U.S. patent application number 11/985125 was filed with the patent office on 2009-05-14 for electro-hydraulic hybrid camshaft phaser.
Invention is credited to Jongmin Lee, Elias Taye.
Application Number | 20090120388 11/985125 |
Document ID | / |
Family ID | 40622530 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090120388 |
Kind Code |
A1 |
Lee; Jongmin ; et
al. |
May 14, 2009 |
Electro-hydraulic hybrid camshaft phaser
Abstract
A hybrid camshaft phaser comprising a conventional vane-type
hydraulically-actuated phaser to which is coupled an electric motor
and gear transmission. The transmission output shaft is coupled to
the phaser rotor, optionally via an intermediate clutch mechanism.
Under engine operating conditions in which the response of a
hydraulic phaser is poor, the electric motor operates to augment
the hydraulic actuation. Such conditions include at least low
ambient temperatures at which oil viscosities are high, and high
ambient temperatures and/or low engine speeds at which oil
pressures are low. Preferably, at engine speeds above about 1500
rpm, the electric motor is de-energized.
Inventors: |
Lee; Jongmin; (Pittsford,
NY) ; Taye; Elias; (Macomb Twp., MI) |
Correspondence
Address: |
Paul L. Marshall, Esq.;Delphi Technologies, Inc.
Mail Code 480410202, P.O. Box 5052
Troy
MI
48007
US
|
Family ID: |
40622530 |
Appl. No.: |
11/985125 |
Filed: |
November 14, 2007 |
Current U.S.
Class: |
123/90.11 ;
123/90.12; 123/90.17 |
Current CPC
Class: |
F01L 2820/01 20130101;
F01L 1/352 20130101; F01L 2001/34469 20130101; F01L 1/3442
20130101; F01L 1/024 20130101; F01L 1/022 20130101; F01L 2820/032
20130101 |
Class at
Publication: |
123/90.11 ;
123/90.12; 123/90.17 |
International
Class: |
F01L 1/34 20060101
F01L001/34; F01L 9/02 20060101 F01L009/02; F01L 9/04 20060101
F01L009/04 |
Goverment Interests
RELATIONSHIP TO GOVERNMENT CONTRACTS
[0001] The present invention was supported in part by a U.S.
Government Contract, No. DE-FC26-05NT42483. The United States
Government may have rights in the present invention.
Claims
1. A hybrid camshaft phaser, comprising: a) a hydraulic camshaft
phaser having a stator and a rotor disposed for rotation within
said stator, said hybrid phaser being actuable by injection of a
hydraulic fluid into chambers formed between said rotor and said
stator; and b) an electric motor drive operatively connected to
said rotor for selectively augmenting actuating torque of said
hydraulic camshaft phaser.
2. A hybrid camshaft phaser in accordance with claim 1 wherein said
electric motor drive comprises an electric motor and a gear
transmission.
3. A hybrid camshaft phaser in accordance with claim 2 wherein said
electric motor is selected from the group consisting of axial
motor, radial motor, brush, brushless, and combinations
thereof.
4. A hybrid camshaft phaser in accordance with claim 2 wherein said
gear transmission is selected from the group consisting of spur,
helical, planetary, harmonic, and cyclical.
5. A hybrid camshaft phaser in accordance with claim 2 wherein said
gear transmission is selected from the group consisting of single
stage and multiple stage.
6. A hybrid camshaft phaser in accordance with claim 1 further
comprising a clutch disposed between said electric motor drive and
said rotor.
7. A hybrid camshaft phaser in accordance with claim 6 wherein said
clutch is selected from the group consisting of friction clutch and
electromagnetic clutch.
8. An internal combustion engine including a camshaft and a
crankshaft wherein a hybrid camshaft phaser is interposed between
said crankshaft and said camshaft, wherein said hybrid camshaft
phaser includes a hydraulic camshaft phaser having a stator driven
by said crankshaft and a rotor disposed for rotation within said,
stator and attached to said camshaft, said hydraulic camshaft
phaser being actuable by injection of a hydraulic fluid into
chambers formed between said rotor and said stator, and an electric
motor drive coupled to said rotor for selectively augmenting
actuating torque of said hydraulic camshaft phaser.
