precision electric linear mechanism, a sealing ring B is provided on the inner side of the bearing cover B, and a sealing ring B is provided at the corresponding position of the ball guide sleeve, for the purpose of achieving sealing protection.

[0011] Preferably, in the high-rigidity, low-friction precision electric linear mechanism, a left cylinder support and a right cylinder support are respectively provided on both sides of the cylinder body. The left cylinder support and the right cylinder support are fixed to the frame by screws or pins to fix the cylinder body.

[0012] Preferably, in the high-rigidity, low-friction precision electric linear mechanism, the connection between the motor and the lead screw is a key connection or a shrink sleeve connection; a speed reducer can be added between the motor and the lead screw to increase the output thrust of the push rod.

[0013] Due to the adoption of the above solution, the beneficial effects of the present invention are: Low friction and long life: The push rod is supported by two sets of ball bearing assemblies, which transforms traditional sliding friction into rolling friction, significantly reducing the coefficient of friction, reducing component wear, and extending the service life of the electric cylinder. High-precision positioning: The upper dense ball bearing assembly effectively constrains the radial runout of the push rod, while the lower dense ball bearing assembly eliminates rotational clearance through the four-point contact between the V-groove and the steel ball. The two work together to reduce the linearity error of the push rod movement, enabling the positioning accuracy to reach the micron level, meeting the requirements of precision equipment. High rigidity and stability: The outer support (upper and lower ball bearing assemblies) and the inner support (piston) form a collaborative support structure. The ball bearings provide the main support force, and the piston provides auxiliary support, which greatly improves the radial support rigidity of the push rod, ensures structural stability during movement, and avoids deformation affecting accuracy. High adaptability: The upper ball bearing assembly allows the push rod to move along the axis and rotate around the axis, while the lower assembly only allows axial movement. This combination of degrees of freedom design can offset assembly deviations caused by machining errors and temperature changes, avoid motion jamming, and improve the adaptability of the mechanism. Reliable sealing and protection: Key parts are sealed through sealing rings to prevent impurities from entering, while the piston V-groove enables exhaust function, ensuring smooth movement and further improving the reliability of the mechanism. Attached Figure Description

[0014] Figure 1 This is a front view of the electric cylinder assembly of the present invention; Figure 2 This is a three-dimensional view of the electric cylinder assembly of the present invention; Figure 3 This is a top view of the electric cylinder assembly of the present invention; Figure 4 This is a schematic diagram of the base of the present invention; Figure 5 This is a three-dimensional cross-sectional view of the cylinder block of the present invention; Figure 6 This is a three-dimensional cross-sectional view of the cylinder block of the present invention; Figure 7 This is a schematic diagram of the cylinder block cross-section of the present invention; Figure 8This is a schematic diagram of the push rod of the present invention; Figure 9 This is a schematic diagram of the piston of the present invention; Figure 10 This is a schematic diagram of the bead retainer of the present invention; Figure 11 This is a schematic diagram of the bead guide sleeve of the present invention; Figure 12 This is a schematic diagram of the nut of the present invention; Figure 13 This is a schematic diagram of the lead screw of the present invention; The markings in the diagram are as follows: 1-Base, 2-Bearing cover A, 3-Cylinder body, 4-Nut, 5-Lead screw, 6-Bearing seat, 7-Piston, 8-Push rod, 9-Bearing cover B, 10-Sealing ring B, 11-Ball retainer, 12-Steel ball A, 13-Sealing ring B, 14-Ball guide sleeve, 15-Steel ball B, 16-Tap roller bearing, 17-Inner spacer, 18-Outer spacer, 19-Locking nut, 20-Flat key, 21-Motor, 22-Cylinder body V-groove, 23-Piston V-groove, 24-Push rod V-groove, 25-Ball hole A, 26-Ball hole B, 27-Axis, 28-Left support of cylinder body, 29-Right support of cylinder body. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] like Figure 1-13 As shown, this embodiment discloses a high-rigidity, low-friction precision electric linear mechanism, including a base 1, a bearing cover A2, a cylinder 3, a nut 4, a lead screw 5, a bearing seat 6, a piston 7, a push rod 8, a bearing cover B9, a sealing ring B10, a ball retainer 11, a steel ball A12, a sealing ring B13, a ball guide sleeve 14, a steel ball B15, a tapered roller bearing 16, an inner spacer 17, an outer spacer 18, a locking nut 19, a flat key 20, a motor 21, a cylinder V-groove 22, a piston V-groove 23, a push rod V-groove 24, a ball bearing hole A25, a ball bearing hole B26, an axis 27, a cylinder left support 28, and a cylinder right support 29.

