Linear actuator with two-degree-of-freedom fisheye bearing

Abstract

The linear actuator with the two-degree-of-freedom fisheye bearing relates to the technical field of robot manufacturing and comprises a shell, a frameless motor is arranged in an inner cavity of the shell in a sleeved mode, a rotor of the frameless motor is in threaded connection with a push rod, and the push rod can move towards the side close to a port of the shell along the axis of the frameless motor. A guide sliding sleeve for bearing the push rod is arranged on the inner side of the port of the shell; the two fisheye bearings are arranged at the end, close to the end opening, of the push rod and the end, away from the guide sliding sleeve, of the shell respectively, bearing rotating bodies are embedded in the fisheye bearings in a sleeved mode, the fisheye bearings are clamped with limiting grooves of the bearing rotating bodies through stop pins, the extending direction of the stop pins is perpendicular to the axis of the push rod, and the stop pins can slide in the limiting grooves. The technical problems that an existing linear actuator push rod is not well supported and generates large deflection at the stroke tail end, the rotational inertia of a motor rotor is large, a circumferential limiting structure is lacked, a linear actuator body rotates during starting and stopping, and stroke deviation is caused are solved.

Description

Technical Field

[0001] The invention relates to the technical field of robot manufacturing, and in particular to a linear actuator with a two-degree-of-freedom fisheye bearing. Background Art

[0002] As one of the actuating units of humanoid robots, the linear actuator's linear motion can mimic the human trunk and limb muscle groups and provide power for the movement of humanoid robots. However, in the actual application of linear actuators, when the linear stroke of the linear actuator is large, the push rod of the planetary roller screw cannot get good axial support, so it is easy to produce large swings when it is at the end of the stroke. In addition, due to the large rotational inertia of the motor rotor of the linear actuator, there is a certain rotational inertia of the motor rotor when starting and stopping the motor, which can easily cause the linear actuator body to continue to rotate, thereby causing stroke errors.

[0003] In summary, it can be seen that developing a linear actuator that prevents the planetary roller screw from swinging at the end of the stroke and can quickly stop when the operation ends is an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0004] The purpose of the present invention is to provide a linear actuator with a two-degree-of-freedom fisheye bearing, which solves the technical problem that the motor rotor has a large rotational inertia, the linear actuator body is likely to continue to rotate when the motor is started and stopped, and thus causes stroke error.

[0005] To achieve the above object, the present invention provides a linear actuator with a two-degree-of-freedom fisheye bearing, comprising:

[0006] The housing has an inner cavity provided with a frameless motor, a rotor of the frameless motor is threadedly connected with a push rod, the push rod can move along the axis of the frameless motor toward a port side close to the housing, and the housing has a guide sleeve on the inner side of the port for carrying the push rod;

[0007] Two fisheye bearings are respectively arranged at one end of the push rod close to the port and the end of the shell away from the guide sleeve. The fisheye bearing is embedded with a bearing rotating body. The fisheye bearing is engaged with the limiting groove of the bearing rotating body through a stop pin. The extension direction of the stop pin is perpendicular to the axis of the push rod, and the stop pin can slide in the limiting groove.

[0008] Preferably, a plurality of planetary screws are evenly arranged on the outer periphery of one end of the push rod away from its feeding direction, a screw nut is rotatably provided between each planetary screw and the rotor of the frameless motor, and each planetary screw is respectively threadedly connected with the screw nut and the push rod.

[0009] Preferably, a buffer block is fixed between the screw nut and the port, the buffer block is located on a side of the guide sleeve close to the planetary screw, and the buffer block is arranged on the outer periphery of the push rod.

[0010] Preferably, an encoder is provided at the end of the inner cavity of the lead screw nut away from the guide sleeve, and the encoder's code disk rotates with the lead screw nut. The encoder detects the number of rotations and the rotation angle of the lead screw nut through the code disk.

