U.S. patent application number 10/116333 was filed with the patent office on 2003-01-09 for system for the rotation of a camshaft relative to a crankshaft of an internal combustion engine.
This patent application is currently assigned to INA-Schaeffler KG. Invention is credited to Scheidt, Martin.
Application Number | 20030005899 10/116333 |
Document ID | / |
Family ID | 7680308 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030005899 |
Kind Code |
A1 |
Scheidt, Martin |
January 9, 2003 |
System for the rotation of a camshaft relative to a crankshaft of
an internal combustion engine
Abstract
A system for the rotation of a camshaft relative to a crankshaft
of an internal combustion engine, which includes a drive pulley
connected to the crankshaft of the engine through a chain, belt, or
sprocket drive, and includes an electric motor that transfers
torque to the camshaft of the engine. The electric motor is flanged
directly to one end of the and is a primary drive unit of the
camshaft as well as a servomechanism to adjust and maintain a
controlled camshaft angular shift, whereas the drive pulley is
fastened to and moves about the other end of the camshaft within a
defined range of rotation and is provided as a forced
synchronization instrument for the electric motor within the range
of rotation, as well as being a secondary drive unit of the
camshaft. Further, the electric motor (7) is connected to an RPM
controller (10) that synchronizes and modifies the RPM of the
electric motor (7) relative to the RPM of the drive pulley (4).
Inventors: |
Scheidt, Martin; (Adelsdorf,
DE) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.
SUITE 400, ONE PENN CENTER
1617 JOHN F. KENNEDY BOULEVARD
PHILADELPHIA
PA
19103
US
|
Assignee: |
INA-Schaeffler KG
Herzogenaurach
DE
|
Family ID: |
7680308 |
Appl. No.: |
10/116333 |
Filed: |
April 4, 2002 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 1/022 20130101;
F01L 2001/0537 20130101; F02B 2275/18 20130101; F01L 2820/032
20130101; F01L 2201/00 20130101; F01L 1/024 20130101; F01L 2303/02
20200501; F01L 1/34 20130101 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2001 |
DE |
101 16 707.5 |
Claims
1. A system to rotate a camshaft relative to a crankshaft of an
internal combustion engine, comprising a drive pulley (4) that is
connected to the crankshaft of the engine through a chain, belt or
sprocket drive (5), an electric motor (7) that transfers torque to
the camshaft (3) of the engine, the electric motor (7) is attached
to one end (8) of the camshaft (3) directly or through an
intermediate drive mechanism, and acts as a primary drive unit of
the camshaft (3) and as a servomechanism to adjust and maintain a
controlled camshaft angular shift, the drive pulley (4) is fastened
to and moves about an other end (9) of the camshaft (3) within a
defined range of rotation and acts as a forced synchronization
instrument for the electric motor (7) within the range of rotation
as well as a secondary drive unit for the camshaft (3), wherein the
electric motor (7) is connected to an RPM controller (10) with
which an RPM of the electric motor (7) is synchronized and changed
with respect to an RPM of the drive pulley (4) to adjust and
maintain a controlled camshaft angular shift.
2. A system according to claim 1, wherein a wheel hub (11) of the
drive pulley (4) fastened to the other end (9) of the camshaft (3)
rotates about an axial support (12) having sides formed on one side
by a shoulder (13) created by a reduction in diameter in the
camshaft (3) and on the other side by a circular edge (14) of an
annular disk (15) fixed to the end of the camshaft (3).
3. A system according to claim 2, wherein the annular disk (15)
also has a radial follower bracket (16) that sits in a chamber (17)
in a rim (18) of the drive pulley (4) that is shaped as an annular
segment, and a sum of angles between side walls (19, 20) of the
chamber (17), which act as impact surfaces, and lateral edges (21,
22) of the follower bracket (16) equals a maximum angular shift in
the defined range of rotation of the drive pulley (4).
