A reverse end plug type ball screw pair

Abstract

The application provides a reverse end plug type ball screw pair, and relates to the technical field of ball screw pairs, which comprises a ball screw, a first thread raceway and two fan-shaped grooves are arranged on the ball screw, a return ball channel is formed between a first reverser and a second reverser, one end of the return ball channel is communicated with the first thread raceway, and the other end of the return ball channel is communicated with an axial through hole of the ball screw; a ball nut is screwed on the ball screw; a second thread raceway is arranged in an inner hole of the ball nut; a steel ball is arranged in the thread raceway and the return ball channel; the steel ball rolls along the thread raceway, and when the steel ball rolls to the end of the thread raceway, the steel ball enters the return ball channel and the axial through hole of the ball screw, and then returns to the thread raceway from the other end of the return ball channel, so that the ball nut drives the ball screw to move along the axial direction through the steel ball, thereby solving the problems of low efficiency and serious heating of the reverse ball screw pair.

Description

Technical Field

[0001] This application relates to the field of ball screw pair technology, and more particularly to a reversible end-plug type ball screw pair. Background Technology

[0002] As a core functional component for achieving precise motion control in humanoid robots, linear joints function similarly to the bones and muscles of the human body. They are responsible for converting the rotational motion of motors into linear motion and transmitting force and torque. Their performance indicators, such as load-bearing capacity, stiffness, and motion speed, directly determine the overall motion accuracy, load capacity, and dynamic response characteristics of the humanoid robot.

[0003] Currently, the transmission mechanisms used in linear joints of humanoid robots mainly include reversible planetary roller screw pairs, trapezoidal screw pairs, and harmonic reducers combined with ordinary screws. Among these, the reversible planetary roller screw pair has become the most mainstream transmission solution in humanoid robot linear joints due to its advantages such as multiple rollers participating in load-bearing simultaneously, large contact area, high load-bearing capacity, and long service life. This solution achieves motion transmission through the rolling contact between the nut and the screw, theoretically possessing high transmission accuracy and rigidity. However, during operation, complex sliding friction exists between the rollers, screw, and nut in the reversible planetary roller screw pair, causing a large amount of input energy to dissipate as heat, resulting in a significant temperature rise inside the joint.

[0004] To address the severe heat generated during the operation of reversible planetary roller screw pairs, auxiliary cooling devices such as fans, liquid cooling systems, heat sinks, and even ice blocks are typically added externally to the joints. This not only increases the overall weight and structural complexity of the humanoid robot but also occupies internal space, affecting the robot's integration and endurance. Simultaneously, the continuous high-temperature environment accelerates the aging and failure of the lubricating grease inside the screw pair, reducing transmission accuracy and lifespan, and in severe cases, even causing joint jamming or performance degradation. Furthermore, the cooling devices themselves consume additional electrical energy, further shortening the humanoid robot's operating time. Summary of the Invention

[0005] This application provides a reverse end-plug type ball screw pair to solve the technical problems of low efficiency and severe heat generation in existing reverse ball screw pairs.

[0006] This application provides a reversible end-plug type ball screw pair, including: A ball screw is provided with a first thread raceway and two sector grooves; the sector grooves are used to install a first reverser and a second reverser; a ball return channel is formed between the first reverser and the second reverser, one end of the ball return channel is connected to the first thread raceway, and the other end of the ball return channel is connected to the axial through hole of the ball screw. A ball nut is disposed on the outside of the ball screw and screwed to the ball screw; the inner hole of the ball nut is provided with a second thread raceway; The steel ball is disposed within the thread raceway formed by the first thread raceway and the second thread raceway, and also disposed within the ball return channel; The steel ball rolls along the threaded raceway. When the steel ball rolls to the end of the threaded raceway, it enters the ball return channel. The steel ball enters the axial through hole of the ball screw along the ball return channel. The steel ball passes through the axial through hole and enters the ball return channel at the other end, returning to the threaded raceway, so that the ball nut drives the ball screw to move along the axial direction through the steel ball.

