A double screw preloaded reverse planetary roller screw pair with involute and cycloid teeth

Abstract

The present application provides a double-screw pre-tightened reverse planetary roller screw pair with involute and cycloid teeth, which relates to the technical field of precision heavy-load screw transmission, including a first screw and a second screw connected coaxially, the first screw meshing with a first planetary roller of a first bracket, the tooth profile of the first screw and the first planetary roller in a normal plane of a thread raceway is an involute, the second screw meshing with a second planetary roller of a second bracket, the tooth profile of the second screw and the second planetary roller in a normal plane of a thread raceway is an involute, the internal thread of a nut is screwed with the external thread of the first planetary roller and the second planetary roller, the normal tooth profile of the nut is a cycloid, which is a double cycloid spiral surface, and a gasket is provided between the first screw assembly and the second screw assembly, and the gap of a traditional reverse planetary roller screw pair can be eliminated by adjusting the thickness of the gasket, thereby greatly improving the repeatability accuracy and rigidity of the planetary roller screw pair.

Description

Technical Field

[0001] The present application relates to the technical field of precision heavy-load screw transmission, and in particular to a double-screw pre-tightening reverse planetary roller screw pair with involute and cycloid teeth. Background Art

[0002] A planetary roller screw pair is a transmission component that can convert rotational motion into linear motion. A trans planetary roller screw pair is a type of planetary screw pair that uses the nut as the active component, and the rotational motion of the nut drives the screw to move linearly. The trans planetary roller screw pair has a longer nut and only performs rotational motion, so it is particularly suitable for integration with the servo motor rotor to achieve an integrated structural design.

[0003] The reverse planetary roller screw pair has a large number of rollers and a large contact area between the rollers, the screw and the nut, so the load capacity is particularly large. Since the screw, rollers and nuts of the reverse planetary screw pair are all ground on a precision thread grinder, the thread accuracy is high, up to P1 level of GB17587.3. Based on the characteristics of large load, high precision and integration with the servo motor rotor, the reverse planetary screw pair is very suitable for humanoid robot linear joints.

[0004] Since the teeth of traditional planetary screw pairs are all triangular, in order to improve the smoothness of operation, the clearance of the screw pair must be controlled between 0.02 and 0.05 mm. The clearance and easy jamming of rotation during the forward and reverse conversion process are the biggest shortcomings of traditional reverse planetary roller screw pairs. Summary of the invention

[0005] The embodiment of the present application provides a double screw pre-tightening reverse planetary roller screw pair with involute and cycloid teeth. The tooth profile of the screw and the planetary roller is an involute on the normal plane of the contact area. The helix angle of the planetary screw and the nut is opposite. In order to increase the contact area between the nut teeth and the planetary roller teeth, the normal tooth profile of the nut is selected to be a cycloid, and a gasket is arranged between the first screw assembly and the second screw assembly. The annular groove between the gasket and the first screw assembly and the second screw assembly is interference fit, thereby eliminating the gap of the reverse planetary roller screw pair. At the same time, the pre-tightened planetary screw pair can also improve the stiffness. The present application solves the problem that the tooth profile of the traditional planetary screw pair is a triangle. In order to ensure the smoothness of operation, the gap of the screw pair is large, and there is a gap and the rotation is prone to jamming during the forward and reverse conversion process.

[0006] The embodiment of the present application provides a double-screw pre-tightening reverse planetary roller screw pair with involute and cycloid teeth, comprising:

[0007] A first lead screw and a second lead screw are coaxially arranged, wherein the first lead screw and the second lead screw are connected and rotate synchronously;

[0008] A first bracket and a second bracket are respectively arranged on the first screw and the second screw; the first bracket has a plurality of first planetary rollers, the plurality of first planetary rollers are all meshed with the first screw, the first screw and the first bracket constitute a first screw assembly, and the tooth profiles of the first screw and the first planetary rollers in the normal plane of the thread raceway are involutes; the second bracket has a plurality of second planetary rollers, the plurality of second planetary rollers are all meshed with the second screw, the second screw and the second bracket constitute a second screw assembly, and the tooth profiles of the second screw and the second planetary rollers in the normal plane of the thread raceway are involutes;

