BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention generally relates to an internal combustion engine having a
hydraulic control system for controlling the operation of a variable camshaft timing
(VCT) system of the type in which the camshaft position is circumferentially varied
relative to the position of a crankshaft in reaction to oil pressure. In such a VCT
system, an electro-hydraulic control system is provided to effect the repositioning
of the camshaft and a locking system is provided to selectively permit or prevent
the electro-hydraulic control system from effecting such repositioning.
[0002] More specifically, this invention relates to a multi-position VCT system actuated
by engine oil pressure and having a locking piston mounted to a rotor, wherein the
locking piston prevents oscillation of the rotor in an advance position, a retard
position, and multitude of positions therebetween.
2. Description of the Prior Art
[0003] It is known that the performance of an internal combustion engine can be improved
by the use of dual camshafts, one to operate the intake valves of the various cylinders
of the engine and the other to operate the exhaust valves. Typically, one of such
camshafts is driven by the crankshaft of the engine, through a sprocket and chain
drive or a belt drive, and the other of such camshafts is driven by the first, through
a second sprocket and chain drive or a second belt drive. Alternatively, both of the
camshafts can be driven by a single crankshaft-powered chain drive or belt drive.
It is also known that the performance of an internal combustion engine having dual
camshafts, or but a single camshaft, can be improved by changing the positional relationship
of a camshaft relative to the crankshaft.
[0004] It is also known that engine performance in an engine having one or more camshafts
can be improved, specifically in terms of idle quality, fuel economy, reduced emissions,
or increased torque, by way of a VCT system. For example, the camshaft can be "retarded"
for delayed closing of intake valves at idle for stability purposes and at high engine
speed for enhanced output. Likewise, the camshaft can be "advanced" for premature
closing of intake valves during mid-range operation to achieve higher volumetric efficiency
with correspondingly higher levels of torque. In a dual-camshaft engine, retarding
or advancing the camshaft is accomplished by changing the positional relationship
of one of the camshafts, usually the camshaft that operates the intake valves of the
engine, relative to the other camshaft and the crankshaft. Accordingly, retarding
or advancing the camshaft varies the timing of the engine in terms of the operation
of the intake valves relative to the exhaust valves, or in terms of the operation
of the valves relative to the position of the crankshaft.
[0005] Heretofore, many VCT systems incorporating hydraulics included an oscillatable rotor
secured to a camshaft within an enclosed housing, where a chamber is defined between
the rotor and housing. The rotor includes vanes mounted outwardly therefrom to divide
the chamber into separated first and second fluid chambers. Such a VCT system often
includes a fluid supplying configuration to transfer fluid within the housing from
one side of a vane to the other, or vice versa, to thereby oscillate the rotor with
respect to the housing in one direction or the other. Such oscillation is effective
to advance or retard the position of the camshaft relative to the crankshaft. These
VCT systems may either be "self-powered" having a hydraulic system actuated in response
to torque pulses flowing through the camshaft, or may be powered directly from oil
pressure from an oil pump. Additionally, mechanical connecting devices are included
to lock the rotor and housing in either a fully advanced or fully retarded position
relative to one another.
[0006] Unfortunately, the above VCT systems may have several drawbacks. For example, U.S.
4,858,572 to Shirai et al., teaches use of spring-loaded locking pistons in two circumferential
positions to lock the rotor and housing in both a fully advanced and a fully retarded
position. Shirai et al. discloses a first pin extending into a radial bore of the
housing. The pin is urged radially inwardly toward the rotor by a spring mounted between
the pin and the bore. When the VCT is in the fully retarded position, an upper end
of the pin fits into a large radius portion of a radial hole in the rotor. If the
VCT is changed to the advanced condition, the first pin is retracted from the radial
hole by fluid pressure overcoming the spring. Another pin positioned opposite the
first pin similarly locks the rotor in the fully advanced position. Thus, the rotor
is prevented from rotary movement relative to the housing.
