U.S. patent application number 13/336636 was filed with the patent office on 2012-07-26 for direct electrical connection and transmission coupling for multi-motor hybrid drive system.
This patent application is currently assigned to Fisker Automotive, Inc.. Invention is credited to Paul BOSKOVITCH, Uday Deshpande, Michael Groene, J. Axel Radermacher.
Application Number | 20120186391 13/336636 |
Document ID | / |
Family ID | 43386911 |
Filed Date | 2012-07-26 |
United States Patent
Application |
20120186391 |
Kind Code |
A1 |
BOSKOVITCH; Paul ; et
al. |
July 26, 2012 |
Direct Electrical Connection and Transmission Coupling for
Multi-Motor Hybrid Drive System
Abstract
A system of electric power management for a hybrid vehicle
includes an engine, a first inverter, a first electric machine
coupled to the engine and the first inverter, and a first
transmission coupled between the engine and the first electric
machine. The first transmission has a transmission speed ratio
operable such that the first electric machine operating speed
operates independent of an engine operating speed. A second
electric machine is coupled to the second inverter and a wheel axle
of the vehicle. A high voltage battery is coupled to both the first
inverter and the second inverter. A switch box is disposed between
the first electric machine and the second electric machine. The
switch box includes switches adapted to switch open and closed to
allow direct electrical connection from the first electric machine
to the second electric machine.
Inventors: |
BOSKOVITCH; Paul; (Costa
Mesa, CA) ; Radermacher; J. Axel; (Foothill Ranch,
CA) ; Deshpande; Uday; (San Diego, CA) ;
Groene; Michael; (Rochester, MI) |
Assignee: |
Fisker Automotive, Inc.
|
Family ID: |
43386911 |
Appl. No.: |
13/336636 |
Filed: |
December 23, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US2010/040087 |
Jun 25, 2010 |
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13336636 |
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61220421 |
Jun 25, 2009 |
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61288709 |
Dec 21, 2009 |
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61294722 |
Jan 13, 2010 |
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Current U.S.
Class: |
74/661 ;
180/65.245; 903/903 |
Current CPC
Class: |
B60K 6/387 20130101;
B60K 2001/001 20130101; Y02T 10/7077 20130101; B60K 2001/0427
20130101; Y02T 10/6217 20130101; B60K 1/02 20130101; B60K 1/04
20130101; Y02T 10/7072 20130101; Y02T 10/64 20130101; B60K 6/52
20130101; B60L 50/15 20190201; Y02T 10/62 20130101; Y02T 10/6265
20130101; Y10T 74/19014 20150115; Y02T 10/7005 20130101; Y02T 10/70
20130101; Y02T 10/645 20130101; Y02T 10/6269 20130101; B60K 1/00
20130101; B60L 15/007 20130101; B60K 6/46 20130101 |
Class at
Publication: |
74/661 ;
180/65.245; 903/903 |
International
Class: |
F16H 37/06 20060101
F16H037/06 |
Claims
1. A system of electric power management for a hybrid vehicle
comprising: (a) an engine; (b) a first inverter coupled to a second
inverter; (c) a first electric machine coupled to the engine and
the first inverter; (d) a first transmission coupled between the
engine and the first electric machine, wherein the first
transmission has a transmission speed ratio operable such that the
first electric machine operating speed operates independent of an
engine operating speed; (e) a second electric machine coupled to
the second inverter and a wheel axle of the vehicle; (f) a high
voltage battery coupled to both the first inverter and the second
inverter; (g) a switch box disposed between the first electric
machine and the second electric machine, the switch box for
selectively forming a direct electrical connection from the first
electric machine to the second electric machine.
2. The system of claim 1, wherein the switch box includes a
plurality of switches that allow for vehicle operation in a
plurality of operating states.
3. The system of claim 2, wherein the switches are all open in a
first operating state preventing electrical connection between the
first electric machine and the second electric machine.
4. The system of claim 2, wherein the switches are all closed in a
second operating state forming electrical connection between the
first electric machine and the second electric machine.
5. The system of claim 2, wherein the switches are all closed in a
third operating state forming electrical connection between the
first electric machine and the second electric machine such that
one of the electric machines can operate in reverse.
6. The system of claim 1, wherein the electric machine is operable
to be a generator when spinning in a negative torque direction and
a motor when spinning in an opposite positive torque direction.
7. The system of claim 1, wherein power can be transferred from the
engine to the battery and from the battery to the engine and the
wheel axle.
8. The system of claim 1, further comprising a mechanical
engagement device disposed between the engine and the first
electric machine adapted to selectively decouple the engine from
the first electric machine.
9. The system of claim 1, wherein the mechanical engagement device
is a clutch.
10. The system of claim 1, further comprising a third electric
machine coupled to a second wheel axle of the vehicle and the
switch box.
11. The system of claim 10, wherein the switch box allows for
direct electrical connection between both the first and second
electric machine and the third electric machine.