[0009] A gasket is arranged between the first screw assembly and the second screw assembly, an annular groove is formed between the first screw assembly and the second screw assembly, and the gasket is interference-fitted with the annular groove; the gasket has a first plane and a second plane opposite to each other, the first plane and the second plane are respectively in contact with the first screw assembly and the second screw assembly, the parallelism of the first plane and the second plane is A, A is 0-0.005mm; the interference amount of the gasket relative to the annular groove is B, B is 0.001-0.015mm;

[0010] Among them, the interference of 0.001mm~0.005mm is light preload, the interference of 0.005mm~0.010mm is medium preload, and the interference of 0.010mm~0.015mm is heavy preload.

[0011] A nut sleeved on the first bracket and the second bracket, wherein the internal thread of the nut is threadedly connected with the external thread of the first planetary roller and the second planetary roller, the normal tooth profile of the nut is a cycloid, which is a double cycloid spiral surface, and the cycloid is a convex arc toward the outside of the nut.

[0012] In a feasible implementation, the first lead screw, the second lead screw, the first planetary roller, and the second planetary roller have equal normal tooth pitches and equal helix angles;

[0013] The thread heads of the first planetary roller and the second planetary roller are both single-start threads;

[0014] The number of thread starts of the first screw and the second screw is calculated as follows:

[0015] ;

[0016] Where n is the number of thread starts, is the lead of the screw pair, is the lead of the first planetary roller or the second planetary roller, is the pitch circle of the first screw or the second screw, is the pitch circle of the first planetary roller or the second planetary roller;

[0017] The pitch circle of the nut As shown in the following formula;

[0018] .

[0019] In a feasible implementation, the polar coordinate equation of the involute is as follows:

[0020] ;

[0021] in, is the radius of the involute, is the polar angle of the involute, is the involute base circle diameter, is the pressure angle of the involute, is the helix angle.

[0022] In a feasible implementation, the equation of the cycloid is as follows:

[0023] ;

[0024] Among them, π is a constant, a is the radius of the rotating wheel that generates the cycloid, and t is the angle through which the rotating wheel rotates.

[0025] In a feasible implementation, the first lead screw comprises an outer connecting portion, an extending portion, a threaded portion and an inserting portion which are coaxially connected in sequence;

[0026] An inserting hole is provided at the end of the second lead screw, and the inserting portion is inserted into the inserting hole.

[0027] In a feasible implementation, a blind groove is provided on the side wall of the plug-in portion, a snap-in key is inserted into the blind groove, one end of the snap-in key is inserted into the blind groove, and the other end of the snap-in key is higher than the side wall of the plug-in portion;

[0028] The inner wall of the jack is provided with a card slot, and the other end of the card key is plugged into the card slot.

[0029] In a feasible implementation, the gasket is sleeved on the plug-in portion, and the end surface of the threaded portion and the end surface of the second lead screw clamp the gasket.

[0030] In a feasible implementation, the first bracket further includes two first planet carriers respectively arranged at both ends of the plurality of first planet rollers;

[0031] Both ends of the threaded connection portion in the axial direction are provided with first assembly grooves, and the two first planet carriers are respectively arranged in the two first assembly grooves.

[0032] In a feasible implementation, the second bracket further includes two second planet carriers respectively arranged at both ends of the plurality of second planetary rollers;

[0033] Both axial ends of the second lead screw are provided with second assembly grooves, and the two second planet carriers are respectively arranged in the two second assembly grooves.

