U.S. patent application number 09/804528 was filed with the patent office on 2001-09-20 for valve timing control apparatus of an internal combustion engine.
Invention is credited to Golovatai-Schmidt, Eduard.
Application Number | 20010022165 09/804528 |
Document ID | / |
Family ID | 7635424 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010022165 |
Kind Code |
A1 |
Golovatai-Schmidt, Eduard |
September 20, 2001 |
Valve timing control apparatus of an internal combustion engine
Abstract
A valve timing control apparatus, includes a drive wheel in
driving relation with the crankshaft and has a hollow space with at
least one hydraulic working chamber demarcated by two boundary
walls extending inwardly from an inner wall surface of the drive
wheel. Mounted in fixed rotative engagement with the camshaft and
fitted in the hollow space of the drive wheel is a rotatable
impeller having at least one vane to subdivide the working chamber
in two hydraulic pressure compartments. A seal, positioned between
a free end face of the vane of the impeller and the inner wall
surface of the drive wheel, fluidly seals the pressure compartments
from one another and is formed by a roller-type sealing member
spring-mounted in radial direction in an axial groove of the vane.
The inner wall surface forms for the sealing member a slanted ramp
surface which extends radially outwards in a rotation direction of
the impeller, so that a torque is transmittable onto the impeller
by a tangential force component resulting from a combination of the
slanted ramp surface of the drive wheel and a radial spring force
of the sealing member applied upon the impeller.
Inventors: |
Golovatai-Schmidt, Eduard;
(Rottenbach, DE) |
Correspondence
Address: |
HENRY M FEIEREISEN
350 FIFTH AVENUE
SUITE 3220
NEW YORK
NY
10118
|
Family ID: |
7635424 |
Appl. No.: |
09/804528 |
Filed: |
March 12, 2001 |
Current U.S.
Class: |
123/90.16 ;
123/90.15 |
Current CPC
Class: |
F01L 1/3442 20130101;
F01L 2001/34479 20130101 |
Class at
Publication: |
123/90.16 ;
123/90.15 |
International
Class: |
F01L 001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2000 |
DE |
100 13 479.3 |
Claims
What is claimed is:
1. Apparatus for adjusting a rotational relation between a camshaft
and a crankshaft of an internal combustion engine, comprising: a
drive wheel configured as outer rotor in driving relation with the
crankshaft and defining a center axis, said drive wheel including a
cylindrical peripheral wall and two sidewalls for formation of a
hollow space which defines at least one hydraulic working chamber
demarcated by two boundary walls extending inwardly from an inner
wall surface of the peripheral wall in the direction of the center
axis; a rotatable impeller configured as inner rotor and mounted in
fixed rotative engagement with the camshaft, said impeller fitted
in the hollow space of the drive wheel and having a wheel hub and
at least one vane extending radially out from the wheel hub into
the working chamber of the drive wheel to thereby subdivide the
working chamber in two hydraulic pressure compartments acting in
opposition to one another through selective or simultaneous
admission of hydraulic fluid to thereby effect a rotation or
fixation of the impeller with respect to the drive wheel and thus
of the camshaft relative to the crankshaft; and a seal, positioned
between a free end face of the vane of the impeller and the inner
wall surface of the peripheral wall of the drive wheel, for fluidly
sealing the pressure compartments from one another, said seal being
formed by a roller-type sealing member spring-mounted in radial
direction in an axial groove, with the inner wall surface forming
for the sealing member a slanted ramp surface which extends
radially outwards in a rotation direction of the impeller, so that
a torque is transmittable onto the impeller by a tangential force
component resulting from a combination of the slanted ramp surface
of the drive wheel and a radial spring force of the sealing member
applied upon the impeller, thereby matching adjustment speeds of
the apparatus in both rotation directions during operation of the
internal combustion engine and automatically rotating the impeller
into a desired starting position of the camshaft, when shutting
down the internal combustion engine, thereby mechanically coupling
the impeller and the drive wheel, when the camshaft is in the
starting position; and
2. The apparatus of claim 1, wherein the coupling between the
impeller and the drive wheel is releasable through admission of
hydraulic fluid into a respective one of the pressure
compartments.
