Gear structure

Abstract

In a gear structure of a helical gear G2 forming a gear pair with a mating gear G1, a tooth tip-side chamfered portion R1 and a tooth root-side chamfered portion R2 are provided at a pair of a tooth tip-side corner portion C1 and a tooth root-side corner portion C2 having a diagonal positional relationship on a tooth surface F abutting the mating gear G1. An amount of chamfering of the tooth root-side chamfered portion R2 is set to be larger than an amount of chamfering of the tooth tip-side chamfered portion R1, thereby preventing edge contact with the mating gear G1, and achieving a long service life.

Description

Gear structure

[0001] The present invention relates to a gear structure used in various gear mechanisms.

[0002] As a conventional gear structure, for example, there is one described in Patent Document 1. In Patent Document 1, misalignment when arranging gears, that is, parallelism error and run-out error are converted into pressure angle error and twist angle error of the tooth surface, and the minimum crowning amount and tooth profile rounding amount are obtained within a range where no single contact occurs even on a tooth surface having such errors.

[0003] Further, Patent Document 1 describes that when trimming is performed in consideration of manufacturing tolerance (shaded area), the actual trimming amount is measured, and bias trimming is added so that the meshing transmission error is the same as that of trimming at the lower limit of the tolerance, and when the misalignment is small, the trimming amount is reduced for the central part of the contacting tooth surface.

[0004] Japanese Patent Application Laid-Open No. 8-197332

[0005] However, in the above-described conventional gear structure, when the tooth surface correction is divided into two regions in consideration of misalignment, new edge contact with the mating gear occurs, and there is a problem that this may cause a reduction in life, and it is necessary to solve such a problem.

[0006] The present invention has been made in view of the above-described conventional situation, and is a gear structure of a helical gear that constitutes a gear pair with a mating gear, and aims to provide a gear structure that can prevent edge contact with the mating gear and achieve a long life.

[0007] The gear structure according to the present invention is a gear structure of a helical gear that constitutes a gear pair with a mating gear, and on the tooth surface that abuts against the tooth surface of the mating gear, a set of tooth tip side corner portions and tooth root side corner portions in a diagonal positional relationship are provided with a tooth tip side chamfer portion and a tooth root side chamfer portion, and the machining value of the tooth root side chamfer portion is larger than the machining value of the tooth tip side chamfer portion.

[0008] In the above configuration, the machining values ​​of the tooth tip lateral chamfer and tooth root lateral chamfer correspond to the volume removed by chamfering the corners compared to a tooth shape without chamfering, and the curvature (radius of curvature) of the tooth tip lateral chamfer is greater (radius of curvature is smaller) than the curvature of the tooth root lateral chamfer.

[0009] The gear structure according to the present invention, by adopting the above configuration, can prevent edge contact with the mating gear, thereby extending its lifespan.

[0010] This is a perspective view (A) illustrating the first embodiment of the gear structure according to the present invention 2, a front view of the tooth surface (B), and a perspective view (C) showing a bias-in structure in which the twist direction of the teeth and the direction of meshing are aligned. This is a perspective view (A) illustrating the drive gear and the driven gear, and a perspective view (B) showing an enlarged view of the main part of the driven gear.

[0011] <First Embodiment> The gear structure shown in Figures 1 and 2 is a gear structure of a helical gear G2 that forms a gear pair with a mating gear G1. In Figure 1(A), arrow A1 indicates the tooth width direction, arrow A2 indicates the tooth height direction (height direction), and arrow A3 indicates the direction of progression of the meshing between the mating gear G1 and the tooth surface of the helical gear G2. As shown in the figure, this direction of progression is a diagonal downward direction from one side of the tooth tip to the other side of the tooth root.