[0007] One drawback with Shirai et al. is that the pins act to lock the rotor relative to
the housing in only two circumferential positions, either fully advanced or fully
retarded. Another drawback is that the pins may stick in either the fully advanced
or fully retarded position thus jamming the VCT. When the VCT changes from one position
to another, part of the fluid pressure being transferred to the first and second fluid
chambers gets redirected to one of the pins to retract the pin. Accordingly, the fluid
pressure is applied simultaneously to the fluid chambers and the pin. When the fluid
pressure in the fluid chambers is sufficient to start rotating the rotor before the
pin is fully retracted, the rotor side loads the pin causing the pin to stick in the
radial hole and thus renders the VCT inoperative.
[0008] U.S. 5,836,275 to Sato recognized the above-mentioned problem with Shirai et al.
and attempted a solution. Sato teaches use of hydraulic strategy to retract the pin
before charging either the first or second fluid chambers. Accordingly, Sato discloses
fluid pressure supplied to the radial hole in the rotor while simultaneously charging
fluid passages communicating with either the first or second fluid chambers. Because
the fluid passages are initially restricted, and thus only partially in communication
with the first or second fluid chambers, the fluid pressure acts primarily on the
pin to retract the pin before any appreciable rotation of the rotor occurs. After
the pin retracts, the rotor rotates enough to permit the passages to overcome their
restriction and fully communicate with the fluid chambers to effect rotation of the
rotor. Regrettably, however, the Sato invention permits locking of the rotor in only
the fully retarded position.
[0009] U.S. 5,797,361 to Mikame et al. recognized another problem with Shirai et al.. That
is, in the retracted position, the upper end of the pin loads an external surface
of the rotor due to the spring force pushing the pin toward the rotor. This wears
the rotor's circumference creating grooves that facilitate increased leakage between
the housing and the rotor beyond an acceptable level. The leakage lowers the oil pressure
in the chamber and thus deteriorates the responsiveness of the VCT. In addition, the
wear condition hinders smooth relative rotation between the rotor and housing. Finally,
Mikame et al. submits that maintaining fluid pressure in the Shirai et al. invention
at a certain level is difficult, since Shirai et al. relies on fluid pressure caused
by torque fluctuations in the camshaft. Unfortunately, Mikame et al. suffers from
the same drawback as Sato. That is, the locking piston locks the rotor relative to
the housing in only one circumferential position. Finally, the locking piston of Mikame
et al. and the hole with which it interlocks have clearance therebetween that permits
circumferential free play or slack between the housing and the rotor. This slack condition
could lead to noise at engine startup as the locking piston is knocked about within
the hole.
[0010] Accordingly, all of the above mentioned prior art references incorporate a locking
piston mounted within a housing and lockable with a rotor in only one position per
locking piston. For example, the Shirai et al. reference is lockable in only a fully
advanced or fully retarded position using two locking pistons. Furthermore, each locking
piston interlocks with the rotor in diametral engagement, which may lead to sticking
conditions of the VCT, as discussed in Sato.
[0011] Therefore, what is needed is a VCT system that is designed to overcome the problems
associated with prior art variable camshaft timing arrangements using locking pistons,
by providing a variable camshaft timing system that locks a rotor and housing together
in more than one position per locking piston, is not susceptible to unintended lock-up
conditions created by diametral jam conditions between the locking piston and a locking
piston hole, and does not permit rotational slack between the rotor and housing.
SUMMARY OF THE INVENTION
[0012] According to the present invention there is provided a VCT system that is designed
to overcome the problems associated with prior art variable camshaft timing arrangements
using locking pistons, by providing a variable camshaft timing system that locks a
rotor and housing together in more than one position per locking piston, is not susceptible
to unintended lock-up conditions created by diametral jam conditions between the locking
piston and a locking piston hole, and does not permit rotational slack between the
rotor and the housing.
[0013] In one form of the invention, there is included an internal combustion engine having
a camshaft. A rotor is secured to the camshaft and is rotatable with the camshaft,
but non-oscillatable with respect to the camshaft. A housing circumscribes the rotor,
is rotatable with both the rotor and the camshaft, and is further oscillatable with
respect to both the rotor and the camshaft between a fully retarded position and a
fully advanced position. A locking device is also provided for preventing relative
motion between the rotor and the housing. The locking device is mounted within either
the rotor or the housing and is respectively and releasably engageable with the other
of either the rotor and the housing in the fully retarded position, the fully advanced
position, and in at least one and preferably a plurality of intermediate positions
therebetween. The locking device includes a locking piston having keys terminating
one end thereof, and a serrations mounted opposite the keys on the piston for interlocking
the rotor to the housing. Finally, a controlling device for controlling oscillation
of the rotor relative to the housing is provided.
