Bidirectional coaxial electric cylinder based on improved nut reverse planetary roller screw

Abstract

A bidirectional coaxial electric cylinder based on an improved nut reverse planetary roller screw relates to the field of electric cylinders and comprises a cylinder body, a first planetary roller screw pair, a second planetary roller screw pair, a power assembly, a bearing pack and a nut. The special improved nut reverse planetary roller lead screw is adopted as a main component of the electric cylinder, and the transmission efficiency of the electric cylinder is guaranteed while the high load bearing capacity of the electric cylinder is guaranteed; the frameless torque motor is adopted, due to the fact that no power transmission mechanism exists, direct transmission and efficient operation of driving force are guaranteed, the axial size and the radial size are reduced to the maximum extent, the design is more compact, the size of the whole electric cylinder is reduced, and the application range of the electric cylinder is widened; the function that the single nut drives the two lead screws to rotate is achieved.

Description

Technical Field

[0001] The invention relates to the field of electric cylinders, and in particular to a bidirectional coaxial electric cylinder based on an improved nut reverse planetary roller screw. Background Art

[0002] With the advancement of industrial automation and the increasing demand for high-precision and efficient motion control, the market size of electric cylinders has shown an upward trend year by year. In 2022, the market size of China's electric cylinder industry will be approximately 1.156 billion yuan, and demand is still expanding. At present, electric cylinders are used in many fields such as industrial automation production lines, robots, medical equipment, aerospace, and automobiles. In industrial applications, due to factors such as limited installation space, bidirectional electric cylinders are used when linear feed is required in both directions. However, although the current bidirectional electric cylinders can meet basic working needs, they also have disadvantages such as large size and non-coaxial bidirectionality, which will also cause huge shear stress on the electric cylinder body when the two axes are subjected to force. Summary of the invention

[0003] The purpose of the present invention is to solve the shortcomings of the existing bidirectional electric cylinder, such as large volume and non-coaxiality in both directions, and to provide a bidirectional coaxial electric cylinder based on an improved nut reverse planetary roller screw.