4. A system according to claim 3, wherein a base position of the
camshaft (3) to start the internal combustion engine is determined
at a respective impact position of the follower bracket (16) of the
annular disk (15) at one of the two side walls (19, 20) of the
chamber (17) in the drive pulley (4), depending on whether the
camshaft is designed as an inlet or an exhaust camshaft, and the
base position is fixed by a holding torque also acting on the
follower bracket (16) resulting from a braking or an accelerating
RPM control action on the electric motor (7) relative to the drive
pulley (4).
5. A system according to claim 1, wherein the RPM controller (10)
of the electric motor (7) is connected to an electronic controller
(23) that controls the RPM controller (10) of the electric motor
(7), by evaluating data from an instrument (24) to detect a
position of the crankshaft and an instrument (25) to detect a
position of the camshaft (3) as well as other operating parameters
of the internal combustion engine.
Description
BACKGROUND
[0001] This invention pertains to a system for the rotation of a
camshaft relative to a crankshaft of an internal combustion engine,
in which a drive pulley is connected to the crankshaft of the
engine through a chain, belt or sprocket drive, and an electric
motor transfers torque to the camshaft of the engine.
[0002] In addition to known hydraulic systems that rotate a
camshaft relative to a crankshaft of an internal combustion engine,
there are also a number of known systems that use electric motors
to accomplish this relative rotation of the camshaft. Shifting the
angular position of the camshaft electrically has proven to be
advantageous compared to hydraulic angular shifting in that the
necessary electrical energy is already available prior to the
internal combustion engine being started, and is not subject to the
limitations of a hydraulic system's manufacture. What is especially
disadvantageous in hydraulic systems is the feed characteristics of
the hydraulic pressure medium, which is dependent on RPM and
temperature, which only allows the camshaft to shift its angle
relatively slowly at low engine RPM's and/or at low pressure medium
temperatures.
[0003] A system for the rotation of a camshaft relative to a
crankshaft of an internal combustion engine that defines this class
of electrical shifting of angular position is known from DE 198 07
315 A1, for example. This system is formed essentially of a drive
pulley that is connected to the crankshaft of the internal
combustion engine through a chain drive, and an electrical
servomotor that transfers torque to the camshaft of the internal
combustion engine. In this system, a reducing sprocket gear is
located between the servomotor and the camshaft. This sprocket gear
consists in turn of an external rotor with inner teeth fastened to
the camshaft, and an inner rotor with external teeth fastened to
the drive pulley. The servomotor, the drive pulley and the inner
rotor of the sprocket gear form a single assembly that drives the
camshaft through the external rotor of the sprocket gear. The
relative rotation of the camshaft with respect to the crankshaft is
then accomplished through an angular rotation superimposed on the
internal rotor of the sprocket gear by the servomotor. This angular
rotation acts on the camshaft by means of the external rotor of the
sprocket gear.
[0004] However, this very advantageous solution has the
disadvantage, as do other known solutions that use a planet gear,
eccentric gear or helical gear or the like installed between an
electric motor and the camshaft to produce the relative rotation of
the camshaft, in that the reduction gears used to prevent unwanted
noises that result from the alternating moments of the camshaft
have to be either very precisely designed or provided with
additional play-compensating elements. Reduction gears are also not
a cost-effective alternative to hydraulic shifting systems
considering the concomitant increase in costs to manufacture this
kind of electrical shifting system. Moreover, to achieve as much
frictional retention as possible, these types of reduction gears
are usually designed with high reduction ratios, which have the
disadvantage of magnifying the reduction in the backlash of the
gears as well, thus resulting in an imprecise angular shift of the
camshaft.
SUMMARY
[0005] Therefore, the object of this invention is to design a
system to rotate a camshaft relative to a camshaft of an internal
combustion engine that has the advantages of the designs found in
electrical shifting systems and that at the same time avoids the
disadvantages of a reduction gear installed between an electric
motor and the camshaft. This design is more cost-effective and more
functionally accurate.
[0006] According to the invention, this object is met with a system
in which the electric motor is flanged to one end of the camshaft
directly or through an intermediate drive, and is designed as a
primary drive unit of the camshaft as well as a servomechanism to
adjust and maintain a controlled camshaft angular shift. The drive
pulley is fastened to and moves about the other end of the
camshaft, within a defined range of rotation, and is provided as a
forced synchronizing instrument of the electric motor within the
range of rotation as well as a secondary drive unit of the
camshaft. In this manner, the electric motor is connected to an RPM
controller as well, which synchronizes and changes the RPM of the
electric motor relative to the RPM of the drive pulley to adjust
and maintain a controlled camshaft angular shift.
