Floating type roller screw with stable lead and application

Abstract

The invention relates to a floating type roller lead screw with stable lead and application, and relates to the technical field of planetary roller lead screws, the floating type roller lead screw comprises a nut, a lead screw and a plurality of planetary rollers, the planetary rollers are annularly arranged around the lead screw, the nut is arranged on the outer sides of the planetary rollers in a sleeving mode, the planetary rollers are in threaded fit with the nut and the lead screw respectively, and the lead screw is in threaded fit with the nut. The nut and the lead screw are the same in thread turning direction and thread number, so that the lead of the floating type roller lead screw is irrelevant to the middle diameter of the lead screw and the middle diameter of the nut. The lead precision of the floating type roller screw cannot be influenced by the change of the middle diameter of the lead screw and the middle diameter of the nut due to abrasion, so that the floating type roller screw does not need to adjust the zero position again at set intervals, the lead is stable, and the floating type roller screw can be used continuously.

Description

Technical Field

[0001] The present application relates to the technical field of planetary roller screws, and in particular to a floating roller screw with a stable lead and its application. Background Art

[0002] Planetary Roller Screw (PRS) is a precision mechanical transmission device that converts rotational motion into linear motion, or vice versa. It combines the advantages of ball screw and planetary gear transmission, and has the characteristics of high precision, high rigidity, high load, and long life. It is widely used in high-end equipment fields such as aerospace, CNC machine tools, robots, and semiconductor manufacturing.

[0003] Advantages of planetary roller screws:

[0004] High load-bearing capacity: Multiple rollers mesh simultaneously, with a large contact area, which can withstand greater axial and radial loads.

[0005] High rigidity: The roller, lead screw and nut are in belt contact (theoretically, it is line contact, but in practice, due to the large involute surface, it is closer to belt contact). Figure 2 It can be seen more clearly), has high contact stiffness, small deformation during transmission, and high positioning accuracy.

[0006] High speed: The roller is light in weight and has small inertia, which enables high-speed transmission.

[0007] High efficiency: The transmission efficiency can reach more than 90%, and the energy-saving effect is significant.

[0008] like Figure 1 and 2 The figure shows the design of a conventional planetary roller screw thread. Both the nut and the screw are conventional trapezoidal threads, and the roller adopts an involute thread surface, so that the contact surface between the roller and the screw and between the roller and the nut is a band contact. The advantages of this design are: the trapezoidal teeth and other shapes can form a good meshing between the roller and the screw. When transmitting power and motion, the contact area is large and the contact stress distribution is more uniform, thereby achieving a higher transmission efficiency and meeting the transmission requirements of the planetary roller screw in terms of high load and high precision.

[0009] The floating roller screw is a type of planetary roller screw. The difference between the floating roller screw and other planetary roller screws is that the rollers produce axial motion relative to the screw and nut at the same time during operation, so the motion relationship and structure are relatively complex. Of course, this also produces the effect of reducing the actual working lead. Therefore, in the scenario of realizing ultra-high precision lead control in a very small space, the only roller screw that can achieve the effects of small size, small lead, small stroke and high load is the floating roller screw.

[0010] According to experiments, the actual lead of the floating roller screw is related to factors such as the physical pitch of the screw, the number of screw thread heads, the screw diameter, the roller diameter, and the rotation direction of the screw and nut. Among them, the physical pitch of the screw, the number of screw thread heads, the rotation direction of the screw and nut and other parameters can be set in advance and the parameters run through the entire life cycle of the floating roller screw. However, the screw diameter and the roller diameter will gradually change with the use of the floating roller screw, especially after long-term use. With the increase of wear, the belt contact between the roller and the screw is converted into surface contact. The specific values ​​of the screw diameter and the roller diameter cannot be estimated, which greatly affects the accuracy of the actual working lead of the floating roller screw. This is very fatal in situations where the floating roller screw needs to have extremely high lead accuracy (especially dexterous hands). Therefore, it is necessary to improve the floating roller screw to eliminate the uncontrollable actual lead caused by the numerical changes of the screw diameter and the roller diameter. Summary of the invention

[0011] In view of the deficiencies in the prior art, the present invention provides a floating roller screw with a stable lead and its application.

[0012] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0013] A floating roller screw with a stable lead comprises a nut, a screw and a plurality of planetary rollers. The planetary rollers are arranged in a ring shape around the screw, the nut is sleeved on the outside of the planetary rollers, the planetary rollers are matched with the nut and the screw thread respectively, the nut and the screw thread have the same rotation direction and the same number of heads, so that the lead of the floating roller screw is independent of the center diameter of the screw and the center diameter of the nut.

[0014] To optimize the above technical solutions, the specific measures taken also include:

[0015] The outer surface of the planetary roller is provided with a roller thread, the inner surface of the nut is provided with a nut thread, the outer surface of the screw is provided with a screw thread, the planetary roller can move axially between the nut and the screw, and the planetary roller is respectively arranged parallel to the axis of the nut and the screw.