[0011] Preferably, a force-sensitive sensor is provided on the side of the shell facing away from the port, and the force-sensitive sensor is fixedly connected to the fisheye bearing. The force-sensitive sensor is used to detect the magnitude of stress on the two fisheye bearings.

[0012] Preferably, the fisheye bearing includes a connecting part for connecting the force sensitive sensor and the push rod, and a mounting part for connecting the bearing rotating body, and each connecting part is coaxially arranged with the push rod; the bearing rotating body is provided with a connecting hole, and the connecting hole, the limit groove and the mounting part are all coaxially arranged, and the extension direction of the stop pin is perpendicular to the axis of the connecting part.

[0013] Preferably, each connection portion is threadedly connected with an adjusting nut, and the adjusting nut adjusts the screwing angle of each fisheye bearing to make the axes of each connection hole parallel.

[0014] Preferably, the shell includes a casing and a front cover and a rear cover threadedly connected to both ends of the casing, the front cover has an accommodating portion extending along the push rod feeding direction, the guide sleeve is arranged in the accommodating portion, and a sealing ring is arranged in the port of the accommodating portion facing away from the casing.

[0015] Preferably, the outer wall of the screw nut near the front end cover is provided with a shoulder and a four-point contact bearing, and the sleeve of the screw nut near the rear end cover is provided with a deep groove ball bearing. The four-point contact bearing is fixedly connected to the shoulder through a bearing pressure ring, and a bearing seat is clamped between the deep groove ball bearing and the casing, and the deep groove ball bearing is tightened and fixed in the bearing seat.

[0016] Compared with the above-mentioned background technology, the linear actuator with a two-degree-of-freedom fisheye bearing provided by the present invention includes a shell, a frameless motor is arranged inside the shell, and the rotor inner cavity of the frameless motor is provided with a push rod coaxial with the motor, and the push rod is connected to the inner wall of the rotor by a thread, that is, the frameless motor drives the rotor to rotate, and applies an axial thrust to the push rod through the rotating thread, so that the push rod moves toward the side close to the shell port, and a guide sleeve is provided at one end of the shell inner cavity close to the movement direction of the push rod, and the guide sleeve is sleeved on the outer periphery of the push rod. During the movement of the push rod, the guide sleeve carries the push rod in real time to ensure that the push rod moves along the preset direction of the guide sleeve. In addition, a fisheye bearing is provided at the end of the shell away from its port, and a fisheye bearing is also provided at the end of the push rod close to its feed direction. Stop pins are passed through the side walls of the fisheye bearings and extend into the limiting groove of the bearing rotating body in the fisheye bearing seat. The stop pin can slide along the extension direction of the limiting groove, and the bearing rotating body can rotate around the axis of the stop pin. The stop pin abuts against the side wall of the limiting groove. The stop pin limits the rotational freedom of the bearing rotating body around the axis of the push rod to prevent the frameless motor from continuing to rotate a certain angle due to its own inertia when the linear actuator stops moving, causing a stroke error. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0018] Figure 1 A cross-sectional view of a linear actuator with a two-degree-of-freedom fisheye bearing provided by an embodiment of the present invention;

[0019] Figure 2 A cross-sectional view of a fisheye bearing provided by an embodiment of the present invention;

[0020] Figure 3 An exploded view of a fisheye bearing provided in an embodiment of the present invention.