[0004] A bidirectional coaxial electric cylinder based on an improved nut reverse planetary roller screw comprises a cylinder body, a first planetary roller screw pair, a second planetary roller screw pair, a power assembly, a bearing group and a nut; wherein, The cylinder body comprises a housing, a front cover and a rear cover; steps are provided at both ends of the housing to install the first bearing group, and a groove is provided in the middle of the housing to install the stator of the frameless torque motor; The first planetary roller screw pair comprises a first screw, a first planetary roller, a first inner gear ring, a first retaining frame and a first nut end cover; the first planetary roller screw pair is arranged in the first part of the nut, wherein the first planetary roller is arranged between the first screw and the inner thread of the first part of the nut along the circumferential direction; the first screw has a smaller middle diameter and a thread is arranged on the outer surface, and the first planetary roller is provided with a thread whose rotation direction and pitch are equal to those of the outer thread of the first screw for matching; the first screw has a smaller middle diameter and a thread is arranged on the outer surface for matching with the thread of the first roller; a thread is arranged in the middle of the first planetary roller for matching with the thread on the outer surface of the first screw and the thread on the inner surface of the nut, and gears are arranged at both ends of the threaded section for meshing with the first inner gear ring, and there is a The cylindrical segment with a smaller segment radius is used to cooperate with the first retaining frame; the first inner gear ring is divided into two parts, one part is provided with an inner gear with a smaller inner diameter, and the other part has a larger inner diameter and is connected to the first retaining frame; the center of the first retaining frame is provided with a hole slightly larger than the outer diameter of the first lead screw, and small holes distributed in a circumference are provided around it, and the radius is equal to the radius of the cylinder at both ends of the first planetary roller, which is used to fix the first planetary roller; the first retaining frame is respectively installed on both sides of the first part of the nut; the first inner gear ring and the first retaining frame are coaxially installed on both sides of the first part of the nut, wherein the inner gear on one side of the first inner gear ring is meshed with the gears at both ends of the first roller; the first nut end cover is arranged on the outside of the first retaining frame and at both ends of the first part of the nut, for fixing the first retaining frame and the first inner gear ring; The second planetary roller screw pair comprises a second screw, a second planetary roller, a second inner gear ring, a second retaining frame and a second nut end cover; The second planetary roller screw pair is arranged in the second part of the nut, wherein the second roller is installed between the second screw and the internal thread of the second part of the nut along the circumferential direction; the second screw has a larger middle diameter, and the outer surface of the second screw is provided with an external thread, and the second planetary roller is provided with a thread with a rotation direction and a pitch equal to the external thread of the second screw for matching, and the rotation direction is opposite to the first screw and the first planetary roller; the second screw is provided with a hollow circular hole with a radius equal to the outer diameter of the first screw on the side close to the first screw, for matching with the first screw; The second planetary roller has a threaded middle section and gears at both ends, which mesh with the second inner gear ring, and a cylindrical section with a smaller radius at both ends, which is used to cooperate with the second retaining frame; The second inner gear ring is divided into two parts, one part is provided with an inner gear with a smaller inner diameter, and the other part has a larger inner diameter and is connected to the second retaining frame; the second inner gear ring and the second retaining frame are coaxially arranged on both sides of the second part of the nut, wherein the gear on one side of the second inner gear ring is meshed with the gears at both ends of the second planetary roller; A hole slightly larger than the outer diameter of the second lead screw is opened at the center of the second retaining frame, and small holes distributed along the circumference are opened around it, and the radius is equal to the radius of the cylinders at both ends of the second planetary roller, which is used to fix the second planetary roller; the second retaining frame is arranged on both sides of the second part of the nut, and the second retaining frame is provided with circular holes distributed along the circumference, which cooperate with the cylindrical sections at both ends of the second roller, and are used to fix and support the second roller; The second nut end cap is arranged outside the second retainer, and the second nut end cap is arranged at both ends of the second part of the nut, and is connected to the nut by screws, so as to fix the second retainer and the second inner gear ring; The power assembly includes a frameless torque motor stator, a frameless torque motor rotor, an annular magnetic encoder stator and an annular magnetic encoder rotor; one end of the frameless torque motor stator is fixed to the inner wall step of the shell, and the other end is fixed to the shell through the rear end cover; both ends of the frameless torque motor rotor are installed in the grooves formed on the outer surface after the first part of the nut and the second part of the nut are assembled, and fixed to the nut; the annular magnetic encoder stator is arranged on the front end cover, and the annular magnetic encoder rotor is arranged on the first part of the nut, and correctly matches the axial position of the annular magnetic encoder stator; The bearing group includes a first bearing group and a second bearing group; the first bearing group is installed between the housing and the nut, and is used to bear the radial force of the electric cylinder; the second bearing group is installed between the nut and the front cover and the rear cover; and is used to bear the axial force of the electric cylinder; The nut comprises a first nut component and a second nut component; the inner surfaces of the first nut component and the second nut component are both provided with internal threads, the middle diameter of the internal threads of the first nut component is smaller, and the middle diameter of the internal threads of the second nut component is larger, and the second nut component is first matched with the second planetary roller screw pair and then installed together with the first nut component; the connection between the first nut component and the second nut component is respectively provided with a cylindrical protrusion and a cylindrical groove; which are used to assemble and fix the first nut component and the second nut component.

[0005] The front end cover and the shell body, and the rear end cover and the shell body are connected by screws.

[0006] Working process and working principle of the present invention: The frameless torque motor stator and the frameless torque motor rotor form a frameless torque motor; the annular magnetic encoder stator and the annular magnetic encoder rotor form an annular magnetic encoder.

[0007] In the working process of the present invention, the frameless motor directly drives the nut to rotate, and the rotation of the nut drives the first planetary roller screw pair and the second planetary roller screw pair to work simultaneously. When the nut rotates, it drives the first planetary roller and the second planetary roller to rotate while revolving around the first screw and the second screw, further driving the first screw and the second screw to perform linear motion. Since the thread rotation directions of the first planetary roller screw pair and the second planetary roller screw pair are different, the directions of the linear motion of the first screw and the second screw are different, and they extend to both ends at the same time. At the same time, the annular magnetic encoder is used to feedback the angle, angular velocity and angular acceleration of the frameless torque motor. The stroke of the first screw and the second screw is controlled by the motor controller.

[0008] Beneficial effects of the present invention: The present invention adopts a special improved nut reverse planetary roller screw as the main part of the electric cylinder. It not only ensures the ability of the electric cylinder to bear high loads, but also ensures the transmission efficiency of the electric cylinder.

[0009] The present invention adopts a frameless torque motor, which ensures direct transmission of driving force and efficient operation due to the lack of a power transmission mechanism, minimizes the axial size and radial size, makes the design more compact, reduces the volume of the entire electric cylinder, and expands the application range of the electric cylinder.

[0010] The present invention realizes the function of a single nut driving two lead screws to rotate. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view of an embodiment of the present invention.

[0012] Figure 2 The matching principle diagram of the planetary roller screw pair of the embodiment of the present invention is as follows DETAILED DESCRIPTION

[0013] See also Figure 1 and Figure 2 Shown is an embodiment of the present invention.