12. The system of claim 10, further comprising a mechanical
engagement device disposed between the second wheel axle and the
third electric machine adapted to selectively decouple the wheel
axle from the third electric machine.
13. The system of claim 10, wherein the third electric machine is
directly coupled to the second inverter and the second electric
machine.
14. The system of claim 10, wherein the third electric machine is
directly coupled to the first inverter and the first electric
machine.
15. The system of claim 10, further comprising a second switch box
disposed between the third electric machine and the first electric
machine and first inverter adapted to allow for selectively
connecting the third electric machine and the first electric
machine and the first inverter.
16. The system of claim 15, wherein the second switch box is
further disposed between the first electric machine and the first
inverter.
17. The system of claim 1, wherein the switch box includes a
plurality of switches having power-electronic and mechanical
contactors.
18. The system of claim 1, wherein the first transmission includes
a plurality of speed ratios allowing the engine and the first
electric machine to operate at different speeds corresponding to
the transmission speed ratio.
19. The system of claim 1, further comprising a second transmission
coupled between a motor and the second electric machine, wherein
the second transmission has a transmission speed ratio operable
such that the second electric machine operating speed operates
independent of a motor operating speed.
20. A method of operating a hybrid vehicle comprising the steps of:
(a) coupling an engine to a first electric machine adapted to spin
the electric machine to generate power; (b) providing a
transmission between the engine and the first electric machine; (c)
selecting a predetermined transmission speed ratio of engine speed
to electric machine speed and operating the engine at a first speed
and operating the first electric machine according to the
transmission speed ratio; (d) delivering power from the first
electric machine to a switch box and to a first inverter, wherein
the first inverter is coupled to a second inverter and a high
voltage battery and the second inverter is further coupled to a
second electric machine coupled to a wheel axle of the vehicle; and
(e) selectively forming a direct electrical connection between the
first electric machine and the second electric machine.
21. The system of claim 1, the switch box for selectively forming a
direct electrical connection between at least one of the first
electrical machine and the first inverter and the second electrical
machine and the second inverter.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Applications No. 61/220,421, filed Jun. 25, 2009, No.
61/288709 filed Dec. 21, 2009, and No. 61/294722 filed Jan. 13,
2010, the disclosures of which are incorporated herein by reference
in their entireties.
BACKGROUND
[0002] The present disclosure relates generally to a hybrid
vehicle, and more particularly to a series hybrid electric vehicle
power train.
DESCRIPTION OF THE RELATED ART
[0003] Vehicles, such as a motor vehicle, utilize an energy source
in order to provide power to operate a vehicle. While petroleum
based products dominate as an energy source, alternative energy
sources are available, such as methanol, ethanol, natural gas,
hydrogen, electricity, solar or the like. A hybrid powered vehicle
utilizes a combination of energy sources in order to power the
vehicle. Such vehicles are desirable since they take advantage of
the benefits of multiple fuel sources, in order to enhance
performance and range characteristics of the hybrid vehicle
relative to a comparable gasoline powered vehicle.
[0004] A series hybrid vehicle will utilize power provided by an
engine mounted generator to power the motor driving the wheels.
With such an arrangement, energy is transmitted from the engine to
the wheels through various predefined conversion points. While this
system works, each energy conversion point is less that 100%
efficient, therefore there are energy losses throughout the
process. As a result, fuel consumption increases and larger more
expensive components may be required to satisfy power demands.
Additionally, the engine, generator, and generator inverter all
must be sized to handle peak engine power.
[0005] Thus there is a need in the art for a system and method of
reducing energy losses through direct electrical connections
between components and minimizing component size. There is a
further need in the art for a drive system that reduces energy
losses through direct electrical connections between components and
that includes a transmission between the engine and electric
machine (acting primarily as a generator) to improve system
operating efficiency of the engine and electric machine by
controlling the relative speed relationship therebetween.
SUMMARY
[0006] Accordingly, the present disclosure relates to a system of
electric power management for a hybrid vehicle including: (a) an
engine; (b) a first inverter; (c) a first electric machine coupled
to the engine and the first inverter; (d) a first transmission
coupled between the engine and the first electric machine, wherein
the first transmission has a transmission speed ratio operable such
that the first electric machine operating speed operates
independent of an engine operating speed; (e) a second electric
machine coupled to the second inverter and a wheel axle of the
vehicle; (f) a high voltage battery coupled to both the first
inverter and the second inverter; and (g) a switch box disposed
between the first electric machine and the second electric machine.
The switch box includes switches adapted to switch open and closed
to allow direct electrical connection from the first electric
machine to the second electric machine.
