planetary roller screw

Abstract

The application provides a planetary roller screw, which comprises a screw rod, a sleeve and a plurality of rollers.The outer periphery of the screw rod is provided with a first groove extending in the circumferential direction, and the first groove is formed in a ring shape closed in the circumferential direction of the screw rod.The inner surface of the sleeve is provided with a plurality of second grooves extending in the direction of a spiral line, and the first groove and the second groove intersect with each other.The outer periphery of each roller is provided with a plurality of convex teeth, each of which is formed in a ring shape closed in the circumferential direction of the roller, and the convex teeth are embedded in the intersecting positions of the first groove and the second groove.The planetary roller screw adopting the above technical scheme can make the convex teeth move in the ring-shaped closed first groove during the working process of the planetary roller screw, fix the axial position of the roller relative to the screw rod, and make the planetary roller screw have large bearing capacity, high transmission position accuracy, small vibration, small noise and smooth operation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mechanical transmission, and particularly relates to a planetary roller screw. BACKGROUND

[0002] The planetary roller screw is a new type of transmission device which can convert rotary motion into linear motion. The planetary roller screw has higher impact resistance than the traditional ball screw, and the static load of the planetary roller screw is about 3 times that of the traditional ball screw, and the service life of the planetary roller screw is about 15 times that of the traditional ball screw. In addition, the planetary roller screw can have higher rotary speed and rotary acceleration, and therefore is widely used in the fields of precision instruments, weapon equipment, industrial robots and aerospace.

[0003] A standard planetary roller screw in the prior art includes a screw rod, a sleeve and rollers. The outer circumferential surface of the screw rod is provided with external threads, the inner circumferential surface of the sleeve is provided with internal threads having the same number of starts and thread form as the external threads, and the rollers are provided with single-start threads having the same thread form as the external threads. The thread forms of the external threads, the internal threads and the single-start threads are, for example, triangular. The sleeve is sleeved on the screw rod, and the rollers are uniformly arranged along the circumferential direction of the screw rod. When the screw rod rotates, the rollers revolve around the axis of the screw rod and rotate around their own axes. The internal threads and the external threads have the same helix angle, and the rollers and the sleeve can ensure pure rolling when they are engaged, without displacement in the axial direction. This type of planetary roller screw requires high machining precision to machine the threads during processing, and requires a large processing cost.

[0004] Another type of planetary roller screw in the prior art is a circulating type planetary roller screw which includes a screw rod, a sleeve, rollers and a reset ring. The outer circumferential surface of the screw rod is provided with external threads, the inner circumferential surface of the sleeve is provided with internal threads having the same number of starts and thread form as the external threads, and the thread forms of the external threads and the internal threads are, for example, triangular. The rollers are provided with annular threads having a zero helix angle. The reset ring (reset device) is arranged at the end of the roller, and the reset ring is provided with a protrusion. The protrusion resets the position of the roller every time the roller rotates one revolution around the axis of the screw rod. The advantage of this type of circulating planetary roller screw is that it can use smaller thread lead to achieve higher position accuracy, and at the same time, due to more engagement points, the carrying capacity is also larger. However, the reset ring will increase friction and impact, generate vibration and noise, and cause uneven operation. SUMMARY

[0005] Based on the defects of the prior art described above, the present application aims to provide a planetary roller screw which can have large carrying capacity, high transmission position accuracy and no impact, and smooth operation.

[0006] The present application provides a planetary roller screw, which comprises:

[0007] A screw rod, an outer periphery of the screw rod is provided with a first groove extending in a circumferential direction, the first groove is formed as a closed ring in a circumferential direction of the screw rod;

[0008] A sleeve, the sleeve is sleeved on the screw rod, an inner surface of the sleeve is provided with a plurality of second grooves extending in a helical direction, the first groove and the second groove intersect; and

[0009] A plurality of rollers, the plurality of rollers are located between the screw rod and the sleeve, an outer periphery of the roller is provided with a plurality of convex teeth, each of the convex teeth is formed as a closed ring in a circumferential direction of the roller, the convex teeth are embedded in the intersection position of the first groove and the second groove.