[0014] A bidirectional coaxial electric cylinder based on an improved nut reverse planetary roller screw comprises a cylinder body, a first planetary roller screw pair, a second planetary roller screw pair, a power assembly, a bearing group and a nut; wherein, The cylinder body comprises a housing 11, a front cover 12 and a rear cover 13; steps are provided at both ends of the housing 11 to install the first bearing group 51, and a groove is provided in the middle of the housing 11 to install the frameless torque motor stator 41; The first planetary roller screw pair comprises a first screw 21, a first planetary roller 22, a first inner gear ring 23, a first retaining frame 24 and a first nut end cover 25; the first planetary roller screw pair is arranged in the first nut component 61, wherein the first planetary roller 22 is arranged between the first screw 21 and the inner thread of the first nut component 61 along the circumferential direction; the first screw 21 has a smaller middle diameter and a thread is arranged on the outer surface, and the first planetary roller 22 is provided with a thread with a rotation direction and a pitch equal to the outer thread of the first screw 21 for matching; the first screw 21 has a smaller middle diameter and a thread is arranged on the outer surface for matching with the thread of the first roller 22; the first planetary roller 22 is provided with a thread in the middle, which matches with the thread on the outer surface of the first screw 21 and the thread on the inner surface of the nut, and gears are arranged at both ends of the threaded section to mesh with the first inner gear ring 23, and there is a semi-circular section at both ends. The cylindrical section with a smaller diameter is used to cooperate with the first retaining frame 24; the first inner gear ring 23 is divided into two parts, one part is provided with an internal gear with a smaller inner diameter, and the other part has a larger inner diameter and is connected to the first retaining frame 24; the first retaining frame 24 is provided with a hole slightly larger than the outer diameter of the first lead screw 21 in the center, and small holes distributed in a circumference are provided around it, and the radius is equal to the radius of the cylinder at both ends of the first planetary roller 22, which is used to fix the first planetary roller 22; the first retaining frame 24 is respectively installed on both sides of the first nut component 61; the first inner gear ring 23 and the first retaining frame 24 are coaxially installed on both sides of the first nut component 61, wherein the internal gear on one side of the first inner gear ring 23 meshes with the gears at both ends of the first roller 22; the first nut end cover 25 is arranged on the outside of the first retaining frame 24 and at both ends of the first nut component 61, for fixing the first retaining frame 24 and the first inner gear ring 23; The second planetary roller screw pair comprises a second screw 31, a second planetary roller 32, a second inner gear ring 33, a second retaining frame 34 and a second nut end cover 35; The second planetary roller screw pair is arranged in the second part 62 of the nut, wherein the second roller 32 is installed between the second lead screw 31 and the internal thread of the second part 62 of the nut along the circumferential direction; the second lead screw 31 has a larger middle diameter, and the outer surface of the second lead screw 31 is provided with an external thread, and the second planetary roller 32 is provided with a thread with a rotation direction and a pitch equal to the external thread of the second lead screw 31 for matching, and the rotation direction is opposite to the first lead screw 21 and the first planetary roller 22; the second lead screw 31 is provided with a hollow circular hole with a radius equal to the outer diameter of the first lead screw 21 on the side close to the first lead screw 21, for matching with the first lead screw 21; The second planetary roller 32 has a thread in the middle section and gears at both ends, which mesh with the second inner gear ring 33, and a cylindrical section with a smaller radius at both ends, which is used to cooperate with the second retaining frame 34; The second inner gear ring 33 is divided into two parts, one part is provided with an inner gear with a smaller inner diameter, and the other part has a larger inner diameter and is connected to the second retaining frame 34; the second inner gear ring 33 and the second retaining frame 34 are coaxially arranged on both sides of the nut second component 62, wherein the gear on one side of the second inner gear ring 33 meshes with the gears at both ends of the second planetary roller 32; A hole slightly larger than the outer diameter of the second lead screw 32 is formed in the center of the second retainer 34, and small holes distributed along the circumference are formed around the second retainer 34, the radius of which is equal to the radius of the cylinders at both ends of the second planetary roller 32, for fixing the second planetary roller 32; the second retainer 34 is arranged on both sides of the second nut component 62, and circular holes distributed along the circumference are formed on the second retainer 34, which cooperate with the cylindrical sections at both ends of the second roller 32, for fixing and supporting the second roller 32; The second nut end cover 35 is arranged outside the second retainer 34. The second nut end cover 35 is arranged at both ends of the nut second component 62 and is connected to the nut by screws to fix the second retainer 34 and the second inner gear ring 33. The power assembly includes a frameless torque motor stator 41, a frameless torque motor rotor 42, an annular magnetic encoder stator 43 and an annular magnetic encoder rotor 44; one end of the frameless torque motor stator 41 is fixed to the inner wall step of the housing 11, and the other end is fixed to the housing 11 through the rear end cover 13; both ends of the frameless torque motor rotor 42 are installed in the grooves formed on the outer surface after the first nut component 61 and the second nut component 62 are assembled, and fixed to the nut; the annular magnetic encoder stator 43 is arranged on the front end cover 12, and the annular magnetic encoder rotor 44 is arranged on the first nut component 61, and correctly matches the axial position of the annular magnetic encoder stator 43; The bearing group includes a first bearing group 51 and a second bearing group 52; the first bearing group 51 is installed between the housing 11 and the nut, and is used to bear the radial force of the electric cylinder; the second bearing group 52 is installed between the nut and the front cover 12 and the rear cover 13; and is used to bear the axial force of the electric cylinder; The nut comprises a first nut component 61 and a second nut component 62; the inner surfaces of the first nut component 61 and the second nut component 62 are both provided with internal threads, the middle diameter of the internal threads of the first nut component 61 is smaller, and the middle diameter of the internal threads of the second nut component 62 is larger, and the second nut component 62 is first matched with the second planetary roller screw pair and then installed together with the first nut component 61; cylindrical protrusions and cylindrical grooves are respectively provided at the connection between the first nut component 61 and the second nut component 62; they are used to assemble and fix the first nut component 61 and the second nut component 62.

