Rolling nut and rolling screw rod pair thereof

Abstract

A rolling nut and a rolling screw rod pair thereof are characterized in that the rolling screw rod pair is provided with a central screw rod and 2-30 peripheral screw rods which are meshed with the central screw rod and have equal pitch, and the shaft end of each peripheral screw rod is provided with a rolling bearing for bearing axial thrust, a bearing for bearing radial force and a bearing seat. The bearing seat ensures that the meshing center distance and the axis of the central screw rod and the peripheral screw rods are parallel, and all the peripheral screw rods, the bearings at the shaft ends and the bearing seat form a rolling nut; the rolling nut can be a complete cylinder or a part of the cylinder; the central screw rod can actively rotate, or the peripheral screw rods can actively rotate while the peripheral screw rod bearing seats do not rotate, or the rolling nut can integrally rotate, that is, the bearing seats at the two ends of the peripheral screw rods are connected together and synchronously rotate, and the peripheral screw rods rotate and revolve; and a rolling bearing for bearing axial thrust is arranged at the end part of each rotating central screw rod or rolling nut.

Description

Technical Field

[0001] This invention pertains to a type of helical transmission mechanical part, specifically relating to a rolling screw assembly, a rolling nut, and the rolling screw assembly thereof. Background Technology

[0002] Existing rolling screws include ball screws and roller screws. Ball screws have a lower load-bearing capacity and are mainly used in feed mechanisms. Roller screws have a higher load capacity but have not been widely adopted in China due to their high price. Existing roller screws consist of a screw, rollers, and a nut. The nut has a flange on its outer diameter, and the axial thrust is borne by the nut and the flange. When high screw rigidity is required or installation space is limited, it is difficult to select a suitable model. Summary of the Invention

[0003] The problem to be solved by the present invention is to provide a rolling nut and its rolling screw pair. The rolling nut may not have a flange, and the rolling nut may be cylindrical or only part of a cylinder. The diameter of the screw is increased, the rigidity of the screw pair is improved, and the installation size is reduced.

[0004] To achieve the above objectives, a rolling nut and its rolling screw assembly are provided, characterized in that: the rolling screw assembly has a central screw and 2 to 30 peripheral screws with equal pitch meshing with it; each peripheral screw shaft end is provided with a rolling bearing for bearing axial thrust, a bearing for bearing radial force, and a bearing seat; the bearing seat ensures that the meshing center distance and axis of the central screw and the peripheral screws are parallel; all the peripheral screws and the bearings and bearing seats at the shaft ends constitute a rolling nut; the rolling nut can be a complete cylinder or a part of a cylinder; the central screw can rotate actively, or the peripheral screws can rotate actively while the peripheral screw bearing seats do not rotate, or the rolling nut can rotate as a whole, that is, the bearing seats at both ends of the peripheral screws are connected and rotate synchronously, with the peripheral screws rotating on their own axis and revolving around the sun; all rotating central screws or rolling nut ends are provided with rolling bearings for bearing axial thrust.

[0005] Full complement tapered roller thrust bearings and various thrust roller bearings used in rolling mill pressing mechanisms have a greater capacity to withstand axial forces and can be given priority. Tapered roller bearings can also be used at the peripheral screw shaft end to simultaneously withstand axial and radial forces. Depending on the magnitude of the radial force and the space dimensions, the bearing that withstands the radial force can be a rolling bearing or other bearings.

[0006] The rolling nut and its rolling screw pair are characterized in that: the threads of the central screw and the peripheral screw have opposite directions, the force-bearing tooth surface has a small bevel angle and can be self-locking or nearly self-locking in the radial direction, and the tooth profile is designed to ensure that the contact line is near the center line connecting the center of the central screw and the peripheral screw and has sufficient contact strength, and to meet the bending strength of the tooth root, reduce the outer diameter of the rolling nut and the radial load of the rolling bearing.

