Internal circulation ball screw pair reverser arrangement structure for electric cylinder

Abstract

The invention belongs to the technical field of ball screw pairs, and particularly relates to an internal circulation ball screw pair reverser arrangement structure for an electric cylinder. The inverters are non-uniformly distributed along the circumference of the ball nut, namely the interval angle is not equal to 2pi / N; when the inverters are arranged along the complete outer circle, the interval angle in the circumferential direction is theta 1; when the inverters are arranged across the key groove, the interval angle in the circumferential direction is theta 2; on the premise of meeting the load and stroke requirements, the axial length of the nut is shortened by reducing the included angle between the adjacent reversers, the length of each circle can be reduced (2pi-N theta1) P / 2pi N, meanwhile, the lengths of structures such as a ball screw and a cylinder barrel can be correspondingly reduced, the weight of the electric cylinder is reduced, and the production and use cost is reduced; a safe distance is reserved between a nut threaded hole, a key groove and other structures and the reverser, so that the nut is reliably connected with a piston rod, a guide key and other parts.

Description

Technical Field

[0001] The invention belongs to the technical field of ball screw pairs, and in particular relates to an arrangement structure of an internal circulation ball screw pair reverser for an electric cylinder. Background Art

[0002] With the demand for full electrification, electric cylinders have begun to replace hydraulic cylinders in the field of load transmission, and have gradually developed towards large strokes and high loads. At the same time, they require miniaturization and lightweight, which has brought great challenges to the design and manufacturing of their components. Ball screw pairs can realize the mutual conversion between rotational motion (torque) and linear motion (axial force). They have the characteristics of high precision, high efficiency, and long service life. They have been widely used in mechanical processing, aerospace, and nuclear industries. Typical internal circulation ball screw pairs for electric cylinders are as follows: Figure 1 As shown, it includes a ball screw 1, a ball nut 2, a ball 3, a deflector 4, a keyway 5 and a threaded hole 6; the end face of the ball nut 2 needs to be processed with a threaded hole 6 for connecting the piston rod, and the outer circle contains a keyway 5 for installing a guide key to limit its circumferential movement. Internal circulation refers to a circulation method in which the ball never leaves the surface of the screw during the circulation process. Generally, a deflector 4 connected to the adjacent raceway is installed on the side of the nut. The ball return groove on the deflector 4 can guide the ball to climb over the top of the screw tooth and return to the initial raceway to form a circulating ball chain. The number of circulating ball chains determines the load-bearing capacity of the ball screw pair. N circles of balls 3 are equipped with N deflectors 4. These deflectors 4 are evenly distributed along the circumference of the ball nut 2, and the axial spacing between each deflector is (1+1 / N)P (P is the lead of the screw).

[0003] The design requirements and characteristics of the internal circulation ball screw pair for a typical electric cylinder are shown in Table 1: Depend on Figure 1 As can be seen from Table 1, the internal circulation ball screw pair used in typical electric cylinders has a large load-bearing capacity and generally requires a multi-turn arrangement. At the same time, the miniaturization and lightweight requirements of the electric cylinder make the nut length relatively extreme, and there are structures such as threaded holes and keyways, which affect the normal arrangement of the reverser.

[0004] It can be seen from the typical internal circulation ball screw pair structure for electric cylinders and the existing reverser arrangement method that the background technology has the following shortcomings: 1. The axial length of the nut is insufficient like Figure 2 As shown in the figure, when the ball nut reversers are evenly distributed along the circumference, the axial length makes it difficult to arrange all reversers completely, resulting in damage to the end face threaded holes and affecting the connection with the piston rod.

[0005] 2. The circumferential structure of the nut is destroyed like Figure 3If the ball nut reverser shown in the figure is evenly distributed along the circumference, the outer circle keyway structure will be destroyed and the circumferential positioning of the electric cylinder will be affected.

[0006] In summary, under the premise of meeting the load and stroke requirements, when the installation distance is relatively compact, the nut length is often limited, and the existing reverser arrangement method cannot meet the design requirements. Even if the installation space margin is large, the overly long structural design does not conform to the miniaturization and lightweight trend of the electric cylinder. In addition, the uniform distribution of the reverser is likely to interfere with structures such as keyways and threaded holes. Therefore, the internal circulation ball screw pair for the electric cylinder urgently needs a more flexible reverser arrangement structure. Summary of the invention

[0007] The present invention overcomes the shortcomings of the prior art and proposes an arrangement structure of an internal circulation ball screw pair reverser for an electric cylinder that can shorten the nut length and avoid the nut functional structure while meeting the load and stroke requirements. The present invention is achieved through the following technical solutions: An arrangement structure of an internal circulation ball screw pair reverser for an electric cylinder. When multiple deflectors are arranged along the complete outer circle of the ball nut, the interval angle of the deflectors in the circumferential direction is θ1, and Nθ1<2π, and the axial spacing of the deflectors is (1+θ1 / 2π)P; N is the number of deflectors; P is the lead of the screw; When the reversers are arranged across the keyway, the circumferential spacing angle is θ2 and the axial spacing is (1+θ2 / 2π)P; θ2 satisfies the following conditions: θ2H / 2-(L-b1)sinα-b1-2s = arctan(b2 / H) Where: θ2——the angle between adjacent reversers, rad; H——keyway bottom distance, mm; L——reverser length, mm; b1——reverser width, mm; b2——keyway width, mm; α——Angle between the reverser and the nut axis, rad; s——safe wall thickness, mm.