[0007] In an advantageous embodiment of the system designed
according to the invention, the wheel hub of the drive pulley
fastened to the other end of the camshaft is supported in and
rotates about an axial support, the sides of which are formed on
one side by a shoulder created by a reduction in diameter in the
camshaft and on the other side by the circular edge of an annular
disk that is fixed to the other end of the camshaft. This annular
disk is preferably bolted by an axial fastening screw centrally at
the end of the camshaft, and is preferably designed with a bent
edge so that it fits over the end of the camshaft in the shape of a
cap. Its bent edge forms the side of the axial support for the
drive pulley. However, it is also possible to design the annular
disk without such a bent edge and/or to fasten it in another
suitable manner to the end of the camshaft. Between the annular
disk and the shoulder in the camshaft mentioned, the wheel hub of
the drive pulley is then supported on and rotates about the section
of the camshaft with the reduced diameter. It is even more
advantageous, in the case of a drive pulley located in a belt
drive, to place, in addition, a support bushing between its wheel
hub and the camshaft to provide a dry bearing.
[0008] Another important feature of this annular disk fixed to the
camshaft, which axially fixes the drive pulley of the system
according to the invention, is that it also has a radial follower
bracket that sits in a chamber in the rim of the drive pulley that
has the shape of an annular segment. The sum of the angles between
the side walls of this chamber, which are designed as impact
surfaces, and the lateral edges of the follower bracket is equal to
the defined range of rotation of the drive pulley, i.e. the maximum
angular shift of the camshaft. Only allowed timing positions of the
gas exchange valves in the internal combustion engine, which are
actuated by the camshaft, can occur within this range. The chamber
for the follower bracket can be designed as a recess in the rim of
the drive pulley produced by stamping, forming or the like, or as a
penetration in the same produced through cutting or other
means.
[0009] Furthermore, the system designed according to the invention
is characterized in that the base position of the camshaft,
necessary mainly to start the internal combustion engine, is
determined at the respective impact position of the follower
bracket of the annular disk at one of the two side walls of the
chamber in the drive pulley, depending on whether the camshaft is
designed as an inlet or an exhaust camshaft. This base position is
fixed by a holding torque resulting from a braking or an
accelerating RPM control action on the electric motor relative to
the drive pulley, said holding torque also acting on the follower
bracket. In the case of an inlet camshaft, this base position
usually corresponds to a "late" timing position of the gas exchange
valves that can be fixed using a braking RPM control action on the
electric motor relative to the drive pulley when the inlet camshaft
is rotating clockwise as seen from the drive pulley side. This RPM
control action pushes the follower bracket on the inlet camshaft
against the side wall of the chamber in the drive pulley opposite
the direction of rotation of the drive pulley. The base position of
an exhaust camshaft, on the other hand, usually corresponds to an
"early" timing position of the gas exchange valves that can be
fixed using an accelerating RPM control action on the electric
motor relative to the drive pulley when the exhaust camshaft is
likewise rotating clockwise as seen from the drive pulley side.
This RPM control action causes the follower bracket on the inlet
camshaft to push against the side wall of the chamber in the drive
pulley in the direction of rotation of the drive pulley. In this
way, chatter between the follower bracket on the camshaft and the
side walls of the chamber in the drive pulley, caused by the
alternating moments of the camshaft, can be effectively prevented,
especially when the engine is started, but also while the camshaft
is shifted during operation of the engine.