[0007] An advantage of the present disclosure is that a hybrid
vehicle is provided that includes an engine, an electric machine,
and a transmission disposed therebetween. Another advantage of the
present disclosure is that the operating efficiency of the electric
machine is improved, resulting in decreased fuel consumption. A
further advantage of the present disclosure is that the size of the
engine and electric machine can be reduced due to the improved
operating efficiency. Still another advantage is that series drive
efficiency is improved by reducing the AC-DC energy conversion
losses when the engine is operational. Yet another advantage is the
unique power split arrangement of the transmission from 4-N gears
when the engine is operational. Still yet another advantage is that
the unique gear split arrangement implements a 2 speed low loss
transmission for the electric traction system and decouples the
engine gears. A further advantage of the present disclosure is that
it allows for downsizing of the inverters associated with both the
generator and traction motors. Still a further advantage of the
present disclosure is that the low temperature thermal system may
be downsized. Yet a further advantage of the present disclosure is
that peak power at a high speed drive mode is improved. Another
advantage of the present disclosure is the potential to downsize
the engine through a 10-20% reduction in power requirements. Other
potential advantages is that the invention can be used for PHEV or
HEV applications, can be scalable between a PHEV and an HEV, a
reduced power electronics duty cycle improves reliability,
increased number of limp home modes are available and the
architecture is applicable to front, rear or all wheel drive
applications.
[0008] Other features and advantages of the present disclosure will
be readily appreciated, as the same becomes better understood after
reading the subsequent description taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is an example of powertrain architecture for a hybrid
electric vehicle.
[0010] FIG. 2A-2B is a schematic block diagram illustrating a
system of directly connecting electrical machines for the vehicle
of FIG. 1 and associated operating states.
[0011] FIG. 3 illustrate schematic power flow distributions for an
operating state 1 of a switch box of FIG. 2.
[0012] FIG. 4 illustrate schematic power flow distributions for an
operating state 2 of the switch box of FIG. 2.
[0013] FIG. 5 illustrate schematic power flow distributions for an
operating state 3 of the switch box of FIG. 2.
[0014] FIG. 6 is a schematic block diagram having a clutch.
[0015] FIG. 7 is a schematic block diagram having a third
motor/generator coupled to front wheels and a switch box.
[0016] FIG. 8 is schematic block diagram having a third
motor/generator coupled to front wheels and a second inverter.
[0017] FIG. 9 is schematic block diagram having a third
motor/generator coupled to front wheels and a first inverter.
[0018] FIG. 10 is schematic block diagram having a third
motor/generator coupled to front wheels and a first inverter and a
second switch box disposed between the inverter and the third
motor/generator.
[0019] FIG. 11 is schematic block diagram having a third
motor/generator coupled to front wheels with a second switch box
disposed between a first inverter and the third motor/generator and
a first motor/generator.
[0020] FIG. 12. is another schematic block diagram having a third
motor/generator coupled to front wheels with a second switch box
disposed between a first inverter and the third motor/generator and
a first motor/generator showing regenerative flow.
[0021] FIG. 13 is illustrates a second example block diagram of a
switch box.
[0022] FIG. 14 is another illustration of the switch box of FIG.
13.
[0023] FIG. 15 is a further illustration of the switch box of FIG.
13.
DESCRIPTION
[0024] The present disclosure provides for a system and method of
direct electrical connection (e-Direct) combined with a split gear
transmission (e-Split) for a multi-motor hybrid drive system is
illustrated. Referring to FIG. 1, a hybrid vehicle 1l is
illustrated. In this example the vehicle 10 can be a plug-in hybrid
vehicle powered by an internal combustion engine 20 and a battery
16 operable to be charged off-board. Both the engine 20 1and the
battery 16 can function as a power source for the vehicle 10. The
vehicle 10 can be powered by each power source independently or in
cooperation. A hybrid vehicle that uses a series configuration,
such as an engine driving a generator and the generator providing
electrical power to a drive motor, can utilize this architecture.
The vehicle 10 could be a passenger vehicle, truck, off-road
equipment, etc.
[0025] Vehicle 10 also includes a drivetrain 11 that operatively
controls movement of the vehicle. A motor 24, that mechanically
drives an axle of the vehicle that moves wheels of the vehicle, is
powered by the power sources (Le., a battery, engine, and/or
generator). In the example of FIG. 1, vehicle 10 is a rear wheel
drive vehicle with the rear wheels mechanically driven by motors
24. Motors 24 and generator 12 can be referred to as an electrical
or electric machine. In an example, the terms "motor" and
"generator" are directed to the flow of energy since each can be
operated in reverse to accomplish the opposite function. Therefore,
an electric machine can either generate power by operating with a
negative shaft torque (Le., a generator) or distribute power by
producing positive shaft torque (Le., a motor). In FIG. 2a-12, the
electric machine is referred to as a motor/generator ("MG").
Accordingly, the vehicle can include an MG1 12 coupled to the
engine 20 and an MG2 24 coupled to wheels W.
