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Title: Multi-crankshaft, variable-displacement engine
Abstract: An internal combustion engine for a vehicle provides variable displacement by selectively driving one or more engine crankshafts mounted within a single unitary engine block. In several embodiments the crankshafts are connected to a common output shaft with a one-way clutch between the common output shaft and at least one of the crankshafts. In one aspect starter gearing is independently associated with each of the first and second crankshafts and a starter is provided for selective engagement with the starter gearing of either of the crankshafts. In another aspect, an accessory drive for driving accessory systems of the vehicle receives power from any crankshaft which is operating, yet is isolated from any crankshaft that is not operating by a one-way clutch.
Patent Number: 7,024,858 Issued on 04/11/2006 to Gray Jr.
| Inventors:
|
Gray Jr.; Charles L. (Pinckney, MI)
|
| Assignee:
|
The United States of America as represented by United States Environmental Protection Agency (Washington, DC)
|
| Appl. No.:
|
378627 |
| Filed:
|
March 5, 2003 |
| Current U.S. Class: |
60/709; 60/716; 60/718 |
| Current Intern'l Class: |
F01B 21/04 (20060101) |
| Field of Search: |
60/698,709,716,718
180/21
|
References Cited [Referenced By]
U.S. Patent Documents
| 4064861 | Dec., 1977 | Schulz.
| |
| 4069803 | Jan., 1978 | Cataldo.
| |
| 4331111 | May., 1982 | Bennett.
| |
| 4337623 | Jul., 1982 | Kronogard.
| |
| 4373481 | Feb., 1983 | Kruger et al.
| |
| 4385600 | May., 1983 | Sugasawa et al.
| |
| 4421217 | Dec., 1983 | Vagias.
| |
| 4494502 | Jan., 1985 | Endo et al.
| |
| 4512301 | Apr., 1985 | Yamakawa.
| |
| 4566279 | Jan., 1986 | Kronogard et al.
| |
| 4638637 | Jan., 1987 | Kronogard et al.
| |
| 5398508 | Mar., 1995 | Brown.
| |
| 5490486 | Feb., 1996 | Diggs.
| |
| 5595147 | Jan., 1997 | Feuling.
| |
| 5638777 | Jun., 1997 | Van Avermaete.
| |
| 5870979 | Feb., 1999 | Wittner.
| |
| 5890365 | Apr., 1999 | Sisti.
| |
| 5971092 | Oct., 1999 | Walker.
| |
| 6065440 | May., 2000 | Pasquan.
| |
| 6098733 | Aug., 2000 | Ibaraki et al.
| |
| 6306056 | Oct., 2001 | Moore.
| |
| 6365983 | Apr., 2002 | Masberg et al.
| |
| 6371878 | Apr., 2002 | Bowen.
| |
| 6658852 | Dec., 2003 | Frey.
| |
Primary Examiner: Nguyen; Hoang
Attorney, Agent or Firm: Lorusso, Loud & Kelly, Loud; George
Claims
I claim:
1. An internal combustion engine for a vehicle, said internal combustion engine
providing variable displacement and comprising:
a single unitary engine block;
first and second engine crankshafts mounted within said a single unitary engine
block;
at least two first cylinders and pistons received in each of said first cylinders
to define combustion chambers therein and connected to said first engine crankshaft
to rotatably drive said first crankshaft by combustion of fuel in the combustion
chambers of said first cylinders;
at least two second cylinders and pistons received in each of the second cylinders
to define combustion chambers therein and connected to said second crankshaft to
rotatably drive said second crankshaft by combustion of fuel in the combustion
chambers of said second cylinders;
a common output shaft for receiving power output from both of said first and
second crankshafts, for combining the power outputs and for powering travel of
the vehicle with the combined power output;
a first clutch connecting one of said first and second crankshafts to said common
output shaft, whereby said common output shaft can be driven either in a first
mode by outputs of both of said first and second crankshafts with said clutch engaged
or in a second mode by output of only one of said first and second crankshafts
with the other of said first and second crankshafts isolated from rotation of said
output shaft by disengagement of said first clutch;
first and second starter gearing independently and respectively associated with
said first and second crankshafts; and
a starter mounted for selective and direct engagement with the starter gearing
of either of said first and second crankshafts.
2. An internal combustion engine according to claim 1 further comprising a second
clutch, said first and second clutches respectively connecting said first and second
crankshafts to said output shaft, whereby either of said crankshafts can be connected
to said output shaft in said second mode.
3. An internal combustion engine according to claim 1 further comprising:
an accessory drive for driving accessory systems of the vehicle, said accessory
drive being driven by either one of said crankshafts or by both of said crankshafts.
4. An internal combustion engine according to claim 1, further comprising:
third and fourth clutches respectively connecting said first and second crankshafts
to said accessory drive, whereby the accessory drive receives power from any crankshaft
which is operating, yet is isolated from any crankshaft that is not operating.
5. An internal combustion engine according to claim 3 further comprising a motor
for driving said accessory systems when neither of said crankshafts is producing torque.
6. An internal combustion engine according to claim 3 wherein said common output
shaft is driven by said crankshafts at one end of said single unitary engine block
and said accessory drive is driven by said crankshafts at a second end of said
single unitary engine block opposite said first end.
7. An internal combustion engine according to claim 1 wherein said crankshafts
rotate in opposite directions and said starter is bidirectional.