[0014] Accordingly, it is an object of the present invention to provide a VCT system that
obviates or mitigates at least one of the above-mentioned problems of the prior art.
[0015] It is another object to provide a VCT system that is capable of interlocking a rotor
to a housing in not only one or two positions, but in a fully advanced position, a
fully retarded position, and in at least one and preferably a plurality of intermediate
positions therebetween.
[0016] It is yet another object to provide a VCT system that has a locking piston that has
interlocking features terminating one end of the piston, that interlock with other
interlocking features mounted to a component that interlocks with the locking piston,
such that the rotor and housing lock tightly together without slack therebetween and
such that the piston does not jam or become locked up.
[0017] These objects and other features, aspects, and advantages of this invention will
be more apparent after a reading of the following detailed description, appended claims,
and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
Fig. 1 is a perspective view of a camshaft and vane phaser according to the present
invention;
Fig. 2 is an exploded perspective view of the camshaft and vane phaser according to
the preferred embodiment of the present invention;
Fig. 3 is an right end view of the vane phaser of Fig. 2 without the locking plate;
Fig. 4 is a cross-sectional view of components of the vane phaser of Fig. 2 of the
preferred embodiment of the present invention and showing a locking piston engaged
with a locking plate;
Fig. 5 is a cross-sectional view of components of the vane phaser of Fig. 4 and showing
the locking piston disengaged from the locking plate
Fig. 6 is an exploded perspective view of a camshaft and vane phaser according to
an alternative embodiment of the present invention;
Fig. 7 is a cross-sectional left end view of the camshaft and vane phaser of Fig.
6 not including the end plate;
Fig. 8 is a cross-sectional view of components of the vane phaser of the embodiment
of Figs. 6 and 7 of the present invention and showing a locking piston engaged with
a housing;
Fig. 9 is a schematic view of the hydraulic equipment of the camshaft and vane phaser
arrangement according to the preferred embodiment of the present invention and illustrates
a phase shift where the position of the camshaft is changing from neutral position
to a retard position;
Fig. 10 is a schematic view of the hydraulic equipment of the variable camshaft timing
arrangement according to an alternative embodiment of the present invention and illustrates
a phase shift where the position of the camshaft is changing from neutral position
to a retard position in which oil pressure flows from a retard passage to retard chambers
and through a check-valve to a locking piston;
Fig. 11 is a schematic view of the hydraulic equipment of the variable camshaft timing
arrangement according to another alternative embodiment of the present invention and
illustrates a phase shift where the position of the camshaft is changing from neutral
position to a retard position, and further illustrates oil pressure flowing directly
to a locking piston to unlock the housing from the camshaft.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] In general, a hydraulic timing system is provided for varying the phase of one rotary
member relative to another rotary member. More particularly, the present invention
provides a multi-position Variable Camshaft Timing (VCT) system powered by engine
oil pressure for varying the timing of a camshaft of an engine relative to a crankshaft
of an engine to improve one or more operating characteristics of the engine. While
the present invention will be described in detail with respect to internal combustion
engines, the VCT system is also well suited to other environments using hydraulic
timing devices. Accordingly, the present invention is not limited to only internal
combustion engines.
[0020] Referring now in detail to the Figures, there is shown in Figs. 1 and 2 a vane phaser
12 and camshaft 14 according to the preferred embodiment of the present invention.
As shown in Fig. 2, the camshaft 14 has a flange 16 at one end. A flange plate 20
of the vane phaser 12 mounts to the flange 16 and acts as an axial locator for a rotor
22. A housing 68 circumscribes the rotor 22, and the rotor 22 and housing 68 are sandwiched
against the flange plate 20 by a locking plate 58. Three bolts (not shown) fasten
the rotor 22 to the flange 16 of the camshaft 14 so that the rotor 22 is rotatable
with the camshaft 14. Similarly, three other bolts (not shown) fasten the locking
plate 58 to the flange plate 20, thereby securing the housing 68 therebetween. Accordingly,
both the rotor 22 and the housing 68 are rotatable with the camshaft 14 and the rotor
22 and the housing 68 are oscillatable independently of one another.
