Planetary gear train of internal engagement type

Patent metadata

Field	Value
Publication number	US-9856945-B2
Application number	US-201514861365-A
Country	US
Kind code	B2
Filing date	Sep 22, 2015
Priority date	Sep 24, 2014
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

Each of gear teeth of an external gear has a tooth-bottom portion, a tooth-middle portion and a tooth-front portion. The tooth-middle portion is operatively engaged with an internal gear. A cross-sectional shape of the tooth-bottom portion is formed by a hypocycloid curved line. A cross-sectional shape of the tooth-middle portion is formed by an epicycloid curved line. A cross-sectional shape of the tooth-front portion is formed by a first predetermined curved line, which is located at a position closer to a first pitch circle of the external gear in a radial-inward direction from a reference epicycloid curved line. The reference epicycloid curved line is continuously connected to each of the curved lines of the tooth-middle portion at both circumferential sides of each gear tooth. As a result, the tooth-front portion is so formed that a part of the tooth-front portion is escaped in the radial-inward direction from the reference epicycloid curved line.

First claim

What is claimed is:

1. A planetary gear train of an internal engagement type comprising:
an internal gear having multiple internal gear teeth at an inner peripheral portion of the internal gear, each of the internal gear teeth having a tooth-bottom portion, a tooth-middle portion and a tooth-front portion; and
an external gear having multiple external gear teeth at an outer peripheral portion of the external gear, each of the external gear teeth having a tooth-bottom portion, a tooth-middle portion and a tooth-front portion, and the tooth-middle portion of the external gear being internally and operatively engaged with the tooth-middle portion of the internal gear,
wherein some of the external gear teeth are operatively engaged with some of the internal gear teeth in a teeth engagement area, while some of the remaining external gear teeth are dis-engaged from some of the remaining internal gear teeth in a teeth non-engagement area so that the tooth-front portion of the external gear is separated from the tooth-front portion of the internal gear in a radial direction of the external gear,
wherein the tooth-bottom portion of the external gear is located at a radial-inside position of a first pitch circle of the external gear, the tooth-middle portion of the external gear is located at a radial-outside position of the first pitch circle and operatively in contact with the internal gear, and the tooth-front portion of the external gear is located at a radial-outside position of the tooth-middle portion of the external gear,
wherein the tooth-bottom portion of the internal gear is located at a radial-outside position of a second pitch circle of the internal gear, the tooth-middle portion of the internal gear is located at a radial-inside position of the second pitch circle and operatively in contact with the external gear, and the tooth-front portion of the internal gear is located at a radial-inside position of the tooth-middle portion of the internal gear, and
wherein transverse cross-sectional shapes of the internal gear and the external gear are formed in the following manners, the transverse cross-sectional shape corresponding to a cross-sectional shape on a transverse plane perpendicular to a center axis of the internal gear:
a transverse cross-sectional shape of the tooth-bottom portion of the internal gear is formed by an epicycloid curved line;
each of transverse cross-sectional shapes of the tooth-middle portion and the tooth-front portion of the internal gear is formed by a hypocycloid curved line;
a transverse cross-sectional shape of the tooth-bottom portion of the external gear is formed by a hypocycloid curved line;
a transverse cross-sectional shape of the tooth-middle portion of the external gear is formed by an epicycloid curved line, wherein the tooth-middle portion of the external gear is located at the radial-outside position adjacent to the first pitch circle; and
a transverse cross-sectional shape of the tooth-front portion of the external gear is formed by a first predetermined curved line, which is located at a position closer to the first pitch circle in a radial-inward direction from a reference epicycloid curved line in order to avoid a contact between the tooth-front portion of the external gear and the tooth-front portion of the internal gear in the teeth non-engagement area, wherein the reference epicycloid curved line is continuously connected to each of the curved lines for the tooth-middle portion of the external gear, each of the curved lines for the tooth-middle portion of the external gear being respectively connected to each end of the first predetermined curved line for the tooth-front portion of the external gear at both circumferential sides thereof.