8. An internal combustion engine according to claim 1 further comprising an accessory
drive for driving accessory systems of the vehicle, said accessory drive being
driven by said output shaft, whereby said accessory systems can be powered by momentum
of the vehicle.
9. An internal combustion engine according to claim 8 further comprising:
a third one-way clutch connecting said output shaft to said accessory drive.
10. An internal combustion engine according to claim 1 additionally comprising
a flywheel on said second crankshaft and wherein said second crankshaft is operated
as a permanent primary crankshaft while said first crankshaft has no flywheel and
is operated intermittently, as needed, to supplement the output power of said second crankshaft.
11. An internal combustion engine according to claim 1 wherein said starter gearing
includes first and second ring gears respectively mounted on said first and second
crankshafts and wherein said starter has a starter gear axially spaced between
said first and second ring gears for movement between positions engaging said first
and second gears, respectively.
12. An internal combustion engine according to claim 1 wherein said starter is
positioned between said first and second crankshafts.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The general field of application is internal combustion engines, particularly
internal combustion engines for automotive use. More specifically, the invention
relates to variable displacement in an internal combustion power plant.
2. The Prior Art
The growing utilization of automobiles greatly adds to the atmospheric presence
of various pollutants including oxides of nitrogen and greenhouse gases such as
carbon dioxide. Accordingly, new approaches to significantly improving the efficiency
of fuel utilization for automotive powertrains are needed.
In most current automotive powertrain designs, an internal combustion engine
(ICE)
is employed as the source of motive power. The average power demanded in normal
driving is quite small, but intermittent events such as rapid acceleration, passing,
trailer towing, and hill climbing demand power far in excess of the average demand.
Because the ICE must respond in real time to the varying power demands of driving,
it must be powerful enough to accommodate the maximum anticipated power demand
rather than only the average power demand.
From an efficiency perspective, the powertrain required by the above considerations
is far from optimal. The energy conversion efficiency of an ICE is at its optimum
over only a relatively narrow range of its permissible loads and operating speeds.
Efficiency tends to be better at high load than at low load, and better at moderate
speed than at either low speed or high speed. Because an automotive ICE is typically
sized to meet the maximum anticipated power demand (which is experienced over only
a small fraction of a typical driving cycle), the vast majority of the time it
operates at low to moderate power levels where efficiency is relatively poor. This
results in a relatively poor net fuel economy.
Operation of the ICE within its most efficient operating range (i.e. nearer
its peak load) over a larger fraction of the typical driving cycle, would dramatically
improve fuel economy. One possible approach would be to simply size the ICE to
match the anticipated average power demand rather than the anticipated maximum
demand, so that its peak efficiency range would more frequently coincide with the
power actually demanded by the vehicle. However, this would give no capability
for meeting peak power demands, leading to unacceptable problems in performance,
driver confidence, and safety.
The problem of achieving better automotive energy efficiency in an ICE-powered
vehicle can thus be understood as a problem of operating its ICE components at
or near their most efficient operating range during the greatest possible portion
of the driving cycle, while preserving the ability to meet peak power demands however
intermittently they occur.
The techniques of turbocharging and supercharging aim to circumvent the constraint
of a fixed volumetric displacement by compressing the intake air so as to allow
a greater mass of air (and hence fuel) to enter each charge, effectively creating
a variable effective (not volumetric) displacement. It should be noted that these
techniques do not in any way obviate the desirability of achieving true variable
volumetric displacement, because they could equally well be applied to an engine
that has a variable volumetric displacement, providing an even broader range of
power capabilities than either technique alone.
It is well known in the prior art to vary the net displacement of a single engine
by switching one or more of its cylinders between a power producing mode and an
idling mode. Many approaches have been used to control participation of the individual
cylinders. For example, the invention disclosed in U.S. Pat. No. 4,494,502 granted
to Endo et al. (1985) deactivates cylinders by denying them air and fuel; U.S.
Pat. No. 5,490,486 (Diggs 1996) deactivates cylinders via selective valve control,
and U.S. Pat. No. 4,064,861 (Schulz 1977) cuts off fuel flow and engages a compression
release. U.S. Pat. No. 6,065,440 granted to Pasquan (2000) uses similar techniques
to activate and deactivate individual cylinders of varying individual displacements
to provide an even wider range of net displacements than possible with cylinders
of identical displacement. The main shortcoming of designs of this type derives
from the fact that all cylinders are connected to a common crankshaft, and so any
cylinder that is not in a power producing mode continues to have a piston reciprocating
within it, leading to energy losses due to friction and other effects.
It is also known to split a multi-cylinder engine into two or more relatively
independent displacement units. Such so-called "split-engine" designs split the
crankshaft of a multi-cylinder engine into two or more parts, each connecting to
a group of cylinders (or cylinder bank) that now may operate relatively independently
from the other cylinder banks. However, in these designs the cylinders continue
to share a common valve train, which means that each idle crankshaft must regain
its appropriate angular position relative to the others when it is reactivated.
This requires a rather complex synchronization means. For example, U.S. Pat. No.
4,069,803 issued to Cataldo (1978) and U.S. Pat. No. 4,373,481 issued to Kruger
et al (1983) both disclose clutch indexing mechanisms for such an arrangement,
which mechanisms add a layer of complexity, cost, and unreliability to such a power plant.