3. The apparatus of claim 1, wherein the impeller and the drive
wheel are coupled in the starting position of the camshaft in at
least one of a positive engagement and non-positive engagement.
4. The apparatus of claim 1, wherein the impeller has a plurality
of said vane and a plurality of said seal in one-to-one
correspondence for interaction with ramp surfaces of the inner wall
surface.
5. The apparatus of claim 1, wherein the vane includes a slide shoe
for supporting the sealing member, said slide shoe having a top
side, formed as a half-round bearing shell, and a bottom side acted
upon by a spring.
6. The apparatus of claim 1, wherein the vane includes a borehole,
terminating at the axial groove, for accommodating the spring and,
said axial groove having a width, which substantially corresponds
to a diameter of the sealing member and exceeds a diameter of the
borehole, and a depth which is so sized that the sealing member is
almost entirely receivable therein.
7. The apparatus of claim 1, wherein the ramp surface is formed
with a depression in a region of a rotation position of the
impeller corresponding to the desired starting position of the
camshaft, for reinforcing a holding moment of the sealing member,
resulting from the coupling of the impeller with the drive wheel by
force, by an additional positive engagement.
8. The apparatus of claim 7, wherein the depression is formed as a
recessed axial area having a slanted transition at a juncture to
the ramp surface.
9. The apparatus of claim 7, wherein the depression is formed as an
axial trough having a hemispherical profile at a radius
corresponding to a radius of the sealing member.
10. Apparatus for adjusting a rotational relation between a
camshaft and a crankshaft of an internal combustion engine,
comprising: a drive wheel in driving relation with the crankshaft,
said drive wheel having an interior subdivided in several working
chambers, with each of the working chambers demarcated by an inner
wall surface of the drive wheel; a rotor mounted in fixed rotative
engagement with the camshaft, said rotor fitted in the interior of
the drive wheel and having a plurality of radial vanes to subdivide
each of the working chambers in two hydraulic pressure
compartments; and a plurality of roller-type, spring-biased sealing
members, each of the sealing members being disposed between an end
face of a corresponding one of the vanes and an inner wall surface
of the drive wheel for fluidly sealing the pressure compartments
from one another, whereby the sealing members and the vanes are
placed into one-to-one correspondence; wherein the inner wall
surfaces of the working chambers are each configured as a slanted
ramp surface, which extends radially outwards in a rotation
direction of the rotor, and so interact with the sealing members
that the rotor and the drive wheel are mechanically coupled in a
desired starting position of the camshaft by a tangential force
component resulting from a combination of the slanted ramp surface
of each of the inner wall surfaces of the drive wheel and a radial
spring force of the sealing members applied upon the rotor.
11. The apparatus of claim 10, wherein the coupling between the
rotor and the drive wheel in the starting position of the camshaft
is releasable through admission of hydraulic fluid into a
respective one of the pressure compartments.
12. The apparatus of claim 10, wherein each of the vanes includes a
slide shoe for supporting the sealing members, said slide shoe
having a top side, formed as a half-round bearing shell, and a
bottom side acted upon by a spring.
13. The apparatus of claim 12, wherein each of the vanes includes a
borehole for accommodating the spring and has an end face formed
with an axial groove for receiving the sealing member, said axial
groove having a width, which substantially corresponds to a
diameter of the sealing member and exceeds a diameter of the
borehole, and a depth which is so sized that the sealing member is
almost entirely receivable therein.
14. The apparatus of claim 10, wherein the inner wall surfaces are
each formed with a depression in a region of a rotation position of
the rotor commensurate with the desired starting position of the
camshaft, thereby additionally locking the sealing member in a
positive manner.