[0026] The architecture of the drive train is selectively
determined, such as a series, parallel or parallel-split
arrangement of the drive train components. In this example the
drive train includes a MG1 12 and an MG2 24. Various types of MG's
are available, such as an electric motor, or generator, permanent
magnet synchronous machine, induction machine, or the like. The MG1
12 can include a housing, a stator disposed in the housing that is
stationary, and a rotor that rotates about a central shaft that
includes a permanent magnet. The MG1 12 converts mechanical energy
received from engine 20 to electrical energy used to provide power
to the wheels W, charge the on-board battery 16, or power auxiliary
vehicle components. Typically, the output of MG1 12 is A/C power
that is converted to D/C power in an inverter 22A. The D/G power
can then either be delivered to the battery 16 or another inverter
228 to convert back to A/C power before powering any drive motors.
Typical of such MGs and inverters, each has a predetermined
operating efficiency corresponding to a given speed/torque
band.
[0027] In this example, the drivetrain 11 also includes a gasoline
powered engine 20 that provides supplemental power when required
under certain operating conditions. Engine 20 is operatively
coupled to MG1 12, such as via an engine output shaft. Accordingly,
when the engine 20 runs, the MG1 12 typically runs as a result of
their engagement to each other. The engine 20 can also have a
predetermined operating efficiency at a corresponding speed/torque
band. However, the ratio of engine speed efficiency with respect to
generator speed efficiency may not be optimal within a particular
speed/torque band.
[0028] Typical of electric machines, each has a predetermined
operating efficiency corresponding to a given speed/torque band.
However, the ratio of engine speed efficiency with respect to
generator speed efficiency may not be optimal within a particular
speedband. Through the use of an e-Split transmission arrangement,
unique downsizing of the engine is feasible, with a corresponding
reduction in power requirements (i.e. 150 kW to 125 kW -120
kW).
[0029] The drivetrain 11 includes a transmission 14A disposed
between MG1 12 and engine 20. In an example, transmission 14A
provides a mechanical linkage between the engine 20 and MG1 12 in
line with the engine output shaft. The transmission 14A may be of
any type, such as electronic, mechanical or electromechanical, and
can be a multi-speed or continuously variable transmission, or the
like to offer selectable effective gear ratios. The transmission
varies the gear ratios, to facilitate the transfer of engine power
to the generator. For example, it may be desired to run engine 20
at 3000 rpm and MG1 12 at 4500 rpm. Transmission 14A positioned
between engine 20 and MG1 12 can allow each of the engine 20 and
MG1 12 to independently operate at a desired speed and/or torque
for a corresponding speed band. Engine 20 and MG1 12 can each
define different torque/speed efficiency profiles. Allowing each to
operate at different speeds can allow optimization by adjusting
transmission ratio selection to operate each component as close to
its corresponding speed identifiable from a measured efficiency
map.
[0030] Various types of transmissions 14A may be utilized, such as
a multispeed transmission or continuously variable transmission, or
the like. The transmission 14A may incorporate multiple gear sets
between the engine 20 or MG1 12. Similarly, transmission 14A may
utilize planetary gears. An arrangement of transmission 14A between
engine 20 and MG1 12 may be incorporated with many different hybrid
powertrain architectures. Transmission 14A allows for more
efficient system operation as compared to a standard powertrain
without a transmission. As a result of the enhanced efficiency,
excess power may result and be supplied to an external component
while the vehicle is parked. In an example, the vehicle can store
excess power and distribute that power to an external source such
as a grid or an external energy storage device.
[0031] The MG1 12 operating speed may be independent of the engine
20 operating speed. As a result, the use of a transmission 14A
therebetween to control the transfer of power through different
transmission ratios, the efficiency of the system can be enhanced.
Operating efficiency profiles provide an engine designer with
increased freedom in selecting the various engine operating points
corresponding with predetermined vehicle operating conditions.
Thus, an electric machine having lower torque characteristics can
be selected, since the constant power operating region of the
electric machine can still be utilized thereby still exhibiting the
same performance. Variable speeds between the engine and generator
can align the maximum efficiency of the generator with the current
operating point of the engine.
[0032] In an example, the system can also include a second
transmission 148 operatively positioned adjacent an inverter 228
located at the rear drive shaft coupled to MG2 24. The addition of
another transmission 148 provides for the selection of drive gears
depending on the operation mode of the vehicle, in a manner to be
described. In this example, the inverter 228 has a power capacity
of 150 kW.
[0033] Various types of transmissions may be utilized for either
the first or second transmission, such as a multi-speed
transmission or continuously variable transmission, or the like.
The transmission may incorporate multiple gear sets between the
engine and/or electric machine. Similarly, the transmission may
utilize planetary gears. The arrangement of a transmission between
the engine and electric machine may be incorporated with many
different hybrid powertrain architectures. As a result of the
enhanced efficiency of the transmission placement, excess power may
be supplied to an external component while the vehicle is
parked.
[0034] Referring to the FIGS. 2a-12, exemplary systems and methods
of direct electrical connection (e-Direct) combined with a
transmission split (e-Split) for multi-motor hybrid drive systems
are illustrated. The vehicle 10 includes a power train that
controls the operation of the vehicle. In these examples, the power
train is a plug-in hybrid, and includes at least two electrical
machines.