[0007] In some embodiments, a spring sheet is provided on the outside of the first inverter, and an elongated groove is provided between the spring sheet and the first inverter; the spring sheet is provided with a vertical state position and a bent state position; A snap fastener is provided on the side of the spring sheet away from the long groove, and the snap fastener is engaged in the mounting groove of the fan-shaped groove; the snap fastener has a conical structure. When the spring sheet changes from the vertical position to the bent position, the buckle disengages from the mounting groove, causing the first reverser to be disassembled from the ball screw. When the first reverser is installed on the ball screw, it is installed in the sector groove. As the first reverser enters the sector groove, the spring plate tilts to one side of the long groove under the action of the buckle. When the first reverser is fully inserted into the sector groove, the spring plate changes from the bent state to the vertical state, and the buckle engages in the mounting groove, so that the first reverser is installed on the ball screw.

[0008] In some embodiments, the first reverser is provided with a positioning pin hole and a first ball return channel, the cross-section of the first ball return channel being semi-circular; the second reverser is provided with a cylindrical pin and a second ball return channel, the cross-section of the second ball return channel being semi-circular. The cylindrical pin is engaged with the positioning pin hole, which engages the second reverser with the first reverser, thus forming a ball return channel between the first ball return channel and the second ball return channel.

[0009] In some embodiments, the first inverter is provided with a first curved surface; the second inverter is provided with a second curved surface; When the second inverter is engaged with the first inverter via the cylindrical pin, the first curved surface fits against the second curved surface.

[0010] In some embodiments, the centerline of the bead return channel is a multi-segment tangent three-dimensional spatial L-curve, the L-curve is continuous and its partial derivatives are second-differentiable; the L-curve is formed by the intersection of a first cylindrical surface and a second cylindrical surface, the first cylindrical surface being the surface where the first bead return channel is located, and the second cylindrical surface being the surface where the second bead return channel is located. The parametric equation of the L-curve is: ; ; ; In the formula, t represents an arbitrary parameter; a and b represent parameters controlling the radius of curvature of the first cylindrical directrix arc, with the ratio of the radius of curvature to the radius of the steel ball being greater than 2.5; c represents a parameter controlling the center coordinates of the L-curve; and R represents the radius of curvature of the second cylindrical directrix arc. The coordinates of the arc center are represented by the directrix of the second cylindrical surface.

[0011] In some embodiments, a ball block is provided on the outside of the first reverser. The ball block is a structure that gradually becomes thicker by cutting the curved surface where the thread raceway is located and the L-curved surface where the return ball channel is located. The ball block is used to control the steel ball to enter the return ball channel.

[0012] In some embodiments, the length of the ball nut is in the range of 5 to 10 times the length of the ball screw.

[0013] In some embodiments, the normal cross-sections of the first thread raceway and the second thread raceway are parabolic structures.

[0014] In some embodiments, the diameter of the ball return channel is 1.1 times the diameter of the steel ball; the internal thread length of the ball nut is in the range of 5 to 10 times the pitch diameter.

[0015] This application provides a reversing end-plug type ball screw assembly, comprising: a ball screw, the ball screw having a first threaded raceway and two sector grooves; the sector grooves being used to install a first reverser and a second reverser; a ball return channel being formed between the first reverser and the second reverser, one end of the ball return channel being connected to the first threaded raceway, and the other end of the ball return channel being connected to an axial through hole of the ball screw; a ball nut, the ball nut being disposed on the outside of the ball screw, the ball nut being screwed to the ball screw; the inner hole of the ball nut having a second threaded raceway; and steel balls, the steel balls being disposed in the first threaded raceway and the second threaded raceway. The ball screw is formed by the threaded raceway and is located in the ball return channel. The steel ball rolls along the threaded raceway. When the steel ball reaches the end of the threaded raceway, it enters the ball return channel. The steel ball then enters the axial through-hole of the ball screw along the ball return channel. The steel ball passes through the axial through-hole and enters the ball return channel at the other end, returning to the threaded raceway. This causes the ball nut to drive the ball screw to move along the axial direction via the steel ball, thereby improving the efficiency of the reverse end-plug type ball screw pair, avoiding severe overheating in the reverse planetary roller screw pair, and achieving higher operating speeds due to its high efficiency and low heat generation. Attached Figure Description