15. The apparatus of claim 14, wherein the depression is formed as
a recessed area having a slanted transition at a juncture to the
ramp surface.
16. The apparatus of claim 14, wherein the depression is formed as
an axial trough having a hemispherical profile at a radius
corresponding to a radius of the sealing member.
17. A valve timing control apparatus for an internal combustion
engine, comprising: a drive-side structure secured to a crankshaft;
and a driven-side structure secured to a camshaft and moving
between two end positions relative to the drive-side structure,
said driven-side structure having a roller-type, spring-biased
sealing member rolling on an inner wall surface of the drive-side
structure; wherein the inner wall surface is configured as a
slanted ramp surface, which extends radially outwards and so
interacts with the sealing member as to mechanically couple the
drive-side structure and the driven-side structure in one of the
end positions, commensurate with a starting position of the
camshaft, by a tangential force component generated as the sealing
member rolls on the slanted ramp surface at application of a radial
spring force.
18. The apparatus of claim 17, wherein the inner wall surface is
formed with a depression in the region of the one of the end
positions, thereby additionally locking the sealing member in a
positive manner.
19. The apparatus of claim 18, wherein the depression is formed as
a recessed area having a slanted transition at a juncture to the
ramp surface.
20. The apparatus of claim 18, wherein the depression is formed as
an axial trough having a hemispherical profile at a radius
corresponding to a radius of the sealing member.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the priority of German Patent
Application, Ser. No. 100 13 479.3, filed Mar. 18, 2000, the
subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates, in general, to a valve timing
control apparatus for an internal combustion engine, and more
particularly to a valve timing control apparatus for application as
a hydraulic camshaft adjustment device of rotary piston type
configuration.
[0003] German Pat. No. 197 26 300 A1 describes a valve timing
control apparatus as so-called rotation-type adjustment device
which includes a drive shaft, configured as outer rotor in driving
relationship with a crankshaft of the internal combustion engine,
and an impeller, configured as inner rotor and mounted in fixed
rotative engagement on the camshaft of the internal combustion
engine. The drive wheel defines a hollow space, which is demarcated
by a cylindrical peripheral wall and two sidewalls, for
accommodating the impeller. The hollow space is divided in three
hydraulic working chambers formed by three boundary walls extending
inwardly from the peripheral wall in the direction of the center
axis of the drive wheel. The impeller has thus three vanes radially
extending from a hub into the working chambers of the drive wheel.
As a consequence, each working chamber is subdivided into two
hydraulic pressure compartments which are fluidly sealed from one
another by seals, disposed between the hub of the impeller and the
boundary wall of the drive wheel as well as between the free end
face of each vane of the impeller and the inner wall surface of the
peripheral wall of the drive wheel. When hydraulic fluid is
admitted selectively or simultaneously into the pressure
compartments, the impeller is rotated or fixed in place with
respect to the drive wheel and thus the camshaft is rotated or
fixed in place relative to the crankshaft. A torsional spring,
disposed in a separate space, extends between the impeller and the
drive wheel for applying auxiliary energy to match different
adjustment speeds, resulting from the camshaft friction, in both
rotation directions of the device, on the one hand, and to rotate
the camshaft into a base or starting position that is preferred at
the start of the internal combustion engine, after the internal
combustion engine has been shut down or in the event the pressure
of the hydraulic fluid in insufficient to adjust the apparatus. The
camshaft is held in the starting position during start of the
internal combustion engine in addition by a separate locking
mechanism for mechanically coupling the impeller with the drive
wheel. The locking mechanism is substantially configured as
stopper, which is resiliently received in a vane of the impeller
and axially shiftable in a pocket of a sidewall of the drive wheel,
with the stopper hydraulically connected with the pressure
compartments of the apparatus and releasable when the apparatus is
acted upon by hydraulic fluid again.