[0015] The front end cover 12 and the housing 11 as well as the rear end cover 13 and the housing 11 are connected via screws.

[0016] The working principle and working process of this embodiment: The frameless torque motor stator 41 and the frameless torque motor rotor 42 constitute a frameless torque motor; the annular magnetic encoder stator 43 and the annular magnetic encoder rotor 44 constitute an annular magnetic encoder.

[0017] In the working process of the present invention, the frameless motor directly drives the nut to rotate, and the rotation of the nut drives the first planetary roller screw pair and the second planetary roller screw pair to work simultaneously. When the nut rotates, it drives the first planetary roller 22 and the second planetary roller 32 to rotate while revolving around the first screw 21 and the second screw 31, further driving the first screw 21 and the second screw 31 to perform linear motion. Since the thread rotation directions of the first planetary roller screw pair and the second planetary roller screw pair are different, the directions of the linear motion of the first screw 21 and the second screw 31 are different, and they extend to both ends at the same time. At the same time, the annular magnetic encoder is used to feedback the angle, angular velocity and angular acceleration of the frameless torque motor. The stroke of the first screw 21 and the second screw 31 is controlled by the motor controller.

Claims

1. A bidirectional coaxial electric cylinder based on an improved nut reverse planetary roller screw, characterized in that: It includes a cylinder body, a first planetary roller screw pair, a second planetary roller screw pair, a power assembly, a bearing set and a nut; wherein, The cylinder body comprises a housing (11), a front end cover (12) and a rear end cover (13); steps are provided at both left and right ends of the housing (11) for mounting a first bearing group (51); a groove is provided in the middle of the housing (11) for mounting a frameless torque motor stator (41); The first planetary roller screw pair comprises a first screw (21), a first planetary roller (22), a first inner gear ring (23), a first retaining frame (24) and a first nut end cover (25); the first planetary roller screw pair is arranged in the first nut component (61), wherein the first planetary roller (22) is arranged between the first screw (21) and the inner thread of the first nut component (61) along the circumferential direction; the first screw (21) has a relatively small middle diameter and is provided with a thread on its outer surface; the first planetary roller (22) is provided with a thread having a rotation direction and a pitch equal to those of the outer thread of the first screw (21) for matching; the first screw (21) has a relatively small middle diameter and is provided with a thread on its outer surface for matching with the thread of the first roller (22); a thread is provided in the middle of the first planetary roller (22) for matching with the thread on the outer surface of the first screw (21) and the thread on the inner surface of the nut; gears are provided at both ends of the threaded section for meshing with the first inner gear ring (23), and a section with a relatively large radius is provided at both ends. a small cylindrical section for cooperating with the first retaining frame (24); the first inner gear ring (23) is divided into two parts, one part is provided with an inner gear with a smaller inner diameter, and the other part has a larger inner diameter and is connected to the first retaining frame (24); a hole slightly larger than the outer diameter of the first lead screw (21) is opened at the center of the first retaining frame (24), and small holes distributed along the circumference are opened around the first retaining frame (24), the radius of which is equal to the radius of the cylinder at both ends of the first planetary roller (22), and is used to fix the first planetary roller (22); the first retaining frame (24) is respectively mounted on both sides of the first nut component (61); the first inner gear ring (23) and the first retaining frame (24) are coaxially mounted on both sides of the first nut component (61), wherein the inner gear on one side of the first inner gear ring (23) meshes with the gears at both ends of the first roller (22); the first nut end cover (25) is arranged on the outside of the first retaining frame (24) and at both ends of the first nut component (61), and is used to fix the first retaining frame (24) and the first inner gear ring (23); The second planetary roller screw pair comprises a second screw (31), a second planetary roller (32), a second inner gear ring (33), a second retaining frame (34) and a second nut end cover (35); The second planetary roller screw pair is arranged in the second part (62) of