High-rigidity ball screw

Abstract

The invention discloses a high-rigidity ball screw, which belongs to a mechanical engineering transmission device and is characterized in that a return raceway and a curve raceway are arranged between the inner wall and the outer wall of a nut body, the return raceway is communicated to a nut load rolling groove through the curve raceway, and the nut load rolling groove and a screw load rolling groove define a load raceway; the load raceway, the curve raceway and the return raceway form a circulation channel, and the balls can circularly move in the circulation channel under the driving of the lead screw body. Thus, an embedded spiral backflow raceway structure is formed, and the number of load balls is increased through the return raceway and the curve raceway. Compared with a traditional insertion pipe type ball screw and a traditional internal circulation type ball screw, the embedded ball nut with the same appearance comprises a large-capacity load ball located in a return stroke raceway, so that more axial and radial loads from the aspects of workpieces, clamps, workbenches, the self weight of the screw and the like can be borne, and the tension and compression rigidity of the screw is compensated.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical engineering transmission devices, in particular to a high-rigidity ball screw. Background Art

[0002] The ball screw is the main transmission component of CNC machine tools, and its deformation directly affects the surface quality of the workpiece being processed. However, the tensile and compressive stiffness is a measure of the ball screw's ability to resist deformation when subjected to tension or pressure, which is the main reason for the deformation of the ball screw. Fig.21 As shown in the figure, when subjected to external forces, ball screws with high tensile and compressive stiffness can better maintain their position stability, thereby ensuring the accuracy and reliability of the equipment; while ball screws with low tensile and compressive stiffness are prone to deformation and displacement, affecting the working accuracy and stability of the equipment. However, few people have studied and analyzed the variation law of tensile and compressive stiffness and designed compensation. Therefore, analyzing the variation of tensile and compressive stiffness of ball screws and providing feasible solutions are of reference significance for ball screw stiffness compensation. Summary of the invention

[0003] The object of the present invention is to provide a high-rigidity ball screw that can compensate for the tensile and compressive stiffness of the screw in order to solve the above-mentioned problem.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A high-rigidity ball screw comprises a screw body, a nut body and a ball. The outer wall of the screw body is provided with a screw load rolling groove, which spirally extends from the left end of the screw body to the right end of the screw body. The inner wall of the nut body is provided with a nut load rolling groove, which spirally extends from the left end of the nut body to the right end of the nut body. The nut body is sleeved on the screw body. The nut load rolling groove and the screw load rolling groove form a load rolling path. The load rolling path extends from the left end of the nut body to the right end of the nut body in a cylindrical spiral line. The load rolling path is adapted to the ball. The nut body is provided with a return rolling path and a curved rolling path adapted to the ball. The return raceway is between the load raceway and the outer wall of the nut body, the return raceway is spirally extended from the left end of the nut body to the right end of the nut body, the curved raceway is used in pairs with the return raceway, the curved raceway includes a left curved raceway and a right curved raceway, the left end of the return raceway extends inwardly through the left curved raceway to the left end of the nut load rolling groove, the right end of the return raceway extends inwardly through the right curved raceway to the right end of the nut load rolling groove, the load raceway, the curved raceway and the return raceway form a circulation channel, the circulation channel is arranged with balls, and the balls can circulate in the circulation channel when driven by the screw body.

[0006] Among them, the pitch of the return raceway is greater than or equal to the nut load rolling groove.

[0007] The central axis of the curved raceway is in the shape of a spline curve, and it (the spline curve) is tangent to the central axis of the load raceway and tangent to the central axis of the return raceway, or it (the spline curve) is tangent to the central axis of the load raceway and smoothly connected to the central axis of the return raceway, or it (the spline curve) is smoothly connected to the central axis of the load raceway and tangent to the central axis of the return raceway. In this way, a smoothly connected raceway is formed.

[0008] The spiral direction of the return raceway is opposite to that of the load raceway. In this way, the ball is driven by the screw to move in the positive spiral direction along the load raceway, and then smoothly enters the return raceway along the spiral direction, and then moves in the reverse spiral direction along the return raceway, and then smoothly enters the load raceway along the spiral direction, completing the cycle smoothly.