[0021] Still referring to Fig. 2, the locking plate 58 includes an array of female interlocking
features or serrations 60 therein. The array of female serrations 60 includes a retard
serration 62, an advance serration 64, and a multitude of intermediate serrations
66 therebetween. The housing 68 includes sprocket teeth 70 disposed about its periphery
and includes an internal surface 72 and radially inwardly extending lobes 74 circumferentially
spaced apart with an outwardly extending radial slot 76 in each lobe 74. Each radial
slot 76 is open to the internal surface 72 and extends radially outwardly therefrom.
As shown in Fig. 3, the housing 68 includes a driving vane 78 that is radially and
slidably disposed in each radial slot 76. Each driving vane 78 has an inner edge 80
that engages an external surface 24 of the rotor 22. Each driving vane 78 may be spring-loaded
by a bias member (not shown) radially inwardly to ensure constant contact with the
external surface 24 of the rotor 22.
[0022] Still referring to Fig. 3, the rotor 22 includes radially outwardly extending lobes
26 circumferentially spaced apart, around the external surface 24. One lobe 26 includes
a piston passage 40 for housing a generally T-shaped axial locking piston 42 therein.
Each lobe 26 also includes an inwardly extending radial slot 28 disposed therein.
[0023] The rotor 22 further includes a driven vane 30 radially and slidably disposed in
each radial slot 28. Each driven vane 30 has an outer edge 32 that engages the internal
surface 72 of the housing 68. Each driven vane 30 may be biased radially outwardly
by a bias member (not shown) to ensure constant contact with the internal surface
72 of the housing 68. In that regard, each outer edge 32 of each driven vane 30 of
the rotor 22 slidably cooperates with the internal surface 72 of the housing 68. Likewise,
each inner edge 80 of each driving vane 78 of the housing 68 slidably cooperates with
the external surface 24 of the rotor 22 to permit limited relative movement between
the rotor 22 and the housing 68. The rotor 22 and housing 68 define a fluid chamber
34 that is divided up into advance chambers 36 and retard chambers 38 by the circumferentially
alternating driving and driven vanes 78 and 30. Therefore, the advance and retard
chambers 36 and 38 are also alternately circumferentially interspersed between the
rotor 22 and the housing 68. In addition, the advance and retard chambers 36 and 38
are fluid tightly separated from one another.
[0024] As shown in Fig. 4, the vane phaser 12 is in a locked condition. The axial locking
piston 42 is interlocked with the locking plate 58. The axial locking piston 42 is
disposed within the piston passage 40 of the rotor 22 and has an outer shank end 44
with male interlocking features such as keys 46 thereon and further has an opposite
inner head end 48. The piston and piston passage are axially aligned with the female
serrations 60 in a fully retarded position, a fully advanced position, and in a multitude
of positions therebetween. These positions correspond accordingly with the retard
serrations 62, advance serrations 64, and intermediate serrations 66 of the locking
plate 58. A return spring 50 is disposed against the inner head end 48 of the piston
42 to bias the piston 42 into engagement with the locking plate 58 under a predetermined
biasing force. The male keys 46 engage with the female serrations 60 of the locking
plate 58. Therefore, this design relies on axial interlocking of features and not
on diametral fit. Furthermore, the keys 46 and serrations 60 are designed such that
there is no clearance therebetween. Accordingly, the keys 46 and serrations 60 positively
interlock with one another such that there is no slack between the rotor and housing.
[0025] Circumscribing the outer shank end 44 of the piston 42 is a collar 52 that pilots
the piston 42 in place, acts as a stop for the piston 42, and combines with the inner
head end 48 of the piston 42 to define a piston chamber 56 therebetween, where oil
pressure may build up to retract the piston 42. An unlocking passage 54 provides communication
to the piston chamber 56 from a port 14P in the camshaft 14. Fig. 5 shows the piston
42 disengaged from the locking plate 58 and the return spring 50 fully compressed.