Rather than selectively actuating individual cylinders connected to a common
crankshaft, or cylinder banks connected to split synchronized crankshafts, another
approach would selectively actuate two or more separate engines. For example, an
ICE-based powertrain having a second engine is disclosed in U.S. Pat. No. 5,495,912,
"Hybrid Powertrain Vehicle" (Gray, Jr., et al). A multiple engine system might
in one version consist of a primary engine sized to match average power demand,
supplemented by a secondary engine that can be activated to meet peak demand. In
another version, multiple engines could be individually sized to each serve a specific
range of power demands at which its respective efficiency is greatest.
The concept of achieving variable displacement via a combination of engines is
not new. Several U.S. patents describe separate engines mechanically tied through
a gearing arrangement. U.S. Pat. No. 4,392,393 (Montgomery), "Dual Engine Drive"
describes two engines tied together by a planetary gear set, with a torque converter
uniting the power of the two engines, one or both of which may be active at any
time. In U.S. Pat. No. 4,481,841 (Abthoff et al), "Multiple Engine Drive Arrangement",
a minimum of three engines are connected by means of freewheeling clutches, and
can be selectively operated in parallel or in a series arrangement. Kronogard in
U.S. Pat. No. 4,337,623 suggests a universal base block onto which multiple standard
engines may be connected to form variable displacement power plants of increasing
size. U.S. Pat. No. 4,421,217 (Vagias 1983) teaches a dual-engine system in which
a clutching means is employed to unite the output of two engines and/or operate
one independently of the other. The larger engine when activated delivers its power
through the crankshaft of the smaller engine in a tandem arrangement. Another example
of a multi-engine powertrain is disclosed in U.S. Pat. No. 5,398,508 (Brown 1995)
and employs a primary engine supplemented by an auxiliary engine.
Multiple-engine powertrains such as described above present several
engineering difficulties that limit their practicality in automotive applications.
The need to frequently start and stop the engines is one difficulty. Conventional
ICEs employed in such a system would encounter significant efficiency losses and
increased emissions as a result of frequent restarting. Driver confidence might
also be negatively influenced if the driver perceives the frequent starting and
stopping of the engines as a reliability risk. Accessories present another difficulty
because conventional accessories are powered by direct engine power, meaning that
at least one engine capable of driving accessories must always be running. This
is especially problematic in certain hybrid vehicle applications, in which there
may be times when no engine power is needed at all, in which case accessories would
have to be driven by a different power source entirely. The method of operation
of the power plant is also critical. For example, a method of operation that requires
one engine to run more frequently or to routinely experience greater loads might
cause it to wear out faster and increase the frequency of trips to the repair shop.
Yet another concern is the need for multiple starting means for multiple engines.
For example, the powertrain disclosed in U.S. Pat. No. 4,512,301 (Yamakawa 1985)
requires a separate starter for each engine unit. The inertia of the moving vehicle
may alternatively be employed to start an offline engine, but inertia is not available
if the vehicle is at a stop. Still another concern is the inertial load imposed
on the system when an engine that is offline is reactivated. In particular, if
a reactivation event coincides with a demand for greater power, the need to get
the inactive engines and their heavy flywheels up to speed competes with the need
to deliver power to the vehicle just when it is needed most.
In review of these general methods of providing variable displacement, it becomes
clear that there are a number of features that would be required for such a system
to be commercially successful in today's automotive market.
Vehicle accessories that are operated by direct drive must always be available
when needed and their function must be satisfied cost effectively. Direct drive
accessories include at the minimum the alternator, power steering pump and air
conditioning compressor. If conventional off-the-shelf accessories are connected
in the manner that is conventional for single-crankshaft powertrains, that is,
by a belt and pulley drive connected to the engine crankshaft, then one must choose
which of the two crankshafts will be so connected, and that crankshaft must always
be operating in order to drive the accessories without interruption. This precludes
some promising operating strategies that would call for more flexibility. For example,
certain operating strategies may call for both displacement units to be turned
off at times when no power is demanded from the engine, for example at a dead stop
or during a long deceleration, or with certain methods of operation for hybrid
powertrains. While each displacement unit could be supplied with its own set of
power drive accessories so that the needs of the vehicle may be met whenever either
unit is operating, this would add weight, cost, and complexity to the vehicle.
The cost of manufacture should be as low as possible in volume production. This
again precludes having multiple sets of the same components, such as a duplicate
accessory set for each displacement unit. It also suggests that cooling, lubrication,
and other support systems should be combined to the extent possible. All engines
should also be started by a common starting means to eliminate the need for multiple
starters. The ability to interface the power plant with conventional downstream
and peripheral automotive components is also very desirable because it allows the
use of components that are already in mass production and available at low cost.
Most significantly in this respect, the output of the power plant should be compatible
with a conventional transmission, and it should be able to drive conventional power
drive accessories by the conventional means for which they are designed (i.e.,
belts and pulleys).
Transitioning from one level of displacement to another level of displacement
should be rapid and seamless to the vehicle operator. Regardless of the form of
each displacement unit (whether a cylinder, cylinder bank, or separate engine),
transitioning would require the starting of an additional displacement unit (initially
not in motion) and then adding its torque output to that of the already operating
displacement unit. Therefore, rapidly starting the second displacement unit in
a manner that does not affect the motion of the vehicle or reduce the available
power is critical.
