Linear actuator driven by planetary roller screw rod

Abstract

The utility model discloses a linear actuator based on planetary roller screw transmission, and relates to the technical field of linear driving. Comprising a shell with two open ends, and the two ends of the shell are connected with end covers; a nut and a lead screw are coaxially installed in the shell, the front end of the lead screw penetrates through the end cover at the front end in a sliding mode and is connected with a first rod end knuckle bearing, and the center of the end cover at the rear end is connected with a second rod end knuckle bearing. An axial positioning bearing is integrally arranged at the front end of the outer cylindrical face of the nut, the front end of the nut is rotationally connected with the shell and the front end cover through the axial positioning bearing, a radial positioning bearing is integrally arranged at the rear end of the nut, and the nut is rotationally connected with the shell through the radial positioning bearing. The axial positioning bearing, the radial positioning bearing and the nut are arranged to be of an integrated structure, the radial size of the actuator is reduced, meanwhile, the axial positioning bearing is clamped between the front end cover and the shell, a positioning locking nut is omitted, and therefore the axial size, the radial size and the weight of the actuator are effectively reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of linear drive, in particular to a linear actuator based on planetary roller screw drive. Background Technique

[0002] As Figure 4 shown, the existing linear actuator includes a housing 28 with openings at both ends, and end caps 29 are connected to both ends of the housing 28; a nut 30 and a lead screw 31 are coaxially installed in the housing 28, and a plurality of planetary rollers 32 respectively thread-engaged with the lead screw 31 and the nut 30 are arranged between the lead screw 31 and the nut 30. A drive motor 33 for driving the nut 30 to rotate is also installed in the housing 28. The front end of the lead screw 31 slides through the front end cap 29 and is connected with a first rod end joint bearing 34, and the center of the rear end cap 29 is connected with a second rod end joint bearing 35.

[0003] The front end of the outer cylinder surface of the nut 30 of the above actuator is rotatably installed in the housing 28 through a bearing 36, and the rear end of the nut 30 is rotatably connected with the housing 28 through a bearing 38 arranged on a swivel joint 37. In the actual application process, there are obvious defects: 1) The front end of the nut is installed in the housing 28 through a commercially available bearing, and the radial dimension is large. Moreover, the front end also needs to be limited by the nut, which increases the radial dimension and the axial dimension, and at the same time increases the overall weight of the actuator. However, in the current humanoid robot industry, there are requirements for the linear actuator to be lightweight and small in volume; 2) The rear end of the nut is rotatably connected with the housing through a bearing arranged on the swivel joint, which increases the length of the swivel joint, thereby increasing the overall length of the linear actuator, and does not meet the requirements of lightweight and small volume for humanoid robots. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a linear actuator based on planetary roller screw drive, which can effectively solve the problems in the background technique.

[0005] The technical solution to achieve the above purpose is: A linear actuator based on planetary roller screw drive includes a housing with openings at both ends, and end caps are connected to both ends of the housing; a nut and a lead screw are coaxially installed in the housing, a plurality of planetary rollers respectively thread-engaged with the lead screw and the nut are arranged between the lead screw and the nut, a drive motor for driving the nut to rotate is also installed in the housing, the front end of the lead screw slides through the front end cap and is connected with a first rod end joint bearing, and the center of the rear end cap is connected with a second rod end joint bearing;

[0006] It is characterized in that: an axial positioning bearing is integrally arranged at the front end of the outer cylindrical surface of the nut, and the front end of the nut is rotationally connected to the housing and the front end cover through the axial positioning bearing. The axial positioning bearing is radially clamped between the front end cover and the housing at the same time. The radial position of the axial positioning bearing is determined by the front end cover and the housing. A radial positioning bearing is integrally arranged at the rear end of the nut, and the nut is rotationally connected to the housing through the radial positioning bearing.

[0007] Further, the axial positioning bearing includes a protrusion integrally arranged on the outer circular surface of the nut. Symmetrically arranged conical surfaces are provided on both sides of the convex body, and the small ends of the conical surfaces are arranged back to back. A pair of first bearing outer rings are sleeved outside the conical surfaces. The two first bearing outer rings are radially clamped between the front end cover and the housing. A ring of first rollers is installed between the first bearing outer ring on the corresponding side and the conical surface. The first rollers are respectively installed between the first bearing outer ring and the corresponding conical surface through a conical cage.

[0008] Further, the axial positioning bearing includes a protrusion integrally arranged on the outer circular surface of the nut. The cross section of the convex body is rectangular. A bearing housing is arranged outside the protrusion. The bearing housing is axially clamped between the front end cover and the housing. A ring of first rollers is installed between the bearing housing and the two side surfaces and the peripheral surface of the protrusion respectively. The first rollers are respectively installed between the bearing housing and the protrusion through a first roller cage.

