Tooth profile of pin gear in pin gear drive

Abstract

The present invention relates to the tooth profile of a pin gear in a pin-tooth drive. The starting point of the conjugate tooth profile curve of the pin gear in the prior art is above the pitch circle. At this time, the curvature radius at and near the pitch circle is a relatively small transition arc radius. According to Hertz theory and the basic law of tooth profile meshing, a greater adverse effect is generated during the meshing of this section, thus affecting the load-carrying capacity and transmission performance of the pin-tooth drive. The solution of the present invention is that the section above the pitch circle is a section of conjugate tooth profile curve. Since the curve participating in the meshing is always a conjugate tooth profile curve, the strength check is accurate, and its comprehensive curvature radius is much larger than the existing fixed value of 1.5d, while the tooth profile transition curve has a relatively large curvature radius, increasing the bending strength at the tooth root; since the pin gear and the pin wheel operate in the correct trajectory, the load-carrying capacity, transmission smoothness, service life and transmission efficiency are improved, the performance of the pin-tooth drive in low-speed heavy-load is fully exerted, and it is beneficial to the speed increase transmission of the pin wheel as the driving wheel.

Description

Technical Field

[0001] The present invention relates to a tooth profile of a pin gear in pin-tooth transmission, and is used for the tooth profile design of a pin gear in pin-tooth transmission. Background Art

[0002] Pin-tooth transmission has three transmission types: internal and external meshing and rack meshing, all of which belong to conjugate meshing. It is mainly used for mechanical transmissions with low speed and heavy load, and occasions with harsh environments such as a lot of dust and poor lubrication conditions. In the above working occasions, compared with the gear transmission with a large diameter, the pin-tooth transmission has the advantages of simple structure, easy processing, low cost, and convenient disassembly and repair. The quality of its operation directly affects the reliability and service life of the pin-tooth transmission. At present, the starting point of the conjugate tooth profile curve of the pin gear is above the pitch circle, and the curve participating in the meshing is a smooth curve composed of two curve segments connected, that is, the tooth profile transition arc near the pitch circle and the conjugate tooth profile curve above it. As Figure 1 shown, at this time, the radius of curvature at the pitch circle and nearby is relatively small for the transition arc radius. According to Hertz theory and the basic law of tooth profile meshing, a large contact stress is generated during the meshing of this section at the pitch circle and nearby. Since the load borne at the pitch circle is relatively large, pitting and wear of the tooth surface are likely to occur in this section. At this time, the tooth profile transition arc curve belongs to a non-conjugate tooth profile curve, and the tooth profile transition arc radius R′ is selected within a certain range according to the design manual in relation to the diameter d (radius r) of the round pin teeth of the pin wheel. Moreover, the radius of curvature at the contact of the pin gear teeth is a fixed value ρ1 = 1.5d related to the diameter d of the round pin teeth of the pin wheel. Therefore, the contact strength check is not accurate enough to meet the working conditions of low speed and heavy load of the pin-tooth transmission, further aggravating the wear of the pin gear and the round pin teeth of the pin wheel, thus causing the entire pin-tooth transmission to fail in advance; because a large contact stress is generated during the meshing of this section at the pitch circle and nearby, a large sliding friction is likely to occur on the tooth surface of this section, resulting in a reduction in the transmission efficiency of the pin-tooth transmission and the loosening and falling off of the round pin teeth of the pin wheel on the rim, thus affecting the smoothness, service life and load-bearing capacity of the pin-tooth transmission. Summary of the Invention

[0003] The purpose of the present invention is to provide a tooth profile of a pin gear in which the curve participating in the meshing is always a conjugate tooth profile curve, that is, the tooth profile of a pin gear in a pin-tooth transmission where the pitch circle and above is a conjugate tooth profile curve.

[0004] The technical solution of the present invention is: a tooth profile of a pin gear used in pin-tooth transmission. On the basis of the tooth profile of the pin gear in the existing pin-tooth transmission as shown in Figure 2 shown, that is, on the basis of what is shown in Figure 1 shown, to ensure that the pitch circle and above is always a conjugate tooth profile curve, extend the conjugate tooth profile curve from the starting point to the starting point pitch circle of the conjugate tooth profile curve. In this way, the meshing interval of the round pin teeth of the pin wheel is a conjugate tooth profile curve from the pitch circle to the tooth top circle; due to the tooth root arc Rf The radius is slightly larger than the radius r of the circular pins of the pin gear, and the distance c from the center of the tooth root arc to the pitch circle. It is well-known in the art that there is no conjugate tooth profile curve within the pitch (base) circle. Therefore, the conjugate tooth profile curve and the tooth root arc cannot intersect at a point at the pitch circle. So, the tooth root part of the pin gear consists of a tooth profile transition curve and a tooth root arc R f The two curves are smoothly connected. To ensure that the tooth profile curve of the pin gear is a smoothly connected curve, the tooth profile transition curve is tangent to the conjugate tooth profile curve at the starting point on its pitch circle and the tooth root arc R f is tangent. The tooth profile curve of the pin gear is composed of these three curves smoothly connected.