Maximum lifetime and reliability are also very important from a marketing
perspective. To reduce the frequency of repair, it would be desirable to alternate
which engine receives the heaviest duty cycle, to prevent uneven wear and premature
failure. The ability to alternate engines could also improve safety and reliability
of the vehicle overall. If a failure occurred in one of the engines, the other
engine could be used to power the vehicle to a repair facility.
Finally, to be compatible with emerging hybrid automotive technologies that
may become popular in the future, the power plant should optionally offer more
than a single shaft output, perhaps having one shaft output going to the drive
wheels and another going to an auxiliary power unit (for a parallel hybrid), or
both shafts going to auxiliary power units (for a series hybrid).
To summarize, the following features are desirable for a commercially successful
variable displacement automotive power plant:
- 1. Uninterrupted accessory drive;
- 2. Low cost of manufacture;
- a. Shared starting means;
- b. Shared cooling and lubrication/support systems;
- c. Compatibility with conventional transmissions and accessories;
- 3. Smooth transitioning;
- 4. Good lifetime and reliability; and
- 5. Possibility of multiple output shafts.
There exist a variety of prior art power plant designs that have some of these
features, but in contexts unrelated to variable displacement engines. For example,
multi-crankshaft designs are well known in the prior art. Usually, multi-crankshaft
engines were used for high power density applications (such as piston-engine military
aircraft) where compact packaging with high power were especially important. The
crankshafts of such prior art engines were "fixed" together (e.g., with gears or
by chain), and all crankshaft power was added together and discharged through a
single output shaft. For example, U.S. Pat. No. 4,331,111 granted to Bennett (1982)
discloses dual crankshafts which are geared to a common output shaft. This design
is typical of high power density designs which merely combine the output of multiple
crankshafts without providing for variable displacement by switching one crankshaft
in or out. In other designs, it is not uncommon to find each crankshaft geared
to a separate output shaft, which allowed output shaft speed to be changed relative
to the speed of the crankshafts. This was especially useful for propeller aircraft
engines which allowed the crankshafts to have a higher speed than the propeller
shaft. Another motivation leading to multiple crankshafts is related to the cancellation
of gyroscopic effects by having each piston drive two counter rotating crankshafts
via two connecting rods. See, for example, U.S. Pat. No. 5,595,147 (Feuling 1997)
and U.S. Pat. No. 5,870,979 (Wittner 1999). Although all of these inventions do
possess multiple crankshafts, none of them achieve variable displacement.
Similarly, the housing of multiple crankshafts in a common engine block
is not new. U.S. Pat. No. 5,638,777 (Van Avermaete), "Compression or SI 4-Stroke
IC Engines", has two parallel crankshafts each connected to a separate bank of
pistons and each having a different stroke, and residing in a common block. But
the Van Avermaete invention seeks to provide a variable compression ratio for supercharging
effects, not a variable displacement for varying the power capacity of the engine,
and so these apparent similarities are motivated by concerns unrelated to the aims
of the current invention.
However, there is a limited amount of prior art that does have some of these
elements in a variable displacement power plant. One good example is the splitting
of an engine into more than one fully independent displacement unit as taught in
U.S. Pat. No. 4,566,279 granted to Kronogard et al. (1986). Two relatively small
internal combustion engines, referred to as "engine parts", are placed with their
respective crankshafts in line and each connected to a central power output or
take-off shaft via a continuously variable transmission. A second torque transfer
path parallel to the transmission is also provided for driving accessories. U.S.
Pat. No. 4,638,637 also granted to Kronogard et al (1987) discloses a more integrated
version of this concept, including an internal combustion power plant having an
arrangement of two parallel banks of cylinders driving two corresponding parallel
crankshafts, all within a single engine block. A clutching means allows the crankshafts
to be clutched in or out so that either of the displacement units may run by itself
or both may operate together. Alternatively, one of the crankshafts is clutched
in and out while the other is permanently coupled to the drivetrain. The output
of the two crankshafts is combined by a gearing means, and the combined power is
delivered via a single output shaft. Combining the two subengines within a common
block, Kronogard asserts, achieves the advantage of having a single cooling and
lubrication system common to both displacement units. However, there is no mention
of how the individual piston/crankshaft subsystems may be started by a single starter,
nor any mention of how vehicle accessories may be driven while one or the other
crankshaft is offline.
This concept of multiple integrated displacement units also appears in U.S.
Pat. No. 5,971,092 granted to Walker (1999), which discloses an automotive drivetrain
featuring a "split" engine. Although the two parts of the split engine do not reside
in a common block, this invention has many features similar to Kronogard's invention.
A single cooling system (although not a single lubrication system) is shared by
the two engine parts. An overrunning clutch and gearing arrangement allows either
engine unit to operate alone, or both units to operate together. Accessories are
driven by a direct shaft that is backdriven by the transmission, that is, by transmitting
the momentum of the vehicle back through the transmission to power the accessories
while the vehicle is in motion. The disclosure cites the ability to provide a single
set of accessories as an advantage of the invention. Of course, accessory backdrive
is not available while the vehicle is stationary, which presents problems for continuous
loads such as the air conditioning compressor, and for intermittent loads such
as power steering. The disclosure admits that an auxiliary electric power plant
may be necessary to provide power steering and presumably other devices such as
air conditioning. The starting means for the two engine units is not mentioned,
which suggests that two separate starters would be needed.
