JPH0252135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a modified transposition WN gear that is an improved point contact WN gear.

[Conventional technology]

Point contact obtained by creating dislocations using a reference rack with a tooth profile that combines uneven arcs and straight lines, which is currently in practical use in Japan as a gear with tooth surface strength superior to involute gears.
An example of a WN gear (WN is the initials of Messrs. Wildhaber and Novikov, who were the first inventors of this type of gear) is shown in Japanese Patent Application Laid-open No. 132459/1983.

[Problem to be solved by the invention]

Conventional point contact WN gears have many features compared to existing ones, but the change in meshing pressure angle due to center distance variation is from around 30° to the larger side (toward the tooth tip). steep in range;
A slight change in the center distance causes a large change in the meshing pressure angle. This sometimes causes contact with the ridgeline of the tooth tip, which is unfavorable not only in terms of tooth surface strength but also in terms of bending strength.

Figure 3 is a diagram drawn by the present inventor for a conventional WN gear (Japanese Unexamined Patent Publication No. 132459/1982) showing the relationship between the variation in the center distance of the gear and the meshing pressure angle at the contact point. Specifications are shown in the figure. Third
In the figure, the origin where the center distance variation on the horizontal axis is zero is when the center distance is (center distance with no dislocation) + (sum of dislocation amounts of both gears).

The above-mentioned properties of the meshing pressure angle are such that, as in the example of a cam waltz pinion supported by metal bearings that drives the rolling rolls of iron-making machinery, the center distance varies greatly between no-load and loaded conditions, and the meshing pressure angle under load. of
If a suitable value around 30° is selected, the range of use of this gear will be limited if the center distance fluctuation during no load extends to the negative side of the horizontal axis.

In contrast, the present invention eliminates the above-mentioned disadvantages of conventional point contact WN gears by replacing the tooth profile of the standard rack with an involute curve for the portion of the tooth end arc portion near the tooth tip. It is.

[Means to solve the problem]

In order to achieve the above object, the modified dislocation WN gear of the present invention has a tooth profile consisting of an uneven circular arc with the same radius and an intermediate straight line connecting them. It is characterized in that it is obtained by creating a dislocation using a reference rack that has been modified to replace a part near the tooth tip with an involute curve whose radius of curvature gradually decreases toward the tooth tip.

〔Example〕

Embodiments of the invention will be described with reference to the drawings.

FIG. 1 represents the tooth profile of a reference rack for creating the shifted WN gear of the present invention. Since the WN tooth profile is a helical gear and the rack is also helical, the reference rack tooth profile is defined on an appropriate cross section of the helical reference rack (hereinafter referred to as the reference plane). FIG. 3 also shows a tooth profile on one reference plane, with the arc (broken line) from points A and E (pressure angle αm) on the tooth tip to the tooth tip replaced by an involute curve (solid line). The tooth profile below αm is the conventional WN gear (Japanese Patent Application Laid-Open No. 55
132459), it is a combination of circular arcs and straight lines. Due to this modification, the diagram in FIG. 3 changes as shown in FIG. 2. That is, the permissible range of center distance variation is expanded to the negative side as well. This is because when the involute part shown in Figure 1 participates in meshing, the tooth surface retreats toward the substance side compared to the original arc, and this plays a role in shortening the center distance of meshing. As a result, it is possible to expand the above-mentioned allowable center distance range to the negative side, that is, to mesh at a center distance smaller than (center distance without dislocation) + (dislocation amount of both gears).

Conventionally, in involute gears, a so-called tooth tip modification technique has been used to provide relief to the tooth tip in consideration of tooth deflection due to load, but the modification of the present invention is essentially different from this. That is, in the case of involute gears, the modification is a simple one in the sense of relieving the tooth tips, and usually no detailed study has been done on the function of the modification curve. On the other hand, the tooth profile of the present invention is different from that of the conventional WN gear (Japanese Patent Application Laid-Open No.
No. 132459), it is named as an amendment.
It is not just a relief, but an important function for WN gears, which is to move the contact point, and the design consideration is to set the point of point contact at the desired mesh pressure angle position on the modified tooth profile. It makes it possible.

The diagrams in Figures 2 and 3 were drawn using the following formulas, with the angle α (radian) being the radius number. See ``Tooth profile theory of dislocated WN gears using non-conjugate interference reference racks'' (Shoichi Ishikawa) in the collection of lecture papers (published in August 1985)].

△ _a / m _o = a _w − (z ₁ + z ₂ /2cosβ+x _o1 + x _o2 ) ...(1) α _tw = cos ^-1 (z ₁ +z ₂ /2cosβ・cosα _t /a _w ) ...(2) Here x _e =x _o1 +x _o2 +ρ _i /m _o {cosα _n −cosα − (α − α _n ) sinα} ...(4) α _t = tan ^-1 (tanα・cosβ ₀ /cosβ) ...(5) The symbols in the above formula have the following meanings.

△a: Amount of change in center distance (mm) m _o : Perpendicular module (mm) a _w : Nondimensional center distance used z ₁ , z ₂ : Number of teeth of small and large gears x _o1 , x _o2 : Normal gear shift coefficient β for small and large gears: Helix angle β ₀ : Angle between the reference plane and the normal plane α _tw : Face mesh pressure angle α _t : Face generated pressure angle α: Reference plane generated pressure angle (radians) (Use this α as the radius number) α _n : Pressure angle at the junction point between the tooth end arc on the reference plane and the involute (in radians) x _e : Effective total shift coefficient ρ _i : Reference circle radius of the involute (mm) Top The formula is shared between FIGS. 2 and 3. However, when used in FIG. 3, ρ _i =0 and α _n =γ (pressure angle at the intermediate straight portion).

〔Effect of the invention〕

According to the present invention, the sensitivity to center distance errors in the range of the meshing pressure angle from around 30° to the tooth tips, which is normally used in conventional shifted WN gears, is greatly alleviated, and a point contact WN gear that is easy to use is obtained. be able to. In addition, an analytical representation is given regarding the selection of the shift coefficient for a given reference rack tooth profile in order to make the variation range of the meshing pressure angle appropriate within the desired center distance variation range. , can greatly contribute to the design of point contact WN gears.

[Brief explanation of drawings]

Fig. 1 is a diagram of the standard rack tooth profile of the present invention, Fig. 2 is a diagram showing the relationship between center distance variation and meshing pressure angle of the modified dislocation WN gear of the present invention corresponding to Fig. 3, and Fig. 3 is a diagram of the conventional gear. FIG. 3 is a diagram showing the relationship between the variation in the center distance of the WN gear and the meshing pressure angle at the contact point. △ _a ...Amount of change in center distance, m _o ...Normal angle module, α _tw ...Front meshing pressure angle.

Claims (1)

[Claims] 1. An involute which has a tooth profile consisting of an uneven circular arc with the same radius and an intermediate straight line connecting them, and where the radius of curvature gradually decreases toward the tip of the tooth in the convex arc portion of the tooth tip. A modified dislocation WN gear obtained by creating dislocation using a reference rack that has been modified to replace it with a curve.