U.S. patent application number 14/538590 was filed with the patent office on 2016-05-12 for hybrid vehicle having an engine and a flywheel which alternatively drive the vehicle at low speed in a pulsatile way.
The applicant listed for this patent is Denis Ernest Celestin BUFFET. Invention is credited to Denis Ernest Celestin BUFFET.
Application Number | 20160129777 14/538590 |
Document ID | / |
Family ID | 55859851 |
Filed Date | 2016-05-12 |
United States Patent
Application |
20160129777 |
Kind Code |
A1 |
BUFFET; Denis Ernest
Celestin |
May 12, 2016 |
HYBRID VEHICLE HAVING AN ENGINE AND A FLYWHEEL WHICH ALTERNATIVELY
DRIVE THE VEHICLE AT LOW SPEED IN A PULSATILE WAY
Abstract
A hybrid vehicle having a series-parallel architecture, i.e. a
mechanic (gears) and an electric (generator (4), inverter (7), and
motor (6)) propulsion chains associated by a planetary gear
mechanism (2) powered by an engine (1). The generator rotor (4),
with or without a flywheel (3), provides a kinetic energy storage
due to its high inertia and speed. The stored energy is sufficient
to drive simultaneously, the vehicle at low speed, and the
not-fueled engine (1), during short periods. Between these periods,
the fueled engine drives the vehicle and restores the stored
kinetic energy. The succession of these periods made operation
pulsatile at higher maximum power. Higher power means better
efficiency. In addition, less pollution and perturbation compare to
the "stop and start" are expected.
Inventors: |
BUFFET; Denis Ernest Celestin;
(Paris, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BUFFET; Denis Ernest Celestin |
Paris |
|
FR |
|
|
Family ID: |
55859851 |
Appl. No.: |
14/538590 |
Filed: |
November 11, 2014 |
Current U.S.
Class: |
701/22 |
Current CPC
Class: |
B60K 6/30 20130101; B60K
6/445 20130101; Y02T 10/60 20130101; B60W 10/06 20130101; Y02T
10/40 20130101; B60K 6/24 20130101; B60W 10/10 20130101; B60W 20/00
20130101; B60W 20/40 20130101; F02D 13/08 20130101; Y02T 10/62
20130101; B60W 20/30 20130101; Y02T 10/12 20130101; B60K 6/105
20130101; B60W 10/08 20130101; B60W 10/115 20130101; B60K 6/365
20130101; F01L 13/06 20130101; F01L 9/00 20130101; F02D 29/02
20130101; B60K 6/26 20130101; B60W 20/10 20130101 |
International
Class: |
B60K 6/48 20060101
B60K006/48 |
Claims
1. A power transmitting system for hybrid vehicle comprising: a
first planetary gear mechanism (2) for power derivation, having an
input shaft, an output shaft, and a pilot shaft; an electric
generator (4) connected to the pilot shaft, having a high inertia
rotor or a rotor coupled to a flywheel (3) which drives the
vehicle, the generator (4) and the engine (1) during the passive
phases; an electric motor (6) able to absorb power from the
generator (4) coupled to the output shaft driving the vehicle
wheels (5); a battery (8) able to absorb or to release the electric
power balance of the vehicle; an engine (1), including an engine
shaft connected to the input shaft of the planetary gear mechanism
(2), which drives the vehicle, the generator (4) and the flywheel
(3) during the active phases; a valve system (11) for cyclically
shutting down the fuel supply for the engine (1) during the passive
phases and opening the fuel supply for the engine (1) during the
active phases; an inverter (7) able to transfer and to control the
electrical energy between the generator (4) and the motor (6) both
reversible; a control-command unit of the system which provides
calculation resources and triggers the actives phases and the
passive phases.
2. The power transmitting system for hybrid vehicle according to
the claim 1 comprising in addition: a second planetary gear
mechanism (9), for power derivation with a higher gear ratio than
the first planetary gear mechanism (2), having also an input shaft
and an output shaft respectively connected to the input shaft and
to the output shaft of the first planetary gear mechanism (2); a
selector (10) for choosing one of the first and the second
planetary gear mechanism (2) or (9) to be in operation by
connecting the relevant pilot shaft to the rotor of the generator
(4).
3. (canceled)
4. The power transmitting system for hybrid vehicle according to
the claim 1, where in the valve system (11) cyclically closes and
opens the fuel supply of each engine cylinder with a phase
displacement to create, active phases where thermodynamic cycles
are unchanged except power and passive phases where active
thermodynamic cycles become passive.
5. The power transmitting system for hybrid vehicle according to
the claim 4, where in the ratio between the number of the active
thermodynamic cycles and the number of the passive thermodynamic
cycles is used to adapt the power and torque capabilities of the
engine (1) to the actual maximum power of the electric propulsion
chain.
6. The power transmitting system for hybrid vehicle according to
the claim 4, where in the suction or the exhaust valves (13) of the
engine (1) are kept open during the passive phases in order to
remove useless air compressions and associated losses in the
cylinders.
7. The power transmitting system for hybrid vehicle according to
the claim 4, where in the suction or the exhaust valves (13) of the
engine (1) get opening during air compression in the passive phases
in order to increase and to control the braking torque of the
engine (1).
8. (canceled)
9. The power transmitting system for hybrid vehicle according to
the claim 1, where in the behavior of the flywheel (3) is taken as
reference by the control-command unit for calculating the actual
inertia of the vehicle.