[0034] The embodiment of the present application provides a double-screw pre-tightened reverse planetary roller screw pair with involute and cycloid teeth, wherein the first screw and the second screw are coaxially connected and rotate synchronously, the first screw is meshed with the first planetary roller of the first bracket, the tooth profile of the first screw and the first planetary roller in the normal plane of the thread raceway is an involute, the second screw is meshed with the second planetary roller of the second bracket, the tooth profile of the second screw and the second planetary roller in the normal plane of the thread raceway is an involute, the internal thread of the nut is screwed with the external thread of the first planetary roller and the second planetary roller, the normal tooth profile of the nut is a cycloid, which is a double cycloid spiral surface, and the cycloid is a convex arc toward the outside of the nut, and a gasket is provided between the first screw assembly and the second screw assembly, and the gap of the traditional reverse planetary roller screw pair can be eliminated by adjusting the thickness of the gasket, thereby greatly improving the repeatability accuracy and rigidity of the planetary roller screw pair. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the double-screw pre-tightening reverse planetary roller screw pair with involute and cycloid teeth provided by the present application;

[0036] Figure 2 It is a cross-sectional view of a double screw driven shim preloaded reverse planetary roller screw pair;

[0037] Figure 3 is a schematic diagram of the structure of the first bracket and the second bracket;

[0038] Figure 4 is a schematic diagram of the matching state of the first lead screw, the second lead screw and the gasket;

[0039] Figure 5 yes Figure 4 The enlarged view of point A in the middle;

[0040] Figure 6 is a structural schematic diagram of a first lead screw and a second lead screw in a connected state;

[0041] Figure 7 is a structural schematic diagram of the connection state of the first lead screw and the clamping key;

[0042] Figure 8 is a schematic diagram of the structure of the second lead screw;

[0043] Fig. 9 It is a schematic diagram of the structure of the first lead screw.

[0044] Description of reference numerals:

[0045] 10-first screw; 20-second screw; 30-first bracket; 40-second bracket; 50-gasket; 60-nut; 70-clamping key;

[0046] 11-external connection part; 12-extension part; 13-screw connection part; 14-insertion part; 15-blind groove; 16-first assembly groove; 21-insertion hole; 22-card slot; 23-second assembly groove; 31-first planetary roller; 32-first planetary carrier; 41-second planetary roller; 42-second planetary carrier. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0048] The tooth shape of a traditional planetary screw pair is usually triangular. However, this design has certain drawbacks. In order to ensure the smoothness of its operation, the clearance of the screw pair has to be set larger, and the clearance of the screw pair is controlled between 0.02 and 0.05 mm. However, this exposes many problems in practical applications.

[0049] When performing forward and reverse conversion operations, due to the large gap, obvious gap phenomenon will occur. The gap phenomenon refers to some specific phenomena caused by the gap between mechanical parts during the movement process. This leads to unstable and uncontinuous energy transfer during the conversion process. Moreover, the large gap can easily cause the rotation to stagnate, greatly affecting the normal operation of the equipment.

[0050] The existence of gaps destroys the ideal mechanical movement, causing the movement results to deviate from the ideal state, especially under high-speed movement. The existence of gaps causes the elements of the moving pairs to alternate between losing contact and re-contacting under high-speed movement, thus causing violent impacts and collisions, increasing the dynamic stress of the mechanism parts, and further leading to greater elastic deformation of the components, aggravated wear, vibration, noise, etc., resulting in reduced efficiency.

[0051] This gap and jamming problem not only reduces work efficiency and increases maintenance costs, but may also have a serious negative impact on the accuracy and reliability of the entire system. For application scenarios that pursue high precision and high stability, this is undoubtedly a difficult problem that needs to be solved urgently.

[0052] The double screw pre-tightening reverse planetary roller screw pair with involute and cycloid teeth provided by the present application has the tooth profile of the screw and the planetary roller as involute on the normal plane of the contact area, and the helix angle direction of the planetary screw and the nut 60 is opposite. In order to increase the contact area between the nut teeth and the planetary roller teeth, the normal tooth profile of the nut 60 is selected as cycloid, and a gasket 50 is arranged between the first screw assembly and the second screw assembly. The annular groove between the gasket 50 and the first screw assembly and the second screw assembly is interference fit, thereby eliminating the gap of the reverse planetary roller screw pair. At the same time, the pre-tightened planetary screw pair can also improve the rigidity.