[0009] Further, the axial positioning bearing includes a protrusion integrally arranged on the outer circular surface of the nut. Arc grooves are provided on the two side walls of the convex body. A pair of first bearing outer rings are sleeved on both sides of the convex body. A ring of balls is arranged between the protrusion and the first bearing outer ring on the same side. The balls are installed between the protrusion and the first bearing outer ring through a ball cage and are respectively in angular contact with the protrusion and the first bearing outer ring to form an angular contact bearing.

[0010] Further, the bearing inner ring of the radial positioning bearing is integrally arranged on the outer circular surface of the nut. A second bearing outer ring is externally fitted to the bearing inner ring. A ring of second rollers is arranged between the peripheral wall of the bearing inner ring and the second bearing outer ring. The second rollers are installed between the bearing inner ring and the second bearing outer ring through a second roller cage.

[0011] Further, an encoder housing is connected between the rear end cover and the housing. A adapter is connected to the rear end of the nut and extends into the encoder housing. An encoder is installed on the adapter.

[0012] Further, the second bearing outer ring of the radial positioning bearing is radially clamped between the housing and the encoder housing.

[0013] Advantages of the present utility model: 1) The axial positioning bearing and the radial positioning bearing of the present utility model are respectively arranged as an integral structure with the nut, reducing the radial dimension of the actuator. At the same time, the axial positioning bearing is clamped between the front end cover and the housing, omitting the positioning lock nut, thus effectively reducing the axial dimension, radial dimension and weight of the actuator; 2) The radial positioning bearing of the present utility model is installed between the nut and the housing, so the axial length of the adapter can be reduced, thereby further shortening the length of the linear actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic structural diagram of the first embodiment;

[0015] Figure 2 is a schematic structural diagram of the second embodiment;

[0016] Figure 3 is a schematic structural diagram of the third embodiment;

[0017] Figure 4 is a schematic structural diagram of an existing product. DETAILED DESCRIPTION OF THE EMBODIMENTS Embodiment 1

[0018] As Figure 1 shown, this embodiment discloses a linear actuator based on planetary roller screw drive, including a housing 1 with openings at both ends, and end covers 2 are connected to both ends of the housing 1; a nut 3 and a screw rod 4 are coaxially installed in the housing 1, and a plurality of planetary rollers 5 respectively in threaded engagement with the screw rod 4 and the nut 3 are arranged between the screw rod 4 and the nut 3. A drive motor 6 for driving the nut 3 to rotate is also installed in the housing 1. The front end of the screw rod 4 slides through the front end cover 2 and is connected to a first rod end joint bearing 7, and the center of the rear end cover 2 is connected to a second rod end joint bearing 8.

[0019] An axial positioning bearing 9 is integrally provided at the front end of the outer cylindrical surface of the nut 3. The axial positioning bearing 9 includes a protrusion 10 integrally provided on the outer cylindrical surface of the nut 3. Symmetrically arranged conical surfaces 11 are provided on both sides of the convex body 10, and the small ends of the conical surfaces 11 face away from each other. An axially opposed first bearing outer ring 12 is sleeved on the conical surface 11. The two first bearing outer rings 12 are axially clamped between the front end cover 2 and the housing 1, and a ring of first rollers 13 is installed between the first bearing outer ring 12 and the corresponding conical surface 11. The first rollers 13 are respectively installed between the first bearing outer ring 12 and the corresponding conical surface 11 through a conical cage.

[0020] An encoder housing 14 is connected between the rear end cover 2 and the housing 1. A transfer joint 15 extending into the encoder housing 14 is connected to the rear end of the nut 3, and an encoder 16 is installed on the transfer joint 15.

[0021] A radial positioning bearing 17 is integrally provided at the rear end of the nut 3. The rear end of the nut 3 is rotatably connected to the housing 1 through the radial positioning bearing 17. The bearing inner ring 18 of the radial positioning bearing 17 is integrally provided on the outer wall of the nut 3. A second bearing outer ring 19 is provided in cooperation with the outside of the bearing inner ring 18. A circle of second rollers 20 is provided between the peripheral wall of the bearing inner ring 18 and the second bearing outer ring 19. The second rollers 20 are installed between the bearing inner ring 18 and the second bearing outer ring 19 through a second roller cage. The second bearing outer ring 19 is simultaneously clamped between the housing 1 and the encoder housing 14 in the radial direction. Embodiment 2

[0022] As Figure 2 shown, the difference between this embodiment and the first embodiment lies in the axial positioning bearing. The axial positioning bearing in this embodiment includes a protrusion 21 integrally provided on the outer cylindrical surface of the nut. The cross-section of the protrusion 21 is rectangular. A bearing housing 22 is provided outside the protrusion 21. The bearing housing 22 is axially clamped between the front end cover 2 and the housing 1. A circle of first rollers 23 is respectively installed between the two side surfaces and the peripheral surface of the bearing housing 22 and the protrusion 21. The first rollers are respectively installed between the bearing housing 1 and the protrusion 21 through a first roller cage. Embodiment 3