10. The power transmitting system for hybrid vehicle according to
the claim 1, where in the engine (1) or each of its cylinders is
fueled at a cycling flow rate which has a maximum during the active
phases and a minimum during the passive phases.
Description
TECHNICAL FIELD
[0001] The present invention relates to hybrid vehicles at low
speed thus at low resistive power. At low power, engine efficiency
is poor. The invention intends to improve this situation.
BACKGROUND OF THE INVENTION
[0002] The U.S. Pat. No. 8,845,469 B2 filled May 31, 2011,
describes a double planetary gear mechanism for hybrid vehicles,
while the U.S. Pat. No. 8,840,499 B2 filled Feb. 13, 2012 is about
how to store and recover kinetic energy from the generator rotor.
The present invention combines the two devices and makes them work
on a pulsatile way that is new.
[0003] Compare to the French patent application FR 14/01 126 filled
on May 19, 2014 about the same topic, the present invention is more
complete. Particularly in a new option, the invention is applied to
the thermodynamic cycles in each engine cylinder instead to the
whole engine.
[0004] The hybridization of a vehicle consists to associate a
thermal propulsion chain to an auxiliary propulsion chain which can
be electric, hydro pneumatic or mechanic. The auxiliary propulsion
chain allows shifting the operating point of the thermal propulsion
chain to make it work under better conditions at higher efficiency.
Generally, best efficiency is obtained by lowering engine speed and
by increasing its torque for the same output power. Unfortunately,
at low vehicle speed, the engine speed can't be lowered below its
stability limit, around 800 rpm. That limits benefit of vehicle
hybridization. The usual solution at low speed is to stop the
thermal propulsion chain and to continue with the auxiliary
propulsion chain only. This last is less powerful and well adapted
to low power. Of course, this option is limited by the stored
energy to be consumed in the auxiliary propulsion chain, and the
engine has to be restarted soon. This technique is commonly known
as "stop and start." If the storage capacity is small, frequency of
the stops and starts has to be high, looking as pulsations.
[0005] Stop and start technique is used whatsoever power-train
architecture is: parallel, series, series-parallel, etc. . . . and
whatsoever auxiliary energy is: electric, mechanic,
hydra-pneumatic, etc. . . . . But, it has some important
disadvantages. Numerous stops and starts disturb smooth driving and
punctually increase fuel over-consumptions and CO2 emissions.
Benefit balance is not always positive. It depends of the driving
style and the road profile. In addition, heavy and costly energy
storages are required.
[0006] In the patent application FR 12 58707 dated Sep. 17, 2012,
WO 2014/041275 A1 issued on Mar. 20, 2014, the low capacity of
hydra-pneumatic storage is compensated by frequent engine stops and
starts. Higher the frequency is, less positive the benefit balance
is.
[0007] Many power-train architectures and storage types exist. Some
are marketed on a large scale. A flywheel coupled to the vehicle
wheels through a speed variation system, such as KERS, is one of
them. Unfortunately, this technique requires high speed flywheels
to store enough energy and high-techs to stand the centrifugal
stress. Applications are limited to specific cases: race cars,
frequent stop bus . . . . Differently to the state of art, the
patent application U.S. Ser. No. 13/371,697 considers energy
storage in the generator rotor, with or without an additional
flywheel, driven by the pilot shaft (the 3rd shaft) of a planetary
gear mechanism. First, we get a multiplication effect on speed
variations thus on stored energy. Second, a speed variation system
has not to be provided. Third, same for a system to extract power,
which is the Generator stator itself. Consequently, the flywheel
speed is moderate and technology is kept basic.
[0008] "cylinders on demand" system has similitude with stop and
start system. Some engine cylinders are stopped or restarted
according to power requirements.
[0009] The purpose of the present invention is to improve the here
above techniques, at low vehicle speed, particularly regarding
costs, efficiency and CO2 emissions.
BRIEF SUMMARY OF THE INVENTION
[0010] The patent application U.S. Ser. No. 13/371,697 shows how to
store kinetic energy in the generator rotor of a hybrid
power-train. In the present invention, the stored kinetic energy is
sufficient to drive simultaneously the vehicle, the generator and
the engine, during a short period. During the next period, the
engine drives the vehicle and restores kinetic energy to the
flywheel.
[0011] The succession of these periods creates pulsations with:
[0012] active phases in which the fuel supply for the engine is
open, and the fueled engine drives the vehicle, the generator and
the flywheel, [0013] passive phases in which the fuel supply for
the engine is closed, and the stored kinetic energy drives the
vehicle, the generator and the not-fueled engine.
[0014] For simplification in the following explanations, "the
flywheel" refers to the generator rotor, which has a high inertia
or which is coupled to a flywheel. When the fuel system is "open,"
it does not mean that the fuel is arriving inside cylinders. It
just means that the engine fuel system is allowed to send fuel
inside the cylinders at the right time. Same, when the fuel system
is "closed" or "shut," the engine fuel system is not allowed to
send fuel inside the cylinders at any time.
[0015] The invention principle can be applied to the whole engine
or to individual engine cylinders. In each cylinder during active
phase, thermodynamic cycles remain active when they are active and
passive when they are passive. During passive phase, all
thermodynamic cycles are or become passive. The advantage from the
cylinder arrangement compared to the global engine arrangement is
that the frequency of the active thermodynamic cycles can be higher
for better propulsion regularity and lesser torsion vibration. For
that, phase displacement of the phases in each cylinder has to be
optimized according to the limited possibilities offered by the
original stalling of the engine and their best distribution. To sum
up, each engine cylinder is cyclically fueled to create, active
phases where thermodynamic cycles are unchanged except power, and
passive phases where active thermodynamic cycles become passive,
with phase displacements in each cylinder.