[0053] The specific structure of the double-screw pre-tightening reverse planetary roller screw pair with involute and cycloid teeth provided by the present application is described in detail below in conjunction with the accompanying drawings.

[0054] Reference Figure 1-Figure 9 As shown, the embodiment of the present application provides a double-screw pre-tightening reverse planetary roller screw pair with involute and cycloid teeth, including:

[0055] A first lead screw 10 and a second lead screw 20 are coaxially arranged, the external threads of the first lead screw 10 and the second lead screw 20 are in the same direction, the ends of the first lead screw 10 and the second lead screw 20 are connected, and they rotate synchronously;

[0056] The first bracket 30 and the second bracket 40 are respectively arranged on the first screw 10 and the second screw 20; Figure 3 As shown, the first bracket 30 has a plurality of first planetary rollers 31, which uniformly surround the first screw 10, and the plurality of first planetary rollers 31 are all meshed with the first screw 10, the first screw 10 and the first bracket 30 constitute a first screw assembly, and the tooth profiles of the first screw 10 and the first planetary rollers 31 in the normal plane of the thread raceway are involutes; the second bracket 40 has a plurality of second planetary rollers 41, which uniformly surround the second screw 20, and the plurality of second planetary rollers 41 are all meshed with the second screw 20, the second screw 20 and the second bracket 40 constitute a second screw assembly, and the tooth profiles of the second screw 20 and the second planetary rollers 41 in the normal plane of the thread raceway are involutes;

[0057] A gasket 50 is disposed between the first screw assembly and the second screw assembly. The gasket 50 is an annular gasket and has a certain elasticity. An annular groove is formed between the first screw assembly and the second screw assembly. The gasket 50 is interference fit with the annular groove.

[0058] The nut 60 is sleeved on the first bracket 30 and the second bracket 40, and the internal thread of the nut 60 is screwed with the external thread of the first planetary roller 31 and the second planetary roller 41. The clearance between the first screw assembly and the second screw assembly and the nut 60 is controlled between 0.02 and 0.05 mm. The normal tooth profile of the nut 60 is a cycloid, which is a double cycloid spiral surface, and the cycloid is a convex arc toward the outside of the nut.

[0059] When the nut 60 is driven by the roller screw pair, it can rotate along the central axis, and the first screw 10 and the second screw 20 can move up and down along the axis according to the lead relationship. When the nut 60 rotates one circle in the positive direction, the first screw 10 and the second screw 20 both move one lead in the positive direction. If the nut 60 rotates n times, the first screw 10 and the second screw 20 both move n times. The nut 60 rotates in the opposite direction, and the first screw 10 and the second screw 20 move in the opposite direction immediately, and no gap is generated in the screw pair during this process.

[0060] An embodiment of the present application provides a double-screw pre-tightened reverse planetary roller screw pair with involute and cycloid teeth. This component can convert the rotational motion of the nut 60 into linear motion of the screw. The nut 60 can run in forward and reverse directions without gap, has large load-bearing capacity, high precision, high transmission efficiency, and can achieve a large transmission ratio.

[0061] The component adopts a double-screw gasket pre-tightening structure, and the nut 60 is meshed with the first screw 10 and the second screw 20 at the same time through the planetary rollers.

[0062] The first lead screw 10 is meshed with a plurality of first planetary rollers 31 , the thread direction of the first lead screw 10 is opposite to that of the first planetary rollers 31 , and the helix angle of the lead screw thread pitch circle is equal to the helix angle of the roller thread pitch circle.

[0063] A gasket 50 is added between the assembly of the first screw 10 and the assembly of the second screw 20. By adjusting the thickness of the gasket 50, the gap of the traditional reverse planetary roller screw pair can be eliminated, greatly improving the repeatability and rigidity of the planetary roller screw pair. The tooth profile in the normal plane of the thread raceway of the screw and the roller adopts an involute, while the tooth profile in the normal plane of the raceway of the nut 60 adopts a double cycloid helical surface, and the cycloid is a convex arc toward the outside of the nut 60.