[0010] Preferably, an outer peripheral surface of the screw rod is provided with a first engagement part, an outer peripheral surface of the roller is provided with a second engagement part, the roller makes pure rolling on the outer peripheral surface of the screw rod through cooperation of the first engagement part and the second engagement part.

[0011] Preferably, the first engagement part and the second engagement part are straight teeth, the second engagement part is formed at the convex teeth at the axial two ends of the roller.

[0012] Preferably, a plane where the first groove is located is perpendicular to the axial direction of the screw rod, a plane where the convex teeth are located is perpendicular to the axial direction of the roller.

[0013] Preferably, all or part of the first groove is embedded with the convex teeth; and / or,

[0014] All or part of the second groove is embedded with the convex teeth.

[0015] Preferably, a distance between any two adjacent first grooves of the plurality of first grooves is the same or different.

[0016] Preferably, an axial length of the screw rod occupied by the first groove is less than an axial length of the sleeve occupied by the second groove.

[0017] Preferably, a distance between two adjacent convex teeth is an integer multiple of a distance between two adjacent first grooves and / or a pitch of the second groove.

[0018] Preferably, in the working process of the planetary roller screw, the convex teeth are embedded in the closed ring-shaped first groove, and the axial position of the roller relative to the screw rod is fixed.

[0019] Preferably, the planetary roller screw does not provide a reset device for resetting the roller.

[0020] Preferably, a cross section of the first groove along a plane perpendicular to an extending direction of the first groove is triangular, a cross section of the second groove along a plane perpendicular to an extending direction of the second groove is triangular, and a cross section of the convex tooth along a plane perpendicular to an extending direction of the convex tooth is triangular.

[0021] Preferably, the planetary roller screw further comprises a cage, the cage is arranged between the screw rod and the sleeve in a radial direction of the planetary roller screw, and the cage is provided with positioning grooves for accommodating the rollers.

[0022] The planetary roller screw adopting the technical scheme has the advantages that during operation of the planetary roller screw, the convex tooth moves in the annular closed first groove, so that the axial position of the roller relative to the screw rod is fixed, and a reset device is not needed for resetting, so that the planetary roller screw can have large bearing capacity, high transmission position precision, small vibration and noise, and smooth operation. BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 A sectional view of the planetary roller screw according to the first embodiment of the present application is shown (the cage is not shown).

[0024] FIG. 2 A partial enlarged view of FIG. 1 is shown.

[0025] FIG. 3 An exploded structural schematic view of the planetary roller screw according to the first embodiment of the present application is shown.

[0026] FIG. 4 A sectional view along a cross section of the planetary roller screw according to the first embodiment of the present application is shown (the cage is not shown).

[0027] FIG. 5 A partially sectional structural schematic view of the planetary roller screw according to the second embodiment of the present application is shown.

[0028] FIG. 6 A sectional view of the planetary roller screw according to the second embodiment of the present application is shown.

[0029] FIG. 7 A partial enlarged view of FIG. 6 is shown.

[0030] FIG. 8 A partially sectional structural schematic view of the planetary roller screw according to the third embodiment of the present application is shown.

[0031] FIG. 9 A partial enlarged view of FIG. 8 is shown.

[0032] Reference numeral explanation

[0033] 1. Lead screw; 11. First groove; 12. First meshing part

[0034] 2 shaft sleeve 21 second groove

[0035] 3 rollers 31 teeth 32 second meshing part

[0036] 4. Cage 41. Positioning Slot

[0037] A is axial, R is radial, and C is circumferential. Detailed Implementation

[0038] Exemplary embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are for teaching those skilled in the art how to implement the present invention, and are not intended to exhaustively describe all possible ways of the invention, nor to limit the scope of the invention.

[0039] First embodiment

[0040] like FIG. 1 to FIG. 4 As shown, the present invention provides a planetary roller screw, which includes a screw 1, a bushing 2, and rollers 3.

[0041] The lead screw 1 is cylindrical in shape, and its outer circumference is provided with multiple first grooves 11 extending in the circumferential direction C. For example, the number of first grooves 11 is greater than or equal to two. The multiple first grooves 11 are arranged parallel to each other. The first grooves 11 are formed into closed rings, and the cross-section of the first groove 11 along a plane perpendicular to its extension direction can be, for example, triangular. The plane containing the first grooves 11 can be perpendicular to the axial direction A of the lead screw 1.