[0016] During the active phases, the succession of the passive and
the active thermodynamic cycles is still the same whatsoever we are
in pulsatile or non-pulsatile mode. Only cycle power is increased
to compensate the loss of power in the passive phases. During the
passive phases, the number of the passive cycles increases along
with the length of the phases. The ratio between the number of
active thermodynamic cycles and the number of passive thermodynamic
cycles determines the power and the torque capabilities of the
engine. The power of the passive thermodynamic cycles is negative,
almost null due to internal engine friction and air compression
losses. These last are already low under no fired load, but they
can be minimized by keeping the suction or the exhaust valves open
during the passive phases in order to remove useless air
compressions and associated losses in the cylinders.
[0017] At contrary, the engine suction or the exhaust valves can
get an opening during air compression in the passive phases in
order to increase engine losses and to control the reverse torque
at the engine shaft. To get additional engine braking "on demand"
is very interesting because powerful regenerative braking or
flywheel propulsion induces reverse torques at the engine shaft
through the planetary gear mechanism. While engine braking torque,
has a negative effect in normal propulsion.
[0018] In another way of using the invention, the passive phases go
partially below the stability limit for the engine speed. In fact,
the flywheel provides some stability to the engine. Thus, the
average speed of the engine can be lowered, that implies less
friction power and even fewer thermodynamic losses within the
engine.
[0019] To describe the power-train according to the invention it
comprises: [0020] a first planetary gear mechanism for power
derivation, having an input shaft, an output shaft and a pilot
shaft, [0021] an electric generator connected to the pilot shaft,
having a high inertia rotor or a rotor coupled to a flywheel,
[0022] an electric motor able to absorb power from the generator
coupled to the output shaft driving the vehicle axle, [0023] a
battery able to absorb or to release the electric power balance of
the vehicle, [0024] an engine, including an engine shaft connected
to the input shaft of the planetary gear mechanism to provide power
to the system, [0025] a valve system for cyclically shutting down
the fuel supply for the engine, [0026] an inverter able to transfer
and to control electrical energy between the generator and the
motor both reversible, [0027] a control-command unit of the
system.
[0028] The device according to the invention is particularly
recommended for a power-train with a double planetary gear
mechanism for power derivation, as described in the U.S. Pat. No.
8,845,469 and U.S. Pat. No. 8,840,499. In these arrangements, power
in the electric propulsion chain is roughly divided by two compare
to known architectures with only one planetary gear mechanism, and
speed variations of the shafts are more suitable for flywheel
efficiency.
[0029] Comparing to the previous architecture, the double planetary
gear mechanism architecture comprises in addition: [0030] a second
planetary gear mechanism for power derivation with a higher gear
ratio than the first planetary gear mechanism, having an input
shaft and an output shaft respectively connected to the input shaft
and the output of the first planetary gear mechanism, [0031] a
selector for choosing one of the first and the second planetary
gear mechanism to be in operation by connecting the relevant pilot
shaft to the generator rotor.
[0032] To maintain a continuous vehicle speed while the flywheel is
decelerating, the engine has to slow down a little bit and then to
re-accelerate at the pulsation rhythm following the Willis formula
establishing shaft speeds in a planetary gear mechanism. Negative
gear ratio determines adequate direction for speed variations of
the flywheel. It's important to point out that the engine is never
totally stopped or restarted at each pulsation like in the patent
application FR 12 58707.
[0033] As the engine is never completely turned off or restarted,
we get, little perturbation on propulsion and quicker availability
for any call of power. In addition, the pulsation frequency can be
higher than in a classic stop and start system that improves engine
regularity.
[0034] Global efficiency is improved, because required power during
the active phases is higher than the average power. It is well
known that an engine has a higher efficiency at high torque and low
speed than at low torque and high speed. Higher power means a
higher temperature for the thermodynamic cycles and a better
efficiency according to the Carnot's law. In addition, no load
during the passive phases makes engine frictions and thermodynamic
losses lower even if they are increased a little bit during the
active phases.
[0035] A sequencer in the control unit triggers the active and the
passive phases and provides calculation resources. During a
sequencer period, the invention arrangement makes possible to
calculate resistive power and even power in all the shafts from the
speed behavior of the flywheel during the previous sequencer
period. Thanks to the flywheel, we have an accurate reference which
does not change during vehicle lifetime and does not depend upon
external conditions.
[0036] The vehicle inertia may change in a +/-10% range due to
vehicle load variations. When the engine speed is constant during a
sequencer period, there is a mathematic relation between the
flywheel inertia and the actual inertia of the vehicle. As the
flywheel is a good reference, corrected vehicle inertia can be
introduced in the following calculations. We can also calculate the
actual mass and load of the vehicle with the same method.
[0037] The present invention adds a pulsatile mode to the five
optional modes already described in the U.S. Pat. No. 8,840,499.
The choice of the mode is partially manual and partially
computerized in the control unit following preloaded criteria. For
instance, low resistive power during a pre-set period initiates
pulse mode and a quick pressure on the accelerator pedal shifts
pulse mode into hybrid mode at low speed.