[0008] Furthermore, it includes a ball screw, a ball nut, a ball and a reverser; the outer circle of the ball screw and the inner hole of the ball nut are both provided with spiral raceways that match each other.

[0009] Furthermore, the ball nut is provided with a waist-shaped hole on the side, and the deflector is installed in the waist-shaped hole.

[0010] Furthermore, an inner circulation raceway is provided on the reverse device, and the two ends are respectively connected to the starting and ending positions of the circulating balls, and the balls always move along the spiral raceway and the inner circulation raceway.

[0011] Furthermore, the ball nut is provided with a threaded hole and a keyway.

[0012] The beneficial effects of the present invention compared with the prior art are as follows: 1) The reversers of the present invention are non-uniformly distributed along the circumference of the ball nut, that is, the interval angle is not equal to 2π / N; under the premise of meeting the load and stroke requirements, the axial length of the nut can be shortened by reducing the angle between adjacent reversers, and the length of each circle can be reduced by (2π-Nθ1)P / 2πN. At the same time, the lengths of structures such as the ball screw and the cylinder can be reduced accordingly, thereby reducing the weight of the electric cylinder and reducing the production and use costs.

[0013] 2) The threaded hole, keyway and other structures of the ball nut should be kept at a safe distance from the reverser, so that the ball nut can be reliably connected to the piston rod, guide key and other parts.

[0014] Since the present invention can realize the flexible arrangement of the reverser of the inner circulation ball screw pair, the present technology can be widely applied in the arrangement of the reverser. When the ball nut is provided with a trunnion or other structure, the safe wall thickness can also be reserved by referring to this method. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an internal circulation ball screw pair for a typical electric cylinder; Figure 2 This is a schematic diagram of the insufficient axial length of the nut when the reversers are evenly arranged; Figure 3 It is a schematic diagram of the nut structure being destroyed when the reversers are evenly arranged; Figure 4 It is a schematic diagram of the lateral expansion structure of the nut when the reverser of the present invention is flexibly arranged; Figure 5 It is a schematic diagram of the circumferential arrangement structure of the reverser of the present invention when it is flexibly arranged.

[0016] In the figure: 1. ball screw; 2. ball nut; 3. ball; 4. reverser; 5. keyway; 6. threaded hole; 7. oval hole. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0018] See also Figure 4 and Figure 5 , this embodiment proposes an arrangement structure of an internal circulation ball screw pair and a reverser for an electric cylinder; wherein, the internal circulation ball screw pair for the electric cylinder is a known existing structure, including a ball screw 1, a ball nut 2, a ball 3 and a reverser 4. The outer circle of the ball screw 1 and the inner hole of the ball nut 2 are both provided with spiral raceways that match each other. The ball nut 2 is provided with a waist-shaped hole 7 on the side, and the reverser 4 is installed in the waist-shaped hole 7. The reverser 4 is provided with an internal circulation raceway, and the two ends are respectively connected to the starting and ending positions of the circulating balls, and the balls always move along the spiral raceway and the internal circulation raceway. The ball nut 2 includes functional structures such as a threaded hole 6 and a keyway 5.

[0019] When the deflectors 4 are arranged along the complete outer circle of the nut, the interval angle in the circumferential direction is θ1 (Nθ1<2π), and the axial spacing is (1+θ1 / 2π) P. N is the number of deflectors 4; P is the lead of the screw; that is, the deflectors 4 are unevenly distributed along the circumference of the ball nut 2, and the interval angle is not equal to 2π / N; When the reverser 4 is arranged across the keyway 5, the circumferential spacing angle is θ2, and the axial spacing is (1+θ2 / 2π) P. θ2 satisfies the following conditions: θ2H / 2-(L-b1)sinα-b1-2s = arctan(b2 / H) Where: θ2——the angle between adjacent reversers, rad; H——keyway bottom distance, mm; L——reverser length, mm; b1——reverser width, mm; b2——keyway width, mm; α——Angle between the reverser and the axis of the ball nut, rad; s——safe wall thickness, mm.