[0035] The system includes an energy storage device 16, such as the
battery 16 that is in communication with the components that adds
or subtracts power within the vehicle system. Various types of
batteries are available, such as lead acid, or lithium-ion or the
like.
[0036] A first inverter 22A is operatively in communication with a
second inverter 228, and the second inverter 228 converts DC
electrical power back to AC electrical power. The second inverter
228 is operatively in communication with a second electrical
machine MG2 24. MG2 24 converts the AC electrical power into
mechanical energy that is available for use in the operation of the
vehicle. In this example, the mechanical energy is transmitted to a
drive shaft in order to control operation of the vehicle wheels W,
i.e. front wheels or rear wheels.
[0037] It should be appreciated that the energy conversion process
is less than 100% efficient, resulting in losses throughout the
system. In an example, loss across an inverter can range from about
3% to 10%. The first electrical machine (MG1 12) is directly in
electrical communication with the second electrical machine (MG2
24), so that AC power from the first electrical machine directly
provides power to the second electrical machine. It should be
appreciated that the first electrical machine may be operated at a
speed and load wherein the power may be directly transferred to the
second electrical machine. Various different examples and
illustrations of the present disclosure are described in FIGS.
2a-12.
[0038] FIG. 2a illustrates an example schematic system for a
vehicle 10 including a switch box 21 that allows for direct AC/AC
connection between MG1 12 and MG2 24. Loss across a switch box 21
is relatively low and far less than an inverter. In this example,
engine 20 is coupled to MG1 12 which can deliver electrical power
to an inverter 22A to be received by a battery 16, another inverter
228 or a switch box 21. The energy can then be transferred to MG2
24 and then the wheels W. Energy then can flow in either direction
as shown by the other FIGS. An exploded view of various operating
states of box 21 is further shown in FIG. 2a. In this example, the
switch box 21 can operate in three operating states represented by
state 1 (21A), state 2 (218), and state 3 (21C). Various modes of
energy flow for different switch box modes are shown in FIGS. 4-12.
Table 1 below illustrates various characteristics associated with
each operating state.
TABLE-US-00001 TABLE 1 Mode Engine Battery Inverter1 MG1 Switch
Inverter2 MG2 Description Mode 1 Off Power State 1 DC to AC AC to
EV-drive Out mechanical Mode 2 Crank Power DC to AC AC to State 1
DC to AC AC to Engine crank Out mechanical mechanical while driving
Mode 3 Power Power AC to DC Mechanical State 1 DC to AC AC to
HEV-Engine to in/out to AC mechanical wheels, battery boost or
charge as necessary Mode 4a Power Mechanical State 2 AC to
HEV-Engine to to AC mechanical wheels Mode 4b Power Power out DC to
AC Mechanical State 2 DC to AC AC to HEV-Engine to to AC mechanical
wheels w/battery boost using one or both inverters Mode 4c Power
Power in AC to DC Mechanical State 2 AC to DC AC to HEV-Engine to
to AC mechanical wheels w/battery charge using one or both
inverters Mode 4d Power Power AC to DC Mechanical State 2 DC to AC
AC to HEV-Engine to in/out/non to AC mechanical wheels using AC and
DC power, battery charge/boost as needed Mode 5 Spinning Power in
AC to DC AC to State 2 AC to DC Mechanical Braking - Wheel
(passable) mechanical to AC power to battery using one or both
inverters. Engine may spin if extra power is available Mode 6a
Power Mechanical State 3 AC to HEV-Engine to to AC mechanical
wheels (inverse), drive motor spinning backwards Mode 6b Power
Power out DC to AC Mechanical State 3 DC to AC AC to HEV-Engine to
to AC mechanical wheels (reverse), drive motor spinning backwards
w/battery boost using one or both inverters Mode 6c Power Power in
AC to DC Mechanical State 3 AC to DC AC to HEV-Engine to to AC
mechanical wheels (reverse), drive motor spinning backwards
w/battery charge using one or both inverters Mode 6d Power Power AC
to DC Mechanical State 3 DC to AC AC to HEV-Engine to in/out/non to
AC mechanical wheels (reverse), using AC and DC power, battery
charge/boost as needed
[0039] Power is transferred across a 3-phase AC bus. Switch box 21
includes three lines/switches 25 for the three-phase AC transfer.
State 1 is represented by box 21A where all three switches 25 are
open. When the switches 25 are open, energy cannot transfer
directly between MG1 and MG2. Accordingly, the energy is converted
from AC (leaving MG1) to DC through inverter 22A and then is either
received by battery 16 for charging or reconverted back to AC in
the second inverter 228 before being delivered to MG2. Having two
inverters allows for operation of either MG's without direct
influence on the other. MG1 12 can run idle or be completely turned
off while battery 16 delivers energy to MG2 24 through the second
inverter 228. Energy can be transferred from battery 16 to both MG1
12 and MG2 24. This can be desirable for cranking the engine and
thus needing MG1 12 to operate as a motor rather than a generator
to deliver energy to the engine 20. In an example, power can flow
from MG1 12 to charge battery 16 and drive MG2 24
simultaneously.