U.S. Pat. No. 6,306,056 B1 granted to Moore (2001) similarly discloses several
embodiments of a hybrid automotive powertrain consisting of first and second engine
units and an electric motor/generator. In one embodiment of this powertrain, the
two engine units are provided in a single block, with a dual parallel crankshaft
design similar to that of Kronogard. A designated first primary crankshaft can
operate alone, or a secondary crankshaft may operate to supplement the primary
crankshaft via a clutching means, to power a single output shaft. Sharing of a
single oil pump, water pump, cooling system, lubrication system, air filter, fuel
system, engine block, exhaust system, and oil pan are cited as advantages of this
integration. To ensure a rapid and smooth transition when additional power is needed,
the electric motor/generator portion of the powertrain supplies additional power
during the period in which the secondary engine is getting up to speed, after which
the secondary engine takes over and the electric motor is returned to its previous
status. Although the engine design of Moore arguably provides many advantages over
a conventional engine, it has several shortcomings. First, the two engine units
will receive uneven wear because the designated primary engine unit will run more
frequently than the second unit. This is especially a problem in the integrated,
single-block embodiment because worn components would be less accessible for repair.
While the components of the first unit could be designed to be more durable than
those of the second unit, it may be difficult for like components of varying quality
or tolerancing to coexist in a common block while sharing so many support systems.
Second, it is not clear how the primary and secondary units may individually be
started without requiring two separate starters, which would add cost and weight
to the vehicle. Finally, the disclosure makes no mention of how accessories will
be driven. Presumably they will be powered directly by the primary engine, or electrically
powered by the motor/generator. In the first case, it is not clear how they will
continue to receive power when the primary unit is shut off at times of zero or
low power demand. In the second case, conventional power drive accessories would
have to be replaced by electrically powered versions which are not as well established
in the industry. Also see Gray, Jr., et al U.S. Pat. No. 5,495,912.
In summary, no prior art system provides variable displacement in an automotive
powerplant while providing all of the commercially desirable features enumerated above.
SUMMARY OF THE INVENTION
The present invention adopts a variable displacement approach to provide multiple
peak power capabilities, and thus multiple peak efficiency ranges, by varying the
net volumetric displacement of the power plant. The term "volumetric displacement"
refers to the cylinder volume that is swept by a piston in a cylinder as it travels
between the extremes of its stroke. The "net volumetric displacement" (NVD) of
a multi-cylinder engine is the sum of the volumetric displacements of its cylinders.
NVD is a general indicator of engine power because in a naturally aspirated engine
it is the controlling factor in the amount of air that can be inducted in each
intake cycle, thus controlling the mass of each fuel-air charge, and accordingly
the gross energy that is available in each power generating cycle. In a conventional
engine, the volumetric displacement of each cylinder, as well as the NVD of the
engine, is fixed, which means that the peak power capability and the corresponding
range of peak efficiency are also fixed. However, in the present invention the
engine possesses more than one peak power capability, and can thus provide a corresponding
peak efficiency at each of its power output levels rather than just one.
Accordingly, the present invention provides an internal combustion engine
for a vehicle having variable displacement and including first and second crankshafts
mounted within a single unitary engine block. At least two cylinders receiving
pistons defining combustion chambers therein are provided for rotatably driving
each of the first and second crankshafts by combustion of fuel in the combustion
chambers. In one aspect of the present invention, a common output shaft receives
power from both of the first and second crankshafts thereby combining the power
outputs of the first and second crankshafts to propel the vehicle with the combined
power outputs. In this first aspect of the present invention the first and second
crankshafts are connected to the common output shaft through respective clutches
whereby the common output shaft can be driven either in a first mode by outputs
of both of the first and second crankshafts or in a second mode by output of only
one of the first and second crankshafts, with the other of the first and second
crankshafts isolated from rotation of the output shaft by its associated clutch.
The clutches are preferably one-way clutches. This first aspect of the present
invention further includes starter gearing independently associated with each of
the first and second crankshafts and a starter mounted for selective engagement
with the starter gearing of either of the crankshafts.
In a second aspect the present invention provides an internal combustion engine
for a vehicle having variable displacement and including first and second engine
crankshafts mounted within a single unitary engine block. As in the first aspect
of the present invention, each of the crankshafts is connected to at least two
pistons received in respective cylinders and defining combustion chambers therein
whereby each crankshaft is rotatably driven by combustion of fuel in the combustion
chambers associated with the connected pistons. Also in common with the first aspect,
a common output shaft receives torque from both of the first and second crankshafts
for powering the vehicle with the combined power outputs. First and second clutches
respectfully connect the first and second crankshafts to first and second output
gears which drive an input gear fixed on the common output shaft. In the second
aspect of the invention an accessory drive for driving accessory systems of the
vehicle is driven off of the common output shaft, for example, through an output
gear on the common output shaft or through the input gear of the common output shaft.
A third aspect of the present invention provides an internal combustion engine
for a vehicle having variable displacement and including first and second engine
crankshafts mounted within a unitary single engine block. As in the other aspects
of the present invention, each of the crankshafts is connected to at least two
pistons respectively received in cylinders to define combustion chambers therein
whereby each crankshaft is rotatably driven by combustion of fuel in the combustion
chambers associated therewith. As in the first and second aspects of the present
invention a common output shaft receives torque from both of the first and second
crankshafts and powers travel of the vehicle with the combined power. At least
one of the first and second crankshafts is connected to the common output shaft
through a clutch whereby the common output shaft can be driven either in a first
mode by outputs of both of the crankshafts or in a second mode by only one of the
crankshafts with the other crankshaft isolated from rotation of the output shaft
by the clutch. In this third aspect an accessory drive for driving accessory systems
of the vehicle is connected to the first and second crankshafts through respective
one-way clutches whereby the accessory drive receives power from any crankshaft
which is operating, yet is isolated from any crankshaft that is not operating.