[0005] A further technical solution of the present invention is that for the conjugate tooth profile curve with a relatively large comprehensive curvature radius and the tooth root arc R with a relatively small radius f at the two tangent points, it is not appropriate to use an arc curve as the tooth profile transition curve for connection; for the convenience of smooth, natural and flat connection and the tooth profile transition curve having a relatively large curvature radius to improve the bending strength at the tooth root, the tooth profile transition curve is selected from any one of the following: ellipse, parabola, hyperbola.

[0006] A further technical solution of the present invention is that the conjugate tooth profile curve has a relatively large comprehensive curvature radius and the tooth root arc R f has a relatively small radius. Since the curvature radius at the vertex of the minor axis of the ellipse is the largest and the curvature radius at the vertex of the major axis of the ellipse is the smallest, for the convenience of the tooth profile transition curve to be smoothly and smoothly connected with the tooth root arc and the conjugate tooth profile curve, the tooth profile transition curve is selected as an elliptical curve.

[0007] A still further technical solution of the present invention is that the elliptical curve is externally tangent to the starting point of the conjugate tooth profile curve on its pitch circle near the vertex of the minor axis, and the elliptical curve is internally tangent to the intersection point of the tooth root arc R f and the circle where the center of the tooth root arc R f is located near the vertex of the major axis. The elliptical curve between the internal and external tangent points is a concave curve on the tooth profile, making full use of the advantage of the large change in the curvature radius between the vertex of the minor axis and the vertex of the major axis of the elliptical curve. At this time, the connection of the three curves is smooth without obvious mutation and appears natural and smooth. Therefore, the bending strength at the tooth root is the largest, and at the same time, there will be no meshing interference with the circular pins of the pin gear. The tooth profile curve of the pin gear is a smoothly connected curve composed of these three curves.

[0008] The so-called smoothly connected curve refers to a smooth connected curve without obvious sharp turns (twists) and relatively flat connections between curves. A smoothly connected curve must be a smooth connected curve, but a smooth connected curve is not necessarily a smoothly connected curve; in comparison, a smoothly connected curve has relatively better machining processability than a smooth connected curve, and the curve can withstand large loads.

[0009] The beneficial effects of the present invention are as follows: In the pin gear drive with the pin gear tooth profile adopting this technical solution, since the conjugate tooth profile curve is from the pitch circle and above, its comprehensive curvature radius is much larger than the existing fixed value of 1.5d, and much larger than the tooth profile transition arc radius. When meshing with the pin teeth of the pin wheel, the contact stress generated is small, and it is not easy to occur pitting and wear, improving the service life of the pin gear and the pin teeth of the pin wheel; at the same time, due to the reduction of the contact stress, there will be no large sliding friction on the tooth surface, and the load-carrying capacity and transmission efficiency are also improved; since the curve participating in meshing is always a conjugate tooth profile curve, the load-carrying capacity, transmission smoothness, service life and transmission efficiency are further improved, giving full play to the performance of the pin gear drive at low speed and heavy load, and being conducive to meshing in and out, facilitating the speed-increasing transmission with the pin wheel as the driving wheel, and reducing the looseness and falling off of the pin teeth of the pin wheel on the rim, reducing maintenance, with accurate strength check, reducing transmission noise and vibration. In addition, the bending strength of the pin gear with a non-circular elliptical curve as the tooth profile transition curve is improved, thereby obtaining a smooth pin gear tooth profile curve composed of three connected curves. In short, since the curve participating in meshing is always a conjugate tooth profile curve, the load-carrying capacity, service life and transmission smoothness are improved, the transmission efficiency is also improved, maintenance is reduced, the strength check is more accurate, further improving the performance at low speed and heavy load, and being conducive to the speed-increasing transmission with the pin wheel as the driving wheel. Brief Description of the Drawings

