Tooth profile of small-diameter, large-pitch and large-lead screw and design method

Abstract

The invention discloses a small-diameter, large-pitch and large-lead screw tooth profile and a design method, and relates to the technical field of screw nut transmission, the small-diameter, large-pitch and large-lead screw tooth profile comprises two half tooth profiles, each half tooth profile is formed by sequentially connecting an MA section, an AB section, a BC section, a CD section, a DE section and an EF section, F points in the two EF sections coincide, and an M point is arranged on the inner circular ring side of a screw; the MA section, the BC section and the DE section are all arc sections, the AB section and the EF section are elliptical arc sections, and the CD section is a linear section; the arc section and the elliptic arc section are sequentially arranged at the two ends of the CD section, the fluency of the tooth-shaped edge of the lead screw is uniform, the fluency uniformity is good when a nut and the lead screw move relatively in the use process, the contact part of the tooth surface is the CD section, and the portions, at the two ends of the CD section, of the tooth-shaped part are each provided with an elliptic arc structure, so that the size of the CD section is increased, and the service life of the nut is prolonged. The length of the contact line is slightly larger than half of the tooth height, the contact area is increased, the tooth surface contact strength is improved, and the tooth surface bearing capacity is improved.

Description

Technical Field

[0001] The invention relates to the technical field of screw rod and nut transmission, in particular to a tooth shape and a design method of a screw rod with a small diameter, a large pitch and a large lead. Background Art

[0002] Trapezoidal lead screw nut transmission belongs to spiral motion, which can realize the conversion between rotation and linear movement. It is widely used in industrial automation, smart consumption, automotive electronics and other fields. As the application range becomes wider, the use of lead screw transmission with small diameter, large pitch and large lead is required.

[0003] Most of the screws in the prior art are trapezoidal screws, whose tooth profile is trapezoidal and the smoothness of the tooth edge is poor. When the nut and the screw move relative to each other, the smoothness is not uniform, and the tooth profile of the screw with a small diameter, large pitch and large lead has a low processing accuracy during processing.

[0004] In view of this, there is an urgent need for a tooth profile and design method for a small-diameter, large-pitch, and large-lead screw. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention solves the problems with the following technical structure.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A tooth profile and design method for a small-diameter, large-pitch, and large-lead screw, comprising two half-tooth profiles, the two half-tooth profiles being symmetrically arranged with the radial direction of the screw as the symmetry axis, the half-tooth profile being sequentially connected from one side of the screw to the side away from the screw by a MA segment, an AB segment, a BC segment, a CD segment, a DE segment, and an EF segment, the F points in the two EF segments coincide, and the M point is arranged on the inner ring side of the screw;

[0008] The MA segment, the BC segment, and the DE segment are all circular arc segments, the AB segment and the EF segment are elliptical arc segments, and the CD segment is a straight line segment.

[0009] It is further characterized in that

[0010] The MA segment is tangent to the inner circle of the screw rod.

[0011] The AB segment is tangent to the MA segment and the BC segment respectively.

[0012] The BC segment is tangent to the AB segment and the CD segment.

[0013] The CD segment is tangent to the BC segment and the DE segment.

[0014] The DE segment arc is tangent to the CD segment and the EF segment.

[0015] The EF segment is tangent to the DE segment and the outer circle of the screw rod.

[0016] The center of the MA segment is located on the extended radius line of the screw rod passing through point M.

[0017] The CD segment is located on a ray of the tooth profile angle.

[0018] A design method for a small-diameter, large-pitch, and large-lead screw tooth profile, comprising the following steps:

[0019] Get the outer diameter and lead of the screw;

[0020] According to the outer diameter and the lead, the number of teeth, the tooth angle and the minor diameter of the screw rod are obtained;

[0021] Draw the outer circle of the screw rod according to the outer diameter; draw the inner circle of the screw rod according to the minor diameter; draw two rays of the tooth angle according to the tooth angle;

[0022] Draw the CD segment, where the CD segment is located on the ray of the tooth angle;

[0023] Draw the MA segment, the MA segment is tangent to the inner circle of the screw rod, the tangent point is point M, and the center of the MA segment is located on the extension line of the radius of the screw rod passing through point M;

[0024] Draw the AB segment, which is tangent to the MA segment respectively, with the tangent point being point A. The AB segment conforms to the ellipse equation:

[0025]

[0026] Where a and b are the major and minor axes of the ellipse respectively;

[0027] Draw the BC segment, the BC segment is tangent to the AB segment and the CD segment, and the tangent points are point B and point C respectively;

[0028] Draw the DE segment, the DE segment arc is tangent to the CD segment, and the tangent point is point D;

[0029] Draw the EF segment, which is tangent to the DE segment and the outer circle of the screw rod, with the tangent points being point E and point F respectively. The EF segment conforms to the ellipse equation:

[0030]

[0031] Where m and n are the major and minor axes of the ellipse respectively.