[0012] The gear structure described above is one in which, on the tooth surface F of the helical gear G2 that contacts the mating gear G1, a pair of tooth tip-side corners C1 and tooth root-side corners C2 are provided with tooth tip chamfers R1 and tooth root chamfers R2, which are located diagonally opposite to each other. In this case, the tooth tip chamfers R1 and tooth root chamfers R2 are provided on the tooth tip-side corners C1 and tooth root-side corners C2, which are located diagonally opposite to each other across the meshing direction (arrow A3) described above.

[0013] Furthermore, the gear structure described above has a configuration in which the machining value of the tooth root chamfer R2 is greater than the machining value of the tooth tip chamfer R1. The machining values ​​of the tooth tip chamfer R1 and the tooth root chamfer R2 correspond to the volume (amount of machining) removed by chamfering compared to the tooth shape without chamfering, which is shown by the dotted line in Figure 1(A). The structure has a configuration in which the curvature (radius of curvature) of the tooth tip chamfer R1 is greater than the curvature (smaller radius of curvature) of the tooth root chamfer R2. The tooth tip and tooth root chamfers R1 and R2 may be formed after the gear is formed, or they may be formed simultaneously during the gear's formation.

[0014] Here, in the gear structure described above, as shown in Figure 2, the drive gear (G1) and driven gear (G2) that constitute the gear pair are such that the drive gear G1 is fixed to the output shaft S of a motor or the like, and the tooth surface F of the driven gear, a helical gear G2, has a tooth tip chamfer R1 and a tooth root chamfer R2 formed thereon. The tooth tip chamfer R1 and tooth root chamfer R2 are formed on all teeth of the helical gear G2.

[0015] Furthermore, as shown in Figure 1(B), in the above gear structure, when the tooth surface F is viewed from the front, the tooth tip chamfer R1 has a triangular shape including the tooth tip side corner C1, and the tooth root chamfer R2 has a trapezoidal shape including the tooth root side corner C2. In Figure 1(B), the upper side of the tooth surface F corresponds to the effective tooth tip diameter of the helical gear (driven gear) G2, and the lower side corresponds to the effective tooth tip diameter of the mating gear (driving gear) G2.

[0016] More specifically, in a rectangular tooth surface F viewed from the front, the tip chamfered portion R1 is triangular in shape, determined by three sides: an upper side 1A along the tooth width direction, a vertical side 1B along the tooth height direction, and a hypotenuse 1C connecting the upper side 1A and the vertical side 1B. On the other hand, the root chamfered portion R2 is trapezoidal in shape, determined by four sides: an upper base 2A along the tooth width direction on the tip side, a lower base 2B along the tooth width direction on the root side, a leg side 2C along the tooth height direction, and a hypotenuse 2D connecting the upper base 2A and the lower base 2B.

[0017] Furthermore, in a more preferred embodiment, the gear structure described above can employ a configuration in which the length dimension a of the tooth tip chamfer R1 in the tooth height direction is half or less of the length dimension b of the tooth root chamfer R2 in the tooth height direction (a ≤ 1 / 2b).

[0018] Furthermore, in a more preferred embodiment, the gear structure described above can adopt a configuration in which the tooth surface F, excluding the tooth tip chamfer R1 and tooth root chamfer R2, that is, the tooth surface region between the hypotenuse 1C of the triangular tooth tip chamfer R1 and the hypotenuse 2D of the trapezoidal tooth root chamfer R2, is flat.

[0019] In the gear structure having the above configuration, the tooth surface F that contacts the mating gear G1 is provided with a tooth tip chamfer R1 and a tooth root chamfer R2, and the machining value of the tooth root chamfer R2 is made larger than the machining value of the tooth tip chamfer R1, thereby preventing edge contact with the mating gear G1 and extending the lifespan.

[0020] When two gears mesh, edge contact occurs, leading to localized stress accumulation. This is a concern in gear mechanisms that require high torque while miniaturization is progressing. In particular, in gear pairs where the drive gear and driven gear are helical gears, the driven gear meshes from the tooth root side, raising concerns about stress concentration on that tooth root side.