[0042] The bushing 2 can be cylindrical in shape and is fitted onto the lead screw 1. The axis of the bushing 2 and the axis of the lead screw 1 can coincide. The inner surface of the bushing 2 is provided with a second groove 21 extending along a helical direction. Multiple second grooves 21 can be provided. In this embodiment, the multiple second grooves 21 can have the same pitch and are evenly spaced along the axial direction A of the bushing. Preferably, the number of second grooves 21 is greater than or equal to three, for example, six. The cross-section of the plane perpendicular to the extension direction of the second groove 21 can be, for example, triangular.

[0043] The pitch of the second grooves 21 can be equal to the distance between two adjacent first grooves 11. It should be noted that the distance between two adjacent first grooves 11 refers to the distance between the same positions of two adjacent first grooves 11, for example, the distance between the center lines of two adjacent first grooves 11. For a multi-start thread, the pitch is the distance between two adjacent second grooves 21, and the pitch is equal to the lead divided by the number of starts. The first grooves 11 and the second grooves 21 intersect, and in this embodiment, each first groove 11 forms six intersection positions with six second grooves 21.

[0044] Further, the axial length of the lead screw 1 occupied by the plurality of first grooves 11 is less than the axial length of the sleeve 2 occupied by the second grooves 21. In particular, a portion of the axial direction A of the lead screw 1 is provided with the first grooves 11, for example, the middle portion of the axial direction A of the lead screw 1 is provided with the first grooves 11, and the entire position of the axial direction of the sleeve 2 is provided with the second grooves 21.

[0045] The rollers 3 can be cylindrical in shape, and the rollers 3 are located between the lead screw 1 and the sleeve 2, and the axis of the rollers 3 is parallel to the axis of the lead screw 1. The rollers 3 can be provided in a plurality, and preferably, the number of rollers 3 is greater than or equal to 3, for example, the rollers 3 are provided in 6. It can be understood that the number of rollers 3 can be the same as the number of starts of the first grooves 11, or less than the number of starts of the first grooves 11. The plurality of rollers 3 are uniformly spaced apart in the circumferential direction C of the sleeve 2.

[0046] The outer periphery of the roller 3 is provided with a plurality of teeth 31 extending in the circumferential direction C, the teeth 31 engage with the first grooves 11 and the teeth 31 engage with the second grooves 21, that is, the teeth 31 are located at the intersection positions of the first grooves 11 and the second grooves 21. The cross section of the teeth 31 in a plane perpendicular to the extension direction of the teeth 31 can be, for example, triangular. The plane in which the teeth 31 are located can be perpendicular to the axial direction A of the roller 3. Any two adjacent teeth 31 of the plurality of teeth 31 have the same distance, that is, the plurality of teeth 31 are uniformly arranged in the axial direction A. The distance between the two adjacent teeth 31 can be equal to the pitch of the first grooves 11. It should be noted that the distance between the two adjacent teeth 31 refers to the distance between the same positions of the two adjacent teeth 31, for example, the distance between the center lines of the two adjacent teeth 31. The axial length of the roller 3 can be substantially the same as the axial length A of the lead screw 1 occupied by the plurality of first grooves 11.

[0047] The distance between two adjacent convex teeth 31 can be an integer multiple, such as one, two, etc., of the distance between two adjacent first grooves 11 and / or the pitch of the second grooves 21. In this embodiment, the distance between two adjacent convex teeth 31 is equal to the distance between two adjacent first grooves 11, and the distance between two adjacent convex teeth 31 is equal to the pitch of the second grooves 21. All the first grooves 11 are embedded with the convex teeth 31, and all the second grooves 21 are embedded with the convex teeth 31.

[0048] Further, the planetary roller screw further comprises a cage 4, which is cylindrical in whole, and is sleeved on the screw rod 1. The cage 4 is located between the screw rod 1 and the sleeve 2 in the radial direction R. The cage 4 is provided with a plurality of positioning grooves 41 for accommodating the rollers 3, and the positioning grooves 41 can be long holes extending in the axial direction A of the cage 4.