[0040] As shown in box 21B, state 2 is an operating state where the
three switches 25 are closed providing a direct electronic link
between MG1 12 and MG2 24. Switch box 21B allows AC power generated
in MG1 12 to flow directly to MG2 24. In this example, the energy
flow bypasses the inverters and therefore removing undesired
efficiency loss associated with the inverters 22. In this
embodiment, MG1 12 is directly linked to MG2 and thus are operating
at proportional speeds. This is ideal for cruise control conditions
for example and increases efficiency of the power distribution of
the vehicle. Energy loss across the switches associated with 21A is
far less than that of inverters 22, Energy can flow directly
through switch box 21A as well as through the inverters 22 and to
battery 16 or the other inverter, Energy can be delivered in both
directions (i.e., in and out of the battery 16 from and to MG1 12
and MG2 24). Accordingly, the wheels W can be powered by A/C power
from the engine 20 and DC power from the batter 16. The battery can
also be charging simultaneously while direct power is transferred
from MG1 to MG2. The battery 16 can boost or charge using one or
both inverters 22.
[0041] A third state (state 3) energy flow path associated with an
operating state of switch box 21C. In this embodiment switches 27
(shown open in box 21A and 21B) are closed along with one switch
25. Switches 27, when closed, allow for a cross energy linkage
across the three phases which allows direct energy flow between MG1
12 and MG2 24 while either MG1 or MG2 is operating in reverse.
Accordingly, MG1 12 can spin forward while MG2 can spin
backward.
[0042] FIG. 2b illustrates an example box diagram of the system of
FIG. 2a with a transmission 14A disposed between engine 20 and MG1
12 and a second transmission 148 disposed between MG2 and a wheel
axle associated with wheels W. Referring to FIGS. 4-12, two
transmissions 14A and 148 are provided, each being a two-speed
transmission and thus effectively making the vehicle a 4-speed
transmission system. It should be appreciated that the gear split
arrangement selected is for exemplary purposes and other multiple
or single transmission gear arrangements have been considered and
within the scope of the present disclosure. Further in this
example, there is an electrical split between the physically
separated gear sets. Advantageously, the vehicle only utilizes the
number of gears required to meet a particular speed/load
requirement. The system can change gearing to operate at another
speed/load band to match gearing to the requirement. Energy
requirement are reduced by the number of gears selected for a
particular operating mode.
[0043] In an example of an e-Split arrangement, gears are
positioned between the engine 20 and MG1 12 and the wheel axle of
wheels Wand MG2 24. Note that 2 engine gears and 2 motor gears
effectively provide 4 speeds with engine running The inclusion of 2
or 3 gears at the engine provides for compact packaging, such as
via a single simple planetary (2 gears at the engine) or a single
compound planetary (3 gears at engine) arrangement. The system may
further include one or more clutches, such as two clutch
arrangement to implement either 3 or 2 engine gears. Typically, the
transmission can include a clutch impact by decoupling. It should
be appreciated that the use of 3 gears at the engine and 2 gears at
the motor effectively translates into 6 gears.
[0044] The drivetrain may include other components that are known
in the art. For example, a clutch, such as a wet or dry clutch, may
be located on the shaft to switch between different speed ratios.
Additional powertrain components may be included and are
conventionally associated with the operation of the vehicle.
[0045] FIGS. 4-12 illustrate various exemplary embodiments
associated with the present disclosure. The example systems include
a third electrical machine MG3 26 coupled to front wheels W. These
embodiments allow for selective four-wheel drive modes for example
vehicles associated with the present disclosure. MG3 26 is can be
linked directly to the switch box 21. Power can be delivered
directly from engine 20 to MG3 26. In these embodiments, a second
switch box 31 is provided along with a third inverter 22C, both
coupled to MG3 26. Accordingly, the presence of a third inverter
and a second switch box allows for various energy flow patterns
between the engine, battery, inverters, and motors/generators. FIG.
3 is a chart illustrating functional descriptions for different
modes associated with the multiple switch box, inverter, and
motor/generator embodiments. Modes 1-11 are exemplary states of
operation associated with the operating status of the switch boxes,
battery, inverters, and motors/generators. Mode 7 shows an example
where a synchronization happens which makes sure the switches can
close so the phases are in line. In the battery column, "D" stands
for discharging and "C" stands for charging.
[0046] Operating the vehicle in e-Direct (i.e., the switches 25
and/or 27 are closed) significantly reduces load on the inverters
of the vehicle 10. Accordingly, inverter size can be reduced
relative to standard inverters used in vehicles without a switch
box 21 and/or 31. Reducing inverter size can reduce hardware costs
of the vehicle and overall system efficiency.