[0017] The specific assembly and working process is as follows: The base 1 serves as the basic load-bearing component. First, a pair of tapered roller bearings 16 with a "back-to-back" configuration are installed at the center hole of the base 1. An inner spacer 17 and an outer spacer 18 are installed between the two sets of tapered roller bearings 16 along the axis 27. The preload of the tapered roller bearings 16 is adjusted by adjusting the thickness of the spacers. The bearing end of the lead screw 5 is fitted with the inner hole of the tapered roller bearing 16, and the lead screw 5 is fixed to the inner ring of the tapered roller bearing 16 with two lock nuts 19. Finally, the bearing cover A2 is fixed to the upper end of the base 1 with screws to limit the axial displacement of the tapered roller bearing 16 and ensure that the lead screw 5 can rotate stably around the axis 27 together with the inner ring of the bearing.

[0018] The cylinder body 3 is fixed to the base 1 with screws to form a rigid frame for the entire electric cylinder assembly; the piston 7 is fixed to the upper end of the lead screw 5 with screws, and the piston 7 and the lead screw 5 are inserted together into the blind hole of the push rod 8. The piston 7 and the push rod 8 are fitted with clearance, which not only provides auxiliary support for the push rod 8, but also realizes the exhaust function through the piston V-groove 23 on the outer surface of the piston 7.

[0019] A ball bearing guide sleeve 14 and matching steel balls B15 are installed at the lower end of the push rod 8. The steel balls B15 are arranged in three layers along the axial direction, with eight balls evenly distributed around the circumference in each layer. The position of the steel balls B15 is limited by the ball bearing holes B26 of the ball bearing guide sleeve 14. The flange face of the nut 4 is fixed to the lower end face of the push rod 8 with screws. The nut 4 is then connected to the lead screw 5 to form a ball screw assembly. The steel balls B15 form a "four-point contact" engagement with the eight cylinder V-grooves 22 on the inner wall of the cylinder body 3 and the eight push rod V-grooves 24 at the lower end of the push rod 8. The three sets of steel balls B15 together constrain the push rod 8, allowing it to move only along the axis 27, thus achieving rotational limitation.

[0020] The bearing housing 6 is fixed to the upper end of the cylinder 3 with screws. A ball retainer 11 and three sets of steel balls A12 are installed in the gap between the bearing housing 6 and the push rod 8. The ball retainer 11 has three sets of ball holes A25 distributed along the axis 27. Each set of holes is evenly distributed along the circumference and staggered in pairs. The steel balls A12 are housed in the ball holes A25. The bearing cover B9 is fixed to the upper end of the bearing housing 6 with screws to restrict the linear displacement of the ball retainer 11. At the same time, the sealing protection is achieved by the sealing ring B10 on the inner side of the bearing cover B9 and the sealing ring B13 at the corresponding position of the ball guide sleeve 14.

[0021] At the lower flange of the base 1, the motor 21 is fixed to the base 1 with screws. The motor 21 and the lead screw 5 transmit rotational motion through the flat key 20. Alternatively, a shrink sleeve can be used for connection as required, or a speed reducer can be added between the two to increase the output thrust. Finally, the cylinder body 3 is fixed to the frame with screws or pins through the left cylinder body support 28 and the right cylinder body support 29 on both sides of the cylinder body 3, thus completing the overall assembly.

[0022] When in operation, the motor 21 is powered on, and the motor rotor rotates and drives the lead screw 5 to rotate around the axis 27 through the flat key 20. Since the rotational freedom of the nut 4 is constrained by the fit structure of the steel ball B15 and the V-groove, the rotational motion of the lead screw 5 is converted into the axial translational motion of the nut 4. The nut 4 is fixedly connected to the push rod 8, which in turn drives the push rod 8 to perform linear extension and retraction motion along the axis 27, thereby realizing precise linear transmission.