[0026] An alternative embodiment of the present invention is shown in Fig. 6 in exploded
view. The camshaft 14 has the flange 16 at one end for mounting the flange plate 20
thereto. The flange plate 20 acts as an axial locator for a housing 168, which in
turn circumscribes a rotor 122. The rotor 122 and housing 168 are sandwiched against
the flange plate 20 by an end plate 158. Three bolts 92 fasten the end plate 158,
the rotor 122, and the flange plate 20 to the flange 16 of the camshaft 14, in turn
trapping the housing 168 between the flange plate 20 and end plate 158. Accordingly,
the rotor 122 and housing 168 are oscillatable independently of one another.
[0027] The rotor 122, housing 168, and driving and driven vanes 78 and 30 are the same as
those of Fig. 2. Here, however, the rotor 122 includes a piston passage 140 radially
disposed within one of a set of lobes 126. A generally T-shaped radial locking piston
142 and the collar 52 are likewise disposed in the piston passage 140. Additionally,
the housing 168 has an array of female serrations 160 disposed in an internal surface
172 thereof for interlocking with the piston 142. As illustrated in Fig. 7 by way
of a cross-sectional end view, an outer shank end 144 of the radial locking piston
142 is shown in engagement with one of the female serrations 160 of the housing 168.
The array of female serrations 160 includes a retard serration 162, an advance serration
164, and a multitude of intermediate serrations 166 therebetween. Similarly, as shown
in Fig. 8 in cross-sectional view, the radial locking piston 142 is engaged with the
housing 168 and is similar in structure to the axial locking piston 42 of Fig. 4.
[0028] In operation, when the engine is off, the vane phaser 12 does not rotate and no engine
oil pressure is present in the vane phaser 12, as shown in Fig. 4. Accordingly, the
return spring 50 biases the axial locking piston 42 into engagement with the locking
plate 58 to lock the vane phaser 12 in place thereby preventing any relative motion
of the vane phaser components. When the engine is on, however, the assembly that includes
the camshaft 14 with the rotor 22 and housing 68 is caused to rotate by torque applied
to the housing 68 by an endless chain or toothed belt (not shown) that engages the
sprocket teeth 70, so that motion is imparted to the endless chain by a rotating crankshaft
(not shown) of the engine. The housing 68, rotates with the camshaft 14 and is oscillatable
with respect to the camshaft 14 to change the phase of the camshaft 14 relative to
the crankshaft.
[0029] According to the preferred embodiment, and referring now to Fig. 9, the vane phaser
12 of the variable camshaft timing system is provided in schematic form. Pressurized
engine oil begins to flow through a camshaft bearing 18, into a 3-way on/off control
valve 82, and through the 3-way on/off control valve 82 into a 4-way pulse-width-modulated
(PWM) control valve 84. An electronic engine control unit 86 processes input information
from sources within the engine and elsewhere, then sends output information to various
sources including the 3-way on/off control valve 82 and 4-way PWM control valve 84
to effect unlocking and phasing of the vane phaser 12.
[0030] A locking and unlocking arrangement is enabled using the pressurized engine oil flowing
into the 3-way on/off control valve 82. When the 3-way on/off control valve 82 is
on, it directs engine oil pressure to the unlocking passage 54 based upon output from
the engine control unit 86. As shown in Fig. 5, oil pressure accumulates in the piston
chamber 56 and thereby urges the axial locking piston 42 against the force of the
return spring 50. This moves the piston 42 to a position where the axial locking piston
42 releases the vane phaser 12 to an unlocked condition, which then allows the vane
phaser 12 to oscillate or shift phase. Consequently, the axial locking piston 42 is
capable of locking the housing 68 in a fixed circumferential position relative to
the camshaft 14 at a multitude of relative circumferential positions therebetween.
This occurs whenever hydraulic pressure in the unlocking passage 54 falls below a
predetermined value needed to overcome the force of the return spring 50. Referring
again to Fig. 7, an alternative locking arrangement would include the radial locking
piston 142 normally biased out of engagement with the housing 168. The vane phaser
112 would lock up in one of the circumferential positions above a predetermined rotational
speed of the rotor 122. Here, the radial locking piston 142 would engage the housing
168 under a centrifugal force induced above the predetermined speed of the rotor 122.