[0016] The floating roller screw with a stable lead also includes an annular retaining frame, which is located on the inner side of the nut. The screw passes through the annular hole of the retaining frame. The retaining frame can move axially relative to the nut. A plurality of hollows are arranged on the retaining frame. Both ends of the planetary rollers can be installed in the hollows for circumferential rotation and axial positioning.

[0017] The axis of the retainer overlaps with the axis of the nut, and the retainer is clearance-matched with the nut and the screw rod at the same time.

[0018] A push rod is fixed on the nut.

[0019] One end of the screw rod is provided with a docking joint for connecting with the rotation power input end.

[0020] The number of starts of the above-mentioned roller thread and nut thread is 6.

[0021] The number of the planetary rollers is 6, and correspondingly, the number of the hollows on the cage is 6.

[0022] The invention discloses an application of a floating roller screw with a stable lead in an electric cylinder.

[0023] The invention discloses an application of a floating roller screw with a stable lead in a robot.

[0024] The beneficial effects of the present invention are:

[0025] 1. The floating roller screw with a stable lead of the present invention sets the roller thread and the nut thread to have the same rotation direction and the same number of heads, so that the lead of the floating roller screw is independent of the center diameter of the screw rod and the center diameter of the nut. The change of the center diameter of the screw rod and the center diameter of the nut due to wear will not affect the lead accuracy of the floating roller screw of the present invention. Therefore, the floating roller screw of the present invention does not need to readjust the zero position at regular intervals, and the lead is stable and can be used continuously.

[0026] 2. The present invention adopts a floating roller screw, the diameter of the screw can be as small as 1.69mm, the outer diameter of the nut can be 6mm, and the lead can be 0.25mm. It has a small size, a small lead, a small stroke, and a high load-bearing capacity of more than 15kg. It has a simple structure and is particularly suitable for micro and small lead scenarios. Specifically, it is particularly suitable for scenarios such as robot dexterous hands that require 10 to 20 active degrees of freedom to be arranged in a small space.

[0027] 3. The floating roller screw with stable lead of the present invention can be used to make roller screws with various leads by adjusting the number of screw rods and nut heads, and is suitable for a wide range of occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the existing planetary roller screw structure.

[0029] Figure 2 It is a detailed diagram of the matching between the screw thread and the roller thread in the existing planetary roller screw structure;

[0030] Figure 3 A cross-sectional view of a floating roller screw with a stable lead according to the present invention;

[0031] Figure 4 This is a structural disassembled diagram of a floating roller screw with a stable lead according to the present invention;

[0032] Figure 5 A schematic diagram of an electric cylinder using a floating roller screw with a stable lead according to the present invention;

[0033] Figure 6 for Figure 5 Internal structure diagram;

[0034] Figure 7 For application Figure 5 Schematic diagram of the robot with the electric cylinder shown.

[0035] Description of the accompanying drawings: planetary roller 1, roller thread 11, nut 2, nut thread 21, screw 3, screw thread 31, cage 4, hollow 41, push rod 5. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0037] Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0038] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0039] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation, and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or units (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" / "several" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0040] like Figure 3-4 As shown, the floating roller screw with stable lead of the present invention comprises 6 planetary rollers 1, 1 nut 2, 1 screw 3, 1 cage 4 and 1 push rod 5, and its main structural composition is the same as that of the conventional floating roller screw, that is, the planetary rollers 1 are arranged in a ring shape around the screw 3, the nut 2 is sleeved on the outside of the planetary rollers 1, the outer surface of the planetary rollers 1 is provided with roller threads 11, the inner surface of the nut 2 is provided with nut threads 21, the outer surface of the screw 3 is provided with screw threads 31, the planetary rollers 1 are threadedly matched with the nut 2, and the planetary rollers 1 are also threadedly matched with the screw 3, and the planetary rollers 1 are located in the hollow 4 of the cage 4. 1, the retainer 4 is clearance-matched with the nut 2 and the screw 3 at the same time, the two ends of the planetary roller 1 are positioned and installed in the retainer 4, one end of the nut 2 is fixed to the push rod 5 by a thread, and one end of the screw 3 is provided with a docking joint for connecting with the rotary power input end. When the rotary power input end rotates the screw 3, all the planetary rollers 1 will roll around the screw 3 and also rotate, and the nut 2 will produce axial displacement, thereby converting the rotation of the screw 3 into the axial displacement of the nut 2. In this process, the planetary roller 1 and the retainer 4 will produce axial displacement together, and the displacement direction is related to the rotation direction of the roller thread 11.

[0041] When installing the floating roller screw of the present invention, the planetary roller 1 is inserted into the hollow 41 of the retaining frame 4, and then the entire planetary roller 1 is placed into the nut 2, and finally the screw rod 3 is screwed into the ring hole formed by the planetary roller 1 and the retaining frame 4.

[0042] It is worth noting that, although the present embodiment adopts 6 planetary rollers, the effects produced by other numbers of planetary rollers are the same or similar. For example, in other embodiments, the number of planetary rollers can be 5 or 8, which does not affect the protection scope of the present invention.

[0043] The innovation of the present invention is that the thread direction of the nut 2 and the screw rod 3 of the floating roller screw are the same and the number of threads is the same.