[0009] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0010] The present invention provides a return raceway and a curved raceway between the inner wall and the outer wall of the nut body, and the return raceway is connected to the nut load groove via the curved raceway, the nut load groove and the screw load groove form a load raceway, the load raceway, the curved raceway and the return raceway form a circulation channel, and the balls can circulate in the circulation channel when the screw body is driven. In this way, an embedded spiral return raceway structure is formed, and the number of load balls is increased by using the return raceway and the curved raceway. Compared with traditional insert-tube type and internal circulation type ball screws, the embedded ball nut of the same shape contains a large capacity of load balls in the return raceway, so that it can bear more axial and radial loads from the workpiece, fixture, workbench, screw deadweight, etc., and compensate for the tensile and compressive stiffness of the screw. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of ball screw nut example 1 of the present invention. Figure 2 yes Figure 1 An axial cross-section of . Figure 3 yes Figure 1 Another axial cross-sectional view of . Figure 4 yes Figure 1 A cross-sectional view of . Figure 5 yes Figure 1 Another cross-sectional view of . Figure 6 yes Figure 1 Schematic diagram of the end sealing structure.

[0012] Figure 7 It is a structural schematic diagram of ball screw nut example 2 of the present invention. Figure 8 yes Figure 7 Schematic diagram of the nut main structure. Fig. 9 yes Figure 8 Another perspective structural diagram of . Fig.10 yes Figure 7 Schematic diagram of the upper structure. Fig.11 yes Fig.10 Another perspective structural diagram of . Fig.12 yes Figure 7 Schematic diagram of the lower set structure. Fig.13 yes Figure 7 Schematic diagram of the processing process.

[0013] Fig.14 It is a structural schematic diagram of ball screw nut example 3 of the present invention. Fig.15 yes Fig.14 An axial cross-section of . Fig.16 yes Fig.14 Another axial cross-sectional view of . Fig.17 yes Fig.14 A cross-sectional view of . Fig.18 yes Fig.14 Another cross-sectional view of . Fig.19 yes Fig.14 Another cross-sectional view of . Fig. 20 yes Fig.14 Another cross-sectional view of .

[0014] Fig.21 This is a schematic diagram of an experiment in which an existing ball screw is deformed when subjected to load due to insufficient stiffness. Fig. 22 It is a curve diagram showing the relationship between the tensile and compressive stiffness of the existing ball screw and the distance between the center of the nut and the bearing fulcrum. Fig.23 It is a schematic diagram of the tensile and compressive stiffness distribution of the existing ball screw. Fig.24 This is a schematic diagram showing how the surface processing appearance is affected by changes in the screw stiffness. Fig.25 This is an example connection diagram of the right-handed load raceway and the left-handed return raceway of the present invention. Fig.26 This is another example connection diagram of a right-handed load raceway and a left-handed return raceway according to the present invention. Fig. 27 This is an example connection diagram of a right-handed load raceway and a right-handed return raceway of the present invention. Fig.28 It is a schematic diagram of the principle of the circulating ball raceway motion of the present invention. Fig.29 It is a simulation schematic diagram comparing the recirculating raceway ball compensation before and after the present invention. Fig.30 It is a curve comparison diagram of the relationship between the radial deformation of the screw and the distance between the center of the nut and the fulcrum of the single-sided bearing of the present invention. Fig.31 It is a comparison diagram of the relationship curve between the compressive stiffness of the ball screw of the present invention and the effective number of turns of the load ball. Fig.32 It is a comparison diagram of the relationship curve between the rated dynamic load of the ball screw of the present invention and the effective number of turns of the load ball. DETAILED DESCRIPTION

[0015] The specific implementation of the invention is further described below with reference to the accompanying drawings.

[0016] Example 1

[0017] like Figure 1-Figure 5 As shown, a high-rigidity ball screw of this embodiment 1 includes a screw body, a nut body 1, and a ball. The outer wall of the screw body is provided with a screw load groove, which spirally extends from the left end of the screw body to the right end of the screw body. The inner wall (inner boring wall) 11 of the nut body 1 is provided with a nut load groove 10, which spirally extends from the left end of the nut body to the right end of the nut body. The nut body 1 is sleeved on the screw body, and the nut load groove 10 and the screw load groove form a load raceway. The load raceway extends from the left end of the nut body to the right end of the nut body in a cylindrical spiral line. The load raceway is adapted to the ball, and the nut body 1 is provided with a return raceway 40 and a curved raceway adapted to the ball. The return raceway 40 is located between the load raceway and the outer wall (outer cylindrical wall) 12 of the nut body 1. The return raceway 40 spirally extends from the left end of the nut body to the right end of the nut body. The curved raceway is used in pairs with the return raceway. The curved raceway includes a left curved raceway 20 and a right curved raceway 30. The left end of the return raceway 40 extends inward through the left curved raceway 20 to the left end of the nut load rolling groove 10, and the right end of the return raceway 40 extends inward through the right curved raceway 30 to the right end of the nut load rolling groove 10. The load raceway, the curved raceway and the return raceway form a circulation channel, and the circulation channel is arranged with balls, and the balls can circulate in the circulation channel when the screw body is driven.