[0031] Referring again to Fig. 9, once the vane phaser 12 is unlocked, oscillation control
of the vane phaser 12 is enabled using pressurized engine oil supplied from the camshaft
bearing 18 that flows through the 3-way on/off control valve 82 into the 4-way PWM
control valve 84 under closed-loop control. The 4-way PWM control valve 84 is in fluid
communication with an advancing fluid passage 88 and a retarding fluid passage 90
in the camshaft 14 that respectively communicate with the advance and retard chambers
36 and 38 between the rotor 22 and housing 68. The engine control unit 86 may signal
the 4-way PWM control valve 84 to direct oil pressure from a supply port 84S to a
retard port 84R through to the retarding fluid passage 90 and into the retard chambers
38. Simultaneously, engine oil is allowed to exhaust from the advance chambers 36
through the advancing fluid passage 88 into an advance port 84A of the 4-way PWM control
valve 84 and out an exhaust port 84E. Accordingly, the rotor 22 will move toward a
fully retarded position relative to the housing 68.
[0032] Alternatively, the engine control unit 86 may signal the 4-way PWM control valve
84 to direct oil from the supply port 84S to the advance port 84A through the advancing
fluid passage 88 and into the advance chambers 36. Simultaneously, engine oil is allowed
to exhaust from the retard chambers 38 through the retarding fluid passage 90 into
the retard port 84R of the 4-way PWM control valve 84 and out the exhaust port 84E.
Accordingly, the rotor 22 will move toward a fully advance position relative to the
housing 68.
[0033] Additionally, the rotor 22 is capable of locking in the fully retarded position,
the fully advanced position, or a multitude of positions therebetween. The rotor 22
is oscillatable with respect to the housing 68 within a range of at least 30 degrees,
in at least six different circumferential positions. Once the desired phase shift
has been achieved, the engine control unit 86 will signal the 3-way on/off control
valve 82 to permit the oil to exhaust from the piston 42 through the unlocking passage
92 through a locking port 82L of the 3-way on/off control valve 82 and out an exhaust
port 82E. Simultaneously, all engine oil flow to and from the advance and retard chambers
36 and 38 with respect to the 4-way PWM control valve 84 will cease.
[0034] Fig. 10 illustrates an alternative vane phaser 212 of the present invention in schematic
form, where locking control is effectuated by sharing oil pressure from the advance
and retard passages 36 and 38 with the unlocking passage 254. Here, pressurized engine
oil flows through the camshaft bearing 18 and directly into the 4-way PWM control
valve 84 having a closed center. From the 4-way PWM control valve 84 oil flows through
advance and retard passages 88 and 90 to the advance and retard chambers 36 and 38
as per the phaser control configuration of the preferred embodiment. Additionally,
however, a check valve 94 permits engine oil to flow from the retard passage 90 to
the piston 42 to retract the piston 42. Therefore, with the closed center 4-way PWM
control valve 84, oil flows to the piston 42 to unlock the vane phaser 212 only when
the vane phaser 212 changes phase. Alternatively, the 4-way PWM control valve 84 could
have an open center to permit oil flow to the piston 42 any time the engine is in
operation, thus allowing for continuous oscillation control.
[0035] Fig. 11 illustrates a vane phaser 312 according to another alternative embodiment
of the present invention in which the locking piston 42 is always disengaged while
oil flows through the camshaft bearing 18. Here, the unlocking passage 54 communicates
directly with the camshaft bearing 18 to permit engine oil to flow directly to the
piston 42. In this configuration, once oil pressure is high enough to overcome the
force of the return spring 50, the piston 42 will disengage (as shown in Fig. 5).
Therefore, the piston 42 will be disengaged all the time that the engine is running
and supplying sufficient oil pressure. Accordingly, the vane phaser 312 will be able
to move to any position within the accuracy of the phaser control scheme any time
during engine operation.
[0036] From the above, it can be appreciated that a significant advantage of the VCT of
the present invention is that the rotor and housing are lockable relative to one another
in not just one or two positions, but in an advance position, a retard position, and
a multitude of positions therebetween. Additionally, only one locking piston is required
to effect locking the VCT in all of the positions.
[0037] An additional advantage is that the locking piston will not jam with the component
with which it interlocks, since at least the preferred embodiment of the present invention
does not rely on diametral interlocking. Likewise, the present invention will not
be susceptible to free play or slack conditions between the rotor and housing arising
from clearance between locking members.