[0038] The accelerator pedal has different effects in each mode,
while the driver should always have the same acceleration feeling,
and propulsion power should be maintained during the shifting,
whatsoever the mode in operation. An electronic convertor corrects
the pedal position according to the mode in order to meet such
conditions.
[0039] The here above fuel supply is either open or closed. But,
the invention can also work at cycling flow rate. If so, the fuel
flow is maximum during the active phase and minimum during the
passive phase which is no longer totally passive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 shows a typical graph of the engine efficiency.
[0041] FIG. 2: FIG. 2a shows the speeds characteristics; FIG. 2b
shows the power characteristics; of the device according to the
invention at very low vehicle speed.
[0042] FIG. 3: FIG. 3a shows the speeds characteristics; FIG. 3b
shows the power characteristics; of the device according to the
invention at low vehicle speed.
[0043] FIG. 4 schematizes a series-parallel power-train; with one
planetary gear mechanism on the FIGS. 4a and 4b, with a double
planetary gear mechanism on the FIGS. 4c and 4d, and the invention
applied to each cylinder on the FIG. 4e.
[0044] FIG. 5 shows the periodic fluctuations of the engine and the
flywheel powers in the pulsatile mode.
[0045] FIG. 6 is the common part of the logic-diagram for setting
the generator power in all the modes.
[0046] FIG. 7 is the specific part of the logic-diagram to set the
generator power in the hybrid mode at low vehicle speed.
[0047] FIG. 8 is the specific part of the logic-diagram to set the
generator power in the pulsatile mode.
[0048] FIG. 9 shows a hydraulic device for keeping an engine valve
open during the passive phase.
DETAILED DESCRIPTION OF THE INVENTION
[0049] The U.S. Pat. No. 8,840,499 B2 filled Feb. 13, 2012
describes how to store and recover kinetic energy from the
generator rotor of a series-parallel power-train of a hybrid
vehicle. The present invention makes the system work on a pulsatile
mode.
[0050] At low vehicle speed, therefore, at low resistive power, the
system becomes cyclic. The cycle is split into: an active phase,
where the engine provides not only energy for vehicle propulsion
but also energy for accelerating the flywheel; and a passive phase,
where only the energy stored in the flywheel propels the vehicle
and the not-fueled engine. The fuel supply is thus cyclic,
alternatively open and closed. The interest is to make the engine
work, when it works, at a higher power than the average power
therefore, with a better efficiency according to the engine
characteristics. In addition, engine losses are minimized during
the passive phases and compensated by energy previously produced at
a higher power at a better efficiency. At higher vehicle speed, the
engine has not to be cyclic because required power is sufficient
for getting a good efficiency.
[0051] When installed on each engine cylinder, the device
determines the number of active and passive thermodynamic cycles in
the cylinders. Only the passive phase makes the active
thermodynamic cycles become passive while they are unchanged during
the active phase except power. When the period of fuel shutting is
increasing, we get more passive thermodynamic cycles for the same
number of active thermodynamic cycles. Usually, the passive phases
are longer than the active phases.
[0052] For maintaining a continuous vehicle speed while the
flywheel is decelerating to deliver its energy, the engine has also
to slow down a little bit and then to re-accelerate at the
pulsations rhythm. The device has an advantage: An important part
of the energy required for reaccelerating the engine is directly
supplied by the flywheel through the gears with a high efficiency.
Same when the engine has to reaccelerate the flywheel. That eases
the work of the battery comparing to a classic stop and start
system.
[0053] The phase displacement in each cylinder must take into
account the original stalling of the engine. Consequently, active
thermodynamic cycles have to be regularly distributed, as far as
possible, following the stalling possibilities of the engine.
Theoretically, the frequency of the active thermodynamic cycles can
be multiplied by the number of cylinders for the best regularity
and less torsion vibration.
[0054] One active thermodynamic cycle per several passive
thermodynamic cycles is an interesting minimum corresponding to the
highest frequency. Nevertheless, ratios between active and total
cycle numbers are limited to: `1/2, 1/4, 1/6, 1/8, 1/10 . . . 2/4,
2/8 . . . which also correspond to the fraction of the active cycle
power delivered by the engine. Consequently, it is possible to
adapt the power and torque capacities of the engine to another
limitation which is due to the actual maximum power of the electric
propulsion chain. It would be useless to get engine capacities that
we cannot reach for another reason. Good power adaptation of the
engine provides efficiency gains even at high vehicle speed and
high power. The flywheel can follow because a flywheel can deliver
high power during a short period.
[0055] Of course, frictions and thermodynamic losses in the engine
are not totally eliminated during the passive phases, but we do not
have to consume energy for restarting the engine like in the usual
stop and start systems. However, these losses can be minimized in
many ways: three cylinders engine, low speed engine, cam-less
engine, etc. . . . . The passive phases provide new opportunities
because, during these phases, we can open the suction valves in
order to avoid useless air compressions and associate losses in the
cylinders. In addition, we preserve compressed air at the engine
intake, if any.
[0056] For opening the suction valves, additional actuators are
anticipated alongside the existing valves system. They do not
require the same level of accuracy than the valves system does.
Consequently, many actuators such as, electric, hydraulic,
electro-hydraulic, pneumatic . . . can be designed for this
function. Some of them are currently under development. Thanks to
the synchronous electric machines of the propulsion chain, we can
easily determine piston positions in the cylinders and trigger the
valve openings at the right time.
[0057] At contrary and still during the passive phases, if the
suction valves are opened during unfired air compression,
thermodynamic losses drastically increase alongside the engine
braking torque. By controlling the opening point, we can control
the engine braking and even get an engine braking "on demand."