Again, the clutches may be one-way clutches.
In a fourth aspect, the present invention provides an internal combustion engine
for the vehicle having variable displacement and including first and second engine
crankshafts mounted within and extending through a single unitary engine block
and providing independent first and second torque outputs at one end of the engine
block. As in the other aspects of the present invention each crankshaft is connected
to at least two pistons received in respective cylinders to define combustion chambers
therein whereby each crankshaft is driven by combustion of fuel in the combustion
chambers associated therewith. This fourth aspect of the present invention also
includes an accessory drive for driving accessory systems of the vehicle, which
accessory drive is connected to the first and second crankshafts through respective
one way clutches, whereby the accessory drive receives power from any crankshaft
which is operating yet is isolated from any crankshaft that is not operating.
The present invention provides a first option (strategy A) in which the first
crankshaft unit always provides the first increment of displacement and power,
with the second unit being added as needed, or a second option (strategy B) of
either the first crankshaft unit or the second crankshaft unit providing the first
increment of displacement and the remaining unit being added as needed. No prior
art device is capable of carrying out both strategies while retaining all of the
commercially desirable advantages cited above.
Additional advantages of the invention under operating strategy A include:
(1) lower hardware cost owing to fewer clutch means (for example, the accessories
can be driven directly by the first crankshaft); (2) flexibility for the second
crankshaft unit to be different from the first, e.g., because the second unit is
expected to be rarely used it can be constructed from less expensive materials;
(3) the secondary unit need not have a flywheel because, being used primarily to
match the speed of a primary unit, it will never operate at a low speed where a
flywheel is needed to smooth the speed fluctuations of the crankshaft. This also
reduces cost and allows a quicker "spin up" to add the second increment of power
more quickly.
Advantages of strategy B include: (1) each crankshaft unit can be identical,
allowing cost savings associated with higher volume of components, e.g., pistons;
(2) increased durability, because each crankshaft unit would equally likely serve
as the first crankshaft unit and thus would likely last approximately twice as
long, and regular operation (at least every other engine start) reduces engine
starting wear; (3) increased reliability, i.e., if a failure occurred in one of
the crankshaft units, the other unit could immediately be transferred to the status
of the primary crankshaft unit for reliable operation in travel to a repair facility.
The present invention varies displacement by use of a multiple-crankshaft engine
design in which at least two distinct crankshafts and cylinder banks are contained
within a single engine block. The crankshafts are independent so that each can
rotate either singly or in combination. A first crankshaft operates pistons which
represent a first displacement, for example, two liters of displacement, and a
second crankshaft operates pistons which provide an additional or "second" displacement
which may be the same as or significantly different from the first displacement,
for example, two liters of displacement. When relatively low power is needed the
first crankshaft unit is operated alone at a higher relative load, i.e., higher
than that at which it would run if all crankshaft units were operating, thus allowing
it to operate at a higher relative efficiency. When higher power is commanded than
can be supplied by the first crankshaft unit, the second crankshaft unit is activated,
and together the two crankshaft units supply the commanded power.
The preferred embodiment to be described in the following has dual crankshafts
in a parallel configuration, but it should be understood that there are many alternative
configurations that lie within the spirit of the invention and the scope of the
claims and that, upon reading the disclosure, will become apparent to those skilled
in the art. For example, additional crankshaft units can optionally be utilized
to progressively add additional power in the same manner. Although the crankshafts
can be arranged in various relative positions, the most likely configurations are
series (end to end) and parallel (side by side). The present invention can readily
be seen to include a family of engines, for example with each crankshaft unit having
one, two, three, four, five or more pistons. In a two-crankshaft embodiment the
corresponding result would be a two, four, six, eight, ten or more piston engine.
The two or more crankshafts and their associated cylinder banks preferably share
one or more of a single oil pump, single water pump, single cooling system, single
lubrication system, single air filter, single fuel system, single engine block,
single exhaust system and single oil pan.
Preferred embodiments of the invention will now be described with reference
to the appended set of drawings.
Through the above and other features to be disclosed herein the present invention
provides on-command variable displacement. Further, the present invention also
provides the previously mentioned features considered necessary for commercial
practicality and acceptance: (a) uninterrupted accessory drive; (b) low cost of
manufacture, including operability with conventional automotive components, and
minimal duplication of components (starting, cooling, lubrication, accessories,
and other support systems); (c) smooth transitioning among units of displacement;
(d) good lifetime and reliability; and (e) an option for multiple output shafts
for use with unconventional hybrid drive systems.
(a) Uninterrupted Accessory Drive
The invention utilizes a unique means to allow a zero displacement mode without
interrupting power to accessories that require a direct power drive. A first preferred
embodiment provides a separate power drive accessories system which operates the
accessories with a drive motor (e.g., electric or hydraulic) independent of either
crankshaft unit. This option allows the accessories to be driven at a speed that
is optimum for the demands being placed on the accessories. In another preferred
embodiment, this drive system is mounted to the engine with drive attachments (through
clutch means) to each crankshaft, as will be described later, and in this configuration
the separate drive motor drives through clutch means as well. When either crankshaft
unit is operating, the accessories are directly driven by power from the operating
crankshaft(s). When neither crankshaft unit is operating, the drive motor drives
accessories through its clutch drive means. A third preferred embodiment for satisfying
accessory needs insures at least one crankshaft unit is operating when accessory
needs exist, whereby the separate drive motor of the previous embodiments can be omitted.