[0047] The addition of a compliant mechanical coupling device (such
as a clutch) can increase the versatility of the system, such as
the use of e-Direct to direct power distribution between front axle
and rear axle of the vehicle 10. The e-Direct hardware can be
positioned such that either the front MG1 12 or rear
motor/generator MG2 24 can be engaged. This can also be implemented
wherein both drive motors 24 and 26 are engaged at the same time or
independently.
[0048] The transmissions of the vehicle can operate as a mechanical
coupling device. An example of a mechanical coupling device may be
a clutch, such as in a conventional manual transmission or a dual
clutch transmission, a wet clutch as found in an automatic
transmission, a torque converter as found in an automatic
transmission, a dog clutch, or any other mechanical linking device
that allows -100% torque transfer in one operating mode and -0%
torque transfer in another operation mode. The mechanical coupling
device may also be able to transfer a wide range of torque from
0-100% or have torque multiplying capacity, such as in an automatic
transmission torque converter. As a result, a generator 12 may be
disengaged from the engine 20 and power or torque may be
transferred to the generator MG1 12 while the engine 20 is spinning
at a speed independent of the generator. A feature such as e-Direct
can be enhanced by allowing e-Direct to be engaged when the vehicle
is stopped through the use of the mechanical slip device (i.e.,
coupling device or the transmission). The generator 12 can be hard
coupled to the motor 24 through the 3-phase bus, making the
generator/motor 12/24 act as if they are mechanically linked.
Another advantage is that the transmissions 14A/148 allow the
vehicle 10 to be started without the need for either inverter 22 or
battery 16.
[0049] The inclusion of a switch box 21 with switches 25, such as a
two-position switch, allows e-Direct operation to either the front
or rear wheels W. The pole/gear ratio can be optimized so that the
engine 20 can transfer power through e-Direct in multiple gears,
Le. at multiple optimized engine speeds. In an example, the system
may include hard coupling the 3-phase AC power cables to the same
bus as the generator MG1 12 or the rear drive motor MG2 24. A front
drive motor MG3 26 can have the same electrical frequency as the
rear motor MG2 24. This means that the two motors will always spin
at speeds inversely proportionally to their relative number of
pole. However, the axle speed can vary as the vehicle drives around
turns, tire wear, gearing, etc. and therefore the compliant
mechanical coupling accommodates for these variations. As the
vehicle goes around a turn, the front wheels W travel a further
distance than the rear wheels W. This means that the front motor
MG3 26 spins proportionally faster than the rear motor MG2 24.
Since the e-Direct configuration hard couples the electrical
phases, the front motor MG3 26 can benefit from a compliant
coupling between the motor and wheels W. The compliant coupling
(with similar possibilities as described by the engine/generator
compliant coupler) and drive unit between the front motor MG3 26
and wheels W can be configured so that the motor always spins
faster than the coupling output speed (using the transmission).
This means that the motor may provide power to the wheels.
[0050] In another example the front wheel drive motor MG3 26 may be
hard coupled to the generator MG1 12. Thus, the front drive motor
MG3 26 and generator MG1 12 may spin at a constant proportional
speed. The inverter 22A can either power the front wheels W, absorb
power from the generator MG1 12, or modulate power as the generator
MG1 12 powers the front wheels W during e-Direct operation. A
second e-Direct switching device 31 may be added so that the front
and/or rear motor is proportionally hard-coupled coupled to the
generator MG1 12. As a result, the first inverter 22A may power the
front motor MG3 26 or electric machine. The generator MG1 12 will
spin the front motor MG1 26 so that the engine 20 can be decoupled
if so required.
[0051] In operation, numerous variations can be made using the
above described configuration as its basis. For example: [0052]
Switching inverters on/off to either operate conventionally or
through inverter-less operation. [0053] Using IGBTs or other
controlled circuitry to switch between routing electrical machine
power to the inverter or to other electrical machine. [0054] Using
different types of motors such as permanent magnet synchronous
machines or AC induction machines in order to increase or reduce
the tolerance for timing variations between the two electrical
machines. [0055] Rectifying or otherwise modifying the magnitude or
timing of the AC signal to control output power. [0056] Adjusting
phase or bus capacitance, inductance or any other characteristic in
order to manage the power or robustness between the two electrical
machines. [0057] Actively or passively controlling engine power to
align timing between the electrical phases of each electric
machine.
[0058] Referring to FIGS. 13-15, the electrical energy power
management system includes an e-Direct switch box 21 or 31 that
controls the distribution of power between the engine 20 and a
drive motor MG2 24 or MG3 26, depending on the operating mode of
the vehicle. The switch box 21 can be located between the engine 20
and MG1 21, and eliminates AC/DC power conversion losses throughout
the system due to the direct connection thereof. It should be
appreciated that the energy conversion process is less than 100%
efficient, resulting in losses throughout the system. As shown in
the FIGS., the first electrical machine MG1 12 is directly in
electrical communication with the second electrical machine MG2 24
via the switch box 21, so that AC energy from the first electrical
machine MG1 12 directly provides power to the second electrical
machine MG224. It should be appreciated that MG1 12 may be operated
at a speed and load wherein the power may be directly transferred
to the second electrical machine.