[0004] This conventional valve timing control apparatus suffers
shortcomings because matching of the adjustment speeds and the
rotation of the camshaft into the starting position of the camshaft
at start of the internal combustion engine is realized by an
additional spring, resulting in a significant increase in size of
the axial installation space. In order to apply the required
torque, the spring must be sized accordingly, and thus needs
sufficient space, which may lead up to a doubling of the necessary
axial installation space. Moreover, the spring represents an
additional component so that fabrication and assembly results in an
increase of production costs of the valve timing control apparatus.
Another drawback is the required separate locking mechanism for
implementing a mechanical coupling between the impeller and the
drive wheel to hold the starting position of the camshaft during
start of the internal combustion engine, because the resiliently
supported stopper is also composed of a plurality of additional
components and thus complicates the fabrication and assembly and
ultimately to higher production costs for the valve timing control
apparatus.
[0005] It would therefore be desirable and advantageous to provide
an improved valve timing control apparatus, which obviates prior
art shortcomings and is simple in structure and yet reliable in
operation.
SUMMARY OF THE INVENTION
[0006] According to one aspect of the present invention, an
apparatus for adjusting a rotational relation between a camshaft
and a crankshaft of an internal combustion engine, includes a drive
wheel configured as outer rotor in driving relation with the
crankshaft and including a cylindrical peripheral wall and two
sidewalls for formation of a hollow space which defines at least
one hydraulic working chamber demarcated by two boundary walls
extending inwardly from an inner wall surface of the peripheral
wall in the direction of the center axis of the drive wheel, a
rotatable impeller mounted in fixed rotative engagement with the
camshaft and configured as inner rotor fitted in the hollow space
of the drive wheel and having a wheel hub and at least one vane
extending radially out from the wheel hub into the working chamber
of the drive wheel to thereby subdivide the working chamber in two
hydraulic pressure compartments acting in opposition to one another
through selective or simultaneous admission of hydraulic fluid to
thereby effect a rotation or fixation of the impeller with respect
to the drive wheel and thus of the camshaft relative to the
crankshaft, and a seal, positioned between a free end face of the
vane of the impeller and the inner wall surface of the peripheral
wall of the drive wheel, for fluidly sealing the pressure
compartments from one another, with the seal formed by a
roller-type sealing member spring-mounted in radial direction in an
axial groove, wherein the inner wall surface forms for the sealing
member a slanted ramp surface which extends radially outwards in a
rotation direction of the impeller, so that a torque is
transmittable onto the impeller by a tangential force component
resulting from a combination of the slanted ramp surface of the
drive wheel and a radial spring force of the sealing member applied
upon the impeller, thereby matching adjustment speeds of the
apparatus in both rotation directions during operation of the
internal combustion engine and automatically rotating the impeller
into a desired starting position of the camshaft, when shutting
down the internal combustion engine, thereby mechanically coupling
the impeller and the drive wheel, when the camshaft is in the
starting position.
[0007] According to another feature of the present invention, the
coupling between the impeller and the drive wheel can be released
through suitable admission of hydraulic fluid into the respective
one of the pressure compartments.
[0008] According to another feature of the present invention, all
seals arranged at the vanes of the impeller may be formed as
spring-biased roller-type sealing members and accordingly all
portions of the inner wall surface of the peripheral wall of the
impeller in the working chambers may be configured as radially
outwardly extending ramp surfaces. Such construction results in an
increase of the effective mean torque acting on the impeller. Of
course, depending on the number of vanes of the impeller, it may
also be possible to configure only seals of some vanes as
roller-type sealing members and to configure the pertaining
portions of the inner wall surface of the peripheral wall of the
impeller as outwardly extending ramp surfaces to implement an
effective mean torque. Further measures, such as modification of
the ramp angle of the ramp surfaces and/or modification of the
radial spring force of the sealing members may also be used to suit
the effective means torque to conditions of the internal combustion
engine at hand.