[0018] The return raceway 40 is in the shape of a cylindrical spiral, a spherical spiral or a conical spiral. For example, the return raceway is in the shape of a conical spiral, the number of the return raceway is one, and the radial width thereof gradually increases from left to right. For example, the return raceway is in the shape of two spherical spirals or conical spirals arranged in opposite directions, the number of the return raceway is one, and the radial width thereof first increases and then decreases from left to right. Figure 1-Figure 5 As shown, in this embodiment 1, a cylindrical spiral return raceway is used as an example for explanation, and the number of the return raceway is 1.

[0019] The return raceway 40 has a circular cross section and an inner diameter that matches the ball so as to be fitted therein.

[0020] The pitch of the return raceway 40 is greater than or equal to the nut load groove 10. Figure 1-Figure 5 As shown, the cross-section of the nut load rolling groove has a semicircular groove diameter of 1 cm, an axial length of 30 cm, and a pitch of 2 cm. The pitch of the return raceway 40 is twice that of the nut load rolling groove 10, which is 4 cm.

[0021] The central axis of the curved raceway is in the shape of a spline curve, including spline curves such as circular arcs and elliptical arcs, and it (the spline curve) is tangent to the central axis of the load raceway and tangent to the central axis of the return raceway, or it (the spline curve) is tangent to the central axis of the load raceway and smoothly connected to the central axis of the return raceway, or it (the spline curve) is smoothly connected to the central axis of the load raceway and tangent to the central axis of the return raceway. In this way, a smoothly connected raceway is formed. Figure 4-Figure 5 As shown, the central axis of the curved raceway in this embodiment 1 is illustrated by taking a circular arc as an example; the central axis of the left curved raceway 20 is tangent to the central axis of the return raceway 40, and smoothly intersects with the central axis of the nut load groove 10, thereby smoothly connecting; the central axis of the right curved raceway 30 is tangent to the central axis of the return raceway 40, and smoothly intersects with the central axis of the nut load groove 10, thereby smoothly connecting.

[0022] The spiral direction of the return raceway and the load raceway can be the same spiral direction, or the opposite spiral direction. Figure 1-Figure 5 As shown, this embodiment 1 is described by taking the spiral direction of the load raceway as right-handed and the spiral direction of the return raceway as left-handed, and the return raceway 40 is opposite to the spiral direction of the load raceway, and the number of the return raceway 40 is 1. In this way, the ball is driven by the screw body to move along the load raceway in the positive spiral direction, and then smoothly enters the return raceway along the spiral direction, and then moves along the return raceway in the reverse spiral direction, and then smoothly enters the load raceway along the spiral direction, and smoothly completes the cycle motion.

[0023] The processing method of the nut body is as follows: S1. Design processing parameters: Use 3D software to design the nut body model and the nut load groove, curved raceway and return raceway on it, so that each return raceway is smoothly connected to the nut load groove, and obtain the processing parameters; S2. Perform 3D printing according to the processing parameters: Output the printing drawings according to the 3D software, and use metal 3D printing technology to print the nut body. Among them, metal 3D printing technology is an existing technology, and its metal printing materials include titanium alloy, aluminum alloy, stainless steel, mold steel or nickel-based high-temperature alloy, etc., usually using 316L stainless steel or A1Si10Mg aluminum alloy.

[0024] During assembly and use, the nut body is sleeved on the screw body, and then the balls are inserted one by one through the load raceway at the through end until it is full and the load raceway is blocked. After assembly is completed, the screw can be rotatably equipped to application equipment such as CNC machine tools; the load raceways of the screw and the nut body are cylindrical spiral lines. When in use, the motor is started to drive the screw to rotate forward or reverse, thereby driving the nut body to move left or right through the balls. Among them, the load raceway blocking structure is an existing technology, which is briefly described here; Figure 6As shown, a sealing hole 101 is machined at the end of the nut body, which is an axial blind hole that penetrates and protrudes into the load raceway. Then a screw is screwed in, and the side wall of the screw protrudes out of the load raceway beyond the matching clearance between the ball and the load raceway, thereby achieving the function of blocking the ball.

[0025] A return raceway and a curved raceway are provided between the inner wall and the outer wall of the nut body, and the return raceway is connected to the nut load groove through the curved raceway. The nut load groove and the screw load groove form a load raceway. The load raceway, the curved raceway and the return raceway form a circulation channel, and the balls can circulate in the circulation channel when driven by the screw body. In this way, an embedded spiral return raceway structure is formed, and the number of load balls is increased by utilizing the ball idle return stroke (return raceway and curved raceway). Compared with the traditional plug-in type and internal circulation type ball screws, the embedded ball nut of the same shape contains a large capacity of load balls in the return raceway, so that it can carry more axial and radial loads from the workpiece, fixture, workbench, screw deadweight, etc., and compensate for the tensile and compressive stiffness of the screw.