[0049] It can be understood that, compared with the prior art planetary roller screw, the convex teeth 31 can be embedded in the intersection position of the first grooves 11 and the second grooves 21. Moreover, the cage 4 for positioning the rollers 3 is not necessarily provided.

[0050] When the sleeve 2 rotates to move the screw rod 1 along the axial direction A relative to the sleeve 2, the sleeve 2 applies a frictional force to the rollers 3 to make the rollers 3 rotate around the axial line of the rollers 3. Although the rollers 3 move along the second grooves 21 of the sleeve 2, the rollers 3 do not leave the first grooves 11 in which the rollers 3 are located. Therefore, the rollers 3 as a whole move along the axial direction A of the screw rod 1 with the screw rod 1.

[0051] Second embodiment

[0052] The planetary roller screw according to the second embodiment of the present application has the same overall structure as the planetary roller screw according to the first embodiment. In this embodiment, the same reference numerals are used for the same or similar components as those in the first embodiment, and detailed descriptions of these components are omitted.

[0053] As shown in FIG. 1, FIG. 5 to FIG. 7 The present application provides a planetary roller screw, which comprises a screw rod 1, a sleeve 2, and a roller 3.

[0054] The screw rod 1 is cylindrical in whole, and the outer periphery of the screw rod 1 is provided with a plurality of first grooves 11 extending in the circumferential direction C. The first grooves 11 are formed in a closed ring shape. The plurality of first grooves 11 are arranged parallel to each other, and the distance between any two adjacent first grooves 11 can be the same.

[0055] The bushing 2 can be cylindrical in shape and is fitted onto the lead screw 1. The axis of the bushing 2 can coincide with the axis of the lead screw 1. The inner surface of the bushing 2 is provided with a second groove 21 extending in a helical direction, and multiple second grooves 21 can be provided. The first groove 11 and the second groove 21 intersect.

[0056] The pitch of the second groove 21 can be an integer multiple of the distance between two adjacent first grooves 11, such as twice. It can be understood that the distance between two adjacent first grooves 11 can also be an integer multiple of the pitch of the second groove 21.

[0057] The roller 3 can be cylindrical in shape and is located between the lead screw 1 and the bushing 2. The axis of the roller 3 is parallel to the axis of the lead screw 1. Multiple protrusions 31 extending circumferentially C are provided on the outer periphery of the roller 3. The protrusions 31 engage with the first groove 11 and the second groove 21, meaning that the protrusions 31 are located at the intersection of the first groove 11 and the second groove 21. In this embodiment, the distance between two adjacent protrusions 31 is equal to the pitch of the second groove 21, and the distance between two adjacent protrusions 31 is an integer multiple of the distance between two adjacent first grooves 11, for example, twice. Protrusions 31 are embedded in a portion of the first groove 11 and in all of the second grooves 21.

[0058] In the second embodiment, the cage in the first embodiment is omitted. It can be understood that, compared with the planetary roller screw of the prior art, since the tooth 31 is located at the intersection of the first groove 11 and the second groove 21, it is not necessary to use the cage 4 to position the roller 3.

[0059] When the bushing 2 rotates and causes the lead screw 1 to move relative to the bushing 2 along the axial direction A, the bushing 2 applies a frictional force to the roller 3, causing the roller 3 to rotate around its axis. Although the roller 3 will move along the second groove 21 of the bushing 2, the roller 3 will not leave the first groove 11 in which it is located. Therefore, the roller 3 moves as a whole along the axial direction A of the lead screw 1.

[0060] Third embodiment

[0061] The overall structure of the planetary roller screw according to the third embodiment of the present invention is the same as that of the planetary roller screw according to the first embodiment. In this embodiment, the same reference numerals are used for components that are the same as or similar to those in the first embodiment, and detailed descriptions of these components are omitted.

[0062] like FIG. 8 and FIG. 9 As shown, the present invention provides a planetary roller screw, which includes a screw 1, a bushing 2, and rollers 3.