[0038] While the present invention has been described in terms of a preferred embodiment,
it is apparent that other forms could be adopted by one skilled in the art. For example,
an open-loop control strategy could be employed to achieve the phase shift of the
camshaft. The variable valve timing/variable camshaft timing system of the present
invention can also be controlled during operation either by an open loop system or
a closed loop system, again depending on the needs or wishes of the user. In an open
loop control system, there are only two control positions, either a position where
the rotor moves at a fixed rate to full advance or a position where the rotor moves
at the fixed rate to full retard, without any effort to modulate the rate of movement
of the rotor to its full advance or full retard position, as the case may be, or to
stop the movement of the rotor at any position in between such full advance and full
retard positions. In a closed loop control system, on the other hand, the position
of the rotor relative to the housing is monitored and the system is locked at one
or another of a multitude of possible relative positions of the rotor and the housing
between the full advance and full retard positions.
[0039] Likewise, alternative control valve devices may be employed to control fluid flow.
Finally, female interlocking features may be placed on the locking piston rather than
male interlocking features, and correspondingly male interlocking features may be
mounted on the component that interlocks with the locking piston instead of female
interlocking features. Additionally, the reader's attention is directed to all papers
and documents filed concurrently with or previous to this specification in connection
with this application and which are open to public inspection with this specification,
and the contents of all such papers and documents are incorporated herein by reference.
Accordingly, the scope of the present invention is to be limited only by the following
claims.
[0040] The present invention, in which an exclusive property or privilege is claimed, is
defined as follows:
1. An internal combustion engine comprising:
a camshaft (14);
a rotor (22) secured to said camshaft (14) for rotation therewith, said rotor (22)
being non-oscillatable with respect to said camshaft (14);
a housing (68) circumscribing said rotor (22) and being rotatable with said rotor
(22) and said camshaft (14) and being oscillatable with respect to said rotor (22)
and said camshaft (14) between a fully retarded position and a fully advanced position;
locking means for preventing relative motion between said rotor (22) and said housing
(68), said locking means mounted within one of said rotor (22) and said housing (68)
and respectively and releasably engageable with other of said rotor (22) and said
housing (68) in said fully retarded position, said fully advanced position, and in
at least one intermediate position therebetween; and
means for controlling oscillation of said rotor (22) relative to said housing (68).
2. The internal combustion engine as claimed in claim 1, wherein said locking means is
axially moveable along the axis of rotation of said rotor (22).
3. The internal combustion engine as claimed in claim 1, wherein said locking means is
radially moveable relative to the axis of rotation of said rotor (22).
4. The internal combustion engine as claimed in claim 3, wherein said locking means is
releasable from engagement by a centrifugal force incurred above a predetermined rotational
speed of said engine:
5. The internal combustion engine as claimed in claim 1, wherein said locking means further
comprises means responsive to engine oil pressure for disengaging said locking means
to permit oscillation of said housing (68) with respect to said camshaft (14) in response
to engine oil pressure when said engine is in operation.
6. The internal combustion engine as claimed in claim 5, wherein said means for engaging
comprises a passage (54) extending through said camshaft (14) for delivering a supply
of engine oil pressure from said engine directly to said locking means, said supply
of engine oil pressure acting against said locking means to disengage said locking
means.
7. The internal combustion engine as claimed in claim 5, wherein said means for engaging
comprises:
a control valve (82); and
a passage (54) extending through said camshaft for delivering a supply of engine oil
pressure from said engine through said control valve (82), said supply of engine oil
pressure acting against said locking means to disengage said locking means.
8. The internal combustion engine as claimed in claim 5, wherein said means for engaging
comprises a passage (54) extending through said camshaft (14) for delivering a supply
of engine oil pressure from said engine and extending through said means for controlling,
said supply of engine oil pressure acting against said locking means to disengage
said locking means.
9. An internal combustion engine according to any of the preceding claims, wherein said
locking means comprises at least one member mounted on one of said rotor (22) and
said housing (68) and at least three openings associated with the other of said rotor
(22) and said housing (68), said member being moveable into engagement with said openings
so as to lock said rotor to said housing in said fully retarded position, said advanced
position, and at least one intermediate position therebetween.