[0010] Finally, in a useful extension of the system designed
according to the invention, it is proposed to install an electronic
controller ahead of the electric motor's RPM controller that can
regulate the electric motor's RPM controller through the evaluation
of data from an instrument to detect the position of the crankshaft
and from an instrument to detect the position of the camshaft, as
well as other operating parameters of the internal combustion
engine. The RPM controller can be designed as a known potentiometer
or the like, which imposes different RPM's on the electric motor
based on its different currents. Likewise, the instruments to
detect the positions of the camshaft and the crankshaft are
preferred to be designed as known induction or photo sensors that
cooperate with triggering disks located on the camshaft and
crankshaft accordingly. The other detected operating parameters in
the controller are the motor load, motor temperature and motor RPM,
which together with the positions of the camshaft and crankshaft
are evaluated and converted into an appropriate control signal for
the electric motor's RPM controller. By constantly detecting and
evaluating this data in the controller, it is possible to react to
all operating conditions of the engine by appropriately changing
the RPM of the electric motor and thus changing the angular
position of the camshaft with respect to the crankshaft. Basically,
the adjustment of a controlled camshaft angular shift is
accomplished based on the base position of the camshaft in that
first the RPM of the camshaft is synchronized to the RPM of the
drive pulley so as to introduce the angular shift of the camshaft
starting from this synchronized RPM by braking or accelerating the
electric motor. After attaining the shift angle of the camshaft,
the RPM of the electric motor is again synchronized with respect to
the RPM of the drive pulley and the next angular shift of the
camshaft is made from that point, with the drive pulley "idling" at
all positions of the follower bracket other than its impact
positions in the chamber of the drive pulley.
[0011] The system designed according to the invention to rotate a
camshaft relative to a crankshaft of an internal combustion engine
thus has the advantage, when compared to systems known from the
state of the technology operated by electric motors, in that there
is no longer a need for a reduction gear installed between the
electric motor and the camshaft since the camshaft is driven
directly by an electric motor to shift the angular position of the
camshaft. Since this also eliminates all means necessary to
compensate for play and for retention within these gears, and since
the drive pulley of the camshaft can also be designed as a
conventional chain, belt, or sprocket pulley, the system according
to the invention has, above all, considerable cost advantages in
comparison with the known electrical shifting systems and at the
same time also represents a valuable alternative to the known
hydraulic shifting systems. Moreover, direct drive of the camshaft
by the electric motor at all times guarantees a precise angular
positioning of the camshaft with respect to the crankshaft with no
play, wherein by forced synchronization of the camshaft
mechanically by means of the follower bracket on the camshaft and
the chamber in the drive pulley, it is also ensured that only
allowed timing positions of the gas exchange valves, which are
actuated by the camshaft, can occur during disruptions, during
shutoff and startup of the engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] This invention is explained in more detail below with on the
basis of a preferred embodiment and is shown schematically in the
associated drawing. In the drawings:
[0013] FIG. 1 is a schematic representation of a cylinder head of
an internal combustion engine designed with two overhead camshafts
with the system according to the invention attached to one of the
two camshafts;
[0014] FIG. 2 is an front view of the drive pulley of a system
according to the invention; and
[0015] FIG. 3 is a cross section through the drive pulley mounted
to the camshaft of the system according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] Shown in FIG. 1 is the cylinder head 1 of an internal
combustion engine with two overhead camshafts 2, 3. Of these,
camshaft 3, which is designated as an exhaust camshaft, includes a
system to rotate camshaft 3 relative to the crankshaft of the
engine (not shown). This system includes a drive pulley 4, which is
connected to the crankshaft belt pulley 6 of the engine through
belt drive 5, and an electric motor 7 that transfers torque to
camshaft 3 of the engine.
[0017] Moreover, it can be seen in FIG. 1 that the electric motor 7
is directly attached to the end 8 of the camshaft 3 according to
the invention, and thus forms the primary drive unit of the
camshaft 3 as well as the servomechanism to adjust and maintain a
controlled camshaft angular shift. The drive pulley 4 is fastened
to and moves about the other end 9 of the camshaft 3 within a
defined range of rotation. Within this range of rotation, it is
designed as a forced synchronization instrument of the electric
motor 7 as well as a secondary drive unit of the camshaft 3. The
electric motor 7 is also connected to an RPM controller 10 that
synchronizes the RPM of the electric motor 7 to maintain a
controlled camshaft angular shift and modifies it to adjust a new
camshaft angular shift.
