JPS61244966A - Gear having relative curvature at contact point - Google Patents

Abstract

PURPOSE:To enhance the strength of a gear, by forming such a tooth shape that a continuous and differentiable function which does not change monotonously, is selected for the curvature of a tooth shape curve, the locus of the curvature center being a continuous serise curve exsisting in the vicinity of the pitch circle. CONSTITUTION:The tooth shapes 1, 3 of gears are formed such that their radii of curvature change from their pitch lines to their addendum and dedendum with the repetition of increase and decrease in the radii of curvature. The relative curvature between the tooth shapes 1, 3 becomes zero at a point where the radius of curvature is minimum, and it has a cyclic characteristic such that there are a plurality of such points per pitch. Therefore, the relative curvature may be made small, and it is possible to make the meshing rate of the teeth more than 1 without the meshing pressure angle being made to be excessibly large, thereby it is possible to enhance the strength of gear teeth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to gears, and in particular to gears with a small relative curvature at the contact points.

[Conventional technology]

The typical power transmission gear is an involute tooth profile, but other gears include a cycloid tooth profile and a circular arc tooth profile.

Looking at the radius of curvature of each of the above tooth profiles, the radius of curvature changes monotonically and continuously for tooth profiles with a 72-arc tooth profile or more. Therefore, it is impossible to keep the relative curvature between tooth profiles small or constant during occlusion. be.

Furthermore, the strength of a tooth profile has a limit determined by its bending stress and a limit determined by the surface pressure between the tooth surfaces. However, in general, in involute gears, the limit due to bending stress is higher than the limit due to tooth surface pressure, so it is necessary to increase the limit due to tooth surface pressure stress, so-called.

Since the relative curvature between the south faces affects the so-called Hertzian stress, in order to increase the above value, a tooth profile with a small relative curvature at the occlusal point is required.

A tooth profile with a small relative curvature is the Wildhaber Novikov tooth profile, but since this tooth profile is a point contact tooth profile (occlusion = 1) that occlusions only at one point on the tooth profile, the above Wildhaber Novikov tooth profile is used for power transmission. To use it as a gear, it must be a wide helical gear.

[Problem that the invention seeks to solve]

The present invention has been made based on the above-mentioned viewpoints, and its purpose is to bring the relative curvature closer to the Wildhaber Novikov tooth profile, increase the occlusion ratio to 1 or more, and further increase the occlusal pressure. The purpose is to significantly increase the strength of the tooth profile by making the corners relatively small to prevent surface pressure and bearing stress from increasing, and by keeping the relative curvature between the tooth flanks of the gear small.

To explain this specifically, unlike conventional tooth profiles, the radius of curvature does not monotonically change from the pinch line toward the tooth tip and crest, but repeats increases and decreases.
At the point where the radius of curvature is minimal, it is desirable that the center of the radius of curvature be located on the pitch line. If this is done, the relative curvature between the tooth profiles will be zero at that point, but
In the gear of the present invention, points at which this relative curvature becomes zero appear many times periodically within 1 pitch.v.

[Means for solving problems]

The above objective is that the curvature of the tooth profile is a continuous and differentiable function that does not change monotonically, and that the locus of the center of curvature is a continuous series of functions that normally exist in the vicinity of the pitch circle. This is achieved by providing a curved tooth profile.

[For production]

By configuring as above, the relative curvature is close to the value in the involute gear and the value in the Wildhaber Novikov tooth profile, so it is possible to increase the occlusion ratio to 1 or more, and furthermore, the occlusion pressure angle can be increased. By making it relatively small, it is possible to prevent the surface pressure and bearing stress from increasing, and as mentioned above, the relative curvature between the tooth surfaces of the gear can be kept smaller than that of the conventional one. The strength of the tooth profile can be greatly increased.

〔Example〕

Hereinafter, the details of the present invention will be specifically explained with reference to the drawings.

1 and 2 are partially enlarged fragmentary views showing an example of the tooth profile of a gear with a small relative curvature at the contact point according to the present invention, respectively, and FIG. 3 is an explanation showing the meshing state of the gear. 4 are explanatory diagrams showing the structure of the tooth profile curve.

In Figures 1 to 3, 1 is the tooth profile curve of a gear with 15 teeth;
2 is its pitch circle, 3 is the tooth profile curve of the gear with 5 teeth, and 4 is its pitch circle.