the nut, wherein the second roller (32) is installed between the second screw (31) and the internal thread of the second part (62) of the nut along the circumferential direction; the second screw (31) has a relatively large middle diameter, and the outer surface of the second screw (31) is provided with an external thread, and the second planetary roller (32) is provided with a thread having a rotation direction and a pitch equal to the external thread of the second screw (31) for matching, and the rotation direction is opposite to that of the first screw (21) and the first planetary roller (22); the second screw (31) is provided with a hollow circular hole having a radius equal to the outer diameter of the first screw (21) on a side close to the first screw (21) for matching with the first screw (21); The second planetary roller (32) is provided with a thread in the middle section and gears at both ends, meshing with the second inner gear ring (33), and having a cylindrical section with a smaller radius at both ends, for cooperating with the second retaining frame (34); The second inner gear ring (33) is divided into two parts, one part is provided with an inner gear having a smaller inner diameter, and the other part has a larger inner diameter and is connected to the second retaining frame (34); the second inner gear ring (33) and the second retaining frame (34) are coaxially arranged on both sides of the second nut component (62), wherein the gear on one side of the second inner gear ring (33) meshes with the gears at both ends of the second planetary roller (32); The second retaining frame (34) has a hole at its center which is slightly larger than the outer diameter of the second lead screw (32), and has small holes distributed along a circumference around it, the radius of which is equal to the radius of the cylinders at both ends of the second planetary roller (32), for fixing the second planetary roller (32); the second retaining frame (34) is arranged on both sides of the second nut component (62), and the second retaining frame (34) has circular holes distributed along a circumference, which cooperate with the cylindrical sections at both ends of the second roller (32) for fixing and supporting the second roller (32); The second nut end cover (35) is arranged outside the second retaining frame (34), and the second nut end cover (35) is arranged at both ends of the second nut component (62) and is connected to the nut by screws, so as to fix the second retaining frame (34) and the second inner gear ring (33); The power assembly comprises a frameless torque motor stator (41), a frameless torque motor rotor (42), an annular magnetic encoder stator (43) and an annular magnetic encoder rotor (44); one end of the frameless torque motor stator (41) is fixed to the inner wall step of the housing (11), and the other end is fixed to the housing (11) through the rear end cover (13); both ends of the frameless torque motor rotor (42) are installed in grooves formed on the outer surface of the nut first part (61) and the nut second part (62) after assembly, and are fixed to the nut; the annular magnetic encoder stator (43) is arranged on the front end cover (12), and the annular magnetic encoder rotor (44) is arranged on the first nut part (61), and correctly matches the axial position of the annular magnetic encoder stator (43); The bearing group comprises a first bearing group (51) and a second bearing group (52); the first bearing group (51) is installed between the housing (11) and the nut, and is used to bear the radial force of the electric cylinder; the second bearing group (52) is installed between the nut and the front end cover (12) and the rear end cover (13), and is used to bear the axial force of the electric cylinder; The nut comprises a first nut part (61) and a second nut part (62); the inner surfaces of the first nut part (61) and the second nut part (62) are both provided with internal threads, the middle diameter of the internal threads of the first nut part (61) is relatively small, and the middle diameter of the internal threads of the second nut part (62) is relatively large; the second nut part (62) is first matched with the second planetary roller screw pair and then installed together with the first nut part (61); a cylindrical protrusion and a cylindrical groove are respectively provided at the connection between the first nut part (61) and the second nut part (62); and the cylindrical protrusion and the cylindrical groove are used to assemble and fix the first nut part (61) and the second nut part (62).

2. A bidirectional coaxial electric cylinder based on an improved nut reverse planetary roller screw according to claim 1, characterized in that: The front end cover (12) and the housing (11), as well as the rear end cover (13) and the housing (11), are connected via screws.

Images