[0026] Example 2

[0027] The difference between this embodiment 2 and the aforementioned embodiment 1 lies in the method for preparing the nut body. For other matters not fully described, please refer to the aforementioned embodiment 1.

[0028] like Figure 7-Figure 13 As shown, a high-rigidity ball screw of this embodiment 1, its nut body includes a nut body 101 and a nut sleeve 102, the outer wall of the nut body 101 is provided with a main return groove 401, the inner wall of the nut sleeve 102 is provided with a sleeve return groove 402, the main return groove 401 and the sleeve return groove 402 surround a return raceway 40 adapted to the ball, and the return raceway 40 extends from the left end of the nut body to the right end of the nut body in a cylindrical spiral line. Correspondingly, the curve raceway has a main curve groove and a sleeve curve groove, for example, the right curve raceway 30 includes a main right curve raceway 301 and a sleeve right curve raceway 302. In this way, the nut body and the nut sleeve are fixed by welding or bolting, and the process is completed.

[0029] Taking bolt connection as an example, the processing method of the nut body is as follows:

[0030] Step S1, designing processing parameters: using 3D software to design a nut body model and a nut load rolling groove, a curved raceway and a return raceway thereon, so that each return raceway is smoothly connected to the nut load rolling groove; dividing the nut body model into a nut main body model and a nut sleeve body model with the nut and the cylindrical surface where the return raceway is located as the boundary, and obtaining processing parameters;

[0031] Step S2, performing turning processing according to the processing parameters obtained in step S1, including:

[0032] Clamp the nut body blank on the lathe and start the machine tool for processing; perform outer diameter cutting on the nut body blank to obtain the outer circle; perform rough machining and then fine machining of the main return groove on the outer circle; perform through hole machining on the nut body blank along the axis; enlarge the through hole and perform rough machining and then fine machining of the inner bore; perform rough machining and then fine machining of the inner bore to process the nut load groove; then, perform curved raceway machining to complete the nut body machining;

[0033] Clamp the nut sleeve blank on the lathe and start the machine tool for processing; process the through hole of the nut sleeve blank along the axis; enlarge the through hole and perform roughing and finishing on the inner bore; perform roughing and finishing on the inner bore, and process the sleeve return groove to complete the nut sleeve processing; cut the nut sleeve along the axial surface into an upper sleeve 1022 and a lower sleeve 1021, and process the countersunk hole 50 and the threaded hole 501 on both sides of both ends of the upper sleeve and the lower sleeve respectively;

[0034] According to the pre-marked alignment lines, snap the upper and lower sleeves onto the nut body, and then tighten the screws to complete the assembly installation; then, use the abrasive flow method to penetrate the return raceway and complete the polishing of each inner hole.

[0035] like Fig.13 As shown, the specific operation instructions of the turning process are as follows:

[0036] 1. Clamp the nut blank on the lathe and start the machine tool for processing; 2. Turn the outer circle and cut the outer diameter of the blank; 3. Process the external thread, first rough and then finely process the nut return raceway; 4. Drill and process the through hole of the blank along the axis; 5. Expand the hole, expand the through hole, and first rough and then finely process the inner bore; 6. Process the internal thread, first rough and then finely process the nut load groove; 7. Take out the nut body and complete the nut body (nut body) processing. Similarly, complete the nut shell processing, and the nut shell is cut into two parts by wire cutting to obtain the upper and lower sleeves, and the countersunk holes and threaded holes are opened. 8. Combined installation, the nut shell (upper and lower sleeves) that have been pre-processed and matched with the return groove thread are snapped and installed on the nut body, and the tightening screws are inserted; 9. Polish the inner hole, use the abrasive flow method to penetrate the return raceway to achieve the polishing effect.

[0037] Among them, the curved raceway is divided into a main curved groove and a sleeve curved groove. As shown in the figure, the right curved raceway 30 is directly processed into a circular channel on the end face according to the designed arc curve (or a nut plug is configured and the right curved raceway is supplemented at the end of the nut plug). If the left curved raceway is not on the end face, a small hole (a straight hole or an angle connection hole) is drilled and then expanded to achieve smooth connection.

[0038] In this way, the nut body is wrapped by the nut shell (nut sleeve), and the nut shell is connected by screws to complete the design of the rigidity enhanced nut (nut body).