[0021] Among them, 1-housing; 2-frameless motor; 21-screw nut; 3-push rod; 31-planetary screw; 4-guide sleeve; 5-buffer block; 6-encoder; 7-front cover; 8-rear cover; 9-fisheye bearing; 91-connecting part; 92-installing part; 93-stop pin; 10-bearing rotating body; 101-limiting groove; 102-connecting hole; 11-sealing ring; 12-force sensitive sensor; 13-four-point contact bearing; 14-deep groove ball bearing; 15-bearing seat; 16-adjusting nut; 17-bearing pressure ring. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0024] The present invention provides a linear actuator with a two-degree-of-freedom fisheye bearing, comprising a shell for accommodating various components, a frameless motor 2 is arranged inside the shell, a push rod 3 coaxial with the frameless motor 2 is arranged inside the frameless motor 2, the push rod 3 and the frameless motor 2 are connected by a thread, the frameless motor 2 drives the thread of its own inner cavity to rotate, the thread applies an axial thrust to the push rod 3, the push rod 3 moves toward the side close to the shell port, a guide sleeve 4 is arranged on the side of the shell inner cavity close to the port, the push rod 3 is penetrated in the guide sleeve 4, a fisheye bearing 9 is arranged on the side of the push rod 3 close to the shell port, and a fisheye bearing 9 is also arranged at the end of the shell away from the guide sleeve 4, the two fisheye bearings 9 are coaxially arranged, each fisheye bearing 9 is penetrated by a stop pin 93, the stop pin 93 passes through the side wall of the fisheye bearing 9, and is engaged with the limit groove 101 of the bearing rotating body 10 in the fisheye bearing 9, so as to connect the fisheye bearing 9 with the bearing rotating body 10. It should be noted that the stop pin 93 can slide along the limiting groove 101 , and the stop pin 93 extends into the limiting groove 101 , and the bearing rotating body 10 can rotate with the stop pin 93 as the rotating axis.

[0025] When using the linear actuator provided by the present application, the frameless motor 2 is started. It should be noted that the frameless motor 2 includes an outer stator and a rotor arranged in the inner cavity of the stator. When the stator is energized, a magnetic field is generated to drive the magnetic rotor to rotate. The rotor cooperates with the push rod 3 through threads. When the rotor of the frameless motor 2 moves, the rotor drives the threads on its inner wall to rotate. The threads apply axial thrust to the push rod 3, causing the push rod 3 to move toward the side close to the shell port, and the fisheye bearing 9 connected to the push rod 3 moves toward the side away from the shell. During the movement of the push rod 3, the side wall of the push rod 3 is always in contact with the inner wall of the guide sleeve 4. Fitting, when the push rod 3 extends most of the section out of the shell, the inner wall of the guide sleeve 4 abuts against the side wall of the push rod 3, and the inner wall of the guide sleeve 4 balances the bending moment generated by the push rod 3 extending out of the shell, ensuring the stability of the feeding direction of the push rod 3. After the linear actuator completes the target action, the frameless motor 2 stops running, and the position of the bearing rotating body 10 connected to the driven component is fixed. When the push rod 3 continues to rotate due to its own inertia, the stop pin 93 of the fisheye bearing 9 abuts against the side wall of the limit groove 101, preventing the fisheye bearing 9 and the push rod 3 from continuing to rotate, thereby avoiding the stroke error of the linear actuator due to the inertia of the push rod 3.

[0026] Please refer to the instruction manual Figure 1, a plurality of planetary screws 31 are provided on the outer periphery of the end of the push rod 3 that deviates from its own movement direction, each planetary screw 31 is arranged parallel to the push rod 3, and a screw nut 21 is provided between the planetary screw 31 and the inner cavity of the frameless motor 2. It should be noted that the screw nut 21 is specifically a cylindrical shell, and the magnetic steel of the rotor of the frameless motor 2 is adhered and fixed to the outer wall of the screw nut 21. That is, when the frameless motor 2 is running, the stator generates a magnetic field after power is turned on, and an electromagnetic force is applied to the rotor provided with the magnetic steel. The magnetic steel drives the screw nut 21 to rotate together, and a thread matching the planetary screw 31 is provided in the inner cavity of the screw nut 21. During the rotation of the screw nut 21, the planetary screw 31 is driven to rotate around the push rod 3, and each planetary screw 31 applies an axial force to the push rod 3, so that the push rod 3 moves along its own axis direction. Preferably, the movement direction of the push rod 3 extending out of the shell port is recorded as the feed direction of the push rod 3.