9. A hybrid electro-hydraulic phaser, for shifting the angular
phase of a first shaft relative to a second shaft comprising: a) a
stator rotatable by one of said first and second shafts; b) a rotor
disposed for rotation within said stator and rotatable with the
other of said first and second shafts, said hybrid phaser being
actuable by injection of a hydraulic fluid into chambers formed
between said rotor and said stator; and c) an electric motor drive
operatively connected to one of said rotor and said stator for
selectively augmenting actuating torque of said phaser.
Description
TECHNICAL FIELD
[0002] The present invention relates to camshaft phasers for
varying the phase relationship between crankshafts and camshafts in
internal combustion engines; more particularly, to such phasers
wherein the rotor is actuated either hydraulically or electrically;
and most particularly, to a hybrid camshaft phaser (HCP) wherein
hydraulic rotor actuation torque is selectively supplemented by
electrical actuation torque to improve the speed of response under
operating conditions that are borderline for hydraulic actuation
alone.
BACKGROUND OF THE INVENTION
[0003] Camshaft phasers for varying the phase relationship between
the crankshaft and a camshaft of an internal combustion engine are
well known.
[0004] A prior art hydraulically actuated camshaft phaser typically
comprises a plurality of outwardly-extending vanes on a rotor
interspersed with a plurality of inwardly-extending lobes on a
stator, forming alternating advance and retard chambers between the
vanes and lobes. Engine oil pressurized by the engine's oil pump is
supplied via a multiport oil control valve (OCV) directed by an
engine control module (ECM) to either the advance chambers or the
retard chambers as required to meet current or anticipated engine
operating conditions.
[0005] A prior art electrically actuated camshaft phaser typically
comprises a DC electric motor coupled through a gearbox
transmission to a phaser rotor attached to the engine camshaft. The
rotor is disposed within a stator driven conventionally by the
engine crankshaft and supportive of the motor and gearbox.
Operation of the motor serves to vary the phase relationship of the
rotor to the stator.
[0006] Some benefits of a typical hydraulic phaser are that it
requires relatively little electric current from the engine's
electrical system, generally less than about 5 amps; it is
hydraulically self-locking of the rotor within the stator at any
position; it is capable of defaulting to a specific rotor angle;
and it is low in cost.
[0007] Weaknesses are that it is slow to respond under conditions
of high oil viscosity (low temperatures, as at startup in some
climates) or low oil pressure (low engine speed or hot engine oil);
has a limited rotational range of authority; and has delayed
phasing operation after engine startup due to time required to fill
and stabilize the phaser system.
[0008] Some benefits of a typical electric phaser are very fast cam
phasing, if sufficient current is supplied; a wide range of phasing
operating temperatures (relative insensitivity to oil or coolant
temperatures); prompt phasing, even at engine startup; and
insensitivity to oil contamination, a significant problem when
using hydraulic phasers on diesel engines.
[0009] Weaknesses are that it is expensive to manufacture, costing
several times the cost of a comparable hydraulic phaser; requires
high current, typically in the range of 10-15 amps, requiring a
separate driver box and complex EMS system; has no inherent default
position capability; and requires use of a gearbox transmission
having poor efficiency to provide self-locking, resulting in high
current demand with a large DC motor.
[0010] Increasingly strict engine emissions requirements and
advanced engine technologies can both benefit from a camshaft
phaser having improved speed of response and greater range of
temperature and engine speed operation.
[0011] What is needed is a camshaft phaser having the mechanical
properties of a hydraulic phaser and the response times and
operating range of an electric phaser.
[0012] It is a principal object of the present invention to
increase the speed of response and the operating range of a
camshaft phaser.