[0063] The screw rod 1 is cylindrical as a whole, and a plurality of first grooves 11 extending in the circumferential direction C are provided on the outer periphery of the screw rod 1. The first grooves 11 are formed in a closed loop. The plurality of first grooves 11 are arranged parallel to each other, and the distance between any two adjacent first grooves 11 can be the same.

[0064] The screw rod 1 is provided with a first engagement portion 12 provided on the outer peripheral surface of the screw rod 1. The first engagement portion 12 can be straight toothed, and the first engagement portion 12 can be provided on the portions of the screw rod 1 at both ends in the axial direction A of the first grooves 11.

[0065] The sleeve 2 can be cylindrical as a whole, and the sleeve 2 is sleeved on the screw rod 1. The axis of the sleeve 2 can coincide with the axis of the screw rod 1. The inner surface of the sleeve 2 is provided with a second groove 21 extending in the direction of a spiral line. The second groove 21 can be provided with a plurality of second grooves 21. The first grooves 11 and the second grooves 21 intersect.

[0066] The roller 3 can be cylindrical as a whole, and the roller 3 is located between the screw rod 1 and the sleeve 2. The axis of the roller 3 is parallel to the axis of the screw rod 1. The outer periphery of the roller 3 is provided with a plurality of convex teeth 31 extending in the circumferential direction C. The convex teeth 31 engage with the first grooves 11 and the convex teeth 31 engage with the second grooves 21, that is, the convex teeth 31 are located at the intersection positions of the first grooves 11 and the second grooves 21.

[0067] The roller 3 is provided with a second engagement portion 32 provided on the outer periphery of the roller 3. The second engagement portion 32 can be straight toothed and can engage with the first engagement portion 12. The second engagement portion 32 can be provided on the portions of the roller 3 at both ends in the axial direction A. The second engagement portion 32 is provided on the convex teeth 31, so that the second engagement portion 32 can cooperate with the first engagement portion 12 and also cooperate with the second grooves 32.

[0068] Through the cooperation of the first engagement portion 12 and the second engagement portion 32, the roller 3 can make pure rolling on the outer peripheral surface of the screw rod 1. The roller 3 will not slide in the first grooves 11, and there will be no slippage between the roller 3 and the screw rod 1, thereby improving the transmission accuracy of the planetary roller screw.

[0069] Although the specific technical solutions of the present application are described in detail in the above specific embodiments, it should be noted that:

[0070] (1) In the above embodiment, the distance between any two adjacent first grooves 11 in the plurality of first grooves 11 is the same. However, the present application is not limited to this, and the distance between any two adjacent first grooves 11 in the plurality of first grooves 11 can be different. For example, the distance between a certain first groove and another adjacent first groove on the one side of the axial direction A of the certain first groove and the distance between the certain first groove and another adjacent first groove on the other side of the axial direction A of the certain first groove can be different.

[0071] (2) In the above embodiment, the plurality of second grooves 21 are evenly spaced on the circumference C of the screw rod 1. However, the present application is not limited thereto, and the plurality of second grooves 21 can have the same lead and the plurality of second grooves 21 can be unevenly spaced on the axial direction A of the sleeve 2, so that the distance between the adjacent two second grooves 21 can not be equal.

[0072] (3) In the above embodiment, the plurality of convex teeth 31 have the same distance between any two adjacent convex teeth 31, i.e. the plurality of convex teeth 31 are evenly arranged along the axial direction A. However, the present application is not limited thereto, and the plurality of convex teeth can have different distances between any two adjacent convex teeth, i.e. the plurality of convex teeth are unevenly arranged along the axial direction A.

[0073] (4) In the above embodiment, the convex teeth 31 are embedded in all the second grooves 21. However, the present application is not limited thereto, and the convex teeth can be embedded in part of the second grooves, for example, the distance between the adjacent two convex teeth is an integer multiple of the distance between the adjacent two second grooves.

[0074] (5) In the above embodiment, the plurality of rollers 3 are evenly spaced on the circumference C of the sleeve 2. However, the present application is not limited thereto, and the plurality of rollers 3 can be unevenly spaced on the circumference C of the sleeve 2, for example, there are 8 second grooves and 3 rollers.