[0039] Example 3

[0040] Based on Example 1 or 2, this Example 3 has a plurality of return raceway structures. For other unexplained details, please refer to the aforementioned Examples 1-2.

[0041] A high-rigidity ball screw of the present embodiment 3 has more than two return raceways. For example, the return raceway is in the shape of a cylindrical spiral, the more than two return raceways are on the same cylindrical surface, the pitch of each return raceway is the same, and each return raceway is staggered at a certain angle. For example, the return raceway is in the shape of a cylindrical spiral, the more than two return raceways are on different cylindrical surfaces, the pitch of each return raceway is the same, and each return raceway is staggered at a certain angle. For example, the return raceway is in the shape of a conical spiral, the more than two return raceways are on different conical surfaces, the pitch of each return raceway is the same, and each return raceway is staggered at a certain angle, and its radial width gradually increases from left to right.

[0042] like Figure 14-Figure 20 As shown, this embodiment 3 takes one load raceway combined with two cylindrical spiral lines as an example, the spiral direction of the nut load groove 10 is right-handed, and the spiral direction of the return raceways 40a and 40b is left-handed. The pitch of the return raceways 40a and 40b is twice that of the load groove. In the circumferential direction, the return raceways 40a and 40b are staggered with the nut load groove 10 by 90°, and in the axial direction, the return raceways 40a and 40b are staggered by 1 pitch. In this way, the left ends of the return raceways 40a and 40b are connected to the left end of the nut groove 10 through the left curve raceways 20a and 20b respectively, and the right ends of the return raceways 40a and 40b are connected to the right end of the nut groove 10 through the right curve raceways 30a and 30b respectively, and are realized by 3D metal printing or turning.

[0043] In this way, it is assembled on the screw, and the load raceway, the curved raceway and the return raceway form a circulation channel, and the ball can circulate in the circulation channel when the screw body is driven. Compared with the case of one return raceway, the flexibility of the ball and the mechanical properties of the nut will be improved by setting two return raceways, and the ball jamming phenomenon in one return raceway will be prevented, which will affect the smooth operation of the entire ball system. Of course, in other examples, two load raceways can also be set up for use with two return raceways, which will not be explained in detail here.

[0044] Example 4

[0045] This embodiment 4 provides supplementary explanations based on embodiments 1, 2, and 3. For other unexplained details, please refer to the aforementioned embodiments 1-3.

[0046] Fig.21A schematic diagram of a simulation experiment of deformation of an existing ball screw due to insufficient stiffness under load is given, wherein the screw is subjected to an axial load experiment with an axial displacement ΔL (unit μm) and a radial load experiment with a maximum radial displacement Δh (unit μm). Fig. 22 A curve diagram showing the relationship between the tensile and compressive stiffness of an existing ball screw and the distance between the center of the nut and the bearing fulcrum is given. The schematic diagram of the tensile and compressive stiffness distribution of the existing ball screw is shown in FIG. Fig.23 shown.

[0047] Changes in the screw stiffness will affect the surface processing appearance. Fig.24 As shown, a schematic diagram of the effect of changes in screw stiffness on surface processing is given.

[0048] Among them, the tensile and compressive stiffness of the ball screw is not fixed, but changes all the time. Its value is related to the displacement of the nut. The change law is distributed in the form of a quadratic parabola function with high values ​​on both sides and low values ​​in the middle, and there are maximum and minimum values. The calculation formula for the screw stiffness is:

[0049]

[0050] Among them, L k is the effective travel of the screw thread; the minimum screw stiffness is The maximum screw stiffness is

[0051] In order to solve the technical problem of deformation caused by insufficient rigidity of traditional ball screws, the present invention makes an improved design.

[0052] As described in the above-mentioned embodiments 1 to 3, a high-rigidity load ball screw of the present invention includes a screw body and a nut body, the screw is matched with a rigidity-enhanced nut (nut body), the nut body contains a return raceway, and is divided into a nut body and a nut sleeve body for arranging the return raceway. The nut body is wrapped by a nut shell (nut sleeve body, or an upper sleeve and a lower sleeve), and the nut shell (upper sleeve and lower sleeve) is radially connected by screws. The nut body is processed with a load rolling groove and a return raceway, and the load rolling groove of the nut body and the load rolling groove of the screw body form a load raceway, and a large number of load balls are contained in the load raceway and the return raceway. Among them, the nut shell is cut into two parts by a wire cutting method to cut the processed return raceway.