SUMMARY OF THE INVENTION
[0013] Briefly described, a hybrid camshaft phaser in accordance
with the invention comprises a conventional vane-type
hydraulically-actuated phaser to which is coupled an electric motor
and gearbox. The gearbox output shaft is coupled to the phaser
rotor. Under engine operating conditions in which the speed and/or
torque response of a hydraulic phaser is poor, the electric motor
augments the hydraulic actuation. Such conditions include at least
low ambient temperatures at which oil viscosities are high, and
high ambient temperatures and/or low engine speeds at which oil
pressures are low.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will now be described, by way of
example, with reference to the accompanying drawings, in which:
[0015] FIG. 1 is an exploded isometric view of an electro-hydraulic
hybrid camshaft phaser in accordance with the invention; and
[0016] FIG. 2 is an assembled isometric view in cutaway of the
hybrid phaser shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Referring now to FIGS. 1 and 2, a first embodiment 100 of an
electro-hydraulic hybrid camshaft phaser in accordance with the
invention includes a vane-type camshaft phaser 10 comprising a
pulley or sprocket 12 for engaging a timing chain or belt (not
shown) operated by an engine crankshaft (not shown). A stator 14 is
disposed against and rotates with pulley/sprocket 12. Stator 14 is
provided with a central chamber 16 for receiving a rotor 18 having
a hub 20. Hub 20 is provided with a recess coaxial with a central
bore in sprocket 12, allowing access of an end 22 of engine
camshaft 24 into rotor hub 20 during mounting of phaser 10 onto an
internal combustion engine 26 during assembly thereof. Central
chamber 16 is closed by a cover plate 28 (omitted from FIG. 2 for
clarity) having a central opening 30, forming advance and retard
chambers between the rotor and the stator in chamber 16.
[0018] A power transmission 31 comprises a planetary gear
transmission box 32 having an internal ring gear 34 mounted to
stator 12 and containing a plurality of planet gears 36
rotationally mounted on fixed shafts 38 to an output plate 40
having a central output shaft 42 engaged into rotor hub 20.
Optionally, a friction or electromagnetic clutch (not shown) may be
disposed between output shaft 42 and rotor hub 20. A sun gear 44 is
disposed in mesh with planet gears 36.
[0019] An electric motor drive 46, shown here generically, has an
output shaft 48 to which sun gear 44 is mounted. The entire
assembly 100 is held together by a plurality of binder screws 50
engaged into threaded bores in stator 14.
[0020] Power transmission 31 is shown here preferentially as a
planetary gear system, although it should be understood that any
type of reduction gear transmission is fully contemplated by the
invention. Examples of contemplated alternate gear arrangements are
spur, helical, harmonic, and cycloidal, which may be single stage
or multiple stage.
[0021] Further, a preferred motor arrangement for electric motor
drive 46 is a small size pancake DC motor disposed axially or
inline, although other motor types and arrangements such as a
standard radial or transverse DC motor are fully contemplated by
the invention. The motor may include brushes or may be
brushless.
[0022] In operation, electro-hydraulic camshaft phaser 100 is
operated like a conventional hydraulic camshaft phaser. As is well
known in the prior art, hydraulic fluid (not shown), typically in
the form of pressurized engine lubricating oil, is supplied to the
advance and retard chambers within the phaser to cause the rotor to
change rotational phase with the stator, thus changing the
rotational phase of the camshaft with respect to the engine
crankshaft to achieve desired engine operating characteristics.
Selective oil flow is typically provided by a spool valve (not
shown) controlled by an Engine Control Module (ECM) (not
shown).
[0023] In addition, the ECM selectively controls the energizing of
electric motor drive 46 and also any optional electromagnetic
clutch. When energized, electric motor drive 46 provides added
torque to rotor 18 that complements the available hydraulic torque
also applied.
[0024] In a presently preferred operating algorithm, electric motor
drive 46 is energized whenever engine 26 is started, to eliminate
the phasing lag characteristic of a hydraulic phaser.
[0025] If the ambient operating temperature of the engine oil is
below a predetermined value, for example -7.degree. C., at which
temperature oil viscosity may be too high for properly responsive
phasing, the electric motor assist is operative.
[0026] Similarly, under conditions of low engine speed and/or high
oil temperature wherein engine oil pressure may be too low for
responsive phasing, the electric motor assist is also
operative.
[0027] Thus, the operating range of thermal conditions and engine
speeds is significantly greater for an electro-hydraulic hybrid
phaserin accordance with the present invention than for a prior art
hydraulic phaser alone. Preferably, the electric motor assist is
de-energized during other engine operating conditions, although
full-time or other scheduled energizing of the electric-motor
assist is fully contemplated by the invention.
[0028] While the invention has been described by reference to
various specific embodiments, it should be understood that numerous
changes may be made within the spirit and scope of the inventive
concepts described. Accordingly, it is intended that the invention
not be limited to the described embodiments, but will have full
scope defined by the language of the following claims.
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