(b) Low Cost of Manufacture
Low cost of manufacture involves both maintaining operability with conventional
automotive components and minimal duplication of components.
The invention utilizes a single starter to start both displacement units. A preferred
embodiment includes a single starter which can engage a first crankshaft unit to
start it and then when more power is commanded than the first crankshaft unit can
supply alone, the starter engages a second crankshaft unit to start it, by means
as will be described later. In another embodiment the first crankshaft unit is
started with a dedicated starter and the second unit is started by activating its
clutch to rapidly raise its speed to that of the first crankshaft unit.
By integrating the separate crankshafts into a common block, each displacement
unit shares the same cooling system and lubrication system.
Compatibility of the power plant with existing automotive components
is assured by (a) providing means as described above to drive conventional power
drive accessories without interruption, allowing off-the-shelf components to be
used without substantial redesign; and (b) delivering a single output shaft for
attachment to conventional transmissions by means of a unique clutching and gearing system.
(c) Smooth Transitioning
Smooth transitioning among various units of displacement is achieved in one
embodiment by adopting an operating strategy in which one displacement unit is
designated as a permanent secondary unit and its flywheel is eliminated, allowing
it to spin up faster.
(d) Reliability and Lifetime
Reliability and lifetime are improved by a first preferred operating
strategy in which the two displacement units interchangeably serve as primary or
secondary displacement units, thereby reducing the potential for uneven wear and
guaranteeing that a first increment of displacement is always available for emergency
use even when one of the units has failed.
(e) Option for Multiple Output Shafts
The present invention can also provide separate crankshaft outputs to provide
certain advantages for powertrains which transmit power to the drive wheels by
electric or hydraulic motors.
In addition to the preferred operating strategy described in the foregoing, a
second operating strategy designates one displacement unit as a secondary unit
that receives intermittent use which, in turn, allows it to be constructed less
expensively than the primary unit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view illustrating two operating strategies in which the
utilization of (for example) two displacement units is dependent on the relative
amount of power demanded;
FIG. 2 is a schematic view of a first embodiment in which the crankshafts of
the two displacement units rotate in the same direction;
FIG. 3 is a schematic view of another embodiment in which the crankshafts rotate
in opposite directions;
FIG. 4 is a schematic view depicting an alternative version of the embodiment
of FIG. 2 with accessories driven at the front, rather than the rear;
FIG. 5 is a schematic view of an embodiment which is a modification of the embodiment
of FIG. 4 wherein the starter motor 15 and crankshaft gearing associated
with same is located at the rear of the engine, rather than at the front;
FIG. 6 is a schematic view of yet another embodiment, this embodiment having
only a single crankshaft clutch which simplifies the structure but limits the operation
to a strategy "A";
FIG. 7 is a schematic view of still another embodiment wherein the output shaft
is integral with one of the crankshafts;
FIG. 8 is a schematic view depicting an alternative version of the embodiment
of FIG. 3, also with accessories driven at the front;
FIG. 9 is a schematic view of an embodiment in which accessories are driven
by a jackshaft connected to the common power output shaft;
FIG. 10 is a schematic view of an alternative version of the embodiment of FIG.
2 in which one flywheel has been omitted; and
FIG. 11 is a schematic view of an alternative embodiment in which the common
power output shaft of the other versions is omitted and instead both crankshafts
deliver their power independently via two respective output shafts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
All of the preferred embodiments shown in the drawing figures and described in
the ensuing discussion illustrate a pair of two-cylinder displacement units in
a parallel arrangement for the purpose of clarity, with the realization that more
than two displacement units, more or less than two cylinders per unit, and/or such
units disposed in a series arrangement rather than a parallel arrangement, could
equally well be employed within the scope of the invention.
FIG. 1 illustrates two different operating strategies, termed "A" and "B". According
to operating strategy "A", a primary displacement unit "Unit 1" operates
alone to power the vehicle when power demand is low to moderate. When power demand
increases past a predetermined level (either a fixed level or a computed level
based on operating conditions), "Unit 2" which is designated as a secondary
unit begins operating to supplement the power of Unit 1. When the power
demand once again drops below the predetermined level, Unit 2 shuts off
and Unit 1 continues to power the vehicle by itself.
In the alternative operating strategy B, neither of Unit 1 and Unit 2
is permanently designated as primary or secondary, meaning that either may take
on the role of primary or secondary unit arbitrarily. Operating under this strategy,
when power demand is below the predetermined level, either Unit 1 or Unit
2 will have been selected to power the vehicle at this relatively low power
demand. The selection might have been made randomly, in an alternating sequence
between Unit 1 and Unit 2, or by a different selection method. When
power demand exceeds the predetermined level, the unit which is not already in
operation is activated to supplement the power of the operating unit. When the
power demand again drops below the predetermined level, either Unit 1 or
Unit 2 is shut off, leaving the other unit to power the vehicle by itself
until power demand increases to the predetermined level again.