2. The planetary gear train according to claim 1 , wherein
the transverse cross-sectional shape of the tooth-front portion of the external gear is formed by an interpolation curved line, which passes over connecting points “A 0 ” and runout points “C 1 ” to “C N ” in each of the external gear teeth of the external gear,
wherein the connecting point “A 0 ” and the runout points “C 1 ” to “C N ” are respectively defined by the following manners:
a point, at which the tooth-front portion is continuously connected to the tooth-middle portion, is defined as the connecting point “A 0 ”;
a point, which is located at a most-radial-outside position of the reference epicycloid curved line , is defined as a most-front point “A N ”;
an amount, which corresponds to a distance between the most-front point “A N ” of the reference epicycloid curved line and a most-front point of the first predetermined curved line for the tooth-front portion, is defined as a first runout amount “t 1 ”;
respective points, each of which corresponds to a respective point of division when the reference epicycloid curved line between the connecting point “A 0 ” and the most-front point “A N ” is divided into N-number portions, are defined as a division point “A 1 ” to a division point “A N-1 ”, wherein the division points “A 1 ” to “A N-1 ” are located in a direction from the connecting point “A 0 ” to the most-front point “A N ”;
a circle, which is concentrically located with the first pitch circle “Sp 1 ” and passes over the connecting point “A 0 ” is defined as a first circle “S 0 ”;
a circle, which is concentrically located with the first pitch circle “Sp 1 ” and passes over the division point “A 1 ” is defined as a second circle “S 1 ”;
a straight line, which connects the most-front point “A N ” to a center axis “AX 2 ” of the first pitch circle “Sp 1 ”, is defined as a central straight line “L N ”;
straight lines, each of which is parallel to the central straight line “L N ” and passes over the respective division points “A 1 ” to “A N-1 ”, are respectively defined as straight lines “L 1 ” to “L N-1 ”
intersection points, at each of which the second circle “S 1 ” intersects with the respective straight lines “L 2 ” to “L N ”, are respectively defined as intersection points “B 2 ” to “B N ”;
a point, which corresponds to the most-front point “A N ” when the most-front point “A N ” is moved by the first runout amount “t 1 ” in a direction to the intersection point “B N ” along the central straight line “L N ”, is defined as a central runout point “C N ”;
a number from “2” to “N−1” is defined as an integral number “K”;
a point, which is located on the straight line “L K ” and satisfies the following condition, is defined as a runout point “C K ”;
[a line segment “ A K C K ”:a line segment “ C K B K ”=a line segment “ A N C N ”:a line segment “ C N B N ”];

an intersection point between the straight line “L 2 ” and the first circle “S 0 ” is defined as an intersection point “D 2 ”;
an intersection point between the straight line “L 1 ” and the first circle “S 0 ” is defined as an intersection point “D 1 ”;
a transfer point, which is located on the straight line “L 1 ” and satisfies the following condition, is defined as a transfer point “E 1 ”:
[a line segment “ A 1 E 1 ”:a line segment “ E 1 D 1 ”=a line segment “ A 2 C 2 ”:a line segment “ C 2 D 2 ”]; and

a point, which is a middle point between the division point “A 1 ” and the transfer point “E 1 ”, is defined as a runout point “C 1 ”.

3. A planetary gear train of an internal engagement type comprising:
an internal gear having multiple internal gear teeth at an inner peripheral portion of the internal gear, each of the internal gear teeth having a tooth-bottom portion, a tooth-middle portion and a tooth-front portion; and
an external gear having multiple external gear teeth at an outer peripheral portion of the external gear, each of the external gear teeth having a tooth-bottom portion, a tooth-middle portion and a tooth-front portion, and the tooth-middle portion of the ex

Assignees

• Denso Corp

Inventors

• Tabuchi Toru
• Nakayama Seiji

Classifications

• F16H2055/0893

  for parallel shaft arrangement of toothed members · CPC title

• F16H55/08

  Profiling · CPC title

• F16H1/32 Primary

  in which the central axis of the gearing lies inside the periphery of an orbital gear · CPC title

• F16H2001/325

  comprising a carrier with pins guiding at least one orbital gear with circular holes · CPC title