Electric phasing of a concentric camshaft

Patent metadata

Field	Value
Publication number	US-9249695-B2
Application number	US-201313779265-A
Country	US
Kind code	B2
Filing date	Feb 27, 2013
Priority date	Feb 28, 2012
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

A concentric cam shaft assembly, including: a first camshaft; a second camshaft including at least a portion disposed radially within the first camshaft; and at least one phasing assembly including first and second electric motors and a first input gear arranged to rotate at a first speed in response to receiving rotational torque from a crankshaft of an engine. The rotational torque is arranged to rotate the first and second camshafts. The first electric motor is arranged to circumferentially off-set the first camshaft with respect to the first input gear. The second electric motor is arranged to circumferentially off-set the second camshaft with respect to the first input gear.

First claim

What is claimed is:

1. A concentric cam shaft assembly, comprising:
an electric motor;
a first camshaft;
a second camshaft including at least a portion disposed radially within the first camshaft;
an input gear:
non-rotatably connected to the first camshaft such that relative rotation between the input gear and the first camshaft is not possible; and,
arranged to rotate at a first speed, with respect to an axis of rotation for the first and second camshafts, in response to receiving rotational torque from a crankshaft of an engine;

an output gear non-rotatably connected to the second camshaft; and,
a harmonic drive including:
a wave generator; and,
a flexible gear radially disposed about the wave generator and including a radially inner circumference in contact with the wave generator, and a radially outer circumference with a plurality of drive teeth, wherein:

the input gear is arranged to rotate the first and second camshafts at the first speed;
the electric motor is arranged to rotate the wave generator, with respect to the flexible gear, about an axis of rotation for the wave generator:
to change respective radial distances of a plurality of points on the outer circumference of the flexible gear with respect to an axis of rotation for the flexible gear;
to urge only a respective portion of the plurality of drive teeth, and not all of the drive teeth, into contact with the one of the input or output gears; and,
to circumferentially off-set, using an engagement of the respective portion of the plurality of drive teeth with the one of the input or output gears, the second camshaft with respect to the first camshaft.

2. The concentric cam shaft assembly of claim 1 , wherein:
the respective portions of the plurality of drive teeth include:
a first portion; and,
a second portion aligned with the first portion via a first straight line passing through the first axis of rotation.

3. The concentric cam shaft assembly of claim 2 , wherein:
the plurality of drive teeth include third and fourth portions not in contact with the input or output gears when the first and second portions are in contact with the input and output gears; and,
the third and fourth portions are radially closer to the axis of rotation for the wave generator than the first and second portions.

4. The concentric cam shaft assembly of claim 1 , wherein:
the flexible gear is arranged to rotate at the first speed.

5. The concentric cam shaft assembly of claim 1 , wherein:
the one of the input or output gears includes a first plurality of teeth having a first number of teeth in a first circumferential span of a portion of the one of the input or output gears including the first plurality of teeth;
the flexible gear includes a second plurality of teeth having a second number of teeth in a second circumferential span, equal to the first circumferential span, of a portion of the flexible gear including the second plurality of teeth; and,
the first number is less than or greater than the second number.

6. The concentric cam shaft assembly of claim 5 , wherein:
the first number is greater than the second number;
increasing a speed of rotation for the wave generator increases a circumferential off-set between the first and second camshafts; and,
decreasing the speed of rotation for the wave generator decreases the circumferential off-set.

7. The concentric cam shaft assembly of claim 5 , wherein:
the first number is less than the second number;
increasing a speed of rotation for the wave generator decreases a circumferential off-set between the first and second camshafts; and,
decreasing the speed of rotation for the wave generator increases the circumferential off-set.

8. A method of operating a concentric cam shaft assembly including an electric motor, a first camshaft, a second camshaft including at least a portion disposed radially within the first camshaft, an input gear, an output gear non-rotatably connected to the second camshaft, and a harmonic drive including a wave generator and a flexible gear radially disposed about the wave generator and including a radially inner circumference in contact with the wave generator, and a radially outer circumference with a plurality of drive teeth, the method comprising:
non-rotatably connecting the input gear to the first camshaft such that relative rotation between the input gear and the first camshaft is not possible;
receiving, with the input gear, rotational torque from a crankshaft of an engine;
rotating, with the input gear, the first and second camshafts;
rotating, with the electric motor, the wave generator, with respect to the flexible gear, about an axis of rotation for the wave generator;
changing, with the wave generator, respective radial distances of a plurality of points on the outer circumference of the flexible gear with respect to an axis of rotation for the flexible gear;
urging, with the wave generator, only respective portions of the plurality of drive teeth, and not all of the drive teeth, into contact with one of the input or output gears;
engaging the plurality of drive teeth with the one of the input or output gears; and,
circumferentially off-setting, using an engagement of the respective portion of the plurality of drive teeth with the one of the input or output gears, the second camshaft with respect to the first camshaft.

9. The method of claim 8 , wherein:
engaging the plurality of drive teeth with the input and output gears includes aligning first and second portions from the respective portions of the drive teeth with a first straight line passing through the first axis of rotation.

10. The method of claim 9 , wherein:
engaging the plurality of drive teeth with the input and output gears includes:
keeping third and fourth portions of the respective portions of the drive teeth out of contact with the input and output gears when the first and second portions are in contact with the input and output gears; and,
displacing the third and fourth portions radially closer to the axis of rotation for the wave generator than the first and second portions.

11. The method of claim 9 , wherein:
the one of the input or output gears includes a first plurality of teeth having a first number of teeth in a first circumferential span of a portion of the one of the input or output gears including the first plurality of teeth;
the flexible gear includes a second plurality of teeth having a second number of teeth in a second circumferential span, equal to the first circumferential span, of a portion of the flexible gear including the second plurality of teeth; and,
the first number is less than or greater than the second number.

12. The method of claim 11 , wherein:
the first number is greater than the second number, the method further comprising:
increasing a speed of rotation for the wave generator to increase a circumferential off-set between the first and second camshafts; and,
decreasing the speed of rotation for the wave generator to decrease the circumferential off-set.

13. The method of claim 11 , wherein:
the first number is less than the second number, the method further comprising:
increasing a speed of rotation for the wave generator to decrease a circumferential off-set between the first and second camshafts; and,
decreasing the speed of rotation for the wave generator to increase the circumferential off-set.

14. The method of claim 8 , further comprising:
rotating the flexible gear at the first speed.

Assignees

• Schaeffler Technologies Ag

Inventors

• Burke Steven
• Dupuis Craig
• Chung Inhwa
• Kohrs Mike
• Schaefer Jens

Classifications

• F01L2001/0473

  Composite camshafts, e.g. with cams or cam sleeve being able to move relative to the inner camshaft or a cam adjusting rod · CPC title

• F01L2001/3521

  Harmonic drive of flexspline type · CPC title

• F01L1/352 Primary

  using bevel or epicyclic gear · CPC title