10. An internal combustion engine comprising:
a camshaft (14);
a rotor (22) secured to said camshaft (14) for rotation therewith, said rotor (22)
having an external surface (24) thereon, said rotor (22) further having at least one
outwardly extending lobe (26) thereon, said at least one outwardly extending lobe
(26) having an inwardly extending radial slot (28) open to said external surface (24),
said rotor (22) being non-oscillatable with respect to said camshaft (14);
a housing (68) circumscribing said rotor (22), said housing (68) having an internal
surface (72) thereon, said housing (68)further having at least one inwardly extending
lobe (74) thereon, said at least one inwardly extending lobe (74)having an outwardly
extending radial slot (76)open to said internal surface(72), said housing (68) being
rotatable with said rotor (72)and said camshaft (14) and being oscillatable with respect
to said rotor (22) and said camshaft (14)between a fully retarded position and a fully
advanced position, said housing (68)and said rotor (22) defining a fluid chamber (34)
therebetween;
a driving vane (78) radially and slidably moveable in said outwardly extending radial
slot (76)of said housing (68), said driving vane (78) having an inner edge (80) engaging
said external surface (24) of said rotor (22), said driving vane (78) being spring-loaded
radially inwardly to ensure constant contact with said external surface (24) of said
rotor (22);
a driven vane (30) radially and slidably disposed in said inwardly extending radial
slot (28) of said rotor (22), said driven vane (30) having an outer edge (32) engaging
said internal surface (72)of said housing(68), said driven vane (30) being spring-loaded
radially outwardly to ensure constant contact with said internal surface (72) of said
housing (68);
said driving and driven vanes (78 and 30) defining at least one advance chamber (36)
and at least one retard chamber (38) alternatively interspersed within said fluid
chamber (34), said advance and retard chambers (36/38) being fluid tightly separated
from each other;
a locking plate (58) secured to one of said rotor (22) and said housing (68);
locking means for preventing relative motion between said rotor (22) and said housing(68),
said locking means mounted within one of said rotor (22) and said housing (68) and
respectively and releasably engageable with other of said rotor (22) and said housing
(68) in said fully retarded position, said fully advanced position, and in at least
one circumferential position therebetween, said locking means being reactive to said
engine oil pressure, said locking means comprising:
a piston passage disposed in said rotor;
a locking piston (42) slidably positioned within said piston passage (40), said locking
piston (42) having an inner end (48) thereon and an outer end (44) oppositely disposed
said inner end (48), said locking piston (42) having male keys (46) on said outer
end (44);
female serrations (60) disposed in one of said plate (58) and said housing (68), said
female serrations (60) being aligned with said piston passage (40) in said fully retarded
position, in said fully advanced position, and in at least one position of said rotor
(22) with respect to said housing (68) and being adapted to receive said male keys
(46) of said locking piston (42) in said fully retarded, in said fully advanced, and
in said at least one intermediate position to prevent oscillation of said housing
(68) with respect to said camshaft (14);
a collar (52) circumscribing a portion of said locking piston (42) to support and
locate said locking piston;
means for engaging said locking piston (42) into engagement with one of said plate
(58)and said housing (68) under a predetermined biasing force when said engine is
out of operation, said means for engaging resiliently acting on said inner end (48)
of said locking piston (42) to urge said outer end (44) of said locking piston (42)
outwardly from said piston passage (40); and
means for disengaging said locking piston (42) from one of said plate (58) and said
housing (68), said means for engaging comprising said piston passage (40)being adapted
to receive engine oil pressure from said means for controlling, said means for engaging
further comprising engine oil being under pressure and being capable of overcoming
said biasing force of said biasing means to slide said locking piston (42) in a direction
opposite of said female serrations (60) to release engagement between said locking
piston (42) and said female serrations (60) and maintain said locking piston (42)
out of engagement with said female serrations (60) to permit oscillation of said housing
(68) with respect to said camshaft (14) in response to engine oil pressure when said
engine is in operation; and
means for controlling oscillation of said rotor (22) relative to said housing (68),
said means for controlling comprises:
means for porting said advance chamber (36); and
means for porting said retard chamber (38);
said means for controlling being capable of supplying said advance and retard chambers
(36/38) with engine oil pressure or exhausting said advance and retard chambers (36/38)
of engine oil pressure to relatively displace said driving and driven vanes (78/30).