[0044] The formula for calculating the lead of a floating roller screw is:

[0045]

[0046] Where p is the lead of the floating roller screw, s is the physical pitch of the screw 3, and n s is the number of threads of screw 3, n n is the number of threads of nut 2, the rotation direction of screw rod 3 and nut 2 is opposite, k is the diameter of screw rod 3 s And the diameter of nut 2 is d r ratio.

[0047] It can be seen that when n s Equal to n n , and the screw 3 and nut 2 have the same rotation direction, the formula can be simplified to

[0048] p=s·n n (2)

[0049] Thus, the parameter k is eliminated, and the diameter d in the screw 3 is s And the diameter of nut 2 is d r It does not participate in the calculation of the lead of the floating roller screw, thereby achieving the technical effect that the lead of the floating roller screw is independent of the center diameter of the screw rod 3 and the center diameter of the nut 2.

[0050] This embodiment provides 6 sets of measured data to support the above conclusion. Among them, the first to third sets of data have different numbers of heads of the nut 2 and the screw rod 3 and different rotation directions. The fourth to sixth sets of data have the same number of heads and the same rotation direction of the nut 2 and the screw rod 3.

[0051] Group 1:

[0052]

[0053]

[0054] Group 2:

[0055]

[0056]

[0057] Group 3:

[0058]

[0059] Group 4:

[0060]

[0061]

[0062] Group 5:

[0063]

[0064]

[0065] Group 6:

[0066]

[0067]

[0068] From the first to the third set of data, it can be seen that when the thread direction and number of threads of nut 2 and screw rod 3 are different, once the screw rod 3 passes through d s And the diameter of nut 2 is d r The final lead will also change. From the fourth to sixth groups of data, it can be seen that when the thread direction and number of threads of nut 2 and screw 3 are the same, the thread d in screw 3 s And the diameter of nut 2 is d r It will not cause changes, nor will it cause changes in the final lead. This proves that by setting the nut 2 and the screw rod 3 to have the same thread rotation direction and the same number of heads, the lead of the floating roller screw can be independent of the center diameter of the screw rod 3 and the center diameter of the nut 2, thereby greatly improving the lead accuracy of the floating roller screw, achieving a technical effect of stable lead and sustainable use without the need for regular readjustment of the zero position.

[0069] The floating roller screw of the present invention is mainly used in electric cylinders, and the electric cylinder using the floating roller screw is very suitable for dexterous hands. Figure 5 and 6 The structural diagram of the electric cylinder is given, and Figure 7 A schematic diagram of a manipulator (dexterous hand is a type of manipulator) is given.

[0070] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A floating roller screw with a stable lead, comprising a nut (2), a screw (3) and a plurality of planetary rollers (1), wherein the planetary rollers (1) are arranged in a ring shape around the screw (3), the nut (2) is sleeved on the outside of the planetary rollers (1), and the planetary rollers (1) are respectively threadedly matched with the nut (2) and the screw (3), wherein: The nut (2) and the screw rod (3) have the same thread direction and the same number of threads, so that the lead of the floating roller screw is independent of the center diameter of the screw rod (3) and the center diameter of the nut (2).

2. A floating roller screw with a stable lead according to claim 1, characterized in that: The outer surface of the planetary roller (1) is provided with a roller thread (11), the inner surface of the nut (2) is provided with a nut thread (21), and the outer surface of the screw rod (3) is provided with a screw thread (31). The planetary roller (1) can move axially between the nut (2) and the screw rod (3), and the planetary roller (1) is respectively arranged parallel to the axis of the nut (2) and the screw rod (3).

3. The floating roller screw with a stable lead according to claim 1, characterized in that: The invention also comprises an annular retaining frame (4), the retaining frame (4) being located inside the nut (2), the screw rod (3) passing through the annular hole of the retaining frame (4), the retaining frame (4) being able to move axially relative to the nut (2), the retaining frame (4) being provided with a plurality of hollows (41), and the two ends of the planetary roller (1) being able to rotate circumferentially and be axially positioned and installed in the hollows (41).

4. A floating roller screw with a stable lead according to claim 1, characterized in that: The axis of the retaining frame (4) overlaps with the axis of the nut (2), and the retaining frame (4) is clearance-matched with the nut (2) and the screw rod (3) at the same time.

5. The floating roller screw with a stable lead according to claim 1, characterized in that: A push rod (5) is fixed on the nut (2).

6. A floating roller screw with a stable lead according to claim 1, characterized in that: One end of the screw rod (3) is provided with a docking joint for connecting with a rotating power input end.

7. The floating roller screw with a stable lead according to claim 1, characterized in that: The number of heads of the roller thread (11) and the nut thread (21) is 6.

8. The floating roller screw with stable lead according to claim 3, characterized in that: The number of the planetary rollers (1) is 6, and correspondingly, the number of the hollows (41) on the retaining frame (4) is 6.

9. Application of a floating roller screw with a stable lead as claimed in claim 1 to an electric cylinder.

10. Application of a floating roller screw with a stable lead as claimed in claim 1 to a robot.

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