[0058] In the passive phases, the torque necessary to propel the
vehicle creates a reverse torque on the engine shaft due to the
planetary gear mechanism. The equilibrium is achieved by adjusting
the power going through the electric propulsion chain but this last
has power limits. Consequently, we may have, to increase the
resistive torque of engine and, to call for more engine
braking.
[0059] The engine braking "on demand" can be also very useful
regarding the regenerative braking because the torque for
accelerating the flywheel might be limited by the reverse torque at
the engine shalt, for the same reason. Consequently, more kinetic
energy can be recovered and save. Note that in electric vehicles,
the braking power often exceeds the battery capability and only a
modest percentage of the kinetic energy is effectively
recovered.
[0060] With electric valves the closing-opening sequence can be
easily modified at the control unit level and additional actuators
are no longer necessary. They bring flexibility to the
invention.
[0061] Torsion vibrations can greatly reduce crankshaft life, if
not cause instantaneous failure, if the crankshaft runs at or
through resonance. Torsion vibration peaks occur when frequency of
a repeated external torque gets close to one of the crankshaft
natural frequencies. In the invention, a brief positive torque
during the active thermodynamic cycles is followed by a relatively
long and weak negative torque. Vibrations in the first period are
deadened in the second period. In addition, more the vehicle speed
is low; more the flywheel is mechanically connected to the
crankshaft through the gears. That eases the work of the damper
installed at the end of the crankshaft. This last can have a
narrower operating range centered on high vehicle speeds. Gears
fatigue increases a little bit, but torques and stresses can be
accurately controlled through the pilot shaft in this type of
power-train. It is due to the proportionality of the torques in a
planetary gear mechanism.
[0062] Many well-known means can be used to shut down the fuel
supply most depending upon engine system type. In direct or
indirect fuel injection, the simplest is to keep injectors closed
during the passive phases. Direct injection is convenient when
invention is applied to each cylinder. For a carburetor, the best
is to close the fuel input at the Venturi level with a small valve.
Numerous configurations exist, but as they all compete for the best
control of the flow, the fuel shutting should not be an issue.
[0063] At continuous vehicle speed, the flywheel is progressively
slowed down, for minimizing air friction, for increasing
regenerative braking availability and for reducing power in the
electric propulsion chain. It is why the control unit takes into
account a preset "power wearing" which permanently decreases the
flywheel speed in the calculations.
[0064] To control a series-parallel architecture built around a
planetary gear mechanism is usually made through the pilot shaft
either by controlling its rotation speed or its torque or its power
or a combination of the three. Here after, power option has only
been considered for simplification.
[0065] When starting in another mode, power levels have to be
maintained during the shifting while the accelerator pedal gets a
different effect in the coming mode. To tackle the situation is the
pedal corrector function, provide it receives reliable information.
In the invention arrangement, it is possible to calculate the
resistive power and even power in all the shafts from the speed
behavior of the flywheel during the previous period of the control
unit sequencer. Thanks to the flywheel, we have an accurate
reference which does not change during the vehicle lifetime and is
not affected by external events. The aerodynamic forces on the
flywheel can also be introduced into the calculations for better
accuracy.
[0066] The actual inertia and mass of the vehicle can also be
calculated but only when the engine speed is constant during a
sequencer period. At this condition, there is a mathematical
relation between the vehicle and the flywheel inertia.
[0067] The invention is compatible with most of the known
techniques for improving engine efficiency: EGR, downsizing, air
compression, injection, etc. . . . , with impacts only at low
vehicle speeds; impacts, which are not necessary negative.
[0068] The invention principles could also be considered for
parallel hybridization, i.e. an electric motor directly actuating
the wheels in parallel with the engine, with or without clutches.
During the passive phase, the battery or the super-capacity should
provide necessary power to drive simultaneously the vehicle and the
engine. During the active phase, the engine reloads the electricity
storage, thanks to the motor working as a generator. Unfortunately,
the battery cannot stand frequent cycles without lifetime damage,
so flywheel has been proposed as an alternative more resistant to
cyclic stress. However, in this power-train architecture, an
additional system to handle speed variations is required. It should
allow vehicle and engine constant speed while the flywheel has to
continuously slow down for delivering its energy. Unfortunately,
such systems use friction. They are not reliable; they don't have a
good efficiency, and they cannot avoid some sliding. Nevertheless,
this solution works in specific cases, and theoretically the
invention could be also applied for this type of power-train.
[0069] Whatsoever how the invention is used; it can be combined
with additional energy sources as batteries or ultra-capacities.
The batteries can be designed for electrical balance only, or sized
to be plug to the national grid. The principle is to benefit of
temporary useless capacities of the electric propulsion chain for
increasing electric mobility share. These combinations increase the
applicability of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0070] The variables and parameters used in the control-command are
listed here after. Some are definitions only; some others should be
preloaded or measured or calculated in the Control unit.