[0007] Because the peripheral lead screw is equipped with rolling bearings to withstand axial thrust, its diameter is larger. However, the difference in helix angle between the peripheral and central lead screws is reduced, resulting in a longer width of the tooth root subjected to bending moment. Under sufficient tooth surface contact stress, a shorter contact line leads to less sliding friction loss on the tooth surface. The stressed tooth surface has a smaller chamfer, which increases the radius of the two contact surfaces at the contact line and reduces contact stress. The chamfer angle of the stressed tooth surface of the sawtooth thread is 3 degrees, which allows for self-locking in the radial direction. The chamfer angle of the non-stressed tooth surface is 30 degrees, which can increase the thickness of the tooth root and is a usable tooth surface chamfer angle.

[0008] Most existing roller screws use triangular tooth profiles. The radial friction of the rollers cannot self-lock, and the rollers are subjected to large radial forces. However, there is a fixed nut outside the rollers to bear the radial and axial forces. The rollers are in a state of equilibrium under radial forces. The difference in helix angle between the rollers and the fixed nut is large, requiring a large radial tooth surface bevel angle.

[0009] The rolling nut and its rolling screw assembly are characterized in that: the rolling nut is composed of 2 to 15 coaxial short rolling nuts connected in series to reduce the load on the rolling bearings of each short rolling nut; the axial thrust of the rolling screw assembly is directly transmitted between the bearing seats of each short rolling nut, or it can be transmitted separately to the component that installs the short rolling nut by the bearing seats of each short rolling nut; each short rolling nut only bears part of the axial thrust of the rolling screw assembly; or, 2 to 5 rolling nuts are connected in series coaxially, and some or all of the bearing seats of the rolling nuts are equipped with springs to limit the axial thrust they receive, thus becoming a rolling nut that only bears part of the preset axial thrust of the rolling screw assembly; the axial thrust can also be transmitted separately by each rolling nut and its spring to the component that installs the rolling nut.

[0010] Along the meshing length of the lead screw and nut, the force on each tooth is uneven. When performing strength calculations, there is a limit to the number of teeth used for calculation. Some rolling nuts have springs in the bearing housing to limit the axial thrust they receive, which can increase the number of teeth used for calculation. They can also be used in equipment with impact forces.

[0011] The beneficial effects of this invention are: when the requirements for screw stiffness are high or the installation space is limited, the rolling nut and its rolling screw pair of this invention can meet the requirements, and various connection methods can be designed independently. Combined with the promotion and application of full complement tapered roller thrust bearings and various thrust roller bearings for rolling mill pressing mechanisms, the application of rolling screw pairs in various forging and pressing equipment can be expanded. Attached Figure Description

[0012] Figure 1 , Figure 2 This is a schematic diagram of Embodiment 1 of the present invention. Figure 2 for Figure 1 A magnified view of a portion of the image;

[0013] Figure 3This is a schematic diagram of Embodiment 2 of the present invention;

[0014] Figure 4 This is a schematic diagram of Embodiment 3 of the present invention;

[0015] In the figure, 1 is the upper bearing housing of the peripheral lead screw, 2 is the radial rolling bearing of the peripheral lead screw, 3 is the peripheral lead screw, 4 is the thrust rolling bearing of the peripheral lead screw, 5 is the thrust rolling bearing of the rolling nut, 6 is the central lead screw, 7 is the lower bearing housing of the peripheral lead screw, 8 is the end gear of the peripheral lead screw, 9 is the main drive gear, 10 is the short rolling nut, and 11 is the disc spring. Detailed Implementation

[0016] Example 1:

[0017] Figure 1 This is an eleven-roll plate straightening machine. Eleven working rolls are respectively installed on the upper movable beam and the lower fixed beam. Pressing devices are set at the four corners of the upper movable beam. The pressing devices are driven by two motors, which drive two pairs of gear reducers and rolling screw pairs respectively. The pressing devices realize the pressing and swinging of the entire upper movable beam.