[0075] (6) In the above embodiment, the first engagement part 12 and the second engagement part 32 can be straight teeth that can cooperate with each other, however, the present application is not limited thereto, and the first engagement part 12 and the second engagement part 32 can also be helical teeth.

[0076] (7) In the above embodiment, the cross section of the convex teeth 31, the first grooves 11 and the second grooves 21 is triangular, however, the present application is not limited thereto, and the cross section of the convex teeth 31, the first grooves 11 and the second grooves 21 can also be arc-shaped or other shapes. It can be understood that if the cross section of the convex teeth 31, the first grooves 11 and the second grooves 21 are all arc-shaped, the convex teeth 31 are embedded in the first grooves 11 and the second grooves 21, which can increase the contact area of the screw rod 1 and the sleeve 2, improve the impact resistance of the planetary roller screw, increase the carrying capacity, and prolong the service life. Moreover, there is no need to set the reset ring (reset device) in the prior art, which avoids the impact of the reset ring on the roller when performing reset, reduces vibration and noise, and makes the planetary roller screw run smoothly.

[0077] Further, the first grooves 11 and the second grooves 21 can be Goedel grooves. By applying appropriate pre-tightening load to the planetary roller screw, the axial gap is eliminated, which can make the planetary roller screw have better rigidity and achieve higher precision.

Claims

1. A planetary roller screw comprising a ringed screw mated with a threaded sleeve, characterized in that, The planetary roller screw comprises: a screw rod, an outer periphery of the screw rod being provided with a first groove extending in a circumferential direction, the first groove being formed in a closed ring shape in the circumferential direction of the screw rod; a sleeve, the sleeve being sleeved on the screw rod, an inner surface of the sleeve being provided with a plurality of second grooves extending in a helical direction, the first groove and the second groove intersecting; and a plurality of rollers, the plurality of rollers being located between the screw rod and the sleeve, an outer periphery of the roller being provided with a plurality of protrusions, each of the protrusions being formed in a closed ring shape in the circumferential direction of the roller, the protrusions being located at the intersection positions of the first groove and the second groove, the protrusions being engaged with the first groove and the protrusions being engaged with the second groove, an outer peripheral surface of the screw rod being provided with a first engagement part, an outer peripheral surface of the roller being provided with a second engagement part, the rollers being caused to make pure rolling on the outer peripheral surface of the screw rod through cooperation of the first engagement part and the second engagement part, the first engagement part and the second engagement part being straight-toothed, the second engagement part being formed at the protrusions at the axial two ends of the roller, a cross section of the protrusion along a plane perpendicular to the extending direction of the protrusion being triangular or arc-shaped, an axial length of the screw rod occupied by the first groove being smaller than an axial length of the sleeve occupied by the second groove, during operation of the planetary roller screw, the protrusions are embedded in the closed ring-shaped first groove, so that the axial position of the roller relative to the screw rod is fixed, the planetary roller screw is not provided with a reset device for resetting the rollers.

2. The planetary roller screw according to claim 1, characterized in that a plane in which the first groove is located is perpendicular to the axial direction of the screw rod, and a plane in which the protrusion is located is perpendicular to the axial direction of the roller.

3. The planetary roller screw of claim 1, wherein, all or part of the first groove is embedded with the protrusion; and / or, all or part of the second groove is embedded with the protrusion.

4. The planetary roller screw of claim 1, wherein, any two adjacent first grooves among the plurality of first grooves have the same or different distances.

5. The planetary roller screw of claim 1, wherein, the distance between two adjacent protrusions is an integer multiple of the distance between two adjacent first grooves and / or the pitch of the second groove.

6. The planetary roller screw of claim 1, wherein, a cross section of the first groove along a plane perpendicular to the extending direction of the first groove is triangular, and a cross section of the second groove along a plane perpendicular to the extending direction of the second groove is triangular.

7. The planetary roller screw of claim 1, wherein, the planetary roller screw further comprises a retainer, the retainer being provided between the screw rod and the sleeve in the radial direction of the planetary roller screw, the retainer being provided with a positioning groove for accommodating the roller.

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