[0016] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the reverse end plug type ball screw pair in this application; Figure 2 This is a schematic diagram of the structure of the reverser located in the axial through hole of the ball screw in this application; Figure 3 This is a schematic diagram of the structure of the first inverter in this application; Figure 4 This is a schematic diagram of the first curved surface in this application; Figure 5 This is a schematic diagram of the first return channel in this application; Figure 6 This is a schematic diagram of the structure of the second inverter in this application; Figure 7 This is a schematic diagram of the second curved surface in this application; Figure 8 This is a schematic diagram of the second return channel in this application; Figure 9 This is a schematic diagram of the intersection of the first and second cylindrical surfaces in this application on the XOY plane; Figure 10 This is a schematic diagram of the intersection of the first and second cylindrical surfaces in this application on the XOZ plane.

[0018] Explanation of reference numerals in the attached figures: 1-Ball screw; 2-First reversing device; 21-Spring plate; 22-Long groove; 23-Snap fastener; 24-Positioning pin hole; 25-First ball return channel; 251-First cylindrical surface; 26-First curved surface; 27-Ball block; 3-Second reversing device; 31-Cylindrical pin; 32-Second ball return channel; 321-Second cylindrical surface; 33-Second curved surface; 4-Ball nut; 5-Steel ball. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0020] Because in some technologies, reverse ball screw pairs are inefficient and generate significant heat, this application provides a reverse end-plug type ball screw pair to solve this problem. The reverse end-plug type ball screw pair is described below: like Figure 1 The diagram shown is a structural schematic of the reverse end plug type ball screw pair in this application.

[0021] This application provides a reversible end-plug type ball screw pair, including: Ball screw 1, wherein the ball screw 1 is provided with a first thread raceway and two sector grooves; the sector grooves are used to install a first reverser 2 and a second reverser 3, such as Figure 2 As shown; a ball return channel is formed between the first reverser 2 and the second reverser 3. One end of the ball return channel is connected to the first thread raceway, and the other end of the ball return channel is connected to the axial through hole of the ball screw 1.

[0022] A ball nut 4 is disposed on the outside of the ball screw 1 and screwed to the ball screw 1; the inner hole of the ball nut 4 is provided with a second thread raceway; the length of the ball nut 4 is within the range of 5 to 10 times the length of the ball screw 1.

[0023] The steel ball 5 is disposed within the thread raceway formed by the first thread raceway and the second thread raceway, and also disposed within the ball return channel.

[0024] The steel ball 5 rolls along the threaded raceway. When the steel ball 5 rolls to the end of the threaded raceway, it enters the return ball channel. The steel ball 5 enters the axial through hole of the ball screw 1 along the return ball channel and returns to the threaded raceway through the axial through hole. This causes the ball nut 4 to drive the ball screw 1 to move along the axial direction through the steel ball 5.

[0025] This application provides a reversing end-plug type ball screw assembly, including: a ball screw 1, a ball nut 4, steel balls 5, a first reversing device 2, and a second reversing device 3, as shown below. Figure 1 As shown. The ball screw 1 has a threaded raceway and two fan-shaped slots machined for mounting reversing devices. Each fan-shaped slot houses a reversing assembly consisting of a first reversing device 2 and a second reversing device 3. The reversing assembly includes a ball return channel, one end of which connects to the threaded raceway of the ball screw 1, and the other end leads to the axial through-hole of the ball screw 1. The ball return channel is a three-dimensional L-curve with multiple tangent segments at its center. The L-curve is continuous and its partial derivatives are second-differentiable. The ball return channel is formed by rotating a groove orthogonal to the L-curve. The diameter of the ball return channel is 1.1 times the diameter of the steel ball 5. The internal thread length of the ball nut 4 is 5 to 10 times its pitch diameter. A raceway with a parabolic cross-section is ground into the inner hole of the ball nut 4. The normal cross-section of the helical raceway of the ball screw 1 is also parabolic. The double parabolic raceway allows adjustment of the curvature of the ball contact area, thus facilitating the adjustment of the rated load of the reversing end-plug ball screw pair. During operation, the ball nut 4 rotates, and the raceway of the ball nut 4 drives the ball screw 1 to move back and forth along the axial direction via the steel balls 5. With the ball screw 1 as a reference, the steel balls 5 roll along the threaded raceway of the ball screw 1. When the steel balls roll to the end of the threaded raceway, they enter the return ball channel of the reversing component. Along the return ball channel, the steel balls 5 enter the axial through-hole of the ball screw 1, pass through the axial through-hole, enter the return ball channel of the reversing component at the other end, and then return to the threaded raceway of the ball screw 1. The reversing end-plug ball screw pair provided in this application has a compact structure, a large load-bearing capacity with its double parabolic raceway, and can be applied to linear joints of humanoid robots.