[0027] It should be noted that the shell includes a casing 1 and a front end cover 7 and a rear end cover 8 threadedly connected to both ends of the casing 1, and the rear end cover 8 and the front end cover 7 are arranged in sequence along the feeding direction of the push rod 3, wherein the port of the shell is arranged on the end face of the front end cover 7, the push rod 3 is passed through the port on the front end cover 7, and the front end cover 7 extends along the feeding direction of the push rod 3 with an accommodating portion, the diameter of the accommodating portion is smaller than the diameter of the shell, and the guide sleeve 4 is arranged in the accommodating portion of the front end cover 7. On the premise of ensuring that the inner wall of the guide sleeve 4 can be close to the side wall of the push rod 3, the space occupied by the shell is reduced.

[0028] A buffer block 5 is provided on the side of the guide sleeve 4 close to the planetary screw 31. Figure 1 The buffer block 5 includes a locking portion for fixing the position and a buffer portion abutting the planetary screw 31. The locking portion is clamped between the screw nut 21 and the front end cover 7. A fixing bolt is passed between the locking portion and the front end cover 7 to further determine the setting position of the buffer block 5. The buffer portion is arranged around the outer periphery of the push rod 3 and is located between the guide sleeve 4 and the planetary screw 31. When the push rod 3 moves to the end of the stroke along the feed direction, the end face of the planetary screw 31 abuts against the buffer portion. Preferably, the buffer block 5 is made of a relatively flexible and vibration-absorbing material such as nylon and plastic. When the linear speed of the push rod 3 is faster, the buffer block 5 is used to prevent the end of the planetary screw 31 from directly colliding with the front end cover 7, thereby affecting the connection reliability of the front end cover 7 and the casing 1. At the same time, it can also prevent the planetary screw 31 from having an excessive impact on the front end cover 7, causing damage to the equipment.

[0029] Preferably, an encoder 6 is provided at the end of the inner cavity of the screw nut 21 away from the feeding direction of the push rod 3. The encoding disk of the encoder 6 can rotate together with the screw nut 21. The encoding disk can record the number of rotations and the rotation angle of itself. The encoding disk transmits data to the encoder 6 and converts the moving distance of the push rod 3. It should be noted that the encoder 6 is connected to the external control system through a signal cable. The control system receives the displacement signal of the push rod 3 fed back by the encoder 6 in real time. When the displacement distance of the push rod 3 reaches a preset value, the control system stops the operation of the linear actuator frameless motor 2.

[0030] A force-sensitive sensor 12 is provided on the end face of the rear end cover. Another fisheye bearing 9 is fixed on the end face of the force-sensitive sensor 12 away from the guide sleeve 4. The force-sensitive sensor 12 is also connected to the control system through a signal cable. The force-sensitive sensor 12 is used to detect the stress on the fisheye bearing 9. When the linear actuator of the present application is used, the fisheye bearings 9 at both ends of the linear actuator are respectively fixed on the driven member. That is, when the push rod 3 in the linear actuator moves along the feed direction, the distance between the fisheye bearings 9 on both sides becomes larger, and the fisheye bearings 9 move away from each other. The force sensor 12 feeds back the pressure signal received to the control system. When the push rod 3 moves away from the feeding direction, the distance between the two fisheye bearings 9 decreases. The fisheye bearings 9 pull the driven parts on both sides. The force sensor 12 receives the tension exerted on the fisheye bearings 9 and feeds back the tension signal to the control system. The control system analyzes the stress exerted on the linear actuator. When it exceeds the load range of the push rod 3, the push rod 3 is controlled to run in the reverse direction to release the stress exerted on the push rod 3 and avoid damage to the push rod 3.

