Patent Application
20120186391
The present disclosure relates generally to a hybrid vehicle, and more particularly to a series hybrid electric vehicle power train.
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.
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.
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.
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.
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.
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.
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
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
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 MG112 and an MG224. Various types of MG's are available, such as an electric motor, or generator, permanent magnet synchronous machine, induction machine, or the like. The MG112 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 MG112 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 MG112 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.
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 MG112, such as via an engine output shaft. Accordingly, when the engine 20 runs, the MG112 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.
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).
The drivetrain 11 includes a transmission 14A disposed between MG112 and engine 20. In an example, transmission 14A provides a mechanical linkage between the engine 20 and MG112 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 MG112 at 4500 rpm. Transmission 14A positioned between engine 20 and MG112 can allow each of the engine 20 and MG112 to independently operate at a desired speed and/or torque for a corresponding speed band. Engine 20 and MG112 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.
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 MG112. Similarly, transmission 14A may utilize planetary gears. An arrangement of transmission 14A between engine 20 and MG112 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.
The MG112 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.
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 MG224. 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.
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.
Referring to the
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.
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 MG224. MG224 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.
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 (MG112) is directly in electrical communication with the second electrical machine (MG224), 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
a illustrates an example schematic system for a vehicle 10 including a switch box 21 that allows for direct AC/AC connection between MG112 and MG224. Loss across a switch box 21 is relatively low and far less than an inverter. In this example, engine 20 is coupled to MG112 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 MG224 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
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. MG112 can run idle or be completely turned off while battery 16 delivers energy to MG224 through the second inverter 228. Energy can be transferred from battery 16 to both MG112 and MG224. This can be desirable for cranking the engine and thus needing MG112 to operate as a motor rather than a generator to deliver energy to the engine 20. In an example, power can flow from MG112 to charge battery 16 and drive MG224 simultaneously.
As shown in box 21B, state 2 is an operating state where the three switches 25 are closed providing a direct electronic link between MG112 and MG224. Switch box 21B allows AC power generated in MG112 to flow directly to MG224. In this example, the energy flow bypasses the inverters and therefore removing undesired efficiency loss associated with the inverters 22. In this embodiment, MG112 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 MG112 and MG224). 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.
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 MG112 and MG224 while either MG1 or MG2 is operating in reverse. Accordingly, MG112 can spin forward while MG2 can spin backward.
b illustrates an example box diagram of the system of
In an example of an e-Split arrangement, gears are positioned between the engine 20 and MG112 and the wheel axle of wheels Wand MG224. 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.
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.
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.
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 MG112 or rear motor/generator MG224 can be engaged. This can also be implemented wherein both drive motors 24 and 26 are engaged at the same time or independently.
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 MG112 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.
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 MG112 or the rear drive motor MG224. A front drive motor MG326 can have the same electrical frequency as the rear motor MG224. 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 MG326 spins proportionally faster than the rear motor MG224. Since the e-Direct configuration hard couples the electrical phases, the front motor MG326 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 MG326 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.
In another example the front wheel drive motor MG326 may be hard coupled to the generator MG112. Thus, the front drive motor MG326 and generator MG112 may spin at a constant proportional speed. The inverter 22A can either power the front wheels W, absorb power from the generator MG112, or modulate power as the generator MG112 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 MG112. As a result, the first inverter 22A may power the front motor MG326 or electric machine. The generator MG112 will spin the front motor MG126 so that the engine 20 can be decoupled if so required.
In operation, numerous variations can be made using the above described configuration as its basis. For example:
Referring to
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.
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.
In an example rotary switch box 21 as shown in
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.
In an example where close to identical speed alignment between MG112 and MG224 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.
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.
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.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 61220421 | Jun 2009 | US | |
| 61288709 | Dec 2009 | US | |
| 61294722 | Jan 2010 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2010/040087 | Jun 2010 | US |
| Child | 13336636 | US |