DEFINITIONS
[0071] i Time index of the sequencer [0072] A % Accelerator pedal
position [0073] A' % Corrected position of the accelerator pedal in
active phase [0074] A'' % Corrected position of the accelerator
pedal in passive phase [0075] B % Braking pedal position [0076] Ao,
A'o %, A''o % Initial values of the accelerator pedal positions
[0077] Preloaded Data: [0078] Wemax Electric motor maxi speed
[0079] Wgmax Generator maxi speed [0080] Wmmax Engine maxi speed
[0081] R Gear ratio of the planetary gear mechanism in operation
[0082] If Flywheel Inertia [0083] Iv Vehicle Inertia at the motor
shaft [0084] Pw Power wear of the flywheel [0085] Pfmax Flywheel
maxi power [0086] Limits Generator, inverter and motor limits
[0087] (Torques, Powers, Base speeds, Maxi speeds) [0088] S Maxi
engine speed variation for setting the vehicle inertia [0089] Cmf
Engine friction torque in passive phase [0090] Tlow Period of low
power before shifting in pulsatile mode
[0091] Measured or calculated data: They are gathered in a
"Calculation Block" which is used by all modes with minor
differences, which appear on the Logic-diagrams.
TABLE-US-00001 Wei Electric motor speed @ time i Memory Wgi
Generator speed @ time i Memory We Electric motor speed Measured Wg
Generator speed Measured Wm Engine speed f(We, Wg) Pkf Flywheel
kinetic power f(If, Wgi, Wgi + 1) Pke Vehicle kinetic power f(Iv,
Wei, Wei + 1) Pchi Electric chain power @ time i Memory Pch
Electric chain power F(Pchi, Pke, Pkf, Pw) Pchmax Electric chain
maxi power f(We, Wg, Limits) Pm Engine power f(Pkf, Wm, r) Pv
Vehicle resistive power f(Pkf, Wm, r) Pg Generator power f(Pchi,
Pkf, Pke)
[0092] FIG. 1 shows typical curves of engine efficiency with its
best zone. By way of an example, A is an engine operating point at
low vehicle speed without the invention thus with an engine
continuously working. In B, the engine with the invention develops
the same amount of energy but discontinuously. To produce the same
amount of energy, power in B should be higher than in A when the
engine is working. Passive phases four times longer than the active
phases request power five times higher during the active phases
that roughly double the efficiency.
[0093] FIG. 2: The FIG. 2a shows the speeds characteristics while
the FIG. 2b shows the power characteristics of a planetary gear
mechanism which has a negative gear ratio and a power derivation
arrangement. The two figures are vertically aligned to point out
their geometric relationship. Here, they particularly show a case
at very low vehicle speed, even null.
[0094] As represented, the generator speed oscillates between 2500
and 6000 rpm, whereas the engine speed oscillates between 900 and
1660 rpm, with a 6000 rpm limit for the generator speed. For this
particular case, the control unit should maintain the engine
operating point in the trapezoid CDEF.
[0095] The points G, H and I give the relationship between the
direct power (part of the engine power going to the output shaft)
and the derived power (part of engine power going to the pilot
shaft) for some particular engine speeds: 900, 1000 and 1660 rpm.
For each point inside the trapezoid CDEF, we can associate a ratio
between the direct and the derived power (ex: IQ/IP). This
planetary gear balance gives the opportunity to the electric
propulsion chain to control not only the derived power but also the
direct power, even if the total power exceeds its maximum allowable
power. This remark is important because it contributes to minimize
the electric propulsion chain, so its cost.
[0096] In the trapezoid CDEF, oscillations of the generator speed
should not place the engine speed below its stability limit if this
option is chosen. At very low vehicle speed, even null, the
oscillation range (ex: FE) becomes narrow to meet this requirement.
Fortunately, oscillation amplitude could be reduced to the minimum
kinetic energy necessary for maintaining the passive phase.
[0097] FIG. 3: The FIG. 3a shows the speeds characteristics while
the FIG. 3b shows the power characteristics of a planetary gear
mechanism which has a negative gear ratio and a power derivation
arrangement. The two figures are vertically aligned to point out
their geometric relationship. Here, they particularly show a case
at low vehicle speed, around 30 km/h.
[0098] On the segment KJ, the generator speed oscillates between
5000 and 6000 rpm and those of the engine between 1940 and 2100
rpm, with 6000 rpm limit for the generator. The points L and M give
the ratio (ex: LS/LR) between the direct power and the derived
power. This ratio is close to 0.5, which makes it possible to the
electric propulsion chain to control roughly the double of its
allowable power. This remark is important because it contributes to
minimize the electric propulsion chain, so its cost. In addition,
we can see that the phases can be short and speed variations narrow
for a better driving comfort.
[0099] FIG. 4: The FIGS. 4a and 4b schematize a series-parallel
power-train with a first planetary gear mechanism for power
derivation V (2) according to the invention which comprises: [0100]
a first planetary gear mechanism (2) for power derivation, having
an input shaft, an output shaft and a pilot shaft; [0101] an
electric generator (4) connected to the pilot shaft, having a high
inertia rotor or a rotor coupled to a flywheel (3); [0102] an
electric motor (6) able to absorb power from the generator (4)
coupled to the output shaft driving the vehicle axle; [0103] a
battery (8) able to absorb or to release the electric power balance
of the vehicle; [0104] an engine (1) including an engine shaft
connected to the input shaft of the planetary gear mechanism (2) to
provide power to the system; [0105] a valve system (11) for
cyclically shutting down the fuel supply for the engine (1); [0106]
an inverter (7) able to transfer and control the electrical energy
between the generator (4) and the motor (6) both reversible; [0107]
a control-command unit of the system (not represented).