[0031] Please refer to the instruction manual Figure 1 To Attachment Figure 3 The fisheye bearing 9 includes a connecting portion 91 for connecting the force sensitive sensor 12 and the push rod 3, and a mounting portion 92 for supporting the bearing rotating body 10. Preferably, the connecting portion 91 is a threaded rod, the mounting portion 92 is a circular ring, and the stop pin 93 is penetrated on the side wall of the stop pin 93 along the diameter direction of the mounting portion 92. There are two stop pins 93, and the extension directions of the two stop pins 93 are opposite, and the extension direction of each stop pin 93 is perpendicular to the axis of the push rod 3. The bearing rotating body 10 is specifically a sphere, and an annular limiting groove 101 is provided on the outer wall of the bearing rotating body 10. The outer diameter of the limiting groove 101 is equal to the diameter of the bearing rotating body 10. The stop pin 93 is inserted into the limiting groove 101 to connect the bearing rotating body 10 with the mounting portion 92. A connecting hole 102 is provided in the bearing rotating body 10, and the connecting hole 102 is used to install the driven part. When the linear actuator is not driving, the connecting hole 102, the limiting groove 101, and the mounting portion 92 are all coaxially arranged.

[0032] Preferably, an adjusting nut 16 is provided on the connecting portion 91 of each fisheye bearing 9, and the remaining section of the connecting portion 91 is used to connect the push rod 3 and the tension sensor. The adjusting nut 16 is rotated to adjust the screwable angle of the connecting portion 91 so that the fisheye bearings 9 at both ends of the linear actuator are located in the same plane; in addition, a sealing ring 11 is provided at the port of the front end cover 7. The sealing ring 11 is used to prevent foreign objects such as foreign matter and dust from being brought into the interior of the linear actuator along with the linear movement of the push rod 3, thereby affecting its reliability, and can also prevent the lubricating grease inside the linear actuator from leaking.

[0033] When the linear actuator moves the driven part, the bearing rotating body 10 can rotate along the preset direction of the limit groove 101, and the stop pin 93 engages with the limit groove 101 to prevent the bearing rotating body 10 from falling off. In addition, the rotating bearing body can also rotate with the stop pin 93 as the axis. Preferably, the width of the limit groove 101 is equal to or slightly larger than the diameter of the stop pin 93. When the bearing rotating body 10 rotates with the axis of the push rod 3, the stop pin 93 perpendicular to the push rod 3 abuts against the inner wall of the limit groove 101 to prevent the bearing rotating body 10 from rotating. That is, the stop pin 93 limits the rotational freedom of the bearing rotating body 10 along the axis of the push rod 3, thereby preventing the screw nut 21 and the magnet from continuing to rotate due to inertia when the linear actuator stops running, causing stroke error.

[0034] Preferably, a four-point contact bearing 13 and a shaft shoulder are provided at one end of the screw nut 21 close to the front end cover 7, and the side of the four-point contact bearing 13 is in contact with the shaft shoulder, and a bearing pressure ring 17 is passed between the shaft shoulder and the four-point contact bearing 13. The bearing pressure ring 17 is screwed to make the shaft shoulder and the bearing pressure ring 17 tightly connected, and the four-point contact bearing 13 provides a relatively stable axial support for the screw nut 21; a deep groove ball bearing 14 is provided on the side of the screw nut 21 close to the rear end cover 8, and the inner ring of the deep groove ball bearing 14 is interference fit with the screw nut 21, and a bearing seat 15 is clamped between the outer ring and the housing 1, and the bearing seat 15 tightens and fixes the deep groove ball bearing 14 in the bearing seat 15, and the bearing seat 15 is interference fit with the housing 1.

[0035] In summary, the linear actuator provided in the present application detects the movement process of the push rod 3 through the encoder 6 to prevent the push rod 3 from exceeding the maximum displacement range, and a guide sleeve 4 is set at the front end cover 7 to ensure the smooth movement of the push rod 3. By setting a stop pin 93 and a limit groove 101 on the fisheye bearing 9, while limiting the rotation of the push rod 3 around its own axis, it does not affect the rotational freedom of the push rod 3 about the axis of the stop pin 93 and the axis of the limit groove 101.

