Epicycloidal gear train including bushing-free planetary gear

Patent metadata

Field	Value
Publication number	US-9856944-B2
Application number	US-201514848784-A
Country	US
Kind code	B2
Filing date	Sep 9, 2015
Priority date	Sep 9, 2015
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

An epicycloidal gear assembly for use in a vehicle seat actuator includes a planetary gear that is driven by a worm gear. The planetary gear has an outer edge surface that extends between opposed sides of the gear and has a first set of external teeth, and an inner edge surface that extends between the opposed sides and defines a central opening. The worm gear includes a gear head defining a second set of external teeth, and a gear stem extending from the gear head and passing through the central opening. An outer surface of the gear stem is configured to engage the planetary gear inner edge surface in such a way as to drive the planetary gear, and the planetary gear inner edge surface defines a smooth curve between the first side and the second side.

First claim

The invention claimed is:

1. A gear assembly comprising
a first gear, and a second gear that is engaged with the first gear, the first gear including
a first side,
a second side opposed to the first side,
an outer edge surface that extends between the first side and the second side, the outer edge surface defining a first set of external teeth, and
an inner edge surface that extends between the first side and the second side and defines a central opening,

wherein the inner edge surface defines a smooth curve between the first side and the second side, and
the second gear includes
a gear head defining a second set of external teeth, and
a gear stem extending from the gear head in a direction parallel to a rotational axis of the second gear and through the central opening,

wherein
an outer surface of the gear stem is configured to engage the inner edge surface in such a way as to drive the first gear, and
the first gear is bearing free and bushing free such that the outer surface of the gear stem directly contacts the inner edge surface.

2. The gear assembly according to claim 1 , wherein the smooth curve is defined by a logarithmic function according to the following formula:

p
=

f
⁡

(
x
)

=

a
⁢

⁢
log
⁢

⁢
x

bx
+
c

and wherein p refers to the deviation from perpendicularity, and is a function of the distance x from an origin located midway between the first side and the second side; x refers to a distance from the origin toward one of the first side and the second side; a is a constant that is a function of material rigidity and load; b is a constant that corresponds to the height of the first gear; and c is constant corresponding to an optimized shape.

3. The gear assembly according to claim 1 , wherein the smooth curve is defined by an exponential function according to the following formula:
p=f ( x )= ax n +bx n-1 +c

and wherein p refers to the deviation from perpendicularity, and is a function of the distance x from an origin located midway between the first side and the second side; x refers to a distance from the origin toward one of the first side and the second side; a is a constant that is a function of material rigidity and load; b is a constant that corresponds to the height of the first gear; and c is constant corresponding to an optimized shape.

4. The gear assembly according to claim 1 , wherein the gear stem is formed integrally with the gear head such that the second gear is a monolithic unit.

5. The gear assembly according to claim 1 , further comprising a third gear and a gear shaft that extends through the third gear and is coaxial with the rotational axis,
the third gear having a first end and a second end opposed to the first end, wherein the first end defines a third set of external teeth that serve as an output gear of the gear assembly, and
the second end has a recess, and a surface of the recess defines a first set of internal teeth, the first set of internal teeth sized and dimensioned to engage with the first set of external teeth.

6. The gear assembly according to claim 5 , wherein
the gear stem includes an eccentric through opening that defines an axis parallel to, and spaced apart from, the rotational axis,
the gear shaft protrudes from the second end of the third gear and is received within the gear stem through opening, and
the first gear is constrained by a housing to movements within a plane parallel to the first gear first side and to maintain its rotational orientation,

whereby rotation of the second gear about the gear shaft results in the first gear revolving eccentrically about the longitudinal axis.

7. An actuator including a drive motor having an output shaft and a gear assembly operatively connected to the output shaft, the gear assembly comprising
a first gear including
a first side,
a second side opposed to the first side,
an outer edge surface that extends between the first side and the second side, the outer edge surface defining a first set of external teeth, and
an inner edge surface that extends between the first side and the second side and defines a central opening,

wherein the inner edge surface defines a smooth curve between the first side and the second side, and
the gear assembly comprises a second gear that includes
a gear head defining a second set of external teeth, and
a gear stem extending from the gear head in a direction parallel to a rotational axis of the second gear and through the central opening,

wherein
an outer surface of the gear stem is configured to engage the inner edge surface in such a way as to drive the first gear, and
the first gear is bearing free and bushing free such that the outer surface of the gear stem directly contacts the inner edge surface.

8. The actuator according to claim 7 , wherein the smooth curve is defined by a logarithmic function according to the following formula:

p
=

f
⁡

(
x
)

=

a
⁢

⁢
log
⁢

⁢
x

bx
+
c

and wherein p refers to the deviation from perpendicularity, and is a function of the distance x from an origin located midway between the first side and the second side; x refers to a distance from the origin toward one of the first side and the second side; a is a constant that is a function of material rigidity and load; b is a constant that corresponds to the height of the first gear; and c is constant corresponding to an optimized shape.

9. The actuator according to claim 7 , wherein the smooth curve is defined by an exponential function according to the following formula:
p=f ( x )= ax n +bx n-1 +c

and wherein p refers to the deviation from perpendicularity, and is a function of the distance x from an origin located midway between the first side and the second side; x refers to a distance from the origin toward one of the first side and the second side; a is a constant that is a function of material rigidity and load; b is a constant that corresponds to the height of the first gear; and c is constant corresponding to an optimized shape.

10. The actuator according to claim 7

Assignees

• Ortiz Luis Angel Ramirez
• Robert Bosch Llc

Inventors

• Ortiz Luis Angel Ramirez

Classifications

• F16H57/022

  Adjustment of gear shafts or bearings (for compensating misalignment of axes of toothed gearings without orbital motion F16H1/26; for compensating misalignment of axes of planetary gears F16H1/48) · CPC title

• F16H1/26

  Special means compensating for misalignment of axes · CPC title

• F16H55/17

  Toothed wheels (worm wheels F16H55/22; chain wheels F16H55/30) · CPC title

• F16H1/48

  Special means compensating for misalignment of axes {, e.g. for equalising distribution of load on the face width of the teeth} · CPC title

• B60N2002/0236

  Operations & Transport · mapped topic