[0032] The above structure of the present invention can achieve the following beneficial effects:

[0033] 1) The present application arranges circular arc segments and elliptical arc segments at both ends of the CD segment in sequence, so that the edge smoothness of the screw tooth profile is relatively uniform. When in use, when the nut and the screw move relative to each other, the smoothness is uniform. In addition, since the contact portion of the tooth surface is the CD segment, an elliptical arc structure is arranged at both ends of the CD segment of the tooth profile, so that the size of the CD segment becomes larger, the length of the contact line is slightly larger than half of the tooth height, the contact area is increased, the contact strength of the tooth surface is improved, and the bearing capacity of the tooth surface is improved;

[0034] 2) In the present application, the AB and EF segments of the tooth shape are designed with an elliptical arc, the MA segment is tangent to the inner circle of the screw, and the EF segment is tangent to the outer circle of the screw, that is, the minimum point of the tooth shape at the small diameter is the tangent point, and the maximum point at the large diameter is the tangent point, which can ensure smoothness during processing, help improve accuracy, and facilitate the processing of screws with small diameter, large pitch, and large lead. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the structure of this application. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0038] The following is combined with Figure 1 This application is described in further detail.

[0039] Example 1, reference Figure 1 The tooth profile and design method of a small diameter, large pitch, and large lead screw as shown in FIG. 1 include two half tooth profiles, the two half tooth profiles take the radial direction of the screw as the symmetry axis (the symmetry axis is as shown in FIG. Figure 1The semi-tooth shape is connected in sequence from one side of the screw to the side away from the screw, and the F points in the two EF segments coincide, and the M point is set on the inner ring side of the screw; the MA segment, the BC segment and the DE segment are all arc segments, the AB segment and the EF segment are elliptical arc segments, and the CD segment is a straight line segment. By sequentially arranging arc segments and elliptical arc segments at both ends of the CD segment, the edge smoothness of the screw tooth shape is more uniform. When in use, when the nut and the screw move relative to each other, the smoothness is more uniform. Moreover, since the contact part of the tooth surface is the CD segment, elliptical arc structures are set at both ends of the CD segment of the tooth shape, so that the size of the CD segment becomes larger, the contact line length is slightly larger than half of the tooth height, the contact area is increased, the tooth surface contact strength is improved, and the tooth surface bearing capacity is improved.

[0040] Further optimization is that the MA segment is tangent to the inner circle of the screw rod, the center of the MA segment is located on the extension line of the radius of the screw rod passing through point M, the EF segment is tangent to the DE segment and the outer circle of the screw rod, the AB segment is tangent to the MA segment and the BC segment respectively, the BC segment is tangent to the AB segment and the CD segment, the CD segment is located on the ray of the tooth profile angle, the CD segment is tangent to the BC segment and the DE segment, the DE segment arc is tangent to the CD segment and the EF segment, the AB segment and the EF segment are designed with elliptical arcs, the MA segment is tangent to the inner circle (minor diameter) of the screw rod, and the EF segment is tangent to the outer circle of the screw rod, that is, the minimum value point of the tooth profile at the minor diameter (the tangent point of the MA segment and the inner circle, that is, point M) is the tangent point, and the highest value point at the major diameter (the tangent point of the EF segment and the outer circle, that is, point F) is the tangent point, which can ensure smoothness during processing, help improve processing accuracy, and reduce the processing difficulty of screw rods with small diameters, large pitches, and large leads.

[0041] Embodiment 2, the present application also includes a design method for designing a screw tooth shape with a small diameter, a large pitch, and a large lead as described in Embodiment 1, the steps comprising:

[0042] S1: Get the outer diameter and lead of the screw;

[0043] S2: The designer selects the appropriate number of teeth and tooth angle of the screw according to the size of the outer diameter and lead ( Figure 1 α in the figure indicates half of the tooth angle) and the minor diameter (for example, when the outer diameter of the screw is 14mm and the lead is 800mm, the optimal number of teeth is 8, the pitch is 100mm, the optimal tooth angle is 30°, and the optimal minor diameter is 10mm);

[0044] S3: Draw the outer circle of the screw rod according to the outer diameter; draw the inner circle of the screw rod according to the minor diameter; draw two rays of the tooth angle according to the size of the tooth angle;

[0045] S4: Draw the CD segment, which is located on the ray of the tooth angle;

[0046] S5: Draw the MA segment, which is tangent to the inner circle of the screw rod, with the tangent point being point M, and the center of the MA segment is located on the extended radius line of the screw rod passing through point M;

[0047] S6: Draw segment AB. Segments AB are tangent to segment MA, and the tangent point is point A. Segments AB conform to the ellipse equation:

[0048]

[0049] Where a and b are the major and minor axes of the ellipse respectively;

[0050] S7: Draw segment BC, which is tangent to segments AB and CD, with the tangent points being point B and point C respectively;

[0051] S8: Draw segment DE. The arc of segment DE is tangent to segment CD, and the tangent point is point D.