Therefore, the tooth profile 1.3 of the gear according to the present invention is configured such that the radius of curvature thereof changes while increasing and decreasing repeatedly from the pinch line toward the tooth tip and tooth root, and the curvature radius At the point where the radius is minimum, the center of the radius of curvature is on the pitch line, so when they engage under such conditions, the relative curvature between the tooth profiles 1 and 3 becomes zero.

Therefore, the gear according to the present invention has a periodic characteristic in which there are a plurality of points in one pitch where the relative curvature between the tooth profiles 1 and 3 becomes zero.

Next, the curve of the tooth profile will be specifically explained based on FIG.

The X axis in the figure is the pitch line, and 5 is a part of the tooth profile curve. .

Therefore, the arcs C and C1 are involutes of the small arc gogI having the center of curvature Ao on the addendum side, and the arc ClC
2 has the center of curvature A1 on the dedendum side, and the small arc g
It is an involute of the small arc g+g2 that shares the normal line with ogr and point gI, and the arc C2C5 has the center of curvature A2 on the addendum side, and is the involute of the small arc g2g3 that shares the normal line with the small arc g1g2 and point g2. It is involute.

Therefore, the end point g of one of these arcs. , g2 are on the pitch line, and the other end point g+, g3 is on the opposite side of the tooth profile 5 near the pinch line.

From this figure, the radius of curvature in the arc CoC1 is rQ from co toward C, and rQ = Ao go to r1-At g
+, but in arc clc2, C
From 1 to C2 r+ = A+ gl to r2 = A
2 g2, and furthermore, in the arc C2C5, C
From 2 to C3 r2 = A2 g2 to g3 = A3
It is known that it monotonically increases again up to g3.

The actual tooth profile is obtained by extending the tooth profile curve from side to side in the figure using the same method as above.

Further, the angle that each small circular arc makes with respect to the center of curvature is approximately 1 to 5 degrees, preferably approximately 2 to 3 degrees.

Therefore, if this angle is converged to O, the tooth profile becomes a Wildhaber Novikov tooth profile, and if the angle is large,
This essentially results in an involute gear, and in either case, the object of the present invention cannot be achieved. From this point of view, it is known that the gear of the present invention is positioned between an involute gear and a Wildhaber Novikov gear.

If the above-mentioned angle is about 3 degrees, gears as shown in FIGS. 1 and 2, for example, can be obtained. These gears can be designed relatively freely without making the pressure angle too large, and the radius of curvature increases and decreases repeatedly along the tooth bracket, so the relative curvature at the occlusion point can be made small. .

Note that the present invention is not limited to the embodiments described above. For example, in the embodiment, the arc constituting the tooth-shaped curve is a circular involute, but this is not necessarily limited to this, and other appropriate curves can be adopted as appropriate. It is.

〔Effect of the invention〕

Since the present invention is constructed as described above, it is possible to reduce the relative curvature and increase the occlusal ratio to 1 or more without increasing the occlusal pressure angle too much, thereby suppressing the increase in surface pressure and bearing stress. Since this can be prevented, the strength of the tooth profile can be significantly increased.

[Brief explanation of drawings]

1 and 2 are partially enlarged fragmentary views showing an example of the tooth profile of a gear with a small relative curvature at the contact point according to the present invention, respectively, and FIG. 3 is an explanation showing the meshing state of the gear. 4 are explanatory diagrams showing the structure of the tooth profile curve.

Claims (1)

[Claims] 1) A continuous series in which the curvature of the tooth profile curve is a continuous and differentiable function that does not change monotonically in the tooth direction, and the locus of the center of curvature is in the vicinity of the pitch circle. A gear with a small relative curvature at the contact point, which is characterized by a curve of . 2) A gear having a small relative curvature at a contact point according to claim 1, wherein the center of curvature corresponding to the point of minimum curvature is located on the pitch line. 3) A series in which the locus of the center of curvature is made up of a large number of small circular arcs whose centers are within the pitch circle and small circular arcs whose centers are outside the pitch circle, connected alternately so that the normal line is common at one end of each. , and the tooth-shaped curve is a curve formed by alternately and smoothly connecting the extension lines of the two types of small circular arcs. Gears with small curvature.