[0018] Figure 2 for Figure 1 A partial enlarged view shows six peripheral lead screws (3) meshing with the central lead screw (6). The peripheral lead screws (3) and the central lead screw (6) have opposite thread directions but the same pitch. Each peripheral lead screw (3) has two sets of peripheral lead screw radial rolling bearings (2) and one set of peripheral lead screw thrust rolling bearings (4). One set of peripheral lead screw radial rolling bearings (2) is installed on the upper bearing seat (1) of the peripheral lead screw, and the other set of peripheral lead screw radial rolling bearings (2) and one set of peripheral lead screw thrust rolling bearings (4) are installed on the lower bearing seat (7) of the peripheral lead screw. The six peripheral lead screws (3), all peripheral lead screw radial rolling bearings (2), and all peripheral lead screws... The rolling nut is composed of the thrust rolling bearing (4), the upper bearing seat (1) of the peripheral screw, and the lower bearing seat (7) of the peripheral screw. The rolling nut and the central screw form a rolling screw pair. The central screw is fixed. The lower bearing seat (7) of the peripheral screw is equipped with a rolling nut thrust rolling bearing (5). The peripheral screw (3) rotates on its own axis and revolves around the central screw. The upper bearing seat (1) and the lower bearing seat (7) of the peripheral screw are fixed together. The motor and gear reducer of the pressing device drive the rolling nut to rotate as a whole, so as to realize the lifting and swinging of the upper movable beam. The two bearing seats ensure the meshing center distance and axis parallelism of the central screw (6) and the peripheral screw (3).

[0019] The rolling bearing installed on the lower bearing housing (7) of the peripheral screw can be a combination of a full complement tapered roller thrust bearing and a radial needle roller bearing for the rolling mill pressing mechanism.

[0020] Figure 2The enlarged view in section A shows that the rolling screw pair has a trapezoidal tooth profile, a tooth pitch of 22mm, a basic tooth height of 5mm, a central screw outer diameter of 200mm, a peripheral screw outer diameter of 120mm, a tooth surface bevel angle of 3 degrees, and the rolling screw pair is self-locking under radial force.

[0021] The overall efficiency of the pressing device can reach 75-80% or more, enabling online adjustment of the pressing amount, and no creeping occurs during the load pressing process.

[0022] The diameters of the center lead screw and the peripheral lead screw are larger than those of the existing roller lead screws, resulting in better rigidity and meeting the high rigidity requirements of the straightening machine. Since the pressing device is directly connected and has no frame, the rigidity of the whole machine is mainly determined by the rigidity of the pressing lead screw.

[0023] Example 2:

[0024] Figure 3 This is a seven-roller plate straightening machine with three layers of rollers. The upper roller has a larger diameter and no support roller or support beam. The lower roller is slightly thinner. The two middle rollers have support rollers. The lower roller and support rollers are located on the lower fixed beam. The center distance between the bearings at both ends of the upper roller is longer than that between the bearings at both ends of the lower roller. The upper roller is a single-roller direct-connect pressing device. The pressing force does not pass through the frame. The pressing device consists of a motor, a reducer, and a rolling screw pair. The pressing device is installed on the lower fixed beam. The pressing amount of the two rollers can be adjusted online. The upper roller bearing seat is directly connected to the pressing device through a pin, thread, and pull rod.

[0025] Figure 3 In the middle (7), there is a lower bearing housing for the peripheral screw. A set of radial rolling bearings and a set of thrust rolling bearings for the peripheral screw are installed on the lower bearing housing (7). In the middle (1), there is an upper bearing housing for the peripheral screw. A set of radial rolling bearings for the peripheral screw is installed on the upper bearing housing (1). In the enlarged sectional view AA, there are four peripheral screws (3) meshing with the central screw (6). The four peripheral screws (3) are not evenly distributed on the circumference. The rolling nut is part of the cylinder. In the enlarged sectional view BB, the main drive gear (9) on the reducer drives the end gears (8) of the four peripheral screws. The peripheral screws rotate actively and the central screw rotates passively while the peripheral screw bearing housing does not rotate. The end of the central screw is provided with a rolling bearing that bears the axial thrust.

[0026] The reduction in gear ratio of the pressing device reducer is due to the reduction of the peripheral screw (3) and the central screw (6). The reducer is one grade smaller, which makes up for the limitation of the small space of the single roller pressing size, so that the pressing reducer can be installed just right.

[0027] The rolling screw pair of the pressing device has a large diameter and good rigidity. The peripheral screw (3) is not circumferentially distributed, which also meets the limitation of small space for single roller pressing. The existing roller screw can only be a complete cylinder.