[0053] like Figure 25-27 , which is an example of the connection between the load raceway and the return raceway of the present invention; Fig.25 and Fig.26 The load raceway and return raceway spiral directions are opposite. Fig.25 Three arc sections (curved raceway 30) are used for smooth connection. Fig.26 A circular arc (curved raceway 30) is used for smooth connection, and the ball rotation direction remains the original direction after passing through the curved raceway; Fig. 27 The load raceway and return raceway shown have the same spiral direction. Fig. 27 Two arcs (curved rollers '30') are used for smooth connection. After the curved rollers, the ball rotates in the opposite direction to the original direction, and energy loss is required to make it rotate in the opposite direction. The following will explain in detail the working principle of the tensile and compressive stiffness compensation of the ball screw.

[0054] 1. Ball circulation principle

[0055] like Fig.28 As shown, the ball moves in the load raceway and completes the motion cycle through the return raceway. Among them, different from the aforementioned embodiments 1-3, the load raceway here is 2 right-handed spirals, both marked in yellow as shown in the figure, and the return raceway is 2 left-handed spirals, distinguished by green and red as shown in the figure, to form 2 circulating raceways respectively. The flexibility of the ball and the mechanical properties of the nut will be improved by setting up 2 circulating raceways, and the ball jamming phenomenon in the circulating raceway will be prevented to affect the smooth operation of the overall ball system. The following descriptions are all based on this test. Fig.28 As shown in the figure above, the screw drives the nut to move forward along the x-axis. The double-row balls (green and red) first enter the return raceway (return raceway) entrance A1 and B1, pass through the return raceway A and B respectively and make spiral motion, then flow out from the return raceway exit A2 and B2 respectively and enter the load raceway, completing a motion cycle. Fig.28 As shown in the figure below, the screw drive nut moves in the opposite direction along the x-axis, and the overall movement path of the double-row ball bearings is shown.

[0056] 2. Ball stiffness compensation principle

[0057] By designing a spiral recirculation raceway, the number of load balls is increased, thereby dispersing the effect of external loads on the screw and reducing the impact of external loads on the ball screw.

[0058] Different from the traditional ball screw internal circulation reflux type and the plug reflux type. The embedded reflux raceway contains a large number of balls, and the return space is used to increase the number of load balls. Therefore, the nut with large-capacity load balls can not only improve the rigidity of the ball screw pair but also increase its dynamic load performance. At the same time, it can increase the dynamic response of the ball screw, thereby reducing ball wear and extending the service life of the ball screw.

[0059] like Fig.28 As shown, the ball moving in the nut load raceway is an effective load ball. At this time, the load ball is in contact with both the screw and the nut, and can withstand loads from radial (y-axis) and axial (x-axis) directions. Therefore, theoretically, the greater the number, the higher the stiffness of the ball screw.

[0060] Although the balls in the return raceways A and B do not come into contact with the screw, they are also subject to radial and axial loads, but the loads borne by the balls in the load raceways are smaller.

[0061] In terms of radial load, the balls in the load raceway are mainly affected by the direct contact force of the screw, so they are subject to a large radial load. The radial load on the balls in the return raceway mainly comes from the radial load on the outer diameter of the nut from the workbench, workpiece and fixture, and the outer diameter of the nut acts on the return ball, which is an indirect effect, so the radial load is relatively small.

[0062] In terms of axial load, the balls in the load raceway are also directly affected by the contact force of the screw, so they are also subject to a large axial load. The axial load on the balls in the return raceway mainly comes from the moving nut, and the power of the moving nut comes from the ball drive in the load raceway. This driving force comes from the screw, so the axial force of the balls in the return raceway is indirectly transmitted by the screw, so the axial load is relatively small.

[0063] Based on the above analysis, the load on the load raceway ball is directly acted by the screw. The radial and axial loads on the return raceway ball are indirectly acted by the weight of the workbench and the moving nut. Therefore, the effective load of the ball in the unit load raceway is approximately equal to the effective load of three return raceway balls. The relationship between the equivalent load quantity of the balls is:

[0064] Z H ≈0.3Z F

[0065] In the formula, Z F Indicates the number of balls in the load raceway, Z H Indicates the number of balls in the recirculation raceway.

[0066] like Figure 29-Figure 32 , and conduct verification tests on it. Fig.29 A simulation schematic diagram of the recirculating ball raceway compensation before and after is given. Fig.30 A comparison curve of the relationship between the radial deformation of the screw and the distance between the center of the nut and the fulcrum of the single-sided bearing is given. Fig.31 A comparison curve of the relationship between the compressive stiffness of the ball screw and the effective number of turns of the load ball is given. Fig.32 A comparison curve of the relationship between the rated dynamic load of the ball screw and the effective number of turns of the load ball is given. It can be seen intuitively from the figure that compared with the traditional plug-in type and internal circulation type ball screw, the solution of the present invention includes a large-capacity return load ball in the embedded ball nut of the same shape, which can effectively compensate for the deformation of the screw due to insufficient tension and compression stiffness. Fig.29The deformation comparison of the screw ball before and after compensation is shown, so that it can carry more axial and radial loads from the workpiece, fixture, workbench or the screw itself.