It can be seen that under operating strategy A, Unit 1 will always come
into operation before Unit 2, will accumulate more hours of duty than Unit
2, and will see a more constant (less intermittent) duty cycle than Unit
2. On the other hand, under operating strategy B, both units may take turns
acting as primary or secondary, and so each will see very similar patterns of duty.
Clearly operating strategy B is to be preferred for durability reasons, because
each unit receives the same amount of use and sees the same patterns of duty. This
also allows both units to be constructed of similar quality if not identical parts,
improving economies of scale in mass production. Reliability and safety are also
improved because if one unit fails, the other unit can be used to drive the car
to the shoulder of the road or even to a repair facility. Accordingly, operating
strategy B is the currently preferred operating strategy for the present invention,
although it should be noted that any hardware capable of enabling operating strategy
B is also capable of operating in accordance with strategy A if so desired.
FIG. 2 depicts a preferred embodiment in which two displacement units have crankshafts
that rotate in the same direction. Engine block 1 contains internal combustion
engine cylinders 21 and 22 with pistons 21a and 22a
mounted therein to define combustion chambers and connected with first crankshaft
31 in the usual manner via connecting rods and wrist pins (not shown). The
same is true for cylinders 23 and 24 and pistons 23a,
24a, which connect to second crankshaft 32, all of which are
also mounted within engine block 1. Connected to first crankshaft 31
are ring gear 11 and flywheel 12, and similarly second crankshaft
32 is supplied with ring gear 13 and flywheel 14. The ring
gears 11 and 13 and gear 15a of starter 15 are
all axially spaced. In this and all other embodiments in which crankshafts 31
and 32 rotate in the same direction, starter 15 preferably selectively
engages with ring gear 11 or 13 in order to start the respective
crankshaft 31 or 32, the starter gear 15a being made
to selectively engage and disengage with either ring gear by conventional engagement
means such as a Bendix style solenoid mechanism. Accordingly the starter is preferably
provided with two solenoid actuation positions, one to engage only ring gear 11
and another to engage only ring gear 13, rather than the single engagement
position that is familiar to those skilled in the art of single crank engines.
In all embodiments described herein the flywheels 12, 14, and accordingly
starter 15, may be placed on either end of the crankshafts. One-way clutches
41 and 42 (such as Sprague clutches that clutch in one rotational
direction and overrun in the other) are disposed on the first and second crankshafts
and transmit their output to gears 51 and 52, respectively, thereby
causing output gear 53 and output shaft 60 to rotate in a direction
opposite to that of the crankshafts. The placement of output gear 53 between
gears 51 and 52 allows both gears 51 and 52 to transmit
their respective shares of the total power output directly to the output gear 53,
and allows for the cancellation of gear separation forces encountered among gears
51-53, for the bearings of gear 53. The provision of one-way
clutches 41 and 42 ("first and second one-way clutches") allow either
crankshaft unit to operate alone and independently of the other. For example, if
crankshaft 31 is not operating while crankshaft 32 is operating,
one-way clutch 41 isolates crankshaft 31 from gear 51 which
rotates regardless. The same behavior is true of the converse in which the operating
status of crankshafts 31 and 32 are switched. In a motor vehicle
application, output shaft 60 would be connected to a conventional transmission
in the same way as would the output shaft of a normal internal combustion engine.
To start either displacement unit independently, starter 15 is disposed
to selectively engage with either ring gear 11 or 13 ("starter gearing")
in order to start either crankshaft 31 or 32 respectively. At the
other end of the power plant, crankshafts 31 and 32 rotate two pulleys
71 and 72 through one-way clutches 43 and 44 ("third
and fourth one-way clutches") respectively. Belt 73 connects these pulleys
with the pulleys of an accessory set 81, thereby providing the accessory
set with a direct power drive. The accessory set 81 for example may include
a power steering pump, air conditioner compressor, and/or similar automotive power
drive accessories. Owing to the operation of one-way clutches 43 and 44,
the accessory drive receives power from any crankshaft that is operating, yet is
isolated from any crankshaft that is not operating. All embodiments described herein
may, in the alternative, have the accessories driven through gears or chain rather
than with a belt.
Operating strategy B might dictate that power demands of less than 30 HP,
for example, be served by a single displacement unit while greater power demands
shall be served by both units (it should be noted that the operating strategy could
alternatively utilize a variable power threshold rather than a fixed value). For
example, if 25 HP were demanded, and the control strategy had previously selected
crankshaft 32 to supply that power, crankshaft 32 would be placed
in operation while crankshaft 31 would remain inactive. As crankshaft 32
rotates counterclockwise (for example), with one-way clutch 42 transmitting
power downstream in that direction, gear 52 rotates counterclockwise and
causes output gear 53 to rotate clockwise, delivering 25 HP, for example,
from crankshaft 32 to the drivetrain. Simultaneously, the clockwise rotation
of output gear 53 causes gear 51 to rotate counterclockwise, but
because one-way clutch 41 does not transmit power upstream in that direction,
inactive crankshaft 31 is not affected. Accessories 81 are driven
by a similar power transfer path. One-way clutch 44 transmits power to pulley
72, while one-way clutch 43 isolates inactive crankshaft 31
from the resultant rotation of pulley 71. Belt 73 thus transmits
power to accessory set 81. Auxiliary accessory drive 91-92
is preferably not in operation in this mode.
If the power demand were t
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