[0021] In contrast, in the gear structure described above, by providing a tooth tip chamfer R1 with a relatively small machining value and a tooth root chamfer R2 with a relatively large machining value on the tooth surface F of the helical gear (driven gear) G2 that meshes with the mating gear (drive gear) G1, a bias-in structure can be created, as shown in Figure 1(C), in which the twist direction of the tooth and the direction of meshing progression (arrow A3) are aligned. This ensures that the surface for power transmission is secured while avoiding edge contact, reducing the generated stress and ensuring strength, thereby achieving a longer lifespan. Moreover, the bias-in structure described above enables smooth meshing.

[0022] Furthermore, the gear structure described above has a triangular shape for the tooth tip chamfer R1 and a trapezoidal shape for the tooth root chamfer R, and more preferably, the length dimension a in the tooth height direction of the tooth tip chamfer R1 is less than or equal to half the length dimension b in the tooth height direction of the tooth root chamfer R2 (a ≤ 1 / 2b). As a result, the gear structure described above suppresses the effect of edge contact on the end of meshing and can secure a wide tooth contact area without reducing noise and vibration performance.

[0023] Furthermore, the above gear structure avoids a decrease in noise and vibration performance by making the areas of the tooth surface F other than the tooth tip chamfer R1 and tooth root chamfer R2 flat, thereby aligning the tooth twist direction with the direction of meshing progression (arrow A3) and using a flat shape.

[0024] Furthermore, the above gear structure is used for the driven gear, a helical gear G2, in relation to the mating gear G1, which is the driving gear. That is, since both gears constituting the gear pair are helical gears, the two gears mesh starting from the tooth tips of the driven gear (G2). As a result, contact occurs at the tooth surfaces at a single point, causing stress concentration.

[0025] Therefore, in the gear structure described above, a chamfered portion R1 is provided on the tooth tip of the driven gear (G2), which is the side to which the load is applied. Furthermore, in the gear structure described above, the contact area shifts due to meshing with the drive gear (G1), so the chamfered portion R2 at the tooth tip is also chamfered in the tooth width direction with a size X, as shown in Figure 1(B).

[0026] Furthermore, in the above gear structure, there is a risk of vibration input if point contact occurs at a location offset from the direction of meshing. Therefore, the tooth root chamfer R2 is chamfered widely in the tooth width direction on the tooth root side. In other words, the above gear structure can contribute to vibration reduction by adopting a trapezoidal tooth root chamfer R2 with the tooth tip as the upper base and the tooth root as the lower base, and also reduces unnecessary machining as the tooth surface of the drive gear (mating gear G1) can be made flat.

[0027] The gear structure according to the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention.

[0028] C1 Tooth tip corner C2 Tooth root corner F Tooth surface G1 Mating gear (driving gear) G2 Helical gear (driven gear) R1 Tooth tip chamfer R2 Tooth root chamfer

Claims

1. A gear structure for a helical gear that forms a gear pair with a mating gear, wherein a pair of tooth tip-side corners and tooth root-side corners are provided on the tooth surface that contacts the mating gear, and the machining value of the tooth root-side corner is greater than the machining value of the tooth tip-side corner.

2. The gear structure according to claim 1, characterized in that, when the tooth surface is viewed from the front, the tooth tip chamfer has a triangular shape including the tooth tip side corner, and the tooth root chamfer has a trapezoidal shape including the tooth root side corner.

3. The gear structure according to claim 2, characterized in that the length dimension a in the tooth height direction of the tooth tip chamfer is half or less of the length dimension b in the tooth height direction of the tooth root chamfer.

4. The gear structure according to claim 1, characterized in that the tooth surface, excluding the tooth tip chamfer and the tooth root chamfer, is flat.

5. The gear structure according to any one of claims 1 to 4, characterized in that the mating gear is a driving gear and is used in a driven gear that constitutes a gear pair with the driving gear.

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