[0067] Example 5

[0068] The aforementioned embodiments 1-4 include a ball screw nut solution, which will be briefly described in this embodiment 5. For details on the preferred solution feature combinations that are not fully described, please refer to the aforementioned embodiments 1-4.

[0069] See also Figure 1-Figure 32 A ball screw nut of embodiment 5 includes a nut body, an inner wall of the nut body is provided with a nut load rolling groove, the nut load rolling groove is spirally extended from the left end of the nut body to the right end of the nut body, the nut body is provided with a return raceway and a curved raceway adapted for the ball, the return raceway is between the load raceway and the outer wall of the nut body, the return raceway is spirally extended from the left end of the nut body to the right end of the nut body, the curved raceway is used in pairs with the return raceway, the curved raceway includes a left curved raceway and a right curved raceway, the left end portion of the return raceway extends inwardly through the left curved raceway to the left end of the nut load rolling groove, the right end portion of the return raceway extends inwardly through the right curved raceway to the right end of the nut load rolling groove, the nut load rolling groove, the curved raceway and the return raceway can be arranged with balls, so that the balls can circulate between the nut load rolling groove and the return raceway when the screw body is driven.

[0070] Among them, the central axis of the curved raceway is in the shape of a spline curve, and is tangent to the central axis of the load raceway and tangent to the central axis of the return raceway, or is tangent to the central axis of the load raceway and smoothly connected to the central axis of the return raceway, or is smoothly connected to the central axis of the load raceway and tangent to the central axis of the return raceway.

[0071] The return raceway has a spiral direction opposite to that of the load raceway. The pitch of the return raceway is greater than or equal to the nut load groove.

[0072] The return raceway is in the shape of a cylindrical spiral line, and the number of the return raceways is more than 2. The more than 2 return raceways are located on the same cylindrical surface, the pitches of the return raceways are the same, and the return raceways are staggered with a certain rotation angle.

[0073] In this way, the load raceway, the curved raceway and the return raceway form a circulation channel, and the balls can circulate in the circulation channel when driven by the screw body. The return raceway and the curved raceway are used to increase the number of load balls, so that more axial and radial loads from the workpiece, fixture, workbench, screw weight, etc. can be carried, and the tensile and compressive stiffness of the screw can be compensated.

[0074] It should be pointed out that the examples of the above-mentioned embodiments can be preferably combined with one or more of them according to actual needs, and multiple examples use a set of drawings to illustrate the combined technical features, which will not be described one by one here.

[0075] It should be noted that the orientation or position relationship indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation.

[0076] The above descriptions are detailed descriptions and illustrations of the preferred embodiments of the present invention, but these descriptions are not intended to limit the scope of protection required by the present invention. All equivalent changes or modified modifications accomplished under the technical teachings suggested by the present invention should fall within the scope of patent protection covered by the present invention.

Claims

1. A ball screw nut, comprising a nut body, wherein the inner wall of the nut body is provided with a nut load rolling groove, wherein the nut load rolling groove spirally extends from the left end of the nut body to the right end of the nut body, wherein: The nut body is provided with a return raceway and a curved raceway adapted to the ball, the return raceway being located between the load raceway and the outer wall of the nut body, the return raceway spirally extending from the left end of the nut body to the right end of the nut body, the curved raceway and the return raceway are used in pairs, the curved raceway comprises a left curved raceway and a right curved raceway, the left end portion of the return raceway extends inwardly through the left curved raceway to the left end of the nut load groove, the right end portion of the return raceway extends inwardly through the right curved raceway to the right end of the nut load groove, the nut load groove, the curved raceway and the return raceway can be arranged with balls, so that the balls can circulate between the nut load groove and the return raceway when driven by the screw body.

2. The ball screw nut according to claim 1, characterized in that: The central axis of the curved raceway is in the shape of a spline curve, and is tangent to the central axis of the load raceway and tangent to the central axis of the return raceway, or is tangent to the central axis of the load raceway and smoothly connected to the central axis of the return raceway, or is smoothly connected to the central axis of the load raceway and tangent to the central axis of the return raceway.

3. The ball screw nut according to claim 1, characterized in that: The spiral direction of the return raceway is opposite to that of the load raceway; the pitch of the return raceway is greater than or equal to the nut load groove.