[0010] Figure 1 Schematic diagram of the tooth profile of the pin gear in the prior art (R a is the addendum circle radius of the pin gear, R is the pitch circle radius of the pin gear, R' is the tooth profile transition arc radius, R f is the root arc radius, c is the distance from the center of the root arc to the pitch circle, r is the radius of the pin teeth of the pin wheel, R c is the radius of the circle where the center of the root arc is located, the starting point or tangent point 4' of the conjugate tooth profile curve 1, the tangent point 5' of the tooth profile transition arc 2' and the root arc 3, and the tooth profile transition arc 2' is between the tangent point 4' and the tangent point 5')

[0011] Figure 2 Schematic diagram of the tooth profile of the pin gear of the present invention (the starting point or tangent point 4 of the conjugate tooth profile curve 1 on the pitch circle, the intersection point 5 of the root arc R f 3 and the circle where the center of the root arc is located, and the tooth profile transition curve 2 tangent to the conjugate tooth profile curve 1 and the root arc R f 3 between the two points 4 and 5) Detailed Description of the Invention

[0012] The tooth profile of the pin gear in the prior art is as Figure 1As shown in the figure, the pin-tooth drive has three types: external meshing, internal meshing, and rack meshing. The conjugate tooth profile curves of the pin gears are respectively equidistant externally tangent epicycloids, equidistant internally tangent epicycloids, and equidistant involutes. The tooth profile of the pin gear is composed of two parts of curves: the tooth tip above the pitch circle and the tooth root below the pitch circle. The tooth tip part is composed of two smoothly connected curves: the conjugate tooth profile curve 1 close to the pitch circle and a part of the tooth profile transition arc 2' above the pitch circle and the pitch circle. The tooth profile curve of the tooth tip part is the working part of meshing. The tooth root part is composed of a part of the tooth profile transition arc 2' below the pitch circle and the tooth root arc R f 3, which are two smoothly connected curves. The tooth profile transition arcs 2' are respectively internally tangent to the conjugate tooth profile curve 1 and the tooth root arc R f 3 at the tangent points 4' and externally tangent at the tangent points 5'. And the tangent points 4' and 5' are respectively located in the tooth tip part above the pitch circle and the tooth root part below the pitch circle. Therefore, the tooth profile of the pin gear is composed of the conjugate tooth profile curve 1, the tooth profile transition arcs 2' near the pitch circle (above and below the pitch circle), and the tooth root arc R f 3, which are smoothly connected by three curves. That is to say, the starting point 4' of the conjugate tooth profile curve 1 of the pin gear is above the pitch circle. Near the pitch circle is the tooth profile transition arc curve R'2'. The tooth profile transition arc curve R'2' is respectively tangent to the conjugate tooth profile curve 1 and the tooth root arc R f 3. And the tooth profile transition arc curve R'2' is internally tangent to the conjugate tooth profile curve 1 at the starting point 4', and the tooth profile transition arc curve R'2' is externally tangent to the tooth root arc R f 3 at the end point 5'. As described above, the tooth profile of the pin gear in the prior art solution is composed of the conjugate tooth profile curve 1, the tooth profile transition arc 2', and the tooth root arc R f 3, which are smoothly connected by three curves. And the working curve participating in meshing is a smooth curve composed of two curve connections, that is, a part of the tooth profile transition arc 2' near the pitch circle and the conjugate tooth profile curve 1 above it. As shown in the present invention Figure 2 , to ensure that the tooth profile curve of the tooth tip part is always a conjugate tooth profile curve 1, that is, the working meshing part above the pitch circle is always a conjugate tooth profile curve 1. On the basis of Figure 1 , the conjugate tooth profile curve 1 is extended from the starting (tangent) point 4' to the starting point 4 of the conjugate tooth profile curve on the pitch circle. In this way, the tooth tip part above the pitch circle is a conjugate tooth profile curve 1. Because the conjugate tooth profile curve 1, the tooth root arc 3, and the pitch circle cannot intersect at one point, the tooth root part is composed of the tooth profile transition curve 2 below the pitch circle and the tooth root arc R f 3, which are two curves. The conjugate tooth profile curve 1 and the tooth root arc R f 3 are smoothly connected by the tooth profile transition curve 2. The tooth profile transition curve 2 is respectively tangent to the conjugate tooth profile curve 1 at its starting point 4 on the pitch circle and the tooth root arc R f3 is tangent, and the tooth profile of the pin gear is composed of a conjugate tooth profile curve 1 in the tooth top part, the pitch circle in the tooth root part, the following tooth profile transition curve 2 and the tooth root arc R f The three curves are smoothly connected. At this time, the tooth profile transition curve 2 is a non-circular arc curve, and the curve participating in the meshing is always a conjugate tooth profile curve 1