[0009] According to another feature of the present invention, the
roller-type sealing members may be supported upon the vanes of the
impeller by slide shoes having a top side, formed as a half-round
bearing shell, and a bottom side acted upon by a spring. Thus,
despite the relatively high radial spring force applied by the
springs for urging the sealing members against the inside wall
surface of the peripheral wall of the impeller, the configuration
of the top side of the slide shoes as bearing shells as well as the
lubrication by means of the hydraulic fluid ensure that the sealing
members properly roll along the ramp surfaces and are prevented
from jamming.
[0010] Suitably, the springs are configured as helical compression
springs which are fitted in radial boreholes in the vanes of the
impeller, with the boreholes terminating at the axial groove of the
sealing members, for accommodating the spring. Helical compression
springs are suitable as relatively high forces can be realized when
being accordingly sized so that the magnitude of the mean torque
applied upon the impeller can be suited to the situation at hand.
Of course other constructions of spring elements are possible as
well, such as, for example, chimney springs or elastomeric
spring-type cushions, received in respective receptacles in the
vanes of the impeller.
[0011] According to another feature of the present invention, the
axial groove may have a width, which substantially corresponds to a
diameter of the sealing member and exceeds a diameter of the
borehole. In this way, sealing gaps are formed between the sealing
members and the groove walls of the axial grooves to allow the
required turning of the sealing members during rotation of the
impeller, on the one hand, and to prevent fluid leakages between
the pressure compartments of the hydraulic working chambers via the
axial grooves. The depth of the axial grooves is suitably so sized
that the sealing member can be almost entirely received therein so
as to avoid a contacting of the slide shoes upon the groove base,
when the sealing members are positioned at the radially innermost
area of the ramp surface. This position normally corresponds to one
of the two end positions of the vanes of the impeller upon the
boundary walls of the drive wheel, whereby in this end position the
spring elements of the sealing members apply a greatest spring
force and thus realize a maximum torque upon the impeller.
[0012] According to another feature of the present invention, the
ramp surfaces are formed with a depression in a region of a
rotation position of the impeller corresponding to the desired
starting position of the camshaft, for reinforcing a holding moment
of the sealing member, resulting from the coupling of the impeller
with the drive wheel by force, by an additional positive
engagement. The depression may be formed as a stepped recessed
axial area having a slanted transition at a juncture to the ramp
surface. Taking into account the width of the vanes of the
impeller, the recessed area is so arranged that the impeller is
blocked in one rotation direction through abutment of its vanes
upon the boundary walls of the drive wheel, whereas the other
rotation direction of the impeller is barred in positive manner
through impact of the sealing members upon the slanted transitions
as well as in non-positive manner through the spring force of the
spring elements of the sealing members.
[0013] In accordance with a variation, the depression may also be
configured as an axial trough having a hemispherical profile at a
radius corresponding to a radius of the sealing member. The
depression is incorporated in the ramp surface such that the
impeller can be locked in place in both rotation directions,
shortly before impact of the vanes upon the boundary walls, in
positive manner through engagement of the sealing members in the
troughs as well as in non-positive manner by the spring force
applied by the spring elements upon the sealing members.
[0014] Regardless of the configuration of the local depressions in
the ramp surfaces, the impeller is coupled with the drive wheel
only when the hydraulic pressure fails to adjust the impeller, e.g.
at shutdown of the engine, so that through admission of hydraulic
fluid into the pressure compartment that is of minimum volume at
coupling position of the impeller, the coupling of the impeller
with the drive wheel is reversed again hydraulically.
