Organize the names of each part to know when trying to design a gear. By understanding what elements each gear is composed of, it is possible to know how to set the shape determination parameters.
Terminology of each part
The names of the parts are organized as shown in Fig. 1. The names are listed in the following order: (1) Each name (2) English name (3) Parameter letter. The names of the parts are listed in the following order: (1) Each name (2) English name, (3) Parameter letter.
(i) tooth surface: The part where the gear teeth mesh.
(ii) pitch circle: A circle whose locus is the contact point between two meshing gears.
(iii) addendum circle, outside circle: A circle passing through the tooth tip and concentric with the pitch circle.
(iv) dendum circle, root circle: A circle concentric with the pitch circle passing through the root of the tooth. The tooth is formed in the area between the tip circle and the root circle.
(v) tooth face: the tooth surface on the apical side of the tooth, above the pitch circle.
(vi) tooth flank: The tooth flank on the root side of the tooth, opposite to the tooth end flank.
(vii) tooth flank (addendum): the distance from the pitch circle to the tooth tip circle.
(viii) dendum (dedendum) \((h_f)\): Distance from the pitch circle to the bottom circle of the tooth.
(ix) whole depth \((h)\): Distance from the tooth bottom circle to the tooth tip circle. It is expressed by \(h=h_k+h_f\).
(x) pitch \((p)\): Length of arc from a point on the pitch circle of one tooth to the corresponding point on an adjacent tooth.
(xi) tooth thickness \((s)\): The arc length of the portion of the above pitch where the tooth substance is located.
(xii) tooth slot width (space thickness) \((e)\): The arc length of the portion of the above pitch where there is no tooth substance, as opposed to the tooth thickness.
(xiii) face width \((w)\): Length of the tooth in the axial direction.
(xiv) base circle: The circle used as a reference for determining the tooth profile.
(xv) pressure angle \((\alpha)\): The angle between the locus of the contact point of two gears (common tangent) and another common tangent of the pitch circle passing through the contact point.
(xvi) involute curve: The trajectory of the tip of a thread wound around a base circle when the thread is removed so that it does not sag. It is used in designing standard tooth profiles for industrial gears. More information about involute curves is given in a previous article.
In addition,
top clearance: The height \(h_f-h_k^\prime\) of the tooth end of another gear with which it is meshed.
Backlash: The backlash \(e-s^{\prime\prime}\) when the tooth thickness of the other meshing gear is set to \(s^\prime\).
The term backlash is used to refer to the backlash of a gear.
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