[0020] like Figure 4 As shown, in the lateral development diagram of the ball nut 2, 10 waisted circular holes 7 are arranged, and the arrangement position of the waisted circular holes 7 is the arrangement position of the deflector 4. The angle between two adjacent waisted circular holes 7 in the circumferential direction is θ1 or θ2, and the angle between the deflector 4 and the axis of the ball nut 2 is α; Figure 5It is a schematic diagram of the circumferential arrangement of the reverser. Under the premise of meeting the load and stroke requirements, this embodiment shortens the axial length of the ball nut 2 by reducing the angle between the adjacent reversers 4. The length can be reduced by (2π-Nθ1)P / 2πN per turn. At the same time, the length of the ball screw 1, cylinder and other structures can be reduced accordingly, so as to achieve the weight reduction of the electric cylinder and reduce the production and use costs; the threaded hole, keyway 5 and other structures of the ball nut 2 are kept at a safe distance from the reverser 4, so that the ball nut 2 is reliably connected to the piston rod, guide key and other parts. Since this structure can realize the flexible arrangement of the reverser of the internal circulation ball screw pair, this technology can be widely used in the arrangement of the reverser. When the ball nut 2 is provided with an ear shaft or other structure, the safe wall thickness can also be reserved by referring to this method.

[0021] If selected Figure 1 The implementation object is the internal circulation ball screw pair 16025 for the typical electric cylinder. The screw lead is 25mm, the number of load circles is 10, the bottom distance of the keyway 5 is 223mm, the length of the reverser 4 is 62mm, the width of the reverser 4 is 26.5mm, the width of the keyway 5 is 30mm, and the angle between the reverser 4 and the axis of the ball nut 2 is 60°. When the deflectors 4 are evenly distributed along the circumference of the ball nut 2, the angle between adjacent deflectors 4 is 2π / N=36°, and the axial spacing is (1+1 / N)P=27.5mm; when the inner circulation ball screw pair deflector arrangement structure for the electric cylinder is adopted, when the deflectors 4 are arranged along the complete outer circle of the ball nut 2, the spacing angle in the circumferential direction is 18°, and the axial spacing between adjacent deflectors 4 is (1+θ1 / 2π)P=26.25mm, and each circle is shortened by (2π-Nθ1)P / 2πN=1.25mm. The nut length can be shortened by 11.25mm in 10 circles, and only the ball screw 1 and the ball nut 2 can achieve a weight reduction of 3kg; when the deflectors 4 are distributed across the keyway 5, if a safety wall thickness of 1.137mm is reserved on both sides, then θ2H / 2-(L-b1)sinα-b1-2s = Arctan (b2 / H) can be calculated to show that the two reversers 4 should be adjacent to each other for at least 46° along the circumference to avoid damaging the structure of the keyway 5. The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiment of the present invention is limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the scope of patent protection determined by the submitted claims of the present invention.

Claims

1. An arrangement structure of an internal circulation ball screw pair reverser for an electric cylinder, characterized in that: When a plurality of deflectors (4) are arranged along the complete outer circle of the ball nut (2), the interval angle of the deflectors (4) in the circumferential direction is θ1, and Nθ1<2π, and the axial spacing of the deflectors (4) is (1+θ1 / 2π)P; N is the number of deflectors; and P is the lead of the screw. When the reversers (4) are arranged across the keyway (5), the spacing angle in the circumferential direction is θ2 and the spacing in the axial direction is ; θ2 satisfies the following conditions: θ2H / 2-(L-b1)sinα-b1-2s = arctane(b2 / H) Where: θ2——the angle between adjacent reversers, rad; H——keyway bottom distance, mm; L——reverser length, mm; b1——reverser width, mm; b2——keyway width, mm; α——Angle between the reverser and the nut axis, rad; s——safe wall thickness, mm.

2. The arrangement structure of the inner-circulation ball screw pair reverser for an electric cylinder according to claim 1, characterized in that: The invention comprises a ball screw (1), a ball nut (2), a ball (3) and a reverser (4); the outer circle of the ball screw (1) and the inner hole of the ball nut (2) are both provided with spiral raceways which match each other.

3. The arrangement structure of the inner-circulation ball screw pair reverser for an electric cylinder according to claim 2, characterized in that: The ball nut (2) is provided with a waist-shaped circular hole (7) on the side, and the deflector (4) is installed in the waist-shaped circular hole (7).

4. The arrangement structure of the inner-circulation ball screw pair reverser for an electric cylinder according to claim 3, characterized in that: The reverse device (4) is provided with an inner circulation raceway, and the two ends are respectively connected to the starting and ending positions of the circulating balls, and the balls (3) always move along the spiral raceway and the inner circulation raceway.

5. The arrangement structure of the inner-circulation ball screw pair reverser for an electric cylinder according to claim 3, characterized in that: The ball nut (2) is provided with a keyway (5) and a threaded hole (6).

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