[0015] A valve timing control apparatus in accordance with the
present invention has many advantages compared to conventional
apparatuses. The need for a separate spring element that
significantly enlarges the axial installation space is eliminated
to provide the required auxiliary energy between the impeller and
the drive wheel for matching the adjustment speeds of the apparatus
and for rotating the camshaft into the starting position desired at
the start of the internal combustion engine. Rather, the
transmission of a torque upon the impeller is implemented in
accordance with the present invention by a tangential force
component resulting from the slanted ramp surface of the drive
wheel and the radial spring force of each roller-type sealing
member. Thus, space demands for an additional spring element are
reduced and fabrication of such a separate spring element is
avoided so that fabrication and assembly costs can be significantly
reduced. By integrating in the function of the sealing members and
the ramp surfaces at the same time the function of a locking
mechanism to mechanically couple the impeller with the drive wheel
in the starting position of the camshaft, the need for a separate
locking mechanism and the ensuing complexity in conjunction with
fabrication and assembly can be saved and the production costs can
be further reduced.
BRIEF DESCRIPTION OF THE DRAWING
[0016] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
preferred exemplified embodiments of the invention with reference
to the accompanying drawing, in which:
[0017] FIG. 1 is a cross sectional view of a valve timing control
apparatus according to the present invention;
[0018] FIG. 2 is a sectional view of the valve timing control
apparatus, taken along the line II-II in FIG. 1; and
[0019] FIG. 3 is a sectional view of a variation of the valve
timing control apparatus of FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] Throughout all the Figures, same or corresponding elements
are generally indicated by same reference numerals.
[0021] Turning now to the drawing, and in particular to FIG. 1,
there is shown a cross sectional view of a valve timing control
apparatus according to the present invention, generally designated
by reference numeral 1 for application as hydraulic camshaft
adjustment. The valve timing control apparatus 1 is designed as a
rotary piston type unit for attachment to a, not shown, camshaft to
allow variations of a rotational relation between the camshaft and
a crankshaft (not shown) of an internal combustion engine to
thereby open and close gas exchange valves (not shown).
[0022] The valve timing control apparatus 1 substantially includes
a drive wheel 2, which forms an outer drive-side rotor and is
operatively connected to the crankshaft of the internal combustion
engine, and an impeller 10, which forms an inner driven-side rotor
and is mounted in fixed rotative engagement to the camshaft of the
internal combustion engine. The drive wheel 2 is defined by a
center axis C and has a cylindrical peripheral wall 3 and two
sidewalls 4, 5 arranged in spaced-apart disposition on either side
of the peripheral wall 3 to define a hollow space 6 in which the
impeller 10 is fitted. As shown in particular in FIG. 2, which is a
sectional view taken along the line II-II in FIG. 1, the drive
wheel 2 includes four boundary walls 4 projecting inwardly from the
inner wall surface 7 of the peripheral wall 3 in the direction
toward the center axis C to thereby define four hydraulic working
chambers 9.
[0023] The impeller 10 includes a hub 11 and a four vanes 12
extending radially out from the periphery of the hub 11 for
projection into the working chambers 9 in one-to-one
correspondence, thereby subdividing each working chamber in two
pressure compartments 13, 14, acting in opposite directions through
admission of hydraulic fluid through suitable passageways. Of
course, the provision of four working chambers and four vanes is
done by way of example only, and other configurations which
generally follow the concepts outlined here are considered to be
covered by this disclosure.
[0024] As shown in particular in FIG. 2, the pressure compartments
13, 14 of each working chamber 9 are fluidly sealed from one
another by a roller-type sealing member 6 disposed between a free
end face 15 of the associated vane 12 of the impeller 10 and the
inner wall surface 7 of the peripheral wall 3 of the drive wheel 2.
Hydraulic fluid can be admitted selectively or simultaneously into
the pressure compartments 13, 14 to thereby implement a rotation or
fixation of the impeller 10 with respect to the drive wheel 2 and
thus of the camshaft relative to the crankshaft.