[0036] It should be noted that, in this specification, relational terms such as first and second are merely used to distinguish one entity from other entities, but do not necessarily require or imply any actual relationship or order between these entities.

[0037] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the present invention.

Claims

1. A linear actuator with a two-degree-of-freedom fisheye bearing, characterized in that: include: A housing, wherein an inner cavity of the housing is provided with a frameless motor (2), a rotor of the frameless motor (2) being threadedly connected to a push rod (3), the push rod (3) being able to move along an axis of the frameless motor (2) toward a side close to a port of the housing, the housing being provided with a guide sleeve (4) on the inner side of the port for carrying the push rod (3); Two fisheye bearings (9) are respectively arranged at one end of the push rod (3) close to the port and at one end of the housing away from the guide sleeve (4); a bearing rotating body (10) is embedded in the fisheye bearing (9); the fisheye bearing (9) is engaged with a limit groove (101) of the bearing rotating body (10) through a stop pin (93); the extension direction of the stop pin (93) is perpendicular to the axis of the push rod (3); and the stop pin (93) can slide in the limit groove (101).

2. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 1, characterized in that: A plurality of planetary screws (31) are evenly arranged on the outer periphery of one end of the push rod (3) away from the feeding direction thereof, a screw nut (21) is rotatably provided between each of the planetary screws (31) and the rotor of the frameless motor (2), and each of the planetary screws (31) is respectively threadedly connected to the screw nut (21) and the push rod (3).

3. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 2, characterized in that: A buffer block (5) is fixed between the screw nut (21) and the port, the buffer block (5) is located on a side of the guide sleeve (4) close to the planetary screw (31), and the buffer block (5) is arranged on the outer periphery of the push rod (3).

4. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 3, characterized in that: An encoder (6) is provided at an end of the inner cavity of the screw nut (21) facing away from the guide sleeve (4); a code disk of the encoder (6) rotates along with the screw nut (21); and the encoder (6) detects the number of rotations and the rotation angle of the screw nut (21) through the code disk.

5. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 1, characterized in that: A force-sensitive sensor (12) is provided on a side of the housing facing away from the port, the force-sensitive sensor (12) being fixedly connected to the fisheye bearing (9), and the force-sensitive sensor (12) being used to detect the magnitude of stress applied to the two fisheye bearings (9).

6. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 5, characterized in that: The fisheye bearing (9) comprises a connecting portion (91) for connecting the force sensitive sensor (12) and the push rod (3), and a mounting portion (92) for connecting the bearing rotating body (10), and each of the connecting portions (91) and the push rod (3) are coaxially arranged; the bearing rotating body (10) is provided with a connecting hole (102), and the connecting hole (102), the limiting groove (101) and the mounting portion (92) are all coaxially arranged.

7. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 6, characterized in that: Each of the connecting portions (91) is threadedly connected to an adjusting nut (16), and the adjusting nut (16) adjusts the screwing angle of each of the fisheye bearings (9) so that the axes of the connecting holes (102) are parallel.

8. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 2, characterized in that: The housing comprises a casing (1) and a front cover (7) and a rear cover (8) threadedly connected to both ends of the casing (1); the front cover (7) has a receiving portion extending along the feeding direction of the push rod (3); the guide sleeve (4) is arranged in the receiving portion; and a sealing ring (11) is arranged in the port of the receiving portion facing away from the casing (1).

9. The linear actuator with a two-degree-of-freedom fisheye bearing according to claim 8, characterized in that: The outer wall of the screw nut (21) near one end of the front cover (7) is provided with a shaft shoulder and a four-point contact bearing (13); the sleeve of the screw nut (21) near one end of the rear cover (8) is provided with a deep groove ball bearing (14); the four-point contact bearing (13) is fixedly connected to the shaft shoulder via a bearing pressure ring (17); a bearing seat (15) is clamped between the deep groove ball bearing (14) and the housing (1); the deep groove ball bearing (14) is tensioned and fixed in the bearing seat (15).

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