[0108] The FIGS. 4c and 4d schematize a series-parallel
power-train, with a first and a second planetary gear mechanism V
(2) and Y (9) for power derivation according to the invention which
comprises in addition to the previous architecture: [0109] a second
planetary gear mechanism (9) for power derivation with a higher
gear ratio than the first one, having an input shaft, and an output
shaft respectively connected to the input shaft and output of the
first planetary gear mechanism (2); [0110] a selector (10) for
choosing one of the first and second planetary gear mechanisms (2)
or (9) to be in operation by connecting the relevant pilot shaft to
the generator rotor (4).
[0111] It is reminded that the double planetary gear mechanism is
recommended for the invention because it allows: [0112] to decrease
the gear ratio of V (2) for improving kinetic energy storage at low
vehicle speed, [0113] to increase the gear ratio of Y (9) for
minimizing inertia effect at high vehicle speed.
[0114] Fuel supply for the engine (1) is cyclically open and closed
by the valve (11), or by other shutting devices, to create engine
active and passive phases. The shutting point can be single or
multiple and close to each cylinder in order to be more efficient
and quicker to operate.
[0115] The FIG. 4e represents the invention when it is applied on
each cylinder. Each cylinder has its own valve (11a, 11b, 11c,
11d). This arrangement is most dedicated to the engine with direct
fuel injection, each injector playing the role of a valve. The dash
line indicates the main actions of the control unit on the valves
and on the inverter (7).
[0116] The arrows indicate the direction of the power flows
depending to the cases: To simplify, resistive power on the vehicle
has only been considered positive but obviously, the system can
work in regenerative braking mode also. [0117] Configuration with
one planetary gear mechanism V (2): [0118] FIG. 4a: the valve (11)
is open, and the engine (1) is active, [0119] FIG. 4b: the valve
(11) is closed, and the engine (1) is passive. [0120] Configuration
with two planetary gear mechanisms V (2) and Y (9) at low vehicle
speed: [0121] FIG. 4c: the valve (11) is open, and the engine (1)
is active while Y (9) is idle, [0122] FIG. 4d: the valve (11) is
closed, and the engine (1) is passive while Y (9) is idle.
[0123] FIG. 5 shows the periodic fluctuation of the engine and the
flywheel powers in pulsatile mode. The trapezoid TUVW represents
the engine power during the active phase and the segment WX the
same during the passive phase. The segments TU and VW are tilted
because power variations take time to be completed. On UV, engine
is the unique source of power for vehicle propulsion. On WX, the
negative engine power represents its losses.
[0124] On T'T the flywheel continues to lose power to compensate
power ramps, then on TU' the flywheel starts to store the excess of
the engine power. Kinetic energy continues to be stored on U'V'W,
after that, kinetic energy is progressively restored to propulsion
on WW' to compensate engine ramps. On W'X' kinetic energy is the
unique source of power for propulsion and engine losses.
[0125] FIG. 6 shows the logic-diagram which is common to all modes
when the electric chain power, so the generator power, Pg, has been
set. This power is calculated by a Calculation Block with minor
adaptations to the mode in operation. The logic-diagrams are
self-explanatory, so only additional explanation is provided here
after.
[0126] Bock 101, If Wmmax>Wpmax and Wemax, the condition
Wm<Wmmax is sufficient to get Wp<Wpmax and We<Wemax due to
the characteristic of a planetary gear mechanism which has a
negative gear ratio.
[0127] Step S108, when alarm sounds, the driver should
progressively release the accelerator pedal of the engine.
[0128] Step S102, when the brake pedal is activated B % of its
first stroke, the electric propulsion chain works reverse in a
regenerative braking mode: the motor works as generator and the
generator works as motor. Above 100%, the remaining part of the
pedal stroke is used for a classic hydraulic braking.
[0129] Step S106, the regenerative braking should be progressive
for that power of the electric propulsion chain is proportional to
B %.
[0130] Steps S103, S104 & S105, the calculated generator power,
Pg, should be compatible with the actual maximum power of the
electric propulsion chain, Pchmax, which is regularly reevaluated
by the Calculation Block.
[0131] FIG. 7 shows the logic-diagram to set the generator power
Pg, in hybrid mode at low vehicle speed.
[0132] Step S107, A Mode Manager decides the vehicle mode according
to a mix of preloaded criteria and driver instructions.
[0133] Step S108, the task of the Calculation Block at this step is
to initialize variables at the time "i" which are necessary in the
calculation at the time "i+1" of the sequencer.
[0134] Step S109, at the time "i+1", the generator power during the
period "i" is corrected of the difference between the kinetic power
variation of the vehicle and those of the flywheel during the
period "i". In addition a wearing power, Pw, is added in order to
slow down progressively the flywheel for minimizing its friction
losses and for reducing power in the electric propulsion chain.
[0135] Steps S110 &111, the purpose is to calculate actual
inertia of the vehicle when the engine speed is constant during a
sequencer period. As perfect equality is difficult to achieve, we
accept a small margin, "s" before preceding the calculation. The
current vehicle inertia is deducted from the flywheel inertia which
is an invariant all along vehicle lifetime.
[0136] Step S112, here the generator speed is maintained close to
the motor speed to ease an eventual shifting of mode.
[0137] Step S114, at each sequencer period, the Mode Manager checks
if current mode has to be changed according to some preloaded
criteria or driver instructions.
[0138] FIG. 8 shows the logic-diagram to set the generator power,
Pg, in hybrid pulsatile mode at low vehicle speed.
[0139] Step S107, the Mode Manager decides vehicle mode according
to a mix of preloaded criteria and driver instructions.