[0026] like Figure 3 The diagram shown is a schematic diagram of the structure of the first inverter in this application.

[0027] In this embodiment, a spring sheet 21 is provided on the outside of the first inverter 2, and an elongated groove 22 is provided between the spring sheet 21 and the first inverter 2; the spring sheet 21 is provided with a vertical state position and a bent state position.

[0028] The spring sheet 21 is provided with a buckle 23 on the side away from the long groove 22, and the buckle 23 is engaged in the mounting groove of the fan-shaped groove; the buckle 23 has a conical structure.

[0029] When the spring sheet 21 changes from the vertical position to the bent position, the buckle 23 disengages from the mounting groove, causing the first reverser 2 to be disassembled from the ball screw 1.

[0030] When the first reverser 2 is installed on the ball screw 1, the first reverser 2 is installed in the sector groove; as the first reverser 2 enters the sector groove, the spring plate 21 tilts to one side of the long groove 22 under the action of the buckle 23; when the first reverser 2 is fully entered into the sector groove, the spring plate 21 changes from the bent state position to the vertical state position, and the buckle 23 is engaged in the mounting groove, so that the first reverser 2 is installed on the ball screw 1.

[0031] Specifically, the reversing assembly of the ball screw pair consists of a first reversing device 2 and a second reversing device 3. The assembly includes a ball return channel, the centerline of which is a multi-segment tangent three-dimensional L-curve. The first curved surface 26 of the first reversing device 2 mates with the second curved surface 33 of the second reversing device 3. Two locating pin holes 24 are located on the mating surfaces. A corresponding cylindrical pin 31 on the second reversing device 3 mates with the locating pin holes 24. A long groove 22 is located at the lower part of the first reversing device 2, and a spring plate 21 is located to the right of the long groove 22. During normal operation, the spring plate 21 is in a vertical position. When disassembling the reversing assembly, simply bend the spring plate 21 towards the long groove 22, and the clip 23 on the right side of the spring plate will disengage from the corresponding mounting slot of the ball screw 1. The latch 23 has a tapered structure that is wider on the outside and narrower on the inside. When installing the reverser assembly, as the assembly enters, the spring plate 21 gradually tilts towards the long slot 22 under the action of the tapered surface of the latch 23. After the reverser assembly is in place, the latch 23 springs into the corresponding mounting slot of the ball screw 1 under the action of the spring plate 21. The latch 23 closes and prevents the reverser assembly from falling off.

[0032] like Figure 6 The diagram shown is a schematic diagram of the structure of the second inverter in this application.

[0033] In this embodiment, the first reverser 2 is provided with a positioning pin hole 24 and a first ball return channel 25, such as Figure 5 As shown, the cross-section of the first bead return channel 25 is semi-circular; the second reverser 3 is provided with a cylindrical pin 31 and a second bead return channel 32, as shown. Figure 8 As shown, the cross-section of the second bead return channel 32 is semi-circular.

[0034] The cylindrical pin 31 engages with the positioning pin hole 24, causing the second reverser 3 to engage with the first reverser 2, thus forming a ball return channel between the first ball return channel 25 and the second ball return channel 32. The normal cross-section of the first and second thread raceways is a parabolic structure. The diameter of the ball return channel is 1.1 times the diameter of the steel ball 5; the internal thread length of the ball nut 4 is within the range of 5 to 10 times its pitch diameter.