[0023] The scope of protection of this invention is not limited to the above embodiments. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. For example, the connection method between the motor and the lead screw, the number and distribution of steel balls, and the structural form of the spacers can all be adjusted according to the actual application scenario. As long as they do not depart from the core technical solution of this invention, they all fall within the scope of protection of the appended claims. The above description of the embodiments is intended to enable those skilled in the art to understand and use the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the principles of the present invention without departing from the scope of the invention should be within the protection scope of the present invention. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-rigidity, low-friction precision electric linear mechanism, characterized in that, It includes base (1), cylinder (3), motor (21), screw (5), nut (4), push rod (8), moving pair of bearing assembly, cylindrical pair of bearing assembly and piston (7); the cylinder (3) is fixed on the base (1) by screw, the motor (21) is fixed on the lower end of the base (1) and is connected with the screw (5) by means of flat key (20), the screw (5) and the nut (4) are matched to form ball screw assembly, the nut (4) is fixed with the push rod (8); the moving pair of bearing assembly is composed of cylinder (3), push rod (8), tight bead guide sleeve (14) and steel ball B (15), the cylindrical pair of bearing assembly is composed of bearing seat (6), push rod (8), tight bead retainer (11) and steel ball A (12), two groups of components are respectively arranged on the lower end and the upper end of the push rod (8); the piston (7) is fixed on the upper end of the screw (5) and is inserted into the blind hole of the push rod (8), and is matched with the push rod (8) to realize auxiliary support.

2. The high-rigidity low-friction precision electric linear mechanism according to claim 1, characterized by The inner wall of the cylinder (3) is provided with eight cylinder V-shaped grooves (22) which are uniformly distributed along the circumference, and the outer surface of the lower end of the push rod (8) is provided with eight push rod V-shaped grooves (24) which are correspondingly matched with the cylinder V-shaped grooves (22); the steel ball B (15) is limited in position by the tight bead guide sleeve (14) and is arranged in three layers along the axial direction, and each layer is uniformly distributed with eight steel balls B (15) along the circumference, and the steel ball B (15) forms four-point contact with the cylinder V-shaped groove (22) and the push rod V-shaped groove (24), so as to constrain the push rod (8) to move only along the axis (27).

3. The high stiffness low friction precision electric linear mechanism according to claim 1, characterized by, The bearing seat (6) is fixed on the upper end of the cylinder (3) by screw, the tight bead retainer (11) is arranged at the gap between the bearing seat (6) and the push rod (8), and the upper end is limited in position by bearing cover B (9); the tight bead retainer (11) is provided with three groups of tight bead holes A (25) which are distributed along the axis (27), each group of tight bead holes A (25) is uniformly distributed along the circumference, and the three groups of tight bead holes A (25) are alternately distributed, the steel ball A (12) is accommodated in the tight bead hole A (25), and the push rod (8) has two degrees of freedom of moving along the axis (27) and rotating around the axis (27).

4. The high stiffness low friction precision electric linear mechanism according to claim 1, characterized by, A pair of "back-to-back" conical roller bearings (16) are installed in the center hole of the base (1), and an inner spacer ring (17) and an outer spacer ring (18) are arranged between the two groups of conical roller bearings (16) along the axis (27), the screw (5) is matched with the inner ring of the conical roller bearing (16), and is fixed by two locking nuts (19), and the upper end of the base (1) is provided with bearing cover A (2) to limit the axial displacement of the conical roller bearing (16).

5. The high stiffness low friction precision electric linear mechanism according to claim 1, wherein The outer surface of the piston (7) is provided with piston V-shaped grooves (23) which are distributed along the axial direction, and the piston V-shaped grooves (23) are used to realize the exhaust function.

6. The high stiffness, low friction precision electric linear mechanism of claim 1, wherein, The inner side of the bearing cover B (9) is provided with a sealing ring B (10), and the tight bead guide sleeve (14) is provided with a sealing ring B (13) at the corresponding position, which is used to realize sealing protection.

7. The high stiffness low friction precision electric linear mechanism of claim 1, wherein The cylinder body (3) is respectively provided with a cylinder body left support (28) and a cylinder body right support (29) on two sides, the cylinder body left support (28) and the cylinder body right support (29) are fixedly connected with the rack through screws or pins, and are used for fixing the cylinder body (3).

8. The high stiffness, low friction precision electric linear mechanism of claim 1, wherein, The motor (21) is connected with the lead screw (5) in a way of a flat key connection or an expansion sleeve connection; a speed reducer can be additionally arranged between the motor (21) and the lead screw (5) to improve the output thrust of the push rod (8).

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