4. The ball screw nut according to claim 1, characterized in that: The return raceway is in the shape of a cylindrical spiral, and the number of the return raceways is more than 2; wherein the more than 2 return raceways are located on the same cylindrical surface, the pitches of the return raceways are the same, and the return raceways are staggered with a certain angle.

5. A high-rigidity ball screw, comprising a screw body, a nut body, and a ball, wherein the outer wall of the screw body is provided with a screw load groove, wherein the screw load groove spirally extends from the left end of the screw body to the right end of the screw body, and the inner wall of the nut body is provided with a nut load groove, wherein the nut load groove spirally extends from the left end of the nut body to the right end of the nut body, and the nut body is sleeved on the screw body, wherein the nut load groove and the screw load groove form a load raceway, wherein the load raceway extends from the left end of the nut body to the right end of the nut body in a cylindrical spiral line, and the load raceway is adapted to the ball, and is characterized in that: The nut body is provided with a return raceway and a curved raceway matched with the ball, the return raceway is located between the load raceway and the outer wall of the nut body, the return raceway is spirally extended from the left end of the nut body to the right end of the nut body, the curved raceway is used in pairs with the return raceway, the curved raceway includes a left curved raceway and a right curved raceway, the left end portion of the return raceway extends inwardly through the left curved raceway to the left end of the nut load rolling groove, the right end portion of the return raceway extends inwardly through the right curved raceway to the right end of the nut load rolling groove, the load raceway, the curved raceway and the return raceway form a circulation channel, the circulation channel is arranged with balls, and the balls can circulate in the circulation channel when driven by the screw body.

6. A high-rigidity ball screw according to claim 5, characterized in that: The central axis of the curved raceway is in the shape of a spline curve, and is tangent to the central axis of the load raceway and tangent to the central axis of the return raceway, or is tangent to the central axis of the load raceway and smoothly connected to the central axis of the return raceway, or is smoothly connected to the central axis of the load raceway and tangent to the central axis of the return raceway.

7. A high-rigidity ball screw according to claim 5, characterized in that: The spiral direction of the return raceway is opposite to that of the load raceway; the pitch of the return raceway is greater than or equal to the nut load groove.

8. The high-rigidity ball screw according to claim 5, characterized in that: The return raceway is in the shape of a cylindrical spiral, and the number of the return raceways is more than 2; wherein the more than 2 return raceways are located on the same cylindrical surface, the pitches of the return raceways are the same, and the return raceways are staggered with a certain angle.

9. A high-rigidity ball screw according to claim 8, characterized in that: The nut body includes a nut body and a nut sleeve. The outer wall of the nut body is provided with a main return rolling groove, and the inner wall of the nut sleeve is provided with a sleeve return rolling groove. The main return rolling groove and the sleeve return rolling groove form a return raceway that is compatible with the ball. The return raceway extends from the left end of the nut body to the right end of the nut body in a cylindrical spiral line.

10. A high-rigidity ball screw according to claim 9, characterized in that: The processing method of the nut body is as follows: S1. Design processing parameters: Use 3D software to design the nut body model and the nut load rolling groove, curved raceway and return raceway thereon, so that each return raceway is smoothly connected to the nut load rolling groove; divide the nut body model into a nut main body model and a nut sleeve body model based on the cylindrical surface where the nut and the return raceway of the nut body model are located, and obtain the processing parameters; S2. Carry out turning and cutting according to the processing parameters, including: Clamp the nut body blank on the lathe and start the machine tool for processing; perform outer diameter cutting on the nut body blank to obtain the outer circle; perform rough machining and then fine machining of the main return groove on the outer circle; perform through hole machining on the nut body blank along the axis; enlarge the through hole and perform rough machining and then fine machining of the inner bore; perform rough machining and then fine machining of the inner bore to process the nut load groove; then, perform curved raceway machining to complete the nut body machining; The nut sleeve blank is clamped on the lathe, and the machine tool is started for processing; a through hole is processed for the nut sleeve blank along the axis; The through hole is enlarged, and the inner bore is first roughed and then finely bored; in the inner boring, the sleeve return groove is first roughed and then finely bored to complete the nut sleeve processing; the nut sleeve body is cut into an upper sleeve and a lower sleeve along the axial surface, and countersunk holes and threaded holes are processed on both sides of the ends of the upper sleeve and the lower sleeve respectively; Align the markings according to the pre-marks, snap the upper and lower sleeves onto the nut body, and tighten the screws to complete the assembly installation; then, use the abrasive flow method to penetrate the return raceway and complete the polishing of each inner hole.

Images