[0035] In this embodiment, the first inverter 2 is provided with a first curved surface 26, such as... Figure 4 As shown; the second inverter 3 is provided with a second curved surface 33, as... Figure 7 As shown.

[0036] When the second inverter 3 is engaged with the first inverter 2 by the cylindrical pin 31, the first curved surface 26 is attached to the second curved surface 33.

[0037] Specifically, the right side of the second reverser 3 is a second curved surface 33, which contacts the first curved surface 26 of the first reverser 2. There are two cylindrical pins 31 on the second curved surface 33. When installing them with the positioning pin holes 24 on the first reverser 2, the two cylindrical pins 31 need to be inserted into the positioning pin holes 24. At this time, the first ball return channel 25 of the first reverser 2, with a semi-circular cross-section, and the second ball return channel 32 of the second reverser 3, with a semi-circular cross-section, form a complete circular channel. When the product is working, the steel ball 5 circulates and rolls in this combined channel.

[0038] In this embodiment, the centerline of the bead return channel is a multi-segment tangent three-dimensional spatial L-curve, the L-curve is continuous and its partial derivatives are second-differentiable; the L-curve is formed by the intersection of a first cylindrical surface 251 and a second cylindrical surface 321, the first cylindrical surface 251 being the surface where the first bead return channel 25 is located, and the second cylindrical surface 321 being the surface where the second bead return channel 32 is located. The parametric equation of the L-curve is: ; ; ; In the formula, t represents an arbitrary parameter; a and b represent parameters controlling the radius of curvature of the arc of the first cylindrical surface 251, and the ratio of the radius of curvature to the radius of the steel ball 5 is greater than 2.5; c represents a parameter controlling the center coordinates of the L curve; and R represents the radius of curvature of the arc of the second cylindrical surface 321. The coordinates of the arc center of the second cylindrical surface 321 are represented by the coordinates of the arc center.

[0039] Specifically, the centerline of the return curve is an L-curve with continuous second-order partial derivatives. The L-curve is formed by the intersection of two cylindrical surfaces, such as... Figure 9 and Figure 10 As shown, the first cylindrical surface 251 and the second cylindrical surface 321 intersect to form an L-curve. The directrix AB segment of the first cylindrical surface 251 in the XOY plane is shown below. Figure 9 As shown, the equation of the curve segment AB is as follows: .

[0040] The second cylindrical surface 321 has a directrix in the XOZ plane that is a large-radius circular arc curve, such as... Figure 10 As shown, the equation of the directrix is ​​as follows: .

[0041] In this embodiment, a ball block 27 is provided on the outside of the first reverser 2. The ball block 27 is a structure that gradually becomes thicker by cutting the surface where the thread raceway is located and the L-shaped surface where the return ball channel is located. The ball block 27 is used to control the steel ball 5 to enter the return ball channel.

[0042] Specifically, the outer side of the first reverser 2 is the bead block 27, which is a structure formed by cutting a solid with a spiral surface and an L-shaped surface, gradually becoming thicker. Its main function is to control the steel ball 5 to enter the return bead channel.