[0059] Various types of switches are contemplated, such as the
rotational switch of this example. Switch 21 reduces losses
associated with power conversion between AC-DC or electrical to
mechanical sources.
[0060] In an example, switch box 21 includes a contacting mechanism
and a sensing and control element. Switch box 21 can be a 3-phase
AC switch although other embodiments are considered. One side of
the contacting mechanism is connected to the 3-phase output from
the generator while the other side is connected to the 3-phase
input to the traction motor. In addition, there are means to allow
for phase reversal by swapping two of the phases. In a further
example, a rotary (where the contacting mechanism is actuated by
means of a rotary actuator) or linear (where the contacting
mechanism is actuated by a linear actuator or a relay or the like)
switch is provided. The sensing mechanism senses the voltage,
frequency and phase relationship between the voltage at either side
of the switch box 21. Based on this input and using a suitable
control algorithm depending in the state of the drive, the switch
box 21 can be actuated to engage the e-Direct mode (Le., close the
switches 25). The switch box 21 can be in communication with a
vehicle/hybrid controller to coordinate the switch operation. This
communication can be effected via CAN protocol or the like.
[0061] In an example rotary switch box 21 as shown in FIGS. 13-15,
includes two parts - a stationary one that connects to the
generator output and a part that can rotate relative to the
stationary one that connects to the motor input. The rotary part
can include copper (or other conducting material) bars to which the
connections are made. The connections from the stationary part to
the rotary part are made through brushes (metallic, graphitic or
combination) that are able to slide on the surface of the rotary
part. There may also be a wiper integrated or co-located with the
brushes to help clean any conductive debris. The rotary part may be
connected to a rotary actuator such as a stepper motor or the like.
Once the sensing circuit and controller determine that the
conditions to engage the switches 25 are satisfied, the rotary
actuator is energized to actuate the rotary part and connect the
motor input to the generator output. The linear example can be
similarly be implemented by replacing the rotary elements above
with linear ones.
[0062] In a further example, switch box 21 is an electro-mechanical
switch where the mechanical contactor are actuated using a relay
mechanism or the like. A variation of the electro-mechanical switch
is a hybrid electronic and electro-mechanical switch. In this
example, there is a power electronic device (IGBT, MOSFET or the
like) in parallel with each connector of the electromechanical
switch. Upon receiving the command from the controller, the power
electronic device is closed first then the electromechanical switch
is activated. The power electronic device closure is much faster
than the electro-mechanical switch and so permits effective closing
sooner. The electro-mechanical switch can handle the operating
currents and so the power electronic device needs to only handle
peak current for a short duration.
[0063] In an example where close to identical speed alignment
between MG1 12 and MG2 24 is not possible, then the switches in box
21 need to close relatively quickly. Mechanical contactors can be
used since they have a high level of efficiency, however, their
response time may not be adequate in some situations. A hybrid
powerelectronic/mechanical contactor as shown in box 21 can be
used. In an example, two IGBTs for each mechanical contactor are
included that allow current to flow in either direction, however
only one IGBT may be necessary. This can be used with other power
electronics devices, including but not limited to, MOSFETS,
thyristors, SCRs, etc. When the switches are closed allowing direct
power transfer between electric machines, voltage levels can be
monitored by a controller. When the 3-phase voltage aligns (even if
just for a brief moment) the solid state switching device engages
locking the phases together. This keeps the voltage over the
mechanical contactors near zero, which allows them to close with
little risk.
[0064] In operation, various potential operating modes are
described, by way of example, and others are contemplated. For
example, braking of the vehicle closes or shuts off the e-direct
feature by opening the circuit. In another example, during
acceleration the e-direct switch is closed below a predetermined
speed, such as 5-15 mph, and above which the switch is further
closed to fully implement the e-direct feature. In another example,
during transitional modes, such as power demand modes, e-direct is
implemented. It should be appreciated that the use of e-direct and
e-split may be implemented together or independently.
[0065] The system can sense a generator/motor speed using a sensor,
and engine speed using a sensor. Each of the speed signals are sent
to a processor. Logic within the processor evaluates both speed
signals and transmits a signal to the transmission to selectively
control the transmission gears to further control the transfer of
engine power to the generator/motor. As a result, the
generator/motor can operate at a speed that is independent of the
engine speed in order to maximize the efficiency of the system. As
a result of these efficiencies, a vehicle designer has increased
freedom in the selection of the engine operating points for
maximizing system efficiency. Further, a signal is sent to the
e-direct switch to control power distribution.
[0066] The hybrid vehicle may include other features conventionally
known for a vehicle, such as a gasoline motor, other controllers, a
drive train or the like. Many modifications and variations of the
present disclosure are possible in light of the above teachings.
Therefore, within the scope of the appended claim, the present
disclosure may be practiced other than as specifically
described.
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