[0064] The screw thread and roller thread have opposite rotation directions, which can ensure that their normal planes in the meshing area coincide with each other. Taking the planet carrier as a reference, the screw and planetary rollers are parallel axis fixed axis epicyclic gear trains. In order to realize the spiral transmission function of the screw pair as a whole, the rotation direction of the nut 60 must be the same as that of the screw;

[0065] Taking the lead screw as a reference, in order to prevent the axis of the planetary roller from being deflected, the normal planes of the meshing areas of the lead screw and the roller must coincide, so the spiral directions of the lead screw and the roller must be opposite. As a result, the center spiral line of the nut 60 raceway intersects with the center spiral line of the planetary roller raceway.

[0066] In order to avoid the small contact area and large sliding friction caused by the intersection of the spiral lines of the planetary rollers and the nut 60, the normal cross-section shape of the raceway of the nut 60 of the present application adopts a cycloid, which can increase the contact area between the planetary rollers and the raceway of the nut 60, thereby improving the load-bearing capacity of the planetary roller screw pair while reducing sliding friction.

[0067] In some embodiments, the normal pitches of the first lead screw 10, the second lead screw 20, the first planetary roller 31, and the second planetary roller 41 are equal, and the helix angles are equal;

[0068] The thread heads of the first planetary roller 31 and the second planetary roller 41 are both single-start threads, that is, there is only one helical line;

[0069] The number of thread starts of the first screw 10 and the second screw 20 is calculated as follows:

[0070] ;

[0071] Where n is the number of thread starts, is the lead of the screw pair, is the lead of the first planetary roller 31 or the second planetary roller 41, is the pitch circle of the first screw 10 or the second screw 20, is the pitch circle of the first planetary roller 31 or the second planetary roller 41;

[0072] Pitch circle of nut 60 As shown in the following formula;

[0073] .

[0074] In some embodiments, the polar coordinate equation of the involute is as follows:

[0075] ;

[0076] in, is the radius of the involute, is the polar angle of the involute, is the involute base circle diameter, is the pressure angle of the involute, is the helix angle.

[0077] In some embodiments, the equation of the cycloid is as follows:

[0078] ;

[0079] Among them, π is a constant, a is the radius of the rotating wheel that generates the cycloid, and t is the angle through which the rotating wheel rotates.

[0080] In some embodiments, the gasket 50 has a first plane and a second plane opposite to each other, the first plane and the second plane are respectively fitted with the first screw assembly and the second screw assembly, and the parallelism between the first plane and the second plane is A, and A is 0 to 0.005 mm;

[0081] The interference of the gasket 50 with respect to the annular groove is B, and B is 0.001 to 0.015 mm;

[0082] Among them, the interference amount of 0.001mm~0.005mm is light preload, the interference amount of 0.005mm~0.010mm is medium preload, and the interference amount of 0.010mm~0.015mm is heavy preload.

[0083] Reference Figure 4-Figure 9 As shown, in some embodiments, the first lead screw 10 includes an outer connecting portion 11, an extension portion 12, a threaded portion 13 and a plug-in portion 14 which are coaxially connected in sequence. The outer wall of the outer connecting portion 11 is provided with an external thread for easy connection with an external device. The extension portion 12 is a rod body with a smooth outer wall and a certain length. Parts of the extension portion 12 and the outer connecting portion 11 are located outside the nut 60. The outer wall of the threaded portion 13 is meshed with the first planetary roller 31, and the plug-in portion 14 is connected to the second lead screw 20.

[0084] An inserting hole 21 is provided at the end of the second lead screw 20 . The inserting hole 21 may be a circular blind hole. The inserting portion 14 is plugged into the inserting hole 21 to connect the first lead screw 10 and the second lead screw 20 .