[0013] Adopting this technical solution, since the curve participating in the meshing is always a conjugate tooth profile curve 1, the pin gear and the pin wheel operate in the correct trajectory. At this time, the comprehensive curvature radius of the pin gear is much larger than the existing fixed value of 1.5d, the strength check is accurate, and the tooth profile transition curve 1 has a large comprehensive curvature radius, increasing the bending strength of the tooth root, improving the bearing capacity, transmission smoothness, service life and transmission efficiency, giving full play to the performance of the pin gear drive for low-speed heavy loads, and being more advantageous for the speed-increasing drive with the pin wheel as the driving wheel

[0014] A further technical solution is: for the conjugate tooth profile curve 1 with a larger curvature radius and the tooth root arc R with a smaller radius f At the two tangent points on 3, it is not appropriate to use an arc as the tooth profile transition curve for connection; in order to facilitate smooth connection and the tooth profile transition curve 2 to have a larger curvature radius to improve the bending strength of the tooth root, the tooth profile transition curve 2 is selected from any one of the following: ellipse, parabola, hyperbola

[0015] An even further technical solution is: the conjugate tooth profile curve 1 has a larger comprehensive curvature radius, and the tooth root arc R f 3 has a smaller radius. Since the curvature radius at the vertex of the minor axis of the ellipse curve is the largest and the curvature radius at the vertex of the major axis of the ellipse curve is the smallest, in order to facilitate the smooth and seamless connection of the tooth profile transition curve 2 with the tooth root arc R f 3 and the conjugate tooth profile curve 1, making the connection of the three connecting curves of the tooth profile appear natural and smooth, increasing the bending strength of the tooth, the tooth profile transition curve 2 is selected as an ellipse curve

[0016] An even more further technical solution is: to ensure a suitable starting or ending point position of the tooth profile transition curve 2, another tangent point 5 is located at the intersection of the tooth root arc R below the pitch circle f 3 and the circle where the center of the tooth root arc is located. The circle where the center of the tooth root arc is located is a circle concentric with the pitch circle; the ellipse curve is externally tangent to the starting point 4 of the conjugate tooth profile curve 1 on its pitch circle near the vertex of the minor axis, and the ellipse curve is near the vertex of the major axis f 3 and the tooth root arc R fIt is inscribed at the intersection point 5 of the circle where the 3 centers are located, so that the elliptical curve between the inner and outer tangent points is a concave curve on the tooth profile, making full use of the advantage of the large change in the radius of curvature between the vertex of the short semi-axis and the vertex of the long semi-axis of the elliptical curve. At this time, the connection of the three curves is smooth without obvious mutation and appears natural and smooth. Therefore, the bending strength at the tooth root is the largest, and at the same time, it will not cause meshing interference with the pin teeth of the pin gear and is convenient for the machining of the tooth profile. The tooth profile curve of the pin gear is a smooth connection curve composed of the connection of these three curves.

[0017] Adopting this technical solution, since the vicinity of the vertices of the long and short semi-axes of the elliptical curve are respectively tangent to the tooth root arc R f 3 and the conjugate tooth profile curve 1, such a smooth connection of a relatively large radius of curvature corresponding to a relatively large radius of curvature makes the connection of the curves much smoother. And the tooth profile transition curve 2 is an elliptical curve with a relatively large comprehensive radius of curvature, so that the bending strength at the tooth root is the largest.

[0018] The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those of ordinary skill in the relevant technical fields can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the scope of the present invention. The patent protection scope of the present invention shall be defined by each claim.

Claims

1. A tooth profile of a pin gear in a pin-and-rack drive, characterized in that The tooth profile of the pin gear consists of a conjugate tooth profile curve (1) above the pitch circle, a tooth profile transition curve (2), and a root circular arc R f (3). The tooth profile transition curve (2) is tangent to the starting point (4) of the conjugate tooth profile curve (1) on its pitch circle and the root circular arc R f (3). The curve of the tooth profile of the pin gear participating in meshing is always a conjugate tooth profile curve (1); The tooth profile transition curve (2) is selected as an elliptical curve. The elliptical curve is externally tangent to the starting point (4) of the conjugate tooth profile curve (1) on its pitch circle near the vertex of the minor axis, and the elliptical curve is internally tangent to the intersection point (5) of the tooth root circular arc R f (3) and the circle where the center of the tooth root circular arc R f (3) is located near the vertex of the major axis. The tooth profile curve of the pin gear is a smooth and continuous curve composed of a conjugate tooth profile curve (1) above the pitch circle, a tooth profile transition curve (2), and a tooth root circular arc R f (3) connected in three sections.

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