[0140] Step S115, the purpose of the Calculation Block at this step
is to initialize variables at the sequencer time "i" which are
necessary for the next calculation at the time "i+1". The maximum
flywheel power is added to the initial engine power.
[0141] Step S116, to maintain initial power of the engine, a table
provides a theoretical position A'o % of the accelerator pedal
while its actual position is Ao %. Consequently, a pedal converter
has to convert A % in A'%. For instance: A'%=A %*A'o %/Ao %. The
driver should also have a same acceleration feeling what so ever
the mode. Note: As acceleration in the hybrid mode low speed is
taken as reference, pedal position has not to be reconverted when
we shift to this mode.
[0142] Step S117, the Calculation Block should take into account
the energy stored in the flywheel. Consequently, Pkf is replaced by
Pkf-Pfmax in the calculation.
[0143] Step S118, when the flywheel meets its maximum speed, fuel
supply is closed shifting the engine into the passive phase.
[0144] Step S119, the generator power has to be initialized at the
sequencer time "i" for the next calculation at the time "i+1" with
Pg=Pv+Cmf*Wm. Here, engine friction losses are assumed to be
proportional to a constant torque.
[0145] Step S120, a table provides the theoretical position A''o %
of accelerator pedal while its actual position is Ao %.
Consequently, the accelerator converter should compensate pedal
position in order to maintain the initial power and the same
acceleration feeling. For instance: A'' %=A %*A''o %/Ao %.
[0146] Step S121, the calculation of the Calculation Block has to
be adapted because the power is only provided by the generator.
Consequently, Pg should be replaced by Pg=A'' %*Pgmax.
[0147] Step 122, when the flywheel meets its minimum speed, fuel
supply is opened shifting the engine into the active phase.
[0148] Step 123, prior to the mode shifting vehicle resistive power
has to be recalculated: Pv=Pch+Cmf*Wm.
[0149] FIG. 9 shows a hydraulic device for keeping a valve open
during the passive phase or during a non-fired air compression. In
the passive phases, the valve (13) is pushed upward by the spring
(14) through the guide (15) in order to close the air intake
arranged in the engine body (12). For opening the valve (13) during
the active phases, an overhead cam shaft (18) consecutively forces
downward, the plunger (16), the hydraulic lash adjuster (17) and
finally the valve (13). For opening the valve (13) during the
passive phases, the oil pressure (dotted areas represent oil) is
increased in the jack chamber (20) successively pushing the ring
(19), the plunger (16), the hydraulic lash adjuster (17), and
finally the valve (13). The springs (21) and (14) ensure the
reverse operation when the oil pressure returns to being low. The
hydraulic lash adjuster (17) is a known device. The concept is a
self-adjusting thickness by pumping oil in its inner chamber
without return due to the chock valve (22). That keeps the plunger
(16) and the adjuster outer cylinder (17) in contact with the cam
shaft (18) and the valve (13) at all times when the valve (13) is
actuated by the cam shaft (18). The adjusted thickness should be
maintained during the passive phases that imply relative oil
tightness and high frequency. The originality of this device is to
integrate the hydraulic lash adjuster (17) in the hydraulic jack
(20) and to use the same oil intake.
[0150] The embodiments and its example explain above are considered
in all aspects as illustrative and not restrictive. There may be
many other modifications, changes and alterations without departing
from, the scope or spirit of the mains characteristics of the
present invention.
INDUSTRIAL APPLICABILITY
[0151] The technique of the invention is preferably applicable to
the manufacturing industries of automobiles and other relevant
industries. To illustrate, we propose here after, a sized and
nonrestrictive example:
[0152] A 1500 kg vehicle which requires 4 Kw for running at 20 km/h
without road grade or wind is considered. Its 10 Kw electric chain
limits the engine power at 24 Kw (10.times.2+4), refer to [0051]
for multiply by 2.
[0153] Its 0.7 Kg*m.sup.2 flywheel is pulsed between 5000 and 6000
rpm. The variation of the kinetic energy, 42 KJ, drives the vehicle
during a passive phase of 10 seconds. Then the engine is fueled in
order to reach 24 Kw during an active phase of 2.2 seconds, raising
the pilot shaft speed up to 6000 rpm.
[0154] The power is increased around 6 times (24/4) during the
active phase compare to the power average. We can expect a twice
better efficiency according to the usual engine performances.
[0155] For a three cylinders engine running at 1800 rpm, we get 100
active thermodynamic cycles for 1000 passive thermodynamic cycles
(1.times.3 cycles per one complete rotation of the crankshaft). In
a planetary gear mechanism with a gear ratio of -0.2, 100% at 0
km/h, 73% at 10 km/h, 57% at 20 km/h, 47% at 30 km/h of the power
transit between the flywheel and the engine through the gears
without any energy conversion so without transformation losses.
[0156] It is possible to lengthen the active phase but that
increases the speed variations. A compromise has to be found with
the driving comfort. A higher frequency eases the compromise. Note
that the frequency can be much higher than in any stop and start
system.
[0157] When the invention is applied to each cylinder of a three
cylinders engine, rotating at 1800 rpm, with one active
thermodynamic cycle for seven passive thermodynamic cycles (one
cycle for a complete rotation of the crankshaft per cylinder). We
get 11 active thermodynamic cycles per second (30.times.3/[1+7]). A
11 Hz frequency is also the frequency of the flywheel speed
variations. At this frequency, the speed variations are small and
let the flywheel available for its other functions (engine working
point, regenerative braking, performances boosting).
* * * * *