[0023] As Figure 3 shown, the difference between this embodiment and the first embodiment lies in the axial positioning bearing. The axial positioning bearing in this embodiment includes a protrusion 24 integrally provided on the outer cylindrical surface of the nut. Arc grooves 25 are provided on the two side walls of the protrusion 24. Oppositely arranged first bearing outer rings 26 are sleeved on both sides of the protrusion 24. A circle of balls 27 is provided between the protrusion 24 and the first bearing outer ring 26 on the same side. The balls 27 are installed between the protrusion 24 and the first bearing outer ring 26 through a ball cage and are in angular contact with the protrusion 24 and the first bearing outer ring 26 to form an angular contact bearing.

[0024] The above axial positioning bearing 9 and radial positioning bearing 17 are respectively arranged as an integral structure with the nut 3, reducing the radial size of the actuator. At the same time, the axial positioning bearing 9 is clamped between the front end cover 2 and the housing 1, omitting the positioning lock nut, thereby effectively reducing the axial size, radial size, and weight of the actuator. At the same time, the radial positioning bearing 17 is installed between the nut and the housing 1 and the encoder housing 14. Therefore, the axial length of the adapter 15 can be reduced, thereby further shortening the length of the linear actuator.

Claims

1. A linear actuator driven by a planetary roller screw, comprising a housing with openings at both ends, and end caps connected to both ends of the housing; a nut and a screw rod are coaxially installed in the housing, a plurality of planetary rollers are arranged between the screw rod and the nut and are respectively engaged with the screw rod and the nut by threads, a driving motor for driving the nut to rotate is also installed in the housing, the front end of the screw rod slides through the end cap at the front end and is connected to a first rod end joint bearing, and the center of the end cap at the rear end is connected to a second rod end joint bearing; Features: An axial locating bearing is integrally provided at the front end of the outer cylindrical surface of the nut, and the front end of the nut is rotatably connected to the shell and the front end cover via the axial locating bearing. The axial locating bearing is radially clamped between the front end cover and the shell at the same time, and a radial locating bearing is integrally provided at the rear end of the nut, and the nut is rotatably connected to the shell via the radial locating bearing.

2. A linear actuator driven by a planetary roller screw according to claim 1, characterized in that: The axial locating bearing includes a protrusion integrally arranged on the outer cylindrical surface of the nut, symmetrically arranged conical surfaces are arranged on both sides of the protrusion, the small ends of the conical surfaces are arranged back to back, and the outer sleeves of the conical surfaces are provided with a first bearing outer ring arranged in a mating manner. The first bearing outer rings on both sides are radially clamped between the front end cover and the housing, a circle of first rollers is installed between the first bearing outer ring and the conical surface on the corresponding side, and the first rollers are respectively installed between the first bearing outer ring and the corresponding conical surface through conical retaining frames.

3. The linear actuator driven by a planetary roller screw according to claim 1, characterized in that: The axial locating bearing includes a protrusion integrally arranged on the outer circumferential surface of the nut, the cross-section of the protrusion is rectangular, a bearing shell is arranged outside the protrusion, the bearing shell is clamped axially between the front end cover and the housing, a circle of first rollers are respectively installed between the bearing shell and the two side surfaces and the circumferential surface of the protrusion, and the first rollers are respectively installed between the bearing shell and the protrusion through the first roller retainer.

4. The linear actuator driven by a planetary roller screw according to claim 1, characterized in that: The axial locating bearing includes a protrusion integrally arranged on the outer cylindrical surface of the nut, arc grooves are arranged on the two side walls of the protrusion, and the first bearing outer ring is arranged in a matched manner on both sides of the protrusion. A circle of balls is arranged between the protrusion and the first bearing outer ring on the same side. The balls are installed between the protrusion and the first bearing outer ring through a ball retainer, and are in angular contact with the protrusion and the first bearing outer ring respectively to form an angular contact bearing.

5. The linear actuator driven by a planetary roller screw according to claim 1, characterized in that: The bearing inner ring of the radial locating bearing is integrally arranged on the outer circumferential surface of the nut, and a second bearing outer ring is matched with the bearing inner ring. A circle of second rollers is arranged between the peripheral wall of the bearing inner ring and the second bearing outer ring, and the second rollers are installed between the bearing inner ring and the second bearing outer ring through a second roller retainer.

6. A linear actuator driven by a planetary roller screw according to claim 5, characterized in that: An encoder housing is connected between the end cover at the rear end and the shell, and an adapter extending into the encoder housing is connected to the rear end of the nut, on which an encoder is installed.

7. A linear actuator driven by a planetary roller screw according to claim 6, characterized in that: The second bearing outer ring of the radial locating bearing is clamped radially between the housing and the encoder housing.

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