[0052] S9: Draw segment EF. Segment EF is tangent to segment DE and the outer circle of the screw rod. The tangent points are point E and point F. Segment EF conforms to the ellipse equation:

[0053]

[0054] Where m and n are the major and minor axes of the ellipse respectively.

[0055] What is further optimized is that the specific values ​​of a, b, m, and n are based on the CD segment contact strength as a constraint condition and the goal of facilitating screw processing. The optimization iterations are performed to obtain the optimal values ​​of the major and minor axes of the ellipse, that is, the values ​​of a, b, m, and n.

[0056] In summary, the AB segment and EF segment of the tooth profile in the present application adopt an elliptical arc design, the MA segment is tangent to the inner circle (minor diameter) of the screw rod, and the EF segment is tangent to the outer circle (major diameter) of the screw rod, that is, the minimum value point of the tooth profile at the minor diameter is the tangent point, and the maximum value point at the major diameter is the tangent point, which can ensure smoothness during processing, is conducive to improving accuracy, and is conducive to processing screw rods with small diameters, large pitches, and large lead;

[0057] The contact part of the tooth surface is CD segment (straight line segment). Because the tooth profile has two elliptical arc structures, the CD segment size becomes larger while the minor diameter size remains unchanged. The contact line length is slightly larger than half of the tooth height size, the contact area is increased, and the tooth surface load-bearing capacity is improved.

[0058] Since the tooth shape described in this application can be used to process a screw with a large lead, and the sliding speed of the nut on the screw is inversely proportional to the lead, the total lead is large and the relative sliding speed of the tooth surface is low, wear is reduced, wear resistance is improved, and the service life of the screw nut is increased.

[0059] The above are only preferred embodiments of the present application, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A tooth shape of a small diameter, large pitch, and large lead screw, characterized in that: It comprises two half-tooth shapes, which are symmetrically arranged with the radial direction of the screw as the symmetry axis, and the half-tooth shape is composed of MA segment, AB segment, BC segment, CD segment, DE segment and EF segment connected in sequence from one side of the screw to the side away from the screw, and the F points in the two EF segments coincide, and the M point is arranged on the inner ring side of the screw; The MA segment, the BC segment, and the DE segment are all circular arc segments, the AB segment and the EF segment are elliptical arc segments, and the CD segment is a straight line segment.

2. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 1, characterized in that: The MA segment is tangent to the inner circle of the screw rod.

3. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 1, characterized in that: The AB segment is tangent to the MA segment and the BC segment respectively.

4. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 1, characterized in that: The BC segment is tangent to the AB segment and the CD segment.

5. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 1, characterized in that: The CD segment is tangent to the BC segment and the DE segment.

6. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 1, characterized in that: The DE segment arc is tangent to the CD segment and the EF segment.

7. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 1, characterized in that: The EF segment is tangent to the DE segment and the outer circle of the screw rod.

8. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 2, characterized in that: The center of the MA segment is located on the extended radius line of the screw rod passing through point M.

9. The tooth shape and design method of a small diameter, large pitch, and large lead screw according to claim 1, characterized in that: The CD segment is located on a ray of the tooth profile angle.

10. A method for designing a small diameter, large pitch, and large lead screw tooth profile according to any one of claims 1 to 9, characterized in that: include: Get the outer diameter and lead of the screw; According to the outer diameter and the lead, the number of teeth, the tooth angle and the minor diameter of the screw rod are obtained; Draw the outer circle of the screw rod according to the outer diameter; draw the inner circle of the screw rod according to the minor diameter; draw two rays of the tooth angle according to the tooth angle; Draw the CD segment, where the CD segment is located on the ray of the tooth angle; Draw the MA segment, the MA segment is tangent to the inner circle of the screw rod, the tangent point is point M, and the center of the MA segment is located on the extension line of the radius of the screw rod passing through point M; Draw the AB segment, which is tangent to the MA segment respectively, with the tangent point being point A. The AB segment conforms to the ellipse equation: Where a and b are the major and minor axes of the ellipse respectively; Draw the BC segment, the BC segment is tangent to the AB segment and the CD segment, and the tangent points are point B and point C respectively; Draw the DE segment, the DE segment arc is tangent to the CD segment, and the tangent point is point D; Draw the EF segment, which is tangent to the DE segment and the outer circle of the screw rod, with the tangent points being point E and point F respectively. The EF segment conforms to the ellipse equation: Where m and n are the major and minor axes of the ellipse respectively.

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