[0025] Each of the vanes 12 includes a radial borehole 21 for
accommodating a spring element 20, such as a helical compression
spring, extending between the base of the borehole 21 and a bottom
side of a slide shoe 18 which has a top side in the form of a
half-round bearing shell 19. The borehole 21 terminates at an axial
groove 17 formed at the free end face 15 of each vane 12 for
supporting the sealing member 16 in a resilient manner in
conjunction with the bearing shell 19 of the slide shoe 18. As the
vanes 12 in the working chambers 6 are of an identical
construction, it will be understood by persons skilled in the art
that a description of one of the vanes 12 is equally applicable to
the other vanes 12. The sealing member 16 rolls on portions of the
inner wall surface 7 of the peripheral wall 3 in the working
chamber 9, whereby the portions are configured as slanted ramp
surfaces, which extend radially outwards in rotation direction,
indicated by arrow 24, of the impeller 10.
[0026] As a consequence of the configuration of the sealing member
16 in the form of a spring-biased roller and the inner wall surface
7 of the peripheral wall 3 in the form of a slanted ramp surface,
the interaction of the ramp slant and the radial spring force
results in a tangential force component which transmits upon the
impeller 10 a torque by which the adjustment speeds of the
apparatus are matched in both rotation directions during operation
of the internal combustion engine, on the one hand, and the
impeller 10 is rotated into the desired starting position for the
camshaft at start of the internal combustion engine, after shutdown
of the engine, whereby the impeller 10 and the drive wheel 2 are
coupled in this starting position in a non-positive and positive
manner.
[0027] The axial groove 17 of each vane 12 has a width, which
substantially corresponds to a diameter of the sealing member 16
and exceeds a diameter of the borehole 21, and a depth which is so
sized that the sealing member 16 can be almost entirely received in
the axial groove 17, thereby preventing an impact of the slide shoe
18 upon the base of the borehole 21, when the sealing member 16 is
moved to the radially innermost area of the ramp surface of the
inner wall surface 7.
[0028] As further shown in FIG. 2, the ramp surface of the inner
wall surface 7 is formed in proximity of the radially outermost
area, which corresponds to a rotation position of the impeller
commensurate with the desired starting position of the camshaft,
with a local depression 22 by which the holding force of the
sealing members 16 as a result of the engagement of the impeller 10
with the drive wheel 2 by force, is reinforced by an additional
positive engagement. The depression 22 is formed by a step-shaped
recessed area in the ramp surface with a slanted transition from
the recessed area 22 to the ramp surface. By means of the recessed
area 22, the impeller 10 is blocked in the rotation direction 24
through abutment of the vanes 12 upon the boundary walls 8 of the
drive wheel 2, and blocked in the other rotation direction,
indicated by arrow 25, in positive manner through abutment by the
sealing members 16 upon the slanted transitions of the recessed
area 22 as well as in non-positive manner by the spring force
applied by the springs elements 20 upon the sealing members 16.
[0029] Turning now to FIG. 3, there is shown a sectional view of a
variation of the valve timing control apparatus of FIG. 1. Parts
corresponding with those in FIG. 2 are denoted by identical
reference numerals and not explained again. In this embodiment,
provision is made for depressions in the form of half-round axial
troughs 23 having a radius in correspondence with a radius of the
sealing members 16. The axial troughs 23 are so incorporated in the
ramp surface of the inner wall surface 7 that the impeller 10 can
be locked in place in both rotation directions, shortly before
impact of the vanes 12 upon the boundary walls 8, in positive
manner through engagement of the sealing members 16 in the troughs
23 as well as in non-positive manner by the spring force applied by
the spring elements 20 upon the sealing members 16.
[0030] Both configurations of mechanical coupling between the
impeller 10 and the drive wheel 12, as shown in FIGS. 2 and 3, are
automatically released only after buildup of sufficient pressure
through admission of hydraulic fluid in the pressure compartment
14, minimized in volume, of each working chamber 9 to rotate the
impeller 10 in rotation direction 25.
[0031] While the invention has been illustrated and described as
embodied in a valve timing control apparatus of an internal
combustion engine, it is not intended to be limited to the details
shown since various modifications and structural changes may be
made without departing in any way from the spirit of the present
invention.
[0032] What is claimed as new and desired to be protected by
Letters Patent is set forth in the appended claims:
* * * * *