[0043] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the embodiments of this application. It should be understood that the above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solutions of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. A reversible end-plug type ball screw pair, characterized in that, include: A ball screw (1) is provided with a first thread raceway and two sector grooves; the sector grooves are used to install a first reverser (2) and a second reverser (3); the first reverser (2) is provided with a first ball return channel (25), the cross-section of the first ball return channel (25) is semi-circular; the second reverser (3) is provided with a second ball return channel (32), the cross-section of the second ball return channel (32) is semi-circular; a ball return is formed between the first ball return channel (25) and the second ball return channel (32). Channel; one end of the ball return channel is connected to the first thread raceway, and the other end of the ball return channel is connected to the axial through hole of the ball screw (1); the center line of the ball return channel is a multi-segment tangent three-dimensional space L curve, the L curve is continuous and the second derivative is continuous; the L curve is formed by the intersection of the first cylindrical surface (251) and the second cylindrical surface (321), the first cylindrical surface (251) is the surface where the first ball return channel (25) is located, and the second cylindrical surface (321) is the surface where the second ball return channel (32) is located; The parametric equation of the L-curve is: ； ； ； In the formula, t Characterized as arbitrary parameters; a , b The parameter is characterized as the radius of curvature of the directrix arc of the first cylindrical surface (251), and the ratio of the radius of curvature to the radius of the steel ball (5) is greater than 2.5; c These parameters are used to control the coordinates of the center of the L-curve. R The radius of the arc is represented by the directrix of the second cylindrical surface (321). The coordinates of the arc center of the directrix of the second cylindrical surface (321) are represented; A ball nut (4) is provided on the outside of the ball screw (1) and is screwed to the ball screw (1); the inner hole of the ball nut (4) is provided with a second thread raceway; Steel ball (5), the steel ball (5) is disposed in the thread raceway formed by the first thread raceway and the second thread raceway, and is disposed in the ball return channel; Among them, the first reverser (2) is provided with a ball-blocking block (27) on the outside. The ball-blocking block (27) is a structure that gradually becomes thicker by cutting the surface where the thread raceway is located and the L-shaped surface where the return ball channel is located. The ball-blocking block (27) is used to control the steel ball (5) to enter the return ball channel. The steel ball (5) rolls along the threaded raceway. When the steel ball (5) rolls to the end of the threaded raceway, it enters the return ball channel. The steel ball (5) enters the axial through hole of the ball screw (1) along the return ball channel. The steel ball (5) passes through the axial through hole and enters the return ball channel at the other end, returning to the threaded raceway, so that the ball nut (4) drives the ball screw (1) to move along the axial direction through the steel ball (5).

2. The reversing end-plug type ball screw pair according to claim 1, characterized in that, A spring plate (21) is provided on the outside of the first inverter (2), and a long groove (22) is provided between the spring plate (21) and the first inverter (2); the spring plate (21) is provided with a vertical state position and a bent state position; A buckle (23) is provided on the side of the spring sheet (21) away from the long groove (22), and the buckle (23) is engaged in the mounting groove of the fan-shaped groove; the buckle (23) has a conical structure; When the spring sheet (21) changes from the vertical position to the bent position, the buckle (23) disengages from the mounting groove, causing the first reverser (2) to be disassembled from the ball screw (1). When the first reverser (2) is installed on the ball screw (1), the first reverser (2) is installed in the sector groove; when the first reverser (2) enters the sector groove, the spring plate (21) tilts to one side of the long groove (22) under the action of the buckle (23); when the first reverser (2) is fully entered into the sector groove, the spring plate (21) changes from the bent state position to the vertical state position, and the buckle (23) is engaged in the mounting groove, so that the first reverser (2) is installed on the ball screw (1).

3. The reversing end-plug type ball screw pair according to claim 1, characterized in that, The first inverter (2) is provided with a positioning pin hole (24); the second inverter (3) is provided with a cylindrical pin (31); The second reverser (3) is engaged with the first reverser (2) by the cylindrical pin (31) being engaged with the positioning pin hole (24).

4. A reversing end-plug type ball screw pair according to claim 3, characterized in that, The first inverter (2) is provided with a first curved surface (26); the second inverter (3) is provided with a second curved surface (33); When the second inverter (3) is engaged with the first inverter (2) by the cylindrical pin (31), the first curved surface (26) is attached to the second curved surface (33).

5. A reversing end-plug type ball screw assembly according to claim 1, characterized in that, The length of the ball nut (4) is within 5 to 10 times the length of the ball screw (1).

6. A reversing end-plug type ball screw pair according to claim 1, characterized in that, The normal cross-sections of the first and second thread raceways are parabolic.

7. A reversing end-plug type ball screw pair according to claim 1, characterized in that, The diameter of the ball return channel is 1.1 times the diameter of the steel ball (5); the internal thread length of the ball nut (4) is within the range of 5 to 10 times the mean diameter.

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