[0085] Furthermore, the side wall of the plug-in portion 14 is provided with a blind groove 15, which can be a rectangular groove body, and a snap-in key 70 is inserted into the blind groove 15, and the snap-in key 70 is a rectangular card block, such as Figure 7 As shown, the bottom end of the snap-in key 70 is inserted into the blind groove 15, and the top end of the snap-in key 70 is higher than the side wall of the plug-in portion 14;

[0086] The inner wall of the insertion hole 21 is provided with a slot 22 which can be a rectangular slot body. The extending direction of the slot 22 is parallel to the axis of the lead screw. The outer end of the coupling key 70 is inserted into the slot 22 to make the first lead screw 10 and the second lead screw 20 rotate synchronously.

[0087] The gasket 50 is sleeved on the plug-in portion 14 , and the end surface of the threaded portion 13 and the end surface of the second lead screw 20 clamp the gasket 50 .

[0088] Reference Figure 3As shown, in some embodiments, the first bracket 30 further includes two first planetary carriers 32 respectively disposed at both ends of the plurality of first planetary rollers 31, the first planetary carrier 32 is an annular structure, and the first planetary carrier 32 is provided with a plurality of circular holes for connecting the first planetary rollers 31;

[0089] Both ends of the threaded portion 13 in the axial direction are provided with first assembly grooves 16 , and two first planet carriers 32 are respectively arranged in the two first assembly grooves 16 , and the center of the first planet carrier 32 and the center of the first lead screw 10 are matched with a small gap.

[0090] The second bracket 40 further includes two second planetary frames 42 respectively disposed at two ends of the plurality of second planetary rollers 41 . The second bracket 40 has the same structure as the first bracket 30 .

[0091] The second screw 20 is provided with a second assembly groove 23 at both ends of the axial direction. The two second planet carriers 42 are respectively arranged in the two second assembly grooves 23. The center of the second planet carrier 42 and the center of the second screw 20 are matched with a small gap.

[0092] The present application provides a double-screw pre-tightened trans planetary roller screw pair with involute and cycloid teeth, in which the tooth profiles of the screws and the planetary rollers are involutes on the normal plane of the contact area, and the helix angles of the planetary screw and the nut 60 are in opposite directions. In order to increase the contact area between the nut teeth and the planetary roller teeth, the normal tooth profile of the nut 60 is selected to be cycloid, and a gasket 50 is arranged between the first screw assembly and the second screw assembly. The gasket 50 is interference fit with the annular groove between the first screw assembly and the second screw assembly, thereby eliminating the gap of the trans planetary roller screw pair.

[0093] It is easy to understand that those skilled in the art can combine, split, reorganize, etc. the embodiments of the present application to obtain other embodiments based on the several embodiments provided in the present application, and these embodiments do not exceed the protection scope of the present application.

[0094] The above specific implementation methods further explain in detail the purpose, technical solutions and beneficial effects of the embodiments of the present application. It should be understood that the above are only specific implementation methods of the embodiments of the present application and are not used to limit the protection scope of the embodiments of the present application. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A double screw preloaded reverse planetary roller screw pair with involute and cycloid teeth, characterized in that: include; A first lead screw (10) and a second lead screw (20) are coaxially arranged, wherein the first lead screw (10) and the second lead screw (20) are connected and rotate synchronously; A first bracket (30) and a second bracket (40) are respectively arranged on the first lead screw (10) and the second lead screw (20); the first bracket (30) has a plurality of first planetary rollers (31), the plurality of first planetary rollers (31) are all meshed with the first lead screw (10), the first lead screw (10) and the first bracket (30) form a first lead screw assembly, and the tooth profiles of the first lead screw (10) and the first planetary rollers (31) in a normal plane of the thread raceway are involutes; the second bracket (40) has a plurality of second planetary rollers (41), the plurality of second planetary rollers (41) are all meshed with the second lead screw (20), the second lead screw (20) and the second bracket (40) form a second lead screw assembly, and the tooth profiles of the second lead screw (20) and the second planetary rollers (41) in a normal plane of the thread raceway are involutes; A gasket (50) is arranged between the first screw assembly and the second screw assembly, an annular groove is formed between the first screw assembly and the second screw assembly, and the gasket (50) is interference-fitted with the annular groove; the gasket (50) has a first plane and a second plane opposite to each other, the first plane and the second plane are respectively in contact with the first screw assembly and the second screw assembly, the parallelism of the first plane and the second plane is A, and A is 0 to 0.005 mm; the interference amount of the gasket (50) relative to the annular groove is B, and B is 0.001 to 0.015 mm; Among them, the interference of 0.001mm~0.005mm is light preload, the interference of 0.005mm~0.010mm is medium preload, and the interference of 0.010mm~0.015mm is heavy preload. A nut (60) is sleeved on the first bracket (30) and the second bracket (40), wherein the internal thread of the nut (60) is threadedly connected to the external thread of the first planetary roller (31) and the second planetary roller (41), and the normal tooth profile of the nut (60) is a cycloid, which is a double cycloid helical surface, and the cycloid is a convex arc toward the outside of the nut.

2. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to claim 1, characterized in that: The first lead screw (10), the second lead screw (20), the first planetary roller (31), and the second planetary roller (41) have equal normal tooth pitches and equal helix angles; The thread heads of the first planetary roller (31) and the second planetary roller (41) are both single-start threads; The number of thread starts of the first screw (10) and the second screw (20) is calculated as follows: ； Where n is the number of thread starts, is the lead of the screw pair, is the lead of the first planetary roller (31) or the second planetary roller (41), is the pitch circle of the first lead screw (10) or the second lead screw (20), is the pitch circle of the first planetary roller (31) or the second planetary roller (41); The pitch circle of the nut (60) As shown in the following formula; 。 3. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to claim 1, characterized in that: The polar coordinate equation of the involute is shown below: ； in, is the radius of the involute, is the polar angle of the involute, is the involute base circle diameter, is the pressure angle of the involute, is the helix angle.

4. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to claim 1, characterized in that: The equation of the cycloid is shown below: ； Among them, π is a constant, a is the radius of the rotating wheel that generates the cycloid, and t is the angle through which the rotating wheel rotates.

5. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to any one of claims 1 to 4, characterized in that: The first lead screw (10) comprises an outer connecting portion (11), an extending portion (12), a threaded portion (13) and an inserting portion (14) which are coaxially connected in sequence; An insertion hole (21) is provided at the end of the second lead screw (20), and the insertion portion (14) is plugged into the insertion hole (21).

6. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to claim 5, characterized in that: A blind groove (15) is provided on the side wall of the plug-in portion (14), a snap-in key (70) is inserted into the blind groove (15), one end of the snap-in key (70) is inserted into the blind groove (15), and the other end of the snap-in key (70) is higher than the side wall of the plug-in portion (14); The inner wall of the insertion hole (21) is provided with a card slot (22), and the other end of the card connection key (70) is plugged into the card slot (22).

7. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to claim 5, characterized in that: The gasket (50) is sleeved on the plug-in portion (14), and the end surface of the threaded portion (13) and the end surface of the second lead screw (20) clamp the gasket (50).

8. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to claim 5, characterized in that: The first bracket (30) further comprises two first planetary frames (32) respectively arranged at two ends of the plurality of first planetary rollers (31); Both axial ends of the threaded connection portion (13) are provided with first assembly grooves (16), and the two first planet carriers (32) are respectively arranged in the two first assembly grooves (16).

9. The double-screw preloaded reverse planetary roller screw pair with involute and cycloid teeth according to claim 5, characterized in that: The second bracket (40) further comprises two second planetary frames (42) respectively arranged at two ends of the plurality of second planetary rollers (41); Second assembly grooves (23) are provided at both axial ends of the second lead screw (20), and the two second planet carriers (42) are respectively arranged in the two second assembly grooves (23).

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