[0028] Example 3:

[0029] Figure 4 4a is a rolling nut composed of two coaxial short rolling nuts (10) connected in series, in order to reduce the load of the rolling bearing that bears the axial thrust of each short rolling nut (10). The axial thrust of the rolling screw pair is directly transmitted to each other by the bearing housing of each short rolling nut (10), which is used when the rated load of the rolling bearing that bears the axial thrust is insufficient.

[0030] Axial thrust can also be transmitted to the component that mounts the short rolling nut by the bearing housing of each short rolling nut. Each short rolling nut only bears part of the axial thrust of the rolling screw pair.

[0031] Figure 4 In section 4b, a disc spring (11) is provided between the bearing seats of the two rolling nuts to limit the axial thrust of one of the rolling nuts, so that the rolling nut only bears part of the preset axial thrust of the rolling screw pair. The length of the rolling nut whose axial thrust is limited is determined according to the magnitude of the axial thrust.

[0032] Along the meshing length of the lead screw and nut, the force on each tooth is uneven. When performing strength calculations, there is a limit to the number of teeth used for calculation. The bearing housing of some rolling nuts is equipped with springs to limit the axial thrust it receives, which can increase the flexibility of the rolling nut and increase the number of teeth used for calculation. This is useful when the load of a single rolling nut is insufficient, and it can also be used in equipment with impact forces.

[0033] Axial thrust can also be transmitted to the component that mounts the rolling nut by each rolling nut and its spring.

[0034] When the ball screw pair cannot self-lock and requires pressure holding or positioning, the rotary drive mechanism is equipped with a braking device.

[0035] The use of large pitch and high-strength steel, along with the hardened tooth surface, can improve the load-bearing capacity of the rolling screw pair.

Claims

1. A rolling nut and its rolling screw assembly, characterized in that: The rolling screw is equipped with a central screw and 2 to 30 peripheral screws with equal tooth pitch that mesh with it. Each peripheral screw shaft end is provided with a rolling bearing that bears axial thrust, a bearing that bears radial force, and a bearing seat. The bearing seat ensures that the meshing center distance and axis of the central screw and the peripheral screws are parallel. All the peripheral screws and the bearings and bearing seats at the shaft ends constitute a rolling nut. A rolling nut can be a complete cylinder or a part of a cylinder; it can be a central lead screw that rotates actively, or a peripheral lead screw that rotates actively while the peripheral lead screw bearing housing does not rotate, or the rolling nut as a whole can rotate, that is, the bearing housings at both ends of the peripheral lead screw are connected and rotate synchronously. The peripheral lead screw rotates on its own axis and revolves around the center. All rotating central lead screws or rolling nut ends are equipped with rolling bearings that bear axial thrust.

2. A rolling nut and its rolling screw assembly according to claim 1, characterized in that: The threads of the center lead screw and the peripheral lead screw have opposite directions of rotation. The force-bearing tooth surface has a small bevel angle and can be self-locking or nearly self-locking in the radial direction. The tooth profile design ensures that the contact line is near the center line connecting the center of the center lead screw and the peripheral lead screw and has sufficient contact strength. It also meets the bending strength requirements of the tooth root, reduces the outer diameter of the rolling nut, and the radial load on the rolling bearing.

3. A rolling nut and its rolling screw assembly according to claim 1 or 2, characterized in that: A rolling nut consists of 2 to 15 coaxial short rolling nuts connected in series to reduce the load on the rolling bearings of each short rolling nut. The axial thrust of the rolling screw pair is directly transmitted between the bearing seats of each short rolling nut, or it can be transmitted separately to the component that mounts the short rolling nut. Each short rolling nut only bears a portion of the axial thrust of the rolling screw pair. Alternatively, 2 to 5 rolling nuts can be connected coaxially, with some or all of the rolling nut bearing seats equipped with springs to limit the axial thrust they receive, thus becoming a rolling nut that only bears a portion of the preset axial thrust of the rolling screw pair. The axial thrust can also be transmitted separately by each rolling nut and its spring to the component that mounts the rolling nut.

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