[0018] FIGS. 2 and 3 show, moreover, that the wheel hub 11 of the
drive pulley 4 fastened to the other end 9 of the camshaft 3 turns
about an axial support 12 to realize the range of rotation. The
sides of the axial support are formed on one side by a shoulder 13
created by a reduction in diameter in the camshaft 3 and on the
other side by the circular edge 14 of an annular disk 15 that is
non-rotably fixed to the end of the camshaft 3. In FIG. 3, it can
be clearly seen that the annular disk 15 is bolted to the other end
9 of the camshaft 3 with an axial fastening screw 27, and has a
bent edge 14 in this design that fits over the other end 9 of the
camshaft 3 like a cap, the end of which constitutes one of the
support sides of the axial support 12 for the drive pulley 4. To
improve the radial support of the drive pulley 4, in this case
designed as a belt pulley, an additional support bushing 26, also
indicated in FIG. 3, is placed between its wheel hub 11 and the
camshaft 3. This support bushing guarantees a dry bearing for the
support of the drive pulley 4, which must be kept free of
lubricants where belt drives are used.
[0019] Furthermore, FIGS. 2 and 3 show that the annular disk 15
also has a radial follower bracket 16 on the camshaft 3 that sits
in a chamber 17 in the rim 18 of the drive pulley 4 that is in the
shape of an annular segment. This chamber 17 is designed as a local
recess in the rim 18 of the drive pulley 4 that had been formed
into the drive pulley 4 when it was produced, in this case from
sintered metal. The size of the segment of the chamber 17 and the
width of the follower bracket 16 are selected such that the sum of
the angles seen in FIG. 2 between the side walls 19, 20 of the
chamber 17 designed as impact surfaces for the follower bracket 16
and the lateral edges 21, 22 of the follower bracket 16 is equal to
the defined range of rotation of the drive pulley 4, i.e. is equal
to the maximum angular shift of the camshaft 3.
[0020] Finally, with the help of the representation according to
FIG. 2, it can be seen that the base position of camshaft 3, which
is designed as an exhaust camshaft, which is needed mainly to start
the internal combustion engine, is determined by the position at
which the follower bracket 16 of the annular disk 15 impacts the
side wall 19 of the chamber 17 in the drive pulley 4. This impact
position of the follower bracket 16 corresponds to an "early"
timing position of the gas exchange valves of the internal
combustion engine that are actuated by the camshaft 3. In this base
position, the camshaft 3 is fixed by a holding torque that acts on
the follower bracket 16 in addition by means of an accelerated RPM
control action on the electric motor 7 relative to the drive pulley
4 so as to prevent the follower bracket 16 from chattering in the
chamber 17 as a result of alternating moments on the camshaft 3
when the engine is started. In this way, the control of the RPM of
the electric motor needed to accomplish this is done, as is the
control of the RPM to adjust and maintain a controlled camshaft
angular shift, by a electronic controller 23 installed ahead of the
RPM controller 10 of the electric motor 7, indicated in FIG. 1
only. As shown in FIG. 1 schematically as well, this electronic
controller in turn is connected to an instrument 24 to detect the
position of the crankshaft and to an instrument 25 to detect the
position of the camshaft 3 as well as to other measurement points
to detect various operating parameters of the engine, which are not
shown. The data collected by the instruments 24, 25 and the other
measurement points are evaluated by this electronic controller 23
and are converted to a signal with which the RPM controller 10 of
the electric motor 7 can be controlled such that the camshaft 3 has
an optimum angular position with respect to the crankshaft in every
operating state of the engine.
1 List of Elements 1 Cylinder Head 2 Camshaft 3 Camshaft 4 Drive
Pulley 5 Belt Drive 6 Crankshaft Belt Pulley 7 Electric Motor 8 One
End of 3 9 The Other End of 3 10 RPM Controller 11 Wheel Hub 12
Axial Support 13 Shoulder 14 Edge 15 Annular Sisk 16 Follower
Bracket 17 Chamber 18 Rim 19 Side Wall 20 Side Wall 21 Lateral Edge
22 Lateral Edge 23 Controller 24 Instrument 25 Instrument 26
Support Bushing 27 Fastening Screw
* * * * *